A Study on the Effect of Process and Material Variables on the Hot Stamping Formability of Automotive Body Parts

Abstract

Hot stamping is a method capable of manufacturing high-strength automotive body parts by inducing a martensitic phase transformation through forming and die quenching after heating a metal sheet into a high temperature austenite phase. However, it is not easy to solve various formability problems occurring in the hot stamping process due to the complexity of the process and material behavior during high temperature forming. In this study, fracture-related forming limits and martensite phase ratio were selected as criteria for evaluating hot stamping formability. First, a hot stamping test was performed on a T-type part that simplified the B-pillar, an automotive body part, and the fracture behavior according to the temperature and thickness of the sheet blank was investigated. Additionally, forming analysis was performed on the hot stamping process of mass-produced B-pillar parts by varying the temperature of the sheet blank, the thickness of the sheet blank, the die-blank friction coefficient, and the strain-rate sensitivity of material among various process and material variables. Based on the analysis results, the effect of each process and material variable on the hot stamping formability of B-pillar parts was quantitatively analyzed. By utilizing the results of this study, it will be possible to solve the formability problem that occurs in the mass-production hot stamping process for automotive body parts and improve the quality of parts in the future.

Keywords

• hot stamping
• formability
• forming limit
• martensite
• B-pillar
• forming analysis