| 摘要 |
PROBLEM TO BE SOLVED: To obtain a steel sheet good in coating film characteristics such as adhesion and having an excellent high-tension coating film by providing an insulating coating film consisting essentially of phosphates, chromates and colloidal silica having a specified glass transition point on the surface and specifying the coating weight. SOLUTION: An insulating coating film is formed with phosphates, chromates and colloidal silica having 950-1200 deg.C glass transition point. By using such colloidal silica, a large tension is imparted to the steel sheet when coated and baked. The insulating coating film weight of the product is controlled to 2.5-7.0 g/m<2> . In the coating film processing soln., 100 pts.wt. of the colloidal silica, expressed in terms of solid, is mixed with 145-225 pts.wt. of the phosphates of Al, Mg and Ca, and 10-45 pts.wt. of the chromate, expressed in terms of CrO3 , is mixed with 100 pts.wt. of the colloidal silica, expressed in terms of solid. |
