Mechanisms of electrode degradation when spot welding coated steels

Abstract

The present work compares the behaviour of precipitation hardened and dispersion strengthened electrodes during the manufacture of resistance spot welds in coated steel sheet. The primary mechanism causing the failure of spot welding electrodes was growth of the electrode tip. Under normal welding conditions electrode tip growth was primarily dependent on local alloying morphology so that deterioration was mainly a function of the type of coating present on the steel. However, welding with high currents or use of current stepping programmes could extend electrode performance such that softening became a more dominant electrode degradation mechanism. Under these conditions, use of dispersion strengthened material could extend electrode campaign life.