According to the experimental phenomena and thermodynamics mechanism of heterogeneous nucleation

combined with mathematic calculation

a dynamics model of intra-granular ferrite nucleation induced by inclusions has been established. Results show that in the nucleation model basal phase is a triangular pyramid with apex angle a; the nucleation phase is spherical nucleating model; as the volume of basal phase embedded nucleation phase is bigger with small wetting angle and there is an optimum value of apex angle α- about 34°

it is easiest to nucleate. The test of 0.45% C steel casting billet with heating at 1 150 °C for 10 min then cooling to 500 °C by 30 %：/min rate and cooling to ambient by 100 ℃/min rate show that a lot of titanium nitride inclusions are got in steel to induce intra-granular ferrite nucleation

cut off austenite grain and fine structure.