The most critical stages in the metallurgical production of steel products are casting and hardening of steel, since it is during the hardening process that most of the imperfections of future products are formed. These stages become even more important in the production of products for heavy and energy engineering, which involve casting steel into ingots, due to the high requirements for reliability, durability and safety of the manufactured products (critical products), as well as with a significant mass of billets requiring casting of ingots weighting hundreds of tons. Despite the importance of casting and hardening of a steel ingot, by now, relatively little information about the billet being transferred was received for subsequent alterations (forging, heat treatment): average chemical composition of the steel, geometric dimensions of the ingot, its mass, temperature, and surface quality. At the same time, a number of imperfections that can lead to the rejection of a future product (for example, pores exceeding a critical size) are detected using ultrasound control only at the final stages of production, after completion of long and labor-intensive operations of thermal deformation and thermal treatments. The authors described the principle of modeling the main types of inhomogeneities of a steel ingot: physical (porosity), chemical (dissolution) and structural (distance between the vertical axes, grain size). When using specialized software, for example, the Large Ingot software (JSC “RPA “CNIITMASH”), numerical information about these types of inhomogeneities can be obtained over the entire section of the ingot. This topology of the distribution of inhomogeneities, calculated for a specific ingot based on the actual conditions of the technological process, makes it possible to form the so-called technological summary of the ingot, which is transferred along with the billet itself to the following alterations. The paper presents an approach to applying the ingot technological summary in subsequent alterations, which implements the idea of an end-to-end description of the entire technological process of metallurgical production of critical products. This approach makes it possible to increase production efficiency and reduce the cost of manufactured products.
Obtaining an ultra-low carbon content in steel at a level of less than 0.002 % is a critically important task of modern metallurgy, which determines the quality of such high-tech products as electrical, superferritic and austenitic stainless steels. In the presented study, an in-depth comprehensive analysis of the kinetics and mechanisms of decarburization of a metallic melt under conditions of a circulating vacuum unit (CVA/RH process) was carried out. Five competing processes were studied in detail: desorption of gases from the melt surface, homogeneous formation of carbon monoxide bubbles in metal volume, heterogeneous formation of bubbles on lining surface, diffusion of an inert carrier gas into bubbles, and intense interaction of metal sprays with a vacuum medium. The dominant mechanism of carbon removal is the homogeneous formation of {CO} bubbles in the melt depth, the efficiency of which is 25 times higher than the efficiency of bubble formation on the lining. Microstructural and X -ray spectral analyses confirmed that nonmetallic inclusions (5 – 140 μm in size) are present in the non– deoxidized metal, which can serve as active centers of {CO} bubble nucleation. Based on the industrial tests, optimization of technological parameters was proposed: reduction of the inert gas flow rate to 80 m 3 /h to increase the contact surface of the phases and the residence time of bubbles in the melt, strict observance of the holding time before casting in the range of 20 – 30 min, as well as the mandatory use of carbon-free lining in the steel ladle to minimize secondary carburization. The integrated application of these measures makes it possible to consistently achieve a target carbon content of less than 0.002 %, which is confirmed by industrial practice.
The article presents an innovative approach to processing man-made waste using bubbling technology. A general technological scheme of a complex employing hot air blast instead of oxygen-enriched air is described. The results of an example economic efficiency calculation demonstrate that the estimated investment payback period for constructing a plant based on a unit with bubbling molten slag (UBMS) with annual iron production capacity of 250,000 tons is approximately 1.5 years of operation. Photographs illustrate the design solutions implemented in a pilot industrial bubbling unit where expensive copper water-cooled panels were replaced with more efficient and cost-effective pipe panels. The article outlines the main technological and economic advantages achieved through the use of bubbling technology in the UBMS process, including the production of iron and ferromanganese at approximately half the cost compared to blast furnace and electric furnace methods, the production of commercial slag-based materials (fused cement clinker, crushed stone and stone products), the low-cost production of fused phosphates, as well as environmentally friendly and economically efficient recycling of all types of solid household waste (unsorted waste, sorting residues, and waste stored in old landfills). An example cost calculation for producing iron from low-grade ore using UBMS technology is presented confirming that the investment payback period is about 1.5 years. The article concludes by formulating the key advantages of bubbling technology as a promising solution for industrial waste processing and resource recovery.
Using physical modeling methods, the authors studied the processes of hydrocarbon oxidation of oiled mill scale oil, as applied to its loading into a blast furnace inside metal containers measuring 85×83.4 mm, when an oxidizing reagent is included in the composition of the loaded material. The oil’s hydrocarbon oxidizer was ammonium nitrate (NH 4 NO 3 ), which undergoes thermal decomposition with the release of oxygen at a temperature of 210 °C corresponding to a temperature range of 200 – 400 °C with the highest intensity of oil vapor release from oiled scale and allows the oxidizer to actively interact with oil vapor. The proportion of the oxidizer changed in the range from 15 to 40 % of the oiled scale mass. With a saltpeter content of 40 % of the loaded oiled scale mass, the degree of oil decomposition in the blast furnace reaches 90 %. Chemical composition of the liquid products in oxidized and non-oxidized oil samples was determined by gas chromatography, and based on the data obtained, the group chemical composition of the samples was evaluated. In the group chemical composition of the products of hydrocarbon oxidation with ammonium nitrate, an increase in the content of oxygen compounds was revealed, compared with the remaining oil in the experiment without using a reagent, from 10.58 to 20.54 %, while the content of saturated hydrocarbons decreased from 35.44 to 29.64 % and the content of unsaturated hydrocarbons from 18.09 to 16.20 %. Since all saltpeters have a high solubility in water, and their aqueous solutions are explosion- and fire-proof, it is recommended to load an oxidizing reagent into a tank with oiled scale of current production, which has a high (from 10 to 30 %) humidity and a liquid consistency.
JSC Ural Steel is a large full-cycle metallurgical enterprise, which celebrated its 70 th anniversary in 2025, and in 2024 the Ural Steel Shaped Castings Shop (SCS) celebrated its 65th anniversary. Since its foundation, SCS mastered the technology of producing castings from gray cast iron weighing up to 6 tons in accordance with GOST 1412 – 85. In 2018, SCS organized a large-scale casting site (LSCS SCS) for production of steel large-scale metallurgical castings, and in 2022, as part of the expansion of the large-scale site range, it was decided to develop the technology for the production of castings weighing more than 110 tons from high-strength ductile iron (DCI). The team began to solve this task sequentially dividing it into the stages that gradually revealed the additional potential of the enterprise. In 2022 the production of castings from DCI weighing up to 6 tons was mastered at the small casting site in SCS. In 2023 – 2024 the technology for the production of castings weighing up to 6 tons from DCI was tested as a part of commercial orders, a unique technology for the production of gray cast iron for large castings (more than 30 tons) in electric arc flexible modular furnaces of the EAF-shop from hot metal from the blast-furnace shop was developed and tested. In 2024 – 2025 further development of the technology for the production of hot metal for castings was carried out, as well as the development of technology for modifying the melt with magnesium-containing materials in the conditions of the LSCS SCS for the production of large-scale castings from DCI weighing more than 40 tons. Testing of the technology for production of castings weighing up to 100 tons was carried out within the framework of commercial orders. Analysis of the experimental castings material showed that the developed production technology ensured the production of DCI grade HC40 according to the State standard GOST 7293. This large work resulted in expansion of the product line of JSC Ural Steel.
Based on theoretical and experimental studies, the authors consider the features of the formation of metal losses during lancing of a converter bath with immersion oxygen-gas combustion torches using natural gas. The main approaches and the concept of oxygen-fuel converter equipment for the implementation of processes with elements of liquid-phase recovery of various man-made waste were formulated. The causes of possible metal losses are the development of dust release processes associated with the removal of metal and slag droplets, and smoke release processes during evaporation of substances in a high-temperature reaction zone. The main reasons that cause increased metal loss include the crushing of metal into droplets due to the dynamic energy of gas jets followed by the ejection of droplets into the jet, the splashing and spraying of metal by CO bubbles upon reaching the bath surface, and the evaporation of metal in high-temperature reaction zones. The measures allowing to reduce metal losses during the implementation of oxygen-fuel processes in converters were analyzed. The addition of gaseous or liquid fuel to the oxygen stream reduces dust carryover from the evaporation of iron in the reaction zone. This method is quite easy to implement in practice. At the same time, such lancing reduces the influence of other factors that cause additional dust formation. With a decrease in the reaction zone temperature, the manifestations of the smoke emission process decrease.
Under the conditions of pipe rolling mill, during the production of 12 heats of medium-carbon aluminum-killed steel, 10 samples were taken from each heat at different stages of production – from the beginning of ladle treatment to pipe rolling. The samples were examined by high-temperature extraction in a carrier gas to determine the total oxygen content and by scanning electron microscopy to determine the composition and size distribution of non-metallic inclusions. The dynamics of change in the content of inclusions was established according to the following criteria: total oxygen content, volume fraction, density and average diameter of inclusions. The composition of non-metallic inclusions was plotted on ternary diagrams: the oxide component on the diagrams CaO – Al 2 O 3 – SiO 2 and CaO – Al 2 O 3 – MgO, the sulfide – on Ca – Mn – S. The trajectory of change in the chemical composition of inclusions in the steelmaking process was established. The paper shows the role of steel treatment with calcium and importance of observing thermodynamic conditions. A relationship is established between deviations in calcium treatment parameters, composition of non-metallic inclusions, steel castability and sorting of pipe products by surface and internal defects. Decreasing total oxygen content, practically does not occur at the main stage of ladle treatment. The highest intensity of steel refining from inclusions is observed at the stage between the samples before and after steel treatment with calcium, this time interval is less than 10 min. Comparison of the obtained data on the chemical composition of inclusions with the calculated data on the boundary of liquid phase region of the CaO – Al 2 O 3 – SiO 2 – MgO system shows that at this stage, the chemical and phase composition of non-metallic inclusions is transformed. After the addition of calcium, the composition of oxide non-metallic inclusions shifted to the liquid region of the CaO – Al 2 O 3 – SiO 2 system at MgO content of 10 wt. % and 1600 °C.
Ferrous metallurgy is considered as one of the most difficult industries to decarbonize due to the high heat requirements of using carbon as a process feedstock, low profitability, high capital intensity, and long asset life. The authors review the latest researches in the field of technology and practice of decarbonization of cast iron and steel production. The paper evaluates existing and new decarbonization methods, as well as potentially revolutionary technologies. The analysis showed that there are several promising ways to produce iron on an industrial scale without CO 2 emissions. Currently, two advanced technologies for carbon-free steel production are at the stage of piloting and transition to demonstration projects. These are direct reduction of iron with “green” electrolytically produced hydrogen and direct electrolysis of iron ore. The review focuses on innovative technologies for carbon capture, use and storage (CCUS), especially promising technologies such as carbonization of steelmaking slags. The authors discuss the existing barriers to decarbonization and the tools that can help to overcome them. In general, although advanced decarbonization technologies are key levers for reducing emissions, they are still very expensive and are mostly at the pilot stage. From an economic point of view, it is more profitable to modernize existing facilities using CCUS than to build new facilities using alternative technologies. The review also highlights gaps in previous research works.
Plasma surfacing in a nitrogen environment on medium-carbon steel 30KhGSA was used to form a deposited layer of high-speed molybdenum steel with a thickness of 9 – 10 mm. The authors utilized the methods of modern physical materials science to study the structural-phase states and defective substructure, mechanical and tribological properties of the surface after double high-temperature tempering and electron-beam processing with low-energy high-current beams. It is shown that the deposited layer in the initial state has a polycrystalline structure and contains eutectic interlayers. Double high-temperature tempering of the deposited layer does not change the morphology of the structure formed by eutectic grains and grains of a solid solution based on α-iron (bcc crystal lattice). The main phases are α-Fe (85 wt. %) and complex carbides Me 23 C 6 (9 wt. %) and Me 6 C (6 wt. %), which form eutectic grains. High-temperature tempering of the deposited layer is accompanied by additional transformation of the residual austenite with the formation of nanosized particles of iron and chromium carbides along the boundaries of martensite crystals. After irradiation with pulsed electron beams, a structure of high-speed cellular crystallization is formed with cell sizes varying within 0.15 – 0.25 μm. Two isolated areas are distinguished, in one of which the cell boundaries do not contain precipitates of the second phase. In the cells of the second type, carbide phase interlayers are located along the boundaries - carbides of complex composition such as Me 23 C 6 , chromium carbides Cr 3 C 2 and molybdenum carbides MoC. Their size varies within 25 – 43 nm. The authors made a comparative analysis of mechanical and tribological properties of the surface layer of high-speed molybdenum steel after formation, tempering and electron-beam processing.
The author examines the key mechanisms for the removal of non-metallic inclusions during electroslag remelting (ESR) emphasizing the importance of three reaction zones: a liquid film at the end of the electrode, droplets of electrode metal, and a liquid bath in the mold. The analysis is based on the application of the Stokes formula to estimate the rate of inclusions floating, where particle size plays a crucial role. The enlargement of inclusions contributes to their more efficient removal, while liquid inclusions float faster than solid ones due to their lower viscosity. An important factor is the shape of inclusions, which affects the rate of their removal, as well as convective flows in the metal contributing to the enlargement and removal of inclusions to the metal–slag interface. Experimental data demonstrate that the main refining occurs in the area of the liquid film at the end of the electrode, where up to 80 % of the inclusions turn into slag. Purification of metal droplets in slag is less effective, but its role increases with a decrease in droplet size and an increase in the time of interaction with the slag. The results confirm that a decrease in the melting rate of the electrode contributes to the formation of a thin film and improves the quality of the metal in terms of the content of non-metallic inclusions. It is noted that providing a metal bath that is not deep and uniform in height makes it possible to create an axial crystal structure and eliminates blocking the inclusions floating. The solution to this problem is based on the well-tested technology in the laboratory with rotating consumable electrode. The control of the centrifugal forces that arise in this case makes it possible to comprehensively solve the problem of reducing the concentration of non-metallic inclusions of 10 μm or less, while maintaining all the advantages of electroslag technology.
Strengthening the role of pellets as an iron ore raw material sets the task of ensuring their high quality. One of the most important factors affecting the structure and metallurgical properties of pellets are the structural features of the pore space. The relationship between the pore parameters (volume, specific surface area) and metallurgical properties is realized through the size of the surface in contact with the reducing agent gas and strength of the mineral pellet frame. The aim of the work is to study the mechanism of pore formation in pellets using the methodology of cellular automata. The study was conducted using two-dimensional cells with a square lattice and a Moore neighborhood. The calculated field value was 8064 cells. The simulation was performed in the MS Excel environment. Studies have shown that already at the third or fourth step, the pores are localized and their size is stabilized. According to the data obtained, at the second step of modeling, the largest pores are formed, which further grow due to the absorption of small voids. In addition, relict pores remain inside the solid, which could not assimilate with larger ones due to the stochastic nature of the process. Thus, the localization of pores in the structure is mainly determined by the first stage of structure transformation. For sinter and pellets, this is the granulation of the charge. At this stage, pores are isolated and localized. They have a statistical advantage (initial size, presence of other pores nearby) and during further heat treatment they grow due to the absorption of other pores. The specific surface area of pores in pellets due to sintering, determined using the cellular automaton model, is reduced by 3.0 – 3.5 times.
The article presents the results of a study on the melting processes of ferroalloy grades FeMn78, FeMn88, MnS17, FeSi65, FeSi75, SiCa15, and AB87 in an iron-carbon melt during the production of steel grades 08U, 3Sp, E3A, and S355MC. The research was conducted using a mathematical model developed by scientists from the Institute of Metallurgy, UB RAS and the Ural Federal University, which accounts for heat and mass transfer coefficients, as well as the physicochemical and thermophysical characteristics of the ferroalloys and steel. It is shown that the lump size of the ferroalloys at different temperatures of the iron-carbon melt significantly affects the change in their melting (dissolution) time. An increase in the lump size leads to an increase in the mass of the ferroalloy, which results in a thicker frozen steel shell and higher heat content. With an increase in the lump diameter, the total melting time of the ferroalloy increases. All studied ferroalloys belong to the group of low-melting alloys. Among the considered ferroalloys, high-carbon ferromanganese grade FeMn78 has the longest melting time; the total melting time of its 100 mm diameter lump in 08U steel can exceed 160 s at a bath temperature of 1650 °C. Reducing the ferroalloy lump size to 60 mm leads to a twofold reduction in its melting time. Based on the conducted research, rational conditions and technological features for the addition of manganese- and silicon-containing ferroalloys in the production of 08U, 3SP, E3A, and S355MC steels were developed. The research results are of great importance for improving steel smelting technologies, as they allow for optimizing the duration of melting and holding periods, the ferroalloy addition scheme, and the degree of metal deoxidation.
Due to the constant increase in axial loads and the weight of rolling stock intended for passenger and freight heavy traffic, more stringent requirements are being put forward by consumers of rail products. The pearlite-grade carbon steels currently used for the industrial production of rails have high consumer properties, namely, resistance to wear and the formation of contact and fatigue defects, which makes it possible to ensure operability in a wide range of operational and climatic conditions along the entire length of the railway network. An important technical task is to establish the patterns of formation of the microstructure of rails depending on the chemical composition of steel and influence of the structure on properties of the finished products. One of the main parameters determining the structure and consumer properties of pearlite steel railway rails is the size of the interlamellar spacing. Improving the operational stability of rails is one of the main tasks of the specialists of JSC EVRAZ ZSMK, the Kuzbass Metallurgical Plant, one of the five largest manufacturers of railway rails in the world. The results of a comparative analysis of chemical composition, size of the interlamellar spacing, as well as the strength and plastic properties of the metal of pearlite-class railway rails are presented. In accordance with GOST R 51685-2022, 90KhAF steel is hypereutectoid in terms of carbon content. As a result of the conducted research, the relationships between parameters of the structure and the physico-mechanical properties of rails, as well as between content of the main chemical elements in steel and the interlamellar spacing of perlite, were established.
The authors investigated the microstructure and mechanical properties of the samples obtained by the method of wire electron beam additive manufacturing (WEBAM), and their machinability by milling forces using the Taguchi method. Grains of previous austenite and annealed martensite were observed in the samples in various directions. The grains of the previous austenite grow along the surfacing direction and exhibit a pronounced orientation. On the lateral surface of the sample, the grains of the previous austenite are columnar, their hardness is approximately 505 HV 0.1 . On the upper surface of the sample, the grains of the previous austenite are isometric, their hardness is approximately 539 HV 0.1 . The degree of transformation into martensite varies in different parts of the sample. In the part close to the lateral surface, martensite is shallower and the previous austenitic grain boundaries are not observed. Its hardness is approximately 514 HV 0.1 . In the lower part of the sample, due to multiple thermal cycles, martensite decomposes, while its hardness is low and is approximately 480 HV 0.1 . In the upper part of the sample, martensite and the previous austenitic grain boundaries are observed, the hardness is approximately 513 HVelectron beam additive manufacturing, microstructure, hardness, machinability, martensitic stainless steel, Taguchi method. Due to the high hardness of the sample during climb milling, a stronger impact of the cutting edge on the sample leads to an increase in cutting force. Due to the low plasticity of the sample during conventional milling, a decrease in the volume of material pressed into the back surface of the tool leads to a decrease in cutting force. As the feed rate to the tooth increases, deformation of the material increases, the temperature increases, which leads to a decrease in the material strength. Reducing the material strength slows down the growth of cutting force.
The problem of differences in surface quality exists in the production of amorphous alloy (AA) ribbons by ultra-fast single-roll melt spinning. Structural inhomogeneities that can disrupt the isotropy of properties occur on the side of the ribbons adjacent to the quenching drum. In this regard, there is a need to develop a promising surface modification technology of AA which will not only eliminate roughness, but also controllingly manage the structure along the ribbon depth, as well as selective processing of its individual sections to improve mechanical, magnetic and catalytic characteristics. Application of short-pulse laser systems has great potential for achieving these goals. In this research work, the effect of an excimer ultraviolet laser operating in nanometer wavelength range on the structural evolution, mechanical behavior and morphological changes of the surface of Fe 53.3 Ni 26.5 B 20.2 AA with varying the pulse number and their frequency were comprehensively studied using profilometry, indentation, optical and transmission electron microscopy methods. It is shown that laser irradiation of the contact matte side of the studied AA ribbon according to the selected mode (100 pulses, f = 20 Hz, E = 150 mJ, W = 0.6 J/cm 2 ) effectively acts upon the surface relief and smoothes out production irregularities (pores, gas lines, scratches, etc.). In addition, the laser processing parameters are established that contribute to the AA structure softening, and therefore improve workability for possible forming, as well as the mode of transfer AA to an amorphous-nanocrystalline state with increased hardness and preservation of the ability to flow shear.
The article solves the problem of determining thermoelastic stresses in calibrated strikers in a unit of combined casting and deformation during production of hollow steel billets using the calculation methodology developed by the authors. The authors substantiate the relevance of determining thermoelastic stresses in insulated strikers when compressing the wall of a hollow billet and at idle run when cooling the strikers with water, and describe the striker geometry to produce a hollow billet in one pass. The paper considers the initial data and temperature boundary conditions for calculating the temperature field of the striker during production of hollow billets in a unit of combined casting and deformation. The boundary conditions are given to determine the striker temperature as well as the values of heat flow and effective heat transfer coefficient. The results of calculating the temperature fields are performed in four sections and are presented for characteristic lines and points located on the striker contact surface and in the contact layer at a depth of 5 mm from the working surface. Dimensions of the finite element grid are given to calculate thermoelastic stresses in calibrated strikers using the finite element method with ANSYS package. The authors determined the magnitudes and patterns of distribution of thermoelastic stresses in a calibrated striker when compressing the wall of a hollow billet and at idle run when such a billet is produced in one pass in a unit of combined casting and deformation. Based on the calculated temperature values and the magnitude of the maximum compressive thermoelastic stresses on the contact surface of the strikers, it is proposed to use a pipe billet as a material for making strikers.
Development of metallurgy provides for further increase and improvement of steel production volumes through the introduction of various advanced resource- and energy-saving technologies. The main and most universal control actions that affect the course and technical-economic indicators of the process are inextricably linked to the optimization of technology parameters which is focused on achieving the best results in the field of productivity, product quality and reduction of resource costs. This is achieved through the regular monitoring and analysis of key indicators, as well as making necessary adjustments to process management. A successful combination of these factors contributes to maximizing the production efficiency and increasing the competitiveness of products on the market. To calculate the process static parameters, it is advisable to use the resources of mathematical modeling and development of an instrumental system. When creating a static calculation model, the electric steelmaking process was considered as a complex thermodynamic system into which condensed and gaseous input media enter, and the final products are metal, slag and gas. Calculation of the static modes of the electric steelmaking process is carried out on the basis of calculations of material and thermal balances based on the laws of mass and energy conservation relative to the components of a heterogeneous system. The solution of the optimization problem based on formal methods involves selection of various criteria and setting a system of restrictions (requirements for metal composition; ranges of change in the cost of components of charge materials and system state parameters; compliance with the law of mass conservation at the level of fluxes, substances and elements; compliance with the law of energy conservation). A feature of the developed method of mathematical modeling and optimization of the electric steelmaking process is the systematic solution of a set of interrelated optimization problems to determine the optimal conditions for the processes in the metallurgical system and the optimal solutions for implementation of electric smelting technology.
The work is devoted to the study of the possibility of obtaining carbide steel based on powdered high-speed steel 10R6M5 with additives of tungsten (WC) and titanium (TiC) carbides by induction surfacing. The selected compositions of the deposited charge and the proposed composition of the flux based on fused borax with additives of boric acid and a number of oxides satisfy the technology. The developed technology includes a flux, a method of briquetting charge using a piston device that minimizes the movement of ferromagnetic components of the charge under the influence of inductor electromagnetic field during surfacing. Deposited layers of carbide steel based on high-speed steel reinforced with tungsten and titanium carbides were produced and studied. The obtained layers were analyzed using optical and electron microscopy (using a microanalyzer), phase composition of the deposited layers was controlled by the X -ray phase method, and hardness of the layers was measured by the Rockwell method. Addition of tungsten carbide to powdered high-speed steel leads to the formation of ledeburite structure during surfacing, which is characteristic of high-tungsten high-speed steels. An increase in the amount of tungsten carbide in the carbide steel leads only to its partial melting in liquid steel, which helps to preserve the particles of introduced carbides in the microstructure. Titanium carbide added to the carbide steel composition significantly changes the morphology of ledeburite precipitates. According to X -ray phase analysis data, a number of carbides of Me 12 C, Me 6 C, Me 2 C and Me C types were observed in the composition of carbide steels, which are characteristic of carbide steels obtained by various methods (plasma surfacing, sintering, impregnation of a carbide frame, etc.). It is shown that hardness of the samples of carbide steels with additives of tungsten and titanium carbides varies from 59 to 63 HRC, depending on the composition and technological modes of surfacing.
The authors studied the tribotechnical behavior of C235 steel under conditions of dry sliding electrical contact with a current density of more than 100 A/cm 2 at different transformation coefficients of the supply transformer. A decrease in the transformation coefficient leads to a decrease in the wear resistance and electrical conductivity of the contact. Metallographic methods revealed the formation of transfer layers on the contact surfaces. Thickness of the transfer layers does not exceed 20 μm. Morphological patterns of worn contact surfaces on the scale of the nominal (geometric) contact area consist of two sectors, where one sector has signs of melting. X -ray phase analysis has shown that the transfer layers contain more than 70 vol. % FeO. That is why the transfer layers could be represented as a quasi-dielectric medium, where FeO acts as a dielectric. The authors assume that strong self-induction pulses occur in the contact zone, which cause high-density displacement currents. These currents act directly on FeO ions and convert them into a melt. These concepts allow us to assert that the melt consists of atoms or ions of iron and oxygen. A decrease in the transformation coefficient (that is, an increase in the inductance of the secondary winding of the supply transformer) causes an increase in self-induction pulses and displacement currents, which leads to an increase in the amount of FeO melt, its easy removal from the contact area, and a corresponding decrease in the wear resistance and electrical conductivity of the contact. The data obtained can serve as guidelines when choosing wear-resistant materials for high-current sliding contact and, in particular, when defining its design.
The paper is intended for researchers studying of supercooled metallic melts. It addresses an important theoretical problem: the possibility of establishing local thermodynamic equilibrium at the phase boundary during crystallization from a supercooled melt. Such processes play a crucial role in determining the microstructure of materials during solidification, particularly under rapid cooling conditions characteristic of modern metallurgical and powder technologies. During supercooling, nuclei of a new, solid phase begin to form in the melt. To mathematically describe the growth of such nuclei, it is necessary to specify boundary conditions that define the composition of the adjacent liquid phase. Traditional models assume that local equilibrium can be established near the nucleus and that its parameters can be derived from the equilibrium phase diagram. However, as demonstrated by our study of binary systems, local equilibrium may, in some cases, be fundamentally unattainable. This article presents a theoretical analysis of the conditions under which equilibrium may or may not be established. The analysis considers chemical potentials of the components in both the solid nucleus and the liquid melt. Based on the equilibrium phase diagram of the corresponding macrosystem, one can infer the relative chemical potentials of the components in each phase. It is shown that when the nucleus consists of a single component, local equilibrium is always possible in principle. However, when the nucleus is a solution, equilibrium may only be realized under specific thermodynamic conditions. In such cases, the application of first-kind boundary conditions becomes invalid, and it is necessary to take into account the rates of chemical reactions involved in the interphase transfer of each component.
