20钢Φ300mm圆铸坯中间裂纹成因分析和改善工艺措施

An Analysis on Cause of Formation of 0.20C Steel Φ300 mm Round Casting Bloom Intermediate Cracks and Improved Process Measure

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。

According to location and morphology of intermediate cracks occurred in macrostructure of 0. 20C steel qb300 mm round casting bloom and combining with analysis on casting equipment and process, it is obtained that with une- ven shell thickness formed in mold, larger fluctuation of hydraulic force of withdraw straightening stands on bloom, the in- termediate cracks along intergranular boundary form in bloom under action of heat stress and straightening stress. With im- proving the quality of mold softened water and secondary water for casting, decreasing superheating extent of liquid from 25 - 35 ℃ to 20 - 30 ℃ , decreasing mold electromagnetic stirring current from 550 A to 350 A, stabling the hydraulic force, and straightening bloom temoerature 9950 ℃. the intermediate cracks in round casting, bloom are eliminated.