Study on hot deformation behavior and processing maps of SA508-IV steel for novel nuclear reactor pressure vessels

The hot deformation behavior and microstructural evolution of SA508-IV steel for a novel nuclear reactor pressure vessels were studied by hot compression tests in the strain rates 0.001-1 s(-1) and temperature ranges 950-1250 degrees C respectively. The results showed that the high temperature (1250 degrees C) and low strain rate (0.001 s(-1)) were more likely to induce the abnormal growth of grains, resulting in the decrease of the power dissipation efficiency. The flow instability region covered the temperature and strain rate ranges in 950-1200 degrees C and 0.1-1 s(-1) with inhomogeneous microstructure. The optimal processing window of SA508-IV steel was obtained in the temperature ranges 1050-1175 degrees C and strain rates 0.01-0.1 s(-1) respectively with a peak efficiency of 45%. By analyzing the microstructure of the steel in this zone mentioned above, fine recrystallized grains were got.