中牌号无取向硅钢冷轧钢带表面黑斑的研究

Research on Black Spots on Cold-rolled Medium-grade Non-oriented Silicon Steel Strip

某钢铁厂生产的冷轧中牌号无取向硅钢带表面出现黑斑缺陷。采用SEM和GDS分析了黑斑的微观结构和成分分布。通过模拟钢带的冷轧及冷却过程,研究了黑斑的形成机制。研究结果表明:中牌号无取向硅钢钢带上的黑斑为1～2μm厚的薄膜,主要成分为氧化物,并含有少量的有机物和乳化液。黑斑的形成原因为:冷轧过程中,乳化液、铁粉附着在钢带表面,其中的水分在高于100℃的轧制温度下汽化从而腐蚀钢带表面;在卷取后的冷却过程中,钢带表面金属原子离子化,产生电化学腐蚀,最终形成了黑斑。根据产生黑斑的原因,提出了有效的预防措施:更换乳化液,减少混入乳化液的杂质,改善钢带表面的吹扫效果,缩短钢带的储存时间。

The cold-rolled medium-grade non-oriented silicon steel strip produced in one steel mill exhibited unacceptable black spots on surface.Microstructure and composition distribution of the black spot were analyzed by using SEM and GDS.The mechanism whereby the black spots formed was investigated by simulating cold-rolling and cooling processes of the steel strip.The results showed that the black spot on the medium grade non-oriented silicon steel strip was a film 1μm to 2μm in thickness,and consisted essentially of oxides and a small amount of organic matter and emulsion.The reason why the black spots formed was as follows:emulsion and iron powders adhered to the surface of steel strip,steam formed at rolling temperature above 100℃and therefore made the strip surface to be corroded during the cold-rolling;metallic atoms were ionized and electrochemical corrosion occurred during cooling after coiling,finally resulting in the formation of black spots on the strip surface.On the basis of the cause for the black spot formation,some effective precautions,such as(a)to replace emulsion,(b)to reduce impurities in emulsion,(c)to improve air blow of the strip surface,and(d)to shorten storage period of the strip,were put forward.