Metallurgist最新文献

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.

The ladle refining of iron-carbon melts is an essential component of the modern technology used in the production of iron and steel, ensuring the high quality of metal products. However, in the context of mini- and micro-factories using technological units of a limited volume, it is often unfeasible to implement modern, highly efficient refining, deoxidation-alloying, and heating schemes that are commonly used by ladle furnaces and degassers. In addition, the issue of the widespread use of various production wastes for the production of cast iron and steel in order to recycle them and reduce the consumption of conventional charge materials is relevant. Therefore, a new method of submerged arc reduction of elements useful for metallurgy from industrial waste and secondary materials directly into an iron-carbon melt for its deoxidation-alloying (refining), homogenization, and heating by a submerged electric arc is proposed. This technology eliminates the use of expensive reagents, ferroalloys, and alloying elements. Based on the conducted research, a scheme of the processes of submerged arc reduction of elements was established, the design of submerged arc furnace assemblies and their composition were proposed, and the high efficiency of the new method of ladle refining in comparison with conventional analogs was demonstrated.

The paper describes the existing technologies and challenges associated with galvanized metal production at the Novolipetsk Steel (NLMK) plant. Possible ways to improve the process using machine-learning tools are proposed.

The production of direct reduced iron production is accompanied by the generation of by-products, specifically gas purification sludge and metallized fines with a high iron content. Processing this iron poses certain technical and technological challenges. Studies were conducted at the Lebedinsky ore mining and processing plant to analyze the chemical composition, phase distribution, and particle size distribution of iron ore sludge. Pilot smelting of iron-containing hot briquetted iron sludge was carried out in a 100-kW electric arc furnace, resulting in the production of foundry cast iron. The sludge and coke screenings were layered in a ratio of 15 g of coke screenings per 100 g of sludge. Complete melting of the entire charge volume was achieved at 1340 °C. This developed technology is protected by a patent from the Russian Federation.

New dependencies and relationships were identified for the first time after the implementation of abrasion-resistant surfacing technology on heat-strengthened steel 65G. This technology revealed the nature of the Vickers hardness distribution in the vertical and horizontal directions of the surfacing area and demonstrated their identity. It has been established that the thermal effects from the welding arc reduce the hardness of the base metal located directly in the lower part of the surfacing area. Compared with the planar direction, the thermal influences on metal hardness, size of the thermal influence zone, and the heat-affected zone are more pronounced in the depth of the surfacing area. This study clarifies the changes in HV hardness in various zones is provided based on recent studies in materials science and metallurgy.

The article describes modern methods for controlling and optimizing the energy mode of melting in electric arc furnaces and units for out-of-furnace steel processing using optical emission spectroscopy systems. These systems enable the determination of melt and slag temperatures, plasma temperatures in the arc combustion area, and slag composition, as well as the analysis of emission intensity from the melt and slag surfaces. The analysis revealed that depending on the range of steel to be smelted and the peculiarities of smelting technology at a particular electric arc steel-making furnace, control systems for smelting monitoring can be developed according to the obtained indicators of one or a combination of the abovementioned parameters.