Processes for improving formability of wrought copper-nickel-tin alloys
Disclosed are processes for improving the formability of a copper-nickel-tin alloy having a 0.2% offset yield strength that is above 115 ksi. The alloy includes about 14.5 to about 15.5 wt % nickel, about 7.5 to about 8.5 wt % tin, and the remaining balance is copper. The copper-nickel-tin alloy is mechanically cold worked to undergo between 5% and 15% plastic deformation. The alloy is then heat treated at elevated temperatures of about 450° F. to about 550° F. for a period of about 3 hours to about 5 hours. The alloy is then subsequently mechanically cold worked again to undergo between 4% and 12% plastic deformation. The alloy is then further heated to an elevated temperature of about 700° F. to about 850° F. for a period between about 3 minutes and about 12 minutes to relieve stress. The resulting alloy has a combination of good formability ratio and good yield strength.
1. A process for improving the formability of a wrought copper-nickel-tin alloy having a 0.2% offset yield strength that is at least 115 ksi, comprising:
performing a first mechanical cold working step on a copper-nickel-tin alloy to a percentage of cold working (% CW) of about 5% to about 15%; and
relieving stress in the alloy through a heat treatment step.
2. The process of claim 1 , wherein the heat treatment for relieving stress in the alloy is performed at a temperature in the range of 700° F. to 950° F. for a period of about 3 minutes to about 12 minutes.
3. The process of claim 1 , wherein the heat treatment for relieving stress in the alloy is performed at a temperature in the range of 775° F. to 950° F. for a period of about 3 minutes to about 12 minutes.
4. The process of claim 1 , wherein after the heat treatment for relieving stress, the alloy has a yield strength of at least 130 ksi.
5. The process of claim 1 , wherein after the heat treatment for relieving stress, the alloy has a formability ratio that is below 2 in the transverse direction.
6. The process of claim 1 , wherein after the heat treatment for relieving stress, the alloy has a formability ratio that is below 2.5 in the longitudinal direction.
7. The process of claim 1 , wherein after the heat treatment for relieving stress, the alloy has a yield strength of at least 130 ksi, a formability ratio that is below 2 in the transverse direction, and a formability ratio that is below 2.5 in the longitudinal direction.
8. The process of claim 1 , wherein after the heat treatment for relieving stress, the alloy has a formability ratio that is below 1.5 in the transverse direction.
9. The process of claim 1 , wherein after the heat treatment for relieving stress, the alloy has a formability ratio that is below 2 in the longitudinal direction.
10. The process of claim 1 , wherein after heat treatment, the alloy has a formability ratio that is below 1.5 in the transverse direction, and a formability ratio that is below 2 in the longitudinal direction.
11. The process of claim 1 , wherein after heat treatment, the alloy has a yield strength of at least 135 ksi.
12. The process of claim 1 , further comprising:
heat treating the copper-nickel-tin alloy after the first cold working step; and
performing a second cold working step on the copper-nickel-tin alloy to a % CW of about 4% to about 12% prior to relieving stress in the alloy through heat treatment.
13. The process of claim 12 , wherein the heat treating after the first cold working is performed by exposing the alloy to a temperature from about 450° F. to about 550° F. for a period of from about 3 hours to about 5 hours.
14. The process of claim 12 , wherein the heat treatment for relieving stress in the alloy is performed at a temperature in the range of 700° F. to 850° F. for a period of about 3 minutes to about 12 minutes.
15. The process of claim 12 , wherein after the heat treatment for relieving stress, the alloy has a formability ratio that is below 1 in the transverse direction.
16. The process of claim 12 , wherein after the heat treatment for relieving stress, the alloy has a formability ratio that is below 1 in the longitudinal direction.
17. The process of claim 12 , wherein after the heat treatment for relieving stress, the alloy has a yield strength of at least 115 ksi, a formability ratio that is below 1 in the transverse direction, and a formability ratio that is below 1 in the longitudinal direction.
18. The process of claim 12 , wherein the copper-nickel-tin alloy includes from about 14.5 wt % to about 15.5 wt % nickel, and from about 7.5 wt % to about 8.5 wt % tin, with the remaining balance being copper.
19. The process of claim 12 , wherein the alloy is a spinodally-hardened material.
20. A process for improving the formability of a wrought copper-nickel-tin alloy having a 0.2% offset yield strength that is at least 115 ksi, comprising:
performing a first mechanical cold working step on a copper-nickel-tin alloy to a % CW of about 5% to about 15%;
heat treating the copper-nickel-tin alloy after the first cold working by exposing the alloy to a temperature from about 450° F. to about 550° F.;
performing a second mechanical cold working step on the copper-nickel-tin alloy to a % CW of about 4% to about 12%; and
relieving stress in the alloy through heat treatment by exposing the alloy to a temperature from about 700° F. to about 850° F.