Univ.-Prof. Dr. -Ing. W. Bleck (Institut für Eisenhüttenkunde, RWTH Aachen University)
In collaboration with the participating cooperation partners, Faurecia Autositze GmbH (hereinafter Faurecia), ThyssenKrupp Steel Europe AG (hereinafter ThyssenKrupp) and Hoesch Hohenlimburg GmbH (hereinafter referred to as Hoesch), a systematic investigation of the possible properties of industrially processed high-Mn-alloyed TWIP steels with different manufacturing and post-rolling parameters is planned. The aim of the joint work is to explore the excellent material properties of these steels for different applications in the area of car seat constructions. The Faurecia identifies potential components and defines appropriate measurable target values based on their requirements. ThyssenKrupp and Hoesch introduce an existing hot and cold strip concept for high manganese steels as well as already existing knowledge about the properties and microstructural conditions in the project. This initial setup is used to perform the structural component optimization. The necessary deformation and crash simulations are carried out primarily by Faurecia, while ThyssenKrupp and Hoesch support this process with their experience in the field of forming simulation. In addition, models developed in the SFB for the description of the flow- and strengthening-behavior should be tested and further developed under application-oriented conditions in order to better predict the complex behavior of high manganese steels with TWIP effect.
The mechanical characterization of the different material states is carried out at the Institut für Eisenhüttenkunde (hereinafter "IEHK"). Apart from structural and crashrelevant parameters, attention is paid to the bake-hardening potential of the materials under investigation. Due to the face-centered-cubic (fcc) microstructure and the occurring mechanisms, this cannot be explained by the known approaches for base-centered-cubic (bcc) materials. A model developed in the SFB for the correlation of short range order phenomena and mechanical properties is to be used here in order to describe the material behavior after the baking treatment. The results of the characterization are used, on the one hand, to match the structural component design and the material properties profile. On the other hand, the correlation of the microstructures in the various intermediate states and on the finished component with the mechanical properties provides a documentation of the entire process chain. This aims at identifying the essential process parameters for the metalphysical phenomena observed in the material and at the same time at defining the respective target structures. In order to evaluate the process chain in terms of robustness and industrial feasibility the optimized microstructures are evaluated by ThyssenKrupp and Hoesch concerning their processability. Faurecia produces demonstrator components based on the optimized component concepts and tests under real crash conditions. After the completion of the work, a comprehensive assessment is presented, which shows the possibilities, limits and problem areas of the industrial use of high manganese steels, for example, of crashrelevant components of the automotive industry.