A nonconstact technique for reducing the core loss of a grain oriented silicon steel has been developed by the use of Q-switched laser irradiation. Vaporization of the surface layer of the silicon steel by the laser irradiation induced a stress which resulted in a refinement of 180° domain wall spacing. This phenomenon reduced the core loss of the steel. It was found that the laser irradiation was more effective in a specimen with a higher magnetic induction and the core loss reduced by more than 10% under the optimum condition of the laser irradiation. Since the laser processing is a noncontact technique, it is easily applicable to the production line of the silicon steel.

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Artificial domain control has been applied to grain oriented Si-Fe. Lines are scribed on the surface of the sheet by a ball with 1.0 mm diameter, on one side of sheet surface. Directions of scribing are cross grain, with grain, and 10 °, 20 °, 30 °, 45 °, 60 ° from the rolling direction. Spacing of lines is 10mm. Scribing produces slight plastic deformation at the surface of the sheet. Scribing in the cross grain direction reduced total loss in the rolling direction, 7% at a flux density of 1.7 Tesla. Scribing in the cross grain direction causes refinement of 180 ° domains which are the primary structure in (110) [001] oriented Si-Fe. Scribing in the with grain direction improves the total loss in the cross grain direction. Scribing 30 ° to 60 ° to the with grain improves the total losses in both the grain and cross grain direction. The improvement in total loss by scribing may be caused by slight local plastic deformation. Heat treatment, which causes recovery, cancels the effect of scribing.

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