Metadynamic recrystallization behaviors of SA508Gr.4N reactor pressure vessel steel during hot compressive deformation

Abstract

The two-pass isothermal hot compression method was used to study the effect of different thermal deformation conditions on static recrystallization behavior in Ni–Cr–Mo series SA508Gr.4N low alloy steel with interval holding time ranging from 1 to 300 s, temperature ranging from 950 to 1150 °C, strain rate ranging from 0.01 to 1 s−1, true strains ranging from 0.1 to 0.2, and initial austenite grain size ranging from 175 to 552 μm. It can be concluded that the static recrystallization volume fraction gradually increases with the increase in the deformation temperature, strain rate, strain and pass interval, and the decrease in the initial grain size, which is mainly due to the increase in the deformation energy storage and dislocations. Moreover, strain-induced grain boundary migration is the nucleation mechanism for static recrystallization of SA508Gr.4N low alloy steel. Based on the stress–strain curve, the predicted value obtained from the established static recrystallization kinetics model is in good consistence with the experimental value, and the static recrystallization thermal activation energy of SA508Gr.4N steel was calculated as 264,225.99 J/mol.