COATING AGENT FOR INSULATING COATING FILM EXCELLENT IN HEAT RESISTANCE FOR NONORIENTED SILICON STEEL SHEET AND FORMATION OF INSULATING COATING FILM

摘要

PURPOSE: To impart superior interlaminar resistance and heat resistance after strain relieving annealing and to ensure superior magnetic characteristics in the case of use at high frequency by specifying the compsn. of a coating agent. ;CONSTITUTION: This coating agent is an aq. soln. contg. a silica sol and aluminum phosphate in which the molar ratio of Al₂O₃ to P₂O₅ is 0.25-0.37 so that the weight ratio of SiO,:(Al₂O₃+P₂O₅) is regulated to 70:30 to 90:10. It is preferable that the aq. soln. further contains a certain amt. of chromic anhydride, a chromate, a dichromate, boric acid, an acrylic acid or methacrylic acid polymer, an acrylic acid-methacrylic acid copolymer or a salt of the polymer or copolymer. The surface of a steel sheet is coated with this coating agent and baking is carried out in the temp. range of 350-550°C to form the objective insulating coating film.;COPYRIGHT: (C)1995,JPO