GRAIN ORIENTED ELECTRICAL STEEL SHEET, METHOD FOR MANUFACTURING GRAIN ORIENTED ELECTRICAL STEEL SHEETS, METHOD FOR EVALUATING GRAIN ORIENTED ELECTRICAL STEEL SHEETS, AND IRON CORE

摘要

A method for manufacturing a grain oriented electrical steel sheet having a forsterite film is provided, the method comprising: a step of measuring a distribution of the amount of the forsterite film on the grain oriented electrical steel sheet, and a step of screening a grain oriented electrical steel sheet based on whether or not the total area percentage of defective parts scattered on the forsterite film as viewed from above the surface is within a prescribed range, wherein the distribution of the forsterite film on the grain oriented electrical steel sheet is derived by scanning a sample of the steel sheet with an electron beam by an electron beam irradiation unit (11), measuring the signal intensity or the brightness of light, which is emitted from the sample by excitation with the electron beam, in a cathodoluminescence image with an optical measurement section (120) in an optical evaluation unit (12), and determining the amount of the forsterite of the sample in a quantitative analysis section (121), based on the signal intensity or brightness of the light corresponding to the locations of the electron beam scanning and a correlation between the signal intensity or the brightness of light emitted from a forsterite-containing sample being excited by an electron beam and the amount of forsterite, the correlation being stored in a correlation storage section (122) in the optical evaluation unit (12).