TWI Industrial Member Report Summary 77/1976
By R M Rivett
Work was carried out to determine the influence of electrode configuration and material on the number of welds which can be made with a pair of electrodes when resistance welding 1mm 2117 aluminium alloy. It was found that 4.8mm 1%Cr-Cu truncated cone electrodes gave an average life of 1380 welds compared to 400 welds with 75mm radius domed 1%Cr-Cu electrodes. Consistent results could not be obtained with pimple electrodes, the maximum life being 200 welds. For the welding conditions employed, electrode life was found to be dependent on the mechanical properties of the electrode material and independent of softening temperature. The best results were obtained with Class 3, 2.5%Co-0.42%Be-Cu electrodes (average 1700 welds) and the shortest lives with the high conductivity Class 1 materials usually recommended for resistance welding of aluminium.
Electrode approach rate was found to influence electrode life. The life was reduced from an average of 1380 welds with an approach rate of 88mm/sec to an average of 500 welds with an approach rate of 175mm/sec.