Nippon Steel Corporation

Jiro Harase

Shozaburo Nakashima

Katsuro Kuroki

Toshiya Wada

Kunihide Takashima

Michio Endo

Tetsurou Takeshita

Kuniteru Ohta

The present invention relates to an improvement in the precipitation annealing of a hot-rolled steel sheet or strip which is carried out immediately before cold-rolling in the production of a grain-oriented electromagnetic steel sheet or strip. Conventionally, precipitation annealing is carried out by heating a steel strip to a temperature of from 750.degree. to 1200.degree. C. and then quenching it. The present invention proposes to control the cooling rate during primary cooling, i.e. from a holding temperature (T.sub.1 temperature) of from 1080.degree. to 1200.degree. C. down to an intermediate temperature (T.sub.2 temperature) of from 900.degree. to 980.degree. C., and to control the staying time during primary cooling so that excellent magnetic properties can be obtained regardless of the unavoidable variation in the Al and Si content. The present invention also proposes to control the rate of temperature elevation between 800.degree. C. and the holding temperature as to obtain AlN particles having an optimum size.

Process for producing a grain-oriented electromagnetic steel sheet

The Cr-series stainless steel sheet heretofore produced by a method including annealing a hot-rolled strip for decomposing the .alpha.'-phase or .gamma.-transformed phase therein, can be produced by omitting this annealing. In the method according to the present invention, a thin casting is cooled from the solidification temperature to the end temperature of the .gamma.-phase-precipitation at a cooling speed at least equal to the air cooling-speed, thereby avoiding the .gamma.-phase-precipitation. Then, the precipitation treatment for precipitating the supersaturated C, N, and S, or the heating to the .alpha.+.gamma. dual phase-temperature region for precipitating the .gamma.-phase, is carried out.

Method for producing a thin casting of Cr-series stainless steel

In a process for producing a grain-oriented silicon steel strip, comprising the steps of: hot rolling, annealing, if necessary; heavy cold rolling; decarburization-annealing, and; final annealing, an improvement which comprises controlling a coiling temperature after the finish rolling of the hot rolling step within a range of from 700.degree. to 1000.degree. C. As a result of the coiling temperature control, the annealing of the hot rolled strip can be simplified or omitted, while the behavior of a grain-growth inhibitor is equivalent to that in the conventional process including the annealing step. The magnetic flux density of the material produced by the process of the present invention is excellent, notwithstanding the simplification or omission of the annealing.

Process for producing grain-oriented silicon steel strip

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Kitakyushu, Japan

Jiro Harase