Numerical Simulation of the Cooling of Melt Droplets as Applied to the Technology of Production of Metal Powders
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Journal of Engineering Physics and Thermophysics, Vol. 93, No. 6, November, 2020
HEAT TRANSFER IN PHASE TRANSFORMATIONS NUMERICAL SIMULATION OF THE COOLING OF MELT DROPLETS AS APPLIED TO THE TECHNOLOGY OF PRODUCTION OF METAL POWDERS K. N. Volkov and V. N. Emel'yanov
UDC 532.529
Problems on the development of mathematical models for control of the technological processes of producing powders of metals from their melts and for optimization of these processes were considered. A numerical simulation of the solidification of melt droplets in a turbulent cold-gas jet has been performed with the use of a complex mathematical model, and results of this simulation were used for estimating the influence of different factors on the flying of a melt droplet in a gas flow until it is solidified. Keywords: plasma technology, droplet, melt, powder, numerical simulation. Introduction. A science-based prediction of the structure and properties of powder and composite materials in the process of their production is useful in increasing the quality of the finished products of them and in reducing the cost of these products. In this connection, of importance is the development of methods for mathematical simulation of the technological processes of obtaining high-quality powders, including powders of refractory metals and multicomponent melts [1]. In the production of powders, a fairly simple and reliable PREP method of plasma spraying of a rotating workpiece, making possible the obtaining of a powder homogeneous in particle size with a small specific surface, is used widely [2]. One of the main factors of the production of a powder from a metal solution is the rate of crystallization of its particles. In the case where this rate is high, the cellular structure of the metal powder is formed as a result of the dispersion of the structural elements of the metal solution and increase in the content of the alloying elements in it. The rate of crystallization of a molten-metal droplet is usually increased by decreasing its volume, which leads to an increase in the rate of heat transfer from it, as well as with the use of highly heat-conducting media. To prevent the crystallization of a melt in the process of its cooling and to provide the attainment of the amorphous state by it in this process, it is necessary to cool the melt with a high rate [3], which is a complex technological problem that can be solved, e.g., by the spraying of thin melt films over an intensively cooled substrate. In this case, the amorphization of the melt is disturbed by the heterogeneous crystallization of it in the process of its interaction with the substrate. The most efficient method of prevention of the heterogeneous crystallization of a molten metal is the gasdynamic cooling of its droplets [4]. Since the obtaining of a powder from a molten metal by its spraying is a complex process determined by many factors, of importance is the construction of mathematical models of optimization of this process as well as the substantiation of the design parameters of t
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