Patent ID: 7763120
Filing Date: 2010-07-27
Classification: B23K,C21D

Abstract:
1. A method of improving magnetic properties of a grain-oriented electrical steel sheet, comprising focusing a laser beam on the surface of the grain-oriented electrical steel sheet and irradiating the surface of the grain-oriented electrical steel sheet by said laser beam in a sheet width direction to cyclically impart residual stress, said method characterized in that, the laser beam is a power modulated beam obtained by cyclically power modulating a continuous wave laser, said power modulated beam having a power modulation duty Dp of 70% to less than 100%, wherein Dp is defined as Dp=Tn/Tm×100(%), Tm is a modulation period, Tn is defined as Tn=Tm−Tf, and Tf is a time period in which the power of said power modulated beam is 10% or less of a maximum value Pp, and wherein a minimum value Pb of power of said power modulated laser beam is 10% or less of the maximum value Pp.