MAGNETIC STEEL SHEET EXCELLENT IN RUST RESISTANCE AFTER STRESS RELIEVING ANNEALING

摘要

PURPOSE: To improve the rust resistance after stress relieving annealing of a magnetic steel sheet having a chromic acid-org. resin insulating film on the surface. ;CONSTITUTION: A processing soln. formed by mixing an aq. chromic acid soln. contg. soluble aluminum hydroxide, boric acid, a compd. of bivalent metal (Mg, Ca, Zn, etc.), if necessary, an aq. emulsion resin and an org. reducing agent (e.g. glycerin) is applied on the surface of a steel sheet consisting of, by weight, ≤0.01% C, ≤4% Si, 0-2.0% Al, ≤5% (Si+Al), ≤0.5% Mn, 0.01-0.1% Cu and the balance Fe with inevitable impurities and baked to form an insulating film. In this case, the H₃BO₃-to-CrO₃ molar ratio in the soln. is controlled to 0.1-1.5, the Me²⁺-to-Al³⁺ molar ratio to ≤7.0 and (Al³⁺+Me²⁺)-to-CrO₃ molar ratio to 0.2-0.5. A magnetic steel sheet satisfying electric insulating properties, magnetic characteristic and other requirements and excellent in rust resistance is obtained in this way at a low cost.;COPYRIGHT: (C)1995,JPO