| 摘要 |
PROBLEM TO BE SOLVED: To stably obtain a primary film of an ultrahigh magnetic flux density grain oriented silicon steel sheet used for a transformer. SOLUTION: The method for producing a grain oriented silicon steel sheet comprises: a hot rolled sheet produced by using a slab contg., by weight, 0.03 to 0.15% C, 2.5 to 4.0% Si, 0.02 to 0.30% Mn, either or both of S and Se by 0.005 to 0.040%, 0.015 to 0.040% acid-soluble Al, 0.0030 to 0.0150% N, 0.0005 to 0.05% Bi, and the balance Fe with inevitable impurities as a starting material, heating this slab and thereafter executing hot rolling is subjected to hot rolled sheet annealing and is subsequently subjected to finish cold rolling, or subjected to plural cold rolling including process annealing, or subjected to plural cold rolling including process annealing after hot rolled sheet annealing to finish into a product sheet thickness, which is subjected to decarburizing annealing, thereafter, the surface of the steel sheet is coated with a separation agent for annealing essentially consisting of MgO, and finish annealing is executed. In this case, at the time of the start of the finish annealing, the content of water in the coating film of the separation agent for annealing is regulated to 0.3 to 3%. |
