The article considers the features and characteristics of spreading of neutral gas jets in the gas-dynamic section before interaction with the slag melt, which is further inflated to apply a refractory skull to the unit lining. The flow of a supersonic jet into the working space of the converter after tapping has the wave structure. The model for calculation of attached mass of the surrounding gas located in the converter working space is considered. The problem statement takes into account the known data on gas dynamics during the formation and flow of the jet, which affect the efficiency of turbulent transfer in the boundary layer. The calculation scheme is based on the hypothesis of existence of an initial boundary through which a chemically active gas from the environment penetrates into the gas jet, and the shape of the limit boundary is assumed to be cylindrical with a radius equal to the maximum radius of the first barrel of the non-calculated jet. Numerical calculations make it possible to determine the average mass velocity and temperature in an arbitrary section of a supersonic non-calculated jet before its introduction into the slag melt. The authors describe the influence of the relative temperature θ, nitrogen temperature in front of the nozzle T₀ during spreading of the jet in the converter cavity, and nitrogen flow through the nozzles V_н on value of the attached mass q, the averaged values of velocity and temperature W_x and T_x in an arbitrary cross-section x of a supersonic non-calculated jet in the gas dynamic section. The information obtained can be used in the development of gas-powder purging systems in aggregates and steel ladles, shotcrete systems and the supply of neutral gas jets when replacing oxygen flows during purging and using two-tier tuyeres.

The authors analyzed the state of tool production in Russia. The main manufacturing companies and the main brands of materials used in the production of domestic tools are highlighted. Powder high-speed steels are practically not used in the domestic market, but they are widely distributed in the foreign market of tool steels due to their significant advantages in terms of basic and technological properties (including the possibility of using high-carbon and high-alloy high-speed steels). There is a new group of economically alloyed tungsten-free high-speed steels with a high content of carbon and vanadium, which are practically impossible to manufacture and apply in our traditional technology due to low technological properties. The authors give recommendations on the technology of manufacturing such steels by powder metallurgy and on the modes of their heat treatment. The paper studies a set of properties of these steels, including: basic mechanical properties (hardness, bending strength, toughness, and heat resistance), basic technological properties (pressure, cutting, grinding) and operational properties (evaluated by tool durability during turning). Structural and phase compositions of the steels and their influence on the basic and technological properties were investigated. The compaction mode affects the density of the billets. The paper presents distribution of alloying elements in the microstructure of powder high-speed steel and results of their relative grindability. Also the durability of tools was tested. There are significant advantages of high-carbon high-vanadium high-speed steels, especially in terms of technological properties, compared with traditional high-speed steels. It is possible to produce high-alloy tool steels using inexpensive carbide-forming alloying elements. The steels under consideration can be used to manufacture a wide range of tools, including hot-forming die tools. The use of powder technology opens up the prospect of developing universal economically alloyed powder tool steels.

The sliding of edge and screw dislocations in Hadfield steel and in pure HCC iron (austenite) depending on temperature and deformation rate was studied by the method of molecular dynamics. The complete dislocation appears in the present model immediately in the form of a split into a pair of partial Shockley dislocations separated by a packing defect. The distance between partial dislocations is several nanometres. As the shear rate increases, this distance decreases. According to the data obtained, the energies of edge and screw dislocations in steel are higher than in pure austenite. The energy of the total edge dislocation in γ-iron and Hadfield steel averages 2.0 and 2.3 eV/Å, helical – 1.3 and 1.5 eV/Å respectively. Dependences of the sliding velocity of the edge and screw dislocations on the shear rate and temperature were obtained. The sliding velocity of the edge dislocation is in all cases higher than the screw one, which is explained by the difference in the propagation velocity of longitudinal and transverse waves in the material. With an increase in the shear rate, the sliding speed increases to a certain limit, depending on the propagation velocity of the corresponding elastic waves. At low and normal temperatures, the sliding velocity of dislocations in Hadfield steel is significantly (about one and a half times) lower compared to pure HCC iron. In pure iron, the sliding velocity of dislocations decreases with increasing temperature. However, for Hadfield steel, this dependence is nonmonotonic: as the temperature increases to about 500 K, the dislocation rate increases. That is probably due to the intensification of diffusion of impurity carbon atoms; then, as in iron, it decreases.

The relationship between strain hardening and kinetics of deformation γ → αʹ phase transformation in chromium-nickel steel Fe–19Cr–9Ni–0.7Ti–0.06C wt. % obtained by electron beam additive manufacture was studied under uniaxial static tension at room temperature and at liquid nitrogen temperature. Additively-produced steel had a two-phase (γ + δ) structure with an increased content of δ-ferrite (≈14 %). Post-production heat treatment at 1100 °С (for 1 h) allowed to reduce its volume content down to 6 %, that is, a predominantly austenitic structure in steel was close to those for analogues obtained by traditional metallurgical methods. Plastic deformation of additively-produced steel was accompanied by the formation of deformation αʹ-martensite, the volume fraction of which increased with an increase in the strain and with a decrease in the test temperature. Using the method of magnetophase analysis, it was shown that at room temperature, kinetics of the deformation γ → αʹ transformation was sluggish and it, as well as the stage and magnitude of the strain hardening, weakly depended on the content of δ-ferrite in the structure of steel obtained by the additive method. At the same time, increased content of the δ-phase under these deformation conditions contributed to an increase in the yield strength and reduced elongation to failure of the additively obtained samples. At low-temperature deformation, when the rapid kinetics of deformation γ → αʹ transformation was observed, the formation rate of αʹ-martensite under plastic deformation was slower and strain hardening was weaker in steel with a larger volume fraction of δ-ferrite than those in the samples with low content of δ-phase.

The paper studies the influence of boundary conditions and the loading rate on the strain behavior and fracture of Cr – Mn – C – N austenitic steel in the cast state without additional heat treatment. Regularities of steel strain and fracture were analyzed on the basis of three-point bending test data of square-section samples with and without a notch, placed with a rib on supports. In addition to the initial stage of the steel elastic strain, this unconventional arrangement of the sample on supports enabled the detection of two more stages of strain development under the effect of an external applied force: the stage of nonlinear strain and the stage of discontinuous strain preceding the moment of sample failure. As the loading rate increases, it was demonstrated that the fracture resistance and the extent of the nonlinear strain stage of the sample with a notch decreases, and the extent of the discontinuous strain stage increases. The sample without a notch has a prolonged nonlinear strain stage and exhibits maximum strength in the absence of the discontinuous stage. The end of the nonlinear strain stage corresponds to the moment of sample failure. A characteristic property of cast steel under the given loading conditions is that the fracture of the sample is brittle, despite the prolonged stage of non-linear strain. Structural metallographic and diffractometric studies have shown that in all tests the steel fracture is brittle with-out traces of plastic yield. The nonlinear strain stage of steel is determined not by dislocation plastic yield, but by the mechanism of γ → αʹ transformation in austenitic interlayers between nitride and carbide particles under the effect of an external applied force. The discontinuous strain stage of steel is associated with the process of stable crack propagation across the sample.

Based on experimental data on microstructure parameters of the reactor high-strength high-chromium (12 % Cr) ferritic-martensitic steel EP-823, the authors identified the main factors responsible for its strength properties. The hardening mechanisms of this steel were analyzed after processing according to the modes that provide different level of steel strength properties. Traditional heat treatment (THT) and promising modifying high-temperature thermomechanical treatment (HTMT) are considered. The main mechanisms of steel hardening, regardless of the processing mode, are: dispersed hardening by nanoscale particles of the MeX type (Me = V, Nb, Mo; X = C, N) by the Orovana mechanism; grain-boundary hardening by high-angle boundaries of martensitic blocks and ferrite grains; substructural hardening by small-angle boundaries of martensitic lamellae; dislocation hardening by increased dislocation density. HTMT mode, which includes hot deformation in the austenitic area, leads to a significant modification of the structural-phase state of steel relative to THT: a decrease in the average size of blocks and lamellae of martensite, as well as ferrite grains, an increase in the density of dislocations and the volume fraction of nanoscale particles of the MeX type. At the same time, the corresponding contributions to value of the steel yield strength from grain boundary, substructural and dispersed hardening increase by 1.2, 1.3 and 1.8 times in comparison with THT. The relative contributions of the considered hardening mechanisms to the yield strength of ferritic-martensitic steel EP-823 were discussed. The values closest to the experimental yield strength after two treatment modes studied are obtained when the Langford-Cohen model is used to estimate the magnitude of substructural hardening.

The use of complex strontium-containing alloys with alkaline earth metals for ladle refining of steel allows the efficiency of steel refining and modifying to be improved. Based on binary state diagrams of double systems SrO – CaO, SrO – Al₂O₃, Al₂O₃ – CaO and data on the possibility of formation of solid solutions, the state diagram of the SrO – Al₂O₃ – CaO system in the temperature range of 1600 – 2600 °С was simulated. Theories of perfect solutions (for solid solutions of strontium and calcium aluminates), regular solutions (for solid oxide solutions) and subregular ionic solutions (for oxide melt) were used to build the liquidus lines. The thermodynamic analysis of the Fe – Sr – Ca – Al – O system as applicable to steel refining processes with calcium and strontium alloys at 1600 °С was carried out. Simulation results show that the complex mechanism of interaction of active elements with oxygen will be implemented in the process of refining steel deoxidized with aluminum. In this case calcium and strontium interaction with oxygen occurs both for elements dissolved in iron, and at the boundary of the gas phase containing calcium and strontium with molten liquid iron. The interaction of calcium and strontium with oxygen in the presence of aluminum (0.05 %) results in a high probability of formation of SrO – Al₂O₃ – CaO liquid oxide melts. This greatly facilitates the removal of reaction products from the melt. The resulting non-metallic inclusions are most likely complex calcium and strontium aluminates which are easily assimilated by slag due to the presence of strontium. The formation of undesirable corundum inclusions when treating metal with complex alloys containing strontium and calcium is unlikely.

The improvement of management mechanisms for the formation and calendar planning of development programs is the most important direction for improving the productivity (achievement of goals) and efficiency (reduction of the amount of resources consumed) of the activities of metallurgical companies. Currently, it is necessary to ensure the mobilization of companies’ assets to solve the tasks of their sustainable development. The task of forming a program for the development of a metallurgical enterprise (company) is considered. The program includes several different areas of development: improvement of existing business processes (sales, supply, production, repair of equipment, etc.), production technologies of various stages (production of coke, agglomerate, cast iron, steel, rolled products), implementation of digital transformation tasks, etc. Each of the directions of the development program contains projects described by effect, size of investments, changes in the expenditure items of operating budget related to the costs of operating those systems and processes that the project is aimed at improving, as well as an indicator describing the risk of project implementation. One of the directions of the development program may include multi-purpose projects, the implementation of which leads not only to changes in its own performance indicators, but also to changes in the performance indicators of projects of other (non-multi-purpose) directions of such development program. The case is considered when management of the development program includes the management of the overall budget and achievement of overall goal of the program (the maximum effect from implementation of all projects). At the same time, project risk management and changes in the operating budget are implemented at the level of project portfolio management of individual program areas (there are no restrictions on risks and changes in the operating budget common to the development program). The stated formalizations of the problems, their decomposition and composition schemes, and the developed procedures for solving individual subtasks are based on the provisions and methods of the theories of system analysis and a new section of discrete mathematics (network programming).