60Si2Mn弹簧钢150 mm x 150 mm铸坯缺陷分析与工艺优化

针对60Si2Mn弹簧钢(/%:0.56～0.64C,1.50～2.00Si, 0.70～1.00Mn,≤0.025P,≤0.020S)的150 mm×150 mm连铸坯角部存在横向表面裂纹缺陷问题，通过采用金相显微镜和扫描电镜对铸坯角部横向表面裂纹缺陷进行分析及试验比对。结果表明：结晶器铜管锥度过大、拉坯阻力大、保护渣润滑效果差以及二次冷却不均匀导致角部产生横向表面裂纹。通过将结晶器铜管锥度从2.2 mm降到1.6 mm、保护渣熔化温度从1182℃降到1072℃、粘度从0.76 Pa·s降到0.52 Pa·s以及二次冷却比水量从0.45L/kg降到0.32L/kg等措施，降低铸坯在铜管内拉坯阻力，改善结晶器冷却传热和二冷段喷淋冷却效果，提高铸坯冷却均匀性，使得铸坯缺陷得到有效控制，铸坯表面探伤合格率从35%提高到92%。

Defects Analysis and Process Optimization of 150 mm x 150 mm Casting Billet of 60Si2Mn Spring Steel

Facing the quality problems of transverse surface crack at the comer of 150 mm x 150 mm continuous casting billet of 60Si2Mn spring steel(/% ：0.56-0.64C, 1.50-2.00Si,0.70-1.00Mn, ≤0.025P, ≤0.020S) , the transverse surface crack defects at the comer of casting billet are analyzed by metallographic microscope and SEM and it is carrying out test comparison. The result indicates that the defect is caused by the large drag force of the large taper of crystallizer copper tube and the poor lubrication effect of shielding flux and the uneven secondary cooling. By reducing the mold steel tube taper from 2.2 mm to 1.6 mm and the melting temperature of protective slag from 1 182 °C to 1 072 °C and its viscosity from 0.76 Pa·s to 0.52 Pa·s and the secondary specific water from 0.45 L/kg to 0.32 L/kg,to reduce the drag of casting billet in copper tube and improve the cooling heat transfer of the mold, the cooling effect of the secondary cooling section and the cooling uniformity of casting billet, the defects of casting billet have been effective controlled, and the qualified pass rate for casting billet surface defect detection increases from 35% to 92%.