Degradation mechanism of electrode tip during resistance spot welding of aluminium alloy sheets

This study investigated the electrode life and the electrode degradation characteristics during resistance spot welding of aluminium alloy sheets. When a long welding time and the DR type electrode shape were used, the electrode life was much longer than that with a short welding time and the R type electrode shape. The degradation mechanism of electrode tip was explained in the following way; firstly, Al-Cu alloy layers were formed at the electrode top during consecutive welding, and then the layers stuck easily to the surfaces of aluminium alloy sheets so that notable wear took place and the surface profile of electrode tip became flat. In order to eliminate the direct contact between the electrode and the sheet, a special Cu-foil insert device for resistance spot welding of aluminium alloy sheets was developed and achieved an extremely long electrode life.