Martensitic stainless steels with 13 % Cr are widely used in many industries due to their high level of mechanical properties and acceptable corrosion resistance. The paper consolidates information on the guaranteed level of properties and heat treatment conditions required for its implementation. The properties after treatments proposed by researchers are compared with those known for industrial metal. The dependences of the hardness of 13Cr type hardened steels with 0.20 – 0.50 % C on the austenitization temperature and the accompanying changes in structure have been analyzed. The temperatures providing maximum hardening and the temperatures at which the steel ceases to harden have been revealed. The effect of the duration of austenitization, heating and cooling rates on the properties of steels has been considered. The mechanical properties and corrosion resistance after quenching, quenching and tempering in relation to structural-phase states of steels are considered. It is discussed in detail how the type of secondary phases during tempering, their amount, and distribution affect the corrosion resistance of steels with 13 % Cr. It increases with increasing heating temperature during austenitization and decreases with increasing tempering temperature due to the precipitation of Cr₂₃C₆ carbides and depletion of the matrix in chromium to the concentrations below 12 %. The tempering temperature of 500 – 550 °С is recognized as the worst: due to intensive precipitation of carbides the steel is not passive, and the corrosion rate is maximum. Quenching with low tempering is recommended for 20Cr13 steels (to combine high strength, good corrosion resistance and satisfactory plasticity), or, more often, quenching with high tempering is recommended at ~(650 – 700) °С (good plasticity, satisfactory corrosion resistance). For steels of 40Cr13 type the temperature of ~700 °С is not recommended because of the increased concentration of carbides and insufficient corrosion resistance. Examples of increasing the wear resistance properties of 40Cr13 steels due to surface treatments, from nitriding to laser and plasma surface quenching, are presented.

In this paper we studied the synthesis of composite core-shell powders sprayed as wear-resistant metal-ceramic coatings. High-hardness TiB₂ and HfB₂ powders form the core, and the shell is made of titanium. The cladding was applied by iodide transport technology. This cladding method involves deposition by gas transport with iodine as an agent. The TiB₂/Ti and HfB₂/Ti composite powders were sprayed using microplasma technology. In contrast to conventional plasma spraying, it minimizes the phase transformations in the composite powders induced by heating. Analysis of the final coating on polished cross sections revealed that during microplasma spraying, the titanium is oxygenated and it produces a titanium dioxide phase. As a result, the TiB₂/Ti and HfB₂/ Ti composite powders are transformed into TiB₂(TiB)/Ti(TiO₂) and HfB₂/Ti(TiO₂) coatings. We also studied the distribution of the components across the coating. The hardness measurements showed that the titanium diboride coatings obtain microhardness of 1300 HV. The microhardness of the hafnium diboride coatings is about 1600 HV. For abrasion testing of the TiB₂(TiB)/Ti(TiO₂) and HfB₂/Ti(TiO₂)) coatings we used uncoated alloyed 45Kh steel (similar to EU grade: 41Cr4) and the specified coatings as an abradant material. Despite their lower microhardness, the TiB₂(TiB)/Ti(TiO₂) coating showed the highest abrasion resistance.

In order to assess the resistance to hydrogen embrittlement caused by the presence of hydrogen in the transported product, and, accordingly, the suitability of pipes for transporting hydrogen, we studied the metal of large-diameter X52 strength class pipes manufactured by JSC “ChelPipe” (a TMK Group company). The work included the study of pure gaseous hydrogen effect under pressure up to 10 MPa on change in mechanical characteristics of the base metal of large-diameter pipes (LDP) during preliminary hydrogen charging for various periods in a stationary autoclave under pressure, and during simultaneous loading with a slow strain rate (SSRT) under expected operating conditions. Results of the X52 LDP metal study show that there is no significant impact on the effect of gaseous hydrogen under pressure for up to 144 hours on mechanical characteristics of the base metal determined by static uniaxial tension (decrease in ductile characteristics does not exceed 9 %). During SSRT at a rate of not more than 1·10^–6 s^–1 in a pure gaseous hydrogen environment under a pressure of 10 MPa, the change in strength and ductile characteristics does not exceed 13 % in comparison with the reference tests in a nitrogen environment under the same pressure. The results obtained allow us to consider that the base metal of low-alloy pipe steel with ferrite-perlite microstructure of X52 strength class is sufficiently resistant to hydrogen embrittlement. Final confirmation of the possibility of using LDP made from steel under study will be the results of further qualification tests, including the study of the weld metal and heat-affected zone properties.

The authors studied the structure, properties, and corrosion resistance in different acids of the nickel-phosphorus coatings with the dispersed silicon carbides after crystallization annealing in different modes. Crystallization onset temperatures after heating at rates of 1, 5, and 20 °C/min and the percentage of crystalline phases formed under isothermal conditions (nickel phosphide Ni₃P and nickel) were determined. It was determined that a high microhardness of more than 1000 HV is achieved in the composite nickel-phosphorus coating with dispersed particles of the silicon carbides also during prolonged low-temperature annealing, accompanied by crystallization with the formation of already insignificant (10 %) amounts of Ni₃P. The revealed dispersed Ni₃P located both inside the grains and along the boundaries of the grains make the main contribution to the increase in microhardness. Yield strength and tensile strength of coatings increase during crystallization annealing by only 12 – 15 MPa, and elongation drops to zero, due to the formation of the brittle Ni₃P compounds. Annealing with a short-term soaking at crystallization temperatures leads to the fact that the silicon carbides exhibit a barrier effect. This reduces the intensity of the formation of crystalline Ni₃P and corrosion resistance, while a long-term soaking at lower crystallization temperatures forms about 70 % Ni₃P, contributing to consistently high hardness and improved corrosion resistance. Corrosion resistance of the composite Ni-P coatings with the silicon carbides, regardless of heat treatment modes, is maximum in acetic and orthophosphoric acids at the 70 % nickel phosphide and minimum in nitric acid and its mixtures with other acids.

The defective substructure of polycrystalline bodies preconditions substructural hardening and mechanical properties. Pearlite, which is the main structural component of rails, is subjected under deformation to considerable transformation accompanied by a number of processes. In the present work, methods of the modern physical materials science were used to study and analyze the defective substructure of pearlite with lamellar morphology and properties of rail steel subjected to fracture under the conditions of uniaxial tensile strain of flat samples. It was established that the ultimate strength changes from 1247 to 1335 MPa, and the relative strain-to-fracture is from 0.69 to 0.75. The formation of three zones of the fracture surface is observed: fibrous, radial and shear zones. Their shapes and sizes have been analyzed. The deformation of rail steel is accompanied by fracture of cementite plates of pearlite colonies and re-precipitation of nanosized particles of tertiary cementite about 8.3 nm in size in the volume of ferrite plates. The main mechanisms of cementite plate fracture are cutting and dissolution. Dislocation substructure is represented by chaotic distribution of dislocations and their clusters. Scalar density of dislocations in ferrite increases from 3.2·1010 cm-2 in the initial state to 7.9·10¹⁰ cm^–2 at failure. Deformation is accompanied by the formation of internal stress fields which manifest themselves as bending contours of extinction. The sources of stress fields are the interfaces of cementite and ferrite plates as well as grain interfaces. Fragmentation of ferrite and cementite plates has been revealed. The average size of cementite fragments is 9.3 nm. In the fracture zone of the rail steel sample, rotation of pearlite grains has been noted, indicating the presence of a rotational mode of strain. The electron microscopic images of cementite plates show a change in the contrast, which may be related to formation of the Cottrell atmospheres.

In this paper we studied the possibility to enhance the microhardness of Ni₃Al intermetallic compound by reducing the average grain size and the effect of the mixture deformation during self-propagating high-temperature synthesis (SHS) on the Ni₃Al grain size and microhardness. We used an SHS extrusion test bench to continuously monitor the synthesis variables. One of the key factors affecting the grain structure and microhardness is deformation rate of the synthesis product. Increasing the extrusion nozzle diameter from 3 to 5 mm results in a longer displacement of the press plunger since it takes less force to extrude the material through the larger diameter orifice. It is assumed that the resistance to deformation under pressure decreases, while the deformation rate increases for the material in the mold, and decreases for the extruded material. As a result, the average grain size of Ni₃Al remaining in the mold after synthesis decreases by 40 % (from 7 to 5 μm), while the grain size of the extruded material is doubled (from 3 to 6 μm). Compared to Ni₃Al produced by SHS compaction, the average grain size of extruded Ni3Al is 82 % less (17 and 3 μm, respectively). Reducing the average grain size of extruded Ni₃Al leads to a 600 MPa increase in microhardness. The results obtained may assist the development of guidelines for fine grain, high microhardness intermetallide/alloy manufacturing.

The development and success of the physical science of strength and plasticity allow the main aspects of dislocation physics to be proposed. This work considers the current state of this issue as part of a multilevel approach: patterns of dislocation accumulation in a material after deformation with various degrees. The main mechanism of hardening of a metal polycrystal is the accumulation of dislocations in its grains, while the main hardening parameter is the mean scalar density of dislocations. The scalar density of dislocations is divided into the following components: the density of statistically stored (ρ_S); and the density of geometrically necessary (ρ_G) dislocations. The transmission diffraction electron microscopy (TEM) is used to study the stages of dislocation substructure (DSS) types development in Cu – Mn alloys depending on the concentration of an alloying element during active plastic deformation. Polycrystal alloys are studied in a wide concentration range: from 0.4 to 25 % Mn (at.). A number of dislocation substructure parameters are measured using electron microscope images: mean scalar density of dislocations <ρ>; density of statistically stored (ρ_S) and geometrically necessary (ρ_G) dislocations; curvature-torsion of the crystal lattice (χ); density of microstrips (P_strip); and density of broken sub-boundaries (M_{br.  bnd.}). A sequence of transformations of the DSS types with an increase in the deformation degree and amount of the second element to form the substructure type and parameters was established. The influence of the second element and grain size on the mean scalar density of dislocations and its components was experimentally determined. The presence of disorientations in the substructure during deformation is based on the measurement of these parameters using the TEM.

Studying the flow stress of various steel grades is one of the key issues for the viable operation of automation systems which support the production of rolled products with the required precision based on geometrical properties. A knowledge of flow stress is also important for the design of rolling mill equipment. The properties of flow stress are published mainly in the form of coefficients of various equations (for instance, the Hansel–Spittel equation). However, these equations are quite often limited in terms of process variables where they provide accessible result. It also should be taken into account that the existing rolling industry fabricates tens of steel grades, the chemical composition of which can vary in wide range depending on final thickness of the rolled products, customer requirements, or on the basis of economic considerations. Studies of the rheological properties of such amount of materials under laboratory conditions is expensive, time and labor consuming and published data does not provide data completeness. This work demonstrates that, using data from industrial rolling mills and methods of machine learning, it is possible to obtain data on material rheology with satisfactory precision. This allows laboratory studies to be avoided. Similar studies are possible due to high intensity of various sensors and instrumentation in modern rolling mills. The results of industrial data were compared with flow stress measured by   Gleeble. On the basis of this comparison the model was trained using gradient boosting in order to consider peculiarities of industrial production process.

Stainless steel spherical powders are commonly used as additives in such manufacturing processes as selective laser melting, selective laser sintering, direct laser sintering, electron beam melting, and others. These processes require high-quality spherical powders. The purpose of this study is to develop a manufacturing process for making spherical powder by plasma spraying of a 1 mm dia. wire, stainless steel 03Cr17Ni10Mo2 (US analog: 316L steel grade) and to analyze the powder suitability for additive manufacturing. We refined the spherical powder manufacturing process and studied the spraying conditions vs. –160 μm fraction yield relationship, since this fraction is required for additive manufacturing. As the arc power gas flow rate increases, the –160 μm fraction yield increases to over 70 %. The powder has high fluidity (17.6 ± 1 s), bulk density (4.15 ± 0.1 g/cm³), and tapped density (4.36 ± 0.2 g/cm³). It is suitable for additive manufacturing applications. We also studied the effect of the spherical powder fraction size distribution on the fluidity, bulk density, and tapped density. The best results (fluidity: 16.64 ± 1 s; bulk density: 4.16 ± 0.1 g/cm³; tapped density: 4.38 ± 0.2 g/cm³) were obtained for –90 μm fraction. With these properties, the powder meets the basic additive manufacturing requirements: less than the 30 s/50 g fluidity, and bulk density exceeding 3 g/cm³.

This paper examines the crack geometry of briquettes in magnesium oxide (MgO), a slagging material widely used in iron and steel making applications. Geometry measurement data and crack layout in briquettes are produced by roll briquetteizing. Cracking in briquettes is likely due to the workflow of roll briquetteizing. This defect affects the strength of briquettes and yield ratio (plus productivity rate) during briquetteizing using roll baling presses. A number and angles of cracks in respect to the briquetteizing direction were identified in accordance with photos of briquette side surfaces using graphical software.

Smelters in the Urals procure only 50 – 60 % of raw materials from local sources. The rest is imported from Central Russia, the Kola Peninsula, and Kazakhstan. Switching to local raw materials would increase the competitiveness of the Urals metals, so local alternatives should be considered, such as siderite ore from the Bakal deposit. The ore is in low demand due to its low iron content and high magnesium content. The higher the siderite content in the charge, the higher the magnesium oxide content in the slag. This affects the slag viscosity, so for siderite content exceeding 20%, melting is difficult or impossible. We proposed the addition of boric oxide to liquefy the slag. The simulated slag (CaO 26.8 %; SiO2 38.1 %; Al2O3 11.8 %; MgO 23.6 %) identical to that produced by the Magnitogorsk Metallurgical Plant (MMK) blast furnaces with the addition of 30 % of calcined siderite is short and unstable. The temperature when the slag viscosity is equal to that at the blast furnace taphole (0.5 Pa·s) is 1390 °C, while the melting point (2.5 Pa·s viscosity) is 1367 °C. The addition of boric anhydride makes the slag long and stable. As the B2O3 content is increased from 0 to 12 %, the temperatures at which the slag viscosity is 0.5 and 2.5 Pa·s decrease to 1260 and 1100 °C, respectively. The study shows it is possible to significantly increase the siderite content in blast furnace charge.

Increasingly rigid requirements in terms of the steel products quality are forcing the metallurgy technologists to search for innovative solutions to stabilize the steel quality. Much attention is paid to ladle treatment of melt and selection of rational composition of modifiers, which enables the content of non-metallic inclusions to be reduced. In order to solve the formulated problem, complex modifiers are used containing both calcium and other alkaline earth metals (barium and strontium). This article presents the results of a pilot campaign on metal ladle treatment by complex modifiers with alkaline earth metals (calcium, barium, strontium) upon production of steel with higher requirements for non-metallic inclusions under conditions of electric-furnace melting at JSC “Ural Steel”. In the course of experimental activities, the maximum level of inclusions content of sheet rolled products from pipe steel grades was decreased in terms of brittle silicates (according to State Standard GOST 1778) from 4.0 to 1.5 – 2.5, and in terms of non-deforming silicates from 4.0 to 3.0 – 3.5. Substitution of silicocalcium, grade SK40, with experimental modifiers resulted in improvement of strength properties of rolled products both during tension tests and during impact bending tests at lower temperatures. This influence was observed in all variants of consumption of the experimental modifiers. With increase in the consumption of modifiers positive influence on steel mechanical properties also increased. As a consequence of substitution of silicocalcium with experimental modifiers, the calcium recovery with the use of Si – Ca – Ba increased in average by 1.6 times, and with the use of Si – Ca – Ba – Sr in average by 2.4 times. The use of the complex modifiers enabled the targeted value of residual calcium in steel sample from tundish to be obtained at significantly lower calcium consumption.

The article describes the determination of level of zonal and dendritic segregations in slabs cast by thin slab technology. The calculated coefficients of variation of content of main and impurity chemical elements over slab cross-section do not exceed 10 %, while the zonal segregation are moderate. The content of manganese measured by the surface area occupied by dendritic axes and interdendritic spaces determines the level of dendritic segregation. The manganese concentration varies from 0.6 to 1.1 %, respectively. It was established that the dynamic soft reduction during solidification allows the primary dendritic structure to be refined, in order to form additional centers upon phase transformation of δ ferrite into austenite. The sizes of initial austenite grains formed accounting for the primary dendritic structure are 3 times lower in a thin slab than in a slab with the thickness of more than 200 mm. Transformations of dendritic structure during reductions demonstrate the high level of conditioning required for the formation of uniform austenite grains in semifinished rolled stock before finish rolling. The studies did not confirm the hypothesis that bainite of coarse morphology in the microstructure of hot rolled products is formed in segregation sites. The inherited influence of the primary dendritic structure on structure formation during rolling was detected. The manganese concentration varies between bainite and neighboring structure from 0.68% to 1.01% similarly to the level in initial dendritic segregation. The difference in the content of chemical elements influences on recrystallization of austenite grains during high temperature roughing. Bainite was formed in the frames of chemically depleted coarse austenite grains steady upon phase transformation.

Slabs are preheated before hot rolling to achieve the required metal plasticity. Walking beam furnace is the most efficient form of equipment since it heats the slab from all sides. Nevertheless, the bottom surfaces in contact with the water-cooled support beams are shielded from the heat radiated by the lower part of the furnace, and their heat is transferred to the beams. We developed and implemented by means of software a simulation model to study the non-uniformity of the temperature distribution across the slab and how the slab transportation system design affects it. Thesimulation model includes a numerical solution of a 3D thermal conductivity problem with piecewise defined boundary conditions on the slab bottom surface. Identical boundary conditions were applied to both the top surface and the open areas of the slab bottom surface. For the areas of contact with the beams, we applied modified boundary conditions to account for the duration of the contact. We numerically solved the system of difference equations with the layer-by-layer method, in order to obtain a system defined by a tridiagonal matrix. The slab-to-beam contact heat transfer was assumed to be adiabatic during the entire contact period. The calculations produced the temperature fields at different cross-sections of the slab. As a result, we discovered a significant non-uniformity of the temperature field on the lower surface of the slab leading to the entire  temperature field non-uniformity of the slab. We developed simulation and visualization software to study the slab temperature field under various heating conditions. The simulation model is refined from the experimental data available.

Metallurgical plants (smelters) adjust their production plans to match changing global demand. EVRAZ West Siberian Metallurgical Combine JSC  (EVRAZ ZSMK) employs furnace charges and pellets containing 110 components, with a product range exceeding 2000 items that vary from month to month. The production plan is optimized individually for each manufacturing process, with the goal of minimizing costs and maximizing output. This paper discusses the development and deployment of the smelter simulation system currently in use at EVRAZ ZSMK. Unlike other solutions, this system performs concurrent, end-to-end optimization of all smelter processes, with the ultimate goal of maximizing the company's profit. During the system's operation from 2019 to 2020, users encountered tedious and time-consuming tasks, such as creating 60 production plans per year, conducting 10,000 test iterations, and analyzing 30 scenarios. To gather statistical data, a feedback form was used, which identified several issues. Firstly, the mathematical model fails with incorrect input data. Secondly, repeated analyses are required to identify and interpret the plan/actual cost discrepancies. Thirdly, data validation errors, such as incorrect chemical composition or model settings unsuitable for the specific timeframe, were observed. To address these shortcomings, several measures were developed: an input data validator (before and after analysis) was introduced; sensitivity and factor analysis modules were developed to aid in identifying and interpreting cost discrepancies; a chemical composition uploading tool was developed to ensure data validation. Finally, the system was retrained on historical datasets to improve its accuracy.

The selective reduction process generates products in the form of concentrates and tailing/by-products. There is high percentage of iron and other elements in the tailings that are not extracted in selective reduction process. Properties of by-products of selective reduction were investigated using X-ray diffraction (XRD), inductively coupled plasma optical emission spectroscopy (ICP–OES), ultraviolet-visible (UV–VIS), and scanning electron microscopy energy dispersion spectroscopy (SEM–EDS). Based on the results of this study, the properties of iron-sulfur, iron-magnesium-aluminium, and silica phases in the tailings can be interpreted experimentally. For future research, it can be the reference for such processes as acid and base leaching. Pure iron extracted from tailings can be used for metal fuel in the future. The tailings composition data will help future researchers to find optimal processes for the tailings.