Inorganic/organic insulating coating for nonoriented electrical steel

Abstract

The present invention relates to a nonoriented electrical steel sheet coated on both surfaces with a cured insulative coating for providing a high level of surface resistivity to minimize interlaminar power losses. The cured insulative coating on the steel sheet includes, based upon 100 parts by dry weight, 20-60 parts of aluminum phosphate, 20-70 parts of at least one inorganic particulate silicate and 10-25 parts of an acrylic resin. The cured coating is formed from an acid aqueous suspension that may include up to 1 part by weight of a water-soluble organic solvent per each part of the resin. The aqueous suspension has a pH of about 2-2.5, a silicate particle size of 0.3-60 mu m, a resin particle size of less than 1 mu m, less than about 0.5 wt. % unreacted phosphoric acid and a specific gravity of about 1.0-1.3. The silicate may be one or more from the group consisting of aluminum silicate, aluminum potassium silicate and magnesium silicate. After curing, the coating has a thickness on each sheet surface of 0.5-8 mu m. The insulative coated nonoriented electrical steels may be used to minimize power losses in laminated magnetic cores of motors, generators, transformers, and other electrical equipment.

Description

Background of the invention

[0001] The present invention relates to an inorganic / organic insulating coated semi-finished or fully finished non-oriented electrical steel to provide a high level of surface resistivity to minimize interlayer power loss. More specifically, the insulating coating is formed from an acidic aqueous suspension comprising a monoaluminum phosphate solution, at least one inorganic silicate particulate and an organic acrylic latex. The insulation-coated non-oriented electrical steel of the present invention can be used to minimize power loss in magnetic cores of motors, generators, transformers and other electrical equipment.

[0002] Non-oriented electrical steel sheets for medium or large electric motors and transformers are provided with an insulating coating to provide a high level of surface resistivity so that power losses between layers are reduced when laminations formed of electrical steel are used in the as-punched state. to minimum. This high ...