Structure and mechanical properties of DP-type and TRIP-type sheets obtained after the thermomechanical processing

The chemical composition of the C–Mn–Si steel with Nb and Ti microadditions was established. The rolling and cooling conditions of the thermomechanical processing of DP-type and TRIP-type sheets were developed. The conditions of the thermomechanical processing were selected on a basis of the determined DTTTc-diagram of plastically deformed undercooled austenite and dissolution kinetics of TiN and NbC in the austenite. It was found that thermomechanically processed sheets have more fine-grained structure and better mechanical properties than after the classical underhardening or isothermal quenching from the temperature slightly higher than Ac1 of the investigated steel.