Effects of welding current on the microstructure and mechanical behavior of resistance-welded WC-Co/B318 steel joints

Abstract

Using resistance welding of WC-Co pellets to steel to manufacture carbide band-saw blades can reduce production costs. In this study, the effects of welding current on the welding process, dynamic resistance, joint appearance, interface microstructure, element diffusion, and fracture morphology were investigated. By considering both the dynamic resistance and penetration depth, it was found that when the welding current was over 900 A, extruded welding slag can make contact with the electrode to cause a short circuit. A larger welding current resulted in a shorter elongation time. The penetration depth can act as an indicator for adjusting the welding current and time. An analysis of joint appearance, element diffusion, and fracture morphology revealed that when the welding current was small, there were insufficient metallurgical reactions at the interface and the joint fractured at the interface. When the welding current was large, serious deformation and loss of Co elements decreased the shear force and the joint broke on the WC-Co side. In contrast, when the welding current was moderate, an appropriate reaction layer was generated at the joint interface and the joint fractured in the heat-affected zone of the steel. This joint had a maximum shear force of 1228.5 N.