Jfe Steel Corporation

Kazuhiro Hanazawa

Shigehiro Takajo

Hiroi Yamaguchi

Seiji Okabe

Hirotaka Inoue

Tomohiko Ito

Junichi Yotsuji

Yasunari Koga

Yoshihiko Oda

Masatoshi Kumagai

Yoshiaki Zaizen

Masanori Uesaka

Masayasu Nagoshi

Hiroaki Toda

Takako Yamashita

Kenji Tahara

Koichiro Fujita

Taro Kizu

Eiko Yasuhara

Yukio Usui

Hideharu Koga

A method of manufacturing a grain-oriented electrical steel sheet is provided. When irradiating the surface of a grain-oriented electrical steel sheet having a sheet thickness t with an electron beam in a direction intersecting a rolling direction, the irradiation energy E(t) of the electron beam is adjusted to satisfy Ewmin(0.23)&#xd7;(1.61&#x2212;2.83&#xd7;t (mm))&#x2264;E(t)&#x2264;Ewmin(0.23)&#xd7;(1.78&#x2212;3.12&#xd7;t (mm)) (Expression (1)) using the value of the irradiation energy Ewmin(0.23) that minimizes iron loss for material with a sheet thickness of 0.23 mm.

Method of manufacturing grain-oriented electrical steel sheet exhibiting low iron loss

The present invention provides a grain-oriented electrical steel sheet with reduced iron loss over a wide range of sheet thickness by providing a grain-oriented electrical steel sheet with an actually measured sheet thickness t (mm) that includes a closure domain region extending linearly in a direction from 60&#xb0; to 120&#xb0; with respect to the rolling direction on a surface of the steel sheet, the closure domain region being formed periodically at a spacing s (mm) in the rolling direction, such that h&#x2265;74.9t+39.1 (0.26&#x2265;t), h&#x2265;897t&#x2212;174.7 (t&#x3e;0.26), (w&#xd7;h)/(s&#xd7;1000)&#x2264;&#x2212;12.6t+7.9 (t&#x3e;0.22), and (w&#xd7;h)/(s&#xd7;1000)&#x2264;&#x2212;40.6t+14.1 (t&#x2264;0.22), where h (&#x3bc;m) is the depth and w (&#x3bc;m) is the width of the closure domain region.

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

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

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 steel slab having a chemical composition including C: not more than 0.005 mass %, Si: not more than 4 mass %, Mn: 0.03-2 mass %, P: not more than 0.2 mass %, S: not more than 0.004 mass %, Al: not more than 2 mass %, N: not more than 0.004 mass %, Se: not more than 0.0010 mass % and the balance being Fe and inevitable impurities is subjected to hot rolling, cold rolling and recrystallization annealing up to 740&#xb0; C. at an average heating rate of not less than 100&#xb0; C./s to produce a semi-processed non-oriented electrical steel sheet being high in the magnetic flux density and low in the iron loss after stress relief annealing.

Method for producing semi-processed non-oriented electrical steel sheet having excellent magnetic properties

The location where forsterite is present is checked in a region from which light excited by an electron beam is emitted when a material containing forsterite is irradiated with an electron beam. The material is preferably a grain oriented electrical steel sheet having a forsterite layer. In addition, it is preferable that the accelerating voltage be 10 kV or more when an electron beam is radiated when the material is a grain oriented electrical steel sheet having a tension coating layer on the forsterite layer.

Method of checking forsterite, apparatus that evaluates forsterite, and production line that manufactures steel sheet

An electron gun abnormality detecting device for detecting an abnormality in first and second electron guns of a magnetic domain refining device for an electrical steel sheet includes: a magnetooptic element configured to contact with and separate from an inspection region set to include a boundary between a magnetic domain discontinuity generated by irradiation of a surface of the electrical steel sheet with an electron beam by the first electron gun and a magnetic domain discontinuity generated by irradiation thereof with an electron beam by the second electron gun, and configured to detect a steel sheet magnetic domain structure in the inspection region as an optical property; a light source configured to irradiate the magnetooptic element with linearly polarized light; and a detector configured to detect polarized light rotated by the steel sheet magnetic domain structure transferred to the magnetooptic element.

Electron gun abnormality detecting device and electron gun abnormality detecting method

A cold-rolled steel sheet includes, on a percent by mass basis: C: 0.0010% to 0.0030%, Si: 0.05% or less, Mn: 0.1% to 0.3%, P: 0.05% or less, S: 0.02% or less, Al: 0.02% to 0.10%, N: 0.005% or less, and Nb: 0.010% to 0.030% and the remainder composed of Fe and incidental impurities, wherein values in a rolling direction and a direction perpendicular to the rolling direction are within a range of 1.0 to 1.6, and a mean value Elof elongations in the rolling direction, a direction at 45&#xb0; with respect to the rolling direction, and the direction perpendicular to the rolling direction is 40% or more, where El=(El+2&#xd7;El+El)/4 and El: elongation in the rolling direction, El: elongation in the direction at 45&#xb0; with respect to the rolling direction, and El: elongation in the direction perpendicular to the rolling direction.

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Tokyo, Japan

Kazuhiro Hanazawa