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Characteristics of Inclusions in Alloying Structural Steel during Refining

Tue, 29 Oct 2013 14:19:58 +0200

Characteristics of Inclusions in Alloying Structural Steel during Refining

Abstract: Systematic industrial experiments were carried out to investigate the characteristics of non-metallic inclusions with the aim of reducing their harmful effect on SAE4145 steel properties. Factsage thermodynamic software was used to simulate the conditions under which the inclusions occur. The number of inclusions in molten steel decreased rapidly with refining time. The inclusion morphology changed from an irregular initial shape to predominantly spherical inclusion. After vacuum treatment, almost all of the inclusions were CaO-SiO2-Al2O3-MgO composites. To form low melting point inclusions of CaO-SiO2-20%Al2O3-MgO,the corresponding activities of [O], [Ca], [Mg] and [Al] should be controlled in the range of a[O] 0–10 ppm, a[Ca] 0–45×10-10 ppm, a[Mg] 0–0.3 ppm, and a[Al] 0~20 ppm.
Key words: alloying structural steel; non-metallic inclusions; ladle furnace-vacuum degassing; thermodynamic

1. Introduction

SAE4145 is an alloying structural steel often used for engine crankshafts. Because of the severe conditions under which they operate, such as dynamic loads, high torque, alternating bending stress, and long-term high-speed running, crankshafts are often destroyed by torsional vibration, bending deformation and even fatigue fracture [1]. Thus, higher fatigue strength, impact toughness, and wear resistance are required in the crankshafts [1-4].Numerous studies [5-9] show that fatigue is the dominant mechanism for crankshaft failure and fatigue cracks are likely to initiate from non-metallic inclusions [10]. The detrimental effect of inclusions depends on the difference between the thermal expansion coefficient of the inclusion and that of the steel matrix. Hard, large, brittle, and un-deformable inclusions should be avoided, because they cannot be deformed with the steel matrix during hot rolling and could result in stress concentrations at the steel/inclusion interface [11].
Many studies have been carried out on the characteristics of steel inclusions, such as spring, bearing, hot work die steel, tire cord, gear, and electrical steel [12-15]. These studies [11] show that inclusions with a low melting point and good plasticity can be formed by controlling the deoxidant alloys (or a mixture of deoxidant and flux), the synthetic top slag and/or the flux injection. However, no reports exist on the characteristics of SAE4145 steel inclusions.
In this paper,industrial experiments were carried out to investigate systematically the characteristics of non-metallic inclusions during ladle furnace-vacuum degassing (LF-VD) refining. Furthermore, discussions are presented on the formation conditions of the desired inclusions, which were based on the thermodynamic equilibrium between the steel and the inclusions.

2. Experimental

In this work, the experimental steel is SAE4145 with a composition (wt.%) of C 0.45, Si 0.20, Mn 0.80, P 0.02, S 0.008, Mo 0.15, Cu 0.07, and Cr 0.94. The process to produce SAE4145 is as follows: 50 t electric arc furnace (EAF) → 50 t LF-VD → CaSi treatment → Continuous Casting The LF refining time is approximately 75 min and the VD treatment time is 70 min.
Steel samples were taken during four different runs at different refining stages, such as before LF refining (Sample 1), in the middle of LF refining (Samples 2 and 3), at the end of LF refining (Sample 4), and at the end of VD (Sample 5). During sampling, the samplers were immerged in the molten steel 300 mm below the bath surface. Inclusions were observed and analyzed using scanning electron microscopy-energy dispersive spectroscopy. The total oxygen content (T[O]) was determined using the GALILEO ON/H analyzer.

3. Results and discussion
3.1 Total oxygen and amount of inclusions

Figure 1 shows the change in total oxygen content and amount of inclusions during LF-VD refining. The T[O] content decreased from 260 to 10 ppm and the amount of non-metallic inclusions in the molten steel decreased rapidly with refining time. The removal rate over the entire refining process was 88.8%, which indicates that the LF-VD process is able to remove oxide inclusions.

Fig. 1 Change in T[O] and amount of inclusions during LF-VD refining

3.2 Morphology and composition of typical inclusions

The morphologies of typical inclusions in each sample are shown in Figs 2–6 with inclusion compositions listed in Table 1.
As shown in Fig. 2 (a), irregular cluster-like inclusions of alumina or spinel were observed in Sample 1. Figure 2 (b) shows other typical inclusions that are rectangular in shape. Large amounts of Al2O3 formed with the addition of deoxidizers like aluminum, ferrosilicon, and ferromanganese after EAF tapping. Meanwhile, in the FeO-SiO2-Al2O3-MnO system, complex inclusions containing less CaO were formed by a reaction of the deoxidation products (SiO2, Al2O3, MnO) and high oxide slags.
As can be seen in Fig. 3, the Al2O3 inclusions were encased in complex inclusions. The inclusion shape changed from irregular to ellipsoidal. During the first stage of LF refining, the basicity of the slag was in the range of 2.0–2.5 and the oxygen content in the steel reached up to 50 ppm. The low basicity and high SiO2 content could result in the coexistence of both Al2O3 and Ca-Si-Mn-Mg-O inclusions with higher Si and/or lower Al content.
Figure 4 shows the morphologies of the CaO-SiO2-Al2O3-MgO inclusions in Sample 3. The formation mechanism of these inclusions is explained as follows. After Al-deoxidization, a great number of Al2O3 inclusions formed in the steel melt. As the refining process progressed, the Mg content in the steel increased, possibly because of the erosion of magnesia carbon brick by a chemical reaction (1). However, because of the low level of FeO content in the slag, alumina inclusions are unstable even when low levels of Ca exist in the steel. Ca could be reduced from the slag by reaction (2). The Mg activity was higher than that of Ca and the Al2O3 inclusions formed would react with dissolved Mg and change into MgO-Al2O3 system inclusions, as expressed by reaction (3). The formed MgO-Al2O3 is not stable when Ca enters the steel and would be transformed into calcium aluminates by reaction (4) and surround the original MgO-Al2O3 inclusion core [16].

(a) (b)
Fig. 2 Morphologies of a typical inclusion in Sample 1


Fig. 3 Morphologies of CaO-SiO2-MnO-MgO inclusions in Sample 2	Fig. 4 Morphologies of CaO-SiO2-Al2O3-MgO inclusions in Sample 3

Typical inclusions found after LF refining in Sample 4 are displayed in Fig. 5. With time, MnO disappears from the inclusions while the content of CaO increases. Thereafter, most inclusions are CaO-Al2O3-SiO2-MgO.
3(MgO) + 2[Al] = (Al2O3) + 3[Mg]                                                                                                                        (1)
3(CaO) + 2[Al] = 3[Ca] + (Al2O3)                                                                                                                         (2)
[Mg] + n/3(Al2O3) = (MgO·(n-1)/3Al2O3) + 2/3[Al]                                                                                            (3)
x[Ca] + (yMgO·zAl2O3) = (xCaO·(y-x)MgO·zAl2O3) + x[Mg]                                                                           (4)
As shown in Fig. 6, after vacuum treatment, almost all inclusions were CaO-SiO2-Al2O3-MgO with highest CaO and lower Al2O3 content. The MgO content in the inclusions was close to that of the furnace lining. In VD refining, the oxygen and sulfur content is reduced further by vacuum degassing and stirring with Ar. However, the furnace lining is eroded under the high basicity, low oxygen, and high vacuum conditions. Most of the alumina can be floated and captured by the top slag, while some complex inclusions remain in the liquid steel formed by the interaction of CaO, SiO2, MgO, and a small amount of fine residual Al2O3.


Fig. 5 Morphologies of typical CaO-SiO2-Al2O3-MgO inclusions in Sample 4	Fig. 6 Morphologies of typical CaO-SiO2-Al2O3-MgO inclusions in Sample 5

Table.1 Inclusion compositions/wt%

*Code*	*Morphology*	*Location*	O	Al	Si	Ca	Mg	Mn	Fe
1-a	Irregular		10.56	84.07					5.37
1-b	Rectangular		8.50	32.28	23.67	3.55		16.43	4.06
2	Ellipsoidal	3	8.53	4.50	34.18	31.98	6.07	13.06	1.67
3	Spherical	1	40.06	19.05	9.54	31.36
4	Spherical		21.42	10.73	19.27	41.65	3.70		3.19
5	Spherical	1	5.20	3.47	20.59	57.87	6.35		2.56

3.3 Thermodynamic calculation of optimization

Because residual inclusions in steel are unavoidable and brittle and undeformable inclusions are undesirable, it is important to modify the inclusions into liquid inclusions in the molten steel [17]. Previous reports show that when the inclusion melting point is below 1673 K, good deformation ability is exhibited in the rolling process [14]. In this paper, Factsage software was used to calculate equilibrium and phase diagrams with the liquid zone in the CaO-SiO2-Al2O3-MgO system under 1873 K and the activities of CaO, SiO2, and MgO calculated by Factsage. The activities of Ca, Mg, Al, and O in the liquid steel bath were computed in equilibrium with inclusions. The soluble aluminum content in the steel is 0.03% at 1873 K.
Iso-activity lines of MgO, CaO, and SiO2 in the liquid zone are shown in Fig. 7. Regions enclosed by heavy lines and short dot lines represent the liquid zones of 1873 and 1673 K, respectively. To obtain CaO-SiO2-20%Al2O3-MgO system inclusions with a low melting point under 1673 K, the chemical composition (mass percent) of inclusions should be controlled in the region with MgO and CaO (mass percent) lower than 24% and 40%, respectively, and SiO2 (mass percent) between 32% and 68%. Accordingly, the activities should be: MgO from 0.001 to 0.1, CaO from 0.00001 to 0.01, and SiO2 greater than 0.05.
Fig. 7 Iso-aMgO, iso-aCaO, and iso-aSiO2 lines in the liquid zone of the CaO-SiO2-20%Al2O3-MgO system
Equilibrium activities of Ca, Mg, Al, and O in steel were calculated and are shown in Fig. 8. The region enclosed by heavy lines is the liquid zone (≤ 1873 K) and the lines with figures within the liquid zone are the iso-activity lines of [Ca], [Mg], [Al], and [O]. The activities of Ca and Mg increase with an increase in CaO and MgO content in the inclusions. However, the Al and O activities decrease with an increase in SiO2 content in the inclusions. At 1873K and 0.03% (mass percent) soluble aluminum in steel, to form low melting point inclusions, the activities of [O], [Ca], [Mg], and [Al] should be in the following ranges: a[O]: 0–10 ppm, a[Ca]: 0–45×10-10 ppm, a[Mg]: 0–0.3 ppm, and a[Al]:0–20 ppm.

(a) (b)

(c) (d)
Fig.8 Iso-a[Ca], iso-a[Mg], iso-a[Al], and iso-a[O] lines in the liquid zone of the CaO-SiO2-20%Al2O3-MgO system

4 Conclusions

The number of inclusions in molten steel decreases rapidly with refining time. The inclusion morphology changes from irregularly shaped to predominantly spherical. After vacuum treatment, almost all inclusions were smaller-sized CaO-SiO2-Al2O3-MgO.
To obtain CaO-SiO2-20%Al2O3-MgO inclusions with low melting point, their chemical composition should be controlled as follows: MgO and CaO (mass percent) should be present at less than 24% and 40%, respectively, and SiO2 (mass percent) between 32% and 68%. The activities should be: MgO from 0.001 to 0.1, CaO from 0.00001 to 0.01, and SiO2 greater than 0.05.
To form low melting point inclusions, the corresponding activities of [O], [Ca], [Mg], and [Al] should be controlled in the following ranges: a[O]: 0–10 ppm, a[Ca]: 0–45×10-10 ppm, a[Mg]: 0–0.3 ppm, and a[Al]:0–20 ppm.

Acknowledgments

The authors are grateful for support from the National Science Foundation China (grant no.51304016 and 51074021)

References

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YOUN-BAE K, HAE-GEON L. Inclusions chemistry for Mn/Si Deoxidized Steels: Thermodynamic Predictions and Experimental Confirmations [J]. ISIJ International, 2004, 44(6): 1006-1015.

Sulfur Control in Ultra-Low Sulfur Steel Refined byLadle Furnace-Vacuum Degassing

Wed, 30 Oct 2013 14:20:32 +0200

Sulfur Control in Ultra-Low Sulfur Steel Refined by Ladle Furnace-Vacuum Degassing

Abstract：Sulfur is deleterious in most kinds of steelMany factors influence the sulfur content in steel. We have investigated how ladle furnace (LF) slag deoxidizers, LF dynamic conditions and Ca-treatment after Ruhrstahl-Heraeus treatment affect desulfurization. The (FeO+MnO) content can be controlled below 0.5% after the addition of more than 300kg aluminum particles and sulfur in the steel is reduced from 30 to 6ppm. When the bottom gas flowrate is 500NL/min, sulfur in the steel can be reduced to 6ppm after 10min. Too high or too low an argon flowrate reduces the desulfurization efficiency.Vacuum degassing followed byCa-treatment has no effect on desulfurization, but Ca input helpsmaintain a low sulfur content.
Keywords: Ultra-low sulfur steel; desulfurization; ladle furnace-vacuum degassing refining; Ca-treatment
Sulfur is deleterious in most kinds of steel. Itnot only causes hot brittleness and impacts ductility,toughness and weldability, but can also form MnS inclusions, which become extended and elongated in the rolling process and lead to an increase in mechanical anisotropy. To achieve good resistance to the corrosion by hydrogen sulfide, the sulfur content in steel must be controlled below 0.0020%. Refining by desulfurization of clean steel hasbecome the focus of many studies. High basicity refining of slag and calcium treatment can be used to control the sulfur content and reduce MnS inclusions.

1. Experimental methods

Ultra-low sulfur steel is produced bythe basic oxygen furnace-ladle furnace (LF)-Ruhrstahl-Heraeus-Ca-treatment-continuous casting method. The effect of (FeO+MnO) content in the LF slag, the kinetic conditions for LF refining and vacuum degassing (VD)with late calcium treatment on desulfurization were studied. Five industrial trials were carried outto determine the effect of (FeO+MnO) content in the LF slag on sulfur content. Inthe LF unit process, 100, 200, 250, 300 and 320 kg of aluminum particles were added into the furnace. Twenty five steel samples and 25 slag samples were taken before refining which lasted 10, 20, 30 and 45 min. After determining the optimal amount of aluminum particles required, a furtherfive trials were carried out. Fifteen steel samples and 15 slag samples were taken at the LF refining slagstage withargon inflow at the bottom of the furnacefor 5 and 10 min. The optimum input of aluminum and argon flowin the LF process was determined using these trials.Fourteen steel samples from sevensteel trials were taken before and after VD. The elemental content in the steel samples and chemical composition of the slag samples were analyzed.
The basicity of the LF slag is high and up to 9.9 on average during production. The average massratio of CaO/Al2O3 is 2.0.The composition of molten steel produced by the converter is shown in Table 1.The composition of the LF slag produced by LF refining is shown in Table 2.

Table 1.Molten steel composition (%)

Elements in steel	C	Si	Mn	P	S	Als
Content / %	0.18	0.26	0.54	<0.17	0.0025–0.0035	0.020–0.350

Table 2. LF slagcomposition (%)

Composition	CaO	SiO2	MgO	TFe	Al2O3	MnO	P2O5	S	R
Maximum	57.293	10.285	10.169	4.024	36.252	0.267	0.068	0.300	23.056
Minimum	46.347	2.209	4.831	0.379	24.034	0.010	0.012	0.198	5.176
Average	52.583	6.076	7.247	0.782	28.863	0.041	0.019	0.250	9.899

2. Results and Discussion
2.1 Effect of (FeO+MnO) content in LF slag on desulfurization

The oxygen content in the slag depends on the(FeO+MnO)content in the slagand(FeO+MnO) content alsodesulfurization is limited andincreases thedesulfurization time. The relationship between (FeO+MnO) content and distribution ratio of sulfur (Ls) in the initial slag is shown in Fig. 1.The ability of the slag to be oxidized has an obvious influence on the desulfurization efficiency of molten steel. The lower the (FeO+MnO) content in the initial slag, the higher theLs.To limit desulfurization, the (FeO+MnO) content in the initial slag should be below 1%.
A chemical analysis was conducted on the slag samples taken afterLF refining with different aluminum particle input masses.Results from the analysis of (FeO+MnO) content are shown in Table 3.If the initial (FeO+MnO) content is below 0.5%, the desulfurization rate increases. The addition of a certain amount of deoxidizer in the LF refining process can reduce the FeO content in the slag. In this study,aluminum was selected as the deoxidizer.
Results from the experiments investigatingthe change of sulfur content in molten steel from different aluminum particle input masses are shown in Fig.2.To effect desulfurization and to achieve sufficient reactionbetween the deoxidizer and oxide, aluminum particles were added into the slag on average three times. As shown inFig.2, with the addition of 300kg of aluminum particles, the sulfur content in the molten steel after refining for 45min was reduced from the original 29to 7.9ppm and from 30 to 6 ppm with the addition of 320kg.

Table 3 (FeO+MnO) composition in LF slags with different Al input masses (%)

Al input /kg	100	200	250	300	320
(FeO+MnO) / %	1.01	0.77	0.52	0.39	0.46

Fig. 1. Relationship between sulfur ratio and

Fig. 2.Relationship between sulfur in molten steel and aluminum particle input in slag

2.2 Effect of dynamic conditions on desulfurization

Fig. 2 also shows that the sulfur content in is reduced rapidly over 30 minfromthe beginning of LF refining.The sulfur content in the molten steel is reduced slowly between 30 to 45 min. When the sulfur content in molten steel is reduced to a certain concentration, the diffusion of [S] in the molten steel is a restrictive step in the desulfurization reaction .Thekinetic conditionsfordesulfurization need to be improved to obtain further desulfurization.
To study the effect of the dynamic conditions on desulfurization, some steel samples were taken after LF refining slag melting ,argon inflow at the bottom of the furnace for 5 and 10 min to determine the sulfur content in molten steel. Aluminum particles (320 kg) were added in the LF refining process. To study the effect of argon flow on desulfurization during gas stirring, the sulfur content in molten steel was analyzedat different argon flowrates, as shown in Fig.3.
In the trials, temperatures were chosen atwhich the sulfur content in the molten steel differs little before argon stirring . Argon flowrates of 400, 500, 600, 700 and800 NL/min were selected. The sulfur content in the molten steel is reducedrapidly inthe 5 min before argon stirring andis reduced more significantlyduringheatingwhen the initial sulfur content is high.After stirring for some time and with an argon flow for 5 and 10 min,the sulfur content in the molten steel is reduced slowly and decreases to approximately 2 ppm. The results shown in Fig. 3 indicate that when the argon flow is 400 NL/min, the sulfur content in the molten steel is reduced theleast. The results shown in Table4 indicate that when the argon flow is 500 NL/min, the sulfur content in the molten steel is reducedby 62.50% from 16to 6ppm.When the argon flowrate increases,higher quantities of largebubbleswill be produced. An increased argon flow facilitates the formation of abare slag surface inmolten steel, which leads touptake by the molten steel and reduces the desulfurization efficiency. A large flow rate can cause the turbulence of molten steel, slag entrapment,severe erosion of the ladle lining and anincrease in the quantity and size of inclusions. Too high or too lowan argon flowratenegatively affects the desulfurization of molten steel under dynamic conditions. In this study, theargon flowrate is 500 NL/minas the sulfur content in the molten steel can be reduced from 16 to 6ppm.

Table4 Relationship between argon flowrateand desulfurization efficiency

Argon inflow at furnace bottom / NL/min	400	500	600	700	800
Reduction in sulfur content/%	30.71	62.50	50.00	52.94	14.06

Fig.3.Relationship between sulfur in molten steel and argon flow

2.3 Relationship between calcium treatment and sulfur content

After the ultra-lowsulfur steel has been treated by VD, the molten steel is fed with silicon-calcium wire to the calcium treatment stage. At this point, the temperature of the molten steel is approximately 1580°C.The [Ca]-[S] reaction calculated at 1580°C is given below.
There is a balance between the [Ca] and[S] in the molten steel:
[Ca]+[S]=CaS (s); (1)
; (2)

.; (3)

When,.; (4)
The activity interaction coefficient in literature was used to calculatethe activity coefficient of the [Ca] solution in steel.

(5)
, , , ,,
(6)
,, ,,
where, and .When the temperature is 1873K, .Because the value changes little at the steelmaking temperature, it is assumed to be constant.
The [Ca]-[S] balance()is shown in Fig.4 at 1580°C.
"
Fig. 5.Sulfur content in molten steel after Ca-treatment

The seven pointsin Fig.4 show the sulfur content before feeding with silicon-calcium wire and the calcium content after feeding calcium with the molten steel in a different furnace. These points are located below the [Ca]-[S] equilibrium line at 1580°C.This indicates that calcium has no desulfurization ability. Fig.5 shows the sulfur content in molten steel after Ca-treatment and feeding with silicon-calcium wire. The sulfur content in the molten steel is essentially invariant and allare below 10ppm except for the sample from the seventhtrial. Feeding calcium with the molten steel helps retain the calcium content in the steel, inhibitsresulfurization and keeps the sulfur content low.

3. Conclusions

The ability of the slag to be oxidized has an obvious influence on the desulfurization efficiency of molten steel. The lower the (FeO+MnO) content in the initial slag, the higher the Ls. To obtain desulfurization, the (FeO+MnO) content in the initial slag should be below 1%.
When the argon inflow at the bottom of the furnace is 500 NL/min, the sulfur content in the steel is reduced to 6 ppm after 10 min. Too high or too low an argon flowrate will reduce the desulfurization efficiency.
The [Ca] content in the molten steel is under the [Ca]-[S] equilibrium line when the steelmaking temperature is 1580°C. Under these conditions, calcium has no desulfurization ability. Addition of calcium into the molten steel is useful forinhibitingresulfurization and helps maintain the sulfur content at a low level.

Acknowledgments

The authors are grateful for support from the National Science Foundation China(grant no.51304016)

References

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Evaluation of circular welds strength capacity with corrosive defects

Fri, 25 Oct 2013 14:19:11 +0300

EVALUATION OF CIRCULAR WELDS STRENGTH CAPACITY WITH CORROSIVE DEFECTS

The results of experimental studies and analyzed the impact of long-term operation of gas pipelines, as well as natural stress concentrators on the physico-mechanical properties of welded joints of steel 17G1S. The technique and the regularities of the destruction of the material of welded joints of gas pipelines under static and low frequency loading for long term use, as well as stress concentrators. Some aspects of the mechanism of fracture of welded zednantruboprovodiv who are in long-term operation, as well as stress concentrations.
Key words: fatigue, floods, stress concentrators, weld of unity, weld, gas, static load, low-frequency loads.

Oleg Tarayevs'kyy

Doctor of Science, docent of transport and storage of oil and gas department,

President’s award holder for

young scientists of Ukraine (from 3.11.2009 No 891/2009)

Introduction
The problem of maintenance of high service reliability of main pipelines is of great importance for the Ukrainian national economy because most of them are operated for a long period of time and have already depleted their rated recourse. The stable operation of main pipelines and their high economical efficiency first of all depends on their technical condition. While evaluating of technical condition of a pipeline it is important to determine with assurance stressed-deformed state its infrastructure as one of the main factors to which the level of service reliability of the construction is related. Otherwise pipelines can be subjected to the alarm condition.
Analysis of the reasons of main pipelines accidents helped in most cases to establish that the failures during operation are connected with shatterings along the metal in its entirely or along the circular butt-jointed seams. More then 50% of constructions are ruined due to the
corrosive damages, 37% of accidents are caused by the bad quality of metal
(insufficient malleability, impact hardness, bad weld junctions etc.)
Detailed analysis of the reasons of accidents enabled in most cases to determine direct connection between the source of failure initiation and any, even stealthy defect of metallurgical, industrial, construction and mounting or operational nature, which is a stress riser on the interior and exterior surface of the pipe. Manufacturing defects appear as metal failures of the pipe,
nonmetallic impurities appear as sulphide zones, scabs, partial removal of
residual stress of the weld bead, defects of mechanical damage of the interior surface of the pipe. During pipelaying and pipe handling different mechanical damages such as buckles, plough defects, bands and also the defect of cross butt joint especially incomplete penetration are prevalent.
For the development of influence of the operational corrosive medium over durability and enduring quality of pipe steel one should characterize corrosive medium. The medium and metal cooperation depends on:

constitution and certain components
large and anelastic deformation
surface condition

One should distinguish three possible cases of metal behavior while hydrogenation :

metal hydrogenation with strain-free lattice
metal hydrogenation with deformed lattice ( processes of cold metal deformation)
hydrogenation during the deformation process of metal

The structural condition of steel and its deformation affects essentially on the electrochemical corrosive processes as well as on diffusion processes and the greater phase instability, the higher and its sensitivity to corrosion.
Efficiency upgrading of gas pipeline network is a very important problem, which needs to be solved. Engineering and operational processes of such gas pipeline networks are characterized by a set of specific features. Nonconformity of supplied gas volume and its consumption lead to the unsteadiness of gas flow, that combined with complicated manufacturing system of pipelines and its location in the distorted surface lead to the complexity of working regime forecast and their control. Scientifically based determination of plan tasks of gas supply in conditions of unsteadiness lie in necessityto have the exact information about days, seasonal and other types of irregular gas consumption.
At the moment the two main ways of forecasting are forming: the irregular gas consumption is the task of engineering and developing (advanced forecasting) of gas supply system; forecast of consumption schedules for controlling the regimes in actual gas transport systems.
It is considered, that industrial customers consume gas uniformly during a day. This statement is not always correct as the quantity of the utilized gas as a fuel in the industry is defined by many factors, for example, irregular fuel supply,requirements of technical process to the production quality etc. That is why for the industrial gas customers there also exists irregular fuel consumption during a day, that can essentiallydiffer from irregular fuel consumption of domestic customers, which are defined mostly by the scheme of life of the society and connected with that type of energy usage. Buffering consumers can use different types of energy materials (including natural gas), their usage in the region lead to the smoothing the ripple of gas consumption.
The running pressure disturbance in the pipeline during a day is determined by the way of consumption in this region, which have the fixed number of gas consumers. On the quantity of the consumers and the way of their daily gas consumption depends the discharge fluctuationin the gas-transport system, which in its turn lead to the pressure disturbance. The gas consumers, concerning the way of gas consumption, are divided into three groups: industrial gas consumers, domestic gas consumers and buffering consumers. But this division carries conditionality.
For the operative executive controlis mostly of great importance accounting the fluctuation of daily gas consumption. For such researches it is important to find out the reason of the appearance of nonsteady process, which in its term in most cases determines the character of its course. All the reasons of nonsteady processes can be divided into regular and impulsive.
Besides, the sharp increase or fall of intake by the consumers leads to the fugitivenessof its course in the pipeline, moreover the unstable processes due to the changes of the gas density can last for hours or even days. To the similar consequences lead the decrease or increase of gas priming, sudden switching on/off of booster station, opening or closing the gate valves etc. That is why the general process of pressure fluctuation in the pipeline is characterized by the frequency spectrum.

Problem state

Underground main gas pipelines in spite of the complex protection from the corrosion, which includes the passive protection by anticorrosive coating and active pipeline electrochemical protection, are rather often subjected to corrosive damages. But still the common factors of strength behavior of corrosive damages are examined incompletely.

Table 1 Targets of research and their main characteristics

No of the pipe	Dн×δ, steel grade, mm	Run life before trim, years	The cause of a trim based on the type of defect	The size of critical defect, mm	The terminal pressure (MPa), the character of damages
1	1220 × 12, 17Г1С	13	Corrosion in accordance with fabrication document	1100 × 520 × 2,8	9,2 fluidity
2	1220 × 14,5, 17Г1С	13	Corrosion in accordance with the fabrication document	3000 × 3,5	12,0 slabby
3	1220 × 12, 17Г1С	17	Damage because of the stress-corrosion cracking	General corrosion 800 × 0,5	9,8 slabby
4	1220 × 12, 17ПСУ	6	Corrosion in accordance with fabrication document	General corrosion 800 × 4,4	11,0 slabby
5	1020 × 9; 17Г1С, thermostabilized	18	Corrosion in accordance with fabrication document	Pit corrosion 900 × 4,4	8,0 slabby
6	1020 × 9; 17Г1С, thermostabilized	18	Corrosion in accordance with fabrication document	Pit corrosion 300 × 3,0	10,5 slabby
7	1220 × 10,5; 17Г2СФ, thermostabilized	23	Damage, structural defects	Opens up to 2,5 depth	11,3 slabby
8	1220 × 12,5, 17ГС	30	Gas main, surfaced on the muskeg	Wrinkling, buckles 1220 × 800 × 109, corrosion pits up to 2,0	11,0 slabby

The existing normative requirements for the safe and fault-free operation of main gas pipelines provide expressly the immediate clearing of corrosive damages that are above norm. Meanwhile progressing of corrosive damage on the underground pipeline is of the latent character and appears as the emergency failure of different complexity. In this situation there are some unfinished methods allowing to estimate the working speed of the gas pipeline strength value during development of corrosive damages. Otherwise, the modern ways of pig inspection allow to indicate the vast majority of corrosive damages by direct measurement during one inspection. In this case the plurality of corrosive damages is fixed and their clearing needs scientific evidence of time priority, as single- step clearing, in accordance with normative requirements, is impossible for technical reasons.
On the research- and- industrial stand for the gap specification the full-scale hydrostatic testing of corrosive-damaged pipelines, which were rejected from working gas pipe, was performed.
In the given classification group the results of testing of eight objects (see table 1), subjected to the corrosive damages depth more than 10% of the wall thickness.
It should be marked that corrosive damages were found only on the outer surface of the pipe in places of end-to-end or closed damages of the insulation blanket. It is clear that corrosive thinning of a pipe provides the in-situ growth of stressed-deformed state and strength retrogression of a pipe. Visually it can be seen while comparing deformation of nondefective and defective zones during testing pipe seams No 12 and 13. The results of testing are shown in the table 2.
From the table 2 one can see that the actual deformation of a pipe in the nonfailed zone is correlated with rated value, calculated in accordance with Hook’s generalized law for biaxial tension, i.e. the achieved results, excluded the abnormal indications of some tensometers, monitored during the prime stages of the stress, should exactly reflect the proceeded processes.
Turning to the results achieved, one can state, that the number of tensometers (No 2, 4, 6) installed usually in zones of areal damages have monitored the deformation correlated with the deformation of nonfailed pipe, i.e. such failures have not caused the noticeable reduction of strength.
At the same time pit zones ( tensometers No 1, 3, 8, 9) have deformed more than nonfailed pipe, i.e. these zones had higher voltage. Further stresses showed that disjunction # 12 arose in zone of tensometer No1, where the largest deformation was monitored. It was 2,52 times higher than deformation of nonfailed zone. Concerning the stalk No 13, some artificial flaws were applied, which turned to be the center of damages.
Along with abovementioned the real integral criterion of availability and the rate of stress reduction of damaged pipe can be determined only after its damage, that was carried out while the final stages of weld bead (No 2,3,9,13,18,19) testing.
The results of testing and calculations are shown in the table 3. From this table one can see that five weld beads tested ( No 1,2,9, 12,13) have pits, that are defined by acting governing documents as out-of-tolerance.

Table 2 – the results of pipe deformation in the cross sectional area from interior pressure impact.

No	Location of the tensometer	Incrementation of indication of tensometer during the pressure change, MPa								Mean normal strain during the pressure change on 1, MPa
No	Location of the tensometer	0÷1	1÷2	2÷3		3÷4	4÷5		5÷6	Devisions of tensometer	Relatival deformation % × 102
Weld bead No12
1	Extensive corrosion zone up to 4,4 mm depth	-1	32		29	28		22	24	27	6,75
2	Short defect up to 4,4 mm depth	13	14		13	13		10	12	12,5	3,13
3	Extensive corrosion zone up to 4,4 mm depth	56	27		20	17		15	15	18,8	4,70
4	Short defect up to 5,2 mm depth	16	14		6	8		8	11	10,5	2,63
5	Short defect up to 4,5 mm depth	34	20		16	17		13	12	14,4	3,60
6	Long defect up to 43,5 mm depth	19	12		9	10		7	9	9,4	2,35
Weld bead No 13
7	Extensive corrosion zone up to 1 mm depth	53	17		18	14		13	10	14,4	3,60
8	Extensive corrosion zone up to 3 mm depth	80	29		26	18		17	13	20,6	5,15
9	Extensive corrosion zone up to 2,5 mm depth	63	28		22	16		5	22	18,6	4,65
10	Undamaged pipe	10	9		14	11		10	10	10,7	2,68

The availability of such damages requires their maintenance or reduce of the pressure till the safe value ( 4.3…30% from design pressure).

Figure 1 Comparison of the designed and real coefficient of safety of the pipes tested.

During the analysis of inspected defects in the category of damages requiring the complemental repair got the defect of pipe weld bead No18. Herein the level of reduction of working pressure (if the repair cannot be fulfilled) in all tested objects increases (about 4.3….27.1% comparing with the original scheme).
Along with this, correlation of real (Cr) and design (Cd) coefficient of safety, graphic presentation of which is shown on the fig. 1 and 2. This correlation shows that only in one instance (weld bead No 12) the necessary pipe reliability is not provided.
If it is impossible here to carry out the repair operations, it is necessary to reduce the working pressure in accordance with [5,6] 3.78 MPa, that is 70% of design pressure. On the results of hydraulic testing of this weld bead it is noticeable that the design coefficient of safety is provided when the working pressure is 8/1,71 = 4,68MPa ( 86,7% of the design pressure) i.e. it is 23,8 % more then extent.

The results of testing and design of pipe weld beads corrosion damages

Parametr			No of weld bead tested
Parametr			1	2	3	9	12	13	18	19
Diameter and nominal wall thickness, mm			1220×12,0	1220×14,5	1220×12,0	1220×12,0	1020×9,0	1020×9,0	1220×10,5	1220×12,0
Steel grade			17Г1С	17Г1С	17Г1С	17Г1СУ	17Г1С	17Г1С	17Г2СФ	17ГС
Normative mechanical data, MPa	Break point, σt		520	520	520	520	600	600	550	520
Normative mechanical data, MPa	Yield point, σy		360	360	360	360	420	420	380	350
Pit	Short Long		Long	Long	Long	Long	Long	Long	Short	Long
	maximum depth of the defect	mm	2,8	3,5	0,5	4,4	4,4	3,0	2,5	2,0
	maximum depth of the defect	%	23,3	24,1	4,2	36,7	48,9	33,3	23,8	16,0
Allowable depth of the defect [58,59] , %			21,2	21,7	21,2	21,2	28,1	28,1	70,0	22,2
Pressure of weld bead break, MPa			9,2	12,0	9,8	11,0	8,0	10,5	11,3	11,0
Design load factor coefficient, Кts			1,8	2,15	1,8	1,8	1,71	1,71	1,8	1,8
Design margin for liquid limit coefficient Cd			1,05	1,26	1,05	1,05	1,0	1,0	1,05	1,05
Real coefficient of safety, Cs			1,48	2,22	1,81	2,04	1,48	1,94	2,09	2,04
Coefficient of strength safety, Cd/Cr			1,41	1,03	1,006	1,13	0,87	1,13	1,16	1,13
Safe working pressure [58, 59]			5,17	5,15	5,4	4,27	3,78	4,94	5,4	5,4
Safe working pressure [61]			4,14	4,22	5,17	3,42	2,76	3,6	4,11	4,54

Figure 2. The coefficient of strength safety for the testing weld beads

For other pipe weld beads the real degree of safety compared with design degree of safety, excluding object No 1, where the pipe was lead to yielding of metal makes 0,6 ÷ 16 % ( fig.2), i.e. the necessary pipe safety is provided if there is a need in repair operations in accordance with existing norms or technological measures reducing the working pressure ( weld beads No2,9,13).
So, in result of hydraulic testing of pipe weld beads concerning interior pressure it was established that if there any corrosion damages exceeding standard values, the current level of strength recourse of gas pipeline occurs to be nonunique. It can be enough for further safe operation (weld beads No 9, 13, 18, 19), to be critical or equitable (weld beads #No 2, 3), indefinite for grading (weld bead No 1) or really dangerous (weld bead No 12). Each of these conditions requires an individual control of the use reliability level of gas transmission object. In the first case – it is just a system monitoring, in the second case - maintenance prevention, in the third case – formulation of detailed examination, in the forth case - emergency repair etc. Such control should be based on the criterial priority for evaluation of the pipeline operation capacity, which were subjected to corrosion.

Conclusions

This testing shows that the calculation of safe stress arisen inside gas pipeline as a result of uneven gas consumption in the hydrogen-charged media should be computed in respect with coefficient bcr, that allows to increase it, and this will lead to the evaluation of main gas pipeline coefficient of flow due to the pressure increase. The given approach will let to determine correct and reasonable choice of the value of safe stress while operation for working medium and with small quantity cycle of loads.
Indeed the endurance processes in steel are of probabilistic nature. This together with non-destructive testing method and risking analysis with safety concept “realize and correct” and to keep the pipeline in workable condition. But negative here is that in such longtime operating condition (combined action of fluctuating loads and the medium) there accumulate defects in the pipe, which lead to its damage. Particular risk is in the hard-to-reach places ( it is impossible to remove the danger in time) or in complicated operating condition ( ex. the pipeline is in shift zone). Here the new concept of risking analysis should work – “foresee and keep ahead”.

References

Karpenko G.V. Steel Durability in the corrosive medium/ Karpenko G.V.//M: Mashgiz, 1963, 188p.
Pokhmurs'kyy V.I. Corrosive mechanical damages of welded constructions./ Pokhmurs'kyy V.I., Melekhov R.K.// K.: Naukova dumka, 1990, 347p
Pokhmurs'kyy V.I. Corrosion fatigue of metals./ Pokhmurs'kyy V.I.// M.: Metalurhyya, 1985, 207p
Kryzhanivs'kyy Ye.I. The influence of hydrogenation on corrosive mechanical propreties of weld beads/ Kryzhanivs'kyy Ye.I., Tarayevs'kyy O.S., Petryna D.Yu. //Exploring and developing of oil and gas fields. – 2005. - No1 (14). – P.25-29.
Kryzhanivs'kyy Ye.I. The influence of gas consumption unevenness on the pipeline stress condition / Kryzhanivs'kyy Ye.I., Tarayevs'kyy O.S.//Exploring and developing of oil and gas fields.– 2004. - #3(12). – p.31-34.
Kryzhanivs'kyy Ye.I. The responsiveness to hydrogen embrittlement of main gas pipeline steel 17Г1С weld bead/ Tsyrul'nyk O.T., Kryzhanivs'kyy Ye.I., Tarayevs'kyy O.S. // Phis..-chem. materials mechanic . – 2004. –No 6. – p. 111-114

History of cranebuilding and crane household until now

Fri, 15 Nov 2013 14:24:23 +0200

History of cranebuilding and crane household until now

Gennadii Kanov

            In the CIS countries according to the "Pod’emtranstechnika” association there work 17 cranebuilding companies, which continue travelling cranes, portal bridge cranes and special cranes building in accordance with the chief institute "All-Soviet Union research institute of heavy engineering enterprises" documents and self-design projects. Earlier this institute published annually collected papers on solution of cranebuilding, operating, handling machinery and railway track maintenance and repair problems. Certain problems in a detailed and searching way are stated in numerous thesis works, where the guidelines for their solution are given. The integrated information in the best way is collected and represented in “ Crane guide”, Mashinostroenie publishing house, 1988, in two volumes under the general editorship of M.M. Gohberg, Doctor of Engineering Science, professor.
In the eighties the total volume of travelling crane building in the USSR made six or seven thousands cranes annually and after 2000 it stabilized at ten—fifteen thousands per year.
            In spite of the limitations, mentioned in GOST 27584-88 “Travelling and portal bridge electric cranes”, ISO 8306 “Travelling and portal bridge cranes. Tolerance for cranes and railway tracks” and GOST 28648-90 “Crane wheels. Specification”, the quantity of crane types and the variety of engineering solutions of their units, especially wheels comprises thousands of titles. Herewith each cranebuilding plant works under self-design standards. The full list of crane types and their characteristics are given in the catalogue “Travelling cranes of general purpose”, Moscow, 1995.
            One failed to unify crane details and its units until now, that’s why every company using cranes solves the problem of the replacement parts by itself, mostly in the way of lost surface renewing by overlaying or producing the new wheels by maintenance service. If earlier the operating costs, handling machinery and systems maintenance were taken as they arise, then recent years these costs are rigidly limited with accordance of multiple increases of metal, surfacing materials and energy supply prices. As a result the problem of reliability increasing and endurance of details and crane units escalated sharply.
            According to literary sources the external value of wheel salvage towards the value of a new wheel makes, %

wheel dia 800mm the repair of one ledge 22, roller face 44, roller face and two ledges 62-75
wheel dia 900mm the repair of two ledges 22-36, roller face and two ledges 45-50.

            Herewith, as a rule, the ledges are repaired with the help of 4 times overlaying and the roller face – twice, that is limited to appearance of iterative seams in the wheels.
            Numerous monographs, normative-technical and special literature contain the information about all the items and aspects of handling machinery. But still it is essential the problem of reliability growth and the endurance of the cooperating pair railway track- wheel.
            In accordance with Public health regulations 111-18-75 for the railway track the displacement towards wall axis should not exceed 15-20mm, i.e. the rail axes nonparallelism is to be herein. Mutual displacement of join rails in track edges in plan and in elevation are to be 2-3 mm. Rails interface gaps are to be up to 4 mm. The rail bend from the straight line is to be up to 10 m (flexion) up to 15-20 mm.
In accordance with State Committee for Supervision of Safe Working Practices in Industry and for Mine Supervision 0.51 the rail wear on the roller face may be 4-8 mm, on the rail face surface 10 mm (5 mm at each side). These tolerances predetermine the wheel width between ledges, which can be reduced if the wheel construction can self-center towards the rail position.
            The projects devoted to solution of this complex task are of high priority nowadays. The analysis of patent information shows the attempts of self-center crane wheel creation, which partially compensates the railtrack disadvantages. However, it is impossible to escape the rail wear until there is a friction couple. The creation of travelling crane on the magnetic cushion solves the problem in a big way, but still the financial status of companies does not let to order such projects and the existing company infrastructure can not provide the maintenance of new generation technology.
            The given work deals with creation and usage in manufacturing of crane wheels of pin and link type with shock compensator, that allows to increase the longevity of the pair railway track – wheel.

Basing on a large body of researches and static information the main reasons influencing on the crane runways wear are:

the poor rigidness of bridge truss
the mismatched runway and ledges of traveling crane wheels profile
construction and the type of bridge rail
stress caused in crane runway elements that is higher than the chosen materials allow.
the low quality of bench-work and assembly and construction and erection work while crane and its runway erection
failures in the travel mechanism of crane bridge and crane runway elements
quantity, capacity and operating regimes of crane, working on the same railway track
violation of crane maintenance rules
simultaneous combine of the factors mentioned above accelerates the wear.

For simplification of studying and analysis, all the existing crane runway damages are divided into two groups.
The first group includes all the cases of crane runway breakdown by virtue of natural wear during the target life. The second group includes all the types of premature failures of any of these elements by the action of the project uncounted factors.

The analysis of crane runway breakdown as a result of its certain parts natural wear is less actual than the study and disposal of principles causing premature failure of crane runway.
In the practical part of the work the following types of crane runway damages (wears) were specified:

all the types of bridge rail damages
the damage of rail supporting members
bed construction units of crane runway damage
bed clamps of crane runway to the beams damage
the upper surface of bridge rail damage
the post set of work shop columns.

            Cutting of the rail side face as a result of frame running wheels and bridge swash or local/general constriction of the distance between crane runways axes are related to the most common crane runway damages.
            While crane travelling, one side of a bridge overleap, running wheels ledges bearing against the side face of bridge rail cut down the facing as a result of bridge truss poor hardness and the absence of acceleration for running wheels. When the wheels are exhausted the crane runs off the rails. High efforts arising while bridge blocking, stop not only the crane but also damage crane runway fastening, that in its turn requires long and costly repair. Usually while repairing the crane frame is strengthened by means of diagonal rod welding to the frame and to the cross beam walls, the specified running wheels are changed into the high wheels with smooth profile ledges and hereafter the lubricants for rails side face is used regularly. The last is not always acceptable as the lubricant ingress on the wheel and rail surface reduces the dragging, causing frictional sliding and scuffing.
            The rails side face cutting can be also caused in result of running wheels misalignment of axes or narrowing of distance between runway wheels centers in one half of the crane bridge truss.
            At rails joint the side face cutting and rolling surface damage is more intensive because of secondary actions of impulsive loads.
            The rail deflections and wheel slip causes the scalloping wear and potting on the upper working plane of rails.
            In result of action of fluctuating loads in rails the fatigue cracks are formed, that leads to cross breaking and the residual stresses and defects while rails welding at the attaching points as stress concentrators lead to the sudden rails damage with unpredictable effects.
            The non-standard rails and fastening installation, below-standard rails parts, high clearances at joints and disalignment (more than 5 mm) during the crane runways repair cause an accident.
            The mentioned reasons shorten the life of railway track from designed 8 years (at average) till the general maintenance 2-3 years.
            The working time of railway track shorten also in result of steel quality and hardness of race track and crane wheels ledges mismatches in comparison with hardness of bridge rails.
            In result of wheel wear unevenness there appears substantial difference in wheel diameters at different bridge sides, which leads to bridge cocking and heavy wear of wheel flanges and rails side face.
            The great impact on the crane runway and wheel flanges wear has assembly cocking of traveling wheels towards each other and the rails. The most typical cocking combinations are:

both wheels have cocking towards the rail on one side
one wheel has cocking, the other located on the other side of the transmission shaft is placed correctly
both driving wheels have cocking inside different sides towards the rails
both driving wheels have cocking outwards different sides towards the rails

            All the cases of wheel cocking lead to appearance of flexural stress, tensile stress and compression stress in the bridge truss and proportional deformations of crane metal structures depending on the combination of these stresses. On the whole, all the bridge deformations in the temporary limits centralize their action in the places of wheel and rail contact. As a result all the crane wheels (4 or 8) operate under different loads and in different conditions. The bigger sampling length of the bridge, the bigger strain level and wheel load imbalance. Besides, the location of a loaded crab is very important, and the closer crab to column lines the higher crane cocking and its wear.
            The analysis of different information sources allows to draw conclusions that the wear rate of a pair rail-wheel predominates over the cross slip action and the long rolling leads to heavy wear only in regimes of slippage and scuffing. The wheel and rails wear is more intensive under the influence of impulsive loads.
            The locating accuracy of crane wheel on the axes, their alignment towards each other and axle body, rails alignment and difference in height, their flection and condition requires inaccessible exemplarity, that’s why the design crane and its units lifetime differs from the real terms. In Kirichenko’s monograph “Crane runway” is mentioned that in case of crane excursion from the railway track on point more than 1'43''there may appear cross slip of wheels over the rails. That is why the solution of this problem may be automatic crane wheels.
            Installation tolerance of bridge crane traveling wheels is provided by GOST 24378-80 : departure from vertical plane of wheel end surfaces and from gear crown gear general plane of end girder or balance-beam no more than 0,002D, D – the wheel diameter;   parallel misalignment of wheel general plains at rails bay no more than 22.5 m – less than 5 mm, at rails bay more than 22.5 m – less than 8 mm; the deviation of crane base length no more than 5 mm; lack of perpendicularity of wheel end surfaces f = 2/1000D.
            The main dimension ratios of crane wheels are provided by GOST 28648-90 and technical regulations by GOST 28648-90.
            In Gohberg’s monograph “Metal constructions of carrying and lifting machines” is given the calculation methods of side forces affecting on the wheel ledges while friction on side head of rails. At average the side force rate equals to 0.1 from vertical action on the wheel, max. 0.15. These forces are vertical to the traveling direction of traveling wheel ledge and may be directed both inside and outwards the bay.
            Traditional decisions concerning increasing the life of a wheel is given in work of “Moscow branch office” “Hardening and increasing of endurance of crane traveling wheels".
At present time the method of traveling wheel computation according to Industrial Standard 24.090.44-82 is the most preferable. It includes three-dimensional stress state in zone of wheel contact with a rail and the wheel rate speed while its lifetime (in average 10000 rotations). The wheel diameter and the rail type is chosen depending on the highest deadweight load on the wheel (200-1000 kN) i.e. proportionally the crane capacity with account of its specific speed 1.0-3.0 m/s).
            As the railway track is more expensive and requirements for the rails are strict, the wheel should have the lower properties, i.e. it should be produced from the low-priced steel grades or iron with level of hardness after heat treatment 190-350 HBand the level of safe design stresses 600-900 MPa. So the wheels are regarded as replacement parts.
            In CIS countries the wheels are produces from steel forgings 45, 50, 75, 65 Mn, rolled steel 75 and 65 Mn, steel castings 55 and 35 MnA.
            In accordance with foreign literary sources recently the crane wheel are casted from high-grade cast iron with globular graphite and self-lubrication or from alloy steel. For example, according to alerting service No 5, Moscow 1981, in France the wheels are produced from forged steel 35C14 of chemistry: С-0,3…0,4, Мn-0,4, Si-0,35, Ni-3,2…3,7, Cr-1,2…1,5, Мо-0,2…0,3 with level of hardness 450-500 HB. As one can see, the level of wheels abroad increased by virtue of high-grade materials usage. Cranebuilding experience of Germany is given in two-volume book “Cargo cranes”, translation from German under the editorship of M.P. Alexandrova, Moscow, Machine building, 1981.
The problems of wheels force impact with rails are stated detailed in A.S. Konoplya’s thesis work, Leningrad, 1969
            The statistical analysis of lateral forces, appearing while crane travelling, is stated in A.N. Zubkov’s thesis work, Moscow, 1967.
            Kinematics and force interaction of bridge cranes with crane runways while restraining and speeding-up are stated in G.P. Ermakov’s thesis work, Chelyabinsk, 1973.
            The action of impulsive loads is analyzed in N.A. Lobov’s monograph “Dynamic of cargo cranes”, Moscow, 1967.
            Hereafter, the author fulfilled research-and-development activities concerning making the design of crane traveling wheels of new generation, improving reliability and life of the pair wheel-rail thanks to the axially self-adjustment and dynamic forces absorbing, that reduces the operational costs. Wheel alternative constructions are protected by Ukrainian licenses No 76582 C2 from 01.08.06, No 77062 С2 from 16.10.06, No 85081 С2, MPK В66С 9/00, В60В 9/00 with confirmation of absolute-novelty.
            Due to the appearance of new crane wheels constructions with characteristics that are higher, than that of GOST and the manufacture is realized in accordance with project specific technical specifications, confirmed and registered at GosStandart in accordance with the established procedure. For example, offered in the license wheel constructions may be produced according to Technical specifications-31.7829-24439835-2000.
            All people, who are interested in solution of perpetual problems of crane household, should try to manufacture and test in commercial operations the new-generation crane wheels. The design of such wheels provides straightness of crane traveling with minimization of side forces and compensation of impulsive loads. This will solve in an integrated manner the foregoing problems of the pair railway track- crane wheel, improving the reliability and lifetime of the system with conforming operating expenses level recession.
            The technical and economic assessment for crane wheels of new generation can be developed in accordance with technology pull, considering the specific nature of enterprise performance and each crane. The formulation of a problem may be specified and agreed while negotiations concerning cooperation or licensing.
            As manufacturing of replacement parts does not require execution of special permits at public authorities, the wheel brassboard production can be fulfilled by the factory maintenance service of work drawing, designed by the order’s planning and design office with the author’s consulting participation relating to the concrete crane with its following participation when mounting of wheels on the crane and designer supervision in the period of operation till the wear limit.

Principles of diplomatic etiquette and business communication with foreign partners (II)

Thu, 13 Feb 2014 10:47:20 +0200

Principles of diplomatic etiquette and business communication with foreign partners (II)

The article is devoted to Ushakov B.G.
Foreign Trade Academy, Moscow.

Receptions and their organization

Receptions may be: afternoon and evening; receptions with seatting at the table and without. To afternoon may be referred receptions of “champagne glass”, “wineglass” type and breakfast. In international practice afternoon receptions is considered to be less ceremonial than evening ones. To evening may be referred receptions of “jour-fixe” type, cocktail, “a la fourchette’, lunch, lunch-bar, supper.

Reception types

“Champagne glass” starts as rule at 12 o’clock and lasts for an hour. The reason for organization may be anniversary of national holiday, presence of delegation in the country, departure of embassador, exhibition or festival opening. Beverages and snacks are served by waiters. From the point of view of organization, it is the simplest type of reception that does not require long preparation. The similar reception is “wineglass”. In this case the name underlines special character of reception.
Breakfast is arranged between 12 and 3 p.m. The most common time for breakfast is from 12 till 1 p.m.. Breakfast menu is composed in respect with existing in the country traditions and customs. It usually consists of one-two dishes of cold food, one hot fish plate, one hot meat course and dessert. It is not customary to serve soups, though it will not be a mistake. After breakfast some coffee or tee is provided. Before breakfast a cocktail (dry wine, juices) is provided, during breakfast – mineral water and sometimes juices. After all the guests took a meal, man of the house or mistress stands up and offers the guests to go into the other hall, where coffee is served. Duration of breakfast is 1-1.5 hours (approximately 45-60 minutes at the table and 15-30 minutes for coffee). The main guest gives an initiative for leaving the breakfast. Dress code for breakfast: in general it is casual wear, but while solemn occasions it may be dinner jacket. Usually dress code is stated in the invitation.
Tea is arranged between 4 and 6 p.m., only for women as a rule. For example, Foreign Secretary’s wife holds a reception for post heads’ wives, and legate’s wives hold a reception for other legate’s wives. It is possible to invite men for this reception. For tea one or several tables are served, depending on the amount of persons invited, pastry or bun goods, fruits, dessert or dry wine, juices and water are served. Snacks (roed sandwiches, sandwiches with fish, cheese and sausages) are rarely served after tea, but if served, then in small amounts. Duration of tea time is 1-1.5 hours. Dress code: casual wear or dress.
Reception of “Jour-fixe” type is held by Foreign Secretary’s wife or other cabinet minister or by legate’s wife once a week at the same day and time while autumn-winter season (from autumn till summer). Invitations for such receptions (“Wednesdays”, “Thursdays”, “Fridays”) are sent once in a season and good till the end of the season, if there is no special notice about pause. This reception does not differ from tea. Sometimes such receptions are of musical nature or literary evening. For “jour-fixe” reception also men may be invited.
Cocktail or reception standing are held between 5 p.m. and 20.00 and last for two hours. Among food there are different cold dishes, pastry and fruits. Sometimes even hot dishes are served. Food should not be spread. At the receptions of such type, alcoholic beverages are on the tables or, being poured in the glasses, are served by waiters. Sometimes in one of the halls there is a refreshment room, where the waiters serve drinks. At the end of reception champagne may be served and then coffee. Receptions of cocktail type are also standing. Guests come up to the tables, take snacks on their plates and walk off the table in order to give an opportunity other guests to approach. Dress code: casual wear or dinner jacket, depending on the event and whether it is stated in the invitation.

Lunch starts within 8 and 9 p.m. and is considered to be the most honourable type of reception. Lunch menu consists of one or two cold dishes, soup, one hot fish dish, one hot meat dish and dessert. After lunch there served tea or coffee in the living room. Lunch menu differs from breakfast one with soup serving after cold dishes. There is no need to serve sherry with soup. With cold dishes may be served vodka or liqueur (cooled), to fish dish - dry white wine (cooled), to meat dish – dry red wine (at room temperature), for dessert – champagne (cooled), for coffee – lace (at room temperature). Lunch usually lasts 2-2.5 hours, at the table approximately – 50-60 minutes, the rest time in the living rooms. Dress code: black suit, dinner jacket or tail coat, depending on the event and whether it is stated in the invitation; for women - evening dress is the most preferable.
In some official cases just after lunch the reception standing is held. Guests those were present at dinner, after its end go to the reception standing. Such combination of two receptions is organized in connection with residence in the country of foreign statesman or foreign delegation, in honor of which the reception is held. Dress code: the same as while dinner.
Supper starts at 9 p.m. and later. Menu and vines are the same as while dinner. Dress code: black suit, dinner jacket or tail coat; for women – evening dress. Supper differs from dinner only with time for beginning – not earlier 9 p.m.
Evening reception “a la fourchette” is held in special events (in honor of foreign state prime-minister, foreign government delegation, on the occasion of national holiday, etc). It begins at 8 p.m. and later. Food is the same as at cocktail reception and reception standing, but more various and full. Dress code: black suit, dinner jacket or tail coat; for women – evening dress.
Lunchbar supposes general seating at small tables for up to six persons. The tables with food are served, there is bar with beverages, the same as at the reception standing. Guests take snacks and sit down to any table. Such reception is often organized after a concert, film watching, within the pause of dancing-party. Lunchbar is less official then lunch.
The kinds of receptions are cinema shows, musical and literary evenings, evenings of friendship, meetings for golfing, tennis, chess and other sport games.
All these events are accompanied with light food. Dress code for such events: casual wear; for women – suit or dress.
Preorganization of receptions
Any reception must be prepared in every manner. Reception organization includes: choice of type of reception, making a list of guests, distribution of invitations, making seating plan at the table while breakfast, lunch or supper, making the menu, table setting and service. Preparation of toasts or speeches, plotting (procedure) the reception.
While determining the data of reception, one should consider that receptions are not held on holidays, in paynim countries – on religious holiday Ramadan. Receptions are not held while national mourning and those, which were appointed, should be canceled.
Choice of type of reception
The type of reception should be chosen in respect with the event, in honor of which the reception must be held. Herewith the international diplomacy, according to which the most ceremonial and honorable type of reception is lunch or evening reception, should be considered. If it cancerns foreign head of state or prime-minister, Minister of Foreign Affairs, other cabinet ministers of country visited, then one should choose lunch. In less important cases, the other type of reception should be chosen. Herein one should always consider protocol traditions and customs, established in this country. These traditions will help to chose the type of reception.
Making a list of guests
One of the most important moments of reception organization is making the list of guests. Invtation for diplomatic reception is always of political character that is why making the list of guests should be encharged to responsible person and confirmed by man of the house. List maker first of all should determine the total amount of guests, who are supposed to be invited. This amount should not exceed normal serviceability and sufficiency of space, where the reception will take place; herewith it is important to consider certain percentage of guests, which may decline the invitation.
To the list of gusts first of all representatives of government officials, diplomatic service, members of the public must be included. To the receptions (breakfast, lunch, supper, cocktail or reception standing), held in restricted attendance, one should not invite those with opposite views. In order such receptions were successful, persons with similar party identification or those in friendly relations should be invited.
Invitations and distribution
Invitation to a reception is sent on a pre-printed form, typographically printed. Name and post of the invited are written in handwriting or with the help of printing device. For receptions on the occasion of national holiday or in honor of a statesman or delegation, special pre-printed forms are ordered, where the reason is stated. While breakfast, lunch and other type of reception organization, with seating at the table, in the invitation there is reply request (R.S.V.P. or “please reply”). In case when breakfast or lunch are served in honor of Prime-minister or Foreign Secretary or other person of high standing, the invitation is sent only after acceptance an oral invitation.
In this case inscription R.S.V.P. is crossed out and over is written letters "p.m." or "pour memoire” or "to remind". When under the letters R.S.V.P. “regrets only” is written, then you should answer only in case of declination the invitation because of different reasons. Such invitations are sent not later than in one-two weeks prior, depending on the local practice. Depending on circumstances, the invitations are sent by courier or by post. Invitations for official persons and central figures should be always sent with courier.
Seating
Seating at official breakfast, lunch or supper should be performed in accordance with generally accepted protocol rules. Seating requires strict observance of accepted official or social position of guests. Breaking the main rule of seating may be interpreted as willful prejudice (towards both the guest and the country he represents) and may lead to disagreeable circumstances or misunderstanding in relations. To avoid difficulties while seating, one should have an accurate picture, before sending invitations, where the invited guests will be sitting. With this aim an outline plan of guests seating is made beforehand, and if there appear some difficulties, this plan is amended.
Certain routine concerning denoting places at the table has been formed: seating cards or couvert cards – small white bars of heavy paper with names of all the guests in script or printed.
There is seating plan on a small table in the hall, where guests are gathering. In strict accordance with this plan, each place is denoted with couvert card. Guests get acquainted with seating plan, find their places and check the names of neighborhood to the right and left. At the receptions with a lot of guests, special cards with statement of the place at the table are used.
To avoid mistakes in seating the precedence of guests is checked in protocol service or any other.
The following rules of seating are observed: the first seat - is to the right hand of the mistress, the second – to the right hand of the man of the house; if there are no women, the first seat is to the right hand of the man of the house, the second – to the left hand of him; highly positioned guest should seat opposite man of the house, in this case the second seat will be to the right hand of the man of the house. If the mistress is absent, one of the women invited may seat on her place (if she doesn’t mind) or a man of the highest position. Woman does not seat next to woman, husband next to his wife, women do not sit at the ends of the table. Language skills of neighbors are considered. In the house of foreign diplomat the preference is given to local guests towards foreign diplomatic representatives and vice verse. After (or during) bilateral conference it is possible to seat one delegation opposite the other while breakfast, lunch or supper. Place of honor is near the entrance door, but if the door is sideways, then – the side of the table, which is exposed to front window. If it is necessary, interpreters may seat behind the guests.
Menu
While menu making, one should consider tastes of guests, their national and religious traditions, etc. To include in menu wild game, while its hunting is forbidden or meat in banian days, or pork, when there are Moslems among guests, is considered bad style. Vegetarian dish should be served for guest- vegetarian.
Toasts
Exchange of toasts may take place at the official receptions. On breakfast, lunch or supper toasts are pronounced after dessert (when it is eaten by all the guests) and when all the guests have champagne in their glasses. At other types of reception toasts are pronounced not earlier than in 10-15 minutes after its beginning.
One should not pronounce toasts while entre at official breakfast, lunch or supper.
One may smoke while breakfast or lunch only after dessert.
Arrangements for reception
In order the reception was well-organized, the scheme of its realization should be thought over beforehand. Time and place for meeting guests, time for inviting to the table, toasts proclamation is planned. Division of responsibilities for diplomatic personnel at the reception is composed (devoting attention to certain guests, surveillance over the audience). Sometimes at great receptions there is a parlor or separate place for the most outstanding guests, which should not be isolated from other guests. The man of the house should allow time to pay attention to all the guests.

Table setting. Behavior at the table.
For table setting one should invite skilled headwaiter or charge this to the able and experienced person. Congestion at the table is non-recommended. It leads to inconvenience both for guests and service staff. The table should be decorated with natural flowers if it is possible. At breakfast, lunch or supper all the dishes are served handily. Great importance is attached to knowing the rules of table settings and the course of instrumentation.
At diplomatic receptions different tableware is used, the main are:
Spoons:

Tablespoon for soup served in the plate; dessert-spoon (smaller than tablespoon) serves for porridge, soup in the cup, dessert, fruits;
teaspoon for thin dishes served in the cup, grapefruit, eggs and smoothie;
coffee spoon (half smaller than teaspoon) for coffee served in dobbin; long-handled spoon for chilled tea and beverages served in tumblers.

Forks:

big fork for dishing out from the large tray. It reminds big dinner fork in form, but oversized; big dinner fork for meat dishes; little fork for refreshments and desserts; fish fork for fish plate; fork for oysters, crabs, chilled fish cocktails. It is of small size: 15cm in length, width at the end – 1.5 cm.
fork for fruits. It is served in the end of dinner together with cup for fingers washing.

Knifes:

big dinner knife for meat dishes; little knife for refreshments and other dishes, except meat and fish;
fruit knife (with the same handle as fruit fork has) for fruits;
fish knife for separation fish bones;
butter knife serves only for butter pasting; dessert knife – for cheese, dessert and farinaceous dishes.

One should know that all the tableware are not used simultaneously. That is why while table setting not more than three wares are used. Other knives, forks and spoons are served as and when necessary.
The seat at served table usually looks like: big plate, plate of smaller size for refreshments, a napkin in triangle or cap form. On the left hand of the plate there are forks (in accordance with sequence of plate service): small fork for refreshments, fish fork and big fork – for main course. On the right hand of the plate there is small knife for refreshments, table-spoon (if the soup is served), fish knife and big dinner knife.
Tableware lies one by one over a distance 1 cm and over the same distance from table edge, forks - turned-down, knives – with their edges to the plate.
To the left hand, aside on the plate, there is a monkey-dish for bread and butter knife on it. Fruit knives are served along with fruits.
To the right hand, obliquely to the plate, there is stemware for drinks (from left to right): water goblet, flute, white wine glass, a little smaller red wine glass and one more smaller for dessert wine. Such stemware order is explained that drinks are served from the right. On the highest wineglass there is a name card of a guest, for whom the place is.
Sometimes the range of stemware ends with balloon glass. It is put in the case when after breakfast (lunch) the guests are served with coffee at the table, i.e. they do not change the room. If brandy is served in special big glass with wide bottom, then it is poured in small portions.
On the receptions at Russian, Ukrainian, Belorussian embassies there are small glasses for vodka, which is served with refreshments.
For dessert and fruits there is sometimes a spoon, knife or fork behind a glass – all these with handle turned to the right and with convex side to the table.
One begins to use tableware with that lying from the edge, than from the plate and holds them in the hand where they lied near plate. Knives, forks and spoons lying closer to the plate are used the last.
In most countries there is the following order of courses:
Refreshments
Are eaten with the help of fork and small knife (so called small ware);
Soup
Soup, beef tea, tea with slices of bread, etc. If soup is served in the plate, it should be eaten with soup spoon; if it is served in the cup, it should be eaten with dessert spoon, moreover when the soup is half eaten it may be drunken.
Fish dish
Is eaten with the help of fish ware, if there is no such, use forks.
Meat dish
Roast meat, beefsteak, etc are eaten using big ware.
Dessert
It is eaten with the help of dessert forks and spoons. Special spoon is served with ice-cream.
Fruits
Are eaten with the help of fruit ware; small spoons are served for stoned berries.
Coffee
Coffee spoon is served.
The most common two types of service at the receptions:
“on table” – when all the dishes are on the table
“serve round” – the guests are served by waiters. Abroad this type is more common.
During such service, waiters come up to guests, fill glasses with water and other beverages, than serve dishes in the order stated in menu. Waiter starts with the lady sitting to the right hand of the man of the house. If there are two or more waiters, the service begins at both ends of the table.
Food, that guests should take themselves are served from the left hand. Guests place this food with the help of serving fork or spoon on their plates. Food is taken with spoon that is in the left hand holding it with a fork that is in the right hand. To use own forks or spoons is forbidden. One should take single serving of a dish as they may be cooked strictly in a number of guests.
Dishes served by waiter are brought from the right hand. It is not customary to start eating until the mistress starts. Moreover, men should wait until woman to right or left hand of him will start eating. In some countries it is common to say grace (silently). In this case all are sitting in silent and with heads bowed. Till the end of grace nobody starts eating.
During meals you should sit squarely and natural. Do not cross your legs under the table and put the elbows on the table. One should look up to the others, finish with dish in time in order not to restrain the table.
One must not aspire to make drunk all the guests, offering the toasts, which can not be declined out of courtesy.
When you need to take bread, glass, fork and knife should be put on the plate criss-crossed: knife – with its edge to the left, fork is placed above with its back up. The place of crossing should be at prongs and one third of a knife. Fork and knife also may be put with handle on the table and the other side in the plate.
During course the plates with used ware are taken away by waiters. In order waiter knew that the guest has finished with meal, knife and fork are put parallel on the plate with shafts to one side, a little to the right. Here, the fork should be with prongs up, knife- with edge inside.
At the end of dinner (after dessert and fruits) special plates with a slice of lemon for washing hands may be served.
Finger-ends are dipped in this water, and then you should dry them with a napkin. As soon as everybody finished with meal, mistress stands up and all the guests do the same. Men help women to leave the table, setting their chairs back. With mistress and honoured guest in the head, all the guests go from dining-room to the hall, where coffee, brandy and lace are served. Responsibilities of men towards their neighbors are finished in the hall.
Before leaving lunch (supper) the guests say goodbye to mistress and man of the house, thank for dinner (supper), but not for the tasty food.
Clothes at receptions
Personal appearance is of great importance. Usually dress code is stated in the invitation. If dress code is stated (official character of reception is emphasized), then officers wear formal military, civilians - evening wear (tail coat, dinner jacket), women – evening dress.
If there is no dress code in the invitation, one should observe the following rules.
For men
Suit. For breakfast, cocktail and other types of reception that start from 8 p.m., one may wear a suit of any soft color, if only the reception is not in honor of national holiday or Head of state or Minister of Foreign Affairs.
It is recommended to wear dark colored suit at the receptions held on the occasion of national holiday, in honor or on behalf of the head of the state, government or Minister of Foreign Affairs and also at the receptions that start at 8 p.m.
The suit should always be clean and ironed.
In the cases when dinner jacket should be put on, it is stated in the invitation (cravate noir, black tie).
If tail coat should be put on, it is also stated in the invitation (cravate sagc, white tie).
Shirt and tie. White shirt with starched or roll collar and tie of any but not high color should be put on. One should avoid coloured shirt, especially woven nylon and also black ties. Black tie is put on only when mourning.
Socks. They should not be loud-coloured. Black or grey are the most common.
Shoes. Black low ankle boots are recommended. When summer time colored shoes may be combined with light-colored suit. To wear sandals is not customary. Patent leather shoes may be worn only with dinner jacket. Shoes must be shiny.
Hat. Depending on the season, light-coloured hats are worn in spring and summer, dark-colored in autumn and winter. During the late evening dark-colored hat should be put on. One should not wear velour hat and black hats with suit or coat of another color. It should be marked that fashion in business world spreads no so quickly as among Bohemians. That is why businessmen do not keep to fashion but defined level. Sound conservatism is an attribute of good courtesy.
For women.
Women should wear classical clothes with modest lines and of moderate tone.
For breakfast, tea or cocktail one should wear dress of common length, suit-dress or suit, small felt, silk or other material hat, which should not be put off during reception. Mistress do not wear hat.
At receptions, which start at 8 p.m. and later, evening dress (more elegant) should be put on. Evening dresses may be of common length and floor-skimming. Recently there is a tendency to wear floor-skimming evening dresses. Hat is not common for evening dress.
Shoes. Leather or chamois shoes with heels should be put on. Sport shoes or shoes with crepe or rubber sole are not allowed.
Gloves and handbag. At the reception starting till 8 p.m. one may wear silk, cloth or kid gloves. Handbag may be made of leather or chamois.
Silk, lace and other gloves may be put on with evening dress and the shorter dress arm, the longer gloves and vice versa. Small handbag of silk, gold-cloth or bedazzler.
Dress material for women. Color and density of the material should correspond to season and weather conditions: in summer light materials are used, in winter – dark and close materials.
For receptions till 8 p.m. wool, silk ad other materials may be used. For evening dress – silk, taffeta or gold-cloth may be used.
One should not wear a lot of jewelry at the receptions.
Woman enjoys more freedom in choosing the style of clothing, material and color then a man, the clothes of which is often uniform. This allows woman to pick such style of clothing that will correspond to her individual tastes and stature. Herein should be mentioned that the style of one’s clothing should accentuate good features and correct drawbacks.
The main rule while choosing clothes is time and place conforming. That is why it is not common to take in guests or during visit at day time wear sumptuous clothes. It is enough to have dainteth dress-suit on.
Casual day dress for reception is skimpy dress of classical style, high-necked dress with small neckline and 3/4 length or long sleeves. Material may be of any color, smooth or embossing.
Day-time dress of high quality material (silk, wool, etc) are used for receptions “a la fourchette” from 5 till 8 p.m.
Evening dress (one more time more precise).
Usually evening dress is more elegant then the dress for day-time reception. It may be of common length and also long. Evening dress may be sewed of silk, lace, crape, etc. The main rule is rather simple: the more ceremonial and official reception and the later it is held, the more elegant you should look. One should not overuse perfume and deodorant.
Evening shoes (one more time more precise).
Going-out shoe may be of colored leather, weight silk, gold-cloth and other materials. Handbag should be small, sometimes it is made of the same color with shoes leather, sometimes of bedazzler or silk.
Clothes is businessman’s “business card”, because while meeting partners pay attention to clothes first of all. Initial impression remains in memory for a long time. That is why disregard to own appearance is an unforgettable error. For example, neatness in clothes often associates with organized nature of business, skill to value time. Untidiness is the synonym of fussiness and obliviousness.
Today the most common businessmen’s clothes is suit. Business etiquette provides several ways of suit wearing.

If you wear suit, you should wear a tie. Exception is hacking jacket, which may be even put on the T-shirt. But it does not belong to business clothes. It is impossible to wear double-breasted coat without tie.
Shirt put on with jacket must be with long sleeves. It is concidered elegant if its cuffs may be seen from sleeves of jacket approximately 1.5 – 2 cm. It is better to choose the shirt without lapel pockets.
One should exclude the rear apron to be seen from the front apron. The tie should touch with its end the buckle.
One should never wear suit and sport shoes simultaneously. Such clothes are incompatible in their nature.
Having put on the suit, do not take the bag of sport type. It is desirable to carry paper and necessities in diplomat or brief case.
One should not show himself during business hours. During usual communication to wear suit is considered to be good courtesy.
One should not wear too light suits. The most common colors: dark navy, dark gray, black.
Do not wear colorful shirts.
Do not wear too bright-colored ties with loud pattern. A tie should be lighter then suit and darker then the shirt.
Avoid mismatches of figures on your clothes.
Always wear socks of dark colors.

Some rules:

Wear light suits at day-time, dark – in the evening. Evening suit matches with a tie of natural or artificial silk.
In formal setting a jacket should be buttoned. The jacket may be unbuttoned while evening meal or in the theatre. Standing up, one should button the jacket on the upper button.
One should always keep holiday wear in perfect order. This also concerns shoes, socks and collar buttons.
One should not keep up with fashion. It is better to look non-stylish but well, then to look stylish and bad.
Have two handkerchiefs (minimum). The first “working” should be placed in the trousers pocket. The second one – always squeaky clean – in the inside pocket of jacket.

Poise, as well as neat clothes, courteous treatment while communication, tactfulness are the ways to show respect to other people. Habits play significant role in behavioral pattern. They may accentuate good points and bring to naught all the good features as well.
Sometimes person acts unnaturally. Naturalness is one of the features of businessman’s behaviour, as an attempt to look differently is notable. Gestures and movements are the part of image. Often happens that gesture shows person’s mood and face even when he does not want that. Movements should not be harsh and rapid. While communication one should not depress his eyes for a long time and sit in relaxed pose. You may relax during leisure time, but during business hours one should be well groomed.
Sitting on the seat, one should not wiggle and seat at the brink. It is not also recommended to lean the elbows on the table. Sit and stand up one must do softly. Chair is not moved along the floor, it is shifted taking by the back. Such habits as reflexive leg swaying, shifting in chair, tapping with a heel are undesirable. Such behavior may be perceived as disinterest to talk, etc.
While talking it is better to sit squarely, do not lean or recline. The most common posture for businesswoman is: knees together, foot one near another, shanks turned obliquely. It is impossible to hold up the head while communication. It may denote boredom or weariness. Crossing of arms is acceptable, but this gesture is perceived as discontent or desire to stop communication. Lifted shoulders or indrawn head mean tension and make an impression of secretiveness. To prepossess someone to talk, you should incline your head on one side. This gives the impression of being all ears. You should not do the thing that may be estimated as footdragging (smoking a cigarette, sponging of glasses). This looks like an attempt to avoid the answer.

Analysis of electron-optical studies of experimental alloys of Fe-W and ferrotungsten

Fri, 22 Nov 2013 10:20:38 +0200

Analysis of electron-optical studies of experimental alloys of Fe-W and ferrotungsten

In this paper the experimental alloys of the Fe-W, which melted with refractory W - Ni - Fe scrap, compared with the standardized grade ferrotungsten ФВ 70. The comparative analysis of the microstructure, phase and chemical composition of the experimental alloys. Investigated the number of non-metallic impurities, the number of which is within the nominated GOST 17293-93. It is proposed to re-use as a substitute for ferrotungsten alloys for the manufacture high tungsten special materials based on iron.
Keywords: electron-optical analysis, structural-phase composition, the alloys of the Fe-W non-metallic impurities, ferrotungsten.

Alexandr Glotka

Doctor of Science, docent of material physics department,

Zaporizhzhya Natuional Technichal University

Phone: +380617698282; +380617698284

E-mail: Glotka-alexander@rambler.ru

While using high-melting temperature alloying elements, when they are pure, their solution in the liquid alloy requires a lot of energy input. With the purpose of cost cutting the ferroalloys are used. They dissolve quickly in steel bath as they contain ferrous elements. The time of solution shortens while the iron content increases [1].
Ferrotungsten is smelted with the usage of tungsten-containing ores with addition of iron cutting wastes or scale. For the reduction reaction oil or coke pitch, granulated ferrosilicon or powdered aluminum are added [2]. In accordance with GOST 17293-82 the quantity of tungsten in alloys hovers around 65-80%.
Recently the price for alloying elements jumped essentially, that is why the usage of highly alloyed steel, to which tailored materials are related, which are used in gas and power engineering are limited greatly. Metal products market shows that the value of ferrotungsten varies within 220 - 230 hr/kg [3, 4]. At the same time the prices for refractory scrap containing tungsten is 55-80 hr/kg [5]. In such a way, the usage of scrap containing certain amount of alloying elements for smelting of alloys of Fe-W will reduce essentially the prime cost of highly tungsten tailored materials and other tungsten containing alloys [6].
The aim of this work is to provide the comparative analysis of electron-optical researches of Fe-W alloys and ferrotungsten for determination the opportunity of experimental alloy further usage while manufacturing tailored materials used in gas and turbine manufacturing.

Research methodology

For the alloy of Fe-W type producing the refractory scrap of W-Ni-Fe was used, containing about 80% of tungsten [7] and commercially pure iron. Alloy rendering was performed in OKB 862 furnace in air in the graphite crucible, heating was executed till full liquefaction of the components. Six ingots mass 200g were liquated with concentration of tungsten 30, 50, 70% (by two melting operations thereafter).
The alloys phase composition analysis is executed on DRON-1 diffractometer in copper radiation with monochromatization of diffractive beams. The phases nature was determined by comparing experimental value of interplanar distances with tabulated data [8]. The margin of error did not exceed 1.36 × 10-4nm.
Chemical composition and microstructure of samples were studied with the help of JSM 6360 electron-scan microscope (produced by JEOL, Japanese) and 106I electron-scan microscope (produced by SELMI, Ukraine), which are fitted with X-ray spectral energy-dispersive microanalysis (EDX) under accelerative stress 20 kV and sonde current strength 4 nA in secondary electrons. The quantity of each element was determined by comparison of sample radiation rate with the intensity of basic standard element which are supplied with software. The study was carried out using mechanically polished samples with the following chemical milling (using agent “Marbl” within 5-10 seconds).

Results of analysis and its discussion

While smelting of alloys of Fe-W a change in ingot mass compared with charging mass was fixed. The difference fluctuated within 1% (for the alloy with 30% of W) and 6.7% (for the alloy with 70% of W).
Samples for microstructure analysis were cut out parallel to vertical axis of the ingot in order to analyze tungsten allocation.
Analysis of alloys microstructure showed that alloy of Fe-30% W has heterogeneous structure with great amount of impurities of secondary phase, which has heterogeneous morphology (from needlelike to spherical inclusions) (fig.1). Such structure nonuniformity is explained by nonequilibrium of ingot crystallization.
X-ray structure analysis showed that the structure consists of iron-based a-solid solution and intermetallic compound Fe2W ( l- phase). Intermetallide is formed by peritectoid reaction at the temperature 1060 C with a (Fe) and m- phase (Fe7W6) [9]. Fe2W disappears at continuous quenching (2000 hours) at the temperature 1000C and has the lattice constant а = 0,4737 nm b = 0,7700 nm.

а b
Fig. 1 Alloy microstructure of Fe-30% W system (а-×300; b-×2000)

With the help of EDX analysis the difference in chemical composition of basic metal and impurities was determined. The average value of chemical composition for base metal is within 67,14 % Fe - 1,45 % Ni -31 , 41 % W; while the impurities have the following composition : 25,58 % Fe - 0,63 % Ni -73 , 79 % W.
According to this data, the impurities chemically will approach to the intermetallide stoichiometry of Fe2W type.

а b
Figure 2 Alloy microstructure Fe-50% W (а-×150; b-×1200)

Alloy microstructure of Fe-50% W of scrap is given in figure 2 at different magnifications. The structure is rather developed with dendritic branches of different degree, between which there are areas with eutectic structure. Eutecticum has a platelike shape associated with “basketwork”.
The alloy phase composition analysis showed that the structure consists of iron-based a-solid solution and intermetallide Fe7W6. This compound ( m - phase) is formed in the system under peritectic reaction from the melting containing 20.6% (atomic mass) of tungsten [9]. According to the data [10], intermetallide is stable in large temperature ranges from 1637 C to ambient temperature and disappears only at soaking 1000C during 2000 hours. m- phase has the homogeneity limit from 39% to 45% W [11]. Depending on the chemical composition lattice constant also changes: а = 0,4755 nm b = 2,583 nm – for alloys rich in iron, а = 0,4771 nm , b = 2,596 nm – for alloys rich in tungsten.
The groundmass has such chemical composition: 59,34 % Fe - 7,85 % Ni -32 , 81 % W, while platelike inclusion - 41,24 % Fe - 4,91 % Ni -53 , 85 % W. According to chemical composition, the platelike phase does not correspond to intermetallide stoichiometry Fe7W6, but the experimental alloy should be considered as the one, containing not two but at least three elements (W - Fe - Ni ). This can lead to dislocation of concentrated interval of m-phase existence in the limits less than tungsten concentration. Besides, in the work [12] one may see that phase can correspond to the formula Fe3W2, i.e. it can change the relation between elements content, depending on conditions of crystallization and amount of tungsten.

а b
Figure 3 Microstructure of Fe-70%W alloy (а- ×100; b - ×400)

Fe-70% W alloy has the similar ingot microstructure with Fe-50% W alloy. Together with dendritic inclusions of needlelike type, it can be seen eutectic component of platelike type (fig.3). However, in certain areas of ingot there are spherical inclusions, which were not observed in any of the materials mentioned above (fig. 3, a)
Phase-shift analysis showed that apart from a-phases (Fe) and Fe7W6 that are present in alloy of Fe-50%W, there appears tungsten-based a-solid solution. The analysis of elements allocating over the metallographic sample surface showed the presence of tungsten in lamellar precipitate with the reducing amount of it from the center to the edge. Rounded particles are the solid solution, tungsten-based with its amount at the rate of 90-95 %. Probably, tungsten particles, which entered the alloy with refractory scrap and have not dissolved in melting, become origination centers of m-phase. Undersupply of iron for intermetallide formation is also possible.

а b
Figure 4 Ferrotungsten microstructure FeW 70 (а-×120; b - ×600)

The comparison of alloy microstructure of Fe-70%W and general ferroalloy FeW 70 (fig. 4) let us know there are greater amount of spherical inclusions in ferrotungsten, which are classified as tungsten-based solid solution and the amount of laminose phase is far less. Such difference leads to the increase of heat amount and dissolution continuance of alloy compared with experimental alloys.
The EDX method is used for impurities presence test. Such elements as sulphur, phosphorus, silicon, manganese and carbon are beyond the range of indicator sensitivity. Sulphur and phosphorus identification threshold is calculated basing on the content of element 0.05%, silicon ad manganese – 0.3%, carbon – 0.1%. Comparing the results with GOST 17293-93, we achieved the conformation to chemical composition of tungsten alloys.

Conclusions

In such a way after the experimental alloys analysis and structural and phase composition analysis it may be concluded that according to chemical composition, structure and impurities the produced alloys are equated with ferrotungsten alloys, and in some cases they are much better and can be used for addition of some elements in iron-based alloys. Hereafter the manufacturing of highly tungsten tool alloys with usage of experimental alloys is planed and analysis of its structural and phase condition.

REFERENCES

Durrer, R., Volkert, G. Metallurgy of ferroaloying [Metallurgie der ferrolegierunger ](1972). Springer – Verlag Berlin, Heidelberg New York, pp. 1972 – 675

Interactive environment (2013), Available at: http://www.pmt.ru

Glotka, O.A., Koval, A.D. Manufacturing of Ni-W ligature for alloying of nicel-based stacks (2008). Engine-building reporter No 1, pp. 139-142.

Glotka, O.A., Koval, A.D., Stepanova, L.P. Study of refractory scrap containing tungsten .New materials and technologies in metallurgy and machine-building (2007). pp.17-20.

Kirshner, G., Harvig, H., Uhrenius, B. Metall. Trans (1973). V. 4 N. 4 pp. 1059-1064.

Lyakishev N.P. Сonstitutional diagram of double metal systems (1997). Machine-building, 1025 p.

Mirkin L.I. Reference book for X-ray structure analysis (1978). Metallurgy, 678 p.

Ryss, M.A. Manufacturing of ferroalloys (1985). Metallurgy, 345 p.

Sinha, A. K., Hume-Rothery W, J. Iron Steel Inst. 1967. V. 205. N. H. P. pp. 1145-1149.

Sykes, W. P. Trans. ASM. (1936). V. 24. pp. 541-550.

United Ferro Alloys Systems (2013), Available at: http://www.ufas.ru

Vtorcvetmet (2013), Available at: http://www.vtorcvetmet.ru

Billet СС’s moulds heat engineering parameters monitoring system

Tue, 26 Nov 2013 10:32:20 +0200

System for billet continuous caster’s mould heat engineering parameters monitoring based on APCS standard gauges set signals profound interpretation is created. This system allows maintaining change in time of such important parameters that characterize mould heat work as average heat flux density, average overall heat exchange coefficient in the mould, average heat transfer coefficient to mould inner surface, effective gas gap thickness. It is proved that effective gas gap thickness control in real time makes possible operative mould inner surface wearing control, practical check of mould taper and billet shrinking correspondence, choice of better moulds for concrete industrial conditions, learning dependence of mould wearing and billet’s form defects formation.
Key words: billet, continuous caster’s mould, heat dissipater, mould wearing, effective gas gap thickness

Alexei Birukov

Doctor of Science, docent of technical thermophysics department,

Donetsk National Technical University

Billet СС’s moulds heat engineering parameters monitoring system
Problem and its connection with scientific and practical tasks

Reliable operation of continuous casting machine and the quality of sections depend greatly on continuous casting machine heat parameters. That is why researches and developments focused on the advance of heat engineering parameters of all continuous casting machine elements are essential. Significant role in support of reasonable characteristics of working continuous casting machines plays Automatic process control systems (APCS), which integrate constantly and in prospect should carry the function of full control and rapid analysis of all the continuous casting machine parameters.

Evaluation of publications concerning the topic of research

Generally accepted fact about the direct dependence of billets quality and casting process reliability on accuracy of the continuous casting processes, thermal first of all [1]. Probably, nowadays all the continuous casting machines are fitted with such monitoring levels as differential temperature of cooling water in continuous caster’s mould [1-3]. It contains the indirect information about heat amount transferred in the mould, that in its turn characterize heat-exchange between ingot shell and inner face of the mould. The increase of cooling water differential temperatures in the continuous caster’s mouldindicates the increase of heat amount, taken off from the billet surface and vice versa [3].
But this value does not allow to intercompare mould work of both different continuous casting machines and one and the same aggregate, but in various periods of time as the variations between differential temperatures could be caused by some changes in costs for continuous caster’s mould primary cooling water [4].

Research problem statement

Aim of the given research is developing of scientific bases of heat engineering parameters control system for billet СС’s moulds, based on the typical detector signals of APCS advanced interpretation and allowing to get the information, upon which the comparison of thermal performance of different moulds and their reasonable design factors and operational parameters specification are possible.

Presentation of material and results

In continuous caster’s mouldthe heat from melted steel is transferred to cooling water through the placed in series range of thermal resistances [5] (fig.1).

For the adequate comparison of moulds thermal performance can be used the values not depending on primary water flow. In the role of such values it makes sense to use heat flow average density from the surface of billet in the mould (), heat-transfer coefficient average value in the mould (), average ratio of heat transfer from billet shell to inner surface of the mould tube (), effective gas gap thickness (deff). Methodology of these values determination is given below.
The value of average density may be determined from the equation of the mould average temperature balance:
,                                        (1)
where G – bulk water flow through the mould, kg/sec;
c – water heating capacity J/(kg×Cal);
Dt - differential temperature of cooling water in the mould, C;
F – the billet and mould contact surface, м2
According to the heat-transfer law the average density of heat flow mat be expressed as
,                                      (2)
where ts - solidus temperature for pouring steel grade, C;
twav – average temperature of cooling water in the mould.
As in the function of heat transmission moving force in the expression (2) the differential temperature from solidus to the average temperature of cooling water is taken, value acts as “conduction” of thermal chain, including thermal resistance to heat transferring through solid shell, gas gap, mould liner wall and from its outside surface to cooling water.
Having determined the average density of heat flow from the billet surface in the mould, one can find the average value of heat-transfer coefficient in the mould from the heat-balance equation:
.
Using with some dependence allowances, true for steady-state heat transfer, one may state the dependence of heat transmission average ratio in the mould on all the thermal resistances
,                                      (3)
where aw - heat-transfer coefficient from the outer surface of the mould tube to the water (W/m2×Cal);
dm – mould tube wall thickness, m;
lm   - thermal conductivity of the mould tube material, (W/m×Cal);
- the average thickness of metal shell in the mould, m;
lsh - heat conduction coefficient of the billet shell at its integral temperature, (W/m×Cal).
With the help of equation (3) one can calculate the average heat transfer coefficient from billet shell to inner surface of mould tube:
.                          (4)
This value contains integrated information about thermal-mechanical processes proceeding in the mould. The analysis of its values for moulds of different degrees of taper allows to specify the concept of heat exchange in the mould. As the value is known, it is possible to determine the value of effective thickness of gas gap between billet shell and the inner surface of mould tube (deff). Once while usage of gas gap effective thickness value for studying of heat exchange in the mould is supposed that heat flow from the billet surface is formed according to two mechanisms: radiating and heat conduction through a gas gap, than we have the following formula:
,                                       (5)
where - gas space heat conduction, W/(m∙Cal);
ar - radiation coefficient from the billet shell to inner surface of mould tube, W/(m2×Cal).
The ar value is calculated on the basis of the known dependence describing radiant heat exchange:
,                                 (6)
where Ts -   temperature of the billet surface, K;
Тst– temperature of the inner mould tube surface, K (temperature of steel);
Cg – the given coefficient of radiating while radiant heat exchange between billet surface and inner mould tube surface.
The values Тs and Тst can be determined with rather small accuracy on the basis of dependences that are true for steady-state heat transfer through the range of placed in series thermal resistances:
       (7)
One may conclude that on the basis of analysis of the given dependences (1-7) under APCS in real-time mode the changes of all values (, , , deff) may be determined, depending on such parameters as differential temperature of cooling water in the mould, usage of primary water, thermal and physical characteristics of the poured steel, geometrical parameters of the mould tube (Figure2).

The example of determination of dependence effective thickness of gas gap on the differential temperature of cooling water in the mould with the help of proposed calculated dependences for the following initial data ( billet 130х130 mm, usage of primary water 30kg/s, mould tube material is copper, mould tube wall thickness 0,01 m) is given in the fig. 3.
Monitoring of value of gas gap effective thickness in real-time mode with the help of APCS allows the following:
- operational control of mould tube interface wear on the basis of changing analysis at time of the value deff;
- practical checking of correspondence of mould degree of taper to the billet shrinking-off on the basis of average level comparison deff for concrete combinations of the mould sections and steel grades with optimal values of gas gap effective thickness, determined while practical studies;
- choice of the best moulds for the concrete manufacturing conditions on the basis of analysis of corresponding data files about average value of effective gas gap wall thickness;
- estimating of relationships between mould tube wear and defect formation of rhombic form. It is achieved by cooperative data processing about heat and speed rates of steel pouring, grades of steel, moulds taper, corresponding them effective gas gap thickness and data on the billet of rhombic form with the help of mathematical statistics device.

Conclusions and the follow-up study perspective view

In this work the billet СС’s moulds heat engineering parameters monitoring system is created, based on the deepened interpretation of typical detector signals of APCSdue to their usage as argument in specifically developed dependences.
The given system fixes change in parameters time, which allows to compare the values of thermal performance of different moulds and estimate the operational efficiency: the average density of heat flow, the average coefficients of heat transmission in the mould and heat transmission to the inner surface of the mould, effective gas gap thickness.
It is shown that control of the effective gas gap thickness value in real-time mode makes it possible to monitor the wear of mould tube inner surface, checking of the correspondence of mould taper to the billet shrinking-off , choice of the best moulds for concrete manufacturing conditions, estimating relationships between mould tubes wear and defect formation of rhombic form.
The significant trend of follow-up studies is the creation of methodology allowing to predict dissymmetric features of the inner surface tube mould wear on the basis of APCS, averaged for the whole mould tube surface values of heat-flow rate and effective gas gap thickness.

References

Birukov, A.B. The modern aspects of CC machine heat monitoring (2008). Metal and casting of Ukraine, 37-40.

Djudkin, D.A. The quality of continuously cast steel workpiece (1988). Technique, 253.

Emel’yanov, V.A. Thermal performance of CC machine: teaching aid for HEIs V.A. (1988). Metallurgy, 143.

Smirnov, A.N., Smirnov, Kuberskii, S.V., Podkorytov, A.L. Continuous casting of billet. (2012). 417.

Smirnov, A.N., Kuberskii, S.V., Shtepan, E.V. Continuous steel casting (2001). DonNTU, 482.

Business communication style and the ways to improve

Fri, 29 Nov 2013 10:23:51 +0200

Business communication style and the ways to improve

The article is devoted to Yuri Zuev,
Professor of Russian foreign trade academy, Moscow

There are two types of service in theory and practice of business communication:

Material – price, quality, quantity, fitting, food, convenience, informative intenseness, routine, efficiency, i.e. the criteria satisfying the claims of business partner.
Psychological - sense of well-being and self-significance, arising for the partner using our services; this realized expectation from the partner the concrete personality or congeneric social group.

Reserves for improving of business communication style:

adoption of favours;
self-control of mind and behavior;
adoption of nonverbal connection signs;
positive thinking, attitude and behavior.

Adoption of favours

Favours in business communication are choosing a partner from people and his personality evaluation. Psychological basis for any favour is the person’s interest in self- evaluation, one’s significance and comparison with surrounding evaluation. There are three types of favours:

Positive (compliments, attention, gratefulness, interest to the partner's personalty, deep admiration of his propositions and actions); any good news satisfying the partner, proving his value.
Negative favours ( dislike, distrust, disappointment, ridiculing, showing ingratitude, criticism), all the criteria causing a sensation of indignity and melancholy.
Neutral favours ( the absence of any favours at the moment when a partner is waiting for the evaluation of his initiatives, propositions and actions).

The usage of favours while business conversation means:
to be natural and sincere to the maximum; go for showing affection in the sphere that is important for the partner and where he strives to deep self-evaluation. Any favour should be reasonable, direct, correspond to the objective evaluation of made. The members of services sector (secretaries, assistants, drivers and others) need positive favour most of all. Directors should not loose the partner from their field of vision and support each of them by favours.
The notion of stress theory.
There are three concepts in stress theory:
1. Stress is the tension state, stipulated by the extreme reaction of nervous system under influence of tension internal and external factors.
2. Stress factor – is the factor of tension:
a) physical – heat, cold, noise, hunger, fire, disorders, illness etc.
b) social-psychological – rudeness, frustrated hopes, grudge, material problems, race for power, differences in lifestyle, unfairness, treason, holding time.

3. Signal of stress factor – any signal of nervous system about wrong condition of the body (irritancy, hearburn, intermittent pain in column or in temples, intermittent heaviness in the heart, desire to smoke, polydipsia or dryness of the mouth, a wish to talk more than usually or reticence, chronic headache, chronically poor sleep quality, profound indifference to work, total loss of appetite or the reduction of vital tone, steady feverish glint in the eyes).

4. Distress
Prevention of negative influence of stress while business conversation means:

realization what usually causes stress;
systematic analysis and preliminary preparation of countermeasures against stress factors;
reasonable choice of tactics ( take necessary steps to prevent the event, avoid the development, take the tactics of waiting, make adjustments to your own attitude to up-coming event - estimate realistic the probable consequences and avoid negative thoughts).

Adoption of nonverbal connection signs

Practice of business communication shows that while first 5 minutes of meeting up to 75% of source information about partner is received through nonverbal connection, i.e. owing to estimation of face, eyes, tone, gestures, position, demeanor, clothes, symbols indicating the partner’s official position. The skill of reading nonverbal connection signs means:

knowing of panhuman gestures;
knowing of nation-specific gesticulation;
one should remember, while reading the sign language, our partners read the forms of our nonverbal connections as well, hereof arise the necessity of strict and incessant control of our own gestures, mimics and position.

Nonverbal connection is typically subconscious and that is why sincere. The gesture is hard to change, but it is possible and necessary to prevent by means of free efforts.
The man of business is characterized by positive-persevering behavior. A person of such behavior maintains his rights but does not derogate from rights of others; expresses his point of view honestly, clearly and directly and at the same time stresses the understanding of partner’s position. The positive-persevering behavior of a man of business means good self-comprehension of his own dignity and personal professional background. People with such type of behavior are inclined to express in short and essentially, use “I” pronoun very carefully, draw a clear distinction between fact and someone’s opinion, rest on facts, avoid didacticism, raise a question without reserve, straight to one's face easy, look the ways of settling a problem, do not avoid it. While communication with aggressively-spirited partner, a man with positive-persevering behavior avoids the question “Why?” as it may be provocative, requiring the explanation of the motive, that is often concealed by partners. The question “Why?” should not be risen at all. It may be replaced by questions “Who?“, “How?” “When?” , “Where?” as they require new information and that is easier than to explain the motive .

Referenses

Klaus Mueller.
D. Nerenberg, G. Kalero.
D. Karnegi, Moscow, “Progress”, 1989.
Hans Selye “ Stress without distress”, Moscow “Economy”, 1979.
Kitaev – Smyk L.A. “Psychology of stress “. Moscow, "Science", 1983.
Eric Berne “ Games people play” “People play games". Moscow, "Progress", 1989.

New magnesium alloy with promote properties for automobile construction

Fri, 06 Dec 2013 10:43:30 +0200

The effect of scandium on structure and phase composition of the heat-resistant magnesium alloy ML10. Shown its positive effect (0.07%) on the mechanical properties and long-term strength at elevated temperatures castings of magnesium alloys for the automotive industry.
Key words: magnesium alloy, structure, mechanical properties, heat-resistance, intermetallic phase.

Vadim Shalomeev

Professor of material physics department,

Zaporizhzhya National Technical Uneversity

Eduard Tsivirko
professor of machinery and foundry operation technology department,

Zaporizhzhya National Technical University

Yurii Vnukov
pro-rector for research,
mechanical engineering department chairman

Zaporizhzhya National Technical University

Dmitrii Vnukov

student of Zaporizhzhya National Technical University

New magnesium alloy with promote properties for automobile construction

Automobile transport weight-saving is the priority task for producers as it allows to increase their coefficient of efficiency, reduce fuel consumption and increase reliability and endurance of service [1]. But in spite of all the efforts the structural weight of autos tended to increase because of the addition of numerous auxiliary devices and mechanisms, improving convenience and safety of traffic. Solution of this problem is possible by means of light materials, magnesium alloys in particular, developing.
Magnesium alloys have a lot of advantages compared with other alloys on the basis of non-ferrous metals: low-density, high strength-to-density ratio and ratio of elastic, the ability to absorb hit energy and vibrational motion energy. That is why they are suitable for automobile industry. Nowadays the forces of world automobile industry are focused on the enhancement of magnesium alloys casting usage [2].
For manufacturing of combustion engines and transmission systems magnesium alloy ML10 is used (% mass: 0,1…0,7 Zn, 2,2…2,8 Nd, 0,1…1,0 Zr, the other - Mg). Its basic elements, forming heat-resistant intermetallic phases, provide good efficiency characteristics of alloy at high temperature [3].
However, technical requirements submitted to modern systems and mechanisms, stiffen the conditions of their operation and require steady increase of their characteristics. The most reasonable decision of the given task is improvement of materials used by means of controlling their structure and properties [4,5,6].
The scandium is known to affect positively on mechanical and heat-resistant properties of aluminum- containing alloys by forming complex heat-resistant intermetallides [7]. That is why the influence of scandium on structure and properties of heat-resistant alloy ML10, having in its composition heat-resistant intermetallides phases (MgZr)12Nd, that will allow to increase reliability and endurance of produced parts and broaden the area of its application, is of great interest.
The influence of scandium on mechanical properties and heat-resistance of magnesium alloy ML10 was studied.
The magnesium alloy ML10 was smelted in series in induction crucible furnace IPM- 500. Alloy finishing was executed in holding furnace with partial extraction. Into alloy some increasing ligature agents were added (10 % Sc, 90 % Mg) and standard samples for mechanical test were poured into sandshale casting box. These samples were subjected to heat treatment in Belvju furnaces and PAP-4M furnaces under following modes: quenching from 415±5 оС, soaking during 15 hours, cooling in the air and age-hardening at 200±5 оС, soaking during 8 hours, cooling in the air.
Rupture strength (σr) and elongation ratio (δ) of samples with 12 mm functional diameter were determined with the help of R5 pull test machine under normal temperature.
Creep rupture strength (σ) was determined at different temperatures with the help of AIMA 5-2 pull test machine on the samples with 5 mm functional diameter.
Microtexture of castings was examined with the help of microscope “Neophot 32” after etching operation by agent containing 1% of nitric acid, 20% of acetic acid, 19% of distilled water and 60% of ethylene alcohol.
Microhardness of alloy microconstituents was determined with the help of “Buehler” microhardness tester under load 0.1N.
Electron probe microanalysis of microconstituents was executed on the “JSM-6360LA” electron microscope.
The macrofractographic analysis of sample fractures of examined metal showed that with increasing of scandium content the macrograin broke, the nature of fracture was dull and finely crystalline (fig.1). However, if the scandium content more than 0.7% there appeared defects in fractures of metal that are typical for rough microporosity and film impurities (fig2).

а b c

Figure 1 Macrostructure of ML10 alloy with different scandium content: a - without Sc, b - 0,05 % Sc, c - 0,1 % Sc, d - 0,3 % Sc ( х 3)

Figure 2 Coarse scabs in samples of ML10 alloy with additive 1.0 % Sc, х100

Microstructure of heat-treated ML10 alloy, casted according to standard process, is presented as δ-solid solution with eutectoid δ+(MgZr)12Nd in form of spherical shape areas. With increasing of scandium content there was increasing of the size of spherical areas of eutectoid escape in the alloy (fig. 3 a, c). While introduction into the alloy over 0.07% of Sc, the size of eutectoid spherical areas increase in four times compared with standard alloy, while the size of δ –phase was more or less stable (fig. 4).

a b c

d e f

Figure 3 Microstructure of ML10 alloy without addition of Sc (a, d) with addition 0.05% Sc.
(a, d) and 1.0% Sc (c, f) x: 500 a, b, c - after standard heat-treatment,
d, e, f - after examination at 150 C (1252 h) +250 C (strain 80 MPa)

а

Figure 4 Sizes of microconstituents (A) of heat-treated ML10 alloy with different scandium content:
а - δ+(MgZr)12Nd – phase,
b - δ – phase

Heat treatment contributed to increasing of alloy homogeneity as result of elements reassignment between axes and interaxes of dendrite spaces, and complemental alloying of a die by means of the elements diffusion from interfacial phase separation (MgZr)12Nd.
Electron probe microanalysis provided by electron microscope "JSM-6360LA” showed, that spherical areas are treated mostly by zirconium, neodymium and scandium (fig. 5). In modified alloys the scandium content in spherical areas of eutectoid separation δ+(MgZr)12Nd in ~ 1.5…2.0 times higher, than in δ-solid solution.

No of the area	Content of elements, % *						Total, %
No of the area	Mg	Al	Si	Sc	Zr	Nd	Total, %
007	97,59	-	0,1	0,19	0,1	2,02	100
008	93,07	0,45	0,08	0,57	1,83	4	100
009	92,36	-	0,17	0,54	4,03	2,9	100
010	96,1	-	0,17	0,24	0,53	2,96	100

* - the data is of evaluative character
Figure 5 Electron probe microanalysis of microconstituents of ML10 alloy with addition 0.5 % of Sc

There was grain refinement while increasing scandium concentration in the alloy to 0.3%. Further increasing of scandium addition (to 1.0%) leads to enlargement of micrograin size to 160 micron (at 0.02…0.3 % Sc the micrograin size is ~ 75 micron).
In heated to 150…250оС samples there was resolution of eutectoid (fig. 3 d-f). Microstructure analysis showed, that while thermal effect and prolonged keeping together with resolution of eutectoid there took place its solution in the die with further separation of complex intermetallide phase of (MgZr)12Nd type with scandium in form of fine particles (fig. 6). Whereby fine intermetallide particles separated inhomogeneously, forming the areas of dark streak pattern, that is characterized by increasing of microhardness.

Figure 6 Inhomogeneous separation of secondary intermetallide phase in the sample of ML10 alloy after prolonged keeping (1252 hours, σr = 80MPa) at the temperature 150оС, х750

It was established that, to more complete resolution of eutectoid phase serves the time of keeping at the given temperature and strain. At temperature 270оС there observed roughening of the structure as a result of intensive separation of intermetallides, especially at the grain boundaries. It explains the sharp drop of refractory qualities of the material. Coarse interfacial separations were found in the structure of samples, containing over 0.07% Sc, which led to the rapid damage of samples while creep-rupture test.
Microhardness of δ-solid solution of standard alloy (before heat treatment) is more than 3 times lower than microhardness of separations in spherical eutectoid areas. After heat treatment there was increasing of a die microhardness and reduction of eutectoid hardness value. It indicates the increasing of heat-treated alloy homogeneity (table 1).

Table 1 Microhardness of microconstituents in samples of ML10 alloy after creep-rupture test

Amount of Sc, % mass	Microhardness after creep-rupture test. (σr80 MPa) HV, MPa
	die			eutectoid
	Тt50оС	Тt50оС	Тt70оС	Тt150оС	Тt250оС	Тt270оС
-	824.0… 894.1	824.0… 1064.0	894.1… 1354.4	1026.6… 1114.1	1225.5… 1504.7	1589.5… 2011.7
0.02	894.1… 1064.0	894.1… 1017.3	681.0… 824.0	1114.1… 1167.8	1167.8… 1225.5	733.4… 857.3
0.05	894.1… 1017.3	894.1… 1017.3	733.4… 857.3	1114.1… 1167.8	1167.8… 1225.5	824.0… 949.5
0.07	894.1… 973.5	1064.0… 1114.1	894.1… 914.1	1114.1… 1167.8	1167.8… 1225.5	973.5… 1167.8
0.10	894.1… 973.5	1064.0… 1114.1	894.1… 914,1	1114.1… 1167.8	1167.8… 1225.5	973.5… 1167.8
0.30	894.1… 973.5	1064.0… 1114.1	894.1… 914.1	1114.1… 1167.8	1167.8… 1225.5	973.5… 1167.8
0.50	894.1… 973.5	894.1… 1064.0	933.4… 973.5	1114.1… 1167.8	1167.8… 1354.4	1167.8… 1225.5
0.70	824.0… 894.1	994.1… 1164.8	923.1… 932.5	1064.0… 1167.5	1225.5… 1354.4	1167.8… 1649.5
1.00	967.8… 1114.5	1044.1… 1184.3	923.1… 932.5	1167.8… 1354.4	1225.5… 1504.7	1167.8… 1649.5

It is shown that, increasing of scandium concentration in ML10 alloy leads to the increasing of microhardness values of microconstituents before and after heat treatment.
With increasing of keeping time at temperatures 150…250 оС there was reduction of microhardness of the examined alloys by means of more complete resolution of eutectoid of δ+(MgZr)12Nd type.
The addition of scandium to the ML10 alloy to 0.07% contributed to the improving of the mechanical and heat-resistant properties (table 2).
Further increasing of scandium content in alloy leads to some reduce of mechanical characteristics of the material.
Increasing of the creep rupture strength test temperature to 270C has reduced the time to fracture in ~ 6 times. Samples with addition 1.0% Sc have damaged when subjected to loadings at temperature 250 оС because of formation of the porosity and film impurities.
Table 2 – Mechanical properties and creep rupture strength* of ML10 alloy

Amount of scandium, % mass	Mechanical properties		Creep rupture strength, σr=80 MPa, hour.
Amount of scandium, % mass	σr, MPa	δ, %	T**t.=150/250оС;	Tt=250оС;	Tt.=270оС;
-	235.0	3.6	125130/2615	4730	900
0.02	253.0	4.6	125200/5600	5310	1110
0.05	245.0	6.3	125200/4845	7130	1600
0.07	240.0	4.0	125230/6400	6140	1220
0.10	232.0	3.5	125230/4800	3630	1320
0.50	235.0	4.0	125130/3410	2400	645
1.00	169.0	3.3	125230/800	-	-

Note: * - average values;
** - testing of the samples for creep rupture strength was executed on a staggered basis: at 150 оС (numerator), then at 250 оС (denominator).

Conclusions

Modification of ML10 alloy with scandium in the amount of 0.05…0.07 % improves the micro- and macrostructure of the metal that contributes to improving of mechanical properties and refractory qualities of magnesium casting.
The usage of magnesium alloy castings of ML10 type, modified by scandium for automobile manufacturing will allow reduce their weight, improving the reliability and endurance of operation.

References

Al’taman M.B. Magnesium alloys/ M.B. Al’taman, A.F. Belov, V.I. Dobatkin. – Moscow: Metallurgy, 1978. – 294 p.
Каmbe H. Application of alloys of magnesium for details of cars [Текст] / Н. Каmbe // Metals and Technol. - 2001. - 71, № 6. - P. 51-54.
Kraus J. Richtig kombiniert : Leichtbaukonzepte bei Automobilen sind nur uber Verbundsysteme realisierbar [Текст] / J. Kraus // Maschinenmarkt. - 1998. - Sonderausg. - P. 152-154.
Gulyaev B.B. Solved and unsolved problems of casting process theory [Text] / B.B. Gulyaev Foundry engineering. - 1990, № 9, P.2 - 3.
Drits M.E. Magnesium alloys for working at high temperatures/
М.Е. Drits. – Moscow: Science, 1964. - 229 p.
Wang Q. Effects of RE microstructure and properties of AZ91 magnesium alloy [Теxt] / Wang Qu-dong, Lu Yi-zhen, Zeng Xiao-qin // Trans. Nonferrous metals Soc. China. - 2000. - 10. - №2. - Р. 235-239.
Shalomeev V.A. The quality of castings of ML5 alloy modified by scandium [Text] // V.A. Shalomeev, E. I. Tsivirko, N.A. Lisenko // New materials and technologies in metallurgy and machine building. - 2007, № 2, P. 34-40.

The influence of plastic deformation on properties of gazars.

Fri, 06 Dec 2013 10:56:24 +0200

Processes of change of mechanical properties and microtexture of castings from gazars, deformed through rolling and drawing are introduced. The undertaken studies showed that while rolling the deformation of billets is greater than while drawing. The hardness of deformed billets in the as-annealed condition in 1.5 – 2 times higher than the hardness of uniform-sized monolithic rod. The hardness of pieces in the non-annealed condition was still higher. Effect of monolithic areas formation inside the porous structure was identified, which is connected with motion of defects of crystalline lattice. The ways of rolled stock hardening from gazars are suggested.

Key words: rolling, drawing, strength-to-density ratio, strain, porosity, flow limit.

Vladimir Karpov

doctor of Engineering Science, professor,

National Metallurgical Academy of Ukraine

Ol'ga Komissarchuk

post-graduate student of material science department,

National Metallurgical Academy of Ukraine

The influence of plastic deformation on properties of gazars

Intoduction

Aim of research is to study the changes of new type of cast porous anisotropy material mechanical properties, gazars, under their cold plastic deformation.
Conventional technology of gazar production [1, 2] allows to obtain porosity 20-25 micron dia at 25-30 % of total porosity. To get diametrically smaller pores is more complicated, but manufacturing industry requires a lot the reduction of pores basic size [3, 4]. Plastic deformation allows to get the samples of gazars with the necessary size of pores.

Material and equipment

         For strain test of gazars the billets of brass casting form of 10 and 20 mm dia and 100 and 130 mm in length were produced.
         Phenomenology of gazars cold strain was performed both for free longitudinal rolling and for drawing of round. Rolling was performed on double-pass mill in each groove and tipping of the billet through 90°. Squeezing of a billet diametrically was ~ 40%, the strain of a billet in each groove was ~ 10%.
         Drawing of billets was executed on articulated drawing mill. The die blocks with hole conical camber (canting angle to the axis of drawing is 14°), die block material – WCo8 alloy with abraded surface. Drawing speed was 0.2 m/ sec. As grease the soap powder was used. One-time squeezing to diameter in one pass was ~ 10%.
         Mechanical properties of the material were determined on completion of elongation testing of test rods, run on the multiple-purpose pull test machine of TTDM-L type at strain rate 3х10-3 с-1.

Research results

Deformed pieces of gazars showed better mechanical characteristics under all degrees of strain. Rolled rod of the gazar at 10 mm thickness after annealing for stress relief had hardness in 1.5- 2 times higher than a uniform-sized monolithic one. Non-annealed deformed gazar piece had hardness in 2-3 times higher than a monolithic rod 10 mm dia.
While instrumental examination of deformed gazar pieces there observed the dependence of their flow limit on degree of strain ( fig. 1a). With increase of strain degree of copper gazars the flaw limit increased, but this dependence is not lineal. Ultimate resistance of gazars pieces with increase of porosity reduced (fig. 1b).
Fine-structural investigations showed that there take place opinion of changing the thin division walls between pores into areas with small amount of structural defects (similar to a structure of metallic whiskers) [5, 6]. While reducing intervals between pores, the hardness of gazars pieces was increasing (fig. 2).
The ultimate resistance increase of deformed gazars was fixed along the horizontal of real cross-section that is connected with decrease of division walls thickness between pores. In 115-40 micron interval of thicknesses the ultimate resistance has not changed and in 40-20 interval there was its increase, which grew along with decrease of division walls thickness (fig. 3).

а b
Figure 1 a – the influence of degree of strain on flow limit of gazars;
b – the influence of porosity on the ultimate resistance of gazars;
1 – along the plane section, 2 – along the real section

The results obtained confirm the suggestion about the fact, that increasing of gazar hardness may be achieved through thinning of division walls between pores, that is possible only if the strain of pieces is strong. At high-grade plastic strain the rim zone of gazars densifies up to welding of pores parts with formation on the surface almost monolithic highly-defective layer, which also improves hardness of deformed pieces of gazars.

Figure 3 The influence of intervals between pores on:
1 – hardness of copper gazars along the surface of real cross section of the sample
2 - ultimate resistance along the surface of real cross section of the sample

Figure 3 The influence of intervals between pores on hardness of copper gazars samples deformed in 30% and annealed

The analysis of microstructure showed, that porosity and cross section of gazar pores reduction while rolling run more intensive than while drawing. While rolling the metal piece in deformation zone flows both along the longitudinal and radial directions. When drawing the deformation of pieces run by means of additional longitudinal tensile stress formation, while radial metal flow reduces. The metal part moving radially is much smaller. Thereafter piece deformation along the longitudinal direction is stronger, than while free rolling. Total deformation of pieces while drawing is always smaller (fig. 4). This difference may be about 20-40 %.

а b

Figure 4 The influence of deformation on gazar porosity: deformation through drawing; (b) – deformation through rolling: 1 - P – porosity = 15%, 2 – P= 30%

While study of piece structure after recrystallization process it was fixed that in porous metal structure there exist coarse monolithic buildups (fig.5). Before annealing there were no such buildups. It may be connected with secondary recrystallization process and migration of crystal defects to the pores, acting as active substitutional sites. This theory is confirmed by the great amount of small crystals and the structure of pores around monolith.
The results obtained show the necessity of further researches concerning the structure and properties of gazars in the course of their cold plastic strain and after it. This research work may contribute to receipt of new easier, but harder constructional materials for modern manufacturing industry needs.

Figure 5 Monolithic formations inside porous structure of gazar after annealing, x 50

Conclusions

High degree of gazar deformation changes the structure of pores and the distance between them. While thinning of division walls between pores up to 10-20 micron one may observe hardening process of the pieces, which is similar to the hardening effect of metallic whiskers. This is true both for rolled and drawn pieces.
Flow limit and ultimate resistance of gazar pieces depending on the type of deformation reduces in 2-3 times compared with monolithic pieces.
Fine-structural investigation showed, that while rolling the reduction of porosity and cross section of gazar pores run more intensive, than while drawing. For achievement of similar properties and structure of gazar pieces while drawing their deformation should be 25-40% higher than while rolling.
The shape of gazar pores, subjected to strong deformation, changes from cylindrical into slit-like.
Rim zone of deformed pieces with great amount of flaws increases gazar hardness, but after annealing their hardness reduces due to the degradation of defect structure of rim zone.
Active increasing of substitutional sites and dislocations during recrystallization process inside the porous structure leads to formation of monolithic areas, that is explained by defects transversion into pores, which are the active flows for them.

References

Karpov V. Jur., Shapovalov V.I., Karpov V.V. Hydrogen is alloying element of eutectic alloys- gazars // Theses of international conference VOM- 2007, Donetsk, - May 21-25, P. 577-580.
Karpov V. Jur. Mechanical-and-physical properties of gazars// PCMM.2007.- No5. - P. 34-37.
Continuous plugless rolling technology// Guliaev G.I., Ivshin P.M., Erochin I.N. and others// - Moscow: Metallurgy, 1975. – 263p.
Andrievskii A.S. Priperties of sintered pieces.// Powder metallurgy. – 1982. – No 1. – P. 37-42.
Berezhkova G.I. Whisker crystals // - Moscow: Science, 1969. – 155p.
Bokstein S.Z. Structure and properties of metallic alloys // - Moscow: Metallurgy, 1971. - 495p.

Influence of main pipelines continuous exploitation on their physical and chemical properties

Fri, 13 Dec 2013 11:00:45 +0200

Influence of main pipelines continuous exploitation on their physical and chemical properties

The processes taking place in the metal pipe during prolonged use can affect both the standard mechanical properties, and the custom, estimated by a specially developed technique. In this regard, for the assessment of metal pipes after their prolonged use is necessary to study the complex physical and mechanical properties to assess the resistance to the destruction of the metal in the environment closest to the operating conditions.
Key words: fatigue, hydrogenation, stress concentrators, weld seam, gas pipeline, static load, low-frequency loads.

Oleg Tarayevs'kyy

Doctor of Science, docent of transport and storage of oil and gas department,

President’s award holder for

young scientists of Ukraine (from 3.11.2009 No 891/2009)

Crack formation is known to be the localized process and it depends on local variations in metal structure [2]. In this respect the researches on local variations in metal structure should be carried out to specify the influence of continuous exploitation on resistance to breakage of pipes. The researches on the evaluation of metal inclination to strain age-hardening, resistance to origination and developing of cracks, crack growth resistance characteristics, delayed brittle fracture in conditions of strain, corrosion medium and hydrogen should be carried out as well. Determination of steel inclination to brittle fracture while decrease of temperature during tests is no of less importance. This fracture depends on the interacting process of impurity atoms with defects of crystalline structure and it is one of the criteria of steel evaluation that is fracture sensitive [3,4].
While continuous exploitation except strains, the pipe metal may be subjected to corrosion medium. It is believed that the major cause of fracture while metal contact with corrosion medium is the localized metal corrosion leading to the reduction of throat area and formation of a crack. Another cause contributing to crack formation while exploitation is metal hydrogenization. The crack in this case may be formed while keeping under strain below the flow limit as a result of delayed fracture developing. It should be marked that inner microstrains, connected with localized metal cold work and crystalline transformations, contribute to the delayed fracture developing [5].
For overall estimation of structural strength and development of pipe reliability criteria series of tests should be carried meeting the structural condition of metal, stages of crack origination and developing, influence of corrosion medium and hydrogen [6].
Some results of analysis of pipes samples of 19 main pipelines from the localities with different environmental conditions are given. Their percentage sharing is given in the figure 1, which shows that similar in chemical composition steels 17GS, 17G1S and 19G make 81% of the total number of analyzed steels. That is why the main statistical analysis was carried out with these steels, named hereafter as steels of 17GS type.
The total amount of analyzed pipes is 106 samples. 86 samples of them are carrier pipes, 9 – pipes of emergency reserve, 7 – emergency pipes, 3 – pipes of extra branches, 1 – pipe of current output and also corresponding amount of welded seams, among which there predominated plant longitudinal seams. There were defects in all site welds and in 8 plant longitudinal seams.
All the pipes were operated in different force conditions. The most severe pipe operating conditions were at the start of segments. Arrangement of pipe samples along the route was as follows: from the beginning of linear sections – 28, from the middle – 17, from the end- 22 samples.

Figure 1 Percentage sharing of pipes steels samples according to the grades

For evaluating mechanical properties the samples of pipes and welded seams were taken that are from 17GS steel, they collected from active pipelines, emergency spools and emergency reserve. The pipes were 425-1220 mm dia and 7-15.2 mm wall thickness. Working service was from 4 to 60 years. As initial condition the properties of pipes of emergency reserve from the similar steel grade and current metal was taken.
According to the results obtained, hardness, flow limit and malleability are almost unchanged, depending on operating time.

Figure 2 Characteristics curve of stress changes during the long period of pipeline operation.
1 -stress limit sr, 2 – flow limit s0,2

Averaging of values was carried out in accordance with the number of analyzed pipes for each working service. For pipe metal the value of ultimate resistance to separation sr in the interval of experimental dispersion 480-670 N/mm2 are close to standards for the given steel grade (at least 520 N/mm2) and are remained on this level during operating time.
The similar results are also observed for the flow limit s0,2, where within the limits of dispersion it remains near-constant. Pipe metal ductility - percentage extension d and reduction in area y - almost does not change during all the period of operation and is on the level of GOST claims and Technical specifications( at least 24 % for d, standarts for y are absent). Percentage extension changes within the limits 22-31.5 % and reduction in area within the limits 50-64 %. Therefore, 60 years of exploatation have not led to noticeable reduction of ductility index.The analysis of mechanical properties of welded seams showed that similar to pipe metal there is no any dependence of properties on the operating time. The value sr changes within 462-640 N/mm2 limit, s0,2,- within 338-474 N/mm2 . It almost coinside with corresponding characteristics of the pipe parent metal while close dispersion of properties. Ductility indexes of welded seams are lower, than of parent metal. So, d changes within 15-26 % limit, y - within 36-61 % limit. Dispersion of these parameters a little greater, than of parent metal, that is connected with welded seams defects, which show themselves while testing.

Figure 3 Change of mechanical properties of operated pipelines:
1 - relative reduction j 2- absolute elongation d

The standard mechanical properties – strength, flow limit and ductility – are almost not sensitive to structural changes in metal pipes while operating. For revealing the properties that are sensitive to structural changes, the other types of testing were executed, including tests on the samples with sharp stress concentrator and beforehand created crack and also evaluating of the work of crack formation and developing.
In such a way, the change of structural condition in metal pipe during operation took place, which leads to brittle fracture resistance reduction. One may suppose that one of the main reasons of increasing the inclination of metal to coldbrittleness and reduction to crack formation resistance is strain age-hardening, connected with interstitial atoms cooperation (carbon and nitrogen) with dislocations [2].
The change of structural condition of metal during long-time operation of pipelines may be connected not only with aging process, but also with flaws upbuilding process as a result of stress impact, corrosion medium and hydrogen. Corrosion processes cause the change in surface condition of pipe metal, leading to defects formation, such as corrosive opens, corrosion pits, pitting corrosion, etc [6].
Hydrogenization of metal contributes to formation of inner flaws such as microcracks in the areas of localized microstress impact [6]. It should be mentioned that hydrogenization of metal may run as a result of developing of electrochemical corrosion process. Hydrogenization process may be improved by cathodic protection.
Flaws upbuilding process, such as microcracks and failures during static or quasistatic stress below the maximum destructive force and steel yield point as well, is usually nominated as delayed fracture. Testing on the tendency to delayed fracture while simultaneous stress, corrosion medium and hydrogen impact, imitate the process of damage in real exploitation conditions while electrochemical corrosion process. This type of testing is the most strict and can be useful for evaluating the susceptibility to cracking of pipe metal, operating severe conditions (high-pressure, corrosive medium, etc).
For examining of pipe steels testing technique on the delayed material fracture in conditions of simultaneous stress, corrosive medium, hydrogen and mechanical stress impact, which imitate the real conditions of construction exploitation with forces concentrator was developed. For this the standard samples (10x10x55) mm with sharp notch after static bending test for determination of common yield force in the notch are put into the tank with standard solution of sulfuric acid of 0.1 density and addition of thiourea. Hereafter these samples are loaded on the “Instron” machine beyond the yield point, and then electric tension with 10mA/cm2 current density is turned on. In such a way there arises hydrogenezation of metal while of corrosive medium and mechanical stress impact.

Conclusions

Delayed fracture runs in three stages that can be fixed while changing a certain property: electrical resistance, mechanical compliance etc. The first stage is incubation time, the stage of crack origination, the second – developing of stable crack, the third is rapid rupture. Delayed fracture testing is executed under different stages of applied load. The lower the value of applied load, the more time till damage. Herewith the durability of incubation time usually longer than the period of stable cracks developing, especially under great stress. Under low tensions the durability of nucleation and developing stages are comparable. Consequently for evaluating the reliability of pipeline operation in conditions of possible contact with corrosive medium the most important is determination of crack nucleation and developing resistance, not rapid as during impact tests, but slow. That is why the level of impact toughness does not reflect crack resistance in pipelines.

References

Karpenko G.V. Steel strength in corrosive medium/ Karpenko G.V.//Moscow: Mashgis, 1963, 183p.
Pochmyrs’kyy V.I. Corrosive-mechanical damage of welded constructions. /Pochmyrs’kyy V.I. , Melechov R.K.//Kyiv: Scientific thought, 1990, 347p.
Pochmyrs’kyy V.I. Corrosive metal fatigue./ Pochmyrs’kyy V.I. //Moscow: Metallurgy, 1985, 207p.
Kryzchanivs’kyy E.I. The influence of hydrogenization on corrosive-mechanical properties of pipeline welded seams/ Kryzchanivs’kyy E.I., Tarayevs'kyy O.S., Petryna D.Yur.//Exploration and development of oil and gas occurrences. – 2004. – No 3(12). – P.31-34.
Kryzchanivs’kyy E.I. Sensibility of main pipeline welded seam of 17G1S steel to carbonous brittleness. / Tsyrul’nik O.T., Kryzchanivs’kyy E.I.,Tarayevs'kyy O.S// Physical-chemical mechanics of materials. – 2004. - No6. – P. 111-114

Сoncepts of professional career of future engineers-metallurgists

Fri, 27 Dec 2013 11:04:25 +0200

Сoncepts of professional career of future engineers-metallurgists

The article reflects the results of investigation into actual concepts of professional career of future engineers-metallurgists. The aspect of concepts contents depending on the type of attitude towards professional careers is analyzed.

Marina Suryakova

Candidate of Psychological Scienses,

docent of pedagogics department of

National Metallurgical Academy of Ukraine

Importance of the problem

The study of peculiarities of career expectations of future engineers-metallurgists assumes the researches of their common view about professional life phenomenon, determination of its value and place in the person’s life, revelation the degree of career desirability and also the level of understanding of necessary conditions and possible difficulties in professional life realization. Essential understanding of future specialists, on our opinion, is the basis for their relation to professional career, which has formed in result of lifetime and professional experience accumulation at the stage of education.
The notion “professional career” means the realization of professional opportunity of a person and leads to subjective and objective success in professional career [3]. Professional career is understood as professional advancement, growth as the process of professionalization, the result of which come personal changes, leading to a high level of professionalism, achievement of occupational status and providing a feeling of satisfaction [5].
Career expectations appear to be the regulator of professional behavior and activity; they expose the peculiarities of objective reality reflection and allow to determine the degree of adequacy of this reflection, i.e. to determine the character of personal and objective interrelation. Career expectations are the emotional-evaluative attitude to a certain stage of professional activity development, which forms the professional position of a specialist, point him at the realization of professional aims, stimulates to person’s self-determination in professional activity [2,4].

Concepts of professional career reflect cognitive aspect of career expectations and contain the current knowledge of a specialist about personal qualities, professional background currently formed, knowing of the peculiarities of socioeconomic situation, working conditions of the profession, and forecast of successful intercommunication within the system of professional activity. Such concepts reflect the interrelation formedness level of the subject of professional activity with the labour object.

Formulation of a problem

Career expectationsof future engineers-metallurgists while choosing concrete place of employment are determined by some specific content connected with specific nature of their professional activity and professional education, complexity of modern socioeconomic conditions, peculiarities of engineering and manufacturing process [1].

That is why the concept of professional career of future engineers-metallurgists should be examined on time with the aim to clear many important moments, such as: if the future specialist aimed at realization of his career; if he distinguishes his professional career as the opportunity for self-development; if he realizes the aim of his professional career; if he is intended to plan its stages; what the subjective meaning and career success should be expressed in; to what extant the personal qualities, which could help in achievement of career objectives are realized, etc.
The aim of the article is to exposure the researches results of peculiarities of content and character of professional career concept in career expectations of future engineers-metallurgists. This study was undertaken among the metallurgical universities students, studying at different metallurgical specialties, that are kindred according to similarity of generalized structure of activity, specialty 0904 “Metallurgy”, the educational and qualification level is “bachelor”.

Research methodology

Future engineers-metallurgists concept of professional career, their content and attitude to various aspects of professional career was examined with the help of “Sentence fragment” methodology (author’s development) [6]. This methodology involves semiprojective questioning in the form of sentence fragments and includes 4 conceptual blocks (each contains 4 incomplete phrases), which show:

General meaning of the notion “career" (meaning - what?).
Subjective meaning (aim – what for?)
Implementers (conditions – how?)
Difficulties in realization (negative conditions - what prevents?)

The answers were analyzed with the help of content analysis. The peculiarities of attitude to professional career were determined through the definitions of “career”, “profession”, “work”, “individual career success”, “personal qualities of a specialist”, “difficulties in achieving the goals".
All the answers, basing on certain characteristics, may be combined in three types of attitude to professional career: positive-active, positive-medium, negative, which have their peculiar content. Analysis of the sentences content allows to study direct the concept of professional career, determining attitude to it that forms in common the peculiarities of career expectations of students under test.

Results of research

The content of students-metallurgists’ concept that reflects their positive-active attitude to professional career and also a number of notions, connected with it, is given in the table 1.

Table data in students-metallurgists’ utterances shows the presence of signs with positive meaning content concerning professional activity of a person, which correlates with their positive attitude to professional career.
Positive-active attitude to professional career develops through recognition the career as important, main and essential event in person’s life.
The notion “career” is understood by the students under test as a possibility to realize their own potential, achieve higher level of development, strengthen their professional and social position and obtain success.

Table 1 Content of the perceptions reflecting positive-active attitude to professional career (n=282)

No	Category of content analysis	Content of perceptations (positive-active attitude to career)
1	Career is an important place in one’s life.	lifestyle; it is very important; the main; is of great importance; meaning of life; play a critical role; important; must be successful; support; joy; power; the main; all; realization of potential; stability factor; determines the place in society.
2	Profession as an important lifeside.	to work successfully; to find a job; in order to be in-demand; in order to have a knack for doing something; in order to learn the world; in order to advance in job ladder; in order to build your own future; in order to work on a higher level; land a job under calling; get an appointment; in order to connect the life with it; to be happy;in order to find yourself in the life;in order to be keen in it; work and ejoy; to become the great names of history; assurance of the future; to carry out responsibilities qualitatively; the ability to charge myself with job; to build an interesting life; self-knowledge; to know profwssional details; to make the way; to find the place in life; to gain knowledge in certain field; to find the calling; in order to simplify working activity; to leave something after yourself; to increase the level of intelligence; clear future.
3	Work as the conditions for career realization.	activity, to which a person espouses completely; the way of realization and improvement; in order to make good career; favorite activity; self-improvement; way out to the world; freedom; career development; the second home; art; dignity; the way for discovering and realization of your abilities.
4	Career as self-realization and development.	personal success; prove something to yourself; in order it was interesting; in order to discover the best qulities; n order to realize yourself; in order to develop yourself; to grow in own eyes; in order to express yourself; realization of ambitions; to feel yourself in adventure; in order to learn something new; to be in demand and cultural people; in order to realize yourself; in order to develop yourself; self-affirmation; in order to imagine somebody on your place; an important factor of person's development.
5	Career as the possibility for achievement of high level of professionality.	to be specialist in your field; to be high-level specialist; getting an experience; commitment to excellence in your profession; improvement in profession; knowing of your profession; the work in which I keen; in order to a professional;the ability to work and enjoy; skill development.
6	Realization of a career in the own profession.	It is not easy, but possible; possible; it is good; to be the first in metallurgical industry; necessary; good income; duty; result of my efforts; certainly must be; great responsibility and big money; I want; it is possible by a long stretch of the imagination; learning of your profession; I hope it is possible; the way of self-expression; will build quickly ; essential; the benefit of my country; psychic income; constant training; it is real; not quick ; I steadied for a reason; to become a director of a plant; more duties and responsibility; position on the shop floor; rearrange me own manufacture; development of the branch; an appointment of chief engineer; steady future; achieving of advanced degree; result; quantity and qulity of a metal.
7	Career as high social status and acknowledgment.	respect of partners; respect of others; to be respected and well-heeled; to be successful and on the top; solidity; in order to hold necessary appointment; to become valued and respected; in order to realize yourself in society; popularity; to become manager of an enterprise.
8	Internality, self-belief, person’s active position.	depends on the person; refine yourself; the level of cvalification; believe in yourself; to be better than others; to deal with labour of love; one should love his work; one should live by labour; one should strive, work hard; accuracy; the with to work; make efforts to be noticed; one should strive; think out a plan; one should be strong; one shouldn’t keep his fingers crossed; love to the profession; one should be educated; hard work; dedication, with of the person; one should work hard; study; put the career to the foreground ; cultivate your own abilities; do not stop; live with your work; readiness to recommend yourself; activity ; initiative.
9	Necessity of knowledge and skills.	deep knowledges; to know your business perfectly; erudition; the ability to make decisions; well-bred speech; the ability to learn quickly; the ability to find solutions in difficult situations; engineer way of thinking; the quality of study at the university; to know people’s psychology.
10	Necessity of time for career building	a lor of time is required; work twenty-four seven; persistent striving for many years .
11	Inner (psychological) obstacles.	absence of wish; lack of self-trust; short of adequate; short of knowledge; incomprehension of your profession; short of experience; bad build-up; unorganizedness; incorrect profession; short of perseverance; short of skills; short of intellect; low self-attitude; uncertainty of the aim; weakness; age; feer of risk; absence of practical efficiency; absence of will power; failing to come over his defeat; indifference to the profession.
12	Necessity of positive personal qualities.	kindness; intellect; diligence; to be a good person; hard worker; honesty; leadership skills; self-confidence; optimism; strength; quickness; purposeful; communicativeness; dedication; honesty; judiciousness; insistence; endurance; devotion; attention; accuracy; the ability to persuade; diligence; responsibility; reliability; curiosity; managerial abilities; competence; organised nature; strength and will; commitment to principles; justice; pragmatism; business acumen; wisdom; strongheadedness; reliability; optimism ; trust to people; strength of mind; patience; appearance ; sound estimation; charisma; intuition; politeness; decency; inspiration; loyalty; vitality; ambition; facility ; accuracy; thrift; talent; creativity; beauty ; moderation; calm; reserve.
13	Personal readiness to career realization (responsibility).	Difficulties connected with yourself; failed to open completely; ready to strive; ready to persevere; one should sacrifice himself ; ready to hurdle barriers, work a lot; to do the best; ready to learn the profession meticulously; ready to improve myself; ready to refine myself, time, sleep, rest; ready to further studying; to practice; ready to risk; start from the beginning; ready to start with second fiddle; ready to failures; ready to everything except indignity; ready to low wages; ready to take the responsibilities; ready to except the difficulties; ready to work properly; to read a lot; ready to run at work mornings.
14	Positive metaphora.	stairs, steps, spiral stairs; ascension; climbing; climber atop; Everest; iceberg ; person’s growth , stages of person’s development; development of mankind; sense of life; competitions, olympiad, sport, marathon; rece; status, stage in the society; duet of striving and success; achieving of a goal; energy; hard working , hard work , business; pyramid; building; building of a house; a tree, flower production( what will take a root ); computer game (the higher the level, the better), a car by road; games of chance; bird; ascent; sea; river; flow of water; mountain and waterfall; zebra; zigzag; pair of scales; merry-go-round; future; dream; money and power ;success in prival life; fancy cake; good marks; victory and preference; reliability; freedom in life; independance; satisfaction; triumph; win in lotto, the second family, love, feeling; art; brthday ; favorite hobby ; elevator.
15	Negative qulities and other events that connot be combined with career.	carelessness; drunkenness, alcoholism, drugs; laziness, the absence of with to develop; wimpishness; lack of determination; absence of purpose; irresponsibleness; absence of human dignity; bad qulities; lack of discipline; meaninglessness; uncertainty; bumptiousness; lie, craft, dishonesty; stupidity; greediness; pessimism and fear; absence of aim; ignorance; pride; inactivity; indifference to life; irascibility; rebellion; inactivity; meanness; incompetence; despair; sloth; compassion; pride; bad reputation; unorganizedness; dislike of the profession; uncertainty; dishonesty; puerility; demonstrativeness; bad language, gossips; bad health, illness; entertainment; parties, rest.

Career in one’s profession is considered to be necessary, important, even if it is hard to achieve success; the due cognizance is devoted to time, which is necessary for career plans realization.
The notion “profession" is understood by these students as the main condition for getting a job, appointment, deepening of professional knowledge and acquisition of desired skills, developing of their intellectual qualities, professionality in their branch. The notion “work” is connected with obtained profession and career in the future; it is observed as the possibility for getting respect of others and retaining a dignity.
Among the means of career plans realization of future engineers-metallurgists in the group mentioned, professional knowledge, skills, positive personal qualities, readiness to overtake the responsibility for the actions, activity in professional career realization, readiness to make efforts and overcome difficulties predominate. Difficulties are understood first of all as inner, psychological obstacles, negative person’s features, and absence of dedication to the profession.
In figurative associations concerning the notion of “career” there dominate clichés connected with images of steps, building, competition, where one may observe dynamism, activity, person’s insistence. Substantial part of metaphors is devoted to the images of awards, prize - the final result of efforts. In common, metaphors containing images that are positive in character, allow to render their formation as factor of positive attitude to the professional career.
Content of perceptions reflecting positive – medium attitude of students-metallurgists to the professional career and also the range of notions connected with it, are given in the table 2.
The results obtained show that positive-medium attitude to professional career reflects its secondary place in person’s life, acknowledgment of career as unessential and unimportant. Career by this testing group is determined as preferable thing but not of high priority. Subjective meaning of professional career comes down to the possibility of material support and guarantee of well-being.
Please note that the absence of concretion in determination of common meaning of career, generality of believes about its place in person’s life do not contribute to formation of positive attitude to professional career.
The notion “work” is distinguished by students-metallurgists of this testing group as the means for person’s living, which do not have anything common with self-realization and revelation of professional facilities. Work is determined as necessity, duty, and the builder of family facilities, strengthening of personal establishment.

Table 2 Content of perceptions, reflecting positive-medium attitude to professional career (n=282)

№	Category of content-analysis	Content of perceptions (positive-medium attitude to professional career )
1	Career takes a minor place.	the second place after the famil; important, but not the main thing; not the most important; supplement to the happiness, one of the constituent of success; is not connected with me; of less importance; not necessary; I don’t need it; not for me; not the first place.
2	Work as means of living.	means of living; the ability to earn money; source of income; earnings; survival; duty; money only; one of the ways to earn money; method for providing a family.
3	Career for material support.	to live comfortably; to provide yourself; earn more, to be self-reliant; prosperity; big income; to have fair wage; to have more money; in order to earn money; desired economic status; in order to earn for living.
4	Career for well-being of the family.	worth living life of the family; to provide family; in order my family was proud of me; in order to provide capricious wife; to provide the children and family.
5	Absence of concretion in determination of career meaning.	basically it is possible; easier to live; to get something done; achieving of a goal; to live a fulfilled life; to do myself proud; it must be so; necessary; to prove to everybody.
6	The necessity to support others.	authority; friends; team; good colleagues; successful parents; tutor; wife; people’s trust; sound and loving family.
7	Happening, luck, success, connections.	connections; life circumstance; luck; money; connections; close acquaintance; high-powered acquaintance; miracle happens; correct time and place .
8	Unforeseen event	home front; obstacles; war; governmental action; social problems; misfortune; circumstance.
9	Negative external obstacles.	competition; misunderstanding of other people, dispute with authority; grudge; bad people; corruption; circumstances; sponsorship; clannishness; absence of finances; absence of well-paid work; unfairness; absence of work positions; dysnomy; partners’ treason; bad collective; absence of mutual help; absence of work position perspectives; privately owned.
10	Absence of concretion in concept of difficulties.	good-for-anything (almost anything) sacrifice anything (almost anything) sacrifice anything at all, many; so not sleep and eat; lots; myself; depending on the situation; in different ways; we will see.

Support of others by this testing group is determined as desired, career planning includes the help of high-powered friends and relatives, that is possibly connected with substantial degree of uncertainty in own abilities, absence of experience to solve tasks, arising in social environment, independently. Concepts of career plans realization feature externality, hope for success, happy occurrence, luck, which suppose decreasing of personal responsibility and explanation of misfortune by external forces.
Among the possible obstacles, which in future specialist's opinion may prevent to realize the professional career; there is an obstacle of social-economic character and also negative actions from other people and events in collective that stop specialist’s development.
According to the concretion factor in concepts of students-metallurgists of the mentioned group concerning the possible obstacles and difficulties on the way of professional advancement, there is a low level of it that does not contribute to authenticity and reality of perceptions.
Negative attitude of future engineers- metallurgists to professional career and also the range of notions connected with it, reflects the content of their perceptions shown in the table 3. In perceptions reflecting the negative attitude to professional career, the notion “career” is determined as an event, which is undesired and even harmful in people's live, accompanied with hard work and is of doubtful value. Such understanding of the career may explain its value as people’s ascendant, superiority over them. Acknowledgment of career as rigid event for people allows to determine its assignment for action on other people.
In favor of such explanation of the notion of “career” within understanding of students of this group are the results of content-analysis, containing the concept of impossibility to join career with family, friends, and private live. These notions are positive, they do not have anything common with the notion causing negative feelings that form negative attitude of these students-metallurgists to professional career.

Table3 Content of concepts reflecting the negative attitude to professional career (n=282)

No	Category of content-analysis	Content of concepts (negative attitude to professional career )
1	Career as adverse experience	takes a lot of time and efforts; boring growth along the career ladder.
2	Work as annoying necessity	work as hard labor in exile; hard and churlish; routine; desperate measure; dawdle; hard awakening; necessity; burden; boredom; heel in existence; indifferent for person; tiredness; laziness; dull occupation; income without satisfaction; erase from one’s life a lot of time; burden for pocket change; heavy load; serfdom; rough monotony; load; boring routine; burden; unpleasant moment; imminence; pangs; confinement.
3	Career as power over the outer world, superiority over them.	they want to find themselves superior alle the people; power over the outer world; to manage people; to be better then others; to be cleverer then others; to castigate others; to manage.
4	Negation of the opportunity to have career in profession.	is be achieved long and hard ; unreal within my profession; impossible; sustained effort; doen not attract; difficult; my profession is slavery, almost impossible; hardly it will be successful; breaks no squares; dirt and sweat; very long; I am not planning; there is no career in my profession; does not interesting; spent life; only for experience; non-perspective; negligeable success rate; you should forget about that.
5	Necessity of negative personal qualities.	slyness, dexterity, to do the elbow work; to destroy others; to flannel; impudence; to go bald-headed; rigidity; to be impudent; outgun everybody; adulation; cynicism; to able to overstep personal principles; to be able to flatter; cruelty.
6	Impossibility to combine career, family, friends and private life.	is not compatible with family life; with life; with personal life; personal time; with sport; love; silence; good mood; friendship; time with family; big family; birth and breeding the child; comfort; friendship.
7	Negative metaphor.	beam; rat races; aquarium with sharks, struggle for existence; monkey plays with document; revolver; heap of iron ore materials (where there is more heavy pieces on the bottom); hen house; hard life.

The negative attitude to career of students under test is also shown in data, where mentioned negative personal qualities among necessary for career realization ones. Probably in perceptions of these students the negative feature is presented by career, which renders such qualities. Students’ metaphorical associations of this group confirm negative evaluation of career: images given in metaphors are of aggressive cruel and even derogatory character.
The negative attitude to professional career is characterized by negation of opportunity to build career in own profession, determination of it as to be out of interest, non-perspective or too hard and boring.

Conclusions

Study of actual concepts of future engineers-metallurgists underling in attitude to professional career allowed to mark the following peculiarities:

- In concepts of overwhelming majority of students under test the notion “career” is confessed as the value that takes an important place in person’s life. The notion “profession” is determined as opportunity for self-realization and self-determination. The notion “work” is understood as opportunity to to realize the professional career. In common students - metallurgists determine career as, first of all, as the means for improving of financial situation ad the possibility for self-realization and development of professional. With that determination of value and meaning of career personally for everybody is rather assure in nature, but under students – metallurgists’ estimation, there is a difficulty in building career in own profession.
- In concepts of students-metallurgists there marked high level of understanding the means for career realization, conditions under which it is possible to build it, acknowledgment of personal qualities as the main and shaping factors in career realization, activity and responsibility of own actions. Concerning some anticipate difficulties in career plans realization there observed a very generalized representation of students under test, absence of reality in combination career with other parts of human's life, concretion in concepts of efforts, which may be necessary in career realization, uncertainty in own abilities to control and manage the realization of professional career.
- Prevailing type of attitude to professional career of future engineers-metallurgists is positive-active one.
So, the research results of actual concepts of professional career and career expectations of future engineers-metallurgists reflect the degree of readiness of young people to accept adequate decisions connected with employment, planning and realization of professional career and also the degree of reality, understanding the aim of professional career, means of it achievement.
The results obtained may be applied while educational activity with students, aimed to formation of professional position and due care toward professional activity.

References

Higher education industry standard of Ukraine. Course description of bachelor of profession 0904 “Metallurgy”. - Kyiv, 2004.
Lomov B.F. Methodological and conceptual problems of psychology – Moscow: Publishing house “Science”, 1984. – 444p.
Mall E.G. Control of manager career. – Petersburg, 2003. - 352p.
Myasischev V.N. Psychology of relations: under the editorship of A.A. Bodalev - Moscow: Voronezh: SPA “MODEK”, 1995. - 356p.
Pochebut L.G. Chiker V.A. Organizational social psychology: work-book. – Publishing house “Rech”, 2002.-298 p.
Working technologies of organizational psychists: Work book for students of universities and student of postgraduate education universities / under the editorship of L.M. Karamushki. – Kyiv: “Inkos”, 2005. P. 122-123.

Career expectations as the basis of future engineers-metallurgists professional identity

Fri, 27 Dec 2013 10:11:43 +0200

Career expectations as the basis of future engineers-metallurgists professional identity

Marina Suryakova

Candidate of Psychological Scienses,

docent of pedagogics department of

National Metallurgical Academy of Ukraine

Complication of social and economic working conditions for modern specialists of any branch requires the skill to analyse these conditions, explore options of professional career development, plan its stages, compare professional requirements and real abilities, the skill to set objectives and determine the ways of career achievement. Professional self-realization of specialist is achieved within professional career, where the first becomes possible under conditions of effective career progression.
Today career in science and society is understood as the way for realization of professional potential, building of career is observed as dynamical characteristic of process leading a person to success in his professional branch.
Recently in psychology there increases an interest to studying of different aspects of career (A.G. Mall, A.N. Tolstaya, M.V. Saphonova, V.A. Chiker, E.Schein , D.Super , D. Hall and others), which is determined as extra-preferable professional event in person’s life, where his professionalism forms, occupational status is acquired, feelings of satisfaction and confidence are provided.
Such understanding of career is observed among the large amount of modern youth and determines their attitude to this event as to something positive, valuable and expectative in one’s professional future. That is why before employment at the end of study the future specialist has some vision of the future professional way that is objectified in their career expectations. Career expectations play substantial part in professional self-determination because on their base the professional behavior and activity form.
Career expectations (works of A.N. Ivanova, V.A. Tolochek, A.G. Mall, V.I. Solobotchikov, N.A. Isaeva, D.A. Leont'eva, A.M. Shevelev and others) may be determined as subjective perceptions of future specialist concerning optimized advancement in professional sphere, which provides personal and professional self-realization, which is based on practical and emotive-notional experience and gives to professional activity stable and designed character.
Still, it should be marked the range of essential problems connected with the presence of this psychological event in professional consciousness of future specialist and also to reveal the specific problems concerning career expectations in professional self-determination of future engineers-metallurgists.
In professional self-determination the main value has the activity of a person, his responsibility for socialization and professionalization, the scheme of professional development is the base for subjective living satisfaction. Success, effectiveness of professional determination in common and also circumspect, considered choice of employment after graduating the university, on our opinion, determine the grade of reality (adequacy, authenticity) of future specialists career expectations. While choosing the place of employment there is a lack of reality, built under influence of some factors, in career expectations of modern graduates, according to the mind of certain authors (D.A. Leont’ev, N.V. Kopylov, A.V. Moskalenko, L. Mitina). First of all psychological (the level of personal enhancement, professional training experience), social (for example stereotypes of professional evaluating by society, its status value, significance, etc) and also economical ( the level of wages, production and technical conditions, etc).
The reality of perseptions conditions the adequacy of specialist’s professional education according to the modern social-economic requirements that is why it should be formed at university. Career expectations of future engineers-metallurgists at the moment of employment are determined by specific content connected with peculiarities of their professional activity and education. Psychological analysis of engineers-metallurgists professional activity determines complex analytical, structural, organizational and calculation activity of specialist in the field of real metallurgical production to which he should be prepared with the help of theory and practice during study.
However, nowadays there appeared problematic situation connected with the realization of curricular practical training for metallurgists at the metallurgical companies, which were removed from government property. These companies do not show interest in providing the place for practice, that is why the practice is of fragmentary and reduced character. This fact does not contribute to the reality of expectations concerning professional activity of metallurgist. From the other hand companies show low activity according to employment of graduates because of insufficient quality grade of professional education and other reasons [1,5]. Besides, in modern society there exists certain opinion on professional activity of engineer-metallurgist as non-prestigious, with hard working conditions and with low salary work.
Under such conditions during employment future engineer-metallurgist undergoes difficulties connected with his professional self-determination, that is felt on personal, field and social level. Nevertheless, the choice of workplace should be fulfilled in metallurgical branch and career expectations of future engineers-metallurgists should be connected with profession acquired during study.
That is why career expectations of future engineer-metallurgist should be examined in time with the aim to clear all the important moments: to what degree future specialist considers social-economic working conditions; if he considers professional career as the possibility for development; if he realizes the aim of professional career; if he intended to plan its stages; in many thing the subjective meaning and success of career should be expressed; how conscious professionally important features; if he considers learning stage as the base for his career.
The study of concepts of future specialists’ abilities realization should also contribute to determination of the aim, means for its achievement, personal meaning of professional activity, planning of personal professional program on the base of concretion and reality. It is obvious that solution of these tasks may be useful both for future specialist, his professional establishment at the beginning of career and for any economic branch.
Career expectations should also be analyzed because such work provides for future specialists understanding of direct connection between study at university and further stage of professional realization. In scientifical literature period of studies is determined as the period before career – “prior” stage, when educational-professional activity and primary choice of professional career takes place [2,4].
It is obvious that such understanding of place and role of educational stage in individual professional career contributes to increasing the level of responsibility for own professional education to date and more detailed planning of future professional way.
Professional education at universities should provide success in further professional realization of a specialist and be the reason of his competitive ability and occupational mobility on the labor-market in modern social-economic conditions. Effectiveness of professional education of future specialists on the learning stage, on our opinion, depends on solution of such tasks: formation of real precipitations about chosen professional activity, understanding of professional development alternatives, study of own personal characteristics, understanding of connection between personal and professional development, modeling of own professional career etc.
Leading to realization of these important tasks to students may be possible with the help of special hands-on training, hands-on classes focused on determination of higher education subjective meaning, the ability to analyze essential working conditions, to plan own professional way and way of living, state desired results of development in professional sphere.

References

Industry in education// Metal. – 2005.No7, p.34-48.
Leont’ev D.A. Shelobanova E.V. Professional self-determination as building of images of possible future// Questions of psychology. – 2001. – No6.
Mitina L.M. Psychology of competitive person. – Moscow: Moscow psychology-social institute, 2002.
Phonarev A.R. Forms of achievement of personhood in the process of his professionalization// Questions of psychology. – 1997. – No2.
Chernega D.F. Organization of learning process and practice for students of metallurgical specialties// Metal and casting of Ukraine. – 2006. – No1, p. 15-18.

Refined mathematical model of vibroactivity of tube screw-rolling mill mandrel bar

Wed, 15 Jan 2014 11:14:23 +0200

The task concerning vibroactivity for refined dynamic model of mandrel bar acoustic positioning system of screw-rolling mill is solved. Difference equations of oscillatory motion are made and mathematical model of mandrel bar with account for cooperation with rolled pipe is refined. Analysis of vibroactivity and other dynamic processes in mechanical system of screw-rolling mill is carried out.

Key words: dynamic, vibroactivity, core, bloom, mass, stiffness, mandrel, oscillations, centering unit, variation in wall thickness, pipe.

Suleiman Rakhmanov

National metallurgical academy of Ukraine,

theoretical mechanics department.

LLC "VOSTOK PLUS"

Refined mathematical model of vibroactivity of tube screw-rolling mill mandrel bar

While piercing of hollow billet the mandrel bar and rolled bloom on the axis of rolling are functionally hold by the complex of special supporting mechanisms called centering unit. On delivery ends of piercing mills of pipe-rolling plant alongside centering unit base and auxiliary operations are fulfilled, including: holding of fast-rotating, large and long mandrel bar along the geometrical axis of rolling; centering of piercing bloom that while rolling which has complex screw motion and vast inertial properties; delivery of rolled blooms from one mill to another ones [1]. For stable configuration of rolled pipes formation oscillations of rotating mandrel bar are of practical importance. For realization of necessary and stable technological operations of hollow billet piercing at the delivery end of piercing mills numerous guides, centering units, supporting and adjusting gears are used. Rotating long mandrel bar takes critical deadweight and changing in time dynamic loads from the piercing hollow billet. Because the mandrel bar is more flexible and inertial it causes in considered mechanical system critical in length and changing in time dynamic loads, which provide its bend along the piercing axis on sinusoidal forms. As a result of uncontrolled wide oscillations the core along with mandrel moves in deformation zone along rolling axis (centering holder parallel goes off from overclamping of working rolls), causing variation in pipe wall thickness. It is obvious that dynamic phenomena arising in mandrel bar influences negatively on the history of hollow billet piercing that is reflected on bloom configuration and the quality of pipes. The ways of technological process intensification and upgrade points of rolled pipes dictate the necessary conditions for improving the design of mandrel bar centering unit, located along processing line and properly to delivery ends of screw-rolling mills. The influence of different characteristics and technological peculiarities of pipe rolling on behavior of the system and quality of the finished product should be deeply studied in order to set scientifically based offers concerning the improvement of design of mandrel bar centering unit of piercing mills and pipe production technique. Solution of this task often determines refinement of design model and development of mathematical model of experimental TPA piercing mill which reflects sufficiently real processes taking place in the initial mechanical system. In this work as subject of research the developed dynamic and mathematical models of holding device frame structure of TPA piercer plug are considered which differs from already known [1,2] in characteristics of moving updated centering units. Change of degree of impact, mass of hollow billet and dynamic parameters of mandrel centering unit, traveling while piercing along the rolling axis, complicates considerably the description of dynamic processes.

а) b)
Figure 1 Developed generalized dynamic model a) and construction of fixed non-updated moving enclosed centering unit b) of TPA piercer plug holding device (designed by OJSC “EZTM”)

Research of developed dynamic model “framed structure – hollow billet” will allow to analyze dynamic behavior of framed structure with mandrel within all the process of hollow billet piercing and, based on the above, to solve the task concerning upgrading of mill centering units (figure 2).

Figure 2 Design model of framed structure of piercer plug holding device

Let us assume the design model of framed structure of screw-rolling mill as hollow core of uniform section with hinged bearings on the ends and moving elastic supports (centering units) between them. The core rotating with angular rate around rolling axis , is subjected to the force of piercing from the side of deformation zone. Herewith along the core with semi-constant rate of piercing (uniformly) distributed load of rolled bloom with intensity and mass per unit length moves and rotates along with the core.
For building the refined system mathematical model and evaluating of dynamic condition of the core with mandrel and processes of hollow billet piercing let us use difference equation of oscillations of rotating uniform core on the elastic foundation of centering units [3,4].
(1)
where EI, m - bending stiffness of the core and its mass per unit length respectively; uz – movings along z axis; c,k – coefficients of elastic foundation of centering units which depend on moving and speed respectively; coefficient reflecting viscous friction within the system while oscillation of mandrel bar; – eccentricities specifying the mass unbalance of mandrel bar round the axis of rolling. Under the assumption of the fact that internal friction within the system is miserable as compared with technological and dynamic loads, and mass unbalance of mechanical system belongs to one subspace according to [3,5], we may have the simple difference equation
(2)
where is angular velocity of rotation of mandrel bar round rolling axis. Let us substitute the elastic foundation of mandrel bar with finite number of yielding supports of movable centering units. Then the difference equation (2) is expressed as the following
, (3)
where is Dirac delta function; design positions of supporting nodes of centering units along the axis of mandrel bar; is the moving velocity of corresponding centering units of mandrel bar along the rolling pipe axis.
Taking into account that Dirac function has the following typical filter property, according to [5]
,
in respect with changing of longitudinal compression force (piercing strain), according to [2] and to the law and impending bloom strain with intensity and elastic supports (movable centering units) the difference equation will be as following

(4)

where is the degree of impact of piercing hollow billet on the mandrel bar which is of certain degree of heaviness and which may be found in accordance with [2,4] as following

. (5)

Here, are the intensity and mass per unit length of rolled bloom respectively; is traveling speed (piercing) of a bloom along the mandrel bar; relative acceleration of a bloom; translational acceleration of a bloom; Coriolis acceleration of rolled bloom. In respect with typical shape of bent flexible bar while piercing of a bloom in a first approximation let us assume eccentricity equation of its axis towards the axis of piercing in sinusoidal form

. (6)

For solution of the equation (4) let us use the well-known scheme of Bubnov- Galerkin

. (7)

Herein, for Bubnov- Galerkin scheme, according to [2,3], functional of difference equation (4) in respect with (5) and (6) will be expressed as

(8)

Inserting (8) into (7), in respect with natural mode shape orthogonality of mechanical system, after integrating and rearranging we will have the best possible difference equation of representation point movement on the axis of mandrel bar

(9)

Dynamic of simulated bar system in respect with different modes of rolled pipes on the TPA 140 piercing mill is represented with numerous solutions of difference equation (9) in accordance with Runge-Koht method. Derived curves, which are given on the figure 3, denote extremely unsatisfactory conditions for operation of delivery end devices of piercing mill. While realization of technological process there occurs formation of increased variations in wall thickness of blooms that in the following may be of congenital and hard to remove character.

Figure 3 Dynamic of holding motion core of TPA 140 piercing mill mandrel ( bar of 130 mm in diameter, material – steel 20)

With the help of mathematic modeling the influence of different characteristics of mandrel bar holding device and technological peculiarities of pipe manufacturing process on the behavior of developed dynamic model of mechanical system was established. Herein certain principal measures on updating of equipment, adoption of reasonable hollow billet piercing modes are developed and some suggestions on updating of pipes manufacturing processes, for example using TPA 140 piercing mill, are offered.

а) b)
Figure 4 Holding device of TPA piercing mill mandrel bar with moving centering units a) and updated centering unit of mandrel bar of TPA140 piercing mill b)

Analysis and design of complex mechanical system vibroactivity is executed by step-by-step modeling of dynamic processes that allows to abandon from expensive and complex experimental investigations of TPA mills. Analysis of refined and developed mathematical model of piercing mill mechanical system and further design of results obtained defines the influence of piercing velocity, relativities of system mass, piercing strain, degree of impact of rolled bloom, rate speed of the core and stiffness of moving supporting mechanisms (centering units) on vibroactivity of bar system mechanism of mandrel holder. Results of system vibroactivity calculations denote high instability of dynamic, susceptibility of dynamic model to changes of dynamic parameters of mechanical system and technological processes. It is obvious that vibroactivity of bar system while realization of necessary technological piercing processes goes to mandrel located in overclamping of deformation zone, that leads to distortion of deformation zone shape and degeneration of quality of piercing blooms (tubes). Realization of stable manufacturing processes of piercing is provided by choice of reasonable characteristics of system dynamic model and best performance of mills on the appropriate projecting phases and system operation. Peculiarities of TPA 140 piercing mill operation denote the necessity of updated moving centering unit’s system usage. For reduction of vibroactivity of core holding device of a mandrel the delivery end of TPA piercing mill (figure 4) should be updated, the chain of moving automatically installed centering units with longish body of centering roller should be placed along the rolling axis (developed construction of OJSC “EZTM”, Russia) [1,6].

Conclusions

Solution of a problem concerning vibroactivity for developed dynamic model of mandrel holding device of screw-rolling mill is given. Refined mathematical model for core holding device of a mandrel and dynamic model of mechanical system in respect with characteristics of supporting mechanisms of moving centering units of a mill delivery ends is made.
With the help of mathematical model of vibroactivity of mandrel holding device the best regimes of hollow billet piercing in respect with forecasting quality index of produced pipes and specifications of allowable vibroactivity of mill mandrel bar are determined.
Updating of TPA piercing mill delivery end with further installation along the piercing axis series of moving automatically installed centering units with longish body of centering rollers (l=900 – 1100mm) is suggested.

References

Potapov I.N. New technology of screw rolling. / Potapov I.N., Poluchin P.I. // - Moscow: Metallurgy, 1975. – 344 p.
Rachmanov S.R. Dynamic of bar system of mandrel holding device of a piercing mill of pipe-rolling plant. Materials of international conference “Current trends in manufacturing of welded and seamless pipes from ferrous and non-ferrous metals”, Dnipropetrovsk. – 2007. P. 45-51.
Vibrations in technology. Reference book in 6 volumes. Volume 3 / under the editorship of F.M. Dimenberg, K.S. Kolesnikov. – Moscow: Machine building, 1980. – 544p.
Kuchma T.K., Morgaevskii A.B. Plating design on movable loads. Works VII Conference on the theory of plate and shell. – Moscow: Science, 1970. P. 346-350.
Novitskii V.V. Delta-function and its usage in structural analysis. Calculation of space structures. Issue VIII / under the editorship of A.A. Umanskii. – Moscow, 1962
Danchenko V.N. Technology of pipe manufacturing. Workbook for universities. / V.N. Danchenko, A.P. Kolikov, B.A. Romantsev, S.V. Samusev //. – Moscow : Engineering, 2002. – 640 p.

Free time self-organization of competitive personality

Thu, 23 Jan 2014 11:29:17 +0200

Free time self-organization of competitive personality

The article covers the results of the particular correlation of aspects of time perception, attitude to it, individual psychological aspects of personality and the content of free time, and methods of its organization.

Keywords: time self-organization, free time, time perception, choosing of free time content, ways of free time organization.

Marina Suryakova

Candidate of Psychological Scienses,

docent of pedagogics department of

National Metallurgical Academy of Ukraine

Competitive environment requires from a person observation of strict time organization in life, because only under this condition a person is able to achieve certain results in professional area. Competitive ability of a personality is directly connected with skills to organize life time – professional and private. High level of development of self-organizational skills allows a person to use his own abilities more effective and to determine the place in competitive environment.
Skills and abilities to organize independently in time his own actions form gradually within childhood, youth and in the beginning of adulthood and acquire established features. Special attention from the point of skills and abilities development of a person concerning organization of own life is worth the stage of professional training. Foundation of future success in profession and life lays on this stage.
Peculiarities of time self-organization of a person are demonstrated in organization and content of free time when a person should independently chose his own actions and plan them in time. Peculiarities of organization of free time of a person, his general attitude to lifetime is the unique attribute of aptitude to achieve the aim purposefully. The task to determine and realize the peculiarities of own skills concerning self-organization of life time is of great importance for a personality, and in case of revelation of their low level, to implement corresponding correctional actions that should promote competitive ability of a person.
The problem of person attitude to time is developed in psychology for a long time. Discussion of psychological problem of time speak for its baffling complexity, insufficient level of its development, uncertainty, ambiguousness of used while its study notions. Along with this, requests of theory and practice require development of this problem.
Acting in the variety of its aspects, the problem of time was studied in researches of home and foreign philosophers and psychologists ( E. Husserl, A. Bergson, M. Heidegger, P. Fress, Sch. Bühler, J. Nuttin, L. Frank, D.G. El’kin, S.L. Rubinstein, R.A. Al’bukhanova – Slavskaya, B.G. Anan’ev, A.K. Bolotova, Yur. K. Strelkov, B.I. Tsukanov and others). Along with this, there is no common approach in psychological literature to understanding the specific nature of mental reflection of time and attitude to it as to one of the aspects of its perception.
Reflection of time is studied sufficiently on psychophysiological and physiological levels. Psychological and personal levels are still understudied. In particular there is no notion in psychological literature of such subjective perception of time as attitude to free time. Still, there is understudied question concerning individual and psychological determinants of time perception and its organization.
While study of time problems in life one should mark the works of such scientists as S.L. Rubinstein, B.G. Anan’ev, R.A. Al’bukhanova – Slavskaya, V. Sch. Sovalev, A.A. Kronik, E.I. Golovakha, L. Yur. Kublitskine, V.F. Serenkova, O.B. Orlov, V.E. Chudnovskii and others. Problems of subjective time, peculiarities and dependences of time perception on individual peculiarities were developed by such authors as B.I. Tsukanov, V.N. Lysenkova, N.V. Ogorodnikova and others. Dependence from activity content was studied by S. G. Gellerstein, D.G. El’kin, S.M. Gareev, T.N. Osipova, N.I. Moiseevs, N.I. Karaulova, the influence of emotional peculiarities on time perception - D.G. El’kin, N. Marin, A.S. Dmitriev, V.I. Lebedev; type of activity – E.M. Gareev, L.M. Korobeinikova, mental strain – E.V. Frishman, study of role of influence in one’s activity structure and its place in personality structure was studied by A.K. Bolotova.
Talking about time orientation or time perspective, scientists distinguish some aspects connected with time perception.
First, it is the level of time perception. This notion reflects subjective perception of time, its individual representation to a person. One pole expresses person perception of speed of time flowing, solicitude of its running, the feeling of time insufficiency (syndrome “time is money”). At the opposite pole there is extremely “slow” attitude to time, indifference to its flow, irresponsibleness concerning time content (syndrome “sleep on”).
Second, depth of time perception. This refers to what time a person determines as significant and important: immediate, nearest future, future or past time. Most commonly nearest future, sometimes far time are important. But short term and long term perspective may be determined apart direction of gaze, either frontwards or back in the past. The most short term orientation in time is determined as “presenteeism” or “immediate”.
Third, commitment to the future or past. Person’s perception of real time depends on if he sees in present time the “tool” for building the future, or takes it as a result of prior life stage. In this connection we are able to determine retrospective and promising orientations.
Fourthly, interpretation of the future. Future may be perceived by a person passively as the phenomena to which one should only submit and it requires active planning from a person. Such susception means agreement and adaptation, active – means planning and building. So, we may say passive is fatalistic perception and active is voluntaristic perception of the future.
These aspects are very important for scientifically correct understanding of time concept.
Special attention in the problem “human-time” is given to a problem of person’s free time, its perception, organization and attitude to it. In philosophy free time is considered as field for unique social processes fulfillment. Revelation of source of free time origin and its connection with working time, its social value becomes the subject of research in philosophy. Sociology and economy analyze these processes quantitatively and statically, explore features and content of person’s free time, activity of social institutions of leisure with its filling and axiology of leisure. Psychology pays attention on needs and grounds, which determine human’s behavior in temporary area. Taken together the data of these two sciences we may say that free time is predominant area, where physical development and intellectual development take place.
Nowadays a person does not have the right for inactivity, he has to and is able to become active in his own self improvement, creative work, activity. Active position of a person, the possibility of his development, self improvement, and presentation of the individual self in external reality opens new aspects in studying of free time. Free and balanced growth of a personality is not only social ideal but also the most important condition for development of society directed to universal humanistic and democratic values. Theoretical understanding of this process is one of the fundamental problems of modern social science. Significant trend in solution of this problem is fundamental study of free time, its role and place in formation of the individuality.
Free time acquires great importance in the process of person’s development and it is characterized with variability and increasing of the variety of offers. Free time is a time available, judging from person’s interests and needs, according to his ideals, living position and faith. This is the area of being where people are free as nowhere else; here there is a possibility to display negative or positive latitude (E. Fromm, R. Harry). This the area of choice that is mostly free from regulations. Free time is peculiar only to a human as a result of his ability to make choice, structure his existence independently, abilities for self improvement and self development (A. Maslow, C. Rogers and others).
In social world with high level of regulations a person receives one of the possibilities to make good the deficit of freedom with the help of free time area, where personal realization is possible. Right during free time a person is able to organize own existential area (he has right for it).
Research problem of free time becomes especially updated because of the following reasons. In the process of socioeconomic and culture-historical development of society bigger time volume is devoted to leisure time, mass of people increases, involved in the problem of free time organization both as customers and as organizing staff, the variety of ways of time spending broadens.
All of this causes increment of variability of possible solution of the problem concerning content and organization of leisure time and complication of own choice effectiveness.
Free time is one of the existential areas of a personality where he receives circumstantial opportunity (as compared with time, study, work) of realization his aspiration to self-actualization by demonstration of subjective position in choice of content and forms of activity. Feeling of freedom is the criteria of belonging certain type of activity to free time. Leisure time content may be conditioned by many factors, for example:
1. Personality's orientation is the system of impulses determining selectivity of relations and person’s activity. Main forms of personality orientation are such interests as electorial attitude of a person to the object by virtue of its meaning and emotional attractiveness; interests on the base of needs felt as necessity in certain life and development conditions and inducing a person to activity; worldview; ideals; beliefs, psychological patterns; intentions; vital aims.
2. Habits are regular actions, which become routine for a person by virtue of their constant repetition.
3. Skills as individual peculiarities of a person, which are the subjective conditions of successful fulfillment of certain activity. Skills do not come down to existing knowledge, and person’s know-how. They reveal in quickness, depth and strength of methods and technique of certain activity acquirement and act as mental regulators stipulating the possibility of their acquirement.
Special attention is given to the problem of study of time perception, choice of free time content in connection with personal characteristics and skills concerting leisure time organization of students. The main characteristics of psychological connection between a personality and his life time are created on the emerging adulthood stage.
That is why we undertook this study with the aim to examine peculiarities of vision of young people concerning time, content of free time and its organization in connection with communicative and organizational peculiarities of a personality. Fundamental hypothesis of the study became the supposal that peculiarities of vision of time, attitude to it and also individual- psychological makers of a person determine free time content and the way of its organization.
Revelation of peculiarities of time imagery, attitude to it, peculiarities of content and determination of the level of skills to organize free time is fulfilled with the help of authors questionnaire. Individual-psychological makers of students under test were determined under the methodology of R. Cattell 16-factor personality questionnaire (subtest of communicative properties and peculiarities of interpersonal interaction) and under C. Jung methodology, which allows to reveal typological personality characteristics.
In the research participated 60 persons, 33 female, 27 male in the age of 19-21. They are students of different specialties of the city of Dnepropetrovsk.
Generalization of answers concerning questionnaire defined four groups of attitude to time.

1 Necessary account of time attitude.

For this group of students (10%) time account is hard, they cannot confine fixed time, distribute certain actions in time. They feel strains if there is forced lack of time, but do not try to prevent it. While asking what time looks like, under their opinion, they distinguish “imminence”, “boring thing”; they consider time to be “great grief”, “illusion”, time is necessary for “killing time”, “consideration of performed deeds”, “correction of mistakes”. Negative emotional overtone of metaphorical comparisons reflects due attitude to time. It is obvious that time is determined as past, action in present time seems not to be foreseen, there observed avoidance of this subject. Connection of self and time is determined as “incompatibles”, “parallels” which maintain resistance to students under study in accounting and apportioning one's time.

2 Contemplative attitude to time.

The second group of students determined time with such metaphors as “sandglass”, “air”, and “river”. In answers there underlined calm and unhasting time perception. Herewith the students of this group do not show aspiration to use time more actively, they confirm that time is necessary only for “rest and sleep”. In visions of this group, person and time exist independently and the only thing that person can do is just observe the march of time.

3 Active attitude to time.

The third group of students (32%) determined time as “water waves”, “mountain river”, “quick engine”, “bird”, “life”. Such comparisons reflect concepts of time as dynamic, fleeting phenomena, such that is important to consider and use it in own interests: for “meeting the needs”, “life worth living”, “determination of your own in life”, “self-realization”, “consummation of work”. Time is determined as surely essential and valuable phenomena; one accepts the necessity of productive time usage. For this group of students time is inseparable from their own, person and time are determined as “stream and ship”, “one unit”, partnership relations with time are emphasized on.

4 Pragmatic attitude to time.

The fourth group (31%) determines time as an instrument with the help of which a person can achieve his aims. Time is compared with “race track”, “constant motion forward”, “precipitate movement”, “adrenalin” .Time in this group is perceived as “for me” and is determined as “first string”, “endless possibilities for self-realization”, “the opportunity to leave imprint”. There is the fact that time is impossible to be back, that time may be not enough. Generally time and person are determined as “inseparable, created for each other”.
The next task of research was to study the content of free time of students under study. Basic occupations, chosen by students independently in time free from study or work, are revealed. In Table 1 one may observe the data of research concerning content of free time.

Table 1 Occupation chosen by students in free time (n=60).

No	Content	Amount (%)
1	Internet	20.0
2	Communication with friends	19.0
3	Meeting with boyfriend/girlfriend	13.0
4	Watching films	8.3
5	Physical activity	7.2
6	Reading of belles-lettres	6.2
7	Communication in family	6.2
8	Walking	5.0
9	Domestic activity	3.4
10	Public activity	3.4
11	Creative activity	3.4
12	Study of foreign language	2.7
13	Play on the computer	2.2

All the revealed occupations, making free time of the students under test may be grouped in content: entertainment (Internet, communication in virtual environment and time-wasting, computer games, watching films, walks) make 35.5%; communication in reality ( with friends, meeting with boyfriend/girlfriend, relatives) makes 38.2% ;self-development (physical activity, reading belles-lettres, domestic activity, public activity, creative activity, study of foreign languages) makes 26.3%.
The results obtained show that in most cases young people tend to chose communication in reality and entertainment when they have free time, in a less degree to give time for self-development (searching of extra-information, reading of scientific and business literature, attendance of trainings, seminars and other) revealed the following: 63% of students under test spend less than two hours, 30% - 3-4 hours, 6.7% said that do not give time for self-development.
Organization of free time is impossible without perception of necessity of knowledge clear distribution and adequate control of time. That is why the research of the part of time unequivocal use and part of spending time by young people are of great importance. So the analysis of data obtained revealed definite difference in the usage of time relating to time spent in Internet (Table2).

Table 2 Aimless Internet penetration while having free time (n=60)

Amount of time	Students (%)
Less that 2 hours	38
3–4 hours	16
5–6 hours	6.6
More than 7 hours	4.9
Do not use it aimless	34.5

The data shows that the overwhelming majority of the students under test (66%) supposes dissipation of time in varying degrees, only the third part (34.5%) shows that it does not use Internet aimless. On the question if any of them use Internet conditionally, contrary to unsolved tasks, 70% answered in the affirmative (20% of them – “often”) and only 30% denied that. There is spontaneous wasting of time, which is typical for most of the test students. It becomes conscious fact only after realization of appropriate actions. Such impulsive, aimless usage of leisure time shows insufficient level of its control and absence of advanced planning.
The time devoted to art should not be left unnoticed: 60% of students say they do not find time for art, 32% - find less that an hour per day.
22 % of students (at the age of 19-21) do not find time for physical activity.
One of the most important tasks of this research became the study of the level of students’ organizational skills, for example the ability to time according to the degree of task importance. The results obtained showed low, middle and high level of such skills formedness. 31% of students have high level of skills to structure free time, 53% - middle level, 16% - low level. Such data indicates the necessity of development of youth's organizational skills.
Some inconsistencies concerning planning i.e. set objectives, aims, determine means and conditions for their achievement were determined. On the one hand 63% of students under test plan their activity beforehand, 37% plan their activity sometimes. On the other hand high level of development of leisure time planning was discovered only among 2% of students, 88% have middle level, 10% - low level. Besides, examined group in its majority does not see the value of life planning; they do not see setting goals and determining actions for their achievement proper.
Study of the level of self-control was fulfilled according to the R. Cattell methodology. We considered such parameters: arbitrariness of actions, level of discipline, level of inconsistency in own perceptions, observance of social imperatives, and level of responsibility for certain case. The results obtained show that most of the students under test (56.7%) have the middle level of self-control. There is no doubt that the level of self-control is connected with the level of life time organization.
The ability to structure one’s time is connected with adequacy of perceptions concerning total amount of free time. 31% of students under test with high level of skills to structure free time have fair presentations about its amount, 18% - with middle level have adequate representation of amount of free time, with low level – only 10%.
So, the higher level of skills to structure own free time, the closer to reality the estimation of its amount.

Table3 Concept of free time amount in accordance with skills to structure free time

The level of ability to structure free time	Concepts of amount of free time
The level of ability to structure free time	Accurate	Wrong
High level	31%	69%
Middle level	18%	72%
Low level	10%	90%

While research the comparison of peculiarities of perceptions about free time amount in different groups divided in accordance with type of attitude to time was fulfilled (Table 4).

Table 4 Concepts of amount of free time in connection with typical attitude to time

Group by type of attitude to time	Concepts of amount of time
Group by type of attitude to time	Accurate	Wrong
Necessary account of time attitude	17%	83%
Contemplative attitude to time.	35%	65%
Active attitude to time	46%	54%
Pragmatic attitude to time	80%	20%

More fair perceptions about amount of free time are observed among students referred to group of “Pragmatic attitude to time”. Counting, distribution and planning of lifetime are typical for this group. The least fair perception about free time amount is observed among the group of “Necessary account of time attitude”. Such phenomena may be explained by close psychological connection of a person with time phenomena, which provides more effective usage of time.
Peculiarities of free time organization to a wide extent depend on peculiarities of its correlation with other things in social environment. That is why in the research comparison of communicative peculiarities of students and skills to organize free time was fulfilled. With the help of R. Cattell 16-factor personality questionnaire such personal characteristics of students as restraint- sociability, dependency- dominancy, shyness – courage, trustingness - suspiciousness, conformism – recusancy were studied and also individual type under C. Jung methodology was determined. Generalization of results allowed to determine several types of examined students in accordance with conceptual personality characteristics criteria.
Type “A” (16%) is characterized by true extraversion; openness, kind-heartedness, sociability, easiness, prudence, this type is mostly dominant, self-assured, and even obstinate; socially brave, active, is ready to deal with unknown circumstances and people, very trustful, tender and patient; depends on team, follows in public opinion, is geared to social approval.
Type “B” (20%) is characterized by extraversion, but in less degree, also sociable, informal, attentive, kind in relations, dominant, imperious, independent, self-confident, brave, risk-prone and active in communication, trustful in less degree, less patient and conformal, sometimes depends on team but shows initiative in making decisions.
Type “C” (45%) is characterized by “middle” criteria of extraversion and introversion (ambiverts), they are sociable and mainly open, more trusted than suspicious, this type can be referred neither to predominant nor to obedient; they may show different features depending on the situation, but in common they are socially brave people, without extra “superstition”; rather conformal than recusant, behavior is determined by the situation.
Type “D” (12%): they mostly have features of introvert; are not characterized by extra sociability and openness, depending on the situation they can obey, in common show social initiative, but rarely take the risk, suspicious; do not show conformism, prefer their own decisions.
Type “E” (7%) is characterized by introversion; restrict, may be unnecessarily strict at people’s estimation, shy, inclined to step aside, they take the blame upon themselves, worry about potential mistakes; demonstrate humility to complete passivity, may be both brave and shy depending on the situation, rather trustful, than suspicious, may be dependant on the team.
Comparison of personal characteristics of students, their communicative characteristics and organizational skills and also concept of time and leisure content, allows to determine certain common factors.
Type “A” has the middle level of skills to structure their own time, middle level of skills to plan actions, middle (partially high) level of self-control, attitude to time in most cases is “active” or “pragmatic”. Free time content of this group is represented in real communication, uneven waste of time in Internet.
Type “B” also has middle level of skills to structure time and plan actions, the level of self-control is mostly high, and attitude to time is “contemplative”. They need real and on-screen communication, there is interest for physical activity.
Type “C” is characterized by middle or high level of skills to structure their time, middle level of skills to plan and middle (or high) level of self-control, attitude to time is mostly “active”; they prefer communication in reality, dissipation of time in Internet, physical activity, create and give time to self-development.
Type “D” is characterized by middle (or low) level of skills to structure time, middle level of skills to plan and middle level of self-control, attitude to time is mostly “contemplative”. Range of interests during leisure time tapers to real communication, wasting time in Internet and physical activity.
Type “E” is identic to type “D” by its main characteristics and free time content, attitude to time is also “contemplative”. But the level of skills to structure own time is middle (see Table 3.10).
Generalizing the results, it should be marked that for extroverted type peculiar communication when free time and the level of its organization is mostly middle. While lowering of extroversion features there appears interest for physical activity. Ambiverts have the tendency to self-development, except for physical activity, the level of time organization is above the middle level. Introvert type has the tendency to creativity, control of own time, middle and high level of leisure time organization.
In such a way, there is certain dependence of peculiarities of time perceptions, attitude to it, individually- psychological characteristics of a personality and free time content and also means of its organization. Probably the level of competitive ability is determined between others and choice of free time content, the ability to control and organize it that is conditioned by person’s characteristics.

References

Albukhanova K.E., Berezina T.N. , Time of personality and lifetime / K.E. Albukhanova, T.N. Berezina. – Saint P.: Aleteiya, 2001. – 304p.
Bolotova A.K. Time organization psychology/ A. Bolotova. – Moscow: Aspekt Press, 2006. – 260p.
Bolotova A.K. Human and time in perception, activity, communication / A.K.Bolotova. – Moscow., 2007. - 283 p.
Golovakha E.I. Kronik A.A. Notion of psychological time / E.I. Golovakha, A.A. Kronic // Categories of materialist dialectic in psychology/ under the editorship of L.I. Antsiferovoi. – Moscow: “Science”, 1988. – P. 199-215
Eliseev O.P. Practicum in psychology of personality/ O.P.Eliseev // 2nd issue. – Saint P., 2002 – 512p.
Zinchenko V.P. Time – is character. / V.P. Zinchenko // Questions of psychology. – 2001. –No6 – P. 37-54.
Kovalev V.I. Categories of time in psychology (personal aspect) / V.I. Kovalev // Categories of materialist dialectic in psychology/ Under th editorship of L.I. Antsiferovoi. – Moscow: “Science”, 1988. – P. 216-230.
Serenkova V.F. Typical peculiarities of personal time planning / V.F. Serenkova // Humanistic problems of psychological theory. – Moscow: “Science”, 1995. – P. 192-204.

Mathematical modelling of history of seamless pipes pressing

Wed, 29 Jan 2014 12:59:46 +0200

The mathematical model of process of pressing of seamless pipes is developed and influence of different forms is set formative matrices on character of forming of energy power parameters of hearth of deformation. In interpretation of base variation of Euler’s task for the case of the direct pressing of pipes on the cylindrical mandrel the rational form of type (calibration) of matrix is certain.

Key words: pipe, technology, press, matrix, deformation zone, mandrel, model.

Suleiman Rakhmanov

National metallurgical academy of Ukraine,

theoretical mechanics department.

LLC "VOSTOK PLUS"

Mathematical modelling of history of seamless pipes pressing

Manufacturing operations of seamless pipes with usage of hollow billet pressing methodology in various modifications are based on the variety of physical peculiarities and technological advantages as compared with other methods of metal treatment under pressure [1].

It is known that while pressing of hollow billet there takes place the scheme of strained uniform compression in deformation zone, which is most advantageous from the point of view of increasing the values of metal workability. This provides high level of metal ductility, allows to deform the billet of low-ductile materials during single cycle of processing. The hypothesis is physical base for favourable conditions of hollow billet forming, especially from hard-to-deform alloys which are often subjected to crack formation (damage) during other deformation processes [2].

However, together with positive aspects, the processes of seamless pipes pressing have some disadvantages, which restrict the area of their usage. The most common among them are: low quality of service tool conditioned by its operation in bad conditions (high temperatures and critical contact voltages); relatively high metal consumption index, values of which, first of all, are determined by relatively high level of end pipe shearing [3,4].

Removal of disadvantages of pipepressing machines is possible through choice of effective process conditions of pipepressing processes, including grooving of reasonable processing tool (for example, matrix design).

Pressing process optimization of seamless pipes is based on the following groups of fundamental scientific researches and engineering developments: determining of the real deformation and speed parameters of pipe pressing; choice of effective geometrics of deforming instruments; selection of appropriate lubricants with optimal combination of antifriction properties; updating of press construction.

The main criteria of technological process optimization are minimization of energy-power parameters of hollow billet deformation process and increasing of single deformation of metals, that will lead to increase of presses productivity and accuracy increase of dimensions of pipes (hollow billet).

A lot of works are devoted to theoretical study of pressing process and pipe pressing in particular [1-6]. Let us analyze some works and mathematical models, where there is simultaneous analysis of stressed and deformed condition while seamless pipes pressing. For example, in work [3] there was a hypothesis, which stated that there is flat axial flow in the deformation zone. Such hypothesis obviously distorts true picture of hollow billet pressing process, as while realization of technological process there tales place critical velocity of metal flow gradient between points making contact with deforming tools and points, which are in the volume (central plies) of metal under press.

The most exact in basic view the task of pressing is represented in works [3,6], but while analysis of certain tasks there appear the range of difficulties, conditioned by the peculiarities of study of mathematical model of similar processes.

It should be marked that until now in literature there is no identical generalizing recommendations concerning choice of effective technological parameters of the process of pipepressing.

Below there is an attempt to get the refined mathematical model of seamless pipe pressing process, which is the closest to real processes, physical and boundary conditions of the task.

The main purpose of the proposed researches is getting the real image of distribution of energy-power parameters, development of generalized practical recommendations concerning choice of effective parameters of pipepressing process, design of service tools range and effective technological process of pipe manufacturing with the help of specialized presses.

Well-known methods of mathematical modeling of pressing processes, because of their peculiarities of deformable medium rheology, do not offer an opportunity for detailed analysis of dynamic peculiarities of technological processes of seamless pipes manufacturing.

In this case the usage of theoretical basis of continuum mechanics in interpretation of known class tasks of fluid-flow analogy allows to broaden the range of questions under consideration and solve some tasks concerning optimization the manufacturing process of seamless pipes with the help of extrusion press.

Considering that fact, that line-binding and viscoplastic medium models are proximal to real dynamic behavior of many metals, below is given the reason of fluid-flow analogy of deformation zone usage for study of pipe pressing process character. In this work adapted version of hydrodynamic model for fundamental research of dynamics of deformation zone and seamless pipe pressing process design is given. Further, for a first approximation, there observed the most common scheme of direct extrusion of seamless pipes on the extrusion press [1,5]. This scheme is the scheme of direct extrusion of seamless pipes, which supposes extrusion of hollow billet through ring-shaped channel formed by cylindrical mandrel and standardized die orifice.

Herewith pipe pressing process under this scheme is fulfilled as follows. Hollow billet heated to the necessary temperature (1200 – 1250ºС) is put to the orifice, then it is pressed with the help of ram through annular slit, formed by die orifice and cylindrical mandrel, forming pipe of desired geometry [1,3].

Let us assume the model of binding noncontractible operating environment with given viscosity factor ( medium rheology), which essentially depends on mechanical properties and temperature of hollow billet, as one of the successive refined mathematical models of metal flow while seamless pipe extrusion. Suggestions about appliance of such dynamic model but in other interpretation was proposed in the work [3], and practical usage of this model for determination of frictional force in deformation zone is fulfilled in work [4].

Let us consider the dynamic processes of seamless pipes extrusion on the pipe section press, design model of which is given in figure 1.

Figure 1. Design model of the processes of seamless pipes extrusion: 1 – ram; 2 – extrudable metal (hollow billet); 3 - die orifice; 4 – orifice; 5 – mandrel; 9 – press run-out chute.

Viscoplastic medium dynamics, forming metal flow in deformation zone, let us consider axiosymmetrical. For research of dynamic processes in deformation zone let us use Navier-Stokes’ system of equations in cylindrical coordinate system. This equations [7,8] take the following form:

(1)

where – are corresponding components of the velocity in the cylindrical coordinate system; – is pressure in deformation zone; – components of body force; ; – viscosity of metal; – density of operating medium (of metal).
Let us make some simplifying assumptions. We will consider that cross-section area of deformation zone, where monaxonic metal flow takes place, changes continuously, so we may ignore radial and tangential components of the speed and but not axial component .
Next, we will consider, that the pressing process runs rather slowly, so inertial component of the equation (1) (derivative )may be ignored. Besides, we will not take into account matching components of body force.
Under suggestions abovementioned the Navier-Stokes equations (1) are simplified and take on the following form:

(2)

Whence it follows that the pressure of metal in deformation zone is determined - function of disposal variable x.
Equation of metal flow continuity we will depict as integrated equation of conservation of space velocity of operating environment in ring-shaped channel of deformation zone

It follows from the last equation, that the axial component of metal flow velocity in the zone in general terms strictly depends on coordinates and , respectively, but taking into account the suggestion about continuous changing of cress-section area of deformation zone, taken by the metal flow, we will ignore the derivative as compared with other additive components in the on the right side of the equation (2). As the result we may form the modified equation of Navier-Stokes [8]

(3)

This equation is the adapted variant of Poiseuille equation [7,8]. So, the considered hydrodynamic model of deformation zone is charecrerized by the fact that monaxonic pressed metal flow in each cress-section of deformation zone with sectional area ;is the same as Poiseuille motion in ring-shaped channel and the same fixed area. Solution of the equation (3) for axial metal flow in deformation zone in accordance with [8] is as follows:

(4)

where values and are not just arbitraty constants (as in case of Poiseuille motion), but they are some functions from coordinate, values of which are determined from the conditions of pressed metal and tool (on the mandrel and orifice ) cooperation on the corresponding area boundary of metal flow in deformation zone. Therefore, the common solution of Poiseuille equation (4) contains two parameters and ,which is determined from boundary conditions of the matter. It is obvious that for viscid model of operating medium (of metal) boundary conditions of the matter are the conditions of cooperation of metal with processing tools, which are as follows

and (5)

Inserting the boundary conditions (5) into the expression (4) respectively, we will have two equations

where the values of required parameters and are determined

(6)

In result of (6) substitutions into (4) for axial component of metal flow velocity in deformation zone, we will have the following equation

(7)

where values and – are the corresponding die and mandrel radiuses (external and inner boundaries of deformation zone), which are the functions of ccordinate.
In curvilinear ring-shaped channel with variable cross-sectional area limited by die and mandrel generatrices, velocity of metal flow is also taken the same as Poiseuille motion. In such a way, during solution of this task we use “Poiseuille’s hypothesis of local flow”.
One may see that formula (7) contains the value – pressure gradient, which is unknown in advance, but can be found out, if the value of metal outflow through the ring-shaped channel of deformation zone is defined or may be set experimentally. Judging from the hypothesis concerning incoercibility of pressing metal (of operating medium), output of operating medium in the ring-shaped channel of deformation zone equals

After integrating and some generations we will have

(8)

On the other hand, it should be marked that the value of metal usage expressed through the speed of ram motion in container ,which is strictly defined by moving hydraulic power of the ram while pipe manufacturing process, and may vary in the course of pressing operation within some tolerance range of technical characteristics of press hydraulic system operating [2].

(9)

Than from (8) and (9) we will definitely get the expression for determining pressure gradient:

(10)

where

It is obvious that in the function of operating medium outgo in the expression (10) must be (9). Consequently, the value of pressure gradient is proportional to expenditure of ram velocity and viscosity factor of pressing metal μ, which is constant throughout the height of each section of deformation zone under consideration.
Herefrom follows that the pressure gradient (10) is the function of coordinate only. . Except that, metal pressure in deformation zone subsides from ran surface to field shapers (die and mandrel) because meridional radius of a die subsides in the coordinate (figure 1). .
Let us denote the pressure under ram in the beginning of coordinates with the help of . Than the pressure in some section of deformation zone is determined

. (11)

By virtue of the fact that in free cross-section (while metal fall) the upacting pressure is equal to zero, from the formula (11) we will have the following pressure ratings under ram:

(12)

Knowing the pressure under the ram , full pipe pressing power, which is necessary for providing predetermined rate of ram motion , we may determine as:

(13)

It is characteristic that this force is proportional to , μand pressing characteristics.
Experience of existing pipe pressing machines operation shows that in course of pipe pressing operations, both on the die and mandrel there appear great frictional forces [5]. In usual task approximating, according to the Newton law of viscous friction [7,8], in the pressing layer of metal there appear typical transverse strains

(14)

Consequently, frictional constraint on the working surface of the mandrel equals

(15)

Then on the matrix generator we have

(16)

Let us insert into (16) , deduced from the formula (7). Then we will get the final expression for determining and distribution of shearing stress on the mandrel and matrix respectively as:

(17)
(18)
where (19)
(20)

The expressions for determining transverse strains allow to calculate total frictional forces, affecting on mandrel and die in the deformation zone

(21)
(22)

Let us consider the most commonly used geometry of borders of deformation zone in respect with the form, forming the die:
1. Die generator of conic shape.

2. Die surface of toroid shape.

3. Die generator of parabolic shape.

4. Die generator in the shape of cubical parabola.

Distribution of frictional forces along the length of working area of a die in respect with its generating form and mandrel are given on the figure 2 and 3. Typical friction resistance forces on the die and mandrel are divided into two additive components: the force , corresponding to the area with the length ( with constant container radius ) and the force , corresponding to the area of a die and deformation zone (with the length and changing radius). ).
On the curvilinear area of working surface of the die and deformation zone, except transverse strains, values of which were determined previously, normal pressure forces are acting, which contribute to resistance of the mentioned area to flow of pressing metal. Strain on the area with normal

is equal to

and its X-component is equal to

Consequently, for strains and respectively we have

If– is the equation of die meridian, then

Axial component of the force affecting the elementary area of carrier stream of pressing material is equal to

(23)

It is obvious that from the side of pressing metal on the area the force is acting, which is opposite to (23) and is determined

(24)

The expression (24) consists of two additive components, affecting the die: the first one acts by means of normal voltage ; the second one - by means of transverse strain, which was determined above. Due to normal voltage (pressure forces) on the curved part of a die acts the force

(25)

where

Inserting into (25) the pressure from (11) and expression from (7), we will find

(26)
(27)

Consequently, the total force while pipe pressing process consists from frictional force on the corresponding area of mandrel cooperation with metal in deformation zone

(28)

and frictional force at the die area

(29)

pressure force (24) and secondary force (25) Then total resistance force at this areas of deformation zone is equal to

(30)

This force, as one may see from (30), depends on the form of generator of die working surface (equation ). This allows to set up the equation and solve variational problem appropriately: to find such shape of generator form of die working surface , when the total resistance of working area would be the smallest if the length of deformation zone , maximum and minimum radius at the pipe output from deformation zone are defined.

In the expression (30) the composite function, which depends on the equation forming dies , is the last integral, which after some transformations can be expressed as

(31)

As subintegral function in (30) does not depend on the coordinate, the first integral of Euler equation [9] for composite function (31) will be the expression

, (32)

where – is arbitrary constant.
It is obvious that the equation (30), considering the composite function (29) is as follows

(33)

Proceeding from the position that there is fluent reduction in area of deformation zone , then from (33) we may state

. (34)

For determining the equation of effective cross section of die working area (gage), constant , should be picked out in such way, that the gage element passed always through two places of its working surface known in advance and .
The results of solution of variational problem and differential equation (33), trough determination of effective cross section of die generator (gage) of 50MN pipe section press on the basis of original problem ( billet: material Х18Н10Т, 204х9 in diameter; diameter of a mandrel 186 mm; bloom: 196х9 in diameter) are given on the figure 2 and 3.

а) Cone b) Torus

c) Parabola d) Cubic parabola

e) Effective

Figure 2. Distribution of standard pressures , transverse strains on the die and transverse strains on the mandrel in deformation zone in respect with the shape of die generator and velocity of pipe pressing process.

а) Effective V0=0.2 m/s b) Effective V0=0.25 m/s

c) Effective V0=0.3 m/s г) d) Effective V0=0.35 m/s

e) Effective V0=0.4 m/s

Figure 3. Distribution of standard pressures , transverse strains on the die and transverse strains on the mandrel along the length of deformation zone in respect with the shape of die generator .

Conclusions

1. With the help of refining the mathematical model of deformation zone dynamics and strain-stress state of metal (operating medium), the possibilities for design and realization of augmented high speed manufacturing processes of seamless pipes pressing are determined.
2.The influence of various shapes of die generators and methods of pipe pressing on the formation of energy-power characteristics of deformation zone was discovered. Dependences, characterizing energy-power parameters of deformation zone and parameters of manufacturing process, for different shapes of die generators and methods of pipe pressing were formed.
3. With the help of mathematical modeling of pipe pressing process it was determined, that along the whole length of deformation zone with increase of metal flow velocity on the die and mandrel generator, that is of conic, torus, parabolic and cubic parabola shape, there is notable increase of transverse and normal strains. It should be marked, that for die generator that is in the shape of cubic parabola, these values lower than for others. With the increase of pressing velocity, energy-power parameters of deformation zone become of dynamic character.
4. The task concerning determination of effective cross-section (gage) of a die in the interpretation of Euler’s base variational problem for certain composite function of pipe pressing on the cylindrical mandrel is solved.
5.With the help of analysis of stressed state and pressing conditions of hollow billet, the ways for process optimization and upgrading of pressing pipes are nominated. Notable increase of working tools strength (dies and mandrels) is achieved.

References

Danchenko V.N. Pipe and tube production technology. Textbook for universities. / V.N. Danchenko, A.P. Kolikov, B.A. Romantsev, S.V. Samusev. 2002 – 640p.
Kolikov A.P. Machines and components for pipe and tube production: Textbook for universities/ A.P. Kolikov, V.P. Romanenko, S.V. Samusev, A.D. Sheikh-Ali, V.V. Frolochkin, - 1998. – 536 p.
Gulyaev G.I Pressing of steel pipes and sections./ G.I. Gulyaev, A.E. Pritomanov, O.O. Drobich//1973. – 192 p.
Gildengorn M.S. Treatment process of light and heat-resistant alloys. 1981. – 326 p.
Perlin I.P. Theory of metal pressing - 1964. – 344 p.
Gun G.L. theoretical science of metal treatment under pressure, 1980. – 456 p.
Loitsyanskii L.G. Mechanics of fluids, 1978. – 736 p.
Kochin N.E.,Kibel I.A. Roze N.V. Theoretical hydromechanics, part II, 1963. – 728 p.
Gun G.L., Yakovlev V.I. Mathematical modeling and optimization, 1974. – 336 p.

Principles of diplomatic etiquette and business communication with foreign partners (I)

Mon, 03 Feb 2014 11:04:12 +0200

Principles of diplomatic etiquette and business communication with foreign partners (I)

The article is devoted to Ushakov B.G.
Foreign Trade Academy, Moscow.

General concepts and fundamental principles of diplomatic etiquette are briefly described in this work. Business cards as an instrument of communication with business partners. Business conversation with partners. Land arrangement of delegation (taking, automobiles, time, place, menu, invitation list, etc.). Onsite visit. Problems of etiquette. The dos and don'ts of polite manners.
Diplomatic etiquette is the complex of customaries, rules, habits, observed by government facilities, organizations, authorities, businessmen and others, who participate in external communication.
Principles of diplomatic etiquette:

Comity of nations
International character of diplomatic etiquette

Any foreign person, who in the host state, should be respected on the part of official persons and government of this country. Each foreigner should show respect to the government, customs, traditions, lows of the host state.
3. Principle of mutuality

Etiquette at the formal events

To formal events one may refer different receptions and ceremonies, held on the occasion of national holidays, historically significant dates, arrival of foreign delegations, heads of state and government, etc. Such receptions are navigated by heads of state, government, ministers, and also embassies, consular agencies, trade delegations of the state abroad.
Military attaches, commanding officers, who have the visit of friendship at foreign base, representatives of local military command and civil authorities in accordance with the procedure of solemnities extension to military guests may also navigate receptions.
Diplomatic receptions are given independent from any event in the procedure of daily diplomatic operation. For diplomatic mission such receptions are the most common. Because of the fewness of guests, such events may be a good possibility for conversational gambit, strengthening and extension of contacts, getting of the necessary information, influence on the local circles at the necessary way, specification of external policy of the country.
Independent from purpose, size and type, diplomatic reception carries political character, as it provides meeting of foreign representatives.
Being abroad, the visitor should respect rules and customs, accepted in this country. Inviting the foreigner to a formal event, one should take care of not to put him into the state, abasing or offending his national dignity, otherwise he may estimate it as contempt to his state and nation.
First of all one should strictly observe business etiquette. While discharging of own functions, formal events planning, participating in ceremonies and procedures, diplomatists act in respect with business etiquette, which suggests a complex of generally accepted rules, traditions, conventionalities, observed by governments, national representatives abroad (embassies and consular agencies) in the process of communication with each other. Nowadays a lot of elements of formal diplomatic etiquette are the part of customaries and rules of business etiquette.

Common rules of etiquette

Greeting in certain countries have national overtone. Handshake is the main form of greeting. But in some countries handshake with women is not customary. Buccally kisses are typical for France and Mediterranean countries, hugs – for Latin America. Two palms held together is national Indian greeting. In many countries religion influences business a lot. One should know about doxies of the host country, but not get into argument concerning this topic. One should know that Buddhistic ikons are sacral: they should not been photographed or touched without permission. One should always be diligent, take into account road traffic and flock in the streets.
Clothes are an essential element, because it is a part of appearance. It should be low-key, well-tailored and of high quality. White shirts and dark suits are the most common. Women in business travels should not wear trousers and too short skirt or sleeveless dress as well.
If one comes to the country not for the first time, he should care for having on the back of the business card information in the language of this country. In South-east Asia, Africa and Middle East business cards are always offered with the right hand. In Japan it is offered with two hands with appropriate side to the partner.
One should respect national traditions in food, holidays and nation's leadership of the country visited. To eat local food is considered good style in many countries. During meal, if it is unknown for a visitor, he should not ask “what is this”, just eat what is offered. One should cut the portion small.
Do not criticize.
One should be acquainted with monetary system of country visited.
Do not boast with big money.
Communication should be of strictly official character.
If you do not know the language of the country visited, you should have an interpreter during conversations. To know some general expressions is important. While conversation through an interpreter, the presence of a person knowing both languages is desirable in order to control the interpretation and correct mistakes. If the partners speak too quickly for you, you may ask them do it more slowly explaining incompleteness of language proficiency. But never accuse them of speaking quick. If negotiations are held in your native language, you should not accuse the partner for accent as well; you should speak slowly and clean. Do not joke, because national humor is very specific, as well as slang, which also should be avoided.
One should show respect to elders everywhere. They are the ones, who should start the conversation first. When elder people are entering the room, one should stand up.
The other separate and delicate matter is perquisite. It is not common for Islamic countries, New Zealand and CIS countries. In Italy perquisite makes 23% from the cost of services, in Egypt it is greater and quite considerable. In Japan, when having received tab, one should put the money into envelope. One cannot demand everything to be as at home: food, service etc.
One should not spend at the hot country too much water, heat and light. Some countries have phone counters. That is why it is polite first to offer the host to pay the call. One should keep in mind the names. If the name is complicated, you should train its pronunciation. Note that names may point to social status and family status. One should not mention people by name, if they do not suggest that.
One should certainly stand up when national anthem of the country visited sounds. Observe and repeat the actions of the host.
Not wear specific traditional costumes, like toga or sari, as it may happen to be of religious character.
One should remember that in pagoda, mosque, Japanese, Indian and Indonesian houses and restaurants it is forbidden to be booted. Shoes must be left at the entry with toes to the door.
To be careful with usage of habitual gestures. In different countries they have different meanings, not always gentlemanlike.

Reply to an invitation

In all cases when in the received invitation for breakfast, dinner or supper or other type of reception, the letters R.S.V.P are left non-struckout, or there is phrase “Please reply”, you must beforehand answer whether the invitation is accepted, by phone or in written form. The absence of answer or its lateness shall be regarded as discourtesy and rudeness. If the invited cannot reply to an invitation beforehand, he should decline it, rather than keep silence and drag it.
After affirmative reply, visit the reception is obligate. Only in extreme case, if there appeared any unforseen or exigent circumstances that prevent from visiting, one may refuse to accept, but with reasonable notice for the host. If in the invitation the letters R.S.V.P. are struckout or absent (such comes around when it is standup reception, without sitting at the table), there is no need in reply.
Arrival and departure. For breakfast, dinner or supper or other type of reception, which contains reply request, one should come at specified time sharp. Arriving late is considered to be breach of etiquette and may be perceived negatively and even offendedly. If from one administration or institute several representatives are invited and they come for reception together, then first come those, who are junior by virtue of his position and then elder ones. If the reception without sitting at the table and in the invitation there is time of its beginning and end (15.00-17.00; 19.00-20.00 etc.), then one may come and leave at any moment within specified time.
There is no need to come to the beginning of reception and stay till its end as well. Still, it is considered that coming at such reception in its beginning and departure in its end speaks for respect to the partner and friendly relations. And vice versa, if one wants show or emphasize chill or tension in relations, he should stay at the reception for 15-20 minutes and then take leave.
In any case, official person should not leave the reception before elder visitors.
Manners at diplomatic receptions. Any diplomatic reception is the meeting place for foreign representatives, who in their relations with each other follow common rules of politeness, kindness and touch.
Foreign guests, come for the reception, pay honour the diplomatic representative and his country that is why they must be taken with honor and care. Diplomatic representative and his colleagues take care of the convenience, talk with guests and treat them. It cannot be tolerated that diplomatic representatives gathered in their own circle, forgetting about the guests.
At cocktail receptions or perpendiculars that are standup, guests come up to the tables, take snacks in their plates and leave the tables in order to allow others guests to come to the table. This rule should not be ignored.
One should not remain unnecessarily at the receptions, where residence time is stated, as it may be burdensome for the host. Unfavourable impression may make the cases, when the guests at the reception leave it just after leaving the main guest. It is better to clear gradually.
The younger greet the elder first, men greet women, a woman greets a man, who is much older than she is. An exception from this rule is a person, come into the room, whether he is male or female, so he greets those there present, the leaving parts with remaining.
In case, when there are some people in the room, one should greet the mistress, then other women, then the man of the house and other men.
Greeting a man, a woman should offer her hand first. If she gives a bow only, a man should not offer his hand. The same concerns the elder and younger men.
A man always stands up (except very aged and ill, who cannot stand up easily) greeting both woman and man. A woman greeting a man does not stand up. A man greeting a woman stands up. The exception is a mistress; she always stands up, when takes in guests, greets them. In official situation a man may not stand up when greeting a woman. Women stand up greeting very aged men.
Having greeted your counterpart, a man may sit down. If he greets someone who is older than he, he may sit down only after they do or with their allowance. If the mistress suggests to sit down and keep on standing, you should not sit down.
When greeting a woman, a man may kiss her hand. But this may be done only indoors!
It is not customary to greet someone through the sill, table or any other baffle.

Principles of diplomatic etiquette and business communication with foreign partners (III)

Fri, 21 Feb 2014 16:15:30 +0200

Principles of diplomatic etiquette and business communication with foreign partners (III)

The article is devoted to Ushakov B.G.
Foreign Trade Academy, Moscow.

Business cards. Instructions for use.

Exchange of cards is the integral form of business communication in external relations. Business card is the norm and rule of good courtesy. Business card is widely used in business communication and protocol diplomatic practice. They are exchanged during acquaintance, for long-distance introduction, extension of thanks or sympathy, flowers and presents are sent with them. Business cards are made typographically. The text is printed in Russian and overleaf in foreign language. The name of institute (company), name of a person is stated and the post of owner below. Scholastic degree must be also stated, in the bottom left corner – full address, in the right corner – phone numbers and fax.
Size of business cards and printing type are not restricted. Local practice influences them. In Ukraine there is the following standard - 70х90 or 50х90 mm.
Women according to the traditions state their full name only. But nowadays they participate in business life and with increasing frequency give more details about their post or scholastic degree. There are common rules regulating the peculiarities of business cards during their usage by women: on sent and left cards the post is not printed.
As a rule business cards are exchanged personally, adhering to a principle of mutuality. A person, having visited the other person, leaves his business card. If a business card is delivered personally, but without visiting, he fractures it from the right side in full width. This rule is referred to diplomatic practice. In some cases business cards are sent by post or by courier (the last guaranties delivery performance).
Leaving or sending business cards that substitute personal visit, in the bottom left corner, depending on the situation, there made the following inscriptions with lead pencil:

- p.r. (pour remercier) - extension of thanks;
   - p.f. (pour feliciter) – congratulations on the occasion of holiday ;
   - p.f.c. (pour faire connaissance) – expression of satisfaction from acquaintance;
   - p.f.N.a. (pour feliciter Nouvel an) - New Year's Day congratulations;
   - p.p.c. (pour prendre conge) – during leave-taking, when the visit was not made;
   - p.c. (pour condoler) - expression of sympathy;
   - p.p. (pour presenter) – during introduction or recommendation of other person.

In case of long-distance friendship, business card of introducing person is sent along with recommending one, where the inscription "p.p." is made. Business card is sent without subscription as the answer to introducing person.
There may be other inscriptions on business cards. Herein one should remember that this inscription is made from the third person, for example: “Thanks for congratulations”, “Congratulates with a holiday” , etc.
These rules are of protocol character and are observed in most cases in diplomatic practice. Certain peculiarities of business cards usage have been formed in business sphere. They have particular importance during business communication, where persons of different cultures and nations participate.
Strict regulation of business cards usage, first of all, concerns such type of business communication as negotiation process. Herein the mandatory attribute of first meeting with foreign partner is the exchange of business cards.
The exchange of business cards begins from the most high-ranking members of a delegation and goes in accordance with subordination. According to etiquette business cards of heads of the house are given fist. The Japanese and Koreans follow this rule especially strict, for which the breach of hierarchy is equal to offence. The Americans and Europeans are more liberal here. There are simple but obligatory rules of business card handing: one should give it to the partner with the appropriate side in order to read it. The other part should pronounce aloud his name in order the partner to learn pronunciation of your name.
In Asia it is common to hand them with both hands, on the West there is no special procedure. Accept cards one should with both hands as well or with right hand. During exchange both partners bow in a lissome way. Having accepted the business card, one should read the name in the presence of a partner and enquire about his post. While communication one should put business cards in front of yourself in order not to confuse the names. It is better to sort them in the order how the partner sit in front of you. One cannot rumple someone else’s business card, mark it up and twist it reflectively when the owner watching. This can be accepted as disrespect or even offence. If you do not recognize a person whom you have already met and with whom you have already exchanged with business cards, it will damage your reputation.

The history of business cards usage started long ago and nowadays there are certain common norms and rules of their usage.
As a rule business card is made as square-angled piece of white semicompact cardboard of good quality, which has a clear imprint of full name along with other information, which the owner wants to state. There are no clear regulations concerning business card size, but usually men’s cards are bigger then women’s ones (90 х 50 mm and 80 х 40 mm). In Great Britain vice versa. Business card of a young lady may be even smaller - 70 х 35 mm. One should think over the business card was of the standard size in order to avoid its bending for keeping in special album for business cards.
The most common rule for printing type of business cards is easiness in reading. The name is usually written semi-bold of large size. It is not recommended to use complex Gothic or fantasy text. One should be careful in usage of italic text, if you have hardly pronounceable surname, or if it concerns business card in foreign language.
As a rule a business card should have black text on a white background without any decoration. Recently there is wide choice of plastic colored cards or even made of leather. But the norms of etiquette do not recommend to vary from standard black-white chord. One should rather concentrate on the choice of high-grade paper, which may be a little toned or have satin finish. One should avoid glazed surface of a card. Colored and unusual cards are appanage of artists, service industry staff and advertising agents. Black frame on a business card may be present in a sign of mourning.
In some countries there are double-sided cards with the text in foreign language on the back. If one keeps the strict norms, it is not correct, because back side is distinguished for some marks. That is why it is better to order separate cards in both languages. But nevertheless, double-sided cards are possible in common. The main here is following the rules of card in foreign language decoration.
In current practice there are business, personal and family cards. There are also cases of combined business cards, where there is both personal and service data of the owner.
Business cards are the integral feature of modern business communication. The first meeting usually starts with business cards exchange. They have particular significance while cooperation with foreigners and people, which do not speak your native language. The owner’s full name, name of organization must be clearly printed on the business card. Business card may also contain a rank or handle to one's name, post at your organization, phone numbers, fax and e-mail. Business card without address does not correspond to the norms of etiquette (the exception is diplomatic community and higher government officials). If your address is changing and you still do not know your new phones, it is better to state official company address, secretariat or administrative office telephone. If the organization has several branches, then there may be stated several addresses on its representatives’ business cards.
Clerks’ or service companies’ business cards in their decoration may vary from etiquette standard – it is not just informational but also promotional products. Such business card may contain photo of its owner, colorific company symbol, company motto and on the back sometimes there is small scheme of localities.
Except your full name, business card may contain additional information, which you would like to present. As a rule it is printed with a small text and in the right lower corner.
On the business card under the name may also be printed your scholastic degree (professor, doctor, major general, candidate of engineering sciences, etc). You should not be surprised when finding on personal business card of your foreign partner club address instead of his home address (there are cases when both club address – in the left corner and home address – in the right corner). Women do not usually state any additional information on their private business card.
The other kind of business cards is family card. It is used during acquaintance or sending congratulations to friends with attached business card. One should remember that the name of husband goes after wife’s one. There may be no address on the family business card.
Turning to usage of cards in business, it is important to mention, that business card should contain not only the data you should present, but also promote image cultivation by your partner. Etiquette in business cards usage plays significant role.
There are several types of business cards: standard card of a businessman, wife’s card, card for a couple, commercial card.
Sending a business card in some cases is equal to visit. There should not be any postscript on a business card, except standard abridgements or phrases in French. If the card is left personally, it is fractured in a specific way (figure 1). Sometimes the card may be sent by courier (or driver). In this case the card must not be fractured (it is tasteless). If the card is sent by post (non-recommended), then the inscription on the envelope is made clearly in ink or ball-point pen. If the card is sent per carrier or driver, then the inscription on the clear envelope is made with a pencil.

Figure 1. Fracture line of a business card.

As an answer for business card one should sent within 24 hours his business card. Pone call is also possible.
It is not customary to hand personally cards of expression of thanks or any other feelings.
On the occasion oh holiday first congratulate those, who are working in the host country or foreigners.
Business cards are the integral feature of modern business communication.
If your phone number has changed, it is possible to write in carefully a new one, having crossed the old one (non recommended).
Business card without address does not correspond to norms of etiquette (the exception is diplomatic community and higher government officials).

Usage of business card

Business cards are widely used to express good feelings, congratulations and condolences. To enclose a business card with post card or small letter is full of decency. One may write a few words from the third person on a card. Business card attached to bunch of flowers is a gesture of gratitude to an actor, artist or just familiar in special day.
First of all, business cards are used during acquaintance - long-distance or private friendship. During first personal meeting after the words of introduction one may hand the business card to the partner. Having received the card, one should read the name closely, especially if its pronunciation is difficult.
During such acquaintance it is possible to make notes in a pencil from the third person.
If you do not have your business card, you must sent it.
Unlike the business cards, exchange of combined cards may take place in the end of acquaintance while negotiation about further communication.
Business cards of salesmen, restaurant-keepers and printers may lie on the desk. In this case the visitors may take them themselves. In other cases the card is handed, but it is normal to ask for the business card of the interesting for you person, having proposed him yours one.
There are common principles of business cards exchange, the same as for acquaintance: the younger hands his card first to the elder, man to woman (woman is not obliged to hand her card in reply). Business cards exchange, as a rule, is accompanied with short conversations as the aim of business card is to secure first impression. One should not give his business card to unknown people, as well as one should not expect to receive a business card from little-known person, with whom you had exchanged a few polite words at a public reception.
If you send business card to a married woman, you should send it in a set of two. Woman as a diplomatic member should send to a married couple two business cards.
In a residence of a married couple, one should also leave his business card in a set of two (especially if it concerns a bachelor).
After being introduced to a woman, man should send his business card in a set of two within seven days.
A woman never leaves her business card in the house of a bachelor and in the house of a married couple leaves two cards.
A married couple leaving business cards in the house of other married couple, leaves one husband’s business card for the man and one family card – for woman (in England two husband’s business cards and wife’s card are left).

Main principals of design and adoption experience of Automatic Control System by plate mills

Mon, 24 Mar 2014 14:00:51 +0200

The functional structure of Automatic Control System of plate mill reflecting the development experience of Kiev automatic controls institute is given. Control functions of rolling modes are characterized, approaches of mathematical models of rolling characteristics building and adaptation are described, the results of Automatic Control System adoption are presented.
Key words: plate mill, Automatic Control System (ACS), strategies of control, mathematical models.

Plate mill operating benefit is determined by quality index of rolled stock and rolling process.
Quality index of rolled stock includes:

geometry fidelity: average thickness hav of a plate, longitudinalδhl and transverse gage interference δhtr, width b, length l;
plate shape (flatness fault);
mechanical properties (yield point, tensile strength, elongation ratio, impact resistance at different temperatures, etc.).
surface condition.

Process performance includes:

productivity (operating time for rolling of one strip);
power consumption;
metal take for slabs per ton of rolled stock, which depends on rolling accuracy, amount of cutoff pieces and the last on strip shape;
expenses for repair-and-renewal operations.

The aims of automatic control of rolling process lie in achievement of optimum relationship of described process rates and, on occasion, control channel separation, achievement the most optimal values of the rates given above. Generalized functional structure of Automatic Control System (ACS) of plate mill, which reflects the experience of developments, fulfilled by Kiev Automation Institute, is given on the figure 1.
The structure refers to multilevel hierarchic decentralized structures. Functions of plate mill ACS according to the character of connections with an object, operating and administration personnel are divided into management and informational functions.
Automatic control of reverse sheet rolling contains three intelligence levels:

Program-logical and situational control of mill mechanisms, including roller bed, mill rolls, screw-down gears, manipulator heads, anti-crossbreak, descale sprays, etc.
Automatic control of rolling parameters: longitudinal and transverse thickness, width, temperature lengthwise the strip.
Control the rolling schedule with output of setpoints to the first and second intelligence levels for achievement the best values of rolling process described.

Figure 1 Generalized functional structure of plate mill ACS.

On the figure 2 there depicted three-stand mill (vertical and two horizontal mills) for reverse rolling of thick sheet with traditional control channels and means (parameters) of technological control of the rolling process, also the three mentioned above intelligence level of automatic control. Control of rolling process (cobbing trough passes, velocities, cooling) provides the main effect in formation of quality indexes of rolled stock and rolling process, mentioned above.

The main control level functions of rolling schedule are given on the figure 3 and 4. The choice of optimized index in the task of rolling automatic control is conditioned by its economical significance, character of affiliation with technological parameters and management. Billet metal-flow coefficient per ton of rolled stock is one of the most economically significant for plate mill, or the output of metal yield, which depends on the accuracy of realization of specified geometrical dimensions of rolling line. The accuracy of geometrical dimensions of thickness (h) and width (b) is connected with accuracy of choice and realization of guiding (roll opening) in dimensional gaps.

Figure 2 Automatic plate mill

Figure 3 Functions of modes controlling

Figure 4 Functions of dimensions controlling

In respect with characteristics of the object mentioned above, proving the minimum value of deviation in the thickness (width) of the bar from the fixed value (hз, bз) is an independent task, which lies in determination of roll opening of horizontal and vertical stand (НN and ВK) till metal pickup [1]:

(1)

(2)

where σ is root-mean-square deviation of actual values from fixed ones; P, Р* are actual and fixed possibilities of arising of minimized deviations; , are parameter vectors of mill and rolling stock.
The tasks (1 and 2) solution is provided by forecast of corresponding parameters of the mill and rolling stock in accordance with mathematical models. Along with the tasks (1 and 2) there exists the task of optimization according to one of the three indexes (Мe - equivalent torque of the spindle drive, W - electric energy consumption for rolling , Тc- rolling cycle time, which is determined by all the course of rolling) at fixed on the accepted level values of other indexes of feed and rolling process. This task is phrased as follows [2]:

Find , , , N,

providing min Тc where Мe= Мst,
or min Мe where Тc = Тcd,
or min W where Мe = Мst, Тc = Тcd
within the restrictions

(3)

where is the summary (defined) reduction per cycle (stage) of rolling; number of pass; , – minimum and maximum accepted reduction in the i-th pass; , , M nom, M st i, M acc – nominal, static, acceded torques of rolling engine; C – coefficient, connecting acceleration with dynamic torque of engine; А, C – constant values for defined feed; , - minimum and maximum temperature limit of the end of rolling; Тcd – defined rolling time; C – cross; – relative cross gage interference of feed; j – number of pass, where feed deformation takes place (nonflatness); – the velocity in i-th pass and its minimum and maximum accepted values (restriction concerns the capture velocity ,steady , discharging and velocity of roller bed ).
On the stage of width breakup from the task (3) the two last conditions are excluded – rolling of plane sheet and observance of finishing temperature of rolling. Solution of the task of automatic control with rolling modes is based on the usage of formalized description of process (mathematical models), adaptation of this description according to the results of measuring the coordinates of process states, usage of state values of controlled object of automatic aggregate and neighboring plots of processing line. Under the conditions of absence the full analytical process description (for example, description of forming the line in plane, formation of mechanical properties of rolling and condition of its surface, etc), absence of automatic means for determination of values for some object state (flatness, roll surface condition, etc) and condition of external, in regard to automatized field, parts of processing line, human’s participation is necessary condition for solution of all the tasks of automatization.

Although human is inferior to automatics in speed and accuracy of information processing, the reliability of performance (operating quality depends on a lot of factors, including psychological), he may gather experience and in future use unformalized experience while operating, orient and make decisions in unforseen situations , control his organs of the senses and estimate values and changes in process state, means for estimation of which, are absent in Automatic Control Systems.

Rolling control process may be divided into three main stages: choice of controlling strategy (for example, variation law of energy-power parameters in passes); choice and realization of management providing the strategy fulfillment (for example, calculation of thickness and openings in passes and processing with fixed accuracy of all these openings); receiving information about objects condition and neighbouring with it parts of processing line, estimation of control results.

While plate mill automatization there appeared an approach, which provides the usage of set of “rough” control strategies received beforehand (apart the process movement) for certain process performance envelope. The choice of one of the strategies is fulfilled in respect with concrete situation at the automatic object. As a rule such choice is made by an operator, who has information concerning the controlled object state in general. In the initial phase of ASC conversion by rolling on the plate mill control strategy is used, which uses the experience of operators and mill technologists and also experience fixed while manual operation of rolling (i.e. the strategy is set by an operator). This allows on the initial stages of ACS adoption to get an effect from automatization and to store static data, necessary for adoption of “rough” control strategy optimizing the whole process [3].

In such a way while rolling modes control on the plate mill, the principals of automatic man-computer control are used. The strategies of automatic rolling modes control must provide computation and realization of control in accordance with strategies found in advance, which guarantee optimal or almost optimal process in specific ranges of process variations. Strategies realization in appropriate conditions of technological process flowing is based on forecast of its parameters. The task of forecast of characteristics for process flowing (energy-power parameters, elastic deformations, etc) is independent and the possibility of its solution depends on the required forecast term (pass, stage, cycle) and required accuracy. Herein, all the rolling control strategies may be divided into two classes: to the first one refer strategies requiring short-range forecasting for realization (a pass ahead), to the second one refer strategies requiring long-range forecasting (for a stage, cycle of rolling). To the first ones mentioned above one may refer, for example, critical strategy from the beginning of the cycle for which each of the reductions (starting from the first pass) are chosen maximum allowable in energy-power and technological limits in respect with defined overall reduction per stage or cycle of rolling.

To the second class refer the strategies of rolling with uniform distribution of torque along the passes with permanent drawing, critical strategy from the end of cycle, and also strategy providing the equality of reductions in the pair of passes at even summary number of passes at the stage. The described division of strategies into classes reflects the peculiarities of their algorithmic realization.

So, algorithms of realization of short-range forecasting strategies of rolling parameters are characterized by minimal amount of computations and use less complex (often recurrence) mathematical models for rolling parameters forecasting.

Realization of strategies, requiring long-range forecasting of technological parameters, are usually build on control computation before starting the rolling process with usage of mathematical models of roll force and mill deformation. As actual parameters differ from expecting ones, in result of calculations there appear mistakes leading to understatement or overstatement the number of passes. In the first case it may lead to limit exceedance of energy-power parameters, which is inadmissible, in the second case – to decrease of productivity. That is why after each pass the control calculation on the remaining portion of cycle is repeated, the accuracy of calculations increases thanks to reduction of forecasting term and also thanks to refining the models, executed with the help of adaptation.

But mistakes, accumulated in the beginning of rolling process will condition not only non-optimal control distribution at passes, but also may lead to increase of numbers of rolling passes at least for the first billet in the lot. Besides, as the mistakes with understatement of passes rate are impossible, there added the necessary shift of calculation data to the area, where the probability of mistakes with overstatement of passes amount increases. It should be also noted that the amount of computations realizing the described choice of control is rather great and causes some difficulties while their realization in real scale of time.

Considering abovementioned, algorithmic realization of strategies of the 2nd class is supposed with exclusion of long-range forecasting. It is based on the reconstruction of mechanism of control choice from cycle to cycle according to actual data and also under the following statements:

Rolling of the fist billet in the lot under the critical strategy from the beginning of the cycle, in all the cases guarantees rolling in respect with all the limits for minimal number of passes and do not require long-range forecasting;
For each following billet the rolling parameters may be calculated with usage of mathematical models of forecasting the necessary parameter under its actual meaning in the same-name pass (the same number) of the executed cycle.

The described reduction calculation of the lot of identic billets provides asymptotic convergence of the reduction program to the definitive one. As it was mentioned above, the calculation of control action is based on the forecast of technological parameters of rolling with the help of mathematical models. Herein the models of metal plastic deformation (rolling force) and elastic deformation of the mill, rolling torque models, thermal processes while rolling, models describing the process of feed formation in space and plan [4,5].

The two approaches are used while building mathematical model. The first supposes the obtainment of initial mathematical model on the basis of physical process analysis taking place while formation of certain parameters, and development of the procedure of further model adaptation under the actual rolling parameters (theoretical models). Initial constants data entering theoretical models, is determined during experiments. The second approach supposes model formation by means of static analysis of surveillance over the technological process run and establishing correlation relationship between its main parameters (experimental models).

Continuous theoretical and experimental process analysis precedes the development of theoretical models; model of such type are accessible due to their flexibility. However, theoretical models describing the rolling process, as a rule, are complex and lengthy. It is explained by high complexity of theoretical description of the process, considering all the factors taking place while real rolling. Besides, some arguments of models are nonobservable in the process of real rolling on the plate mill as a result of measuring equipment absence.

While development of control algorithm with usage of computers, static models are frequently used. Herein the structures of models, received on the same mill, as a rule, may be applied on the other mills with similar rolling conditions.

Mathematical modeling of an object or process under experimental information is usually fulfilled by means of regression analysis. Except regression analysis one of the methods of object modeling is the method of compound arguments accounting. In ACS of plate mill there used both of the described above model types and also semiempirical models combining the characteristics of both types of models. In automatic control algorithms the rolling modes widely use recurrent models, which use actual values of rolling force and parameters of deformation zone in realized passes thus allowing to exclude from the model structure quantitative variables that are difficult to determine (deformation resistance, coefficient of friction), which remain almost changeless within the cycle of rolling or even rolling of a lot of billets. These recurrent dependences are as follows:

Pi=Рi-1 f(Gi,Gi-1), (4)

where Pi, Рi-1 are foreseeable force in the i-th pass and actual in the (i-1) pass; Gi, Gi-1 – expectable parameters of deformation zone in i-th pass and actual in (і-1)-th pass.

Recurrent dependences allow to speed up the calculation process with rather high accuracy of forecast, excluding the cycle first pass or rolling stage forecast.

The variation ranges of mathematical models parameters are determined by both rolling strips characteristics and by change of plate mill machinery condition while rolling, which may essentially change with time. This is explained by mechanical wear and change of thermal profile of working rolls while rolling and after roll change, change of strip cooling conditions depending on the temperature of the medium, variation of chemical composition and physic-mechanical properties of rolled metal, change of area input variables of models and other factors.

In respect of existing mill nonstationarity as an object of control, caused by abovementioned reasons, mathematical models obtained during object analysis and used while designing of automation system, should be continuously specified (adopt) while exploitation at the working object. If the specification is not fulfilled, the models will not sufficiently reflect the process and with their help it will be impossible to forecast behavior of an object and control it. As a result one is forced to face with less or more initial uncertainty.

The possibility of forecast at short priori information is provided by appliance of adaptation methods, which reduce the initial uncertainty thanks to information, received in the process of object operation. Information about the process is used for adaptation of mathematical models with the aim of maximum approximating of calculated values of parameters to their true values. The task of adaptation comes down to estimation of model parameters under the results of evaluation of input and output variables, received in conditions of normal object operation. Here under parameters evaluation one means experimental determination of their values under the condition that the structure of model is already known. Herein it is supposed that the input and output variables, which are connected, are already known and that this variables may be determined during normal exploitation.

There exists rather great amount of models adaptation algorithms. They differ both in memory size, and the number of calculation on each stage of adaptation. One of the most widespread multistage adaptation algorithms is ordinary least squares technique (OLS) or recursive least-square method. However, these adaptation algorithms require greater volume of experimental data. Single-stage algorithms became widely used in ACS. The most widespread among single-stage algorithms is stochastic approximation algorithm and phased training algorithm (Kaczmarz algorithm). The results of the abovementioned adaptation methods applied to mathematical models of ACS of plate mill are described in work [2].

As it was mentioned above, in the process of automatic calculation of reduction mode control mathematical models of main rolling parameters are used, which provide the required accuracy of output coordinates fixed values of automation objects. Herein the receipt of highly neat characterizations is connected with requirement strengthening to the quality of technological information, complicating of models and adaptation procedure. The tolerated error in getting the specified coordinates of state depends on the value of concrete parameter in technological process. So the mathematical models of rolling force and stand deformation are the main ones for control calculation, which condition the defined geometrical parameters of a sheet and consequently should provide reasonable accuracy of calculation. There are other, more simple requirements for models of calculation of limiting draft values.

There given an impact assessment of mathematical models accuracy of different parameters on the deviation of the last from the fixed values and their significance in observation of fundamental requirements for ACS of plate mill in [1]. Creation of ACS of plate mill presents systemic problem, where the tasks of mills analysis are solved as objects of automatization, developments of mathematical and technical system supply and adoption of ACS on the object.

On the initial operating stages concerning plate mill automatization it has already became obvious that ACS development engineer, who is keen in the control engineering area and monitoring, but who has not studied the peculiarities of manufacturing process and mill equipment, that is tended to be rearranged on an automatic basis of control, they will not be able to get high capacity results while ACS introduction. Attempts to fill these gaps by means of cooperation with technologists of particularized institutes and enterprises could give only narrow positive result.

As a result the development team of ACS of plate mill fulfilled technological researches of rolling process on the plate mill in the former USSR and abroad. There was accumulated technological knowledge on the level of highly-skilled professionals technologic research institutes and corresponding companies, that allowed to develop and implement in operation a series of effective ACS on the plate mill 2250 on Alchevsk metallurgical complex, plate mill 3600 on the “Azovstal” metallurgical complex and plate mill 3600 on the Bchilaiskii metallurgical complex, plate mill 5000 on the “Izhorsk Plant”, sheet mill 1500 on Moscow metallurgical complex “Serp i Molot”. These systems are characterized by modern level of automatization of technological process and high efficiency of their usage.
Analyzing the results of ACS introduction on the plate mill, one may mark the following main criteria of automatization efficiency:

improvement of rolled stock quality, first of all owing to reduction of tolerances on geometry of sheets;
metal saving;
energy saving;
increasing the frequency of rolling;
reduction of breakdown rate and increase of equipment longevity;
relieving of operational staff working.

So, for example, on the mill 2250 on Alchevsk metallurgical complex the mean-square error of width spacing has reduced from 20 mm at manual control to10 mm at automatic, and mean-square error of finite thickness has reduced from 0.21mm to 0.11-0.13 mm. On the mill 3600 on “Azovstal” metallurgical complex the adoption of ACS allowed to reduce mean-square error of sheet finite thickness from 0.15-0.24 mm to 0.07-0.11mm. This data visually characterize the efficiency of automatic modes of mill operation.

The experience of exploitation of ACS of technological rolling process on plate mills has confirmed the actuality and efficiency of works concerning automatization. In conditions of intensification of production, automatic control allows the rolling process to be sound and to use the resources available optimally.

Conclusions

Presented in the article main principals of ACS design for plate mill were used during development and ACS adoption in some plate mills. The results of adoption of ACS for plate mill have confirmed the effectiveness of these principals usage.

References

Grabovskii, G.G., Ievlev, N.G. (2002) Forecast of rolling force in ACS technical process on plate mill. Automation of production processes. Kiev, 2(15).

Grabovskii, G.G., Ievlev, N.G. (2003) Forecast of rolling force in ACS technical process on plate mill. Automationofproductionprocesses. Kiev, 1(17).

Ievlev N.G., Grabovskii G.G. Matematicheskie modeli i algoritmyi upravleniya v ASU TP tolstolistovyih prokatnyih stanov (Mathematical modeling and algorithms of control in ACS of plate mills). Kiev, Tehnika, 2001.248 p.

Ievlev N.G. (2007) Automatic control strategy of rolling modes on plate mills. Automationofproductionprocesses. Kiev, 1 (24).

Lugovskoi V.M. Algoritmyi sistemyi avtomatizatsii listovyih stanov (Algorithms of automatization system for sheet mill). Moscow, Metallurgiya, 1974, 320p.

Ultrasonic facilities for the ground materials characteristics control

Mon, 07 Apr 2014 14:49:07 +0300

Krivyi Rih National University, Krivyi Rih, 44 Pushkina Street, 50002, Ukraine

Abstract:The principal results of the technical facilities complex creating for ultrasonic control of the ground (milled) materials characteristics and adaptive systems for grinding (milling) and ore classification process control on its basis are presented.
Key words: Ultrasound, ore reduction, pulp solid phase, particles density.

Vladimir Morkun
Vice-Rector for research, Doctor of Science, professor of Computer Science, Automation and Control Systems department
Krivyi Rih National University

Natalia Morkun
PhD, Associate professor of Economic Cybernetics and Project Management Department
Krivyi Rih National University

Andrey Pikilnyak
PhD- student of Computer systems and networks department
Research Assistant of the Computer Science, Automation and Control Systems department

The ore reduction department is an intermediate element in mineral processing production line, but despite this it affects on the course of the following operations and final performance of the whole concentration plant.
The ore reduction operating costs during its benefication are about 50% which determine the final product cost price. Power consumption on ore reduction, depending on the initial ore quality and its final fineness within the limits of 55 % to 70 % of the total plant power [1].
Under the conditions of the feed ore characteristics and process equipment conditions changing the final performance of the ore reduction department significantly depend on the grinding and classifying units automatic control effectiveness which is primarily determined by the quality of informational and algorithmic support [2].
Thus replacement of the pulp density automatic stabilization system in the classifier overflow by the pulp solid phase autostabilization system on the basis of the granulometer allows to decrease the content variations of the crushed material control fraction from ±5 to 1,5 % and only due to this allows to increase the recovery of the useful component in the concentrate by 0,1-0,8 % [3].
Existing operational control facilities of qualitative and quantitative characteristics of ground material don't meet modern requirements.
The problems of control actions formation in the ore grinding-classification processes automatic control closed systems require the solutions. These systems allow to minimize the main technological equipment operation time in transitional regimes during which the qualitative and quantitative characteristics of the grinding cycle product output varies greatly[4].
In the R&D section of Krivyi Rih National University the theoretical basis for the ultrasonic testing of industrial suspensions main characteristics are developed [5, 6].
It was established that the weight percent of the pulp solid phase particle size control class definition can be carried out by measuring of two signals S1 and S2 the values of which can be determined by following expression [7]
                                                     (1)
                                    (2)
where and the intensity of the high frequency bulk ultrasonic oscillations which passed the distance z in pure water and pulp; I*lv and Ilv - the Lamb waves intensity at a distance of l from the source during the contact of pure water and pulp with the plate by which the Lamb wave propagate.
From (2) the value S2 is determined by the pulp solid phase concentration, and the relation between S1 and S2 characterizes the particle size distribution of the investigated medium.
,                                    (3)
where
The S value depends only on the particle size distribution and respectively defines the control size class concentration of solid phase particles. Furthermore, it does not depend on the the suspension gas phase content, i.e. in this case, the pulp pre-degassing is not required.
Several ultrasonic testing techniques of the pulp solid phase particles density and the extent of minerals disclosure (useful component) during ore reduction are proposed and investigated.
One of the proposed methods is based on the gamma-radiation and Lamb waves [8].
The mass attenuation coefficient of the gamma radiation by pulp can be presented in the following form
,                                       (4)
where and are the mass attenuation coefficients of water and pulp solid component; and are the density of water and pulp solid particles; W - the volumetric fraction of pulp solid particles.
The amount of gamma-ray detector current is proportional to the radiation intensity I, therefore the S3 signal value at the output of the logarithmic amplifier is proportional to ln I.
The signal difference S3 and ( - signal in clear water), determined by the formula
,                                     (5)
where A – is the proportionality coefficient; l-is a distance between the gamma radiation source and its detector.
Similar difference in the channel of the Lamb waves SL is also proportional to the volume fraction of W.
The signals SL and Sγ relationship depends only on the mean density of solid particles
,                                                       (6)
where B is a proportionality coefficient.
A method of the useful component extent disclosure estimation, based on the preliminary test material sampling, in which the particle sizes are limited to a range from r1 to r2 is proposed. The selected sample is placed into the measuring vessel where the particles of the ground ore are freely deposited. At the depth of Z there is a measuring channel based on the volumetric ultrasonic oscillations.
The next signal is generated
,                                                     (7)

where
,
N - is the number of particles; - particle size distribution function according to the degree of useful component disclosing;- is step function that takes two values- 0 and 1, by negative and positive arguments resp.; ; S- cross sectional area of the vessel; ; ; - is the density of particles with degree of disclosing; and - are the density of the useful component material and waste.
It was established that the distribution functioncan be evaluated according to the results of value St measuring by using the expression
,                                          (8)
where .
As a perspective direction in the development of the grinding and classifying processes automatic control is using of adaptation algorithms based on the forming of pre-set characteristics of transient processes in the closed loop automatic control systems.
These algorithms provide for a preliminary identification of the static and dynamic process characteristics with subsequent correction of controller parameters according to the obtained estimations.
The transitional process begins when e.g. the reference value changes by the g-value in a closed loop automatic control system [9].
At its initial stage the PI regulator parameters correction carries out according to the following expressions
,                              (9)
,                                            (10)
where ;;K0 and T0 - are the static transmission factor and the process time constant, T— the time delay; tp - switch moment (correction); and - are controllable coordinate and its first derivative.
The current values of K0 and T0 determination is carried out according to the measured values of and at the initial stage of the transient process in the closed loop automatic control system.
Analysis of the developed algorithm applicability limits has shown that for the object, (which transient function is approximated by the product of two inertial components with time delay) the controller parameters correction is advisable under the condition when and the best correction results can be obtained by the switch from the condition .
To reduce the random noise influence on the correction results the controlled z(t)- signal digital filtering is carried out. This signal along with the useful component x(t) includes noise R(t).
Granulometer “Pulsar” is considered to be a basic device of the developed systems. It consists of three principal parts: Sample forming unit, electronic bloc and the estimator on the basis of micro-PC.
The sample forming unit serves for pulp sampling, stable flow forming within the ultrasonic measurement zone and its return to the technological process. The unit includes the measuring modulus and a sampling system with the elements of initial starting and self-regulating of the selected pulp samples amount. The measuring modulus is the device to form a directed pulp flow within the measurements zone. The piezoelectric transducers of the high frequency and forming prisms of measuring channel on the basis of Lamb-waves are fixed on the measuring modulus.
The simplified diagram of electronic block and estimator of the "Pulsar" granulometer is shown on the Fig. 1.
The following designations are listed in the block diagram: 1-9 - ultrasonic oscillations generators; 2- firing pulses formers; 3-10 - gating pulses formers; 4,20 - read-out pulses former; 5,11 - amplifiers; 7,13 - pulse transducers; 8,14 - analog-digital converters; 15 - micro-computer; 16,18 - digital-analog converters; 17, 19 - information mapping devices; 21 - switch for channel selection; 22 - measuring modulus on-line; 23 - measurement module (bearing).

Fig. 1. Block diagram of the ultrasonic granulometer ’’Pulsar”.
The basis algorithm elements for ultrasonic measurements of the solid phase concentration γ and content η of several ground material fineness grades in the pulp flow used in estimator of ’’Pulsar” granulometer are shown in the Fig. 2.

Fig. 2. Measurement algorithm block diagram of the ’’Pulsar” granulometer.

Conclusions

The production tests results and introduction of the developed test (control) facilities witness their high efficiency and this fact gives an occasion to recommend these facilities to wide utilization in the ore-mining enterprises.

References

Automated control systems of concentrating plants technological process

ТЕKA. Commision of Motorization and Energetics in Agriculture

Control and regulation of ground product particle size distribution

AMMTIAC

ELSEVIER

Method and apparatus for measuring parameters of solid phase of slurries

Lamb and Love ultrasonic surface waves in measuring systems

KTU

Adaptive systems of technological processes optimal control

Mineral,

Iron ore flotation process control and optimization using high-energy ultrasound

Mon, 07 Apr 2014 15:17:21 +0300

Krivyi Rih National University, Krivyi Rih, 44 Pushkina Street, 50002, Ukraine

Abstract: The paper describes method allowing to effectively control the composition of iron ore pulp solid and gas phases to form the desired gas bubble size distribution function, which would coincide with the pulp solid particle size distribution in the flotation process using high-energy ultrasound.
Key words: mineral processing, high-energy ultrasound, particle size distribution, the characteristics of pulp.

Vladimir Morkun
Vice-Rector for research, Doctor of Science, professor of Computer Science, Automation and Control Systems department
Krivyi Rih National University

Natalia Morkun
PhD, Associate professor of Economic Cybernetics and Project Management Department
Krivyi Rih National University

Andrey Pikilnyak
PhD- student of Computer systems and networks department
Research Assistant of the Computer Science, Automation and Control Systems department
Krivyi Rih National University

1. Introduction
The flotation machines processes analysis, allows to identify the main input and output parameters, as well as disturbances [1,2].
The input parameters are: pulp density, reagents flow rate, compressed air flow rate, the pulp level, the pulp aeration degree. The disturbing effects are: the metal content in the ore, floatability of raw materials, particle size distribution of the ground product. The output parameters are: the metal content in the concentrate, the metal content in the tailings, plant productivity, concentrate output, the output of the tails.
Efficiency of the flotation process is directly related to the number of collisions between particles and bubbles, which are strongly dependent on the ratio of particle diameter to bubble diameter. Bubble size is considered to be one of the most important parameters affecting the performance of froth flotation cells.
In a flotation system if the bubbles are much larger than the particles, the hydrodynamic flow near the surface of the bubble will take away particles and thereby prevents attachment of valuable mineral particles to the bubble. If bubbles is much smaller than the particles, they can’t raise the hydrophobic ore particles to the pulp surface.
Hence, in order to provide optimal conditions for the flotation, it is necessary to generate bubble size distribution which would coincide to the particle size distribution of the pulp.
The task solution condition is to create such gas bubbles and iron ore particle size distributions in flotation process which provides disclosure of a useful component in the degree which technologically and economically proved for realizable beneficiation circuit.
High-intensity ultrasonic oscillations can speed up the traditional and implement new processes in liquid, solid and gaseous media. The efficiency of these processes are driven by the appearance of non-linear phenomena during the propagation of high-amplitude oscillations that cause cavitation, radiation pressure, micro-and macro flows, leading to rupture of mechanical and chemical bonds, increase the surfaces and speed of interaction, and the acceleration of the mass and heat transfer [3].
The use of ultrasound in the flotation technology related to a number of specific phenomena accompanying the propagation of ultrasonic vibrations in liquid media. Among these phenomena the special place is taken by cavitation. It is expressed in the appearance of gas bubbles (cavities) in the liquid in which ionization of molecules and atoms, pressure (up to several thousand atmospheres) and temperature (hundreds of degrees) increasing. It is known that gas (cavitation) bubbles are formed easily at the liquid-solid interface and energetic acting on the surface of the latter [4].
The task of research is mathematical modeling of the high-energy ultrasound radiation pressure effects on iron ore pulp flow to form the desired gas bubble size distribution function, which would coincide with the pulp solid phase particle size distribution in the flotation process.

2. Materials and methods
Let’s examine one of the possible ultrasonic measuring methods of pulp solid phase particle size distribution. As a rule, there are gas bubbles in the pulp. These bubbles affect ultrasonic waves, which propagates in such medium. Let N1 is the number of gas bubbles and N is the number of solid phase particles in the tank with pulp of volume V. Let F(R) is the solid phase particles distribution function and f(R) is the bubble size distribution function. The ultrasonic wave amplitude attenuation which passed the distance z in the medium can be described with formula [5,6]
,                       (1)
where is the amplitude of the wave which passed the same distance through the water. is the part of ultrasonic wave attenuation of frequency on the bubble with the radius R. is the part of attenuation on sphere particle with the radius R and the density .
The ultrasound attenuation on gas bubbles is the result of the absorption and dispersion and its have resonance character. Attenuation on the solid phase particles is the result of viscous-inertial losses and diffractional wave scattering.
The amplitude attenuation of the passed wave is a random value, because a number of solid phase particles and gas bubbles fluctuate in the controlled volume V. The mean value of the amplitude vibrations can be defined using Poisson’s law of particles number distributions in the volume V. In that case can be express as
,                        (2)
Where and are the volume fractions of the solid and gas phase in liquid.
,                                    (3)
,                                              (4)
,                                     (5)
,                                              (6)
In the most cases the pulp solid phase particle size distribution function is based on the log-normal distribution and for the gas bubbles it’s can be determined by experiments.
On the base of ultrasonic vibration experimental measurements it is possible to formulate the signal with the following equation [7]
,                                                 (7)
According to the eq. (2), the signal can be presented with the following equation
,                                   (8)
This signal depends on the pulp solid phase volume fraction and particle size distribution function. Fig. 1 shows the dependence of the signal from the ultrasonic frequency for solid particles with lognormal distribution (curves 1- 4). Curve 5 corresponds to the dependence of the signal only in the presence of gas phase with the volume fraction . It is clear from the figure that the influence of gas phase on the becomes slight for the ultrasound frequency MHz.
It is caused by resonance character of the ultrasonic waves attenuation on the gas bubbles.

Fig. 1. The dependence of the signal from the ultrasonic frequency: (curves 1- 4) - for solid particles with lognormal distribution; (curve 5) - only in the presence of gas phase with the volume fraction .

To form the required gas bubble size distribution function, which would coincide with the pulp solid phase particle size distribution in the flotation process, it is proposed to affect on the pulp flow with high-energy ultrasonic wave with given frequency and amplitude, resulting in a gas bubbles concentration change, and redistribution of their size. Character of redistribution depends on the size of the bubbles themselves, the frequency and amplitude of the incident radiation. Increasing the frequency and amplitude to the values at which the transition cavitation starts, bubble size will decrease due to crushing of larger bubbles. When decreasing the amplitude and frequency the bubbles will rise due to coalescence of smaller bubbles.
To account for the gas pressure in the bubble, and pressure varying in the liquid, the viscosity and surface tension it is advisable to use a cavitation bubble dynamics equation of Rayleigh-Plesset in which the driving pressure Pi(t) given as a short pulse [8]
,                          (9)
,                       (10)
where P0 – is static pressure in the liquid, R(t) – is current bubble radius, R0 – is initial bubble radius, Pi(t) – is pressure in the incident wave, σ – is surface tension, μ- is dynamic viscosity of the fluid, ρ – is density of the liquid, с – is speed of sound in the fluid (water σ = 0.07 N/m, μ = 0.001 N×s/m2, ρ = 103 kg/m3, c = 1500 m/s), γ – is adiabatic exponent of gas in the bubble (air γ = 1.33). The initial conditions are given as, (t = 0) = 0.
To initiate appropriate processes, due to the extreme nature of cavitation in liquids, it is necessary not only to form a certain amplitude and frequency of oscillations, but also to maintain their optimal values when changing the medium parameters and the impact of factors such as: changing the temperature of the medium and the material of the piezoelectric transducer, the damping action of the medium.
For this purpose, the ultrasonic effect with specific amplitude and frequency, in the working area of flotation machine, at each current moment is generated. This allows to obtain the desired gas bubble size distribution function in the pulp flow.
To solve this task, let’s form the control action based on the dynamic effects of high-energy ultrasound using phased array technology, which have many advantages compared to conventional single-element transducers is proposed.
The main feature of ultrasonic phased array technology - computer-controlled driving pulses amplitude and phase of the individual piezoelectric elements in multi-element transducer. Piezoelectric excitation is performed such a way that to control the parameters of the ultrasound beam, for example, angle, focal length, focal spot size.
The acoustical pressure of the array was calculated by modeling every element of the array as an independent simple source and summing the contribution of each simple source at each point in the field. The acoustic pressure p(x,y,z) at a specific point (x,y,z) in the field due to a simple source was calculated using the Rayleigh-Sommerfeld equation [9]
,                                    (11)
where W - is total acoustical power output from the array, ρ – is density of the medium, c – is speed of sound in the medium, A – is active transducer aperture, f – is frequency, S – is area formed by source, d – is distance from the source to the point (x, y , z), φ – is phase of oscillation, λ – is wavelength, and α – is attenuation in the medium.
The active aperture (the total length of the array) is calculated by the following formula [10]
,                                                   (12)
where A - is active aperture; g – is gap between nearest elements; e – is width of one element (typically e <λ / 2); n – is number of elements.
The net pressure due to all the elements was determined by summing the effects of each simple source:
.                                           (13)
The net power deposition at point (x,y,z) was the result of the attenuation [11]
,                                           (14)
The phase of each element of the array was determined by
,                                         (15)
where φi is phase of element i in degrees, di is distance from the center of element i to the focus, d0 is the focus depth, n is an integer used to maintain 0 <= φi <= 360°.

3. Results
The phased array configuration (size) used in the simulation with software and hardware tools package TAC (Transducer Array Calculation) is presented on Fig. 2 [12].

Fig. 2. 16-element phased array.

The 16-element transducer acoustic pressure field in the focal plane xz at y = 0,01 m is presented on Fig. 3.

Fig. 3. Acoustic pressure field in the focal plane x-z.

Let’s consider the forming of gas bubble size distribution using phased array technology. When using this approach, the gas bubbles are subjected to elements of the phased array, which having different characteristics. Numerically this effect can be expressed as a weighted sum of the individual bubble size distributions generated by each element of array.
, (16)
with
,
where N - is the number of array elements, αj – are weights which can be regarded as the probability of sampling bubbles generated from j-element of array.
fj(х) - is the bubble size density distribution function generated from j- element of array.
After receiving a series of sound velocity and attenuation measurements in a bubbly medium with a set of frequencies covering the range of interest, the inverse problem is to determine the bubble size distribution corresponding to the obtained measurements. A series of tests using various combinations of air and water flow rate through the pump was carried out.
Identification of the obtained dependences at the stage of experimental research was carried out using the software MATLAB 7.0 [13]. Fuzzy Logic Toolbox package, which is part of MATLAB, contains a set of GUI modules that provide the stage of structural identification in the dialog mode. At this stage the number of inputs and outputs of the model are specified by the number of terms and the types of membership functions, the knowledge base is formed. Fuzzy Logic Toolbox package for Sugeno models automates the stage of parametric identification. The setting of Sugeno type fuzzy model is convenient to carried out in a dialog mode using the GUI module anfisedit. The setting is made using the ANFIS technology (Adaptive Network based Fuzzy Inference System) It is editor of Matlab 7.0. ANFIS package. The editor automatically synthesizes data from experimental neuro-fuzzy network, which can be considered as one of the varieties of Takagi-Sugeno type fuzzy logic output [14].
Setting is an iterative procedure for finding the parameters of membership functions that minimize the differences between the actual and the desired behavior of the model. As adjusting the method of backpropagation or its combination with the method of least squares is used. Fuzzy Logic Toolbox can automatically synthesize data from a fuzzy knowledge base for Sugeno type model. For this purpose the two algorithms - gridpartition and subtractive clustering are used. At the output of the first algorithm the knowledge base containing all sorts of rules is obtained. As a result of the subtractive clustering the rules corresponding to regions of greatest concentration data are generated.
The experiments were performed using either a single frequency range, or an average of 100 for the series of experiments. In this case, the program considers the values of u and v for each series (Fig. 4), and then generates a curve of average values u(f) and v(f), and displays the average number of bubbles. These sizes and the amount of bubbles considered to be uniformly distributed in the volume between the two transducers. This volume is used to deduce the bubble size distribution per unit of volume in test liquid [15,16]

Fig. 4. Bubble size distribution: 1- initial; 2 - resulting.

CONCLUSIONS

Simulation results of the high energy ultrasound impact on the pulp solid and gas phases allow to form the required gas bubble size distribution function, which will coincide with the pulp solid phase particle size distribution in the flotation process.
Thus, the proposed flotation control method based on ultrasonic phased array technology allows to implement efficient control of the iron ore pulp solid and gas phases composition, improve the quality of the concentrate and the efficiency of the beneficiation process.

REFERENCES

Molodozh i nauka

Arch. Min. Sci

ТЕKA. Commision of Motorization and Energetics in Agriculture

Non-ferrous metals

AMMTIAC

ELSEVIER

Problems of nonlinear acoustics. XII-th International symposium on nonlinear acoustics

Introduction to Fourier Optics

Introduction to phased array ultrasonic technology applications. R/D tech guideline

. IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control

Transducer Array Calculation (TAC) GUI.

SIAM

Journal on Optimization

The MathWorks Inc

Journal of Krivyi Rih Technical University

KTU

Thermal conductivity of the gas in small space

Tue, 08 Apr 2014 10:28:10 +0300

Thermal conductivity of the gas in small space

Ph.D., associate professor Hanna Koshlak

Dr. sci, professor Anatoliy Pavlenko

Postgraduate Bohdan Usenko
Poltava National Technical Yuri Kondratyuk University, Poltava

Thermal conductivity of the gas in small space

The article is devoted to research of peculiarities of porous materials with micropores thermal conductivity. The temperature influence pattern of heating surface on the process of heat transfer by convection in the pores is given. Mathematical model of gravitational convection, which allows to predict the intensity of the convection current is proposed.
Key words: convective heat exchange, the particulate material, thermal gradient.

Convective heat exchange arising in the pores of the material dominates the elementary components of heat exchange in porous materials. That is why theoretical analysis of convective heat transfer is the actual problem, which comes to development a methodology for quantitative evaluation of convective heat transfer in the pores of heterogeneous systems.
Traditional methodology of evaluation the nature of heat transfer in enclosed space is based on the calculated Grashof number (Gr) and Prandtl (Pr) for particular environment.
Correlation of these numbers in a given range of values makes it possible to establish the presence of convection currents in the heated surface. One may judge about the accuracy of such assessment from the change of intensity of heat transfer under the conditions of heat conditions change. Such qualitative characteristic of heat transport process in our view does not reflect real physical processes occurring in confined space. The intensity of gravitational convection current is determined not only by thermophysical characteristics of contacting media, scaling factors, but also by orientation of the heating surface in space. Heat is transferred from the surface in the near-wall region, the thickness of which is sufficiently small. If one takes it as a scale factor for Grashof’s equation, the number of Gr will not exceed the critical value corresponding to a heat transfer conduction. But when heating the space through the side surfaces the convection currents are always present. And the question of what they contribute to the heat transfer remains relevant.
The process simulation of heat transfer by convection was performed using an application software package Flow Vision. In the function of variables dimensions of the closed cell and the surface temperature of the gas were selected. For the numerical solution of the Navier-Stokes and continuity equations describing the convective current, conservative scheme for unsteady equations [1]. Solution is shown in Figure 1.

Fig.1 Distribution of velocities and temperatures
The figure shows that along the walls of the layers with relatively high flow rate are forming. Isolines in the center tend to a horizontal position. Such current distribution was more typical for all calculated cases. When large numbers Gr gasflow from the heated surface is formed. It is for these cases in the literature critical numbers Gr are shown, which formalize the heat transfer process in closed area. But convective heat transfer can occur along the surface, wherein the moving in the center of motion is absent. Such a case in the literature is considered to be the heat transfer by thermal conductivity. Obviously, the energy transfer in the boundary layer can be significant.
To estimate the intensity of heat transfer, mathematical model connecting the surface temperature with the speed of convective current was developed [1].
Mathematical model of gravitational convection includes the following equations:
                             (1)
                                                         (2)
                                                   (3)
where n = h/r0 – kinematic viscosity coefficient; - thermal diffusivity, values which correspond to the tabular ones for Т=Т0. The unknown functions: V - velocity vector, р – pressure, Т – absolute gas temperature, r - density, h - dynamic viscosity, l - thermal conductivity, t - time, g – acceleration of free fall.
For simplicity we may use the Oberbeck-Boussinesq approximation.
Т0 – some value from the interval of temperature change in the medium, at which the density equals . Let us suppose that the temperature T in the medium deviates a little from Т0. Then the equation of state may be linearized, leaving only a member of the 1st-order of smallness in the expansion of a function r(Т) in a Taylor series in the neighborhood of the value Т0: ,
where - coefficient of thermal expansion of the gas at Т=Т0.
Density dependence on the temperature is taken into account only in the term with volume force of gravity, but in other cases they consider. Under such assumptions, the problem becomes as follows:
Let us find a solution to the boundary value problem:
                                           (4)
for partial differential equations:
                                                 (5)
here:   ;                                               (6)

then:
(7)
Approximate solution of the problem for equation (5) becomes:
(8)
Solution of equation (8) is shown in the graph of Figure 2.

1 - the pore radius r =2.5 mm; 2 - the pore radius r =4.5 mm;
3 - the pore radius r =7.5 mm
Fig. 2 The solution of equation (8)

For vertical heating wall the calculated values of the number are given in Figure 3.

Fig. 3 - Change the number Nu in time for the conditions of the Figure 1

Conclusions

The calculations performed confirm the presence of convective current on the heating surface in closed gas volumes with any geometric and energetic characteristics.
According to computation data it is possible to determine the basic stages of heat transfer and set their boundaries. On the graph of Figure 3 in the time interval one may observe the relaxation period of gas(air) heat exchange with the surface. If convective heat transfer was absent, meaning of the number would approach to Nu to 1, i.e. heat flux transmitted by convection would be equal to the heat flux thermal conductivity. The minimum value of Nu number on the graph corresponds to the beginning of convective transfer.
Thus, the above mathematical model and calculations allow to perform a quantitative analysis of the convective heat transfer in dependence on the temperature of the heating surfaces in a closed volume.

References

Pavlenko, A.M., Basok, B.I., Avramenko, A. A. (2005). Heat Conduction of a Multi-Layer Disperse Particle of Emulsion. Heat Transfer Research. 36, (1,2), 55-61.

Analysis of thermal peculiarities of alloying with special properties

Tue, 08 Apr 2014 10:09:41 +0300

Analysis of thermal peculiarities of alloying with special properties

Ph.D., associate professor Hanna Koshlak

Dr. sci, professor Anatoliy Pavlenko

Postgraduate Bohdan Usenko
Poltava National Technical Yuri Kondratyuk University, Poltava

Analysis of thermal peculiarities of alloying with special properties

Abstract. In this paper an algorithm solving the problem of high-speed thermal cooling of molten metal and alloys in order to form an amorphous structure is developed. The rate of alloy cooling was calculated by numerical solution of the problem of heat transfer between melt thin layer and solid metal plate with high heat conductivity. Basing on the results of field research an amorphous structure of the deposited metal was obtained; conditions for this technology realization were defined.

Keywords: quenching; amorphous structure; cooling rate; surfacing

Introduction

Alloys with amorphous structure have high hardness and strength, which vary depending on the chemical composition of an alloy. For alloys based on iron subgroup elements (Fe, Co, Ni) hardness according to HV may reach the values > 1000. High strength and wear-resistance make amorphous metals ideal materials for use in heat power engineering, in particular for hardening turbine blades, spindles, which are under dynamic loads during operation.

Amorphous structure cannot be obtained without super-high cooling rates in the process of structure formation. Thus, the study of thermophysical processes during formation of amorphous structure will allow to determine the most optimal technology of amorphous metal layer and the conditions for realization of this technology.

In the earlier studies a variety of realization ways of this principle was proposed. There are discrete and continuous methods for obtaining amorphous metal [1]. The methods of drops catapulting on the cold plate, spraying jets of gas or liquid, ultra-fast cooling from the gas medium, etc. are known [2-4]. The usage of these methods allows obtaining a stripe with 15 mm width and 30 ... 40 mm thickness, wire and powders, but for obtaining a surface layer with an amorphous structure these methods are unappropriated. In the technology of quenching from the liquid state the layer of melted metal contacts with the surface of massive body (a body-fridge) and is cooled by means of heat removal in its internal layers. In this case the processes of formation of the primary alloys structure, as well as subsequent solid phase transformations are accompanied with formation of different structural types of metastable states (amorphous structure), analysis of which this paper is devoted to. For obtaining the amorphous structure of the metal the surfacing of samples from low-alloy steel presented in the Figure 1 was performed.

The structure of welding metal is determined by the cooling conditions which affect the processes of metal solidification and diffusion processes. Therefore, on the experimental installation there available a system of forced cooling of the coating surface of melt.

To study the regularities of structuring and dependence of its effect on the mechanical, electrical and other properties of the metal after surfacing, metallophysical researches were performed, in result of which it was established that deposited layer has a crystal structure, mainly ferritic one.

When the layer is cooling down (Figure 1), the crystals grow in the direction opposite to heat removal, deep into the liquid bath and the metal acquires a columnar structure. Crystallite consists of several dendrites, which have a general directionality, and may have different degree of branching. Under higher cooling rates, in the welded metal of these steels, besides ferrite and pearlite, there also may be present martensite, bainite and residual austenite. Martensite in such steels is distinguished as structureless and bainite is represented as a ferrite-carbide mixture of high dispersion. The amount of structural components is changing depending on the temperature cycle of surfacing. As the structure of analyzed samples, shown in the Figure 1, has a crystalline structure, one may conclude that without usage of technological process while surfacing, which is aimed to increase of cooling rate of the melt, with a view to rapid heat removal, to receive amorphous structure of welded metal is impossible.

Figure 1 - Structure of the deposited metal

It is known that while surfacing cooling rate of the melt directly depends on the heat input of the process, with decrease of heat input rate, cooling increases. Surfacing rate Vs is significant parameter of surfacing regime, which influences the heat input. With increase of surfacing rate, the heat input decreases, which in its turn increases the speed of cooling process [5]. Surfacing of subsequent samples was carried out with increasing surfacing rate Vs, 16...18 m/h, the other mode parameters were left unchanged. The results of metallophysical studies are presented in the Figure 2, whence it follows that the increase surfacing rate has led to grain refinement and improvement of metal structure.

Figure 2 - Structure of the deposited metal

To produce the amorphous structure of deposited metal one should apply technique that will ensure rapid heat removal from the place of surfacing, provide a high cooling rate 104 ... 105 K/s and above. In order to remove the heat from surfacing place rapidly, the constructive device for cooling the melt was made on surfacing equipment; this allowed to achieve required cooling rate. With increasing the rate of heat removal metallophysical studies fixed the amorphous structure of deposited metal (figure 3).

Figure 3 – Amorphous structure of the deposited metal

The desired structure of deposited metal may be obtained only under the conditions of interaction of such factors as cooling rate, melt layer thickness and deposited metal mass. The rate of alloys cooling was calculated by numerical solution of the problem of heat exchange between melt thin layer and a solid metal plate with high heat conductivity. While cooling of the smelted layer of metal, the temperature of upper layers of the solid mass increases and corresponds to the conditions of heat transfer from the melt, whereas over large distance from the working surface its temperature does not change [6-7] (figure 4). A simplified scheme of heat removal on the condition that the melt temperature is changing in the direction perpendicular to the contact surface, may be represented by heat conduction equation [8]:

where - , , , - temperature, heat capacity, density and thermal conductivity of the melt respectively; t - time.
The initial condition

where - melting temperature of the sampling metal;
- degree of the previous melt overheating.
Boundary conditions:
when х1=0:
when х1=l:
where - coefficient of heat transfer on the boundary of melt-solid mass;
- the temperature of solid-mass.

Figure 4 - Scheme of cooling: l – thickness of the melt layer; x1 – coordinate in the direction of heat transfer within the boundaries of melt layer (0≤ х1≤ l); х2 – the coordinate in direction of heat removal within the boundaries of substrate (0≤ х2≤ ∞).

General equation of heat conduction for the relevant material for formalization of the process of heat removal to the solid mass was used, as well as conditions reflecting the physical aspects of the thermal problem:

where , , - heat capacity, density and thermal conductivity of the substrate;
- initial temperature of the solid mass (х=0).
In result of solving the equations the dependency diagrams of cooling rate for aluminum and nickel on the thickness of the melt at different values of heat transfer coefficient α are obtained (figure 5).

Figure 5 Dependence of aluminum and nickel cooling rate on the thickness of the melt at different values of the heat transfer coefficient α.

For formalization of the concept of materials structure let us introduce the value - degree of amorphization (metal volume and crystals volume ratio). Figure 6 shows a graph characterizing dependence of the amorphization degree on the thickness of the melted layer and the mass of deposited metal at the cooling rate of 104 K/s.

Conclusions

As one may see from the graphs the values of cooling rate have significantly advanced with decreasing of the melt thickness. Other technological factors, with the help of which one may control the mode of rapid cooling of the melt, are the degree of overheating of the melt overheating and the initial temperature of the solid mass. With the change of substrate temperature from -200 to 200 ° C, there observed the decrease of cooling rate, so it may be concluded, the lower the temperature of substrate the higher cooling rate. Theoretical calculations even under the simplified mathematical model make it possible to estimate the rate of melt cooling and the probability of obtaining the amorphous structure of the metal.

References

Dahlgren, S.D. Treatise Mater. Sci. and Technol. (1980), v.19, Exp. Meth., Part A, N.Y., p.213-251.
H.Fujimori, N.S.Kazama (1979). 1869-th report on the Research Institute of Iron, Steel and other materials., p.177-192.
Metallicheskie stekla (Metallic glasses). Moscow, Metallurgiya, 1984, 264 p.
Miroshnichenko I.S. Zakalka iz zhidkogo sostoyaniya (Hardening from the liquid state). Moscow, Metallurgiya, 1982, 168 p.
Molodyk N.V., Zenkin A.S. Vosstanovlenie detaley mashin. Spravochnik. (Recovery of machine parts. Reference book). Moscow,Mashinostroenie, 1989, 480 p.
Pavlenko, A.M., Basok, B.I., Avramenko, A. A. (2005). Heat Conduction of a Multi-Layer Disperse Particle of Emulsion. Heat Transfer Research. 36, (1,2), 55-61.
Ruhl R.C. Mater. Sci. Eng., 1967, 1, 313-320 p.
Suzuki K., Fujimori H., Hashimoto K. Amorfnyie metally (Amorphous metals). Moscow, Metallurgiya, 1987, 328 p.

Testing complex-structural magnetite quartzite deposits chamber system design theme

Thu, 24 Apr 2014 12:13:01 +0300

UDK 622.274

Stupnik N.I., Kalinichenko V.A., Kolosov V.A. /Dr. of Technical Sciences/
Pismenniy S.V., Fedko M.B. / Cand. of Technical Sciences/
State Higher Educational Institution "National University of Krivoy Rog"

Testing complex-structural magnetite quartzite deposits chamber system design theme

Development of iron ore by underground methods in terms of the Krivoy Rog iron ore basin is considered. The methods of the inclined pillars parameters calculation at level room-work of thick complex-structural magnetite quartzite are suggested.

Keywords:quartzites, system development, class, pillar, rock inclusion

The problem and its connection with the scientific and practical task
In Krivoy Rog iron ore basin rich and poor iron deposits are generally mined by open face development method or bulk-caving method (table 1).

Table 1. Development methods applied in enterprises with underground mining

Enterprise	Mine	Mining depth, m	Mining methods
PJSC “Krivbaszhelezrudkom”	Rodina	1315	sublevel ore caving
	Octyabrskaya	1190	sublevel ore caving, room and pillar caving
	Lenin mine	1275
	Gvardeiskaya	1270
PJSC “ArcelorMittal Krivoy Rog”	№1 Artem mine	1135	sublevel ore caving
PJSC “Evraz Sukha Balka”	Yubileinaya	1260	sublevel ore caving, room and pillar caving
PJSC “Evraz Sukha Balka”	Frunze mine	1135	sublevel ore caving, room and pillar caving

The main efficiency indices of mining methods are production costs, which are largely determined by the level of ore losses, degree of waste rock clogging and the specific volume of the breakoff, table 2
Table 2. Technical and economic indices of mining methods in Krivoy Rog iron ore basin

Indicator name	Mining methods
Indicator name	Level room-work	Sublevel room work	Sublevel ore caving
Specific weight in annual production, %	35.0	20.0	45.0
Specific volume of preliminary development and breakoff m/th. t	1.9-3.0	2.5-4.5	3.0-5.0
Ore losses, %	5.0-10.0 17.4-25.0	7.0-12.0 16.9-20.0	14.7-18.0
Ore clogging, %	4.0-7.0) 13.0-16.0)	4.0-6.0) 11.4-14,0)	16.5-18.0
Iron reduction in output in ore mass, %	0.5-2.0	0.3-1.5	1.5-3.0
Note: * - without pillar and ceiling recovery

Table 2 represents that the bulk-caving methods reduce iron ore content in ore output almost by two times in comparison with the room-work [1-3]. Taking into account that magnetite quartzite deposits are composed of very thick hard rocks technological advancement of their room-and-pillar methods is rather essential.

Investigation and publication analysis
Iron ore deposits in Krivoy Rog basin, reach the horizontal area of more than 1500 m2 and strike length of more than 700 m, of ore bodies ranging in size from 50 to 500 m2 and strike length from 10 to 75 m. The share of large deposits is 80% from the ore area in the basin. Their thickness varies from 20 to 150 m and more. The ore bodies are extended in the north-east direction and lie at angle from 20 to 80 degrees with the recovered grade of solid ore from 36 to 64%. Physical and mechanical properties of iron ore of Krivbass basin vary widely. Some mine fields have one or two parallel iron deposits containing about 70% of the reserves of the mine field, others have more than 20 separate ore bodies having a strike length from 150 to 500 m with the recovered grade of solid ore from 58 to 64% [2].
According to the deposit position iron ore deposits are divided into homogeneous and heterogeneous [3,4]. There are inclusions of dirt area or ores with low recovered grade quality of solid ore in heterogeneous deposits. The thickness of dirt areas vary from 3.2 m to 6 m in some areas to 10.6 m. The specific area of dirt area within the level (sublevel) is 10 ... 15-18%. The deposits with the presence of dirt area, are usually throw back with bulk mining, see table 1.
The problem statement
Application of traditional mining methods with ore bulk extraction at ore deposits mining, including dirt area inevitably leads to a decline of the recovered grade quality from 3 to 10%, which significantly affects the sale price of commercial products and increases the cost of extraction, transportation, hoisting of extracted rock mass and its dressing.
Thereby, the development of improved version of mining methods for deposits with dirt area inclusions, allowing to increase the quality of extracted ore mass, is an important scientific and technical task for enterprises with underground mining.
Material presentation and results
Ore deposits of Krivoy Rog iron ore basin according to their structure can be divided into five types: 1 - without dirt area inclusions, 2.3 and 4 - mining ore area has single, double and triple dirt area inclusions, 5 - ore area has combined dirt area inclusions, figure 1.

Fig. 1. The structure of ore deposits of Krivoy Rog iron ore basin

The first type includes all single and parallel and contiguous deposits that don’t contain dirt area inclusions or the thickness of dirt area inclusions between the ore deposits is more than 15 m. In this case, it should be noted that the parallel and contiguous deposits are mined separately. Deposits which have one dirt area inclusion with the thickness of not more than 10 m belong to the second type. The third and the fourth type are ore deposits having two or more dirt area inclusions, the distance between dirt area inclusions vary from 15 to 35 m and more. The fifth type is ore deposits with dirt area inclusions of irregular shape.
Based on researches, the classification of ore deposits of Krivoy Rog iron ore basin tend to be mined by room and pillar systems is given, table 3.

Table 3. Morphological classification of ore deposits of Krivoy Rog iron ore basin

Name	Without dirt area inclusions	Single dirt area inclusions		Doubled by dirt area inclusion		Tripled by dirt area inclusion	Combined dirt area inclusions
Deposit type	1	2		3		4	5
Dip angle of ore deposits, degree	45-90	45-60	60-90	45-60	60-90	60-90	45-60	60-90
Thickness of ore deposits, m	10-150	60-150	40-150	80-150	60-150	120-150	35-150	35-150
Dip angle of dirt area inclusions, degree	—	45-90	60-90	45-60	60-90	60-90	45-70	60-90
Thickness of dirt area inclusions,m	—	5-8	5-10	5-8	5-10	5-10	5-8	5-10
Rigidity of ore body	+/-	+/-	+/-	+/-	+/-	+/-	+/-	+/-
Rigidity of hanging wall rock	+	+	+/-	+	+	+	+	+/-
Rigidity of bottom wall rock	+	+/-	+	+/-	+	+	+/-	+
Rigidity of rock inclusions	—	+	+/-	+	+	+	+	+/-
Notе: + hard ores or rock; - soft ores or rock

For mining of iron ore deposits with dirt area inclusions (type 2-5) it is necessary to use selective extraction, leaving dirt area inclusions in the waste area [4]. This can be achieved by using level (sublevel) room and pillar systems with the pillars and ceiling caving or leaving. However, their use has a number of boundary conditions, which include: the minimum allowable thickness of dirt area and ore deposit, the amount of extraction panels, the thickness of slope dirt area inclusion [5].
The minimum allowable thickness of dirt area inclusion is conditioned by inclined pillar integrity support, normal conditions of ore crashing and determined by
,                                                            (1)
where mn – is the minimum allowable thickness of dirt area inclusion, m; W – is the line of least resistance at longhole work, m.
The minimum allowable thickness of ore body limited by the dirt area inclusion depends on the underground mining technology, height of level (sublevel) and is determined by
,                                                 (2)
where mр – is the minimum allowable thickness of ore body which is situated near dirt area, m, h – is the height of level, m.
The amount of extraction panels in the stope limited across by dirt area inclusions is determined from
,                                                               (3)
where N – is the amount of extraction areas in the stope limited across by waste rock inclusions; M – is the horizontal thickness of ore deposit, m, n – the amount of dirt area inclusions the thickness of which are ranged from 5 to 8…10m.
The thickness of the inclined dirt area inclusion that will ensure its stability for a period of the panel mining is determined by the conditions of the longitudinal compressive forces Рпр in which there is no integrity. Side forces Рб, are directed towards the previously mined room filled with caved rocks [5]. The design formula for determining the width of the inclined interstall pillar is
,                                                      (4)
where Рпр – isthe longitudinal compressive forces work along the inclined pillar; Кд – is the ratio depending on the tensile stress and rock deformation; ξ – is the ratio ofrock creeping; σр – rock tensile strength, kPa; nц – the amount of longitudinal pillars for one room; σсж – rock compressive strength; Кзап –inclined pillar stability factor; γ – specific weight of rock, forming the inclined pillar, kg/m3.
In the case when there is no tensile stress and deformation in the pillar Kd is 1.15 ... 1.41, when inclined pillar subjected to maximum deformation without affecting its integrity Kd is 1.41 ... 1.73, in the laminated fractured ground with possible or partial pillar caving Kd is 1.63 ... 2.0, and at crack initiation with the following caving Kd is 2.0 ... 2.44 [6].
So, the width of the inclined barren pillar defined by the expression (4) should be 1.5 times greater than the thickness power of barren area inclusion. As a result of researches an improved version of the level room mining methods with pillars and roof caving is developed.
A distinctive feature of the proposed version of the room mining method shown in Figure 2, from the traditional is the following. Mine section is divided into extraction panel according to the thickness. The first section is limited by hanging wall rock and hanging wall of dirt area inclusion, the last one is limited by hanging wall of dirt area inclusion and bottom wall. Section mining is carried out by extraction panel from hanging to bottom wall.

Fig.2. Level room development with dirt inclusions leaving in the section: I – primary stope (room); 2 –hauling roadway; 3, 4 – ventilation and manway raise , ore-pass; 5, 10 – draw entry; 6 – loading rooms; 7 – ditch undercutting; 8 – stope of the second turn (room fender); 9 –vertical compensation room; 11 spiral ramp; 12 rings of block caving deep holes; 13 –cutoff ditch ort; 14 – cut raise.

The panels are processed separately by level, (sublevel-) room and pillar system with the formation of a separate compensation space, drilling and receiving levels. Between the extraction panels the inclined pillar consisting of dirt inclusion is left. Interpanel inclined pillars (dirt inclusions) are not developed but remain unaffected between panels. Ore pillars and ceiling development is carried out according to the traditional technology. The results of calculation of improved mining method application compared with traditional technologies are shown in table 4.

Table 4. Technical and economic indices of development methods at mining of deposits with dirt area inclusions

Name	Room and pillar mining without pillar caving	Ore and cover caving methods	Proposal room and pillar mining method
Block (panel) parameters
Block strike length, m	50	50	50
Extraction thickness, m	100	100	80
Level height, m	90	90	90
Dirt inclusion thickness , m	10	10	-
Dip angle of ore deposits, degree	80	80	80
Dirt inclusions amount, pieces	2	2	-
Mined blocks (panels) amount, pieces	1	1	3
Ore volume weight, t/m3	2.8	2.8	2.8
Dirt inclusions volume weight, t/m3	2.2	2.2	-
Ore mass reserve in the block, th.. t	1206	1206	1008
- ore reserve in the block, th. t	1008	1008	1008
- dirt inclusion reserve in the block, th.t	198	198	-
Recovered grade, %:
- in ore	46.0	46.0	46.0
- in rock	24.0	24.0	24.0
- in dirt inclusionsв	16.0	16.0	-
Specific rate of preliminary development and breakoff, m/th.	2.8	36	3.8
Ore output per hole meter run, ton/m	21	20	25
Output per man-shift, t/ per shift	136.2	1548	155.72
Recovered grade of extraction block (panel) %	40.0	40.0	46.0
Ore loss, %	10.0	16.0	10.0
Ore clogging, %	7.0	15.0	7.0
Ore body amount, th. t	1084.5	1191.8	975.5
Recovered grade of extracted ore body, %	38.9	37.6	44.5

Conclusions and directions of further research
Performed researches have determined that the use of inclined pillars consisting of dirt area inclusions allows to increase the iron content in the mined ore body from 37.6 ... 38.9% to 44.5%, and to reduce drilling, output and minerals processing costs. Thus, the ore output is reduced by 10-18%, which significantly reduces the rock processing and haulage costs.
The given method of pillars determination is applicable under condition when the calculated width of inclined pillars is equal to or less than the dirt inclusion thickness. In the case when the calculated width of the inclined pillar is more than the dirt inclusion thickness, the traditional ore and cover caving method is applied.

References
1. Stupnik N.I., Pismennyi S.V. Advanced technology options of further iron-ore deposits optimization by the systems of with mass caving of ore. Reporter of Krivoi Rog national university, 2012, No30, p.3-7
2. Khivrenko V.O., Schelkanov V.A., Technological classification of complexstructural pools. Krivoi Rog, KTU, 2001, No 76, p. 26-29.
3. Development of opening scheme, preparation and scouring removing for complexstructural pools while further recovery of resources at great depth: Account from NDR No GR 0109U002336/ Kryvorizkyj Natsionalnyj Universytet, No 30-84-11, 2012, 306p.
4. Bizov V.F., Stoyarchak S.O., Sirichko V.O., Cherednichenko O.E., Garkusha A.F., Vitryak V.O., Plotnikov V.F., Repin O.G., Khivrenko O. Ya.,Schelkanov V.O., Andreev B.M., Khivrenko V.O. Patent No 37982А Е 21 С41/16 UA The way of development of orebodies, which contain gangue inclusions.
5. Stoyarchak S.O., Schelkanov V.O., Karamanits F.I., Andreev B.M., Korzh V.A., Pismennyi S.V. (Ukraine) Patent No 62168 UA, МКІ Е21С41/06. The way of development of raw materials pools. Published 15.12.2003.
6. Slesarev V.D. Geomechanics and mining restraint. Moscow, Ugleizdat, 1948, 45p.

Advantages of High HIP Temperature for Titanium-based Alloys Structure and Properties

Fri, 25 Apr 2014 13:17:02 +0300

Advantages of High HIP Temperature for Titanium-based Alloys Structure and Properties

Olga Sergeevna Sergienko
Zaporozhye National Technical University,
Zaporozhye

The paper discusses hot isostatic pressing (HIP) parameters optimum values to eliminate titanium castings porosity and improve their properties. Author suggests using high temperature instead of conventional treatment at 15 to 20oС lower than solid-state transformation of alpha-titanium to beta-titanium. According to research beta-titanium is more suited for HIP. It possesses lower creep resistance and yield strength, higher ductility and diffusion rate, low anisotropy of physical and mechanical properties. Researcher used different treatment parameters, all of which included rapid cooling in order to restrain grain growth. Fine structure and high mechanical properties were obtained using pressure of 140 MPa, holding at 960oС for 2 hours, subsequent holding at 1050oС and rapid cooling.
Keywords: titanium, hot isostatic pressing (HIP), casting defect, temperature

Introduction

Hot isostatic pressing (HIP) is a process that subjects a component to elevated temperature and inert gaseous isostatic pressure in a high-pressure vessel. Under these conditions internal defects within solid bodies collapse and weld up. When choosing HIP parameters the combination of pressure, temperature and holding time must provide the best conditions to eliminate internal cavities and microporosity and at the same time to prevent phases melting and merging and grain growth [1].
HIP has the same effect on alloy microstructure, as any other kind of heat treatment; therefore HIP has a direct impact on mechanical properties of titanium alloys [2]. High HIP temperature and low cooling speed is the reason of coarse platelet structure which is the main reason of properties decrease. These factors influenced conventional choice of HIP temperature [3].
Titanium has two allotropic forms: low-temperature alpha-phase and high-temperature beta-phase. Alpha-titanium has hexagonal close-packed (HCP) lattice and exists up to the temperature of 882oС, while at a higher temperature beta-titanium is formed with body centered cubic (BCC) lattice. To prevent grain growth conventional HIP temperature is chosen to be 15oС to 20oС than solid-state transformation. For titanium alloys this temperature varies from 870oС to 1000oС, while holding time differs from 2 to 10 hours depending on casting size and wall thickness. Pressure is chosen be higher than yield strength at HIP temperature [4,5]. Table 1 contains HIP parameters proposed by different researchers.
Table 1. HIP parameters proposed by different researchers.

Temperature, oС	Pressure, MPa	Holding time, h	Reference
900	100	-	6
1000-1150	100	-	7
950-1000	75-100	-	7
954	103	2	8
900-1000	100-120	-	9
900-950	103	2-4	5
950-1000	120	2-4	10
845-970	103	2-4	1
899	103	2	11

Despite a wide use of HIP modes with temperatures lower than solid-state transformation and taking into account characteristics of HCP and BCC lattices, high-temperature beta-titanium possesses following advantages, which can be used during HIP:

Low plastic resistance;
High ductility;
Low mechanical and physical properties anisotropy;
High diffusion rate of BCC lattice;
Low creep resistance.

These properties should encourage quick and effective defects elimination in titanium alloys castings at a temperature higher than solid-state transformation point.

Research Procedure

Research results showed that traditional HIP parameters, used for VT20 alloy, which includes 5.5-6.8% Al, 0.5-2.0% Mo, 0.8-1.8% V, 1.5-2.5% Zr, (960±10оС, 140 MPa, cooling speed – 5-8 oС /min) sometimes lead to tensile strength decrease. Researchers were faced with a task to create new HIP technology which would improve alloy properties.
In order to find the best HIP mode for VT20 alloy castings were submitted to treatment at different temperatures in Quintus QIH 0,9x1,5x2070-1400 MURC press. The chosen temperatures were: 960oС, 1020oС (solid-state transformation point) and 1050oС. Cooling rate of 40 to 50oC/min was provided to prevent grain growth. Different HIP modes used the same pressure of 140 MPa. Holding time consisted of 2 hours at 960oС with consequent holding at 1020oС or 1050oС for 1 hour. After HIP treatment mechanical tests and microstructure analysis were conducted. Mechanical properties of VT20 alloy are presented in Table 2 and microstructures can be seen in Figure 1.

Results and Discussion

As cast samples possess fine platelet structure and their mechanical properties are within norm. After conventional HIP mode with slow cooling fine structure turned coarse, this led to a drop in mechanical properties. Treatment at 1020oС with rapid cooling at 40oС /min resulted in a fine structure, though properties didn’t reach the needed level. Fine lamellar structure and high mechanical properties were obtained only by samples, which were treated at 1050oС and cooled from beta-titanium temperature at 45-50oС/min.
Research results prove that the optimal HIP mode for titanium alloy VT20 must include temperature higher than solid-state transformation point. Rapid cooling from beta-titanium phase creates fine platelet alpha-titanium structure. While low temperature treatment doesn’t allow to manipulate alpha-titanium grain size without its growth.

Conclusions

High-temperature beta-titanium properties are better suited for HIP treatment than alpha-titanium. According to this data, several experiments were conducted, including different treatment modes, microstructure analysis and mechanical properties tests. Based on research data the optimal HIP mode was chosen. It consists of holding at 960oС for 2 hours, subsequent heating to 1050oС and holding for 1 hour with cooling rate 45-50oС/min. This mode provides fine lamellar structure of alpha-titanium phase and high mechanical properties.
Table 2. Mechanical properties of VT20 alloy samples after different HIP modes

HIP mode	Mechanical properties
HIP mode	σВ, MPa	δ, %	ψ, %	KCU, kJ/m2	НВ
As cast	962	6.80	19.25	568.8	346
As cast + HIP, 960oС, 1 h, cooling rate 5-8oС/min (conventional technology)	889.50	10.50	21.93	653.3	360
As cast + HIP, 960oС, 2 h, 1020oС, 1 h, cooling rate 40oС/min	894.75	7.40	19,15	653.5	365
As cast + HIP, 960oС, 2 h, 1050oС, 1 h, cooling rate 45-50oС/min	923.25	6.20	16.78	600.3	349
Standard norms	≥900	≥5	≥12	≥280	320-360

a) b)

c) d)

References

J. R. Newman, D. Eylon, J. K. Thorne. Titanium and Titanium Alloys. ASM Handbook Vol.15 Casting, 1992, pp. 1811-1836.

Myer Kutz J. Handbook of Materials Selection. New York, Wiley &Sons, 2002., 1497p.

Donachie M. J. Jr. Titamium: a Technical Guide. USA, ASM International, 2000, 216p.

Galdin N.M., D.F. Charnega, D.F. Ivanchuk Non-ferrous Casing Guide. Moscow, Mashinostoeniye, 1989, 528 p.

Eridon J. M. Hot Isostatic Pressing of Castings. ASM Handbook Vol.15 Casting, 1992, pp. 1173-1187

Leyens C., M. Peters. Titanium and Titanium Alloys Fundamentals and Applications WILEY-VCH GmbH & Co., 2003, 513 p. ISBN 3-527-30534-3

Iljin A.A., B.A. Kolachev, I.S. Polkin. Titanium Alloys: Composition, Structure, Properties. Moscow, VILS-MATI, 2009, 520 p.

Campbell F.C. Manufacturing Technology for Aerospace Structural Materials. F.C. Campbell– Elsevier Ltd., 2006, 617 p.

Bratuhin A.G., E.L. Bibikov, S.G. Glazunov. Production of Titanium Alloys Castings. Moscow, VILS, 1998, 292 p.

Padalko A.G. Hot Isostatic Pressing of Non-organic Materials Practical aspects. Moscow, Akademkniga, 2007, 267 p.

Billinghurst E. E. Jr. Tensile Properties of Cast Titanium Alloys Titanium-6Al-4V ELI and Titanium-5Al-2.5Sn ELI, NASA Technical paper 3288, 1992, 16 p.

WORLDWIDE MARKET OF MANGANESE ORE AND FERROALLOYS IN THE FOURTH QUARTER OF 2013.

Tue, 08 Apr 2014 10:10:47 +0300

WORLDWIDE MARKET OF MANGANESE ORE AND FERROALLOYS IN THE FOURTH QUARTER OF 2013

Grischenko S.G.Doctor of Technical Sciences, professor (PMO “Transgeorudmet”)

Ukraine, as for assured resources of manganese ore, takes the 2nd place after Republic of South Africa; it is a large manufacturer of raw materials and ferroalloys and one of the leading competitors on the worldwide market of manganese-ore materials and ferroalloys [1,2].
Performance of analysis of market situation and estimation of sources reliability concerning prices for these products, which became the topic of this article, is of practical interest.

1. Market of manganese materials

Known to many specialists edition “CRU Bulk Ferroalloy Monitor” publishes information about two types of prices for manganese ore: 1) averaged prices of imported spot transactions excluding loading port in terms of the ore with 44% manganese content; 2) averaged prices according to transactions, including loading port per month, preceding summary, in terms of 43% manganese content, CIF China. But, we believe that, being averaged and not considering the data concerning loading port or reflecting just one direction of delivery, the data of this edition cannot be applied for reliable estimation of concrete ore cost and may be only used as informational material.
“Metal-Ekspert” edition publishes the data about three types of prices: 1) price for import of Australian ore with 48% manganese content to China on CIF-China terms (without fixing a port) 2) price for import of Australian ore with 46% manganese content to China on CIF-China terms (without fixing a port); 3) price for import of Kazakh ore with 38-40% manganese content to China on CPT terms.
It should be marked that these data do not take into account shipping port and also reflect only one direction of the delivery – CIF-China, without fixing certain port; that is why these data cannot be used for reliable estimation of concrete ore cost and may be only used as a review (referential).
“Ryan's Notes” edition publishes prices for manganese ore (36-39%; 44%; 46% Mn) delivered on the market of North America.
Since 19th October “Metal Bulletin” source has stopped publishing averaged prices for manganese ore without fixing certain shipping port. The data published concern two types of prices:
1) Manganese Ore Price Index for the ore with 38% manganese content on the terms of FOB Port Elizabeth, in dollars for 1% of manganese, contained in one ton of ore (concentrate or agglomerate) on dry basis (dry metric ton unit (dmtu) index). Please note that this approach is quite sound, as Republic of South Africa is the world's largest producer of iron ore with middle and high content of manganese, seaborne (according to “Global Trade Atlas” data, export of manganese ore from Republic of South Africa in 2013 made 9.7 million tons).
2) Manganese Ore Price Index for the ore with 44% manganese content on the terms of CIF Tianjin in dollars for 1% of manganese, contained in one ton of ore (USD/dmtu). We believe, this approach is also rather sound, as China is the world’s largest consumer of manganese ore. According to “Global Trade Atlas” data, import of manganese ore to China in 2013 made 16.6 million tons, herein 31% fell on the Republic of South Africa ore, and 31% - on the Australian ore. Here one should consider that Tianjin is not the only transshipment port for manganese ore to China, total reserves of this ore in China ports teetered between 2.29 -3 million tons during 2012-2013. The cost of delivery and transshipment of manganese ore through China ports may vary depending on some factors.
In such a way, in our opinion, namely indexes of “Metal Bulletin” edition characterize global market tends the most precisely and reasonably reflect the dynamics of international prices for manganese ore. On this basis, while comparing the prices for manganese ore, imported on the territory of Ukraine, to use “Metal Bulletin” indexes is the most reasonable.
Herein, for reasonable comparing the prices, the last should be at least: first, they should be determined on the equal basis of delivery; second, they should set for commodities equal in quality; third, they should be in the same equality.
In order to make the prices for ore “comparable”, it is possible to apply specifically developed recosting methods.
With the aim to render the price, reflecting the world level, (for example, on CIF terms, China port) as targeted price (for example, CPT- railroad station of Black Sea port), principal associated costs must be held back and/or added to “international price”.
According to the example given above, the price arithmetic formula will be as follows:
PUrk = PCh - C1 + C2 + C3
where: PUrk - price for manganese ore, CPT- railroad station, Ukrainian port;
PCh – price for manganese ore, CIF China port;
C1 - shipping costs from the port of state of origin of the cargo under consideration to China port (redatuming from CIF China to FOB country of cargo origin);
C2 - shipping costs from the port of state of cargo origin to the Ukrainian port (redatuming from FOB, country of cargo origin to CIF, Ukraine);
C3 – cargo transfer from the warehouse of Ukrainian port to the wagons at port railroad (redatuming from CIF, Ukraine to CPT, Ukrainian railroad port).
While performing accounting all the costs should be given in the same pecuniary unit; generally accepted world pecuniary unit concerning manganese ore is the sum in dollars for 1% on manganese, contained in one ton of ore - USD/dmtu.
Price recosting methodology of shipped manganese ore of one type to another type of the similar good is based on the principal of proportional price change, depending on the content of main element (Mn%). For example, recosting of price for manganese ore with 44% Mn content, with the price for 1% of manganese, contained in one ton of ore, equals 5 USD/dmtu, to the price for ore with 40%Mn. We use the following formula for recosting:
P = 5 : 44 x 40 = 4.55 USD/dmtu
Inaccuracy of this recosting methodology usage is connected with the fact, that, herewith, the content of basic element is taken into account and the content of harmful impurities (phosphorus, sulfur, etc) is ignored. Moisture content, ignition losses, fineness ratio, mineralogical composition of ore material and gang mineral, etc – all these factors are also ignored, values, which significantly influence the technical-economic values (TEV) of ore processing on ferroalloy enterprises.
Application of method of proportional recosting concerning manganese content for ores with manganese content not lower than 44% requires the appliance of adjustment factors. For each type of ore the value of coefficient depends on concrete situation, in particular requirements to the quality of output. For example, in Ukraine for filling of order for manganese ferroalloys smelting with high content of manganese and low content of phosphorus, there is a need in raw materials with low content of phosphorus and iron.
Qualitative characteristic analysis of manganese ores from different deposits in different countries shows that manganese ore from Ghana is almost world's only manganese ore with manganese content lower than 40% and which possesses both properties. Considering different positive moments, but rather low manganese content (28%Mn), for this ore is acceptably to use 1.20- 1.30 scaling ratio, depending on the current situation on the market and with account of availability and price level of other similar ores.
There are supplies of manganese ore with relatively low manganese content and high iron content from Republic of South Africa. Such ores at the moment are presented on the worldwide market by such producers as BHP, Assmang, UMK, Tshipi. It is known, that for carbonates decompounding, while ferroalloy smelting, there is a need in additional electrical power in electric furnace [1], but stable chemical composition and low moisture content in this ore (this fact sufficiently influences transportation costs of manganese unit) allows to apply 0.95-1.05 scaling ratio.
According to Metal Bulletin information, real cost situation on the market of manganese ore, was characterized by multidirectional trends in September 2013. Prices for South African manganese ore with 38% manganese content were continuing to grow: from 3.35 USD/dmtu to 3.64 USD/dmtu on the terms of FOB, Elizabeth port. Price indexes started growing since the 6th of September, when the prices for manganese alloys in China have heightened. It should be noticed that the prices for manganese ore with 38% manganese content were reducing within several months in connection with weakening of ZAR Rand and as a result the producers in Republic of South Africa were forced to cut the volumes of material suggested for curbing the price drop. Price index according to Metal Bulletin for the ore with 44% Mn, by contrast, was reducing from 5.15 to 5.11 USD/dmtu on the terms of CIFTianjin; this is connected with weakening of demand for this ore grade.
In October, 2013 price index of Metal Bulletin for South African manganese ore with 38% manganese content increased from 3.73 to 3.82 USD/dmtu, but in November, 2013 slowly returned to the level of beginning of October. Similar situation was observed concerning index of this edition for the ore with 44% manganese content: rise in October, 2013 from 5.19 to 5.23 USD/dmtu succeeded by rollback in November, 2013to the level of 5.15 USD/dmtu. Consumers have fulfilled earlier shortened ore reserves. Some Chinese traders have declared, that they have overestimated the demand for manganese ore, the number of spot transaction was very small, and as a result the received to Chinese port material were purchased more slowly, than it was expected, this has affected the price curve.
In December, 2013 price index of Metal Bulletin for South African manganese ore with 38% manganese content in the run-up to Christmas holidays, remained stable on the level of 3.7- 3.71 USD/dmtu, and price index for ore with 44%Mn continued reduction from 5.12 to 5.08 USD/dmtu.
When using abovementioned methodology, it is easy to show that while this period (September, 2013) for the ore from Republic of South Africa with 37% manganese content at real price index of “Metal Bulletin” edition5.11 USD/dmtu, calculative price for analogue on the terms of CPT, Ukrainian port station while using 1.0 coefficient makes 5.00 USD/dmtu. For Ghana ore with 28% Mn at real price index of “Metal Bulletin” edition 5.11 USD/dmtu, calculative price for analogue on the terms of CPT, Ukrainian port station while using 1.3 coefficient makes 4.81 USD/dmtu.
In performed calculation of transshipment rate the results obtained with the help of shipping agents questionnaire in the Ukrainian ports; freight rates are calculated on the basis of “BALTIC EXCHANGE” indexes and fuel cost at a given period of time.

2. Ferroalloy market

The leading competitor of world market of ferroalloys, doubtless is China, where in recent years app. 45% of world volume of ferroalloys is produced, which are used both for smelting in great volumes of steel by Chinese metallurgists and for export.
Since 1st January 2008 the Chinese government has imposed special export tariffs for certain products through the program concerning removal from service of outdated and unsustainable manufacturing facilities in the country. As of September-October, 2013, export tariffs for Chinese ferroalloys were: 20% - for ferrosilicon manganese and ferromanganese, 25% - for ferrosilicon; since 1st January, 2013 export tariff for metallic manganese has been canceled.
As a result of imposition of export duties, Chinese ferroalloy export reduced significantly. Ferrosilicon manganese export redused from 740 000 tons in 2008 to 17 000 tons in 2013, i.e. 44 times; high-carbon ferromanganese export decreased from 180 825 tons in 2008 to 5 195 tons in 2013, i.e. 35 times; intermediate- and high-carbon ferromanganese reduced from 184 407 tons in 2008 to 6 539 in 2013, 28 times. There marked facts of reexport of Chinese ferroalloys lots through Vietnam, in order to avoid export duty.
Export-import statics shows that under actual low level of export, the prices for ferroalloys on FOB terms, China, which are published both by Chinese and international sources, do not reflect market tends, but are of informational nature, demonstrate “artificial” level (according to analysts estimation), according to which Chinese part could offer ferroalloys at outside market allowing for export duty (20-25%). In such a manner, prices published on FOB terms, China should not be accepted as the base while estimation of costs of ferroalloys delivery at the world market.
For understanding which sources are able to reflect price trends correctly, let us pay attention to the world export-import statistics concerning ferroalloy trade for 2008- 2013 (see the given above note).
The largest exporters of ferrosilicon manganese, according to Global Trade Atlas data, are India (in 2013 – 955.6 ths tons), Ukraine (466.6 ths tons) and Norway (281.9 ths tons); this data should be taken into account. In 2013 Russia exported only 139 tons of ferrosilicon manganese, importing more than 180 ths tons of this alloy, mainly from Ukraine (138.8 ths tons). Therefore, export prices for ferrosilicon manganese, published by Chinese source “Asia Metal” on FOB terms, Black Sea port of Russia, are incorrect and are not recommended for usage while trends evaluation on the market of Russian Federation.
The largest exporters of high-carbon ferromanganese are Republic of South Africa (2013 – 525.4 ths tons), South Korea (170.9 ths tons), India (140.3 ths tons), Russia (54.6 ths tons) and Spain (39.7 ths tons). The leading exporters of intermediate- and low carbon ferromanganese are Republic of South Africa (2013 – 118.2 ths tons), South Korea (102.1 ths tons) and Spain (28.6 ths tons).
The main ferrosilicon exporters are Russia (2013 – 397.7 ths tons), Norway (204 ths tons), Iceland (119.3 ths tons), Brazil (98.7 ths tons), Ukraine (64.7 ths tons) and China (reexport through Vietnam).
The most active importers of ferrosilicon manganese over a period of September-December of 2013, were Japan, Turkey, Russia, Italy, USA and Great Britain; all these countries and also Iran appeared to be the main importers of high-carbon ferromanganese; Canada may be added to this list as for ferromanganese import with less that 2% of carbon. All these countries were the main importers of ferrosilicon in September-December, 2013.
Considering the above mentioned, one may conclude that while analysis of price level for ferroalloys, one should found on the sources, which give prices on DDU - Europe, FOB –ports of India and South Korea, CIF- Japanese ports, DDU- USA market (North America), DDU- Russian market basis.
Let us consider price information on the main markets of ferroalloys in September-December 2013 according to FACOM (as we mentioned above, this price is artificial and further it is given as informational), “CRU Bulk Ferrolloy Monitor”, “Metal Bulletin”, “Metal Expert” (russ. “МеталлЭксперт”), “Ryan' Notes” editions data. In figure 1 there is data concerning dynamics of prices for ferrosilicon manganese in accordance with information of mentioned above sources on European markets.

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Figure 1. Dynamics of prices (Euro/mt) for ferrosilicon manganese on the European market in September-December 2013

As one may see from data, presented in the figure 1, the edition “CRU Bulk Ferrolloy Monitor” reflects the market trend of average price for ferrosilicon manganese on the European market the most precisely; one may also consider as comparatively accurate information, the data of “Metal Bulletin”, “Metal Pages” and “Metal Expert” editions. The difference in data of these sources may be conditioned by the presence or absence of minimum and maximum reflection in the edition, and also various periodicities (Metal Bulletin and
Metal Pages publish data weekly, Metal Expert and CRU Bulk Ferrolloy Monitor – monthly) that affects calculation of average price per month.
Quite possibly that the presence of price range is connected with the information published, which does not reflect the content in alloy such important for metallurgists element as phosphorus. It is obvious that production expenditures and prices for ferrosilicon manganese with 0.15-0.35% and 0.35-0.5% phosphorous content vary greatly, although the information about prices for these ferroalloys is considered according to the single category.
Dynamics of prices for high-carbon ferromanganese on the European market, according to the same sources, is shown in the figure 2.

Figure 2. Dynamics of prices (Euro/mt) for high-carbon ferromanganese on the European market in September- December 2013

As it may be seen from the data in the figure 2, the edition “Metal Bulletin” reflects the prices for high-carbon ferromanganese on the European market the most precisely, one may also consider as comparatively accurate information, the data of “Metal Expert” edition. On our opinion, not exact data concerning market trends is provided by “Ryan' Notes” and “Metal Page” editions. The reasons of variations in prices for ferromanganese, according to different sources, are obviously the same as for ferrosilicon manganese.
In the figure 3 there is data about prices on the European market for intermediate-carbon ferromanganese, according to the data of CRU Bulk Ferrolloy Monitor and Metal Pages; the data about prices for this alloy and also low-carbon ferromanganese is published by FACOM, but as it was mentioned above, its data is artificial and may be used as informational only.
As it is shown in the figure 3, “CRU Bulk Ferrolloy Monitor” edition reflects the price market tendency for middle-carbon ferromanganese on the European market the most precisely, while “Metal Pages” editionreflects market tends incompletely.
Dynamics of prices on the European market of ferrosilicon, according to “CRU Bulk Ferrolloy Monitor”, “Metal Bulletin”, “Metal Expert” , “Ryan' Notes” and “Metal Pages” data, is shown in the figure 4.

Figure 3. Dynamics of prices (Euro/mt) for intermediate-carbon ferromanganese on the European market in September-December 2013

Figure 4. Dynamics of prices (Euro/mt) for ferrosilicon on the European market in September-December 2013

From the data in the figure 4 one may conclude that “Metal Bulletin” edition reflects price market tendency for ferrosilicon on the European market the most precisely, one may also consider as comparatively accurate information, the data of “Metal Expert” edition. The reasons of data variations are analyzed above and connected, first of all, with different frequency of the editions and absence of data about price extremum.
Ryan'sNotes, MetalBulletin, CRUBulkFerrolloyMonitor, МеталлЭксперт и MetalPages publish data about prices for ferrosilicon manganese on the USA market. During analysis of this data, one should consider that there is import tax (163%) for ferrosilicon manganese produced in Ukraine and China. In such a way, prices, published by the specified editions for USA market, may be used as informational ones for evaluating the level of material cost on the markets of far-abroad countries.
Dynamics of prices in September-December 2013 for ferrosilicon manganese and high-carbon ferromanganese on the USA market is shown in the figure 5 and 6 respectively, and demonstrates various trends, not conforming to averaged revealed level.
When working with this price information, we recommend to base upon “Ryan's Notes” edition, as its central office is on the territory of USA; in such a way, analytics of this edition have close contact both with consumers and suppliers of ferrosilicon manganese on the US and North America markets. It is obvious, that this allows the edition to react in timely on the tendencies and publish the hardest news.

Figure 5. Dynamics of prices (USD/mt) for ferrosilicon manganese on the USA market in September-December 2013

Figure 6. Dynamics of prices (USD/mt) for high-carbon ferromanganese on the USA market in September-December 2013

Information concerning prices on North American market of intermediate-carbon ferromanganese is published by Ryan's Notes, Metal Bulletin, CRU Bulk Ferrolloy Monitor, and data about low-carbon ferromanganese is published by “Ryan's Notes” edition, which data is recommended to use because of the mentioned above reasons.
The mentioned above concerning greater accuracy of Ryan's Notes data, because of the same reasons is true for price information on the USA market of ferrosilicon.
The data about prices for ferrosilicon manganese on the market of Southeast Asiais published by “Tex Report” edition (supplies of Indian material on the Japanese market), “Metal Expert” edition (South Korea, India), “Ryan's Notes” edition (China), “Metal Bulletin” edition (China), “CRU Bulk Ferrolloy Monitor” edition (Japan, China), “Metal Pages” edition (China). All the sources may be recommended for usage, except the data concerning China, which, as it was mentioned above, is of artificial character.
The same concerns publication of data about price for high-carbon ferromanganese on the market of Southeast Asia, where we recommend to use such sources as “Metal Expert” and “Metal Pages” editions. As for data about prices for intermediate- and low-carbon ferromanganese on the market of Southeast Asia, it is published only by FACOM, and by virtue of analyzed above reasons, they should be considered false.
Price information for ferrosilicon on the market of Southeast Asia is published by Metal Expert (China), Metal Bulletin (China), CRU Bulk Ferrolloy Monitor (Japan), Metal Pages (India); this information may be considered as rather reliable, excluding the data concerning China.
“Metal Expert” edition publishes information about prices for ferrosilicon manganese and ferrosilicon on the market of Turkey; data about price for ferromanganese of all types on the Turkish market is absent in all world information sources.
This edition “Metal Expert” publishes data about prices for manganese and silicinate ferroalloys on the Russian market. Incorrectness of prices for ferrosilicon manganese, which are published by Chinese source Asia Metal on the terms of FOB, Black Sea port of Russia, was analyzed above. The data about prices for intermediate- and low-carbon ferromanganese on the market of Russia is absent in all world information sources.
To analyze the data about level of costs during export of Ukrainian ferroalloys on various markets is of great interest.
According to analysis of information about prices for ferroalloys according to various world sources, the level of prices is given in respect with delivery of material before basis of publication. This price display takes into account some range of costs, which are borne by supplier while material realization from production plant of the basis on one or another market and may include railway tariff; shipping costs on the board; customs duty; customs clearance of cargoes; freight costs; delivery in stock (including storage and security); delivery from stock to the buyer; payment of auditor service; commission fee of trader; insurance charge; cost of financing; other costs.
During export in September- December, 2013 on the EU to end-consumers, spending level of Ukrainian suppliers made for ferrosilicon manganese – from 63 to 181 Euro/t, ferrosilicon – 93-242 Euro/t, high-carbon ferromanganese – 63-141Euro/t, metallic manganese – 274 Euro/t.
During the same period while export to end-consumers in Turkey, costs for ferrosilicon manganese made 90-225 UDS/t; ferrosilicon – 11-277 USD/t. During export of ferrosilicon manganese to South Korea, the costs made 180-303 USD/t and while export of the same alloy to Japan - 111-204 USD/t.
Difference in costs, in some cases very essential, is connected with shipment and unloading of goods in various ports of various distances from the buyer, different freight conditions (type of ship, the year of launch, etc), various packing, different storage conditions and transport condition (for example, to dispatch goods on the return trip of empty vessel is usually cheaper than according to normal fare), etc.
The given above data about costs is typical also for other world markets, herein the specific numbers may be corrected depending on seasonal factor, changes on freight market, variation of prices for fuel and other global trends.

CONCLUSIONS

The data concerning situation on the world markets of manganese materials and ferroalloys in September-December 2013 is analyzed. The reliability of various sources, characterizing prices for specified products for EU, USA and Southeast Asia markets is estimated. The appropriate calculation methodology of price characteristics of Ukrainian manganese crude ore, considering the peculiarities of its material composition, is suggested. Cost data, connected with export of manganese ore and ferroalloys from Ukraine on different markets (EU, USA, Southeast Asia, Turkey) is systematized and analyzed.

References

Grischenko S.G., Kutsin V.S., Kravchenko P.A. Ferroalloy industry of Ukraine : current state and development trends. Ecology and industry.2013,No 3, p. 4-9

Velichko B.F., Gavrilov V.A., Gasik M.I. Manganese metallurgy of Ukraine, Kiev, Tekhnika, 1996, 472p.

Process lubricant for deforming broaching of pieces made of titanium

Wed, 14 May 2014 13:03:56 +0300

UDK 621.919

Process lubricant for deforming broaching of pieces made of titanium

Sheikin S.E. D.Sc. in engineering, head of the department “Advanced resource efficient technologies of mechanical operation” of Bakulya institute of superhard materials”, Kiev, Ukraine.

Paschenko E.A. D.Sc. in engineering, head of the department “ Physico-chemistry and technology of compositional abrasive materials, development and appliance of instruments made of them” of Bakulya institute of superhard materials”, Kiev, Ukraine.

Rostotsky I.Yu., junior research scientist of the department “Advanced resource efficient technologies of mechanical operation” of Bakulya institute of superhard materials”, Kiev, Ukraine.

Gavrilova V.S., chief engineer of the department “Physico-chemistry and technology of compositional abrasive materials, development and appliance of instruments made of them” of Bakulya institute of superhard materials”, Kiev, Ukraine.

Protsishin V.T. PhD in Technical Sciences, chief of laboratory of lubricant-cooling technological agents (MChTZ, GP “UkrNIINP “MASMA”).

The results of process lubricant development for deforming broaching and tube drawing of titanium alloy are presented. Their tribotechnical characteristics and boundary conditions of their appliance are determined. Technological recommendations for their usage are formulated.
Key words: lubricant, titanium alloy, plastic deformation, specific friction force, seizure.

Introduction
Deforming broaching (figure 1) is the process of hole-making operations in pieces such as thimbles and tubes with the help of cold plastic deformation in stages. With the usage of this process, the reduction of labor intensity of processing, rise of metal recovery coefficient, resistance to fatigue failure, improvement of coating surface, significant reduction of surface undulation are achieved. Besides, there is an opportunity to replace alloyed steels with more simple ones by means of strain hardening both coating surface of a work piece and its core.

During deforming broaching the instrument in the form of flattened cone is moved through the hole of work piece. Herein, the diameter of an instrument is several times larger than diameter of a hole in the billet, which is called interference. The conditions of contact interaction of an instrument with work piece may be characterized as extremely rough, because normal contact stress in the interaction area of an instrument with work piece may reach the value 6-8 σt of work material at coefficient of friction 0.05-0.1 and higher [1]. This means that deforming broaching may be referred to that category of processes of cold plastic deformation, where contact friction at high normal contact stress takes place.
Stable flow of deforming broaching process (absence of seizure between instrument and work piece) is provided by the usage of process lubricant, the choice of which should be fulfilled separable for each composition of instrument and work piece. The experience has shown that hard alloy metal VK 15 has the most beneficial combination of mechanical and tribotechnical characteristics, providing the reliability of its appliance as material of work pieces of deforming broaching. Herein, during deforming broaching of pieces from constructive carbon steels, the reliable operation of an instrument is provided by the usage of liquid process lubricants, which are normally used at pressure metal treatment (sulfofrezol, lubricants of MP type, on the base of machine oil).
However, application of these process lubricants during processing of pieces from non-ferrous metals and alloys (including titanium), as a rule, is impossible because of seizure of work piece with the instrument [2]. In this case (as a way out) solid lubricants with high screening capacity may be used. For example, for deforming broaching of billets from stainless steel, solid lubricants on the base of molybdenum disulfide are used [4], cadmium iodide is applied for processing of titanium alloys. However, as experiments have shown, lubricants on the base of molybdenum disulfide while processing of titanium alloys is not effective as it cannot provide treatment without seizure. Application of cadmium iodide is undesirable in virtue of its toxicity. Herein it should be considered that usage of solid lubricants complicates processing technology significantly as it requires extended operations for their laying and removing after drawing.
The presence of effective process lubricants allowed to use deforming broaching process (drawing) while manufacturing of axisymmetric titanium pieces such as cylinder or rod, which are widely used in aeronautical engineering and to reduce significantly its labor intensity.
There is data in literature about process lubricants allowing to perform treatment of titanium alloys by means of cold plastic deformation.

There is short overview of experimentations in work [5], fulfilled earlier by native and foreign researches; they concern creation of lubricants for titanium and its alloys processing. It is mentioned that investigations of polychlorofluorosiloxanes liquids with various viscosity and chlorine and fluorine content while friction of pieces from titanium and steel appeared to be noneffective. At the same time some positive results concerning negative skin friction while usage of range of chlorated hydrocarbon with different chlorinity (from 28% to 70%) as lubricants were obtained. Lubricants on the base of chlorated hydrocarbon are marked to increase significantly seizure load while titanium treatment under pressure. Positive effect was discovered while usage of the lubricant on the base of correlation of oleinic acid and crystalline iodine.
Referring to foreign patents, the authors of [6] mentioned that during cold treatment of titanium and its alloys by pressure, the composition on the base of highly viscous lubricating mineral oil, mixture of lubricating mineral oil of various viscosity, vegetable oil and animal fatty substances, higher fatty acids and their derivatives are used. Chlorated lubricating mineral oil, polymerized and sulphurated vegetable oil, polyol are also used.
For cold rolling of pipes from titanium alloys on Russian Verkhsaldinskyi metallurgical complex, water-based lubricant [7] was created, which contains still bottoms, got in process of freons production on the stage of their water refining from НСl and HF, sodium soaps of higher fatty acids, borax and talcum powder as filler.
Concentration of lubricant-cooling process agent [8] is known, which is used for pressure shaping (rolling and drawing) of refractory metals and alloys: zirconium, titanium, etc, containing triethanolamine salts of mono- and diester of orthophosphoric acid and monoethanolamides of carboxylic acids, triethanolamine salts of caronic acids, complex estercarboxylic acids and polyatomic alcohol, polyoxiethylene ethers of allylphenol.
Technical result from appliance of mentioned above technological means – reduction of coefficient of friction in the system instrument-billet, improvement of heat-removal, that allows to eliminate metal pickup on the instrument and reduce undulation of work surface.
But it should be mentioned that performance characteristics of mentioned lubricant compositions cannot guarantee the treatment of titanium pieces without seizure. Thus, effective process lubricants for titanium and its alloys treatment by cold plastic deformation, where contact friction at high normal contact stresses takes place are absent on the market of CIS countries. Consequently, engineering and manufacturing development of such lubricants is relevant objective.
The aim of this research is creation of effective process lubricants for titanium alloy treatment by cold plastic deformation and study of their processing capabilities.

Testing methods

For research of operational characteristics of process lubricants in the processes of cold plastic deformation there developed a lot of methods [2, 5].
It would be the most accurate and right to perform testing of samples of process lubricants in conditions of that manufacturing processes, for which they were aimed. However, in some cases it is connected with formidable difficulties, which forces to use simplified laboratory technique for initial test.
In our researches for preliminary study of sealing properties of process lubricants the methodology, residing in process lubricants tests according to the smoothening of outside surface of cylindrical work scheme, on which the lubricant is laid, is applied. [2] (fig. 2). Work piece (1) with applied testing lubricant was put into the disc chuck. Deforming instrument in the shape of core from hard alloy VK 15 (2) with spherical end faces (fig. 2,b) was placed into stiff holder (3) with an indicator (4) and was forced against the billet with Ps force. The instrument was moved along the generating rotating billet. Herein the force Ps was stepwise increased and the treatment was fulfilled on one and the same area and in the same direction.
Installation was preliminary calibrated. While treatment the undulation of work surface was increasing. With increase of the force Ps there was increase of contact pressure. Discontinuance of surface (in case of solid lubrication testing) and increase of surface undulation indicates the seizure. Herein on the working shank end there formed processing metal pickup (figure 2c). Sealing properties of the lubricant may be estimated from the value of effective pressure, which precedes seizure, or from the way scale, run by the piece before seizure.

Advantage of this technology is the possibility of quick achievement of results and also the possibility of multiple use of the billet. Considering that the price of materials is continuously increasing, the last fact is of no little interest. Disadvantage is impossibility of exact determination of contact pressure while testing. This methodology allows only to estimate qualitatively the working ability of lubricants under test and ranging them from sealing properties.
More precise estimation of operation characteristics of process lubricants was fulfilled under the methodology, corresponding the real process of deforming broaching. The range of hard-alloy deforming elements is flown through the hole of thimble with applied lubricant on it [1]. The size of each following element is greater the previous one on some value. Herein, the contact pressure increases at each successive pass by means of strain-hardening of processing material. While usage of liquid lubricants, the surface undulation decreases. One provides measurements of axial force while testing.
Its increase, material pick up on the instrument and discontinuance of surface layer witnessed about seizure. Contact pressure at the moment, preceding seizure and also the amount of omitted before seizure deforming elements may characterize operation parameters of process lubricant. High accuracy and great information content may be referred to its advantages. The fact that thimble under test as a rule cannot be used in further operations refers to disadvantages.
In testing under the first methodology, cylindrical billet Ø60 mm was used, line feed of an instrument made S = 0,097 mm/r., rotating speed - n = 80 rpm. Ps force was increased stepwise at a pitch of 50 N.

For determination of specific friction force of testing lubricant, the methodology developed at Superhard material Institute of National Academy of Sciences of Ukraine was used. This methodology is based on two statements, determined in [2]. The first is what the value of real force while deforming broaching does not depend on conditions, influencing the friction on contact surface, i.e. lubricant and type of instrument material. The second is what the solid lubricant on the base of molybdenum disulfide (toluene, lacker F9-K, MoS2 in special value) has constant specific friction force τ = 65,3 MPa, not depending on contact pressure. Specific friction force was calculated as friction force, referred to the instrument contact area with work piece.

. , where τ – specific friction force, D – mean diameter of contact surface, l – stretch of the instrument contact with work piece [2].

F1 = Q1·cosα - P1·sinα (1)
F2 = Q2·cosα - P2·sinα (2)

where F1, Q1, P1 - friction force, axial force of broaching and radial force respectively, during treatment with lubricant on the base of molybdenum disulfide [2]; F2, Q2 and P2 - friction force, axial force of broaching and radial force respectively, during treatment with experimental lubricant.
From condition of equality of radial forces P1 = Р2 taking into account (1,2) specific friction force equals:

F1 = F1 + ( Q2 - Q1)·cosα (3)

Experimental results and their discussion
Liquid process lubricants for deforming broaching of pieces from titanium alloys

High chemical activity is peculiar to titanium, that is why there forms thin viscous oxide film ТіО2 on its surface in the air or other medium containing oxygen. It is marked that films on titanium appear as a result of access to water surface, even if its amount is too small and it is available in the form of vapors. Oxyde,
being formed on the processed titanium surface at room temperature or higher, was recognized with rutile (tetragonal modification of titanium dioxide). In normal conditions, except rutila, titanium dioxide may have rhomb-shaped modification –brookite and tetragonal – athanase, i.e. oxidized surface of titanium is nonhomogeneous. At temperatures higher than 400 ºС all modifications of dioxide turns into rutile. Except dioxide there is significant quantity of anion impurities on the surface, they influence significantly on the surface chemistry.

The presence of this film explains low chemical activity of titanium surface, i.e. the absence of chemical interaction with components of lubricating medium at normal temperatures. When lubricant application there takes place physical adsorption. During adsorption on polymorphic materials of titanium dioxide type there may affect the influence of various crystal faces and side planes with different adsorptive characteristics.
The main requirement to the lubricant for treatment of titanium alloys is its ability to resist high pressure without breakdown of lubricant film. In our researches there were tested 120 different in composition lubricating mixtures.
They included components, providing high lubricating and adhesive properties; viscous, antioxidative and other additives.
Lubricants on the base of hydrocarbon fractions with kinematic viscosity at 20°С - 1-10 mm2/s, contained chlorinated paraffin wax from 10 to 50 % and phosphorus-bearing additives of tributyl phosphate type. As solvents there used dichloroethane, chloroform, ethylene tetrachloride, etc.
As thickener there used polyisobutylene of different molecular weight from 400 to 6000 units, polypropylene glycol with molecular weight 400-1500 units, synthetic rubbers, high molecular hydrocarbon, plant products. Concentration of thickener in lubricants compositions made from 5 to 20%. Besides, in the composition there were included some elements, which provided high adhesive properties in relation to titanium surface: sulphurated fats, amidoetherial mixtures and other.
Herein there were used several ways for lubricant appliance on the surface of titanium billets:

one layer was applied, soaking for predetermined time;
doubled layer o lubricant was applied, i.e. liquid low-viscosity lubricant was used and then high-viscosity one, containing the same components and thickener;
lubricant was applied on the heated work piece;
heated lubricant was applied;
work surface was preliminary mechanically prepared (provisioning of necessary undulation);
work surface was preliminary chemically prepared to create adhesion layer between lubricant and work surface.

When applying one layer of lubricant with soaking for predetermined time, the best results showed the mixture on the base of tall oil, partially saponified by potassium hydroxide with addition of oxyethylated higher fatty acids, aminokalium soaps of acids of plant oils, ethers of alkohole and aminoalcohol of acids of plant oils. Seizure during testing under the first methodology was achieved only after holddown pressure Рh = 200 N. However, during broaching seizure elements were observed after the first deforming cycle at contact pressure 0.8GPa. Considering the level of normal contact pressures, taking place in real process of deforming broaching, this lubricant mixture may be recommended for titanium alloys processing.
In case of putting double lubricant layer, the best sealing properties during tests under first methodology (seizure at Рh = 250 N) showed double-layer lubricant mixture, when on the surface of titanium low-viscosity lubricant of high surface activity and penetrability (on the base of methyl ethers of fat acids of plant oils) was applied. This lubricant contains approximately 30% of active additives (sulfital, tributyl phosphate, etc.). Its task was to create a key between titanium surface and the second layer of lubricating grease, which contains highly viscous hydrocarbon, ethers of higher fatty acids and aminoalcohol, mixed borate and colophony. Testing through deforming broaching showed that the given mixture also does not possess enough screening capacity. Seizure appeared on the second cycle of deforming under contact pressure 1.0 GPa.
For creation of adhesion layer between lubricant and work piece surface, primary chemistry of the titanium alloy surface was used by immersion (with heating and without it) into aqueous solutions of acids (citric, formylic, oxalic, chlorohydric, etc.) with surface-active agents additions (SAA), and also highly-concentrated alkaline solutions with active additions and followed by lubricant appliance. Better results was obtained during usage of RODEL R11 content as SAA.
More than 60 mixtures were tested with SAA. Process lubricants on the base of hydrocarbon fraction, chloroform, dichloroethane, ethylene tetrachloride showed better results than others, also all the mixtures used 10-50 % of chlorinated paraffin wax at usage of colloidal graphite as filler. Amidoether mixes and sulphurated fats also were included.
During testing of lubricants with such composition under the smoothening scheme, there was no seizure at a load Рh = 300 N.
During testing under the scheme of deforming broaching while thimbles processing from VT1-0 with a hole Ø 19 mm and wall thickness 11 mm the seizure took place on the second pass at contact pressure 0.7 GPa. When wall thickness 2 mm and contact pressure 0.7 GPa, the seizure took place on the 8th cycle. However, it should be marked that one failed to repeat obtained result.
In such a way, tested compositions of liquid lubricants cannot be recommended for usage while titanium alloys treatment by means of cold plastic deformation (CPD), where contact friction takes place at high normal contact stress, but the results obtained may be useful for further researches.
Solid process lubricants on the base of polymer composites for deforming broaching of pieces from titanium alloys.
Table one shows the compositions of tested lubricating compositions

Table 1
Composition	Base	Filler	Solidifying agent
1.1	Diane ethoxyline resin 75%	Polytriazine 25%	Isomethyltetrahydrophthalic anhydride
1.2	Diane ethoxyline resin 50%	Alumino silicate mineral , 50%.	Isomethyltetrahydrophthalic anhydride
1.3	Diane ethoxyline resin 50%	urea-formaldehyde resin and alumino silicate mineral 50%.	Isomethyltetrahydrophthalic anhydride
2.1	Epoxy-novolak resin 85%	ASM 3/2 15%.	Isomethyltetrahydrophthalic anhydride
2.2	Epoxy-novolak resin 70%	АSМ 3/2 15%; Graphite 15%.	Isomethyltetrahydrophthalic anhydride
2.3	Epoxy-novolak resin 65%	Graphite 15%; tin powder 20%.	Isomethyltetrahydrophthalic anhydride
2.4	Epoxy-novolak resin 65%	Molybdenum disulfide 15%; tin powder 20%.	Isomethyltetrahydrophthalic anhydride
3.1	Diane ethoxyline resin , modified by maleic anhydride 80%	Copper oleate 20%.	Isomethyltetrahydrophthalic anhydride
3.2	Diane ethoxyline resin , modified by maleic anhydride 80%	Calcium stearate 20%.	Isomethyltetrahydrophthalic anhydride
3.3	Diane ethoxyline resin , modified by maleic anhydride 70%	Colloidal graphite 30%.	Isomethyltetrahydrophthalic anhydride

Appliance of these compositions is grounded by modern trends of polymer composites of triboengineering use development, but it is based on the usage of available components, which are produced by SIS countries companies [7,8].

During testing according to the first methodology (fig. 2) of compositions 1.1 - 1.3, 2.1 - 2.4, 3.1 - 3.2, solid lubricant material delamination from the surface of the billet and seizure of an instrument by processing material on the first stage of loading at Рh = 50 N.
Composition 3.3 showed higher sealing properties – seizure was not found at load Рh= 200 N. As a result, its researches were continued under the second, more precise, method.
During testing according the scheme of deforming broaching, thimbles from titanium alloy VT 1-0, hardness НВ160 with a hole Ø 35 mm, with various wall thickness t0 = 4, 7, 9 mm were used. For comparison the thimbles of the same size and hardness from the steel 20 were also broached. Herein solid lubricant on the base of molybdenum disulfide with known specific friction force was applied on the pieces from the steel 20 [2]. Composition 3.3 was applied on the internal surface of thimbles from VT 1-0. Interference on each deforming element was 0.1 mm. There are dependences of changes of contact pressures and axial forces respectively in the course of experiment in the figures 4,5.

The results obtained show that testing lubricant has high sealing properties. Discontinuance of lubricant film and steplike increase of axial force of broaching was observed only during broaching of work piece with wall thickness 9 mm on the 8th stage of deforming at contact pressure ~ 1.6 GPa (fig. 4).

Considering the fact, that geometry and hardness of steel and titanium thimbles is equal, distinction in values of axial forces is explained by distinction in values of friction forces, i.e. the difference in tribotechnical characteristics of applied lubricants.

As one may see from the given graphs, with usage of composition 3.3 the axial force of broaching in all cases is smaller than in case of appliance of solid lubricant on the base of molybdenum disulfide, which witness about antifriction properties of testing lubricant.
Calculation data of specific friction force of testing lubricant is given in the figure 6. One may see that the value of specific friction force of the developed lubricant is much lower than of lubricant on the base of molybdenum disulfide.
Increasing type of the dependence 2, shown in the figure 6, is conditioned by accumulation of ageing in the layer of polymer coating in conditions of contact interaction of an instrument with work piece.
From the represented data one may see that the sphere of application of developed lubricant on the base of epoxidation tar, with anhydride solidification is limited by contact pressure 1.6 GPa. Consequently, for increasing of its screening capacity, cohesion strength and adhesion strength to titanium, the lubricant was modified by addition of organosilicon and finely-dispersed carbon filler. It has rather high hardness (0.22-0.25 GPa), strong depletion effect and the ability to provide lubricating action in wide range of temperature.

While testing of modified lubricant, thimble of titanium alloy VT 1-0 with hole Ø 35 mm, wall thickness 11mm and interference 0.1mm was broached. Specific friction force was calculated under the methodology described above.

Dependences of changing of axial forces and contact pressure, presented in the experiments, are shown in the figures 7 and 8 respectively. The value of specific friction force of modified lubricant from cycle numbers of deforming is shown in the figure 9. Herein the dashed line shows in contrast the value of specific friction force of solid lubricant on the base of molybdenum disulfide.
One may see that in all the range of contact pressure the value of specific friction force of modified lubricant is lower than of lubricant on the base of molybdenum disulfide, till the contact pressure 2.2 GPa.
Thus, this lubricant has higher sealing properties than lubricant without fillers.
Process lubricant, modified by organosilicon and finely-dispersed carbon filler was examined during deforming broaching of thimbles from titanium alloys VT 6 (HB 250) and VT 22 (HB 285) with diameter 19 mm, wall thickness 11 mm and interference 0.1 mm. The values of axial forces and contact pressures are given in the figure 9 and 10 respectively. One may see that this lubricant does not lose its screening capacity at contact pressure 2.8 GPa and 3.1 GPa (fig. 11), for VT 6 and VT 22 respectively. During broaching of the alloy VT 22 on the seventh cycle of deforming, there appeared light scratches on the instrument.

On the basis of results obtained, one may represent the following technological recommendations for application of the developed lubricating compositions.
The first of the tested solid lubricants (without organosilicon and finely-dispersed carbon filler) is more technological and in cases when contact pressure in zone of instrument interaction with titanium piece does not exceed 1.6 GPa, this lubricant is more preferable. Process lubricant, modified by organosilicon and finely-dispersed carbon filler, should be applied at pressure more than 1.6 GPa.
Besides, one should consider that the process of solid lubricant laying is the additional process stage, which includes unavoidably drying period, which in its turn may continue for several hours. This will lead to the product appreciation. Besides, one should remember that after cold plastic deformation, solid lubricant is still on the processing surface and in case when technical requirements do not allow that, for its removal one will have to remove the envelope of metal, i.e. one more process stage. Thus, their usage may be driven by economic considerations, for example, in cases when it is necessary to approximate the size of the piece to the size of ready work piece to the maximum by means of cold plastic deformation and minimize the amount of facing.

Conclusions:

1. Examined compositions of liquid lubricants on the base of hydrocarbon fraction cannot be recommended for application during processing of tube pieces of titanium alloys by means of cold plastic deformation, where contact friction at high normal contact stresses takes place, and the results obtained may be useful in further researches.
2. The developed process lubricant on the base of polymer composites without filler allows to perform multicycle deforming broaching of titanium pieces at contact pressure to 1.6 GPa.
3. Introduction of fillers allowed to rise significantly lubricant sealing properties and perform multicycle deforming broaching of pieces from titanium alloys VT 1-0 and VT 22 at contact pressures to 2.2 GPa ans 3.1 GPa respectively.
4. The developed solid lubricants can be applied while cold plastic deformation of constructional titanium alloys of aircraft, rocket and shipbuilding application. All the high-strength alloys (from VT 1-0 to VT 22), developed by VIAM (All-Russian Research Institute of Aviation Materials), are among them [11]. Analyzing chemical composition of tested titanium alloys, one may conclude that screening capacity of process lubricant does not depend on the quality and quantity of titanium alloy addition elements.

References

1. O. A. Rozenberg. Mekhanika vzaimodeystviya instrumenta s izdeliem pri deformiruyushchem protyagivanii.(Mechanic of instrument interaction with work piece during deforming broaching). Kiev, Naukova dumka, 1981. 288 p.
2. Kritskiy A.D. Osobennosti razrabotki tverdosplavnykh deformiruyushchikh protyazhek dlya obrabotki otverstiy v detalyakh iz trudnoobrabatyvaemykh detaley i splavov: Avtoreferat dissertatsii kandidata tekhnicheskikh nauk. (Peculiarities of development of hard-alloy deforming drawing for treatment of holes in pieces from hard-to-treat pieces and alloys: Author's abstract of PhD in Technical Sciences). Kiev, 1983. 26 p.
3. Tishchenko V.T., Rozenberg A.M., Rozenberg O.A. Copyright certificate 273357 (USSR). Lubricant for cold metal working. B.I. 1970, No20.
4. Pasechnik M.S. Teoreticheskie osnovy razrabotki smazok dlya obrabotki metallov davleniem (Theoretical bases of lubricant development for metal treatment under pressure). Tekhnologicheskie smazki, Kiev, UkrNI-INTI, 1971, p.5-16.
5. Grudev A.P., Zil'berg Yu.V., Tilik V.T. Trenie i smazki pri obrabotke metallov davlenie.Spravochnik (Friction and lubricants during metal treatment under pressure). Moscow, Metallurgiya, 1982. p.310.
6. Chechulin B.B., Ushkov S.S., Razuvaeva I.N., Gol'dfayn V.N. Titanovye splavy v mashinostroenii (Titanium alloys in machine building). L. Mashinostroenie, 1977, p. 248.
7. Patent RU 1531470. Lubricant for cold metal treatment under pressure (Korol'kova L.V., Alikina N.A., Kuvaeva G.A and others). Publishe 15.11.1994.
8. Patent RU 2230777 Concentrate of lubricant-cooling processing mediums (Agapitov V.A., Zamuraeva S. E., Kudryashchov P.A and others). Published 20.06.2004.
9. Wang Z., Pinnavaia T. J. Hybrid organic-inorganic nanocomposites. Chem. Mater., 1998.,10. P. 1820 – 1826.
10. Lan T., Pinnavaia T. J. Clay-reinforced epoxy nanocomposites // Chem. Mater. – 1994. – 6. – P. 2216
11. I.V. Gorynin, B.B Chechulin Titan v mashinostoenii (Titanium in machine building). Moscow, Mashinostrenie, 1990. 400 p.

Adaptive identification of load moment on the working rolls of break-down mill based on inverse dynamic problem

Mon, 19 May 2014 13:16:19 +0300

Adaptive identification of load moment on the working rolls of break-down mill based on inverse dynamic problem

There considered the method of identification of load moment on working rolls of break-down mill on blooming on the base of inverse dynamic problem with implementation of adaptation of model coefficients by Kachmazh modeling algorithm.
Keywords: identification; algorithm; adaptation; model.

The main technological element of blooming is break-down mill, working rolls which are situated under the permanent random load. This object is characterized by the following specific phenomena such as slip, caused by sharp change of the external friction moment. Meanwhile there occurred redistribution of load moments on the working rolls. By the nature of one redistribution it is possible to define the type of slip and intensity of load on working rolls. Therefore, for formation of control actions appropriate to the technological situation it should be determined uncontrolled static moments Мbu(t) and Мbl(t) for the upper and lower working roll respectively.
To solve this identification problem, it was decided to use the method of inverse operator based on the theory of inverse dynamic problem (IDP). Application of IDP enables, on the known motion trajectory of phase coordinates, to determine the forces affecting on the object management controlling.
The inverse dynamic problem is defined as follows [1]. Let the known mathematical model of system is F(t),its initial state is established as , . The desired motion trajectory is determined and , t≥0. It is necessary to find out the force , t≥0, which stimulates movement of system on the known motion trajectory , , t≥0.

In general terms, structural scheme of model, which realizes the identification IDP methods can be represented as follows (Fig. 1).

Fig. 1. Generalized scheme of identification based on IDP

Vector of perturbations for the working rolls of the crimp cage, that need to be identified is N(t)=[Мbu, Мbl], vector of input measuring signals - y(t)=[Usu, Іu, Usb, Іb], where Usu and Usl - set point voltage for the upper and lower drive motors respectively. Meanwhile the total current is the sum of the currents through the burden channel and set point Іu(b) = ІМb + ІUs.
Then, the signal of the burden current ІМb equals ІМ(u)b= Іu(b) - ІUsu(b).
Structural scheme describing the subsystem of identification of the load moment on working rolls by OM method is shown in the Fig. 2. The basic idea is to determine the burden current ІМb by the known transfer function according to the channels "burden moment - burden current Мb-ІМb and "set point signal - set point current" ІUs, and by known input influence І and ІUs. This signal is the input influence of transfer function, inverse to transfer function of the channel "burden moment - burden current" Мb - ІМb. However, if the time constants are calculated basing on the parameters of the object, which may vary depending on the conditions of rolling, in the subsystem of identification there foreseen blocks of adaptation of parameters of transfer functions.

Fig. 2. Structural scheme of the subsystem of moment identification of burden on working rolls by inverse model method

Let us consider the problem of parameter estimation of transfer functions , , , , which dynamics, in general, can be described by the equation , where , - input and output signals, respectively for TF, which parameters should be set up, - vector of parameters that should be set up.
For this problem the algorithm of Kachmazh is better to introduce in iterative form [2]

where n = 1, 2, 3 ... m - iterations of the algorithm.
In spite of the stability and permissible convergence of the Kachmazh algorithm, its drawback is that, when the components of the vector are tended to zero, value of may become equal to zero, i.e. parameter estimation, which is formed by the expression (1) may become unstable [2].
Therefore it is advisable to use modification of Kachmazh algorithm proposed in [2]

(2)

where , .
Fig. 3 shows modeling results of the subsystem of identification during unilateral slip on the lower working roll.

Fig. 3 Modeling results of identification of the static moment on the working rolls of the break-down mill during unilateral slip on the lower working roll: a) identified static moments of working rolls (1 – lower roll, 2 - upper roll) while loading the lower roll, Нс m; b) error of static moment identification,%

In this case there is a redistribution of load moments, and herewith there takes place load decrease on the lower roll Мbl(t)=40 Нс· m and and increase of load on the upper roll to Мbu(t)=135 Нс·m.
Conclusions. The author suggests to identify the load moment on the working rolls of break-down mill. Herein, Kachmazh modeling algorithm of adaptation, as the most suitable for identification in real-time mode is proposed to be used in order to adapt coefficient identification model. Fulfilled modeling showed the effectiveness of using this algorithm for adaptation of non-stationary coefficients of the load moments identification model. Analysis of the results obtained showed the asymptotic character of change of model parameters that should be set up. Convergence of parameters to actual values occurs for allowable time - tсonv=0.3с.

References

Krut’ko P.D. Obratnye zadachi dinamiki v teorii avtomaticheskogo upravleniya (Inverse problems of dynamics in the theory of automatic control). Moscow, Engineering, 2004, 576 p.
Lyashenko S.А. , Lyashenko А.S. Evaluation of the pseudo regression model. ААECS. 2010. No1(25), p.36 – 41.
Goodwin G.C., Ramadge P.J., Caines P.E. Discrete time multivariable adaptive control. IEEE Trans. Aut. Control. 1978. Vol. AC-25. No2. p.449 – 456.

Design and Fabrication of a Four-piece Channel Type ESR Mould of Mild Steel

Wed, 11 Jun 2014 11:04:48 +0300

Design and Fabrication of a Four-piece Channel Type ESR Mould of Mild Steel

ESR mould design and construction are constantly under review and development to cater the demands of a wide range of shapes and cross section of ingots to be produced by the ESR process. In the present study, initially four-piece channel type split-mould of mild steel was designed and fabricated for production of ESR ingots of rectangular cross-section 78 × 68 mm and around 350 mm height. The initial design developed a problem of localized over-heating at the bottom of the mould resulting in welding with the solidified ESR ingot. The problem was studied through a Perspex model of the broad face of the mould. Based on this study the mould was redesigned. The redesigned mould performed satisfactorily and used for production of ESR ingots of larger sizes.

Keywords: ESR, water jacketed split mould, over-heating, perspex model

T. R. Bandyopadhyay

Ex-faculty of Metallurgical Engineering,

National Institute of Technology, Durgapur-713209,

West Bengal, India and presently ‘Visiting Faculty’

in Biju Patnaik National Steel Institute, Odisha,India

Introduction

The electroslag remelting is a consumable electrode remelting process in which the metal in the form of a bar or rod, which is the consumable electrode, is melted under a layer of molten slag which is super heated by the passage of electric current. The slag used has specific electrical resistivity of the order of 0.002 – 0.008 ohm-m and provides heat due to resistance heating [1]. The tip of consumable electrode, which is kept immersed in the molten slag, melts due to high temperature of slag bath. The droplets of molten metal fall through the slag bath and join the metal pool below it. The metal pool progressively solidifies in a water-cooled mould resulting in the formation of ESR ingot. As the process continues and the growing ingot displaces the slag bath in an upward direction, the molten metal pool and the ingot below it are enveloped by the solidified slag skin. On stripping the ingot from the mould, the solid slag shell flakes off and leaves behind a smooth and shiny ingot surface.

Mould for Electroslag Remelting (ESR) has to perform multifarious functions: it holds the liquid slag bath which provides heat due to passage of current through it, contains the molten metal as it accumulates and imparts the required shape to the solidified metal. Apart from these, the mould is also required to transfer a major portion of the heat generated in the process through its wall to the cooling water and also, to conduct a substantial current during the process. Efficient mould design and fabrication, therefore, has a considerable bearing on the production of ingots through ESR

The main criteria for the selection of the material for mould fabrication are good thermal conductivity and ability to withstand the thermal shock. Copper is the favourite choice for the mould material because of its high thermal and electrical conductivity. As a result copper can be used for fabrication of mould up to a section thickness of around 20 mm [1]. But the main disadvantage with copper is its cost. Moreover, it has been found that mild steel moulds, for short runs e.g. 50-60 heats, are more economical than copper moulds because of noticeable lower cost, high adaptability to manufacture and ease of repair 1.

In the present investigation four–piece rectangular channel type mould of smaller dimension was initially fabricated from mild steel, tested and subsequently larger moulds were fabricated to carry out ESR melts.

Experimental

Four mild steel channels, two channels each of 450 mm high, 150 mm width and 7.5 mm thickness and the other two each of 450 mm, 75 mm width height and 7.5 mm were selected for fabrication of the four–piece rectangular channel type mould. Both the inner and specially the outer surface which will form the mould face of each of the channel was ground and cleaned.

Back side of each of the channel was welded with a back up plate of 430 mm high and 6.5 mm thick with the help of spacer pins in order to keep a uniform gap of 5 mm throughout and also to form opening in the form of slit for inlet and outlet of water at the two ends of the channel. The slit at each end was covered by a distribution box for cooling water into the slit.

In the present investigation ESR ingots of 78 × 68 mm cross section and around 350 mm height were produced from 40 mm round electrodes in a water jacketed four-piece split-mould of mild steel (Fig. 1). Out of the four-piece split-mould, two–piece each is of 75 mm width and 450 mm height (narrow-face) and the other two–piece each is of 150 mm width and 450 mm height (broad-face). The cooling water entered through a pipe fitted at the bottom into a distribution box (pressure equalizer) that in turn fed the water into cooling channel of 5 mm gap through an opening. The cooling water outlet pipe was fitted at the top of the mould. During ESR, the current, voltage and average power input were maintained at 1300 A, 32 ± 2 V and 41 kW respectively.

Over-heated zone

Figure 1 ESR mould showing 2 pieces forming half the mould

The value of heat flux in ESR mould is usually of the order of 1 MW m-2 which is far less than in continuous casting of the order of 2-2.5 MW m-2 1. This is because the ESR process is characterized by the formation of thin solidified slag skin of around 1-2 mm on the inside face of the mould which reduces heat transfer from the solidified ingot to the cooling water via mould. Accordingly, water flow velocity in the water-cooling channel is required to be 1.4 m s-1 1. In the present case the cooling water velocity was maintained at 1.08 m s-1 resulting in volumetric water flow rate of 40 L min-1.

Initially at the bottoms of the both broad and narrow–face mould a cut out was given with the view of obtaining a smoother flow of water into the cooling channel. But, in the initial melts moulds were getting overheated at a height of about 40 mm from the bottom (Fig. 1). As a result, the solidified ingot used to stick with the mould at that over-heated zone causing great difficulty in stripping of the solidified ingot. Therefore, a Perspex model of the broad face of the mould was made to visualize the effect of the shape and width of the cut out through which water entered into the cooling channel from the pressure equalizer, on the flow characteristics of the cooling water (Fig. 2).

Figure 2 Perspex model of the broad face of the ESR mould

During the study of the model it was observed that the water entered the cooling channel right through the edge of the contour of the cut-out since this offered a less resistance path to the flow of water. This resulted in non-wetting of the space between the bottom of the mould and the edge of the contour causing entrapment of air bubbles. Eventually, the mould got over-heated in that zone. Based on this study two faces of the mould were redesigned by replacing the contour in the form of cut-out with an opening in the form of a slit of 10 mm for the entry of the cooling water in the channel. The new design of the mould is shown in Fig 3.

Figure 3 Two faces of the ESR mould

During the trial runs with the redesigned mould the current, voltage and average power input were maintained at 1300 A, 34 ± 2 V and 41 kW respectively during ESR of mild steel electrode. The difference in temperature between the outlet and inlet water during ESR was found to be 50C. The redesigned mould performed satisfactorily and ESR ingots were produced without any problem of sticking of the ESR ingot with the mould. An ESR ingot produced during the trial runs is shown in (Fig. 4). The average weight of the ESR ingots produced during the trial runs was 12 kg.

Figure 4 ESR ingot produced using redesigned mould in trial runs

After successful trials with the mould, the design was employed for fabrication four - piece mild steel channel mould for production of larger size ESR ingots (Fig. 5a and 5b). The ESR ingots produced were of various cross sections in the form square (500 x 150 x 150 mm) to slab (600 x 280 x 80 mm). The power input was in the range from 100 - 120 kW.

Figure 5a ESR slab produced by using produced by redesigned mould redesigned mould

Figure 5b ESR ingot of square cross section produced by using redesigned mould

Due to formation of scaling due to passage of cooling water at the back wall of the each piece of the mould there is a possibility of narrowing down the gap. This can be prevented by passing HCl at typically 18% concentration periodically through the mould to remove rust or iron oxide scale.

Conclusion

The redesigned mould four-piece mild steel channel mould performed satisfactorily. ESR ingots of various cross-sections were produced without any problem of sticking of the ESR ingot with the mould surface. Split mould renders very convenient and easy way of stripping off the solidified ESR ingot

Reference

[1]. G. Hoyle: ‘Electroslag processes principles and practice’, 1983, 121-123, London and New York, Applied Science Publishers.

Diffusing Behaviors of Si in Silicon Steel during Annealing Process

Thu, 22 May 2014 15:39:52 +0300

Hui Li

Key Laboratory of Ministry of Education for Modern Metallurgy Technology, College of Metallurgy and Energy, Hebei United University, Tangshan, China

Jinglong Liang

Key Laboratory of Ministry of Education for Modern Metallurgy Technology, College of Metallurgy and Energy, Hebei United University, Tangshan, China

Yungang Li

Key Laboratory of Ministry of Education for Modern Metallurgy Technology, College of Metallurgy and Energy, Hebei United University, Tangshan, China

Fenping Zhang

Key Laboratory of Ministry of Education for Modern Metallurgy Technology, College of Metallurgy and Energy, Hebei United University, Tangshan, China

Shufeng Yang

School of Ecological and Metallurgical Engineering
University of Science and Technology Beijing; Beijing

Diffusing Behaviors of Si in Silicon Steel during Annealing Process

Abstract: This paper studies on the influence of annealing temperature on the distribution of Si content in the electro-deposition samples of high silicon steel, and the content distribution of Si, the section layer textures and the texture distribution are also analyzed. The results show that higher the temperature is, bigger the diffusion coefficient gets. When the temperature reaches 1050 С, the annealing time is 210min, in which case the crystals in the samples are distributed well. Si is also well distributed, with the average concentration 6.3715%. Analyzing the textures in the samples, the content of easily magnetic textures of {100} and {110} with high density increases, while the density of bad textures decreases.
Key words: silicon steel, diffusion coefficient, annealing, texture

With the increase of silicon content, the increased brittleness of silicon steel makes the subsequent processing of materials difficult. It has found that 6.5wt%Si steel is the ideal material for the iron core in high frequency, low noise, and low core loss [1]. In order to obtain high silicon steel sheet which can be a good magnetic properties of silicon, researches for new technology have been become a pressing matter at the moment. The molten salt electro deposition for making high silicon steel can avoid the problems of rolling difficulties. The test used cold-rolled silicon steel sheet as the base to get high silicon content by electro-deposition in molten salts. By high temperature diffusion annealing obtains the high silicon steel sheet that Si concentration distribution. Research results [2] show that: The diffusion activation energy and diffusion frequency factor of Si in Fe-Si are associated with not only the temperature but the Si content in the alloy. Derived by computer simulations that the effect of temperature on the diffusion coefficient is great[3]. At 1100 C the diffusion coefficient is two orders of magnitude bigger than the high diffusion coefficient at 900 C. The analysis results of Mehrer[4] are similar with the above research results. Fe, Si atoms diffusion and transfer ability changed with the environment and temperature in Fe-Si thin films [5]. In current study, the concentration of Si changed with the thickness in the annealed samples, and the relationship between temperature and Si atomic diffusion coefficient is linear through the theoretical calculation. To determine the optimal annealing temperature this study analyzes the microstructure and texture of the annealing sample under different temperatures, to form the theoretical basis for the preparation of silicon steel sheet with high silicon content.

1 Experiment Methods

The material in the experiment is non-oriented silicon steel sheet with 1.6% silicon consent, 20×20×0.5mm3. Measure the experiment temperature with platinum rhodium-platinum thermocouple, with the error range of ±10 C. Make the silicon steel sheet as cathode. Put the graphite with NaCl-KCl-NaF-SiO2 into the resistance furnace to heat. The electro-deposition time is 60min and 50mA·cm-2 for the current density. The front-to-back ratio of pulse in current study is 9:1 and the electro-deposition temperature is 800 C. Take the deposited samples into the 900～1050 C SRAF to diffuse and anneal. The GDA-750 GDS, JXP-10 metallographic microscope and D5000 X-RAR DIFFRACTOMETER were used to analyze and test these samples.

2 The Result and Analysis

2.1 Effect of annealing temperature on diffusion of Si content in samples

Fig.1 Effect of annealing temperature on distribution of Si content in samples(a) 900℃(b) 950℃(c) 1000℃(d) 1050℃

The concentration of Si content influenced by annealing temperature is shown in Fig 1. It is clear that the concentration of Si content changes greatly before and after annealing. High temperature annealing promotes the internal diffusion of Si in deposition layer. The Si content in surface layer decreases, while the depth of diffusion increases. When the temperature gets to 1050 C, the concentration tends to be more evenly distributed.
2.2 Diffusivity
In the process of annealing and homogenization diffusion, the samples after electro-deposition have obvious diffusing character: the total account of Si in samples is constant, and does not change with the change of diffusion conditions. As shown in the fig 1, the concentration of Si appears exponential decaying. With the increase of x, the concentration reduces rapidly. The shorter the diffusing time is, the higher the concentration gradient is. With the extension of diffusing time, the speed of reduction decreases, which means the formation of the concentration gradient decreases. So, it is clear that the diffusion process satisfies one dimensional film source unsteady diffusion model.
Take the concentration of Si content in electro-deposition as the result of that the components diffuse towards the substrate in the condition of annealing temperature for time t0, the concentration distribution of the samples after annealing as the concentration distribution of that the components diffuse towards the substrate for time t0+t. The changes of concentration are not higher than 20%, and the influence of the electro-deposition time on the diffusivity of Si has been proved. Use the Gaussian solution of Fick's second law to solve:
（1）
The concentration distribution of Si content in the samples can be shown as:
（2）
The concentration distribution of Si content in the samples after annealing can be shown as:
（3）
In the above formulas,
c(x, t0) ---- the concentration of Si content corresponded to the depth x after the electro-deposition %.
c(x, t1) ---- the concentration of Si content corresponded to the depth x after annealing %.
M ----the total amount of diffusion components of Si content %.
A ---- constant. During the calculation, the concentration of Si content is treated as 1.6%.
Before the concentration of Si content becomes homogenization, as the diffusion time t is certain, and M and D are also certain constants, is constant. So the decay factor of concentration can be used to solve the diffusivity of Si in the samples. To facilitate the calculation, take logarithm on both sides of (2) and (3):
（4）
（5）
Based on the above equations, linear fitting concentration curves before and after annealing can be made. The results are as follows:
900℃：
Before （6）
After （7）
950 C：
Before （8）
After （9）
1000 C：
Before （10）
After （11）
1050 C：
Before （12）
After （13）

Table1 Effect of annealing temperature on diffusion of Si in samples

Samples	Annealing tem/℃	Diffusion timet0/min	DiffusivityD×1013/m2·s-1
(a)	900	27.526	1.016
(b)	950	11.184	2.15
(c)	1000	9.617	2.448
(d)	1050	16.500	4.102

Because the concentration distribution of the electro-deposition samples is supposed as the distribution when the thin film components diffuse for t0, and the concentration distribution after annealing is the distribution when the thin film components diffuse for t1, so we should make sure the occurrence of t0. According to the slope of the fitting result before and after annealing, it is not difficult to see that the radio of t0 and t1 is inverse radio. Use k to stand for the slope of a line. Then kbefore/kafter= t1/ t0 and t1=( t0+60)min. Put the value of t0 into (4) and (5), and we can get the diffusivities of different annealing temperatures. The effects of annealing temperature on diffusion of Si in samples are shown in table 1, It is clear that the diffusion of Si in the samples increases obviously, as is shown in article [6].

3 The analysis of sample structure and texture after annealing

The concentration distribution of sample in the process of electro-deposition has little influence on the diffusion of Si content. So, at a certain temperature, the annealing time of homogenizing annealing diffusion is mainly determined by the Si content in the electro-deposition silicon layer. Changing the parameter of the electro-deposition, the samples with different concentrations need to be determined the annealing time based on the Si content in the electro-deposition. According to the influence of the temperature on the diffusion of Si we get above, the study choose temperature at which higher diffusivity can be obtained to do the annealing experiment. The samples are analyzed after annealing. The result is shown in Fig 2.

Fig. 2 the metallographic photos of samples after the annealing and the Si concentration distribution metallographic photos (a) the metallographic photos (b)Si concentration distribution

As it is shown in Fig 2, the size of the crystal grains of the section in the samples are big, about 188.840μm, on the average of 1.5, which just falls into the best iron losses size range (100～200μm). The annealing process can improve the growth of crystal grains. The annealing temperature has great influence on the growing of the crystal grains. With the increase of the annealing temperature, the growing speed of the crystal grains increases. And after a certain period of time, coarse grains are generated. According to the relationship between the temperature and the diffusivity of Si content, the diffusivity of Si is bigger when the temperature is higher, the energy of the atom is bigger, and the diffusion is easier, too. High temperature annealing contributes to the diffusion of Si with high concentration from the surface into the inside of the samples. The concentration of the sample surface decreases. The depth of the diffusion increases. Finally the concentration of Si gets homogenization. At the temperature of 1000 C, 210min for annealing. the concentration tends to be evenly distributed, with the concentration of 6.3715%, close to 6.5%.
To get well-magnetic silicon steel, we need to improve the strength of the {100} and {110} texture, and decrease the strength of {111}[7-9]. It is mainly influenced by annealing conditions whether the texture after annealing the same as the texture after cold rolling. That is to say, it is mainly influenced by the annealing temperature and time. Fig 3 is the φ2=45°sections of ODF for samples with different temperatures. It is known that after annealing, the textures in the sample mainly center on the {111}<112>, {111}<110> textures of γ fiber component, {100}<011>, {110}<490>, and {100}<001> textures of α fiber component, and {011}<100> Goss textures. Compared with the cold rolling sheet in 3(a), the density of the textures after annealing in γ fiber component decreases, in which the density of {111}<110> textures declines obviously. The components in cold rolling samples are mainly {111}<112>, {111}<110>, {100}<011>, {011}<100> and {112}<110>. The storages of every component, from strong to weak, are in turn {111}<112>, {111}<110>, {112}<110>, {100}<011>[10-11]. While annealing, nucleation and growth during Re-crystallization proceed in the {111} plane on the textures of higher storages {111}<112>、{111}<110>, while it is hard to form nucleation in the textures of low storages. So, the annealing textures priority in {111} plane. The grains in Goss texture {110}<001> gradually grows through consumption around {111} {111} orientation face in <112> texture components. When the annealing time reaches 210 min, the density of γ fiber component declines obviously. The density of Goss texture {110}<001> is high, about 6.20.

Fig.3 φ2=45°sections of ODFs for sample(levels: 1, 2, 4, 5, 6, 9, 9.2)
3 Conclusions

The main annealing conditions are the influence of the change of temperature and time on the density of Si and the size of the grains, as well as the textures. The following conclusions can be made.
1) The Si content in surface layer decreases and tends to get homogenization. With the increase of the annealing temperature, the diffusivity of Si increases.
2) When the temperature gets to 1000 C, and annealing time is 210min, the size of the crystal grains is 188.840μm, falling into the best iron losses size range (100～200μm). The concentration of Si in the sample becomes homogenization, and gets thin silicon steel sheet with the Si content of 6.3715%, close to 6.5%.
3) The density in {100} and {110} is high, the density in {111} texture decreases.

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (Grant No. 51274082), the Science and Technology project of Tangshan City (No. 131302108b)

References

1. J. S. Yang, J. X. Xie, C. Zhou. Preparetion technology and prospect of 6.5%Si steel[J]. Journal of Functional Materials, 2003, 34(3): 244-246.
2. W. J. Yuan. Study on the process and principle of powder rolling technology for preparation[D]. Wuhan University of Technology, 2007: 87-88.
3. Y. D. Wang, J. Z. Xu, L. Zuo, Z. D. Liang. Computer simulation on the deposition-diffusion process in Fe-65mg·g-1Si alloy thin ribbon[J]. Chinese Journal of Material Research, 1996, 10(2): 125-129.
4. Mehrer H, Eggersmann M, Gude A., Salamon M, Sepiol B. Diffusion in intermetallic phases of the Fe–Al and Fe–Si systems [J]. Materials Science and Engineering A, 1997(239-240): 889-898.
5. J. M. Zhang, Q. Xie, Y. Liang, W. X. Zeng. Formation of silicides and oxidation for the Fe/Si layers[J]. Chinese Journal of Material Research, 2008, 22(6): 297-301.
6. D. K. Shi. Foundation of material science[M]. Beijing: Machinery Industry Press, 1999(1): 227-228.
7. Jong-Tae Park, Jerzy A Szpunar, CHA Sang-yun. Effect of heating rate on the development of annealing texture in non-oriented electrical steels[J]. ISIJ International, 2003, 43(10): 1611-1614.
8. Jong-Tae Park, Jerzy A Szpunar. Texture development during grain growth in non-oriented electrical steels[J]. ISIJ International, 2005, 45(5): 743-749.
9. Marcos F de Campos, Fernando J G Landgraf, Ivan G S Falleiros. Texture evolution during the processing of electrical steels with 0.5% Si and 1.25% Si[J]. ISIJ International, 2004, 44(10): 1733-1737.
10. Jong-Tae Park，Jerzy A Szpunar. Evolution of recrystallization texture in non-oriented electrical steels[J]. Acta Materialia, 2003, 51(11): 3037-3051.
11. Sidor Y., Dzubinsky M., Kovac F. Characterization of microstructures in non-oriented electrical steels utilizing weighted sum of elementary data[J]. Czechoslovak Journal of Physics, 2004(54): 105-108.

Modeling of ultrasonic waves propagation in inhomogeneous medium using fibered spaces method (k-space)

Mon, 19 May 2014 16:03:13 +0300

Abstract:The method for more accurately parameters estimation of the ultrasonic waves propagating in random heterogeneous media, including solid, liquid and gas phases is described.

Key words:phased array, ultrasound, pulp, control.

Vladimir Morkun
Vice-Rector for research, Doctor of Science, professor of Computer Science, Automation and Control Systems department
Krivyi Rih National University

Natalia Morkun
PhD, Associate professor of Economic Cybernetics and Project Management Department
Krivyi Rih National University

Andrey Pikilnyak
PhD- student of Computer systems and networks department
Research Assistant of the Computer Science, Automation and Control Systems department

1. Introduction. For the control of the basic technological parameters and mineral beneficiation process control, an important task is to control the parameters of complex heterogeneous mediums, including solid, liquid and gas phases.
The basic relations describing the ultrasonic oscillations and waves in the medium, follow from the equation of medium state, Newtonian equations of motion and the continuity equation [1-3]. The result are the wave-type equations that can be solved with appropriate initial and boundary conditions.
Let’s introduce differential characteristic to describe the ultrasonic waves radiation field. By we mean the intensity of the ultrasonic wave (with wavelength ), which is defined as radiation power per solid angle unit which passing through a unit area perpendicular to the direction of the point . Here is the unit vector defining the direction in space, is the radius vector defining the position of a given point in space.
The purpose is to study the volume ultrasonic waves propagation in the gas-containing iron ore slurry, defining of ultrasonic field characteristics in a liquid medium containing solid particles and gas bubbles, influence laws of the suspended in a liquid particles fluctuations on the performance of the ultrasonic field.
The presence of solid particles and gas bubbles introduces some features to the process of ultrasonic wave energy attenuation and scattering [4].
Wave scattering on the solid phase particles becomes significant when the wavelength is commensurate with the size of the particles. Consequently, the total intensity of the ultrasonic wave at a given point equal to the sum of the intensities of waves coming from all scattering centers. Scattering cross sections in this case are additive, so the linear absorption and scattering coefficients can be determined by the formulas
,
,                                            (1)
where n - is the particle concentration; and s(l) - total cross sections of the acoustic wave absorption and scattering on the particle.
Total cross sections of absorption and scattering depends not only on the wavelength of the ultrasonic vibration, but also on the particle size r. The main characteristic of the ultrasonic radiation field must be determined from the kinematic equation. Before write this equation, we introduce the concept of the differential at the corners scattering coefficient
,                         (2)
where - is differential at the corners energy scattering cross section on the solid phase particle.
The value represents a part of the energy which scattering by particles in the element of solid angle . Obviously, the total scattering cross section ss associated with differential scattering cross section ratio
,                                (3)
The kinetic equation which is solved by function can be obtained by considering the energy balance in a volume element of the phase space
               (4)
where . - is the ultrasound source radiation density function, which determines the average amount of energy emitted per unit time single phase volume.
Under the phase coordinates means the totality of variables r and W, while elementary phase volume is determined by the product .
Equation (4) can be reduced to an integral equation of the form (5)
                         (5)
where , is the Dirac delta function; - is the free term of the integral equation (5), which determines the intensity of the unscattered ultrasonic wave; .
The solution of equation (5) can be written in the form of a Neumann series [5], which is the expansion of the ultrasonic waves scattering multiplicity solution.
However, to obtain an expression analytically even for the singly scattered radiation is impossible. Therefore it is necessary to apply numerical methods for solving integral equations of the form (5).
Let's consider the method of fiber spaces (k-space) for modeling of ultrasonic wave propagation in inhomogeneous medium using coarse grids, with maintaining the required accuracy [6 -8].
We describe the ultrasonic waves propagation depending on the mass conservation equations, momentum conservation law and the equation of state using the first order dual equations, which can be summarized as follows [8, 9]
,                      (6)
,                               (7)
where - the time and space dependent ultrasound pressure perturbations (x - 3D Cartesian axis (x, y, z)); - is the spatially dependent density; - is the spatial dependent sound speed; - is the velocity of the particle and - is the absorption coefficient which equivalent to the inverse of the relaxation time.
Let's represent the all absorption effects with one relaxation time. From (7), the simplified equation can be written as follows

We differentiate (6) with respect to time and variations in (7), and the final equation can be represented as follows
,            (6’)
,               (7’)
Taking into account the permutations (6')

By substituting this equation in (7'), we obtain
,            (8)
The simplification of the pressure deviation to the density gradient can be represented as follows
,                           (9)
Taking into account (8), eq. (9) can be represented as follows
,    (10)
This is a linear wave equation of ultrasonic wave propagation in the heterogeneous medium with the absorption parameters.
Let's simplify (10) by separating the parameters of the sound velocity and density from the second derivatives of pressure taking into account the spatial and temporal variables to solve the problem of ultrasoundpropagation using the fiber space method.
The original equation can be written in the form
,              (11)
The normalized pressure can be represented as follows

By substituting this equation in (11) we obtain

After simplifying

Taking into account further simplifications the equation takes the form

Even more simplification can be obtained by determining the functions q(r, t) and v (r, t)efficient sources, which can be summarized as follows

By simplifying (11) we obtain
,                 (12)
This equation can be easily transformed into the frequency domain by using the three-dimensional spatial Fourier transform as follows
,                            (13)
where F(k,t), Q(k,t) и V(k,t) – three-dimensional spatial Fourier transformation of values , and respectively. Equation (13) satisfies the total wavefield, and is defined as the sum of the incident and scattered field , and the scattered wave field.

For the case of an inhomogeneous medium, we introduce an additional source and by substituting it into (13) we obtain the following expression
,               (14)
where

where F - is a spatial Fourier transform.
Let's use the substandard finite difference approach to solve this equation [7]. Discretization of the time derivative gives
,                  (15)
Consider the wave equation on the gray scale for the fiber space method (k-space), which includes the non-linear characteristic of ultrasound, which can be represented as follows [10]:

where - is the nonlinearity source, - is the nonlinearity coefficient. The harmonic oscillations equation can be represented as follows
,           (16)
where – additional source; - is a spatial Fourier transform.

After the spatial Fourier transformation the equation can be expressed as follows

The introduction of the nonlinearity term in fiber space method makes it easier to calculate the actual relief temperature in heterogeneous large scale models.
Conclusions. To build a model of the ultrasonic field in a randomly inhomogeneous medium, the fiber spaces method (k-space), which increased the accuracy of parameter estimation field is used.
References

Kochura Ye.V. Avtomatizatsiya kontrolya kachestva usredneniya syr'ya pered yego obogashcheniyem, Obogashcheniye rud,no. 6 (1995): 41-43.
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Modification Kinetics of MgO–Al2O3 Inclusions by Ca-treatment

Thu, 22 May 2014 14:39:24 +0300

Shufeng Yang

State Key Laboratory of Advanced Metallurgy
University of Science and Technology Beijing, Beijing, China

School of Ecological and Metallurgical Engineering
University of Science and Technology Beijing, Beijing, China

Jingshe Li

State Key Laboratory of Advanced Metallurgy
University of Science and Technology Beijing, Beijing, China

School of Ecological and Metallurgical Engineering
University of Science and Technology Beijing, Beijing, China

Xiangzhou Gao

State Key Laboratory of Advanced Metallurgy
University of Science and Technology Beijing, Beijing, China

School of Ecological and Metallurgical Engineering
University of Science and Technology Beijing, Beijing, China

Yu Ma

State Key Laboratory of Advanced Metallurgy
University of Science and Technology Beijing, Beijing, China

School of Ecological and Metallurgical Engineering
University of Science and Technology Beijing, Beijing, China

Modification Kinetics of MgO–Al2O3 Inclusions by Ca-treatment

Abstract: In this paper, high-temperature experiments were first carried out to study the modification kinetics of MgO–Al2O3 inclusions by Ca-treatment, and then a kinetic model for modification of MgO–Al2O3 inclusions by Ca-treatment was developed. The results predicted by the kinetic model agree well with the experimental results, and both show that the diffusion of Mg replaced by Ca in the inclusions is the rate-controlling step and full modification of MgO–Al2O3 inclusions requires a long time. For example, to fully modify a 12 μm inclusion, at least 20 min is required after Ca-treatment. In practice, to fully modified MgO–Al2O3 Ca-treatment should be carried out as far as possible in advance.
Keywords: MgO–Al2O3 inclusions, modification, Ca-treatment, kinetics

1. Introduction

MgO–Al2O3 spinel inclusions are unfavorable for both the quality of products and the castability of the steel because of their high melting point and high hardness.[1] To reduce the negative effects of MgO–Al2O3 spinel inclusions, it is important to modify the inclusions into liquid inclusions in the molten steel. Many studies[2–6] have investigated the modification of MgO–Al2O3 inclusions by Ca-treatment. Itoh et al.[2] found that even a very small amount of Ca in the steel can significantly decrease the stability of spinel inclusions and dramatically increase the stability of liquid MgO–Al2O3 inclusions. Young et al.[3] studied the formation mechanism of liquid calcium alumina inclusions originating from MgO–Al2O3 spinel materials, and found that spinels reacted with the dissolved Ca, forming a liquid calcium aluminate phase. Pistorius et al.[4] suggested that MgO could substantially contribute to liquefy inclusions by calcium treatment, so less calcium was needed when MgO was present in the starting inclusions. They concluded that calcium treatment can successfully modify spinel inclusions to mixed alumina–lime–magnesia inclusions and they change from irregular to globular in shape.
However, Yang et al.[7] found that many MgO–Al2O3–CaO inclusions have a two-layer structure after Ca-treatment: an outer CaO–Al2O3 layer and an Al2O3 core. YoungJo [3] found that even after 60 min of calcium treatment refining, there was still pure MgO–Al2O3 component inside the resulting MgO–Al2O3–CaO inclusion, indicating that 60min calcium treatment does not fully modify the MgO–Al2O3 inclusion into uniform CaO–MgO–Al2O3 or CaO–Al2O3 inclusions for long time calcium treatment. Therefore, the kinetic conditions are one of the key factors to determine whether the modification of MgO–Al2O3 spinel inclusions by Ca-treatment is effective.
In this study, modification of MgO–Al2O3 spinel inclusions by Ca-treatment was first investigated by laboratory experiments. Then, a kinetic model for the modification of MgO–Al2O3 inclusions by Ca-treatment was developed, and the results of model predictions and laboratory experiments are compared and the rate-controlling step for Ca-treatment is discussed.

2. Kinetic Experiments of Ca-treatment

2.1 Methodology

The description of the equipment used to carry out the experiments for modification of MgO–Al2O3 inclusions by Ca-treatment can be found in this literature.[7] The experimental steel is 30CrMo, with a composition (in wt%) of C 0.30, Si 0.22, Mn 0.52, P 0.015, S 0.007, Mo 0.10, V 0.12, Cu 0.07, and Cr 0.94. The experimental procedure is as follows. A total of 390 g of 30CrMo steel was melted in a crucible at a temperature of 1600 °C for homogenization. 0.3 g of aluminum wire was then added to the melt for . After about 5 min, 4 g of Mg was added into the melt. Ca-treatment using 4 g calcium silicide addition in powder form was performed about 10 min later. Liquid steel samples were taken by quartz tubes at various times after Ca-treatment: 1, 3, 5, 7, 12, 20, and 30 min. Some of the samples were used to analyze the composition of the steel and the others were used for the observation of inclusions.
The chemical compositions of the steel samples were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP–AES) and the inclusions were analyzed by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDX) and optical microscopy. For each sample, the compositions and morphologies of 40 inclusions were analyzed by SEM–EDX and the sizes of 1000 inclusions were observed by optical microscope.

2.2 Variation of Inclusion Composition

Figure 1 shows the variation of the average composition of the inclusions. After Ca-treatment, the average content of CaO sharply increases in the first 7 min, and then gradually increases from 7–30 min. After about 20 min, the value changes little and remains at about 20%. The MgO and Al2O3 contents in the inclusions rapidly decrease after Ca-treatment.

Figure 1. Variation of inclusion composition after Ca-treatment.

3. Kinetic Model of Ca-treatment for MgO–Al2O3 Inclusions

As discussed above, deoxidation by Al generates a mass of Al2O3 inclusions that will react with Mg existing in the melts. Thus, the inclusion components change from Al2O3 to MgO–Al2O3. The Mg in the melts is artificially added, although in practice MgO in the slag or ladle lining can be reduced by Al and the reaction product Mg enters into the molten steel. Calcium treatment can modify irregular-shaped spinel inclusions into globular CaO–Al2O3–MgO inclusions. The modification mechanism is (1) diffusion of the dissolved Ca in the boundary layer, (2) diffusion of Ca in the CaO–Al2O3–MgO inclusions, (3) reaction between Ca and MgO–Al2O3 at the interface, (4) diffusion of the dissolved Mg in the inclusions, and (5) diffusion of the dissolved Mg in the boundary layer.
The rate of chemical reaction occurring at the interface is much faster than the transfer rate of element diffusion in the molten steel or in the inclusions. Thus, the chemical reaction cannot be the rate-controlling step during Ca-treatment. In the following discussion, two cases were analyzed for the kinetics between the molten steel and inclusions. The first case is when the diffusion of Ca or Mg in the boundary layer is the rate-controlling step, and the second is when the diffusion of Ca or Mg in the inclusions is the rate-controlling step. This assumes that Ca first reacts with MgO–Al2O3 inclusions at the external surface, and a product layer of MgO–Al2O3–CaO inclusions forms. For simplification, in this reaction model the inclusions are treated as globular-shaped and the radius does not change with time.
The MgO in the MgO–Al2O3 inclusions is reduced by Ca during Ca-treatment, which will result in an decrease of MgO content and a increase of CaO in the inclusions. The content of MgO in spinel inclusions is 38%, so the saturation content of CaO in the inclusions after modifying by Ca-treatment should be 35.4%. Experimentally, the content of MgO in inclusions cannot be saturated, and Ca cannot decrease the total amount of MgO in MgO–Al2O3. Therefore, the actual CaO content after Ca-treatment is less than 35.4%. In this article, the saturation content of MgO in the inclusion was set at 20%, because when Ca-treatment reaches the equilibrium state in kinetic experiments the average content of CaO in the inclusion is close to 20%.

3.1 Diffusion of Ca or Mg in the Inclusion Layer as the Rate-Controlling Step

The kinetic equations and the method of calculation are completely different when treating the diffusion of Ca and Mg in the inclusion as the rate-controlling step separately, which is due to the different diffusion coefficients of Ca and Mg in MgO–Al2O3–CaO inclusions. Here, only the diffusion of Ca as the rate-controlling step will be discussed in detail. For the case of Mg, we will only show the calculated results.
Figure 2 distribution of the Ca content when the rate-controlling step is the diffusion of Ca within the MgO–Al2O3–CaO inclusions. Sp represents the MgOAl2O3 inclusion and SpC is the MgO–Al2O3–CaO inclusions. [Ca] represents the calcium content in the melt, which in this case is constant, [CaO] is the calcium oxide concentration in the MgO–Al2O3–CaO inclusions, [Ca]* is the calcium concentration at the reaction interface, ro is the radius of the inclusion, which is assumed to be constant, and r is the radius of MgO–Al2O3 inside the inclusions, which will decrease with time. The thickness of the MgO–Al2O3–CaO inclusion layer can be expressed as ro−r, and changes with time.

Fig. 2 Distribution of Ca content when treating the diffusion of Ca in the inclusion layer as the rate-controlling step.

The kinetic equation is built based on the relationship that the change of the CaO content in the inclusion is equal to the amount of diffusion per unit time:

(1)

Equation (1) is a type of partial differential equation that is difficult to solve through analytical methods, and it is better to employ numerical methods to obtain the approximate solution at a certain precision. In this kinetic model, we used the finite difference method to solve the basic equation. Finite difference methods can be divided into direct difference and implicit difference methods. Starting from the differential equation, the method replaces the derivative by the difference quotient, and connects the differential equation and the solution under definite conditions into a linear system, which can be solved to obtain a numerical solution of discrete points. Therefore, the choice of space and time step is limited during the process of equation discretization. This model adopts the implicit difference method to solve the equation, and then based on the discrete equations we wrote a code to solve the equation. Treating the concentration range of CaO in the inclusion as the boundary condition, the model will calculate the time for a given size inclusion particle to grow to saturation.
The boundary conditions in this calculation are that at t=0 and r=r0 then [CaO]=20%, at t=0 and r≠r0 then [CaO]=0, and when t≠0 then [CaO]=0 at the interface between the MgO–Al2O3 and MgO–Al2O3–CaO inclusions. For the diffusion coefficient of Ca in the MgO–Al2O3–CaO inclusion, we used the diffusion coefficient of Ca in the MgO–Al2O3–CaO inclusion layer: DCa-Inc = 2.5 × 10−9 m2/s.[9] In the calculations, we chose r0=6 μm.
According to the boundary conditions and parameters, we use the computer code to carry out the calculations and obtained the results shown in Fig. 3. The content of CaO rapidly increases in the initial stage after Ca-treatment, at about 100 s the CaO content is close to saturation, and the CaO content is fully saturated at 200 s.

Fig. 3 Calculated result of the CaO content in an inclusion when treating the diffusion of Ca in inclusion layer as the rate-controlling step.

As mentioned above, when the rate-controlling step is the diffusion of Mg in the inclusion layer, the kinetic equation, the calculation method, and the boundary conditions are the same as when Ca is considered to be the rate-controlling step. The only difference is the diffusion coefficient. For the diffusion coefficient of Mg in the spinel inclusion, we used the diffusion coefficient of Mg in the MgO–Al2O3–CaO inclusion layer: DMg-Inc = 3.2 × 10−13 m2/s.[9] The change of CaO content with time is shown in Figure 4, which shows that the time needed for the CaO content to become saturated in the inclusion is about 1200 s.

Fig. 4 Calculated result for the CaO content in inclusions with respect to time of Ca-treatment(s) when treating the diffusion of Mg in the inclusion layer as the rate-controlling step.

3.2 Diffusion of Ca or Mg in the Boundary Layer as the Rate-Controlling Step

When diffusion of Mg and Ca in the inclusion is sufficiently fast, the rate-controlling step will be the diffusion of Ca or Mg in the boundary layer during the process of Ca-treatment, and the concentration of Ca and Mg in the inclusion is assumed to be constant. The diffusion of Ca and Mg in the boundary layer and the diffusion equations of Ca and Mg are the same. Because the difference between the diffusion coefficients of Mg and Ca is small, they will be regarded as the same during the calculations. Thus, they will also have the same kinetic model. Consequently, only the diffusion of Ca in the boundary layer will be discussed.
Figure 5 shows the distribution of Ca content when the rate-controlling step is the diffusion of Ca within the boundary layer. Thus, based on the equilibrium state of [Ca] at the interface between the molten steel and the inclusions, the kinetic equation is

, (2)

, (3)

Fig. 5 Distribution of Ca content when the diffusion of Ca in the steel boundary layer is the rate-controlling step.

where (Ca) is the concentration of calcium in the inclusion, [CaO] is the concentration of calcium in the steel, [Ca]* is the calcium concentration close to the steel side on the reaction interface, and (Ca)′ is the calcium concentration close to the inclusion side on the reaction interface. Because the size of the inclusions is quite small ((1.0–5.0) × 10−6 μm), we assume that there is material transmission only on the liquid steel side of the interface; namely, (Ca) is equal to (Ca) ′.
L represents the equilibrium distribution ratio of Ca on the steel/inclusion interface. The Ca-treatment reaches an equilibrium after adding 0.0078% SiCa powder (Ca content = 1.87 × 10−7%), and the inclusion content is 13.6 × 10−2% in which CaO accounts for 20.9%, and thus L = 6.0 × 105. The diffusion coefficient of Ca and Mg in steel is Dm=3.5 × 10−9 m2/s.[10]
From Eqs. (2) and (3), and assuming that the content of Ca in steel is constant, (Ca) in the inclusion can be expressed as follows:

(4)

The relationship between the time of the Ca-treatment and the CaO content in the inclusion is shown in Figure 8.

Figure 6 Content of CaO in inclusions when treating the diffusion of Ca and Mg in the boundary layer as the rate-controlling step.

Figure 6 shows that when the diffusion of Ca and Mg in the boundary layer is the rate-controlling step, CaO in the inclusion quickly becomes saturated (40 s), which indicates that Ca and Mg diffuse faster in the boundary layer of molten steel than the diffusion of Ca and Mg in the inclusion layer.
Based on the discussion above, when Ca diffusion in the inclusion is the rate-controlling step, it will take 200 s for CaO to be saturated in the inclusion, while if Mg diffusion in the inclusion is the rate-controlling step, it will take 1200 s for CaO to be saturated in the inclusion. When diffusion of Ca and Mg in the boundary layer of molten steel is the rate-controlling step, it will take 40 s for CaO in the inclusion to become saturated. For the Ca-treatment, the diffusion of Mg in the inclusion is the slowest, thus diffusion of Mg in the inclusions is the rate-controlling step.
Figure 7 shows the comparison of the experimental and prediction results for diffusion of Mg in the inclusion. The results are in good agreement, which means that the diffusion of Mg in the inclusion is the rate-controlling step in Ca-treatment, and proves the reliability of the model. However, in Figure 7 at the earlier stage of Ca-treatment there is a significant difference between the experimental and predicted results, with the experimental results being greater than the predicted results. This may be due to the non-continuity of sampling in the earlier stage and taking too many samples, because in the sampling process with quartz tubes this may cause stirring of the molten steel and speed up the reaction. In addition, it takes longer for saturation of CaO in the experimental results than in the predicted results, which may be caused by assuming that diffusion of Ca in the inclusion is too fast in the predictions; even though Ca diffuses faster than Mg in the inclusions, their diffusion rates only differ by one order of magnitude.
Both the experimental and predicted results show that 20 min of Ca-treatment is required for modification of MgO–Al2O3, although this time can be shortened by gas blowing stirring in the real manufacturing process. However, it is still recommended that Ca-treatment is performed during the refining process and not after.

Figure 7 Comparison of the results of the model and experiment of the CaO content in inclusions with Ca-treatment time.

4. Conclusions

1)    A kinetic model is developed based on the experiment results to predict the time of modification of MgO–Al2O3 inclusions. The results predicted by the kinetic model and those obtained by experiments are in good agreement.
2)    Ca and Mg diffuse faster in the boundary layer of molten steel than in the inclusions, and Ca diffuses faster in the inclusions than Mg. Thus, diffusion of Mg in the inclusions is the rate-controlling step.
3)    It takes considerable time for the MgO–Al2O3 inclusions to be fully modified. For a 12 μm inclusion, at least 20 min are needed after Ca-treatment. Thus, for fully modified MgO–Al2O3 in practice, Ca-treatment should be carried out as far as possible in advance.

Acknowledgments

The authors are grateful for support from the National Science Foundation China(51304016).

References

Shufeng Yang, Jingshe Li, Lifeng Zhang. Behavior of MgO∙Al2O3 based inclusions in alloy steel during the refining process. Journal of iron and steel research international, 2010,Vol. 17(7): 1-6 .
H. Itoh, M. Hino and S. Ban-Ya. Thermodynamics on the Formation of Spinel Nonmetallic Inclusion in Liquid Steel. Metallurgical and Materials Transactions B, 1997, vol. 28 (5), pp. 953-56.
YoungJo, K., Fan,L.,Kazuki, M. and Du, S. Mechanism study on the formation of liquid calcium aluminate inclusion from MgO-Al2O3 spinel. Steel Research International, 2006, vol. 77 (11), pp. 785-92.
P.C. Pistorius, P. Presoly and K.G. Tshilombo. Magnesium: Origin and role in calcium-treated inclusions. Procceding of TMS Annual Meeting and Exhibition, San Antonio, TX,2006, vol. 2, pp. 373-78.
Shufeng Yang, Lifeng Zhang, Liyuan Sun, Jingshe Li, Kent D. Peaslee. Investigation on MgO∙Al2O3-Based Inclusions in Steels. AIST Translations, Vol.9(8), 2012, pp. 1-15
Shufeng Yang, Jingshe Li, Zaifei Wang. Modification of MgO•Al2O3 spinel inclusions by Ca-treatment in Al-killed steel. International Journal of Minerals, Metallurgy and Materials, 2011,18(1):18-23
Shufeng Yang, Lifeng Zhang, Jingshe Li, Kent Peaslee. Formation and Modification of MgO∙Al2O3 Based Inclusions in Alloy Steel. Metallurgical and Materials Transactions B 2012, pp.731-750
J.H. Park, D.S. Kim and S.B. Lee. Inclusion control of ferritic stainless steel by aluminum deoxidation and calcium treatment. Metallurgical and Materials Transactions B, 2005, vol. 36 (1), pp. 67-73.
G. Okuyama, K. Yamaguchi, S. Takeuchi and K.I. Sorimachi. Effect of slag composition on the kinetics of formation of MgO•Al2O3 inclusions in aluminum killed ferritic stainless steel. ISIJ International, 2000, vol. 40 (2), pp. 121-28.

Individual personal characteristics and his tendency to conformity

Thu, 23 Jan 2014 10:10:36 +0200

Individual personal characteristics and his tendency to conformity

The article is devoted to conformism of an individual as a result of social influence. Social and economic factors, influencing on formation of individual’s tendency to conformism are presented. Personal – psychological peculiarities, promoting the exertion of conformal behavior, are analyzed.

Keywords: conformism, conformal behavior, social-psychological influence, personal characteristics, tendency to conformality.

Marina Suryakova

Candidate of Psychological Scienses,

docent of pedagogics department of

National Metallurgical Academy of Ukraine

Social-psychological influence and conformal behavior of an individual

Conformism in social psychology is determined as a kind of social influence, the result of which is considered to be striving to correspond to opinion of majority. Conformism is considered to be conditioned by social influence from the one hand and personal influence from the other hand. Social influence is conditioned by feeling of belonging to a group or society and also the necessity in approval of others. Personal influence reveals itself in case of lack of confidence and the wish of a person to act correctly.
Social conformity is understood as liability of individuals, groups of people to the influence of social, national traditions, forms of behavior, revealing in adoption of social and national regulations, stereotypes without internal resistance and enough reasoning.
On the unconscious, emotional level, social and ethnic conformity reveals itself in forms of such processes as particular suggestibility, capacity and necessity to imitate bearers of social or national traditions, different cultures and communities [7].
On the unconscious, emotional level social, ethnic conformity shows itself in such processes as special suggestibility, ability and necessity to imitate the bearer of social or national traditions, different cultures and communities [7].
As some researches show, persuasion of influence may be intensified with the help of some external factors.
So, Robert B. Cialdini defines variety of causes on the background of which an individual shows extra-conformity: uncertainty of the situation, high authority status in society (from here there is a tendency to obey); trust in society to the majority opinion; and other [13].

Hadley Cantril mentions the activity in the country and world as the reasons, from which depends the development of personal characteristics. In the case of bad financial condition of the country, contradictions to economical and political program, danger of expansion from the side of other countries, long-term unemployment, impossibility to influence or change the developments – these factors cause emotional unsteadiness and on the back of it – tendency to conformity.
Besides, the significant role in taking decisions plays authoritativeness factor of mass media in society, public authority, existing standards of thinking in society, which determine conceptional construct of an individual.
The additional factors may be also individual’s economic condition, there is more intensified tendency to conformity at low economic level. Whatever economic status is, the important factor here is education, the higher it is, the less individual is inclined to conformity. Age peculiarities also have some impact – the older an individual, the greater the tendency to conformity [1].
Researches show, that individual’s personal characteristics reveal themselves in the context of certain external impacts, tendency of an individual to conformity is closely connected with an influence of external social environment.
David Myers marks that “suggestions cannot determine behavior if external impact is stronger than internal conviction” [9, p.187]. In favor of this statement speaks Granovskaya R.M. “ In Zimbardo experiments persons under test …acted cruelly not because of personal peculiarities, but in accordance with his role and situation.” [7, p.524].
In such a way, the persuasion of social-psychological influence on the individual may be intensified with the help of different external factors, on which the reveal of personal characteristics depends considerably.

Personal characteristics of an individual allowing to increase the degree of persuasion of social-psychological influence

Except social-psychological influence, on the tendency of an individual to conformity have an influence such factors as age, sex, profession.
It is kwon, for example, that in growing-up years, adolescent, tendency to conformity the highest, then reduces and after 25 years stays on its individual level.
Women’s conformity is considered to be higher than men’s one but if the discussed problem refers to mainly women’s type of activity, women do not defer and men are more conforming.
As the researches mark, the more individual’s profession is connected with collective activity, the greater tendency to conformity. For example, high level of conformity is observed among orchestra participants (70%), among military it is higher than among engineers.
Besides, some other peculiarities of individual may be distinguished, which allow to increase the degree of persuasion of social-psychological influence on an individual, in consequence of this factor, tendency to conformity increases. To such psychological peculiarities one may refer anxiety, low self-evaluation, feeble-mindedness.

Anxiety

Recent researches concerning anxiety are directed to differentiation of situational anxiety, connected with concrete external situation, and personal anxiety, which is a stable quality of a person [8, p.395].
In psychology anxiety is observed as personal quality, which may condition individual’s tendency to conformity in the context of social-psychological influence.
In situations, connected with social interaction some individuals are tended to have anxious feeling. Ch. Spilbergs’s researchers revealed, that “individuals, characterized by high degree of anxiety, are more prone to feel extra-anxiety in situations, which have a threat for their self-estimation, especially in situations of interpersonal relations, where their personal adequacy is estimated.” [5,p.100].
Researches Hodges and Felling, Spilberger have discovered correlation between presence in individual of personal anxiety and intensiveness of its development in socially important stress situations (for example, during public speech or test performance). Researches consider that “the factor of threat mediates such type of interrelation – “I” or “self-evaluation threat” [5, p.101].
Prikhozhan A.M., during study of anxiety forms, distinguishes aggressive-anxious type and anxiety-dependant type. The typical feature of aggressive-anxious type is “strongly marked sense of threat, peculiar mix of aggression and anxiety: committing an aggressive action, an individual is seeming to apologize, being afraid of his “bravery”.
Anxiety-dependant type demonstrates various forms of dependences: from excessive obedience (or predominant disobedience) to extra carefulness, attention to people. Such dependence individuals may realize, feel it as a burden, but cannot get rid of it. In Prikhozhan opinion, “appearingly, dependence is closely connected with anxiety, because in this case the feeling of helplessness, impossibility to cope with a situation, bleakness causes the need of help, support of others, dependence on these people.”
The main feature of anxious type, according to Leongard’s description, is “anxiety about presumable failures, anxiety about your own fate and fate of relatives. Herein there are no objective matters or they are negligeable for such anxiety. They are notable for shyness and sometimes for obedience. Constant vigilance towards external circumstances is compound with diffidence in own abilities.”
It is obvious, that such personal feature as anxiety may reduce effective activity of an individual in society. And the degree of persuasion of social-psychological influence for such individual will be rather high and this fact may condition the tendency to conformity.

Low self-evaluation

Anxiety as personal feature may develop in the person with low self-evaluation. Self-evaluation – person’s estimation of his own, his abilities, qualities and place among other people. Person’s mutual relations with other people, his criticism, self-exactingness depends on self-evaluation; self-evaluation influences the person’s activity.
It is known, that stable, too low self-evaluation involves overdependence on other people, dependence and even ingratiating manner, shyness, restraint and even disturbed percipience of others.
R.M. Granovskaya points at the connection between anxiety and self-evaluation: “Low self-estimation appears in permanent anxiety, fear of negative opinion heightened vulnerability”. Such individuals “react more vehemently to the criticism, laughing, blames and as a result of it, more dependant…They are passive, hypnotizable and shy” [6, p.506].
F. Zimbardo has fixed correlation between shyness and low self-estimetion in his research: “Such people are too sensitive to criticism, supposing it speaks for their inferiority” [11, p. 282]. It is marked, that too sensitive to criticism individuals tend to find “confirmation” of their inferiority. This gradually forms low self-estimation.
The conditions for self-estimation formation are known - this happens during individual’s activity and interpersonal interactions. A.A. Rean marks: “Society influences greatly the formation of individual’s self-estimation”. Therefore, individuals with low self-estimation are subjected to social-psychological influence more than others. There is a high degree of possibility that low self-estimation may condition the tendency of individual to conformity.

Insufficient expressiveness of individual’s volitional powers

According to Maklakov’s opinion, the quality of self-control depends greatly on person’s self-evaluation. Low self-evaluation, as it was marked above, leads an individual to the loss of self-belief. Diffidence, feeling of inferiority may lead to gradual die of individual’s aiming at end of his purpose and desired will never be realized. In case of individual’s steady demonstration of such manifestations, one may speak about insufficient expressiveness of volitional powers.
According to Smirnova and Il’ina’s opinion, volitional powers are “peculiarities of voluntary regulation, revealing themselves in concrete specific conditions, stipulated by the nature of overcoming difficulty” [7, p. 116]. E.P. Il’in considers that volitional powers may be regarded as “phenotypical characteristic of person’s abilities, as a composition of inherited and acquired” [7, p.117].
E.P. Il’in distinguishes the ability conditioned by inherited disposition (particularly, typological peculiarities of nervous system properties) as inherited component. And as acquired while ontogeny component – experience of a person: his abilities and skills, which are connected with self-stimulation; formed voluntary mindset not to yield towards the difficulties, which becomes customary while overcoming difficulties.
Researches distinguish complex moral-volitional powers, such as independence, initiativity and vitality, insufficient formedness of which may condition weak voluntary regulation of individual’s activity.
Some authors, for example, K.N. Kornilov, studying individual’s exertion of feeble-mindedness, characterize suggestibility as lack of volitional power: “a person cannot critically take advises or suggestions what to do” [7, p.99].
Therefore, one may suppose that certain typological peculiarities of nervous system properties, insufficient formedness of volitional powers linked with low self-evaluation of individual may increase his dependence on socio-psychological influence and strengthen the tendency to conformality.

Tendency to conformality in connection with professional immaturity

Tendency to conformality in conditions of choice of professionally significant information may be conditioned also by professional immaturity of the entrant.
Professional immaturity, on our opinion may be characterized, on the one hand, by non formedness of professional concepts, and on the other hand, by absence of or insufficient expressiveness of professionally significant personal qualities of the entrant.
It should be marked that insufficiently precise, approximative professional knowledge and skills creates the base for uncertain, nonformed professional position. One may suppose that entrant with nonformed professional presentations in conditions of choice of professionally significant information will show the tendency to conformality.
In such a way, to the factors conditioning the tendency to conformality in conditions of socio-psychological influence, one may regard the influence of external environment, such psychological peculiarities of individual as anxiety, low self-evaluation, insufficient expressiveness of volitional powers and also the presence of immature position.

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Beron R., Birn D., Jonson B. Sotsialnaya psihologiya: klyuchevyie idei (Large psychological dictionary: key ideas). Piter, 2003.
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Il’in E.P. Psihologiya voli (Psychology of will). Piter. 2013, 364
Krys’ko V.G. Sotsialnaya psihologiya: slovar-spravochnik (Social psychology: dictionary – reference). Minsk, Harvest, 2004. 688 p.
Mayers D. Sotsialnaya psihologiya (Social psychology). Piter, 2001. 750 p.
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Pains E., Maslach K. Praktikum po sotsialnoy psihologii (Social psychology practicum). Piter, 2000.
Parygin B.D. Sotsialnaya psihologiya. Problemyi metodologii, istorii i teorii (Social psychology. Problems of methodology, history and theory. IGUP, 1999.
Ross L., Nisbeth R. Chelovek i situatsiya (Person and a situation). Moscow, Aspekt-Press, 2000, 429 p.
Chaldin R. Psihologiya vliyaniya (Psocology of influence). Piter, 2000, 272 p.

Stress calculation of moment transmitting roll with profile on the base of Reuleaux triangle

Thu, 19 Jun 2014 09:30:22 +0300

Detailed calculation of polar moment of inertia for cross section of Reuleaux triangle form is considered. With the help of received dependences, it is possible to determine to a high precision concerning stress, appearing in profile connection during torque transmission. Also software module for strength prediction of profiling rolls is described. It allows to fulfill strength check and adjustment of overall parameters of profile momenttransmitting connection on the base of Reuleaux triangle.
Key words: polar moment of inertia, axial moment of inertia, twisting, Reuleaux triangle, profile connection, tangential stress.

UDK 531.8

Razumov Mikhail Sergeyevich
candidate of science, senior teacher of the city,
road building and the building mechanics department SWSU

Gladyshkin Aleksey Olegovich
candidate of science, senior lecturer of the city,
road building and the building mechanics department SWSU

Kassikhin Vladimir Nikolayevich
senior teacher of the city,
road building and the building mechanics department SWSU

Pykhtin Aleksey Ivanovich
candidate of science,
executive secretary PK SWSU

Skripkina Yelena Vasilyevna
candidate of science,
senior lecturer SWSU

South-West State University, Kursk, Russia

Stress calculation of moment transmitting roll with profile on the base of Reuleaux triangle

Torsion analysis of moment transmitting connections lies mainly in determination of maximum tangential stress in cross section. Basic calculating formula for determination of tangential stress in the point y

where Т_max – maximum torque, transmitted by the roll,
I_ρ – polar second moment of area;
y – coordinate, where stress must be determined.
When cross section is of simple form, calculation of I_ρ is easy to perform. In general terms it may be presented as the sum of two axial moments of inertia

(1)

where I _xc and I_yc - axial moments of inertia.
Moment transmitting connection, performed on the base of Reuleaux triangle (figure 1) has rather complex profile in cross section. It consists of three circular segments (1, fig. 1) and a triangle (2, fig.1). Centers of circles, describing circular segments, lie in the corners of triangle.

Figure 1 Determination of polar moment of inertia of Reuleaux triangle

Triangle side c (parameter R in the fig. 1) may be determined from the formula

Altitude of the triangle h may be determined as follows

Triangle polar moment of inertia is equal to

(2)

Polar moment of inertia of circular segment may be determined from the formula (fig. 2):

(3)

where I _{X1 segm} and I _{Y1 segm} - axial moments of segment;
A – circular segment area;
y_c – coordinates of segment gravitational center.

Figure 2 a Determination of polar moment of inertia of circular segment about the axis XC1

Now let us determine axial moment of inertia I _{X1 segm}, I _{Y1 segm} and circular segment area (fig. 2, b).

Figure 2 b Determination of polar moment of inertia of circular segment about the axis Y_C.

As one knows from mechanics of solid deformable body:

and

Calculating I _{X1 segm}, surface element is located at a distance y = R•sinα. Correspondingly dy = R•cosα dα. Value b = R•cosα. Area of surface element equals dA = 2b•dy. The angle may change within. Circular segment area is equal to

(4)

Moment of inertia concerning X _C1 axis equals

(5)

Let us calculate I _{Yc segm}

where x= Rcos t - distance from Y axis to surface element.
To take this integral in parametric form is the most preferable. Let us introduce the parameter t as follows:

Correspondingly, dx = -Rsin tdt . Consequently, limits on integral will be changed: at x₁=0, , at , . As a result we will get

(6)

First moment of area of segment in x-axis equals

Coordinate of gravitational center may be determined from the formula

(7)

Finally, inserting (4), (5), (6) and (7) into (3), we will get polar moment of inertia of circular segment:

(8)

Let us assume polar moment of inertia of Reuleaux triangle in the form of the sum oftriangle polar moment of inertia and tripled polar moment of inertia of circular segment:

(9)

On the base of these calculations, computer program was developed. Width across corners and maximum torque, being transmitted by profile connection, are the input data. Program interface is shown in the figure 3.

Figure 3 Program interface a) calculation route selection b) calculation in accordance with allowable carrier power c) selection of minimum size of cross section

The given above mathematical tool may be reprocessed and realized for calculation of five-cornered connection. However Reuleaux pentagon is impractical among machine-building profiles.
In such a way, this methodology will allow to shorten time, spent for design of profile moment transmitting connections, received on the base of Reuleaux triangle.

Research article is fulfilled with funding from RF President’s grant for government support of young Russian scholars - Doctors of Philosophy MK - 2653.2014.8.

References

Kassikhin, V.N., Razumov, M.S., Gladyshkin, A.O., Bykovskaya, N.E. (2012). Automatization of strength prediction of many-sided rolls on twisting. Izvestiya YuZGU. 2(2), 179-181.
Emel'yanov, S.G., Gladyshkin, A.O., Razumov, M.S., Yatsun, S.F. (2012). Automatization of work preparation of profile rolls. Izvestiya YuZGU 1(1). 113-116.
Timchenko A.I. Tekhnologiya izgotovleniya detaley profil'nykh besshponochnykh soedineniy [Manufacturing technology of keyless connection of profile pieces]. Moscow, VNIITEMR, 1988, 160 p.
Pisarenko G.S. Spravochnik po soprotivleniyu materialov [Structural resistance reference guide]. Kiev, Naukova dumka, 1988. 736 p.
Darkov A.V., Shpiro G.S. Soprotivlenie materialov [Structural resistance]. Moscow, Vysshaya shkola, 1975. 656 p.

Automatic Transportation Management System of Vehicles in Open Pit based on 3PGS and GPS

Thu, 19 Jun 2014 13:14:55 +0300

The management of mining trucks and other vehicles in the process of transportation is an important issue, in order to prevent from ore stealing and guarantee the obedience of scheduling commands in many open pits. In this paper, a new automatic management and control strategy - “three point guarding system(3PGS)” and GPS truck tracking strategy have been proposed. The objective of these strategies is to prevent stealing ore and monitor vehicles in real time. In 3PGS, three points should be arranged, which consist of weighing point in mining area, passing verification point of entrance and exit in open pit, and weighing point in unloading area. Using weighing sensor, radio frequency identification, automatic barrier control, Ethernet network technologies and systems engineering theory, the trucks and vehicles can be managed and controlled well through to pass three points orderly. Using GPS, the positions of trucks can be monitored in real time in the whole transportation process. Based on 3PGS and GPS, a new automatic transportation management system of vehicles in open pit has been designed and developed. The system has been applied in Sandaozhuang Molybdenum open pit. The application results show that it is an effective solution to prevent from ore-stealing, to manage inlet and outlet automatically and to monitor the trucks in real time in open pit mine.
Key words: Open pit; Vehicles; Stealing ore; Automatic management; 3PGS ; GPS

Automatic Transportation Management System of Vehicles in Open Pit based on 3PGS and GPS

GU Qing-hua
associate professor,
visiting scholar at department of computer science and tenology
College of Engineering, Ohio State University, Columbus, USA
Xi’an University of Architecture & Technology, Xi’an, Shaanxi, China

FENG Zhi-dong
Xi’an University of Architecture & Technology, Xi’an, Shaanxi 710055, China

LU Cai-wu
Xi’an University of Architecture & Technology, Xi’an, Shaanxi 710055, China

JOHN Arand
College of Engineering, Ohio State University, Columbus, OH 43202, USA

Introduction

The transport vehicles in stopes of open pit are roughly divided into two kinds: mining trucks and auxiliary transportation vehicles. The mining trucks mainly transport ore and waste rock in open pit. The auxiliary vehicles usually give a ride to people and other materials between inside open pit and outside. The two kinds of vehicles play an important role in the transportation system of open pit. Most of trucks basically carry ore and unload ore inside open pit. But some trucks carry ore to ore-dressing plant outside or store ore outside. Some drivers always want to pursue more personal gain in the process of transportation. Thus, stealing ore often happens after the trucks are driven outside of the open pit. Also, some trucks don’t obey scheduling commands in transit. For example, some trucks go wrong way and stop and unload in wrong places intentionally. Besides, some auxiliary vehicles also steal ore when they exit the stope. According to statistics, since 2002 there are about 20 million yuan of average-lost each year due to stealing molybdenum ore in china. Therefore, prevention of ore-stealing should be addressed as an important issue in all open pit, in order to reduce the companies’ loss.
At present, the means of management and control of vehicles in open pit domestically and internationally are tracking and positioning, automatic barrier gate and video monitoring. Tracking and positioning technology is most widely used in the management of mining trucks [1-2]. Examples are: Dispatch system developed by Modular Mining Systems in USA, Intelligent Vehicle Scheduling System developed by Dongfang Measurement and Control in china and Intelligent dispatching and monitoring system for trucks and shovels developed by Mining System Institutes in Xi'an University of Architecture and Technology. All these systems can track and obtain vehicles’ positions in real time using GPS, WIFI or RFID[3]. The historical paths of vehicles can be shown in the map of open pit and can also be found in database at any time[4-5]. The systems can manage vehicles’ transportation effectively and guarantee that vehicles are under dispatching commands. But one of the major disadvantages of these systems is that they only monitor vehicles’ paths. If ore-stealing events happened in transit, they cannot be found and cannot be effectively managed. Video monitoring is typically used at some key points to monitor vehicles[5]. Monitoring equipments can gather the real-time scene and transfer it to the data center. The vehicles can be monitored in real time in this way. But the disadvantage is that there are often some blind spots, which cannot be monitored from limited number of cameras. Monitoring all routes requires more cameras than one can afford. The increased number of cameras also increases labor cost. The whole cost is pretty higher. Thus, it is not a reasonable way to this issue. The barrier gates are another way, which consist of two types, manual and automatic[6-8]. Manual barrier gates are usually installed in the entrance and exit of open pit. When a vehicle passes the entrance or exit, the worker here will check approved receipts according to his personal subjective judgment. Then the on-site worker will decide if the vehicle can pass through. In this case, fraud may happen. While the automatic barrier gates consist of barriers, barrier controller, induction coil, RFID reader, RFID tags and computer server so on. First, each vehicle is equipped with a RFID tag and the information of tag and vehicle is registered in the database. When the vehicle passes through entrance or exit, RFID reader obtains the exact number from tag and then by this number, the vehicle’s information can be automatically queried and analyzed from the database. Then, according to this vehicle’s permission type, the system will send commands to barrier controller. The vehicle can be determined to pass through. In this case, vehicles’ access still depends on human assignment. Moreover, only vehicles in the gate can be monitored. So ore-stealing is still possible in transit. There are other methods to manage trucks’ transportation process [9-10]. However, the goals of these systems aren’t to solve the transportation problem in open pit.
To solve the above problem, this paper proposes a novel automatic transportation management system of vehicles in open pit that utilizes 3PGS(Three Points Guarding System) and GPS technologies. It can monitor automatically the whole transport process of vehicles. It is an effective solution to prevent stealing ore, control inlet and outlet automatically and monitor the trucks in real time in transit. With the application of this system, the loss of ore in open pit has been significantly reduced.

1. Three Points Orderly Guarding Model

(1) Basic Theory

In this section, the basic theory of setting up 3PGS model will be proposed. The core idea of the whole strategy is that the amount of truck’s ore loaded in starting point is always equal to the amount of truck’s ore unloaded in unloading spot in all trips. Assuming that truck T, weight of ore W, the loading point S, the unloading point E, and S_W_(i,j) is the weight of ore carried by truck i from loading point at j trip. E_W_(i,j) is the weight of ore carried by truck i from unloading point at j trip. The result is stated in following theorems:
THEOREM 1: when one truck T_i transports at j trip, the weight of ore in loading point should equal to the weight of ore in unloading point

S_W_(i,j) = E_W_(i,j) (1)

Note that if the above equation is satisfied, there is no ore-stealing behavior for truck T_i at j trip.
THEOREM 2: when the truck T_i transports at all n trips, the weight of ore in all loading points should equal to the weight of ore in all unloading points, where loading points and unloading points may be different.

(2)

Note that if the above equation is satisfied, there is no ore-stealing behavior for truck T_i at all n trips.
THEOREM 3: when all trucks T₁,T₂...T_m transport at all n trips, the total weight of ore in all loading points should equal to the weight of ore in all unloading points.

(3)

Note that if the above equation is satisfied there is no ore-stealing behavior for all trucks at all n trips.
In actual process of transportation, due to measuring scale variances, ore weight loss and the computational variances, the exact weight of ore at loading point is not necessarily equal to the accurate weight of ore at unloading point. So within a given range of deviation, we can deduce that stealing ore doesn’t happen in transit. For example, in practice, the equation (2) can be used as follows:

(4)

Where 0< δ<1,δ , is an acceptable range of variation, which usually depends on measuring equipment, ore type and transport environment.

(2) Three Points Management Model

Based on the above theorems, three points orderly management model is proposed, three points are weighing point in pit, entrance and exit of the open pit and weighing point in unloading point. The main idea of the model is that: first, automatic weighing scales are deployed at important points of open pit, for example, crusher station. Before the truck carrying ore goes out from the crusher station, total weight of the truck and ore will be obtained automatically at the weighing point and weight data will be transmitted to the central server. When the truck approaches to the exit of open pit, truck’s information from the central server including its last weight data and permission can be read by RFID tag. According to the information, the system will automatically judge whether the truck can be permitted to go out. Then, if the truck exits and arrives at the unloading point, normally a processing plant. The combined weight of the truck and the ore will be weighed again at the unloading point. The weight data will also be transmitted to the central server. All the data from those three points can be collected by Ethernet synchronously. In a transportation process of truck, all the data from three points will be gathered, analyzed and evaluated based on the theorems. The overall design of three points is shown in Fig.1.

Figure 1 The orderly layout based on three points

In an open pit, some vehicles are auxiliary, so that they can be managed only by automatic barrier gate at the entrance or exit. Most of the others are mining trucks, which should be managed and controlled by two points or three points. All vehicles in open pit are grouped into three categories. The first is the auxiliary vehicles that transport materials except ore and don’t need to be weighed. If the vehicles are attended to enter or exit, their permission must be accepted. The second kind is trucks that transport only inside the open pit. When these trucks are trying to exit, they must be permitted by scheduling manager via electronic audits. Audit result will be recorded in the database. Then the truck can pass the barrier gate. The third is the trucks that carry crushed ore to extract processing plant. Those should be orderly managed by three points. Before the trucks exit from open pit, they should be weighed. In the whole process, the most important and complex process is to analyze whether the vehicle is permitted when it passes through the barrier gate. The activity diagram of the running mechanism in barrier gate point is shown in Fig.2

Figure 2 Activity diagram of the running mechanism in verification point

2. Tracking trucks strategy based on GPS

Based on GPS, tracking trucks strategy can gather real time positions of trucks carrying ore in the transportation process. First, GPS mobile terminals are equipped in the trucks. The terminals can receive and send real time GPS satellite signals in any weather conditions. Then it can calculate relative position information of the truck spontaneously. The truck position data mainly includes longitude, latitude, altitude, speed and time. All data will be transmitted to the central server by wireless networks(GPRS or WiFi). The trucks’ position data usually can be transmitted periodically in 10-15 seconds. In the central server, any truck’s historical paths including speed can be found at any time, which also can be displayed in GIS. The electric fence can also be set up in GIS. The system will detect and alarm, if the truck goes beyond the fence. Using this, the trucks can be managed in stope[6-8]. The whole system data flow diagram is shown in Fig.3.

Figure 3 The whole system data flow diagram

3. Automatic transport management system of vehicles based on 3PGS and GPS

(1) System design and composition

Based on 3PGS and GPS, the automatic transportation manage system mainly consists of hardware subsystem and software subsystem. The hardware subsystem are mainly scales, scale data terminals, RFID readers, RFID tags, LED display screens, barrier controllers, barriers, GPS mobile terminals, database server and communication server. Based on c#.net, serial port communication, MapX and database, four software clients are designed and developed. They are 3PGS vehicle communication and automatic control client, 3PGS remote authentication client, 3PGS and GPS data collection and analysis server and GPS vehicle tracking client, which can be shared with existing dispatch client.
The most important advantage of the whole system is that it is automatic in all process, especially in barrier gate. Through RFID remote identification technology, all vehicles can be identified automatically. Each mining truck carrying ore will be weighed twice in pit and outside automatically. The weight of ore will be checked at loading point and unloading point. Using auto barrier gates and using registry setting in advance to classify permission, automatic access control management of different vehicles can be realized. Using GPS tracking position technology, all mining trucks can be tracked in real time. So trucks’ paths and quantity of ore can be monitored in the whole transport process. Combining the above technologies, the access to open pit and vehicle transport can be managed effectively. The composition of automatic transport manage system is shown in Fig.4.

Figure 4 The composition of automatic transport manage system

(2) System development

The automatic weighing and GPS tracking parts had been discussed in our research group’s previous literatures[2,6]. So they can be omitted in this paper. The automatic access control at entrance and exit is complex, so we discuss it in this section. The automatic access control involves the remote RFID readers equipped in the entrance and exit, barrier controller, barriers, access control software and SQLServer database. As shown in Fig.5, the barriers are installed in the entrance and exit of open pit. By default, two barriers are shut down and two lights in front of barriers are red. When a vehicle attends to enter the open pit, the RFID reader asks its tag for the number from first. Then according to the number, for example, 55737, all vehicle’s information and permission can be queried in the central database. If the vehicle is permitted to enter, the access control system will send and ‘open’ signal to barrier controller. The barrier gate can be opened and the lights will change to green. Finally, when the vehicle passed, the barrier shut down immediately using ground sense coil. With similar process, the control of exit can be achieved. The overview of barrier gates in access point is shown in Fig.5.
One barrier controller is applied at an access point, which can control at least two barriers. Barrier controllers at different locations are connected via Ethernet, so that data consistency and synchronization can be guaranteed. Every barrier controller is also connected with upper computer by COM1, which can control the entrance barrier and exit barrier simultaneously by different addresses. RFID readers communicate with upper computer based on RFID communication protocol by COM2 and COM3. When the barrier controller communicates with upper computer, the computer sends command according to their protocol and then the barrier controller will make corresponding response. For instance, the command consists of an array of bytes, namely {barrier gate address, instruction}, such as {0x02,0xBF,0x01}. Where 0x02 is the barrier gate address, 0xBF and 0x01 is the command to turn red light on. The barrier can be only controlled by the above data from barrier controller via SerialPort.

Figure 5 The view of barrier gates in access point

In some particular cases, all the RFID readers are remote and automatic in the entrance and exit. If the distance between two RFID readers is close, false scanning will probably be caused. For example, if vehicle’s RFID tag is read by entrance reader when it goes out, the barrier gates in entrance and exit are both opened. This problem is solved by enlarge isolation distance or by software. In software development, a flag is set up to mark vehicle in or out. Before the vehicle goes out from exit, the flag should be check and the flag should be mark vehicle out. If not, false scanning happened. The request will be cancelled. This method is called “in and out discrimination mechanism”. Due to improper distance between two RFID readers, after the vehicle passed the exit barrier, it’s tag is still scanned by opposite entrance reader and then entrance barrier open. This also is not conform to the actual. So the “repeat read oversight mechanism” is designed to solve it. After the exit barrier opens, the time from last scanning will be calculated. If the total time is less than assigned value, for example, 3 minutes, the scanning information from this vehicle will be ignored. So, if all vehicles’ information can be initialized correctly, the problem of scanning tag by mistake can be solved through above methods.

System deployment and application

The Sandaozhuang open pit is a super-huge molybdenum and tungsten open pit, one of the world's three largest molybdenum, China's second great tungsten, which belongs to mining company of Luoyang Luanchuan Molybdenum Industry Group.Inc. It’s mining capacity has been up to 30000 tons/day since june 2006. Molybdenum is a rare metal and more expensive than simple metal. The behavior of stealing ore often happens in the transport process, especially in the night. Some trucks also violate dispatching command. Due to three shifts a day, it is highly difficult to monitor and manage all vehicles in all day everywhere. So far, there are all kinds of vehicles about 208, where 40 tons haulage trucks is 40, 32 tons haulage trucks is 5, other heavy-duty trucks is 152, daily service bus is 8 and other pickup truck is 3. Some haulage trucks transport crushed ore from open pit to extract processing plants and other trucks always transport ore from blasting muck pile to crushing station. But all vehicles will go out from the barrier gate if they need repairing. Due to more vehicles in stope and complex situation, so access management and transportation is very important work in daily production management in the open pit.
In view of the above situation, with a series of advanced technologies such as 3PGS, GPS, GIS, wireless communication, electronic weighing, RFID technologies and system engineering theory,the new automatic transport management system of vehicles has been developed and successfully used in Sandaozhuang open pit since 2012.

Figure 5 The typical application in automatic transport management system

At present, based on the enterprise Ethernet, automatic weighing points inside and outside have been successfully deployed. There are 10 automatic weighing points in the open pit, which normally are installed in important points, for example crushing station. And one automatic weighing scale is installed below the draw shaft from Taibaoshan crushing station, which is responsible for weighing ore transported to extract processing plant from draw shaft. There are 3 automatic weighing points in the unloading points outside the open pit. The two sets of inlet and outlet have been set up in 1309 and 1801 in the open pit, which can automatically read related vehicle’s information by RFID and permit passing vehicle to enter or go out. There are 4 barrier machines, 4 RFID readers installed in inlet and outlet points. And there are 208 GPS mobile terminals and 208 RFID tags equipped in each vehicle, which can track each vehicle in real time. In the data center, there are 2 IBM3500 servers, one for communication, the other for database.
Since march 2012, the system has been improved continuously. The SQL server had been installed in all weighing stations, inlet and outlet points and central server. Adapting this method not only makes software faster and more effective due to local store, but also guarantees software to run if the network doesn’t work well. Under the condition of local authorization, the software will automatically switch to run locally. Besides, the barrier control subsystem supports emergency open. Once several vehicles need to pass continuously, the barrier can always be opened until all the vehicles pass, which need authorized by different departments. Through the application of the system in Sandaozhuang open pit, stealing ore is prevented effectively and the whole transport process is monitored in real time. The system largely improves the level of vehicles management in the open pit.

Conclusion

(1) 3PGS management model makes weighing station in loading point, access to open pit and weighing station in unloading station work cooperatively. The involved technologies are reliable and mature. The application in Sandaozhuang open pit shows that the model is used effectively to prevent stealing ore in the transport process. It largely reduces the loss of ore in mining enterprises.
(2)with the wide application of GPS technology, GPS is combined with 3PGS in this system. On the one hand, the quantity of ore is monitored in transport by 3PGS, on the other hand, the transport path is monitored real time in whole process by GPS. The two are complimentary to realize the management of vehicles in open pit.
(3) Based on 3PGS and GPS automatic transport management system of vehicles in open pit is not only available in open pit, but also can be used to manage vehicle in other fields. for example, it can be available in logistic vehicles management.

Acknowledgments

The work was supported by by Research Fund for the Doctoral Program of Higher Education of China(20126120120019) and the key discipline of Shaanxi Province(E08001) .The authors gratefully acknowledge the cooperation of the Luoyang Luanchuan Molybdenum Industry Group Inc. The authors also thank other participants for their support in OSU.

References

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[2] Gu Qinghua,Lu Caiwu,Guo Jinping,Jing shigun. Dynamic management system of ore blending in an open pit mine based on GIS/GPS/GPRS[J].Mining Science and Technology,2010(1):132-137.
[3] Wu Wenjun, Jing Shigun, Gu Qinghua. The Digital Dispatching System of Open Pit Mine Based on WiFi[J].Metal Mine, 2010,8:132-126.
[4] Li Fa-ben , Ruan Shun-ling.Dynamic Path Generation Algorithm for Open Pit Based on GPS[J]. Computer Engineering, 2012, 38(01) 236-238,241.
[5]Choi, Yosoon, Nieto, Antonio.Optimal haulage routing of off-road dump trucks in construction and mining sites using Google Earth and a modified least-cost path algorithm, Automation in Construction, v 20, n 7, p 982-997, November 2011
[6]Bu yange.The Application of RFID Technology in the Truck Transportation System of the Open-pit Mine[D].Xi'an:Xi'an University of Architecture & Technology,2008,1-67.
[7] Guo Wentao, He Yigang.The Research and Design of Management System of Intelligent Parking Based on RFID,2010,29(6):60-64
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Ultrasonic phased array parameters determination for the gas bubble size distribution control formation in the iron ore flotation

Wed, 16 Jul 2014 14:59:09 +0300

A method for the effective control of the pulp gas phase composition in the flotation process using dynamic effects of high energy ultrasound on the base of phased array technology and determination of its parameters are described.

Key words: phased array, ultrasound, pulp, control, flotation

Ultrasonic phased array parameters determination for the gas bubble size distribution control formation in the iron ore flotation

Vladimir Morkun
Vice-Rector for research, Doctor of Science, professor of Computer Science, Automation and Control Systems department
Kryvyi Rih National University

Natalia Morkun

PhD, Associate professor of Economic Cybernetics and Project Management Department
Kryvyi Rih National University

Andrey Pikilnyak
PhD- student of Computer systems and networks department, research assistant of the Computer Science, Automation and Control Systems department
Kryvyi Rih National University

Introduction.

Flotation is the most widely used separation process in the processing industries and is the most complete and versatile mineral processing operation.
The existing methods and automatic systems of flotation process control does not allow to efficiently control the gas phase parameters in terms of changing characteristics, medium parameters and equipment state.
For an understanding of the physical processes that determine flotation the accurate information about the gas phase parameters, the most important of which are the size and bubbles size distribution is required. These parameters are strongly dependent on the various operational, technical, physical and chemical factors, the effects of which should be considered in flotation process modeling [2,3].
It is known that for the pulp solid phase particle size distribution may exist the optimal gas phase bubbles size distribution in the flotation process.
Thus, the task of research is to form and maintain a specified gas bubble size distribution which would correspond to the ground ore particle size distribution.

Materials and methods.

To solve this task, let’s form the control action based on the dynamic effects of high-energy ultrasound using phased array technology, the main feature of which is computer-controlled driving pulses amplitude and phase of the individual piezoelectric elements in multi-element transducer to control the parameters of the ultrasound beam, for example, angle, focal length, focal spot size [5,6].
Taking into account the above in the proposed method using the ultrasonic phased array mounted on the external wall of the flotation machine chamber, in the working area, at each current moment of time we generate the high energy ultrasound effect with a given frequency 0.7 - 2.5 MHz, (because the value lower than 0.7 MHz does not give a stable effect of bubble size changes, which is caused by the extreme nature of cavitation, and a value above 2.5 MHz is not affect the change of necessary indicators) and the pressure amplitude of 102 -5×106 Pa, (because the value lower 102 Pa not sufficient to effectively control the gas phase, and the values above 5×106 Pa not give quality indicators growth), wich focused on the window in the interchamber septum. The gas bubbles which formed in the aeration step, after impeller dispersing are exposed to focused ultrasound, which leads to variations in their concentration and desired size redistribution in the pulp flow.
To focus precisely on the window in the interchamber septum it is necessary to calculate the parameters of a phased array and to construct its directivity pattern.
The acoustical pressure of the array was calculated by modeling every element of the array as an independent simple source and summing the contribution of each simple source at each point in the field. The acoustic pressure p(x,y,z) at a specific point (x,y,z) in the field due to a simple source was calculated using the Rayleigh-Sommerfeld equation [7,8]
,                               (1)
where W - is total acoustical power output from the array, ρ – is density of the medium, c – is speed of sound in the medium, A – is active transducer aperture, f – is frequency, S – is area formed by source, d – is distance from the source to the point (x, y , z), φ – is phase of oscillation, λ – is wavelength, and α – is attenuation in the medium.
The active aperture (the total length of the array) is calculated by the following formula [6].
,                                            (2)
where A - is active aperture; g – is gap between nearest elements; e – is width of one element (typically e <λ / 2); n – is number of elements.
Active aperture projection onto a plane seen along the refracted rays (effective active aperture Аeff) is given by
,                                             (3)
Recommended passive aperture is determined by probe frequency and the focal depth range as follows
,                                 (4)
Its contribution to the focal depth (near-field length) is given (for nonfocused probes) by formula (5)
,                          (5)
Array pitch of p is determined by the formula:
,                                                 (6)
where g – is the element gap; e – is the element width.
The maximum width of a single element, which is determined by the maximum beam refracted angle by electronic control emax can be represented as follows
,                                          (7)
Note that the beam width is dependent on the focal length and the angle of entry.
A focused beam is characterized by the focusing factor or normalized focus depth
,                                               (8)
with 0 < Sac < 1 and Fac < N0, andFac – is the actual focal depth.
An optical focus point is defined by
,                                    (9)
where R - lens curvature radius.
The optical focusing factor is defined by
,                                              (10)
The net pressure due to all the elements was determined by summing the effects of each simple source:
.                            (11)
The net power deposition at point (x,y,z) was the result of the attenuation [5]
,                             (12)
The total energy at a point (x, y, z) is given by [8,9]
,                             (13)
where - intensity at the point (x, y, z), W∙m -2
The phase of each element of the array was determined by
,                                         (14)
where φi is phase of element i in degrees, di is distance from the center of element i to the focus, d0 is the focus depth, n is an integer used to maintain 0 <= φi <= 360°.

Results.

Figure 1. Phased array configuration

Figure 2. Directivity pattern of a rectangular phased array with Z=16, j=0°

Figure 3. Directivity pattern of entire arrangement

Taking into account the above, for the method implementation we form the ultrasonic action with certain amplitude and frequency using phased array at each current moment of time in a flotation machine working zone that will provide the required gas bubble size distribution in the pulp flow.

Conclusions

Simulation results of the high energy ultrasound impact on the pulp gas phase using ultrasonic phased array allow to form the required gas bubble size distribution function, which will conform with the pulp solid phase particle size distribution in the flotation process. Thus, the proposed flotation control method allows to implement efficient control of the pulp gas phase composition, improve the quality of the concentrate and the efficiency of the beneficiation process.
References

Brewis T. Flotation cells. Mining Magazine, 1996,160(7), p.p 18–24.
Miskovic S. An investigation of the gas dispersion properties of mechanical flotation cells: an IN-SITU approach. Blacksburg, Virginia, 2011.
Morkun V. S., Morkun N. V,. Pikilnyak A.V. Ultrasonic facilities for the ground materials characteristics control, Metallurgical and Mining Industry, 2014, No2, p.p.31-35. http://www.metaljournal.com.ua/assets/Journal/a6.pdf
Morkun V. S., Morkun N. V,. Pikilnyak A.V. Iron ore flotation process control and optimization using high-energy ultrasound, Metallurgical and Mining Industry, 2014, No2. p.p. 36-42. http://www.metaljournal.com.ua/assets/Journal/a7.pdf.
Morkun V. S., Morkun N. V,. Pikilnyak A.V. Modeling of ultrasonic waves propagation in inhomogeneous medium using fibered spaces method (k-space), Metallurgical and Mining Industry, 2014, No2, p.p. 43-48. http://www.metaljournal.com.ua/assets/Journal/a8.pdf
Olympus NDT. Introduction to phased array ultrasonic technology applications. R/D tech guideline, 2007.
Goodman, J. Introduction to Fourier Optics. 2rd ed New York: Stanford University,1968.
Sun, L. Collins C.M., Schiano J.L., Smith M.B., Smith N.B.. Adaptive Real-Time Closed-Loop Temperature Control for Ultrasound Hyperthermia Using Magnetic Resonance Thermometry. Concepts in Magnetic Resonance Part B (Magnetic Resonance Engineering), 2005,Vol. 27B,No1,p.p. 51–63
Seip, R., VanBaren, P., Cain, C., Ebbini, E. Noninvasive real-time multipoint temperature control for ultrasound phased array treatments, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 43, no.6, (1996): 1063-1073
Kohout, B. Transducer Array Calculation (TAC) GUI.http://www.mathworks.com/ matlabcentral/fileexchange/35657- transducer-array-calculation-tac-gui.

Modeling of stopes in soft ores during ore mining

Tue, 15 Jul 2014 13:14:20 +0300

UDK 622.272.4

	Nikolay Stupnik D.Sc. in engineering, professor, discharging responsibilities of rector of Public higher education institution Kryvyi Rih National University, head of Underground mine development chair
	Vsevolod Kalinichenko D.Sc. in engineering, professor Kryvyi Rih National University
	Valeriy Kolosov Sc. in engineering, Director General of “Ukrrudprom” association Kryvyi Rih
	Sergey Pismennyy PhD in Technical Sciences, docent Kryvyi Rih National University
	Aleksandr Shepel' Master, teaching assistant of Underground mine development chair Kryvyi Rih National University

Modeling of stopes in soft ores during ore mining

Results of physical modeling of stopes in soft ores on substitutes are presented. Stope of cusp form is found to be more stable as compared with square chambers.
Keywords: stope, cusp form, time, volume

Introduction

Ore deposits of Kryvyi Rih iron-ore basin are divided into solid and parallel –contiguous. A lot of researches, fulfilled by Malakhov G.M., Kaplenko Yu.P., Shchelkanov V.A., Lavrinenko V.F., Dedyulin V.V., Rymarchuk B.I., Andreev B.N., Storchak S.A., Tsarikovskiy V.V., Faustov G.T., Stupnik N.I., Kalinichenko V.O., Khivrenko O.Ya., are devoted to the questions of underground development of solid deposits of Kryvyi Rih iron-ore basin.

They suggested different variants of supporting systems; definition methods for: degree of extraction, structural members of supporting system, reasonable output, delivery and breaking-out out of ore were developed [1-4].
From the mining depth, mining and geological conditions are complicated by: variable power and dip angle, difference in mechanical-and-physical properties within mine section and also presence of dirt inclusions.
The authors developed classification of complex-structural ore deposits, which allows to simplify the choice of supporting system during development of substantial and non- substantial ores [3]. Existing supporting systems during development of complex-structural deposits in soft ores lead to increased losses of ore, because of increase in width of solid blocks during application of systems with open face or chocking – system with mass caving of ore and overlying rock [5-6].

Statement of a problem

With the help of theoretical researches [6] it is stated that while processing of complex-structural deposits in soft various- module mass, the usage of system with mass ore caving and overlying rock with stope of cusp form closed to the maximum allowable stable contour of cropping, fig. 1.

Figure 1 The scheme of stope of cusp form

The stope of cusp form provides its stiffness due to decrease of cropping passage and its optimal parameters [7]. Parameters of the stope are determined from the formula
(1)
where h and b – vertical and horizontal semi-axis of the curve, m; Рh, Рv – radius of maximum allowable stable horizontal and vertical respectively stope of cusp form, m (in accordance with pilot testing for conditions of Kryvyi Rih iron-ore basin make Рh= 1-6 m, Рv= 30-90 m).
In order to confirm theoretical researches, it is necessary to fulfill laboratory studies for determination of stable parameters of the stope in the non-stable various-module mass.

Research results

For determination of stiffness of stope of cusp form, laboratory studies on substitute models were fulfilled. 1:100 geometric scale value of modeling was adopted. Substitute material in respect with modeling scale was selected in accordance with physic-mechanical properties of subsurface rock of “Yubileinaya” mine.
There were carried out 16 series of laboratory studies, which differ from each other by stope form and tensile strength in uniaxial compression (rock hardness), table 1. Each study repeated 3-5 times.
Substitute material, which was loaded by external stress corresponding to the depth of development (1260m) in respect with modeling scale determined under the expression given below, set into laboratory model

(2)
where Nm, Np – some characteristic of model or prototype material, having force dimension, modified to the unit of area (compressive strength, extension, etc, elasticity, stress modulus);γm, γp – material density, model and prototype respectively; lp, lm – linear dimensions, in model and prototype respectively; M - a nondimensional number, which is characteristic criterion of similarity.
According to the calculations under the formula [2], vertical and horizontal pressure in the model makes 13,2 and 6,4 kg/sm2 at 1260 m depth of the development and 0.25 Poison's ratio.
In 3 days substitute material from back side was cut out, creating the necessary form of the stope with 45 sm3 volume, and within 36 days (which corresponds to 12 months in prototype) they inspect its conduct.
During modeling in accordance with behavior of vertical stope, within 12 days (4 months), the stope keeps its initial parameters, table 1. After 15 days, there observed cleaving of substitute in the top part of the stope and giving it domed shape.

Table 1 Results of modeling of stope stiffness in unstable rock

No of experiment	Stope parameters, sm			Ore hardness	Volume of the stope since its existence, months
No of experiment	height	length	width	Ore hardness	4	6	8	10	12
stope rectangular in shape
1	90	50	10	4	46	55	63	71	75
2	90	50	10	6	45	51	61	66	71
3	90	50	10	8	45	47	58	62	68
4	90	50	10	10	45	45	47	55	66
5	30	150	10	4	53	64	80	-	-
6	30	150	10	6	51	60	68	79	-
7	30	150	10	8	48	55	67	73	80
8	30	150	10	10	46	54	66	72	78
hipped stope
9	90	75/25	10	4	45	48	53	54	55
10	90	75/25	10	6	45	47	50	50	50
11	90	75/25	10	8	45	45	47	48	50
12	90	75/25	10	10	45	45	45	46	49
stope of cusp form
13	75	50	10	4	45	45	47	48	50
14	75	50	10	6	45	45	45	46	48
15	75	50	10	8	45	45	45	45	45
16	75	50	10	10	45	45	45	45	45

With the increase of stope lifetime up to 36 days, its shape becomes of ellipsoid form; this fact confirms the results of Kulinkov’s researches [8]. It should be marked that changing of mountain mass hardness from 10 to 4, the volume of stope increases 1.5-1.6 times respectively without sacrificing its stiffness in time up to 12 sec.
During modeling of horizontal stope stiffness, experiments No5-8, table 1, it was found that if one increases stope volume more than 1.6 times, it will be destroyed (experiment No 5,6, table 1). During modeling there was observed formation of destruction crown on the top part of the stope. After 18-20 days, depending on the tensile strength of substitute, there observed cleaving of the material not only in the top part but also from the side of its blocks.
Stability analysis of the stope of hipped form while modeling showed that destruction of substitute along the outline of the stope flows less intensively as compared with stopes, rectangular in shape. It should be marked that after 30 days the stope of hipped form takes cusp form, and its volume increases not more than 1.1 -1.2 times within 36 days (a year) of existence.
The stope fractures mainly in its top part. With the help of laboratory studies it was found that destruction power, affecting the sides of stope will be the lowest.
The results of laboratory modeling (fig.2) confirm that formation of the stope of cusp form increases its stiffness without disturbance of substitute along its perimeter. The table 1 shows that within 36 days the stope of cusp form has expanded not more than 1.1 times.

Figure 2 Modeling of stope stiffness of cusp form with substitute tensile strength corresponding specifically 100 MPa: a, b- stages of modeling, before and after modeling respectively; 1 - laboratory model; 2 - external loading; 3 – substitute (mountain mass); 4 – horizontal stope.

In such a way, the results of theoretical researches may be confirmed, and the expression (1) is true.
Figure 3 reflects combined outlines of stopes before and after modeling with substitute tensile strength, which equals specifically 100 MPa (10 on-scale of prof. Protod'yakonov).

Figure 3 Combined outlines of stopes: a,b – stope configuration before and after modeling; 1,2 - rectangular in shape; 3 – of hipped shape; 4 – of cusp shape.

Analysis of the figure 3 shows that in geological conditions, when vertical stresses more than horizontal ones, stopes of vertical and hipped form take cusp form in course of time.

Figure 4 Dependences of change of stope volume on its lifetime and its shape at substitute tensile strength, which equals specifically 100 MPa.

Figure 4 shows that at substitute tensile strength, which equals specifically 100 MPa and lifetime of the stope of cusp form stays constant, square stopes in their turn start expanding in 6-12 days.

Conclusions

The results obtained showed that the stope of cusp form in unstable rock is more stable as compared with stopes of rectangular or hipped shape. Also while modeling it is proved that the volume of stope increases not more than 1.1 times under the characteristics determined by theoretical researches.

References

Malakhov, G.M., Lavrinenko, V.F., Kucheryavenko, I.A. (1961) Reasonable course of stoped excavation for mines of Krivorozhskyi basin. Gornyyzhurnal, No3, pp. 19-24.
Shchelkanov V.A., Khivrenko O.A., Khivrenko V.O.(2002). Analysis og complex-structure deposits of Krivbass basin. Oremining. KryvyiRih, KTU, No7, pp. 30-35.
Stupnik N., Kalinichenko V., Pismennyi S. Pillars sizing at magnetite quartzites room-work. Mining of Mineral Deposite. A Balkema Book. 2013, pp. 11-15.
Korzh V.A., Kudryavtsev M.S., Lavrinenko A.F. (1985). Calculation methods of stay bar value of superincumbent bed of broken ore. Ore mining.Kryvyi Rih, KTU, No40, pp. 48-52.
Stupnik, N.I. Pis'mennyy, S.V. (2013). Parameters of store- pillar mining of ferruginous quartzite with inclined pillars. Gіrnichiy vіsnik, No 96, pp. 89-93.
Stupnik, N.I., Pis'mennyy, S.V. (2012). Advanced technological variants of further treatment of iron-ore deposits by systems of mass caving of ore. Vіsnik Krivorіz'kogo natsіonal'nogo unіversitetu, No 30, pp.3-7.
Pis'mennyy S.V., Khivrenko V.O., Sbitnev V.A., Polukhina N.V. (2002). Parameter determination of balance chamber of domed shape. Ore mining.Kryvyi Rih, KTU, No79, pp. 48-52.
Kulikov V.V. Vypusk rudy (Ore drawing). Moscow, Nedra, 1980, 303 p.

Simulation of high-energy ultrasound propagation in heterogeneous medium using k-space method

Wed, 16 Jul 2014 15:02:55 +0300

The method and software based on this method for parameters estimation of the ultrasonic waves propagating in random heterogeneous medium are described
Key words: phased array, ultrasound, pulp, control, k-space

Simulation of high-energy ultrasound propagation in heterogeneous medium using k-space method

Vladimir Morkun
Vice-Rector for research, Doctor of Science, professor of Computer Science, Automation and Control Systems department
Kryvyi Rih National University

Natalia Morkun
PhD, Associate professor of Economic Cybernetics and Project Management Department
Kryvyi Rih National University

Andrey Pikilnyak
PhD- student of Computer systems and networks department, research assistant of the Computer Science, Automation and Control Systems department
Kryvyi Rih National University

Control of mineral beneficiation process requires controlling the parameters of complex heterogeneous mediums, including solid, liquid and gas phases.
Ultrasonic oscillations are periodic disturbances of the elastic medium state, characterized by a change in its physical properties, which occur synchronously with perturbation. During ultrasonic propagation the local medium volume oscillations are transmitted to adjacent areas by means of elastic waves, characterized by a change in medium density in space and which transfer the fluctuations energy [1-3].
The basic relations describing ultrasonic oscillations and waves in the medium, follow from the equation of medium state, Newtonian equations of motion and the continuity equation [4,5]. The results are the wave-type equations that can be solved with appropriate initial and boundary conditions.
The equations of ultrasonic waves nonlinear propagation in heterogeneous medium can be derived from the mass, momentum, and energy conservation laws under the assumption of a quiescent, isotropic, and inviscid medium as follows[6,7]

, , (1)

where p is the acoustic pressure, ρ is the density, u is the particle velocity, ρ0 is the ambient density. The second order terms in (1) can be re-written in terms of the Lagrangian density by the repeated substitution of the acoustic equations in linearized form [8]. The Lagrangian density terms can be neglected as follows.

, . (2)

Let’s neglect thermoviscous losses and include a phenomenological loss operator to account the arbitrary power law absorption [8], then the equation of state from the total pressure expansion using a Taylor series can be written as follows

, (3)

where c0 is the isentropic sound speed, d is the particle displacement vector, and τ and η are the absorption and dispersion proportionality coefficients where and . α is the acoustic absorption where , α0 is the absorption coefficient prefactor and y is the power law exponent [9].
The expressions given in (2) and (3) are the acoustic particle velocity, density, and pressure coupled set of equations.
Let’s combine these expressions into a single second order wave equation for the acoustic pressure. The modiﬁed Westervelt equation by neglecting higher order absorption, nonlinearity, and heterogeneity terms, can be written in the following form

, (4)

where is the nonlinearity coefficient.
By neglecting higher order absorption and nonlinearity effects, the conservation equations in (2) using a k-space method [10] can be written as follows

(5)

where i is the imaginary unit, kξ is the wavenumber in the ξ direction, κ is the k-space adjustment where κ =sinc(c0kΔt/2), F and F−1 denote the forward and inverse Fourier transform, Δt is the time step.
The corresponding equation of state in discrete form is

, (6)

where the total density is given by and the discrete loss term is

, (7)

Let's simulate the ultrasonic pressure field propagation in a heterogeneous medium using k-Wave toolbox (Matlab) which is designed for time domain ultrasound simulations in complex media like heterogeneous pulp. The simulation functions of this software are based on the k-space method and are both fast and easy to use [10].
The net pressure of all piezoelectric elements can be obtained by adding the effects of each source and written in the form

. (8)

Due to attenuation, the useful power at the point (x, y, z) is given by [11]

, (9)

The total energy at a point (x, y, z) is given by

, (10)

where - intensity at the point (x, y, z), W/m.2
The results of the ultrasonic wave propagation through a heterogeneous medium with density kg/m3, for source strength of 1MPa and tone burst frequency of 1MHz for 16-element phased array with focus distance of 20mm are shown in Fig. 1. The central slice absorption distribution in grayscale as a background and the square of the pressure distribution on the surface of this background are shown.

Fig.1. Total beam pattern using maximum of recorded pressure
The final pressure field (a), the maximum pressure (b) and standard pressure (c) of the beam are shown on Fig. 2. The transducer focus and sidelobes are visible.

Fig. 2. Ultrasonic wave propagation in heterogeneous medium: a) the final pressure field, b) the maximum pressure c) the rms pressure

Fig. 3. The shape of the main wavefront
The linear cross-section of the focus in x direction is shown on Fig. 4: 1) for the single source; 2) simulation by k-space method in the water; 3) in a heterogeneous medium.

Fig. 4. The simulation results comparison of the normalized square of pressure for: 1) a simple screened source, 2) modeling by k-space method in a homogeneous medium (water) and 3) in the inhomogeneous medium (pulp) along the axis: a) - z and b) - x.
For the process of energy accumulation and transfer in a certain point of space can be given a numerical estimate by measuring the temperature. The simulation of temperatures was performed using the heat transfer equation [12]. The accumulated power was extracted from the three perpendicular lines that crossed the values of the simulated and measured ultrasound pressure focal area change (Fig. 5).

Fig. 5. The simulation results comparison of the temperature distribution for: 1) a simple screened source, 2) modeling by k-space method in a homogeneous medium (water) and 3) in the inhomogeneous medium (pulp) along the x axis.

Conclusions

To build a model of the ultrasonic field in a randomly inhomogeneous medium, the fiber spaces method (k-space), which increased the accuracy of parameter estimation field is used.

References

Morkun, V. Ultrasonic control of random heterogeneous mediums parameters.-Non Destructive Testing, ELSEVIER 92, (1991):989-993.
Morkun V. S., Morkun N. V,. Pikilnyak A.V. Ultrasonic facilities for the ground materials characteristics control, Metallurgical and Mining Industry, 2014, No2, p.p.31-35.
Morkun V. S., Morkun N. V,. Pikilnyak A.V. Modeling of ultrasonic waves propagation in inhomogeneous medium using fibered spaces method (k-space), Metallurgical and Mining Industry, 2014, No2, p.p. 43-48.
Morkun, V., Goncharov, S., Pikilnyak, A., Krivenko, A. Iron ore benefication processes optimization. ТЕKA. Commision of Motorization and Energetics in Agriculture 12, no.4 (2012): 162-166.
Morkun V. S., Morkun N. V,. Pikilnyak A.V. Iron ore flotation process control and optimization using high-energy ultrasound, Metallurgical and Mining Industry, 2014, No2. p.p. 36-42.
Morkun, V. Ultrasonic Control of Random Heterogeneous Mediums Parameters, AMMTIAC, no. 42(1992): http://ammtiac.alionscience.com/ammt/iacdocs.do?NT-49740.
Treeby B., Tumen M., Cox B. Time domain simulation of harmonic ultrasound images and beam patterns in 3D using the k-space pseudospectral method, MICCAI 2011, Part I, LNCS 6891, (2011): 363–370
Aanonsen, S., Barkve, T., Tjotta, J., Tjotta, S. Distortion and harmonic generation in the nearﬁeld of a ﬁnite amplitude sound beam, J. Acoust. Soc. Am. 75, no.3, (1984):749–768.
Treeby, B., Cox, B. Modeling power law absorption and dispersion for acoustic propagation using the fractional Laplacian, J. Acoust. Soc. Am. 127, no.5, (2010):2741–2748
Internet resource: http://www.k-wave.org/
Seip, R., VanBaren, P., Cain, C., Ebbini, E. Noninvasive real-time multipoint temperature control for ultrasound phased array treatments, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 43, no.6, (1996): 1063-1073
Pennes H. H.Journal of Applied Physiology'1, 93 1948.

The processes of heat and mass exchange in the vortex devices

Wed, 16 Jul 2014 15:06:08 +0300

The article suggests physical and mathematical models used in the design of vortex evaporation chambers for separating multicomponent media.
Key words: vortex, heat and mass transfer, model calculation.

Dr. sci, professor Anatoliy Pavlenko

Ph.D., associate professor Hanna Koshlak

Postgraduate Bohdan Usenko
Poltava National Technical Yuri Kondratyuk University, Poltava

P - pressure, Pa; W - circumferential component of the velocity, m/s; a - fluid tube; I - enthalpy; S -entropy; V - velocity phase, m/s; T - temperature, K; ρ - density, kg/m3; r - radius, m; z - coordinate axis of the vortex chamber, m; Mx - Maxa Number; V - the radial velocity component, m; γ(r) - mass removal rate, presented as a series with coefficients A1, A2, and the exponent a; B - hydrodynamic characteristics of the devices, K-the adiabatic index; U - axial component of velocity, m / s.

Introduction

For the design of vortex evaporation chambers extensive theoretical and experimental researches of aerodynamics of swirling flow in respect with changing in the volume and mass of the setting are required. The basis of investigation should provide a model of liquid flow in the vortex chamber [1] and analyze the possibility of using these results to describe the boiling of vortex flows.
The studies [2] indicate that the relative rotational speed with an increase in temperature (burning oil) in 1.5times increase relative to the speed of the cold flow. Axial velocity increased in 4 times. Relative values of total and static pressures for the heated chamber are higher than for the cold one. At the same time, the qualitative picture of the chamber remained without significant changes.
Let us consider first the physical representation of the process of the vortex flow boiling liquid, thus will be based on a physical model "cold" flow, presented in work [3].

1. Statement of the Problem

Figure 1 shows the diagram flashing flow. Due to the interaction along the boundaries a1, a2, a3 for cocurrent flow portion due to abrupt speed change section a1, a3 stream breaks up into vortex bundles, elongated along the surfaces parallel to the axis of flow. Vortex model of turbulent mixing layer is also discussed in detail in this work [4]. The resulting structure begins to move under the action of radial pressure drop.
In general, boiling in the flow occurs when the local pressure becomes lower than saturation value at the corresponding saturation temperature. If the device provides a global reduction in pressure, the liquid evaporates completely. When analyzing the results of research [5], a multi-stage model of superheated liquid boiling is traditionally adopted. In the first stage vapor bubbles are generated,

Figure 1: a - settlement scheme (the shaded area two-phase flow)

confluenting then into the flow tubes, which are accelerated to a greater extent than the main stream. The more the pressure gradient, the more clearly appear these stages of boiling up. The proposed model describes boiling up flow without reversibility. Application of this approach to the flow without gradient, could idealize this decision. But as vortex motion possible with significant pressure gradient, the assumption of irreversibility is justified and does not contradict the model of hydrodynamic and thermodynamic laws. Thus, referring to the figure 1, there are three areas of single-phase and two-phase flows. When the pressure drops to Pn the steam is generated, which flows in the form of separate tubes without friction heat exchange and stirring. By increasing the volume of the medium and lower density the speed leap is obvious. Tubes of current are characterized by isentropic flow.
The temperature and velocity in section tubes are not changed. With a further drop in pressure new tubes of current steam are created, the amount of liquid decreases. In the case of enough amount of overheating, the liquid evaporates completely. The non-evaporated portion of liquid is distributed in the tube of current in the form of droplets, and moves with the same speed as the steam. Evaporation process inside the vortex is conveniently represented on I-S diagram (Figure 2).
Using the basic thermodynamic relations, we can write an equality which follows from the diagram:

This equation is taken as the basis for further development of the model of evaporation and also fully characterizes presented physical model of flashing flow: boiling liquid formed cylindrical zone of vaporization, in which the saturation by vapor increases at approximation to the radius of the vortex while the pressure drops.
Evaporation rate and the final pressure value is determined by the level of overheating, on the hypothesis that the size of outlet opening corresponds to the mass flow of the setting. Following a reduced representation of flow phases, their speeds are different inside the vortex flow [8]. Let us assume that an increase of vapor content the phase velocities are approaching in their values and are aligned in the nozzle [9].

Figure 2 Representation process of boiling up I-S - diagram

2.Numerical simulation

The proposed above physical model of boiling process of superheated liquid in vortex devices can be represented by the following system of equations for the main area of the vortex:

(2)

Flows in areas of vortex flow can be represented by the following mathematical model:

(3)

Figure 3 shows the combined solution of (2) and (3) for flashing and "cold" flows. Graphic dependences illustrate the proposed physical representation of the process of liquid boiling in the vortex and are consistent with experimental data of this work[3]. These mathematical models can be at the core of calculation and design of vortex contact apparatus, or vortex devices in which the mass flow is variable, for example, devices for thermal separation of emulsions [6]. Considering the experience of exploitation of such devices, it should be noted that, as a rule, a vortex flow in the evaporation process is almost completed. Therefore, in many cases g( r)=0 can be taken without substantial error calculation in the system of equations (3).

Figure 3 - The solution of equations (2) and (3)

Solution of the equations can be written as:

(4)

(5)
Let us make calculations if

(6)

We form, nonlinear right side of the first equation.
Desired equation to calculate the pressure field can be represented in the form of:

(7)

where:

4. Discussion of results

From the graph in Figure 3, which reflects the dependence of medium pressure on the radius of vortex follows that the qualitative characteristics of this function remain unchanged when heated. However, in case of reaching the saturation temperature, pressure field deforms substantially up to keeping a constant value, which is almost equal to the inlet pressure. Such critical modes of the device operation should be assessed on the stage of forecasting of working structural and technological parameters.
The graphs of Figure 3 also reflect a change in the flow rate in the case of phase transition, i.e. increase or reduction of medium volume in the vortex layer.
Calculated dependences are in satisfactory agreement with the experimental data obtained in a vortex device, through which superheated water relatively by normal conditions was passed.

5. Conclusion

To determine the quantitative characteristics of the process, it is necessary to know the mass flow rate (mass removal) g(r) and also to clarify the pole slipping coefficient value.
From the represented data follows that the change of vortex flow weight at EFV boiling in the vortex evaporator (during combustion, condensation, etc.) leads to deformation of pressure fields and velocity components. This feature should be considered when designing of appropriate devices.

References

1. A.M. Pavlenko, Stability of emulsions in technological influences. Dnepropetrovsk, Science and Education, 2000, P.140
2. Dolinskiy A.A., A.M. Pavlenko, B.I. Basok Thermophysical processes in the emulsions. Kiev, Naukova Dumka, 2005. P.268.
3. Pavlenko A.M., Basok B.I. Integration emulsions in vortex devices. DGTU, Dnepropetrovsk, 2009. P.247
4. Pavlenko A.M., Basok B.I, Avramenko A.A. Heat Conduction of a Multi-Layer Disperse Particle of Emulsion. Heat Transfer Research, 2005, Vol.36, Nos.1&27, P.55-61.
5. Shlikhting G. Boundary-layer theory. Moscow, Science, 1974. P.711
6. Deych M.E.Technical gas dynamics. Moscow, Energy, 1974. P.592
7. Lyakhovsky D.N. Questions aerodynamics and heat transfer in the boiler furnace processes. Gosenergoizdat, 1958. P.97.
8. Pavlenko A.M., Usenko B.O., Koshlak A.V. (2014). Analysis of thermal peculiarities of alloying with special properties. Metallurgical and Mining Industry, No2, pp. 15-19.
9. Koshlak A.V., Pavlenko A.M., Usenko B.O.(2014). Thermal conductivity of the gas in small space. Metallurgical and Mining Industry, No2, pp. 20-24.

Basic principles of gas hydrate technologies

Thu, 17 Jul 2014 14:30:13 +0300

The gas hydrate technologies can be alternative to the traditional methods of the rational use of hydrocarbon gases. However the known constructions of apparatuses for the production of gas hydrates cannot fully satisfy the condition of their industrial use. Authors offer to carry out the high-quality contact of gas and water at formation of gas hydrate by jet apparatuses with a free falling jet. On their basis a technological chart for realization of continuous cycle of production of gas hydrate is offered. Method of production, the main technological parameters and principal scheme of the installation for the production of associated petroleum gas of hydrate are developed. Technology provides their production in the form suitable for transportation and long term storage without addition of cooling. The modular gas hydrate laboratory setting for testing elements of gas hydrate technology in oil and gas sector has been developed and created. Method of intensive hydrate formation and the device for contacting phases on the basis of jet system with free falling jet are developed. The mathematical model of the process is developed and empirical equation coefficients are determined. Parameters of continuous cycle of gas hydrates are substantiated.
Key words: gas hydrate, jet apparatus, free falling jet, continuous cycle of production, coagulation, heat of gas hydration.

Dr. sci, professor Anatoliy Pavlenko

Ph.D., associate professor Hanna Koshlak

Postgraduate Bohdan Usenko
Poltava National Technical Yuri Kondratyuk University, Poltava

1. Introduction
1.1. Problem definition and its relationship with important scientific and practical tasks.

In many cases, the traditional assembly technology, and use (consumption) much of the resources of hydrocarbon gases (associated petroleum, deposits, in-pit) are ineffective or economically unjustified. At the same time in recent years there happened rapid development of technology accumulation (storage), transportation and long term storage of hydrocarbon gases in hydrate form. However, widespread implementation due to insufficient testing of its elements has not yet acquired. The main problems that hinder the production of gas hydrates of natural gas, and hence the widespread introduction of gas hydrate technology is creating a closed cycle, withdrawal of gas hydrates formed, its maximum dehydration, maintaining the integrity of the formed hydrates. Plants for the production of semi hydrates, as applicable, and those that are under development, there are still quite underdeveloped in terms of energy consumption and optimizing industrial operations. The analysis of the structural features of known reactors showed that none of them, in our opinion, can fully meet the requirements of industrial applications.

1.2. Analysis of recent research and publications in which a solution of this problem

Equipment for the production of synthetic hydrates, different ways of creating contact between the liquid and gas: spray water into the gas phase (by spraying water into the gas fed through nozzles, conductors and sprayers), the introduction of gas into the liquid phase by bubbling or stirring method and combined input reagents.
During spraying water in gas at the stage of gas-water interconnection is hydrating. Its mechanism consists of the following steps [1]: 1) the embryo formed hydrates, 2) drop cover gas hydrate crust thickness 0.04 mm 3) crust thickens to 0.24 mm. The water in the hydrate capillaries rises to the gas phase. Since the fluid is compressed enough, the external gas pressure can break hydrated crust. Thus, hydrate enjoys the water.
During the bubbling gas to its liquid bubble covered hydration rind. As the gas is compressible, in this case appears "effect of eggs" [2]: crust under pressure breaks inside. Around formed crust particles have formed hydrate. So, with this method of hydrate water is much less taken.
The process of hydrate formation is to create a contact interface for dissolving gas in water at appropriate thermobaric conditions, the formation and growth of hydrate structures and allocate the appropriate amount of heat hydrate. Depending on how the contact phase in the gas hydrates can be a different, sometimes very large amount of water. And in the case of the captured water (water droplets covered with hydrate crust) it is difficult to remove or tie in gas hydrates. Capture by hydration structures of gas bubbles ultimately leads to improving the quality of the resulting product as bubbles covered hydrated crust, relatively easily broken, or there is a gradual diffusion of gas hydrate due to contact with free water and its binding. Therefore, for the production of gas hydrates with minimal water content appropriate to apply a way that provides for the introduction of gas in water volume. Bubbling gas into the bottom part of the reactor volume is being doing in such a way. However, the main problem of this method and the main direction of its improvement is to reduce the size of the bubbles to increase contact area phases, as well as extending the time of the bubbles in the liquid.

2. Result and discussion
2.1. Excretion of the unsolved earlier aspects of the problem which the article is dedicated

Depending on how the supply of energy to the working environment in order to create a contact phase contact apparatus for gas hydrate formation, similar to the absorptive devices can be divided into units of energy supply gas phase, liquid phase, mechanical agitators and their combinations.
A characteristic feature of the apparatus of power supply liquid and gas phase is the presence or mechanical or hydrodynamic mixing device. The most widely used devices with mechanical mixers that are installed, usually over gas distribution device. The main disadvantage of apparatus with mechanical mixing devices are unreliable operation of these devices.

2.2. Article purposes formation

The aim is to develop technical solutions and process parameters of continuous production of gas hydrates, which would satisfy the requirements of industrial application.

2.3. Presentation of the main material

The study of the mechanism of free jet injection of gas involved many researchers [3]. Upon entering the free jet in the liquid volume (fig. 1) injection of gas into a liquid and its dispersion to form tiny bubbles is in entry point, that is absorption of gas. Number of injected gas depends on the geometrical parameters of the nozzle and the hydrodynamic regime of the liquid supply. Bubbles of gas in the formation of hydrated crust around them will be subjected to variable deformation due to mechanical action liquid jet. Formed in such a way watergashydrate mixture, in our opinion, will be the best quality, as containing the minimum number of enthusiastic hydrate water drops. This in turn will facilitate its further qualitative separation.

Figure 1 Scheme of the mechanism of free jet injection gas

To extend (increase) in time of the bubbles in the water until complete dissolution and binding them to hydrate we suggested to provide additional mixing of the reactor contents with a relatively low speed (30 - 60 r / min). On this basis, and considering the process of gas hydrates as a whole and setting the target of its maximum and integrated optimization, we propose to make bubbling gas into a liquid and its mixing with one or more free jets of water at the appropriate places and at certain angles interact with the surface of the liquid.
When directing jets of water at an angle other than vertical, due to the transfer of kinetic energy to the contents of the reactor (a mixture of water and gas hydrates) will be moving it around the axis of the reactor and the relative movement of layers of a mixture of water and hydrates the height of the reactor. Thus, the proposed mixing free jet, except the extension time of the bubbles in the liquid, would reduce the thickness of the layer of liquid in the reactor, and hence its volume and evenly distribute heat hydrate. To improve the method of contacting gas and water in the continuous production of gas hydrates, the input of feed gas flow should carry through its bubbling in the bottom part of the reactor. At the top of the reactor should include the presence of a certain volume (eg 25% of the volume of the reactor) for the accumulation of gas. With this circuit and the technological solution circulation of gas takes place in the reactor volume without additional equipment, and the process of feeding raw gas will be binding on the relevant part of gas hydrates. The effectiveness of the method of contacting phases (mixing) free jet injection fluid determines its ability Q_g and coefficient of injection and gas. Based on the above informed appropriate orientation of liquid jet mixers at an angle to the surface of the liquid in the reactor other than direct, the most appropriate to describe the dependence of this process is given in the paper.

Q_g= 5,4 × 10-6 (ρ_р× d0³ v0³/s)× (l₀ / d₀)^0,75× (sin a)^-0,2, (1)

where Q_g - injection capacity, m³ / s; rl - density of liquid, kg/m³; d₀ - nozzle diameter, m; V₀ - average velocity of fluid at the outlet of the nozzle, m / s; s - surface tension, N / m ; l0 - the length of the nozzle, m; a - injected jet angle to the horizontal plane.
To implement a continuous process of gas hydrates is mandatory to create conditions for continuous and uninterrupted his removal from the reactor, the reactor feed gas, and water and heat dissipation hydrate. The difficulty is that the parameters of the thermo baric property shown rapid enlargement of gas hydrate structures in a process of coagulation of micro particles and their subsequent agglomeration patterns in the critical size. However, accumulation of solid hydrate phase is undesirable, because it leads to complications related to the closing process lines and dead zones of the reactor, heat and mass transfer deterioration. Therefore, the production of gas hydrates, we offer to provide measures to prevent the consolidation of hydrate structures at the time of their arrival in the separation device.
Based on the proposed method of hydrate formation is proposed diversion of the basic process to make energy from the target stream (a mixture of water and gas hydrates) outside the reactor during its circulation through the heat exchanger. This method of heat removal will be simple and effective.
In order to confirm the fundamental possibility of continuous production of gas hydrates in the application of inkjet machine with free-falling stream as a device for contacting phases of a series of experiments were conducted on a laboratory gas hydrate installation diagram is shown in Figure 2. In addition, experiments established the rate of hydrate formation and verification capabilities of processes uninterrupted output produced mixture from the reactor prior to agglomeration of particles of hydrated mass circulation separated fluid to remove heat hydrate formation, agglomeration and accumulation of gas hydrate formed in the separator.
In experiments gas composition: CH₄ - 92.8%, C₂H₆ - 5.1%, C₃H₈ - 2.1%, with a density of 0,595 were used. Nozzle diameter was 2.05 mm. Circulation of fluid through the heat exchanger 18, the temperature in the reactor was maintained at 276 K. The gas pressure in the reactor was maintained at 3.6 MPa. Jet angle was 30 degrees. Distance from the jet nozzle apparatus to the surface of the liquid was 105 mm. In the process water fed to it under pressure 9.5 MPa at a rate of 6 l / min.

Figure 2 Laboratory hydrate installation of the technology of continuous production of gas hydrates:

1 - reactor, 2 - temperature sensors, 3, 5 - observation windows, 4 - jet unit, 6 - output choke watergashydrate mixture, 7 - backlight system, 8 - bubbling unit 9 - swivel, 10 - rod press(stem press), 11 - piston with filter element 12 - building separator 13 - viewing window separator, 14, 18 - heat Exchangers, 15 - gas Cylinder, 16 - cooling unit, 17 - pump, 19 - stirrer, flow: I - water under pressure, II - gas, III - watergashydrate mixture

By creating pressure difference between the suction line of the pump 17, the separator 12 and1 reactor 1 circulation occurred watergashydrate mixture from the reactor through a pin socket 6 to a separator, and from it (the water) to the pump 17. These hydrate particles that have not passed through the filter of the piston 11 remain in the separator. Fluid before and after the pump 17 passes through heat exchangers 18, placed in a bath of temperature 273 K (bath filled with water and ice).
During the experiment, the rate of formation of gas hydrates was measured amount of fuel gas per unit time. For this rate of pressure drop fixed in the gas tank. The experiment was continued until the pressure drop in the tank to 2.0 MPa, i.e. 0.5 MPa above the equilibrium hydrate formation conditions for the gas composition.
The average rate of occurrence of gas hydrates in the composition was 2.42 liters per NU per liter of water per minute. A substantial portion of the gas did not have time (and could not) enter into the composition of gas hydrates in the form of bubbles appeared on the surface of the liquid. Therefore a qualitative approach of contacting phases and equilibrium conditions, the main factor in the presence of gas hydrate was not included in the production of gas hydrates under the method proposed (and implemented in the relevant technical solutions) is a way of heat recovery hydrate. Table 1 shows the comparison of experimental data with the speed of hydrate formation data of other authors [3].

Table 1 Comparison of rate of entry of hydrocarbon gases in gas hydrate depending on the type of reactor and method of contacting phases

Authors	Volume of liquid in the reactor, l	Pressure, MPa	Temperature, К	Type mixer	Speed entry gas, l, l/min
Vysniausks, Bishnoi 1983)	0.3	5.5	274.2	Mechanic	0.23
Englezos (1987)	0.3	5.82	276	Mechanic	0.076
Happel, Hnatov (1994)	1	5.4	279	Mechanic	1.3
Takaoki (2002)	5.5	5.3	276	Mechanic	1.8
Mork (2002)	9.5	7.0	282	Mechanic	2.0
Author	3.7	3.6	276	Free jet	2.4

The model consists of three stages: 1st - bubbles of gas molecules are transferred by diffusion in the liquid, and the energy due to the dissolution enthalpy of the gas increases, the concentration of gas molecules in a layer of fluid around the bubble is maximum; 2nd - gas molecules is transferred to a stirred liquid, ensuring uniformity of temperature and concentration of gas molecules, although the latter thus will be lower compared to the surface layer; 3rd - is the diffusion of gas molecules of water to the crystal surface and their incorporation into the structure of gas hydrates. Temperature limit liquid - crystal hydrate formation enthalpy increases due and gas concentration decreases again.
We assume that the gas that comes from the bubbles in the liquid does not accumulate around the gas bubbles. Then the equation for determining the rate of mass transfer (dissolution rate of the gas in the liquid) has the form
r₁= k_LA_g(c_sol - c_b), (4)
where r₁ - the rate of dissolution of gas in liquid, mole/s; k_L - diffusion coefficient of gas in liquid, m/s; A_g - bubble surface area, m²; c_sol-gas concentration at the gas-liquid boundary under pressure and hydrate equilibrium temperature, mole/m³; c_b - the concentration of gas in a liquid at a pressure of hydrate formation and equilibrium temperature, mole/m³;
Gas concentration is on the brink of gas - liquid under pressure hydrate and equilibrium temperature is calculated by the formula

(5)

where x (p, T) - the fate of the molar solubility of gas in water; M_H2O- molar mass of water, kg / mole (0.01802 kg / mole) ρ_H20- the density of water, kg/m3 .
According to the theory of diffusion, proportional to the concentration and without accumulation of gas mass transfer rate (rate of occurrence of gas hydrate) is calculated by the formula

r₂ = k_S A_c (c_b – c_eq), (6)

where r₂ - speed gas hydrate occurrence, mol/s; k_S - diffusion coefficient of gas from the liquid to the crystal hydrate, m/s; A_c - area of the crystal surface, m²; c_eq-gas concentration in the liquid-crystal boundary at a pressure process and equilibrium temperature mol/m³ .
Considering that gas hydrate formation process depends on the diffusion of gas into the liquid and the surface of the crystal, one-component gas hydrate formation rate per 1 m³ of liquid is determined by the formula

r = k (c_col – c_eq), (7)

where r - rate of hydrate formation, mole/m³c; k - coefficient of diffusion of gas bubbles to the surface of the crystal, 1/s.
Equation (7) describes the process of hydrate formation for one hydra creation gas. Furthermore, it ignores the volume and design features of the reactor hydrate.
Speed hydrate mixture of several hydra creation components is calculating by the formula [4]

(8)

where r_h - the rate of hydrate gas mixture mole/m³s, K_i - coefficient hydrate the i-th component of the gas mixture, l /s; n - the number of components of gas; x_i - mole fate component in the gas mixture.
Rate of hydrate formation with hydrate based method and the volume of liquid in the reactor is calculated by the formula

(9)

where R - the rate of hydrate formation, mole/s; k_p - factor that depends on the particular reactor and found experimentally, 1/s, Vв - volume of fluid, which is formed hydrate, m³.

4. Conclusions

1. Production of gas hydrates is proposed to make ejection of gas and mixing the contents of the reactor free liquid jet with the introduction of raw gas in the bottom of the reactor and the derivation watergashydtrate mixture until it is clear phase separation resulting in agglomeration of gas hydrates.
2. Ejection of gas and mixing the contents of the reactor using a free jet will greatly streamline and simplify the design of the reactor. This circulation of fluid in the direction of jet apparatus - reactor - separator - heat exchanger - jet unit will simultaneously perform the ejection of gas, improve the quality of contact phase flow reactor in the required amount of water recharge, heat dissipation and output hydrate formed hydrates.

References

1. Zhong D.L., Liu D.P., Wu Z.M., Zhang L. Natural Gas Hydrate and Growth on Suspended Water Droplet. Proceeding of the 6th International Coference on Gas Hydrates (ICGH 2008), Vancouver, British Columbia, CANADA, July 6-10, 2008.
2. Gumerov N.A., G.L. Chahine Dynamics of bubbles in conditions of gas hydrate formations. Dynaflow Inc. Fulton, Maryland, USA, 1992. - С. 1 – 7.
3. Lara P. Onset of air entrainment for a water jet impinging vertically on a water surface. Chem. Eng. Sei. – 1979. - Vol. 34. - P. 1164-1165.
4. Skovborg P. A mass transport limited model for the growth of methane and ethane gas hydrates. ChemicalEngineeringScience. – 1994. – Vol.11. – P. 1131-1143.

Peculiarities of equipment repair of crushing and grading complex with the help of composite

Thu, 17 Jul 2014 14:29:45 +0300

Range of technological solutions concerning equipment repair, which is being operated in open-cut mining and connected with fine crushing, grinding and screening with application of composite is developed.
Keywords: crusher, bearing, recovery, polymer materials, effectiveness

UDK 622.27

Ischenko A.A.

D.Sc. in engineering, professor
head of Mechanical equipment of iron and steel works department,
Priazovskyi State Technical University, Mariupol, Ukraine

Golinka Sergey

Post-graduate of Mechanical equipment of iron and steel works department,
Priazovskyi State Technical University,
Mariupol, Ukraine

In recent years metal-polymer is used in the process of repair of different types of equipment more often. Metal-polymer is plastic material with metallic, powdered or fiber filler. Thermoplastic polymers, such as polythene, polypropylene, polyamides, polytetrafluoroethylene (fluorine plastic), polyvinylchloride and others are used as binding material, also thermosetting materials - phenol-formaldehyde, polyester, ethoxyline, organosilicone, etc are used. Powders, fibres, bands, received from any metals or alloys, metallised powders and fibers are the fillers. Except filler and polymer binder, non-metallic mineral and organic components, stabilizers, pigments and colourants, plasticizers, surface-active materials may be included into melallopolymeric composition. Type and quantity of these additions is determined by chemical nature of polymer binder.
The usage of these materials was limited by recovery of assemblies and machines, working in gentle operational conditions without impact and vibrational loads. Other conditions follow equipment operation, being used in open-cut mining and connected with fine crushing, grinding and screening. As a rule equipment for granite grinding works in extreme conditions of forcing the main assemblies of vibrational and impact loads. As a consequence of such impact - premature failure, most often bearing assemblies of these machines. Bearing destruction, occurring first of all because of dynamic character of their loading, may be followed by roller failure, where these bearings are placed, because of wear and deformation of centering plug under bearings.
And if bearing replacement is rather expensive procedure and may be fulfilled within short period of time, than the replacement or recovery of the shaft requires full disassembling of crushing equipment. Herein the period of production or repair of the shaft with the length more than 3000 mm puts out of order all this manufacturing area for a long time, say nothing of high cost for both details and erecting work.
The problem of minimization of timing and means for such repair may be solved by usage of metal polymers. Priazovskyi State Technical University (PSTU) has gained an experience of solving such problems on some open-cuts of Donetsk region. In particular, on Telmanovskiy open-cut the mounting face under main bearing on the main shaft Ø460 mm of stone-breaker of SMD-118 type was renewed (figure 1). Technology of accomplishment of such repair is described below. Material, multimetal, which was used while this operation, has passed preliminary tests for durability, which confirmed the possibility of its usage for such type of works [1].

Figure 1 The scheme of recovery of mounting face of crusher shaft

On the worn mounting face with the help of electric welding, beacon lights with diameter 10-15mm and height 2-2.5 mm were deposited (fig. 1a). With the help of machinist ruler, located on the unworn shaft area, filing of beacon lights to coupling size and test bearing fitting on the mounting face together with space sleeves was fulfilled (fig. 1b). In space sleeves there drilled diametrically located holes for injection of polymer material and for its output and also two control holes in perpendicular plane for control of filling of internal voids by metal polymer. Then deoiling of spindle, inside faces of sleeves and bearings.
Inside faces of space sleeves and inner ring of a bearing were treated by release composition. After that the assembly was erected and worked up by a screw. Encapsulating of front mating surfaces of space sleeves and bearing inner race was fulfilled with the help of scotch tape and plasticine. With the help of gun, multi metal-steel FL was discharge through lower holes 1 and 5. After multi metal appearance in the holes 2, 4 and 6, 8, they were closed by wooden plugs. After multi metal appearance in the holes 3,7, they were also closed by wooden plugs together with holes 1 and 5. In 24 hours after material injection, some tests for crusher under load were fulfilled.
Similar case is critical when the bearing was destroyed and mounting face under the bearing was not worked out. However there appears necessity to renew mounting face with interference along the inner ring of a bearing, when the bearing is intact, but the inner ring started turning on the shaft, e.i. the situation is not critical – bearing has not destroyed. In this case another material is successfully used «Y – binding material» for metals, not containing fillers, but modified by special additions, giving to this material extremely good adhesive properties (table 1).

Table 1 Technical characteristics of material «Y – binding material»

Density, g/sm³	1.1
Color	milk
Tensile strength - shear, MPa	30
Chemical durability	to oils, benzine, antifreezes
Partial chemical durability	to alcohols, benzol, water, salt brine
Working time (20 °С), hours.	2
Solidification time (20 °С, 70 % strength), hours	24
Full solidification (20 °С), days	7
Equivalence ratio by volume	1:1

Before application of this material during important repair work in the lab of mechanical equipment of iron and steel works department, there were tests concerning study of mechanical properties of this material. Experimental research was executed on the tensile-testing machine RM-20. For tests samples of steel St45 with dimensions shown in the figure 2 were produced.

Figure 2 Sleeve with mounting face H7 in the system of hole and shaft with different variants of mounting in the shaft system

After deoiling of joint surfaces of sleeve and shaft, there applied a thin layer of «Y – binding material», which is a preliminary mix of two components. The next step means assemblage of pieces and pressing in case of heavy-shrink fitting. Then bonding was soaked within 3 days at the temperature 28°С and was taken to pieces on the machine RM-20.
Testing results and also the results of conversion of pressing force into torque rating, determined from the formula М_tor = Р_pressD/2, are shown in the table 2

Table 2 Results of tests of samples by means of axial force on the tensile-testing machine R-20

No of sample	actual diameter of the shaft, mm	Sample pressing-in force, N	Sample pressing-off force , N Р_press	Effective disconnecting torque, N.m	Accuracy degree of shaft fitting	limit shaft deviation, mm	Accuracy degree across the aperture, limit deviations, mm
1	36.04	8500	132000	2376	36r6	+0.034 +0.050	36Н7+^0.025
2	36.04	7500	146000	2628
3	36.04	4500	157000	2826
4	36.01	-	144000	2592	36k6	+0.018 +0.002
5	36.00	-	146000	2628	36k6	+0.018 +0.002
6	35.99	-	118000	2124	36h6	0 -0.013
7	35.96	-	126000	2268
8	35.92	-	130000	2340
9	35.09	-	130000	2340

As one may see from the given tables, application of «Y – binding material» allows to obtain bonding similar to Н7/u7 fitting almost in any variant of character of mating parts: gapped, across transition fit and heavy-shrink fitting. That is why application of transition fit is more preferable, they provide durable connection, necessary centering of pieces and, at the same time, without requiring of application of special tools for pressing in. The calculated values of disconnecting torque within the limits of 2 300-2 600 Nm allow to draw conclusion concerning application of adhesive bond “shaft-sleeve” instead of feather joint, because the data shown in the table 2 do not exceed effective allowable moment of feather joint with shaft diameter 36 mm and spline length 26 mm in 5 times from shear condition and in 10 times from crumbling condition.
The results obtained confirm the given above technical characteristics of «Y – binding material», as experimentally obtained shear strength makes at average 29 MPa for loosely connections.
In such a way, application of «Y – binding material» allows to remove undesirable phenomena, which accompany appliance of pressure coupling, such as stress factors in pieces and their fatigue failure, excludes application of complex machine-tool attachment for heating or cooling of pieces and also excludes corrosion in fixed joint and probability of further its destruction.
Rather high rates of adhesion strength of this material allowed to use it during recovery of bearing fittings on the shaft by means of pasting-in. The technology of this process lies in the following. In case when heavy-shrink fitting was broken down, but there have not appeared any holes between inner bearing ring and the shaft, the work came down to deoiling of shaft area and bearing race, application of the material on the shaft and race by means of sound rubbing and bearing thrust on the place of installation.
In case when little hole (0.1-0.5 mm) between race and shaft was present, then installation and pasting on the shaft by superglue of beacon lights of appropriate dimensions, check of free bearing thrust on these lights preceded application of the material, only after that came deoiling, material application, as it was described above, and installation of bearing on the permanent operating place. In 24 hours assembling with further run up was fulfilled. For acceleration of material polymerization, seam heating with the help of drying fan to the temperature 40-50°С was used. In this case material consumption and economic efficiency of such repair does not admit of doubt. Some complete renovations of crushers and vibration screens, which have confirmed effectiveness of such method of solution, were fulfilled under the described technology.
Another direction of metal-polymers usage is connected with the necessity of refractory lining for the cone crusher and usage of polymer material in order to fill the hole between lining and crusher shell. For these aims Mechanical equipment of iron and steel works department developed and applies home-produced material, price of which is reasonable and allows to fill in great volumes.
With the help of polymer material, reconstruction of screen decks, made of stainless steel and used for screenings of various materials, is possible. In case of abnormal wear of screen mesh, there developed technology of tipping on metal-base with the help of polymer of rubber coating from previously used conveyer belt with further cutting of desired holes, as it is shown in the figure 3.

Figure 3 Reconstruction of screen deck surface

Exploitation of screens, reconstructed in such way or newly produced from black sheet with such rubber-fabric layer on the sizing screens of blast-furnace department during undersized coke showed economic efficiency of such repair, which may be fulfilled on-place of exploitation and does not require special knowledge and tools.

Conclusions

Remanufacturing techniques for equipment of crushing and grading complex with the help of composite, which allow to minimize material and time expenditures for maintenance, and hereby to extend significantly the life of pieces, meeting vibrational and dynamic loads, were developed and multiple tested.

Reference

Zakhist metalurgіynikh mashin vіd polomok

PNTU

Development of commercial explosive reducing development pressure on the environment

Thu, 17 Jul 2014 14:29:28 +0300

Development studies of nitrateammonium commercial explosive (CE) reducing development pressure on the environment during mining are presented. For providing of waterproofness, ammonium nitrate prills were primed bynitrate cellulose or conversionblasting powder, not suitable for further usage for the purpose specified. By thermodynamic calculation it was stated the correlation of ammonium nitrate and primed coating of commercial explosive, providing the absence of toxic fumes in explosion products. Introduction of coating of surface-active materials allowed to eliminate static characteristic of commercial explosive and make it save at spilling and loading of chinks even by pneumatic transport. New commercial explosive is waterproof, does not form toxic gases at explosive conversion, does not electrify at spilling and transportation, that provides ecological security of its usage.
Key words: ecological security, commercial explosive, gaseous products of explosion, waterproofness, static characteristic

UDK 502.7

Vasyl Zakusylo

PhD, docent of chemical technology of macromolecular compounds department
Shostka Institute of Sumy State University, Shostka, Ukraine

Anna Efymenko

graduate student, department of chemical technology of macromolecular compounds
Shostka Institute of Sumy State University, Shostka, Ukraine

Ecological security when applying commercial explosive for mining is relevant task in mining industry all over the world. Productive activity of metallurgical and mining complex affects greatly environment. At explosive conversion of high energy systems, millions of tons of harmful substances are wasted into atmosphere, millions of cubic meters of polluted wastewater are thrown into water, and huge amount of solid wastes are stored on the top of the ground.
The main commercial explosives used both in Ukraine and abroad, are nitrate ammonium and tolite-containing ones. During application of tolite-containing commercial explosives there forms up to 115 l/kg of carbonic oxide [1, 2]. This substance is very toxic, as it is dangerous not only for air ecosystem but also for a human. During longtime contact of operating personnel with small concentration of carbonic oxide, poisoning is possible, which may lead to fainting. Carbonic oxide affects human’s cerebral cortex, provokes irreversible nervous system disorder. Besides tolite, which is included as coating of ammonium nitrate prills, such CE as grammonite 79/21 GS is dielectric. Pneumatic loading of granulated CE, containing tolite, is followed by intensive electrification of the CE flow, herein electrostatic energy is 52.8mJ at minimum ignition energy of grammonites 1.05 mJ. That is why electrification phenomena should be considered during manufacturing and application of explosives, as it may lead to striking of spark and non-planned explosion during exploitation of CE.
Analysis of existing literary sources showed that existing commercial explosives on the base of ammonium nitrate have the following disadvantages:

pollute the atmosphere by toxic gases exceeding the norms of ecologically permissible concentration;
low water resistance (exept emulsive CE), which is followed by pollution of ground ecosystem by ammonium nitrates;
low energetic characteristics;
low chemical and physic constancy;
granulated CE is tended to electrification, which increases the possibility of explosions during their storage, usage at transportation;
emulsive CE is used for loading of chinks only in hot condition, that determines their usage just after manufacturing;
granulated CE with coating is brittle, breakaway, dust, increasing man-caused load on the environment.

It is possible to create balance between ecological aspects and increased explosive characteristics of CE by means of creation of new waterproof nitrate ammonium CE, which would not have these disadvantages. That is why for environmental security, high water resistance, energetic characteristics and absence of post-detonation toxic fume and electrification during usage, security of high strength as coating of ammonium nitrate prills, high-powered material - nitrate cellulose is chosen [3].
At this stage of industrial development utilization of non-effective armament [4] is fulfilled by means of outdoor burning, which is followed by emission of great amount of nitrogen oxides and carbon. Creation of CE on the base of nitrate ammonium and conversion nitrate cellulose powder explosive provides not only water resistance and high explosive characteristics but also allows to reduce man-caused load on the environment by means of processing of utilizable powders explosive into ecologically clean commercial explosive.
Researches concerning application of colloxylins, conversion pyroxiline and ballistit powders and also ballistite rocket fuel as a composite of nitrate ammonium CE are presented. For reduction of air pollution by post-detonation toxic fume of CE, system oxygen balance was preliminary calculated. For calculation of oxygen balance of the mixture, molecular number of components was calculated:

ammonium nitrate (AN) (NH₄NO₃) with 80 molecular number and +20% oxygen balance;
BP NDT-3 (C_23.00H_30.00N_10.00O_34.00) with 990,00 molecular number and - 44% oxygen balance;
Industrial powder explosive (IPE) (С₆H_7.55N_2.45O_9.9) with 272,25 molecular number and - 38% oxygen balance.

Composition of nitrate ammonium CE with zero oxygen balance contains: 66% AN and 34% IPE; 69% AN и 31% BP or ballistite rocket fuel RSI-12K. Commercial explosive under development is called ammoporom –W [5]. In order to determine amount of gas and thermodynamic characteristics, which is evolved during explosive conversion of CE, there were fulfilled researches in accordance with multi-purpose program “Astra” – “Modeling of chemical and phase equilibrium at different temperatures” and Avakyan methodology .In the base of “Astra” program lies universal thermodynamic method for determination of characteristics of heterogenic systems balance; these systems are based on the basis of maximum entropy. The program allows to calculate the amount and composition of combustion gases. Research results are presented in the table 1.

Table 1 thermodynamic characteristics and gas composition of CE

Indicator name	Values
	Ammoporom –W	Tolite-containing CE
Entalpy H_s, kJ/kg	952.96	44.49
Acidity coefficient, А	101.58	36.36
Coefficient of sales, К %	0.97	0.76
Oxygen balance, %	0.91	-74.01
Heat capacity, cal/mole	149.18	86.68
Explosion heat, kcal/kg	916 - 925	985
Gas volume, l/kg	909 - 920	785
Explosive temperature, К	2642 - 2705	2869
Fougasseness, ml	316	307
Detonation velocity, м/с	5400	4250
Pressure Pr, kg/sm²	59509	58282
Gas composition	Amount of gas, mole/kg
	Ammoporom –W		Tolite-containing CE
Н₂О	21.91		20.36
СО₂	5.25		6.38
СО	0.00		14.78
С	0.00		14.41
Н₂	0.01		2.66
N₂	6.86		10.56
О₂	2.2		1.91
NO	0.4		3.06

Calculations showed that ammoporom –W has high explosive characteristics, and also during its explosion toxic gases are not formed. Gas composition of explosion products is exposed mainly by Н₂О steams, СО₂ and N₂ bioxyde, which are provided by zero oxygen balance.
When applying most of nitrate ammonium explosives in wet holes, there take place scavenging and accumulation of AN in subsurface water and quarry cracks, which pollute them. For lowering of man-caused load on the environment with the help of device with fluidized bed, laquer on the base of utilized powders, saluted in acetic ether, was applied on the ammonium nitrate prills for formation of firm waterproof jacket. Physical form of commercial explosive and section of ammoporom –W granula are shown in the figure 1.

Figure 1 Physical form of CE a; section of ammoporom –W granula, 120^х magnification range – b.

For determination of degree of coating water perviousness special methodology is developed [6]. This method allows to determine water resistance of films at different pressures, from air pressure to 2 kg/sm2, and also within temperatures from 18^оС to 40^оС. This is connected with the necessity of CE application in underground conditions, where increased temperatures and pressures are possible. Increased pressure imitates water flowage.
Research of characteristics of coating on the AN granules is complicated. That is why at technological mode of CE production, nitrate rayon laquer was applied on the glass or plastic plates in order to get the film in the form of sheet material. For reliability of data, density of coating and film was determined. Density of nitrate rayon film and CE coating, which was determined by volume-weight method, was similar and made 1.46 (±0.01) g/sm³.
Research results represented in the form of characteristic curves in the figure 2.

Figure 2 Dependence of water resistance of nitrate rayon film on holding time in the water:

■ – at atmospheric pressure and temperature 18^оС;
● – at atmospheric pressure and temperature 40^оС;
▲– at pressure 1.5 kg/sm² and temperature 18^оС.

It follows from the figure 2 that increase of the temperature and pressure contributes acceleration of diffusion processes of water molecules penetration through nitrate rayon film.
Operating CE grammonite 79/21 GS has coating on the base of tolite with low strength characteristics, up to 1.2 kg/sm². Coating may crack when granules contact with each other, also destroy and peel while exploitation, these provokes man made danger while application of grammonite 79/21, considering its high static characteristic. Nitrate rayon coating ammoporom –W has the strength up to 20 kg/sm², that is why it is not destroyed.
To reduce its static characteristic, 0.1-0.2% of surface-active substance, such as polyoxyethylene allylphenol ethers of OP-4, OP-7 or OP-10 type were included. Volume resistivity of CE reduced from 108 Ohm·m to104 Ohm·m, i.e. ammoporom –W was changed from dielectric to conductor. Absence of ammoporom –W static characteristics provides its save exploitation even during pneumatic conveying and pneumo-loading of holes, which is particularly topical during blasting workings connected with iron ore crop in underground conditions of Kryvyi Rih region.
Developed nitrate ammonium commercial explosive will reduce man-caused load on the environment by means of:

processing of conversion and ballistit powders, rocket fuels, being accumulated in Ukraine and presenting ecological threat for natural environment;
lowering of solvability of nitrate ammonium that will provide reduction of ground-water ecosystem pollution during blasting workings;
reduction of emission of toxic gaseous products during blasting workings connected with mining;
securing of accumulation of static charge on the CE surface, excluding man-induced disaster during spilling, transporting and loading of holes.

References

Pozdnyakov Z. G. Spravochnik po promyshlennym vzryvchatym veshchestvam i sredstvam vzryvaniya [ Reference book about commercial explosives and means of initiation]. Moscow, Nedra, 1977, 253 p.
Калякин С. А. Разработка граммотола 1-1 для замены тротилсодержащих граммонитов / С. А. Калякин, Н. А. Новикова // Сучасні технології в машинобудуванні, транспорті та гірництві. – 2012. – № 1(72). – С. 78–82.
Kalyakin S. A., Novikova N. A. (2012). Development of grammotol 1-1 for replacement of tolite-containing grammonites. Modern technologies in machine building, transport and mining. No 1(7), p. 78-82.
State objective defensive program concerning utilization of general armament, which is unsuitable for further usage and storage for 2008-2017, confirmed by Resolution of the Cabinet of Ministers of Ukraine dated 22 of October, 2008, No 940.
Patent 72202 U Ukraine MPK6 C О6 B 31/28. Commercial explosive. V. P. Kuprіn, V. R. Zakusilo, A. O. Єfimenko, O. V. Kuprіn. No 01085, bulletin No15.
Patent 85425 Ukraine МПК6 G О1 N 9/32. Way of determination of water perviousness of film materials. V. R. Zakusilo, A. O. Єfimenko. No 02657, bulletin No22.

Deformation peculiarities of body of slag car pan

Thu, 17 Jul 2014 15:17:42 +0300

This paper is devoted to an analytical study of wall deformations of slag car pan during its operation. Distribution pattern of deformations in the pan body in the case of its manufacturing of standard material (steel 30) and with the usage of point alloying in the support ring area is determined.
Keywords: slag car, slag pan, construction, deformation, strength, alloying, point alloying.

UDK 669.162.266.452

Valeriy Chigarev

Member of the Academy of engineering sciences of Ukraine,
D.Eng.Sc., professor
Head of Metallurgy and technology of welding production department,
Priazovskyi State Technical University

Dmitriy Rassokhin

Post-graduate of Mechanical equipment of iron and steel works department,
Priazovskyi State Technical University

While operation pan of blast-furnace slag car is filed by smelted slag, temperature of which may achieve 1600°С. After the pan is filled by slag, there occurs intensive heat transfer across the pan section. This is explained by long duration of action and heat source strength. Pan body on different levels has non-uniform thickness. Under the influence of non-uniform heat transfer in the body there appear different in value and index stresses. Nonuniformity of heat transfer is known to be increased in the pieces, which are not symmetrical towards the center of their mass, in massive pieces and also in pieces of irregular shape. Pan of blast furnace slag car is such piece. In case when the values of internal stresses in the material are higher than the yield point, any steel piece starts deforming plastically, this causes imposed stresses and its deformation after cooling. Initial sizes of the construction may change. In case of great temperature differences, causing local heat stresses, exceeding material tensile strength, there appears a possibility of cracks formation. This reduces significantly reliability of separate units and the whole construction. Within long-term usage, there may appear permanent strains in separate elements of slag pan, which influence its holding capacity. The most important task is not only decrease of the level of thermal stresses in the construction on the stages of production process but also its adjustment in terms of volume during operation. There are different ways for solution of this problem, for example by means of point alloying.
S.V. Timoshenko, M.I. Yankovskogo, A.S. Filippova paid great attention on the questions concerning thermal stresses. Analysis of researches of different authors [1-4] shows that in most cases durability of pieces may be decreased because of the influence of thermal stresses, which arise in cross section. This fact should be considered while designing, manufacturing and upgrading of metallurgical pieces and units of high-duty.
The aim of the article is to determine hazardous sections of pan body from the point of view of distraction and also to determine deformation value, which may arise while operating.
Reliability and endurance rate of machines or tools depend on the duration of preservation of main attributes by its separate components – units and pieces. In general, long-term preservation of original size, durability, surface quality, accuracy and class of fit, corrosive resistance, etc. refer to such attributes. Influence of the structure and partial operations of manufacturing process on the quality of pieces, especially on the condition of surface coating and piece material in whole, accumulated hidden energy, phase marginal stability, residual stresses is not clearly understood. Often during exploitation of pieces, the influence of technological heredity on the efficiency characteristics of pieces is so significant as to provide the necessary reliability targets of machine is impossible without regard to them.
One of the factors of technological heredity is formation of thermo stressed state under the influence of different sources of heat generation in the material of the product under examination. Sources may change the structure of material on various stages of casting formation, processing and further exploitation. For example, during formation of casting surface by means of grinding, sources are grinding area. Relatively short duration of influence of medium-powered heat flow, which is being generated in the area of cutting during machining process, will cause formation of thermal-stressed state only at small depth from the surface. Quite different situation is observed while piece operation.
During pan exploitation there occurs contact between rich slag and pan cold body, this causes temperature differential, which is one of the main factors influencing the pan durability. That is why calculation of strain-stress state (SSS) is reasonable first of all for the conditions of maximum load on the construction during operation, and one should start it with specification of temperature field of pan wall.
I.V. Raspopov [5], K.A. Pak and A.V. Chalenko [6] gave attention to this problem. Works on specification of outside surface temperatures of pan bodies were fulfilled by Theoretical and applied mechanics department of Priazovskyi State Technical University. Measurements were fulfilled with the help of optical pyrometer «Rautek» from any height of the pan; from begin of its filling with smelted slag and up to the reaching of maximum temperatures. Values received in the area of deformation development, namely in the area of support ring, are of great interest. Received experimental and comparative data of other researchers are led into the diagram shown in the figure 1.

Figure 1 Temperature variation of pan wall during exploitation

According to the data obtained, maximum temperature of pan wall reaches 410°С, which is in keeping with data obtained by K.A. Pak and A.V. Chalenko. Received temperature values were used for modeling of thermal profile of pan body by means of finite-element method (FEM).
Modeling of temperature fields, which is being formed in the pieces while operation, was fulfilled in the calculation program ABAQUS. Abilities of static and dynamic strength analysis of ABAQUS program are used for determination of moving of stresses, deformations and forces, which arise in the construction or its components as a result of applied forces. The task was solved in static formulation, as inertial effect and energy scattering processes do not have great impact on the construction behavior. Such type of analysis is used by researches in many tasks and applications, for example, for calculation of temperature stresses or for determination of stress concentration in fillets of construction members.
While operation slag car pan takes up temperature loads, which are followed by significant heating of the body, which causes development of stresses and loads in it. In result of strain-stress computation of the pan with ordinal mechanical characteristics of the material (steel 30), there were stated that peak strain arise in the area of expected appearance of “tightening” defect, and namely in the area of pivoted tongue of slag car support ring. Maximum values of deformation for the first variant of calculation make 33 mm (fig.2). The figure reflects strain distribution in the area of pivoted tongue of slag car support ring. Herein deformations in other body areas of the zone of interest is far less (about 15 mm), which speaks for essential strain disparity in the pan body. Area with increased deformations is hazardous zone from the point of view of further destruction. For structural enhancement, it is necessary to enhance first of all this area, which is hazardous. This may be achieved by means of point alloying [7]. The method may be realized thanks to the application of flux-cored wires with ordered composition.
In case of additional alloying of pan body in the area of support ring maximum values of deformation in the area of appearance of “tightening” defect may reduce to 26 mm (fig.3). Mechanical characteristics of cast steel, received by experimental research, were used for design model. These results allow to suppose that additional alloying in the desired place of casting adjusts stress gradient in the field of elevated temperatures and simultaneously reduces maximum stress. The results obtained show that deformation range of variation in the pan body at local hardening makes 11-26mm.

Figure 2 Deformations in the wall of pan (without extra alloying)

Figure 3 Deformation in the wall of pan with installed powder fillers

At the present time there carried out experimental work concerning optimization of manufacturing technique for pieces with hardening of the most loaded areas, the main aim of which is to increase their lifetime and also to minimize production costs.

Conclusions

Distribution pattern of deformations in the pan of slag car depends on its operation practice.
Maximum values of deformation are observed in the area of support ring. This area is hazardous from the point of view of loss of structural behavior by construction.
Alloying of the whole pan as casting – is irrational way for increase of its durability. In case of point alloying of steel body areas with minimal discharge of alloying elements, maximum values of deformation in the pan wall may be reduced in 1.5-1.6 times.
Results of comparative analysis of ordinal and point-alloyed model show that deformation in the body of additionally alloyed pan reduces significantly. This may provide increase of durability of the pan as the construction in conditions of high-temperature loading.

References

Timoshenko S.P. Teoriya uprugosti [Elasticity theory]. ONTI, 1937, 452 p.
Yankovskiy, M.I. Temperature stresses in cylindrical mould (1950). Stal', No1, p. 66-71.
Filippov A.S., Goretskiy. V.A. Obmen opytom po proizvodstvu i ekspluatatsii izlozhnits [Exchange of experience in production and exploitation of moulds]. Moscow, GOSINTI, 1959. 256 p.
Chernoivanov V.I. Vosstanovlenie detaley mashin [Reconstruction of machine parts]. Moscow, GOSNITI, 2003. 488 p.
Hardening of slag ladles: research report: 07–02. Zhdanov Iron and Steel Institute. Leader Raspopov I.V; executor: Krasovitskiy V.S., Zhdanov1956. 43 p.
Pak, K.A., Chalenko, A.V. temperature distribution in the wall of blust-furnace slag ladle (1956). Stal', No7, p. 652-653.
Chigarev, V.V., Rassokhin D.A., Loza A.V. upgrading of castings from carbon steel (2012). Metall i lit'e Ukrainy, No1, 23-26 p.

Experimental research of distribution of strains and stresses in work-piece at different modes of stretch-forging with rotation in combined dies

Thu, 17 Jul 2014 14:28:49 +0300

The characteristics of the stress-strain state in work-pieces are investigated by the experimental method of coordinate grid during new intensive modes of a stretch-forging in combined dies. Lows of influences of modes with the fixed reduction at increase of angle of rotation at common aggravation of compressing of metal layers in a cross-section have been detected. The modes of stretch-forging with the fixed angles of rotation and increasing of reduction leads to the growth of intensity of a strain on a cross-section with the best compressing of metal layers of a medial zone.

Keywords: forging of shafts, stretch-forging, combined dies, coordinate grid, stress-strain state, compacting work of metal layers

UDC 621.73

V.V. Kukhar /D.Sc.(Eng.)/
SHEI “Priazovskyi State Technical University”, Mariupol, Ukraine

O.V. Vasylevskyi
LLC “Metinvest – Mariupol Mechanical-Repair Plant”, Mariupol, Ukraine

Experimental research of distribution of strains and stresses in work-piece at different modes of stretch-forging with rotation in combined dies

Introduction

Increasing of the longitudinal size of the work-piece at stretch-forging is produced by compression of it’s cross-section by different working tools: flat die, convex die, cut-out die, combined dies. The calibers of the traditional cut-out and combined dies for forging of shafts with round cross-sectional have a rhombic or radius(round) profile. Currently there is an active development of innovative ways of forging, which can intensify the compacting work of internal layers of the ingot at low coefficients of total reduction of cross-section [1]. The bulk of these methods are sent to creation of macroshift of material of work-piece in the deformation zone by complication of form of dies for the intermediate forging and combining of tools. From this point of view an actual scientific and practice task is development of the energy-saving modes of deformation of work-pieces at stretch-forging with the use of the traditional combined dies due to realization of methods of intensive strains and achievement of high degree of compacting work of metal layers for providing of production of metal forgings shafts with the required operating properties.

Analysis of the last researches and literature

In the work [2] the process of forging of ingots by profiled dies with receiving of three-beam or four-beam billet is offered. The further stretch-forging with macroshifts from profiled work-piece is demands of tool change and is conducted of a cooling of metal of a semi-product. Technological realization of the method [3] assumes of forging of billet in the beginning by the flat dies and then it’s rotation in round of longitudinal axis in dies with round cut-out without increase in length of a shaft. The article [4] in which conditions of a change of the sizes of work-piece and an emergence of macroshifts are analysed is devoted to researching of a stretch-forging of ingots by profiled dies. It is obvious that achievement of positive influence of macroshifts effect on indicators of quality of forgings due to complication or increase in quantity of sets of the working tool is economically justified only during forging of ingots from the high-alloyed expensive brands of steel.
In the work [5] probes of modes of a stretch-forging of billets in the combined dies with a rotation of work-piece in round of longitudinal axis in relation to conditions of forge and press shop of the LLC “Metinvest – the Mariupol Mechanical-repair Plant” enterprise that organized on the basis of maintenance shops of PJSC "Iyich Iron and Steel Works of Mariupol" are begun. A stress-strain condition of shaft forgings during working was investigated by finite-element modeling. The development of scientifically reasonable recommendations about a choice of rational modes of forging by such tool demands of experimental research of influence of sizes of upset reduction and angles of rotation of billet round of longitudinal axis on compacting work of material of a forging-part and geometrical characteristics of a cross-section.

Object of research and statement of tasks

The aim of this research is experimental studying a stress-strain state at various modes of a stretch-forging of cylindrical billets with rotation in round a longitudinal axis in the combined dies.
For achievement of the specified aim the tasks are set: to develop the methodological approaches for definition of the strain condition of work-pieces in relation to processes of forging of shaft by a stretch-forging in the combined dies; to establish of influence of stretch-forging modes on distribution of strains and stresses in a cross-section of the zone of deformation of work-pieces; to determine the best values of upset reduction and angles of a rotation of work-piece round a longitudinal axis for achievement of high-quality compacting work of metal layers of billet by a cross-section in the deformation zone at stretch-forging.

Materials of research

The six samples with a diameter = 50 mm and length = 100 mm were made from antimonial lead (ССу brand) for performance of experimental research. The samples were made by pressing in the form of two halves of semicircular cross-section, and coordinate grid with a step = 3 mm was put on the inner part of one of halves. The soldering by Wood's alloy was carried out (fig. 1, a) for receiving of continuous samples which marked on one of ends by signs "0", "1", "2", "3", "5", "8" (fig. 1, b), and the marking for the performance of rotation of work-piece a round of longitudinal axis on the fixed corners = 30°, 60° и 90° was put at other end (fig. 1, c).

Fig. 1 Preparation and forging of experimental samples:
a – soldering by Wood's alloy of samples with coordinate grid;
b – marking on the ends of soldered samples;
c – forging of sample with marks in combined dies;
d – sample after forging mode;
e – mechanical scheme of strains

The model of cut-out anvils were made for laboratory experiments in scale 1:10 to the size of a productive nature: width = 30 mm, the radius of the notch in the lower anvil = 30 mm. The material of anvils is steel 45 (0.45% Carbon). These anvils were fixed in a stamp block (Fig. 1, c), mounted on a universal testing machine (0.2 MN), and carried out the deformation of lead samples (Fig. 1, d) with the entire width of the anvil in the middle of the length of the work-piece (which corresponds to the amount of feed = 30 mm, the relative feed rate = 1.0). So, the influence of hard and not deformed ends at modes of stretch-forgings was also taken into account (Fig. 1, d and e), which receives the stretch in the longitudinal direction due to making compressions (Fig. 1, e). In real conditions it is necessary to remove the work-piece along the front of feed with relative feed £ 1.0 and hold running along the diameter, having the given values of upsetting and angles of rotation for the implementation of the next step of stretch forging.
The samples were divided into two groups to study the effect of influence of stretch forging modes on the controlled indicators, each of which was assigned rotation angle, value of reduction (upsetting) and quantity of reduction till to full rotation of the work-piece to 360°. In the first group of samples ("0", "1" , "2") varying of the rotation angle was performed at a fixed value of reduction = 5 mm: a sample "0" – = 30°, n = 12; a sample "1" – = 60°, n = 6; a sample "2" – = 90°, n = 4. In the second group of samples ("3", "5", "8") varying with the value of reduction was performed at a fixed tilting of rotation angle = 60°: a sample "3" – = 5 mm, n = 6; a sample "5" – = 6.6 mm, n = 6; a sample "8" – = 9 mm, n = 6. Thus, the study was carried out at relative reduction: = 0.1; 0.132 and 0.18.
To investigate the stress-strain state as a basis, the experimental method of grids was chosen [6]. The vertical line was determined before the soldering of the samples = 16 (Fig. 2, a), which is at a distance (then ) from the end of the sample. Along this line initial height () and the width () of each cell of the grid was measured. A feature of measurements was that the base rate of the cells of the grid took the width and height with the presence of an orthogonal basis in the form of two crossing lines in the middle of the cells (Fig. 2, b). This facilitates the measurement of the central angle of cell shift of the grid relatively to the initial angle = 90°, as well as finale size and (see Fig. 2, b) after forging and desoldering of the samples. Accordingly, the deformation refers to the center of the cell with the cross of lines in the middle, the material was considered isotropic. Measurements were performed using microscope (model: BMI-10) and according to scanned images of the grid.


а	b

Fig. 2 Measurement scheme of the grid:
a – the numbering of cells at length and height;
b – the cell is before and after forging

The forging with rotation involves the conversion of the original round cross-section of the work-piece into a round section of a forging-part, so the stress-strain state of the material in the area of deformation can be taken as axisymmetric. The components of strains in elementary cells were calculated as
;          ;     .                   (1)
Components responsible for the shift:
;          .                (2)
Accordingly, the intensity of strains for the accepted conditions:
.                                (3)
According to the hypothesis of a unique curve, we have unique functional relationship between the intensities of stresses and intensity of strains eⁱ for given conditions of thermo-mechanical deformation of material: . The similarity of kinematics of deformation of work-pieces from different materials was allowed. Then the quantity of the deformation along the height of semi-finished item depends on the type of curve of hardening. The dependence for antimonide lead CCy was determined after the tests (coefficient of determination = 0.9997):
.                   (4)
The approximation of hardening curve of the steel 12XHMФA (C 0.09-0.16% , Cr 0.6-0.9% , Ni 1,0-1,4%, Mo 0.15-0.3% , V 0.1-0.2% ) at the temperature = 1100° C and velocity of deformation = 10 с-1 [7] gives the following relationship (R² = 0.9838):
.             (5)
The conditions of deformation were taken monotone, so the coefficients of hardness of the scheme of stress and strain state (according to G.A. Smirnov-Aliaev [8]) were considered:
;     ;   .        (6)
where и – the components of stress and strain for -cell.
For axisymmetric deformation the coefficient of hardness of the scheme of stress-strain state was calculated as
.                                           (7)
The results of processing of experimental data are shown in Fig. 3 and Fig. 4.
The increasing of the angle of rotation of the work-piece at a fixed relative reduction ( = 0.1) is accompanied by a decrease of the average values of the intensities of strains in the deformation zone, deterioration in compacting work of metal layers (see Fig. 3). The moving of values of the coefficients of hardness of stress-strain state in the middle of the height of the cross-section in a hard area also confirms the ability of appearance here of stretching stresses at angles of rotation = 60° and 90°, despite the fact that the maximum values of parameter are not in the central area of the work-piece.

Fig. 3 Graphs of the distribution of intensity of strains ,
intensity of stress for lead CCy () and steel 12XHMФA () billets, and coefficients of hardness of scheme of stress-strain state at height:
а – sample "0" ( = 0.1; = 30°);
b – sample "1" ( = 0.1; = 60°);
c – sample "2" ( = 0.1; = 90°);
1 – experimental points, 2 – data approximation

Fig. 4 Graphs of the distribution of intensity of strains ,
intensity of stress for lead CCy () and steel 12XHMФA () billets, and coefficients of scheme of stress-strain state at height:
а – sample "3" ( = 60°; = 0.1);
b – sample "5" ( = 60°; = 0.132);
c – sample "8" ( = 60°; = 0.18);
1 – experimental points, 2 – data approximation

At different values of reduction and angle of rotation = 60° the maximum of intensities of strains is observed at middle of height of the samples (see Fig. 4), increases with a rise of values of upsetting . Growth of reduction values also leads to fewer of layers of metal of billet which are located in a hard area, and the average value of coefficients of harness of stress-strain state belongs to a soft area. The qualitative difference between the stress intensity values for the same deformation modes of work-pieces from different materials connected with different mechanism of their hardening under given thermo-mechanical conditions of deformation.

Conclusions

The technique of experimental determination of the influence of the modes of the stretch forging on the distribution of the strains and stresses in a cross-section of the work-piece, which takes into account the mechanical and kinematics conditions of its deformation with rotation in combined anvils, is developed. The fact that in fixed reductions (upsetting) the increasing of the angle of rotation of the work-piece around the longitudinal axis allow to reducing an average value of intensity of deformation along the cross-section with increasing of a share of stretching deformation on the midpoint of the height of the work-piece was found. At fixed values of the angle of rotation the increasing of reduction (upsetting) leads to rising of all-average intensity of strains with a maximum in the middle of the height of the deformation zone and reduction of dispersion of values of the coefficients of hardness of scheme of stress-strain state. The best results from the point of view of achieving a qualitative compacting works of the metal on the cross-section of deformation zone showed the modes with the angle of rotation = 60° and relative reduction = 0.18.

References

1. Markov O. New technological process of shafts forging. New technologies and achievements in metallurgy and materials engineering, Czestochowa, Quick-druk, 2012, pp. 414-418.
2. Kargin S.B., Markov O.E. and Kukhar V.V. Teoreticheskij analiz naprjazhenno-deformirovannogo sostoyanija slitka pri kovke na trekhlepestkovuju zagotovku (Theoretical analysis of the stress-strain state of the ingot at forging for trilobal billet). Obrabotka materialov davlenijem: sbornik nauchnykh trudov (Materials processing by pressure: collection of scientific works), Kramatorsk, DGMA, 2011, vol. 1(26), pp. 17-21.
3. Toshihiko Obata. Method for forging round bar. Patent JP3,120,591 Japan, B 21 J 5/00; B 21 J 5/02; B 21 J 5/06; B 21 K 1/06, Ishikawajima Harima Heavy Ind. Co. Ltd., Oct. 20, 2000.
4. Banaszek G. and Szota P. A comprehensive numerical analysis of the effect of relative feed during the operation of stretch forging of large ingot in profiled anvils. Journal of Materials and Processes Technology, 2005, vol. 169, pp. 437-444.
5. Vasilevskii O.V., Grushko A.V. and Kukhar V.V. Issledovanije deformirovannogo sostojanija pokovok tipa valov pri kovke v kombinirovannykh boykakh (Investigation of deformed state of forgings such as shafts at forging in combined anvils). Obrabotka materialov davlenijem: sbornik nauchnykh trudov [Materials processing by pressure: collection of scientific works], Kramatorsk, DGMA, 2011, vol. 3(28), pp. 78-82.
6. Renne I.P. Teoreticheskije osnovy eksperimentalnykh metodov issledovanija deformacij metodom setok v processakh obrabotki metallov davlenijem (Theoretical foundations of experimental ways of research of deformation by the method of grids in metal-forming processes), Tula, TPI, 1979, 96 p.
7. Polukhin P.I., Hun G.J. and Halkin A.M. Soprotivlenije plasticheskoj deformacii metallov i splavov. Spravochnik (Resistance to plastic deformation of metals and alloys. Reference book), Moskow, Metallurgija, 1983, 352 p.
8. Smirnov-Aliaev G.A. Soprotivlenije materialov plasticheskomu deformirovaniju. Inzhenernyje raschety processov konechnogo formoizmenenija materialov (The resistance of materials to plastic deformation. Engineering calculations of the processes of finite forming of materials), Leningrad, Mashinostroenie, 1978, 368 p.

A mathematical background for information technology of project’s processes integration taking into account risk factors

Fri, 18 Jul 2014 09:10:18 +0300

The necessity of researches in given sphere was shown by analysis of existent approaches to integration of main project processes and mechanisms of rectifying the after-effect of risk factor. Main goals and problems of integration method were formulated. Preconditions for transformation of work package into language of regular scheme of process network were defined. And also methods of solving such problem as reduction of work package to aggregable view were developed. The experiment based on the actual data was conducted. As well practical aspects of methods were formulated.

Keywords:project, integration, processes, networks, work package

UDK 005.8:004.9

S.G. Kiyko
PJSC Dneprospetsstal (DSS)

E.A. Druzhinin / D.Eng.Sc./
National aerospace university 'Kharkov Aviation Institute'

S.A. Koba
National aerospace university 'Kharkov Aviation Institute'

B.V. Haidabrus / PhD in Engineering/
Sumy State University

Introduction

While analyzing technical-economic values of the project, one should consider all the processes as the whole entity in accordance with the system concept. This is needed in order to get jail time, costs and resource loading of the project. Varied character of the processes prevents their integration. Some processes are constantly present in the structure of project works and most often are yielded to some formation rules, such processes are called the main ones. The other processes may appear occasionally or with some probability. Special model of project plan is necessary for combination of various processes. Plenty of processes of various characters leads to that fact, that combination of processes manually is almost impossible, information technology is necessary to be used.

Objectives

The aim of research is to analyze approaches to integration of main project processes and mechanisms of rectifying the after-effect of risk factor. To develop integration method on the base of researches and to undertake an experiment based on actual data with the usage of information technology on the base of developed method.

Analysis of existing methods

Monte Carlo [1] and PERT [2] techniques are widely used analysis methods of influence of risk factors on the project. They use statistical approach for determination of continuance or working costs of the project. Advantages of these methods are their simplicity and small labor efforts for modeling, but they do not give detailed project time schedule and due to this their accuracy falls. Also some technical-economic values (for example resource loading in the point of time) are impossible to determine with the help of static modeling.
Matrix approach is often used while presentation of project plan [3]. It is very accessible while formation of main project processes, as it allows to combine project stages in accordance with different logical conditions, quickly and effectively, using matrix transformation device. However insertion of unrestricted work areas or repeats during the approach is bulky and non- direct operation. That is why for various processes integration this approach is non-effective.
Stochastic modeling methods [4] or modeling with the help of Petri nets [5] may be also used for fulfillment of a task of integration. These methods have not become a frequent practice in the field of project control because of complexities of the implementation or absence of tools. Language of regular schemes of process network (RSPN) is suggested in this research to be used for solution of the integration task.

Modification of project structure with the usage of RSPN language

Within a matter of this article, research of influence of risk factors on the project structure of creation of complex technique includes investigation of project inner risks. Among these are resources fault, defects, and risks of not achieving of program quality. In response to their appearance, in project there set mechanisms of rectifying the after-effect of risk factor. Integration of these mechanisms with the main project processes leads to certain changes in the work structure (fig.1).

Figure 1 Changes in work breakdown structure

The main project processes and changes in the structure of works may be interpreted into the RSPN language in accordance with the table 1.

Table 1 Main processes and changes in the work breakdown structure

Name	RSPN
Sequenced area of work	Y(1)vY(2)vY(3)vY(4)
Parallel area of work	[Y(1)^Y(2)^Y(3)^Y(4)]
“Defect elimination”	Y(1)vY(2)vY(3){DR:0,6:R(1)vR(2)}vY(4)
Repetition of some work	{ER}Y(1)vY(2)vY(3){SR:0,6} vY(4)
Manufacturing system development and repetition of some work	{ER}Y(1)vY(2)vY(3){SR:0,6:R(1)vR(2)}vY(4)

Limitations and initial conditions

Accomplishment of a set of conditions and limitations is necessary for simplification of project range recording of works of complex technique creation on the RSPN language. They are connected both with RSPN language limitations and with logic of project process. Let us assume the range of works as the canonic network model, consisting of tops and connecting arcs.
The network should have the only starting and ending tops. If this condition is not observed, fictitious starting and ending tops should be added (fig.2).

Figure 2 Fictitious starting and ending tops

Then it should be checked that the network does not contain tops, not having followers or predecessors (except starting and ending top). If there are these tops, one should insert fictitious starting or ending top, acting as predecessor or follower respectively.
Network should be transformed to the combination of sequenced and parallel work areas. If this is not the case, the network should be led to aggregate type by means of doubling of some tops (fig.3).

Figure 3 Putting the network into aggregate type

Return and repeat of some range of work cannot be fulfilled if rerun point is not direct or indirect predecessor of the work, where risk factor appeared.

Figure 4 Returns in the project structure

At the left of the fig. 4 allowable return is depicted as Y1 top is indirect predecessor of Y3 top, at the right – there is inadmissible return.

Application of the method on the actual data

Project of creation of pilotless aircraft (PA) was analyzed on the base of this approach. Initial data were provided by NII PFM KHAI (Kharkov institute for scientific research). Seven risks of non-achieving of program quality with different grade of influence on the project structure were marked. Integration of main processes (modeling and design-engineering segmentation, detailed design, work preparation, production and assemblage) with mechanisms of rectifying the after-effect of risk factor was fulfilled.

Figure 5 Project of PA creation

In result of project translation (fig.5) into the RSPN language, the following expression was obtained:

R_projectPA=Y(0){ER(5)}v[Y(1)vY(13){ER(3)}^Y(2)v[Y(3){ER(6)}v[Y(5)vY(17){ER(1)}^Y(6)vY(18)
{ER(2)}]vY(15)^Y(4)v[Y(9)vY(21)^Y(7)vY(10)vY(22)vY(19){ER(4)}^Y(8)vY(11)vY(23)vY(20)
{ER(0)}]vY(16)]vY(14)]vY(12)v[[Y(24)^Y(25)vY(37){SR(3):0,5}]^[[Y(26)^[Y(27)^Y(29)vY(41)
{SR(1):0,65}^Y(30)vY(42){SR(2):0,55}]vY(39){SR(6):0,2}]^[[Y(28)^Y(33)vY(45)]^[Y(31)^Y(34)vY(46)]vY(43){SR(4):0,5}^[Y(32)^Y(35)vY(47)]vY(44){SR(0):0,6}]vY(40)]vY(38)]vY(36){SR(5):0,1}

Conclusion

The article is devoted to approaches of integration of main project processes and mechanisms of rectifying the after-effect of risk factor. Advantages and disadvantages of existing methods were found out. On this base it was concluded concerning the necessity of integration method development. The RSPN language was chosen for that aim.
The usage of developed method allows to submit project plan as the whole entity in the compact symbol form, including the processes of various characters. This method may be successfully used during development of information technology for analysis and synthesis of project structural models under the conditions of uncertainty, for automatization of planning of production and administrative management, for simulation modeling of technical-economic values of the project and also while development decision support system under the conditions of uncertainty.

References

Juneja, Sandeep. Monte Carlo methods in finance: An introductory tutorial. Simulation Conference (WSC), Proceedings of the 2010 Winter, 5-8 Dec. 2010, 95, 103p.
Upravlenie innovatsionnymi proektami [Manegment of innovation projects]. Under the editorship of prof. V.L. Popov. Moscow, INFRA-M, 2009, 336p.
Koba, S.A Method of project plan formation with changing structure during creation of complex technologies (2013). Vostochno-evropeyskiy zhurnal peredovykh tekhnologiy. No1/3 (61), p. 39.
Golenko-Ginzburg D.I. Stokhasticheskie setevye modeli planirovaniya i upravleniya razrabotkami [Stochastic network models for planning and management of developments]. Voronezh, Nauchnaya kniga, 2010, 284 p.
Larichev O.I. Ob"ektivnye modeli i sub"ektivnye resheniya [Objective models and subjective decisions]. Moscow, Nauka, 1987, 191 p.
Druzhinin E.A. Metodologicheskie osnovy risk-orientirovannogo podkhoda k upravleniyu resursami proektov i programm razvitiya tekhniki. Dissertatsiya na soiskanie uchenoy stepeni doktora tekhnicheskikh nauk. Natsional'nyy aerokosmicheskiy universitet im. N.E. Zhukovskogo «Khar'kovskiy aviatsionnyy institut» [Methodological foundations of risk-based approach to the PM resource management and technique development program. Dissertation of competition of Doctor of Engineering Sciences degree. National Aerospace University named after N.E. Zhukovski. Kharkiv Aviation Institute]. Kharkiv, 2006, 403 p.
Druzhinin E.A. , Latkin M.A. , Mitrakhovich M.M. Proektirovanie avtomatizirovannykh proizvodstvennykh system [Designing of automated mechanical structures]. Kharkiv, Kharkiv Aviation Institute, 2002, 41p.

The gas bubble size distribution control formation in the flotation process

Tue, 09 Sep 2014 14:23:51 +0300

A method for the effective control of the pulp gas phase composition in the flotation process using dynamic effects of high energy ultrasound on the base of phased array technology and determination of its parameters are described.

Key words: phased array, ultrasound, pulp, control, flotation, bubble size distribution

The gas bubble size distribution control formation in the flotation process

Vladimir Morkun
Vice-Rector for research, Doctor of Science, Professor, Head of Computer Science, Automation and Control Systems department
State Higher Educational Institution "Kryvyi Rih National University", Ukraine

Natalia Morkun
PhD, Associate professor of Economic Cybernetics and Project Management Department
State Higher Educational Institution "Kryvyi Rih National University", Ukraine

Andrey Pikilnyak
PhD- student, research assistant of the Computer Science, Automation and Control Systems department
State Higher Educational Institution "Kryvyi Rih National University", Ukraine

For the physical processes modeling which determines the flotation it is requires the accurate data on the gas phase characteristics, the most important of which are the concentration and gas bubble size distribution. These parameters are highly dependent on a variety of operational, technical and physical-chemical factors, the effects of which should be considered in flotation process modeling.
The task of research is the control formation of the desired gas bubble size distribution, which would correspond to the pulp solid phase particle size distribution in the flotation process.
To solve this task it is proposed to affect on the pulp flow with high-energy ultrasonic wave with given frequency and amplitude, resulting in a gas bubbles concentration change, and redistribution of their size. Character of redistribution depends on the size of the bubbles themselves, the frequency and amplitude of the incident radiation. To initiate appropriate processes, due to the extreme nature of cavitation in liquids, it is necessary not only to form a certain amplitude and frequency of oscillations, but also to maintain their optimal values when changing the medium parameters and the impact of factors such as: changing the temperature of the medium and the material of the piezoelectric transducer, the damping action of the medium [1-4].
To account for the gas pressure in the bubble, and pressure varying in the liquid, the viscosity and surface tension it is advisable to use a cavitation bubble dynamics equation of Rayleigh-Plesset in which the driving pressure Pi(t) given as a short pulse [5]

, (1)
, (2)

where P0 – is static pressure in the liquid, R(t) – is current bubble radius, R0 – is initial bubble radius, Pi(t) – is pressure in the incident wave, σ – is surface tension, μ- is dynamic viscosity of the fluid, ρ – is density of the liquid, с – is speed of sound in the fluid (water σ = 0.07 N/m, μ = 0.001 N×s/m2, ρ = 103 kg/m3, c = 1500 m/s), γ – is adiabatic exponent of gas in the bubble (air γ = 1.33). The initial conditions are given as, (t = 0) = 0.
The simulation results of the high – energy ultrasound dynamic effects impact on the pulp gas phase allowed to obtain the dependences of the gas bubbles size distribution function parameters on the frequency and amplitude of the applied ultrasonic action.
The dependence of gas bubbles sizes on the ultrasonic oscillation pressure amplitude for different values of its frequency is presented on Fig.1.
At a constant ultrasound frequency of 0,7 MHz and the formed pressure of 102-104 Pa the size of the gas bubble remains constant (5×10-5 m), at a pressure of 104-2×105 Pa there is a gradual decrease in the bubble size (5×10-5 -10-5 m), at a pressure of 2×105 -5×106 Pa the bubble decreases in size (10-5 -1,5×10-7 m), and when varying the ultrasound frequency from (0,7 - 2,5 MHz) and at a pressure of 102 Pa the bubble decreases in size from 5×10-5 to 1,5×10-5 m.

Fig. 1. The dependence of gas bubbles sizes on the ultrasonic oscillation pressure amplitude for different values of its frequency: 1 - 0,7 MHz; 2 – 1,5 MHz; 3 – 2,5 MHz.

Let’s form the control action based on the dynamic effects of high-energy ultrasound using phased array technology, which have many advantages compared to conventional single-element transducers [6].
When using this approach, the gas bubbles are subjected to elements of the phased array, which having different characteristics. Numerically this effect can be expressed as a weighted sum of the individual bubble size distributions generated by each element of array [7].

, (3)
with
, (4)

where N - is the number of array elements, αj – weighting coefficients, which can be considered as a priori sampling probability of bubbles generated by j-element of array, fj(х) - is the size distribution function of bubbles generated by j-element of array.
The structure of the gas bubble size distribution automatic control system based on the technology of ultrasonic phased array for realization of proposed method is
presented on Fig. 2.
The system input receives the information about the solid phase parameters and the estimator determines the gas phase parameters. The signal is then transmitted to the adjusting device, which sets the required amplitude and frequency of ultrasonic vibrations. Then the control action generator transmits the electromagnetic signal to the ultrasonic phased array, whereupon the pulp with the bubbles is exposed to high energy ultrasound emitted from the array elements. That allows to form a predetermined gas bubble size distribution. To maintain or change the required amplitude and frequency the adaptive control algorithm, which control the power for each individual array element is used.

Fig. 2. The structure of the gas bubble size distribution automatic control system based on the technology of ultrasonic phased array.

Simulation results of the high energy ultrasound impact on the pulp solid and gas phases allow to form the required gas bubble size distribution function, which would coincide with the pulp solid phase particle size distribution in the flotation process.

Fig. 4. Bubble size distribution: 1- initial; 2 - resulting.

Conclusions

The results of experimental studies of the proposed flotation control method based on ultrasonic phased array technology allows to implement the efficient control of the iron ore pulp solid and gas phases composition, to improve the quality of the concentrate and the energy efficiency of the whole beneficiation process.

References

Morkun V. S., Morkun N. V,. Pikilnyak A.V. Iron ore flotation process control and optimization using high-energy ultrasound, Metallurgical and Mining Industry, 2014, No2. p.p. 36-42. http://www.metaljournal.com.ua/ assets/Journal/a7.pdf.
Morkun V. S., Morkun N. V,. Pikilnyak A.V. Modeling of ultrasonic waves propagation in inhomogeneous medium using fibered spaces method (k-space), Metallurgical and Mining Industry, 2014, No2, p.p. 43-48. http://www.metaljournal.com.ua/assets/Journal/a8.pdf
Morkun V. S., Morkun N. V,. Pikilnyak A.V. Simulation of high-energy ultrasound propagation in heterogeneous medium using k-space method, Metallurgical and Mining Industry, 2014, No3, p.p. 23-27. http://www.metaljournal.com.ua/assets/Archive/en/MMI3/4.pdf .
Morkun V. S., Morkun N. V,. Pikilnyak A.V. Ultrasonic facilities for the ground materials characteristics control, Metallurgical and Mining Industry, 2014, No2, p.p.31-35. http://www.metaljournal.com.ua/assets/Journal/a6.pdf
Lauterborn, W., Parlitz, U. On the bifurcation structure of bubble oscillations. Problems of nonlinear acoustics. XII-th International symposium on nonlinear acoustics, 75–79. 1987.
Morkun V. S., Morkun N. V,. Pikilnyak A.V. Ultrasonic phased array parameters determination for the gas bubble size distribution control formation in the iron ore flotation, Metallurgical and Mining Industry, 2014, No3, p.p. 28-31. http://www.metaljournal.com.ua/assets/Archive/en/MMI3/5.pdf
Maldonado M. A. Advances in estimation and control for flotation columns. Du programme de doctorat en génie électrique pour l'obtention du grade de Philosophiae Doctor (PhD) .Québec. 2010. p.135.

Development of automatic control system of hydrocyclone based on ultrasonic measurement of input-output parameters

Mon, 21 Jul 2014 12:19:42 +0300

Identification of parameters of some technological objects of the ore processing stage is hampered by the limitations of measuring the state of the control object, impossibility of forecasting noise and disturbance values. Control systems based on minimization of regulatory errors when determining the object state variables take into account intrinsic properties, order of the object, its delays, real change of parameters of noise and disturbances.

Keywords: hydrocyclones, parameter identification, vector control.

V.M. Radionov

junior researcher, graduate student.
National University of Krivoy Rog

When designing a hydrocyclone operated control system it is necessary to consider high speed, nonlinearity of separation processes, rapid stochastic change of properties, and the composition of the pulp. This defines the requirements to the information support system.
To measure the input and output parameters of multiphase flows of the hydrocyclone ultrasonic treatment and control systems are applied [1-4].
The effectiveness of classification management in cyclones depends on the quality of information support at stochastic changes of the pulp parameters. When classifying the iron ore pulp due to the size of the particles of the solid phase the information on the granulometric composition is urgent. Devices of ultrasonic influence and control are applied to determine the pulp granulometric composition. Along with this the pulp is pulsewise affected by means of the high-energy ultrasound and characteristic changes are monitored in the utrasonic probing channel. Solid particles within the slurry are spatially redistributed in the controlled volume being dynamically affected by the high-efficiency adjustable intensity ultrasound. Interdependence of the velocity of particles and the distance from the source of exposure is defined as [6]

, where (1)

The expression shows, that the r -size particle' speed from its z- coordinates, intensity ultrasound exposure I, and the ratio а, which depends on the frequency. Knowing the ultrasound parameters and exposure time we can determine the nature of the spatial redistribution of particles by size.

Figure 1 Variation in the concentration of particles by size grades in the ultrasonic field, 1- r=1mm, 2- r=0.5mm, 3- r=0.2mm, 4- r=0.01mm, 5- r=0.05mm.

Moreover, the analogy of such spatial redistribution to redistribution of particles under the influence of the complex of centrifugal forces in the field of the hydroclone is traced. Change in the intensity of ultrasonic influence by its nature is similar the change in the pulp pressure alteration at the inlet of the hydrocyclone. The forecast is possible, as well as the correction of parameters synchronously with pulp supply to the hydroclone. The present paper considers the content of the control grades in the cyclone feeding and draining systems for the formation of vectors of input-output of the control. Control problem – the maximum transfer of the particles of the control size grades contained in the pulp from the feeding system to the draining system of the cyclone, or minimization of the input-output vector error.
Evaluation of granulometric composition of the solid phase of the pulp or the content of the control size grades performed through the analysing the changes of volume attenuation of ultrasonic waves in the control channel at the moments of high-energy ultrasonic influence , and at the moments of the absence of such effects.

(2)
(3)

The ratio of the decay of these signals depends on the intensity of the ultrasonic field, time of exposure and distribution of particles by size and density. Selecting a strong intensity and frequency of ultrasound, location of probing channel is performed based on the maximum sensitivity value S1/S0 to change of the size or density of the particles.
The dynamics of the object is defined due to the information about the output deviations in the control object depending on the input parameters based on actual noise and disturbances. Control problem can be solved by determining the internal structure of the control error, parameters of which will allow considering internal properties of the object, its delays. For this purpose both controller input values and control object output values shall be measured taking into account the effects of noise and disturbance, as well as time (phase) modulations of these values [5].
The target function of the ACS on the basis of the regulation vector error can be presented as: [2]

(4)

The model of a control system with a nonlinear function of the control object, described by differential equations in the form of Cauchy by the control object output.

(5)

where f(*)-non-linear function of the control object.
For this model, controls by the actual, the imaginary component and of the complex error modulus:

(6)

where К - the corresponding coefficients of the regulator.
To ensure the control system stability based on the second method of Lyapunov's theorem on stability for nonlinear systems, and the definition of the Lyapunov’s function in a square form in reference to the applied component of the complex error at the controller input and control signal [5]. The upper boundary of the regulators’ factor bands in compliance with the conditions of stability of ACS with vector control and the constant coefficient Kв:

(7)

Elimination of influence of nonlinear function f (*) of the controlled system on the stability is possible provided:

(8)

Definition of the setup value pattern of change r, affecting the change in the control input u

(9)

Determining factors ensuring the stability of the ACS nonlinear control object with vector control are those of certain modulations in the phase offset between the change in the vector setting and the output vector of the non-linear process control and the setpoint pattern of change in accordance with (8), (9).
In general, the regulation law for N-PID of the regulator can be presented as

(10)

Overriding regulator factors are defined at each regulation cycle in accordance with the values of actual and imaginary components of the vector error and direct N-PID regulator output u(k-1) at the previous step of regulation. Speed algorithm of N-PID controller based on vector errors

(11)

On the basis of the MATLAB approaches an example of the hydrocyclone particle size distribution drain control is considered, by the pressure regulating of the hydrocyclone sand pump, according to the results of the ultrasonic control of parameters of pulp, on the basis of minimizing the vector regulation error. Presented for comparison are the results of simulation of the control size grades output in the discharge of the hydrocyclone, with the factor of randomization taken into account, at stabilization of pressure pulp at the hydrocyclone inlet, fig.2, and the regulation of particle size distribution to minimize errors in the size grades, fig.3.

Figure 2 The output of the control class size at stabilization of pressure at the cyclone input.

Figure 3 The output of the control size grades at regulation with minimization of the error on the content of the control size grade.

Conclusions

The developed particle-size composition control system of the hydrocyclone drain on the basis of ultrasound information-measuring system can both improve the quality of separation, and reduce the output fluctuation of control class sizes from 10% to 4%. In this case the standard deviation of the simulation results and experimental data by near-mesh grain size - makes up 1, 57%, by control grain size grade – 0, 67%.

References

1. Morkun, V. S., Morkun, N. V., Pikilnyak, A.V. (2014). Modeling of ultrasonic waves propagation in inhomogeneous medium using fibered spaces method (k-space), MetallurgicalandMiningIndustry, No2, p.p. 43-48.
2. Morkun, V. S., Morkun, N. V,. Pikilnyak, A.V. (2014). Iron ore flotation process control and optimization using high-energ yultrasound, MetallurgicalandMiningIndustry, No2. p.p. 36-42.
3. Morkun, V. S., Morkun, N. V,. Pikilnyak, A.V. (2014). Ultrasonic facilities for the ground materials characteristics control, MetallurgicalandMiningIndustry, No2, p.p.31-35.
4. Morkun, V., Goncharov, S., Pikilnyak, A., Krivenko, A. (2012). Iron ore benefication processes optimization. ТЕKA. Commision of Motorization and Energetics in Agriculture 12, no.4,162-166.
5. Agamalov, O.N., Lukash, N.P. (2008). Alternativne neliniyne PID-upravlinnya z vycorystannyam vektjrnoi pomylki. Elektrroinform, No2, p.p. 8-13
6. Radionov V.M. Sposob upravleniea granulometricheskim sostavom vekhoda hydrocyklona na osnove sredstv ultrazvekovogo vozdeystveya I controlya, Vestnyk Krivoy Rog national university, No37, 2014, p.p. 235-238.

Ultrasonic phased array parameters determination for the gas bubble size distribution control formation in the iron ore flotation

Wed, 23 Jul 2014 10:22:50 +0300

Abstract
A method for the effective control of the pulp gas phase composition in the flotation process using dynamic effects of high energy ultrasound on the base of phased array technology and determination of its parameters are described.

Key words: phased array, ultrasound, pulp, control, flotation

Ultrasonic phased array parameters determination for the gas bubble size distribution control formation in the iron ore flotation

Vladimir Morkun
Vice-Rector for research, Doctor of Science, professor of Computer Science, Automation and Control Systems department
Kryvyi Rih National University

Natalia Morkun
PhD, Associate professor of Economic Cybernetics and Project Management Department
Kryvyi Rih National University

Introduction

Materials and methods.

To form the required gas bubble size distribution function, which would conform with the pulp solid phase particle size distribution in the flotation process, it is proposed to affect on the pulp flow with high-energy ultrasonic wave with given frequency and amplitude, resulting in a gas bubbles concentration change, and redistribution of their size. Character of redistribution depends on the size of the bubbles themselves, the frequency and amplitude of the incident radiation. Increasing the frequency and amplitude to the values at which the transition cavitation starts, bubble size will decrease due to crushing of larger bubbles. When decreasing the amplitude and frequency the bubbles will rise due to coalescence of smaller bubbles [4].
To solve this task, let’s form the control action based on the dynamic effects of high-energy ultrasound using phased array technology, the main feature of which is computer-controlled driving pulses amplitude and phase of the individual piezoelectric elements in multi-element transducer to control the parameters of the ultrasound beam, for example, angle, focal length, focal spot size [5,6].
Taking into account the above in the proposed method using the ultrasonic phased array mounted on the external wall of the flotation machine chamber, in the working area, at each current moment of time we generate the high energy ultrasound effect with a given frequency 0.7 - 2.5 MHz, (because the value lower than 0.7 MHz does not give a stable effect of bubble size changes, which is caused by the extreme nature of cavitation, and a value above 2.5 MHz is not affect the change of necessary indicators) and the pressure amplitude of 102 -5×106 Pa, (because the value lower 102 Pa not sufficient to effectively control the gas phase, and the values above 5×106 Pa not give quality indicators growth), wich focused on the window in the interchamber septum. The gas bubbles which formed in the aeration step, after impeller dispersing are exposed to focused ultrasound, which leads to variations in their concentration and desired size redistribution in the pulp flow.
To focus precisely on the window in the interchamber septum it is necessary to calculate the parameters of a phased array and to construct its directivity pattern.
The acoustical pressure of the array was calculated by modeling every element of the array as an independent simple source and summing the contribution of each simple source at each point in the field. The acoustic pressure p(x,y,z) at a specific point (x,y,z) in the field due to a simple source was calculated using the Rayleigh-Sommerfeld equation [7,8]
,                               (1)
where W - is total acoustical power output from the array, ρ – is density of the medium, c – is speed of sound in the medium, A – is active transducer aperture, f – is frequency, S – is area formed by source, d – is distance from the source to the point (x, y , z), φ – is phase of oscillation, λ – is wavelength, and α – is attenuation in the medium.
The active aperture (the total length of the array) is calculated by the following formula [6].
,                                            (2)
where A - is active aperture; g – is gap between nearest elements; e – is width of one element (typically e <λ / 2); n – is number of elements.
Active aperture projection onto a plane seen along the refracted rays (effective active aperture Аeff) is given by
,                                             (3)
Recommended passive aperture is determined by probe frequency and the focal depth range as follows
,                                 (4)
Its contribution to the focal depth (near-field length) is given (for nonfocused probes) by formula (5)
,                          (5)
Array pitch of p is determined by the formula:
,                                                 (6)
where g – is the element gap; e – is the element width.
The maximum width of a single element, which is determined by the maximum beam refracted angle by electronic control emax can be represented as follows
,                                          (7)
Note that the beam width is dependent on the focal length and the angle of entry.
A focused beam is characterized by the focusing factor or normalized focus depth
,                                               (8)
with 0 < Sac < 1 and Fac < N0, and Fac – is the actual focal depth.
An optical focus point is defined by
,                                    (9)
where R - lens curvature radius.
The optical focusing factor is defined by
,                                              (10)
The net pressure due to all the elements was determined by summing the effects of each simple source:
.                            (11)
The net power deposition at point (x,y,z) was the result of the attenuation [5]
,                             (12)
The total energy at a point (x, y, z) is given by [8,9]
,                             (13)
where - intensity at the point (x, y, z), W∙m -2
The phase of each element of the array was determined by
,                                         (14)
where φi is phase of element i in degrees, di is distance from the center of element i to the focus, d0 is the focus depth, n is an integer used to maintain 0 <= φi <= 360°.

Results

Normalized directivity pattern for a rectangular array with Z = 16 elements equally spaced from each other d = 0,6 mm in the plane (Fig. 1) used in the simulation with software and hardware tools TAC (Transducer Array Calculation) [10] is presented on Fig. 2.

Figure 1. Phased array configuration

Figure 2. Directivity pattern of a rectangular phased array with Z=16, j=0°

Figure 3. Directivity pattern of entire arrangement
Taking into account the above, for the method implementation we form the ultrasonic action with certain amplitude and frequency using phased array at each current moment of time in a flotation machine working zone that will provide the required gas bubble size distribution in the pulp flow.

Conclusions

References

Brewis T. Flotation cells. Mining Magazine, 1996,160(7), p.p 18–24.
Miskovic S. An investigation of the gas dispersion properties of mechanical flotation cells: an IN-SITU approach. Blacksburg, Virginia, 2011.
Morkun V. S., Morkun N. V,. Pikilnyak A.V. Ultrasonic facilities for the ground materials characteristics control, Metallurgical and Mining Industry, 2014, No2, p.p.31-35. http://www.metaljournal.com.ua/assets/Journal/a6.pdf
Morkun V. S., Morkun N. V,. Pikilnyak A.V. Iron ore flotation process control and optimization using high-energy ultrasound, Metallurgical and Mining Industry, 2014, No2. p.p. 36-42. http://www.metaljournal.com.ua/assets/Journal/a7.pdf.
Morkun V. S., Morkun N. V,. Pikilnyak A.V. Modeling of ultrasonic waves propagation in inhomogeneous medium using fibered spaces method (k-space), Metallurgical and Mining Industry, 2014, No2, p.p. 43-48. http://www.metaljournal.com.ua/assets/Journal/a8.pdf
Olympus NDT. Introduction to phased array ultrasonic technology applications. R/D tech guideline, 2007.
Goodman, J. Introduction to Fourier Optics. 2rd ed New York: Stanford University,1968.
Sun, L. Collins C.M., Schiano J.L., Smith M.B., Smith N.B.. Adaptive Real-Time Closed-Loop Temperature Control for Ultrasound Hyperthermia Using Magnetic Resonance Thermometry. Concepts in Magnetic Resonance Part B (Magnetic Resonance Engineering), 2005,Vol. 27B,No1,p.p. 51–63
Seip, R., VanBaren, P., Cain, C., Ebbini, E. Noninvasive real-time multipoint temperature control for ultrasound phased array treatments, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control 43, no.6, (1996): 1063-1073
Kohout, B. Transducer Array Calculation (TAC) GUI.http://www.mathworks.com/ matlabcentral/fileexchange/35657- transducer-array-calculation-tac-gui.

Study on Arcing Phenomenon in Electroslag Remelting Process

Thu, 11 Sep 2014 14:25:54 +0300

Arcing often happens in the electroslag remelting(ESR) process and will lead arc point on the ingot surface which affect the quality seriously of ESR ingot. In this paper, the causes of arc point were analyzed for 200kg iron-chromium alloy ESR ingot and influence factors of causing arc point were studied by industrial experiment. The results show that the measures that control of low voltage and high current of the power system and using the Al₂O₃×24%＋CaO×3%＋CaF₂×70%＋MgO×3% slag can prevent the generation of arc spot for the for 200kg iron-chromium alloy ESR ingot effetely and to improve the stability of the smelting process greatly.

Key Words: ESR, Arc spot, Power system, Refining slag

Study on Arcing Phenomenon in Electroslag Remelting Process

Shufeng Yang¹, Jing she Li¹, Wei Liu¹, Xiangzhou Gao, Gang Li^1,2

¹School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing

² Beijing Shougang GITANE, Beijing.

Introduction

The process, that the power pole was melted by the high temperatures which generated from the slag resistance region by the large current through, is called ESR process [1]. The main loop of the smelting process is composed of the electrode, slag pool, metal bath, steel ingot, tank bottom and short net and transformers [2]. The main circuit current is not smooth when the process parameters are instability sometime, which leads to divert traffic between the ingot and mold. If the divert traffic is too high in one place, the slag jacket will rupture, and arc discharge is generated due to the conduction between the ingot and mold, resulting the holes formed in the ingot surface [3]. At present, there were few reports on arcing phenomena in remelting process. In this paper, effect of power systems, the composition of slag and thickness of the slag layer on arcing was studied in electroslag remelting process.

Industrial Experiments

The electrodes used in this experiment are cast from smelting furnace, the diameter is 140mm, and the capacity of electroslag remelting furnace is 200kg. The main parameters of electroslag process were shown as Table I.
The arc points appearing in smelting process are shown as Figure 1. As can be seen from Figure 1, the ESR ingot body is impacted to produce some small holes. It brought to the defects for surface quality and internal organization of the ESR ingot, and is not conducive to the subsequent forging rolling process.

Table 1 Parameters in ESR smelting process

Ingot shape/kg	Smelting time/min	Amount of slag/kg	Thickness of lower slag layer /mm	Upper slag layer thickness/mm	Slag composition
200	82	12	95	110	24%Al₂O₃+5%CaO +71%CaF₂
Electrode diameter/mm	Voltage/V	Electric current/A	Water Pressure/MPa	Slow cooling method	Inlet pipe size/mm
140	55	5500	4	Sand burial	60

Figure 1. The arc points in the ingot surface

The ingot is cut along the position where the arc point appeared, and the sectional is pickled corrosion. It can be seen from Figure 2, the arc point has a certain depth, and dendrites along the direction of the arc point become equiaxed and extend to the core part. It can be inferred, arc phenomenon is generated that current breakdown from the ingot external to the internal. Dendrites are re-melted and then solidified by discharge phenomenon of the department, after the formation of it, and then the equiaxed is formatted because of the smaller thermal field gradient surrounding. The grain is large and loose, and undermines the continuity of the columnar grain. The arcs point is deep, and affects the finished product rate.
The instability of the process parameters, the series of problems caused by such as current, the furnace mouth voltage electrode buried depth and the gradual increase thickness of the slag layer, are likely to lead to arcing[4].

Figure 2. The arc points in the sectional of ingots

Results and Discussion

3.1 Power System

The power parameters are explored by regulating the voltage and current in smelting process. Current is less stable in the process that the process current increased from 5000A to 5500A, when voltage to 50V. The current is stability in the range 5200A-5300A in the process, when voltage to 45V. Metal pool depth and the depth of electrode buried is ideal match. This is because that, when the voltage is too high, the electrode buried depth will be too shallow, electro-slag process will become unstable, electrode will float in the slag surface, current will fluctuate, and the slag surface temperature will be too high. This will result that, gas and inclusion in ingot increased, burning of alloying elements increases, especially easily oxidized elements. Simultaneously it result the surface of the ingot is in a poor shape. Therefore, the ideal process parameters are determined as follow: voltage 45V, current 5250A (± 50 A).

3.2 Slag Composition

In order to study the effect of slag on arc points in the smelting process, the changing of the ratio of slag system were tested. The experimental schemes of different slag are shown in Table 2.

Table 2 Experimental schemes of different slag

	Al₂O₃/%	CaO/%	CaF₂/%	MgO/%
Scheme 1	24	5	71
Scheme 2	20	5	75
Scheme 3	15	3	82
Scheme 4	15	8	77
Scheme 5	24	5	69	2
Scheme 6	24	3	70	3

The trial involved four kinds of components and the effect of slag component on thermo-physical properties of system is shown in Table 3:

Table 3 Thermo-physical properties of different slag components

Slag Component	Melting point /℃	Impact on the viscosity	Impact on conductivity
CaF₂	1270-1350℃	Reduced Significantly	Improve
CaO	2580℃	Reduced	Reduced
Al₂O₃	2050℃	Improve	Reduced Significantly
MgO	2852℃	Improve	Reduced

It is concluded through different slag experiments: 1) the establishment of the remelting process stabilizes gradually, when Al2O3 is from 24% to 15%. However, it leads to lower melting temperature of the slag, due to reducing significantly of the resistivity of the slag. And then the heat of the slag is not enough, quality problems is prone to generated, and the point of the arc is generated most likely in the surface of the ingot. 2) When a certain amount of MgO is added, slag smelting stability has improved to some extent, plastic and peeling slag clothing has been some improvement. 3) Since MgO and CaO increases the viscosity of the slag, a certain amount of the CaO content should be reduced while the amount of MgO added, in order to ensure that the slag having a certain degree of mobility. 4) Slag system is relatively stable in the smelting process of Scheme 6, and the ingot surface quality is better.

3.3 Thickness of the slag layer

It has taper along the axial of 200kg ingot mold, the cavity cross-section changes in time, which lead to the change of slag pool depth in melting process. Catchy is 210 mm and bottom is 240 mm, resulting the depth of catchy slag pool is 30% more than the bottom. The refining effect is different due to changes in the upper and lower slag pool depth. The appropriate amount of slag should be selected, so as to ensure the gap of smelting environment is smaller before and after. It is 5% -10% of the consumption residue accounts of slag clothing in the ingot surface (The slag clothing thickness is calculated as 0.5mm-1mm). Variations thickness of the slag layer in bottom and top with the amount of slag is shown as Table IV.
When the amount of slag is 12kg and 16kg, current has some fluctuated in smelting, and it is large in smelting late. When the amount of slag is 10kg, current is very stable in pre-stage, and it has a certain degree of volatility in late stage. When the amount of slag is 8kg, current is stable in pre-stage and mid-stage, and it has a slightly fluctuations in the latter.

Table 4 thickness of slag layer changes with different amount of slag

Amount of slag	the slag layer thickness of bottom	the slag layer thickness of top
8kg	60-65 mm	80mm
10kg	75-80 mm	95mm
12kg	90-95 mm	110mm
16kg	120 mm	140mm

When the amount of slag is 12kg and 16kg, there is more arcs point in the ingot surface. It still has a small amount of arc spot when the amount is 10kg. There is no arc spot when the amount is 8kg, and its surface quality is better. As can be seen from the above phenomenon, the thickness of slag layer is thicker, the molten metal bath is shallower, and the depth of the electrode buried reduces passive, lead to instability of the electrical parameters, thereby affecting the quality of ingot smelting. The correctness and rationality of the simulation, that the slag pool depth on the current density and temperature field is verified directly from the relationship between the stability of the current and the amount of slag.
Sum up, it is can be guaranteed a good stability of the electrical parameters, and also having good slag jacket peel ability, uniformity thickness of slag coat and better surface quality of ingot, what the amount of slag is 8kg.

3.4 Optimization Process

Based on the above results, the optimization smelting has been carried out, which the voltage is adjusted to 45V, current is controlled for 5250A (± 50 A), and 8kg slag Al₂O₃ × 24% + CaO × 3% + CaF₂2 × 70% + MgO × 3% is used in the smelting process .The structure and surface of ingot after optimization is shown in Figure 3.

Figure 3. The structure and surface of ingot after optimization smelting

As can be seen from Figure 7, columnar crystals distribute evenly and consistency, the surface is dense and smooth, quality is good, and there is not arc point of the ingot, after the process is optimized. Therefore, the optimization process can effectively verify and solve the problem of the arc point in ingot surface.

Conclusions

The low voltage and high current of the power system is advantageous to the stability of electroslag remelting smelting process. The ideal parameters of power system are voltage 45V and current 5250A (± 50 A) for 200kg ingot.
Using Al₂O₃×24%＋CaO×3%＋CaF₂×70%＋MgO×3% slag can improve the stability of the smelting process and the smelting effect greatly.
The deep slag pool is prone to make arc phenomenon and can thin slag avoid generating arc effectively.It is can be guaranteed a good stability of the electrical parameters and also having good slag jacket peel ability, uniformity thickness of slag coat and better surface quality of ingot, what the amount of slag is 8kg for the 200kg ESR.

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (Grant No. 51304016 )

References

Fu Jie, Chen Enpu, Zhu Jue. The Arcing of Slag pool in ESR Process[J]. ACTA METALLURGICA, 1965, 5(8): 8-16.
Huang Yongjie, Zhang Xiang, Ma Shaoxuan. Reasons and Solutions of Electric Leakage during ESR Process [J].Heilongjiang Metallurgy, 2001, 11(2): 24-26.
Wu M, Ludwig A. A three-phase model for mixed columnar-equiaxed solidification[J]. Metallurgical and Materials Transactions A, 2006, 37(5): 1613-1631.
Ballantyne A S, Kennedy R J, Mitchell A. The influence of melting rate on structure in VAR and ESR ingots[C]//reference source: Proc. 5. sup. th International Conf. Voc. Met. & ESR. 1976: 181-183.
Ballantyne A S, Kennedy R J, Mitchell A. The influence of melting rate on structure in VAR and ESR ingots[C]// Kr ger J G, Pl ckinger E, Winkler O, et al. Proceedings of the 5th Inter. Conf. on Vacuum Metallurgy and Electroslag Remelting Processes. Munich, Germany: Leybold-Heraeus GmbH &Co., 1976:181-183.

Current approaches to the training of mining engineers

Mon, 28 Jul 2014 10:24:46 +0300

In the article the main current approaches to the training of mining engineers were reviewed. Attention were focused on the person-centered, competency-based, systematic and problem-based approaches. Competences that should be formed in the future mining engineers (personal and social, general scientific, instrumental, general professional, special professional) were defined.

Current approaches to the training of mining engineers

Volodymyr Morkun

Kryvyi Rih national university
11, ХХІІ partz'izdu, Kryvyi Rih, 50027

Zinaida Bakum

Kryvyi Rih national university
11, ХХІІ partz'izdu, Kryvyi Rih, 50027

Keywords: current approaches, competences, competencies, mining engineer, educational objectives.

Analysis of scientific literature shows that each stage of Pedagogics of higher school is characterized by certain approaches. Observation and experience give grounds to state that in the mining engineer training at the current stage the following approaches should be implemented:
1) person-centered (I. Bekh, S. Goncharenko, S. Rubinshtein, O. Savchenko); 2) competency-based (O. Ovcharuk, H. Pometun, S. Sysoieva, O. Savchenko, A. Hutorskoy); 3) systematic (S. Karaman, N. Nychkalo); 4) problem-based approach (M Mahmutov).
In the current context of Higher School person-centered training is dominated, it involves providing optimal conditions for the all-round development of each student, taking into account his/her individual characteristics, cognitive needs, interests and stimulation of independence in various subjects study. Taking all of this into account, person-centered approach can be considered as the main approach that characterizes the current stage of higher school Pedagogics development. Its approval has been caused by changes taking place in society, which gradually turns from industrial to information, places new demands on graduates.
Noted approach in mining engineer training can be realized through the variation of updated educational objectives: the formation of a high level of professional competence and mobility, broad mind, which is based on knowledge of related subjects connected to the major branches; the development of high creativity, which is implemented in creative thinking during solving complex engineering problems in the information environment; the study of the state and dynamics of engineering productivity and intellectual production market at the regional, inter-regional, national and international levels; taking into account the personal organization role of professional engineer in shaping of engineering type thinking, in his own way of entering the engineering culture and professional creativity, etc.
So, person-centered approach ensures the development of the personality, based on the identification of the individual characteristics of the student as the subject of knower and substantive activity.
The competency-based approach, the implementation of which involves students acquiring of necessary life or key, subject or industry competences completes a number of classical approaches. During the implementation of competency-based approach knowledge is acquired, skills deal with improvement of competences are shaped. Under the circumstances, the primary target is not the presence of a certain amount of knowledge, personal skills, but the ability to apply competences in specific situations.
The aim of competency-based approach is to shift in the emphasis from the accumulation of certain regulatory knowledge and skills to the formation and development of the students' ability to act practically, to use individual techniques and experience of successful actions in situations of professional activity and social practices. In other words, it promotes the formation of professional competence.
Professional competence of a mining engineer is considered by scientists as a system of organizational, technological, planning and design, management, social and communicative knowledge and skills, professionally important qualities that ensure their successful implementation and adaptation in professional activity [2].
On the basis of professional competence the definition of engineering competence of the future specialist is based. Researchers in the field of engineering education consider an engineering competence as the presence of fundamental basis in specialist; educational engineering competence as the ability to combine theory with practice; engineering education as knowledge of social, economic and cultural conditions that are shown in the workplace; graduate’s engineering competence as the ability to adapt to the technologies that change constantly, and social conditions; specialist’s engineering expertise as the ability to use the means of interpersonal communication effectively [1, 10].
Nowadays the following system of key competences of future specialists of engineering specialties is pointed out: motivational (for successful acquisition of professional orientation); personal (involves a readiness to the constant improvement of the educational level, needs for implementation of self-potential, the ability to self-education); social (forms: the ability to take responsibility; to make decisions together with others; different religions and ethnic cultures tolerance; reconciliation between the personal interests and the needs of the enterprise and society); methodical (it develops the ability to obtain information independently, to find ways of problem solving, do paperwork); science (it involves data handling of physical phenomena, chemical processes, performing of calculations and application of mathematical apparatus); humanitarian (it promotes reading and translating of foreign documents, mastering of labour and law legislation, psychology of communication); general professional (it involves acquiring of specialized knowledge); special (it promotes the familiarization of production technology).
For example, in the educational and qualification characteristic (EQC) field of knowledge, "Mining of useful minerals" training direction "Mineral processing" qualification "Specialist in the field of mineral processing" competences which should be formed in the future mining engineers: social and personal; general scientific; instrumental; general professional; special professional are defined [3; 4].
Great potential for the formation of professional competence of future mining engineers is laid in studying of the fundamental (mathematics, physics, chemistry, geometry, mathematics, etc.) and professional disciplines ("Fundamentals of the mining industry", "Labour Protection", "Geotechnology in the mining", "Ecology" "Land recultivation", " Rock failure and blast safety", "Fundamentals of the transport theory ", etc.).
Mathematics is the universal language for describing various processes and phenomena of nature, without which it is impossible to solve modern engineering problems, including mining. Studying the experience of mathematical training of mining students in higher educational institutions has shown that quite often it is based on not competent, but subject and knowledge paradigm, that involves the acquisition of basic mathematical knowledge and skills. Junior students are usually not aware of the importance of mathematical knowledge in mastering future profession, poorly motivated to study mathematics course and demonstrate a low level of knowledge. Freshmen, as experience shows, cannot correlate the presence of mathematical knowledge to solution of interdisciplinary and professionally oriented mathematical problems.
Senior students have already been aware of the importance of mathematical knowledge in mastering of special disciplines, but have difficulties in their use during the studying of special subjects.
Analysis of curriculums, math programs, textbooks, and methods of teaching mathematics has shown:

all the mathematical disciplines are studied mainly on the first and second year of university, and special courses related to their future profession are studied on the senior;
math programs are not sufficiently focused on the future profession, their content is not pointed at the necessity of applying of investigated mathematical methods in studying professionally oriented tasks;

3) in the process of mathematical training of mining students low active methods and teaching techniques with targets for the formation of basic skills only are commonly used;
It will be recalled that in the final stage of training at the university future miners study disciplines related to geodesy and surveying, mining machinery and equipment, the mechanics of underground structures, processes of open-pit mining, exploitation of mining equipment, pit designing, mine ventilation, mineral dressing. In the process of teaching of these disciplines mathematical apparatus is used, but senior students as well as junior, have considerable difficulties in applying mathematical knowledge beyond mathematics, in particular in the field of engineering tasks.
Taking in consideration the above, we can state that in the process of teaching mathematics it is necessary to form mining students’ mathematical competence - a set of learned mathematical knowledge and methods of mathematical activity, the experience of their use in problem solving that are beyond the subject, and serve as a basis for professional problem solving [61].
Thus, competency-based approach does not conflict with the academic but deepens, expands and completes it.
Interest in systemacity of investigated objects is now one of the main methodological aims in many fields of science. This aspect is directed to a deep insight into the relationship of categories of the whole and its parts, the interaction of elements and systems. Studying of different systems occurs through a systematic approach, which aim is to develop methods of research and construction of organizationally complex objects as a system. In didactics mentioned approach is aimed to show the integrity of the pedagogical objects, identify different types of links in them and gather them into a single theoretical system. Taking this mining engineer must have profound knowledge of fundamental sciences, an excellent knowledge of the equipment and technology, mastering technical drawing techniques and computer equipment, navigate freely in the economy and the industrial management.
For example, in the context of a systematic approach realization to the process of mining engineer training it is necessary to take into consideration the transformation of engineering education in the field of learning of cognitive and engineering activities, which fundamentally changes the idea of the higher educational establishment. An important direction of engineering education development is a special organization of student’s work throughout the training in the complex multidisciplinary practical-oriented groups, organic engagement of students to creative activity, ensuring their mass participation in scientific and research work, creating goal-defined forms of training. All these create the preconditions of transition in engineering education from educational to scientific and educational process.
Training of mining engineers is based on problem-based approach, which ensures cooperation of teachers and students. In such approach the student is not only the object but also the subject of study. The basic strategy of the teacher is to identify individual potential and bent of the subject of education, create the conditions for the further development, self-knowledge and self-development in a purposeful and harmonious formation of skills, such as analytical and synthetic, perceptual-mnemonic, creative, etc..
To implement problem-based approach in the course of studying of various disciplines students can use models of educational games such as "Analysis", "Solving", "Industrial accident in the mine", "Scientific and Technical Seminar." It is also necessary to conduct a lecture/analysis of the particular professional simulation (PPS), a lecture presentation, create a simulation bank, named "Storage of solved particular professional simulation." To organize the round table discussion on the theme: "Youth for safe work," "Man-made influences of MC (mining complex) on the environment." At this stage, the professional identity begins to form, providing reflexive perception and confirmation of effective internal and external professional identity in a particular area of professional activity, therefore seminars on the theme: "Mineral Resources of Ukraine", "Reconstruction, modernization and development of the oil pipeline system", which contribute to the development of organizational, planning and design, technical, socio-communicative and managerial skills become very important.
Today it is necessary to select certain models on the basis of which it is possible to analyze and develop the educational process: an approach in terms of content, in which the set of students’ knowledge opportunities is the main; approach in terms of the learning process, during its implementation real phenomena occurring in the classroom, when students with the teacher carry out cognitive activities, must be analyzed; approach in terms of results aims at a specific set of competences (knowledge, skills, attitudes, etc..), which have been mastered by the students - future specialists.

References

Belonovskaya, I. D. Formation of a specialist’s professional competence: regional experience. Moscow: Institute of professional education development, 2005.
Golovan M. S., Yatsenko V. V. The essence and the meaning of "research competence". Theory and methodology of fundamental disciplines in higher educational institution: collection of research papers №4. Kryvyi Rih, 2012
Educational and qualification characteristics. Bachelor (optional included). Field of knowledge 0503 "Mining of useful minerals". Kryvyi Rih, 2013
Bachelor Educational and professional program (optional included). Training direction 3.050303 "Mining of useful minerals". Kryvyi Rih, 2013
Komarova, Nataliya.Formation of readiness of future mining engineers to professional activity in the study of natural sciences at the university. Ph.D diss., Kaluga, 2012.

Production of Anticorrosion Coating Material by Converter Dust with MgO and Cr2O3

Tue, 09 Sep 2014 14:26:29 +0300

Using converter dust as, adding MgO and Cr2O3, a high anticorrosion solid coating material was produced. The influences of adding MgO and Cr2O3 (ranging 10%~20%) on the performance of high anticorrosion solid coating were studied. The results show that when the amount of MgO(10%~20%) in converter dust increases, feeding MgO and Cr2O3 is beneficial to the decrease of coating solid component, but feeding only Cr2O3(10%~20%) has little effect. Thus, it is advisable to add MgO and Cr2O3 to improve the resistance of the coating to salt water and acid. The coating of 120h acid corrosion was almost no corrosion phenomenon.

Key words: converter dust, anticorrosion coating, salt spray test, MgO, Cr2O3

Production of Anticorrosion Coating Material by Converter Dust with MgO and Cr2O3

Hui Li ¹, Jinglong Liang ¹, Fei Hao ¹，Shufeng Yang ²

¹Key Laboratory of Ministry of Education for Modern Metallurgy Technology, College of Metallurgy and Energy, Hebei United University, Tangshan 063009, China ,ljl@heuu.edu.cn
²School of Ecological and Metallurgical Engineering University of Science and Technology Beijing

Converter dust is a kind of byproduct achieved by cooling and filtering the converter flue gas in steelmaking process. The dust is characterized with large amount, fine granularity and high metal content and can be used as fillers to make ecofriendly coatings [1]. In addition, the dust is rich in oxides, such as SiO2, CaO, MgO, and Cr2O3 [2], of which MgO is usually employed as inorganic fillers with good insulation (the thermal conductivity is about 341.3W·m-1·k-1); it is also widely used to produce high-temperature refractory materials and coatings [3] based on its thermal conductivity. Cr2O3 plays as an important ingredient in the production of colorant, which generally does not react with acid or alkali solution and is with great corrosion resistance. The current study focuses on the influences of different amounts of MgO and Cr2O3 on the performance of high anticorrosion solid coating [4,5] which is made of converter dust.

1 Experimental scheme

Table1 Experimental formula of added oxides

No.	Fillers					Epoxy resin/g	Thinner/g
No.	Converter dust/g	Mica powder, quartz powder, talcum powder/g		Oxide/g	Total amount/g	Epoxy resin/g	Thinner/g
1	7.74	0.39	0.77		9.68	9.68	0.97
2	7.41	0.39	1.11		9.68	9.68	0.97
3	7.10	0.38	1.42		9.68	9.68	0.97

The total amount of the coating is 30 g and the fillers contain converter dust with a certain amount of stone powder, quartz powder and mica powder. The proportion of converter dust is 3%-5% (4% in this experiment), flatting agent 0.5%- 1% of the main reagent (0.75% with the actual amount is 0.22 g in this experiment); thixotropic agent 0.25%- 0.5% of the main reagent (0.3% with the actual amount of 0.09g in this experiment); dispersant agent 0.5%-1% of the main reagent (0.75% with the actual amount of 0.22g) coupling agent 0.25%-0.5% (0.3% with the actual amount of 0.09g), as shown in Table 1.
The amounts of MgO and Cr2O3 are 10%, 15% and 20% respectively in studied cases. The experimental arrangements are shown in Table 2.

Table2 Experimental arrangements of added oxides

No.	Dust particle / size		Fillers/g	Thinners/g	Oxide/%
1		250	100	10	10
2		250	100	10	15
3		250	100	10	20

The converter dust was firstly filtered by a sifter of 250 meshes. Epoxy resin, thinners, sifted converter dust and promoters were mixed and stirred to get the agent with the consistent content. Then, the agent was coated on the surface of a steel plate, and was dried to measure the performance of the coating.
Laser Particle Size Analyzer (LPS) of JL-1177 and the fluorescent spectroscope, Quanta 650 FESEM, Zeiss microscope, NK-2 viscosity cup, Axiovert200MAT and Salt spray devices were employed to analyze and test the coating.

2 Results and Discussion

Fig. 1 shows the result of the coating surface and the salt fog test without adding oxides. Small shrinkage cavities can be discovered on the surface. After the salt fog test, big corrosion pits and a few corrosion points appear. And after the resistance to acid test, dispersed corrosion points show up on the sample surface.

Fig.1 The result of the coating surface and the salt fog test without adding oxides
(a) coating surface (b) the result of NSS (c) the result of ASS

2.1 The influences on the coating and the coating surface after adding oxide

Different amounts of MgO and Cr2O3 were added and stood for some moments and then observed to test the coating surface. There appears a certain gloss on the coat surface without layering, precipitation or skinning. As the amount of MgO increases from 10% to 20%, the bubbles on the coat surface increase as well. There appears a certain gloss after adding Cr2O3, without layering, precipitation or skinning. Cr2O3 belongs to green fillers. With increased amount of Cr2O3, the color is changed. The coat appears dark green when Cr2O3 reaches 20%.
Zeiss microscope was used to observe the curing coat with different adding amounts of MgO and Cr2O3, which are shown in Fig 2. It can be drawn in the figure that the shrinkage cavities get bigger when oxides are feed. As the amount of MgO and Cr2O3 increases, the shrinkage cavities get increasingly bigger. When the size of MgO and Cr2O3 in the experiment is -2000, the powder is ultrafine, and much likely to gather and then form secondary particles, which means that the particle size increases easily. In addition, the surface of MgO is hydrophilic which is tend to hydrate into Mg(OH)2 and then dissolve the oxide in air or water. Thus air bubbles are easily to generate.

Fig.2 Influence of adding MgO and Cr2O3 on film(a) 10% MgO (b) 15% MgO (c) 20% MgO (d) 10% Cr2O3 (e) 15% Cr2O3 (f) 20% Cr2O3

2.2 The influences on the viscosity and solid component of coatings after adding oxides

Fig.3 The change curve of coating viscosity and solid after adding oxides

After adding MgO and Cr2O3, the test results of the viscosity are shown in Fig 3(a). When the amount of the oxide is increased, the viscosity increases. The viscosity increases more apparent when the same percent of MgO is added. When the percentages of MgO and Cr2O3 are both 10%, the viscosities are 153.25Pa·s and 163.68Pa.s respectively; when 15%, the viscosity of MgO case is 4.18Pa·s larger than that of Cr2O3. This is due to particle size is thinner for MgO, and the inelasticity increases which encourage the increase of viscosity. In addition, the epoxy resin in coat is mostly acidic, and MgO is alkaline oxide. Therefore, the viscosity appears a tendency of apparent increase. Considering the influence of MgO on the viscosity, the amount of MgO cannot be added too much.

After adding MgO and Cr2O3, the change of coating viscosity and solid are shown in Fig 3(b). With the amount of MgO and Cr2O3 of 10%, 15% and 20%, the solid components of the coat are all larger than 99.0%, which can satisfy the solid coat. After adding MgO into the converter dust, the distribution curve becomes steady. But after adding Cr2O3, the solid component plummets. Considering the amount of the volatile matters content in high solid anticorrosion coat, the adding of MgO has no influence but after adding Cr2O3, the solid of the coat falls quickly. So the adding amount of Cr2O3 cannot be too much.

2.3 The influences on film attachment and hardness after adding oxides

Adhesion test and film coating thickness meter were used after adding different amounts of oxide into converter dust to test the attachment and hardness. The result is shown in Table 3. When the amounts of adding MgO are different, the expulsion rates are 3%, 2% and 5%. After adding MgO and Cr2O3, the solid hardly changes. It is shown that the attachment and hardness are seldom influenced by the amounts and types of the fillers added in the converter dust.
Table 3 Influence of adding oxides on film attachment and hardness

The oxide added the amounts of /%		The left tables	Expulsion rate/%	Solid
MgO	10	96	4	4H
	15	100	0	4H
	20	98	2	5H
Cr2O3	10	97	3	5H
	15	98	2	4H
	20	95	5	5H

2.4 The influence on the coating anticorrosion after adding oxides

1) The resistance to salt water for the film coating
The resistances to salt water test was carried out to the prepared coating film for 120h. Observe the corrosion status by Zeiss microscope in 200 times zoom, as is shown in Fig 4.
Compared with (b) in Fig 1, it is clear that after adding MgO in the converter dust, the resistance to the salt water increases greatly. But the resistance changes little. It is known from (b) in Fig 4 that there is a big corrosion point on the surface of the film coating after adding 15% MgO, but there are no other obvious corrosion points. It is known from (a) and (c) in Fig 4 that when the amount of MgO are 10% and 20%, after the salt fog corrosion, there are a few corrosion points on the surface of the film coating, which is slightly corroded. It is known from (e), (f) and (g) that after adding 10% Cr2O3, there are more corrosion points on the surface, while when the amount is 20%, the film coating is perfect.

Fig.4 NSS results after adding MgO and Cr2O3 (a) 10% MgO (b) 15% MgO (c) 20% MgO (d) 10% Cr2O3 (e) 15% Cr2O3 (f) 20% Cr2O3

2) The resistance to acid of the film coating
After adding MgO and Cr2O3, the prepared film coating as color fillers is tested by the acid salt fog test. And then in Zeiss microscope roomed to 200 times, the corrosion status is shown as Fig 5. Compared with (c) in Fig 1, the resistance to acid increases.

Fig.5 ASS results after adding MgO and Cr2O3(a) 10% MgO (b) 15% MgO (c) 20% MgO (d) 10% Cr2O3 (e) 15% Cr2O3 (f) 20% Cr2O3

It can be seen from Fig. 5(a) and (b) that when the adding amounts of MgO are 10% and 15%, after the salt fog corrosion, there are a few corrosion points on the surface of film coating. When the amount is 20%, the film coating is perfect without corrosion points, as is shown in Fig 5(c). It is clear that with the amount of MgO increases, the resistance to acid of the film coating is strengthened. Fig 5(e) shows that after adding 10% Cr2O3, after the salt fog corrosion, there appear many big corrosion points. With the increase of the amounts, the corrosion points decrease. When to 20%, the film coating is perfect, with no corrosion.
The prepared film coating as color fillers are filmed on the silicon steel sheet. When it is corroded, MgO can be corroded as cathode, which can protect the substrate from being corroded. In addition, MgO, used as fillers, which is usually combined with SiO2, exists as 3Mg·4SiO2·H2O. Its oil-absorbed value is high, which can be used to improve the rheological properties, reduce the contraction stress in the film and avoid appearing cracks and voids. At the same time Cr2O3 does not easily make reactions with acid and alkali. When it is added into the converter dust as color fillers, it can increase the resistance to corrosion of the film coating. So, adding MgO and Cr2O3 can both increase the anticorrosion of the film coating.

3 Conclusions

1) The viscosity of the coating increases with the increasing amounts of MgO and Cr2O3, and goes up more obviously by adding more MgO. When the amounts increased to 15%, the viscosity increased largely with adding MgO and is 4.18Pa.s bigger than adding Cr2O3. The paint solids are more than 99% when adding MgO and Cr2O3 separately for 10%, 15% and 20%, but the value slightly changes by adding more Cr2O3.
2) Shrinkage cavities are generated on the surface of film coating by feeding MgO and Cr2O3 in the converter dust, and tend to be bigger when more MgO and Cr2O3 are added.
3) The performance of the high solid anticorrosion coating is improved by adding 10%~20% MgO and Cr2O3 in the converter dust. After adding MgO, the resistance to salt water is enhanced greatly, and it's not sensitive to the amount of MgO. And with the increase of Cr2O3, the resistance of the coating against salt water and acid goes stronger. The coating of 120h acid corrosion test showed nearly no corrosion sign.

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (Grant No. 51104054)

References

[1] Hao Fei, Li Yungang, Li Jing. Anticorrosive coating production method with converter dust gas as filler[J]. Energy for metallurgical industry, 2013，32(3):52-54.
[2] Chen Weixing, Hou Yonggang, Shi Yu. Coating and its detection technology[M]. Beijing: Chemistry Industry Press, 2011:71-73.
[3] Zhai Huazhang, An Xiaoqiang, Cao Chuanbao, Wang Fuchi, Cai Hongnian. Synthesis and characterization of MgO single-crystalline one-dimensional nanostructures[J]. Rare metal materials and engineering, 2008，37(Z1)：667-670.
[4] Zhan Zhenyi. Research and development of anti-corrosion coatings[J]. Henan chemical industry, 2011，28(2):19-21.
[5] Lu Gang. The trend of high solid anti-corrosion coatings development and product promotion and application[J]. Chemical industry, 2013，31(4):35-40.

Environmental competency of future mining engineers

Wed, 17 Sep 2014 15:21:10 +0300

Environmental competencies of future mining engineers are determined in this article.

Key words: environmental competency, future mining engineer, law on mining, sustainable development

Environmental competency of future mining engineers

Vladimir Morkun

Vice-Rector for research, Doctor of Science, professor of Computer Science,

Automation and Control Systems department

Kryvyi Rih National University

Svitlana Hryshchenko

Senior inspector of research and training sector in teaching department,

Information and communication technologies in education

Kryvyi Rih National University

Sergey Semerikov

Doctor of Science Professor,

Information and communication technologies in education

Kryvyi Rih National University

The main regulatory document determining the judicial and basic arrangements for the activity of mining engineers concerning mining works performance, securing emergency protection of mining plants, establishments and organizations is the Law on mining of Ukraine[1, article 5].
A.M. Khasna [3] considers the contribution of the principals stated in the article 7 of the Low on mining of Ukraine into social, economical, ecological and technical development as the function of sustainable development – model of resource use, focused on the satisfaction of human’s wants when preserving of the environment in such a way, that all these wants could be satisfied not only by current generations but also by future ones. In such a way state policy in mining industry focused on the sustainable development of mining industry, science and education.
The main environmental requirements in the field of mining works, prevention of ill effect of mining works and securing of ecological safety during mining works is not only a subject matter of certain articles of the Low on mining of Ukraine, but also obligate constituent of preparation of environmentally competent mining engineer [4; 5; 6].
The results of determining and analysis of environmental competence of future mining engineer are given below.
N.M. Bibik determines competence as “estranged from the subject predetermined social norm (requirement) for educational attainment…, necessary for its qualitative and productive activity in certain field, i.e. socially fixed result” [2, 409]. Precisely in such a way, as predetermined requirement, each of the competences of mining engineer was determined. But “the result of competency acquirement is the competency, which supposes personal characteristic, attitude to the nature of business. Competences may be taken out as real requirements for acquisition of knowledge, work methods, experience of behavior in certain branch of knowledge, qualities of a person, which acts in society” [8, 409].
By definition of DeSeCo specialists ecological sustainability is the basis for key competences of a person connected with his success in society [7, 6]. Consideration of environmental competency is better to fulfill at three levels:

On the educational level of environmental culture and ecological conscienceness (works of S. V. Alekseev, A. V. Gagarin, A. A. Glazachova, L. S. Glushkova, N. V. Gruzdeva, D. S. Ermakov, A. V . Makoedov, S. Yu. Nefedova, N. V. Romeyko, L. M. Titarenko, L. S. Chopenko, Yu. A. Sharonova).
On the obligatory for all professional level of ecological literacy ( works of S. V. Alekseev, A. V. Gagarin, G. M. Galiev, L. S. Glushkova, A. V. Gurenkov, A. M. Dzyatkovskaya, D. S. Ermakov, S. A. Zhdanova, A. N. Zakhlebnyy, K. A. Makarova, N. V. Nasurova, N. Yu. Oleynik, I. V. Petrukhin, L. E. Pistunov, N. V. Romeyko, L. M. Titarenko, V. I. Tomakova, A. L. Khripunova, A. A. Shul'pin).
On the special professional level of environmental competence (works of E. L. Bazarov, V. F. Budnik, L. I. Budnik, G. M. Galiev, A. V. Gagarin, A. A. Litvinova, S. Yu. Nefedova , L. E. Pistunov, A. N. Ryabov, A. L. Khripunov, Yu. A. Sharonova, A. A. Shul'pin).

The carried out analysis gives the possibility to determine environmental competence of future mining engineer as personal formation, which includes the acquired during preparation profession-oriented environmental awareness (cognitive component), adopted ways for securing environmentally safe mining works (praxeological component) in the interest of sustainable development (axiological component) and the qualities of socially responsible ecological behavior (socially- behavioral component) are formed.
By definition, formation of environmental competency of future mining engineer happens during professional education of bachelors, specification 6.050301 “Mining”, that is why for determination of environmental competencies we will refer to the components of developed system of socially-personal, instrumental, general scientific, general professional and specially professional competences of future mining engineer (fig. 1.3).

Figure 3. Environmental competences of future mining engineer

Summarizing, we would like to mark that environmental competency of future mining engineer – personal education, which comprises the acquired during preparation professionally oriented environmental knowledge (cognitive component), adopted ways for securing environmentally safe mining works (praxeological component) in the interests of sustainable development (axiological component) are foremost, the qualities of socially responsible environmental behavior (socially-behavior component) are formed.
Formation of environmental competency is fulfilled during acquirement of the following:

Socially-personal competences: understanding and perception of ethical norms of behavior in respect to other people and nature (bioethics principals); ecological literacy;
General scientific competence: deep knowledge in ecology necessary for usage in professional activity;
Generally professional competence: the ability to use scientific lows and means during evaluation of environmental condition, participate in environmental works, make ecological analysis of events in the field of activity, develop plans on events concerning reduction of manmade load on the environment;
Special professional competence: securing of ecologically balanced activity, working knowledge of reasonable and integrated development of geo-recourses potential.

References

Low on mining of Ukraine: Low No 1127-XIV. The Verkhovna Rada of Ukraine. 06.10.1999. Access mode:http://zakon0.rada.gov.ua/laws/show/1127-14.
Bіbіk N. M. Kompetentsii [Competences] Kiev .Yurіnkom Іnter, 2008. P. 409 – 410.
Hasna A. M. Dimensions of sustainability (2012). Journalof Engineering for Sustainable Development: Energy, Environment, and Health. No (1) 2, p. 47 – 57.
Morkun V. S., Morkun N. V, Pikilnyak A. V. Iron ore flotation process control and optimization using high-energy ultrasound(2014).Metallurgical and Mining Industry, No 1, р.р. 36 – 42.
. Morkun V. S., Morkun N. V, Pikilnyak A. V. Modeling of ultrasonic waves propagation in inhomogeneous medium using fibered spaces method (k-space)(2014).Metallurgical and Mining Industry, No 1, р.р. 43 – 48.
Morkun V. S., Morkun N. V, Pikilnyak A. V. Ultrasonic facilities for the ground materials characteristics control (2014).Metallurgical and Mining Industry. No 1, р.р. 31 – 35.
Report of the World Commission on Environment and Development: Our Common Future [Electronic resource] . United Nations, 1987. 300 p. Access mode : http://www.un-documents.net/our-common-future.pdf
The Definition and Selection of Key Competencies : Executive Summary [Electronic resource]. 20 p. Access mode :http://www.oecd.org/dataoecd/47/61/35070367.pdf.

Model of usage of geoinformation technologies during formation of environmental competence of future mining engineers

Wed, 17 Sep 2014 15:00:33 +0300

The article reveals the model of usage of geoinformation technologies during formation of environmental competence of future mining engineers.
Key words: environmental competence, future mining engineer, model, sustainable development.

Model of usage of geoinformation technologies during formation of environmental competence of future mining engineers

Svitlana Hryshchenko

Senior inspector of research and training sector in teaching department,

Information and communication technologies in education

Kryvyi Rih National University

Prerequisite for development of methodology of usage of geoinformation technologies as a mean for formation of environmental competence of future mining engineers is the solution of the following specific tasks of research: determination of major factors of modernization of professional education of future mining engineer; theoretical justification of competence system of future mining engineers; defining the structure of environmental competence of future mining engineers; earmarking of geoinformation technologies, application of which promotes safe activity of mining plants.
In result of solution of the first task, the major factors for modernization of professional education of future mining engineers is the public contract for preparation of competent specialists were determined. They are specified in the state industry standards of higher education and in the society sustainable development [1; 2; 3].
In result of solution of the second task, it was stated that development of competency building approach to professional education happens, on the one side, under the influence of public contract on the preparation of competent specialists, on the other side – it influences on the formation of such contract in the direction of changing of state industry standards of higher education.
Application of competency building approach to modernization of state industry standards of higher education leads to the necessity of theoretical justification and development of competence system of future mining engineers, the component of which are environmental competences.
In result of solution of the third task it was stated that formation of environmental competence of future mining engineer happens within professional education.
In result of solution of the forth task it was concluded that development of ICT promotes the changes of production technological mode (including mining production), which provides stable technological development.
In their turn the requirements for stable social, economical and environmental society development induce to definition of ICT focused on their support. Securing of sustainable development of mining industry required definition of ICT, which consider scale and influence of mining production – means of ICT.
The outer shell of the model is formed by the major factors of modernization of professional education of future mining engineers and preparation basis of competent mining engineer.
The inner shell of the model is connected with the outer one in the following way: system of competences; environmental competences of future mining engineer; formation of professional competences while studying, in the one hand it is provided by technically sufficient usage of ICT and in the other hand acquirement of professionally oriented means of geoinformation technologies acts to rise ICT-competence of specialist (in particular in geoinformatics).
The inner shell of the model reflects the formation of environmental competency by means of geoinformation technologies during professional education, which provides this process. Purposive formation of environmental competence by means of geoinformation technologies happens within special course of study of “Ecological geoinformatics”, three-component structure of methodic educational system of which is shown in the central part of inner shell of the model: learning needs; education content; education technology ( forms, education organization, means and ways of education, where means of geoinformation technologies are the basic). Determination of education technology in the structure of methodic system of special course of study of “Ecological geoinformatics” is connected with the fact that the acquired while studying abilities concerning the usage of means of geoinformation technologies for solution of environmentally oriented tasks of professional activity of mining engineer are further used during study of the other disciplines of professionally practical training and accomplishment of graduation works.
Initial part of the model of usage of geoinformation technologies in formation of environmental competence of future mining is environmentally competent mining engineer, who is able to use geonformation technologies in professional career effectively.

References

Morkun V. S.,Morkun N. V., Pikilnyak A. V. (2014). Simulation of high -energy ultrasound propagation in heterogeneous medium using k - space method. Metallurgical and Mining Industry, No3. p.p. 23-27.
Morkun V. S.,Morkun N. V., Pikilnyak A. V. (2014). Ultrasonic phased array parameters determination for the gas bubble size distribution control formation in the iron ore flotation. Metallurgical and Mining Industry. No3. p.p. 28-31.
Stupnik М. І., Morkun V. S, Bakum Z. P.(2014).Current approaches to the training of mining engineers. Metallurgical and Mining Industry, No3. p.p. 4-7.

Repair of conveyer belts and expansion bellows of bell-less tops of blast furnaces by elastomers of cold vulcanization

Wed, 17 Sep 2014 15:59:15 +0300

The article covers the results of performed tasks concerning repair of metallurgical equipment including conveyer belts of by-product coke plant and sintering plant and also compensators of bell-less tops of blast furnaces with the help of modern polymer materials, allowing to fulfill hermetization of various assemblies without removal of equipment on-site of exploitation.
Key words: composite, conveyer belt, repair, recovery, compensators, bell-less top, blast furnace.

Repair of conveyer belts and expansion bellows of bell-less tops of blast furnaces by elastomers of cold vulcanization

Ischenko A.A.

D.Sc. in engineering, professor
head of Mechanical equipment of iron and steel works department,
Priazovskyi State Technical University, Mariupol, Ukraine

Golinka Sergey

Post-graduate of Mechanical equipment of iron and steel works department,
Priazovskyi State Technical University,
Mariupol, Ukraine

Grishko V.P.

Senior researcher of Mechanical equipment of iron and steel works department,
Priazovskyi State Technical University,
Mariupol, Ukraine

In recent years there increased an interest to new technologies of repair and renewal operations with application of polymeric materials. This is connected with the fact that such technologies allow effectively to place the equipment into service as soon as possible and avoid the necessity for permanent repair and stoppage of productive process for a long time. It refers considerably to metallurgical equipment and reconstruction first of all conveyer belts.
Two types of polymeric materials refer to two-component elastomers, which allow to solve the problem of conveyer belts. The first one is two-pack glue (for example, of German company «Tip- Top»), which is applied with a thin layer and allows both to join the belts and repair of certain failures with application of prepared patches.
The second one is multifunctional shape-generating two-component elastomer, which allows to grow worn out and damaged areas by material itself without application of patches. At the same time they may fulfill a function of glue, considering their increased adhesive properties (elastomer “diagum” of DIAMANT Metallplastic GmbH Company may be referred to such materials). Priazovskyi State Technical University accumulated unique experience of application of such elastomers in coke chemistry and metallurgy.
Let us consider first the recovery process of conveyer belt. Their damage in the process of exploitation may be of various characters. Figure 1 shows the main and possible types of conveyer belts damages, taking place on one of the coke and by-product processes. Among these are:

Long cuttings of any length (both interface and blind);
Reach-through breakdowns of conveyer belts;
Damages of belt borders;
Crossed cuttings of rubber-fabric belts up to 20% of the belt.

Figure 1. Possible types of conveyer belts damages: 1- long cutting; 2 - reach-through breakdown; 3 – damage of belt border.

Traditional technology of reclamation work lies in the following. Repair of reach-through breakdowns and cuttings of cloth belt 20 – 25 mm in size are fulfilled on the conveyer in the area of minimum tension of the belt.
Primary sectoring of stages of fault locations with the help of samples is fulfilled. The samples feature the set of rectangles. The smallest sample should recover the damaged piece not less than δ=10 mm across-track of the belt and а=60 – 100 mm – lengthwise (fig.1).
Splicing of damaged piece is then fulfilled, rubber lining by a pattern is sliced with the help of special gripper layer by layer and forms stages for patches of squared shape. Then the surfaces of prepared patches are skinned, defatted and greased twice with special glue with further drying, first time- till complete drying, the second time – till formation of adhered layer. After this the patches one by one are applied and rolled down. Before cut by steps gash is filled in layers in the wake of size rising of patches. Then according to traditional technology, it is necessary to fulfill the vulcanization process at t =1450( 50 С) and pressure 1.0 MPa with further press cooling up to t = 700 С. Such process certainly requires conveyer break not less than for a shift and that is why in certain cases, it is necessary to install check clamps, which strap the gust. Within nearest stop the clamp should be removed and the above described operational flow should be fulfilled.
However such technology relates more to the steel-reinforced belts, and rubber-fabric in conditions of continuous coke-chemical or agglomerative production, where scheduled outage under repair may occur once per month, such U-shaped rough mountings destroy the tape base gradually, passing through the areas of bending, which leads to its breakdown.
Two-pack glues, for example «Tip- Top», allow to solve the problem of performance restoration of conveyer much more quickly, as their application excludes glue drying and patch curing with further cooling. But herein the described methodology of patch preparation and stepped layer-by-layer preparation of the belt remains and requires rather long time. One more fact, which restricts application of two-pack glues, is their low thermal endurance (up to 80 0 С), while transporting of hot coke the temperature of mass may exceed 100 0 С.
In connection with this, in Priazovskyi State Technical University there was developed technology of further time cutting for repair of belts and increase of thermal endurance of lining patch by means of application of two-component shape-generating elastomers , which posses unique glue properties and may fill the gashes on defective areas of the belt. Among these are such materials as “diagum” of of DIAMANT Metallplastic GmbH Company with following technical characteristics (Table1).

Table 1. Technical characteristics of “diagum”

Material	Diagum – P	Diagum - Fl
Weight flow ratio	100 : 30	100 : 30
Цвет смеси	black	black
Density (ready mix) g/cm3	1.1	1.1
Initial viscosity25 0 С	thixotropic	fluid
Output time At + 200 С, min	10	10
+230 С, min	5 - 10	5 - 10
Final hardness at 10 -150 С, days.	8	8
Room temperature, days	6	6
+400С, hour	12	12
+60 0С, hour	8	8
Hardness 80 % at room temperature, hour	24	24
+ 40 0С, hour	10	10
+ 60 0С, hour	6	6
Shore hardness (at room temperature)
1day	80	75
2 day	85	78
7 day	90	85
longitudinal strength DIN 53455, MPa	38	40
Elongation at failure according to DIN 53455, %	400 – 500	500 -600
Е - DIN 53455 module, MPa	200 – 350	300 – 350
Range of operating temperatures, 0С	- 40/ +120	- 40/ +120

Chemical resistance
Chemically stable to:	natural oils, diesel fuel, petroleum, salt, water, sea water.
Relatively stable to:	inorganic acids and alkalis (concentration 10 %), benzine.
Unstable to:	ketones, ethers, alkohole.

Application of this material during repair of defective belt areas at one of the by-product coke plants allowed to reduce repair time and also the delay of conveyer up to 1-2 hours. Reclaimed by such material areas of the belt with various damages are shown in the figure 2.

Figure 2. Damaged areas of conveyer belt before (a) and after (b) reclamation:
1 – long cutting;
2 – damage of belt border.

Exploitation results of reclaimed areas of conveyer belts proved economic efficiency and effectiveness of technologies application.
Wide range of possibilities of elastomers of cold vulcanization allowed to solve one more problem connected with reclamation of hermiticity of expansion bellows of bell-less top of blast furnace “Azovmash”.
Expansion bellows are knurled cylinder courses made of multilayer stainless steel, which allow axial and angular displacements. In construction of bell-less top there used expansion bellows of three typical sizes:

expansion bellows DU 400 mm placed on the transmission shaft of shuttle and serving for compensating of angular displacements within the limits of 5 mm.
expansion bellows DU 400 mm, placed between fixed block body of burden valves, bearing on the columns of bell-less top and between moveable loading hoppers. This compensator allows moving within the limit of 5 mm.
expansion bellows DU 400 mm provides assembling and replacement of equipment parts and also movement of isolation gate. Reactivity worth of the block from two expansion bellows makes 30 mm .

Defects arising during exploitation of compensators may be divided into three types:

bends, caused by shear forces and holes, formed at this bending.
holes, formed in result of casual touching by welding electrodes or blow during installation;
leakage (faulty fusion) across the welding seam.

Any of these defects in case of untimely elimination because of extreme pressure of blast-furnace gas and content of flour particles in it, lead to rapid expansion of the hole and occurrence of emergency situation, which requires compensator replacement.
In the cases when it is necessary to eliminate numerous holes, formed as a result of jam on the compensator axis of a shuttle DU 400 mm, there was used a technique of creation of “diagum” polymer solid bed on a top of stainless surface of compensator with application of glass fabric, which is also sodden with this polymer. This technique was repeated twice.
It was rather complicated to secure airtight packing, considering the fact that this work was performed on the acting blast furnace and space-limited environment for repair (the distance between support bearing of underslung gearing of shuttle and between block body of burden gaps was not more than 600 mm). However in 8 hours the repaired unit was operated and provided hermiticity of compensator within 1.5 hours till turnaround maintenance (fig. 3).

Figure 3. Reconstruction of compensator DU 400 before airtight packing a) and after b).

One more repair, which is fulfilled on the operating furnace, referred to hermetization of the blow with the length 150 mm and width 10 mm on the compensator DU 2000 mm. In this case the patch on the defective area was put on with the usage of “diagum” with glass fabric overlapping the defective area twice across the length and width (fig. 4a).The another case of compensator repair refers to recovery of hermiticity of welded seam of double-flanged compensator. In case of welding of stainless thin shell with steel flange of nonuniformity of the seam also lead to “blows”. To exclude this phenomenon before installation of compensator on the blast furnace, it is checked for hermiticity by means of air discharge. Such check revealed air losses in some areas of welded seams, in consequence of which it was decided to encapsulate by “diagum” (fig. 4b). Compensator on the blast furnace was operated for long term without any notes.

Figure 4. Recovered compensators DU 2000 on the blast furnace (a) and DU 1200 in conditions of hermeticity test in the machine workshop (b).

Good adhesive properties and heat stability polymeric material “diagum” in combination with the ability of polymerization without increased temperature and pressure, allow also to encapsulate connectors and jointing, where, for example, oil leak takes place, as a result of failed out compression without dismounting and replacement of compression. In our practice hermetization of connector between body and frame of large marine diesel-generator is fulfilled successfully, local damages of cable sheath were repaired, the surface of rubber-covered roll was recovered, etc.

Conclusions

The technology of application of two-component elastomers during repair of equipment of coke-chemical and blast-furnace departments is developed. Successful exploitation of recovered conveyer belts and expansion bellows proved the effectiveness of application of developed process design solutions when emergency situations arise, when traditional approaches of repair are either inefficient or require big costs.

References

Ishchenko A.A. Tekhnologicheskie osnovy vosstanovleniya promyshlennogo oborudovaniya sovremennymi polimernymi materialami [Background technology for reconstruction of industrial equipmentby modern polymeric materials]. Mariupol', Public higher education institution «PSTU», 2007, p. 250.
DIAMANT Metallplastic GmbH. Available at: http://diamant-polymer.de/

Technological and design features of flat- rod elements with usage of composite reinforced concrete

Wed, 24 Sep 2014 17:19:10 +0300

New elements in relation to machine building and mining industry with application of construction materials using mount system of mine opening as an example are considered. The elements combine durability and reliability necessary for exploitation. Reliability of composite reinforced concrete is confirmed by experimental and theoretical researches. Flat-rod elements with application of composite reinforced concrete are the results of synthesis of structural, steel and concrete elements, acquired during this advantages and peculiarities, determine their efficiency.
Keywords: open composite reinforced concrete, construction, structure, rod, slab.

UDK 624

Technological and design features of flat- rod elements with usage of composite reinforced concrete

Gasii G.M.

Ph.D. in Engineering Science,
Docent of Organization and construction technology and protection of labour department,
Poltava National Technical Yuri Kondratyuk University

Problem statement in general terms and its connection with important practical tasks

Efficiency of bonding technique is of great importance in modern economic conditions. Constructions should provide enough reliability and be simple in fabrication. In recent years mining and geological conditions during mining works changed for the worst considerably. This happens due to gradual depreciation of existing mountings. Repair or building of new mountings is labour-intensive process and requires large material costs. Considering such state of mining industry, solution of task concerning development and implementation of new and reliable ways of rock lining with minimal costs is of high priority.

Analysis of latest researches and publications

Disadvantages of existing mount systems give a rise to great amount of researches, focused on the reliability, efficiency and safety of mine opening improvement. Most of the researches are devoted to improvement of design solution and means of design [3].

Statement of unsettled before parts of general problem

In result of analysis of current state of mining industry and latest researches, one may conclude that today the question of development and study of new ways for secure mounting remains unsolved.

Statement of a problem

To develop new flat-rod elements of rock lining with the usage of composite reinforced concrete and to study their technological and design features.

Base material for research

Having analyzed the fulfilled research [1, 2], advantages and disadvantages of existing mountings [3], the new type of mounting construction was suggested - composite reinforced concrete structural support systems. Assignment of such systems is to provide heavy duty of opening due to increase ofmounting holding capacity. Main point of such constructions is in reduction of production costs, installation lead time and in securing of necessary stiffness and integrity. Support system consists of steel cancellation structure and reinforced concrete slab (fig.1).
Suggested mountings may be used during development of underground deposits and laying of horizontal, vertical and inclined openings. Design feature of mounting is that the steel lattice in it works together with reinforced concrete slab, herein the slab replaces the top boom of framed – archy systems and fulfills preventive function. Such space system of mountings has great stiffness.

Figure 1. Plane-rod element of composite reinforced concrete structural system

1 - reinforced concrete slab; 2 – steel tube; 3 – lattice element; 4 - flange

During design of mountings there is a task to get rid of the disadvantages of steel and concrete elements. The question concerning the choice of strength grade of concrete, steel tubes grade, acceptance of reinforcement ratio is of great importance.
Basic materials for manufacturing of such support system are concrete and steel tubes. Heavy concrete of the following project classes В12,5; В15; В20; В25; В30; В40; В45 should be applied. Steel electric-welded tubes should be used.
Technological peculiarity of developed mounting system is that they are assembled from separate parts (figure 1). Combination of elements into mounting construction is made with the help of flanges. During assemblage there may be some tolerances across the length of elements, but if the tolerances are significant (more than 0.6 sm), it will be impossible to remove them by simple bolt tensioning, special means, which are applied for usual flange mounting, must be used. It is not allowed thread of a screw torn, if it falls outside the range of the middle diameter of the screw in depth or their length exceeds 8 % of the total screw length in helical curve.
Combined action of steel rods and reinforced concrete slab is provided due to the reliable joint connections.

Conclusions and prospects for the development in this direction

Design and technological features of the developed support system allow to save on material due to their rational use - reinforced concrete slab protects from the rock fall, takes up pressure from the ground and equidistributes it into steel elements of the lattice. Usage of developed design elements allows to road lining in deep depth. It is stated that elements of support construction work together under loads. The way of combination of reinforced-concrete and steel elements provide holding capacity of all the construction.

References

Storozhenko L.І., Ermolenko D.A., Gasіy G.M., Gladchenko Yu.L. (2012). Experimental research of models of structural cable-stayed steel and concrete structure. Galuzeve mashinobuduvannya, budіvnitstvo. No 3. p. 243–249.
Storozhenko L.І., Timoshenko V.M, Nizhnik O.V., Gasіi G.M., Murza S.O. Doslіdzhennya і proektuvannya stalezalіzobetonnikh strukturnikh konstruktsіy [Research and designing of composite reinforced concrete of structural construction]. Poltava, ASMІ, 2008, 262 p.
Buys B. J., Heyns Р. S., Loveday P. W. (2009). Rock bolt condition monitoring using ultrasonic guided waves. The Journal of the Southern African Institute of Mining and Metallurgy. p. 95–105.

Analysis of means of reliability and service life growth for open gear drive of ore-pulverizing mills

Fri, 19 Sep 2014 15:32:11 +0300

Critical analysis of approaches for solution of the problem of increase of reliability and service life of open coarse-grained gears of spherical ore-pulverizing mills was carried out. The influence of physical mechanical properties of gear wheels material on the wear rate during running and set uniform wear of teeth contact point was determined. The abilities of their yielding surface plasma quenching were proved.
Keywords: open gear drive, abrasive wear, surface plasma quenching.

UDK 621.926.5

Analysis of means of reliability and service life growth for open gear drive of ore-pulverizing mills

A.A. Ryazantsev

Assistent of Mechanical engineering departement,
State Higher Educational Institution "Kryvyi Rih National University"
Ukraine

Problem statement. Gear drive takes the leading place in mechanical systems (machines and mechanisms) and the industrial safety and output quality depends on its current technical condition. They are operated in conditions of impulsive-cyclic subgrade loads, which cause high requirements for the loadbearing of gear drive. Reduction of loadbearing is determined by such reasons as: weakening of the tooth at its base, fatigue spalling of contact point and wear of tooth profile.
Open gear drives are subjected to abrasive wear of teeth working area during ingress on them some dust or dirt, which act as abrasive. Analysis and evaluation of teeth abrasive wear is made depending on the characteristic of abrasing effect of physical mechanical properties of material, geometric and linkage parameters of conjugations. Lowering of intensity of abrasive wear, both in the area of wear curve running, and in the area of uniform wear, is current problem.
Definition of unsolved problem. For increase of reliability of gear and transmission it is of current interest the following: development of scientifically grounded and proved evaluation criteria for limit state of gear drive; development of methodology for operational evaluation of wear rate of teeth working area; improvement of technology of their case-hardening.
Analysis of recent researches. The range of experimental researches, considering the specific features of mining machinery, in particular - ore-pulverizing mills, are devoted to the abrasive wear, as the most widespread type of wearing. A lot of researches from research-and-development, design-and-engineering and higher institutions from Ukraine and all over the world explored it.
Researches concerning determination of common patterns of abrasive wear are the most interesting. The range of works in this direction is based on the usage of theory of similarity. Researches based on the study of abrasive grain mechanic in the zone of teeth contact (Gavrilenko V.A., Ermichev V.A., Kashcheev V.N.) are of great interest.
Data of the work is further developed by G.Ya. Yampol'skiy, A.P. Natarov, I.V. Kragel'skiy [1, 2, 3, 4].
Literature data analysis on the problem of research represents that the existing recommendations concerning the criteria of limit state of high load gear drive are contradictory and consider the correlation between characteristics of teeth contact damages and performance characteristics of gear not fully, at full assessment of factors influencing the durability of open gear drive, including parameters of hardened work area of gear wheels.

Principal regularities of abrasive wear of open gear drive of ore-pulverizing mills (analysis of experimental data).

Wear of teeth may be divided into three periods: running-in, steady and catastrophic. Considering wear rate of teeth in time within each of the periods, let us replace true relationship with a linier one. Wear intensity and rate during running-in period of open gear drive of ore-pulverizing mills is determined by mutual mismatches of teeth, which lead the loads to significant concentrations across the width of girt gear and presents a random value.

Figure 1. Idealized wear curve of gear teeth. ∆S₁₀, t₁₀ – the value and duration of run-in wear; ∆S΄₁ – permissible value of teeth wear by one active surface; t₁ – duration of the period of set wear.

In result of processing of experimental data, there were stated that the values of running-in wears of gear teeth and ring mainly lie in the range of ∆S₁₀=0.6÷1.5mm, ∆S₁₀=0.3÷0.6mm. The velocity of running-in gear wheel wear at the average is equal to Vn₁≈5V₁ (V₁ – velocity in the period of settled gear wheel wear) and its durability - t₀≈∆S₁₀/5V₁.
During service life of the gear wheel, the settled wear period is the most longstanding. Starting from the wear rate of gear teeth ∆S΄₁=3÷4 mm, catastrophic wear-out failure period starts. Wear rate in this period equals Vx₁≈25V₁.
In connection with this, it is reasonable to set permissible value of gear teeth wear as [∆S₁] ≤ 8 mm (4 mm on each active surface of the tooth).
Exploitation experience and experimental research show that service life of rim is determined by economic aspect, not physical capacity. At certain value of rim wear, service life of gear wheel reduces insomuch that its further exploitation does not make sense. The fig. 2 shows experimental dependence of the wear rate of MB-7000х2300 mills gear wheel in conditions of Inguletsk mining-and-processing integrated works on the averaged value of wear of the rim teeth.
During the initial period of exploitation of MB-7000х2300 mills, longevity of drive gear was 3-3.5 years. After the wear of rim teeth on the value ∆S₂=6.6mm, service life of drive gear reduced to 6-8 months.

Figure 2. Dependence of wear rate of MB-7000х2300 mills gear teeth on the wear value of rim teeth, U₁₀ – wear rate at initial time (at ∆S₂≈0)

Supposing that wear rate of the rim complies with the similar regularity, let us approximate the experimental dependence to exponential function

(1)

In this case coefficients К=0.237 mm-1, х=2.8, where U₁₍₂₎₀ – wear rate of gear teeth and rim during the initial period.
Analytical dependences will be given below.
During design and operation of mills, choice of one or another driver type, one should determine the longevity of tooth gears, estimate the effectiveness of measures focused on its increase.
For heavy-duty elements of friction pairs, to which toothed wheel gearing of exposed drives of mills refers, the wear rate, depending on the conditions of abrasive action A, physic-mechanical properties of materials M1(2), geometrical and linkage parameters of integrations K, may be presented as following.

(2)

where U₁₍₂₎ – wear per one loading;
A=q^a2/3A^0.5σ^2.5; (q_a – concentration of abrasive impurities in the lubricant or air, %; R – their midradius, mm; σ – tensile strength, kgs/ mm²);
(δ₁₍₂₎ – characteristic of surface coating plasticity - elongation at failure; t - contact friction fatigue coefficient; ; – relative radius of curvature of joint surfaces, mm; V₁, V₂ – slip velocities of joint surfaces, m/s).
The data processing shows that analytical expressions quite correctly describe abrasive wear of teeth of exposed drive of mills. Besides, for drives that are in close conditions, quantitative agreement of results is also satisfying.
Considering (3.3) and the results of experimental researches, analysis and evaluation of the wear rate of open tooth gear of ore-pulverizing mills we will fulfill according to the following formula:
U₁₍₂₎=60N₁₍₂₎ Kn₁₍₂₎ υ₂ L₁₍₂₎ (3)
where N₁₍₂₎ – parameter characterizing abrasive effect of the medium and mechanical-and-physical properties of materials for teeth for these experimental conditions (for mills, working in different conditions, averaged values are N1=3.4∙10-10mm1/2, N₁=6.4∙10^-10mm^1/2),
n₁₍₂) – rate speed, rpm,
υ₂– intertwining number of rim teeth per one revolution;
L – coefficient, considering the difference of abrasive affect of the medium, mechanical-and-physical properties of material and conditions of teeth loading for controlling case:

(4)
; ; ;
;

(values with indexes N correspond to those, for which the parameter N₁₍₂₎ is determined, and with P-index – to controlling case).
In the expression (4)it is suggested that during reduction or increase of the load in gear, appearance of accompanying species of wear is possible, the influence of which will be calculated by ξ coefficient. Tooth gears of tested mills are affected by similar loads, this allows to set ξ =1.
The peculiarity of operation of open tooth gear of a mill is that fact, that during exploitation it can be affected by a range of running-in regimes, during which accelerated wear takes place. Multiplicity of running-in regimes of rim is connected first of all with the fact, that in pair with it several gear wheels work, as their service life is considerably smaller. In some cases the repair of the drum (re-lining) is fulfilled on the special stand. The drum together with running-in rim is carried over on the stand, and on its place the drum is placed, the rim of which was operated before in pair with another tooth gear. For this reason in conditions, for example, Inguletsk mining-and-processing integrated works, rim teeth and gear wheel of MB-7000х2300 mill sustain running-in regimes each 5-6 moths.
Let the toothed wheel gearing sustain r _i running-in regimes during service lifetime. Averaging wear rate, the longevity of gear wheel we will determine from the expression

, (5)

where i=1,2,3,…n; (the number of gear wheel, being operated with the rim);
t_i – integral time of teeth wear in steady state mode during service life of gear wheel;
[∆S₁] – permissible value of wear.
Considering that the longevity of gear wheel is equal to , from (5), we will get:

(6)

Wear rate value of the rim teeth may be represented as the sum of wears, from which they suffer during work with each gear wheel.

(7)
Then the longevity of the rim will be:

(8)

Going on to the practical calculations, it should be noticed that the service life of the i-th gear wheel the rim teeth will wear on the value:

(9)

Inserting into (3.12) from (3.8) we will get:

(10)
(11)

Expression (10) and formula (11) show that in spite of the different wear rate and longevity of gear wheel, wear rate of rim teeth during the service life of each gear wheel will be constant (∆S_2i =const) and when all the other parameters are constant, it will be determined by the expression U₂₀/U₁₀. In expressions 5 and 7:

(12)

Expressions (10) and (12) allow to determine ∆S_2i and U_1(2)iсрon the initial stage of calculation.
Calculation of longevity creates no problems at set quantity of running-in regimes during service life (if the gear wheel is reinstalled one time for operation of teeth of another side, r_i=2). In the case when τ time, in which the teeth sustain running-in regimes, is set, the task may be solved by means of stepwise approximation. Gear wheel longevity is determined correctly, if the condition is kept.

Evaluation of factors influencing the longevity of open tooth gear.
Influence of operative conditions.

There are cases when the teeth are worn from one and both sides, depending on operative conditions. Running-in regimes of wear teeth may sustain only twice during service life of gear wheel and through the intervals with duration of each τ.
Running-in of the teeth not more than twice within service life is possible if the repair of a mill is fulfilled on its working place (after assembling of gear wheel for working of teeth with one and then with another side).
More often running-in regimes in τ time take place when the repair of mill shell is fulfilled on the special stand. The gearing is displaced before sending the shell on the stand. Another shell is placed instead of the old one.
Newly arranged gearing during operation sustains running-in regime. Except technological conditions, the amount of running-in regimes depends generally on the reliability of equipment.
Technical failure of one of the mill units may lead to the necessity of dismounting of open tooth gear.
Analysis shows that optimal regimes of exploitation are the ones, under which the wear rate of active teeth surfaces of gear wheels at each side should not exceed 4 mm. Apart from the transfer module, the condition [∆S₁] ≤ 8 mm must be fulfilled. For MMС-9000x3000 mill the assignment of wearing depth value for gear teeth [∆S₁]=16 mm (8 mm at each side of the tooth) will lead to the reduction of longevity of gear wheels and rim up to 40%. Besides, it is necessary to use during exploitation the active surfaces of rim teeth of both sides. Non-observance of this condition will lead to the reduction of longevity of open tooth gear also up to 40%.
In conditions of Inguletskiy mining-and-processing integrated works rim teeth work with both sides. Layout of the mill allows the rim teeth to work with one side then another one, depending on the working place. But during diagramming of repair, the factor of uniform teeth wear is not considered. The mill with rim gets into the places, where teeth work with one side considerably oftener. The above mentioned shows the profile of rim teeth of МB-7000х2300 mill, received with the help of replica (figure 3).

Figure 3. Profiles of rim teeth of МB-7000х2300 mill during its exploitation in conditions of Inguletskiy mining-and-processing integrated works

The influence of abrasive contaminants concentration on the longevity of gear wheels.

As one may see from (2), (4) the concentration of mechanical impurities significantly influences on the wear rate. When reducing the amount of the impurities in 2, 3, 4 times, the velocity decreases in 1.6, 2, 2.5 times.
One may conclude from the analysis of expressions (5), (7) that wear rate reduction affects so much the less the longevity of gear wheels, the greater the role of running-in wear in common balance.
Statement of unsettled part of a task. Large-sized and coarse-grained tooth gears are of widespread occurrence in industry. For example, ball mills, suitable for crushing of various ores, coal, and other raw materials, are built up with open tooth gear, teeth module of which equals m=20…34 mm, face width b=600…1000 mm. They, similar to all exposed drives, work in conditions of impact-cyclical bearing pressures. Characteristic reasons of reduction of holding capacity are determined not only by weakening of a tooth at its bottom, fatigue spalling of contact surface and wear of tooth form. Damage of gear wheels may also arise in result of wavelike wear. This phenomenon is caused by plastic flow of surface coating as a result of cyclic contact in slide-rolling regime and also insufficient hardness. Key aspects during designing of gear wheels are the choice of material or the way of its hardening.
Formulation of work objective. Therefore, in relation to coarse-grained transmissions of spherical ore-pulverizing mills, it is necessary to specify the influence of mechanical-and-physical properties of materials of gear wheels on the wear-out rate during running-in and fixed uniform wear of contact teeth surfaces and also to prove the possibility of their productional surface plasma quenching.
Statement of core material. During evaluation of influence of mechanical-and-physical properties of material of gear wheels, as it was mentioned before, in accordance with (2) the value, characterizing mechanical-and-physical properties of material of gear wheels, influences the velocity of abrasive wear. Value σ is the combined variable of parameter characterizing abrasive action of the medium. Therefore, σ is the function of hardness of active surfaces of teeth. That is why, considering the influence of mechanical-and-physical properties of materials, let us note that the wear rate:

(13)

Increase of hardness of active surfaces of teeth causes the reduction of σ. As one may see from (13) the increase of teeth hardness of one of the wheels leads to the reduction of wear rate as the teeth of the other wheel of gear set.
Increase of hardness of active teeth surfaces of open gear wheels, besides it promotes the reduction of accompanying species of wear, increase of their contact hardness.
Experimental research of influence of hardness of active surfaces of teeth on their longevity was fulfilled in conditions of Pridneprovskiy hydroelectric power plant on Ш-50 mills. Gear teeth were exposed to case-hardening by high-frequency currents. In result of imperfection of production method, surface hardness of various teeth was different. During operation of gear wheel, wear rate of teeth was measured, depending on the hardness of their active surfaces. Experimental results are shown in the figure 4.
Therefore, increase of durability and longevity of coarse-grained tooth gear operation is of high priority for all machine builders.

Figure 4. dependence of the wear rate of gear teeth on the hardness of their active surfaces (Sh-50mill, Pridneprovskiy hydroelectric power plant)

The above mentioned necessitates the researches of existing technologies for solution of task of performance incoordination, increase of service life, wear-resistance of working area of teeth of coarse-grained gear wheels. Upcoming trend here is work-hardening heat treatment of working area by concentrated energy flow [5]. The structures of hardening type, which are formed during flash heat and cooling, have high hardness, wear-resistance, crack strength.
Common use of known ways of work-hardening by concentrated energy flow (laser, cathode ray, cathode- ionic, etc) is restricted by high cost and complexity of equipment, its insufficient reliability and capacity, necessity of vacuum usage, special places with particular requirements, demand for qualified operation, high maintenance charges. In these conditions surface tempering by plasma arc is reasonable in parameters of generality, availability, environmental friendliness and economical efficiency for prolongation of service life of fast wearing parts [5]. Not changing surface roughness parameters, such heat treatment easily fits into production process of prepare and repair of parts, being a final stage, low-cost, rather productional and allows to increase their service durability effectively. Due to this the authors suggest to apply plasma hardening of the profile of gear wheel for increase of contact hardness of teeth working areas.
The aim of plasma tempering is the increase of service life of machine parts due to hardening of their surface coating (several mm in thickness) by thermal treatment of plasma arc at permanent common chemistry of material and retention of initial properties of material in the inner layers.
Hardening in result of high-speed local heating by plasma arc of surface coating to high temperatures (higher than АС3) and its rapid cooling with higher critical speed as a result of heat removing into deep layers (inner) of material. Being formed structures during flash heat and cooling of tempering type have high hardness, wear resistance and crack strength. Effect from plasma tempering is determined by increase of part service characteristics due to change of physical and mechanical characteristics of surface coating, because of formation of specific structure and phase metal content and also formation of compressive residual stresses on the surface.
Structural changes in common correspond to the occurring ones during volume tempering, but the velocities of heating and cooling cause changes of the relations between structural components, their morphology changes as a result of increased defectiveness of crystalline structure (increase of dislocation content, crushing of blocks and stress raisers in crystal latitude) [5].
The purpose is to create the way of heat treatment (case-hardening) of gear wheels, which will allow to obtain variable hardness throughout the height of teeth, decreasing towards the spaces (fig.5). This allows to control the process of teeth wear with the aim to keep constant quality factors of catching of toothed wheels.

Figure 5. Change model of hardness of surface coating of gear teeth in result of hardening

The structure of hardened layer with high hardness and dispersability affects the changes of exploitation parameters of hardened materials - wear-resistance, mechanical properties (durability, plasticity, crack resistance and enduring quality), heat- and corrosion resistance.

Conclusions and development prospects

Analysis of wear types and damage of teeth of open pairs of ore-pulverizing mills is fulfilled. Abrasive wear is stated to the main type. The main source of lubricant pollution is crushing products, which get in gearing as a pulp or crust from dusty air. Concentration of mechanical impurities in the lubricant including wear products makes in average by weight 34%.
Experimental researches concerning teeth wear of open gears of ore-pulverizing mills are fulfilled. In result of processing and analysis of experimental data, the averaged values characterizing various stages of wear are obtained. The dependence of wear speed on teeth wear rate is stated. With the help of comparison of experimental wear rates with computed values characterizing geometry and cinematics of gearing, the parameter considering abrasive affect of medium and physical and mechanical properties of teeth material for experimental conditions is obtained. The last allowed to apply existing regularities of abrasive wear for engineering evaluation of wear of open gears of ore-pulverizing mills.
Calculation method of open gear wheels of ore-pulverizing mills for wear, which considers the peculiarities of their exploitation, is developed. On the base of developed method, the analysis and estimation of factors influencing the longevity of open gear wheels is given. It is stated that only due to optimal conditions of operation while all other conditions remain constant, increase of service life of gear on mining-and-processing integrated works up to (20÷30%) is possible. Amount of running-in regimes affects the longevity detectably. During repair works of open gear in situ, which take place when the drum is not carried on the stand, at all other constant parameters, the longevity of gear increases up to 20%.
4.On the base of experimental data and developed calculation method of open pairs, it was set that the limit values of gear teeth wear and rim wear should be determined not by the ability to fulfill operational functions, but by economic considerations. Limit wear of gear wheel is restricted by fixed wear-out failure period and makes 3÷4mm from each tooth surface for gears under test. Increase of the value of allowed gear teeth wear leads to operation during catastrophic wear and decreases service life of gear considerably.
5. Method of plasma case-hardening for gear teeth of large module (m > 10 mm) is developed. Here not only flank surfaces of teeth are subjected to heating, but also material surface coating, placed near tooth spaces. This method is optimal with generality, availability, environmental friendliness and economical efficiency parameters. It allows to increase the service life of parts minimum in 1,5…2 times and reduce costs for maintenance and repair up to 40..50%. Besides, this technology is more productive and cheaper than the other methods of case-hardening (including high-frequency alternating current).

References

Karagel'skiy I.V., Dobychin M.N., Kombalov V.S. Osnovy raschetov na trenie i iznos [Calculation basis for friction and wear]. Moscow, Mashinostroenie, 1977, 526 p.
Natarov A.P. Issledovanie vliyaniya geometricheskikh parametrov zubchatykh peredach, rabotayushchikh v sredakh s nalichiem abraziva na ikh dolgovechnost': avtoreferat dis. na soiskanie nauch. stepeni kand. tekhn. nauk [Analysis of geometrical effects of gear wheels being operated in mediums with abrasive on their longevity]. Khar'kov, 1978. 28 p.
Yampol'skiy G.Ya., Kragel'skiy I.V. Issledovanie abrazivnogo iznosa elementov par treniya kacheniya [Investigation of abrasive wear of tribological components of rolling]. Moscow, Nauka, 1973, 63 p.
Yampol'skiy G.Ya., Natarov A.P. Raschet abrazivnogo iznosa zub'ev zubchatykh peredach [Calculation of abrasive wear of gear wheels]. Bryansk, 1975, 186-204 p.
Nechaev V.P., Ryazantsev A.A. Modification of properties of surface coatings of heavy-loaded machine parts by means of plasma hardening (2012). Vіsnik Krivorіz'kogo natsіonal'nogo unіversitetu. Zbіrnik naukovikh prats'. No32 123-127 p.

Production conditions of iron oxide black from pickle liquors

Thu, 25 Sep 2014 17:17:28 +0300

In article the research results of terms of formation of iron oxide black from pickle liquor are presented. Interrelation between phase composition of precipitate and basic technological parameters of the process: temperature, speed of air delivery, рН is considered.
Keywords: pickling liquor, black pigment, magnetite, precipitation, goethite.

UDK 678.5

Production conditions of iron oxide black from pickle liquors

Frolova L.A.

Ph.D. in Eng. Sc.

Ukrainian State University of Chemical Technology

At the present time one of the most modern and processable means of iron oxide black production is hydrophase method [1]. Nanodisperse magnetite, obtained under the technology of deposition, is successfully used in many industries as a pigment and reinforcing filler in paint-and-varnish industry and industrial-rubber manufacturing, in polymer compounds [2]. At the same time there exist certain problems during manufacturing of necessary black iron-oxide pigment with predefined properties. Obtaining of specified phase composition, which determines pigment colour and its magnetic characteristics are referred to them. An important problem is also utilization of pickling liquor.
Pickle liquor and rinse waters, formed during steel pickling on the metallurgical and machine building plants are practically not used and not processed. Concentrated wastes contain 100÷300 g/l of iron salts and may be used for synthesis of iron colors [3-5].

General part

Control of manufacturing process of hydroxides and iron oxides with defined granulometric and phase composition is rather important as the properties of end products: pigments, magnitocarriers, catalytic agents, depend on these factors [6-8]. That is why in this work the influence of various technology factors on phase composition of obtained iron powders with the aim to determine the conditions for obtaining of iron oxide black are considered. Phase and dispersive composition of oxide iron compounds, obtained by air oxidation of iron salt solutions (II) or iron hydroxide sludge (II) depend on a lot of factors: value of рн iron salt solution (II) or sludge Fe(OH)₂, temperatures of reaction medium, velocity of agent supply, which acts as oxidizing reactor, its activity and distribution efficiency in reaction medium, iron ions concentration (II) in the solution or iron hydroxide (II) in the sludge.

Experimental

The following conditions were adopted for research: concentration of FeSO₄ – 0.25-0.5 mol/l, concentration of NaOH – 0.5-1.5 mol/l, temperature – 25-40 0С. The air was used as oxidizing agent. Its effective rate of supply for all the experiments was 10 min^-1. As iron oxidation (II) is followed by reduction of pH value, the research was fulfilled in pH-static and pH-dynamic regimes. In the first case acid content of the medium was permanently maintained, adding alkali, in the second case only initial value of pH was set.
Technology of obtaining included the stage of deposition of iron hydroxide (II), its oxidation till oxide and oxihydroxide iron compounds, filtration, washing and drying of powder. The influence of the rate of air supply, temperature and acid content of the medium on the oxidation process was investigated. Phase composition of powders was determined on the diffractometer DRON-2.
The researches show that phase composition of the obtained product to a great degree depends on the pH composition. With the increase of pH from 6 to 12 and at the similar synthesis parameters there is the following sequence of phase formation: g - FeOOH - a - FeOOH - Fe₃O₄ .
Fe₃O₄ is formed with further increase of pH solution. The influence of pH solution in pH-static regime are presented in the figure 1,3, pH-dynamic – in the figure 2. Analysis of dependences testifies that in pH- static and pH-dynamic regimes the conditions of obtaining of magnetite are similar to: рН=9-12, t=20-60 0С.
To find out regularities of changing of phase composition of obtained oxide iron compounds at temperature changes and rate of air supply, the researches at рн = 9, temperature interval 20-60 0С and rate of air supply 4-12 min^-1were fulfilled.
Process end was determined according to the information of changing of oxidation-reduction potential of the system and time of oxidation till achieving potential of constant value.
a - FeOOH и Fe₃O₄

Figure 1. Dependence of phase composition of the obtained residual in the system FeSO₄ - NaOH - H₂O - O₂, on the temperature and pH solution in pH-static regime :1 - Fe₃O₄ , 2 - a - FeOOH , 3 - a - FeOOH + Fe₃O₄ , 4 - g - FeOOH

Figure 2. Dependence of phase composition of residual obtained in the system FeSO₄ - NaOH - H₂O - O₂ on the temperature and pH solution in pH – dynamic regime: 1 - Fe₃O₄; 2 - a - FeOOH

Figure 3. Dependence of phase composition of obtained residual in the system Fe(OH)₂ - H₂O - O₂ on the temperature and rate of air supply in pH-static regime (рН=9)

It has been found out that the end product of oxidation of iron hydroxide (II) depending on the parameters of synthesis may be iron oxyhydroxide (III) of a -modification, mixed iron oxide (II) and (III) or binary mixture.
According to the data of dependences of phase composition of products, being formed during oxidation of iron hydroxide (II), on the parameters of synthesis, there was built system diagram (fig. 3), where in the temperature coordinates - rate of air supply areas of dominant formations each of the phases are reflected.
The diagram reflects the influence of temperature and rate of air supply on the phase composition of oxide iron compounds.
As far as the prime product is magnetite, optimal conditions are the temperature 40-50 0С and effective rate of air supply 4-6 min^-1.
Microphotography of the obtained magnetite powder is presented in the figure 4. As one may see from the figure, average particle size of magnetite is 0.1^-1 mkm.

Figure 4. Microphotography of magnetite

Principal technological scheme of installation for manufacturing of iron oxide black is shown in the figure 5.
Concentration of ferric sulphate in the pickling liquor is predetermined and necessary amount of ferric sulphate or water are doped. Total concentration of FeSO₄ in solution should be within the limits 100-120 g/l. Caustic liquor is prepared in separate aggregate, where the necessary volume of desolt artesian water is added, the temperature 22°С is kept and the alkali to the concentration (60 g/l) is added. Ready solution is poured into the collecting box and then pumped into the daily batchbox.
Considering the duration of the process of black pigment manufacturing, for increase in productivity there provided the usage of large-capacity reaction vessels (18-25 m³), which provides also averaging of the properties of formed magnetite. The vessel is supplied with barbator for air feed, mixing machine or steam heating.
Addition of alcali liquor is stopped when not precipitated ferric sulphate is absent and рН of the medium 9-10 is achieved. After this the suspension is soaked in the reaction cell within 1 hour and is pumped into collectors. From collectors the suspension with the help of impeller pump goes to the automatic chamber filter press, where filtration, washing from ions SO^2-₄, extraction, drying and unloading are performed. After filtration the pigment in the form of paste with moisture content50±5% is fed into cylinder drier (turbine-flange for example) with the help of band conveyer. The drier consists of annular circular flanges, fixed on the stands and rotating around central axis. The flanges are divided into separate sectors. Dryable pigment enters through the feed track on all the sectors of upper flange and remains in them within one rotation.
In such a way drying occurs in the thin layer with continuous surface-renewall of evaporation area. To exclude overwork of the powder on the stages of drying – dehydration-recovery, the drum of the dryer is fitted with narrowed at the ends noses made of refractory steel, meant for equilibrium distribution of gas flows of nitrogen and deentrainment of powder, there are also doors, which are fixed with the help of loops.
Dryer drum is installed with the help of telpher into heated furnace chamber in such a way that the drum bandages were located on the live rollers, connecting branches of nitrogen supply are hooked up with corresponding door, and then the furnace door is closed. Rotating mechanism and heating of the furnace is turned on. Relay switch, which controls the heating of the machine, is installed on the standard conditions.

Figure 5. Process scheme of pilot-plant equipment for manufacturing of iron oxide black: 1,2 - supply tank of pickling liquor, NaOH; 3 – reaction cell; 4 - press filter; 5 – batchbox; 6 - cylinder drier; 7,8,9 - shutoff cock.

Conclusions

As can be seen from the above, in result of undertaken studies, it was stated that phase composition of oxide iron compounds, obtained by air oxidation of salt solutions of iron (II), depends on the value of pH, concentration used for deposition of alkali, temperature of reaction medium, agent rate of supply, which acts as oxidizing reactor, its activity and distribution efficiency in the reaction medium, concentration of iron ions (II) in solution.

References

K.Przepiera , A.Przepiera. kinetics of thermal transformations of precipitated magnetite and goethite. (2001) J. Therm. Anal. and Colorim. 65. No2. P. 497-503.
V.S.Zaitsev , D.S.Filimonov , I.A.Presnyakov , R. I.Ganibino , B.I. Chu Physical and chemical properties of magnetite-polymer nanoparticles and their colloidal dispersions (1999). Colloid and Interface Sci. 212. No1.p. 49-57.
A.K.Zapol'skiy , N.A. Mishikova-Kdimenko, І.M. Astrelin, M.T. Brik, P.І. Gvozdyak, T.V. Knyaz'kova. Fіziko-khіmіchnі osnovi tekhnologії ochishchennya stіchnikh vod (Physics and chemistry of clarification of waste water technology). Kiev, Lіbra. 2000, 552p.
Proskuryakov, S.A., Shmidt L.I. Ochistka stochnykh vod v khimicheskoy promyshlennosti [Clarification of waste water in chemical industry]. Lviv, Khimiya, 1977. P. 464.
Kul'skiy, L.A., Strokach, P.P. Tekhnologiya ochistki stochnykh i prirodnykh vod (Technology of clarification of waste and natural water). Kiev, Vishcha shkola, 1986. 352 p.
Epikhin, A.N., Krylova, A.V. Manufacturing of iron-oxide mineral colours from hard iron-bearing wastes. (2003). Zhurnal prikladnoy khimii. No 1(76), p.p.23-27.
Shabanova N.A., Popov V.V., Sarkisov P.D. Khimiya i tekhnologiya nanodispersnykh oksidov: ucheb. Posobie (Chemistry and technology of nanodispersed oxides). Moscow, IKTs «Akademkniga», 2006. 309 p.
Kleshchev D.G., Sheykman A.I., Pletnev R.N. Vliyanie sredy na fazovye i khimicheskie prevrashcheniya v dispersnykh sistemakh. (Environmental effect on the phase and chemical transformations in disperse systems). Sverdlovsk, 1990. 248p.

Technology of working off pit walls areas, located in the area of funnels formation

Thu, 25 Sep 2014 17:16:02 +0300

The results of studies of technological schemes, allowing to carry out mining steep deposits, while ensuring the safety of technological processes are given.
Keywords: technology, underground cavities, overburden, open pit mining.

Technology of working off pit walls areas, located in the area of funnels formation

The problem of working off pit walls areas located in the area of the possible formation of funnels is particularly relevant for Krivyi Rih iron ore basin [1,2]. During deposit development by underground methods, significant amount of unliquidated cavities was accumulated. During expansion of pit borders, working sites will fall into one vertical plane with used deposits of rich ore. Such situation has developed on Gleevatskiy, Pervomayskiy, Inhuletskiy open pits [3,4].
The main requirements in the development of technology of working off of such areas, is to ensure the safety and efficiency of production processes [5, 6]. It is known that the process of entering the funnel on the surface occurs as a series of rockfalls of the roof of used deposits in the form of successive formation of the dome arches collapse. This happens up to certain limits, either to extinction of cavity, or until an instant breakout bedrock strata. Thus, cavity gradually decreases in volume and plan by a factor of loosening rocks, which allows to make a conclusion: in the case of filling a certain volume of cavity by the material, it will set the stage for further extinction of rocks that fell. The volume of material needed for bypassing may be determined from the expression:
V_p>V_c-V_b·(К_l-1),
where V_p – volume of rock filed into the cavity through the backfill drillhole, m³; V_c –initial volume of cavity, m³; V_b – volume of overlying bedrock over the cavity, m³; К_l - coefficient of loosening rocks overlying.
Crushed waste rock is recommended to be used as filling material, which is extracted directly in open pit. Filling is fulfilled throw the slanted drillholes, drilled from the surface using special rigs. Such drill rigs are widely used for the construction of hollows for various purposes in underground mining. Technological schemes concerning filling of underground cavities with overburden, based on using mobile equipment, were developed.
Filling of the cavities are held on working platform (fig.1) of the bench, when mining works comes to cavity 7. Drilling and filling equipment is located in safe area behind safety berm 8. After drilling of filling drillhole, propelled crusher 1is transported to the point of works. Rock from working bottoms is delivered by trucks to the working platform and unloaded, forming alternately temporary storages 5.

Figure1. The scheme of organization of work concerning filling cavities
1 – mobile crusher; 2 – orifice of filling drillhole; 3 – wheel loader; 4 – dump; 5 – temporary storage of rocks; 6 - axis of the road; 7 – projection exit cavity on the surface; 8 - safety berm.

Wheel loader weighs the rocks from the temporary storage, transports and unloads it into a hopper of mobile crusher. After finishing of filling works, mining operations can be continued. With such organization, operational annual costs will be defined as total cost of all kinds of technological filling operations.
It is necessary to consider shortening of the distance of transportation waste rocks as compared with the external dumping. It happens because of filling the cavities by waste rocks, which are directly excavated from the nearest to filling area bench. Additional costs for mining of undermined pit walls include the costs for filling cavities and exploration costs. Total discounted capital and operational costs for the entire period of mining will be:

+
+.

where C_s – costs for ensuring the safety of technological processes, hrn; D_f.d. – total depth of filling of drillholes in the i-th year, m/year; c_f.d. – prime cost of drilling 1 of meter of filling drillhole, hrn/m; V_і – volume of waste rock used as filling material in the i-th year, m³/year; c_c – prime cost of crushing of 1 m³ of rock, hrn/m³; c_e – prime cost of excavation of 1 m3 of rock, grn/m³; c_t1 – prime cost of transportation waste rocks from bottom to filling area, hrn/t·km; c_t2 – prime cost of transportation of waste rocks from bottom to dump, hrn/t·km; d₁ – distance from bottom to filling area, km; d₂ – distance from bottom to dump, km; c_d – prime cost of dumping, hrn/m³; D_e.d. – total depth of exploration drillholes in the i-th year, m/year; S_g – surface area of the pit walls, researched by means of geophysical exploration, m²/year; c_e.d. – prime cost of 1 meter of exploration drilling, hrn/m; c_g – prime cost of geophysical researches, hrn/m²; C_c – capital costs for purchase of filling equipment, hrn.

Dt=

where Е – discount rate, %.

Estimation of economic efficiency of involvement in working off of undermined pit walls is fulfilled with the help of criteria of discounting profit:

where А_i – mined ore in the i-th year, t/year; γ – iron concentrateoutput from 1t of iron ore; Pc - the price for 1t of iron ore concentrate, hrn/t; c_i – prime cost of 1t ore extraction, hrn/t; c_o - prime cost of 1m3 of overburden extraction, hrn/t; V_i – volume of mined waste rock in the i-th year, m³/year; C_s – costs for ensuring the safety of technological processes in the area of funneling in the i-th year, hrn/year.
The approbation of results was made on Gleevatskiy open pit PJSC "CGOK". The analysis of current condition of mining works and undermining of eastern pit wall of open pit was fulfilled. On the base of data given above concerning previously formed funnels, the coefficient of massive destruction in different parts of eastern pit wall was determined. It was made for further determining of existing danger of underground cavities. After analysis of mine surveying data, using recommendations [7] 17 danger areas in project contours of open pit were determined.
In accordance with approved balance reserves in the eastern part of the open pit, 33602 tons of iron ore are located.
Within the project of open pit working off, annual volumes of ore and overburden mining in the eastern side for determining of cost-effectiveness of its involvement were defined.
At a discount rate of 12% and the price for the iron concentrate 850 hrn/ton the profit as a result of involvement the eastern side Gleevatskyi open pit will be 357,6 million hrn.

Conclusions

Proposed technology of organization of mining works in the area of possible funneling allows working off the pit walls of open pit and expand its borders to mine all balance iron ore.

References

Peregudov I.V. Analysis of geomechanical process and safety the joint mining of deposits in area of possible funneling. Reporter of Kryviy Rig national university, 2012, №30, p. 14-18.
Nicolashin I.M., Peregudov I.V., Analysis of technology open pit mining in areas of possible funneling. Collection of scientific papers “Combined mining technology deep quarries and mines”, 2012, P. 109-112.
Peregudov I.V. Analyses of efficiency open pit mining in areas of possible funneling. Mining Messanger, 2013, №96, P.54-58.
Peregudov I.V., Bilenko A.E., Tereshenko V.V., Pschenichniy V.G., Grigoriev Y.I. Identification of promising contours of Gleevatskiy open pit PJSC “CGOK”. Metallurgical and mining industry, 2013, №7, P. 92-95.
Peregudov I.V. Validation of technology open pit mining in the area of possible funneling. Miners forum-2013. Dnipropetrovsk, 2013, P. 151-155.
Sazonov V.A., Sosik D.I., Sazonov A.V. Ensuring the safety of opencast mining in their combination with underground. Mining Journal, 1985, P. 35-38.
Pravila ohrani sooruzheniy I prirodnih obectov ot vrednogo vliianiia podzemnih razrabotok v Krivorozhskom zhelezorudnom basseine, VNIMI, L, 1975, 67p.

Spline interpolation for data processing at determining heat conduction coefficient of antistick coatings of frozen molds

Thu, 25 Sep 2014 17:13:49 +0300

The usage of spline interpolation for processing of experimental data at determining heat conduction coefficient of antistick coatings used during freezing mold casting.
Keywords: spline interpolation, antistick coatings, heat conduction coefficient, MathCAD

Spline interpolation for data processing at determining heat conduction coefficient of antistick coatings of frozen molds

Lysenko T. V.

D.Eng.Sc, professor
Control technology of casting processes department
Odessa national polytechnic university

Zamyatin N. I.

Head teacher of Control technology of casting processes department
1Odessa national polytechnic university

Khudenko N. P.

Docent of Mathematic department
Odessa national academy of food technologies

Tur M. P.

Master of Control technology of casting processes department
Odessa national polytechnic university

Many of those who face with scientific and engineering evaluations often have to use the values based on experience or obtained by means of random selection. As a rule, on the base of this setup it is necessary to build a function, where the other obtained values could precisely get [1].
Tertiary spline interpolation is the quick, effective and stable way of function interpolation. The main advantages of spline interpolation is its stability and small labour content. Systems of linear equations, which are necessary to be solved to build a spline, are well-conditioned, which allows to obtain polynomial coefficients to a high precision [2].
Let us consider the usage of spline interpolation for increase of stringency of test due to increase of data processing accuracy at determining of heat conduction coefficient of antistick coatings of frozen molds.
The value of heat conduction coefficient is one of the important parameters of antistick coating. Heat conduction of the coating has a very significant effect on the filling of the mould with liquid alloy and also on the course of casting formation. The coating of the following composition was chosen for research:

titanium dioxide – 30-32 % (mass);
disthene- sillimanite - 30-32 %;
bentonite – 1-2 %;
technological lignosulphonate – 3-4,5 %;
water- till the set density.

Heat conduction coefficient of coating is determined by means of submersion [3].
The scheme of experimental assembly is given in the figure 1.
The assembly consisted of two stand rods (10), connected with horizontal (6), where with the help of clamps (3) ceramic lip seals (4) of chromel-alumel thermocouples (5) are fixed. One of the thermocouples was introduced into copper tube (2) and with its junction with the help of spring was retained against geometric center of copper sample (1)

Figure 1. The scheme of assembly for determining of heat conduction coefficient by means of submersion: 1 – copper sample with coating; 2 – copper tube; 3- holders; 4- ceramic tubes; 5 - chromel-alumel thermocouple; 6- bar for fastening of thermo-couples; 7 – millivoltmeters PP -63; 8 - resistance heated furnace; 9 – pot; 10 - stand rod.

Copper sample was of cube form, where there was bored a closed screw hole, coming to its gravitational center. The size of sample was 40x40x40 mm, diameter of screwed in copper tube was 3 mm, chromel-alumel thermocouples were made of wire with diameter 0.5 mm. Sidelong thermocouple was placed near the sample. With the help of thermocouple temperature measurement of liquid bath with metal was fulfilled. During overlaying of the sample, the thickness of the layer is non-uniform in its different parts. That is why in order to apply the paint of certain thickness, copper wire with diameter 0.5 mm was primary fixed. Two wires were fixed in such a way that they grasped four cube faces at a distance of 5 mm from its edges.
To strengthen the wire on the other two faces across all the eight corners, there were made holes along the small diameter. Four section wires, which bordered the two mentioned cube faces, were passed through these holes. The wire was fitted tight to the faces of the sample without any paint. Then the paint with the help of brush was applied, when the wire was fully in paint, the painting was stopped. The superfluous coat of paint was cut down with the help of scraper – plane metal bar. Herein the wire acted as a restrictor, which provided the necessary thickness of the paint layer. In order to avoid paint damage, the wire from the sample after drying of the coating was removed and coating tests were performed with wire. After predrying of paint coat, the cooling of experimental samples by liquid nitrogen in the cooling box was fulfilled. The cooling was stopped when the center of the sample reached specified temperature and was soaked within 5 minutes.

In accordance with methodology [3] the calculation came down to the following.
According to the experimentally obtained data, tangent of angle was determined by temperature line at set regime of heat exchange for two time moments and :

(1)

Where та - differential temperatures of liquid metal and the center of copper sample in the time moment and .
Then under the formula

(2)

the first characteristic root was determined, which characterizes the stable heat exchange of cubic sample and aluminum bath. Herein K criteria, which allows to pass on from nondimensional time F0 to the time in seconds, for our case as follows:

(3)

where а — temperature conductivity coefficient of the sample (а= 0.372 m2/s for copper at the temperature 200 °С); R — radius of equal in area cube by volume of sphere.
Considering that the sample was 40x40x40 mm in size, its volume was 64 c.c., heating area - F = 0.0096 m2, surface area of equivoluminar ball – Fb = 0.00773м2 , radius of equivoluminar ball - R = 0.0248 m, and configuration criterion

(4)

It was calculated under the formula (5)

(5)

where – criterion of sample configuration ; Р – denoted criterion, characterizing the heating rate of the sample.
Then under (6)

(6)

Thermal resistance of coating βc was determined. Heat conduction coefficient was calculated under the formula , where Хc is the layer thickness of coating .

In accordance with suggested above methodology the exact value of heat conduction coefficient of the coating was determined. This value was compared with the value, calculated under the following formula:

(7)

Which is an approximation equation of heat conductance through the layer of coating and the sample (between the sample and liquid metal) without account of nonuniformity of temperature across the section of the sample. In (7) there agreed the following notations: G0 – mass of copper sample (0.555 либо 0.562 kg); С0 – copper heating capacity at 200 °С, J/kg○С;Хc – thickness of coating layer (0.0005 m); F0 – surface area of the sample (0.0096 m2); τ— time from the beginning of the research, с; ta – average temperature of liquid metal per time τ , °С; tcs1 – temperature of the center of sample before research, °С; tcs2— temperature of the center of sample at the moment τ , °С;
Then under the expression

(8)

The fractional error of approximative determination of heat conduction coefficient was evaluated.

According to the experimental and calculated data there was built a graph (fig. 2 and 3).

Figure 2. Change of sample temperature: 1- temperature of smelted metal; 2- temperature of sample center.

Figure 3. Change of tMe – tcs for the sample

Before start calculation of heat conduction coefficient, experimental data was processed with the help of spline interpolation.

Experimental points were connected in pairs by pieces of polynominal. Polynominal of the third degree was chosen for this purpose. To find coefficients of these polynominals, auxiliary conditions of cross-links were attached on the spline - the first and the second ones, derivative on the left and right from each experimental point should be equal. Two auxiliary conditions should be attached at the initial and end experimental points, as they do not have cross-link terms. These conditions may be chosen in different ways. Linear condition is imposed at the initial and end points. Experimental data is given in the figure 2 and 3. Interpolation by cubic splines is given in the figure 4.
Measure of deviation

D1=0

Figure 4. Interpolation by cubic splines

Deviation fault during interpolation by cubic splines equals zero.
After this the calculation of heat conduction coefficient by means of exact and approximate method is fulfilled.
Exact method.
Point 1. τ1=50 с:[lg(tMe — tcs)]1=2.4624. Point 2. τ2=160 с:[lg(tMe — tcs)]2=1.7634

W/m2∙°С
W/m∙°С

Approximate method.

W/m∙°С

λ value failure, obtained during application of both calculation methods.

In such a way the value of heat conduction coefficient of surface is 0.162 W/m∙°С.

Conclusions

Application of spline interpolation during processing of experimental data at determining heat conduction coefficient of antistick coatings of frozen molds allowed to obtain more accurate results of the final calculation.

References

Doroshenko S. P., Drobyazko V. N., Sheyko A. I.Prevention of metal penetration on the castings. Theory and practice (1996) . Liteynoe proizvodstvo. No 4. p. 20-21.
Svarika A. A. Pokrytie liteynykh form [Mould coating] .Moscow, Mashinostroenie. 1977. 216 p.
Doroshenko S. P., Drobyazko V. N., Vashchenko K. I. Poluchenie otlivok bez prigara v peschanykh formakh [Manufacturing of castings without penetration in sand moulds]. Moscow, Mashinostroenie. 1978, 321 p.

The management of the resources educational institution

Thu, 25 Sep 2014 17:15:17 +0300

The structure of the management of higher education according to the criterion of efficiency, which, in contrast to existing, provides control on the achievements of the institution and the level of use of resources, and a model is developed to assess the level of resource management when scheduling classes.

Key words: schedule, Аutomated control systems (ACS) of higher education institutions, resources of the University, the control circuit, management of the educational process, quality of management resources.

The management of the resources educational institution

Vladimir Morkun

Vice-Rector for research, Doctor of Science, professor of Computer Science,

Automation and Control Systems department

Kryvyi Rih National University

Pavel Burnasov

Senior lecturer, Automation and Control Systems department

State Higher Educational Institution "Kryvyi Rih National

University", Ukraine

To solve strategic and operational problems of resource management of the institution must have objective information about the use of resources, processes and results of educational institutions, which requires the creation and maintenance of up to date monitoring and evaluation system-level resource use university. At the stage of creation of such a system it is important to identify priority sites monitoring information that could materially affect management decisions. These facilities primarily include the performance of staff and efficiency of classroom fund educational institution.
Traditionally, ACS is used in the management of various technical systems and technological processes (ACS TP). In the economy it is known as ACS organizational management (ASO), in which the management of people with different functions for the production of a tangible product. In the works of Professor E.V. Lutsenko [1, 2] it is proved that the transfer of huge developments in these areas to a new domain synthesis reflexive ASU University is correct. The learning process is a complex dynamic system of interrelated activities of teachers and students with organizational and leadership educational institutions, managers and the managed systems. The functioning of this system is determined based on the specified meanings, goals and objectives. Outside (external contours) training system is deterministic, since learning in General, in relation to students (knowledge, abilities, skills development and so on), provides specific, planned, expected results. And the internal system is characterized by individual actions of students who are of indeterminately character [2]. Theoretical analysis of scientific papers, familiarization with the practical experience of universities in relation to identified problems revealed a number of contradictions between the requirements of this to learning management and security institutions relevant modern means and methods of their use [2, 3, 4, 5, 6].
In determining processes control educational institution may disengage from school and physical characteristics instead of a real institution consider it adequate model. Applying the basic concepts and provision of general management theory to educational institutions and using resource approach, university management system can be represented as shown in Figure 1.
The control object in this control scheme the "Educational process" as the system performing process of the formation of the activities of the educational institution and needs to be specially organized outside influences for the implementation of the algorithm of its operation. Device management is the structure element "Analysis and correction", as the device is performing in accordance with the control algorithm impact on the control object. The main influence that muddies, xо(t) which acts on the control object is the resource part, and a controlled variable y(t) is the original part that characterize the state of the control object. Then, according to economic theory, the effectiveness of educational institution is defined as the ratio of the obtained achievements in nested resources [7]:

where k – is the efficiency, D – achievements, R – resources.

Figure 1. The structure of University management

As an educational institution is a non-linear organizational system, it requires the formation of a complex, multi-layered, multi-factor and multi-circuit control system. The management of the educational process in the University is carried out through the management of the teaching corps in providing students with educational services and the management of the University in relation to the educational process (classroom Foundation, educational and scientific laboratories, etc). The level of provision of educational services largely determines the rating and performance of the University in the education market. If the structure of management of the educational institution deploys from the point of view of efficiency, it is transformed into the form presented in Figure 2.

Figure 2. The structure of University management based on their performance

The structure component "Achievements" Y combines the following elements: the level of satisfaction of students, enterprises and institutions, consumers, labour, higher education, teaching corps; the educational level of students; impact on society. The structure of the component Resources X includes elements such as: the leading role of leadership and collegiality of decision-making; policy and strategy in the field of quality; financial, logistical and other resources; teaching staff and other personnel; partnerships with businesses and institutions, students, social organizations. Decision-making is about the size of the obtained efficiency. The algorithm of decision-making is presented in Figure 3.

Figure 3. Algorithm for management decision

As a control object in the control structure of the educational institution will be considered by educational service as an essential element of the educational process, and the management will be divided into two circuits: the "resource Management"{g₁, g₂, …, g_n} and "Management advances"{h₁, h₂, …, h_n}. The output parameter is the efficiency of k that characterize the educational service. The input stream in turn, is divided into two components: "Resources" X and "Achievements" Y all participants in the educational process. Both components, in turn, are complex systems with their input and output streams.
The algorithm of functioning of the control device and the algorithm of functioning of the control object will be described dependencies:
g(t) = А_y[X(t), k(t)]
h(t) = А_y[Y(t), k(t)]
k(t) = А_о[g(t), h(t), Z(t)]
Component input stream "Resources" includes two types of resources:

external, which include: financial security r₁; logistical supply r₂; methodical provision r₃; organizational security r₄; provision of professional development r₅; Information security r₆; system of incentives r₇;
the interior: the level of preparedness and adaptation to professional activity.

Each component of the components in the "Resources" and "Achievements" feature or settlement, or expert opinion. Among the characteristics that can be measured and monitored, determining the quality management of the educational process, a significant position indicators of the quality of resource management. Regarding boot classrooms quality criteria are objective and simply defined in a quantitative measure. Quality use of teaching staff, the situation is somewhat more complicated: each teacher has a personal view to the quality made up for him the schedule and quality of the schedules of the students regarding his discipline. As it is known [1, 8], the schedule has a pretty significant impact on the quality of training at all. The purpose of management of the educational process and revealing hidden factors negatively affecting it uses mathematical models, based on the apparatus classical regression analysis. Based on these models, forecasts quality class schedules, which are used in the process of scheduling that allows you to reduce the number of possible schedules when searching for the optimum.

Conclusions

The developed model will allow us to estimate the generalized quality schedules in the process of fromation of the point of view of efficient use of resources of the school (classrooms and teaching staff). To improve the model it is necessary to examine the components of quality schedules and their impact on the efficient use of resources.

References

1. Lutsenko E.V., Korzhakov V.E., Laptev V.N.Teoreticheskie osnovy i tehnologiya primeneniya sistemno-kognitivnogo analiza v avtomatizirovannyh sistemah obrabotki informatsii i upravleniya (ASOIU) (na primere ASU vuzom). Monografiya (nauchnoe izdanie). Maykop, AGU. 2009. – 536 p.
2. Lutsenko E.V., Korzhakov V.E. (2007). Reflexive automatized management system of specialist training qulity. VestnikAdygeyskogogosudarstvennogouniversiteta. Seriya 4: Estestvenno-matematicheskieitehnicheskienauki. No4. p.28-36.
3. Spіvakovs'kiy O.V. (2004). Peculiarities of automated controlling systems by higher educational institutions. VіsnikHarkіvs'kogonatsіonal'nogounіversitetu. No 629. P.86-99.
4. Gevlich I.K. Modeli i algoritmy povysheniya effektivnosti upravleniya obscheobrazovatel'nym uchrezhdeniem na osnove kompleksnoy otsenki deyatel'nosti prepodavatel'skogo korpusa. Astrakhanʹ, 2013. , 16 p.
5. Burnasov P.V. (2012) Optimal control of resources during scheduling of class times. VіsnikKrivorіz'kogotehnіchnogounіversitetu. No 33. – p. 149-153.
6. Morkun V.S., Morkun N.V, Pikilnyak A.V (2014). Modeling of ultrasonic waves propagation in inhomogeneous medium using fibered spaces method (k-space). Metallurgical and mining industry. No. 2. p. 43 – 48.
7. Burnasov P.V. (2008). Quality criteria of automated scheduling of class times. VіsnikKrivorіz'kogotehnіchnogounіversitetu. No 22. P. 136-140.
8. Savel'ev A.Ya., Zubarev Yu.B, Kovalenko B.E. , Koloskova T.A. Avtomatizatsiya upravleniya vuzom [Control automatization of university]. Moscow, Radio i svyaz', 1984.

Research of properties of conditionality of task to optimization of processes of concentrating technology is on the basis of application of neural networks

Fri, 26 Sep 2014 11:03:57 +0300

The paper describes research of properties of conditionality of task to optimization of regime parameters of technological processes of concentrating of iron-stone is on the basis of forming of goal function with application of multi-layered neural networks.
Key words: conditionality of task to optimization, goal function, neural network, concentrating of iron ore.

Research of properties of conditionality of task to optimization of processes of concentrating technology is on the basis of application of neural networks

Andrey Kupin

Dean of IT faculty,
Doctor of Science,
Professor of Computer Science,
Computer Systems and Networks department, Krivyi Rih National University

Complexity indexes of optimization of multidimensional objective functionals in order to fulfil intellectual control in the conditions of technological processes (TP) of iron ore concentration are considered [1, 2]. It is necessary to define whether the task is badly conditioned. The result of such analysis determines efficiency of application of selected method of global optimization. The following factors influence the conditionality of multivariable task: presence of local extremums in search areas, their amount and dimension, bulge and smoothness of objective function, etc. [3]
Let us estimate the conditionality of task of global optimization of multivariable goal function for the conditions of TP section of concentrating complex. Granting the certain stage of concentrating of magnetite quartzites is approximated by a neural network (NN) with one hidden layer (fig. 1).

Figure 1. An example of multi-layered neutral network of direct distribution for approximation of TP of one stage of concentrating

If the function of activating as sigmoid for all types of layers is used, then mathematical expression of neural network appears as:

(1)

where is common expression for the activation function of sigmoid type for the output hidden and input glowed networks; yi – a value of output signal of network; nh – amount of neurons of the hidden layer; n – dimension of input vector; θ – vector of parameters of neural network, which require tuning (contains weight coefficients and neuron changes ); fj(x)– the value of activation function of neurons for an input and hidden glowed; Fi(x)– value of function of activating of neurons of initial layer.
Then on the basis of expression of technological criterion from [1] for one certain stage one can form objective functional for further optimization as follows:

, (5.2)

where і is the number of chosen stage of concentrating; Q _i ,y_i - productivity of the corresponding stage; - quality of output product and tails of the selected stage; ,- minimum and maximum limits on the parameters of quality of industrial product and loss in tails after the stages.
Taking into account the expression (1) a goal function may be presented as optimization task with four conditions:

(3)

For the removal of the marked limitations and decision of such optimization task it is necessary to apply the method of penalty functions or method of the modified Langrangians [3-5]. At the same time the use of the marked approaches lead to worsening of properties of conditionality. Therefore for the estimation of conditionality expression (3) on the first stage can be simplified (to analyse case-insensitive limitations)

(4)

In case if task of search of global extremum as (4) is badly conditioned, then, accordingly, concerning more general and difficult (due to the necessity of taking into account the limitations) task (3) it is necessary to do analogical conclusions. Otherwise it is necessary additionally to check the conditionality of complete optimization task (3).
According to [3] direct method of calculation of conditionality of optimization task is based on the calculation of matrix of Hesse for the goal functional (of flexon ) and for finding the complete great number of own values. Herein, if , then the following expression is true:

(5)

where - local degree of multi-modality (the presence of many extremums) in a point (х); is a spectral number of conditionality of matrix of Hesse ; is a value of own numbers of matrix is the point (х);N_λ - complete amount of own numbers.
The criterion of conditionality of optimization task is the expression

(6)

where is the length of bit net of calculable machine (for the most modern programming language of high level the maximal exactness of calculations may be realized by two types of Double/Extended: range of values of bit net within the limits of 5,0e-324...1,7e+308/3,4e-4932.1,1e+4932 respectively; amount of numbers of mantissa is 15/19 signs; a volume of necessary memory is 8/10 byte [6, 7]).
Fulfilment of condition (6) allows to classify optimization task as badly conditioned. Vector of gradient for goal function (4) equals:

, (7)
where ;

.

Hesse matrix for goal function of (4) type is determined on the basis of vector of gradient

==
, (8)

where

By convention the own numbers of matrix of (8) type are determined as roots of equation:

where E is a single diagonal matrix of dimension n x n.
With taking (8) into account we will obtain:

(9)

After opening of determinant (9), we will get characteristic equalization of the following type:

(10)

where are certain coefficients, which are calculated on the basis of determinant (10).
Hereafter the numeral solution of characteristic equation (10) with selected exactness E_λ is made. Herein the roots λ > 0 are selected. The maximum and minimum values of such roots are placed into expression of criterion (6). After calculation of the value of criterion there made a conclusion about the conditionality of task of global optimization.
Methodology of determination of degree of conditionality of optimization task of goal function of (4) type can be represented as an algorithm (fig. 2).

Figure 2. The general algorithm of determination of conditionality of goal function on the basis of NN

Calculations executed according to the algorithm (fig. 2) with parameterization only of the first stage of TP concentration allow to draw conclusion about bad conditionality of task of global optimization even for a goal function of (4) type. Separate results over and estimation of such calculations are shown in the figure 3.

Figure 3. Indexes of conditionality of optimization task of NN goal functions for TP concentrating at different maximum parameters of computer bit grid of (1 is a trend on the base of application of data types Double; 2 is extrapolation with the use of Extended type).

Analysis of fig 3 shows that at application of 8-byte of Double data type with mantissa of 15 signs the maximum value of spectral number of conditionality (1.7Е+308) is achieved at already at the amount of weights of neural network of less then 1000. At the further increase of weights of NN from 1000 to 10000 a maximum value is achieved for the type of Extern (1.1e+4937).

Conclusions

Undertaken studies allow to confirm that task of global optimization of parameters of TP of concentrating for one or a few stages on the base of NN are goal (with the use of limitations and without them) functions it badly conditioned. The above mentioned shows the limit possibilities of application of traditional methods of multivariable optimization (in particular, gradient) [3]. For the successful decision of the task it is necessary to use the methods, which are proof to the conditions of multi-modality of goal functions.

References

1. Kupin, A. I. Intellectual identification and controls in the conditions of processes of concentrating technology. The monography. Kyiv, Korneychuk's Publishing house, 2008.
2. Kupin, A. I. Neural identification of technological process of iron ore beneficiation. – Proceedings of 4th IEEE Workshop on Intelligent Data Acquisition and Advanced Computing Systems Technology and Applications (IDAACS’2007). Dortmund, Germany, 2007. P.225–227.
3. Chernodutsky I.G. Optimization methods into control theory. SPb, Piter, 2004. 256 p.
4. Karr C.L. (200). Optimization of hydrocyclone operation using a geno-fuzzy algorithm. Computer Methods in Applied Mechanics and Engineering, No 186. P.517–530.
5. Morkun, V., Goncharov, S., Pikilnyak, A., Krivenko, A. (2012) Iron ore benefication processes optimization. ТЕKA. Commision of Motorization and Energetics in Agriculture 12, No.4, P.162-166.
6. Jones M.T. AI Application Programming. Charles River Media, 2003.
7. Popovic D., Bhatkar V.P. Distributed Computer Control Systems in Industrial Automation. CRC Press, 1990.

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