Original plate for oriented electromagnetic steel sheet without glass coating, manufacturing method thereof, and method for producing directional electromagnetic steel sheet having good adhesion to 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