Showing papers in "Steel in Translation in 2020"

Structure, Morphology and Magnetic Properties of Hematite and Maghemite Nanopowders Produced from Rolling Mill Scale

Abstract: The work is devoted to developing a cost-efficient method for the processing of metallurgical wastes such as oiled mill scale formed upon the mechanical cleaning of a hot-rolled steel strip in scalebreakers. The most significant parameters of a chemical-metallurgical process for producing expensive and highly marketed products, such as α-Fe2O3 and γ-Fe2O3 nanopowders, are experimentally determined. The properties of initial materials and nanodispersed products have been studied by X-ray diffractometry, energy dispersive spectroscopy, scanning and transmission electron microscopy, and Mossbauer spectrometry. The temperature and field dependences for the powder magnetization have been plotted according to the measurements performed with the use of a vibration magnetometer. The mill scale under investigation consists of three main phases: wustite, magnetite and hematite at a weight ratio of 6 : 8 : 7, respectively. The initial scale was activated in a magnetic mill in a hydrogen flow and dissolved in a mixture of hydrochloric and nitric acids. The resulting solutions have been used to obtain α-Fe2O3 nanocrystalline hematite by a chemical-metallurgical method, the main stages of which consist in hydroxide precipitation with the use of alkali at constant pH, washing, drying, and dehydration. Maghemite γ-Fe2O3 has been obtained from hematite in two stages. At the first stage, hydrogen reduction has been performed, whereas at the second stage, the obtained magnetite has been oxidized in air. The particles of synthesized nanodispersed oxide powders are in the aggregated condition. The particles of α-Fe2O3 are spherical, whereas the particles of γ-Fe2O3 are rod-shaped. According to Mossbauer spectroscopy, the lattices of both oxides contain magnesium, aluminum, silicon, chromium, and manganese that originate from the initial scale. These elements determine magnetic properties of α-Fe2O3 and γ-Fe2O3 nanopowders. The set of properties inherent in nanodispersed hematite and maghemite powders obtained from metallurgical wastes (mill scale) is recommended for the application in catalytic processes, in the systems of industrial wastewater purification from heavy metal ions, as well as in the manufacturing of blood analysis markers.

Method for Determining Particle Growth Dynamics in a Two-Component Alloy

Abstract: The paper deals with the issue of particle growth in a two-component alloy. The particle is formed from chemical reaction products that occur at the phase boundary. A generalized mathematical model of particle growth includes diffusion equations, mass transfer equations in the boundary layer, and equations characterizing a change in the growing particle radius. The paper proposes an approach that reduces issues to the system of PDEs and ODE that describes the state of growing particle. This approach provides a basis for developing a numerical method for calculating the growing particle radius as a function of time, based on the obtained equations. The computational scheme involves the finite-difference analogues of equations with an additional regularizing functional that ensure method stability with respect to accumulated computational error. In order to verify reliability of the proposed computational scheme and to obtain experimental error estimates of numerical solutions, computational experiments were carried out. In the experiments, the growing particle radius is determined with respect to the time via the proposed method. Also, comparative analysis of the calculated radius with test values was carried out and experimental estimates of deviations of the calculated radius from the test functions were obtained. The experiment results presented in the work indicate sufficient accuracy of the developed numerical method.

Improvement of Technical and Economic Performance of Blast-Furnace Smelting by Pellet Composition Optimization

Abstract: One of the main methods to intensify blast-furnace smelting is to improve the quality of the sintered raw materials. The article presents the study results of the influence of the composition and metallurgical properties of various Mikhailovsky GOK pellets introduced into the blast-furnace charge based on the technical and economic indicators of the blast-furnace treatment. The studies include physical modeling of pellet production of various composition, experimental determination of their metallurgical properties, as well as blast-furnace smelting simulation using the balance logical-and-statistical model of the Institute of Metallurgy, Ural Branch of the Russian Academy of Sciences (IMet). According to the simulation results, the productivity of the blast-furnace process increases when using all the test pellets, and the specific coke consumption decreases. It is revealed that when using iron-rich pellets in the charge, the sulfur concentration in the slag is significantly higher, which creates the risk of producing substandard cast iron. Based on the obtained data analysis, the technology for the use of enriched pellets (SiO2 at the level of 6%) seems to be optimal, as it provides an increase in productivity with a relatively low coke consumption and acceptable slag sulfur content.

Capability Process Assessment of Radial-Displacement Rolling of Heat-Resistant Alloy HN73MBTYU

Abstract: The paper presents an experimental study on the technological capabilities of radial-displacement rolling of small diameter rods. These are made of heat-resistant alloy HN73MBTYU on pilot mills MISIS specifying the ingot rolling schedule with a diameter of 60 mm for a 22-mm-diameter rod. The following was conducted: a quality assessment of the rod obtained, as well as a compliance with the requirements of the current normative and technical documentation. The production possibility of small diameter rods of HN73MBTYU alloy from ingots with a 60-mm diameter that meets the technical documentation requirements, with the use of technology and radial displacement rolling mills, has been proved. The tested technological solutions have a high degree of readiness for industrial introduction in mini- and micro-metallurgical plant environment.

Modeling and Optimizing the Property Choices of Materials and Structures of Shell Molds for Investment Casting

Abstract: The paper presents a mathematical model for optimizing the choice of material and morphological structure of a shell mold (SM) that has the highest resistance to cracking when liquid metal is poured into it. In order to solve this problem, the theory of small elastoplastic deformations, the heat equation, and proven numerical methods are used. The min–max objective function of control variables characterizing the properties of the SM material is constructed. The process of heating an axisymmetric SM by pouring liquid metal into it is considered. The SM resistance is estimated by the stresses arising in it. An algorithm for solving this problem is constructed. Using numerical schemes and software tools developed in previous studies, an algorithm for solving the optimization problem is constructed, and the values of control variables are found, in which the SM cannot be destroyed even being exposed to a rigid process of pouring steel into the cold SM. The analysis of the weight’s influence of each parameter found on the value of the objective function constructed is performed. A mathematical experiment is used to study the morphological structure of the SM. A five-layer SM is considered. The corrected system of equations makes it possible to consider the properties of the layers made of different materials. Calculations are performed for the cases of different positions of one of the mold layers in the mold section. This layer is made of the material found by optimization, while other mold layers are made of traditional ceramics. The optimal location of this layer is found. It is shown that the presence of several layers with the found properties does not influence the increase in the crack resistance of the SM.

Thermal Strengthening of Large Parts Made from High-Strength Sparingly Doped Steel in Air

Abstract: High-strength sparingly doped steel possessing high hardenability has been studied. The degree of mechanical characteristics after continuous cooling with various intensities in the range of 0.02–20°C/s has been determined. Industrial heat treatment of large parts from the steel under study has been implemented using air as the quenching medium. Successful isothermal treatment using air media, as well as preliminary cementation aimed at the increase in the surface’s wear resistance, has been demonstrated.

Measures for Preventing Disruption in the Blast Furnace Operation under Use of Pulverized Coal

Abstract: This article considers the industrial cases of a blast furnace operated with scull slipping and channeling A set of measures for preventing major violations in the run of blast furnaces operated on pulverized coal injection is developed and adopted

Thermal Treatment Effect and Structural State of Rod-Shaped Assortment 40Kh Steel on the Speed of Ultrasound Waves and Poisson Coefficient

Abstract: Propagation rates of ultrasound waves and Poisson coefficients in the rolled stock from 40Kh steel after various types and conditions of thermal treatment were studied. An unambiguous relationship of structural states and hardness with the rates of longitudinal, transversal, and Rayleigh waves and Poisson coefficients with the approximation coefficients of 0.83–0.99 was determined. The developed procedures of studies and special equipment, which implements a shadow–mirror technique of multiple reflections using contactless transmission and surface mount electromagnetic acoustic transducers, provide high exactness, reproducibility, and reliability of the acoustic structuroscopy methods.

Selective Reduction of Iron and Phosphorus from Oolitic Ore

Abstract: The possibility of selective solid-phase reduction of iron from oolitic ore has been experimentally confirmed. Solid phase reduction was carried out at temperatures of 850 and 1000°C in a CO atmosphere and in a mixture with solid carbon. Distribution of iron and phosphorus was investigated with a scanning electron microscope. It was found that at a temperature of 1000°C a minimum amount of phosphorus (up to 0.3%) is transformed into the metallic phase upon reduction with carbon monoxide. Upon reduction in a mixture of ore with carbon, the phosphorus content in the metal phase reaches 1.0–1.3% even at a temperature of 850°C. Thermodynamic modeling of the processes occurring during reductive roasting of oolitic ore was carried out depending on temperature (1000–1400 K) and amount of carbon in the system. It is shown that reduction temperature and degree of phosphorus reduction vary depending on the ratio of CO and CO2 in the gas phase. At temperatures below 892°C, phosphorus is not reduced, and all iron is in the metal phase. With an increase in the amount of carbon in the system, phosphorus appears in the metal phase. With an excess of carbon in the system, all phosphorus is in the metal phase at a temperature of 892°С. Thus, with a certain amount of carbon in the system and, correspondingly, with a certain ratio of CO and CO2 in the gas phase, selective reduction of iron is possible without phosphorus reduction even at a temperature of 1100°С. Comparison of experimental results with results of thermodynamic calculation confirms the possibility of selective reduction of iron without phosphorus reduction only by carbon monoxide.

Liquid-Phase Boriding of High-Chromium Steel

Abstract: The structural-phase states and tribological properties of 12Kh18N10T steel subjected to electroexplosive alloying (EPA) with titanium and boron and subsequent electron-beam processing in various modes in terms of the energy density of the electron beam and the duration of the exposure pulse have been analyzed using methods of modern physical materials science. It has been established that EPA of steel with titanium and boron leads to the formation of a surface layer with multiphase submicro-nanocrystalline structure, characterized by the presence of micropores, microcracks, and microcraters. Complex processing, combining EPA and subsequent irradiation with high-intensity pulsed electron beams, leads to the formation of 60-μm-thick multiphase submicro-nanocrystalline surface layer. It is shown that the phase composition of a surface layer of steel is determined by the mass ratio of titanium and boron during electroexplosive alloying. The microhardness of a modified layer is defined by the relative mass fraction of titanium borides in the surface layer and can be more than 18 times higher than the microhardness of steel in its initial state (before electroexplosive alloying). Modes of complex processing have been determined at which the surface layer containing exclusively titanium borides and intermetallic compounds based on titanium and iron is formed. The maximum (approximately 82% by weight) titanium boride content is observed when steel is processed in a regime with the highest mass of boron powder in the sample (mB = 87.5 mg; mTi/mB = 5.202). With a decrease in mass of boron powder, the relative content of borides in the surface layer of steel decreases. It was found that integrated processing of steel is accompanied by a sevenfold increase in microhardness of the surface layer and wear resistance of the steel increases by more than nine times.

Integral Assessment of the Corporate Strategy Effectiveness in the Iron and Steel Industry

Abstract: The study of the domestic scientific literature, as well as official methods devoted to various issues of assessing the companies operation results, made it possible to conclude that these methods generally do not consider the branch-wise specific nature of production and commercial activities, as well as environmental factors. In the context of cumulative changes, the availability of strategic management tools that provide clear ranking of an enterprise position in the industrial segment, adjust the strategy, and thereby increase the economic effectiveness, is quite relevant. The research is based on the methodological premise that enterprises that have remained afloat in the face of crisis processes in the economy implement their corporate strategies effectively. For the first time, the authors have carried out an integral assessment of corporate strategy results from 28 enterprises in Russia’s iron and steel industry during the 2014 crisis. In the assessment, a methodological toolkit was used based on the benchmarking methodology, gap analysis, process approach, and the use key indicators characterizing the effectiveness of basic functional strategies. The basic functional strategies include financial, marketing, technical and technological strategies, as well as a strategy for human resource management. According to the authors, the successful implementation of these particular strategies is essential for ensuring the enterprise sustainability. In 2014, by ranking the top of the league ironworks and potential bankrupts, the “corridor” boundaries are defined, which allows identifying the current position of a particular enterprise in the studied industry segment. The following assessment considers the possibilities of existing approaches to strategic management: gaps found in the current integral indicator values based on the effectiveness of basic functional and corporate strategies in comparison with the top of the league enterprises and potential bankrupts. The proposed methodological toolkit makes it possible to increase the strategic flexibility in the real sector of the economy under high variability conditions of environmental factors.

Modeling the Stress State of a Steel Strip with a Roller Leveling Machine under Cyclic Alternating Deformations

Abstract: The final stage in the production of hot rolled steel is leveling on roller levelers under cyclic alternating deformation. When laser cuts a sheet, it may bend due to the release of residual stresses that are unevenly distributed over the volume. The majority of roller leveler models for calculating the process under cyclic alternating deformation does not provide an adequate assessment and prediction of residual stresses in a steel sheet. On the basis of finite element analysis, formation of residual stresses due to roller leveling of hot rolled strip is disclosed. The implementation of a leveling process model was performed in SIMULIA Abaqus. Models are verified by comparing forces under the rollers. We have experimentally confirmed the convergence of the simulation results with the measurements of the strip flatness obtained after sheets plasma cutting. It was found that after leveling, tensile longitudinal residual stresses remain on the upper surface of the sheet, compressive ones remain on the lower surface, stresses are zero in the middle in thickness, and the stress values are opposite in sign in the remaining parts of the section. It was established that the same parameters of the leveling process of different strength categories lead to different deviations of stresses. An increase in yield strength of the strip leads to an increase in the deviation of residual stresses along the strip thickness. The proposed method of simulation of roller leveling process should be used to study the stress-strain state of hot-rolled steel and to design improved strip leveling setting modes with minimal residual stress deviations.

Development and Modeling of the Technological Welding Process of Differentially Heat-Strengthened Rails: Industrial Testing

Abstract: The article describes the welding process study with the subsequent control of cooling for full-profile rail joints, produced by passing alternating electric current pulses after welding. The welding mode influence on the welded joint quality was investigated. Welding was carried out on a resistance butt welding machine MCP-6301 in conditions of the rail welding company OOO RSP-M (RSP-29). For research, the samples of P65 type full-profile rails of DT350 category 600 mm long were cut out. The isothermal holding conditions after welding were controlled using a personal computer with a change in the program of the SIMATIC S7-300 industrial controller and the software SIMATIC STEP 7, which allows modes of controlled cooling to be set. The control program was written in the LAD graphic language. To search for optimal modes of controlled cooling, a complete factor experiment N = 2k was carried out. Non-heat-treated joints were tested for three-point static bending according to the state standard STO RZD 1.08.002 – 2009 “Railway rails, welded by electric contact method”. Static bending tests were carried out on the press of PMS-320 type. Values of the force arising during bending Pbend and the bending deflection fdef at which the control sample is destroyed, were determined. The maximum values of these indicators were also determined if the sample was not destroyed during the tests. During the experiments, regression models were obtained for output parameters of the bending force and bending deflection. Sample macrostructure and metal hardness distribution on rolling surface of the rails welded joint were studied. A new method of resistance butt welding was developed, which makes it possible to obtain a welded connection of P65 type rails of DT350 category with properties that exceed the technical requirements of the mentioned state standard.

Determining the Conditions for Selective Iron Recovery by Iron-Manganese Ore Reduction

Abstract: The results are presented for the thermodynamic simulation of reductive roasting of ferromanganese ore with a high phosphorus content in the presence of solid carbon. The simulation has been performed using a TERRA software package. An effect of the process temperature in the range of 950–1300 K at a carbon content amounting to 8.50–8.85 g per 100 g of ore exerted on iron, manganese and phosphorus reduction has been studied. At such parameters of the system, iron can be reduced into the metallic state both by solid carbon and by carbon monoxide CO, whereas manganese can be reduced only to produce manganese oxide MnO. The level of phosphorus reduction depends on the amount of a reducing agent. With the carbon excess in respect to the carbon amount required for the reduction of iron, the entire amount of phosphorus is transferred into metal at a temperature of 1150 K. At a temperature below 1150 K and such amount of carbon, phosphorus cannot be reduced. The process of solid-phase iron reduction from manganese ore with retaining manganese in the oxide phase has been studied under laboratory conditions. Experimental results for the direct reduction of these elements with the use of carbon and those for indirect reduction thereof with the use of carbon monoxide CO are presented. The experiments have been performed using a laboratory Tamman furnace at a temperature of 1000–1300°C and at a holding time of 1 and 3 h. The study results on the phase composition of the reduction products, as well as on the chemical composition of the phases, are considered. It is confirmed that selective solid-phase iron reduction with the use of solid carbon into the metallic state is quite possible. Iron under the studied conditions can be reduced by carbon monoxide CO and is transferred into the magnetic fraction. After the magnetic separation of the products of ore reductive roasting with the use of solid carbon and carbon monoxide CO, the obtained nonmagnetic fraction contains manganese, silicon and calcium oxides. The results of this work could be used for the development of theoretical and technological foundations of the processing of ferromanganese ores that cannot be processed by means of existing technologies.

Study of the Surface Defect Nature of Hot-Rolled Products in the Edge Zone

Abstract: The study results of the edge zone of more than 300 hot-rolled products of steels 09Г2С, 22ГЮ, 20, К56 produced according to the combined technique of smelting, casting, and subsequent rolling in the conditions of casting and rolling complex are presented. Simulation shows that location of imperfections and defects on the slab serves as a prerequisite for defect formation in coil stock. The most common defects include cracks and scabs. The formation of these defects is often associated with the disclosure of oscillation marks during subsequent hot deformation. In such cases, the defect formation nature is difficult to identify by metallographic methods, since signs of the steelmaking nature of their formation are not observed in the cross section of the discontinuity.

Plasticity Origin of Heterophase Inclusions at Steel Forming

Abstract: Plasticity of heterophase nonmetallic inclusions of various types at hot and cold steel forming was studied. Transformation features of inclusions possessing different phase composition and structure were shown. Inhibiting effect of the second phase of inclusions on the formability of plastic phases at hot and cold strain of the steels was determined. Interaction features of the components of inclusion phases were studied, such as interactions in the inclusion–matrix interfaces and internal phase boundaries in inclusions. Features of the plasticity origin of heterophase inclusions possessing various compositions and structures were discussed.

Application of Electric Arc Surfacing in the Manufacturing of Three-Dimensional Steel Products

Abstract: The paper presents the results of research on the influence of the conditions of volume electric arc surfacing on the geometric accuracy of “cube” type objects with dimensions of 20 × 20 × 20 mm made of 09Mn2Si and 06Cr19Ni9Ti steel fillers. It has been found that the actual length and width dimensions of the samples surfaced with 09Mn2Si steel generally are exceeded and the dimensions in height are smaller than the specified dimensions of the model. This may be due to the melt spreading over the substrate during the formation of the first layers. The optimal surfacing conditions for cube type objects made of 09Mn2Si steel have been defined. When surfacing the samples of 06Cr19Ni9Ti steel, spreading does not occur; however, all actual dimensions are smaller than the specified ones. This might be caused by shrinkage processes that proceed in the deposited layers during their solidification. The most optimal mode for samples made of 06Cr19Ni9Ti steel is the mode in which the reduction in length and width was no more than 2.5%, and that in height was 13.5%. Studies on the influence of the welding arc voltage and the grade of the filler material on the width of the deposited track has confirmed the tendency of 09Mn2Si steel to spread over the substrate in the entire voltage range studied (11–19 V). The microstructure of the deposited samples has been investigated. Tensile tests of the deposited samples at room temperature have shown that the samples have a set of acceptable mechanical properties that exceed the reference values. This is a proof that the deposition process occurs at a high level of quality without formation of incomplete fusion and porosity areas.

Current State of Ferroalloys Production in Russia and CIS

Abstract: The development of ferroalloys production directly depends on the progress in the steel industry. Therefore, an increase in steel production inevitably entails an increase in the production of ferroalloys. The global steel production has increased by about 30% in the past decade. This article discusses the general condition of the ferroalloy sector in the CIS countries and, in particular, in Russia. The main consumers of ferroalloy products in the domestic markets among Russian metallurgical enterprises are listed, and the structure of production and consumption in other producing economies (China, India, the EU, the United States, Japan) is examined. It is revealed that the overproduction of ferroalloys in the CIS is nearly 400%. In addition, the ways of developing the ferroalloy sector are considered, that is, aimed at reducing the share of ore raw materials, reducing agent, and electricity in the production cost, which is achieved by using cheaper ore, applying new types of processes and outfits, and designing alternative ferroalloys to replace their conventional counterparts. One of such novelties is smelting in DC furnaces, which allows using unprepared fine chrome ore as a raw material instead scarce lump ore in combination with a cheap fine reducing agent (anthracite) for ferrochrome production. Another promising technology is melting in an oxygen reactor by postcombustion with gaseous oxygen released with the reduction of carbon monoxide inside the outfit. In addition, alternative kinds of ferroalloy products can gain ground, such as KAUR calcium carbon which can replace calcium carbide in steelmaking.

Recycling Dispersed Waste of Ferroalloy Production on the Basis of Metallurgical Self-Propagating High-Temperature Synthesis

Abstract: A review of techniques for recycling dispersed waste of ferroalloy production is conducted. The formation and accumulation of cyclone dust (catch product of crushing or CPC), formed during the grinding and fractionation of ferroalloys is considered. The drawbacks of the known techniques of handling this dust are shown. The possibility of obtaining commercial nitrided hardeners from CPCs and off-spec ferroalloy fines by self-propagating high-temperature synthesis (SPHTS) is studied. The proposed metallurgical SPHTS is used to develop the technology and show the possibility of bulk production of nitrided ferrosilicon, ferrovanadium, ferrochrome, and other composites in demand on the global market. The materials made by SPHTS have better quality than the nitrided ferroalloys made by the common furnace technique; in particular, the former contain less hydrogen, oxygen, and other impurities, and are denser, stronger, more porous, etc. The production of nitrided ferroalloys and composite hardeners by metallurgical SPHTS is developed using the production facilities of the Etalon scientific and technological production company, which includes the potential of annually processing up to 5000 t of cyclone dust of ferrosilicon and other alloys. The new approach to adopting SPHTS in practice is developed, and the possibility of utilizing synthesized products in metallurgy shown. The manufactured products are intended for use mainly as alloying additives in the smelting of transformed, rail, stainless, high-strength structural, and other steels and alloys. Another demanding consumer of composite SPHTS metal materials is the production of refractories. The modification of conventional refractories used in the smelting of cast iron, steel, and nonferrous metals with new composite SPHTS materials based on nitrides, borides, carbides, and other hard-to-melt compounds allows making refractories much more enduring and cut the expenses for them.

Transport Steels Microalloyed with Vanadium and Nitrogen

Abstract: The research results of the effect of small additions of vanadium and nitrogen on the microstructure and mechanical and service properties of high-carbon steels for railway transport are presented. The data on industrial production of metal products from such steels are considered. Medium-carbon bainitic and martensitic steels with a fine structure microalloyed with vanadium and nitrogen have a unique set of properties: a combination of high values of strength, ductility, cold resistance, and endurance under fatigue loading, which will increase the resistance of rails during operation not only at low temperatures, but also under conditions of increased loads, in curves of a small radius and in the event of a risk of thermomechanical damage.

Influence of Plasma Torch Design on Cutting Quality during Precision Air-Plasma Cutting of Metal

Abstract: Optical interferometry and metallographic analysis were used to study the structure of cutting seams obtained after 09G2S steel cutting by a PMVR-5 plasma torch. These plasma torches have many design features in the gas-dynamic stabilization system of the plasma arc. The application of a new plasma torch can obtain higher quality and lower energy costs of cutting medium-thick 09G2S steel. Metallographic analysis has shown that the qualitative composition of the cut surface structure is almost the same, so priority criteria for comparative quality analysis are surface microgeometry parameters. The parameter evaluation shows high quality of cutting almost along the entire length of a cut, since the technological feature influence of plasma arc cut into the metal affects less than 0.3 mm from the sheet edge. The use of additional methods of gas-dynamic stabilization in PMVR-5.2 plasma torch (feed symmetry with a double swirl system of plasma-forming gas) makes it possible to achieve additional advantages in terms of surface quality compared to PMVR-5.1. A number of features that affects cut quality when cutting metals of different thicknesses for welding depends on the inclination angle of a plasma torch during cutting. Estimates of the surface layer hardness indicate minimal deviations from the requirements of GAZPROM Standard 2-2.4-083 (instructions on welding technologies in the construction and repair of field and main gas pipelines), which allows further use of cutting seams obtained by studied plasma torches for welding without removing thermal influence zones. Thus, the application of new plasma torches for precision-finishing plasma cutting of metals, including production of welded joints, is possible.

Improvement and Practical Use of the VNIIMT Method for Thermotechnical Scheme Optimization of Firing Conveyor Machines with Operating Areas of 278, 306, and 552 m 2

Abstract: In this paper, we perform thermotechnical inspection of the operation of Lurgi-278A, OK-306, Lurgi-552A, and Lurgi-552B of SevGOK PJSC firing machines with various operating areas. The operation of various elements of the firing machine, technological drying zones, heating, firing, recuperation, and cooling was studied under industrial conditions. According to the JSC “VNIIMT” method, the following processes were analyzed and performed: the thermotechnical scheme structures of the firing machines and their operating parameters, the thermotechnical calculations of heat transfer and gas dynamics in the layer, the gas-air flow parameters of the firing machine, and the optimizing calculations in order to increase the specific productivity. As a result, technical solutions were developed to increase the specific hourly productivity of firing machines up to 1 t/m2 while maintaining and improving the quality characteristics of the finished pellets.

Structure and Hardness of Wear-Resistant Coatings Deposited on Low-Carbon Steel upon Low-Frequency Current Modulation

Abstract: The effect of manual electric arc surfacing modes of low-alloy 09G2S steel by T-590 electrodes on their structure and hardness has been investigated. It is shown that pulse-arc surfacing of coatings by electrodes forms a fine-dendritic structure of the deposited metal. The microstructure of the heat-affected zone after surfacing consists of several regions: the overheating zone with a Widmanstatten structure and the normalization zone with a characteristic fine-grained ferrite-perlite structure. In the initial state, the base metal (09G2S steel) has a hardness of ~2500 MPa. The hardness of the deposited coating material due to strong mixing with steel is ~2700–3000 MPa and 2100–2300 MPa for the thermal impact zone. When coating in a DC mode, the heating temperature of the surfacing bath is higher, causing grain growth. When coating in pulse modes, a structure with smaller sizes of components is formed by directed low-frequency high-energy impact of the electric arc on the formed metal and due to the constant reciprocating motion of the melt with the frequency of current modulation. It is established that the application of the pulse-arc surfacing method enables preserving the previously formed hardening phases in deposited coatings.

Phenomenological Model of Austenite Decomposition Kinetics in Low-Carbon Low-Alloy High-Strength Steels

Abstract: A phenomenological model of the kinetics of austenite decomposition of low-carbon low-alloy high-strength steels is presented. The model is based on experimentally obtained empirical dependences linking the transformation rates with the specific power of the heat flux from the metal volume and with the temperature of this volume. This model was used to implement the finite-difference scheme to solve the problem of heat conduction in a medium with internal heat release sources. The digital twin of the cooling process, which includes the specified calculation procedure, is integrated into the TLS 5000 automation system of PAO Magnitogorsk Iron and Steel Works. The determined mass fractions of austenite decomposition products are used for both the design certification of the structural state of rolled products and the construction of statistical models to predict mechanical properties.

Production, Properties and Practical Application of High-Entropy Alloys

Abstract: In recent years, the unique physico-mechanical properties of high-entropy alloys (HEAs) have increasingly attracted the attention of researchers. The thermodynamic characteristic study of these materials for formulating the formative principles of structures with necessary functional characteristics is an interesting topic. HEAs are referred to a special group of alloys because they are characterized by significantly different structure and phase formation processes, diffusion mobility of atoms, formation of mechanical properties, and thermal stability when compared to their conventional counterparts. High-entropy alloys based on transition refractory materials, such as Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W, are particularly interesting to consider. Light metals, such as Ti, V, and Cr, are chosen for reducing the mass density. Whereas refractory metals, such as Nb, Ta, and W, are primarily responsible for the strength characteristics of the entire material. This paper presents a brief overview of the results of testing high-entropy alloys at a new laboratory of the Institute of Metallurgy of the Ural Branch of the Russian Academy of Sciences (IMET UB RAS) in 2019. The two groups of alloys tested were AlNbTiVZr HEAs with easily fusible aluminum and (Ti,V)ZrNbHf(Ta,W) HEAs with solely refractory transition metals. For the first group of HEAs at varying component ratios, the tests determined the existence limits of disordered regions of solid solution, as well as the intermetallic regions typical of this system. The predicted phase composition, properties, and structure of the second group were determined by quantum chemical calculations, involving first-principle molecular dynamics. The prediction showed that the formation of disordered solid solution in the foregoing systems with or without concrete chemical elements was either possible or unlikely.

Development and Modeling of Differentially Heat-Strengthened Rail Welding: Welding and Local Heat Treatment Modeling

Abstract: During the manufacturing of continuous welded rail track, the problem of the local hardened points in the welded joint during rail joint welding is resolved by using local heat treatment of the welded joint. As a result, the quenching structure formation is excluded. However, the appearance of new heat-affected zones with reduced hardness is possible. During operation, such rails are characterized by increased tread surface wear in these areas and rail flattening at the welded joint, which is the main reason for retiring the rails from service earlier than the guaranteed service life. A new technology based on the dependence of the structural component dispersion (primarily perlite and carbide particles formed in the process of rail butt welding) is proposed for the steel composition and cooling conditions. The cooling rate has a decisive influence on the dispersion degree of the ferrite-cementite structure formed during the austenite decomposition. During the welding rail process, the granular perlite formation is possible in a butt weld in areas with a temperature ranging within points Ac1 and Acm. To determine these critical temperatures, thermodynamic calculations were performed using the Thermo–Calc® software (TCFE database) allowing the chemical composition of the samples obtained by spectrometry. The iron–carbon state diagrams for rail steel 76KhSF with the minimum and maximum alloying element content according to GOST R 51685–2013 are modeled. To obtain the minimum number of sections with reduced hardness, it is possible to weld rails using shot discontinuous flash welding. In order to eliminate the formation of defective areas with a quenching structure, it is possible to control the cooling of the welded joint by contact heating. Temperature distribution measurement during welding according to given modes and controlled cooling confirms the theoretical conclusions.

Chemical Reactions in the Reduction of Iron from Oxides

Abstract: In this paper, we simulated the chemical process accompanied by the reduction of iron from hematite using the Terra computer program (the product from Bauman Moscow State Technical University). Carbon, hydrogen, and methane were taken as reducing agents. The equilibrium concentrations of the system components were determined by varying the consumption of reducing agents and the process temperature. The change in these concentrations at the boundaries of individual temperature regions was regarded as a result of the passage of corresponding chemical reactions in them. At the same time, it was noted that reactions of the non-variant type begin and end at the same fixed temperatures. Calculations showed that the Fe2O3 → Fe3O4 transformation in all cases was thermodynamically possible at temperatures exceeding 65°C. Consequently, it will be realized without complications at the furnace operating temperatures. The second stage of reduction also proceeded according to the unified scheme Fe3O4 → Fe, bypassing the participation of FeO oxide in it. The temperature of the beginning of the iron reduction by the C, H2, and CH4 components was 680, 350, and 520°C, respectively. In this case, only direct reduction of iron by the indicated components took place. An attempt to record the fact of indirect reduction using carbon monoxide as a reducing agent was unsuccessful even at its high consumption. Carbon monoxide decomposed at low temperatures according to the Boudouard-Bell reaction. Therefore, iron was reduced by “sooty” carbon, i.e., also by a direct method. At the final stage of the carbon-thermal process, depending on the composition of the system, the formation of iron carbide at 720°C can occur with its possible subsequent transformation back into iron, as well as the secondary oxidation of iron with the formation of wustite. Carbon dioxide takes an active part in these reactions. The reduction (or oxidative) efficiency of all elements and components of the Fe–O–C–H system is numerically estimated based on the calculation results of chemical processes at high temperatures. With a high degree of reliability, this allowed predicting the phase composition of the reaction products at the maximal process temperature (1500°C).

Analysis of the Use of Rare-Earth Metals in Ferrous Metallurgy in Russia and the World

Abstract: The current state of production of rare-earth metals (REMs) in Russia and in the world is analyzed. Data on REM production in different countries of the world and on new foreign REM production and processing projects are given. The balance of production, export, and import of raw materials and products with REMs in Russia, including scandium and yttrium, is presented. The maximum volume of REM consumption in Russia is calculated considering imported products with REMs. These data are compared with other countries, including the former Soviet Union. Much attention is paid to REM use in metallurgy. Data on REM influence on cast iron and steel properties are given. Data on the used forms of REMs are given for their use in Russian ferrous metallurgy. The structure of REM consumption by branches of ferrous and nonferrous metallurgy is investigated. The structure of REM consumption for steel alloying by types and areas of its application is studied by the example of two enterprises (one of them specializes in mass production and the other, in special steels). The peculiarities of REM consumption development in Russia’s ferrous metallurgy are investigated, the consumption volume is calculated, data on the import of raw materials with REMs for metallurgy is presented, and information on the producers of REM ferroalloys in Russia is given. The line of ferrous metallurgy products with REMs is analyzed. REM consumption in metallurgy of Russia and foreign countries is compared. The reasons for insufficient REM consumption in Russian metallurgy are considered, the change in production volumes of certain types of steel and cast iron is estimated, and recommendations on growth of REM consumption in metallurgy are developed.

Increasing the Business System Efficiency of an Enterprise Based on the Application of Digital Instruments in Metallurgy

Abstract: One of the promising ways to improve the business system efficiency of enterprises is the use of digital tools. Currently, these tools are often used not in the points where the maximum effect is possible, and the results of their implementation are unstable. To solve this problem, a new approach to deploying a transformational project using digital technologies is proposed. The application of this approach in the steelmaking industry of a large metallurgical company made it possible to achieve an additional EBITDA of 695.5 million rubles.

Manganese Problem in Russian Metallurgy

Abstract: The main manganese consumer is ferrous metallurgy. The global volume of manganese ferroalloys production is ~1% of the volume of steel production. After the collapse of the Soviet Union, Russia was cut off from a manganese ore base. Currently, only high-carbon ferromanganese and ferrosilicomanganese are smelted in Russia from imported ore in a limited amount. The mineral resource base of manganese ores in Russia is quite large: the balance reserves of manganese ores are about 230 million tons (~2% of the world), the projected resources are more than 1 billion tons. The quality of the manganese ores in Russia is lower than that of manganese ores in most of the main producing countries. The average manganese content in Russian ores is 9–23%. The mineral resource base of the manganese ores is made up of carbonate ores, which account for more than 77%. Recovery of manganese ores in Russia is carried out irregularly and does not exceed 66 thousand tons/year. The demand of Russian ferroalloy plants producing manganese ferroalloys for manganese ores and concentrates is covered by imports. The acceleration of the creation of the domestic manganese ore base from the standpoint of economic security is quite a pressing issue. It is necessary to solve a number of issues related to the following: the treatment of poor manganese ores, the development of effective technologies for smelting manganese ferroalloys from concentrates obtained after the treatment of these ores, as well as the creation of more advanced methods for dephosphorization of manganese concentrates. In the production of manganese ferroalloys from ore to finished alloys, about 50% of manganese extracted from the subsoil is lost, a large amount of by-products is formed (treatment sludge, slags, screenings of fine fractions of ore raw materials and finished products, sludge from the smelting process and dust), its utilization makes it possible not only to reduce the consumption of raw mineral materials, but also to increase the efficiency of the main production, as well as to reduce environmental pollution. Additional recovery of manganese from industrial waste and improvement of technological processes for smelting manganese ferroalloys are ways to increase the through manganese recovery.