Comparative Analysis of Microstructure and Collision Performance of TWB Hot Stamped Parts with Various Strength Combinations

Abstract

Hot stamping technology has been steadily developed because it provides both excellent formability and high strength. With the development of TWB hot stamping technology, it is now possible to freely apply the required strength and thickness in the right place. In this study, the microstructure and collision performance of TWB hot stamped parts were evaluated according to their combined strength. Through dilatometry analysis, the hot stamping heat treatment temperatures of 22MnB5 steel and 30MnB5 steel were set at 950 oC and 870 oC. The 5MnB8 steel was composed of Bainite + Martensite when heat-treated at 950 oC and provided a strength of 980 MPa grade. When heat-treated at 870 oC, it was composed of Ferrite + Bainite + Martensite and provided a strength of 780 MPa grade. Simulated rear impact testing showed the 30MnB5- 5MnB8 TWB combination had the best performance, because the 5MnB8 part of the 780 MPa grade absorbed enough energy and the 30MnB5 part of the 1.8 GPa grade fully served as an anti-intrusion.