Nippon Steel Corporation

Mikio Itoh

Yoshiyuki Ushigami

Yozo Suga

Kenji Kosuge

Toyohiko Konno

Kiyoshi Ueno

Takashi Yoshimura

Haruo Hukazawa

Shinji Ueno

Toshio Nishiyama

Kenichi Takimoto

A method of producing a grain-oriented electrical steel sheet with a very low core loss comprises the steps of obtaining a rolled strip of final product thickness using as a starting material molten steel consisting of not more than 0.10 wt % C, 2.5-7.0 wt % Si, ordinary inhibitor components and the balance of iron and unavoidable impurities, heating the strip to a temperature range of not less than 700.degree. C. at a heating rate of not less than 80.degree. C./s and within 0.1 second after the maximum temperature has been reached cooling the strip at a cooling rate of not less than 50.degree. C./s, and subjecting the strip to decarburization annealing and final finish annealing.

Grain-oriented electrical steel sheet with very low core loss and method

A method of producing an oriented electrical steel sheet having superior magnetic properties comprises the steps of, hot rolling a slab containing 0.8 to 6.8% of Si, 0.008% of Al acid soluble, the balance being Fe and accompanying impurities, by weight to form a strip, cold rolling the strip, primary-recrystallization annealing, coating the strip with an annealing separator, and finishing annealing, a nitriding treatment being effected after the primary recrystallization annealing but before the start of the secondary recrystallization of the finishing annealing. According to the present invention, with an atmosphere oxidizing degree (PH.sub.2 O/PH.sub.2): x in a soaking process in said primary recrystallization annealing an annealing is effected in an atmosphere which has an oxidizing degree (PH.sub.2 O/PH.sub.2): y in a range defined by the following inequality, at a temperature ranging from 650.degree. to 800.degree. C. in the heating process, for at least 5 secs. ##EQU1##

Method of producing oriented electrical steel sheet having superior

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Himeji, Japan

Mikio Itoh