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Improved formability and higher heat-resistance are increasingly demanded to materials used for hot end parts of automotive exhaust gas system in order to meet stricter emission regulations. A heat-resistant ferritic stainless steel and pipe with high formability was developed by refining the microstructure of hot rolled and annealed sheets. The newly developed steel showed a remarkable improvement in various forming properties such as limit drawing ratio, limit expansion ratio of pipe, and thickness reduction ratio of pipe after bending in comparison with conventional steels.

Recently, Vibration Damping Steel Sheet (VDSS) has been increasingly used for automobile parts such as dash boards and partition panels. VDSS is also used in oil pans, but the rquirements in this application are much stricter than those in other auto applications. The material must remain sound (show no wall break) and not delaminate during deep drawing press forming. In service, it must be oil tight at the welded drain nut and must maintain good adhesion characteristics at high temperatures of 60-120°C. The VDSS with a thermoplastic resin core used to date in oil pans provides poor baking durability and heat durability in high temperature service. For use in oil pans, the authors therefore developed a new VDSS material comprising two extra deep drawing class steel skin sheets (of ultra low carbon steel) and a thermosetting polyester resin core layer containing metal powder.

Modifications in the properties of galvannealed steel sheet have been made to meet the needs of the automotive industry. The press formability (powdering and flaking) of the galvannealed steel sheet is very sensitive to the phase composition and coating weight of the coating. The allowable coatings for a satisfactory anti-powdering property may fail to provide the anti-flaking property, showing a high coefficient of friction due to the existence of a soft phase, ζ, at the surface. In this study, the effects of an inorganic film on the surface of the galvannealed coating were studied improving press formability. It was found that a thin borax film was effective to minimize surface friction and to improve unti-flaking properties. Short electrode life is another problem, as it limits continuous spot welding of the galvannealed steel sheet. During welding, electrode tips (Cu) are consumed by an interaction with the coating and the steel substrate.