When analyzing a number of phase equilibrium diagrams of various types of systems, the regular relationship was found during the formation of phase crystallization fields in the form of a correlation dependence of the osmotic coefficient of a crystallizing component on the ratio of its activity in the liquid and solid phases. The Bjerrum-Guggenheim osmotic coefficient serves as a measure of the deviation of the energy properties of a real system from the ideal one described by the Schroeder-Le Chatelier equation. Mathematical expressions for the liquidus and solidus lines are obtained in the form of semi-empirical dependences on a single analytical basis, which make it possible to calculate the temperature dependence of the composition. Thus, a theoretically substantiated method for the mathematical description of the lines of monovariant phase equilibria has been developed, based on the regularities of the behavior of components in the melt. Mathematical expressions represent the crystallization fields of the phases of the MnO-SiO 2 system for the corresponding components and compounds using the Schroeder-Le Chatelier equation and the correlation dependence of the osmotic coefficient Ф', experimental and calculated data of the Bjerrum-Guggenheim osmotic coefficient (Ф i ) are calculated. The type of variation in the Bjerrum-Guggenheim osmotic coefficient depends on the intermolecular interaction of the components in the melt. If only van der Waals forces of interaction between the components in the melt prevail, then a correlation dependence is observed. When groups from the initial compounds are formed in the melt, or processes of dissociation or, conversely, association occur, the osmotic coefficient is described by a curvilinear dependence. The paper presents mathematical expressions for the fields of crystallization of phases of the MnO-SiO 2 system in the form of semi-empirical dependencies. The nature of the change in the Bjerrum-Guggenheim osmotic coefficient of the crystallizing component depending on the ratio of its activity in the liquid and solid phases is shown.

This study is devoted to influence of the temperature procedures of high-manganese austenite steel casting on formation of the internal structure and properties of castings. An example of a high-manganese austenite steel Fe-1.1C-16Mn-0.8Si-1.3Cr-Mo-Ni is considered, which differs from the generally accepted composition of Hadfield steel (110G13L) by an expanded Mn content and combined alloying with carbide-forming elements. The study applied an approach to choosing the optimal casting temperature, which is implemented using pre-computer modeling of the cast structure by the Cellular Automaton Finite Element method, followed by verification on physical samples. An analysis of the microstructure of the experimental samples obtained at the selected casting temperatures indicates the accuracy of conducted calculation: the discrepancy between grain sizes does not exceed 5 μm (4.4 %). Rational temperature contributes to formation of more fine microstructure and, accordingly, a high level of mechanical properties: pouring the alloy under study at 1390-1410 °C makes it possible to obtain an average grain size of 113-116 μm, minimal mass loss upon contact with the abrasive (1.74-1.81 %) and increased impact strength (28.5-28.3 kgf•m/cm 2 ). Subsequent approximation of the calculated values and obtaining a regression equation using the Reduced Major Axis method allows in practice to predict reliably (with determination coefficient 0.826) the grain size of the casting at the selected casting temperature without using additional software.

The authors consider the problem of creation, development and putting into practice digital twins for technological processes. Use of digital technologies in metallurgy allows to cut the expenses of manufacturing process, to improve quality of metal products and to widen their grade and dimension ranges. The leadership of Magnitogorsk Iron and Steel Works (MMK) formulates the ambitious aim to create a digital twin for a full-scale technological site, with consequent distribution of a digital platform to the whole enterprise. As soon as production stage is the main part of each metallurgical company, providing receiving of the required profit, stage-by-stage achievement of the formulated goal is starting from the industrial component. Step-by-step process of creation of a digital twin is considered for the section rolling mill 170 at Magnitogorsk Iron and Steel Works. This technological process is also combined and can be presented as separate conditional blocks, such as metal heating, rolling and cooling. Based on the positive result of the successfully realized project of the digital twin for the air cooling lines, it was decided to use this practice to the whole technology of manufacture of section products at MMK 170 rolling mill. The main aims and tasks for the examined project are formulated, it will allow to obtain the first Russian experience of creation of the full-scale digital twin of an industrial object. The features of operation of up-to-date digital twins are considered and the functional restrictions are defined. Structural scheme of the created complex dynamic mathematical model was designed as the base for operation of the ready solution. Expected industrial effects were formed in narrow cooperation with MMK specialists. Taking into account the technical and technological risks, the restrictions for implementation of the digital twin are determined: operation in the advising conditions, use of the complete data spectrum about the object for full-range possibility of digital copy simulation, industrial testing in the real operating conditions of the rolling mill until achievement of preset authenticity. When considering the prospects of creation of similar solutions for other technological objects (rolling mills or other technological stages), up-to-date features of their further development and integration within the company range are revealed. They testify that created digital twin can be a universal testing field, promoting appearance of domestic integration platform for digital twins. Import substitution in this industry is critically important for Russia, because there no such technical solutions at the national market.

Essential part of strategic objects in oil/gas and machine-building complexes, transport industry and bridge building are operated in the conditions of simultaneous effect of low temperatures, static and dynamic loads as well as intensive wear. High-strength cold-resistance steels are considered as one of the materials, which can be used in such conditions. At present time, providing of principally new qualitative combination of properties of such steels is the actual scientific problem; the main parameters of these steels should be superior to the existing international analogues, they should present the unique combination of high strength, ductility as well as wear and cold resistance at the temperatures down to -70 °C. However, improvement of strength properties and hardness of rolled products leads to substantial decrease of cold resistance and ductility of steel; so, reaching of combination between high strength state and cold resistance is possible during definite structural and phase transformations, occurring in steels. Regularities of phase and structural transformations, occurring in high-strength cold-resistant steel with the following chemical composition (%, mass.): 0.15 C; 1.5 Mn; 0.20 Si; 1.7 (Ni+Cu); 0.035 (Ti+V+Nb); 0.0040 B during continuous cooling, were established in this research. Thermokinetic diagram of decomposition of overcooled austenite was built. It is shown, that steel with above-mentioned composition, which contains mainly if lathe martensite with small amount of bainite, is forming during continuous cooling with rate within the range 10-110 °С/с. Most part of martensite with lathe morphology can provide high strength of the researched steel, presence of dispersed structure of low-carbon bainite can provide high characteristics of resistance to brittle destruction, and hardness more than 350 HBW, which is achieved during cooling with rate more than 50 °С/с can provide high wear resistance.

The article is devoted to the development of the heat treatment mode for TRIP steel with a new chemical composition. Aluminum was chosen as an additional alloying element, since by the nature of its effect on the stabilization of overcooled austenite in the temperature range of diffusion transformation, aluminium is similar to silicon, the main alloying element for steels containing metastable austenite in the structure. For the correct development of the heat treatment mode of modified TRIP steel, the critical points were determined by differential scanning calo-rimetry. After determining the temperature limits of the two-phase area, the cast samples were subjected to heat treatment. For all the studied samples, the exposure temperature in the bainite area was 400 °C, and the annealing temperature in the two-phase area was changed from minimum to maximum. The exposure time for both intervals was 20 min and was the same for all samples. As a result, the dependence of the amount of metastable austenite in the structure of modified TRIP steel on the annealing temperature was determined in the intercritical interval (area between the points A c1 and A c3 ). This dependence is of an extreme nature. The article also provides a comparison of the microstructure of modified steel in the cast state and after heat treatment. The analysis of the microstructure allowed us to conclude that continuous monotonous cooling of aluminium-modified TRIP steel made it impossible to obtain a structure containing metastable austenite. In addition, the modified chemical composition of TRIP steel contributes to sufficient stabilization of overcooled austenite in the temperature range of pearlite transformation. The data obtained in this work made it possible to develop a mode of heat treatment of TRIP steel modified with aluminium.

This article discusses application of mathematical modeling based on the finite elements method (FEM) to analyze the process of rolling clad sheets and strips. Examples of studies are given, in which FEM was used to analyze the stress state at the interface between layers, to consider the effect of rolls speed mismatch on the rolling process, to determine the criteria for layer adhesion and other process parameters. However, some of these studies do not take into account a number of aspects that can increase modeling reliability. The article considers the most important aspects of development of the model for rolling clad sheets based on the FEM. Two main ways of modeling the clad and base layers are described, setting different properties of the same body or modeling layers by different contact bodies. Particular attention is paid to the choice of model parameters and the correct division of layers into elements to avoid loss of contact and penetration of elements into each other. This article also provides recommendations on the choice of friction coefficients for various contact pairs. When choosing friction coefficients, it is necessary to take into account the materials of the contact surfaces, their condition and operating conditions. In addition, the friction coefficient is an important factor affecting the accuracy of modeling, and it is recommended to compare the simulation results with experimental data to obtain its refined values. Examples of development of the models based on the FEM are given, which were adapted according to the results of laboratory experiments and applied to calculate the parameters of industrial rolling. Satisfactory convergence of modeling results with the results of industrial rolling is shown.

The article presents the research results aimed at studying the influence of the chemical composition and thermal conditions of crystallization on the level of the properties of cast iron and wear-resistant steels, which are used for manufacture of replaceable components of mining industry units as well as metallurgical production facilities. The literature review states that the level of properties of cast products is significantly influenced by both the alloy chemical composition and the thermal conditions of casting formation in the mold. Managing the process of microstructure of cast products formation at the stages of primary and secondary crystallization, it is possible to obtain various parameters of the structures in the cast state of products. The resulting cast structure will determine further the parameters of microstructure after heat treatment, as well as the level of operation and mechanical properties. Experimental castings made of high-manganese steel, hypereutectoid steel and cast iron for rolls were obtained in laboratory conditions. In order to assess the complex influence of ther-mal conditions of formation of the cast products and the alloy chemical composition, experi-mental castings were obtained in casting moulds that are made from materials with different heat storage abilities. Further, the obtained cast products were tested in the conditions of abrasive and shock-abrasive wear. During the metallographic study of structures of experimental castings, quantitative characteristics of microstructures in the form of grain sizes, amount of carbide and graphite phases were determined, and the influence of thermal conditions of formation of the cast product in the mould on these parameters of microstructure was assessed. Moreover, the influence of alloying elements and nitrogen on the structure of the selected casting alloys was evaluated. At the final research stage, the operation and mechanical properties of the obtained castings were studied. The complex influence of chemical composition and thermal conditions of casting formation a casting mould on the level of operation and mechanical properties was established. The concentration intervals, in which the properties of experimental castings have maximal values, were determined.

Conventional heat-resistant die ferrite-pearlite steels with carbide and mixed (carbide-intermetallic) hardening are softened very intensively after heating above 350-400 °C, what leads to rapid tool failure. Heat-resistant austenite steels and alloys also does not solve the problem of operating resistance of die tools, due to their tendency to cracking, poor machinability by cutting, high cost and scarcity of alloying elements included in their composition. Investigations of structural state, thermophysical properties and physical and technical characteristics of the developed die steel 70Kh3G2FTR(m) were carried out in this work under thermal exposure. Considerations about the structural stability of the alloy are confirmed by the data of X-ray diffraction analysis within the temperature range from -187 °C to 300 °C, as well as of transmission electron microscopy (TEM) at all stages of heat treatment and thermal exposure. It is shown that the developed steel 70Kh3G2FTR(m) after the proposed heat treatment procedure is characterized by thermal and structural stability within the studied temperature range up to 450 °C, due to influence of a microalloying complex in the form of dispersed carbide inclusions registered by TEM. The dispersion hardening mechanism in the developed alloy prevents motion of dislocations during heating, distorts and seals the atomic crystal structure, slowing down diffusion processes and migration transmissions of grain boundaries.

This research is devoted to optimization of the detection system for damages of blades of a gas turbine engine in non-stationary conditions. The system is based on the approach on the method, when capsules with active substance are placed in a steel blade body, then a capsule is bursting due to difference of pressures during the process of crack propagation; as a result, ejected active substance is registered. The problem of this research is connected with optimal distribution of capsules, which contain active substance, in a turbine blade body. The research technique was developed for a modeling problem, when a steel turbine blade with constant cross section, having tensile crack and subjected to the action of extension centrifugal force, was observed. Development of the model with optimal distribution of capsules was based on assessment of pre-critical crack growth: it was required to distribute the capsules along the median line of blade cross section in such way, that it would be possible to detect the crack of pre-critical growth. Analysis of ultimate state of a blade with crack was carried out on the base of stress intensity coefficient, which allows to take into account the feature of crack location and to determine its critical length when its accelerated growth takes place. Variation of the pressure inside a capsule, required for its bursting depending on opening of crack sides. The suggested model takes into account location of the capsule with active substance relating to crack opening sides. Calculation of minimal number of capsules in blade bode depending on pressure inside the capsule and rotating speed of blades was conducted on the example of the steel turbine blade R-5530 B. The obtained dependences allow us to find the optimal combination between the geometric and physical characteristics of the crack detection system and the minimal number of capsules. The application of the proposed approach to the optimal distribution of capsules along the median line of the blade cross section will increase the efficiency of use of the damage detection system in turbine blades in non-stationary conditions, thereby ensuring the safety of operation of gas turbine engines in aviation technology.

A critical comparative analysis of technologies for preparation of ore and technogenic materials before metallurgical processing was conducted in this research. Briquetting, sintering, pelletizing and direct use of fines (processing without agglomeration) were conditionally emphasized among these technologies. The roller-press briquetting, vibropressing briquetting and stiff vacuum extrusion constitute the basis of the briquetting technology, advantages and disadvantages of these methods were analyzed that accompany briquetting. A few modern briquetting plants in CIS countries were commissioned. The main features were provided for agglomeration via pelletizing method. The sintering technology was reviewed, as well as data on new sintering plants in Russia. The technologies of direct processing of fines, which are conditionally divided into "fluidized bed" and direct processing of the fines in the melt, were briefly considered. The restrictions for processing in a "fluidized bed" were described as well as reduction characteristics of pellets and briquettes, which are often accompanied by swelling (variation of linear dimensions). The main causes of swelling of iron ore materials during reduction were described. The political and ecological factors of production and the problems of hydrogen power engineering were examined. The characteristics of total carbon dioxide emissions were provided for different production. It was shown that smelting of briquettes and pellets in arc furnaces, which are preliminary metalized by the gaseous reducing agents, are characterized by the lowest amount of emissions among the existing technologies. At the same time, the maximal carbon dioxide emissions are observed when using the alternative technologies, which utilize lump coal as a reducing agent.