Melting and Mixing of Materials in a Crucible by Electric Induction Heel Process

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 forming a total interior volume of the crucible, the lowest one of the plurality of partial interior volumes comprising a bottom interior volume and the highest one of the plurality of partial interior volumes comprising a top interior volume of the crucible, the method comprising the steps of:

• loading the molten heel of the transition material into at least a portion of the bottom interior volume;
• connecting a bottom volume output of a melting power source to the one of the plurality of induction coils surrounding the bottom interior volume, the bottom volume output of the melting power source operating at a melting frequency and a melting power level to keep the molten heel of the transition material at least at the minimum melting temperature of the transition material;
• sequentially adding the solid or semi-solid charge of the transition material into at least a part of each of the next highest one of the plurality of partial interior volumes up to the top interior volume and connecting a discrete next highest volume output of the melting power source to the one of the plurality of induction coils surrounding the next highest one of the plurality of partial interior volumes to which the solid or semi-solid charge of the transition material is added and a top volume output of the melting power source to the one of the plurality of induction coils surrounding the top interior volume until the crucible is filled to the total interior volume of the crucible with the crucible batch of the transition material, the discrete next highest volume outputs of the melting power source and the top volume output of the melting power source operating at the melting frequency and the melting power level;
• and
• simultaneously disconnecting the top volume output of the melting power source, the discrete next highest volume outputs of the melting power source and the bottom output volume of the melting power source from the plurality of induction coils and connecting a discrete one of a plurality of stir outputs of at least one stirring power source to each one of the plurality of induction coils, the plurality of stir outputs of the at least one stirring power source operating at a stirring frequency and a stirring power level, the stirring frequency being lower than the melting frequency, and the stirring power level being lower than the melting power level, the output stir voltage of each of the plurality of stir outputs of the at least one stirring power source phase shifted from each other to induce an unidirectional electromagnetic stirring of the crucible batch of the transition material in the crucible.