25MnCrNiMoA钢Φ120 mm轧材表面裂纹分析与工艺改进
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摘要
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。
The production flowsheet of steel 25 MnCrNiMoA(/% : 0. 25 ~0. 26 C,0. 22 ~0.25 Si,1. 25 ~1. 30 Mn,0.008 ~0.011 P,0.002~0.004 S,0.45 ~0.50 Cr,0.36~0.38 Ni,0. 24 ~0.26 Mo, 0.04 ~0.08 Cu,0.025 ~0.031 Alt)is 100 t UHP EAF-LF-VD-Φ650 mm bloom casting-rolling to Φ120 mm products. By observing and analysis on structure at crack area, it is found that there is obvious decarburization and inclusions in structure near the cracks,and multi-ferrite strips exist at end of cracks,it shows that the quality defects of casting bloom are main reason to form surface cracks of round bar of steel 25 MnCrNiMoA. With the process measures including controlling [S] ≤0. 003%, liquid surface fluctuation ≤2 mm during casting, casting speed 0. 26 m/min, overheating extent of liquid 20 ~30 ℃, decreasing secondary water rate, straightening temperature of bloom ≥950 ℃ and optimizing ingredient of shielding slag, the surface cracks of hotrolled products of steel 25 MnCrNiMoA are avoided.
The production flowsheet of steel 25 MnCrNiMoA(/% : 0. 25 ~0. 26 C,0. 22 ~0.25 Si,1. 25 ~1. 30 Mn,0.008 ~0.011 P,0.002~0.004 S,0.45 ~0.50 Cr,0.36~0.38 Ni,0. 24 ~0.26 Mo, 0.04 ~0.08 Cu,0.025 ~0.031 Alt)is 100 t UHP EAF-LF-VD-Φ650 mm bloom casting-rolling to Φ120 mm products. By observing and analysis on structure at crack area, it is found that there is obvious decarburization and inclusions in structure near the cracks,and multi-ferrite strips exist at end of cracks,it shows that the quality defects of casting bloom are main reason to form surface cracks of round bar of steel 25 MnCrNiMoA. With the process measures including controlling [S] ≤0. 003%, liquid surface fluctuation ≤2 mm during casting, casting speed 0. 26 m/min, overheating extent of liquid 20 ~30 ℃, decreasing secondary water rate, straightening temperature of bloom ≥950 ℃ and optimizing ingredient of shielding slag, the surface cracks of hotrolled products of steel 25 MnCrNiMoA are avoided.
引文
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[4]王建钢,王皓,李人杰,等.热送裂纹产生机制及生产工艺控制研究[J].连铸,2017,42(2):22-26.
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[6]周云,王世俊,何烈云,等.低碳含铌钢表面裂纹的研究与改进措施[J].钢铁研究学报,2012,24(1):40-43.
[7]苏瑞先.连铸夹渣类缺陷的成因分析和控制措施[J].特殊钢,2011,32(1):27-29.
[8]蔡开科.连铸坯质量控制[M].北京:冶金工业出版社,2010.
[9]李殿明.连铸结晶器保护渣应用技术[M].北京:冶金工业出版社,2008.