ORIGINAL SHEET FOR GRAIN-ORIENTED ELECTROMAGNETIC STEEL SHEET HAVING NO GLASS COATING FILM, METHOD FOR MANUFACTURING THE SAME, AND METHOD FOR MANUFACTURING GRAIN-ORIENTED ELECTROMAGNETIC STEEL SHEET EXCELLENT IN ADHESION OF INSULATING FILM

摘要

To obtain the adhesion of a tension film even when forming an external oxidation layer by thermal oxidation annealing at a soaking temperature of 1,000°C or less before forming the tension film.SOLUTION: In an original sheet for a grain-oriented silicon electromagnetic sheet having no glass coating film before forming a tension film, an oxygen content x per one surface of a steel sheet and a value y of SiOpeak (ΔR/R@1,250 cm) on the surface of the steel sheet obtained by reflection type infrared emission spectroscopy satisfy y≥1,500x. A method for manufacturing the original sheet for the grain-oriented electromagnetic steel sheet having no glass coating film includes subjecting a finish-annealed grain-oriented silicon steel sheet having no glass coating film on the surface of the steel sheet to thermal oxidation annealing at a soaking temperature of 1,000°C or less in an atmosphere having an oxidation potential of 0.005 or less shown by a ratio P/Pof water vapor pressure to hydrogen pressure to form an external oxidation layer including SiOas a main component on the surface of the steel sheet.SELECTED DRAWING: Figure 1