Flat Products and Application Technologies for Automotive Usage in Japan

Yuji Sueki
Nippon Steel Corporation

Automotive Industry has grown significantly in the decades all over the world. Among them, the growth of Japanese auto-manufactures is remarkable and their technologies have been leading the innovation of automotive industry. Needless to say, the development of the cut-edge technology is the key factor of the growth of Japanese auto-manufactures. At the same time, corresponding to it, steel products and their application technologies have also largely contributed as it is said widely.

Not only the performance of the vehicle itself, but also many environmental problems or restrictions have forced automotive technologies being innovative. In steel products, for instance variety of High Strength Steel (HSS) have been developed to enhance weight reduction or to compensate the weight increase for the crashworthiness. Also, for corrosion resistance purpose and the environmental restrictions, many types of galvanized or unique surface treaded products have been developed and commercialized.

In the case of structural parts, HSS up to 590MPa in TS have been widely applied along with improvement of the products themselves and application technologies like parts design supported by improved CAD or FEM analysis technologies. For some specific parts even 780MPa or 980MPa TS-class materials are utilized. Using Hot- Forming or Die-Quench technologies, it has become possible to make a part with above 1500MPa strength in TS.

On the other hand mild steel has been still widely utilized in Skin Panels. In this area, of course, some HSS like 340MPa TS-class or/and Bake Hardenable material are used. However, the key for external parts is extremely critical surface appearance required by customers. Lots of efforts have been made to ensure surface cleanness or less defects products from steel making to final processing.

In terms of corrosion resistance, many kind of galvanized or surface treated material have been developed and commercialized according to the local conditions and auto-manufactures’ policy. In Japan GA (Galva-annealed steel) has become a standard product for corrosion resistance steel in automotive usage among coated products.

Another important steel product is Sn-Zn coated steel for fuel tank specifically. Because of the limitation of lead usage, lead coated steel as well known as Terne sheet is going to be substituted by something else. Newly developed and commercialized Sn-Zn coated steel has become pervasion in Japan and been expanding to all over the world for its well-balanced characteristics.

Although production technologies like Tailored Welded Blanks (TWB) and Hydro-Forming (HF) are specific topics to be addressed, collaboration between auto-manufacture and steel producer is the important key to both development of a new products and a challenge of its application to a leading vehicle. The latest automotive flat steel products and their application technologies are going to be discussed at the symposium in overall manner.

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