Method to prevent abnormal grain growth for beta annealed TI-6AL-4V forgings

Patent metadata

Field	Value
Publication number	US-10094013-B2
Application number	US-201514972972-A
Country	US
Kind code	B2
Filing date	Dec 17, 2015
Priority date	Dec 23, 2014
Publication date	Oct 9, 2018
Grant date	Oct 9, 2018

Abstract

A method for heat-treating a titanium alloy, such as Ti-6Al-4V. The method may occur after or include a step of forging the titanium alloy such that localized, highly deformed grains are formed in the titanium alloy. Then the method may include steps of recrystallization annealing the titanium alloy by heating the titanium alloy to a temperature in a range between 30° F. to 200° F. below beta transus of the titanium alloy for 1 hour to 6 hours and then furnace cooling of the titanium alloy to 1200° F. to 1500° F. at a rate of 50° F. to 500° F. per hour. Following the recrystallization annealing, the method may include beta annealing the titanium alloy. These steps may be performed in a single heat treating cycle.

First claim

The invention claimed is:

1. A method for heat-treating a titanium alloy, the method comprising the steps of:
recrystallization annealing the titanium alloy, wherein recrystallization annealing comprises heating the titanium alloy to a temperature 30° F. to 200° F. below beta transus of the titanium alloy for a length of time in a range of 1 hour to 6 hours followed by slow cooling the titanium alloy after to 1200° F. to 1500° F. at a rate of 50° F. to 500° F. per hour; and
beta annealing the titanium alloy following completion of the recrystallization annealing steps including heating the titanium alloy to a temperature in a range of 10° to 100° F. above the beta transus of the titanium alloy.

2. The method of claim 1 , wherein the beta annealing comprises holding the temperature above beta transus for 30 minutes per inch of thickness of the titanium alloy.

3. The method of claim 1 , wherein the beta annealing further comprises holding the temperature in the range of 10° to 100° F. above beta transus for 15 minutes to 5 hours.

4. The method of claim 1 , wherein beta transus of the titanium alloy is a temperature between 1800° F. and 1850° F.

5. The method of claim 1 , further comprising forging of the titanium alloy prior to the recrystallization annealing step.

6. The method of claim 1 , wherein the titanium alloy is Ti-6Al-4V.

7. The method of claim 1 , wherein the step of slow cooling the titanium alloy comprises furnace cooling the titanium alloy.

8. The method of claim 1 , further comprising a step of gradually heating then holding the titanium alloy at a temperature 30° F. to 200° F. below beta transus of the titanium alloy following the slow cooling of the recrystallization annealing step and immediately preceding the step of beta annealing.

9. The method of claim 8 , further comprising the steps of cooling the titanium alloy to a stabilization temperature between 1200° F. to 1450° F. for one or more hours following the beta annealing step and then cooling the titanium alloy to room temperature.

10. A method for heat-treating a titanium alloy, wherein the titanium alloy is Ti-6Al-4V, the method comprising the steps of:
recrystallization annealing the titanium alloy by heating the titanium alloy to a temperature in a range between 30° F. to 200° F. below beta transus of the titanium alloy for 1 hour to 6 hours and then furnace cooling of the titanium alloy to 1200° F. to 1500° F. at a rate of 50° F. to 500° F. per hour; and
beta annealing the titanium alloy following the furnace cooling step, wherein the beta annealing comprises heating the titanium alloy to a temperature in the range of 10° to 100° F. above beta transus of the titanium alloy for 15 minutes to 5 hours.

11. The method of claim 10 , wherein the beta annealing further comprises holding the temperature above beta transus for 30 minutes per inch of thickness of the titanium alloy.

12. The method of claim 10 , wherein beta transus of the titanium alloy is a temperature between 1800° F. and 1850° F.

13. The method of claim 10 , further comprising steps of forging of the titanium alloy prior to the recrystallization annealing step.

14. The method of claim 10 , further comprising a step of heating then holding the titanium alloy at a stabilization temperature of between 1200° F. to 1450° F. following the step of furnace cooling and immediately preceding the step of beta annealing.

15. The method of claim 10 , further comprising the steps of cooling the titanium alloy to a stabilization temperature between 1200° F. to 1450° F. for one or more hours following the beta annealing step and then cooling the titanium alloy to room temperature.

16. The method of claim 10 , wherein the recrystallization annealing includes holding the titanium alloy at the temperature in the range of 30° F. to 200° F. below beta transus of the titanium alloy for a length of time in a range of 1 hour to 4 hours.

17. A method for heat-treating a titanium alloy, wherein the titanium alloy is Ti-6Al-4V, the method comprising the steps of:
forging of the titanium alloy such that localized, highly deformed grains are formed in the titanium alloy;
recrystallization annealing the titanium alloy by heating and holding the titanium alloy at a temperature in a range between 30° F. to 200° F. below beta transus of the titanium alloy for a length of time in a range of 1 to 4 hours following the forging step, then furnace cooling the titanium alloy to 1200° F. to 1500° F. at a rate of 50° F. to 500° F. per hour, wherein beta transus of the titanium alloy is a temperature between 1800° F. and 1850° F., wherein the recrystallization annealing results in the highly deformed grains forming fine and uniform transformed beta grains throughout the titanium alloy; and
beta annealing the titanium alloy following the furnace cooling, wherein the beta annealing comprises:
reheating then holding the titanium alloy at the temperature in the range between 30° F. to 200° F. below beta transus of the titanium alloy, and
heating then holding the titanium alloy at a temperature above beta transus of the titanium alloy for an amount of time between 15 minutes to 5 hours.

18. The method of claim 17 , further comprising the steps of cooling the titanium alloy to a stabilization temperature between 1200° F. to 1450° F. for one or more hours following the beta annealing step and then cooling the titanium alloy to room temperature.

19. The method of claim 17 , wherein the beta annealing further comprises holding the temperature in a range of 10° to 100° F. above the beta transus for 30 minutes per inch of thickness of the titanium alloy.

Assignees

• Spirit Aerosys Inc

Inventors

• Nasserrafi Rahbar
• Hicks Gerald E
• Walker Michael A
• Clasper Craig M

Classifications

• C22C14/00

  Alloys based on titanium · CPC title

• C22F1/02

  in inert or controlled atmosphere or vacuum (adjusting the composition of the atmosphere C21D1/76) · CPC title

• C22F1/183 Primary

  of titanium or alloys based thereon · CPC title