No 3 (2025)

The selective carbothermic reduction process of lead and zinc oxides from electric arc furnace (EAF) dust in the laboratory horizontal tubular electric furnace in an argon medium with excessive consumption of reducing agent (20 wt.%) during step heating with an exposure for 1 hour at each stage is analyzed. It is established that successive heating and exposure of EAF dust and a reducing agent mixture at temperatures of 1100 and 1200 °C led to the removal of 96.8 and 99.9 rel.% of lead and zinc respectively from the dust. At the same time, iron content in the residue increased to 61.7 wt.%. It is calculated that the introduction of 15.5 wt.% carbon as a reducing agent is sufficient for the reduction of oxides in the considered EAF dust sample. It is experimentally confirmed that when condensate is deposited directly on gas outlet tube in the furnace in an inert medium, the product obtained is mainly in metallic form, while cooling the condensate in traps outside the furnace leads to the formation of lead and zinc oxides, which indicates the oxidation of the material during condensation with air access. The data of X-ray spectral microanalysis of condensate obtained in the furnace in an inert medium indicated the possibility of evaporation from EAF dust no more than 25 rel.% of lead oxide in the gas phase without prior reduction, as well as the fact that lead selective extraction from EAF dust with minimal associated zinc extraction should be carried out at temperatures below 1100 °C.

The structural-phase evolution of the mechanochemical formation of Ni/HfC mechanocomposites containing 50 and 70 wt.% nickel was studied using X-ray diffraction analysis, scanning electron microscopy, and energy dispersive spectroscopy. It has been shown by X-ray diffraction analysis, that during mechanochemical synthesis in a ternary mixture of elemental powders Ni, Hf and C at a stoichiometric ratio of Hf and C, the formation of hafnium carbide occurred already after 40 s. For both compositions, the crystallite sizes of the nickel rapidly decrease upon mechanical activation for up to 4 min compared to the initial. Intensive formation of hafnium carbide is recorded during mechanical activation with duration of 4–8 minutes. With mechanical activation for 12 and 20 min, the processes of secondary structure formation lead to homogenization of the product and depletion of hafnium carbide in carbon to the composition HfС_0.5.

A sequence of structural transformations characterizing the high-temperature nitridization of a zirconium-vanadium bimetallic billet has been established. The mechanism of nitridization of zirconium-vanadium alloy ZrV₂, which is formed during the manufacture of a bimetallic workpiece by electric arc welding, has been established. During high-temperature interaction with nitrogen, the alloy disintegrates, the basis of which is ZrV₂ intermetallic compound, with the formation of stoichiometric zirconium nitride ZrN, solid nitrogen solutions and compounds of the composition Zr_хV_yN_1–х–y with simultaneous segregation of vanadium at the grain boundaries of zirconium nitride. The released vanadium diffuses into the area of a solid solution of zirconium with nitrogen in the individual zirconium, forming a solid solution of the composition Zr_хV_yN_1–х–y. The final products of nitridization at the selected temperature are ZrN and Zr_0,3V_0,6N_0,1. Ceramics is a composite consisting of grains of stoichiometric zirconium nitride distributed in Zr_хV_yN_1–х–y with a limiting composition of Zr_0,3V_0,6N_0,1.

The article presents the results of calculating the emissivity of iron-carbon melts – semi-finished products formed in steel-smelting units: a converter and an electric arc furnace for further production of carbon structural steel grades. The calculation is based on the model of melt cooling due to radiation. Large samples were used for the calculation. The samples were extracted from the aggregate data of systematic measurements of the melt time and temperature in the technological cycle of steel smelting. It is shown that in the temperature range of 1560–1700 °C, the emissivity value lies in the range from 0.01 to 0.058. The dependence of the emissivity on temperature is of an activation nature and is satisfactorily described by the obtained exponential approximation.

The study of the effect of elastic-plastic alternating deformation on the mechanical properties of magnesium strips and low-carbon steel strips after processing on a roller straightening machine was carried out. The application of the strengthening process in 1 and 3 passes does not change the geometry of the strips. The yield strength of steel increases and the yield strength of magnesium decreases; at the same time, the yield plateau disappears on the tensile curve of steel samples, and a region similar to the easy slip stage in a single crystal appears on the tensile curve of magnesium samples after the elasticity stage. For an integral assessment of the effect of alternating deformation on the material and to determine its resistance to deformation, flow curves were constructed using the Nadai model.