方坯表面纵裂的数值模拟研究

Numerical simulation of longitudinal cracks in billet surface

针对ER80-G钢165 mm×165 mm方坯纵裂问题,基于连铸坯壳应力遗传特性,采用有限元软件ANSYS建立二维方坯热力耦合分析模型,对结晶器锥度进行了优化分析。结果表明:原结晶器锥度小,导致"热点"区域坯壳生长减缓;保护渣转折温度高,加剧了气隙影响。原结晶器角部区域最大气隙1.46 mm,坯壳表面温度最高差值130℃,"热点"区域比表面中心坯壳厚度减薄1.5 mm。通过锥度优化消除了热点现象,结晶器出口处距角部15 mm区域坯壳厚度由12.3 mm增加到19 mm;同时将保护渣转折温度由1200℃调整到了1050~1100℃,促进坯壳与结晶器之间的润滑,裂纹发生率由2%下降到0.46%。

According to the actual production conditions of 165 mm×165 mm 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 thickness of the shell in the "hot spot" region was 1.5 mm thinner than that in the central region of 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 was increased from 12.3 mm to 19 mm. Meanwhile, the break temperature of the mold flux was adjusted from 1 200 ℃ to 1 050-1 100 ℃, which promoted the lubrication between the shell and the mold, and incidence of cracks decreased from 2 % to 0.46 %.