Insulating membrane formation manner null of the directivity electromagnetic steel sheet where iron core processability and resistance dust metaplasia

摘要

PURPOSE:To form an insulating film having good lubricating property and excellent iron core machineability and anti-dusting performance by applying a coating material for which a noncolloidal solid is added to a conventional insulating film coating agent before and after imparting linear strain and then baking the coating film. CONSTITUTION:The insulating film coating material is prepared by the following procedure. Per 100 pts.wt. (in term of SiO2) colloidal silica of =50nm particle diameter, 130-300 pts.wt. of one or more phosphates of Al, Mg, Ca and Zn, and 10-100 pts.wt. of one or more compds. selected from chromic aid anhydride, chromate and bichromate are mixed. Further to this mixture, one or more kinds of noncolloidal solid having 5-2000nm particle diameter composed of oxides, carbides, nitrides, sulfides, borides, hydroxides, silicates, carbonates, borates, nitrates or chlorides of Fe, Ca, Ba, Zn, Al, Ni, Sn, Cu, Cr, Cd, Nd, Mn, Mo, Si, Ti, W, Bi, Sr, and V are added by 0.5-25 pts.wt. to prepare the insulating film coating agent. This coating agent is applied to a steel plate before and/or after linear strain is imparted and then baked to form the insulating film.