Nippon Steel Corporation

Toyohiko Konno

Yozo Suga

Hajime Komatsu

Yoshiyuki Ushigami

Tadashi Nakayama

Motoharu Nakamura

Kiyoshi Ueno

Mikio Itoh

Toshio Nishiyama

Mitsuro Tanino

Kenichi Takimoto

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

In the production of a grain-oriented electrical steel sheet, instead of conventional inhibitors a novel (Al, Si)N inhibitor is utilized. This inhibitor is formed by obtaining an incomplete solution of Al and N and then nitriding the decarburization annealed steel sheet prior to initiation of a secondary recrystallization. The fine inhibitor can be formed in a large amount, thereby enhancing the magnetic flux density.

Method for producing a grain-oriented electrical steel sheet

An annealing separator used in a finishing annealing step for producing a grain-oriented electrical steel sheet usually contains magnesia. The present invention is characterized by including, based on 100 parts by weight of magnesia, from 0.2 to 20 parts by weight of ferromanganese nitride or manganese nitride which consists of a composition (Mn.sub.1-x Fe.sub.x)N.sub.y having x and y values corresponding to A, B, C, and D and falling within a region surrounded by A, B, C, and D shown in the appended FIG. 1. The annealing separator according to the present invention is effective for stabilizing secondary recrystallization and improving the properties of a forsterite film.

Annealing separator used in the finishing annealing step for producing a

The present invention relates to a method for producing a grain-oriented electrical steel sheet. A feature of the present invention is to set S.ltoreq.0.007%, Mn=0.08.about.0.45%, P=0.015.about.0.45% in a slab. The present inventive idea does away with the conventional concept of using MnS as an inhibitor. The present invention present incomplete secondary recrystallization by the S content, which is decreased to a level as low as possible. In addition, a product having a high magnetic flux density can be successfully produced by adding appropriate amounts of Mn and P. Due to these advantages, a high Si content of a slab, which leads to a watt loss reduction, can also be employed in the present invention. In addition according to the present invention, the temperature of slab heating, which is carried out prior to hot rolling, can be drastically decreased as compared with the prior art. Thus, an outstanding cost reduction can be realized due to the decrease in heat energy and complete prevention of the slag formation.

Method for producing a grain-oriented electrical steel sheet having a

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Kitakyushu, Japan

Toyohiko Konno