Effect of initial grain size on dynamic recrystallization of ultra-large nuclear rotor steel 25Cr2Ni4MoV

Abstract

The effects of different initial grain sizes on dynamic recrystallization (DRX) of ultra-large nuclear rotor steel 25Cr2Ni4MoV based on the isothermal hot-compression tests under different deformation conditions were systematically investigated. The results show that the strain rate is faster, the smaller the initial grain size, the easier DRX occurs. The average grain size of DRX is positively correlated with deformation temperature, negatively correlated with strain rate, and positively correlated with initial grain size. At higher strain rates, the initial grain size has less effect on the average grain size of DRX. However, the degree of DRX is higher in the specimen with a smaller initial grain size. The DRX model was constructed of 25Cr2Ni4MoV with initial grain sizes of 33μm, 179μm, and 1577 μm based on the experimental data. The DRX average grain size models have good fitting accuracy, and the DRX percentage models are consistent with the DRX degree shown by the flow stress strain curves. when DRX occurs sufficiently and the strain rate is low, the larger the initial grain size is, the smaller the critical strain of DRX is, and the easier it is for DRX to occur.