Increasing the level of automation of metallurgical units and the development of industrial information systems increases the number of p ters of production and technological processes available for analysis. The consequence is an increase in the complexity and duration of preliminary data preparation for subsequent mathematical and statistical analysis. It is therefore important to develop new and improve existing techniques for the automated process of primary data production. When developing methods of primary data preparation, it should be taken into account that accuracy and adequacy of results of subsequent mathematical analysis are determined by accuracy and adequacy of used initial data. The cross-sectional profile parameters of hot-rolled strips, such as wedge, convexity, thickness variation, displacement, wedge in near-rim zones, local thickenings and thinning of the strip are calculated parameters, i.e. secondary to actual strip thickness measurements over the length and width of hot-rolled strips. As technology is improved in cold rolling shops, the number of grade groups is increasing, for which technological modes of units and processing routes are selected. They are based on actual values of parameters of cross-section profile in order to further reduce the probability of formation of inappropriate products and increased metal consumption. The presented article provides an overview of conventional calculation methods for parameters of cross-section profile of hot-rolled strip and gives an assessment of accuracy and adequacy of application of the parameters averaged along strip length to the whole strip.

Practically all technological processes of metal products manufacturing by plastic deformation methods are associated with the formation of a self-balanced system of residual stresses in finished products. Level of residual stresses is in many cases an important parameter that determines the quality of products obtained as a result of plastic deformation. Reasons for the formation of residual stresses are diverse (inhomogeneity of plastic deformation, temperature field, phase transformations, etc.), which in their magnitude can exceed stresses from external loads. Currently, additional requirements are imposed on metal products in order to create machines and structures operating under high loads and speeds, sharp fluctuations in the parameters of the external environment. The experience of operating structures in various fields of technology and the results of numerous experiments show that residual stresses significantly affect the reliability and durability of machines and mechanisms. Based on the A.A. Ilyushin theory of unloading, analytical dependences were obtained for calculating the diagram of the change in residual stresses across the sheet thickness during bending under the rollers of leveler, as well as the springing angle. Formation of a diagram of residual stresses along the sheet thickness during leveling for the second, third and subsequent rollers of the leveler is considered. It was found that as a result of the superposition principle, the residual stresses diagrams under the second and third rollers are added, forming a total diagram after the second and third rollers. For the fourth, fifth, sixth and subsequent leveler rollers, an algebraic addition of the residual stress diagrams also occurs. It is shown that for a 45 steel sheet with a thickness of 10 mm, a width of 500 mm, r/h = 200, the maximum tensile residual stresses of 200 MPa are observed at a distance of Z/h = 0.3 from the neutral line along the sheet thickness. And in this case the discrepancy between the experimental and calculated values of residual stresses is 10 – 26 %, which makes it possible to recommend a method for calculating the residual stresses when leveling a sheet on a roller leveler for estimation of its quality.

One of the effective methods for studying any process is its physical modeling, during which it is possible to verify the concepts and hypothesis obtained previously by theoretical modeling. In the laboratory of metal forming of NUST “MISIS” there is ERW mill 30 – 50 for the production and simulation of processes for the continuous forming of longitudinal welded pipes of small and medium diameter, their welding and calibration. This article discusses the deformation zone of a pipe billet, using the first two stands of a molding mill as an example with a calibration of a roll tool for a pipe diam. 50×1.5 mm. Based on the analysis of methods for calculating the parameters of real roll calibers, a model of contact interaction of the pipe billet with the first and second roll open stands was developed and areas of the deformation zone were determined including their sizes: non-intensive and intense impact; input and output contact zones; springing up. Analyzing the conditions of contact interaction of the pipe billet with roll calibers, parameters of the pipe billet in contact with the first-caliber rolls were determined in seven sections, taking into account the features of continuous forming. An analysis of the results has shown that the maximum longitudinal deformation occurred at the edge of the billet in section B – B and was equal to 1.04 %, and for the pipe billet bottom it was 0.92 %. For the experiment, a grid was applied to the pipe billet using a laser engraver. During forming, the trajectory deviation of the pipe billet bottom from horizontal axis was recorded, and sizes of the forming sections were determined. Comparison of theoretical and experimental values has shown that the discrepancy between them does not exceed 7 %.

Influence of three modes of multi-pass cross-screw rolling (CSR) on microstructure, mechanical properties and fracture toughness of ferriteic-pearlitic 09G2S pipe steel was investigated by methods of mechanical tests, optical metallography, electron transmission and scanning microscopy. After all CSR modes there is a change in parameters of initial grain structure of the billet with formation of lamination in grain distribution by sizes. Near the surface of the billet the size of globular grains is 1 – 4 µm, the length of extended grains in the central part of the billet varies from units to tens µm, width – from 1 to 8 µm. Mechanical tests for uniaxial tension and toughness were performed on the samples cut from the central zone of the billet. It was found that CSR increases the yield and tensile strengths of all test samples with a slight decrease in overall plasticity. The greatest increase in toughness at T = –70 °C is observed after controlled CSR within the 850 – 500 °С temperature range. Electron microscopic studies have shown that features of mechanical behavior of the samples after CSR are related to structural transformations occurring in steel during rolling and cooling. The main hardening factor is the grinding of ferrite grains and the formation of a subgrain structure after CSR. The increase in fracture toughness is related to more uniform ultrafine-grained structure of rolled material, which does not contain plates of cementite and bainite. Fracture processes of initial steel samples and after CSR depending on temperature were analyzed on the basis of recorded diagrams of impact loading and fractures in breakage regions of the Charpy specimens.

Heightened interest to multicomponent alloying of nickel is connected with the search of new compositions of oxidation- and heat-resistant alloys on the basis of nickel solid solution or its intermetallics. In the present work, the author has investigated the resistance to high-temperature oxidation of an alloy of Ni – Al – Mo – W – Nb system which can be used as a basis for creation of dispersion-strengthened inert particles of carbides and nitrides of two-phase thermally stable superalloys with a γ′-phase matrix. Samples of the alloy were subjected to oxidation on air at 900 – 1300 °C during 1 – 125 hours. Weight reduction (ΔМ, gr) was measured which after that was recalculated into indicators of change of samples weight for a time unit, rationing for the area of initial samples surface (Δm, gr/(m² ·hour)) and “burn” rate of surface layer (scaling loss h, micron/hour). It is shown that at oxidation of Ni – Al – Mo – W – Nb alloy at all temperatures there is a reduction of samples weight because of formation of fragile and friable superficial scale. Dependences of this indicator on oxidation time are close to the linear. With growth of temperature, processes of weight reduction are intensified. It is offered to raise oxidation resistance of Ni – Al – Mo – W – Nb alloy by short-term preliminary oxidation at temperature of 1300 °С on air. The observable effect of increase of oxidation resistance is caused by formation in scale of NiAl ₂O₄ layer, more effectively protecting an alloy from interaction with oxygen. Experiences on oxidation with the use of inert platinum marks have shown that it is necessary to consider oxygen diffusion through oxide film into metal as a mechanism, supervising oxidation of Ni – Al – Mo – W – Nb alloy at high temperatures in case of presence of NiAl₂O₄ on the surface layer. Activation energy of oxidation of Ni – Al – Mo – W – Nb alloy was calculated at 900 – 1300 °С and without preliminary oxidation. This value is equal to 220,000 J/mol that is characteristic for activation energy of nickel self-diffusion.

The development of modern technics is limited by the physical and mechanical characteristics of the produced alloys, properties of which are often determined and enhanced by introduced alloying components. One of the alloying elements that have been very actively introduced in recent years is nitrogen. As a rule, alloying with nitrogen is carried out by ferroalloys, less often by gaseous nitrogen, which has significant advantages. In the processes of special electrometallurgy, alloying with nitrogen can be performed using, for example, nitrogen-containing plasma. Such a method may be feasible in the production of powder metal by spraying the ingot with nitrogen-containing plasma. It is known that performance properties of the products made of powder metal are significantly higher than those of cast metal. This served as a stimulus for investigating the properties of a product obtained from nitrided powder alloy EP741NP. In this work, a study of changes in the chemical composition, microstructure and microhardness of EP741NP alloy samples was carried out. The studied material was nitrided metal powders made on a plasma centrifugal spraying (PREP) unit and ingots from granules obtained by hot isostatic pressing (HIP). The chemical composition of the obtained samples was determined by wave dispersion X-ray fluorescence spectrometry. In order to study the microstructure of metal powders and ingots, the methods of scanning electron microscopy with EDXS were used. Microhardness of the samples was assessed using a microhardness tester by the Vickers method. The analysis of gas impurities was carried out on a gas analyzer. It is shown that nitriding of heat-resistant nickel alloy EP741NP is possible at the stage of metal powder production, without significant loss of alloying components and a sharp change in chemical composition. An increase in microhardness of the obtained nitrided samples was noted in comparison with the initial one.

A non-equiatomic high-entropy alloy (HEA) of the Al – Co – Cr – Fe – Ni system was obtained using wire-arc additive manufacturing technology in the atmosphere of pure argon. The initial wire had 3 conductors with different chemical composition: pure aluminum wire (Al ≈ 99.95 %), chromium-nickel wire (Cr ≈ 20 %, Ni ≈ 80 %), and cobalt alloy wire (Co ≈ 17 %, Fe ≈ 54 %, Ni ≈ 29 %). The resulting sample of high-entropy alloy was a parallelepiped consisting of 20 deposited layers in height and 4 layers in thickness. The alloy had the following elemental composition, detected by energy-dispersive X-ray spectroscopy: aluminum (35.67 ± 1.34 at. %), nickel (33.79 ± 0.46 at. %), iron (17.28 ± 1.83 at. %), chromium (8.28 ± 0.15 at. %) and cobalt (4.99 ± 0.09 at. %). Scanning electron microscopy revealed that the source material has a dendritic structure and contains particles of the second phase at grain boundaries. Element distribution maps obtained by mapping methods have shown that grain volumes are enriched in aluminum and nickel, while grain boundaries contain chromium and iron. Cobalt is distributed in the crystal lattice of the resulting HEA quasi-uniformly. It is shown that during tensile tests, the material was destroyed by the mechanism of intra-grain cleavage. The formation of brittle cracks along the boundaries and at the junctions of grain boundaries, i.e., in places containing inclusions of the second phases, is revealed. It was suggested that one of the reasons for the increased fragility of HEA, produced by wire-arc additive manufacturing, is revealed uneven distribution of elements in microstructure of the alloy and also the presence in material volume of discontinuities of various shapes and sizes.

Using the method of experiment planning by simplex, the surface tension of the melts of СаО – SiO₂ – Al₂O₃ – В₂O₃ system was researched. The local part of the system was explored which covered the process of ferrosilicon, silicochrome, cement clinker, ceramics, glass, and sittals production. The amount of oxides in it was (%): 9.8 – 52.0 CaO; 0 – 70.4 SiO₂; 0 – 51.5 Al₂O₃ and 0 – 20 B₂O₃. A mathematical model of surface tension dependence on the melts composition has been created and diagrams in the form of tetrahedron sections in B₂O₃ have been constructed. It was found that, in the CaO – SiO₂ – Al₂O₃ system, which is basic for metallurgy, melts with a high surface tension adjoin the binary side of CaO – Al₂O₃ in the area of calcium aluminates crystallization which have small sizes, high charge and due to this bond to melt volume. With the introduction of SiO₂ , σ of melts decreases due to the formation of large aluminosilicon formations of the [Al₂Si₂O₈]^2– type, rankinite groups Si₂O₇^6-, and ring complex [Si₃O₉]^6- pseudo-wollastonite anion. The complication of anions due to polymerization leads to a drop of surface tension because of a decrease in charge ratio of the latter to the radius and, consequently, the strength of bond with cations. Boron anhydride injection causes a decrease in surface tension of melts СаО – SiO₂ – Al₂О₃ which can be explained by boron transition at high temperature from four oxygen-coordinated (BO₄^5-) to three oxygen-coordinated state (BO₃^3-). Formed flat triangles BO₃^3- or complexes with them are loosely related to the melt’s volume, they are forced out to the surface and reduce surface tension. Mostly this affects the main aluminate melts, rather than acid ones. The latter can be explained by the closeness of the capillary activity of boron – and silicon-oxygen anions. The surface phenomena between the products of blast-furnace smelting of titanomagnetite iron ores have been studied experimentally using the method of lying drop. It was noted that the highest adhesion forces (work of adhesion) take place between slag and grenal (cast iron with a high titanium and silicon content), which is the reason for the loss of metal at the outlet with slags during the processing of such ores. Boron loaded into the blast furnace (in the form of natural ores) is redistributed under reduction conditions between cast iron, grenal and slag. Experiments have shown that the presence of boron in slag at the level of microconcentrations reduces the work of adhesion from 688 to 436 MN/m (by 37 %). Industrial experiments have shown that this helped to reduce the loss of valuable vanadium-containing cast iron with slags by 1.2 – 1.5 times with a simultaneous improvement in smelting performance.

Ferronickel, currently obtained from oxidized nickel ores in various aggregates, contains 5 – 20 % Ni. The possibility of obtaining rich (about 70 % Ni) ferronickel from a melt of silicate-nickel ore during its treatment with reducing gas has been experimentally shown. Features of reduction of high-iron variety of nickel ore from the Serovskoye deposit with carbon monoxide are considered using the methodology of metallurgical processes thermodynamic modeling, adapted to open systems. For the calculations, the following composition of the oxide melt was adopted, mass. %: 60,4 Fe₂O₃; 1,4 NiO; 0,14 СоО; 5,8 Аl₂O₃; 17,0 SiO₂ ; 4,2 MgO; 11,1 CaO. The simulation was carried out at a pressure of 0.1 MPa, at amount of carbon monoxide in one portion – 10.6 dm³/kg and at temperature of 1673, 1723, 1773 K. During the calculations, dependencies were found that bind the content of nickel (C_Ni ), iron (С_Fe2O3, C_Fe3O4, C_FeO) and cobalt (С_СoО) oxides in the oxide melt and metals in the alloy (С_Ni, С_Fe, С_Co) as well as the degree of their transition to the metallic state (φ_Ni, φ_Fe, φ_Co) with the amount of introduced gas. Contents of the components in a single portion of the reduced metal were determined. In the temperature range of 1673 – 1773 K and the introduced amount of CO equal to 190 dm³/kg, the content of Fe₂O₃ in the oxide melt is 0,17 – 0,12 %; Fe₃O₄ – 1,77 – 1,05 %; FeO – 55,6 – 56,5 %; NiO – 0,026 – 0,037 % and CoO – 0,061 – 0,068 %. With a degree of nickel reduction of 98 %, degree of iron reduction is 5 %, and degree of cobalt reduction is 56 – 61 %. An alloy formed from reduced metals contains about 30 % Ni, 63 – 65 % Fe and 2 % Co. Thus, the possibility of selective reduction of nickel and cobalt under certain conditions is shown. The data obtained are significant for substantiating the parameters of technological processes for the production of ferronickel from high-iron oxidized nickel ores.

Hydrogen is mainly used in the reduction annealing of iron powder obtained by spraying liquid metal by water. The chemical aspects of this process were modeled using the TERRA 6.3 software package. In particular, the Fe – O – H thermodynamic system has been analyzed in a wide range of temperatures and hydrogen consumption. The analysis has shown that the main impurity compounds of the sprayed powder will not be iron hydrates, but Fe₂O₃ oxide. But it cannot exist in the atmosphere of hydrogen and is converted to Fe₃O₄ oxide at a low temperature. Therefore, the main reaction for iron reduction will be Fe₃O₄ + 4H₂ = 3Fe + 4H₂O, which ends at 910 °C. It is shown that this reaction temperature can be significantly reduced with an equally significant increase in hydrogen consumption. Taking this factor into account can be useful when working out the powder annealing mode.

The article contains biography of Tsolо Rashev – an outstanding metallurgical scientist of the 20^th century. His life was devoted to the development of metallurgy in Bulgaria, to the research of metallurgical processes related to the production of nitrogen-containing and high-nitrogen steels and their various structural classes. Since his life was inseparable from this work, the article focuses on the main directions of his scientific activity. In particular, Professor Rashev has carried out the work on thermodynamics and kinetics of interaction of unconventional alloying elements with metals and slags in liquid and solid states, including studies on the solubility of nitrogen in melts of various iron-based alloying systems; on mathematical modeling of metallurgical processes; on technology and properties of high-quality, special and high-nitrogen steels and alloys. He has developed and implemented in practice methods and devices for processing and production of steels and alloys, paying particular attention to introduction and retention of nitrogen in steels and iron-based alloys. With his works Tsolo Rashev made an invaluable contribution to the world fund of scientific knowledge.