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Understanding the processes that control the formation of precipitates of alloying element, their composition and morphology is important for the choosing of optimal regimes of thermomechanical treatment, providing the required structural state and properties of low-alloyed steels. The use of modern methods of atomistic modeling and ab initio calculations to study the mechanisms and conditions of precipitation depending on the steel composition and temperature is discussed. The enthalpy of formation of Ti, V, Nb carbides and nitrides in γ-Fe was calculated using the methods of the theory of the electron density functional and the temperatures of their dissolution were determined in dependence on the composition of the steel. The results obtained agree with the experimental data and obtained by the CALPHAD method. Calculations of the electronic structure, enthalpy of mixing, energy of effective interactions between atoms of alloying and impurity elements have been performed. It was shown that an essential factor determining the nature of the interaction between alloying elements was the magnetic state of iron. It has been established that the enthalpy of mixing, which expresses the tendency of the system to decomposition, increases with the transition of α-Fe from the ferromagnetic to the paramagnetic state. In ferromagnetic α-Fe energetically, the formation of precipitates of Cu, as well as particles of a mixed composition of Cu‒Al, Cu‒Ni and an ordered phase of NiAl are preferable. It has been shown that precipitates Cu-based can be formed during technological times. The transition of α-Fe to the paramagnetic state results in increase of interactions between alloying elements (the exception is the interaction of Cu‒Cu and Cu‒Ni). As a result, additional combinations of alloying elements appear, the interaction between which lead to the formation of precipitates. At the same time, in γ-Fe, precipitates can be formed only based on Mo and Nb. The role of magnetism in the formation of precipitates and their influence on the γ→α-transformation is discussed. It has been shown that the results obtained make a base for enhancement technologies of high-strength low-alloyed steel production.

It is noted that the technology for the manufacture of ferrosilicon-magnesium modifiers (crystallization into an ingot in a mold or into a chip on a water-cooled drum) forms their quantitative and qualitative structural differences: the size and distribution of phases, the scatter of the content of elements, etc. The fundamental differences are shown and the features of the distribution of silicon as a base element in ingot and chip modifiers are described. It was found that in ingot modifiers the vast majority of silicon-containing phases are ξ(FeSi) and ζ' (FeSi2), and with a significantly lower content of pure silicon particles and phases, these are α1(Fe3Si) and α2(Fe2Si). The picture of the phase structure of the modifier chip has been determined. In it, the 1st mode corresponds to the presence of a set of phases α1(Fe3Si) and α2(Fe2Si), and the 2nd mode, as well as in the ingot modifiers ξ (FeSi) and ζ'(FeSi2), but is shifted to the lower boundary of the region their existence. Particles of pure silicon are completely absent in the chip modifier.

The paper describes some aspects of a scientific and research project dedicated to mechanical property prediction in plates for pipe production rolled at PJSC MMK 5000 Mill. The prediction is based on billet thermal state modelling by thermo-mechanical control process (TMCP) of rolling and subsequent cooling. The central focus of the modelling is the calculation of billet layer-by-layer cooling trajectory. The paper presents some results of model verification by test rolling.

Purposeful control of structural state of steel at every stage of technological chain of steel goods production is necessary for elaboration of effective metallurgical technologies. The purpose of the complex of research and theoretical studies was development of ideas on peculiarities of structure formation of various steel grades. Current conceptions about phase and structural transformations in steels with different contents of carbon and alloying elements considered. For carbon and alloyed steels, the results of the study of the structure of perlite formed at different temperatures summarized; morphology, crystallography and defects of crystalline structure of cementite, processes of its fragmentation, coagulation and spheroidization; crystallography of austenite degradation products; evolution of the structure during cold and hot plastic deformation; carbon redistribution processes prior to and during diffusion-controlled austenite decay presented. For low-carbon low-and sparingly alloyed cold-resistant weldable steels generalized results of investigation of structure-formation processes, alloying relationships, temperature-deformation rolling conditions, parameters of quenching and high-temperature tempering with structure, mechanical properties and performance characteristics of steel plates presented. The elaborated complex of scientific and technical solutions based on the studies enabled to master and digitize production technologies at PJSC “Magnitogorsk steel-works” of new generation steel rolled products intended for ship-building, oil and gas industries, automobile, hardware and construction industries. The new systems of alloying steels of various application, methods of the new generation steels production and automated control of technological processes protected by 27 patents of RF, are widely used in the production activity of PJSC “Magnitogorsk steel-works”.

The article is devoted to the study of technological modes of hot rolling of tube steel on a thick-sheet mill and mechanical properties of the finished products. Five slabs were rolled under the experimental regime in accordance with the study plan. The temperature conditions of rolling at the final stage of deformation and the modes of accelerated cooling of rolled products were changed. Dependencies between technological parameters and mechanical properties allowed developing recommendations on improvement of technology of rolling and of the subsequent accelerated cooling of metal.

A description of the experience in the development and implementation of a model for forecasting the microstructure of rolled tubular products steel during thermomechanical processing of a semi-finished product and the relative IT-solution for the plate mill 5000 of PJSC MMK is presented. This solution is based on modeling the kinetics of structure formation in the mill technological line. The article describes briefly the result of analysis of a number of existing kinetics models of phase and structural transformations from the point of view of their application under the conditions of interest to us. An empirical study of the thermal effects of phase transformations and the influence of the heat removal mode on the kinetics of structure formation is described. The process of development of an empirical kinetics model and implementation of IT-solution, that implements this model, is also described.

The paper presents comprehensive scientific and technological solutions related to the large-scale production of new-generation rolled steel in an integrated metallurgical plant. The new-generation rolled steel is in the form of a high-duty steel plate, each geometric element of which exhibits a customerspecified complex of physical and mechanical properties. In the linear sections, surface and volume elements are effectively used as geometric elements. The results of research projects aimed at enriching our scientific understanding of the phase and structural transformations in steels are presented. The capabilities of the enterprise production and quality management system employed by the Magnitogorsk Iron and Steel Company are described; this system ensured the transition of the enterprise toward digital, highly efficient technologies for producing metal products.

PJSC “MMK” has developed and implemented technologies for the production of thick plates from low-carbon, low-alloy and sparingly alloyed cold-resistant weldable steels of a wide range of strength grades – from 315 to 690 MPa, as well as rolled steel from high-strength steels with a strength category of 500 MPa for Arctic conditions, with the index “Arc.” The results of the study of the microstructure and properties of the developed materials are presented. The objects, in which the developed materials will be used, are indicated.

Environmentally friendly wear-resistant coatings deposited by a developed rotating flexible tool (metal wire brush) form a layer without visible boundaries inside the coating with a thickness of 3–7 μm. Durometric studies of single-layer coatings (copper, brass, bronze, and antifriction composite consisting of tin, lead, and zinc) and two-layer coatings in combinations of copper-composite and brass-composite showed that the hardness of the latter exceeds the surface hardness of steel samples by 1.2–1.9 times. Single-layer copper M1 (HV0.02 from 1862 to 2254) and two-layer M1-composite (HV0.02 from 1960 to 2362) coatings have the highest microhardness. X-ray tensometry showed that cold-hardening is formed in the surface layer of the sample under the coating: the calculated values of σφ are σφ = 225 MPa for the copper layer and σφ = –280 MPa for the steel base adjacent to the copper. Metallographic studies showed that the formation of the two types of surface structures differs by the absence or presence of an intermediate zone located between the coating and the deformed base. The intermediate zone is formed when the tension is more than 1.8–2 mm. According to a qualitative estimate, the continuity of the coatings is 90–100%, and the porosity is 18–25%.

A phenomenological model of the kinetics of austenite decomposition of low-carbon low-alloy high-strength steels is presented. The model is based on experimentally obtained empirical dependences linking the transformation rates with the specific power of the heat flux from the metal volume and with the temperature of this volume. This model was used to implement the finite-difference scheme to solve the problem of heat conduction in a medium with internal heat release sources. The digital twin of the cooling process, which includes the specified calculation procedure, is integrated into the TLS 5000 automation system of PAO Magnitogorsk Iron and Steel Works. The determined mass fractions of austenite decomposition products are used for both the design certification of the structural state of rolled products and the construction of statistical models to predict mechanical properties.

Orientation microscopy (EBSD) is used to study structural and textural states through the thickness of pipe steel strips after a controlled thermomechanical treatment. It is shown that texture formation in the form of a selection of components (3 – 7) with a large number of versions of crystallographic orientations, arising with shear phase transformations in accordance with the orientation ratios, suggests presence within the steel structure of elements limiting the number of possible α′-phase orientations. It is proposed that these elements are special boundaries formed during hot rolling close to boundaries RSU Σ3 and Σ11 between deformed austenite grains.

This article presents a review of current results of theoretical and experimental studies of the specific features of the structure that is formed in high-strength low-alloy steel in the process of hot rolling and which determines the properties of the steel. The current concepts of the physical processes that are developed at different stages of a thermomechanical treatment depending on the temperature–strain-rate regimes and chemical composition of the steel are considered. Particular attention is paid to the problems of the formation of the structural state that continue to be debated. The simulation methods of different scale level used to solve the problems of controlling structure formation at all stages of thermomechanical processing process are discussed.

A technique is developed for evaluating the impact-abrasive resistance of cast specimens, which allows simulating the conditions of impact and abrasive wear when changing the following factors: impact energy, abrasive impact angle, abrasive type, and its consumption and grain size. The complex experiment results for five carbide-promoting elements effect on abrasive (AR), impact and abrasive (IAR), and antifriction (AFR) steel resistance in the cast and hardened states are presented. The possibility of using the new technique for evaluating wear resistance and optimizing the composition of steel operating under impact-abrasive effects is shown.

The paper describes an analytical model for calculating an extreme pressure lubricant layer thickness with an allowance for oil absorption capacity of contacting surfaces. The model is practically assessed in laboratory conditions. The experimenting work shows that the speed of the relative displacement of contacting surfaces and the oil absorption capacity of their rough layers contributes to the thickening of the lubricant. The analysis of the results shows that it is the oil absorption capacity of rough layers that has the strongest influence on the change in the thickness of the extreme pressure lubricant layer.

In this work, a simulation model of the thermal state of the work rolls at the hot rolling mill 2000 (m) of Public Joint-Stock Corporation Magnitogorsk iron and steel works (PJSC MMK) is built. A neural network was used as a tool for adjusting the thermophysical transfer coefficients of hot rolling mills. The constructed neural network is a multilayer perceptron, consisting of an input layer, two hidden layers, and an output layer. The neural network is implemented in PyTorch, a scientific computing package based on the interpreted Python programming language. To train the neural network, we used the basic data array obtained from the control system of the hot rolling mill. During industrial experiments, the temperature of the work rolls was measured using HotFind-DXT series thermal imagers developed by SDS. A neural network has been built that allows adapting the thermophysical heat transfer coefficients with an average relative error of 11.7%. A neural network will speed up and simplify the selection of thermophysical coefficients for models of the thermal state of work rolls and adequately assess the current thermal state of work rolls during the rolling process. Using a neural network, a model of the thermal state of work rolls was developed

The article discusses the process of wire drawing of circular cross-section. The study of stresses of wire drawing in conditions of plane plastic flow was held. As theoretical framework the study was adopted the method of characteristics, a special case, having the definitive decision. Stresses during wire drawing are defined by decomposing the decision into two components of plane strain and the superposition of these decisions. The results of theoretical solution of the problem of wire drawing were used to determine the coefficients of friction on the surface of contact of the tool and the work piece during the deformation of steel with a diameter of 5.5 mm. It is recommended to use two-dimensional methods of solution in the analysis of the process of wire drawing in conditions with a high hearth of plastic deformation (with the relative height of the hearth of plastic deformation 2 and bigger). The theoretical dependences between the friction coefficients at the contact surface of the work piece and the tool was obtained. The obtained values of coefficients of friction can be used over solving the task of the wire drawing in conditions with a high hearth of plastic deformation.

Самодурова Марина Николаевна, канд. техн. наук, доцент, доцент кафедры процессов и машин обработки металлов давлением, Южно-Уральский государственный университет, г. Челябинск; mar-samodur@yandex.ru, samodurovamn@susu.ru. Огарков Николай Николаевич, д-р техн. наук, профессор, заведующий кафедрой технологии машиностроения, Магнитогорский государственный технический университет им. Г.И. Носова, г. Магнитогорск; ogarkovnikolai@mail.ru. Платов Сергей Иосифович, д-р техн. наук, профессор, заведующий кафедрой машин и технологий обработки давлением, Магнитогорский государственный технический университет им. Г.И. Носова», г. Магнитогорск; psipsi@mail.ru. M.N. Samodurova1, mar-samodur@yandex.ru, samodurovamn@susu.ru, N.N. Ogarkov2, ogarkovnikolai@mail.ru, S.I. Platov2, psipsi@mail.ru 1 South Ural State University, Chelyabinsk, Russian Federation, 2 Nosov Magnitogorsk State Technical University, Magnitogorsk, Russian Federation

The results of studying the surfaces roughness of rolls, dies, and workpiece are presented and analyzed. Recommendations are formulated on selecting rational surface finishing methods for rolls and dies and methods for preparation of blanks for drawing. The oil absorption capacity of surfaces depending on their roughness caused by the machining method used is determined. The results can be used for choosing surface finishing methods, tools, and materials, depending on the intended metal-forming process.

In this paper, the modeling of a roll roughness transfer process to the strip in terms of skin-passing conditions was carried out. In the present paper, the analysis of the strain–stress state of material imprinted into microcavities of roll face is made, for which reason the latter is presented in the form of V-shaped grooves. The model of roll roughness transfer to the strip was developed by taking into account the real distribution of material in the rough layer of the roll and the strip, as well as according to the type of roll processing and skin-pass conditions that allows evaluating the degree of filling a singular microcavity under known pressure values of the strip on contact with a roll, friction coefficient, roll roughness parameters, and skin-pass conditions. The findings afford to forecast a reproduction of roll microrelief of the surface of deformed strip.

The materials used for preliminary graphitizing treatment of cast iron melt (pre-modification), of which silicon carbide has the greatest technical and economic advantage, are considered. The features of the graphitizing effect of silicon carbide during the preparation of a gray cast iron melt on its structure and properties in standard cylindrical samples and clutch plate castings are analyzed. It is shown that its graphitizing effect on the cast iron melt begins to partially manifest itself already at the stage of introduction into the furnace and enhances the action of the main graphitizing modifier during subsequent ladle treatment as a result of a decrease in the content of interdendritic graphite in the microstructure.

There are many problems when creating digital doubles. One of which is the definition of the source data: in this case, the definition of private reductions (coefficient ratios) in a continuous finishing group of stands of the broadband hot rolling mill 2000 of PJSC Magnitogorsk Iron and Steel Work. Algorithms were developed to calculate the thickness of the breakdown bar, the number of stands involved, power required for rolling and coefficient ratios to solve this problem. The algorithms are based on well-known solutions (the Imai method) using neural networks. The training of neural networks was conducted on a sample collected for the period from 01.01.2017 to 01.01.2019 work of the mill in the PyTorch library of the interpreted programming language Python. The average error ϵME of the calculation of coefficient ratios (according to the developed algorithms with neural networks) does not exceed 8.9% and the standard deviation σ does not exceed 0.074. © Published under licence by IOP Publishing Ltd. This work is carried out within a framework of the government order (No. FZRU-2020-0011) of the Ministry of Science and Higher Education of the Russian Federation.

Scanning electron microscopy with orientation analysis by the electron backscatter diffraction (EBSD) method is used to study microstructures and textures formed in low-carbon low-alloy pipe steel after thermomechanical controlled processing (TMCP) and subsequent quenching with cooling rates of 50 to 700 °/s. It has been established that, in the range of industrial rates of cooling between 50 and 350 °/s from austenitic regions, the γ→α transformation starts at temperatures of 700-670 °C and proceeds by the shear mechanism. As a result, a bainite structure of different dispersity with martensitic inclusions is predominantly formed. © 2018 Author(s).

The article is devoted the experimental studies of deformation and temperature parameters of rolling the pipe steel on the rolling mill 5000 PJSC “MMK”. Knowledge of the regularities of the change in the surface temperature of work piece during hot rolling under the conditions of thermo mechanical deformation processes is of great theoretical and practical importance. The temperature conditions determine the energy and force parameters of rolling, as well as the mechanical properties and microstructure of the finished products. The experimental rolling was carried out in two stages: roughing at 6 passes at a temperature of 1050-900 ° C and finishing at 18-20 passes at a temperature below the start of the phase transformation of 900 ° C. The finishing rolling has been carried out in a two-phase region at the stage of polymorphic transformation in the steel. Significant differences in the nature of temperature changes at different stages of rolling are revealed.

The article presents the investigation of the thickness of lubricating film between contacting surfaces in heavy loaded friction units, taking into account oil absorption of rough layers. Oil absorption index depends on the kind of mechanical treatment of the surfaces and makes it possible to determine necessary characteristics of the used lubricant at the design stage of a friction unit.

The axial stress, absolute margin of safety, and Perlin’s safety factor of wire are calculated, and assessment of the shaping efficiency in drawing round nonhollow wire is discussed. With optimal drawing angle, when the axial stress is minimal, maximum margin of safety and shaping efficiency will be observed.

The article is devoted to the study of mechanical properties of pipe steels after rolling on a broadband hot rolling mill. Using the methods of mathematical statistics, a close pair correlation between all the characteristics of the mechanical properties of hot-rolled sheet pipe steel is revealed. The results are obtained in production practice, they create additional opportunities to verify the results of expensive mechanical tests of pipe steels in order to reduce the cost of testing and improve the reliability of the results of their evaluation.

The fraction for forming texture of rolls surface of the training mills is investigated in this work. The fraction from various manufacturers has been estimated by comparing the most important characteristics. Metallographic studies of the steel fraction microstructure were carried out on the MEIJI 2700 optical microscope (Japan). Automated processing of measuring results of various shapes indenters microhardness was conducted. Comparing the obtained results with the characteristics declared by the manufacturers was carried out. The rolling roll surface microstructure with which the texture of the cold-rolled strip surface is formed, is investigated in the paper. Roller steel widely used at present as well as the most common methods of rolling roll surface microrelief forming, such as mechanical and electroerosion ones, are discussed in the work. It was established that with the electroerosion method, a more uniform structure with a smoothly changing microrelief was formed on the surface of the roll as compared with the mechanical action of the abrasive. According to the results of the research, recommendations were formulated on the use of the fraction that has the best performance characteristics and which allows one to obtain surface roughness by transferring it to the surface of a cold-rolled strip in accordance with the requirements of consumers.

The article is devoted to an experimental study of the influence of thermo-mechanical processing parameters on the microstructure of pipe steel. Rational temperature-time modes of hot rolling and parameters of accelerated cooling, which allow obtaining a structural state that ensures the achievement of the required complex of consumer properties were determined.

Roughness is an important factor in the working properties of instruments. Roughness determines such working properties as durability, wear resistance from detritions, density of combinations, chemical fortitude and appearance. A method for evaluating the roughness of wear–resistant electric-spark coatings on a metal cutting instrument and a specimen of fast-cutting steel is a complex parameter of roughness (Δ). Complex parameter of roughness (Δ) allows more accurately estimating the surface roughness after smoothing the mineral ceramics of an electrophysical coating and others types of surface treatment.

To eliminate the main reason for the jamming of continuous-caster rollers-the entry of water, scale, etc., into the region of the bearing assembly-designers have developed a new assembly with rubber and fluoroplastic seals. The seals are composed of rubber (grade TKMShch) and fluoroplastic (fluoroplast-4) rings. To reduce the friction coefficient, the shaft is clad with brass before the fluoroplastic is applied. The bearing cap is cast iron. Mobile-Gris is used as a protective lubricant. A bushing which is kept from rotating by a pin is installed between the shaft and the cap to protect the shaft from wear. The bushing is also clad with brass and then covered with the fluoroplastic to reduce friction.

Improvement of relatively thick strip (16–20 mm) produced on the OAO MMK 2000 broad-strip mill is considered. Artificial neural networks may be used to optimize broad-strip hot rolling, so as to obtain the required mechanical properties of the strip produced. High surface quality of the strip may be ensured on the basis of finite-element models for predicting the behavior of surface defects on rolling and hence identifying effective rolling conditions.

A total of 68 children and adolescents suffering from tuberculosis, chronic pneumonia in the phase of exacerbation, pulmonary cysts and hamartochondroma were examined for the phagocytic activity of alveolar macrophages. In pulmonary tuberculosis, the low absorption properties of alveolar macrophages were established in all the phases of a specific process. The patients afflicted with chronic pneumonia were characterized in the phase of exacerbation by discreteness of the parameters of the activity of alveolar macrophages in the bronchoalveolar lavage fluid withdrawn from the focus of inflammation: the absorption activity increased whereas bactericidal one reduced.

To study the cellular component of local immune defence, bronchoalveolar lavage fluid (BALF) was examined in 69 patients: 24 children and adolescents with primary tuberculosis and 45 patients with secondary patterns of tuberculosis complicated by catarrhal and purulent endobronchitis. With no appreciable lesions in the bronchial mucosa the cellular composition of BALF and functions of alveolar macrophages (AM) in patients with primary tuberculosis are determined by the phase of specific process. In secondary tuberculosis associated with endobronchitis, the cellular composition of BALF is mainly determined by the character of bronchial pathology whereas AM function by the patterns of both specific and nonspecific processes.