Abstract: According to the actual production conditions of 165mm×165mm ER80-G steel, the two-dimensional billet thermal coupling model based on the genetic characteristics of continuous casting billet was established by using finite element software ANSYS. The inner cavity size of the mold was optimized for the longitudinal cracking of the billet. The results show that the small taper of the original mold causes the slow growth of the shell in the "hot spot" region, and the high break temperature of the mold flux aggravates the influence of the air gap. The maximum air gap in the corner area of the original mold was 1.46 mm, the maximum difference of the surface temperature of the shell was 130℃,and the the thickness of the shell in the "hot spot" region of the temperature was about 1.5 mm thinner than that in the central region of the surface. The "hot spot" was eliminated by taper optimization, and the thickness of the shell at the exit of the mold 15 mm from corner increased from 12.3 mm to 19 mm.Meanwhile, the break temperature of the mold flux was adjusted from 1 200℃ to 1 050 – 1100 ℃, which promoted the lubrication between the shell and the mold, and the incidence of cracks decreased from 2% to 0.46%.

Key words: 方坯, 纵裂纹, 热力耦合, 保护渣, 锥度优化