PURPOSE: To improve the insulating performance and adhesiveness by applying a processing soln. consisting of an aq. dispersion of the surface of a magnetic steel sheet and then baking the dispersion.
CONSTITUTION: This magnetic steel sheet having an insulating coating film is appropriately used as the material for the water-wheel generator and large- sized motor. A processing soln. consisting of an aq. dispersion of high-mol.wt. epoxy resin and 1-20 pts.wt., based on 100 pts.wt. of the solid component of the dispersion, of an etherified methylolmelamine as the cross-linking agent is applied on the surface of a magnetic steel sheet and baked to form a desired coating film, and the insulating performance and adhesiveness of the coating film, adhesiveness with the additional coat and the punching property, weldability, corrosion resistance of the sheet are improved. The thickness of the coating film is controlled to 2-20μm and the epoxy resin having ≥4000 number average mol.wt. is used.
YAMAMOTO AKIRA
IZAWA MASAZUMI
