The paper shows the results obtained in experimental studies of zeta potential of ultrafine sulfides (chalcopyrite, tennantite, galena, sphalerite, pyrite, pyrrhotite); floatability of mono-mineral flotation grade sulfide fractions (–0,1 + 0,05 mm) in the mechanical flotation cell; floatability of sludges (–0,041 + 0,010 mm) in the Hallimond tube with adsorption under foamless flotation conditions. The method for preparation of ultrafine powders and sulfhydryl collectors for zeta potential measurement is provided. The paper studies zeta potential of mineral particle surface and insoluble forms of sulfhydryl collectors in the pH range from 2,0 to 12,5 (acidic medium was prepared using H2SO4, alkali medium was prepared using NaOH or Ca(OH)2). The obtained zeta potentials of sulfides were different for sodium hydroxide and lime media. In NaOH medium at pH> 9,5 zeta potential values of all sulfides were negative; in Ca(OH)2 medium at pH > 11 they had positive zeta potential values (1–18 mV); chalcopyrite zeta potential values are positive in the studied range pHCa(OH)2 = 9,0÷12,5. Isoelectric points were identified for chalcopyrite (pH = 6,5 and 8,8), tennantite (pH = 3,0), sphalerite (pH = 5,1 and 6,4), pyrite (pH = 3,1 and 8,9) and pyrrhotite (pH = 7,0) in sulfuric acid and sodium hydroxide medium; for tennantite and sphalerite (pH = 12,0), galena (pH = 11,2), pyrite (pH = 9,5 and 11,2), pyrrhotite (pH = 9,5 and 12,1) in lime medium. Measurements of zeta potential values of ultrafine sulfide particles make it possible to define more exactly the mechanism of interaction between sulfhydryl collectors and sulfides, associate non-selective extraction of sulfide sludges in high-alkali lime medium with the electrostatic component contribution during adhesion of ultrafine sulfide particles on bubbles and their mechanical removal to the froth.

The paper shows the results of simulating physical behavior of bubbles formed by oxygen electrowinning on an inert anode during hightemperature alumina slurry electrolysis in a fluoride melt. As part of the study, similarity criteria were calculated with experiments conducted on a water-based model of a cell with vertical electrodes, and the data on bubble behavior in slurry was obtained by video recording. The 20 % aqueous sulfuric acid solution with 30 vol.% alumina content was used as electrolyte for the model. Experiments were conducted in the electric current density range from 0,05 to 0,25 A/cm2. The video was recorded using the Nikon D3100 camera with 30 frames per second rate. The motion pattern of bubbles was obtained along with the quantitative data describing coalescence and bubble rise velocity. 125 bubbles with a thickness of 0,8 to 2,3 mm were analyzed to determine the average bubble rise velocity. Bubbles rose in a slug regime at 1,0–2,3 cm/s. The thickness of a bubble layer was about 5 mm. Further studies will be conducted to obtain new data on the bubble behavior at different solid contents, current densities, electrodes inclination angles, and particle size distributions.

The Soderberg aluminum reduction technology is associated with high pollutant emissions including gaseous and poorly soluble fluorides. Currently, conventional VSS cells equipped with a standard gas skirt and a burner do not meet the modern hooding efficiency requirements. The existing technology must be upgraded in order to comply with environmental regulations. The environmentally friendly Soderberg technology implemented with an upgraded gas skirt and a fundamentally new 4-dome gas removal system ensures daily average hooding efficiency of 97,4 %.

Metallurgical grade silicon produced in ore-smelting furnaces (OSF) generates a negligible amount of a furnace slag compromising the valuable smelted product quality. The purpose of the study was to analyze the factors of furnace slag formation with its further passing into silicon when released from the ore-smelting furnace, as well as to study the chemical composition of samples. The computer program was developed to forecast the yield of smelting products (crude silicon, dust-gas mixture, furnace slag) depending on the amount and chemical composition of loaded charge material, i.e. siliceous raw ore and carbonaceous reductants. The paper provides the results of studying OSF slag samples from the existing plant by metallographic, X-ray, and X-ray diffraction methods and electron probe microanalysis. The study showed the presence of entrapped silicon prills with intermetallic inclusions (Fe(Ti)Si, CaSi2), silicon carbide SiC, incompletely reduced α-SiO2-cristobalite and Al2O3, and formed complex oxides of impurity elements (CaO·SiO2). It was found that the amount of formed furnace slag and thus the chemical composition of smelted silicon depend on the optimal excess of solid carbon in charge (within 103–111 %) and stable electrical operation of the ore-smelting furnace.

Graphite molds can be used to produce titanium, nickel, copper, aluminum and zinc castings. Using of the graphite molds provides a high cooling rate. Moreover no die coatings and lubricants are required. To get appropriate results of the casting process simulation in graphite molds it is necessary to know thermophysical properties of materials and boundary conditions such as interface heat transfer coefficients, but they are still unknown. The most important properties are heat transfer coefficient between casting and mold, and between mold parts and between mold and environment. The heat transfer coefficient h (iHTC – interface Heat Transfer Coefficient) was determined between cylindrical aluminium (99,99 % Al) casting and mold made of low-ash graphite. The mold was produced by milling graphite blocks on the CNC machine. The heat transfer coefficient was determined by minimizing the error function, representing the difference between the experimental and obtained by simulation temperature in the mold during pouring, solidification and cooling of the casting. The dependences of the iHTC between aluminium and graphite on the temperature of the casting surface and time elapsed from the start of pouring of the casting. Determined values of the heat transfer coefficient at metal temperatures 1000, 660, 619 and 190 °С are 1100, 4700, 700 and 100 W/(m2 ·К) respectively. Therefore, with decreasing of the melt temperature from 1000 °C (pouring temperature) to 660 °C (aluminium melting point), the heat transfer coefficient increases. After casting surface forming and lowering its temperature, the heat transfer coefficient decreases. Decrease of the iHTC at temperatures below 660 °C (lower the melting point) is associated primarily with the appearance of an air gap between the mold surface and casting surface as a result of linear shrinkage. The iHTC between the mold parts (graphite– graphite) is constant 1000 W/(m2 ·К). The heat transfer coefficient between graphite and the air environment is 12 W/(m2 ·К) at the mold surface temperature up to 600 °C.

The study proposes a new method for the cold deformation of cast magnesium. It consists in upsetting using a under lateral pressure. The bar is first placed into a holder made of ductile material, and then into a container. The punch mounted in a container with a gap acts on the blank. Under the press force, the metal contained in the holder flows through the gap and creates a pressure. This increase the level of compressive stresses thus improving magnesium ductility. Deformation tests of cast magnesium specimens were made that showed that the nondestructive reduction of cross-sectional area could be increased from 12–18 to 60–70 %. Such an increase in ductility makes it possible to produce deformed magnesium bars without heating. The method for easier removal of bars from holders after deformation was provided. It was determined that the process could be carried out at moderate upsetting pressures of 820– 830 MPa. This is acceptable for modern tool materials.

The paper covers the effect of material anisotropy on the nature of deformation and geometrical dimensions of the finished capsule made of AD1M aluminum alloy in the drawing process. Metallographic, X-ray diffraction, full-scale production, and computer studies were conducted and the mechanical properties of the material were determined in order to identify the factors of the material anisotropy. Finite element analysis of the drawing process was conducted, where isotropic and macroanisotropic models, together with a model which factored in the microstructure of AD1M aluminum alloy, were considered as the treated material. It was found that only the macroanisotropic model and, to a greater extent, the finite element model which factored in the material microstructure in contrast to the isotropic model, allowed studying the earing process. It was shown that factoring in the sheet material anisotropy in the manufacture of hollow cylindrical parts by die stamping made it possible to determine the nature of metal flow more accurately and realistically and thus determine the final geometry of produced parts and consequently to create a stable process and improve product performance.

The paper specifies the results obtained during hot deformation tests of EP962NP heat-resistant granulated nickel alloy in the Gleeble System 3800, a thermo-mechanical physical simulation system, at deformation temperatures of 1100, 1150 and 1200 °C and deformation rates of 0,1 and 1 s–1. The data on changes in the sample microstructure during deformation are provided. Conditions are determined for obtaining ultrafine alloy structure required to implement the superplasticity mechanism. Based on rheological properties, the paper determines recommended modes for hot deformation treatment of products made of EP962NP that surpasses the most common domestic granulated nickel alloys by the complex of strength properties and heat-resistance. The possibility to make products of this alloy using the «HIP + deformation» technology is of interest: implementation of this approach will further improve the properties of this alloy.

The study determines corrosion rate and covers corrosion damage specifics of AK4-1 aluminum alloy samples in the NACE hydrogen sulfide solution. The alloy was studied in an ultrafine state as compared to the coarse-grained state obtained after standard T6 treatment (hardening + ageing). The alloy was nanostructured by equal-channel angular pressing (ECAP). It was shown that the alloy corrosion rate after ECAP was 1,9 times higher than after T6 treatment. Thus, general corrosion occurred in the alloy after ECAP, while in the T6 state pit corrosion occurred in the alloy in addition to general corrosion. The corrosive effect had a greater impact on surface roughness of samples made of AK4-1 alloy after ECAP as compared to samples after T6 treatment.