Eliminating Vertical Stripe Defects on Silicon Steel Surface by Regularization

The vertical stripe defects on silicon steel surface seriously affect the appearance and electromagnetic properties of silicon steel products. Eliminating such defects is adifficult and urgent technical problem. This paper investigates the relationship between the defects and their influence factors by classification methods. However, when the common classification methods are used in the problem, we cannot obtain a classifier with high accuracy. Byanalysis of the data set, we find that it is imbalanced and inconsistent. Because the common classification methods are based on accuracy-maximization criterion, they are not applicable to imbalanced and inconsistent data set. Thus, we propose asupport-degree-maximization criterion and anovel cost-sensitive loss function and also establish an improved regularization approach for solution of the problem. Moreover, by employing reweighted iteration gradient boosting algorithm, we obtain a linear classifier with a high support degree. Through analyzing the classifier, we formulate a rule under which the silicon steel vertical stripe defects do not occur in the existing production environment. By applying the proposed rule to 50TW600 silicon steel production, the vertical stripe defects of the silicon steel products have been greatly decreased. 1. Introduction Under normal process of silicon steel production, the surface of silicon steel products is smooth, as shown in Figure 1(a), but when production process is controlled imperfectly, the vertical stripes appear on the surface of the silicon steels at times, as shown in Figure 1(b). Such defects (briefly denoted as vertical stripe defects, or VSD in the following) not only affect the appearance effect of silicon steel, but also much degraded the lamination performance, resistance between layers and electromagnetic properties of silicon steel. How to eliminate the VSD problem has become one of the most important technical problems in silicon steel production. Figure 1: (a) A normal silicon steel sheet; (b) a silicon steel sheet with vertical stripes. In [1], the intrinsic mechanism of forming VSD was interpreted as follows: the high contents of Si and Al in silicon steel essentially lead to thick columnar crystals in the casting slab organization, and thus - phase transitions cannot occur in hot-rolling working procedure. Due to slow dynamic recovery and difficult recrystallization in later cold rolling and annealing process, such thick columnar crystals are hard to be completely broken. So, the vertical stripes arise on the surface of silicon steel products. To