| 摘要 |
PURPOSE:To realize the improvement of the core loss of a grain-oriented electric steel sheet so as to allow it to endure stress relaxation annealing by converging laser beams from a pulse CO2 laser having specified performance, and scanning and irradiating the grain-oriented electric steel sheet with the laser beam and forming a specified recessped part. CONSTITUTION:The grain-oriented electric steel sheet is scanned and irradiated with the laser beams to form a recessed part approximately orthogonally to the rolling direction. At this time, as a laser oscillator, a pulse Q switch CO2 laser having pulse half-width with 10nsec to 1musec time width is used. Moreover, the laser beams are converged in such a manner that the photointensity density at the pulse peak part is regulated to 2X10<7>W/cm<2> or higher and their shape is formed into an approximately circular one with 1mm or smaller diameter or a elliptic one with 1mm or smaller diameter in the rolling direction and 3mm or shorter length in the scanning direction. By this method, the recessed part with 0.5mm or smaller width in the rolling direction and 10mum or layer depth is formed with 2mm or smaller interval in the scanning direction and 10mm or smaller interval in the rolling direction. In this way, high productivity, reliability and low cost are simultaneously realized, and the improvement of the core loss in which the effect is not disappeared even by stress relaxation annealing can be obtd. |
