Study on the Dramatic Decrease in Surface Resistance of Insulation Films on Non-Oriented Silicon Steel after Stress Relief Annealing

摘要

Now insulation films are often prepared by smooth rubberroll on the surface of non-oriented silicon steel sheet. Though the surface resistance is enough high to ensure the quality, it will dramatically decrease after stress relief annealing. In order to understand the related mechanism, the film's microstructure was characterized by SEM. The results show that the main composition of semi-inorganic coating is Cr, Mg C and O, in which C come from the organic polymer. According to the composition, the insulation film can be divided into two parts, the outer one is organic polymer and the inner one is chromate. The main reason for the unstable surface resistance is that the coating in the thickness direction is not uniformity.