Papers by Keyword: Melt

Abstract: Metallurgical processes in Me-O-C systems cannot be studied and controlled using conventional analytical and physicochemical techniques. This is due to the complex physical and chemical interactions occurring in high-temperature metallurgical systems with the formation of various compounds. To study such processes, mathematical (thermodynamic) simulation and other techniques are widely used, among which graphical diagrams illustrating the equilibrium between individual phases or their systems occupy a special place. Diagrams have been proposed that are more common, informative, and herewith universal to study pyrometallurgical processes. The main research objective was to determine the equilibrium composition of the Me-O-C system, i.e., the amount or ratio of its various compounds such as carbides, oxides, pure substances, and, possibly, ternary compounds. The equilibrium compositions of the system were obtained to plot diagrams from not only experimental studies but also the chemical equilibria mathematical simulation results using the Selector software package. The diagrams proposed herein allow establishing a quantitative relationship between the temperature, the ratio of independent components (metal, oxygen, and carbon), on the one hand, and the complete equilibrium composition of the system, which implies data on the amount and type of condensed and gas phases in the system and their ratios, on the other hand. This mechanism is a new tool to study chemical conversions in complex metallurgical processes, which will be very useful for metallurgists, chemists, and technologists.

Abstract: Temperature dependences of the kinematic viscosity, density, and electrical resistivity of Fe_72.5Cu₁Nb₂Mo_1.5Si₁₄B₉ and Fe_84.5Cu_0.6Nb_0.5Si_1.5B_8.6P₄C_0.3 multicomponent melts have been studied. We found different behavior of the temperature dependences of viscosity near the critical point T_k = 1760 K during heating, which is associated with different chemical compositions of the clusters in the melt. In the cooling stage, the activation energy of the viscous flow for these two melts is the same and equal to 43 kJ·mol^-1. At a temperature of 1720 K, the relative free volume is 5.1 and 7.5 % of the total melt volume for Fe_72.5Cu₁Nb₂Mo_1.5Si₁₄B₉ and Fe_84.5Cu_0.6Nb_0.5Si_1.5B_8.6P₄C_0.3 respectively. In the cooling stage, the electrical resistance of melt is higher than at the heating stage.

Abstract: Silicon production by silica-containing raw material reduction by carbon in ore-smelting furnaces (OSF) is a complex pyro-metallurgic process. Silicon is produced in a system consisting of charge, furnace electrodes, air, melt, slag, and gases at temperatures above 2000°C, which generates silicon monoxide and carbide unavoidably. The finished product contains impurities (Fe, Ca, Al, Ti, etc.) in small amounts; however, it is still unknown for sure how impurities, contained in raw materials, behave and interact with each other and with silicon. To analyze the distribution of charge components during smelting, the research team used thermodynamic (mathematical) modeling in Selector software. The constructed four-tank silicon production model describes adequately the process. The assumed tank temperatures correspond to the OSF reaction zones (400°C, 1530°C, 2200°C, and 2000°C). Modeling involves 15 charge-carried elements: quartzite from the Cheremshanskoye deposit, charcoal and black coal, petroleum coke, wood chips, and OSF coal electrodes. According to the model, silicon recovery (with a 97.15 wt% silicon content in the melt) is 75%, which is consistent with literature and production data (AO Kremniy, Shelekhov, Irkutsk Oblast).

Abstract: Questions of influence of nanosecond electromagnetic impulses on melts of metals are considered in the article. The analysis of action of impulses on electromagnetic hashing and thermal conditions of a melt showed their small influence. Mechanical (acoustic) action is chosen as the main one. Formulas and values for coefficients of transformation of electromagnetic field to the acoustic one for a number of metals are given. The transformation model in the form of the wave of current running on the radiator is offered. Comparison of action of electromagnetic impulses on melts showed that emergence of acoustic vibrations is the main thing. The theory of contactless transformation of electromagnetic waves in acoustic ones is considered. Comparison with experiments is given. The model of contact electro-pulse processing of metal melts in the form of transition of an electromagnetic wave to acoustic is offered. Acoustic waves change structure of a melt, condition of a crystallization of a melt and improve properties of the hardened metal.

Abstract: Microstructure of ingot and industrial blanks made of copper M2 was examined for quality control. Microstructure was examined by means of traditional metallographic analysis methods. Exogenous nonmetal inclusions and pores in microstructure were found. The transition from exogenous inclusions and pores, which were not removed in initial processing stage, to the crack, which leads to billet destruction on one of last processing stages, is shown. Without quality control of copper blanks by a metallographic method, it is impossible to provide guarantee of reliable operation of machines and responsible purpose constructions. A comparative study of the temperature dependences of the viscosity of the melts of charge materials and finished ingots for copper M2 was carried out. The study of the viscosity of copper melts M2 was carried out with the aim of quality control in the chain of "charge-melt-ingot" at the foundry stage.

Abstract: The comparable study of the structure and structure-sensitive properties of the melt of steel 08H15N5D2T and two melts prepared by electro-slag re-melting (ESR) and vacuum-arc re-melting (VAR) of the steel has been carried out. The temperature dependences have been obtained for the kinematic viscosity, density, surface tension, electrical resistance, and magnetic susceptibility. The short-range structural order of the ESR and VAR melts has been studied by direct diffraction methods. The connection between the method of re-melting and the level of impact strength (KCU) has been established. The reasons for the appearance of the difference in the structure and properties of ESR and VAR steel are discussed.

Abstract: The effect of overheating of the melt and cooling rate of alloys of the Al-Cu system with a copper content of 25.0 – 36.0% ( mass.), the rest of the aluminum is investigated. It is shown that an overheating of the liquid at 50 – 100 K above the liquid-liquid line leads to the formation of a fine-dispersed eutectic structure and the inhibition of the formation of primary aluminum crystals in the pre-evacuation of alloys and the Al₂Cu phase in hypereuvtectic alloys, in accordance. An increase in the melt overheating temperature by 150 K above the liquid-liquid line and the subsequent cooling at 10³ – 10⁴ K/s leads to the complete inhibition of the formation of primary crystals. An overheating of the melt on 100 – 150 K alloys above the liquid line and subsequent cooling with a velocity of 10³ – 10⁴ K /s reduces the rate of corrosion by 30 – 45% and increases the numerical value in 1.3 – 1.45 times the relative wear resistance, and the brittleness of alloys decreases in 1.2 – 1.35 times in comparison with the samples after casting.

Abstract: The work is devoted to the study of contact melting in the Al-Si system, which is an aluminum film deposited on a silicon single-crystal substrate. The impulse action of high-density currents (j> 8.1010 A / m2) passing through an aluminum film is analyzed. It was found that under the considered electric heat loads in the system, the degradation processes associated with the appearance of a molten aluminum zone and subsequent contact melting in the metal-semiconductor system develop. From the analysis of contact melting processes, a technique for estimating the coefficients of multiphase diffusion in the system under consideration is a thin aluminum film-single-crystal silicon substrate.

Abstract: An amoprphous and nanocrystalline ribbon is produced applying the technology of rapid molten metal quenching. The chemical composition of the alloy is required to contain elements ensuring the amorphous structure formation in the course of quenching. A great number of various chemical elements in amorphous and nanocrystalline alloys contribute to the complex process of the structure formation in the course of heat treatment of the amorphous precursor. After heat treatment, the structure of the soft magnetic material can remain amorphous or partially crystallized or nanocrystalline. The results of an investigation into the melts’ property of iron-based amorphous and nanocrystalline alloys are presented in the paper. The structure has been shown to influence mechanical properties of the material in preparing the melt before casting.

Abstract: The article outlines the production of fibrous materials, discloses energy production targets for mineral wool items production, scrutinizes specific features of cupola process. Besides, the article presents the experimental research of mineral wool cupola process. Thus, the article describes the design of a cupola furnace, principles of its operation, and its main performance indicators. A summary of analytical and theoretical research of non-isothermal gas flow motion in shaft furnaces is presented herein. The results of the experimental studies of the patterns of change in gas-dynamic operation of the cupola furnace are also shown in the article. To assess the development of solid fuel combustion in the furnace, the laws that govern the changes in gas composition at the level of stockline have been studied. The results are shown in the Table. The analysis of the current state of thermal and gas-dynamic operation of the mineral wool cupola furnace yielded recommendations for optimization and performance enhancement of the operating cupola furnace.