For high­quality steel smelting, stage­by­stage production is required, which has a complex of metallurgical units capable for producing products with high performance properties and low content of harmful impurities. One of the harmful impurities is hydrogen, so it is important to limit its content in the metal. To ensure the specifed hydrogen content, the metal in the steel out­of­furnace treatment at Converter Shop No. 2 (CS­2) of PJSC “Novolipetsk Metallurgical Plant” (“NLMK”) is subjected to vacuum treatment in a circulating vacuum degasser. Despite the prevalence of circulating vacuum derassers, theoretically, mechanism of hydrogen removal in these metallurgical units has been insufciently studied. To increase efciency of hydrogen removal, theoretical calculations were performed to remove it from the metal. There are several mechanisms for hydrogen removing: direct transfer of hydrogen from metal to the surrounding space; formation of gas bubbles in metal and their direct ascent; nucleation of hydrogen bubbles at the border of refractory wall and metal; removal of hydrogen by metal blowing with neutral gas (argon). It is shown that the main ways of hydrogen removal in a circulating vacuum degasser are direct transfer of hydrogen from metal to the surrounding space and blowing of melt with transporting gas. In the CS­2 of PJSC “NLMK”, both ways are implemented at a circulating vacuum degasser. Vacuum pumps provide pressure in a vacuum chamber of less than 101.3 Pa (0.001 atm.). It promotes intensive removal of hydrogen from the metal surface. To ensure circulation of metal, transporting gas argon is supplied to the inlet pipe of the RH degasser, which also takes part in removal of dissolved gases by transferring hydrogen to neutral gas bubbles. Additionally, performed calculations have shown that the main way of degassing in conditions of CS­2 of PJSC “NLMK” is removal of hydrogen into the bubbles of carrier gas.

Based on the studies of stress­strain metal formation during railway rails rolling in roughing stands of a universal rail­and­beam mill, carried   out using the DEFORM­3D software package, the authors have determined the features of distribution of the Cockcroft­Latham criterion over the cross­section of the rolled stock of various shapes. An extremely uneven distribution of the Cockcroft­Latham criterion over the roll section has been established. According to the data obtained, values of the specifed criterion are minimal in the axial zone, and in the near­surface layers the greatest value of the Cockcroft­Latham criterion and, accordingly, the highest probability of defects formation occur near the gauge vertical axis. In gauges of complex shape (“trapezium”, “recumbent trapezium”, rail gauges), the authors have revealed the presence of local zones with maximum Cockcroft­Latham criterion, located in the places where the foot of the rail profle is formed. And rolling in gauge of the “trapezium” type is marked by the presence of such a zone in the near­surface area near the gauge vertical axis. Within the framework of determining formation regularities of the diagram of metal stress­strain state at the initial stage of rail rolling, direct relationship was established between the uneven temperature distribution over the section of rolling and the values (maximum and average over the section) of the Cockcroft­Latham criterion. At the same time, it was shown that uneven temperature distribution over the cross­section of the roll tends to decrease with an increase in the coefcients of extracts along the passes and increase in tilting frequency, regardless of the shape of the used gauges. For gauges of complex shape, in addition to the listed parameters, an increase in similarity of shape of the roll and gauge used also has a signifcant effect on reducing temperature inhomogeneity. Based on the results of theoretical studies, a new mode of railway rails rolling has been developed. Its pilot testing in the conditions of a universal rail­and­beam mill of JSC “EVRAZ ZSMK” has shown a decrease in rail rejection by 0.78 % compared to the previously used rolling mode.

The adoption of the UN Sustainable Development Goals until 2030 served as an impulse for development and implementation of regulatory legal acts aimed at environmental protection in the Russian Federation, including appropriate fnancial mechanisms. The task of reducing level of air pollution is highlighted in the UN program documents as one of the priorities. The most problematic in terms of air pollution in Russia are 12 cities, seven of which have ferrous metallurgy enterprises. The problems of ecological development of large industrial centers remain (despite the implementation of the state program of the Russian Federation “Environmental Protection” since 2012, and the national project “Ecology” since 2019) introduction of a quota system for pollutant emissions substances, determination of the list of compensatory measures and creation of the federal information system for atmospheric air quality monitoring. In cities such as Krasnoyarsk and Novokuznetsk, the average actual annual concentration of some pollutants, which are highly toxic and carcinogenic substances of I and II hazard classes, exceeds the permissible maximum by 5 – 6 times. We have analyzed content of the reports of the specialized state authorities at the regional level on state and protection of environment. It is concluded that there is no unity of methodological approaches to presentation of analytical information on state and quality of atmospheric air in reports, as well as untimely publication of the reports themselves. The fact of inertia of the institutional environment was revealed in terms of including irrelevant norms in the adopted legal acts, and as a consequence – emergence of expenditure obligations of budgets, without real need for them. It was established that large enterprises of ferrous metallurgy (Chelyabinsk Metallurgical Plant PJSC (Mechel) and Krasnoyarsk Metallurgical Plant LLC), operating in cities with very high levels of air pollution, did not draw up corporate non­fnancial reporting in the GRI format.

Nowadays initial assessment of welding quality is performed by testing equipment with increased loads (high pressure) at technical devices of hazardous production facilities. Test requirements are regulated by standardized documents of the Federal Service for Environmental, Technological and Nuclear Oversight of Russia (Rostekhnadzor). Recently, along with traditional tests, a “stress test” was used – the essence of which is to load pipeline section to the yield point, followed by leak test. However, in scientifc publications there is practically no information about physical processes occurring in the base metal and in welded joints during such tests. In addition, effect of preload (deformation) on the parameters of substructure and internal stresses feld in welded joints of austenitic steels and, consequently, on the further trouble­free operation of the tested equipment was not evaluated. The paper analyzes changes in structural state and values of internal stresses in the samples of austenitic steel under the action of high loads. It substantiates the use of modulated current welding with automatic control of heat input process in molten weld pool. The admissible limits values of plastic deformation are argued when testing technical devices with high pressure for this type of steel. In order to reduce the risk of damage to austenitic steels welded joints of technical devices of hazardous industrial facilities, performed by pulsed welding with small­drop transfer, and to exclude formation of microdefects in them, high pressure tests (stress test) can be performed under loads that create deformations in metal, not exceeding 5 %. For joints welded by manual arc welding, deformations should be less than 5 %. Welded joints made by pulsed welding with large­drop transfer (with and without defects) are not recommended to be tested with high pressure.

An assessment of the possibility of steel direct microalloying with cerium was performed using thermodynamic modeling of cerium reduction from slags of CaO– SiO2– Ce2O3 system containing 15 % Al2O3 and 8 % МgO, additional additives of reducing agents (aluminum or ferrosilicoaluminium), at temperatures of 1550 and 1650 °C using the HSC 6.1 Chemistry (Outokumpu) software package. Depending on the additional additives of aluminum or ferroglycoaluminium, metal temperature, slag basicity and content of cerium oxide, 0.228 to 40.5 ppm of cerium transfers into the metal. With an additional additive of aluminum from slag (Y1) containing 1.0 % of cerium oxide, 0.228 ppm of cerium is transferred to the metal at 1550 °C. An increase in the system temperature to 1650 °C is accompanied by a slight increase in cerium content, reaching no more than 0.323 ppm. When added to ferrosilicoaluminium metal, cerium content in the metal is higher and amounts to 0.402 and 0.566 ppm at 1550 and 1650 °C, respectively. When concentration of cerium oxide in the slag (Y2) increases to 7.0 %, more signifcant increase in cerium content in the metal is observed, reaching in temperature range of 1550 – 1650 °C, 1.65 – 2.31 ppm with aluminum additives and 2.90 – 4.05 ppm with ferrosilicoaluminium additives. The most noticeable increase in cerium content in the metal is observed with an increase in slag basicity. During formation of slags with basicity of 2 – 3, containing 1 – 7 % Ce2O3, the equilibrium concentration of cerium in the metal varies from 0.5 to 4 ppm with aluminum additives and 1 – 7 ppm with ferro­silicoaluminium additives at 1550 °C. Slags transfer to the increased (up to 3 – 5) basicity is accompanied by an increase in the equilibrium content of cerium in the metal to 4 – 12 ppm with aluminum additives and 7 – 20 ppm with ferrosilicoaluminium additives at Ce2O3 content of 3 – 7 % and, as a result, an increase in efciency of cerium reduction process.

The article considers an overview and critical analysis of the digitalization of the leading Russian ferrous metallurgy enterprises in accordance with the Industry 4.0 development concept. It provides for the creation of digital twins of pyrometallurgical technologies, the widespread use of machine vision and artifcial intelligence. The examples of domestic industrial systems using the technologies of machine (technical) vision in production cycle, digital assistants (twins) of metallurgical units and their sets are presented. With regard to blast­furnace production, technical vision systems used to control processes in the upper and lower zones of blast furnace are considered. A promising area is the integration of technical vision and decision support systems, including algorithms and software modules for implementation of deterministic mathematical models of individual phenomena of blast furnace smelting. They are based on fundamental physical concepts of blast­furnace smelting processes. One of the main directions of digital transformation of pyrometallurgical technologies is creation of intelligent control systems for technological process in metallurgy in real time. When formulating and solving problems, it is required not only to study the characteristics describing the effect of change in melting conditions on technical and economic indicators of the operation of individual furnaces, but also a detailed analysis for mathematical description of external and internal constraints. The authors present the examples of subsystems for control of heat losses in a blast furnace, predicting the parameters of tuyere hearths and controlling distribution of blast parameters around the perimeter of a blast furnace, an automated system for analyzing and predicting production situations in a blast furnace. Creation of such systems was carried out on the basis of modern principles and technologies for the development of appropriate mathematical, algorithmic and software support.

The article considers a brief review of the last years of Russian and foreign research on the possibilities of improving mechanical properties of the Cantor quinary high­entropy alloy (HEA) with different phase composition in wide temperature range. The alloy, one of the frst created equimolar HEAs with FCC structure, needs mechanical properties improvement in accordance with possible felds of application in spite of its high impact toughness and increased creep resistance. It has been noted that bimodal distribution of the grains by sizes under severe plastic torsional strain at high pressure of 7.8 GPa of cast alloy and subsequent short­time annealing at 873 and 973 K can change strength and plastic properties. Nanodimensional scale of the grains surrounded by amorphous envelope has been obtained for HEA produced by the method of magnetron sputtering and subsequent annealing at 573 K. In such a two­phase alloy nanohardness amounted to 9.44 GPa and elasticity modulus – to 183 GPa. Using plasticity effect induced by phase transformation in (CrMnFeCoNi)50Fe50 alloy obtained by the method of laser additive technology the ultimate strength of 415 – 470 MPa has been reached at high level of plasticity up to 77 %. It has been ensured by FCC → BCC diffusionless transformation. It is shown that difference in mechanisms of plastic strain of cast alloy at 77 K and 293 K (dislocation glide and twinning) determines a combination of increased “strength­plasticity” properties. Samples for generation of twins prestrained at 77 K exhibit increased strength and plasticity under subsequent loading at 293 K in comparison with the unstrained ones. For HEA obtained by laser additive technology this way of increasing properties is also true. The way of improving mechanical properties at the expense of electron beam processing is noted. The attention is paid to the necessity of taking into account the role of entropy, crystal lattice distortions, short­range order, weak diffusion and “cocktail” effect in the analysis of mechanical properties.

Methodology of normative models, algorithms for their construction, as well as procedures for application in production facilities control and optimization tasks should fully meet modern requirements: multivariance, case­orientation, complexity, optimality, dynamism, flexibility. The listed aspects of construction and application of normative models for functioning of metallurgical enterprise divisions are presented in this work.