Correlation of Hardness with Mechanical Properties of SPCC Steel Spot Weld

Abstract

The goal of this paper is to develop a method to determine the mechanical properties of SPCC steel spot weld. The mechanical properties of a resistance spot weld could not easily be obtained due to the size of spot weld, and the non-uniformity around the weld zone. This research used an altered approach to obtain the mechanical properties of spot welds. The study based on the hardness measured on spot welds heat-treated surrogate SPCC specimens with the same hardness for the tensile tests. With the tensile test results and hardness measurement data, the correlation of the hardness and yielding strength and of the hardness and ultimate strength could be obtained. In this study, SPCC sheets with thickness of 0.8 mm were welded, and their hardness around the spot welds was measured. Based on the measured hardness, SPCC specimens were heat-treated to reach the hardness measured at different sub-zones of the spot weld. The mechanical properties and microstructure of sub-zones were studied. The relationship between hardness and other mechanical properties were established. The study provides good understanding of the potential failure in spot-welded structures. The results can also be further utilized for computer simulation of spot welds with failure modes to predict the performance of spot-welded vehicle body structures.