| 摘要 |
PURPOSE:To manufacture a grain-oriented electrical steel sheet for wound core transformer causing no deterioration in magnetic properties even if subjected to stress-relief annealing by removing a high-tensile film and a glass film on the surface of a magnetic steel sheet into a specific shape to allow the steel-sheet surface to appear and then oxidizing the resulting exposed parts. CONSTITUTION:A slab of a silicon steel with <4% Si content is hot-rolled into a metal plate and, after the surface is subjected to pickling treatment, the above plate is cold-rolled, while process-annealed between the cold rolling stages, to the final sheet thickness, followed by decarburizing annealing. Subsequently, a separation agent at annealing is applied to the above sheet to carry out secondary recrystallization annealing, by which a grain-oriented electrical steel sheet is prepared. Successively, a phosphoric acid-type high-tensile film and a glass film are formed on the above. Then, linear parts of 0.05-0.5mm width or linear parts formed of numerous dots in which mutual spacing is regulated to <=0.7mm are removed at a space of 2.5-10mm from the above high-tensile film and glass film by mechanical means, thermal means, etc., so that they form an angle of 45-90 deg. with the rolling direction of the steel sheet, by which the steel-sheet surface is allowed to appear. The resulting exposed parts are oxidized, by which an oxide film of 0.005-0.06mm depth can be formed. |
