Effects of Nb and Mo addition to 0.2%C-1.5%Si-1.5%Mn steel on mechanical properties of hot rolled TRIP-aided steel sheets

Abstract

The development of high strength hot rolled TRIP (Transformation induced plasticity)-aided steel sheets with 780 MPa was carried out by taking into account the addition of Nb and Mo to 0.2C-1.5Si-1.5 Mn mass% steel and coiling conditions after hot rolling. The results reveal that the addition of 0.05% Nb can attain higher elongation with higher strength compared with Nb-free steel. The obtained tensile strength in this steel was higher than 780 MPa. The multiple addition of 0.2% Mo with 0.05% Nb results in higher TS (Tensile Strength) by the large amount of fine NbMoC precipitates than Nb containing steel without the deterioration of TS-EI (Elongation) balance under the possible hot rolling conditions. The good ductility in 0.05% Nb containing steel was mainly obtained by large volume fraction and high carbon concentration of retained austenite. In addition, finely dispersed retained austenite made some contribution to the improvement of ductility.