A study on resistance spot welding for aluminium alloys with spooling process tapes

Abstract

Aluminum alloys for reducing weight of car body are increasingly applied to automotive industry due to environment regulations such as carbon dioxide emissions. Spot welding is widely useful for joining the sheet steel metals, but this process cannot be used for aluminum because of its high contamination and high electrical conductivity. Hence recently mechanical fastening process, such as riveting and clinching, is used in joining aluminum alloys. Even if this process is useful to join aluminum alloys, there are some problems such as low reliability, high process costs compared to resistance spot welding. In this work, spooling process tapes in conventional spot welding are added to have a good weld quality for aluminum. The absolute innovative features about this process are its unique electrodes and spooling process tapes between electrodes and workpieces. Also, as this process controls electrode force by a servo motor, electrode force is controlled in near real time. In order to improve weld quality of aluminum alloy and steel sheet, electrode shape is analyzed, and characteristics of weldability are observed according to each current and electrode force profile. Also, effect of each welding variable related to weldability is investigated, and the variable condition which has high weld strength and no defect in weld zone is obtained. Finally, a large acceptable area in lobe curve is obtained on Al 6000 and Al 5000 series based on results of the evaluation tests.