铸坯在结晶器内的非均匀传热、凝固、初生坯壳的薄厚以及二冷区铸坯表面温度、应力等均匀程度直接影响铸坯表面与内部质量。以反算热流为结晶器内铸坯边界条件,利用ANSYS有限元软件模拟某钢厂Q235B板坯全流程的温度场、应力场,分析了铸坯表面温度、等效应力、坯壳的不均匀性、遗传性以及裂纹敏感性。结果表明,结晶器内铸坯凝固厚度的不均匀性遗传至二冷区,铸坯表面等效应力的不均匀性遗传程度较小;在二冷区,坯壳厚度不均匀性改善程度较小,表面等效应力不均匀性改善程度较大。本研究案例条件下,内弧左侧角部温度最低,为892 ℃,等效应力最大,为12.2 MPa;内弧偏角部区域温度最高,为1 263 ℃,等效应力最小,为2.54 MPa。铸坯表面裂纹敏感性:1/4中心处＞1/8中心处＞1/2中心处。铸坯表面裂纹敏感性指数在结晶器内达到最大值0.52,在二冷初期回温程度较大阶段裂纹敏感性增大,凝固后期坯壳较厚,裂纹敏感性较低且变化幅度很小。
Abstract
The inhomogeneous heat transfer, solidification, thickness of primary shell, temperature and stress of secondary cooling zone directly affect the surface and internal quality of slab. The temperature field and stress field of the whole process of Q235B slab in a steel plant were simulated by ANSYS Finite Element Software, the surface temperature, equivalent stress, shell inhomogeneity, heredity and crack sensitivity were analyzed. The results show that the non-uniformity of slab solidification thickness in mold is inherited to secondary cooling zone, and the non-uniformity of equivalent stress on slab surface is less inherited, the non-uniformity of surface equivalent stress wasgreatly improved. In the case study, the temperature at the left corner of the inner arc was the lowest (892 ℃), the equivalent stress was the highest (12.2 MPa), and the temperature at the deflection corner was the highest (1 263 ℃), the equivalent stress was the lowest (2.54 MPa). The sensitivity of slab surface crack is 1/4 center > 1/8 center > 1/2 center.The sensitivity index of slab surface crack reaches the maximum value of 0.52 in mold. In the early stage of secondary cooling, the crack sensitivity is increased.And in the late stage of solidification, the shell is thicker, the crack sensitivity is lower and the change range is small.
关键词
连铸板坯 /
反算热流 /
坯壳 /
均匀性 /
遗传性 /
裂纹敏感性
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Key words
continuous casting slab /
back-calculation heat flux /
shell /
uniformity /
heredity /
crack sensitivity
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