Performance improvement of tailored die quenching using material combinations with phase change material in hot stamping

Abstract

The objective of this study is to investigate the performance improvement of tailored die quenching using material combinations with phase change material over the conventional tailored methods in hot stamping. The thermal characteristics of the phase change material, channel, die, block, and blank are analyzed using thermo-fluid transient simulations with the enthalpy method. Four cases of the material combinations with and without the phase change material are adopted as the die and block. A phase change material of lithium nitrate is applied to the soft zone. All cases without the phase change material do not satisfy the soft zone criteria, while all cases with the phase change material satisfy both the soft zone and hard zone criteria, owing to the effects of the heat storage and release in the phase change material. In addition, the martensite finish temperature area ratio increases with increasing the contact pressure, while the martensite start temperature area ratio decreases. The optimum contact pressure is determined to be 15 MPa for H13 and GTCSⓇ with the phase change material to maximize both the strength and ductile area. Overall, the tailored die quenching process using H13 and GTCSⓇ with the phase change material exhibits the best performance for high-quality tailored blanks.