Enhanced material models for the process design of the temperature dependent forming behavior of metastable steels

In this paper, the main parameters for the process design of thermo active deep drawing processes with metastable steels are specified. As a consequence of the strain- and temperature-dependent martensitic phase transformation, the CrNi-steels have a very complex forming and failure behavior. Particularly, the strong heating of the blank, induced by the hardening increase, influences the yield properties, the failure and the tribological system. Hence, a robust process design with FEM is subordinated to the correct virtual description of these process parameters. Both, experimental methods for an accurate measurement of the forming, friction and failure properties, as well as numerical models were introduced in this study. Using these models, temperature dependent parameters like phase transformation from γ-austenite to α′-martensite, yield properties, failure or friction can be easily included into the virtual process modeling. The model was successfully validated by biaxial stretching tests and rectangular cups, drawn at different tool temperatures.