14Mn5Nb无缝钢管“鱼鳞”形外折分析与控制  

Analysis and Control of the“Fish Scale”Outward Folding of 14Mn5Nb Seamless Steel Pipe

作　　者：彭杨 刘荣华 靳博颖 赵健明[1] 牛亮 PENG Yang;LIU Ronghua;JIN Boying;ZHAO Jianming;NIU Liang(Hengyang Valin Steel Tube Co.Ltd.,Hengyang 421000,China)

机构地区：[1]衡阳华菱钢管有限公司,湖南衡阳421000

出　　处：《工业加热》2024年第4期35-39,44,共6页Industrial Heating

摘　　要：某厂14Mn5Nb连铸圆坯(Φ330 mm)轧制成无缝钢管(Φ323.8 mm×8.3 mm)后表面出现大量“鱼鳞”状外折缺陷,影响成材率,成为亟须解决的问题。采用缺陷金相分析,“刻槽”试验,铸坯酸洗确定钢管表面“鱼鳞状”缺陷是由连铸圆坯表面横裂纹造成。采用扫描电镜检测,钢种热溯性分析以及现场数据统计,确定铸坯表面横裂纹产生原因为:Φ330 mm圆坯在当前工艺参数下铸坯进拉矫温度在900~950℃,处于第III脆性区转变温度940℃附近;表面存在较多Nb(C、N)析出物,增加了钢种的裂纹敏感性。通过调整钢种Ti含量至0.02%~0.03%,保护渣碱度由0.97提高至1.14,降低结晶器水量,调整二冷水量配比以确保进拉矫温度≥970℃等措施,有效避免了铸坯横裂纹和无缝钢管鱼鳞外折的产生。After rolling 14Mn5Nb continuous casting round billets(Φ330 mm)into seamless steel pipes(Φ323.8 mm×8.3 mm)at a certain steel plant,a large number of"fish scale"shaped outward bending defects appeared on the surface,which affected the yield and became an urgent problem to be solved.Through metallographic analysis,"grooving"test and pickling,it is determined that the"fish scale"defectis caused by the transverse crack on the surface of round billets.Through means of scanning electron microscopy,steel grade thermal traceability analysis and field data statistics,it is determined that the causes of transverse cracks on the surface are as follows:the drawing and straightening temperature ofΦ330 mm round billet is in the range of 900~950℃under the current process parameters,near the transition temperature of the third brittle zone of 940℃;there are more Nb(C,N)precipitates on the surface,which increases the crack sensitivity of steel.By adjusting the Ti content of steel grade to 0.02%~0.03%,increasing the basicity of mold flux from 0.97 to 1.14,reducing the water quantity of mold,and adjusting the proportion of secondary cooling water quantity to ensure that the drawing straightening temperature≥970℃,the occurrence of transverse cracks in billets and“fish scales”external folding of seamless steel pipe are effectively avoided.

关 键 词：电弧炉炼钢 14Mn5Nb “鱼鳞”形外折 连铸圆坯 横裂纹 矫直温度 

分 类 号：TF741.5[冶金工程—钢铁冶金]