Method for induction stirred, ultrasonically modified investment castings

Patent metadata

Field	Value
Publication number	US-9839958-B2
Application number	US-201615007941-A
Country	US
Kind code	B2
Filing date	Jan 27, 2016
Priority date	Dec 20, 2011
Publication date	Dec 12, 2017
Grant date	Dec 12, 2017

Abstract

A method for making an equiaxed investment casting. The method utilizes an ultrasonic generator to send an ultrasonic pulse into molten metal in an investment casting mold. The investment casting mold is positioned within a working zone of furnace having low output induction coils for generating a convection current in molten metal. The ultrasonic pulse separates dendrites growing from the face of the mold inward into the molten metal. Instead, equiaxed grains can nucleate within the molten metal. In addition, the ultrasonic pulse and the low output induction coils circulate the molten metal as solute is rejected from solidifying equiaxed grains. The mixing reduces the effects of segregation in the solidifying alloy and assists in nucleating equiaxed grains.

First claim

What is claimed is:

1. 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 convection 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.

2. The method of claim 1 , wherein the means for generating a convection current includes a low output induction coil.

3. The method of claim 1 , wherein the means for generating a convention current further includes the ultrasonic source.

4. The method of claim 1 , wherein the ultrasonic pulse is generated in a frequency range from 15 kHz-25 MHz.

5. The method of claim 1 , wherein the molten metal is initially provided into a melting zone in the furnace in an unmelted state, and the metal is melted by a second heating element surrounding the melting zone.

6. The method of claim 1 , wherein the molten metal is provided to the melting zone from a separate source in a molten state.

7. A method for fabricating an equiaxed casting, comprising:
introducing molten metal into a casting unit, wherein the casting unit includes:
an investment casting mold having a mold cavity;
a furnace having:
a first zone that receives the investment casting mold;
induction coils;
a refractory divider surrounding and defining the first zone; and
a first heating element positioned within the first zone between the investment casting mold and the refractory divider, the first heating element being separated from the low output induction coils by the refractory divider;

insulation surrounding the furnace; and
an ultrasonic source;

disposing the investment casting mold into the first zone;
disposing the molten metal into the mold cavity of the investment casting mold;
generating a convection current in the molten metal in the mold using the induction coils; and
applying an ultrasonic pulse from the ultrasonic source to the investment casting mold; and
forming equiaxed grains as the molten metal solidifies.

8. The method of claim 7 , wherein generating the convection current in the molten metal in the mold using the induction coils includes using low output induction coils.

9. The method of claim 7 , wherein generating the convection current in the molten metal in the mold further includes the ultrasonic pulse from the ultrasonic source.

10. The method of claim 7 , further including maintaining an atmosphere in the first zone.

11. The method of claim 10 , wherein maintaining the atmosphere in the first zone includes maintaining the atmosphere selected the group consisting of a non-reactive atmosphere and a vacuum.

12. The method of claim 7 wherein the ultrasonic pulse is generated in a frequency range from 15 kHz-25 MHz.

13. The method of claim 7 , wherein the molten metal is initially provided into a melting zone in the furnace in an unmelted state, and the metal is melted by a second heating element surrounding the melting zone.

14. The method of claim 7 , wherein applying the ultrasonic pulse from the ultrasonic source to the investment casting mold includes applying the ultrasonic pulse as the molten metal begins to solidify in the mold cavity.

15. The method of claim 14 , wherein applying the ultrasonic pulse from the ultrasonic source to the investment casting mold includes continuing to apply the ultrasonic pulse to the investment casting mold as the molten metal solidifies.

16. The method of claim 7 , wherein applying the ultrasonic pulse from the ultrasonic source to the investment casting mold disrupts formation of dendrites growing within the investment casting mold.

17. A method for fabricating an equiaxed casting, comprising:
introducing molten metal into a casting unit, wherein the casting unit includes:
an investment casting mold having a mold cavity;
a furnace having:
a first zone that receives the investment casting mold;
low output induction coils;
a refractory divider surrounding and defining the first zone; and
a first heating element positioned within the first zone between the investment casting mold and the refractory divider, the first heating element being separated from the low output induction coils by the refractory divider;

insulation surrounding the furnace; and
an ultrasonic source;

disposing the investment casting mold into the first zone;
disposing the molten metal into the mold cavity of the investment casting mold;
generating a convection current in the molten metal in the mold using the low output induction coils;
applying an ultrasonic pulse from the ultrasonic source to the investment casting mold as the molten metal begins to solidify in the mold cavity, disrupting formation of dendrites growing within the investment casting mold;
continuing to apply the ultrasonic pulse to the investment casting mold as the molten metal solidifies, disrupting formation of the dendrites growing within the investment casting mold; and
forming equiaxed grains as the molten metal solidifies.

18. The method of claim 17 wherein the ultrasonic pulse is generated in a frequency range from 15 kHz-25 MHz.

19. The method of claim 17 , wherein the molten metal is initially provided into a melting zone in the furnace in an unmelted state, and the metal is melted by a second heating element surrounding the melting zone.

Assignees

• Gen Electric

Inventors

• Park Junyoung
• Parolini Jason Robert
• Ucok Ibrahim

Classifications

• B22D27/02

  Use of electric or magnetic effects {(for continuous casting B22D11/015, B22D11/11)} · CPC title

• B22D27/04

  Influencing the temperature of the metal, e.g. by heating or cooling the mould · CPC title

• B22D27/045

  Directionally solidified castings · CPC title

• B22D27/20

  Measures not previously mentioned for influencing the grain structure or texture; Selection of compositions therefor · CPC title

• B22C9/043 Primary

  Removing the consumable pattern · CPC title