Influence of the preliminary rolling conditions on strength and fracture mechanism of X70 steel

Influence of the preliminary rolling temperature during thermo-mechanical processing of the X70 steel was investigated on its yield stress, ferrite grain size and fracture mechanism. It is shown a decrease of the yield stress with the temperature rise which is accompanied by decreasing the grain size and changing the fracture mechanism from transgranual to intergranual ductile fracture. The results obtained are explained by rapid austenite recrystallization development at the beginning stages of the preliminary rolling