Effects of Nb and Mo addtion on mechanical properties of hot rolled trip-aided steel sheets

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