The features of plastic relaxation and recrystallization processes of steels of various types with different crystal lattices were studied. It was established that structural signs of collective or secondary recrystallization, as well as high-speed shear or rotational plastic deformation, were observed in the laser impact zone. The conditions of the course of these processes associated with the behavior of defects in the crystal structure under pulsed loading were discussed. The conditions of laser action ensured the dynamic processes of restoring the structure of steels.

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.

We study the effect of laser irradiation on the initiation and development of corrosion defects near nonmetallic inclusions in steels. It is established that the procedure of laser treatment improves the corrosion resistance under the conditions of low-cycle fatigue of steels containing various inclusions. It is shown that the effect of laser treatment on the formation of corrosion defects in steels is connected with changes in the state of the inclusion–matrix interfaces, which decreases their permeability for corrosive elements and increases the cohesive strength of these interfaces in active media.

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.

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.

Purpose. The aim of the work was to study of the peculiarities of crack initiation in heterophase inclusions of the "high-melting phase surrounded by a low-melting shell" type during deformation of steels. Methods. The destruction of heterophase inclusions of various types was investigated during deformation of specimens from steels 08T, 08Yu, 12GS, 08kp, 09G2S, NB-57, 08GSYuTF in the temperature range 20...1 200 °C [1; 5]. Samples of steels were subjected to tension, compression and bending in vacuum at temperatures of 20…1 200 °C on Instron-1195 and IMASH-5C with special grippers, the movement speed of which was 20 mm / min. Methods of investigation –petrography and optical microscopy (Neophot-21) were used. Results. It was found that in the process of deformation of the steels in different temperature regimes, microcracks originating near heterophase inclusions of the "high-melting phase surrounded by low-melting shell" type can be brittle and ductile. In this case, the role of the level of plasticity of the phases making up the inclusion, which depends on the deformation temperature, is important. The features of microcrack initiation are shown for different combinations of plastic and non-deformable phases of inclusions. The interaction of heterophase inclusions and a steel matrix during deformation is analyzed. It has been established that the nucleation and growth of microcracks within inclusions of the "high-melting phase surrounded by a low-melting shell" type occurs both in the phases and along the internal interphase boundaries. Scientific novelty. Specific features of the initiation of microcracks associated with heterophase inclusions of the " high-melting phase surrounded by a low-melting shell" type, which have a different combination of brittle and plastic phases during deformation of steels, have been established. It is shown that the critical degrees of deformation of the samples, upon reaching which noticeable microcracks appeared along the internal interphase boundaries, depend on the temperature and the nature of the phases of the inclusions. Practical significance. The use of the results obtained will make it possible to develop technologies for producing steels with regulated types of heterophase nonmetallic inclusions, which will significantly increase their technological and operational characteristics, as well as prevent the formation of various kinds of defects during the processing of steels 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 features of steel plastic flow on the rolling surface of railroad wheels during their long-term operation are considered. A nonuniform character of strain developing on the rolling surface and in the surface layer of wagon and locomotive railway wheels is established. The features of gradient microstructure and mesostructure formation near rolling surface exhibited by a substantial evolution (degradation) thereof are studied. From the standpoint of plastic deformation mesomechanics, it is shown that steel flow occurring in the rim surface layer under operation does not provide any conservation of preset operating properties, as well as promotes wear and fatigue failure of the rolling surface.

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.

Purpose. It is necessary to study of the effect of heterophase inclusions on the technological ductility of steels for various purposes. The goal of the work was to study of the nature and level of plasticity of multiphase inclusions in steels under conditions of hot and cold deformation. Methods. Comprehensive methods for the study of heterophase non-metallic inclusions (metallographic, petrographic, X-ray microanalysis methods) were used. Results. Plastic phases in multiphase inclusions of different types under conditions of hot and cold deformation of steels were investigated. It is shown that each type of multiphase inclusions, which are microcomposite formations in steels, is characterized by its laws of development of deformation processes, which are determined by their chemical and phase composition, structure, deformation ability of the phases of inclusions. Scientific novelty. Peculiarities of plastic behavior of multiphase inclusions of different types are established. The inhibitory effect of non-deformable phases of inclusions on the deformability of plastic phases in a wide range of steel deformation temperatures is established. Peculiarities of the nature of plasticity of multiphase inclusions having different compositions and structure are discussed. Practical significance. Using the results obtained will allow developing technologies for producing steels with regulated content and types of multiphase non-metallic inclusions, which will significantly increase their technological plasticity, as well as prevent the formation of various kinds of defects during the processing of steels by pressure.

The features of structural changes in the cove zone on the tread of worn out railway wheels were investigated. The influence of laser processing in pulsed and continuous mode on the nature of the structure and properties of wheel steel was shown. The influence of laser treatment on the increase in the hardness and wear resistance of wheel steel has been established. It was shown possibility and necessity of local laser hardening of cove zone of railway wheels tread by coming out of bainite structure. A method for improving the wear resistance of the tread by local laser treatment has been proposed.

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.

The relaxation processes that occur near nonmetallic inclusions and take place when thermal and strain stresses appear are discussed. These processes contribute to the formation of local mesoscopic substructures characterized by inhomogeneous dislocation density, plastic rotations, local deformation bands, and slip along inclusion/matrix interfaces. The effect of these processes on the local structural changes in a steel matrix, which determine the role of nonmetallic inclusions and inclusion/matrix interfaces in the formation of a heterogeneous steel structure under various deformation and heat conditions, is shown.

Plasticity of heterophase nonmetallic inclusions of various types at hot and cold steel forming was studied. Transformation features of inclusions possessing different phase composition and structure were shown. Inhibiting effect of the second phase of inclusions on the formability of plastic phases at hot and cold strain of the steels was determined. Interaction features of the components of inclusion phases were studied, such as interactions in the inclusion–matrix interfaces and internal phase boundaries in inclusions. Features of the plasticity origin of heterophase inclusions possessing various compositions and structures were discussed.

The main factors governing a mixed effect of nonmetallic inclusions as internal sources of microalloying on local strengthening of steels upon laser treatment are systematized and analyzed. The processes, which govern the nature of the microcomposite zone formation, heterogenization regarding the structure of steel matrix and inclusion–matrix phase boundaries, as well as the decrease in the sizes of inclusions and their content in the surface layer, are discussed. The effect of preliminary laser treatment on the mechanism and parameters of crack formation near inclusions upon subsequent deformation at 25–900 and 1000–1250°C is shown. The effect of the saturation zones of steel matrix on the form of crack propagation from inclusions is determined.

Wire rod from pearlitic steels and carbon content of 0.7-0.9 % is attributed to the responsible range of metal products, so its quality indicators are subject to very strict regulatory requirements. The results of research indicate that in industrial conditions there are all the necessary prerequisites for the effective impact of deformation-heat treatment on the processes of structure formation and ensure a more uniform distribution of structural components in the cross section of the wire rod. Increasing the average mass temperature increases the stability of austenite before the start of continuous cooling, and together with the lack of water cooling provides the formation of a more dispersed and homogeneous structure of wire rod of pearlitic grade steel.

Purpose. It is necessary to investigate the possibility of crushing graphite inclusions in cast irons. The aim of the work was to study structural changes in graphite under explosive action followed by thermal cycling treatment of gray cast iron. Methods. Gray cast irons were subjected to explosive action (pressure is 90 GPa, the deformation rate is 100 s-1, the time is 10-6...10-7 s). Then the cast irons were subjected to thermal cycling: 950 °C, holding for 20 min, cooling with a furnace; 5 cycles. Metalographic ("Neophot-21"), micro-X-ray spectral ("Nanolab-7"), X-ray diffraction (DRON-2.0) research methods were used. Results. The features of diffusion crushing of graphite in cast irons with different types of metal matrix (ferritic, austenitic) and graphite shape (lamellar, spherical) have been studied. The features of structural changes in the cast iron matrix under explosive action, which determine the conditions for the transformation of graphite during subsequent thermal cycling, are discussed. It is shown that this process of diffusional crushing of graphite can be accompanied by local melting, which leads to the formation of regularly distributed dispersed particles of graphite. Scientific novelty. From the point of view of physical mesomechanics of plastic deformation, the processes of structural changes in the metal matrix of cast irons are considered. It is shown that nonequilibrium defect substructures of the cast iron matrix obtained during the explosion determine the features of diffusion crushing of graphite inclusions during subsequent thermal cycling. The conditions for diffusion crushing of graphite with reflow and in the solid-phase state have been established. Practical significance. It has been established that the complex processing of “explosive loading + thermal cycling” promotes crushing of coarse graphite inclusions, which is favorable for the mechanical and operational properties of cast irons. The use of the results obtained will make it possible to develop technologies for complex processing with regulated parameters of graphite inclusions, which will lead to an expansion of the field of application of gray cast irons. Keywords: cast iron; shock wave treatment; graphite; thermal cycling; stress relaxation

The features of the fracture of the interphase inclusion-matrix boundaries under various thermal-deformation and aggressive actions are investigated. The reasons and conditions for the formation of cracks as a result of decohesion of the inclusion-matrix boundaries associated with the concentration of interfacial thermal and deformation stresses are discussed. It was found that the character of decohesion of the inclusion-matrix boundaries (rupture of interatomic bonds of a nonmetallic inclusion and a steel matrix) caused by interphase thermal stresses is due to the conditions of heating and cooling, depending on the type of processing (conventional heating, laser or electromagnetic treatment), which determines the possibility of passing relaxation processes associated with the redistribution of interfacial defects within the specified boundaries. The mechanisms and features of decohesion of the interphase inclusion-matrix boundaries at different methods and temperatures of deformation are discussed. It is shown that the decomposition of the inclusion-matrix boundaries upon deformation occurs in cases of certain types of nonmetallic inclusions (oxides, spinels, some sulfides). For different types of inclusions and steels, parameters have been determined that characterize the cohesive strength of the inclusion-matrix interface depending on the loading conditions. It is shown that decohesion (fracture) of the inclusion-matrix boundary into two free surfaces can be considered as the transformation of interphase misfit dislocations into surface steps as a result of loss of conjugation. The role of inclusion-matrix boundaries in the formation of cracks of fatigue and fatigue-corrosion origin is considered. 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.

Purpose. It is necessary to investigate the influence of non-metallic inclusions on the formation of defects during laser processing. The aim of the work was to study the defects of the hardened layer of steels under laser action, associated with the presence of non-metallic inclusions. Methods. The materials for investigation were commercial steels containing different non-metallic inclusions. The specimens of different steels with preliminary polished surface were exposed to laser beaming on the installations GOS-30M and GUANTUM-16. The research methods were applied - petrography, X-ray microscopy (MS-46 Cameca) and optical microscopy (Neophot-21) to study defects and identify of inclusions. Results. It has been established that various types of defects appear on the surface and in the surface layer of steel under laser action, which are not connected and are associated with non-metallic inclusions. It is shown that non-metallic inclusions are the reason for the appearance of various kinds of defects in the hardened layer of steel products during laser processing (cracks, cavities, violation of the geometry of the hardened layer). The reasons for the appearance of defects associated with the presence of inclusions of various types are discussed. Scientific novelty. A classification of defects in the hardened layer is presented. The nature and features of the formation of defects, associated with the appearance of high-speed thermal stresses, structural inhomogeneity, as well as melting, thermal destruction and evaporation of inclusions emerging to the surface and located within the hardened layer, have been established. It is noted that the detected defects are ready-made centers of destruction of a steel product or part under conditions of static and dynamic loads, as well as contact stresses. Practical significance. It is shown that the unsatisfactory quality of the hardened layer associated with the presence of various kinds of defects near nonmetallic inclusions contributes to a decrease in the mechanical and operational characteristics of a steel product. The use of the obtained results will make it possible to develop technologies for laser processing of steels with regulated quality parameters of the hardened layer, which will prevent the formation of various kinds of defects. Keywords: steel; laser treatment; defects; cracks; hardened layer; non-metallic inclusions