Development of Spin Electrode Spot Welding(Report 2). Investigation of Mechanism of Electrode Tip Life Improvement in Coated Steel Sheet Spot Welding.

An attempt was made to improve the electrode tip life, which has been a major concern in spot welding of coated steel sheets in automobile assembly lines. Spin electrode spot welding is newly developed. In this spot welding, longer electrode lives are achieved since an electrode tip surface is effectively used by forming multiple contact points and, further more, the successive movement of the contact point provides a type of "self-dressing" action on the electrode surface. The electrode rotation angle of 60° is found to be the most effective on the improvement of electrode tip lives when a radius type electrode of 15R was used and this electrode was inclined at 10°in relation to the force axis. Under this condition, approximately 20 times longer electrode tip lives are achieved irrespective of coated steel types and evaluation test methods.