The article describes state of the Russian market of medical instruments and equipment, the volume of production, import and export of medical instruments based on metals, and assesses the import dependence on various market segments. The comparative analysis of domestic alloys and materials produced by foreign companies has shown that Russia has developed unique alloys and steels that have no analogues abroad, with improved indicators of corrosion resistance, wear resistance, static and cyclic strength. However, metallurgical products supplied to the medical industry do not always meet the quality requirements, and medical industry enterprises use imported types of metallic products. It should be noted that for medical purposes, lowtonnage production batches are required, which are associated with increased costs. The situation is aggravated by the fact that some of the enterprises that produced low-tonnage batches of special steels and alloys were completely liquidated. In this regard, it is necessary to create a specialized manufacture of such materials. Results of the analysis of the Russian market of special metals and alloys used for medical needs are presented, and ways to solve the problem of import substitution in this market are suggested.

The second part of the article is devoted to the practical realizing of D.K. Chernov’s scientific “predictions”. They were confirmed by him in the implementation of the concepts of points “a” and “b”, structure of the ingot and the possibility, taking into account the knowledge of these temperature boundaries, to build basic modes of deformation and subsequent heat treatment of steel ingots. These materials are supported by a modern interpretation of that provisions and additional materials of the authors.

One of the ways to increase the energy efficiency and intensity of blast furnace smelting, especially when using pulverized coal fuel, is to increase the hot strength of coke. In the conditions of OJSC NLMK, an oil additive was introduced into the coal charge to improve the coke quality. At the same time, sulfur content in the coke increases, and, consequently, sulfur content in the cast iron increases as well. In this regard, the task of finding ways to improve the desulfurization of cast iron in blast furnace becomes urgent. The main factors determining the desulfurization of cast iron are slag basicity, content of MgO oxide in it, temperature of the smelting products, and the slag viscosity. The purpose of this work was to compare the efficiency of sulfur removal by increasing the slag basicity and MgO content. On the basis of wellknown equations, an algorithm was developed that allows the problem to be solved. It was established that an increase in MgO content in the slag promotes desulfurization of cast iron to a greater extent than a basicity increase. In addition, an increase in MgO content by 1 % is accompanied by an increase in slag yield by 3.0 – 3.5 kg/t of cast iron. At the same time, an increase in basicity by 0.01 leads to an increase in the slag yield by 4 – 5 kg/t of pig iron. Consequently, reducing the sulfur content in pig iron by increasing the slag basicity requires less heat. In terms of the specific consumption of coke, difference in heat demand is 0.4 – 0.5 kg/t of pig iron. It is shown that with an increase in MgO content in the slag, the slag viscosity at a temperature of 1450 °C increases to a lesser extent than with an increase in basicity.

The article presents results of the research of high-temperature gas corrosion of sections of EcoSoderberg electrolyzers’ gas-collecting bells (GSB) made of high-strength VCh50 cast iron with spherical graphite. The gravimetric method was used to study the specific mass losses of the sections due to corrosion. The microstructure of cast iron, structure, chemical and phase composition of corrosion products were studied using optical, electron microscopy and electron microprobe analysis. It was established that the specific weight loss of the sections during operation reaches 0.36 – 0.46 g/(cm2·month). Corrosion of cast iron sections of EcoSoderberg electrolyzers’ GSB is characterized by high unevenness by area. There are cases of decommissioning sections due to local through “burnouts” with a weight loss of 19 – 24 kg. With relatively uniform corrosion, the maximum allowable weight loss of the sections is 25 – 30 kg. To make predictive estimates based on experimental data, dependence of the sections’ mass loss on the operating time was obtained. It was found that the corrosion products of the sections consist of iron oxides and alloying elements of cast iron. Most samples are characterized by increased content of C, S, F, K, Al, and Na. Corrosion products have a pronounced layered structure and contain a large number of defects in the form of pores and cracks. The layers differ in chemical, phase composition, and macrostructure. All the studied samples are characterized by cyclic alternation of relatively dense layers of iron oxides Fe2O3 and Fe3O4 and more porous layers between them. The layers are characterized by increased content of C and F. Sulfur is evenly distributed over the thickness of corrosion products. The studied samples of corrosion products have high defectiveness, friability, large number of pores, cracks, discontinuities, and low adhesion to the surface of cast iron. This is due to the presence of phases and compounds with different coefficients of thermal expansion. The mechanism of corrosion products layers formation was established and scientifically proved.

From the analysis of data on beneficial use of red mud and oily mill scale, a new direction of recycling has been formulated: the joint processing of these wastes to produce liquid products. Technological modeling of the stage of joint water treatment of a mixture of red mud and oily mill scale was performed at an enlarged laboratory unit. The yields and compositions of the products were determined. A batch of washed sludge was sent for research on obtaining ironcontaining raw materials for subsequent pyrometallurgical processing. With component ratio of 1:1, solid to liquid ratio of 4, temperature of 95 °C and duration of 2 hours, 6.3 kg of the mixture were processed, 6.58 kg of washed precipitate with a moisture content of 21.3 % and 12.6 dm3 of the final solution were obtained. The specific volume of water evaporation was determined to be 31.3 dm3/h per 1 m2 of pulp surface. Compositions of the precipitate iron (54.4 %) and the final solution (1.1 – 1.3 mg/dm3) were established, which indicates an almost complete accumulation of iron in the precipitate. Concentrations in the products of processing impurities were determined: silicon, aluminum, phosphorus, sulfur, sodium oxide and organics. According to the results, a technological scheme for the joint processing of red mud and oily mill scale was developed and ways of using the process products were outlined: sludge – for iron, filtrate – for industrial treatment, evaporated and wash water – for leaching. Using the example of cooperation between enterprises of the Kamensk-Uralsky Industrial Unit, the hardware process diagram is considered. It is advisable to use the data obtained to implement the technology, in particular, to develop technological regulations for the design of a pilot installation.

The effect of silicon (in range 0.14 – 0.78 wt. %), boron, and rare-earth metals (REM) on the corrosion resistance of low-carbon austenitic chromium-nickel steel of 03Kh18N11 (AISI 304L) grade was studied. It is shown that all steels in quenched state when tested in boiling 56 and 65 % HNO3 solutions have comparable corrosion rates, which do not exceed the critical norm (0.5 mm/year) in accordance with GOST 6032 – 2017 (State Standard). Testing samples in boiling 27 % HNO3 + 4 g/l Cr+6 solution are susceptible to intergranular corrosion (IGC). The corrosion rate and the penetration depth of IGC increase with increasing silicon concentration from 0.14 to 0.78 wt. %. Study of the effect of nitric acid concentration and test temperature has shown that steel with 0.78 wt. % Si has significant corrosion losses exceeding the critical ones when testing in 56 and 65 % HNO3 solutions with temperature of 120 and 130 °С. But steel with high silicon content (0.78 wt. %) and low carbon concentration (0.020 – 0.022 %) after quenching in a range of 1080 – 1150 °C and tempering at 650 °C does not exceed the critical norm on average corrosion rate. Only 0.01 wt. % increase in carbon concentration leads to a significant (more than 30 times) increase in corrosion rate of sensitized steel. It is shown that microalloying with REM does not impair corrosion resistance of sensitized steel. In contrast to REM, alloying chromium-nickel steel with even a small addition of boron (0.0015 %) reduces steel corrosion resistance by an order of magnitude. Corrosion rate inverse dependence on quenching temperature is observed when, with increasing temperature, corrosion rate of 02Kh18N11GS0.38R steel increases.

The effect of silicon (in range 0.14 – 0.78 wt. %), boron, and rare-earth metals (REM) on the corrosion resistance of low-carbon austenitic chromium-nickel steel of 03Kh18N11 (AISI 304L) grade was studied. It is shown that all steels in quenched state when tested in boiling 56 and 65 % HNO3 solutions have comparable corrosion rates, which do not exceed the critical norm (0.5 mm/year) in accordance with GOST 6032 – 2017 (State Standard). Testing samples in boiling 27 % HNO3 + 4 g/l Cr+6 solution are susceptible to intergranular corrosion (IGC). The corrosion rate and the penetration depth of IGC increase with increasing silicon concentration from 0.14 to 0.78 wt. %. Study of the effect of nitric acid concentration and test temperature has shown that steel with 0.78 wt. % Si has significant corrosion losses exceeding the critical ones when testing in 56 and 65 % HNO3 solu tions with temperature of 120 and 130 °С. But steel with high silicon content (0.78 wt. %) and low carbon concentration (0.020 – 0.022 %) after quenching in a range of 1080 – 1150 °C and tempering at 650 °C does not exceed the critical norm on average corrosion rate. Only 0.01 wt. % increase in carbon concentration leads to a significant (more than 30 times) increase in corrosion rate of sensitized steel. It is shown that microalloying with REM does not impair corrosion resistance of sensitized steel. In contrast to REM, alloying chromium-nickel steel with even a small addition of boron (0.0015 %) reduces steel corrosion resistance by an order of magnitude. Corrosion rate inverse dependence on quenching temperature is observed when, with increasing temperature, corrosion rate of 02Kh18N11GS0.38R steel increases.

Mathematical modeling of differentiated thermal processing of railway rails with air has been carried out. At the first stage, onedimensional heat conduction problem with boundary conditions of the third kind was solved analytically and numerically. The obtained temperature distributions at the surface of the rail head and at a depth of 20 mm from the rolling surface were compared with experimental data. As a result, value of the coefficients of heat transfer and thermal conductivity of rail steel was determined. At the second stage, mathematical model of temperature distribution in a rail template was created in conditions of forced cooling and subsequent cooling under natural convection. The proposed mathematical model is based on the Navier-Stokes and convective thermal conductivity equations for the quenching medium and thermal conductivity equation for rail steel. On the rail – air boundary, condition of heat flow continuity was set. In conditions of spontaneous cooling, change in temperature field was simulated by heat conduction equation with conditions of the third kind. Analytical solution of one-dimensional heat conduction equation has shown that calculated temperature values differ from the experimental data by 10 %. When cooling duration is more than 30 s, change of pace of temperature versus time curves occurs, which is associated with change in cooling mechanisms. Results of numerical analysis confirm this assumption. Analysis of the two-dimensional model of rail cooling by the finite element method has shown that at the initial stage of cooling, surface temperature of the rail head decreases sharply both along the central axis and along the fillet. When cooling duration is over 100 s, temperature stabilizes to 307 K. In the central zones of the rail head, cooling process is slower than in the surface ones. After forced cooling is stopped, heating of the surface layers is observed, due to change in heat flow direction from the central zones to the surface of the rail head, and then cooling occurs at speeds significantly lower than at the first stage. The obtained results can be used to correct differential hardening modes.

The study was carried out by means of transmission electron microscopy on thin foils to investigate the changes in matrix morphology and phase composition occurring in ferritic-pearlitic steel of St2 grade (Russian) under plasma electrolytic surface quenching. In the original state St2 steel is a material which underwent quenching under the temperature of 890 °C (2 – 2.5 h) with cooling into warm water (30 – 60 °C) and further tempering under the temperature of 580 °С (2.5 – 3 h). Surface quenching was conducted in aqueous salt solution during 4 seconds under the temperature of 850 – 900 °C, voltage of 320 V, and current rate of 40 A. In the original state morphological components of the steel matrix were lamellar pearlite and non-fragmented and fragmented ferrite. Surface quenching resulted in the following transformations of morphology and phase composition: 1 – to martensitic transformation (morphological components are lath martensite, lamellar low-temperature and high temperature martensite), 2 – to steel self-tempering (inside all martensite crystals there are thin plate-like precipitations of cementite), 3 – to diffusion transformation γ → α and precipitation of retained austenite (γ-phase) given as thin layers along the boundaries of laths and plates of low-temperature martensite and inside all the crystals of lamellar martensite in the shape of “needles” like in twin type colonies. Surface quenching led to precipitation of special carbides of Мe23С6 phase. It was revealed that carbide precipitation is attributed primarily to decomposition of retained austenite and martensite and also to partial dissipation of cementite and, moreover, it is due to carbon removal from dislocations and the boundaries of α-phase crystals. That means that in all cases carbon from retained austenite, α-solid solution, cementite particles and defects of crystal lattice is used for the formation of special carbides.

Electro-explosive alloying as a method of pulse-plasma treatment consists in accumulation of energy by a battery of pulsed capacitors and its subsequent discharge for 100 μs through a conductor in form of titanium foil with silicon carbide powder, while conductor is under explosive destruction. Method of electro-explosive alloying of tungsten-cobalt hard alloy includes melting of surface and its saturation with explosion products, followed by self-hardening by removing heat deep into the material and environment. On the surface of VK10KS hard alloy, the coating was obtained with thickness of up to 15 – 20 microns with nanohardness of 26,000 MPa. Using X-ray phase analysis and scanning electron microscopy, it has been established that new phases of TiC, W2C, (W, Ti)C1 – x , WSi2 with high hardness were formed in the surface layer. As a result, friction coefficient decreased to 0.18 compared to the initial 0.41. Investigations with transmission electron microscopy have revealed changes during electro-explosive alloying that occur in surface carbide and near-surface cobalt phases. Dislocations accumulations were found in the carbide phase. In cobalt binder, deformation bands (slip bands), single dislocations, and finely dispersed precipitates of tungsten carbides were revealed. This change can be explained by stabilization of cubic modification of cobalt, crystal lattice of which has a large number of slip planes upon deformation and greater ability to harden in comparison with hexagonal modification of cobalt. Additional alloying with cobalt binder in heat affected zone after pulse-plasma treatment have a positive effect on the service life of tungsten-cobalt hard alloys as a whole due to their stabilization.

Intensification of carburizing and boriding of steel parts is achieved by microarc surface alloying. For carburizing, the parts are immersed in coal powder followed by electric current passing. For boriding, a coating with diffusant is used. Acceleration of diffusion is achieved by action of microarc discharges on the steel surface. The aim of this work was to study the effect of diffusion parameters on thickness, structure, and phase composition of coatings. The samples were made of 20 steel. Surface current density was 0.45 – 0.53 A/cm2. Duration of the process was 2 – 8 min. At the beginning of heating, temperature of the samples increases, and then stabilizes at 930 – 1250 °C due to cessation of micro-formation during combustion of coal particles. After carburizing, a eutectoid mixture is formed on the surface, then, the zone with ferrite-perlite structure is located, which transfers into the original structure. The maximum layer thickness (60 – 390 microns) is reached after 6 – 7 min of heating and then does not increase due to a decrease in the carbon potential during combustion of coal particles. Similar relationship is obtained when boriding: the maximum layer thickness (60 – 340 microns) is reached after 6 – 7 min and then does not increase due to depletion of diffusant source in the coating. At current density of 0.45 A/cm2, the layer consists of a base (a dispersed ferrite-carbide mixture) containing fine inclusions of iron borides and boron carbide. At current densities of 0.49 and 0.53 A/cm2, the layer has heterogeneous structure, with areas of high-hard boride eutectic located at the base. At high current density, diffusion of carbon and boron along the grain boundaries forms Fe – C – B triple eutectic. At lower current density, surface temperature is lower than eutectic formation temperature, so heterogeneous coating structure is not formed. The work results make it possible to choose modes of microarc heating to obtain the required parameters of diffusion layer.

Thermodynamic analysis of chromium reduction from its oxide in gas phase Н₂ – Н₂О – СО – СО₂ in contact with carbon was performed. Oxidation potential (p_O2 ) was determined by two nomograms in the coordinates

and

taking into account condition normalizations xH2O + xH2 + xCO2+ xCO = 1. In calculations, possible parameters of reduction of chromium from Cr₂O₃ oxide were determined by ratio of dissociation elasticity of the oxide and oxidation potential of the gas phase. In the СО – СО₂ – С system, chromium is reduced at temperature of 1505 K if x_CO > 0.9995. At this temperature, Cr₂O₃ compound is reduced in water gas of the following composition x_H2 = 0.0186, x_H2O = 0.28·10–4, x_CO = 0.9809, x_CO2 = 4.86·10–4, for which the oxidation potential is equal to dissociation elasticity of oxide

With an increase in hydrogen concentration from 0.0186 to 0.99, oxidation potential of water gas in contact with carbon decreases by four orders of magnitude to

This should lead to a significant increase in reduction rate. In such a gaseous atmosphere, it is possible to reduce chromium at temperature of 1230 K. It is technologically simple to obtain reducing water gas and at the lowest cost, for example, by heating water vapor in contact with carbon. It is shown that at temperature of 1500 K water gas is obtained with traces of Н₂О and СО₂ compounds with parameters x_H2 = 0.4999, x_CO = 0.4996,

Oxidizing potential of such a gas is less than that of chromium oxide, and this difference significantly increases with increasing temperature.

Thermodynamic modeling results of lanthanum equilibrium content in metal under the slag of CaO – SiO₂ – La₂О₃ – Al₂O₃ – MgO system corresponding to chemical composition of 16 points of local simplex plan are presented using the HSC 8.03 Chemistry (Outokumpu) software package in combination with the simplex planning lattice method. In the work, slag is represented by CaO – SiO₂ – La₂O₃ – – 15 % Al₂O₃ – 8 % MgO oxide system in a wide range of chemical composition for temperatures of 1550 and 1650 °C, and metal contains 0.06 % C, 0.25 % Si, 0.05 % Al (in this expression and hereinafter in mass.%). The results of mathematical modeling are shown graphically in the form of composition - equilibrium content diagrams of lanthanum. There is significant effect of slag basicity on the lanthanum equilibrium content in metal. An increase in slag basicity from 2 to 5 at temperature of 1550 °C leads to an increase in the lanthanum equilibrium content from 0.2 ppm in the region of lanthanum oxide concentration of 1 – 5 % to 7 ppm in the region of increased concentration of lanthanum oxide to 4 – 7 %, hence the increase in slag basicity favorably affects development of lanthanum reduction. Increase in metal temperature also has positive effect on lanthanum reduction process. As temperature rises to 1650 °C, the lanthanum equilibrium content in metal increases from 0.2 ppm in the region of lanthanum oxide concentration of 1 – 3 % to 12 ppm in the region of increased concentration of lanthanum oxide to 4 – 7 %. In diagrams of chemical composition of slag containing 56 – 61 % CaO, 12 – 14 % SiO₂ and 4 – 7 % La₂O₃ , the lanthanum content in metal at level of 7 – 12 ppm is ensured in temperature range from 1550 to 1650 °C. Therefore, there can be confirmed a decisive role of slag basicity, concentration of lanthanum oxide and temperature factor in development of lanthanum reduction from slags of the studied oxide system by aluminum dissolved in metal.

The article presents thermodynamic modeling results of reduction roasting of ferromanganese ore with a high phosphorus content in the presence of solid carbon. The modeling was carried out using TERRA software package. Influence of the process temperature in the range 950 – 1300 K and carbon content in the amount of 8.50 – 8.85 g per 100 g of ore on reduction of iron, manganese and phosphorus was investigated. With these parameters of the system, iron is reduced by both solid carbon and carbon monoxide CO to the metallic state, and manganese is reduced only to MnO oxide. The degree of phosphorus reduction depends on the amount of reducing agent. With an excess of carbon relative to the reduction of iron, all phosphorus is converted into metal at a temperature of 1150 K. Phosphorus is not reduced at temperatures below 1150 K and such amount of carbon. The process of solid-phase reduction of iron from manganese ore with the preservation of manganese in the oxide phase was researched in laboratory conditions. Experimental results of direct reduction of these elements with carbon and indirect reduction with carbon monoxide CO are presented. The experiments were carried out in the laboratory Tamman furnace at a temperature of 1000 – 1300 °C and holding time of 1 and 3 hours. Results of the research of phase composition of the reduction products, as well as chemical composition of the phases are considered. The possibility of selective solid-phase reduction of iron with solid carbon to the metallic state was confirmed. Iron in the studied conditions is reduced by carbon monoxide CO and passes into magnetic part. During the magnetic separation of the products of ore reduction roasting with solid carbon and carbon monoxide CO, the non-magnetic part contains oxides of manganese, silicon and calcium. The work results can be used in development of theoretical and technological foundations for the processing of ferromanganese ores, which are not processed by existing technologies.

The article describes the main loads affecting shaped backups of the unit of combined process of continuous casting and deformation in billets production. Importance of determining the temperature fields and thermoelastic stresses in shaped backups with collars is provided at formation of several billets, at slab compression and at idle during water cooling of backups. The authors describe strength and thermophysical properties of steel from which the backups are made. Geometry of backups with collars used for obtaining billets of three different shapes in one pass is shown. Initial data of the temperature field calculation are given for backups with collars of the combined unit. Temperature boundary conditions are considered for calculation of temperature fields of backups with collars. Boundary conditions determining temperature of such backups are described and values of the heat flow and effective heat transfer coefficient are given. The results of calculation of temperature fields are performed in four sections and are given for typical lines and points located on contact surface of backups with collars and in contact layer at depth of 5 mm from the working surface. The sizes of finite elements grid which is used at calculation of temperature field of backups with collars are provided. Temperature field of backups with collars is determined on the basis of solution of unsteady thermal conductivity equation corresponding initial and boundary conditions. Values and regularities of temperature distribution in bases and in tops of the middle and extreme edges of the shaped backups are presented during slab compression and at idle when obtaining billets of three shapes in one pass at the unit of combined continuous casting and deformation.

The total solubility of alloying elements (chromium, titanium, aluminum) in the iron-nickel matrix (Fe – Ni) of 44NKhTYu alloy, depending on the number of cycles, does not occur during primary thermocycling processing (TCP). This is evidenced by the main replicas of the matrix with (111) reflection plane indexes of the samples X-ray images under the studied modes of thermocyclic processing. The maximum solubility of alloying elements is achieved only at total quenching. Special attention should be paid to the third and fourth cycles in the further study of TCP changing the cooling rate in these cycles due to the cooling medium, since with an increase in the number of cycles in the primary TCP, significant changes do not occur.