Wear Loss and Life of Electrode Tips in Resistance Spot Welding of Aluminum-plated Steel.

Abstract

Pb-8%Sn coated steel sheets are used for the fuel tanks of motor vehicles. Lead-free steel sheets are used to prevent pollution. Aluminum-coated steel sheets are used for vehicle, but the short life of electrodes used for spot welding of the steel sheets is a serious problem. Three kinds of copper alloy electrodes were manufactured and used for the investigation. They are Cu-Cr, Cu-Cr-Zr and alumina dispersed copper alloys. Both sides of aluminum-plated steel sheets 0.8 min in thickness were used for the study. The upper electrodes showed a convex shape and an penetration of aluminum and iron was observed. The lower electrodes showed a concave shape by reverse pick-up. Furthermore, the penetration of aluminum in depth was shorter than that of the upper electrodes and no iron was observed. The results obtained in continuous spot welding with 11 kA shows that the life of alumina dispersed copper alloy electrodes was 800 spots which is two times that of Cu-Cr alloy electrodes.