Thick grain-oriented electrical steel sheet having no glass coating with excellent insulating coating properties and method for producing the same

摘要

PURPOSE: To produce a grain-oriented silicon steel plate excellent in punching properties, cuttability or the like in an iron core working stage by specifying the total content of forsterite and spinel on the surface of a steel plate contg. a specified weight % of Si and specifying film tension and plate thickness. CONSTITUTION: The components of a silicon steel are composed of, by weight, 0.021 to 0.075% C, 2.5 to 4.5% Si, 0.01 to 0.04% acid-soluble Al, 0.003 to 0.013% N, =0.014% S, 0.05 to 0.45% Mn, and the balance Fe with inevitable impurities. The slab of the steel is subjected to hot rolling and is subjected to cold rolling for = two times including process annealing to regulate its final plate thickness to =0.35mm. The total content of forsterite and spinel on the surface of the steel plate is regulated to =0.45g/m2 as MgO, SiO2 and Al2 O3 , and moreover, by an insulating film, tension imparted to the surface of the steel plate is regulated to =0.4kg/mm2 . Thus, the one having no glass film and excellent in the adhesion of the insulating film can be produced.