Wound Core

Abstract: The present invention controls residual stress resulting from the shape of a groove and strain in a curved part to within a given range, thereby further reducing the BF of a wound core. Provided is a wound core configured from a grain-oriented electromagnetic steel sheet, characterized in that: the wound core has a steel sheet surface in which is formed a groove that extends in a direction intersecting a rolling direction (RD direction), the groove-depth direction of the groove being a plate thickness direction (ND direction); the groove pitch in the steel sheet rolling direction (RD direction) is 2-10 mm; the depth of the groove is 10-40 µm; the width of the groove is 10-200 µm; an angle (vertex angle) formed when opposing groove wall surfaces (the wall surfaces being surfaces of the groove that are present at a depth of 25-75% relative to the depth of the groove) are extended in the sheet thickness direction (ND direction) is 90° or less; and a region where residual stress is present, the residual stress resulting from tensile strain of 10 MPa or greater in the steel sheet rolling direction (RD direction), accounts for at least 10 area% of a range within 10 µm in the rolling direction (RD direction) from the groove wall surface present at a curved part of the wound core.

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