Abstract: According to location and morphology of intermediate cracks occurred in macrostructure of 0.20C steel 4>300 mm round casting bloom and combining with analysis on casting equipment and process, it is obtained that with uneven shell thickness formed in mold, larger fluctuation of hydraulic force of withdraw straightening stands on bloom, the intermediate cracks along intergranular boundary form in bloom under action of heat stress and straightening stress. With improving the quality of mold softened water and secondary water for casting, decreasing superheating extent of liquid from 25-35 °C to 20-30 °C , decreasing mold electromagnetic stirring current from 550 A to 350 A, stabling the hydraulic force, and straightening bloom temperature ≥ 950 °C , the intermediate cracks in round casting bloom are eliminated.

Key words: Φ300 mm Casting Round Bloom, Intermediate Cracks, Straightening Force

摘要： 针对20钢φ300mm圆铸坯低倍组织出现中间裂纹的位置和形貌,结合连铸设备和工艺进行分析,得出结晶器内坯壳厚度不均匀,拉矫机矫直压力波动大,铸坯在受到热应力和矫直应力的作用下沿晶界开裂形成中间裂纹。通过改善结晶器软化水和连铸二冷水的质量,钢水过热度由25～35℃降至20～30℃,结晶器电磁搅拌电流由550 A降至350 A,稳定矫直压力,铸坯矫直温度≥950℃,避免了圆铸坯中间裂纹的出现。

关键词: Φ300 mm圆铸坯, 中间裂纹, 矫直力