<p>The accurate establishment of a ferrite transformation start temperature model is crucial to design a reasonable controlled rolling process and ensure uniform microstructure in aluminum bearing dual-phase steel. The measurements of the expansion-temperature curves of aluminum bearing dual-phase steel under continuous cooling and isothermal conditions are presented, utilizing a dynamic transformation dilatometer experiment. Based on these expansion-temperature curves, the start temperature and incubation time of ferrite transformation were determined, elucidating the influence of process parameters on both the incubation time and the start temperature of ferrite transformation. By integrating metallurgical principles with measured incubation time of ferrite transformation, and considering the effects of temperature and strain, a fitting model for the variation in volume free energy during ferrite nucleation was derived. Building upon this foundation, a high-precision incubation time of ferrite transformation mathematical model for the experimental steel was established. To more accurately calculate the start temperature of ferrite transformation under continuous cooling conditions, the Scheil’s additivity rule was modified to account for the effects of deformation and cooling rate. The results indicate that the modification coefficient decreases with increasing the cooling rate and strain, thereby significantly improving the accuracy of calculating the starting temperature of ferrite transformation using the modified additivity rule.</p>