GRAIN-ORIENTED ELECTRICAL STEEL SHEET FOR LOW-NOISE TRANSFORMER, AND METHOD FOR MANUFACTURING SAID SHEET

摘要

An oriented electromagnetic steel sheet processed using magnetic domain segmentation treatment by having the steel sheet surface irradiated with an electron beam measuring 0.40 mm or less in diameter (d) in a linear area having a direction intersecting the rolling direction, wherein: modulated-irradiation linear areas are obtained by connecting repeating units in the linear-area direction; the period of the repeating units in the modulated-irradiation linear area is 2/3 × d to 2.5 × d mm; the repeating interval of the modulated-irradiation linear area in the rolling direction is 4.0-12.5 mm; and the intensity of the electron beam is brought to a level equal to or greater than that at which split magnetic domains are formed extending in the direction of the modulated-irradiation linear area at least on the irradiation-surface side, and up to a level at which the coating is not damaged and no plastic strain areas are formed on the irradiation-surface side. It is thereby possible to carry out the hitherto challenging magnetic-domain segmentation process in a transformer in which iron loss and noise are both low, and obtain an oriented electromagnetic steel sheet that has unprecedentedly low iron loss and magnetic distortion.