Induction stirred, ultrasonically modified investment castings and apparatus for producing

A casting unit comprising:

• an investment casting mold having a mold cavity;
• a furnace having
• a working zone that receives the investment casting mold,
• low output induction coils surrounding the working zone,
• a refractory divider separating the working zone from the low output induction coils surrounding the working zone;
• a first heating element surrounding the investment casting mold and positioned between the investment casting mold and the refractory divider;
• insulation surrounding the working zone;
• a melting zone;
• a fluid communication channel between the melting zone and the investment casting mold;
• a second heating element surrounding the melting zone;
• a stopper to regulate a flow of molten metal from the melting zone, through the fluid communication channel and into the investment casting mold in the working zone;
• an ultrasonic source for delivering an ultrasonic pulse into the mold cavity when provided with molten metal and positioned in contact with the bottom of the mold;
• and
• means for maintaining an atmosphere in the working zone of the furnace.

A method for fabricating an equiaxed casting, comprising the steps of:

• providing an investment casting mold having a mold cavity;
• providing a furnace having
• a working zone that receives the investment casting mold,
• means for generating a convention current;
• a refractory divider surrounding the working zone;
• insulation surrounding the working zone;
• a first heating element positioned inside the working zone and positioned between the refractory divider and the mold cavity;
• and
• an ultrasonic source for delivering an ultrasonic pulse into the mold cavity when provided with molten metal and positioned in contact with the bottom of the mold;
• placing the investment casting mold into the working zone;
• providing molten metal to the investment casting mold;
• as the molten metal begins to solidify in the mold cavity, applying an ultrasonic pulse to the investment casting mold, the pulse having sufficient amplitude to disrupt a formation of dendrites growing within the investment casting mold, the pulse further mixing the molten alloy;
• continuing to apply the ultrasonic pulse to the investment casting mold to disrupt the formation of dendrites, mix the molten alloy and promote the formation of equiaxed grains as the molten metal solidifies.

A method for fabricating an equiaxed casting, comprising the steps of:

• providing an investment casting mold having a mold cavity;
• providing a furnace having
• a working zone that receives the investment casting mold,
• means for generating a convention current, the means for generating surrounding the working zone,
• a refractory divider separating the working zone from the means for generating a convection current;
• insulation surrounding the working zone;
• a first heating element positioned inside the working zone, the refractory divider positioned between the means for generating a convection current and the first heating element;
• a melting zone for receiving metal;
• a fluid communication channel between the melting zone and the investment casting mold;
• a second heating element surrounding the melting zone;
• a stopper to regulate a flow of molten metal from the melting zone through the communication channel into the investment casting mold;
• an ultrasonic source for delivering an ultrasonic pulse into the mold cavity when provided with molten metal and positioned in contact with the bottom of the mold;
• and
• means for maintaining an atmosphere within the working zone of the furnace;
• placing the investment casting mold into the working zone and positioned in fluid communication with the melting zone to receive molten metal;
• providing molten metal from the melting zone;
• optionally heating metal in the melting zone to a first predetermined temperature with the second heating element;
• providing molten metal to the investment casting mold while maintaining an atmosphere within the working zone of the furnace;
• as the molten metal begins to solidify in the mold cavity, applying an ultrasonic pulse to the investment casting mold, the pulse having sufficient amplitude to disrupt a formation of dendrites growing within the investment casting mold, the pulse further mixing the molten alloy;
• continuing to apply the ultrasonic pulse to the investment casting mold to disrupt the formation of dendrites, mix the molten alloy and promote the formation of equiaxed grains.