Processing of alpha-beta titanium alloys

• US 10,502,252 B2
• Filed: 11/23/2015
• Issued: 12/10/2019
• Est. Priority Date: 11/23/2015
• Status: Active Grant

• Current Assignee: ATI Properties LLC
• Original Assignee: ATI Properties LLC
• Inventors: Foltz, IV, John W., Garside, Gavin
• Primary Examiner(s): Wu, Jenny R
• Application Number:
  US14/948,941
• Publication Number:
  US 20170146046A1
• Time in Patent Office: 1,478 Days
• CPC Class Codes: C22C 14/00 Alloys based on titanium
• CPC Class Codes: C22F 1/183 of titanium or alloys based thereon
• CPC Class Codes: F16B 19/04 Rivets; Spigots or the like fastened by riveting lead seals G09F3/00
• CPC Class Codes: F16B 33/00 Features common to bolt and nut
• CPC Class Codes: F16B 37/00 Nuts or like thread-engaging members specially shaped for rotations by a tool F16B23/00
• CPC Class Codes: F16B 39/24 by means of washers, spring washers, or resilient plates that lock against the object locking to the screw-thread F16B39/14 , F16B39/34, F16B39/36
• CPC Class Codes: F16B 43/00 Washers or equivalent devices; Other devices for supporting bolt-heads or nuts circlips F16B21/18; for indicating tensile load F16B31/02; forming a whole with the bolt or nut F16B33/00; locking bolts or nuts by means of a fixed plate or ring, or washer-like resilient plates F16B39/10, F16B39/24

Abstract

A method for increasing tensile strength of a cold workable alpha-beta titanium alloy comprises solution heat treating a cold workable alpha-beta titanium alloy in a temperature range of T_β-106° C. to T_β-72.2° C. for 15 minutes to 2 hours; cooling the alpha-beta titanium alloy at a cooling rate of at least 3000° C./minute; cold working the alpha-beta titanium alloy to impart an effective strain in the range of 5 percent to 35 percent in the alloy; and aging the alpha-beta titanium alloy in a temperature range of T_β-669° C. to T_β-517° C. for 1 to 8 hours. Fastener stock and fasteners including solution treated, quenched, cold worked, and aged alpha-beta titanium alloys are also disclosed.

Claims

1. A method for increasing tensile strength of a cold workable alpha-beta titanium alloy, comprising:

solution heat treating a cold workable alpha-beta titanium alloy by heating the alpha-beta titanium alloy in a temperature range of the alpha-beta titanium alloy'"'"'s beta transus temperature (T_β

)-106°

C. to T_β

-72.2°

C. for 15 minutes to 2 hours;

cooling the alpha-beta titanium alloy at a cooling rate of at least 3000°

C. per minute to ambient temperature;

cold working the alpha-beta titanium alloy to impart an effective strain in the range of 13 percent to 35 percent; and

aging the alpha-beta titanium alloy by heating the alpha-beta titanium alloy in a temperature range of T_β

-669°

C. to T_β

-517°

C. for 1 to 8 hours, wherein after the aging the alpha-beta titanium alloy exhibits an ultimate tensile strength of at least 204.2 ksi.

2. The method of claim 1, wherein the alpha-beta titanium alloy comprises, in weight percentages based on total alloy weight:

2.9 to 5.0 aluminum;

2.0 to 3.0 vanadium;

0.4 to 2.0 iron;

0.2 to 0.3 oxygen;

0.005 to 0.3 carbon;

titanium;

impurities; and

optionally, one or more of tin, zirconium, molybdenum, chromium, nickel, silicon, copper, niobium, tantalum, manganese, cobalt, boron and yttrium;

wherein the sum of the weight percentages of any tin, zirconium, molybdenum, chromium, nickel, silicon, copper, niobium, tantalum, manganese, cobalt, boron, and yttrium present in the titanium alloy is less than 0.5 weight percent;

wherein the individual concentrations of any tin, zirconium, molybdenum, chromium, nickel, silicon, copper, niobium, tantalum, manganese, and cobalt present in the alloy are each no greater than 0.1 weight percent;

wherein the individual concentrations of any boron and yttrium present in the alloy are each less than 0.005 weight percent.

3. The method of claim 1, wherein the alpha-beta titanium alloy comprises in weight percentages:

2.5 to 3.5 aluminum;

2.0 to 3.0 vanadium;

up to 0.20 iron;

up to 0.15 oxygen;

up to 0.050 carbon;

up to 0.030 nitrogen;

up to 0.015 hydrogen;

titanium;

impurities; and

optionally, one or more of tin, zirconium, molybdenum, chromium, nickel, silicon, copper, niobium, tantalum, manganese, cobalt, boron and yttrium;

wherein the sum of the weight percentages of any tin, zirconium, molybdenum, chromium, nickel, silicon, copper, niobium, tantalum, manganese, cobalt, boron, and yttrium present in the titanium alloy is less than 0.3 weight percent;

wherein the individual concentrations of any tin, zirconium, molybdenum, chromium, nickel, silicon, copper, niobium, tantalum, manganese, and cobalt present in the alloy are each no greater than 0.1 weight percent;

wherein the individual concentrations of any boron and yttrium present in the alloy are each less than 0.005 weight percent.

4. The method of claim 1, where the alpha-beta titanium alloy is selected from Ti-4.5Al-3V-2Mo-2Fe alloy, Ti-5Al-4V-0.7Mo-0.5Fe alloy, and Ti-3Al-5Mo-5V-3Cr-0.4Fe alloy.

5. The method of claim 1, wherein cooling the alpha-beta titanium alloy comprises quenching the alpha-beta titanium alloy in water.

6. The method of claim 1, wherein cold working the alpha-beta titanium alloy comprises working the alpha-beta titanium alloy at temperatures less than 676.7°

C.

7. The method of claim 1, wherein cold working the alpha-beta titanium alloy comprises working the alpha-beta titanium alloy at temperatures less than 537.8°

C.

8. The method of claim 1, wherein cold working the alpha-beta titanium alloy comprises at least one of rolling, forging, extruding, pilgering, rocking, drawing, flow-turning, liquid compressive forming, gas compressive forming, hydro-forming, bulge forming, roll forming, stamping, fine-blanking, die pressing, deep drawing, coining, spinning, swaging, impact extruding, explosive forming, rubber forming, back extrusion, piercing, spinning, stretch forming, press bending, electromagnetic forming, and cold heading the alpha-beta titanium alloy.

9. The method of claim 1, wherein cold working the alpha-beta titanium alloy comprises drawing the alpha-beta titanium alloy.

10. The method of claim 1, wherein cold working the alpha-beta titanium alloy comprises swaging the alpha-beta titanium alloy.

11. The method of claim 1, wherein cold working the alpha-beta titanium alloy imparts an effective strain in the range of 13 percent to 30 percent to the alpha-beta titanium alloy.

12. The method of claim 1, wherein cold working the alpha-beta titanium alloy imparts an effective strain in the range of 13 percent to 23 percent to the alpha-beta titanium alloy.

13. The method of claim 1, wherein solution heat treating the alpha-beta titanium alloy comprises heating the alpha-beta titanium alloy in a temperature range of T_β

-97.2°

C. to T_β

-83.3°

C. for 30 minutes to 1 hour.

14. The method of claim 1, wherein aging the alpha-beta titanium alloy comprises heating the alpha-beta titanium alloy in a temperature range of T_β

-622°

C. to T_β

-581°

C. for 1 to 5 hours.

15. The method of claim 1, further comprising, prior to solution heat treating the alpha-beta titanium alloy, hot working the alpha-beta titanium alloy.

16. The method of claim 15, wherein hot working the alpha-beta titanium alloy comprises heating the alpha-beta titanium alloy in a temperature range of T_β

-83.3°

C. to T_β

-28°

C.

17. The method of claim 15, wherein hot working the alpha-beta titanium alloy comprises at least one of rolling, forging, extruding, pilgering, rocking, drawing, flow-turning, liquid compressive forming, gas compressive forming, hydro-forming, bulge forming, roll forming, stamping, fine-blanking, die pressing, deep drawing, coining, spinning, swaging, impact extruding, explosive forming, rubber forming, back extrusion, piercing, spinning, stretch forming, press bending, electromagnetic forming, and cold heading the alpha-beta titanium alloy.

18. The method of claim 1, further comprising, intermediate cooling the alpha-beta titanium alloy and cold working the alpha-beta titanium alloy, surface conditioning the alpha-beta titanium alloy.

19. The method of claim 1, further comprising, intermediate the step of cold working the alpha-beta titanium alloy and the step of aging the alpha-beta titanium alloy, surface conditioning the alpha-beta titanium alloy.

20. The method of claim 1, further comprising, after at least one of the step of cold working the alpha-beta titanium alloy and the step of aging the alpha-beta titanium alloy, finishing the alpha-beta titanium alloy.

21. The method of claim 20, wherein finishing the alpha-beta titanium alloy comprises machining the alpha-beta titanium alloy.