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

Abstract

This study investigated the electrode life and the electrode degradation characteristics during continuous resistance spot welding of aluminium alloy sheets. When a long welding time and dome radius type electrode were used, the electrode life was extended more than that when a short welding time and radius type electrode are used. The electrode tip is considered to degrade by the following mechanism: an Al–Cu alloy layer is formed at the electrode tip during continuous welding, and then it peels off from the electrode tip transferring to the surface of aluminium alloy sheet. Its peeling makes the electrode tip indented and finally the electrode tip flattens with increasing diameter of electrode tip. In order to eliminate the direct contact between electrode and worksheet, a special Cu foil insert device for resistance spot welding of aluminium alloy sheets was developed and an extremely long electrode life was achieved.