Mechanism of Magnetic Domain Refinement on Grain-Oriented Silicon Steel by Laser Irradiation
Hiroshi SUZUKI, Koichi AKITA, Hiroshi MISAWA and Muneyuki IMAFUKU
Abstract:The residual stress distributions near the laser irradiation in a crystal grain of an electrical steel sheet were measured by X-ray stress measurement method for single crystal, in order to investigate the causes of the magnetic domain refinement which can apply to decrease the core loss. The specimen which has only one grain was machined from a grain-oriented silicon steel and the laser irradiation was applied on this specimen. The distribution of the residual stress and the half value width (H.V.W.) of diffraction profile, which indicate the level of the plastic strain, near the laser irradiation were measured and its magnetic domain was observed before and after the stress relieving annealing. Before annealing, the H.V.W. was increased near the laser irradiation because of the local plastic deformation occurred by the effect of the peening on laser irradiation and the process of melting, cooling and solidification after laser irradiation. Therefore the tensile residual stresses were concentrated near the laser irradiation. And then, the magnetic domain was refined more than before the laser irradiation. After annealing, the H.V.W. was constant at the initial value and the residual stress was relieved. And then the magnetic domain returned to its original width. Therefore, it was confirmed that the magnetic domain was refined due to the residual stress occurred by the laser irradiation. Key Words:Grain-oriented silicon steel, Laser irradiation, Core loss, Magnetic domain, Residual stress