| 摘要 |
<p>A grain-oriented electric steel sheet whose 180° magnetic wall interval is reduced by the irradiation of a pulse laser beam to improve its magnetic characteristics. Particularly, a grain-oriented electric steel sheet which is characterized in that the width in the rolling direction of a periodical enclosure domain is not larger than 150 νm, its depth in the plate thickness direction is not less than 30 νm, the product of the length in the width direction and the length in the depth direction is not less than 4500 νm2 and, in addition, its magnetostriction (μ 19 p-p compression) is not larger than 0.9 x 10-6 when the plate thickness is 0.23 mm and not larger than 1.3 x 10-6 when the plate thickness is 0.27 mm. A pulse oscillation Q switch CO¿2? laser beam whose beam shape is elliptical with a long axis in the direction of the sheet width is irradiated to the surface of the grain-oriented electric steel sheet. At that time, the irradiation power density of the single laser pulse is so predetermined as to be lower than the film damaging threshold of the steel sheet surface in order to suppress the formation of a laser irradiation mark. Further, the long axis length of the elliptical beam is so predetermined as to be larger than a pulse beam irradiation interval in the sheet width direction in order to superpose the pulse beams upon each other to provide a sufficient integrated irradiation energy. Moreover, lenses, mirrors, etc. by which a laser beam is condensed are provided in the sheet width direction and in the rolling direction independently, distances between the respective beam condensing components and the irradiated steel sheet surface are independently adjusted, and the sheet width direction diameter and the rolling direction diameter of the irradiated laser beam can be arbitrarily adjusted.</p> |
