Metallurgist最新文献

We perform structural investigations of a molybdenum-based cermet material obtained by the method of selective electron-beam melting. The initial material is an alloy of the Mo–Si–B system alloyed with a reinforcing component in the form of an Al₂O₃–Y₂O₃–ZrO₂ oxide composition. It is shown that, in the process of selective electron-beam melting of spheroidized cermet particles of the alloy of Mo–Si–B system in the optimal technological mode of synthesis, we observe melting both of the molybdenum matrix of the alloy and of the reinforcing particles contained in the original granules. As a result, in the course of crystallization of the melt with formation of a cellular structure on the boundaries of cells, we observe the appearance of finely divided oxide particles 1–5 μm in size, which are also composite particles. On the boundaries of cells and inside oxide inclusions, we reveal the elevated content of silicon as compared to that in the body of cells, which enables us to conclude that the processes of diffusion of this element occur in the analyzed material. At the same time, in the vicinity of the contour of samples of synthesized material, we detect the formation of a structure, which inherits, to a certain extent, the structure of the initial spheroidized granules.

An analysis of new legislative documents on the management, methods, and technologies for assessing environmental risks was performed. The risk assessment algorithm was applied to the foundry shop of a metallurgical enterprise (Proizvodstvennaya Kompaniya) in the city of Irkutsk. The technological process of casting and forming steel products was investigated with a detailed analysis of emissions into the environment for each technological stage. The measures currently used by the enterprise to reduce its negative impact are discussed. When identifying the sources of hazards in the foundry, numerous violations of environmental legislation were identified. A register of environmental hazards with a ranking of consequences was compiled, which showed that the most severe hazard to the ecosystem would occur in the event of a global fire at the foundry shop with a possibly fatal outcome. The scenario of an electric arc furnace accident with the release of pollutants into the atmosphere was calculated as the most negative event. To assess the risks of possible hypothetical accidents, the event tree analysis, failure mode and effects analysis, and failure mode, effects, and criticality analysis methods, which are semiquantitative and suitable for primary risk assessment, were used. The calculation of the probability and criticality of failures of electric arc furnace elements showed that, if the cooling system fails, then the furnace will explode and the foundry shop will catch fire, threatening the lives of workers and emitting a large amount of pollutants into the atmosphere. Equipment modernization was proposed as corrective measures taking into account the best available technologies.

This article discusses the option of upgrading an ore-thermal furnace to produce technical silicon by installing strain gage sensors with signal converters and a rangefinder in the electrode lifting system. This upgrade will enable the reception of real-time data on changes in mass (carbon monoxide) or electrode breakage and the position of the working end of the electrode. The latter parameter is associated with the position of the reaction zone in the furnace, which directly affects the specific amount of electricity consumption, the temperature and volume of silicon leaving the furnace, and heat losses and dust removal with exhaust gases.

The upgrade will increase the observability of the control object, which will improve the quality of control of the technological process of carbothermic silicon reduction.

This work extends the boundaries of a new technology for the complex processing of dust obtained from melting scrap metal in electric arc furnaces at a factory in Kazakhstan by extracting zinc and lead into commercial products. Comprehensive studies of the elemental and phase compositions of dust conducted using a JED-2300 scanning electron microscope showed high contents of zinc (more than 30%), lead (approximately 5%), and iron. A considerable part of the iron in the dust (up to 35%) is represented as magnetite. Because of the lack of rational processing technology, a large amount of dust has accumulated on the plant territory, which requires a solution for its disposal with complex extraction of precious metals.

The general concept of the technology under development is based on an approach that ensures the disposal of multicomponent ferrous metallurgy dust to obtain a wide range of commodity products with high added value. At the same time, the high content of iron present as magnetite demonstrates the effectiveness of isolating iron as an iron-containing commercial product at the beginning of the technological scheme.

This paper shows the fundamental possibility of separating iron from dust from the scrap metal melting in electric arc furnaces by magnetic separation. According to comprehensive studies, including the study of the material composition of the initial dust and magnetic separation products, magnetic dust separation produced an iron-containing product with a high (up to 68%) iron content. The residual minimum limit of the iron content in the nonmagnetic fraction in the form of magnetite has been established as 0.58%. Further processing of such material will considerably simplify the technology, reduce material costs, and improve product quality.

The article provides results of studying the influence of production parameters of prior heat treatment on structure and phase composition of sheets of metastable β‑titanium alloy VT47 manufactured under industrial production conditions. As a result of research experimental methods of combined high- and low-temperature thermomechanical processing of alloy VT47 sheets are developed and their structure and mechanical properties in a thermally hardened state are studied. It is shown that methods of combined TMT of VT47 alloy, including annealing in the two-phase (α + β) region and ageing after rolling, make it possible to provide the required structure of a globular-lamellar type and a balanced set of mechanical properties.

This article presents an overview of the technology employed in the production of special types of coke obtained from non-sintering coals sourced from Kazakhstan. The microstructure of special types of coke is elucidated, and the effect of the heating rate on their microstructure and properties essential for use as a reducing agent in electrothermal processes for the production of technical silicon metal is studied.

The possibility of partial replacement of Ge by Si within the structure of Bi₁₂GeO₂₀ during synthesis from a melt by a casting method is demonstrated. The effect of substitution on the structure of synthesized polycrystalline material is studied. Using X‑ray phase analysis and optical microscopy, it is confirmed that stable bismuth silicate and germanate with a sillenite structure form a continuous series of solid solutions. The possibility of partial replacement of Ge by Si within the structure of Bi₁₂GeO₂₀ during its synthesis from a melt by accelerated cooling (casting method) is demonstrated.

Based on the theory of full and complex compensation, taking into account the charge and technological conditions, the article presents calculations of promising modes of blast furnace smelting with injection of pulverized coal fuel in an amount exceeding 200 kg/t of cast iron.

Influence of boron in a wide content range (0.0004–2.0%) and its joint effect with other alloying elements (Ti, Ce, Nb, Si, Mo, W, Al, N) on the structure and properties of austenitic stainless steels was analyzed. Due to segregation of boron along the grain boundaries and formation of various carbides, it is capable of increasing the strength and ductility, creep resistance and performance properties at high temperatures (> 600 °C). At the same time, a small boron content (≤ 0.004%), for example, in grade 304 stainless steel (Russian analogue—steel 08Kh18N10), leads to an improved corrosion resistance. However, with an increase in boron content (up to 2%), the positive effect disappears and steel becomes more susceptible to corrosion, while becoming stronger and inhibiting cracks formation during deformation due to grain refinement.