Method for forming groove on metal strip surface and method for manufacturing grain-oriented electrical steel sheet

1 . A method for forming grooves comprising:

forming an etching resist coating on at least one surface of a metal strip, the etching resist coating having a lightness L* of 0 or more and 70 or less,

then, irradiating a laser with an output of less than 1.5 kW on the etching resist coating while scanning the laser in a direction that intersects a rolling direction of the metal strip to remove a portion of the etching resist coating irradiated by the laser, and

then, etching a portion of the metal strip below the removed portion of the etching resist coating to form grooves,

wherein the lightness L* is a L* value in a CIELAB color space (CIE 1976 L*a*b* color space).

2 . The method for forming grooves according to claim 1 , wherein a removal width of the etching resist coating is 200 μm or less and a scanning rate of the laser is 111 m/s or more.

3 . The method for forming grooves according to claim 1 , wherein a beam diameter in a direction orthogonal to a scanning direction of the laser on the surface of the metal strip is 200 μm or less.

4 . The method for forming grooves according to claim 1 , wherein the laser is a fiber laser whose beam diameter in a direction orthogonal to a scanning direction of the laser is 200 μm or less.

5 . The method for forming grooves according to claim 1 , wherein a surface roughness Ra of the metal strip in a transverse direction before the etching resist coating is formed is 0.5 μm or less.

6 . A method for manufacturing a grain-oriented electrical steel sheet, comprising

hot rolling a steel slab into a hot-rolled steel sheet,

then, subjecting the hot-rolled steel sheet or a hot-rolled and annealed sheet obtained by applying hot-rolled sheet annealing to the hot-rolled steel sheet to cold rolling once, or twice or more with intermediate annealing performed therebetween to obtain a cold-rolled steel sheet,

then subjecting the cold-rolled steel sheet to primary recrystallization annealing to obtain a primary recrystallized sheet, and

then, subjecting the primary recrystallized sheet to secondary recrystallization annealing to obtain a secondary recrystallized sheet,

wherein grooves are formed on a surface of the steel sheet at any stage after being subjected to hot rolling by the method for forming grooves according to claim 1 .

7 . The method for forming grooves according to claim 2 , wherein a beam diameter in a direction orthogonal to a scanning direction of the laser on the surface of the metal strip is 200 μm or less.

8 . The method for forming grooves according to claim 2 , wherein the laser is a fiber laser whose beam diameter in a direction orthogonal to a scanning direction of the laser is 200 μm or less.

9 . The method for forming grooves according to claim 2 , wherein a surface roughness Ra of the metal strip in a transverse direction before the etching resist coating is formed is 0.5 μm or less.

10 . The method for forming grooves according to claim 3 , wherein a surface roughness Ra of the metal strip in a transverse direction before the etching resist coating is formed is 0.5 μm or less.

11 . The method for forming grooves according to claim 4 , wherein a surface roughness Ra of the metal strip in a transverse direction before the etching resist coating is formed is 0.5 μm or less.

12 . The method for forming grooves according to claim 7 , wherein a surface roughness Ra of the metal strip in a transverse direction before the etching resist coating is formed is 0.5 μm or less.

13 . The method for forming grooves according to claim 8 , wherein a surface roughness Ra of the metal strip in a transverse direction before the etching resist coating is formed is 0.5 μm or less.

14 . A method for manufacturing a grain-oriented electrical steel sheet, comprising

hot rolling a steel slab into a hot-rolled steel sheet,

then, subjecting the hot-rolled steel sheet or a hot-rolled and annealed sheet obtained by applying hot-rolled sheet annealing to the hot-rolled steel sheet to cold rolling once, or twice or more with intermediate annealing performed therebetween to obtain a cold-rolled steel sheet,

then subjecting the cold-rolled steel sheet to primary recrystallization annealing to obtain a primary recrystallized sheet, and

then, subjecting the primary recrystallized sheet to secondary recrystallization annealing to obtain a secondary recrystallized sheet,

wherein grooves are formed on a surface of the steel sheet at any stage after being subjected to hot rolling by the method for forming grooves according to claim 2 .

15 . A method for manufacturing a grain-oriented electrical steel sheet, comprising

hot rolling a steel slab into a hot-rolled steel sheet,

then, subjecting the hot-rolled steel sheet or a hot-rolled and annealed sheet obtained by applying hot-rolled sheet annealing to the hot-rolled steel sheet to cold rolling once, or twice or more with intermediate annealing performed therebetween to obtain a cold-rolled steel sheet,

then subjecting the cold-rolled steel sheet to primary recrystallization annealing to obtain a primary recrystallized sheet, and

then, subjecting the primary recrystallized sheet to secondary recrystallization annealing to obtain a secondary recrystallized sheet,

wherein grooves are formed on a surface of the steel sheet at any stage after being subjected to hot rolling by the method for forming grooves according to claim 3 .

16 . A method for manufacturing a grain-oriented electrical steel sheet, comprising

hot rolling a steel slab into a hot-rolled steel sheet,

then, subjecting the hot-rolled steel sheet or a hot-rolled and annealed sheet obtained by applying hot-rolled sheet annealing to the hot-rolled steel sheet to cold rolling once, or twice or more with intermediate annealing performed therebetween to obtain a cold-rolled steel sheet, then subjecting the cold-rolled steel sheet to primary recrystallization annealing to obtain a primary recrystallized sheet, and

then, subjecting the primary recrystallized sheet to secondary recrystallization annealing to obtain a secondary recrystallized sheet,

wherein grooves are formed on a surface of the steel sheet at any stage after being subjected to hot rolling by the method for forming grooves according to claim 4 .

17 . The method for forming grooves according to claim 1 , wherein the output of the laser is 0.3 kW or more and less than 1.5 kW.

18 . The method for forming grooves according to claim 1 , wherein the output of the laser is 0.3 kW or more and 1.4 kW or less.

19 . The method for forming grooves according to claim 1 , wherein the output of the laser is 0.3 kW or more and 1.25 kW or less.

20 . The method for forming grooves according to claim 1 , wherein the laser heats and vaporizes the etching resist coating formed on the metal strip surface to remove the portion of the etching resist coating irradiated by the laser.