Effects of an inorganic coating on the structure and magnetic properties of a 1 wt. % silicon steel

Various organic and inorganic coatings are used for electrical steels to improve their punchability and interlaminar resistance. However, very little information is available in the literature on the effect of these coatings on structure and magnetic properties of electrical steels. In this study, the influence of a commercial mono-aluminum-phosphate coating was investigated for a 1.0 wt. % silicon steel. It was noted that this type of coating is responsible for the following: (1) rate of decarburization is essentially unaffected, (2) the growth of subsurface oxide is substantially reduced, (3) 1.5 T permeability is improved via reduction in the subsurface oxide layer, and (4) core loss is decreased by reducing anomalous loss. A possible mechanism to suppress the subsurface oxidation by phosphorus segregation is suggested on the basis of results obtained by AES analysis.