The present paper describes the research of structure, hardness and crack resistance indicators before and after plasma treatment of 65G steel of a ploughshare part. As a result of plasma treatment, we obtained the modified layer with increased hardness in the range of 980 – 3558 HV with increase in 3.6 times. Metallographic studies showed that pearlitic-ferritic structure of the original metal transforms into needle martensite with high hardness and strength due to plasma hardening. It is recommended to determine the impact toughness by the Drozdowski method, in which a fatigue crack is pre-created on a special vibrator. Also, before the fatigue crack was grown, lateral V-shaped notches of different depths were made on the sample lateral surface. The relative crack length, λ, varied from 0.27 to 0.65. According to the results of compression tests, it was found that there was a small movement of cracks in the hardened samples in the range from 1.3 to 5.6 mm. The initial unstrengthened samples are in a more brittle state than the quenched ones, and accordingly, significant fracture is observed in the conditions of artificial cracking. The evaluation of 65G steel samples for crack resistance by impact bending tests with subsequent oscillographing showed that plasma hardening inhibits crack growth by increasing impact toughness. Thus, the use of plasma hardening is effective in surface hardening of 65G steel, in particular ploughshares which are constantly exposed to mechanical stresses, friction and wear.

The paper considers the issue of increasing the fatigue strength of high-strength steel grades. Based on the results of experimental measurements of the fatigue strength limit (σ_–1) of spring steel grades, we analyzed the effect of tensile strength, ratio of the yield strength during shear and the fatigue strength limit. The absence of statistical relationship between fatigue strength limit and tensile strength (σ_–1 ≠ f (σ_u)) was established. The ratio τ_t / σ_–1 is the stress concentration coefficient (SCC), which is closely related to the tensile strength of steel. From the theoretical analysis, it follows that in the presence of the same morphological type and size of non-metallic inclusions (NMI) in steel, relationship of SCC with the strength properties of steel is functional. Spread of its actual values is associated with the presence of various morphological types and sizes of NMI in the metal. Each morphological type of NMI is characterized by corresponding physical and mechanical properties (modulus of elasticity, tensile strength and various SCC). SCC increases both with an increase in the strength of steel and with an increase in diameter (thickness) of NMI. It was established that the intensity (rate) of the increase in SCC depends on the size and elastic modulus ЕMNI of NMI (ratio of mass fractions of SiO₂ and Al₂O₃ oxides in NMI). The average intensity of the change in SCC obtained by processing experimental data corresponds to similar indicators for NMI: 13 % SiO₂; 87 % Al₂O₃ (4.0 μm thick); 20 % SiO₂, 80 % Al₂O₃ (5.0 μm thick); 25 % SiO₂; 75 % Al₂O₃ (7.0 μm thick). According to the obtained connections, dimensions of NMI and their morphology are approximately indicated, which make it possible to increase the fatigue properties of spring steels grades in the tensile strength range from 1200 to 2000 MPa. To increase the fatigue life of steel (especially in high-strength condition), it is recommended to use the technology of aluminum-free metal deoxidation during smelting. At the same time, a favorable morphology of NMI with SCC less than 1.0 is provided. Formation of a fine-grained structure of steel after heat treatment is obtained in the absence of aluminum during deoxidation with small additives of vanadium, niobium or titanium.

New possibilities of pelletizing process in pellet production can improve the production performance. The principles of induced nucleation in the pelletizing technique expand its technological capabilities. The technical indicators of the new pellet production technology and the physical parameters of wet pellets make it possible to increase the metallurgical properties of agglomerated raw materials. The presented technical diagrams reflect the production capabilities of induced nucleation in the processes of forming a sprayed layer (SL) of the charge and its division by various technical devices. The design features and technological modes of the developed technical schemes are implemented on a typical disc pelletizer. Experimental data obtained during implementation of the developed technological schemes make it possible to change the relative values of strength, mass and moisture content of the pellets during pelletizing of the iron ore charge. These parameters can be adjusted during loading of charge, its spraying onto the charge shell of the pelletizer, dividing the sprayed layer of the charge into nuclei and further pelletizing of the nuclei to form a pellet shell. An assessment of these technological schemes led to selection of the most effective solutions based on thermal power spraying of wet charge, taking into account its adhesion, material consumption and complexity of the equipment design. For practical use, we recommend a combined technological scheme for the production of pellets using the induced nucleation technology on the basis of SL formation of a single air-charge jet (ACJ) containing strengthening additives, on a pre-profiled skull and dividing the SL into nuclei by a conical drum equipped with a metal string. At the end of the technological cycle of pellet production, increased porosity with a high proportion of open pores is formed in the central embryonic part of the pellets. The pellets have a low moisture content (Θ_W = 0.97) and a favorable pore structure. In the forecast, they require less energy consumption for their subsequent heat treatment. The technology makes it possible to produce pellets with the required and maximum strength (Θ_П ≥ 1.0) 12 – 16 mm in size with higher productivity (Θ_M = 0.68). In the course of experiments, it was found that the technology of preliminary nucleation has high reliability and versatility, and it can be easily introduced into the existing production.

The paper considers the issues related to monitoring the state of snow and soil cover in the zone of influence of industrial emissions into the atmosphere at the borders of the sanitary protection zone (SPZ) of the metallurgical enterprise JSC “EVRAZ United West Siberian Metallurgical Combine” (JSC EVRAZ ZSMK). Sanitary protection zone is the territory separating enterprises (their buildings and structures) with technological processes that serve as a source of impact on the environment and human health from residential development. SPZ is designed to reduce the impact of all factors beyond its limits to the required hygienic standards, to create a sanitary barrier between industrial and residential buildings. Ecomonitoring provides an objective analysis of depositing spheres (snow, soil) on the territory of the SPZ. The method of chemical laboratory analysis is important for the assessment of primary and secondary air pollution (samples of snow, soils and waters). The results of chemical analysis of snow water showed that the dry residue in meltwater is lower (7 – 8 times) MPC at all sites, the content of chloride ions does not exceed the MPC (350 mg/l), the content of sulfate ions at site 1 is 2 times lower than the MPC, at other sites below the detection limit by the methodology set out in RD 52.04.186 – 89. The content of heavy metals and arsenic in the soil at the SPZ test sites does not exceed the values of the established MPC. Soil analysis showed that the active acidity (pH of the water extract) is in the range of 6.30 – 7.40 units, which indicates the absence of technogenic acidification of soils. The content of petroleum products in the selected samples is below the threshold value, which makes it possible to attribute soils at all sites of the SPZ of JSC EVRAZ ZSMK according to the compound under consideration to conditionally pure. The content of benz(a)pyrene in the soil does not exceed the MPC (0.02 mg/kg) at all experimental sites, except site 7. The sulfur content does not exceed the MPC values at all test sites of the SPZ.

The article examines the influence of various heat treatments, their temperature, as well as silver alloying on mechanical properties, phase composition and structure of steel wire from chromium-nickel-molybdenum austenitic stainless steel 03Kh17N10M2. Choice of the amount of silver alloying was based on previous studies of the antibacterial effect of modifying medical steels with silver. Since the antibacterial effect was confirmed on several bacterial strains, for the most efficient operation of alloys, it is necessary to determine the best temperature mode for working with them. Steel for the study was smelted and then transformed into wire through rolling, forging and drawing operations. On the obtained wire samples of different diameters with a silver content (0; 0.2 and 0.5 wt. %) mechanical tests were carried out to determine the elongation, yield strength and tensile strength. Various modes and temperatures of heat treatment were tested on wire of different diameters to study their effect on mechanical properties and structure. Microstructure of the wire samples subjected to heat treatment and obtained after drawing was investigated. A phase analysis was also carried out to determine the effect of silver in various quantities on austenitic steel. According to the results of the phase composition analysis, it was concluded that silver reduces the amount of gamma phase in steel, and this effect increases in proportion to the increase in silver amount. This change correlates with a slight drop in the metal ductility. At the same time, there are no significant changes in the strength characteristics and microstructure from the presence of silver.

Die steels with regulated austenitic transformation during exploitation (RATE steels) are a new class of tungsten-free steels for hot forming at operating temperatures up to 750 – 800 °C. High durability of the pressing tool and its long service life are ensured by the ability of these steels to preservation of hot work hardening. This circumstance distinguishes RATE steels from traditional alloy steels, which are prone to softening at high temperatures. However, the temperature ranges for the preservation of hot hardening in RATE steels was not systematically studied, which makes it difficult to use a pressing tool more efficiently. In this paper, we study the mechanical behavior of RATE die steel during thermo-mechanical treatment in a wide temperature range, including the stage of preliminary deformation at lower temperatures and the stage of main deformation at higher temperatures corresponding to operating temperatures of the pressing tool. The thermo-mechanical treatment was carried out using a hardening-deformation dilatometer DIL 805 A/D according to the compression mode. We obtained the true stress-strain curves and determined the mechanical characteristics and strain hardening index. Size of the former austenite grain in the steel structure after thermo-mechanical treatment was measured. The temperature-force conditions for enhancing hot hardening or stabilizing hot hardening, or softening, were established. It is shown that the hardening achieved at the stage of preliminary deformation at a temperature of 450 °C is enhanced at the stage of main deformation at temperatures in the range from 550 to 800 °C, while in this temperature range the tendency to increase hot hardening is weakened.

Information about the behavior of melts of the high-temperature nickel alloys is the basis for creating new smelting technologies that significantly increase the service properties of metal products, as well as solve a number of technological problems. The results of numerous studies indicate structural changes occurring in various metal melts under the influence of temperature and time. For many years, there has been a scientific discussion about the nature of these phenomena, and a common opinion was formulated on a number of issues. Structural changes in metallic liquids are presented as a second-order phase transition, where a liquid of higher density is replaced by a liquid of lower density. These transformations in the structures of liquid metals are called liquid-liquid transition (LLT). Studies of the structure-sensitive properties of melts of the heat-resistant nickel alloys also reveal structural changes that irreversibly transform the melt into a microhomogeneous state. The research results presented in this article confirmed that structural changes in melts of the high-temperature nickel alloys are also a second-order phase transition, as evidenced by the breakage of atomic microgroups, uniform redistribution of alloying elements, and the formation of new clusters characterized by smaller sizes and greater chemical homogeneity. Therefore, these changes can be characterized as LLT, while this does not contradict the previously substantiated quasi-crystalline model of the microinhomogeneous state of liquid heat-resistant nickel alloys.

The paper considers the study of influence of retained austenite on the mechanical properties of steel of the austenite-martensitic class based on 15 % Cr after various heat treatment. Significant amount of retained austenite remains in the steel microstructure after quenching and subsequent tempering or heating in the intercritical temperature range that makes difficult to achieve a high yield strength. Destabilization of retained austenite with subsequent transformation into newly formed martensite is provided by multi-stage heat treatment which includes quenching, heating in the intercritical temperature range or above the AC3 point and final tempering. It was established that retained austenite remains in the microstructure of two-phase steel and has the form of blocks and thin layers located in the inter-lath space. Tensile testing of steel based on 15 % Cr showed that multi-stage heat treatment provides a high-strength condition corresponding to strength groups Q125 and Q135. A comparative analysis of deformation behavior of semi-austenitic steel in various states indicates that the beginning of the martensitic transformation after the final tempering shifts into the elastic region during tension and leads to the formation of stress-assisted martensite. It was determined that block-shaped retained austenite in steel with 15 % Cr predominantly undergoes martensitic transformation during tensile and impact tests at a subzero temperature. This is supposed to be the reason for the noticeably lower impact toughness of semi-austenitic steel with 15 % Cr compared to martensitic steel with 13 % Cr at equal strength.

The work is devoted to the study of the effect of annealing on mechanical properties and inhomogeneity of plastic deformation of a bimetallic plate made of stainless / carbon steel with the dimensions of the working part 50×7×2 mm. To develop laser technology for producing bimetals of various compositions, the contact zone of two dissimilar steels is of greatest interest. Since the performance characteristics of the entire product as a whole depend on the structure and properties of this zone, interaction of the components of the bimetal in the process of its manufacture leads to appearance of heterogeneity of various types near the interface and in the volumes adjacent to it. The research material was obtained by laser cladding of wire AISI 304 stainless steel on a plate of low-carbon steel St3. Bimetallic samples were subjected to vacuum heating at a temperature of 700 °C at various times from 2 to 8 h. The use of data on the distributions of local strains by the speckle photography method made it possible to consider the process of plastic flow in the initial section of tension diagram and to establish the effect of annealing temperature on plastic strain localization during mechanical tests. For a quantitative assessment of deformation inhomogeneity in the main and cladding layers, we used spatiotemporal distributions of local elongations and the corresponding values of the variation coefficient. It was established that the level of deformation inhomogeneity of microvolumes at the interface during tension is higher than that of the bimetal main layers. With increase in the annealing time, increase in the variation coefficient in the joint zone is noted, which is more significant on the stainless steel side, and this increases the probability of microcracks initiation. The increased level of deformation inhomogeneity of microvolumes of the cladding layer carburized zone is contingent on the increased localization of deformation in nearby microvolumes due to structural heterogeneity.

The article considers theoretical study of solidification of the binary iron–tungsten system at a tungsten content of 18 wt. %. Such tungsten content is typical for heat-resistant alloys used in plasma-arc surfacing on the rolls surface. The axisymmetric Stefan thermal problem is solved for two movable cylindrical boundaries that separate three regions. In region 1, the melt is at the melting point; in region 2, the substance is in a two‒phase state, and in region 3 – a solid. The liquidus temperature was set at the interface of regions 1 and 2, and the solidus temperature – at the interface of regions 2 and 3. At these boundaries, a condition for the heat flows balance was given, from which a system of kinetic equations was obtained. This system was solved by numerical methods, without hypothesizing that the fronts of phase transformations move according to the law R ~ t^1/2. Solution of the system of kinetic equations shows that the solidus boundary moves almost linearly. The liquidus boundary moves according to the parabolic law. For regions of the micrometer range in size, the processes of phase transformations take place in a time of about 5 ns, whereas for regions of the order of 10 μm in size – in a time of about 50 ms. Dependences of temperature fields on the radial coordinate at various points in time show that with increasing time, the dimensions of region 2 decrease, and as soon as coordinates of the liquidus and solidus boundaries become close, thecrystallization process stops. Further development of the model consists in taking into account the rotation of one of the media. The results obtained will serve as a material for the study of the Mullins-Sekerka two-front instability.

Nowadays high-entropy alloys (HEAs) with a hexagonal close packed structure consisting of rare-earth metals (REM) are of particular interest. In this work, we investigated the possibility of using of Al₂O₃ and Al:Zn (1:1) as a  protective coatings for REM HEAs GdTbDyHoSc and GdTbDyHoY. The REM HEAs samples were synthesized from metals of purity ≥99.9 % by melting in an electric arc furnace under Ar atmosphere (99.99 %). The samples were coated by supersonic plasma spraying. Corrosion resistance was determined in a salt mist chamber for 48 h. It was found that for all studied samples corrosive effect in conditions of salt mist leads to degradation of the base material of the alloy. Samples coated with Al:Zn (1:1) under salt mist conditions showed less resistance than samples coated with Al₂O₃ due to the chemical interaction between aluminum and sodium chloride solution. 

The Bakal deposit located in the Southern Urals near the city of Bakal, Chelyabinsk region, is one of the largest deposits of carbonate iron ores (siderites). The total deposit of siderites is about 1 billion tons. They are not in demand among metallurgists because of their low iron content and high magnesium content. At the same time, the Urals metallurgical enterprises are suffering from shortage of iron ore raw materials including steelmaking ore raw materials. The high purity of siderites in terms of phosphorus and non-ferrous metals makes it possible to use methods of coke-free metallurgy for their processing. Pyrometallurgical processing of siderites including their reduction roasting in a rotary furnace followed by grinding and magnetic separation allows obtaining a concentrate to be used as a steelmaking raw material having metallization degree above 90 % and a waste rock content under 3 – 7 %. Calculations showed that the costs of electricity used for melting scrap metal and metallized siderite concentrate containing 30 % of waste rock and loaded into the furnace at temperatures above 1000 °C are close. We propose a siderite processing method including reduction of the initial ore in a rotary furnace, and melting of resulting metallized concentrate hot loaded (at temperatures above 1000 °C) into a furnace. The empty rock of metallized siderite concentrate contains a large percentage of magnesium oxide that makes it refractory. To obtain liquid slag, it is proposed to add boric anhydride in the form of colemanite. To assess the B₂O₃ effect on melting of the metallized siderite oxide phase in the process of electric melting, studies on the viscosity correlation of the magnesian steelmaking slag containing B₂O₃ with temperature and its composition were carried out. It was found that at the discharge temperature (1600 °C) the resulting magnesia slag with the ratio of MgO/SiO₂ in the initial siderite equaling to 0.75 – 1.25 has a low viscosity (less than 3.65 P).

Currently, there is a growing interest in the use of hydrogen in the composition of fuel mixtures for turbojet engines and gas turbine units (GTU). The effect of hydrogen on heat-resistant nickel alloys of gas turbine blades has been little studied. In this regard, this work is devoted to studying the effect of hydrogen on nickel oxide reduction on the surface of the nozzle blade of a gas turbine engine. Hydrogen is a good reducing agent. Therefore, this article discusses the effects of hydrogen under various conditions with metal oxides, and methods of metal oxides reduction on the surface of the blades of a gas turbine engine. The thermodynamics of the interaction of aluminum, titanium, nickel and tungsten oxides with hydrogen fluoride and reactions of fluoride with hydrogen was investigated in the temperature range 273 – 1373 K. It was established that the interaction of aluminum oxide with hydrogen fluoride occurs in the temperature range from 273 to 1073 K, titanium oxide with hydrogen fluoride – from 273 to 373 K, nickel oxide with hydrogen fluoride – from 273 to 873 K. In this case, of the resulting fluorides, only nickel fluoride interacts with hydrogen at temperatures above 673 K. Hydrogen interacts with nickel oxide throughout the entire temperature range, and with tungsten oxide at temperatures above 1173 K. We studied the effect of hydrogen on heat-resistant nickel alloys of gas turbine blades subjected to preliminary fluorination and not treated with fluorine compounds. Nickel oxide reduction with hydrogen proceeds better after the preliminary fluorination process. In this case, particles 2 – 5 μm in size containing 90.16 % Ni are formed on the surface of the blade sample. Without fluorination, this process at 1223 K and duration of 1 h does not occur.

A simple theory of thermodynamic properties of liquid nitrogen solutions in Fe – Co alloys is proposed. This theory is completely analogous to the theory for liquid nitrogen solutions in alloys of the Fe – Cr system proposed previously by the authors in 2019. The theory is based on lattice model of the Fe – Co solutions. The model assumes FCC lattice. In the sites of this lattice are the atoms of Fe and Co. Nitrogen atoms are located in octahedral interstices. The nitrogen atom interacts only with the metal atoms located in the lattice sites neighboring to it. This interaction is pairwise. It is supposed that the liquid solutions of Fe – Co system are perfect. The initial values for the calculation are the Sieverts law constants for nitrogen solubility in liquid iron and in liquid cobalt. Result of the calculation is value of Wagner interaction coefficient in liquid iron-based alloys at 1873 K \(\varepsilon _{\rm{N}}^{{\rm{Co}}}\) = 1.8. This value is in good agreement with the experimental data obtained by Schenck, Frohberg and Graf, 1958; Maekawa and Nakagawa, 1960.

The work makes it possible to simplify development of pulsed metal heating technology. A software product was created to select the optimal values of operating parameters of pulsed heating on a mathematical model, which significantly reduces the setup time of a thermal unit using this technology. Test calculations showed adequacy of the results obtained to the operating parameters of functioning through-pass heating furnaces equipped with high-speed jet burners. The problems of controlling metal heating became particularly relevant due to the proliferation of high-performance rolling mills and increasing requirements for the quality of metal heating. In this regard, full implementation of the research program will make it possible to develop specific recommendations for increasing the productivity of heating furnaces and improving their energy efficiency.

The authors studied the physicochemical characteristics of new complex alloys containing, %: 11 – 30 Nb, 23 – 28 Si, 3 – 10 Al and 3 – 4 Ti. It was shown that complex alloys have the most favorable values of density and crystallization temperatures compared to standard ferroniobium (60 wt. % Nb). Complex alloys with a low concentration of niobium have acceptable crystallization temperatures and optimal density values (5740 – 6560 kg/m³). This allows the pieces of ferroalloy to be completely in the liquid steel when it is released into the ladle, and to be constantly in motion, which increases absorption of the leading components. When the niobium concentration increases to 30 %, phase composition of the alloy changes: a decrease in the proportion of the low-temperature FeSi phase with low density values and an increase in the proportion of the high-density ternary compound NbFeSi₂ with a crystallization temperature of ~1713 °C. An increase in Nb concentration from 11 to 17 % leads to a decrease in the crystallization temperature, and a further increase to 30 % Nb, on the contrary, is accompanied by an increase in the liquidus and solidus temperatures to 1700 and 1610 °C, respectively, which is consistent with liquidus line in phase diagram of the Fe – Nb system with a minimum in Nb concentration range ~18 %. The best characteristics, both from the point of view of obtaining ferroalloys and use for alloying steel, belong to an alloy containing, wt. %: 17.1 Nb, 24.6 Si, 7.6 Al and 3 Ti. This alloy is characterized by the temperature of crystallization onset (1550 °C) below the liquid steel bath temperature and belongs to the category of low-melting alloys. It has optimal density values – 6390 kg/m³, which has a positive effect on the performance characteristics of niobium ferroalloys.

The paper describes the problem of increasing the productivity of electroslag remelting (ESR) furnaces. The remelting technology on direct current is proposed as the most effective method. The description of the technology touches upon positive and negative effects affecting the specific productivity of smelting, energy consumption, and quality of the obtained ingots in terms of their physical and mechanical properties and chemical purity. The authors proposed the electroslag remelting method with rotation of the consumable electrode as a new technology, and realized a brief comparison with the external magnetic field application technology. The schemes that clearly demonstrate the principle of controlling the crystallization front shape and the thermal center localization in the slag bath are considered. A stationary numerical model for the slag bath of the operating semi-industrial furnace ESR A-550 on direct current with polarity reversing ability was developed. The mathematical apparatus consisting of electrothermal, hydrodynamic and convective parts was constructed. The authors designed the mesh domain for a slag bath located between the consumable electrode and the water-cooled crystallizer with diameters of 60 and 90 mm, respectively. The height of the sub-electrode zone is 10 mm. The current limit is 800 A and the voltage is 46 V. Numerical fields of current density and temperature distribution in the slag bath volume are obtained. The range of temperature values is located in the range from 1400 to 2200 °C at the peripheral and subelectrode zones of the slag bath, respectively. The scheme of the ESR furnace modernization is given in terms of mechanical part automation and transferring to direct current.