Performance enhancement of manganese-boron steel sheets for hot stamping (T02#)

• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 394563137

In car body construction, hot stamping components made of MnB steel are used to increase crash safety. The sheets are heated to 950 °C in natural gas-powered roller hearth furnaces, subsequently transferred to a water-cooled hot forming tool, and formed and hardened into components in a single process. In subproject A04 of the CRC 1368, an alternative heating method is developed in which the sheets are heated to target temperature within seconds by introducing an electric current. This resistance heating method can reduce the energy needed by more than 70 %. Additionally, the process completely suppresses undesirable scale formation by using a silane-doped protective gas atmosphere ("XHV- adequate "). One trend is the adaptation of material properties. The necessary increase in strength is associated with a loss of ductility. In order to increase the latter, various concepts are employed on the material or process side, all of which are associated with a loss of strength. The goal of the transfer project is to increase the performance of hot stamped MnB steels by simultaneously increasing strength and ductility. This is to be achieved in an XHV-adequate atmosphere by the combination of ductility-enhancing surface layer decarburization of the MnB steels and resistance heating. The ductility-enhancing surface layer does not oxidize and at the same time strength-reducing significant grain growth in the material is avoided. Both together should lead to the maximum possible increase in performance. In the transfer project, Holländer is responsible for surface layer decarburization and material analyses, Hübner for resistance heating and hot stamping. Both areas of work will be combined in a joint model. The application partner defines the component requirements that can be expected in future with the new possibilities, implements the robot automation and evaluates the range of applications.

• DFG Programme: Collaborative Research Centres (Transfer Project)
• Subproject of: SFB 1368: Oxygen-free production - processes and local mechanisms in oxygen-free atmosphere for the development of sustainable production techniques and manufacturing processes
• Applicant Institution: Gottfried Wilhelm Leibniz Universität Hannover
• Participating Institution: Gottfried Wilhelm Leibniz Universität Hannover; Produktionstechnisches Zentrum; Institut für Umformtechnik und Umformmaschinen; Gottfried Wilhelm Leibniz Universität Hannover; Produktionstechnisches Zentrum Hannover; Institut für Werkstoffkunde
• Business and Industry: Otto-Hahn-Straße 5; 33161 Hövelhof
• Project Heads: Dr. Ulrich Holländer; Dr.-Ing. Sven Hübner