冷坩埚磁悬浮熔炼的电磁场分析

针对冷坩埚熔炼过程的悬浮特性问题,利用准三维耦合电流算法,就坩埚结构、电磁频率及感应圈电流等影响因素进行分析,为冷坩埚结构和磁悬浮熔炼的优化设计提供依据。结果显示,冷坩埚熔炼时,电磁场频率和冷坩埚结构决定坩埚的透磁能力,随频率上升,坩埚内磁通密度下降,且频率高于100kHz时下降趋势加大;其次,冷坩埚的分瓣结构使其涡流损耗降低,且磁场频率越高效果越明显。对100kHz以上的超高频磁场,坩埚应分割为(16~20)瓣;对(10~100)kHz的高频磁场,坩埚可分割为(8~12)瓣;而对低于10kHz的中高频磁场,坩埚只需分割(4~8)瓣。再者,熔体的磁悬浮力与感应圈电流成平方关系,且电磁场频率越高则磁悬浮力越大。

THE ELECTROMAGNETIC FIELD ANALYSIS OF LEVITATION MELTING WITH COLD CRUCIBLE

By using the quasi-3D coupled current method presented, the influences of structure of cold crucible, power frequency, electricity property of charge(melt), coil(inductor)position and current on the electromagnetic field(EMF) and the levitation characteristics in the melting processes are analyzed. It is shown that in the melting process, power frequency and crucible structure are the decisive factors for the ability of penetrating magnetic flux into cold crucible. The magnetic flux density in cold crucible is reduced with the rising of power frequency, and this tendency becomes stronger when that is higher than 100 kHz. The segmented structure of cold crucible can reduce the induction eddy in itself effectively, and the higher the power frequency is, the better the result is. So, a cold crucible can be segmented into(16~20) sectors for higher frequency electromagnetic field(f>100 kHz),(8~12) sectors for high frequency one(10 kHz≤f≤100kHz), and(4~8) sectors for mid-high frequency one(f<10 kHz). It is also shown that the levitation force in melting charge is related to coil current as a parabolic function.