Patent ID: 6638633
Filing Date: 2003-10-28
Classification: C21D,H01F,Y10T

Abstract:
An electrical steel sheet capable of stress relief annealing and having excellent solvent attack resistance comprising an electrical steel sheet,an insulating coating being low in phosphate content and being applied directly to said steel sheet, said insulating coating comprising a water-based resin selected from the group consisting of acryl, alkyd, polyolefin, styrene, vinyl acetate, epoxy, phenol, urethane, melamine resins and polyesters, and mixtures thereof, said resin comprising a single layer and having a glass transition temperature or a softening point of about 30-150Â° C., and said single layer further comprising an inorganic colloid selected from the group consisting of silica, alumina, alumina-containing silica and mixtures thereof, the ratio of said colloid to said resin being 3-300 parts by weight, based upon solid weight, to 100 parts by weight of said resin, said resin of said insulating coating being applied directly to said steel sheet, and wherein said insulating coating contains substantially no hexavalent chromium component and can be baked at a low sheet steel temperature of about 50 to 250Â° C., and wherein, in the case the inorganic colloid comprises silica, said insulating coating further comprises at least one alkali metal selected from the group consisting of Li, Na, K in an amount of about 0.1 to 5 parts by weight expressed as M2O, wherein M is the alkali metal, per 100 parts by weight of silica expressed as SiO2, and said insulating coating has a sulfur content limited to 0-0.05 parts by weight of sulfur per 100 parts by weight of silica expressed as SiO2.