罐箱用316L不锈钢(4.4~4.6)mm×2050 mm冷轧退火板白斑缺陷分析及控制

Analysis and Control of White Spots Defect on(4.4~4.6)mm×2050 mm Cold Rolled Annealed Strip of 316L Stainless Steel for Tank Container

罐箱用316L不锈钢(/%:0.02C,17.12Cr,10.15Ni,2.06Mo)(4.4~4.6)mm×2050 mm宽厚冷轧板在生产过程中表面出现严重的白斑缺陷。运用特征分析、钢种对比、现场缺陷跟踪的方法研究白斑缺陷产生原因,结果表明,白斑缺陷产生原因是带钢轧后表面乳化液残留多,在脱脂清洗效果不足与980℃退火工艺条件下产生分布不均的氧化皮,乳化液残留较多处产生的氧化皮呈白色,酸洗后形成白斑缺陷。系统分析了轧后带钢表面乳化液残留量以及残油去除效果的影响因素,通过轧制工序采用无纺布材质刮油辊,加装风刀吹扫系统,控制乳化液浓度为1.5%~3%,乳化液温度为(55±3)℃,修复两套磁过滤系统;并通过控制脱脂段电导率7.5μs/cm,充套速度50 m/min,调整退火段9~12区炉温到1030℃,白斑缺陷不合格率由10%降低到≤0.5%。

Serious white spots defect occur on the surface of(4.4~4.6)mm×2050 mm wide-thick cold rolled strip of 316 L stainless steel(/%:0.02 C,17.12 Cr,10.15 Ni,2.06 Mo)for tank container in production process.The causes of the white spots are researched by means of feature analysis,steels grades comparison and on-site defect tracking,the results show that there is much emulsion on the surface of cold rolled strip,on which the formed oxide scale is unevenly distributed in case of incompletely degreasing and annealing at 980℃,the color of the oxide scale on the surface with much emulsion is white,these white oxide scales are changed into white spots after pickling.Besides,the influencing factors of the residual emulsion on the surface of rolled strip and the removal effect of residual emulsion are systematically studied.By applying oil scraping system for nonwoven-fabric roller,adding air knife purging system,controlling emulsion concentration 1.5%~3%and temperature(55±3)℃,repairing two sets of magnetic filtration system in rolling process,through controlling degreasing electrical conductivity 7.5μs/cm and loop filling speed 50 m/min,adjusting 9~12 area furnace temperature to 1030℃,the unqualified rate of white spots is reduced from 10%to 0.5%or less.