25MnCrNiMoA钢Φ120 mm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100 t UHP EAF-LFVD-Φ650 mm坯连铸-轧制Φ120 mm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≤2 mm,拉速0.26m/min,过热度20~30℃,降低二冷水量,矫直温度≥950℃,优化保护渣组成等工艺措施,避免了25 MnCrNiMoA钢热轧材表面裂纹的形成。