This review discusses the main methods for producing spherical powder particles of corrosion-resistant steels as a material widely used in all industries. Also the examples of products made by modern additive methods are described. Currently, spherical powder particles of corrosion-resistant steels are used in the following additive methods: selective laser melting, selective laser sintering, direct laser sintering, and electron beam melting. Each of these methods has its own requirements for the characteristics of spherical powder particles of corrosion-resistant steels. The  review provides a brief description of the principles of operation of each method and the requirements for spherical powder particles of corrosion-resistant steels. It also considers a detailed description of each method of additive manufacturing with a description of the principle of operation and specific examples of obtaining spherical particles of corrosion-resistant steel powders with indication of their properties (morphology, structural features, chemical composition, fluidity, bulk density). A comparative analysis was carried out with a description of disadvantages and advantages of each method. Examples of the use of spherical particles of corrosion-resistant steel powders for the manufacture of products by various additive methods (including post-processing) are given with description of the final products characteristics. Based on the data presented, a conclusion was made about the preferred methods for obtaining spherical particles of corrosion-resistant steel powders for specific additive methods used in modern industry. The review considers the following methods for producing spherical powder particles: water atomization (atomization of liquid metal with a jet of water under pressure); gas atomization (atomization of the melt with a jet of inert gas (argon or nitrogen) under pressure); centrifugal atomization (atomization of molten metal with a high-speed rotating disc); ultrasonic atomization (atomization of liquid metal by ultrasound); non-contact atomization (atomization of liquid metal with a powerful pulse of electric current); plasma wire spraying; plasma spraying of a rotating electrode; plasma spheroidization. 

The KV heavy tank stays among the legends of the Great Patriotic War and one of the most recognizable combat vehicles of those years. The assessment of the tank, its design features and practice of operation, in scientific, popular science literature, and journalism, is still ambiguous: from praise to denial. Historical memory of this combat vehicle is actively living its life not only on pages of the books, but also in the virtual space, in the branches of thematic Internet forums and computer games. The heavy tank of KV series was developed and put into service at the very end of 1939. A new grade of 42S armor steel was created especially for it, which was distinguished by a relatively low content of alloying elements and high adaptability for mass production. The authors seriously studied the stages of armor production and the difficulties in its creation. They show the enormous contribution of metallurgists to the creation of a combat vehicle. As a result of engineering research and the decisive contribution of metallurgy, a formidable machine was obtained, possessing thick armor (75 mm) and quite powerful armament (76.2 mm cannon). At the same time, the tank had a whole range of disadvantages that reduce the effectiveness of its combat use. The general lack of development of the design and archaic technological solutions created serious problems both in the production and in the subsequent operation of this tank. History and tradition of searching the tank allows taking a fresh look at the long glorious traditions of the national engineering school in the field of metallurgy, and its decisive contribution to the Victory in the Great Patriotic War. 

The second part of the article presents perspective directions of using boron and its compounds in the preparation processes, metallurgical processing of ore materials and steel smelting in order to improve the quality of the final product. An efficient technology of silicothermal production of ferrosilicoboron containing 0.6  –  2.0  %  B and 60  –  80  %  Si has been developed. The advantage of this scheme is the possibility of obtaining a  boron-containing alloy during ferrosilicon smelting. It has been experimentally shown that ferrosilicoboron has higher performance characteristics than ferroboron both in production and when used for steel processing. The results of industrial tests of the technology for microalloying pipe grades of steel with a new ferroalloy with boron confirmed a high degree of boron assimilation – up to 96  %. The possibility of widespread use of boron for steel microalloying is due to its cheapness, availability and environmental friendliness. According to the calculations, 
boron from complex ferrosilicoboron is the cheapest trace element used to increase the strength characteristics of steel. Additives of B2O3 can be successfully used to form high-magnesium liquid steel-making slags. It is shown that 0.37  –  0.55  %  В2О3 effectively stabilizes the highly basic slags of the steel and ferroalloy industries. This operation allows obtaining a marketable lump material. The above review, results of the laboratory and industrial studies have shown the effectiveness of boron usage at different stages of metallurgical production. An increase in technical and 
economic indicators of production and quality of steel and ferroalloys, and effective disposal of waste slags is shown. The technical solutions advanced and tested at metallurgical enterprises do not require capital expenditures. They are implemented by adding microdosing of boron and 
its compounds to metallurgical production facilities. 

The article considers results of the study of microstructure parameters effect on the impact strength in temperature range from 0 to –80  °C in 20  °C increments of Charpy samples with a sharp stress concentrator and Mesnager test pieces with a circular stress concentrator from rolled coils of low-carbon microalloyed steel with various thicknesses. The used roll products were produced in conditions of JSC “Vyksa Metallurgical Plant”. The tests were performed using optical and scanning electron microscopy. It is shown that with the same chemical composition and thermomechanical treatment modes, the metal of smaller thickness (6, 8 mm) is characterized by higher strength properties (on average, by 10 MPa for temporary resistance, by 30 MPa for yield strength) and a margin for viscous properties at negative temperatures at close values of grain score and average grain size corresponding to 10 – 11 numbers according to the State standard GOST 5639. The metal with a thickness of 12 mm has the lowest level of cold resistance, and the temperature of brittle transition is minus 50 °C. Structure of rolled products of various thicknesses has a variation in grain size. Rolled metal of smaller thicknesses have a smaller grains corresponding to number 14, rolled metal of larger thicknesses has a larger grains corresponding to number 8. By conducting electron microscopic studies using the backscattered electron method, it was found that a greater number of large-angle boundaries, which are barriers for brittle cracks propagation, are observed in the 6, 8 mm thick rolled products. The constructed orientation maps of the microstructure showed the presence of pronounced deformation texture corresponding to the orientations <110>||RD (rolling direction) and (<113>...<112>)||RD for rolled products with a thickness of 6 mm.

The authors have studied the effect of alloying on the structure, microhardness and abrasive wear resistance of electroslag surfacing layers on low-alloy structural steel 09G2S. For modification, mixtures of Si3 N4   +  FeSi2   +  Si powders obtained in the Department of Structural Macrokinetics of  the Tomsk Scientific Centre SB RAS by the method of SHS synthesis, as well as powder compositions based on TiC, were used. A molten electrode was made of low-alloy steel St3, on which modifying compositions Si3 N4   +  FeSi2   +  Si were poured out, in the first case, and modifying compositions  Si3 N4   +  FeSi2   +  Si, located below, in the second case. Metallography and X-ray microanalysis methods were used to determine the structure and  to  analyze the composition of the deposited layers, heat-affected zone (HAZ) and the base metal, on the basis of which assumptions were made about  the nature of the formation of coating properties – hardness and wear resistance. It is shown that the main influence on the wear resistance is exerted  by structure of the surfacing metal. There is a positive effect of modifying coatings by alloying materials with the alloys Si3 N4   +  FeSi2   +  Si  +  St3  and TiC  +  St3. In the molten layer, many new crystallization centers are released in the form of dispersed TiC particles. Dispersed TiC particles with  a  high melting point (3180  °C) are the first to fall out of the melt and not only serve as multiple crystallization centers, but also prevent the growth of  austenitic grains, which ensures the formation of dispersed structure. The coatings contain TiC carbide particles, as well as inclusions of other phases. At the same time, an increase in hardness of the deposited layer containing titanium carbide inclusions is observed in direction of the boundary with the base. Wear resistance of the layer increases when a TiC-based coating is formed. The obtained data can be used to create deposited layers on the metal surface with high resistance against abrasive wear. 

The paper considers the effect of introducing ferroalloys containing titanium and zirconium on the structure and heat-resistance of low-carbon ferroalloys. Theoretically and experimentally, it has been proven that addition of 1.0 mass. % of titanium and 0.1 mass. % of zirconium to a low-carbon iron-aluminum melt containing 12 – 14 mass. % of aluminum, grinds its structure increasing temporary resistance and heat-melting. Titanium and zirconium are strong carbide-forming elements. When introduced into a low-carbon iron-aluminium alloy, they form a large number of crystallization centers, thus affecting its microstructure, allowing to get shredded and more equal grain compared to an alloy without additive. This in turn increases the strength limit of processed alloy. In addition, the use of titanium as a modifying additive in a low-carbon ferroalloy allows increasing its heatresistance, which exceeds several times the heat-resistance of famous chrome-nickel steel of 20Kh23N18 grade. As a result, a new technology for obtaining titanium and zirconium was developed based on research of the effect of their modifying additives on the structure and heat-resistance of low-carbon iron-aluminum alloys. 

The authors propose a simple theory of thermodynamic properties of nitrogen solutions in liquid Ni–Cr alloys. This theory is completely analogous to the theory for liquid nitrogen solutions in alloys of the Fe–Cr and Fe –Mn systems proposed previously by the authors in 2019 and 2020. The theory is based on lattice model of the Ni–Cr solutions. The model assumes FCC lattice. In the sites of this lattice are the atoms of Ni and Cr. 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 assumed that the energy of this interaction depends neither on the composition nor on the temperature. It is supposed that the solutions in the Ni–Cr system are perfect. Within the framework of the proposed theory, a relation is obtained that expresses the Wagner interaction coefficient between nitrogen and chromium in liquid nickel-based alloys. The right-hand part of the appropriate formula is a function of ratio of the Sieverts law constants for solubility of nitrogen in liquid chromium and nickel. The values of these constants for the temperature of 1873  K are assumed to be K′(Cr)  =  15,2; K′(Ni)  =  0,0015 wt.  %. An estimate is obtained for the Wagner interaction coefficient in nickel-based alloys   =  21,4. This corresponds to the value of the Langenberg interaction coefficient  =  –0,105, wich is very close to the experimental estimates  =  –0,108 for the temperature of 1873 K (Surovoi et al., 1971) and   =  –0,11 for the temperature of 1823 K (Stomakhin at al., 1965).