Treatment solution for insulation coating for grain-oriented electrical steel sheets and method for producing grain-oriented electrical steel sheet having insulation coating

A method for producing a grain-oriented electrical steel sheet having an insulation coating, comprising:

• hot rolling a slab for grain-oriented electrical steel sheets into a sheet with a thickness of 1.5 to 3.0 mm;
• subsequently or after subjecting the sheet to normalizing annealing, subjecting the sheet to cold rolling once, or twice or more including intermediate annealing to obtain a selected sheet thickness,
• subjecting the sheet to primary recrystallization annealing at a temperature of 800° C. to 950° C. for ten to 600 seconds,
• coating the sheet with an annealing separator containing MgO as a primary component,
• subjecting the sheet to secondary recrystallization annealing at a temperature of 800° C. to 1250° C. for five to 600 hours,
• coating the sheet with a treatment solution for insulation coating to secure a coating thickness of 1 to 5 μm after baking, and
• baking the sheet at a baking temperature of 350° C. or higher,
• wherein the treatment solution comprises 1) at least one selected from phosphates of Mg, Ca. Ba, Sr, Zn, Al, and Mn, 2) colloidal silica in a proportion of 0.5 to 10 mol in terms of SiO2 and 3) a water-soluble vanadium compound in a proportion of 0.1 to 2.0 mol in terms of V, relative to PO4:1 mol in the phosphates, and
• wherein the water-soluble vanadium compound contains at least one selected from the group consisting of potassium vanadate, ammonium vanadate and vanadium bromide.