Abstract: High-temperature austenite dynamic recrystallization and static recrystallization behaviors of a low Ni type LNG steel were studied through single-pass and double-pass compression tests, and through hot rolling tests under different rolling processes by two-stage controlled rolling and ultra-rapid cooling technologies, and then hot deformation behavior and mechanical properties of the low Ni type LNG steel were studied through thermal simulation and hot rolling test. The results show that dynamic recrystallization of austenite is easy to occur at high temperature (1000-1050 ℃) and low strain rate (0.1-0.5 s^-1), the critical conditions for the occurrence of recrystallization are determined, and a dynamic recrystallization kinetic model is established. The static softening phenomenon of the tested steel is obvious and static recrystallization is easy to occur at higher temperature (800-1050 ℃) and longer pass interval (60 s). According to the results of the thermal simulation test, the hot rolling test process is formulated, and the recrystallization behavior of high temperature austenite is controlled by controlling the finishing rolling temperature and the finishing rolling temperature, so as to refine the grains and improve the impact properties of the low Ni steel. When the finishing rolling temperature is 920 ℃ and the finishing rolling temperature is 770 ℃, the impact absorbed energy at low temperature of the low Ni steel is 180.1 J, the gield strength is 595.1 MPa, and the tensile strength is 717.8 MPa.

Key words: low Ni type LNG steel, recrystallization, controlled rolling, mechanical properties