Connect, no. 108, September/October 2000, p.7
News in brief reports on the outstanding worldwide activity in Friction Stir Welding (FSW), principally of aluminium. It is worth reflecting that 10yrs ago the process did not exist. Six years ago TWI was proudly showing the sponsors of a TWI Group Sponsored Project (GSP) that we had made the first 2m long weld in aluminium 6082. Far-sighted companies have sustained investment and research into the technology ever since to their great commercial advantage.
The opportunity now presents itself to repeat that success with steels, taking FSW into a much higher temperature operational regime than before attempted. This is a considerable technical challenge. Nevertheless, within its Core Research Programme (CRP), TWI has demonstrated the technical feasibility of applying the FSW process to a 12% Cr steel with difficult arc welding characteristics.
There is always a significant task in moving any process from a feasibility study to production status. FSW offers many economic and environmental benefits and there is also a technical driver for those companies which need to join 'difficult-to-weld' alloys. These will include certain alloy and stainless steel grades, even stretching to nickel-based alloys. Just like aluminium, where the early trials used the 'easy' 6082 alloy, it is necessary to develop the process incrementally towards the more difficult materials.
Optimising tool materials and designs that will operate successfully at temperatures in excess of 1000◦C is the priority. The 12%Cr steel mentioned earlier is the benchmark material used to characterise new tool performance. Already the work is progressing successfully with tool materials that are more advanced than those used in the original CRP work.
TWI Group Sponsored Project Friction stir welding of steel began in March 2000. Participants share the costs, risks and successes of developing the process in return for being the first to apply the new technology to their applications. Membership of the project is the only means of influencing the technical priorities. New sponsors are welcome, and can introduce additional materials with the agreement of the existing project members.
For further information on this GSP please contact Richard Johnson, Keith Johnson, or Phil Threadgill at TWI.
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