Abstract: In order to study the springback mechanism of quenched boron steel with tailored properties, hot stamping experiments of U shape part were conducted using partial die method. A three-coordinate measuring machine NDI PROCMM3500 was used to measure the shape precision of the quenched parts at different holding pressures and die temperatures. The microstructure of the quenched parts were observed using SEM. Results show that the springback angles of the hot region, cold region and transition region decrease as the holding temperatures increases. As the die temperature increases the springback angle of the cold region remains unchanged, but the springback angles of the hot region and transition region decrease. Microstructure analysis suggested that more martensite will cause bigger springback angle, while more bainite will cause smaller springback angle.

Key words: material synsthesis and processing technology, boron steel, hot stamping, springback, microstructure