Kawasaki Steel Corporation

Katsuo Iwamoto

Michiro Komatsubara

Yasuyuki Hayakawa

Makoto Watanabe

Takahiro Kan

Yoshiaki Iida

Yoshinori Kobayashi

Mitsumasa Kurosawa

Isao Matoba

Toshio Sadayori

Tomomichi Goto

Toshito Takamiya

Hirotake Ishitobi

Masayuki Sakaguchi

A decarburized steel sheet for a thin oriented silicon steel sheet having improved magnetic and coating characteristics and a method of producing the same. Silicon steel strip is hot-rolled, cold-rolled to a final thickness of about 0.28 mm or less, subjected to decarburization/primary-recrystallization annealing, coated with an annealing separator, and thereafter subjected to finishing annealing. In the decarburization/primary-recrystallization annealing step, a novel subscale is formed at the steel sheet surface having a fayalite-silica composition ratio in accordance with an infrared reflection absorbance ratio of about 0.5 to 5.5, and a marked oxygen amount of about 0.4 to 1.6 g/m.sup.2.

Decarburized steel sheet for thin oriented silicon steel sheet having

A method of producing a grain oriented silicon steel thin sheet having excellent magnetic properties. A silicon steel slab containing Cu, Se and Sb as inhibitor-forming elements is hot rolled to form a hot-rolled sheet, followed by cold rolling at least twice including intermediate annealing to form a cold-rolled sheet having a final thickness of about 0.10 to 0.25 mm, decarburization and primary recrystallization annealing, and then final finish annealing. The temperature of the material to be rolled on the inlet side of the hot finish rolling mill is about 1000.degree. to 1150.degree. C. the surface temperature of the work rolls of the first stand of the hot finish rolling mill immediately before contact with the material to be rolled is about 100.degree. C. or less the total rolling reduction of the hot finish rolling is about 93 to 97%, the intermediate annealing is effected at a temperature of about 900.degree. to 1050.degree. C. within a time of about 50 seconds, and the rolling reduction of the final cold rolling is about 50 to 80%.

Method of producing grain oriented silicon steel sheet having very

In grain oriented silicon steel sheets containing MnSe as a main inhibitor, an iron loss is reduced by increasing the magnetic flux density and realizing the thinning of product thickness and fine division of crystal grains while utilizing the stability of secondary recrystallization as a merit of such a sheet. In this case, 0.02-0.30% of Cu is added to a slab of the above grain oriented silicon steel, and particularly the decarburization annealing and/or the final finish annealing are carried out under particular conditions.

Method of producing grain oriented silicon steel sheets having less iron

An oriented silicon steel sheet having a very high magnetic flux density is produced from an oriented silicon steel containing AlN as the main inhibitor and also containing Sb by a method adapted to prevent the loss of the inhibiting ability of the surface layer of the steel, and to improve cooling conditions in annealing before the final cold rolling. The steel is hot rolled, subjected to at least one time the combination of annealing and cold rolling wherein the final cold rolling is performed with a rolling reduction of about 80 to 95%, subjected to decarburization and primary recrystallization annealing, and subjected to, after coating an annealing separation agent, final finish annealing. Before annealing is performed before the final cold rolling, a nitriding promoter is applied to the surface of the steel sheet, and the partial-pressure ratio of N.sub.2 in the atmosphere for that annealing is adjusted to a value of not less than about 20%. In this way, it is possible to stably produce an oriented silicon steel sheet that exhibits a high magnetic flux density even with a small sheet thickness.

Method of producing oriented silicon steel sheet having very high

A method of manufacturing an oriented silicon steel sheet improved in magnetic characteristics, in which a hot-rolled steel sheet of oriented silicon steel containing about 0.01 to 0.10% by weight of Al and about 0.01 to 0.04% by weight of Sb as inhibitor components is heat-treated and cold-rolled one time or two or more times to have a final thickness. In the final heat treatment and final cold rolling alone, the steel sheet is quenched from a temperature of about 900.degree. to 1,100.degree. C. to a temperature equal to or lower than about 50.degree. C., is heat-treated at about 50.degree. to 150.degree. C. for about 30 sec. to 30 min. while applying a tensile stress of about 0.5 to 20 kg/mm.sup.2, is thereafter cold-rolled by a reduction rate of about 35 to 70% in a tandem rolling method, is aged at about 200.degree. to 400.degree. C. for about 10 sec. to 10 min., and is finished by cold rolling to have the final thickness.

Method of manufacturing an oriented silicon steel sheet having improved

The magnetic properties, particularly magnetic flux density of a grain oriented silicon steel sheet are considerably improved by continuously and/or stepwise forming regions, wherein a temperature difference of a secondary recrystallization starting temperature in widthwise direction and/or longitudinal direction of the steel sheet is within a range of 10.degree. C. to 200.degree. C., in the steel sheet at a stage before the secondary recrystallization annealing step.

Method of producing grain oriented silicon steel sheets having magnetic

A grain-oriented silicon steel sheet having high magnetic induction and low iron loss can be obtained by adhering uniformly at least one member selected from the group consisting of elements of Ge, Sn, Pb, As, Bi and Zn and compounds containing these elements to the surfaces of a silicon steel sheet before or after the decarburization annealing in a method for producing grain-oriented silicon steel sheets. According to this method, a hot rolled steel sheet is subjected to at least one cold rolling, the finally cold rolled steel sheet is subjected to a decarburization annealing, and the decarburized steel sheet is applied with an annealing separator consisting mainly of MgO and then subjected to a final annealing, or by carrying out the adhesion treatment of element in combination with a preliminary annealing before the decarburization annealing in the above described method, or by using the annealing separator further containing Bi or a Bi-containing compound in the above described method.

Method for producing grain-oriented silicon steel sheets

A grain-oriented silicon steel sheet having high magnetic induction and low iron loss can be produced by controlling properly the particle size of carbide precipitated in the crystal grains of the steel sheet before final cold rolling. Further, the magnetic properties can be more improved by adjusting the C content in a starting silicon steel depending upon the Si content in the steel and removing a proper amount of C from the steel during the course after completion of hot rolling and before final cold rolling, in addition to the proper control of the particle size of carbide precipitated in the crystal grains of the steel sheet before final cold rolling.

Method of producing grain-oriented silicon steel sheets having excellent

A grain-oriented silicon steel sheet having excellent magnetic properties can be stably produced by adjusting properly the C content in a silicon steel to be used as a starting material depending upon the Si content in the steel, removing a proper amount of C from the steel during the course after the hot rolling and before the final cold rolling, and further carrying out the final cold rolling at a reduction rate of 40-80%.

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Chiba, Japan

Katsuo Iwamoto