METHOD OF FORMING AN INSULATING FILM ON A MAGNETIC STEEL SHEET

摘要

In order to improve the adhesion property of an electrical steel sheet with no film of inorganic mineral matter on its surface, especially with respect to a tension-imparting insulating film, anodic electrolysis in an aqueous solution of silicate is carried out before insulating film formation to form a silicic film excellent in adhesion property with respect to the insulating film in a thin and strongly attached condition on the steel sheet surface. By this, a tension-imparting insulating film can be formed on a grain-oriented electrical steel sheet with excellent adhesion property to reduce the iron loss of the oriented electrical steel sheet. Also in the case of an insulating film that is not of the tension-imparting type, enhancement of film heat resistance and improvement of insulating property by increasing a film thickness are possible. <IMAGE>