| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for attaining a laser treatment stage suitable for high speed continuos treatment, in which the occurrence of surface laser irradiation marks is prevented and the increase of magnetostriction is minimized, as a method for reducing the iron loss of a grain oriented magnetic steel sheet by laser irradiation. SOLUTION: At the time of irradiating the surface of a grain oriented magnetic steel sheet with a pulsed laser beam, a pulse oscillation Q switch CO2 laser is used as the laser and the shape of the irradiation beam is an elliptical shape having a major axis in a sheet-width direction and, further, the irradiation power density of a single laser pulse is set at a value not higher than the threshold value of damage of a film on the surface of the steel sheet, by which the occurrence of laser irradiation marks can be prevented. Moreover, the length of major axis of the elliptical beam is set at a value not shorter than the pulsed beam irradiation interval in a sheet-width direction to make continuos pulsed beams synergistic at the surface of the steel sheet, by which an integrated irradiation energy necessary and sufficient for the improvement of magnetic properties can be provided. |
