Metallurgist (v.62, #3-4)

Simulation and Hydrodynamic Characteristics of the Motion of a Melt in a Ladle by O. V. Tokarnikova; V. A. Ul’yanov; V. A. Korovin (187-192).
We analyze the processes of modification and refinement of a melt in a casting ladle from the viewpoint of the nature, possibilities, and efficiency of their influence on the metal. The hydrodynamic processes running in the ladle are analyzed in detail by means of the physical simulation. The analysis of the results of simulations and the obtained approximate analytic model is performed for the improvement of the procedures of refinement and modification.
Keywords: melt; refinement; modification; modeling; hydrodynamics; ladle; nonmetallic inclusions; speed of mixing of the liquid bath

Simulation of Structure Formation in Shaped Rolled Steel in the Process of Its Heat Treatment by A. B. Sychkov; A. B. Moller; D. V. Nazarov; G. Ya. Kamalova; S. O. Malashkin (193-202).
We present the results of development of the technology of thermal hardening and thermal straightening of shaped rolled St3 steel (structural angles) based on the mathematical and physical simulation of the process of heat transfer with accelerated water cooling of the metal. For this purpose, we used the DEFORM 3D + HEAT TREATMENT software environment of the finite-element method and carried out laboratory experiments in three furnaces for different temperatures and holding times varying within broad ranges in order to simulate the modes of accelerated water cooling of shaped rolled products. The characteristics of mathematical simulation of the technology of thermal treatment of equal-section rolled structural angles 63 × 63 × 4 mm in size made of St3sp steel are presented with an aim to evaluate the structure and mechanical properties of the rolled metal. It is confirmed that the diffusion phase transformation is accompanied by the heat release (the so-called phenomenon of recalescence). We also present the temperature distributions over the sections and areas of the rolled steel showing that the less massive areas of the profile (edges of the structural angles) are cooled much more intensely than the massive sections (the top of the profile angle). However, the areas accumulating more heat transfer their heat to less massive and hardened areas. As a result, we observe the self-tempering of the martensitic areas accompanied by the formation of tempering pearlitic structure quite efficient for the purposes of operation. The laboratory investigations were carried out on three shaped profiles (equal-leg structural angles 40 × 40 × 4 and 75 × 75 × 8 mm in sizes and channel No. 5). The efficiency of thermal treatment was proved for shaped profiles made of unalloyed ordinary St3sp steel hardened within the range of tempering temperatures 200–650°C, with attainment of the hardening coefficient within the range 1.4–2.6 (according to the temporal rupture resistance). This guarantees the possibility of the production of angled rolled products of elevated strength classes within the range 440–1130 MPa instead of the original hot-rolled strength class of 320 MPa (by the yield strength). The obtained results of modeling of the technology of thermal treatment of structural angles made of St3sp steel can be extended (after the required experiments) to other types of steel (e.g., 09G2, 09G2S, 10KhSND, etc.) with the exception of expensive microalloying with vanadium, niobium, titanium, and other elements.
Keywords: shaped rolling; structural angle; thermal treatment; straightening; mathematical and physical simulation; laboratory experiments; water accelerated cooling; temperature distribution over the rolled section; microstructure; hardness; microalloying; strength class

We describe the results of a study of the longitudinal and circumferential variation in pipe/tube wall thickness as a function of kinematic tension coefficient for pipe/tube passing through three stands of a reduction mill. The study was performed via computer modeling using the DEFORM software. The variation in pipe/tube wall thickness and the mean wall thickness were found to decrease as the kinematic tension coefficient increased, as evidenced by the calculated dispersions, root mean square deviations, and coefficients of variation.
Keywords: pipe rolling; reduction mill; kinematic tension coefficient; variations in pipe/tube wall thickness; finite-element modeling

On the basis of simulation with the help of the QFORM VX software, we study the CONFORM process with an aim to eliminate the delamination defects of products in the course of subsequent heat treatment. In the first stage of the solution, it is necessary to determine the stress-strain state in the deformation zone in the billet and to analyze the behavior of the flow of metal and the appearance of the zones of hindered deformation.
Keywords: pressing; copper; hot forming; stress; strain; CONFORM process; QFORM software

Modeling and Mastering the Forging of Crystallizing Metal by E. N. Sosenushkin; L. S. Frantsuzova; E. A. Yanovskaya; T. A. Kinzhaev (212-217).
The rational use of metal is determined by the use of alternative methods to produce blanks, including forging a crystallizing metal. Application of external pressure to the melt during crystallization completely eliminates gas porosity, which improves the mechanical characteristics of the products, and substantially increases the crystallization rate, which improves the life of dies. The results of mathematical modeling underlie the selection of thermomechanical conditions for forging of metals (iron, steel, and aluminum alloys) that crystallize under pressure. A number of liquid metal forging processes are mastered.
Keywords: melt; crystallization; pressure; die; thermomechanical conditions

About a Possibility of Using Blast Furnace Heat Balance to Control Heat Losses by O. P. Onorin; A. A. Polinov; A. V. Pavlov; N. A. Spirin; I. A. Gurin (218-224).
In this paper, the overall and zonal thermal balances of the blast-furnace smelting were analyzed. Under the current blast furnace smelting conditions, the specific consumption of coke is determined by the development of the heat transfer processes occurring in the lower zone of the furnace. In this case, the heat losses found by using the heat balance of the lower zone of the furnace sufficiently reflect such technological factors as specific coke consumption and silicon content in cast iron. It was shown that the existing methods of analytical calculation of the heat losses occurring during smelting of cast iron in blast furnaces do not adequately reflect the actual melting process. It was established that the analysis of the heat balance of the lower stage of heat transfer enables determining the heat losses in this zone of the furnace and estimating the correction factors when the blast furnace smelting conditions change. The control of heat losses is necessary for estimating the condition of the blast furnace masonry, rational gas distribution, and also, for adjustment of coke consumption.
Keywords: blast furnace process; zonal and overall heat balance; heat losses; heat analysis

Forms of Zinc Occurrence in Blast-Furnace Dust by E. N. Selivanov; S. N. Tyushnyakov; A. A. Pankratov (225-230).
Results are given for a study of the phase and elemental composition of EVRAZ Nizhny Tagil Metallurgical Plant blast-furnace flue dust. An estimate of particle size is performed in a laser analyzer. Dust is represented by a set of particles of calcined charge with sizes from 1.5 to 1170 μm, with a median size of 82.9 μm. The elemental composition of the blast-furnace dust in local sampling points is determined by x-ray microanalysis. The dust consists of large iron oxide particles and fine particles containing MgO, CaO, SiO2, and Al2O3 in the form of complex silicates and ferrites, as well as inclusions of mechanically entrained coke. Zinc is present in form of oxide, sulphide and sulfate compounds as a surface layer on particles with increased thermal conductivity (FeOx). The zinc and sulfur contents in the layer (1–5 μm) reach 45 and 6%, respectively. The data obtained are useful for substantiating dust treatment processes.
Keywords: blast-furnace dust; composition; size; phases; structure; iron oxides; zinc; sulfur

Mechanical Properties and Corrosion Behavior of Bridge Weathering Steels Containing 3.5% Ni by Gao Xinliang; Xiao Yao; Fu Guiqin; Xu Dong; Zhu Miaoyong (231-238).
Two types of steel specimens were prepared containing 3.5% Ni in order to study the mechanical and corrosion properties of bridge steels in a marine atmosphere. Corrosion depth was evaluated by measuring weight loss after accelerated corrosion tests by alternating cycles of immersion and drying. Steel microstructure, and corrosion layer characteristics of bridge steels with different Mn content in different stages of corrosion were studied by using methods of light, transmission, and scanning electron microscopy, and also Raman spectroscopy. Results show that the microstructure of the bridge weathering steels consists of quasi-polygonal ferrite, acicular ferrite and granular bainite. Strength and corrosion resistance are improved with an increase in Mn content. The distribution of Ni and Mn is uniform within corrosion product layers, although there is an increase in Cu content within cracks and pores of the corrosion product layer. Corrosion products mainly consist of α-FeOOH, γ-FeOOH, and Fe3O4, and their content through the corrosion layer differs insignificantly.
Keywords: mechanical properties; corrosion properties; bridge weathering steel; corrosion product layer

We study the technological specific features of the production of steel ingots without zonal chemical inhomogeneity aimed at manufacturing the billets of various parts of power-generating units made of 15KhN3MFA and 15Kh2MFA steels. The technology of pouring in a vacuum is developed with regard for the results of the numerical analysis of the process of solidification of a steel ingot 13.56 tons in weight by using the Poligon system of automatized modeling of the pouring processes. In order to get high-quality ingots, steel was melted in an EAF-12 according to a special technology guaranteeing low contents of sulfur, phosphorus, nonmetallic inclusions, and hydrogen. The specific structural features of an ingot with a mean diameter of 922 mm and the ratio H/D = 2.05 are taken into account in the development of the technology of forging in a 3000-ton press. Forging is performed for billets 900 × 930 × 1200 mm in size with the axial channel located at the top of the billets. To avoid confusions, sulfur prints were made from the top and bottom surfaces of the billet. The investigations demonstrate that the sulfur prints are practically identical for both surfaces, and small separate sulfur inclusions are uniformly distributed. The macrostructure corresponds to the GOST-10243. The results of UT testing demonstrate that the billets of the parts contain no defects with an area greater than 5 mm2. The mechanical properties at temperatures 20°C and 350°C are practically identical and higher more than the requirements of normative documents by 15–20%. For the additional metallurgical quality examination of the metal, we manufactured a test shell with a height of 1100 mm, an outer diameter of 870 mm, and a wall thickness of 250 mm.
Keywords: forged steel ingot without zonal chemical inhomogeneity; production of a 13.56-ton ingot in a vacuum; melting of 15KhN3MFA and 15Kh2MFA steels with low contents of sulfur, phosphorus, and nonmetallic impurities in the EAF-12; forging of billets in the press; absence of defects greater than 5 mm2 in the billets; mechanical properties at temperatures of 20 and 350°C

The effect of various factors (hydrogenation, segregation of phosphorus, arsenic and other elements), which reduce the cohesive strength of grain boundaries, on the ductile-brittle transition in structural steels is considered. It is shown that during brittle fracture accompanied by weakening of cohesive strength of grain boundaries, the free path length of brittle crack of Λb becomes a variable value, i.e., Λb=df+ξfidfi, $$ {Lambda}_b={d}_f+xi {f}_i{d}_f^i, $$ where df is the size of brittle fracture cleavage facet, dfi $$ {d}_{mathrm{f}}^{mathrm{i}} $$ is the size of brittle intercrystalline fracture; ƒi is the frequency of microcracks through grain boundaries, ξ is a geometric coefficient for interrelationship between df and dfi $$ {d}_{mathrm{f}}^{mathrm{i}} $$. For the case of mixed fracture, ductile-brittle transition is described by expression Tc=Tc0+B1−fi/df1+ξfi. $$ {T}_c={T}_c^0+Bleft(1-{f}_i ight)/{d}_fleft(1+xi {f}_i ight). $$ In practice, by measuring the proportion of intergranular fracture in the brittle fracture zone it becomes possible to estimate the change in the Tb level. Results are confirmed by experiments for the phenomena of thermal brittleness and hydrogen corrosion.
Keywords: critical brittleness temperature; ductile-brittle transition; cohesive strength; microstructure; nonmetallic inclusions; brittle fracture facet; pit; brittle microcrack

Effect of Heat Treatment on Impact Strength of Welded Joint Metal Made by Submerged-Arc Welding by L. A. Efimenko; T. S. Esiev; D. V. Ponomarenko; S. P. Sevast’yanov; I. Yu. Utkin (254-260).
A study of the morphology of the metal structure in the near-seam section of the heat-affected zone (HAZ) is performed by simulating pipe manufacture. The influence of microstructure on HAZ metal resistance to brittle fracture is estimated. Causes for low values of the impact toughness of the HAZ metal are revealed as well as the possibility of improvement by carrying out post-welded metal local heat treatment.
Keywords: main pipelines; strength category; near-seam section of the heat-effected zone; metal impact strength; microstructure; structure morphology; heat treatment

Mechanism of Fe2C Type Eutectic Carbide Formation Within Damascus Steel Structure by D. A. Sukhanov; L. B. Arkhangel’skii; N. V. Plotnikova (261-269).
Three stages are developed for forming a Damascus steel structure of high-purity white cast iron BU22A obtained by vacuum melting. In the first stage of the production process, a continuous of carbide sheath is formed along the boundaries of austenitic grains, which morphologically resembles ledeburite inclusions. In the second stage of the process, there is compaction and faceting of large eutectic type carbide formation. In the third stage of the production process (forging), a globular sorbite matrix is formed with faceted eutectic carbides in size from 5.0 to 20 μm distributed unevenly in the deformation direction. It is observed that the stoichiometric composition of faceted eutectic carbides is within the limits of 34 < C < 36 at.%, which corresponds to Fe2C type ε-carbide with a hexagonal close-packed lattice. A two-stage mechanism is considered for conversion of excess secondary cementite into faceted Fe2C type eutectic ε-carbides. It is revealed that isothermal exposure duration on heating to the eutectic temperature, is an integral part of the process of forming new excess Fe2C type carbides with a hexagonal close-packed lattice.
Keywords: Damascus steel; Wootz steel; tool steel; forged white cast iron

Combined Technology of Aluminum Alloy Vertical Casting and Simultaneous Deformation by A. M. Sergeeva; N. S. Lovizin; A. A. Sosnin (270-274).
Technology is developed combining continuous vertical casting of metals with simultaneous deformation, and the device operating principle and implementation of this technology are described. Data are provided for the design features and functioning of the device. Results of experimental studies of AD0 and D16 alloy billets are provided. It is shown that this technology makes it possible in a short production cycle to prepare long metal objects at a rate of 2 m/min. The blanks obtained exhibit a fine-grained structure with a grain size not exceeding 7 μm, and also increased hardness, inferior to the maximum possible by 23%.
Keywords: continuous casting; deformation; combined production processes; crystallizer; metal deformation in a solid-liquid state; aluminum alloys; billet

Features of High-Strength Pseudo β-Titanium Alloy VT47 During Strengthening by Heat Treatment by N. A. Nochovnaya; A. A. Shiryaev; E. A. Davydova (275-282).
Actual information is provided about formation of structural defects typical for highly-alloyed titanium alloys, i.e., α-phase precipitate-free zones. The effect of these defects on the mechanical properties of pseudo β-titanium alloys is considered. The structure is studied for a new pseudo β-titanium alloy VT47 and a correlation is established for mechanical properties and presence of these zones within the structure. x-Ray microanalysis is used for an analytical study of the local chemical composition of alloy VT47 that makes it possible to establish that formation of precipitate-free zones the main and most important features is not connected with the different chemical composition in in the test ranges of alloying element concentration for the zones themselves and areas adjacent to them.
Keywords: pseudo β-titanium alloys; high-strength titanium alloys; VT47; precipitate-free zones; microstructure; mechanical properties

Comparison of Fatigue Properties for Alloy EP708 Specimens Prepared by Selective Laser Melting and Hot Rolling by M. G. Khomutov; A. Ya. Travyanov; P. V. Petrovskii; V. V. Cheverikin; A. I. Dubin (283-288).
Structure and fatigue resistance tests of EP708 alloy specimens prepared by selective laser melting (SLM) and subjected to strengthening heat treatment and hot isostatic pressing (HIP), combined with heat treatment compared with hot-rolled heat-treated specimens, are studied. It is shown that the use of the HIP process significantly reduces specimen porosity obtained by the SLM method for EP708 alloy, and it also increases cyclic endurance. Test specimens prepared by the SLM method, after heat treatment and after HIP and heat treatment, as well as those hot-rolled and heat-treated, withstand 2·106 cycles during the first stage of loading at 340 MPa. With a subsequent increase in the load to 380 MPa, the best cyclic durability is shown by specimens in a hot-rolled heat-treated condition. In this case, specimens after HIP and heat treatment show a reduction of twice the cycle time from the hot-rolled specimens, and the specimens obtained by the SLP method given heat treatment have an operating cycle an order of magnitude lower than for hot-rolled specimens. The SLM-specimens after HIP and heat treatment have characteristics comparable with hot-rolled heat-treated specimens for fatigue resistance required by the standard documents for products made of alloy EP708.
Keywords: selective laser melting; fatigue testing; alloy EP708; hot isostatic pressing

Effect of Heat and Aerothermoacoustic Treatment Regimes on Bronze BrNKhK Structure by G. A. Vorob’eva; E. Yu. Remshev; G. A. Danilin; D. A. Bespalov (289-295).
The effect of heat treatment on structure and mechanical property formation for bronze BrNKhK is considered. Results of research are provided for improving the strength and elasticity of the alloy by optimizing heat treatment regimes. The data presented point to a significant effect of aerothermoacoustic treatment on the structure and the possibility of improving bronze mechanical properties both for coldrolled bronze BrNKhK, and with use of aerothermoacoustic treatment after aging.
Keywords: bronze; heat treatment; aerothermoacoustic treatment; microstructure

Reduction of Arc-Furnace Smelting Cycle Time at Tagmet by V. V. Emel’yanov; P. Yu. Gorozhanin; I. S. Murzin; A. V. Stonoga; E. A. Kolokolov; S. S. Belonozhko; S. V. Tyutyunik (296-299).
We discuss a technology for reducing the smelting cycle time and detecting unscheduled interruptions during unpowered operations associated with steel smelting in arc furnaces. We have implemented several measures to reduce the duration of smelting at TAGMET by 10%.
Keywords: electric steel smelting; steel; ladle metallurgy; steel smelting arc furnace; oxidation; bay window; metal charge; scrap; dephosporization; oxidation period; refining

In the present paper, we reflect the main aim of control over the process of separation of iron ore in the course of wet magnetic dressing. We propose a procedure of deducing equations for the dependence of losses of the useful component in tailings and the mass fraction of magnetite iron in the concentrate on the water flow rate in the separator and the rotational speed of its drum. A mathematical description of some blocks of the automatic system of control over the magnetic separator is given. The results of its modeling in the package of applied programs of the MATLAB Simulink software are presented. The operation of the system is studied under the conditions of drift of the static characteristics of the magnetic separator.
Keywords: extreme regulator; I-regulator; magnetic separation; concentrate; tailings; total iron; magnetite iron

Modeling of the Temperature Field of Air Tuyeres in the Blast Furnaces with Thermal Insulation of the Nose Portion by A. G. Radyuk; A. E. Titlyanov; M. M. Skripalenko; S. S. Stoishich (310-313).
The computer modeling of the dynamics of heating of the nose part of an air tuyere of a blast-furnace is performed with the help of the DEFORM-2D computational environment for finite-element analysis. We investigate the influence of the thickness of heat insulation mounted at the end of the nose portion inside the annular flange on the temperature field. The results of modeling demonstrate that the temperature of the copper flange guaranteeing the protection of heat insulation in the course of transportation of the tuyere and its installation in the furnace does not exceed the temperature permissible for copper. The heat insulation of the end of the nose portion of the tuyere decreases the temperature of its heating, which guarantees a decrease in the heat losses caused by water cooling the tuyere. The increase in the thickness of heat insulation from 10 to 20 mm insignificantly affects the temperature of the end face of the nose under the insulation and, hence, in choosing the thickness of heat insulation, it is necessary to analyze its strength characteristics and the conditions of cooling of the nose part. The possible destruction of heat insulation does not lead to failure of the tuyere.
Keywords: blast furnace; air tuyere; nose part of the tuyere; flange on the end face of the nose; heat insulation of the end; temperature field; finite-element simulation

We consider thermal processes running in the course of cooling of a continuously cast ingot in a continuous billet casting machine with regard for the heat of phase transformations. For the solution of the problem of rational utilization of the heat of melts, we propose to improve the technology of continuous casting of steel, which would make it possible to use the heat of the liquid core of an ingot for leveling the temperature field over its cross section and guarantee the minimum losses of the heat at the exit of the continuous billet-casting machine. We develop a mathematical model of cooling of continuously cast ingots in a two-dimensional space representation with regard for the release of the heat of crystallization in the two-phase zone. The numerical realization of the model is performed with the help of the implicit difference scheme of coordinate-wise splitting. The adequacy of the model is checked by analyzing the convergence of the experimental and numerical data according to the Fisher, Student, and Mann–Whitney criteria. In modeling, we simulated the control action in the zone of secondary cooling. It is established that, in the case of application of the control action in this zone, the surface temperature increases by 160°C, while the average mass temperature increases by 100–160°C. We choose criteria for the rational modes of cooling of continuously cast ingots. To preserve the heat content of an ingot, it is proposed to use heat insulation after the zone of water–air cooling. We determine relationships between the parameters affecting the surface temperature of the ingot and represent them in the form of nomograms. It is shown that, before the machine of gas cutting, as a result of heat insulation in the zone of air cooling, the ingot is thermostatted as a result of which the temperature of its most vulnerable zones (corners and surfaces) increases. It is established that, for the rational modes of casting of steels, the ratio of the length of the zone of heat insulation to the total length of the continuous billet casting machine varies within the range 0.3–0.6. To determine the heat losses in the process of subsequent cooling of the ingot in air after leaving the zone of machine gas cutting, according to the existing technology of transportation of slabs to compression, the time of modeling was set equal to 90–105 min. To preserve the heat content of the ingot and level temperatures over its cross section, it is also necessary either to use a thermally insulated transmission roller conveyer or to hold ingots in a thermostat.
Keywords: continuous billet casting machine; mathematical model of the rational cooling mode; energy saving; temperature field; heat content; heat insulation

Extending the Life of Blast-Furnace Air Tuyeres by L. A. Zainullin; A. Yu. Epishin; N. A. Spirin (322-325).
Air tuyeres are the most thermally stressed components of blast furnaces; therefore, extending their life is of importance. Operating experience suggests that the intensification of cooling alone does not prevent burnout of tuyeres. In this connection, the VNIIMT presents design developments that combine advanced cooling intensification solutions and thermal insulation protection, which can significantly extend the service life of air tuyeres.
Keywords: air tuyer; body; nose; burnout; cooling; blast furnace; cooling passageway; blowpipe; wall

Assessing the Effectiveness of Slag Foaming in Electric-Arc Furnaces by A. A. Kozhukhov; V. I. Kozhukhova (326-330).
The crucial role of foamed slag in improving the effectiveness of the arc-furnace process is beyond any doubt. However, there is no consistent approach to the description of the slag foaming mechanism despite the wide application of this process in modern electric-arc furnaces. Aspects of assessing the effectiveness of slag foaming are considered. A new index characterizing the slag foaming rate is introduced. It allows determining the superficial gas velocity that ensures effective foaming of slag depending on its physical and chemical properties.
Keywords: electric-arc furnace; slag foaming; gas velocity; physical and chemical properties

We have developed an algorithm for diagnosing temperature conditions in metals during heating in a continuous furnace. This algorithm is based on a mathematical model of the process which uses a single differential equation to describe the non-steady-state thermal conductivity and heat exchange boundary conditions based on current measurements of the parameters describing the external heat exchange. We have also developed an approach for real-time monitoring of the quality of the results obtained using the proposed diagnosis algorithm, based on comparison of different determinations of the thermal flux absorbed by the metal.
Keywords: continuous furnace; heating process; temperature field; mathematical model; adequacy of model; external heat exchange

Published sources are reviewed devoted to use of heat treatment for high-strength automotive steels based on the phenomenon of carbon redistribution between martensite and untransformed austenite during quenching and partitioning. The possibility of implementing quenching and partitioning heat treatment providing presence of an increased amount of retained austenite in the microstructure is shown by experiment on the example of silicon-containing steels with good hardenability.
Keywords: steel; heat treatment; stepwise quenching retained austenite; martensite; carbon partitioning

The effect of strain ageing parameters on the impact strength of low-carbon microalloyed C–Mn–Si–Nb–V–Ni–Cu-steel on the example of rolled product 150 mm thick after normalizing and additional heat treatment is demonstrated. The change in steel critical impact strength with the degree of prior cold deformation and with additional heating to 250°C is studied. Tendency towards strain ageing at 1/8 and 1/4 of sheet steel thickness after heat treatment is studied.
Keywords: low-carbon steel; rolled plate; strain ageing; heat treatment; mechanical properties

Preparation of Superconcentrate and Chromium Powder from Chromite Ore by V. A. Martirosyan; M. E. Sasuntsyan; V. V. Savich (355-360).
Non-traditional metallurgical technology of comprehensive processing of Sevan chromite (with a 43–46% Cr2O3 content) is developed allowing chromium extraction from local chromite in the form of more expensive chromium powder. The process of increasing the reactivity of chromite concentrate (with a Cr2O3 content of 53%) as a result of thermal and mechanochemical treatment both in the presence and in the absence of chlorides has been investigated for this purpose. It is found that in both cases, with heating and with grinding in the presence of chlorides, selective chlorination occurs similar to high-temperature chlorination. The resultant iron and magnesium chlorides are removed after washing, and the remaining residue after drying is a super-concentrate with a Cr2O3 content of 74.12% in the case of firing and 77.23% in the case of mechanochemical activation, with a low iron and magnesium content. The possibility of obtaining powder chromium with low content of iron and magnesium by processing the super-concentrate obtained by extra-furnace aluminothermic reduction is demonstrated.
Keywords: chromite concentrate; super-concentrate; chromium powder; chlorination; chloride; thermal and mechanochemical treatment; aluminothermic reduction; iron; magnesium

Development of Alkaline Decomposition of Lepidolite Concentrate by Melting with Calcined Soda and Melt Comprehensive Sulfuric Acid Treatment by V. I. Samoilov; Zh. S. Onalbaeva; M. A. Adylkanova; G. A. Kokaeva; S. A. Abdulina (361-368).
Experimental research is conducted for recovery of lithium from lepidolite. A method is developed for alkaline decomposition of lepidolite based on melting with calcined soda and subsequent melt granulation with water. Lepidolite activated in this way is thoroughly and comprehensively broken down by sulfuric acid. In addition, kinetics are studied for reaction of the granulate obtained with sulfuric acid. It is established that the granulate sulfatization reaction with sulfuric acid proceeds in a diffusion region that makes it possible fundamentally to select equipment formulation for sulfatization.
Keywords: lithium; lepidolite; sulfuric acid; granulate

Effect of Melting Conditions on Chromium-Nickel Alloy Kh20N80 Properties by G. V. Tyagunov; E. E. Baryshev; T. K. Kostina; K. Yu. Shmakova (369-373).
Physical properties of alloy Kh20N80 in a liquid state are studied. Critical temperatures are established above which heating makes it possible to transfer melt into a micro-homogeneous equilibrium state. A timetemperature regime for liquid metal treatment is proposed and tested in industrial conditions. The use of this regime leads to a change in ingot zonal structure and more uniform distribution of alloy property values over its cross-section. At hot plastic deformation temperatures, there is a significant increase in alloy relative elongation (by 15–20%), and in this case strength properties and relative reduction of area are unchanged. In test metal, after deformation there is an increase in density and specific electrical resistance that points to increased alloy uniformity. The yield of metal after hot plastic deformation as a result of TTT increases from 66.8 to 72.3%.
Keywords: Kh20N80 аlloy; liquid metal; kinematic viscosity; time-temperature treatment; ingot structure; physical and mechanical properties

Alloy Ti–3Al–2.5V Hot-Extruded Pipe Metal Structure and Properties by I. Yu. Pyshmintsev; Ya. I. Kosmatskii; E. A. Filyaeva; A. G. Illarionov; F. V. Vodolazskii; N. A. Barannikova (374-379).
Methods of macro- and microstructural, x-ray structural analyses and mechanical tensile tests of the structure and properties of Ti–3Al–2.5V alloy hot-extruded intended for subsequent cold rolling are studied. Hot-extruded pipe is produced according to the scheme: expansion in a vertical press → extrusion in a horizontal press. It is shown that during sleeve expansion structure and phase structure do not change markedly compared with the initial hot-rolled semi-finished product in two-phase (α+β)-region. Hot extrusion in the recommended temperature range provides formation of a sufficiently homogeneous, well worked macro- and microstructure with a tangential basic texture of α-phase. A set of mechanical properties for hot-extruded pipe of alloy Ti–3Al–2.5V required for performing subsequent cold rolling used in the final stages of pipe preparation by TREX technology is provided.
Keywords: hot-extruded pipe; extrusion; pseudo α-alloy; Ti–3Al–2.5V alloy; titanium melt; TREX technology

Structure Formation Features of Corrosion-Resistant Powder Material Type 316L Gas-Flame Sprayed Coating by R. D. Bakaeva; L. Kh. Baldaev; D. Z. Ishmukhametov; V. V. Guk; A. Yu. Rashkovskii (380-388).
Implementation of the extensive possibilities of the gas-flame spraying technique with respect to the main advantages of the powder metallurgy is only possible with a methodologically justified approach to materials selection, a study of gas-dynamic processes taking place in equipment during coating formation (powder flow rate, temperature and fl ame type, etc.), and control of metallurgical processes (structure formation, liquation, phase transitions, etc.). Such phenomena need to be controlled both at the stage of initial wire and powder production, and during coating deposition. In practice, the choice of coating materials for the oil and gas industry (such as pipes, distillation columns, pumping units), should not solely be based on powder chemical composition. Features of coating structure are typically not taken into account, which are interrelated both with the initial powder or wire formation technique, and with coating deposition process parameters. This work demonstrates the differences in structure formation within steels and gasflame coatings of the similar alloy composition. A direct relationship of structure formation in gas-flame coatings is established not only with deposition technology, but mostly the method of forming the initial powder material structure. It is shown that for the effective application of coating material it is necessary to determine the alloy system, the structural class and formation technology of the powder material connected with possible inheritance and/or structure-phase transformations during coating deposition.
Keywords: gas-flame coatings; corrosion-resistant coatings; microstructure; porosity; open porosity; structure formation; alloying