TREATMENT SOLUTION FOR CHROMIUM-FREE INSULATING COATING FOR GRAIN-ORIENTED ELECTRICAL STEEL SHEET AND GRAIN-ORIENTED ELECTRICAL STEEL SHEET COATED WITH CHROMIUM-FREE INSULATING COATING

摘要

By using a treatment solution for chromium-free insulating coating containing one or more of a Mg phosphate, Ca phosphate, Ba phosphate, Sr phosphate, Zn phosphate, Al phosphate, and Mn phosphate, wherein colloidal silica is contained in an amount of 50 to 120 parts by mass per 100 parts by mass of the phosphate in terms of solid content of SiO 2 , and a water-soluble metal salt of Mg, Ca, Ba, Sr, Zn, Al, and Mn is contained to adjust the molar ratio between M 2+ (=Mg,Ca,Ba,Sr,Zn,Mn) and/or M 3+ (=Al) which are metallic elements contained in the treatment solution and P to a range of 0.6‰¤(M 2+ +1.5×M 3+ )/P‰¤1.0, chromium-free insulating coating that provides excellent moisture absorption resistance for a long period and has a sufficient iron loss reduction effect can be obtained at low cost while minimizing the amount of expensive Ti such as Ti chelate used or without using such expensive Ti at all.