TWI

An algorithm and procedure for controlling process zone temperature during friction stir processing are presented. The approach is based on the correlation between weld zone temperature with spindle power. A simplified thermal balance model of the weld has been developed. The effects of process control changes on weld temperature are discussed. Various control algorithms were tested on long butt welds (1-17 m length) in low-carbon structural steel (6.4 mm thickness) using PCBN tools of different grades including MS-80, Q-60 and Q-70. Different types of welding were performed: no active temperature control, process parameters varied; force feedback loop to control temperature; automatic force feedback loop coupled with some manual adjustment; only manual adjustment of spindle speed. The ability of the control algorithm to significantly reduce the magnitude of temperature fluctuations during the welding process is discussed.

8th International Symposium, 18-20 May 2010, Session 11: Process Control, Paper 01