Hot Deformation Behavior of SA508GR. 4N Steel for Nuclear Reactor Pressure Vessels

A hot compression experiment (1073-1473 K, strain rates of 0.001-10s−1) of SA508GR. 4N low alloy steel was performed using a Gleeble-3800 thermal-mechanical simulator, and the hot deformation behavior of the steel was investigated by analyzing both the true stress-true strain curves and its microstructures. The thermal deformation equation and hot deformation activation energy (Q) of SA508GR. 4N steel were obtained by regression with a classic hyperbolic sine function. The hot processing map of SA508GR. 4N steel was also established. An empirical equation for the stress peak was described for practical applications. The SA508GR. 4N steel showed a critical Zener-Hollomon parameter (lnZc) for dynamic recrystallization (DRX) of 37.44, below which full DRX may occur. The sensitivity of the SA508GR.4N steel increased linearly with test temperature, such that higher temperatures led to enhanced workability.