A criterion used to evaluate the efficiency of converter matte foam separation into nickel and copper concentrates is a selectivity index based on the total recoveries of metals into target concentrates that in turn defines their cumulative impurities (secondary metals) content. In addition to various factors (meeting density and reagent flow charts, comminution parameters, etc.), the time of preceding cooling of ingots is also known to have a substantial effect on the process of converter matte separation at commercial scale. Laboratory studies on selective separation were made to evaluate the influence of converter matte crystallization conditions at constant comminution and floatation parameters. Commercial converter matte ingots produced at different cooling rates were ground and floated in the closed circuit under laboratory conditions according to the existing floatation flowsheet. The lab studies allowed to exclude the multifactor nature of the system and to examine the commercial converter separation process only from the viewpoint of converter matte melt cooling rate since the other factors were kept constant during the laboratory tests. The temperature field in the body of the converter matte ingot was measured during its cooling in the conditions of the current production – this is reflected in the chemical and phase composition of various ingot sections. The temperature of the ingot, due to its massiveness, varies considerably throughout the material volume. A small change in the ingot surface temperature can be accompanied by significant changes in the temperature in its body. The measurement results showed that the temperature gradient from the center to the periphery of the ingot exceeds400 °C. In this regard, reducing the time of converter matte cooling can lead to significant violations of the cooling mode in the central zones of the ingot. In accordance with the optical mineralogical analysis of samples, the longer was the ingot cooling time, the higher was its decrystallization implying the formation of coarse-particle structures of copper and nickel sulfides with sharp interface boundaries. The chemical analysis revealed that the highest possible selectivity index of converter matte copper and nickel separation with resulting copper and nickel sulfide concentrates, respectively, is reached after 72 h of cooling for converter matte ingots from the smelting shop of the Nadezhdinsky Metallurgical Plant.

The existing technologies for copper-porphyry ores enrichment, located in deposits in the Urals of Russia, allow the production of chalcopyrite concentrates of the following composition, %: 21.5 Cu, 24.5 Fe, 26.5 S, 0.4 Pb, 17.6 SiO₂, 1.8 CaO, 2–6 Au (ppm), 20– 40 Ag (ppm). A conventional technology for processing such concentrates includes autogenous smelting, matte desulfurization and blister copper refining. Pressure oxidation leaching (POX) is considered the most promising alternative technology for chalcopyrite concentrate processing. The POX of concentrates originated from Mikheevskii GOK allow the production a cake of the following chemical composition, %: 56–65 Fe₂O₃, 25–30 SiO₂, 2.7 Ca, 0.3–1.0 Cu, 2–7 S, 0.6–0.8 Pb, 4–12 Au (ppm), 40–80 Ag (ppm); mass loss was 37–45 %. A standard method of cake cyaniding provides satisfactory indicators of precious metal extraction, but it requires a cumbersome area to be arranged for their processing and offers no solution for residue disposal. In this regard, this paper investigates the method of subsequent cake processing using autoclave treatment (AT) for iron removal. The study shows how the following parameters affect the results of this process: t = 110÷210 °C, H₂SO₄ = 15÷60 g/dm₃, τ = 45÷ ÷120 min. A statistic description of the AT operation is developed. Recommended AT conditions (t = 110 °C, H₂SO₄ = 60 g/dm³, τ = 60÷100 min) allow to obtain the POX cake yield reduced to 30–35 % of the source material with the following composition, %: 28–33 Fe₂O₃, 47–53 SiO₂, 2–5 Ca, 0.6–2.0 Cu, 0.8–1.5 Pb, 2–8 S. At the same time, the content of precious metals in the cake reaches 12–16 Au (ppm) and 80–120 Ag (ppm). Options for using AT products are proposed.

The study covers physicochemical features of dendritic zinc powders and their effect on gold cementation from cyanide solutions. Three zinc powders were obtained in a laboratory environment by electroextraction at different conditions, and these powders featured various particle size and specific surface area. The properties of zinc powders obtained and powder currently used for gold cementation were evaluated using SEM (Jeol JSM-6390LA), BET (Gemini VII 2390) and laser diffraction (Sympatec HELOS & RODOS) methods. It is shown that electrolytic powders have high specific surface area (1.3–2.6 times more) and a low bulk density (3.1–3.8 times less), relative to zinc powder currently used for gold cementation. It was found that due to specific physical properties electrolytic powders have low hydraulic resistance, which eliminates the need for inert additives introduced during cementation, increases unit capacity and reduces the load on equipment. Inert additives elimination will additionally increase the gold content in the resulting product. The dendritic morfology of zinc powders obtained compensates high particle size resulting in the high efficiency of gold precipitation. At the long cementation cycle the effective gold deposition area (with gold extraction of more than 97 %) turned out to be shorter for electrolytic powder compared to fine powder currently used. However, in practice, the cementation cycle is always limited by fine powder throughput and it is not possible to achieve the full zinc potential. The resulting cementation product usually contains 25–35 % of unused zinc. These studies show the effectiveness of using electrolytic zinc powder for gold cementation from cyanide solutions.

The article proposes a process for obtaining semi-finished products in the form of pipes made of copper alloys for electrical applications using the screw rolling method. The paper presents the results of experimental piercing and rolling of pipe samples made of Cu–0.75Cr copper alloy billets with a diameter of 45 mm. The 43.5×10.0 mm samples obtained after piercing using a two-roll screw rolling mill had exact geometrical dimensions: outer diameter deviation at the front end was up to 1 %, at the back end – up to 2.4 %; relative variation in wall thickness at the front end was 0.3÷0.5 %, at the rear end – 0.5÷1.0 %. Then pierced pipe samples were rolled using a three-roll radial-shear rolling (RSR) mini mill with a different total degree of reduction – samples were obtained with an outer diameter of 30, 25 and 18 mm. The reduction process was analyzed from the point of view of internal hole stability and deformation. In case of 30 % relative reduction of the outer diameter, rolling without a mandrel is accompanied by wall thickening. In this case, inner diameter deviations are within acceptable limits. The experiments on obtaining samples from the Cu–0.75Cr alloy by screw piercing and reduction in the RSR mill show that this scheme can be implemented in principle in industry. At the same time it is necessary to define more exactly deformation parameters (degree of deformation, choice of reduction scheme) to obtain a quality product. Various options for heat treatment (HT) of the obtained pipe samples and the effect of the HT method on electrical conductivity and hardness are considered. Samples after piercing had a conductivity of 59.3 % IACS. The maximum electrical conductivity of 76.7 % IACS was obtained on samples after quenching from a temperature of 1020 °C and aging at 450 °C for 3 h. The results of the work show the fundamental possibility of obtaining semi-finished products from copper alloys for electrical purposes using the screw rolling method.

The paper substantiates the composition and prospects of using high strength Al–Zn–Mg–Ca–Fe casting aluminum alloy without heat treatment based on the study on the structure, technological and mechanical properties. Alloys of the base composition Al–5.5%Zn–1.5%Mg (wt.%) jointly and separately doped with 0.5–1.0 % Ca and 0.5 % Fe were obtained as the objects of research. Standard casting alloys according to GOST 1583-93: AK12M2, AMg6lch, AM4,5Kd were the objects of comparison. A hot tensile test using a cast test bar was conducted to check the tendency to form hot cracks due to hindered contraction. It was shown that separate alloying with calcium and iron does not contribute to the improvement of crack resistance and adversely affects mechanical properties. Combined alloying with 1 % Ca and 0.5 % Fe improves the hot tearing resistance to the level of the AMg6lch alloy properties. This effect is due to calcium-containing phases of eutectic origin formed and a favorable grain structure created that is free from columnar grains. Iron in the alloy structure is bound in compact Al₁₀CaFe₂ phase particles as a result of the non-equilibrium crystallization during permanent mold casting. The formation of this phase allowed to reduce the amount of zinc in the (Al, Zn)₄Ca phase and mostly retain the (Al) solid solution composition as evidenced by similar hardness values of the Al–5.5%Zn–1.5%Mg base alloy and Al–5.5%Zn–1.5%Mg–1%Ca–0.5%Fe alloy, and the superiority of the values over the hardness of alloys separately alloyed with calcium and iron. Also the cast hardness of the promising alloy more than 20 HV higher than the cast hardness of commercial cast alloys. The new alloy in the as-cast condition exhibited competitive mechanical tensile properties: UTS ~ 310 MPa, YS ~ 210 MPa, El ~ 4 %.

Scanning electron microscopy and magnetic force microscopy were used to conduct the metallographic study of the surface microstructure of KS25 grade Co–25%Sm sintered rare-earth magnets after Electrical Discharge Machining (EDM). The chemical composition of the studied samples: Sm – 25 wt.%; Fe – 18 wt.%; Cu – 5 wt.%; Zr – 3 wt.%; Co – the rest. One of the sample surfaces was subjected to EDM in various ways with changes in such EDM parameters as the straight-line processing speed and offset. The microstructure of magnets contains four coexisting phases: SmCo₅, Sm₂Co₁₇, Zr₅Co₃FeSm and Sm₂O₃. The grain size is 10–50 μm. Crystals of the Zr₅Co₃FeSm intermetallic compound are 1–5 μm in size, and globular inclusions of Sm₂O₃ samarium oxide are 2–10 μm. EDM affected the thickness and chemical composition of the defective layer. In general, the chemical composition varies slightly in the direction from the defective layer inward the sample: the content of Sm, Cu, O, and Zr decreases; the content of Fe and Co increases. At a distance of 500 μm from the defective layer inwards the sample, the grain size increases by 40–50 %, while the porosity decreases. At the same time, the size of Sm₂O₃ oxides slightly increases. The study of the magnetic structure on surfaces perpendicular to the axis of magnetization by means of magnetic force microscopy revealed the presence of a complex domain structure of grains in the form of a labyrinth with a domain size of ~3÷5 μm. Separate singledomain grains ~30÷50 μm in size were also found. Due to the material heating and oxidation, EDM promotes the domain structure of grains appearing in the form of a labyrinth instead of single-domain grains, and the SmCo₅ → Sm₂Co₁₇ phase transition, which causes a decrease in coercive force.

This paper covers new overburning monitoring methods for D16 and V95 aluminum alloys based on use of a method of an energydispersive X-ray spectral analysis (EDS analysis). It is known that lowered performance of aluminum-based materials is often connected with overburning in their structure. Because the structural changes caused by overburning (flash-off of eutectics and excess low-melting phases and the subsequent crystallization of melted-off microvolumes) are followed by developing porosity, have negative impact on physical and chemical, mechanical and processing properties. The ability to reveal overburning at early stages allows to reject the defective metal. Characteristics sensitive to an early overburning stage are offered based on EDS analysis. A degree of the induced overburning in a D16 sheet is identified. B95 alloy structural components determining the alloy tendency to overburning are revealed. It is found that the EDS analysis makes it possible to reveal changes in the chemical composition of the structural elements of D16 and V95 aluminum alloys and identify an overburning stage quantitatively based on oxygen content. Overburning development leads not only to the higher content of oxygen in the chemical composition of aluminum alloys, but also lowers the electrical conductivity of the material. The paper considers a correlation relationship between the D16 alloy electrical conductivity with overburning induced in it, and oxygen content. The applicability of this method is caused by the method simplicity and a possibility to quantify the defect development in the heat-strengthened deformable aluminum alloys after process heatings. Also this method can be used as an additional research method when metallographic analysis gives no definite answer at identification of early overburning stages.