Volkswagen is the first automotive manufacturer that produces press-hardened parts using two different material concepts. Hot-dip aluminized material is used for the production of most parts in the economic direct process. The manufacturing of highly complex components requires a 2-stage process with cold preforming before the final hot stamping operation. In both process steps, the organic-inorganic x-tec-coating serves as a forming aid and additionally prevents the surface from scaling during austenitizing and hot forming. The interaction of the press-hardening process and the material concept affects the final material properties and all following production steps from cutting and joining to phosphating and painting and thus determines the overall performance of the part in the automobile. For example, the heating time in the furnace directly influences the surface structure of aluminized material and affects both corrosion resistance and weldability. The crash performance of a component can be influenced significantly by elongated manganese sulphides in the microstructure or surface defects in the AlSi-layer. By a comprehensive material qualification process, the challenges of this new material were taken into account and resulted in internal material and process standards and an integrated quality assurance concept. The mechanical properties of press-hardened parts are checked quickly and cost-efficiently using a nondestructive micromagnetic testing method.
Press-hardened steels in automotive applications - changes and challenges
Pressgehärtete Stähle im Automobilbau - Chancen und Herausforderungen
2008
8 Seiten, 13 Bilder, 7 Quellen
Conference paper
English
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