Abstract: Thermo dilatometric curve of 23MnNiMoCr54 steel was measured by a DIL 805A thermal dilatometer, CCT curve of the tested steel was drawn in combination with the hardness test, and the dynamic phase transformation and dynamic recrystallization laws were studied and analyzed. The results show that the critical transformation temperatures of the 23MnNiMoCr54 steel are: Ac₃=806 ℃, Ac₁=713 ℃, and there is no pearlite transformation zone in the CCT curve. When the cooling rate is greater than or equal to 0.5 ℃/s, the martensitic transformation begins. When the deformation amount is 10% and deformed at 850-1150 ℃, the austenite grain boundary of the tested steel is stable, the grain size does not change significantly, no dynamic recrystallization occurs, and the softening mechanism is mainly dynamic recovery. When the deformation amount is 40%, no dynamic recrystallization of the tested steel occurs at 850 ℃, and the softening mechanism is mainly recovery. Unstable austenite grain boundaries and fine grains appear when the deformation temperature is at 900-950 ℃, and dynamic recrystallization begins to occur. At 1000 ℃, complete dynamic recrystallization occurs. When the deformation amount is 50%, unstable austenite grain boundaries and fine grains appear when deformed at 850-950 ℃, and partial recrystallization occurs. At deformation temperature of 1000 ℃, complete dynamic recrystallization occurs. When the deformation amount is 60%, unstable austenite grain boundaries and fine grains of the tested steel appear when deformed at 850-950 ℃, and partial recrystallization occurs. At deformation temperature of 1000 ℃, complete dynamic recrystallization occurs.

Key words: 23MnNiMoCr54 steel, dilatometer method, CCT curve, recrystallization, grain size