Jfe Steel Corporation

Kawasaki Steel Corporation

Hiroi Yamaguchi

Seiji Okabe

Takeshi Omura

Shigehiro Takajo

Hirotaka Inoue

Hiroshi Matsuda

Yasuyuki Hayakawa

Michiro Komatsubara

Takashi Terashima

Yukihiro Shingaki

Kazuhiro Hanazawa

Hiroaki Toda

Yuiko Wakisaka

Takafumi Suzuki

Hideyuki Takahashi

Minoru Takashima

Ryuichi Suehiro

Kunihiro Senda

Mineo Muraki

Masanori Takenaka

Hirotake Ishitobi

Tomohiko Ito

Junichi Yotsuji

Yasunari Koga

Takeshi Imamura

Makoto Watanabe

Mitsumasa Kurosawa

Tadashi Nakanishi

Yuiko Ehashi

Michiro Komatsuhara

Provided is a method of producing a grain-oriented electrical steel sheet having uniform and good coating properties and magnetic properties throughout the length and/or width of the steel sheet. The method comprises: subjecting a steel slab to hot rolling, to cold rolling once or twice or more with intermediate annealing therebetween, and to primary recrystallization annealing; applying a liquid or slurry annealing separator to a resultant steel sheet; and thereafter coiling the steel sheet and subjecting the steel sheet to final annealing, wherein, before, after, or simultaneously with the application of the annealing separator, an additive for changing a composition of the annealing separator is adhered to the steel sheet at a weight ratio of 15% or less to a total of the annealing separator and the additive so as to vary the composition of the annealing separator in a longitudinal direction and/or width direction of the steel sheet.

Method of producing grain-oriented electrical steel sheet and annealing separator application line

In a grain-oriented electrical steel sheet which is manufactured from a thin slab without using an inhibitor forming component, excellent magnetic properties are stably achieved. In a method for manufacturing a grain-oriented electrical steel sheet, a slab heating and annealing are performed under specific conditions.

Method for manufacturing grain-oriented electrical steel sheet

Provided is a method for nitriding a grain-oriented electrical steel sheet which is very useful in obtaining excellent magnetic properties with no variation, that enables generating glow discharge between positive electrodes and negative electrodes disposed in a nitriding zone and irradiating the generated plasma to a strip to perform appropriate nitriding.

Method for nitriding grain-oriented electrical steel sheet

A grain-oriented electrical steel sheet, on which magnetic domain refining treatment by strain application has been performed, has an insulating coating with excellent insulation properties and corrosion resistance. In a grain-oriented electrical steel sheet, linear strain having been applied thereto by irradiation with a high-energy beam, the linear strain extending in a direction that intersects a rolling direction of the steel sheet, an area ratio of irradiation marks within an irradiation region of the high-energy beam is 2% or more and 20% or less, an area ratio of protrusions with a diameter of 1.5 &#x3bc;m or more within a surrounding portion of the irradiation mark is 60% or less, and an area ratio of exposed portions of steel substrate in the irradiation mark is 90% or less.

Grain-oriented electrical steel sheet and method of manufacturing the same

Provided is a method for nitriding a grain-oriented electrical steel sheet which is very useful in obtaining excellent magnetic properties with no variation by immersing a strip in a molten salt bath after cold rolling and before secondary recrystallization annealing during a production process of a grain-oriented electrical steel sheet, to subject the strip to continuous nitriding to uniformly disperse inhibitor forming elements over the full length and full width of the strip.

Method and device for nitriding grain-oriented electrical steel sheet

Provided is an apparatus for continuously nitriding a strip continuously being fed after cold rolling and before secondary recrystallization annealing in a production line of a grain-oriented electrical steel sheet, comprising: a nitriding zone for nitriding the strip; a cooling zone for cooling the strip; and an optional heating zone provided upstream of the nitriding zone for heating the strip, wherein, the nitriding zone is provided with glow discharge electrodes, and by plasma nitriding the strip by glow discharge with the glow discharge electrodes functioning as positive electrodes and the strip functioning as a negative electrode, inhibitor forming elements are uniformly dispersed over the full length and full width of the strip and a grain-oriented electrical steel sheet with excellent magnetic properties with no variation is obtained.

Apparatus and method for nitriding grain-oriented electrical steel sheet

A grain-oriented electrical steel sheet, on which magnetic domain refining treatment by strain application has been performed, has an insulating coating with excellent insulation properties and corrosion resistance. The grain-oriented electrical steel sheet is obtained by irradiating a steel sheet with a high-energy beam to apply, to the steel sheet, linear strain extending in a direction that intersects a rolling direction of the steel sheet, and then re-forming an insulating coating on the steel sheet, in which in an irradiation mark region due to the high-energy beam, a ratio of an area containing defects on the insulating coating is 40% or less, a maximum width of the irradiation mark region in the rolling direction is 250 &#x3bc;m or less, and a thickness of the insulating coating is 0.3 &#x3bc;m or more and 2.0 &#x3bc;m or less.

Grain-oriented electrical steel sheet and method for improving iron loss properties thereof

A steel sheet inspection device includes: a magnetooptic element that is able to detect, as an optical property, a magnetic domain structure of a steel sheet to be inspected; a light source that irradiates the magnetooptic element with linearly polarized light; a detector that detects the linearly polarized light with a polarization plane rotated according to the magnetic domain structure of the steel sheet transferred to the magnetooptic element; and a drive mechanism that drives at least the magnetooptic element so as to contact and separate the steel sheet and the magnetooptic element with and from each other.

Steel sheet inspection device, steel sheet inspection method, and steel sheet manufacturing method

According to the present invention, a grain-oriented electrical steel sheet for iron cores exhibiting excellent transformer iron loss properties in an excitation range from 1.5 T to 1.9 T is provided, in which a residual stress of 150 MPa or more is formed near strain regions, each extending 300 &#x3bc;m or less in the rolling direction and 42 &#x3bc;m or more in the sheet thickness direction, and the strain regions are formed periodically at intervals of 2 mm to 10 mm in the rolling direction, with reduced energy loss in transformers in operation.

Grain-oriented electrical steel sheet for iron core and method of manufacturing the same

A grain-oriented electrical steel sheet to which electron beam irradiation is applied, has a film and a thickness of t (mm), wherein no rust is produced on a surface of the steel sheet after a humidity cabinet test lasting 48 hours at a temperature of 50&#xb0; C. in an atmosphere of 98% humidity, and iron loss Wafter the electron beam irradiation is reduced by at least (&#x2212;500 t+200 t&#x2212;6.5) % of the iron loss Wbefore the electron beam irradiation and is (5 t&#x2212;2 t+1.065) W/kg or less.

Grain-oriented electrical steel sheet and manufacturing method thereof

A grain-oriented electrical steel sheet allows for manufacture of a transformer that exhibits, when the steel sheet is applied to an iron core thereof, extremely low iron loss and extremely low noise properties, makes highly efficient use of energy, and can be used in various environments. The grain-oriented electrical steel sheet has a strain distribution in regions where closure domains are formed, when observed in a cross section in the rolling direction, with a maximum tensile strain in a sheet thickness direction being 0.45% or less, and with a maximum tensile strain t (%) and a maximum compressive strain c (%) in the rolling direction satisfying Expression (1):+0.06&#x2264;&#x2264;0.35&#x2003;&#x2003;(1).

Grain-oriented electrical steel sheet and method of manufacturing same

A method for producing grain-oriented electrical steel sheets includes subjecting a steel slab to hot rolling to obtain a hot rolled sheet, the steel slab having a composition consisting of, by mass % or mass ppm, C: 0.08% or less, Si: 2.0% to 4.5% and Mn: 0.5% or less, S, Se, and O: less than 50 ppm each, sol.Al: less than 100 ppm, N: 80 ppm or less, and the balance being Fe and incidental impurities, and satisfying the relation of sol.Al (ppm)&#x2212;N (ppm)&#xd7;(26.98/14.00)&#x2264;30 ppm; then subjecting the hot rolled sheet to annealing and rolling to obtain a cold rolled sheet; then subjecting the cold rolled sheet to nitriding treatment, under specific condition, before, during or after primary recrystallization annealing; then applying an annealing separator on the cold rolled sheet; and subjecting the cold rolled sheet to secondary recrystallization annealing.

Production method for grain-oriented electrical steel sheet and primary recrystallized steel sheet for production of grain-oriented electrical steel sheet

A method for producing a grain-oriented electrical steel sheets includes subjecting a steel slab to hot rolling to obtain a hot rolled sheet, the steel slab having a specific composition; then subjecting the hot rolled sheet to annealing and rolling to obtain a cold rolled sheet; then subjecting the cold rolled sheet to nitriding treatment with a nitrogen increase of 50 to 1000 ppm, during or after primary recrystallization annealing; then applying an annealing separator on the cold rolled sheet; and setting the staying time in a temperature range of 300 to 800&#xb0; C. in the secondary recrystallization annealing to 5 to 150 hours.

Provided is a grain-oriented electrical steel sheet, with reduced iron loss by magnetic domain refining treatment, exhibiting an excellent noise property and effectively reducing noise generated when stacked in an iron core of a transformer. In a grain-oriented electrical steel sheet including a forsterite film and a tension coating on both surfaces, magnetic domain refining treatment has been performed to apply linear thermal strain to the grain-oriented electrical steel sheet, the magnitude of deflection in the rolling direction of the steel sheet is 600 mm or more and 6000 mm or less as the curvature radius of the deflected surface with the surface having the strain applied thereto being the inner side, and the magnitude of deflection in the direction orthogonal to the rolling direction is 2000 mm or more as the curvature radius of the deflected surface with the surface having the strain applied thereto being the inner side.

Grain-oriented electrical steel sheet

A grain oriented electrical steel sheet has a magnetic domain structure modified by strain introduction without a trace of treatment, in which noise generated when the grain oriented electrical steel sheet is used laminated on an iron core of a transformer is effectively reduced by: setting a magnetic flux density Bto 1.92 T or higher; then setting a ratio of average magnetic domain width of treated surface after strain-introducing treatment Wto average magnetic domain width before strain-introducing treatment Was W/W&#x3c;0.4; and setting a ratio of Wto average magnetic domain width of untreated surface Was W/W&#x3e;0.7; and further setting a ratio of average width of magnetic domain discontinuous portion Win the untreated surface to average width of magnetic domain discontinuous portion in treated surface resulting from strain-introducing treatment Was W/W&#x3e;0.8; and setting W&#x3c;0.35 mm.

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Tokyo, Japan

Hiroi Yamaguchi