Prediction for the austenite grain size in the presence of growing particles in the weld HAZ of Ti-microalloyed steel

A model to predict the austenite grain size in a Ti-microalloyed steel weld heat affected zone (HAZ) was developed. Grain boundary mobility for the austenite grain growth was expressed as a function of aging temperature and alloying elements. By analyzing isothermal austenite grain growth behavior, the Zener coefficient of cubic TiN particle was measured. From quantification of the effect of grain boundary pinning by TiN particle and alloying elements on the grain boundary mobility, an isothermal grain growth model of Ti-microalloyed steel is presented. The predicted austenite grain sizes from the proposed model were in agreement with the experimental results. Finally, combining with the additivity rule, a general austenite grain growth model during the continuous welding thermal cycle was developed.