Die Design for a Center Pillar Part by Process Analysis of Hot Stamping and its Experimental Verification

HSS (high-strength steel) is now commonly employed in various automobile structural reinforcements and crash protection systems. Although HSS has high strength, it has various disadvantages such as springback at room temperature and cracks; also, it is difficult to form HSS into complicated structures. The HPF process is a forming method that offers various advantages such as superior mechanical properties, good formability, and very small springback. However, relatively large-sized parts such as center pillars exhibit poor formability in the HPF process due to the limited material flow and thickness reduction in the process. Also, reduction in thickness leads to cracks. One of the reasons is the relatively high friction between the sheet and the die. In this study, in order to obtain the optimal conditions in the HPF process for center pillars, various process parameters were studied and analyzed by using the sheet forming software, J-STAMP. The effects of various parameters such as the heating temperature, blank holding force, punch speed, clearance (upper and lower dies), distance block, blank shape, and forming type were analyzed and compared.