Melting and mixing of materials in a crucible by electric induction heel process

摘要

Apparatus and method are provided for electric induction heating and melting of a transition material that is non-electrically conductive in the solid state and electrically conductive in the non-solid state in an electric induction heating and melting process wherein solid or semi-solid charge is periodically added to a heel of molten transition material initially placed in a refractory crucible. Induction power is sequentially supplied to a plurality of coils surrounding the exterior height of the crucible at high power level and high frequency with in-phase voltage until a crucible batch of transition material is in the crucible when the induction power is reduced in power level and frequency with voltage phase shifting to the induction coils along the height of the crucible to induce a unidirectional electromagnetic stir of the crucible batch of material.

主权项

1. A method of melting a crucible batch of a transition material by gradually adding a solid or semi-solid charge of the transition material to a molten heel of the transition material in a crucible having a plurality of induction coils surrounding the exterior of the crucible, each one of the plurality of induction coils exclusively surrounding one of a plurality of partial interior volumes of the crucible, a lowest one of the plurality of partial interior volumes comprising a bottom interior volume and a highest one of the plurality of partial interior volumes comprising a top interior volume of the crucible, each one of the plurality of induction coils connected to the output of a separate alternating current power source, the method comprising the steps of:
loading the molten heel of the transition material into at least a bottom portion of the bottom interior volume and adjusting the output of the separate alternating current power source connected to the one of the plurality of induction coils surrounding the bottom interior volume to a melting frequency and a melting power level to keep the molten heel of the transition material at least at a minimum melting temperature of the transition material; simultaneously adding the solid or semi-solid charge of the transition material into at least a top portion of the top interior volume of the crucible subsequent to sequentially adding the solid or semi-solid charge into the bottom interior volume to form the crucible batch of a molten transition material and adjusting the output of the separate alternating current power source connected to the one of the plurality of induction coils surrounding the top interior volume to the melting frequency and the melting power level while synchronizing the phase of an output voltage of the separate alternating current power source connected to the one of the plurality of induction coils surrounding the top interior volume with the phase of the output voltage of the separate alternating current source connected to the one of the plurality of induction coils surrounding the bottom interior volume; and simultaneously reducing the output of each one of the separate alternating current power sources to a stirring frequency and a stirring power level while phase shifting the output voltages of each of the separate alternating current power sources to induce a unidirectional electromagnetic stirring of the crucible batch of the molten transition material in the crucible, the stirring frequency being lower than the melting frequency, and the stirring power level being lower than the melting power level.