Abstract: Austenite dynamic recrystallization behaviors of Ti microalloyed non-quenched and tempered steels were studied by Gleeble-3800 thermal simulation machine with deformation temperature of 850-1200 ℃ and strain rate of 0.1-10 s^-1. The influences of deformation temperature, deformation rate, and precipitation behavior of carbonitrides on the dynamic recrystallization of austenite were analyzed, the activation energy of dynamic recrystallization was calculated, and the dynamic recrystallization state diagrams and processing maps were obtained. The results show that with the Ti content increasing from 0 to 0.042% and 0.063%, the carbonitride precipitation amount in the steels is 0, 0.040 % and 0.038 %, respectively, showing a trend of increasing at first and then decreasing. The corresponding activation energy of dynamic recrystallization of the tested steels is 360.218, 394.015 and 378.247 kJ/mol, respectively, and that with 0.042% Ti is the highest. The processing maps obtained by superposition of power dissipation diagram and plastic instability diagram show that, the optimal thermal processing ranges of the Ti microalloyed non-quenched and tempered steels are the deformation temperature of 900-1050 ℃ with the deformation rate of 0.1-0.2 s^-1, and the deformation temperature of 1100-1200 ℃ with the deformation rate of 0.1-4 s^-1.

Key words: Ti microalloying, non-quenched and tempered steel, dynamic recrystallization, precipitation behavior, thermal processing map