Nippon Steel Corporation

Hajime Komatsu

Yozo Suga

Toyohiko Konno

Yoshiyuki Ushigami

Motoharu Nakamura

Mitsuru Tanino

Susumu Takemura

Fumio Kurosawa

Mitsuro Tanino

In a process for the preparation of oriented electrical steel sheet having a high magnetic flux density a primary recrystallization annealed steel sheet is nitrided for a short period of time in a temperature range of 800.degree. C. or less whereby growth of crystal grains does not substantially occur. The nitrided sheet is held at a temperature range of 700.degree. C. to 800.degree. C. for at least four hours during temperature raising to final annealing temperature whereby nitride formed by the nitriding dissolves and re-precipitates allowing the nitride to transform to a thermally stable nitride containing aluminium.

Process for preparation of oriented electrical steel sheet having high

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 heat treatment process of high-carbon chromium-nickel heat-resistant stainless steels for the purpose of improving the creep rupture strength of the steel at temperatures over about 800.degree. C particularly at about 1000.degree. C. The feature of the present invention lies in that heat-resistant stainless steels containing 0.2 - 1.5% C, 15 - 40% Cr, 10 - 50% Ni, 5% or less Si, 15% or less Mn, with the balance Fe, and impurities are heated for 1 to 60 minutes in a temperature range from 1280.degree. C to 1350.degree. C and then quenched to room temperature at cooling rates higher than 200.degree. C/min. in order to produce the eutectic carbide structure consisted of the matrix metal and carbide phases in which M.sub.7 C.sub.3 -type carbide is contained not less than 25% by weight of the total weight of the carbides, that are present in the said eutectic carbide structure, at grain boundary triple points, along grain boundaries and within grains.

Growing community of inventors

Kawasaki, Japan

Hajime Komatsu