Ultra High Strength FeMn TWIP Steels for Automotive Safety Parts

Energy savings are among the most important goals of steel users. But generally, the increase of Tensile Strength for a given metallurgy is obtained to the detriment of ductility. Arcelor develops new ultra high strength steel with TWinning Induced Plasticity (TWIP) effect for weight reduction and impact resistance. This product, based on manganese (Mn) alloying metallurgy, has a tensile stress higher than 1000 MPa for a total elongation superior to 50%. Mechanical properties of these new steel grades are reported, in terms of tensile and forming behaviour, weldability and fatigue. Optimised designs are presented for safety parts in FeMn TWIP 1000 and assessed against conventional UHS steel. Tensile and formability properties are presented first by means of basic tests (stretching, bending, etc.) in order to classify the different steels. Crash resistance is investigated by using a dynamic axial compression test and a dynamic three point bending test on structural components with closed and open cross sections. For each steel grade, the estimated weight saving potential is compared with respect to parts manufactured in high drawing ability steel. The exceptional mechanical characteristics of this product permit to propose innovative steel design solutions for automotive safety component.