Formation of MHD processes in induction crucible furnace at single-phase supply of inductor

Abstract

It is known that the intensive circulation of metal is an important advantage of an induction crucible fur nace compared to other melting installations. As a result of the axial symmetry of the field created by the inductor and its homogeneity along the crucible sur face electrodynamic forces appear in metal directed toward the crucible axis resulting in the formation of the so called two loop (and in some references four loop) circulation of metal, which is characterized by certain disadvantages, including, first, the low admix ing of metal in the top and bottom parts of the cruci ble, which can delay the melting process when doping additives are used to produce complex alloys;, second, a convex meniscus is formed, which results in the more intensive destruction of the lining of the crucible furnace due to the aggressive impact of slags; and, third, the heterogeneous erosion of the crucible lining. These problems can be solved by developing the one loop circulation (with the formation of a single toroi dal vortex) of metal in the bath of a crucible furnace, which can be achieved by the application of a special design of an inductor and the layout of their connec tions to the power supply source. It is highly desirable that the furnace be supplied from a single phase inter mediate frequency inverter, which is the most widely applied unit for the power supply of existing and newly created furnaces.The authors proposed and studied some possible lay outs of inductor connections consisting of three, four, and six sections supplied from one single phase power source of intermediate frequency. The investigations were aided with software based on the method of detailed magnetic equivalent circuits (electromagnetic calculations) [1] and the finite difference method (cal culation of hydrodynamic phenomena in crucible) [2].This type of inverter is characterized by a voltage cur rent phase angle and amounts to -30…-40 degrees (the current is ahead of the voltage); therefore, for cal culations, the frequency of the power source should be selected to meet this requirement [3]. Figure 1 demonstrates the layout of the connection of a three section inductor developed based the layout that focuses the power described elsewhere [4]. In the studies of the operation of this layout [3] with nonsym metric compensation for the reactive power of the sec tions, it was observed that the phases of the currents are Abstract-The article discusses some technical approaches that enable one to obtain the single loop circu lation of metal in induction crucible furnace without the application of complicated and special multiphase power supply sources (multiphase inverters). The results of investigations into electromagnetic and hydrody namic processes in a furnace with liquid metal charges are presented at different variants of the power supply of multisection inductors of crucible furnaces from a single phase inverter.

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