25MnCrNiMoA钢Φ120mm轧材表面裂纹分析与工艺改进

25MnCrNiMoA 钢(/%：0.25~0.26C,0.22~0.25Si,1.25~1.30Mn,0.008~0.011P,0.002~0.004S,0.45~0.50Cr,0.36~0.38Ni,0.24~0.26Mo,0.04~0.08Cu,0.025~0.031Alt)的生产流程为100t UHP EAF-LF-VD-Φ650mm坯连铸-轧制Φ120mm材。试制过程热轧材出现批量表面裂纹。通过对轧材表面裂纹缺陷部位组织观察和分析，发现裂纹附近组织存在明显的脱碳及夹杂物,并且裂纹末端存在多条铁素体条带，表明连铸坯质量缺陷是25MnCrNiMoA圆钢产生表面裂纹的主要原因。通过控制S]≤0.003% ,连铸时液面波动≤2mm,拉速0.26 m/min,过热度20~30℃ ,降低二冷水量，矫直温度≥950°C，优化保护渣组成等工艺措施，避免了25MnCrNiMoA钢热轧材表面裂纹的形成。