Electrical steel sheet and method for manufacturing the same
Provided is an electrical steel sheet comprising: a groove formed in a surface of a steel sheet, wherein the groove includes a bottom surface, a first side surface extending from the bottom surface, and a second side surface extending from the bottom surface in opposite to the first side surface, wherein the groove has a depth from the surface to the bottom surface, a width in a rolling direction of the steel sheet, and a length in a width direction of the steel sheet, and wherein the groove is formed through laser-irradiation and removal of melt produced by the laser-irradiation; an opening defined by the bottom surface, the first side surface and the second side surface; and a first solidification portion formed on the first side surface of the groove. The first solidification portion is formed by a solidification of part of the melt produced from the laser-irradiation.
1. An electrical steel sheet comprising:
a groove formed in a surface of a steel sheet, wherein the groove includes a bottom surface, a first side surface extending from the bottom surface, and a second side surface in opposite to the first side surface and extending from the bottom surface, wherein the groove has a depth (D G ) from the bottom surface, a width (B W ) in a rolling direction of the steel sheet, and a length (B L ) in a width direction of the steel sheet, and wherein the groove is formed through laser-irradiation and removal of melt produced by the laser-irradiation;
an opening defined by the bottom surface, the first side surface and the second side surface; and
a first solidification portion formed on the first side surface of the groove, wherein the first solidification portion is formed of a solidified part of the melt produced from the laser-irradiation, wherein the first solidification portion has a thickness gradually decreasing toward the bottom surface and gradually decreasing toward the surface of the steel sheet.
2. The electrical steel sheet of claim 1 , wherein the groove has a first side surface distance (C) defined by a straight line distance from a center of the bottom surface to a boundary location where the first side surface intersects the surface of the steel sheet, and
the first solidification portion occupies 2% or more of the first side surface distance.
3. The electrical steel sheet of claim 1 , wherein the groove has a groove shape factor defined by (the depth (D G ))/(a lower full width at half maximum (W 1 )),
wherein the groove shape factor is 0.1 to 9.0, and
wherein the depth (D G ) is a vertical distance between the surface of the steel sheet and the bottom surface, and the lower full width at half maximum (W 1 ) is half of a length of the bottom surface in the rolling direction of the steel sheet.
4. The electrical steel sheet of claim 1 , wherein the width (B W ) is in a range of 10 μm to 70 μm.
5. The electrical steel sheet of claim 1 , wherein the depth (D G ) is in a range of 3 μm to 30 μm.
6. The electrical steel sheet of claim 1 , wherein the solidification portion has a thickness in a range of 0.05 W 1 to 5 W 1 ,
where the W 1 means a lower full width at half maximum, and the lower full width at half maximum (W 1 ) is half of a length of the bottom surface in the rolling direction of the steel sheet.
7. The electrical steel sheet of claim 1 , further comprising: a second solidification portion formed on the second side surface of the groove.
8. The electrical steel sheet of claim 1 , further comprising: a bottom solidification portion formed on the bottom surface of the groove.