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TRIP (TRansformation Induced Plasticity) steels have been studied frequently because of its superior strength and ductility. The high values of tensile strength and elongation are mainly attributed to the strain induce martensite transformation (SIMT) phenomena of retained austenite. Because of the excellent tensile property combination, TRIP steels have many advantages when the steels are used for automotive applications. To produce as-hot-rolled TRIP steels with better microstructure and mechanical properties, an appropriate chemical composition together with the exact control of cooling in run-out table is major parameter. A 3-step cooling pattern in run-out table (ROT) should be employed to secure sufficient amount of ferrite and resultant carbon enrichment in untransformed austenite. Effective carbon enrichment in untransformed austenite is very important to increase stability of austenite in lower temperature region.

Objective of this study was to develop basic techniques in order to apply aluminum sandwich sheets for an automotive hood part. The aluminum sandwich sheet is the material fabricated by adhering two aluminum skins to one polypropylene core. When it has the same bending stiffness as a steel sheet, it is 65% lighter than the steel sheet and 30% lighter than an aluminum alloy sheet. Therefore, it is notified exclusively as good substitutive materials for a steel body to improve the fuel efficiency. Through aluminum sandwich sheet, however, it has relatively lower formability than that of the steel sheet for automotive application. In this study, we fabricated a prototype of the automotive hood panel to develop application techniques of the aluminum sandwich sheet.