Evaluation on the Formability of the Third-Generation Automotive Medium-Mn Steel Based on Experiment and Simulation

Medium-Mn steel is an outstanding representative of the newly developed third-generation advanced automotive steels. In our previous experimental studies, industrial trial production of 0.1C–5Mn medium-Mn steel has been realized, anti-decarburization ability of warm-formed medium-Mn steel has been assessed compared with the conventional hot-formed 22MnB5 steel, and heterogeneous spot-welding performance evaluation has also been completed on the industrial production line. Previous results proved that the medium-Mn steel have a development trend of replacing hot-formed boron steel in the automotive industry. Besides, numerical simulation analysis on the forming process of an actual automotive part is also an important topic of the applicability research of medium-Mn steel. Therefore, in this paper, a warm-formed medium-Mn steel B-pillar part was investigated by simulation in order to elucidate the effects of process parameters. Firstly, mechanical property tests were carried out to obtain the material parameters for establishing an accurate finite element model of the B-pillar part. After that, the warm-forming process was simulated and the effectiveness of the simulation was validated by benchmarking with the experimental result. Finally, the deep drawing zone with maximum fracture risk was focused to analyze the sensitivity of process parameters including initial blank temperature (IBT), blank holding force (BHF), and forming velocity (FV). Research results show that the IBT has the greatest influence on the thickness of the deep drawing zone. The recommended IBT is between 450 and 550 °C, which is favorable to obtain higher total elongation without loss of strength. This study is helpful to provide a theoretical basis for the large-scale application of warm-forming medium-Mn steel.