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25Mn钢(/%:0.24C,0.25Si,0.87Mn,0.016P,0.011S)冷拔管的生产流程为铁水预处理-90tEAF-LFVD-Φ250 mm圆坯HCC-穿孔-热轧至Φ197 mm×17 mm管-冷拔至Φ185 mm×13 mm管。采用光学、扫描电子显微镜、能谱仪和电子探针分析了25Mn钢冷拔管内表面麻点状缺陷。结果表明,麻点状缺陷呈翘皮状和凹坑状,翘皮状缺陷成因是CaO-Al_2O_3-(MgO)复合夹杂与钢基体变形量不一,凹坑状缺陷成因是Al_2O_3-MnS-CaS复合夹杂聚集长大后磨削加工过程中脱落。通过将原铝脱氧精炼工艺优化成硅钙合金脱氧工艺,使精炼渣碱度由原6.76降至2.26,精炼渣中(MgO)由原5.33%提高至7.23%,(Al_2O_3)由26.05%降低至12.76%,使钢中的硬脆性夹杂转变为延展性优良的硅酸盐类夹杂,消除了25Mn钢冷拔管内表面麻点状缺陷。
25Mn steel (/%0.24C,0.25Si,0.87Mn,0.016P,0.011S) cold drawn pipe production process for the hot metal pretreatment -90tEAF-LFVD-Φ250 mm round billet HCC-perforation - hot-rolled to Φ197 mm × 17 mm tube - cold drawn to Φ185 mm × 13 mm tube. Optical, scanning electron microscopy, energy dispersive spectrometer and electron probe were used to analyze the pitting defects on the inner surface of 25Mn steel. The results show that the pitting defects are in the shape of a bilge and a pit. The cause of the bark defects is that the CaO-Al_2O_3- (MgO) composite inclusions have different deformations with the steel base. The reason of the pit-like defects is Al_2O_3-MnS-CaS Compound inclusions grow up after grinding process shedding. By optimizing the deoxidation process of primary aluminum into the calcium-silicon alloy deoxidation process, the basicity of the refining slag is reduced from 6.76 to 2.26, the content of (MgO) in the refining slag is increased from 5.33% to 7.23% and the content of (Al 2 O 3) is reduced from 26.05% to 12.76%, so that the hard and brittle inclusions in the steel into ductile silicate inclusions with excellent ductility, eliminating the 25Mn cold drawn pipe punctate surface defects.