Abstract: The hot deformation behaviors of Ti microalloying high strength steel with yield strength of 390MPa grade (Q390 steel) were investigated by a single-pass compression test. A mathematical model for deformation resistance and dynamic recrystallization of the experimental steel was established. The results show that deformation resistance increases gradually with the decrease of deformation temperature. The feature of stress-strain curves changes from dynamic recrystallization character to dynamic recovery character as increasing the strain rate. The activation energy of dynamic recrystallization for Q390 steel is about 257.142kJ/mol. The mathematical model has been proved to study the hot deformation behavior for Ti microalloying Q390 steel very effectively. Compared with the Q390 steel with the conventional chemical composition， the rolling force of the steel after Ti microalloying is small and dynamic recrystallization occurs more easily， which can facilitate the refining of austenite grain and improve the strength and toughness of the steel more substantially.

Key words: titanium, austenite, deformation resistance, dynamic recrystallization, mathematical model