TWI Industrial Member Report Summary 1046/2013
By R E Andrews
Introduction
The use of FSW for a range of challenging applications is currently limited by unsatisfactory FSW tool probe performance and lifetime. Joining of thicker section (10mm and greater) higher strength aluminium alloys such as the 7xxx series still provide considerable challenges and there are relatively few examples of industrial success in this area. If improved FSW tool probe lifetime technologies were available then a number of new applications would become feasible. This could realise benefits for not only welding these alloys but for FSW applications in general by improving probe life and FSW productivity for a wide range of industries. This report describes work carried out to address improved FSW tool probe lifetime when welding high strength aluminium alloys to support leading edge FSW capability.
Industrial Challenge
In an industrial application of FSW to join a 4mm thick 6xxx series aluminium alloy 1km of weld is produced before the FSW tool probe (pin) is changed but not failed. In contrast, when welding 12mm thick 7xxx series alloy, tool probe failure has occurred after the production of only 2m of weld. This short FSW tool life influences the cost to produce a unit length of weld and thus influences the commercial viability of using FSW for a specific application.
Key Findings
- MP159 alloy FSW probes had the longest life compared with a range of candidate high performance alloys when evaluated in FSW probe lifetime trials.
- Direct comparison trials were carried out using candidate advanced tools in a challenging FSW application (ie welding a high-strength aluminium alloy), with very encouraging results. The weld length produced before probe cracking initiated was more than doubled, as was the weld length produced before probe failure occurred.
- The new FSW tool probe solution identified, will enable the production of 20,000 - 30,000mm weld lengths in high-strength aluminium alloys with the confidence that tool probe failure will not occur
TWI Industrial Member Report Summary 1046/2013