General Research on the Process of the Indirect Hot Stamping Ultra-High-Strength Steel

Aiming at the need for lightweight requirements of the components in the bus, combined with the advantages of the hot stamping ultra-high-strength steel, a new television (TV) bracket was proposed. The finite element (FE) simulation of the beam part in the TV bracket during the indirect hot stamping process was discussed. After two-stages of pre-forming, the blank was in good formability and without visible cracks. According to the FE simulation results, the punch speed, quenching force, and quenching time significantly affected the temperature, microstructure, hardness, and mechanical properties of the beam part during hot stamping. With the increase of the quenching force and quenching time, the martensite fraction of the beam part was increased. For the beam part, the punch speed should be at least 80 mm/s during the forming stage. For complete quenching, the quenching force should be above 1000 kN and quenching time should be up to 10 s. Based on the parameters from the FE simulation, the forming experiment of the beam part was discussed. Microstructure analyses and microhardness tests as well as tensile tests of the hot stamping beam part were performed. The results confirmed that the FE simulation of the beam part was reliable.