Grain-oriented magnetic steel sheet and method of producing the same
View Patent ↗A grain-oriented magnetic steel sheet includes grooves each of which extends in a direction intersecting a transportation direction, the grooves being formed at predetermined pitches PL in the transportation direction by laser beam irradiation, in which a relationship between a standard deviation value D and the pitch PL satisfies the following expression (1), the standard deviation value D being a standard deviation of distances between a linear approximation line, which is obtained from a center line of each of the grooves in a groove width direction by a least-squares method, and respective positions on the center line, and an average angle formed between tangent lines of the respective positions on the center line and a direction perpendicular to the transportation direction is more than 0° to 30°. [Expression 1] 0.02≤( D/PL ) (1)
1. A grain-oriented magnetic steel sheet comprising
grooves each of which extends in a direction intersecting a transportation direction, the grooves being formed at predetermined pitches PL in the transportation direction by laser beam irradiation,
wherein a melt-resolidified portion is formed in the grooves,
wherein each of the grooves is formed to be curved in a length L c when viewed from a direction perpendicular to a surface of the grain-oriented magnetic steel sheet,
wherein multiple grooves are formed in the direction intersecting the transportation direction, and
wherein
a relationship between a standard deviation value D which is defined by the following expression (2) and the pitch PL satisfies the following expression (1), the standard deviation value D being a standard deviation of distances between a linear approximation line, which is obtained from a center line of each of the grooves in a groove width direction by a least-squares method, and respective positions on the center line, and
an average angle formed between tangent lines of the respective positions on the center line and a direction perpendicular to the transportation direction is more than 0° to 30°
0.02
≤
(
D
/
PL
)
(
1
)
D
=
1
L
C
∫
0
L
C
d
X
Y
2
(
2
)
wherein X is an axis which represents a direction of a linear approximation line C and Y is an axis which represents a direction perpendicular to the linear approximation line C, and
when a curve of each of the grooves is expressed by a function of y=f(x) in a coordination system in which an x axis represents a direction perpendicular to the transportation direction of the grain-oriented magnetic steel sheet and a y axis represents the transportation direction, the linear approximation line C with respect to the curve of each of the grooves which is expressed by y=ax+b is obtained using a least-squares method.
2. The grain-oriented magnetic steel sheet according to claim 1 ,
wherein the grooves are formed on a front surface and a back surface of the grain-oriented magnetic steel sheet.
3. The grain-oriented magnetic steel sheet according to claim 2 ,
wherein positions of the grooves formed on the front surface are the same as positions of the grooves formed on the back surface.
4. A method of producing a grain-oriented magnetic steel sheet, the method comprising:
irradiating a grain-oriented magnetic steel sheet with a laser beam to form grooves, each of which extends in a direction intersecting a transportation direction, at predetermined pitches PL in the transportation direction,
wherein a melt-resolidified portion is formed in the grooves,
wherein each of the grooves is formed to be curved in a length L c when viewed from a direction perpendicular to a surface of the grain-oriented magnetic steel sheet,
wherein multiple grooves are formed in the direction intersecting the transportation direction, and
wherein
a relationship between a standard deviation value D which is defined by the following expression (2) and the pitch PL satisfies the following expression (1), the standard deviation value D being a standard deviation of distances between a linear approximation line, which is obtained from a center line of each of the grooves in a groove width direction by a least-squares method, and respective positions on the center line, and
an average angle formed between tangent lines of the respective positions on the center line and a direction perpendicular to the transportation direction is more than 0° to 30°
0.02
≤
(
D
/
PL
)
(
1
)
D
=
1
L
C
∫
0
L
C
d
X
Y
2
(
2
)
wherein X is an axis which represents a direction of a linear approximation line C and Y is an axis which represents a direction perpendicular to the linear approximation line C, and
when a curve of each of the grooves is expressed by a function of y=f(x) in a coordination system in which an x axis represents a direction perpendicular to the transportation direction of the grain-oriented magnetic steel sheet and a y axis represents the transportation direction, the linear approximation line C with respect to the curve of each of the grooves which is expressed by y=ax+b is obtained using a least-squares method.
5. The method of producing a grain-oriented magnetic steel sheet according to claim 4 , wherein a wavelength of the laser beam is in a range of 0.4 μm to 2.1 μm.