Method and apparatus for reducing the watt loss of a grain-oriented electromagnetic steel sheet and a grain-oriented electromagnetic steel sheet having a low watt loss

摘要

The watt loss of a grain-oriented electromagnetic steel sheet can be decreased by known methods in which serrations or scratches are locally formed on said steel sheet or a small ball or disc is rolled or rotated over said steel sheet. The known methods are disadvantageous in that the rate of production is low and in that said steel sheet has a marked unevenness. In the present invention, particles, e.g., steel shots, are projected onto substantially linear selected portions of a grain-oriented electromagnetic steel sheet, thereby producing strain on spot-formed regions. Spotlike indentations are formed in the steel sheet by the projection of steel shots onto the steel sheet.