One of the most dangerous technological defects of welded joints of structures made of high-strength cold-resistant steels are cold cracks, the development of which occurs within several hours after welding. The reason for the development of the cracks is, as a rule, the formation of hardening structures as a result of high cooling rates of the metal of the welded joint. This paper is devoted to evaluation of weldability and analysis of resistance to formation of cold cracks of new low-carbon high-strength cold-resistant steel of 20G2SMRA grade. Technological samples for Tekken-test were prepared from sheet steel with a thickness of 20-25 mm. Samples were welded on the FANUC ARC Mate robotic system 120iC by a consumable electrode of various brands (OK AristoRod 69, Sv-08A) in a protective gas environment. A comprehensive metallographic analysis of welded joints of the steel under study was carried out in various areas: weld metal, heataffected zone, at the transition from the heat-affected zone to the base metal, as well as mainly metal. The distribution of hardness over the cross-section in all zones of the welded joint is given, the relation of the hardness of the HV1 under different welding modes at each area under study. It is shown that the most dangerous areas are those of partial melting and overheating (coarse grain) of the welded joint located in the root of the weld in the zone of the structural stress concentrator. It has been found that the use of low strength filler wire for welding the root pass of thick-sheet rolled products, as well as an increase in the welding start temperature, provide resistance to the formation of cold cracks in welded joints of high-strength cold-resistant steel of grade 20G2SMRA.

Currently, continuous casting is one of the main ways to obtain ingots for subsequent metallurgical processing in the conditions of modern metallurgical enterprises. At the same time, one of the main problems is the organization and maintenance of high sequence of the process, since one of the main technological parameters affecting the cost of production of continuously cast billets is the casting ability of steel in continuous casters. When mastering the production of continuously cast billets from stainless steel grades on existing steelmaking units, problems arise related to poor casting ability. It was found in this work that the reason for the low casting ability in production of stainless steels is the release of refractory oxide (TiO and Al2O3–TiO2) and oxynitride (Al2O3–TiO2 and TiN) inclusions in deposits on the walls of the steel filling tract. The research used optical and electron microscopy methods with an automatic particle analyzer (EDAX Partical/Phase Analysis Software). Identification of non-metallic inclusions in the samples taken at the stages of ladle treatment and casting showed that oxide inclusions (TiO and Al2O3–TiO2), formed after the introduction of FeTi, before the second stage of vacuum processing, nitride (TiN) and oxynitride inclusions (Al2O3–TiO2 and TiN), are formed during continuous casting and solidification of continuously cast billets. Based on the conducted research, measures are proposed aimed at preventing the formation of refractory non-metallic inclusions containing titanium, which made it possible to increase the sequence of casting on existing steelmaking units in the electric steelmaking shop. The increase in serial production to two melts per series led to a reduction in the consumption of the metal coefficient in the production of continuously cast billets by 20 kg/t, as well as to a reduction in the cost of tundish refractories.

Approaches to the numerical study of the thermomechanical state of the shell of a continuously cast billet at the early stage of solidification in a mold are presented. Methods are proposed for constructing finite element models that make it possible to adequately describe the state of a continuously cast billet at the stage of solidification in the mold and in the secondary cooling zone, taking into account the real boundary conditions and properties of the materials of the billets and the mold. An approach has been developed for determining, on the basis of experimental data, the values of material constants of material models under high-temperature creep. For unalloyed carbon steels with a carbon content of 0.005–1.540 %, the form of the most suitable equations has been obtained to describe the state of the billet`s shell in the mold and secondary cooling zone at high homologous temperatures in the strain rate range 2.3∙10-2 – 5.5∙10-6 s-1 and degree ofd eformation up to 2 %. Based on the developed finite element model in a flat formulation, thermomechanical processes occurring in the shell of a continuously cast rectangular billet of 3sp steel during solidification in the mold and secondary cooling zone were studied, taking into account real thermal and mechanical boundary conditions, material properties, as well as the temperature and the stress-strain conditions of the mold were determined. Based on the solution of the iterative problem, a mold profile was found at which heat transfer reaches the greatest value. A numerical study of the operation of a continuous casting machine based on the developed approaches makes it possible to determine the thermomechanical state of the billet and operating modes of the mold, as well as to evaluate the influence of various casting factors on the risk of the initiation and development of cracks of various natures. The work was supported by the Russian Science Foundation grant No. 24-29-00055, https://rscf.ru/progect/24-29-00055/.

For Russian hardware companies following the principles of sustainable development, circular economy and the ESG agenda, environmental issues and tasks related to the reduction of production waste are among the top priorities. The purpose of the work is to develop key areas for increasing the efficiency of working with waste from hardware production generated at the stage of descaling, as well as to identify the main problems that arise on the way to creating a closed-cycle enterprise. The work used the method of expert interviews, during which it was revealed that the greatest burden on the environment during the production of hardware is caused by waste pickling solutions, which indicates the need to implement an investment program aimed at modernizing pickling departments and patenting units. In order to find a possible increase in the efficiency of the enterprise's work with waste during the operation of removing scale from wire rod and rolled stock, the study carried out a comparative analysis of common technologies for descaling. The authors came to the conclusion that the most environmentally friendly method is the mechanical method of descaling, and to scale up this technology, the production of domestic equipment, spare parts, consumables and components are required.

The thermal and electrical conductivity of the hot-dip aluminized Kh15Yu5 (Cr15Al5) alloy after long-term heat treatment at a temperature close to the operating temperature (1100 °C) has been studied. It is shown that the heat treatment of the aluminized alloy for 20 h leads to the formation of a coating with a thickness of ~260 μm of variable composition, which changes from the surface to the base in the following sequence: FeAl(Cr, Si) → Fe3Al(Cr, Si) → Fe(Al, Cr, Si). An increase in the heat treatment time to 100 h is accompanied by the transformation of the coating surface phase composition to a solid solution of variable composition based on αFe. The microhardness of the coating surface decreases during heat treatment from 3.5 GPa to 2.4 GPa after 1000 h. It has been established that long-term high-temperature heating of the Cr15Al5 alloy with an aluminide coating leads to a decrease in its thermal conductivity, in comparison with a pure alloy, by 10–12 % due to the diffusion redistribution of the components that make up the coating. It is shown that the aluminide coating on the Kh15Yu5 (Cr15Al5) alloy surface increases the electrical resistivity of the sample by 0.2 Ohm·mm2/m, and high-temperature treatment contributes to an additional increase and stabilization of the resistance at a level above 1.55 Ohm·mm2/m. The high electrical resistivity of the Kh15Yu5 (Cr15Al5) alloy with an aluminide coating and the stability of properties during hightemperature heating make this material promising for use as heating elements.The study was supported by the Russian Science Foundation grant No. 23-79-01245, https://rscf.ru/project/23-79-01245/.

The paper presents the results of studying the process of asymmetric rolling by the mentioned methods. The creation of different conditions on the upper and lower surfaces of the roll in the deformation zone in the study was performed by lower and upper rolls, with barrels of different diameters, which were given the same angular velocity relative to their axes of rotation. Analytical formulas are obtained that determine the energy-power and structural parameters of an asymmetric deformation zone, which made it possible to determine the patterns of the influence of rolling conditions on the energy-power and structural characteristics of an asymmetric deformation zone. The most significant, interesting factor here was the amount of energy consumption for the conduct of the technological process. It has been established that the asymmetry factor has little effect on the energy efficiency of rolling. The results were checked for validity by modeling the process in the DEFORM environment, the results of such a check confirmed the reliability of the solutions. Experimental rolling of steel samples was carried out on a laboratory mill 400 in rolls with different diameters of the barrels of the upper and lower rolls to assess the distribution of the shape and size of the grain along the height of the section of the finished strip. It was found that the coefficient of grain asymmetry at the surface of the strip that was in contact with the roll barrel, which had a higher speed, was greater than the similar parameter at the surface of the strip, which was in contact with the roll barrel, which had a lower speed. The results of the work can be used in determining the largest allowable difference in the diameters of the barrels of work rolls, obtained as a result of their regrinding, in existing cold rolling mills, taking into account the active layer.The study was supported by the Russian Science Foundation grant No. 23-29-00428, https://rscf.ru/project/23-29-00428/.A. S. Smirnov, K. P. Korepina participated in this work.

The composition of metallurgical slags is complex and is determined by several factors, including the type of received metal, the composition of the ore and the composition of the flux material used in the melting process, the temperature of the melting process. However, it should be considered that most metallurgical slags are liable to the process of self–decomposition, which is associated with the presence of bicalcium silicate (C2S – white) in the slag structure. The paper studies the effect of three different stabilizers (ferrochromium ore, sodo-alkaline melting and arc steelmaking furnaces dust) on the structure and properties of metallurgical slag selected from an arc steelmaking furnace. A comparison of the efficiency of using three stabilizers radically different in composition in terms of the yield of the stabilized slag fraction, depending on the amount of stabilizer and the structural features of the materials obtained, allowed us to establish that arc steelmaking furnaces dust allows us to obtain the largest amount of the stabilized slag fraction with a dense homogeneous structure and the best quality indicators (at 5 % concentration in the slag melt in laboratory conditions, it is possible to obtain 100 % stabilized slag fraction with water saturation of 4.6 % and frost resistance mark F 50, whereas in industrial conditions 2 % is enough). Comparison of energy dispersion analysis maps of a slag sample stabilized with arc steelmaking furnaces dust in industrial conditions showed some differences compared to laboratory samples, which is explained by two factors affecting the crystallization process: the rate of nucleation, the rate of crystal growth. In industrial conditions, the rate of nucleation is higher, which contributes to the formation of a larger number of new crystallization centers, but the intensity of crystal growth decreases after the slag is drained into the slag trench, which is associated with the cooling rate. The study was supported by the Russian Science Foundation grant No. 23-19-00796, https:// rscf.ru/project/23-19-00796/. The work was carried out using the equipment of the Center for High Technologies on the basis of BSTU named after V. G. Shukhov.

The work is devoted to the study of technological plasticity in the cast state of austenitic corrosion-resistant steel grade VNS53-Sh (08Kh21G11AN6-Sh), containing up to 0.6 % nitrogen, at deformation temperatures (precipitation) from 800 to 1200 °С. Steel VNS53-Sh was smelted in an open induction furnace of the IST-0.05 type, followed by electroslag remelting in a semi-industrial plant DESHP-0.1. Corrosion-resistant steel of the austenitic class VNS53-Sh is designed for the manufacture of thin-walled pipes operating under high pressure. Tests for technological plasticity were carried out in accordance with STO 1-595-23-514-2016 by upsetting cylindrical samples with a diameter of 15 ± 0.1 mm and a height of 20 ± 0.05 mm. The analysis of steel microstructure after upsetting at different temperatures was carried out. Microstructure studies were carried out in accordance with instructions no. 804-76 on an OLYMPUS GX-51 optical microscope. Metallographic sections were subjected to electrolytic etching in a 10% oxalic acid solution. It has been established that deformation at 800–900 °С causes the appearance of grain-boundary precipitates in the structure, formed as a result of discontinuous decomposition of the solid solution with the formation of pearlite-like colonies (a mixture of chromium nitride and austenite plates). When samples are compressed at temperatures above 900 °С, recrystallization processes are observed. New austenite grains are formed mainly along the grain boundaries, as along the most defective zones containing additional centers of recrystallization – carbonitrides, while pearlite-like colonies are not detected. The appearance of a nitride-austenitic mixture in the structure does not allow deformation of VNS53-Sh steel with a reduction ratio of more than 20% without cracking. The manufacturability of steel increases with an increase in the upsetting temperature, however, the permissible degree of deformation does not exceed 35%.The work was carried out within the framework of the government contract No. 21411.1770290019.18.006 dated 03/01/2021, code “Height” on the topic Vs-09 “Development of technology for smelting, deformation, heat treatment of pipe billets for the manufacture of thin-walled pipes operating under high pressure conditions from VNS-53Sh class corrosion-resistant austenitic steel ".

The results of a study using the QForm software package and an experiment are presented, determining factors affecting the quality characteristics of vessels made of steel 50 produced on a three-roll screw mill 30–80 and a horizontal press, which are part of the rolling and pressing line of the BF JSC NPO Pribor enterprise. Modeling of the process allowed us to establish that when rolling along the length of the workpiece and a solid piercing mandrel made of 4X5MFS steel, an unevenness of temperature is formed, which is associated with heat transfer during the formation of the cavity. It is shown that the temperature unevenness along the length of the vessel is 200 °C, and the stitching mandrel is 250 °C. At the same time, the bottom part of the vessel and the toe of the mandrel are more heated to 1140 °C and 600 °C compared to the upper part of the vessel and the base of the mandrel 940 and 350 °C, respectively. A hundred-fold simulation of the firmware process allowed us to establish the influence of the heating temperature of the mandrel on its wear of about 0.64 and 2.4 mm from tangential and normal stresses of about, respectively, which does not allow for the specified geometric dimensions of semi-finished products. Modeling has established that the temperature unevenness after rolling persists after stamping and ranges from 950 to 750 °C, the temperature difference is the same 200 °C, which affects the conditions of subsequent cooling when simulating quenching in mineral oil. At the same time, an unevenness of indicators along the length of semi-finished products is formed: hardness from 460 to 740 HV and strength from 1050 to 1700 MPa. The recommendations of repeated heat treatment are given, allowing to align the mechanical properties of rolled products along the length: hardness 500 HV, tensile strength 1000 MPa. The design of a water-cooled mandrel has been developed and tested on a screw mill 30–80, the use of which makes it possible to reduce the temperature of the nose to 400 °C at the base to 150 °C, which positively affects its service life, which increases up to 2.7 times. At the same time, dimensions are formed that meet the requirements of the design documentation for the cavity of the vessel made of steel 50 presented by the BF JSC NPO Pribor. An adequate regression equation is constructed that establishes a linear dependence of the change in the diameter of the cavity on the number of vessels released.

The class of duplex and super duplex steels, with its unique combination of high corrosion resistance and strength, is increasingly used in the chemical, oil and gas and shipbuilding industries The process of formation of intermetallic σ-phase in duplex and super duplex steels is described. The presence of this phase in the structure reduces the physical and mechanical properties of this class of steel. The majority of metallographic research methods allow the most complete identification of the main structural components of duplex steels - α- and γ-phase; however it is rather difficult to determine the presence of intermetallic σ-phase in the structure. In order to reveal this structural component the microstructure of super duplex steel samples after etching by various methods – electrolytic etching in 10% aqueous oxalic acid solution and in 20% aqueous NaOH solution, chemical etching in Beraha, Kalling and Piranha reagents were investigated. Samples for metallographic studies were selected from blanks of different profile sizes, as well as with different heat treatments. Electrolytic etching in both 10% oxalic acid and 20% NaOH solution has a number of drawbacks: deep rastrations (oxalic acid), similar colouring of ferrite and σ-phase (alkali) which can make structure identification difficult when using low magnifications. It has been established that for full visual identification of the structural components of duplex and super duplex steels by means of optical microscopy, the most reliable method is the use of chemical etching techniques with Beraha and Kalling reagents. Both reagents produce a similar colouring pattern for the phases: the austenitic grains are light grey, the ferrite phase is dark grey and the σ-phase remains white.The study was carried out with financial support from the Ministry of Science and Higher Education of the Russian Federation (state assignment for fundamental scientific research No. FENU-2023-0013 (2023013ГЗ)).