Resistance spot welding of aluminium and steel: a comparative experimental study

Abnormal process conditions or faults exist in production. This paper investigates the effect of these abnormal conditions on the quality of resistance spot welding of selected steel and aluminium alloys and compares the results. Various process variables including abnormal process conditions are selected and analysed by using a two-stage, sliding-level experimental method. According to the experiment matrix, acceptable ranges of welding current in their lobe curves and corresponding button diameters are obtained. The effects of the factors and their levels on the welding current and button diameter are discussed and evaluated for both steel and aluminium welding. It is concluded that any abnormal process condition can decrease the width of suitable current ranges in the lobe curve. Among the abnormal process conditions, button diameter is greatly influenced by the electrode size in steel and the poor fit-up condition in aluminium. It is also shown that aluminium has a larger variance in button diameter, showing a less robust process in resistance spot welding.