Optimizing Advanced High-Strength Steel Welds: The Role of Regional Pre-heating in the Heat-Affected Zone

The development of next-generation high-strength steels is crucial for the automotive industry, necessitating advanced joining techniques. This study investigates the joining of STRENX 700 CR and DP 800 steels using resistance spot welding (RSW) with specialized fixtures. Unlike conventional methods, a regional pre-heating treatment was applied exclusively to the heat-affected zone (HAZ) prior to welding. Comparative analyses were performed between pre-heated and non-pre-heated welded joints. The welded joints underwent microstructural analysis, as well as non-destructive and destructive testing. Results revealed that pre-heating led to an expansion of the HAZ and a reduction in hardness. Additionally, there were significant improvements in mechanical properties, including increases in tensile-shear strength, cross-tension strength, and fatigue strength. These findings demonstrate the effectiveness of regional pre-heating in optimizing the mechanical performance of RSW joints, offering valuable insights for the automotive industry's welding applications.