Control Of Surface Linear Defects Of Non-oriented Electrical Steel In CSP Process

Surface linear defect is one of the common surface defects of Non-oriented electrical steel produced by CSP process.The research on CSP control has important application value to reduce the proportion of surface linear defects of non oriented electrical steel.The results show that:（1）Based on the analysis of the samples selected in the field,it is determined that the large inclusions causing the linear defects on the surface of Non-oriented electrical steel are mainly magnesia alumina spinel deoxidization products and ladle top slag.The content of large inclusions is 5.39 mg/10 kg during steady casting.The main types of inclusions are Mg O-Al₂O₃;Cao-Al₂O₃-Mgo;Ca O-Al₂O₃-Mg O-Si O₂;Ca O-Al₂O₃-Si O₂.（2）The influence of unsteady casting on linear defects was determined by analyzing the production process.When the continuous casting process is in the unsteady casting process,the cleanliness of molten steel is greatly affected,and the proportion of linear defects on the surface of hot rolled plate increases.（3）According to the composition characteristics of W800 Non-oriented electrical steel,the physical properties of refining slag were analyzed by fastage7.2software.The ideal composition range of RH refining slag was determined as W_cao=50～60%,W_{Si O2}=0～15%,W_Al2O3=20～30%;the refining slag R≥4 and Ca O/Al₂O₃:1.5～2 were controlled in the refining process.（4）Through practical production and theoretical analysises.The main factors affecting the surface linear defects of hot rolled plate are Ca O/Al₂O₃top slag of RH station,oxygen level at the end of RH deoxidization,reduction rate of rod position,minimum tonnage of ladle during ladle changing established.SPSS software was used to analyze the influencing factors:Y（%）=-407.930+0.054X₁-0.151X₂-0.001X₃-9.065X₄+0.159X₅-0.746X₆-3.067X₇-6.942X₈+9.829X₉+0.795X₁₀+5.986X₁₁+421.743X₁₂-0.723X₁₃-0.00005486X₁²+0.001X_<sup>2+1.985₄²-0.131X₅²+0.008X₈²-93.703X₁₂²+1.542X₄X₅+2.091X₈X₁₂.According to the regression equation,the surface quality prediction model of CSP Non-oriented electrical steel was established.（5）According to the theoretical analysis,both RH refining and continuous casting process control are the key links.Combined with the above theoretical analysis and prediction model,the proportion of linear defects on the surface of products decreased from 31.985%to 0.648%.