Tool Thermal Cycle Design for Manufacturing of Components with Tailored Material Properties

With the press hardening technology, it is possible to produce automotive structural components with a tailor-made material property distribution. The properties can range from a soft ferrite dominated microstructure to ultra-high strength martensitic structure. Tailor-made material property distribution is especially useful in components subjected to crash deformation. With this techhique it is possible to account for structural integrity and in the same time maximize the energy absorption in the structure. The present work is based on a comprehensive thermo-mechanical material model for simulation of press hardening and similar processes. The model accounts for and predicts time dependent and time-independent phase transformations, mechanical and thermal properties as well as transformation plasticity during the complete cooling and deformation process from 900 degrees C to room temperature. The model predicts the microstructure evolution during the complete process and the final fractions of martensite, bainite, perlite and ferrite. The thermal properties in the contact between the blank and the tools as well as the thermal properties in the tools have influence on the processes for tailor-made material properties. In this work, solutions for tool heating and cooling in the design of tools for manufacturing of components with soft zones are studied. Based on the results from the press hardening simulations, thermal properties of special tool materials are taken into account in order to optimise the manufacturing thermal cycle.