Nippon Steel Corporation

Hiroaki Masui

Katsuro Kuroki

Yasunari Yoshitomi

Hiroshi Takechi

Tsuyoshi Kawano

Tsutomu Haratani

Yoshiyuki Ushigami

Hiroyasu Fujii

Shuichi Yamazaki

Osamu Tanaka

Nobuyuki Takahashi

Hiroshi Tamehiro

Takeo Nagashima

Hajime Nakasugi

Hisashi Gondo

Maremizu Ishibashi

Yoshio Nakamura

Takeshi Kubota

Tadashi Nakayama

Kazuo Koyama

Tomoji Kumano

Hotaka Honma

Morio Shiozaki

Hiroo Mazuda

Kazuo Namba

Yoichi Mishima

Tetuo Takeda

Seiji Eiro

Yuji Yoshimura

Hisashi Kabayashi

Yukio Matsuo

Katsurou Kuroki

Kazuo Kovama

Chikara Fujii

A grain-oriented electrical steel sheet comprising 2.5-4.5% Si by weight and measuring 0.36-1.00 mm in thickness is imparted with a good core loss value for its thickness by controlling its C content, flux density, grain boundary configuration, and deviation degree of crystal orientation in the grains.

Thick grain-oriented electrical steel sheet exhibiting excellent magnetic properties

Grain oriented silicon steel sheet on which is formed an insulating coating having a thickness that is not less than 2.5 .mu.m that imparts tension to the steel sheet which does not have an inorganic mineral layer formed during a final annealing step (glass film) and a method of forming on grain oriented silicon steel sheet an insulating coating that is not less than 2.5 .mu.m thick and which imparts tension to the steel sheet which does not have the inorganic mineral layer (glass film) that forms during finish annealing, and a method of forming a tensioning insulating coating on grain oriented silicon steel sheet which has been finish annealed and does not have an inorganic mineral surface layer (glass film), after first forming a layer of SiO.sub.2 not less than 0.001 .mu.m thick on the oriented silicon steel sheet.

Grain oriented silicon steel sheet having low core loss and method of

A grain oriented silicon steel sheet having excellent primary glass film property and magnetic property, comprising 2.0 to 5.0% by weight of Si, wherein a primary glass film formed during secondary recrystallization annealing is composed mainly of forsterite (Mg.sub.2 SiO.sub.4) and an oxide containing Al, mainly of spinel (MgAl.sub.2 O.sub.4), or Al and Si, mainly of cordierite (MgO.sub.2 Al.sub.4 Si.sub.5 O.sub.18) and/or sapphirine (Mg.sub.4 Al.sub.10 Si.sub.2 O.sub.23), and in an analysis of the surface of the steel sheet by glow discharge optical emission spectrometry analysis (GDS analysis), a peak derived from Al is separated from a peak derived from Mg, and, preferably, the peak derived from Al is separated from the peak derived from Mg and the distance (time) from the surface of the steel sheet at which the peak derived from Al is 1.2 times or more the distance from the surface of the steel sheet at which the peak derived from Mg appears.

Grain oriented silicon steel sheet having excellent primary film

In the present invention, grain oriented electrical steel sheets provided by heating a slab comprising, by weight percent, 0.025 to 0.075% of C, 3.4 to 5.0% of Si, 0.015 to 0.080% of sol. Al, 0.0030 to 0.013% of N, 0.014% or less of (S+0.405 Se) and 0.05 to 0.8% of Mn, sol. Al (%)/Si (%) being 0.0080 or more, the balance consisting of Fe and unavoidable impurities at a temperature below 1280.degree. C., hot-rolling the heated slab, subjecting the hot-rolled steel sheet to cold rolling, subjecting the cold-rolled steel sheet to decarbonization annealing with regulating the average diameter of primary recrystallized grains of the steel sheet subjected to decarbonization annealing to 18 to 35 .mu.m in a period between the completion of the decarbonization annealing and the initiation of final annealing, coating the decarburized steel with an annealing separator and subjecting the coated steel sheet to final annealing, wherein the final annealing is effected in such a manner that the partial pressure of nitrogen, P .sub.N2 (%), in the annealing atmosphere is 12.5% or more in a steel sheet temperature range of from 900.degree. C. to 1150.degree. C. in the heating stage of the final annealing, and subjecting the steel sheet to nitriding to cause the steel sheet to absorb 0.0010% by weight or more of nitrogen in a period between the completion of the hot rolling and the initiation of secondary recystallization in the final annealing.

Process for production of grain oriented electrical steel sheet having

A grain oriented electrical steel sheet having no significant glass film and having a high magnetic flux density and an excellent iron loss property, comprising, in terms of by weight, 2.5 to 4.5% of Si, the steel sheet having, as oxides on its surface, a glass film comprising 0.6 g/m.sup.2 or less in total of forsterite and spinel composed of MgO, SiO.sub.2 and Al.sub.2 O.sub.3 and an insulating coating having a thickness of 6 .mu.m or less, the face tension imparted on the surface of the steel sheet by the coating being in the range of from 0.5 to 2.0 kg/mm.sup.2. In the final box annealing of the steel sheet after primary recrystallization annealing, use is made of an annealing separator comprising 100 parts by weight of MgO and, added thereto, 2 to 30 parts by weight of at least one member selected from the group consisting of chlorides, carbonates, nitrates, sulfates and sulfides of Li, K, Bi, Na, Ba, Ca, Mg, Zn, Fe, Zr, Sr, Sn, Al, etc., and the heating in the final box annealing is effected in an atmosphere comprising N.sub.2 and H.sub.2 with the nitrogen content being 30% or more at a heating rate of 20.degree. C./hr or less, and a seam or spotty flaw is imparted at an angle of 45.degree. to 90.degree. to the rolling direction of the steel sheet.

Grain oriented electrical steel sheet having high magnetic flux density

A method of producing non-oriented electrical steel sheet comprising the steps of preparing steel comprising, by weight, up to 2.5% silicon, up to 1.0% aluminum and up to 2.5% (Si+2Al), with the remainder being iron and unavoidable impurities, hot rolling and cold rolling the steel to a final thickness and following this by finish annealing, wherein the average cooling rate between Ar.sub.3 and Ar.sub.1 during cooling transformation (.gamma..fwdarw..alpha.) of the steel is controlled to be 50.degree. C./s or less.

Method of producing non-oriented electrical steel sheet having good

The present invention discloses a process for producing a grain-oriented electrical steel strip having a high magnetic flux density. The process comprises hot-rolling a steel ingot comprising basic ingredients and, added thereto, 0.02 to 0.15% of Sn at a temperature of 1200.degree. C. or below, annealing the hot-rolled strip, cold-rolling the annealed strip with a final rolling reduction of 80% or more and subjecting the cold-rolled strip to decarburization annealing, a nitriding treatment and finish annealing, wherein the temperature, T.degree.C., of annealing of the hot-rolled strip is set so as to fall within the range 1240-2.1.times.Al.sub.R &lt;T&lt;1310-1.8.times.Al.sub.R (wherein Al.sub.R =acid soluble [Al]-27/14.times.[N]) and the strip is soaked for 180 sec or less, maintained at a temperature in the range of from 800.degree. to 950.degree. C. for 30 to 300 sec and then quenched. The grain-oriented electrical steel strip thus produced is not influenced by the variation in the [Al] and [N]. According to the present invention, a grain-oriented electrical steel strip having a very high magnetic density can be stably prepared through the establishment of a proper relationship between the Al and N ingredients and conditions for annealing of a steel strip before final cold rolling and the growth of a primary recrystallized grain to optimize the annealing conditions and the practice of a nitriding treatment after decarburization annealing.

Process for producing grain-oriented electrical steel strip having high

A method for producing a steel sheet having excellent low-temperature toughness, comprising a step of heating to a temperature not higher than 1150.degree. C., a steel slab containing 0.01 - 0.13% C, 0.05 - 0.8% Si, 0.8 - 1.8% Mn, 0.01 - 0.08% total Al, 0.08 - 0.40% Mo and not more than 0.015% S with the balance being iron and unavoidable impurities, and a step of hot rolling the steel slab thus obtained by at least three passes with a minimum reduction percentage not less than 2% by each rolling pass in a temperature range of 900 - 1050.degree. C, a total reduction percentage not less than 50%, and with a finishing temperature not higher than 820.degree. C.

Method for producing a steel sheet having remarkably excellent toughness

The production process characterized in that a steel ingot or slab containing not less than 0.004% of TiN not larger than 0.02.mu. is heated to a temperature not higher than 1150.degree. C and rolled, and growth of the .gamma. grains during this heating and rolling step is prevented by TiN to improve the toughness, and the resultant steel product has an excellent low-temperature toughness with a yield point of 40 kg/mm.sup.2 or higher, and is useful as hot rolled or as heated at a temperature ranging from 300.degree. to 750.degree. C after the hot rolling.

Process for producing a high tension steel sheet product having an

A steel sheet, especially a thin one, can be manufactured from a hot rolled coil through heat treating steps by means of positively applying stress to the material. The product has excellent shape and mechanical properties such as drawability and toughness.

Method and an apparatus for the manufacture of a steel sheet

A hot-rolled steel sheet of high cold formability characterized in that it contains of 0.03-0.30 % C and 0.15-2.0 % Mn as the main ingredients and also by the average length of sulfide inclusions of stringer form and/or silicate inclusions of like form being less than 100 .mu..

Hot-rolled steel sheet of high cold formability and method of producing

A method for producing a cold rolled steel sheet having high strength and stretchability which comprises hot rolling a steel containing 0.03 to 0.30% C, less than 0.7% Si, 0.6 to 2.5% Mn, 0.01 to 0.20% sol.Al, not more than 0.015% O with the balance being Fe and unavoidable impurities, cold rolling with a reduction not less than 30%, heating with an average heating rate not less than 3.degree.C/sec. annealing in a temperature range from 650.degree.C to A.sub.3 transformation point for 1 to 15 minutes, and cooling with an average cooling rate of 0.5.degree. to 30.degree.C/sec. down to 500.degree.C.

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Kitakyushu, Japan

Hiroaki Masui