Impact of Weld Locations of TWBs of Different Thickness Ratios on Dissimilar Steels on its Bulging Formability

Abstract

This study aimed to analyze the impact of the weld location of TWBs of different thickness ratios on dissimilar steels, particularly on its height, which is known as the rigid hemispherical punch bulging formability. Laser welding was conducted on St12 (0.8 mm) and St16 (1.2 mm) samples using three different width ratios (1:2, 1:1, and 2:1). Then, the microstructure and microhardness of the TWBs and welded joints were tested. Finally, a rigid hemispherical punch bulging formability test was conducted to obtain the bulging formability of the TWBs for the study. Further, the results were compared to the bulging formability of the parent metal. The results show that the microstructure of welds contain all types of ferrites, bainites and lath martensites. The hardness on both sides of the weld is different, and it appears to be an asymmetric distribution. The hardness of the weld seam and heat-affected zone is much higher than the parent metal. The limit dome of the TWBs is lower for each side of the parent metal. When the weld location is parallel to the direction of the principal strain, the bulging formability of TWBs of different thickness ratios is much better. Under certain combinations of material and thickness, the thicker the plate is, the better the bulging formability of the different thickness TWBs is.