Research on Rapid-Cooling Press Hardening Process and Its Effect for Formability of Ultra High Strength Steel

摘要

In this study, a new rapid-cooling process in press hardening based on theoretical analysis, experimental test and optimal formability simulation were investigated for improving formability and obdurability of 22MnB5 boron steel. A series of non-isothermal flow behaviors in different plastic strain rates from 0.001s-1 to 0.1s-1 was investigated by thermal-mechanical uniaxial tensile tests. Furthermore, martensite transformation measurement was also involved in the temperature range from 600°C to 800 °C. According to an interrelated Norton-Hoff constitutive model was developed to describe the complicated thermal-mechanical-phase transformation couple model, a typical deep drawing box used to simulate formability so as to compare with actual press hardening experiments used by the self-developed multi-field coupled static-explicit FE software KMAS and dynamic-explicit commercial software LS-DYNA respectively. The results showed the rapid-cooling process indicate the validity and efficiency of meeting the forming performance characteristics and the optimal process which temperature range from 650°C～700°C can contribute to improve formability of press hardening manufacture.