Establishing Empirical Relationships to Predict the Tensile Shear Fracture Properties of Resistance Spot Welded Advanced High Strength Steel Lap Joints

Abstract

The joining of advanced high strength steel (AHSS) of type dual phase 800 (DP800) by fusion welding is challenging owing to its high strength and complex microstructural features. It leads to softening of heat affected zone (HAZ) and cracking due to the high heat input associated with fusion welding processes. This significantly deteriorates the tensile shear fracture properties of DP800 steel joints. To overcome this problem, resistance spot welding (RSW) is employed to join DP800 steel thin sheets. It involves resistive heating of joining surfaces under pressure at a temperature less than melting point of parent metal. This significantly reduces the issues in joining DP800 steel such as softening in HAZ, solidification and HAZ cracking and offers precise spot weld. The tensile shear fracture properties of joints are influenced by RSW parameters such as welding current, welding time, and electrode force. Hence, establishing empirical relationships to predict the tensile shear fracture properties of joints is crucial. So, the main objective of this investigation is to establish empirical relationships to predict the tensile shear fracture properties of resistance spot welded dual phase 800 steel lap joints using regression analysis. The optimal process window of RSW is established using response surface methodology (RSM) to attain superior tensile shear fracture properties of DP800 steel joints.