Grain growth kinetics model of high-temperature ferrite and austenite in Ti microalloyed steel during continuous casting

The microstructural characteristics of austenite in Ti microalloyed steel during continuous casting significantly influence the thermoplasticity, thereby affecting the quality of the slab. In this work, a prediction model for two-stage austenite growth under varying cooling rates was established by incorporating the effect of second-phase pinning and high-temperature ferrite–austenite phase transformation and growth theory. The results indicate that with 0.02wt% Ti, the high-temperature ferrite growth exhibits typical parabolic growth characteristics. When the Ti content increases to 0.04wt%, the high-temperature ferrite grain boundary migration rate significantly slows during the initial solidification stage. The predicted austenite grain sizes for 0.02wt% Ti microalloyed steel at the center, quarter, and surface of the slab are 5592, 3529, and 1524 μm, respectively. For 0.04wt% Ti microalloyed steel, the austenite grain sizes are 4074, 2942, and 1179 μm at the same positions. The average error is within 5%. As the Ti content increases from 0.02wt% to 0.04wt%, the austenite grain refinement at the center is most significant, with an average grain size reduction of 27.14%.