Friction stir welding tool having a counterflow pin configuration

• US 20080251571A1
• Filed: 04/13/2007
• Published: 10/16/2008
• Est. Priority Date: 04/13/2007
• Status: Active Grant

• Current Assignee: Dwight A. Burford, Pamela B. Burford
• Original Assignee: Wichita State University
• Inventors: Burford, Dwight A.
• Granted Patent: US 7,942,306 B2
• Time in Patent Office: Days
• US Class Current: 228/114.5
• CPC Class Codes: B23K 20/1255 Tools therefor, e.g. characterised by the shape of the probe

Abstract

A friction stir welding tool having one or more tapered flats for promoting flow of weld material toward the pin terminus and one or more counter-spiraling channels or threads which for promoting flow of the weld material toward the tool shoulder.

Claims

1. A tool for forming a friction stir weld joint or friction stir processing a workpiece, the tool comprising:

a support body rotable about a first axis, the support body having a shoulder;

a pin extending from said shoulder, said pin having a peripheral surface with an angle α

relative to said first axis;

a first geometric feature on said peripheral surface of said pin comprising at least one tapered flat, said tapered flat angled at an angle θ

relative to said first axis, said angle θ

being larger than said angle α

, and said tapered flat adapted to promote a flow of weld material away from said shoulder;

a second geometric feature on said peripheral surface of said pin comprising at least one counter-spiraling channel or thread, said second geometric feature adapted to promote a flow of weld material toward said shoulder.

2. The tool of claim 1 wherein said first geometric feature comprises a plurality of tapered flats, each of said tapered flats angled at said angle θ

relative to said first axis.

3. The tool of claim 1 wherein said first geometric feature comprises a plurality of tapered flats, wherein said plurality of tapered flats are each angled at a plurality of corresponding angles relative to said first axis, said angles of said tapered flats each being larger than said angle α

of said peripheral surface of said pin.

4. The tool of claim 1 wherein said second geometric feature comprises at least one counter-spiraling channel.

5. The tool of claim 4 wherein said counter-spiraling channel has a uniform width and uniform depth.

6. The tool of claim 3 wherein said second geometric feature comprises at least one counter-spiraling channel between two adjacent flats in said plurality of flats.

7. The tool of claim 1 wherein said first geometric feature comprises at least three tapered flats, wherein said at least three tapered flats are each angled at an angle relative to said first axis, said angle of each of said at least three tapered flats being larger than said angle α

of said peripheral surface of said pin, and wherein said second geometric feature comprises at least one counter-spiraling channel between each tapered flat.

8. The tool of claim 7 wherein said second geometric feature comprises two counter-spiraling channels extending between two adjacent flats.

9. The tool of claim 1 wherein said second geometric feature comprises a counter-spiraling single start thread.

10. The tool of claim 1 wherein said second geometric feature comprises a counter-spiraling multiple start thread.

11. The tool of claim 1 wherein said first geometric feature comprises at least three tapered flats, wherein said at least three tapered flats are each angled at an angle relative to said first axis, said angle of each of said at least three tapered flats being larger than said angle α

of said peripheral surface of said pin, and wherein said second geometric feature comprises at least one counter-spiraling thread between each tapered flat.

12. The tool of claim 1 wherein said pin and support body are integrally formed.

13. The tool of claim 1 further comprising a scroll pattern on said shoulder of said tool.

14. The tool of claim 13 wherein said scroll pattern terminates prior to an edge of said shoulder to create a scroll-free concentric surface area.

15. A weld track produced by the weld tool of claim 1.

16. A method of friction stir welding a workpiece comprising:

providing a friction stir welding tool comprising a support body rotable about a first axis, the support body having a shoulder, a pin extending from said shoulder, and said pin having a peripheral surface with an angle α

relative to said first axis;

a first geometric feature on said peripheral surface of said pin comprising at least one tapered flat, said tapered flat angled at an angle θ

relative to said first axis, said angle θ

being larger than said angle α

, and said tapered flat adapted to promote a flow of weld material away from said shoulder when the tool is rotated in a predetermined direction around said first axis;

a second geometric feature on said peripheral surface of said pin comprising at least one counter-spiraling channel or thread, said second geometric feature adapted to promote a flow of weld material toward said shoulder when the tool is rotated in said predetermined direction around said first axis; and

rotating said support body around said first axis in said predetermined direction such that the pin frictionally engages the workpiece to thereby form a friction stir weld joint.

17. The method of claim 16 wherein said first geometric feature comprises at least three tapered flats, wherein said at least three tapered flats are each angled at an angle relative to said first axis, said angle of each of said at least three tapered flats being larger than said angle α

of said peripheral surface of said pin, and wherein said second geometric feature comprises at least one counter-spiraling channel between each tapered flat.

18. The method of claim 16 wherein said first geometric feature comprises at least three tapered flats, wherein said at least three tapered flats are each angled at an angle relative to said first axis, said angle of each of said at least three tapered flats being larger than said angle α

of said peripheral surface of said pin, and wherein said second geometric feature comprises at least one counter-spiraling thread between each tapered flat.

19. The method of claim 18 wherein said shoulder has a scroll pattern.

20. A method of friction stir welding at least two workpieces together at an interface, comprising the steps of:

providing a friction stir welding tool comprising a support body rotable about a first axis, the support body having a shoulder, a pin extending from said shoulder, and said pin having a peripheral surface with an angle α

relative to said first axis;

a first geometric feature on said peripheral surface of said pin comprising at least one tapered flat, said tapered flat angled at an angle θ

relative to said first axis, said angle being larger than said angle α

, and said tapered flat adapted to promote a flow of weld material away from said shoulder when the tool is rotated in a predetermined direction around said first axis;

a second geometric feature on said peripheral surface of said pin comprising at least one counter-spiraling channel or thread, said second geometric feature adapted to promote a flow of weld material toward said shoulder when the tool is rotated in said predetermined direction around said first axis; and

positioning a first workpiece against a second workpiece to define said interface;

urging said friction stir welding tool against said workpiece and rotating said pin to frictionally engage said workpiece in said predetermined direction wherein said first geometric feature promotes a primary flow of weld material away from said shoulder and wherein said second geometric feature promotes a secondary flow of weld material toward said shoulder.

21. The method of claim 20 wherein said shoulder has a scroll pattern.

22. The method of claim 20 wherein said interface is a lap joint.