Method of grain refinement
1. Shorten the residence time after deformation, accelerate the cooling rate after rolling, and inhibit the growth of grains;
2. Rolling in the austenite non-recrystallization zone to refine the mother phase austenite, and obtain fine ferrite grains after phase transformation;
3. Make the mother phase austenite undergo ferrite transformation in the state of work hardening that has not been recovered;
4. Use the uniformly distributed precipitates in the austenite grains as phase deformation nuclei to refine the grains.