Bainite transformation during continuous cooling of low carbon microalloyed steel

The evolution of the final microstructure for a low carbon Nb-Ti microalloyed plate steel was studied during a simulation of thermomechanical processing for hot rolling following by accelerated cooling. The effects of austenite deformation below the non-recrystallisation temperature T-NR, cooling rate, and interrupt temperature on the formation of conventional (intergranular) bainite (CB), acicular ferrite (intragranular) (AF), and martensite-austenite (MA) constituents were determined. With increases in austenite deformation and cooling rate, and decrease in the interrupt temperature, the final microstructure changed From a mixture of CB-CMA through CB + AF + MA to a dual phase AF + MA.