• A novel mathematical model integrating microsegregation, solidification, and TiN precipitation was developed and validated with high-temperature experiments.
• Positive segregation of Ti and N at the solidifying front leads to maximum TiN precipitation at the 1/4 width of the steel, while high surface cooling rates cause negative segregation.
• Increasing cooling rate reduces TiN precipitation by diminishing solute segregation, whereas higher initial solute content enhances TiN formation.
• The model provides critical insights for controlling TiN inclusions to improve mechanical properties of Ti-microalloyed steels.