The studies were carried out in order to establish the patterns of sulfuric acid dissolution of metal sulfides with the participation of environmentally friendly oxidizing agents – ozone and iron (III) ions, to determine the parameters and intensification modes of metal extraction into the solution, reduce oxidizing agent consumption. The purpose of the studies was to develop the least environmentally intense, cost-effective methods for extracting non-ferrous metals from sulfide ores, concentrates and industrial waste. For study, we used copper sulfide concentrate of flotation concentration of ore from the Udokan deposit with a grain size of 90 % –0.074 mm with a copper content of 24.5 %, ozone with a concentration of 80–180 mg/l in a gas mixture with oxygen, fed to the reactor at a speed of 1–5 ml/s. Patterns were studied in the range of sulfuric acid concentration of 20–100 g/l, Fe(III) ion concentration of 7.8–29.2 g/l, temperature of 18–60 °C in stirred reactors with the solid-to-liquid ratio of 1.1÷1.5. It was found that the use of Fe(III) ions and ozone can significantly intensify copper recovery from sulfides to the sulfuric acid solution. Copper extraction from sulfides increases in proportion to the 2.4-fold increase in the concentration of Fe(III) from 7.8 to 29.25 g/l. Ozone effectively oxidizes Fe(II) and regenerates Fe(III) ions. With the rising temperature and iron concentration, ozone consumption for oxidation increases:0.22 mol of O3 is consumed per 1 mol of Fe that is more than the theoretical value of 0.17. An increase in the rate of copper extraction from sulfides using ozone is achieved by increasing the temperature from 20 to 50 °C (1.4 times), ozone concentration from 85 to 180 mg/l (3 times), feed rate of ozone-oxygen mixture from 1 to 5 ml/s (2.7 times at 20 °C, 3.9 times at 50 °C), by adding Fe(III) ions (~1.5 times at 50 °C [Fe(III)] = 10 g/l). The highest oxidizing activity in a sulfuric acid solution is provided by ozone decomposition products at a temperature of 50 °C when its solubility decreases. Ozone utilization coefficient and specific ozone consumption for extracted copper decrease with an increase in the ozone-oxygen mixture supply rate with oxygen from 1 to 5 ml/s (1.42 times at 20 °C, 1.16 times at 50 °C) and increase with rising temperature and Fe(III) concentration due to the rapid ozone decomposition and unproductive use for iron oxidation.

The paper suggests a mechanism of simultaneous oxide reduction from multicomponent copper-smelting slags during their bubbling with CO–CO₂ reducing mixtures and provides a numerical algorithm developed to implement this mechanism as a mathematical model. The first feature of the suggested mechanism is a statement that the total speed of the overall reduction process is determined by CO consumption during its interaction with oxygen ions formed in slag oxide dissociation. The second feature is a statement about equilibrium achieved between slag, alloy and gaseous phase according to the system oxidizing potential reached at every instant. The paper demonstrates a satisfactory agreement between calculated and experimental data obtained when reducing industrial coppersmelting slags at 1300 °С and СО/СО₂ = 4, 6, 156, and using the first-degree kinetic equation regarding the difference between initial and equilibrium CO contents in the gaseous phase. A generalized kinetic constant of the multicomponent slag reduction reaction rate is calculated as k = 2.6·10^–7, moles _CO /(cm² · sec·%) at 1300 °С. It is shown that during industrial multicomponent slag reduction, reduction speed of copper (I) oxide and magnetite are high and close to maximal ones as early as at the first minutes of slag bubbling with reducing gas. At the same time, for Fe(II), lead and zinc oxides they are low at the first minutes of the process, and increase gradually to reach their maximum, and then decrease again up to near-zero values as the supplied gas and melt come to equilibrium. Generally, oxide reduction speed naturally decreases with approaching to equilibrium between the initial gas and liquid phases, and this should be taken into account when designing continuous slag depletion processes.

The paper presents a new nonstationary three-dimensional mathematical model of an aluminium reduction cell which makes it possible to perform coupled thermoelectric and magnetohydrodynamic calculations taking into account sideledge formation. The model considers the nonlinear dependence of material electrical conductivity and thermal conductivity coefficients on temperature, and the nonlinear dependence of magnetization on the magnetic field strength for ferromagnetic materials. Heat transfer coefficients on outer surfaces included the radiant and convective components of heat transfer and were functions of the ambient temperature and the local surface temperature. The energy equation took into account internal heat sources due to the electric current flow, exothermic reactions and additional thermal effects associated with the raw material loading and phase transitions. The control volume method was used to obtain a numerical solution. The developed mathematical model was experimentally tested at the S8BME aluminium reduction cell. The paper presents the calculated and experimental data of magnetic, electric, thermal and hydrodynamic fields. The comparison of calculation results with the results of industrial experiments showed that the developed model reflects physical processes taking place in the aluminium reduction cell with accuracy sufficient for engineering calculations. The calculated values of electrical voltage, magnetic induction and temperature practically coincide with the measured ones. Velocity directions in the metal and the sideledge profile shape obtained by calculation have insignificant differences from experimental values. The developed model can be used to estimate operation specifications and design parameters for new and modernized aluminium reduction cells. Further studies will be aimed at refining the calculated results by improving the developed mathematical model.

The paper analyzes main tasks related to brass melt processing. It provides a comparison of traditional processing methods with the proposed method of alloy quality improvement. The equilibrium conditions for carbonate decomposition reactions are considered when processing the melt in an open and closed ladle. Conditions for the carbonate decomposition reaction are formulated. The study proves that the resulting gaseous product of carbonate decomposition can have a simultaneous flotation effect on the brass melt refining from dissolved gases and non-metallic inclusions. The paper analyzes thermodynamic conditions of slagging impurities by introducing alkali and alkaline earth metal carbonates through the interaction of their oxides with silicon and aluminum oxides in the melt. The study considers the possibility of enhancing the physical and mechanical properties of brass castings due to the modifying effect provided by the formation of calcium, strontium, barium and sodium oxides resulting from dissociation of their carbonates. The paper describes the technology used for brass melt processing with alkaline earth metal carbonates in a pouring ladle, methods for studying the obtained results from the point of view of microstructural analysis and mechanical test values. It is found that the use of carbonates in brass melt processing creates a more favorable microstructure, contributes to the lower average nominal grain size, increases its uniformity, and reduces the likelihood of enlarged α phase formation. Structural parameters of samples were extensively studied with various options of melt processing with carbonates. Mechanical properties of brass samples were studied before and after melt processing with various combinations of alkaline earth metal carbonates. Compositions of carbonate mixtures that have the most favorable integrated effect on the brass strength with a simultaneous increase in plasticity performance were determined. The optimum carbonate mixture composition was chosen experimentally. Processing efficiency was confirmed by industrial tests. The simplicity and other positive features of the proposed technology for refining and modifying brass melt processing with mixtures of alkaline-earth metal carbonates were observed.

The study covers the free linear shrinkage of non-filled (PS50-50, MVS3-T, Romocast 105, Romocast 152) and filled (Romocast 252, Romocast 325) model compounds depending on the ambient temperature. Research results revealed the following main features in the change of this technological parameter. It is found that the greatest free linear shrinkage is typical for non-filled model compounds, while filled model compounds have a minimum linear shrinkage. At the same time, processes associated with free linear shrinkage occurred in samples for a long time (up to 24 hours). This is probably due to the duration of polymerization processes and low thermal conductivity of model compounds. Changes in the ambient temperature within –5...+35 °C have a significant impact on the degree of changes in linear dimensions of the studied model compound samples. The length of samples changed within +0.3...–0.4 % for non-filled model compounds and within +0.2...–0.15 % for filled compounds. At the same time, non-filled compound samples cooled to –5 °C and then heated to +20 °C reduce their length by 0.2 mm on average. When non-filled compound samples are heated to +35 °C and then cooled to +20 °C, the initial length increases by 0.2÷0.3 mm on average. With similar ambient temperature changes in filled model compound samples, their change in length is not more than 0.1 mm. To eliminate refractory ceramic mould cracking, it is proposed to cool the «lost wax patter –refractory ceramic mold» system to ensure a guaranteed gap between the pattern and the mold and eliminate the negative impact of the expanding pattern composition.

The paper provides the results of studying the technology for producing longish deformed semi-finished products by sheet rolling and direct rolling-extruding of aluminum-magnesium alloys with different scandium contents. Computer and physical modeling methods were used for the research and the results were verified by pilot tests. These alloys were selected for the research due to the fact that Al–Mg aluminum alloys doped with scandium have increased corrosion resistance along with their high strength. In this regard, this research was aimed to obtain longish deformed semi-finished products in the form of sheet metal, rods and welding wire from economically alloyed Al–Mg alloys. Computer simulation was performed using the DEFORM-3D software package to determine rational conditions of hot rolling of large-sized ingots and deformation modes of the combined processing using the method of direct rolling-extruding of rods made of the investigated alloys. At the same time, the technological and force parameters of these processes were justified with the laws of their change presented. Experimental results obtained made it possible to determine the limit values of force parameters and to study the structure and properties of deformed, annealed and welded semi-finished products made of the investigated alloys during the physical modeling of processes studied. In addition, metal properties were determined in a fairly wide range of changes in temperature, speed, and deformation parameters. Based on the results of experimental studies and modeling, recommendations were given for the industrial development of the technology for hot rolling of thick ingots from the investigated alloys. At the same time, technological solutions, regulations and conditions for deformed semi-finished products made of the investigated alloys were developed and batches of sheet metal with the required level of mechanical and corrosion properties were obtained.

Experimental antifriction aluminum alloys based on the Al–5%Si–4%Cu system with the addition of Bi, Pb, In, and Cd low-melting components were studied. An optimal heat treatment mode was selected: hardening at 500 °С with further aging at 175 °С. Tribological tests were carried out according to the «shoe–roller» scheme (investigated material – Steel 45) (at pressures of 0.5, 1 and 2 MPa) simulating the bearing assembly operation. It was shown that all the experimental alloys have similar tribological properties. However, their mechanical properties (in particular, hardness) differ. A cadmium containing alloy had the highest hardness. Electron microscopic studies of the shoe and roller surfaces were carried out for samples made of this alloy before and after tribological tests including the study of topography and elemental composition. The process of active mass transfer in the contact zone during friction was revealed. At the same time, the roller demonstrated a film formed of secondary structures on the roller and its parameters were determined  (uneven pattern of location on the surface, considerable relief with the maximum thickness up to 200 μm). It was shown that such a film leads to score formation with the friction modes used. It was determined that for all experimental alloys scoring occurs after testing at pressures above 1 MPa. Shoe nanoindentation (with 10–100 mN loads) showed increased hardness in the surface layer with a thickness of about 30 μm. This may be connected with the material hardening as a result of plastic strains occurred in the friction zone.

Thermal analysis methods were used to study the super-cooling of gallium-tin system alloys under normal conditions. For this, the following samples were investigated: Ga (I ); two hypoeutectic alloys 95 % Ga + 5 % Sn (II ), 90 % Ga + 10 % Sn (III ); eutectic alloy 96.3 % Ga + 13.7 % Sn (IV ); five hypereutectic alloy with a Sn content of 20 % (V ), 35 % (VI ), 50 % (VII ), 80 % (VIII ) and pure tin (IX ). The nonequilibrium state diagram of this system was constructed. In this case, the eutectic composition does not change, and the eutectic temperature drops to5.5 °C, i.e. 26 degrees below the temperature of three-phase eutectic equilibrium. The eutectic temperature practically does not change when the eutectic alloy cooling rates vary from 0.06 to 60 °C/min. It was established that a slight decrease in supercooling appears in the hypoeutectic region with an increase in super-cooling observed the hypereutectic region as the alloy composition approaches the eutectic one. The activities and activity coefficients of components on equilibrium and nonequilibrium liquidus lines were calculated. It was shown that the activities of components both on equilibrium and nonequilibrium liquidus lines in general naturally decrease, and the activity coefficients increase as the composition approaches the eutectic one. State diagrams show the concentration paths of equilibrium and non-equilibrium crystallization.

The paper provides the results of a comparative corrosion resistance study of the aluminum matrix composite produced by the method of oxygen lancing of pre–hydrogenated Al–Si–Fe aluminum alloy melt with an iron content of over 1.0 % and Al–7%Si alloy with an iron content of 0.3 % modified by the 5Al–Ti master alloy in the amount of 2 %. Corrosion in aluminum alloys is conditioned by the oxide film discontinuity in some phases, primarily Al₅SiFe. Pairs of composite and reference alloy samples with a diameter of 15 mm and a length of 50 mm were tested in a 7 % solution of NaCl salt fog in SFC-1 chamber on suspension brackets at 22 °C for 300 hours. The obtained results show close values of mass losses for samples despite the significantly higher iron content in the material since 100–200 nm particles formed in the melt by oxygen lancing are deposited on the phase boundaries and reduce the area of the surface in contact with the corrosive environment. Literature data show a considerable difference in the corrosion resistance of composites ex situ from in situ due to different sizes and locations in the hardening phase matrix. The studied composite material can be recommended as a corrosion-resistant alternative to alloys with the high iron content that are used for high pressure die casting (HPDC).