Progress in Joining Austenitic Stainless Steels by Friction Stir Welding

摘要

Although friction stir welding is only used commercially for joining aluminium and copper alloys, there has been increasing interest in recent years in developing the process for higher temperature materials, in particular titanium and steels. This work describes some trials undertaken at TWI to investigate the feasibility of friction stir welding of austenitic stainless steels, and reports on some of the typical microstructures that can be found. Examination of the welds shows that the weld centre is as expected, recrystallised, often with a finer grain size than the parent material. The ferrite content is strongly dependent on the thermal cycle. In the thermo-mechanically affected zone (TMAZ), there is some for evidence for re-crystallisation. This is in contrast to aluminium, where it is believed that changes in crystal structure in the TMAZ are largely driven by recovery processes.