The work presents generalized experience in the development and implementation at PJSC Severstal of technological measures to extend the campaign of blast furnace No. 5. The authors carried out an analysis, identified and described the problem areas, generalized the principles for ensuring the safety of the shaft lining, boshes and metal receiver of the blast furnace. The results of a study of the working space of blast furnace No. 5 in 2006 are also presented. The identified technological factors ensure an increase in duration of the unit campaign. Technolo­gical measures are given for: washing the blast furnace hearth, reducing chemical erosion of the carbon blocks of the hearth and flange, forming a protective skull in the blast furnace shaft, special methods for loading solid coke substitutes, and organizing an effective structure of the charge column in the blast furnace. It is necessary to use digital models integrated into the blast furnace expert system for operational control of blast furnace technology. The results of the current blast furnace campaign were compared with previous ones. It was proven that the systematic use of all elements of the developed technology makes it possible to achieve high economic indicators while exceeding the standard duration of the campaign by 1.75 times. Experience in technology development made it possible to increase the furnace campaign duration to 17.46 years, achieve a reduction in specific coke consumption by 15.9 %, and increase the specific consumption of natural gas for cast iron smelting by 46.4 %; reduce the specific carbon consumption for cast iron smelting by 6.3 %. 

In the development of advanced energy saving technologies in the metallurgical industry, a comprehensive approach to managing energy flows is crucial. This article presents an in-depth analysis of the steelmaking and metallurgical industry in China and Russia, focusing on the evolution and current shortcomings of energy saving methods in metallurgical processes. The authors thoroughly analyze various technological processes, including sintering, coking, pellet production, iron production in blast furnaces, steel production in oxygen converters and electric arc furnaces, as well as steel rolling, identifying significant potential for enhancing energy efficiency and reducing harmful emissions. The main outcome of the research is the  development of structural models of technological processes based on the concept of energy saving “temperature matching, cascade utilization, and global linkage”, covering key stages of steelmaking. These models provide detailed descriptions of the role and interrelation of each process within the complete metallurgical cycle and combine into a comprehensive structural model of steelmaking technological process. The model includes not only specific operations and characteristics of each stage but also explains how these processes interact and depend on each other, forming an integrated and interconnected system of metallurgical production. This model encompasses comprehensive temperature-pressure and production links, providing a theoretical basis for the development of mathematical models of energy saving and the design of corresponding computer applications. The structural model of steelmaking technological process is important for understanding and optimizing the entire process of metallurgical production, contributing to its energy and ecological efficiency.

Created one of the first and studied more than 20 years ago, high-entropy five-component alloys CoCrFeNiMn (Cantor alloy) and CoCrFeNiAl still attract the attention of researchers in the field of physical materials science due to their possible application in various industries because of their successful combination of strength and plastic properties. To date, a large amount of experimental materials has been accumulated on the ways to control the properties of these alloys. This article reviews the publications of domestic and foreign authors in two areas of improving the properties of these alloys: alloying, precipitation and heat treatment, and the use of CALPHAD phase diagrams. In the first direction, the role of alloying with B, Al, V, Si, Nb is analyzed; γ and γ′ nanoprecipitations, various modes of thermal and deformation processing. It was concluded that it is necessary to conduct experiments on the alloying of HEAs with Zr and Nb, which have proven themselves well in hardening steels. Creation and modification of the properties of five-component HEAs is possible using the CALPHAD computer programs developed for calculating state diagrams. The results of publications on the thermodynamic description of five-component alloys analyzed in the article are confirmed by comparing the phase diagrams with the available experimental data. In one of the analyzed works on the phase formation of five-component HEAs consisting of Co, Cr, Fe, Ni, Al, Mn, Cu, 2436 compositions were considered, which made it possible to determine 1761 variants of reliab­le prediction of the formation of bcc/B2 and fcc phases, bypassing amorphous phases and intermetallic compounds, thereby designing a certain level of mechanical properties. It is shown that the design of a new generation of HEAs is possible based on calculation of the CALPHAD phase diagrams.

The processability of a material is directly related to the possibility of its production, operation and maintainability. One of the most important indicators of the processability of any metal is weldability. Austenitic steels with a high nitrogen content proved themselves as high-strength, corrosion- and cold-resistant materials, but the issue of their weldability is still not fully understood. The lack of welding filler materials on the market specifically designed for welding high-nitrogen steels is the primary obstacle to solving this problem. Thus, the goal of the work was to develop and obtain a laboratory sample of high-nitrogen welding wire. Based on calculations of nitrogen solubility and the phase composition of the weld metal, the chemical composition of Cr – Mn – Ni – Mo – V, N steel was selected for this wire. A defect-free ingot with 0.57 % N was obtained, and wire with a nitrogen content of 0.57 wt. % was produced using hot plastic deformation and drawing methods. Testing of this wire to obtain a welded joint of austenitic cast steel, close to it in chemical composition, with the welding process carried out according to the developed technological recommendations, made it possible to obtain a defect-free welded joint without loss of nitrogen in the weld metal. With a microhardness of the base metal of 252 HV₅₀, due to the alloying of the welding wire steel with nitrogen and vanadium, the metal of the weld and fusion line had a high microhardness (278 and 273 HV₅₀, respectively), significantly exceeding the microhardness of Cr – Ni cast austenite. The metal of the welded joint has high strength (0.9 of the base metal strength) and high impact toughness. The fracture of impact samples is characterized by a dimple structure characteristic of viscous materials. According to the obtained results, the new welding wire showed itself to be a promising material for welding austenitic high-nitrogen steels.

Currently, the use of additive technologies in industry is becoming more promising. The intensification of development of 3D technologies leads to the need for a more thorough study of the structure and properties of metals obtained by this method. In this paper, the effect of heat treatment on structure of the metal deposited by Wire Arc Additive Manufacturing (WAAM) is considered. The paper describes the effect of quenching at various temperatures and annealing on the structure of austenitic steel 07Cr25Ni13. As a result of the work, it was found that during metal deposition, crystallization occurs according to the FA type with the formation of a coarse dendritic structure with mainly skeletal and vermicular morphology, consisting of δ- and σ-phases. It is noted that quenching at 1070 ℃ practically does not change the metal structure. Despite the fact that quenching at elevated temperatures (1100 ℃) leads to partial dissolution and spheroidization of the dendrites released during surfacing, there are no cardinal structural changes. The most complete dissolution of the dendritic component occurs during quenching at 1150 ℃. The structure after this procedure is predominantly austenitic, remains of the dendritic component are represented by small spherical inclusions. The steel structure after annealing (1150 ℃) practically does not differ from the structure obtained after quenching at the same temperature. A significant increase in grain size, typical for austenitic steels, is not observed in this case. Based on the structure obtained after heat treatment, the most promising treatment options for future physico-mechanical properties are quenching and annealing at 1150 ℃.

Mechanisms of ∑5(210)[001] and ∑5(310)[001] symmetrical tilt grain boundaries migration in bicrystall Fe – 10Ni – 20Cr samples under irradiation were investigated by means of molecular dynamics method. The density of radiation defects grows quite quickly up to a dose of ~0.02 dpa and then reaches saturation. This is due to balancing of the radiation defects generation and annihilation rates. It is shown that at the early stage of irradiation, grain boundaries began to deviate stochastically from their initial positions due to interaction with cascades of atomic displacements and absorption of structural defects. During irradiation, the grain boundary region thickened and became rough. With an increase in the radiation dose, size of the clusters of point defects (tetrahedrons of stacking faults and dislocation loops) increased. Interaction with large clusters of point defects led to the formation of bends on initially flat surfaces of grain boundaries. At small distances between the boundaries, the high driving force between the curved surfaces of grain boundaries significantly increased the rates of their approach. The average migration rates of grain boundaries before their direct interaction with each other were approximately 0.8 m/s. As a result of their approach, the grain boundaries were annihilated, the potential energy of the sample decreased abruptly, and the grains merged. The annihilation of ∑5(310)[001] grain boundaries required twice the radiation dose compared to the ∑5(210)[001] grain boundaries . The direct interaction of grain boundaries with each other abruptly increased the velocity of their migration due to the emergence initiation of a driving force from the curved sections of the grain boundary surfaces. Influence of the radiation dose on deformation behavior features of the samples under uniaxial strains was studied. With an increase in the radiation dose, the elastic limit decreased rapidly and reached saturation at an irradiation dose of ~0.01 dpa.

Diffusion processes play a key role in formation of the structures of new materials and technological processes of strengthening heat treatments, since diffusion is the reason for redistribution of substances in solids. An urgent task is to develop technologically advanced and effective methods for strengthening materials in order to improve their performance properties. There is an increasing need to improve chemical heat treatment methods, which directly affects the wear resistance of working surfaces, and, consequently, the product service life. Near-surface volumes experience increased loads, so the formation of high-strength layers becomes an important task. Quite a few methods of surface hardening are known, among which carburization, nitriding, nitrocarburization and others are widely used. The most interesting is nitriding, since it increases hardness, strength, fatigue limit, and heat resistance. However, despite the proper advantages, nitriding has a number of disadvantages, including the holding duration and small thickness of diffusion layers. The solution is related to intensification of the technological process by increasing the nitriding temperature, activating the nitriding media or directly the parts surface. All these solutions are aimed at accelerating diffusion processes, both in grain volume and along grain boundaries, the velocity along which is many times higher than the velocity of volumetric diffusion. It may be effective to use a new type of structural metal materials with a multilayer structure of hundreds of layers, with thicknesses in the micron and submicron ranges separated by large angular boundaries. The results of metallographic studies showed the effect of the steel layers interchange in the multilayer metal material on diffusion depth after chemical heat treatment. The authors proposed an accelerate diffusion model of diffusible element along the layer boundaries.

At room temperature, the deformation of most bcc metals, which contain a small amount of interstitial elements, is accompanied by the formation of a Lüders band and its monotonic propagation over the tensile yield area. Within the framework of the autowave concept, front of the Lüders band is a switching autowave, which realizes the transition from a metastable elastically deformable state to a stable plastically deformable state. However, in the temperature range of blue brittleness of mild steels of 423 – 510 K, when the interaction of atoms of the dissolved substance with mobile dislocations takes place, propagation of the Lüders band is accompanied by a discrete flow. The patterns of propagation of the Chernov-Lüders fronts in ARMCO iron in the temperature range from 296 to 503 K and strain rates from 6.67·10^–6 to 3.7·10^–2 s^–1 are considered in this paper. It was established that under these conditions both monotonic and discrete kinetics of front movement can be realized. Regardless of the movement nature, the Lüders deformation and width of the front remain unchanged throughout the entire process. The local strain rate at the front depends on magnitude of the effective stress, and with monotonic kinetics it increases with stress according to an exponential law, and with discrete kinetics it increases according to a linear law. This difference is due to different autowave modes that are formed in this case. The autowave of localized plasticity switching corresponds to monotonic kinetics, and the autowave of excitation – to discrete kinetics.

This paper presents results of the studies of hydrogen exposure duration influence on the characteristics of two aviation alloys at atmospheric pressure and room temperature. First alloy (alloy 1) was obtained by hot isostatic pressing, and was used for the manufacture of gas turbine rotor discs. Second alloy (alloy 2) was obtained by directional crystallization, and was used for the manufacture of gas turbine blades. It was determined that microhardness of the samples increased during 1000 h of hydrogen exposure duration. The relative increase of the microhardness was insignificant, and for the sample of alloy 1 it was 2.5 %, and for the sample of alloy 2 – 2 %. Correlation analysis of the XRD diagram parameters indicated positive and negative statistically significant relationships correlation between XRD diagrams peaks parameters, hydrogen exposure duration and microhardness of the samples. It was revealed that XRD diagrams peaks of alloy 1 were broadened and their heights increased during hydrogenation, which can be associated with a decrease of dislocations in the grains and their local accumulation at the grains boundaries. Conterwise, XRD diagrams peaks of alloy 2 were narrowed, which can indicate an increase of dislocations in the material grain structure. XRD diagrams processing demonstrated that the crystallite size and dislocation density for alloy 1 decreased with a delay from the hydrogenation start, but for alloy 2 these parameters monotonically increased, and it corresponds to microhardness changes trends of the samples during hydrogenation.

Corrosion-resistant steels and alloys have a number of unique properties. This allows them to be used in various industries. Despite their name, they are to some extent subject to various types of corrosion and corrosion-mechanical damage. This article discusses cases of corrosion damage of products made of corrosion-resistant steels and alloys in the oil and gas industry. The reasons of material failure can be incorrect exploitation of material, low-quality material of products, and incorrect selection of material for operating conditions. For each group of failure causes the examples from open sources and from the practice of the team of authors of this work are considered. The paper substantiates the importance of preliminary laboratory studies of corrosion-resistant materials and their testing with simulation of environmental factors. It is necessary for reasonable choice under specific operating conditions. It is shown that in practice the reasonable choice of corrosion-resistant materials is not always given due attention, so the seemingly economically favorable solutions may turn out to be incorrect. The main focus is made on the practical side of the issue in order to avoid such problems in the future. The relevance of the work is confirmed by the recent acute problem of substitution of foreign steel grades.

The paper presents the results of a thermodynamic modeling of the chromium and boron reduction from slags of reduction period of argon-oxygen decarburization (AOD) by a complex reducing agent containing silicon and aluminum. Using the simplex lattice method, an experiment planning matrix is constructed containing 16 compositions of the oxide system СаО – SiO₂ – (3 – 6 %) В₂О₃ – 12 % Cr₂O₃ – 3 % Al₂O₃ – 8 % MgO of variable basicity 1.0 – 2.5. The results of thermodynamic modeling are graphically presented in form of dependence of equilibrium distribution of chromium and boron on the slag composition at temperatures of 1600 and 1700 °C. The constructed diagrams make it possible to quantify the influence of the temperature, basicity and B₂O₃ in the slag on equilibrium interphase distribution of chromium and boron. It is established that increasing the slag basicity from 1.0 to 2.5 improves the process of chromium reduction, but restores the boron stability. With an increase in B₂O₃ content in the slag, a slight deterioration of chromium reduction process occurs, while the boron content in the metal increases. With a simultaneous increase in basicity up to 2.5 and a decrease in boron oxide in the slag from 5 to 3 %, the interphase distribution coefficient of chromium is reduced to 1.5·10^–3. Changing the process temperature from 1600 to 1700 °C does not have a negative effect on the process of chromium reduction, but worsens the boron reduction conditions. Based on analysis of the formed slag phases and thermodynamics of the reactions of their formation, it is established that chromium is mainly reduced by aliminum with only partial development of silicothermy. The residual silicon content reduces boron, thereby limiting its concentration in the metal. The results of high-temperature experiments showed high correspondence with the results of thermodynamic studies.

In this paper, the nitriding of chromium ferrosilicon is carried out in the combustion mode under the condition of natural nitrogen filtration. The authors studied the effect of the key parameters (pressure of gaseous nitrogen, diameter and dispersity of starting samples) on the maximum temperature and combustion of the starting powder mixture based on chromium ferrosilicon. The combustion synthesis of chromium ferrosilicon proceeds steadily in the stationary mode with formation of a macrohomogeneous nitrided composition which, according to the results of X-ray phase analysis, contains two nitride phases - chromium nitride and silicon nitride. Interaction of the initial powder with gaseous nitrogen in the filtration combustion mode proceeds by the following probable chemical reaction: 3CrSi₂ + 3Si + 3FeSi₂ + 11.5N₂ = 3CrN + 5Si₃N₄ + 3Fe. Increasing the diameter of the starting samples slightly affects the amount of absorbed nitrogen and slows the propagation of the combustion wave front. An increase in the pressure of gaseous nitrogen increases the amount of absorbed nitrogen and the combustion rate. Increasing the dispersity of the starting powder increases the amount of absorbed nitrogen and the combustion rate. It was found that the combustion reaction is not possible with a dense initial sample. The maximum combustion temperature, depending on the nitriding conditions, varies between 2400 and 2650 °C and increases with increasing gaseous nitrogen pressure, diameter of the initial samples and dispersion of chromium ferrosilicon powder. It is possible to realize nitriding of chrome ferrosilicon in the combustion mode at the pressure of gaseous nitrogen not less than 3 MPa, diameter of initial samples not less than 3.5 cm and size of initial particles not more than 100 μm. Optimal parameters of nitriding are gaseous nitrogen pressure of 5 MPa, diameter of samples 5 cm, size of initial particles less than 100 μm and bulk density of samples (2.23 g/cm³).

In modern industrial and civil construction, various rolled metal products are used in greater volumes. The largest share of them is occupied by rebar profiles produced at small-grade mills. The ever-growing demand for rebar rolling requires an increase in production volumes. The most promising technology in this regard is rolling – separation, which, with relatively low material costs, allows operating rolling mills to significantly increase the production volume of rebar profiles while reducing energy consumption. However, despite the obvious advantages of rolling – separation technology using non-drive dividing devices, it is very difficult to correctly determine the rational modes of conducting the process taking into account the peculiarities of production and equipment layout, which is due to insufficient theoretical knowledge. One of the main problems is determination of the permissible distance in the rolling cage – non-drive dividing device system. The conducted studies allowed us to propose a dependence for determining the maximum permissible distance in the rolling cage – non-drive dividing device system for reasons of longitudinal stability of the strip, taking into account the size and shape of cross-section of the split articulated profile, the nature of pinching, and the backstretch stress. It was experimentally established that when determining the permissible distance between rolling cage and non-drive dividing device, it is advisable to take the length reduction coefficient equal to 0.7.

Slab heating before hot rolling process is necessary for obtaining required metal ductility. The most effective for this purpose are furnaces with walking beams that provide heat supply to all sides of the slab. However, the places of slabs lower surfaces, contacting with water-cooled beams, are shielded from the radiation of the furnace lower heating zones and give the heat to the beams. Previously, the authors developed and programmatically implemented a mathematical model of slab heating in a furnace with walking beams, based on the numerical solution by finite difference method of the three-dimensional heat conduction problem with piecewise defined boundary conditions on the slab bottom surface. In this model, for the open zones of the slab bottom surface, boundary conditions were similar to those on the top surface, and for the zones of contact with the beams were set effective boundary conditions assuming duration of this contact. In this paper, the model was modified to take into account the curvature of the beams and to recalculate the configuration of zones with different boundary conditions on the slab bottom surface for each position of the slab along the furnace. By variant calculations at different values of heat transfer intensity from the slab bottom surfaces to the beams it was determined that curvature of a single beam can significantly change the characteristic of the corresponding “cold” spot, but it practically does not affect the general characteristic of the slab heating non-uniformity. If all fixed beams are subjected to curvature, the final temperature difference across the slab is significantly reduced due to an increase in its minimum temperature. It was found that the influence of beam curvature on the temperature field at the end of heating process is higher the more intensive the heat transfer to the beams is