Abstract: Using Gleeble3180 thermal simulation testing machine, under the conditions of temperature between 950-1100 ℃, strain rate between 0.001-1 s^-1, and true strain 0.7, high temperature unidirectional thermal compression experiments were carried out on X12CrMoWVNbN steel. The effects of temperature and strain rate on mechanical behavior of the tested steel during hot deformation were analyzed by high temperature flow curves under different conditions. Based on the Arrhenius equation as the constitutive model, a constitutive equation that can predict the flow stress of the steel was established. Based on the dynamic material model, experimental parameters and results, the processing maps of the steel under different strains were drawn, and the microstructure analysis was carried out combined with the maps. The results show that the flow peak stress and steady state stress increase with the decrease of temperature and increase of strain rate, the power dissipation coefficient increases with the decrease of strain rate and the increase of deformation temperature, the values of the power dissipation coefficient η in the optimal hot working areas are all above 0.4, and the deformed microstructure in these areas is uniform and fine. The optimal hot working regions at strain of 0.3, 0.4, 0.5 and 0.6 are all in the range of deformation temperature of 1050-1100 ℃ and strain rate of 0.001-0.003 s^-1.

Key words: X12CrMoWVNbN steel, hot compression, constitutive equation, hot processing map, hot deformed microstructure