Problem of generation of local hardened areas in weld metal d ing rails welding in production of continuous welded rails is solved by using local heat treatment of weld joint. As a result, appearance of quenching structures is excluded. However, new zones of thermal influence with reduced hardness may appear. During operation, such rails are characterized by increased wear of the rolling surface in these areas and collapse of the head at welded joint. It is the main reason for removing rails from the track earlier than time guaranteed. Application of new technology based on dependences of dispersion degree of the structural components (primarily perlite and carbide particles formed during obtaining welded butt joints of rails) on steel composition and rails cooling conditions is proposed. Cooling rate has a decisive influence on the degree of dispersion of ferritic-cementite structure formed during decomposition of austenite. When welding rails in a butt weld, generation of granular perlite is possible in the areas with temperature between Ac₁ and Ac_m points. To determine these critical temperatures, thermodynamic calculations were performed using Thermo-Calc^® software (TCFE database) taking into account chemical composition of the samples obtained by spectrometry. Fe – C state diagrams for 76KhSF rail steel were modeled with the minimum and maximum content of alloying elements according to the state standard GOST R 51685 – 2013. To obtain minimal volume of sections with reduced hardness, it is possible to conduct rails welding in hard conditions by electrocontact method using pulsating reflowing. To prevent formation of defective sections with quenching structure, it is possible to control cooling of welded joint using contact heating. Measurement of the temperature distribution during welding according to the given modes and controlled cooling confirms theoretical conclusions.

Possibilities of increasing energy efficiency of steam power plants (SPP) are considered. They are used to generate electricity based on theoretical principles of technical thermodynamics with the use of system analysis. Systematic approach is implemented for the set of energy, environmental and economic problems facing power production. Based on global environmental and energy consumption trends, the article considers the main task of Russian power system – reduction of specific consumption of equivalent fuel per unit of generated electricity. Mathematical model of the task is provided. The main attention was paid to maintaining design parameters of SPP cycle in the capacitor. If it is not possible to provide required temperature and pressure using water cooling source, it is proposed to use heat pumps. In contrast to known methods of installing heat pumps for water cooling waste, it is suggested to collect heat on water supply line, bringing temperature to the designed parameters. We propose not to remove heat obtained from water supplied for condensate cooling, but to send it to the SPP cycle. It is shown that this heat makes possible to abandon device of low pressure heaters (DLPH), which will greatly simplify the design of SPP and allows using of intermediate steam of DLPH to generate electricity. Possibility of heating water in a heat pump to a temperature of 140 °С, which corresponds to the level of heating in DLPH, was calculated. Several ways of applying thermodynamics laws to operation of a steam-powered installation, which are still not used, were indicated: the use of air with negative temperature for cooling cyclone condenser instead of using traditional tubular condenser, and the use of phase transition (boiling) of cooling liquid for a condenser.

Using methods of modern physical materials science, structural-phase states and mechanical properties of the rolling surface have been analyzed at distance of 0 to 22 mm along the central axis and along the fillet of differentially hardened 100 m rails of DT 350 category manufactured by JSC “EVRAZ – United West Siberian Metallurgical Plant” after their long-term operation (passed gross tonnage of 1.411 million tons) on experimental test ring. In terms of chemical composition, metal of the rails meets TU 0921-276-01124323 – 2012 requirements for E76KhF steel. Impact strength and hardness on head surface and along cross-section meet TU specifications. Microstructure of rails metal is represented by finely dispersed plate perlite of 1.5 points with inclusions of excessive ferrite along the grain boundaries (1.5 points by GOST 8233 scale No. 7). Interlamellar distance in the rail head varies between 0.10 and 0.15 microns. Long-term operation of rails is accompanied by development of gradient structure, manifested in regular change in hardness, microhardness, impact strength along cross-section of the rail head. Microhardness at 2 mm depth from the rolling surface is 1481 – 1486 MPa. At 10 mm depth microhardness decreases to 1210 – 1385 MPa, which is caused by an increase in interlamellar distance and decrease in the level of strain hardening of metal during long-term operation of rails. It has been suggested that this may be due to an increase in interlamellar distance and a decrease in level of strain hardening during long-term operation.

Processing of titanium-containing ores with extraction of all the major elements is an urgent task of minerals rational use. It is shown that none of the existing processing schemes allows extracting of all the major useful elements at the same time from titanium-containing iron ores, i.e. – iron, titanium and vanadium. This problem can be solved using selective extraction of these elements based on new ideas about electronic reduction mechanism. Propagation of the process of solid-phase selective reduction of iron with the powder of carbon-containing material deep into the layer of grains of ilmenite concentrate from the surface of its contact was experimentally studied. The results of determining the amount of metal phase released as it moves away from the concentrate – reducing agent contact boundary are presented. Based on the results concerning amount of precipitated metal phase, a conclusion was made about diffusion processes in a layer of concentrate grains contacting only between themselves, limiting process of iron reduction. It is shown that near the plane of contact of solid reducing agent with the layer of concentrate grains, the rate of iron reduction is higher than the rate of high iron content phase precipitation from ilmenite. In depth of ilmenite concentrate layer, process of iron reduction is preceded by formation of iron-containing silicate phase from concentrate grains, where iron is reduced earlier than in ilmenite grains. Formation of iron-containing silicate phase contributes ilmenite grains sintering. It was concluded that in the concentrate layer in contact with solid reducing agent layer in absence of contact of each ilmenite grain with solid reducing agent, the point contact of grains and presence of voids between them in the layer do not prevent propagation of reduction process in the layer of grains contacting with each other only.

Thermodynamic modeling of chromium reduction from the oxide system of the following composition was carried out, (wt %): 25.0 – 37.5 CaO, 25.0 – 12.5 SiO₂ , 25 CrO₃ , 5 FeO; 14 MgO, 3 MnO, 3 Al₂O₃ . Silicon of ferrosilicon of FeSi20, FeSi45, FeSi65 grades was used as a reducing agent in amount of 110 % of stoichiometrically needed for iron, manganese and chromium reduction. Modeling was performed on HSC Chemistry 6.12 software package developed by Outokumpu (Finland). Calculations were performed using “Equilibrium Compositions” module in the initial nitrogen medium at total pressure of 0.1 MPa and in temperature range of 1500 – 1700 °С with step of 50 °С. The thermodynamic characteristics of chemical compound CrO (II) was introduced into the database. Thermodynamic constants of CaCr₂O₄ compound presented in a database have been adjusted. Calculation results were presented in form of graphic dependences of change in degree of chromium reduction η_Cr on temperature t, slag basicity (CaO)/(SiO₂), and silicon concentration in ferrosilicon [Si]_FeSi . It was shown that increase in the process temperature from 1500 to 1700 °C at (CaO)/(SiO₂) = 2 reduces η_Cr by 1.87, 6.04 and 7.38 % when using FeSi20, FeSi45 and FeSi65 reducing agents respectively. It was found that increase in (CaO)/(SiO₂) from 1 to 3 at temperature of 1600 °C leads to an increase of η_Cr 2 by 17.3, 14.2 and 12.5 % using FeSi20, FeSi45, and FeSi65 respectively. Increase in silicon concentration from 20 to 65 % in [Si]_FeSi ferrosilicon facilitates an increase of η_Cr by 9.5, 5.9 and 4.2 % at slag basicity of 1, 2 and 3 respectively and at temperature of 1600 °C. Chemical composition of metal was determined. Results of thermodynamic modeling can be used to calculate degree of chromium reduction from recovery period slags of the argon-oxygen refining process in stainless steel production.

According to the equilibrium state diagrams, when the melt is cooled to a certain temperature below liquidus, compositions of liquid and solid phases are uniquely determined by corresponding curves in the diagram. However, it does not happen in reality. For equilibrium (which the diagram describes), it is necessary that the melt is maintained indefinitely at each temperature, or thermal conductivity of liquid and solid phases, and the diffusion coefficients of their components, are infinitely large. We made an attempt to find out how these processes occur in reality. In this work, we consider the growth of individual crystal during cooling of a two-component melt. Mathematical model is constructed based on the following. 1. The melt area with volume corresponding to one grain, the periphery of which is cooled according to a certain law, is considered. 2. At the initial instant of time, a crystal nucleus of a certain minimum size is in the liquid. 3. At the surface of crystal, compositions of liquid and solid phases correspond to equilibrium state diagram at a given temperature on its surface. 4. Changes in temperature and composition in liquid and solid phases occur according to the laws of heat conduction and diffusion, respectively. As the melt gets cold and the crystal grows, the liquid phase is enriched in one component and depleted in another, the solid phase – on the contrary. Since the diffusion coefficients of the components in the solid phase are small, the composition of the crystal does not have time to completely equalize its cross section. The model proposed in the work allows us to study this phenomenon, to calculate for each cooling mode how the composition of the crystal will vary over its cross section. The calculations have shown that the temperature equalization occurs almost instantly, and composition of the liquid phase equalizes much slower. Equalization of the solid phase composition does not occur in the foreseeable time. The results of the work will help to improve technology of generation of alloys with an optimal structure.

The paper deals with issue of particle growth in a two-component alloy. The particle is formed from the products of chemical reactions that occur at the phase boundary. Generalized mathematical model of particle growth includes diffusion equations, mass transfer equations in boundary layer, and equation characterizing change in radius of the growing particle. The paper proposes an approach that allows reduction of the initial issue to system of PDEs and ODE that describes the state of growing particle. This approach provides basis for developing numerical method for calculating radius of growing particle as a function of time, based on the obtained equations. The computational scheme involves the finite-difference analogues of equations with an additional regularizing functional that ensure stability of the method with respect to accumulated computational error. In order to verify reliability of the proposed computational scheme and to obtain experimental error estimates of numerical solutions, computational experiments were carried out. In the experiments, radius of growing particle is determined with respect to the time via the proposed method. Also, comparative analysis of the calculated radius with test values was carried out and experimental estimates of deviations of the calculated radius from the test functions were obtained. The results of the experiment presented in the work indicate sufficient accuracy of the developed numerical method.

The article presents the initial data for calculation of stress-strain state of a three-layer bimetallic strip. The regularities of distribution of axial and tangent stresses in the zone of cyclic deformation are considered. The main loads acting on the mold strikers are described for the unit of combined continuous casting and deformation at production of steel three-layer bimetallic strips. The authors describe the method for determining total stresses in the installation strikers from the efforts of compression and temperature loads. Also temperature boundary conditions for determining the temperature fields are considered. The procedure for determining temperature fields and thermoelastic stresses in the strikers is shown using the ANSYS package. The calculation results of temperature fields and thermoelastic stresses were made in five sections of the striker and are given for characteristic lines. The nature of temperature distribution over the thickness of the striker is shown when it is cooled with water at idling and in contact with a bimetallic ingot during its compression. For the calculated temperature fields, the authors have determined the axial and equivalent stresses occurring in the strikers without channels when the ingot is compressed and cooled with water during idling. The magnitudes and patterns of distribution of total axial stresses from the compression and thermal loads are also given along the thickness of the contact layer, along the height and thickness of the strikers.

The work is devoted to development of cost-efficient method of processing of metallurgical waste – oily rolling scale formed during hot-rolled steel strip mechanical cleaning in descaling mills. The most significant parameters of chemical metallurgical process for producing expensive and highly marketed products – α-Fe₂O₃ and γ-Fe₂O₃ nanopowders – have been experimentally determined. The properties of initial materials and nanodispersed products were studied by X-ray diffractometry, energy dispersive spectroscopy, scanning and transmission microscopy, and Mössbauer spectrometry. Temperature and field dependences of powders magnetization were built according to vibration magnetometer measurements. It is shown that rolling scale consists of three main phases: wustite, magnetite and hematite in a ratio of 6:8:7 by weight, respectively. The initial scale was activated in magnetic mill in stream of hydrogen and dissolved in mixture of hydrochloric and nitric acids. The resulting solutions were used to obtain α-Fe₂O₃ nanocrystalline hematite by chemical-metallurgical method, the main stages of which were hydroxide precipitation with alkali at constant pH, washing, drying, and dehydration. γ-Fe₂O₃ maghemite was obtained from hematite in two stages. At the first stage, hydrogen reduction was carried out, and at the second stage, the magnetite obtained was oxidized in air. Particles of synthesized nanodispersed oxide powders are in aggregated state. Particles of α-Fe₂O₃ are spherical, and γ-Fe₂O₃ are rod-shaped. According to Mössbauer spectroscopy, the lattices of both oxides contain magnesium, aluminum, silicon, chromium, and manganese that have passed from the initial scale. These elements determine magnetic properties of α-Fe₂O₃ and γ-Fe₂O₃ nanopowders. Set of properties of nanodispersed hematite and maghemite powders obtained from metallurgical waste (rolling scale) allows us to recommend their application as catalysts, in industrial wastewater heavy metal ions treatment systems, and in production of blood analysis markers.

Optical interferometry and metallographic analysis were used to study structure of cutting seams obtained after 09G2S steel cutting by PMVR-5 plasma torch. These plasma torches have a number of design features in the system of gas-dynamic stabilization of plasma arc. It is shown that application of new plasma torch allows obtaining higher quality of cutting 09G2S steel of medium thickness with high productivity and lower energy costs. Metallographic analysis has shown that qualitative composition of the cut surface structure is almost the same, so priority criteria for comparative quality analysis are parameters of surface microgeometry. Evaluation of this parameter shows high quality of cutting almost along the entire length of a cut, since the influence of technological features of plasma arc cut into the metal affects at a distance of less than 0.3 mm from the edge of the sheet. The use of additional methods of gas-dynamic stabilization in PMVR -5.2 plasma torch (feed symmetry with a double swirl system of plasma-forming gas) allows to achieve additional advantages in terms of surface quality compared to PMVR -5.1. A number of features that affects quality of cut when cutting metals of different thicknesses for welding, is noted depending on the angle of inclination of plasma torch during cutting. Estimates of the surface layer hardness indicate minimal deviations from the requirements of GAZPROM Standard 2-2.4-083 (instructions on welding technologies in the construction and repair of field and main gas pipelines), which allows further use of cutting seams obtained by studied plasma torches for welding without removing zones of thermal influence. Thus, application of new plasma torches makes possible precision finishing plasma cutting of metals, including production of welded joints.

One of the interesting technical solutions is technology of ferroalloys smelting using direct current (DC). In DC ferroalloy furnaces, apparently, it is possible to eliminate such a parameter as power factor in furnace circuit after current converter. Many researchers assume that melting at direct current allows intensification of the process of charge melting, increases reduction of leading elements of ferroalloy and reduces specific consumption of electricity. In this paper, brief analysis of carbon ferrochromium smelting in alternating current (AC) and in direct current (DC) furnaces is made based on energotechnological criterion of ferroalloy electric furnace performance. It is shown that with comparable active capacity in bath, AC furnaces have higher energotechnological criteria (0.2185 – 0.2381), compared to DC furnaces (0.1109 – 0.1320), at current level of technology used for carbonaceous ferrochrome smelting. Thus, in AC furnaces, specific electric power consumption in ferrochrome smelting is lower than in DC furnaces by 20 – 28 %.

The article describes the reason of additional dynamic forces occurrence in course of operation of the lever mechanism of jaw swivel drive with gaps in hinges reducing reliability of jaw crushers operation. Gaps sampling mechanisms are equipped with elastic pneumatic elements. These pneumatic elements throughout the entire cycle of the crank-beam mechanism constantly act on the movable body with an anti-friction liner mounted on it. Mechanisms for gaps sampling provide a choice of the gap in the joints of kinematic pairs, prevent the appearance of additional dynamic loads, and reduce the level of vibration of the mechanical system. It has been experimentally established that usage of such mechanisms increases reliability of jaw crushers.