| 摘要 |
PURPOSE:To simplify the prepn. of a treating liq. and to reduce the cost by preparing the treating liq. with magnesium chromate as a base, alumina sol stabilized with acetate ions and alcohol in a specified ratio, applying a specified amt. of the liq. to a steel sheet and baking the applied liq. at a specified temp. CONSTITUTION:A treating liq. contg. magnesium chromate as a base by 10-70g/l (expressed in terms of CrO3), alumina sol stabilized with acetate ions by 25-75wt.% of the amt. of the base and org. alcohol as a reducing agent by 10-40wt.% is prepd. and applied to the surface of an electrical steel sheet by 0.5-4g/m<2> on dry basis and the applied liq. is baked at 200-400 deg.C. By this method, an insulating coating film having superior heat resistance can be formed on the surface of the steel sheet without using alumina sol in combination with colloidal silica. |
