Abstract: The surface quality indexes of grain oriented silicon steel plates/sheets from three different enterprises were tested. The microstructure and chemical composition of the surface layers were examined by scanning electron microscope and energy dispersive spectrometer. Comparing the surface quality indexes and microstructures of the samples from different enterprises, it is observed that both the surface layer qualities and the surface insulation resistances of the three products are different. The surface insulation resistance of A product is higher than B and C products, with the equivalent of the surface insulation resistance of B and C products. The coating adhesion and corrosion resistance of B and C products are better than those of A product. From the analysis of morphology and composition, it can be concluded that one reason for the high surface insulation resistance of A product is the thick insulation layer, and the good adhesion level of B and C products is due to the large spinal/particles pinned on the matrix or close to magnesium forsterite, and the corrosion resistance of A product decreases due to the microcracks on the insulating layer surface. 

Key words: grain oriented silicon steel, insulation layer, magnesium forsterite layer, microstructure