Metallurgist最新文献

At present, the available data on the behavior of osmium in the course of extraction of rhenium from washing sulfuric acid used in the production of copper are extremely limited and contradictory. In this connection, the investigation of its behavior in some processes of processing of osmium-containing raw materials and its purposeful accumulation in cruds prove to be quite urgent. We formulate possible causes of formation of the interphase suspensions (in what follows, referred to as cruds) in the technology of rhenium extraction. We also present the results of investigations aimed at the development of physical and chemical foundations of the processes of getting osmium concentrates. A technology of crud processing based on the processes of repulping, sintering, leaching, and extraction of rhenium is proposed. The optimal conditions for the main operations are studied and selected: for repulping, these are S:L = 1:5 with stirring for 1 h at room temperature; for sintering, the consumption of CaO is 200–300% (1:3) relative to the weight of the sediment, its temperature is 300 °C, and the duration of sintering is 2 h, and, for leaching of the cake, S:L=1:4 at a temperature of 20–40 °C for 1 h. We propose a combined method for the extraction of osmium into a concentrate. This enables us to concentrate osmium in the cake and then use this cake to obtain metallic osmium. In this case, a significant part of rhenium (93%) remains in the solution and is then sent to the operation of getting ammonium perrhenate.

In this work four metal powder compositions of VZL718 (IN718) alloy are produced, one by vacuum induction melting and gas atomization (VIGA) technology and three by plasma melting and rotating billet centrifugal atomization (PREP) technology. Their particle size distributions, distribution parameters, technological properties, moisture content and gas impurity content of VIGA and PREP initial metal powder compositions are investigated. The differences between VIGA metal powder compositions and PREP metal powder compositions are shown and analyzed, and the differences are explained. Four selective laser melting processes are conducted using the VIGA and PREP metal powder compositions investigated. Particle size distributions, distribution parameters and process characteristics of VIGA metal powder compositions and PREP metal powder compositions after a single application in a selective laser melting process are investigated, and the differences between changes in characteristics and particle size distributions of VIGA and PREP metal powder compositions are revealed. The reasons for the changes identified in VIGA metal powder compositions and PREP metal powder compositions after selective laser melting and the relationships with initial metal powder composition characteristics are explained. Derivations and conclusions about further possibility of reuse of VIGA and PREP metal powder compositions after selective laser melting are made.

The study investigated the effect of retrogression and re-aging (RRA) on the structure and properties of the new Al–3.5Zn–3.5Mg–3.5Cu–1.6Er–0.2Zr–0.2Cr alloy through the use of scanning electron microscopy, thermodynamic calculations, hardness tests, current density, and corrosion potential. During the crystallization process, chromium is distributed between primary intermetallic compounds with an approximate composition of (Al,Zn)_79.8Mg_4.7Cu₃Cr_5.5(Er,Ti)₇, with a size of approximately 10 μm and an aluminum solid solution. Following two-stage homogenization heat treatment, the Al₈Cu₄Er and Mg₂Si phases exhibit minimal morphological changes, with the θ‑phase (Al₂Cu) being completely dissolved and the T‑phase (Al,Zn,Mg,Cu) transformed into the S‑phase (Al₂CuMg). Thermodynamic calculations indicate that the alloy should also contain the Al₃Zr and Al₄₅Cr₇ phases, which precipitate from the supersaturated solid solution during homogenization. Age hardening in the temperature range of 150–210 °C occurs due to the release of metastable modifications of the T‑phase. The combination of hardness (140 HV) and corrosion resistance (minimum corrosion current density 1 μA/cm²) is optimized by retrogression and re-aging.

For the first time pilot castings of an aluminum alloy into a patented mold with an evaporative-condensation cooling system are carried out with extraction of the resulting cylindrical billet obtained with a diameter of 62 mm. It is shown that the flow rate of cooling water to a mold may be reduced by a factor of 2–3 by increasing the temperature of the water leaving the condenser to t = 60–80 °C. Adjustments are made to the design calculation of wall temperatures, taking into account preliminary heating of the crystallizer and experimental values of temperatures. The state of the surface of the workpieces obtained is analyzed in two pouring modes. Calculation and comparison of heat supplied to and removed from the mold, and thickness of a billet skin are performed.

The article provides results of research on layer-by-layer plasma surfacing of aluminum alloy AMg5 using vertical supply of de-energized filler wire for product additive formation. Metallographic studies and mechanical tests of surfaced metal are conducted. The metal obtained has a homogeneous structure without defects and has mechanical properties close to those of material prepared by traditional technologies.

High-iron Bayer red mud, containing over 30% of iron, is considered low-grade iron ore. Due to the global iron deficiency in recent decades, the effective utilization of the iron contained in high-iron red mud has received increasing attention. In this work, a technological scheme was developed for the extraction of iron into cast iron from red mud by smelting reduction, followed by rapid cooling to separate the metal from the slag. The influence of various experimental parameters, including temperature, basicity, and reduction time, on the recovery of iron from red mud was studied in detail. The results demonstrated that the separation of metal from slag was complete. The maximum extraction of iron into cast iron was obtained at a temperature of 1450 °C, with approximately 88.5% achieved in the absence of sodium carbonate and 91.5% with sodium carbonate. The optimal experimental result is of great importance for the large-scale and highly efficient recycling of red mud.

New technology is presented in the work for copper wire processing. This technology consists of deforming wire in a rotating equal-channel stepped die and subsequent drawing. The die rotates around the axis of the wire and creates stress due to equal-channel angular broaching and twisting within the die. Results of a laboratory experiment show that after deformation an ultrafine grained graded microstructure with a high content of high-angle grain boundaries is obtained. Tensile strength of deformed copper wire in comparison with undeformed wire increases from 302 to 635 MPa, and yield strength increases from 196 to 406 MPa.

The paper presents the results of cobalt corrosion tests in air at different temperature and humidity values. It was demonstrated that corrosion losses in cobalt at temperatures of 20 and 30 °C and relative humidity of 70, 80, and 95% are insignificant. However, the rate of cobalt corrosion sharply increases at an air temperature of 50 °C, especially at 95% relative humidity. A conclusion about the intensity of the cobalt corrosion processes under these conditions can also be derived from the sample appearance: after testing at 50 °C and 70% humidity, the samples turn black, while at 50 °C and 95% humidity they become covered with black, oily, and easily crumbling flakes, which represent the products of cobalt corrosion. It was found that corrosion film formed on the cobalt surface consists of the eutectic Co–CoO mixture of variable composition and CoO·Co(OH)₂·H₂O complex oxide. At increased corrosion test temperatures, the surface film of hydrated cobalt oxide becomes thicker, develops microcracks, and leads to the formation of cobalt hydroxide flakes, which exhibit weak adhesion to the substrate and crumble.

Currently, silumins, which are aluminum alloys, are most widely used in mechanical engineering, construction, and other industries. The use of silumins is often limited due to the presence of large-crystalline structures, such as α-Al dendrites, needle-shaped crystals of eutectic Si, and intermetallic phases. The effect of various additives on and their relationship with the microstructure and mechanical properties of Fe-containing intermetallic phases (Al–Si–Fe and Al–Si–Fe–Mn) has been studied extensively. However, studies of the effect of various additives on the morphology of Fe-containing phases in industrial Al–Si alloys remain relevant.

The effect of small amounts of dysprosium titanate additives (0.01, 0.05, 0.1, 0.5 wt.%) on the morphology and localization of Fe-containing intermetallic phases is studied. Introducing 0.01 wt.% dysprosium titanate causes the transformation of the needle-shaped β-phase to the α-phase in the form of more compact blocks and polyhedral crystals, the size of the α-phase reducing by more than half. The introduction of 0.05, 0.1, and 0.5 wt.% dysprosium titanate does not change the modification of the α- and β-phases and reduces the size of the phases by a factor of 1.5 on average. After the introduction of dysprosium titanate, θ‑Al₂Cu particles are dissolved and Cu is concentrated/localized in the Fe-containing intermetallic phases in all the modified alloys.

After the introduction of 0.05–0.5 wt.% dysprosium titanate, the tensile strength of AK12 alloys increases due to a decrease in the size of the α- and β-phases. The modification of the Fe-containing intermetallic phases from the β-phase to the α-phase after the introduction of 0.1 wt.% dysprosium titanate decreases the tensile strength and elongation. The optimum is the addition of tungsten in the amount of 0.1 wt.%, as it leads to the optimal ratio between the structure and the mechanical properties. The tensile strength and elongation increase by 23% on average.

A new technology has been developed for restoring worn cast iron parts using electric arc surfacing. This technique uniquely combines the simultaneous introduction of filler materials, both as seamless wire and powder alloys, directly into the weld pool. Additionally, oxygen is supplied to the surfacing zone to decarburize the weld pool. The powder alloys used are enriched with graphitizers and carbide-forming elements to protect the melt during the crystallization process. Research has found that the connection zone between the original material and the added layer consistently features a transition layer, regardless of the specific gases and powder materials used. Notably, the use of NPCh‑3 powder, together with the supply of oxygen and carbon dioxide into the weld pool is 2.0–2.7 times thinner than those produced with either PG-12N-01 or PG-10N-04 powders. This method significantly enhances the quality of the deposited layer by increasing the proportion of finely dispersed complex carbides, obtaining an equilibrium structure of fine-plate pearlite with finely dispersed graphite deposits. This results in minimal porosity and the elimination of microcracks, while also reducing cast iron microhardness in the heat-affected zone by 2.1 times. A technology has been developed for restoring cast iron parts through electric arc gas-electric surfacing. This approach has been tested in industrial settings, demonstrating its ability to reduce metal scattering, porosity, and hardness of the deposited layer and the transition zone,. Furthermore, it significantly lowers the likelihood of crack formation, all while minimizing the expenditure on.