Metallurgist最新文献

The article presents the results of a study on the flotation enrichment of oxidized copper ores from the Zhezkazgan deposit using electrochemical pulp preparation. It is shown that preliminary electrochemical treatment promotes the activation of the mineral surface and increases their flotation. The optimal pulp processing parameters were determined using the mathematical design of experiments. The application of this technology allowed for an increase in copper recovery in concentrate from 75.2 to 85.6% and an increase in the copper content in concentrate from 8.42% to 10.35%. The obtained results confirm the potential of using electrochemical activation for refractory oxidized copper ores [1, 7, 9].

The study is aimed at inactivation of harmful impurities (P, As, Sb, Cu, Sn) in low-carbon steel 17G1S (0.17 C–Mn–Si) by modifying it with rare earth metals (REMs) followed by vacuum refining. Under the laboratory conditions, steel was deoxidized with aluminum followed by introduction of 0.3% cerium (alloy MTs50Zh6: cerium (40–45%); lanthanum (18–25%); iron (15%); neodymium (10–12%); praesodymium (5–7%)) and purging with argon. The presence of the inclusions was analyzed using optical and/or electron microscopy, along with X‑ray microanalysis. Industrial testing included vacuum treatment of ingots weighing 28.5 tons (steel grades 34KhN1M (0.3 C–1.3Cr–1.3Ni–0.2Mo) and 9Kh2MF (0.9 C–1.7Cr–0.2Mo–0.1 V)) with an addition of 3–4 kg/t of REMs. At a Ce content of 0.2–0.3%, the impurities were bound into multiphase inclusions (3–10 μm) of the following composition (wt. %): REMs (70), P (11), S (2), and As (1.5). Purging with argon reduced the size of the inclusions. Vacuum treatment with an REM dosage of 3.9–4 kg/t reduced the sulfur content by 46–73% (up to 0.005–0.008%), regardless of the initial level. Experimental ingots exhibited evenly distributed small inclusions, containing up to 95% of impurities. The combined use of REMs and vacuum refining effectively inactivates harmful impurities, while improving the structural uniformity of steel. The method is applicable to critical alloys with high purity requirements for sulfur and nonmetallic inclusions.

An experimental study was conducted to analyze the distribution of microhardness over the cross-section of cold-worked reinforcement wire produced by drawing with roller dies and subsequent profile application to the wire surface. The distribution of microhardness over the cross-section of a plain wire produced by drawing through a monolithic die followed by straightening was also studied. It was shown that the microhardness of the wire rod is higher in the surface layers than in the center. Similarly, the microhardness of the wire drawn with roller dies (prior to deformation in the profiling head) and wire drawn with monolithic dies (prior to straightening) is higher in the surface layers compared to the center. After the wire surface profiling, the distribution of microhardness over the cross-section of the wire changes to the opposite, i.e., the microhardness in the center of the wire becomes higher than at the surface. A similar effect was observed when straightening the wire drawn through a monolithic die as a result of bending deformation. After straightening, the microhardness in the center of the wire becomes higher than at the surface. The wire strength decreases after straightening. The observed phenomenon is caused by the alternating deformation and the resulting Bauschinger effect in the surface layers during profiling and straightening of the wire. It was shown that the average value of microhardness over the wire cross-section increases at higher deformation levels. At equal deformations, the average microhardness over the wire cross-section is higher after drawing with roller dies compared to monolithic dies.

This study examines the effect of open-die forging parameters on the microstructure and mechanical properties of SP50N4D2M diffusion-alloyed powder steel produced by PJSC Severstal. The hot forging process of cylindrical billets, as well as key factors including the height-to-diameter ratio (h₀/d₀), initial porosity, and heating temperature were examined. The experimental procedure involved preparing a charge by adding ultra-dispersed nickel oxide (NiO) and graphite. This was followed by cold pressing, sintering in a protective atmosphere, and hot upset forging on a stamping press. The results demonstrate that deformation occurs non-uniformly, with the formation of three distinct zones: a minor deformation zone, a major deformation zone, and a zone under tensile stress. This non-uniformity leads to barreling and potential surface cracking of the specimens. Decreasing the h₀/d₀ ratio was found to reduce plastic deformation due to increased contact friction and constrained deformation zones. Reducing initial porosity from 30% to 10% enhances material strength, yet the risk of microcrack formation due to non-uniform densification remains. To improve the quality of the deformed billets, the study recommends accounting for additional tensile stresses and optimizing the upset forging parameters.

Significant technical, economic, and environmental advantages of integrating casting and rolling justify the development and implementation of combined casting-rolling units to produce long and flat steel products. Direct integration substantially reduces energy consumption by using the heat of the cast billet. Furthermore, it significantly simplifies equipment by reducing its mass and footprint. It also enables the full automation of technological processes and drastically cuts the volume of emitted harmful substances.

The hydrometallurgical cycle of the existing zinc core production process at the Chelyabinsk Zinc Plant (CZP), JSC involves a constant circulation of 19,000 to 22,000 m³ of solution, containing the key component (zinc sulfate) and a number of impurities, the presence of which affects the efficiency and techno-economic performance of the production to a varying degree. The sources of such impurities include zinc-containing process materials and reagents used in zinc production. The removal of impurities from the circulating solution is carried out both during its preparation for the core production process (electrowinning), and during the performance of certain technological operations, preparation of raw materials, and processing of intermediate products. A number of impurities, such as salts of alkali and alkaline-earth metals, are classified as those accumulating in the circulating solution due to the fact that the existing production process at the CZP, JSC does not allow for their selective removal. Therefore, one of the main directions of the research activities at the CZP, JSC is the development of a fundamentally new technology for removing accumulating difficult-to-remove impurities with minimal zinc losses, and obtaining residual products that could find wide industrial application.

We perform experimental verification of a new system of filtration in the course of production of consumable electrodes made of ÉEP708-VD heat-resistant alloy containing nonmetallic inclusions, carbonitrides, and crust inversion in a small-capacity electric-arc steel-making furnace under the conditions of the JSC SMK. The alloy was poured from a stopper ladle from above with the help of a specially designed pouring funnel with a system of two filters: a coarse filter with a cell 10 mm in size and a fine ceramic foam filter with cell sizes of 10 ppi and 5 ppi (10 holes per 1 inch and 5 holes per 1 inch, respectively). The efficiency of application of these filters was assessed by comparing the parameters of contamination with similar ingots obtained without filtration according to the methodology applied at the JSC SMK. We also present a plot of casting of a single ingot by using filtration. The chemical composition of inclusions was controlled by the method of energy-dispersive X‑ray spectroscopy (EDS). We perform the comparative analysis of contamination of an ingot of ÉEP708-VD heat-resistant alloy with nonmetallic inclusions, carbonitrides, and scab obtained in an electric arc steel-making furnace according to the classical technology. The presented research results make it possible to clarify the main casting parameters and improve the overall quality of the metal.

We perform the analysis of available publications devoted to the study of high-entropy alloys. A group of refractory high-entropy alloys with satisfactory ductility at room and elevated temperatures (up to 1200 °C) in tension and compression tests is considered in detail. It is indicated that these alloys can be used as heat-resistant materials under the conditions of short-term operation. We also make a conclusion that the application of refractory high-entropy alloys in the course of long-term operation is problematic due to the low characteristics of creep resistance and stress relaxation.

Coatings of the AlMg6–C₆₀–AlN system were deposited by cold gas-dynamic spraying of agglomerated powder mixtures, containing 25, 35, and 50 wt. % AlN particles. The effect of ceramic particle concentration in the powder mixture on the growth efficiency, structure formation, and phase composition, as well as on coating microhardness was studied. Dry sliding wear tests were subsequently carried out. The influence of AlN content on the friction coefficient and wear rate was evaluated. The coating produced from the powder mixture containing 35 wt. % AlN demonstrated the most favorable tribological performance. In this case, the actual content of AlN ceramic particles in the coating was 13.2 wt. %, while the corresponding friction coefficient and wear rate were 0.34 and 2.15 × 10⁻⁴ mm³ × N⁻¹ × m⁻¹, respectively. The specifics of surface morphology evolution under friction were studied. It was shown that a transition layer was formed on the friction surface, protecting it from severe adhesive wear, with contact interaction being realized through the formation of a third body. The developed coatings can be used to enhance the performance properties of machine component surfaces operating under the tribological loading conditions.

This study describes a method for creating new anti-friction alloys. The process involves spark plasma sintering of powder materials produced by electroerosive dispersion of CuSn5Pb25 lead-tin bronze waste in a carbon-containing medium, such as isopropyl alcohol. Experiments shown that the rapid heating and short cycle duration of spark plasma sintering prevent grain growth and promote an equilibrium state with a submicron grain structure. Consequently, this technique produces alloy billets with superior physical and mechanical properties, as well as a pore-free structure, compared to those manufactured using conventional methods. Additionally, the free carbon formed during waste dispersion in the carbonaceous medium acts as a solid lubricant that reduces the friction coefficient of the resulting alloy billets.