Grain-oriented electrical steel sheet and production method therefor

Patent metadata

Field	Value
Publication number	US-10465259-B2
Application number	US-201615552297-A
Country	US
Kind code	B2
Filing date	Feb 12, 2016
Priority date	Feb 24, 2015
Publication date	Nov 5, 2019
Grant date	Nov 5, 2019

Abstract

Disclosed are a grain-oriented electrical steel sheet having strain regions extending in a direction transverse to a rolling direction at periodic interval s (mm) in the rolling direction. Each strain region has a closure domain region whose width in the rolling direction varies periodically on a steel sheet surface. Each closure domain region satisfies: Wmax/Wmin=1.2 or more and less than 2.5, where Wmax and Wmin respectively denote a maximum width and a minimum width on the steel sheet surface as measured in the rolling direction; Wave being 80 μm or more, where Wave denotes an average width on the steel sheet surface as measured in the rolling direction; D being 32 μm or more, where D denotes a maximum depth as measured in the sheet thickness direction; and (Wave*D)/s being 0.0007 mm or more and 0.0016 mm or less.

First claim

The invention claimed is:

1. A grain-oriented electrical steel sheet with a plurality of strain regions locally present in a surface layer of the steel sheet and formed to extend in a direction transverse to a rolling direction at periodic interval s in millimeters in the rolling direction,
wherein
each of the strain regions has a closure domain region that is formed continuously over a distance of 200 mm in a width direction and whose width as measured in the rolling direction varies periodically on a surface of the steel sheet, and
each of the closure domain regions satisfies a set of conditions including:
a ratio of W max /W min being 1.2 or more and less than 2.5, where W max and W min respectively denote a maximum width and a minimum width on the surface of the steel sheet as measured in the rolling direction;
W ave being 80 μm or more, where W ave denotes an average width on the surface of the steel sheet as measured in the rolling direction;
D being 32 μm or more, where D denotes a maximum depth as measured in the sheet thickness direction; and
(W ave *D)/s being 0.0007 mm or more and 0.0016 mm or less.

2. A method of producing the grain-oriented electrical steel sheet according to claim 1 , the method comprising:
irradiating a surface of a grain-oriented steel sheet with an electron beam while scanning the electron beam in a scanning direction transverse to a rolling direction under a set of electron beam irradiation conditions including:
an accelerating voltage being 90 kV or more;
dl being 80 μm or more and 220 μm or less, where dl denotes a beam diameter as measured in a direction orthogonal to the scanning direction,
d2 being (0.8 *dl) μm or more and (1.2*dl) μm or less, where d2 denotes a beam diameter as measured in the scanning direction,
a beam profile having a Gaussian shape, and
the scanning of the electron beam being performed while repeating a process to stop and resume movement by a moving distance p of the electron beam on the surface, where
1.5*d2≤p≤2.5*d2, thereby producing the grain-oriented electrical steel sheet of claim 1 .

3. The method according to claim 2 , wherein the movement of the electron beam is stopped for 2 g±s or more and the scanning is performed with an average rate of 100 m/s or higher.

4. The method according to claim 2 , wherein the movement of the electron beam is stopped for 8 g±s or more and the scanning is performed with an average rate of 30 m/s or higher.

5. The method according to claim 2 , wherein the electron beam is scanned on the surface over a scanning distance as measured in the width direction of 200 mm or more.

6. The method according to claim 2 , wherein the electron beam is scanned on the surface over a scanning distance as measured in the width direction of 300 mm or more.

7. The method according to claim 2 , wherein the electron beam is sourced from LaB 6 .

8. The method according to claim 2 , wherein the electron beam is converged using at least two coils.

Assignees

• Jfe Steel Corp

Inventors

• Takajo Shigehiro
• Omura Takeshi
• Okabe Seiji

Classifications

• C21D2201/05

  Grain orientation · CPC title

• C21D10/00

  Modifying the physical properties by methods other than heat treatment or deformation · CPC title

• C21D8/1294 Primary

  involving a localised treatment · CPC title

• C21D9/46

  for sheet metals · CPC title

• H01F1/16

  in the form of sheets (H01F1/147 takes precedence) · CPC title