5th International High Manganese Steel Conference - HMNS 2022

Press hardening of manganese-boron steels is one of the most efficient production processes for high strength automotive components. However, the residual formability of these sheet components is greatly limited by the formation of fully martensitic microstructure during in-die quenching, which makes them only to a limited extent suitable for crash-relevant anti-intrusion parts of the vehicle body. In order to extend the application range of press-hardened components, the use of third-generation advanced high strength steels achieves increasing attention.
Aim of the presented research is to analyze the potential of press hardening of lean medium manganese steel in combination with a quenching & partitioning (Q&P) treatment. For this reason, dilatometer investigations on Fe-0.3%C-5%Mn-1.5%Si with varying Q&P parameter were performed. By adjusting the heat treatment parameters, the microstructure and hence the mechanical properties were modified to fit the application´s load requirements. The results demonstrated that the performed Q&P treatments lead to multi-phase microstructures, consisting of martensite (tempered and fresh) and retained austenite resulting in high tensile strength, comparable to martensitic 22MnB5, and significantly improved total elongation up to 18 %. Regarding the ductility, it was shown that besides the adjustment of a sufficient austenite content, the reduction of fresh martensite is indispensable to prevent brittle failure. Finally, selected heat treatments were successfully reproduced in a laboratory-scale press hardening system equipped with a heatable hat-shaped pressing tool.