Development of high strength hot rolled steel sheet for wheel disc application

Abstract

A hot rolled steel with unique combination of high strength and excellent ductility coupled with high hole expansion ratio has been developed for automotive applications using a new metallurgical approach. The steel chemistry and processing parameters were designed in such a way that austenite–ferrite phase transformation takes place at lower temperature with interphase precipitation of very fine carbides. A fine ferritic microstructure was produced with an average grain size of 3·4 μm resulting into attractive mechanical properties. Interphase precipitation was used as one of the major strengthening mechanisms apart from grain refinement. This led to an achievement of tensile strength as high as 800 MPa (min.) with an excellent stretch formability and low impact transition temperature. This is a potential grade with unique features which can have wider applications.