Method of producing a copper-nickel-tin alloy
A spinodal copper-nickel-tin alloy with a combination of improved impact strength, yield strength, and ductility is disclosed. The alloy is formed by process treatment steps including solution annealing, cold working and spinodal hardening. These include such processes as a first heat treatment/homogenization step followed by hot working, solution annealing, cold working, and a second heat treatment/spinodally hardening step. The spinodal alloys so produced are useful for applications demanding enhanced strength and ductility such as for pipes and tubes used in the oil and gas industry.
1. A method of producing a spinodal copper-nickel-tin alloy, comprising:
casting a copper-nickel-tin alloy;
homogenizing the alloy;
hot working the homogenized alloy to obtain a reduction ratio which is a minimum of about 5:1;
solution annealing the hot worked alloy at a temperature of from about 1470° F. to about 1650° F.;
cold working the solution annealed alloy until a reduction of area of from about 15% to about 80% occurs in the alloy; and
spinodally hardening the alloy after the cold working to produce a spinodal alloy;
wherein the copper-nickel-tin alloy consists of:
from about 5 wt % to about 20 wt % nickel;
from about 5 wt % to about 10 wt % tin;
minor additions, wherein the minor additions are selected from at least one of a group consisting of boron, zirconium, iron, niobium, manganese and magnesium, and wherein each of the minor additions is present at a content of no more than about 0.3% wt % in the spinodal alloy;
and
balance copper; and
wherein the alloy has a 0.2% offset yield strength of at least 110 ksi, an impact toughness of at least 12 foot-pounds when measured according to ASTM E23, V notch at room temperature, and an ultimate tensile strength of at least 120 ksi, and a minimum elongation of 20%.
2. The method of claim 1 wherein, the copper-nickel-tin alloy consists of from about 14 wt % to about 16 wt % nickel, and from about 7 wt % to about 9 wt % tin.
3. The method of claim 2 , where the alloy consists of about 15 wt % nickel and about 8 wt % tin.
4. The method of claim 1 , wherein the homogenizing occurs at a temperature of about 1400° F. or higher.
5. The method of claim 2 , wherein the homogenizing occurs at a temperature from about 1475° F. to about 1650° F.
6. The method of claim 1 , wherein the homogenizing occurs for a time of from about 4 hours to about 48 hours.
7. The method of claim 1 , wherein the hot working occurs at a temperature of from about 1300° F. to about 1650° F.
8. The method of claim 1 , wherein the hot working occurs for a time of at least 6 hours.
9. The method of claim 1 , wherein the solution annealing occurs for a time of from about 0.5 hours to about 6 hours.
10. The method of claim 1 , further comprising a quenching after the solution annealing.
11. The method of claim 10 , wherein the quenching occurs within 2 minutes of completion of the solution annealing.
12. The method of claim 1 , wherein the cold working occurs at room temperature.
13. The method of claim 1 , wherein the steps of cold working or solution annealing are repeated until a desired size is obtained.
14. The method of claim 1 , wherein the spinodal hardening occurs at a temperature of from about 400° F. to about 1000° F.
15. The method of claim 14 , wherein the spinodal hardening occurs at a temperature of from about 450° F. to about 725° F.
16. The method of claim 1 , wherein the spinodal hardening occurs at a temperature of from about 500° F. to about 675° F.
17. The method of claim 1 , wherein the spinodal hardening occurs for a time of from about 10 seconds to about 40,000 seconds.
18. The method of claim 17 , wherein the spinodal hardening occurs for a time of from about 5,000 seconds to about 10,000 seconds.
19. The method of claim 1 , wherein the spinodal hardening occurs for a time of from about 0.5 hours to about 8 hours.
20. A method of producing a spinodal copper-nickel-tin alloy comprising:
solution annealing a copper-nickel-tin alloy wherein the solution annealing occurs at a temperature of from about 1475° F. to about 1650° F. and for a time of from about 0.5 hours to about 6 hours;
cold working the solution annealed alloy, wherein the cold working results in a reduction of area in the alloy of from about 15% to about 80%; and
spinodally hardening the alloy after cold working, wherein the spinodal hardening occurs at a temperature of from about 500° F. to about 675° F. and for a time of from about 0.5 hours to about 8 hours;
wherein the copper-nickel-tin alloy consists of:
from about 5 wt % to about 20 wt % nickel;
from about 5 wt % to about 10 wt % tin;
a minor addition of at least one element selected from the group consisting of zirconium, iron, niobium, manganese, and magnesium, wherein the minor addition elements and other elements are included at no more than about 0.3 wt % each; and
balance copper; and
wherein the alloy has a 0.2% offset yield strength of at least 110 ksi, an impact toughness of at least 12 foot-pounds when measured according to ASTM E23, V notch at room temperature, and an ultimate tensile strength of at least 120 ksi, and a minimum elongation of 20%.
21. The method of claim 20 , wherein the steps of cold working or solution annealing are repeated until a desired shape is obtained.
22. The method of claim 1 , wherein the spinodal alloy is shaped as a rod, bar, tube, pipe, or plate.
23. The method of claim 1 , wherein the spinodal alloy has an impact toughness of at least 30 foot-pounds and up to about 100 foot-pounds, when measured according to ASTM E23, V notch at room temperature.
24. The method of claim 1 , wherein the spinodal alloy has a magnetic permeability of less than 1.02.
25. The method of claim 20 , wherein the at least one element is zirconium.
26. The method of claim 20 , wherein the at least one element is iron.
27. The method of claim 20 , wherein the at least one element is magnesium.