Influence of the thermo–mechanical treatment parameters on the inhomogeneity of the austenite structure and mechanical properties of the Cr–Mo steel with Nb, Ti, and B microadditions

The paper presents the investigation results of the thermo–mechanical treatment parameters influence on structure and mechanical properties of the Cr–Mo low-carbon steel with Nb, Ti, and B micro-additions, destined for the weldable heavy plates production with the yield point above 960 MPa. Parameters of the thermo–mechanical treatment were chosen basing on investigations of the austenite recrystallization kinetics determined in the hot multi-stage torsion test at the deformation rate of 3 s −1 and deformation ɛ = 0.2 in consecutive stages. It was found out that failing to attain the total static austenite recrystallization between the consecutive deformation stages causes development of the segregation bands, causing the significant deterioration of the crack resistance of steel at the lowered temperature.