Electrode wear in short-pulse resistance spot welding of aluminum AA 6016-T4

Abstract

The influence of current pulse width on electrode wear during resistance spot welding of thin sheets (1 mm, 0.04 in) of aluminum alloy 6016-T4 was studied, and an increase in sheet surface roughness and electrode erosion was evident with increasing pulse time for the same weld nugget size. Aluminum alloy 6016-T4 is an especially critical material concerning electrode wear for resistance spot welding due to rapid onset of electrode sticking and erosion of the electrode surface. Typically, welding of this material therefore requires electrode redressing operations after approximately 20 to 30 welds to maintain constant weld size and sheet surface quality. It was demonstrated that a reduction of current pulse width is a means of reducing electrode wear without affecting joint properties. The electrode wear process involved a pickup of aluminum material from the sheets followed by alloying process, leading to formation of intermetallic phases and erosion of material from the surface of the electrodes with increasing number of welds made. A reduction of current pulse width positively affected electrode wear properties by reducing temperatures at the electrode and sheet surfaces, thereby delaying electrode wear and reducing its severity.