Metallurgist最新文献

This paper demonstrates the feasibility of producing thin-thin slabs from a wide range of aluminum alloys using the twin-roll casting method. In the course of the research, the design and technological solutions of the currently known methods of continuous casting and rolling of sheet metal products were analyzed. In a laboratory setup for strip metal casting, the physical and technological parameters (such as temperature, casting speed, and heat removal rate) were tested to ensure a stable process for the production of thin-thin slabs (1–5 mm) from the aluminum alloys under study. For the first time in the field of metallurgy, the improvement of twin-roll casting technology allowed the cast thin slabs from wide-range aluminum alloys, specifically EN2024 (D16) (≥ 130 °C) and EN7075 (B95) (≥ 160 °C), to be produced.

In the initial phase of the research, the impact of the heat removal rate from the solidifying metal on the primary structure of the cast blank was investigated. It is demonstrated that, irrespective of the cooling rate, the α‑phase serves as the basic structure that determines the mechanical characteristics of the metal in cast workpieces for all the studied aluminum alloys. It was demonstrated that as the cooling rate increases to a level characteristic of twin-roll casting, the α‑phase in cast slabs exhibits a more uniform fine-grained structure. In this case, the small inclusions of dispersed intermetallic and eutectic phases present in the structure of cast slabs are evenly distributed across their cross-sections. As is known, there is a hereditary phenomenon between the primary structure of cast slabs and the quality of the final metal product. This relationship was confirmed by the improved strength characteristics of strips obtained by rolling experimental slabs.

We study the material composition of a ferromagnesian oxidized nickel ore of the Serov deposit. According to the results of chemical analysis, it was found that the studied ore is poor in the nickel content. Note that magnesium and iron are present in the ore as macroimpurities. The main nickel-containing minerals are lizardite and clinochlore; smaller amounts of nickel are contained in talc. To determine the optimal technological parameters of heap leaching and reveal their correlation dependences, we use the mathematical method of data processing, namely, the Box–Wilson steep ascent method. Based on the results of leaching, we compute the values of the efficiency criterion and the variance of the efficiency criterion and deduce a regression equation for the description of the process of leaching. The adequacy of the regression equation is established by using the Fisher criterion.

The results of mathematical processing of the experimental data show that the concentration of sulfuric acid in the solution, the pause between irrigations, and the specific consumption of the leaching solution exert a significant effect on the efficiency of leaching in the stage of nickel extraction from 0–30%.

On the basis of computed values of the efficiency criterion, we determine the values of variable parameters for the second stage of determination of the optimal conditions of leaching guaranteeing the efficient ore opening in the stage of nickel extraction up to 30%.

Structure and mechanical property of mechanically alloyed granules of the Al–7.7Mn–3.1Cu (wt.%) alloy are studied after annealing in the temperature range of 250–450 °C and compaction at 400–450 °C. It is shown that a ball milling for 10 h provides for a formation of aluminum based supersaturated solid solution and Al₆Mn phase. Comparison of X‑ray structural data and differential thermal analysis and the change in granule hardness demonstrates the occurrence of recrystallization processes and decomposition of supersaturated solid solution with precipitation of Al₆Mn and CuAl₂ phases at heating. Compaction of granules at 400 °C provides a sample’s density of 2.87 g/sm³ and microhardness of 310±16 HV. Annealing of the compacts obtained at 400–450 °C leads to an increase in density and strength. Compaction at 450 °C increases the density of material to 3.01 g/sm³ and provides better mechanical properties according to compression tests results. The alloy exhibits yield strength of 910±10 MPa, ultimate tensile strength of 1060±20 MPa, deformation to failure of 0.9% at room temperature and an average value of yield strength of 287±20 MPa without microfailures after 40% of compression at 350 °C.

The study presents findings on the application of various beneficiation methods to low-grade hematite ores, originally characterized as a clay rock with an iron content of 17.2%. The study presents the mineralogical composition of the original ore and examines the effectiveness of different beneficiation techniques, including jigging, magnetic separation (after roasting with additives), and flotation. The results reveal that the simplest method, jigging, significantly enhances the iron content in the concentrate, achieving a total iron content of 50%. However, this outcome is heavily influenced by the size of hematite inclusions within the ore. Further refinement through additional beneficiation methods allows the total iron content in the concentrate to reach 60%.

The paper presents the findings of research on the production of wire from 850 and 585 platinum-based alloys intended for use in jewelry chains. The chemical compositions of two novel jewelry alloys of 585 platinum-containing modifying additives of rhodium and ruthenium are proposed and patented. An analysis was carried out to evaluate the existing section rolling and drawing schedules for the three platinum alloys to identify more efficient drafting methods, with a focus on reducing the labor intensity of metal deformation processes and minimizing the force parameters. A computer model of section rolling for the studied jewelry alloys, based on 850 and 585 platinum, was developed to analyze the shape variation and force parameters of the process and to propose a new deformation schedule for the studied alloys with the accepted reduction distribution per pass. The new deformation schedule was characterized by a more uniform reduction distribution per pass than that observed in the existing schedule, allowing the number of rolling passes to be reduced due to their redistribution. In order to determine the rolling force and to model the process, an approximation formula was used to calculate the time resistance, which is dependent on the total degree of compression. By using proprietary software and computer simulation, the parameters of wire drawing with a diameter of up to 0.25 mm from the studied alloys were calculated, which allowed the deformation and force parameters to be assessed when implementing the proposed drafting schedule. In addition, it was established that the drawing process exhibits a sufficiently high safety factor and low power consumption. It is therefore recommended that the process be subjected to industrial testing. The findings of this research can be recommended for improving the technology of wire manufacturing from the 850 and 585 platinum alloys intended for jewelry chains.

Gas purification in ferroalloy furnaces is vital for the efficiency and quality of the entire production process. To enhance the efficiency of the gas purification system, an upgrade to the bag filter regeneration control system has been proposed. Using the SimInTech dynamic modeling environment, the performance of the control system was evaluated before and after modernization. Key quality indicators and misalignment errors were calculated to assess the proposed engineering solution. The speed increased by 3.8 times, reducing response time to 2.9 s, the stability increased by 3 times, achieving a stability degree of 1.05, the reliability of the control system increased by 4.2%, reaching a reliability rate of 96.3%, and the misalignment error decreased by 30 s, resulting in a misalignment error of 25 s. Operational data from the Aktobe Ferroalloy Plant were used to assess the impact of the modernization on productivity, energy efficiency, and the overall quality of the gas purification system. The average efficiency coefficient of the regeneration system was determined to be 34.75%.

The paper addresses the issue of early detection of steel ladle slag in the continuous casting of steel. In this study, the vibration method of slag detection was evaluated due to the high informative value of the vibration signal. The analysis is based on the variation in the character of the vibration acceleration signal of the protective tube manipulator of the continuous casting machine when slag enters the intermediate ladle. The envelope method of the vibration power spectrum was used to derive five empirical criteria for slag cut-off. In addition, these criteria included data on the molten mass in order to reduce the occurrence of false alarms. A generalized measure was developed to determine the performance quality of the criteria which was estimated to be 91.79%. This result validates the efficiency of these criteria and their suitability for testing in real production conditions.

The composite powder containing Al₃Ni and Al₃Ni₂ intermetallic compounds was obtained by vacuum synthesis to reinforce the aluminum matrix of the developed composite. For this purpose, nickel and aluminum powders were mixed in a ball mill, followed by heating the resulting mixture in vacuum to 650 °C to initiate an exothermic reaction between the powder components. To obtain an Al–Al₃Ni composite, the synthesized composite powder and matrix aluminum powder were mixed in a mill, followed by compacting the resulting mixture and sintering the obtained samples in vacuum. It has been found that vacuum synthesis results in the formation of a composite powder with heterogeneous phase composition, including Al₃Ni, Al₃Ni₂, Al₄C₃, and Al. Carbon formed as a result of thermal decomposition of stearin on the surface of aluminum particles reacts with aluminum to form aluminum carbide. After sintering the compacted mixture of aluminum and composite powders, a composite reinforced with Al₃Ni and Al₄C₃ phases is formed. Tribological tests have shown that the obtained composite is a promising wear-resistant material with hybrid reinforcement by intermetallic and carbide phases.

The paper considers the results of a study on the oxidation kinetics of lead babbit B(PbSb15Sn10) with calcium in a temperature range of 373–473 K. In addition, the resulting oxidation products of alloys and their microstructure are examined. The studies were carried out using the thermogravimetric method in air at atmospheric pressure within the temperature range of 373–473 K. It was found that the oxidation process in the entire studied temperature range can be accurately described by a degree four polynomial. In the experiments, a variation in the oxidation rate was measured over time. The kinetic and energy parameters of the alloy oxidation process were determined. It was found that calcium additives increase the oxidability of the initial alloy B(PbSb15Sn10) in the temperature range of 373–473 K. It was demonstrated that the additives of the alloying component significantly alter the alloy microstructure. X‑ray diffraction analysis revealed that the oxidation products of lead babbit B(PbSb15Sn10) with 1.0 wt % calcium include the following oxides: Pb₂Sn₂O₆; PbO; Sn₂O₄, SnO, Pb_0.866O_{2, Sb2O5}, Ca(Sb₂O₆), and Ca₂Sb.

In this work the effect of 2% calcium on the structure, deformability and physicomechanical properties of Al-3%Mg‑0.8%Mn alloy is investigated. A hot rolling temperature of 400 °C for the alloy with calcium without prior homogenization appeared to be low, resulting in cold rolled sheets containing multiple defects, in contrast to a refrence alloy without calcium. During homogenization annealing at 550 °C aluminum-calcium eutectic is highly fragmented, which facilitates rolling. Evaluation of alloy with calcium resistance to recrystallization shows that hot-rolled sheets begin to lose strength after 250 °C, while for cold-rolled sheets this temperature is limited to 200 °C. Cold-rolled sheets of Al-3%Mg‑0.8%Mn alloy also have a temperature for the start of recrystallization of 250 °C, which is associated with liberation during hot rolling of nanosized dispersoids of Al₆(Mn, Fe) phase, which as a result of heterogenization at 550 °C have micron sizes. At the same time, cold-rolled sheets with added calcium have higher hardness and yield strength after one-hour annealing at 400 °C (71/61 HV and 124/107 MPa). Relative elongation is also better for alloy with added calcium. It is also shown that calcium addition increases corrosion current density from 0.71·10⁵ to 0.92·10⁵ A/m², while its value remains at the level for AMg5 alloy or grade 5182 alloy.