Metal fusion bonding – Process – Using dynamic frictional energy
Reexamination Certificate
1999-03-05
2001-05-15
Shaw, Clifford C. (Department: 1725)
Metal fusion bonding
Process
Using dynamic frictional energy
C228S002100, C148S516000
Reexamination Certificate
active
06230957
ABSTRACT:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable
REFERENCE TO A “MICROFICHE APPENDIX”
Not applicable
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to friction stir welding. More particularly, the present invention relates to using friction stir welding to repair weld defects and to help avoid weld defects in intersecting welds in crack-sensitive material.
Even more particularly, the invention relates to hybrid friction stir welding (FSW) as a defect repair technique and microstructure modification approach to intersection weld crack mitigation for 2195 Al—Cu—Li VPPA/SPA (variable polarity plasma arc/soft plasma arc) weldments.
2. General Background of the Invention
Friction stir welding (FSW) is a solid state joining process developed by The Welding Institute (TWI), Cambridge, England and described in U.S. Pat. No. 5,460,317, incorporated herein by reference. Also incorporated herein by reference are U.S. Pat. No. 5,718,366 and all references disclosed therein.
BRIEF SUMMARY OF THE INVENTION
The apparatus of the present invention solves the problems confronted in the art in a simple and straightforward manner. What is provided is a method of repairing defects in a weld in a welded article, comprising using friction stir welding to rework the weld until a targeted strength is reached or exceeded. Another aspect of the present invention is a method of avoiding defects in intersecting welds in a welded article, comprising using friction stir welding to rework at least one weld of intersecting welds until a targeted strength and/or a targeted integrity is reached or exceeded. Another embodiment of the present invention is a method of avoiding defects in intersecting welds in a welded article, comprising using friction stir welding to create at least one of the intersecting welds. Yet another embodiment of the present invention is a method of producing a welded article having intersecting welds, comprising making at least some of the intersecting welds with weld techniques other than FSW, then reworking at least some of the intersecting welds with FSW. The present invention also includes the products made by the methods of the present invention.
This process is intended to be used on aerospace propellant tank components (such as the LH2 and LOX Barrels of the SLWT (super light weight) External Tank Program) to minimize the number of as-welded and post-proof intersection weld cracks.
Hybrid Friction Stir Welding also has application on ship building, bridge building, aircraft, food processing equipment, and any other industry where aluminum alloys are welded.
During preparation of test panels for this program, it was noted that heavily peaked and mismatched VPPA/SPA panels were essentially de-peaked and were left in a flat configuration after performing the hybrid FSW process. This has implication for using the hybrid FSW process to relieve residual stresses and correct “oil-canning” of propellant tank components (such as LH2 and LOX Tank components).
This process also has potential to repair “Out of Grade” VPPA/SPA welds by defect elimination.
This process is also a candidate replacement for mechanical planishing operations.
This process can be used to rework welds produced by welding methods including, but not limited to, fusion (including resistance, arc ((MIG—metal inert gas (GMAG—gas metal arc welding), TIG—tungsten inert gas (GTAW—gas tungsten arc welding) SMAW (shielded metal arc welding)), electron beam, and laser), and solid state (inertia, friction stir, friction plug, explosive, and ultrasonic).
As used herein, a weld expressed as a percentage indicates the percentage of thickness of the penetration of the pin of the FSW device into the weld—e.g., a 85% weld indicates that the pin penetrates through 85% of the thickness of the weld. In general, the more one goes through the thickness, the stronger the weld becomes, though sometimes it is better not to rework the entire weld.
REFERENCES:
patent: 5460317 (1995-10-01), Thomas et al.
patent: 5697544 (1997-12-01), Wykes
patent: 5713507 (1998-02-01), Holt et al.
patent: 5718366 (1998-02-01), Colligan
patent: 5971252 (1999-10-01), Rosen et al.
patent: 5975406 (1999-11-01), Mahoney et al.
patent: 6050475 (2000-04-01), Kinton et al.
Arbegast William J.
Hartley Paula J.
Garvey, Smith, Nehrbass & Doody, L.L.C.
Lockheed Martin Corporation
Shaw Clifford C.
Stoner Kiley
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