Nippon Steel Corporation

Masayoshi Minakuchi

Katsuro Kuroki

Hisashi Kobayashi

Maremizu Ishibashi

Yasumitsu Kondo

Kenichi Yakashiro

A slab for an electrical steel sheet is heated at a temperature of 1280.degree. C. or below and then hot-rolled. The hot-rolled steel sheet or hot rolled and annealed steel sheet is then cold-rolled once or at least twice with intermediate annealing being performed between rollings. The cold-rolled sheet is decarburized and nitrided to form an inhibitor. The amount of nitrogen of in the steel sheet during the nitriding treatment subsequent to the decarburization annealing and the iron loss value after the withdrawal of the steel sheet from the furnace are measured to estimate the average diameter of a primary recrystallized grain, and next decarburization annealing is performed under conditions regulated in such a manner that the average diameter of the primary recrystallized grain of a product sheet falls within a proper range. The steel sheet subjected to the decarburization annealing is coated with an annealing separator composed mainly of MgO and then subjected to finish annealing.

Process for production of oriented electrical steel sheet having

The present invention relates to an improvement in the technique of heating an electrical steel slab at a low temperature. A grain-oriented electrical steel sheet having excellent magnetic characteristics and film characteristics is prepared by the process characterized in that a slab comprising, as main ingredients, up to 0.012% by weight of S, 0.010 to 0.060% by weight of acid-soluble Al, up to 0.010% by weight of N, 0.08 to 0.45% by weight of Mn, and 0.015 to 0.045% by weight is used as the starting slab, and after the decarburization annealing, the nitriding treatment is carried out at a temperature of 500.degree. to 900.degree. C. in an atmosphere having an NH.sub.3 gas concentration of at least 1000 ppm, while running the strip.

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Kitakyushu, Japan

Masayoshi Minakuchi