Weldability and Fracture Behaviour of Low Carbon Steel/Aluminium/Stainless Steel Clad Sheet with Resistance Spot Welding

Abstract

This paper focuses on the resistance spot welding of low carbon steel/aluminium/stainless steel 3-ply clad sheet. Weldability, microstructure, tensile properties and fracture behaviour of the clad sheet with resistance spot welding were evaluated. A “squeeze-out pulse” was used to melt and squeeze out the core aluminium completely from the vicinity of the weld zone before the application of actual welding current. This enabled the clad sheet to be welded without the formation of any Fe–Al intermetallic compound layer in the weld zone. The fracture mode associated with the peel test of the spot weld was used as the criterion for resistance spot weldability evaluation of the clad sheet. A weldability lobe diagram in the welding current–welding time space based on the fracture mode was constructed and it revealed a wide weldable window especially at a welding time of 18 cy. A tensile shear test with a cross head speed of 1 mm/min was conducted to study the tensile strength and fracture behaviour. It revealed four different fracture modes namely button pull, clad-bond fracture, partial thickness-partial clad-bond fracture and interfacial fracture. The nugget size and melting of clad interface and stainless steel layer were the dominant factors in determining the fracture mode.