A comparative analysis of the athermal martensitic transformation kinetics in low-alloy 30CrMnSi structural steel using dilatometric and calculative methods was carried out. At the initial stage the evolution curve of shear transformation according to the Koistinen–Marburger (K–M) model corresponds well to the experimental dilatometric data, but with further temperature decrease the mathematical modeling causes a significant error in determining the volume fraction of the formed martensite. At the same time, the error in the calculations of the martensitic phase amount can reach 20 vol.

The behavior of heterophase of the eutectic type inclusions (ETI) under different conditions of plastic deformation of industrial steels is studied. It is established that metal near inclusions damages with the formation of cracks and deformational cavitites caused by their melting. The melting temperatures of different ETI, as well as the temperature intervals for the formation of microdamages of various types during their deformation, were established. The melting of eutectic inclusions at the initial stages of deformation causes a sharp growth of cracks and cavities in steels, which promotes their red brittleness.

Purpose. To study features of slippage at the interphase boundaries, heterophase inclusion “refractory phase surrounded by a low-melting shell” − steel matrix in the temperature range of hot deformation. Methods. Samples of steels were subjected to stretching at temperatures of 20...1 200 °C in a vacuum on the IMASh-5S device with special grippers, the speed of which was 20 mm/min. Research methods were used: petrography, micro-X-ray spectral analysis (“Cameca MS-46, Nanolab-7”, optical microscopy (Neophot-21). Results. It was found that the diversity of phases composing the heterophase inclusions of the “high-melting phase surrounded by a low-melting shell” type leads to their different behavior under plastic deformation. It was shown that during the high-temperature deformation the inclusion − matrix interphase boundaries, which are the boundaries between the inclusion-shell phase and the steel matrix, exhibit plasticity as a result of slipping. It was found that depending on the plasticity level of the phases composing the inclusion, the slipping occurs with different intensity. The features of the slipping process for heterophase inclusions of the “high-melting phase surrounded by a light-melting shell” type were analyzedScientific novelty. It is discussed the slipping mechanism for inclusions of the “high-melting phase surrounded by a low-melting shell” type containing phases with different plasticity levels, which is associated with the movement of interface dislocations at the inclusion − matrix boundaries (intrinsic slipping) or inserted dislocations as well as with contact friction and internal friction occurring at the boundaries due to the dislocation movement. It is shown that the activation of the slipping can occur due to the rearrangements of defects located at the interphase boundaries of the inclusion − matrix of steel. It was established that the difference in the nature of the phases-shells, as well as the influence of the second phase of inclusions “high-melting phase surrounded by a low-melting shell” contribute to difference in plasticity of inclusion-matrix boundaries of steel under high-temperature deformation. Practical value. The use of the obtained results will make it possible to develop technologies for producing steels with regulated types of heterophase non-metallic inclusions, which will significantly increase their technological and operational characteristics, as well as prevent the formation of various defects during the processing of steels by pressure and the operation of products.

Problem statement. High-carbon steels, which are additionally alloyed with chromium, molybdenum, and vanadium, are used during the production of large-sized rolling rolls for hot deformation. Rolling rolls are subjected to significant loads during operation, so they must have sufficient hardness and resistance to wear. Steels of the type 65Cr3SiMoV, 80Cr3MoV, 80Cr5MoV have recently been used for the production of hot-formed rolling rolls, but despite this, their resistance to wear in harsh operating conditions is insufficient. There is no information in the literature about the peculiarities of the austenite decay kinetics of the specified rolled steels, therefore, this direction requires appropriate comprehensive research. Purpose. Development of a methodology for predicting the structural state of the working layer of large rolling rolls in the process of thermal strengthening of high-carbon alloy steels, taking into account the determining parameters of the manufacturing technology. Results. A methodology for modeling phase-structural transformations in the process of continuous cooling of high-carbon alloy steels was developed. For steels 65Cr3SiMoV, 80Cr3MoV, 80Cr5MoV were constructed thermokinetic diagrams and on their basis, the peculiarities of the formation of the structural state of the working layer of large rolling rolls (support, working) during thermal hardening were investigated. It has been established that the method of hardening by volumetric heating of support rolls made of 65Cr3SiMoV steel ensures the formation of a bainite structure over the entire normalized depth of their working layer. For working rolls made of 80Cr3MoV and 80Cr5MoV steels, the most effective method is hardening with differentiated heating, while in the latter case continuous cooling should be carried out at a slower speed.

Features of formation and distribution of pearlite disperstion degree in C82D steel (EN ISO 16120-2:2017) billet and after its hot plastic deformation at different stages of rolling, were established. The structure is a lamellar pearlite with different degrees of dispersity, regardless of the technological area of samples selection. The interplate distance of pearlite increases and reaches the largest values in the center with the approach to the axial rolling zone. The hot plastic deformation should be completed at a controlled temperature of the metal output at the last stage of rolling. Here stage of water cooling was excluded what reduces the temperature gradient between the surface and the center rolling.

Peculiarities of the shape change and redistribution of non-metallic inclusions of various types during working by pressure of steels (rolling, forging, drawing) were investigated. The concept of plastic deformation of inclusions is considered from the standpoint of physical mesomechanics of heterophase alloys. It is shown that non-metallic inclusions contribute to the localization of plastic deformation, which is accompanied by the interaction of non-metallic inclusions and the steel matrix, which determines their common plastic change in shape and redistribution of inclusions in the steel matrix. The peculiarities of these processes under different types and temperature regimes of working by pressure, which determines the nature of stresses near the inclusions and the plastic flow of the steel matrix, have been established. It is shown that the temperature regime of pressure treatment determines the possibility of relaxation processes in the steel matrix near the inclusions and the level of plasticity of the inclusions themselves and the inclusion-matrix interphase boundaries. The influence of the temperature regime of hot deformation of sheet steels and wire rod on the nature of shape change and the deformability of plastic inclusions and their destruction (brittle or ductile), as well as the plasticity of the steel matrix, frictional forces at the inclusion-matrix boundaries, and the plasticity of the latter during hot rolling were established. It is shown that when considering the plastic behavior of non-metallic inclusions in a plastic steel matrix, the behavior of the inclusion-matrix interphase boundaries under different deformation conditions is of great importance. Peculiarities of the dynamic character of the joint deformation of the inclusion-matrix system, which is associated with the development of competing processes at the interphase boundaries of the inclusion-matrix: interphase friction and slipping, have been studied. The features of hot and cold slipping occurring at different deformation temperatures are discussed. It is shown that the mechanisms of each of the mentioned processes depend on the temperature regime of the deformation, the level of plasticity of the inclusions and the steel matrix. The influence of the method of cold deformation (rolling and drawing) on the shape change of plastic inclusions and the redistribution of non-deformable inclusions in the steel matrix was established. The processes that determine the level of plasticity of non-metallic inclusions and inclusion-matrix boundaries and significantly affect the nature of the shape change of inclusions and their redistribution in the steel matrix in the process of the working by pressure of steels, which affect their technological plasticity at different temperatures and methods of deformation, are considered.

Purpose of the work – to study of the processes that determine the interaction of non-metallic inclusions and the steel matrix during steel rolling. Methods. The behavior of inclusions was studied during hot rolling of steels 08Yu, 08T, 08kp, NB-57, 08GSYUTF in the temperature range of 1 200...900 °C and cold rolling with degrees of deformation of 35...75 %. The study of hot slipping along the boundaries of the inclusion − matrix was observed during high-temperature (900...1 200 °C) deformation by stretching in a vacuum on the IMASH-5S installation with a gripper movement speed of 1 680 mm/min. According to the study of slipping, steel samples were stretched in a vacuum at temperatures of 25...900 °С on the IMASH-5S installation with a gripper movement speed of 2 000 mm/min. On the surface of the samples, using the PMT-3 device, reference points were applied near the 0° and 90° inclusion poles on both sides of the inclusion − matrix boundary. Research methods are given in works [10; 11]. Identification of inclusions was carried out by metallographic (Neophot-31), petrographic and micro-X-ray spectral (MS-46 Cameca) methods. Results. It is shown that during plastic deformation, there is an interaction between non-metallic inclusions and the steel matrix, which determines their joint plastic shape change and is associated with the development of competing processes at the inclusion − matrix interphase boundaries: interphase friction and slipping (hot or cold depending on the deformation temperature). The mechanisms of these processes are determined depending on the deformation conditions and the level of plasticity of non-metallic inclusions and the steel matrix. Scientific novelty. The peculiarities of interphase friction and hot and cold slipping along the inclusion − matrix interphase boundaries of steel under different conditions of plastic deformation have been established. It is shown that the mechanisms of each of these processes depend on the temperature regime of deformation, the level of plasticity of the inclusions and the steel matrix, as well as on the structure of the inclusion − matrix boundaries, which determines the possibilities of movement and interaction of interfacial defects. It is shown that the specified processes determine the level of plasticity of the inclusion − matrix boundaries and significantly affect the nature of the change in shape of the inclusions and their redistribution in the steel matrix during steel rolling, which inevitably affects the technological plasticity of steels. Practical significance. The use of the results obtained will make it possible to develop technologies for producing steels with regulated types of nonmetallic inclusions, which will significantly increase their technological characteristics, as well as prevent the formation of various kinds of defects during the processing of steels by pressure of products.

In the world, the nuclear industry is considered an ideal option for an environmentally friendly source of energy generation, based on the separation of the radioactive nuclide of the chemical element 235U. When generating electricity from nuclear power plants, the main disadvantage is the generation of radioactive waste. After spent fuel is removed from a nuclear reactor, it is placed in special containers containing absorption and retention elements. It is obvious that the storage and transportation of spent nuclear fuel plays an important role in the development and overall safety of the nuclear industry, and high-quality neutron-absorbing materials are the basis for the successful manufacture of reliable structures and containers. The development of modern neutron absorption materials ensures reliability, safety, storage duration, as well as reducing the cost of logistics operations associated with the transportation of radioactive waste. Based on the results of the analysis of scientific and technical sources, modern ideas about materials for the manufacture of containers, which are used for storage and transportation of nuclear fuel waste, are summarized. The advantages and disadvantages of the main materials used in the disposal of spent nuclear fuel are considered. It has been established that, from an economic point of view, the most rational material for storing and transporting radioactive waste is ferritic stainless steel with a high boron content, which, in addition to absorption abilities, is characterized by other properties required for this type of product. Since boron has a low ability to dissolve in both austenite and ferrite, this leads to the formation of borides of various types, which contribute to the embrittlement of the structural material. At the same time, the distribution of borides over the volume of a metal product is determined not only by a set of properties, but also by the protective properties of the material, as well as the manufacturability of the final product from it. Despite the fact that boron-containing steels of the ferritic class have been known for a long time, issues related to the processes of structure formation, increasing technological and operational properties still remain insufficiently studied and controversial. There is also no information on the influence of heat treatment on the formation of the structure and mechanical properties of finished products made of ferritic stainless steels. Successful solution of these scientific and technical problems will ensure the production of modern high-quality neutron-absorbing containers for off-reactor storage and transportation of spent nuclear fuel.

Purpose. The aim of the work was to analyze the features of the destruction of the inclusion − matrix interphase boundaries under aggressive influences and in the process of wear as a result of the degradation of their structure. Methods. The samples of steels 08, R7, ShKh15 were tested for low-cycle fatigue in air and in corrosive environments (1…5 % aqueous solution of NaCl and 2…1 % aqueous solution of H2SO4). A test method was used to test the tendency of steels to stress corrosion cracking on an IM-12 installation. Fatigue strength tests were carried out on an NU machine. Samples of steels 08kp, 08Yu, 08GSYuTF, ShKh15, R7, M74 were exposed to holding in an atmosphere of hydrogen for 2 h at of 650 and 1 100 °C, the pressure 5 and 10 MPa. The features of the wear of the rolling surface of railway wheels (steel R7), which have worked for 5 years under a passenger train, have been investigated. Research methods: metallographic ("Neophot-21"), electron microscopic ("JSM-35"), petrographic. Results. The features of the fracture of the interphase inclusion − matrix boundaries under various thermal-deformation and aggressive actions are investigated. The role of inclusion − matrix boundaries in the formation of cracks of fatigue, fatigue-corrosion and hydrogen origin is considered. Scientific novelty. It is shown that under the influence of aggressive media and cyclic stresses, the structure of the inclusion − matrix interphase boundaries degrades, which is associated not only with the accumulation of interfacial stresses, but also with the facilitation of the penetration of surfactant atoms from the environment along these boundaries. As a result, fatigue-corrosion destruction of the inclusion − matrix boundaries occurs, and the effect of an adsorptive decrease in their strength is manifested. Practical significance. The research results can be useful in the development of methods of targeted influence on non-metallic inclusions and inclusion − matrix boundaries in various types of steel processing and the operation of steel products.

The purpose of the article − to study of crack nucleation features in heterophase inclusions of the “dispersed phases in a non-metallic matrix” type under the conditions of steels’ plastic deformation. Methods. The research was conducted after deformation for a number of different grades steel samples in the temperature range of 20...1 200 °С on Instron-1195 and IMASH-5C with special grippers, with a gripper movement speed of 1 680 mm/min. Research methods were used: petrography, micro-X-ray spectral analysis (Cameca MS-4, Nanolab-7), optical microscopy (Neophot-21). Results. It is shown that the variety of phases composing the heterophase inclusions "dispersed phases in non-metallic matrix" leads to their different behaviour under plastic deformation conditions. At the same time, the nucleation of brittle or viscous microcracks occurs along the internal interphase boundaries between the "non-metallic" matrix and the dispersed particles of the second phase. The cracks’ character near the inclusions determined by the plasticity level of “matri” and dispersed phases of inclusions and the deformation temperature are revealed. The determined critical degrees of samples’ deformation, upon reaching which appreciable microcracks along the internal interphase boundaries occurred, were depend on temperature and the nature of the “dispersed phases in a non-metallic matrix” inclusions. Scientific novelty. The features of microcracks nucleation associated with heterophase inclusions of the “dispersed phases in non-metallic matrix” type with different combination of brittle and plastic phases during steels’ deformation are determined. The types of microcracks occurring in inclusions of the “dispersed phases in the non-metallic matrix” type and the locations of their formation have been determined. It is shown that the values of the deformation critical degrees determine the level of cohesive strength for internal interphase boundaries in heterophase inclusions “dispersed phases in a non-metallic matrix” at different deformation temperatures. Practical value. The use of the obtained results will make it possible to develop technologies for producing steels with regulated types of non-metallic heterophase inclusions that will allow to increase significantly their technological and operational characteristics, and also to prevent the formation of various defects in the steels' treatment by pressure and the operation of products.

International scientific conference «Information technologies and management in higher education and sciences» : conference proceedings (November 28, 2022. Fergana, the Republic of Uzbekistan). Riga, Latvia : "Baltija Publishing", 2022. Part 2. 388 pages.

The purpose of the work is to study the influence of complex heat treatment on the peculiarities of the formation of the structure and properties of carbon steel alloyed with chromium, nickel, molybdenum and vanadium. Currently, carbon alloy steels (38CrNi3MoV, 65Cr3SiMoV, 80Cr3MoV) containing chromium, molybdenum, nickel, vanadium and other expensive chemical elements are used for the production of various metallurgical and machine-building products (rolling rolls, rulers, piercing mandrels, parts of power equipment). However, the wear resistance of finished products made of specified steels in harsh operating conditions (significant cyclic loads and elevated temperatures) is insufficient in practice. One of the methods of effective influence on the improvement of the operational resistance of alloyed carbon steels may be the use of cryogenic treatment after preliminary thermal hardening. The results of studies of the effect and duration of cryogenic treatment on the features of structure formation, microhardness, hardness, and wear resistance of 38CrNi3MoV steel previously subjected to thermal hardening are presented. It was established that the duration of exposure of 38CrNi3MoV steel in liquid nitrogen should be at least 1.0 hours, which allows to achieve an increase in microhardness and wear resistance by 12 % and 17.4 %, respectively. The obtained results allow us to state that the use of cryogenic treatment at the final stage of thermal hardening will ensure an increase in the operational durability of products of special purpose, which are made of 38CrNi3MoV steel. The developed method can be recommended for the industrial implementation of the technology of complex heat treatment of carbon steels with increased wear resistance, which additionally contain chromium, nickel, molybdenum and vanadium.

The purpose of the work is to study the peculiarities of the influence of the chemical composition on the formation of the primary structure and properties of chromium-manganese alloys. Piercing mandrels belong to the replaceable tool of hot deformation, the operational characteristics of which affect the productivity of pipe rolling mills and the quality of finished products. The costs of the hot deformation tool are a component of the cost price of metal products, so the interest in increasing their operational stability is constantly growing. The development of a rational component composition of alloys is based on ideas about the peculiarities of the course of structural and phase transformations during crystallization, heat treatment, as well as under the influence of high temperatures and loads during operation. To develop an effective mode of final heat treatment of wear-resistant products, one should have an idea about the quality of the cast material and its primary structure, in particular by determining the dynamics of changes in indicators, the formation of which is due to liquidation phenomena. The purpose of the work is to study the peculiarities of the influence of the chemical composition on the formation of the primary structure and properties of chromium-manganese alloys. The peculiarities of the formation of the cast structure, phase composition, and properties of economically alloyed chromium-manganese alloys intended for the manufacture of piercing mandrels have been studied. According to the results of tests on frictional wear, it was established that chromium-manganese alloys have higher wear resistance compared to cast iron of the 300Cr32Ni3V and the “nikorin” alloy (36.0–38.0 % Cr; 57.0–59.0 % Ni). According to the results of the X-ray spectral analysis, it was established that in the structure of the experimental alloys, the highest values of the liquidation coefficients are characteristic of Ni, V and Cu. With an increase in the content of C, Mn, Cr, and Ni, the degree of doping of the matrix and carbides increases, which leads to an increase in the wear resistance of the chromium-manganese alloys. The obtained results with a high probability allow us to state that the further development of effective modes of final heat treatment of the proposed chromium-manganese alloys will ensure an increase in the operational stability of the piercing mandrels of pipe rolling mills while simultaneously reducing the material costs for their manufacture.

The features of wear of rope-block and rope-drum friction pairs of lifting and traction devices operating in the conditions of a hot manufactory of the metallurgical plant and also the mining and beneficiation plant were studied. It is shown that the causes of wear of the elements of the rope-block and rope-drum friction pairs are the interaction in their contact zones, which occurs in the surface layers under the influence of high contact stresses, friction, cyclic loads, abrasive particles, active atmospheric and industrial environments. It was found that these actions lead to irreversible processes of accumulation of stresses and plastic shifts, which have a periodic and heterogeneous character. It is shown that the strength of the lifting or traction rope is determined by the degree of wear of the wires, primarily those in contact with the block and the drum. The structural changes in the surface layers of the wires and the mechanisms of the formation of wear particles were analyzed, which confirm the heterogeneous nature of the wear of the wires in the strands of the rope. Areas of abrasive wear were also observed on the worn surface of the wires, where under the action of solid foreign particles of contamination with sharp corners falling between the wires, the surface of the wires was undercut. It is shown that the presence of non-metallic inclusions leads to the formation of wear particles and fatigue cracks. It was established that the wear of friction pairs of rope-block and rope-drum of hoisting and traction devices has a fatigue-corrosive nature, and the main mechanism of the formation of wear particles is the development of plastic shifts in the surface layers of friction pairs and their separation by plastic exfoliation and abrasive and corrosive destruction. The shape of the wear particles depends on the type of material and the conditions of their formation. It is proposed to take measures regarding structural approaches to friction pairs, taking into account their working conditions, in order to reduce contact stresses and increase their wear resistance, reliability and durability.

Formulation of the problem. Modern research on the phase transformations modeling in low-alloy steels allow solving the problem of phase transformations quantitative determination for a given chemical composition of steel and different cooling rates. However, the possibilities of available universal software products for the complex alloy steels analysis are limited. The impossibility for users to integrate their own subroutines according to the phase transformation diagrams is their main disadvantage. Purpose of research. Modeling phase-structural transformations during cooling of complex-alloy steels taking into account the formation of all structural components, in particular residual austenite. To research, steels 25Cr2Mo1V and 38CrNi3MoV and existing analytical models were used, which were adapted to carry out the relevant calculations. Results. A new method for modeling phase-structural transformations during cooling of alloy steels is developed. Structural diagrams depending on the rate of continuous cooling are constructed for the investigated steels. For the first time, the amount of residual austenite is taken into account according to the developed method. Under developed method thermokinetic diagrams of investigated steels austenite transformation are constructed. According to the diagrams, the decay of austenite steel 38CrNi3MoV begins at lower temperatures compared to steel 25Cr2Mo1V. Steel 25Cr2Mo1V, with continuous cooling at a rate of 1.0 °C/s (conditions close to natural air cooling), consists of 18 % ferrite, 1 % pearlite, 80 % bainite and 1 % residual austenite. Steel 38CrNi3MoV cooled at a rate of 1,0 °C/s consists of 2 % ferrite, 47,5 % bainite, 50 % martensite and 0,5 % residual austenite. It is shown that the calculated data correlate well with practical results at the conditions of natural air cooling.

Purpose of research. Investigation into crack initiation features in heterophase inclusions of the “phase side by side” type during steel deformation. Methods. Destruction of various types heterophase inclusions is investigated during the deformation of samples from steels 08Ti, 08Al, 12MnSi, 08unk, 09Mn2Si, 08GSiAlTiV in the temperature range 20...1 200 °С. Samples of 08Ti and 08Al steels are subjected to tension, compression and bending, steel HB-57 − to tension and compression, steel 08unk, 08Cr, ATs45X ,ATs18XGT − to tension in vacuum at temperatures of 20...1 200 °С on experimental settings with special grips, which motion speed was 20 mm/min. Methods of investigation – petrography, X-ray microanalysis and optical microscopy were used. Results. It has been found that the diversity of phases composing the heterophase inclusions of the “phase side by side” type leads to their different behaviour under plastic deformation. The microcracks nitiation occurs along the internal interphase boundaries. Depending on the plasticity level of the phases composing the inclusion, these cracks can be brittle or ductile, which is also related to the effects of the deformation temperature. The features of microcracks initiation for different combinations of heterophase inclusions plastic and non-deformed phases of the “phase side by side” type are analysed. The interaction between heterophase inclusions of the “phase side by side” type and the steel matrix during deformation is discussed. Scientific novelty. The features of microcrack initiation related to heterophase inclusions of “phase side by side” type with different combination of brittle and plastic phases during steels deformation in a wide temperature range is determined. It was found that the microcracks initiation and spreading within inclusions “phase side by side” type occurs both in phases and along internal interphase boundaries. It is shown that the critical degrees of samples deformation, at which significant microcracks along the internal interphase boundaries occur, depend on the temperature and the inclusion phase. The critical degrees of samples deformation, upon reaching which significant microcracks occurred along the internal interphase boundaries, depended on the temperature and the nature of the “phase side by side” inclusions. The values of the critical degrees of deformation determine the level of cohesive strength of the internal interphase boundaries of the heterophase inclusions “phase side by side”. Practical significance. The use of obtained results will make it possible to develop technologies for producing steels with regulated types of heterophase non-metallic inclusions. This will substantially improve their technological and performance characteristics and prevent the various defects formation in the steel pressure treatment and the products operation.

We conducted a study of the structure, phase composition and wear resistance of iron-carbon alloys used and planned to be used in manufacture of hot deformation tools.As established, chromium-manganese cast iron with chromium content of 12.5…13.5% and manganese content of 15.0…16.0% is advisable to be used as a material, in particular, for piercing mandrels.As shown, reduction of expensive alloying elements (Cr, Ni) contained in chromium-manganese cast iron in comparison with traditional alloys such as 300Х32Н3ФЛ and 'nikorin' is performed due to the higher contents of Mn.It was found that the increase in wear resistance of chromium-manganese cast iron is due to the high microhardness of the matrix, austenite-carbide eutectic based on carbide type Me7C3 and, apparently, it is conditioned by deformation-phase transformations that can occur during abrasion wear.

Invistigations are directed to detection of the metallurgical reasons of the breakage of alloy steels during production of the small diameter wire. Several batches of the coiled bar(s) of low carbon silicon-manganese steels of the Sv-08G2S and G3Si1 were taken as materials for invistigation. The main influence on the metal breakage during drawing is exerted by its structure and mechanical characteristics, it is known. The initial structure of the coiled bar(s) before drawing to small diameters from the differents smelting within one sort was not differ and represented globular pearlite for Sv-08G2S steel, ferrite and pearlite for G3Si1 steel. The influence of equipment and drawing technology on the wire breakage is minimal, as the processing is performed with the same conditnions. Special attention in the invistigations was paid to the contamination of steel with nonmetallic inclusions during the drawing. Analysis is showed in the wire of low carbon silicon-manganese steels the presence of the point oxides, non-deformable silicates and sulfides, and fragile inclusions, which are located along the rolling direction. The feature of the wire, which has observed the breakage during the production, is the presence of the large quantity of the line inclusions (3...5 points), which are located in some cases over the entire surface of the polished section of the Sv-08G2S steel. The structure of all investigated steels does not differ, the mechanical characteristics of the wire with breakage corresponded to the required standard values. It is shown that contamination of the original wire rod with (more than 2 points) of nonmetallic inclusions are significantly increases the chance of difficulties arising during production of the wire with a diameter of 1,2...0,8 mm and can lead to breaks. The high purity of steel in terms of nonmetallic inclusions guarantees the absence of breakage due to this defect during the production of wire, which contributes to increase of the performance and decrease in the cost of finished products.

In accordance with the latest global trends and modern needs of hardware factories, the demand for wire rod made of pearlitic steels has significantly increased, which can undergo cold plastic deformation with large degrees of reduction and is intended for the manufacture of various commercial products (cold-worked reinforcement, reinforcing ropes, spring wire, steel cord, wire for high pressure hoses, construction fiber, etc.). The most promising direction for increasing the strength class of hot-rolled steels is strain hardening during cold plastic deformation. The structure of cold-worked steels has a more uniform distribution over the cross-section, in contrast to thermally hardened ones, which in the latter case are characterized by annular structural zones formed due to different mechanisms of austenite decomposition. In a number of cases, structural heterogeneity causes instability of the mechanical properties of rolled steel, therefore, there is currently no alternative way to strain hardening. The manufacture of high-strength cold-worked metal products is a complex process and depends on the quality of the wire rod. If the cold-worked hardware does not meet the requirements of the normative documentation for the strength class, then it is no longer possible to ensure the correction of this defect using heat treatment. In this regard, scientific and practical interest has arisen to determine the possibility of creating a method for predictive determination of the mechanical properties of cold-deformed metal products made of pearlitic steels. The features of the influence of cold plastic deformation by on the formation of the strength class of pearlite grade steels with a carbon content of 0.7…0.9 % are considered It is established that the temporary resistance to fracture, at the known parameters of structure and carbon content, lends itself well to mathematical calculations and allows to create predictive models. According to the results of the research, a computer program was created that allows to automatically calculate the energy parameters of drawing and determine the tensile strength of the wire after depending on the total relative compression, parameters of the structure of wire rod and the carbon content in the steel.

Formulation of the problem. In the production of coiled rolled products from perlite grade steels, metallurgical enterprises encounter with the sorting of some batches of continuously cast billets or commercial products due to non-compliance with regulatory requirements. One of the alternative ways of using such blanks can be their reassignment for the production of thermally hardened reinforcing bars. In accordance with the edition of GOST 5781-82, it was possible to produce hot rolled reinforcing bars from steel grade 80C (carbon content 0,74…0,82 %), and according to TU 14-15-339-94 – thermally hardened with a carbon content of 0,50…0,85 % C. In world practice, reinforcing bars of a strength class similar to classes A800…A1000 (DSTU 3760:2019) are made mainly of high-carbon steels. The main type of stressed reinforcement in the EU, USA, Canada and Great Britain are rods with a nominal diameter of 26…40 mm of strength class 835…1030 MPa and 26…36 mm of strength class 1080…1230 MPa. An analysis of the requirements for reinforcing bars according to various regulatory documents shows that in the standards of Canada, the USA and the UK, the carbon content is not standardized, but according to the standards of Japan and Ukraine it is 0,45…0,80 % and 0,13…0,37 % respectively. According to the requirements of international standards, the minimum values of the yield strength and strength correspond to the reinforcing bar A800 (DSTU 3760:2019). Therefore, for the possibility of producing reinforcing bars from high-carbon steels, it is necessary to establish rational temperature-time conditions for heat hardening modes, which will ensure that the finished metal products comply with the requirements of DSTU 3760:2019. Purpose. Determine the influence of the parameters of the technology of thermal hardening on the features of the formation of the structure and mechanical properties of reinforcing bars made of steels with a carbon content of 0,50…0,90 %. Results. The possibility of producing reinforcing bars of strength classes А800 and А1000 from steels С56DВ, C70DВ, C80DВ and C82DВ (EN 16120-2:2017) using intermittent and interrupted quenching methods has been scientifically proven. In accordance with the results obtained, the industrial production of reinforcing bars of strength classes A800 and A1000 from these steels is expedient, since it will contribute to the improvement of technical and economic indicators in the production of coiled steel from perlite grade steels intended for high-strength products (cold-worked rebar, metal cord, bead wire, spring wire, reinforcing ropes, etc.). Based on the results of industrial experiments, a technical agreement was developed and approved for the production of pilot batches of thermally hardened reinforcing bars of strength classes A800 and A1000 from steels containing 0.50...0.90 % carbon.