Coating behaviour and nugget formation during resistance welding of hot forming steels

Abstract

In this work, the effects of the coating composition and the welding parameters on the heat generation and nugget formation during resistance spot welding of the hot press forming steels have been evaluated. Two types of coated steels were used, termed as Al–Si and Zn coating. Al–Si coated steel showed rapid nugget growth toward the electrode direction, which is the probable reason of the higher heat conduction from the electrode–sheet surface toward the bulk material. In Zn coated steel, heat was generated and localised at the faying interface and uniformly propagated to the steel substrate. High speed camera images showed that the presence of oxide at faying interface provides inhomogeneous current flow and violent heat generation in the Zn coated steel.