GRAIN-ORIENTED ELECTRICAL STEEL SHEET AND METHOD FOR MANUFACTURING THE SAME

1 . A grain oriented electrical steel sheet comprising: 1.0 wt % to 4.0 wt % of Si, 0.002 wt % or less (excluding 0%) of C and 0.001 wt % to 0.1 wt % of Bi, with the remainder being Fe and other unavoidable impurities.

2 . The grain oriented electrical steel sheet of claim 1 ,

further including 0.05 wt % or less (excluding 0%) of Mn, 0.01 wt % or less (excluding 0%) of Al, 0.001 wt % or less (excluding 0%) of S and 0.001 wt % or less (excluding 0%) of N.

3 . The grain oriented electrical steel sheet of claim 1 ,

further including 0.1 wt % or less (excluding 0%) of P, 0.05 wt % or less (excluding 0%) of Mo, 0.1 wt % or less (excluding 0%) of Sn and 0.05 wt % or less (excluding 0%) of Sb.

4 . The grain oriented electrical steel sheet of claim 1 , wherein:

the volume ratio of the crystal grains having a diameter of 20 μm to 500 μm is 80% or more.

5 . The grain oriented electrical steel sheet of claim 1 , wherein:

the volume ratio of the Goss crystal grains parallel in the error range of 15° or less with respect to the sheet surface of the steel sheet is 80% or more.

6 . A method of manufacturing a grain oriented electrical steel sheet, the method comprising: heating a slab comprising 1.0 to 4.0 wt % of Si, 0.01 wt % to 0.4 wt % of C, with the remainder being Fe and other unavoidable impurities;

hot-rolling the slab to produce a hot-rolled sheet;

hot-rolled sheet-annealing the hot-rolled sheet;

cold-rolling the hot-rolled sheet-annealed hot-rolled sheet to produce a cold-rolled sheet;

decarburization-annealing the cold-rolled sheet; and

final-annealing the decarburization-annealed electrical steel sheet,

wherein after the annealing of the hot-rolled sheet, the average diameter of the crystal grain in the surface layer of the hot-rolled sheet is 150 μm to 250 μm.

7 . The method of claim 6 , wherein

the slab further includes 0.001 wt % to 0.1 wt % of Bi.

8 . The method of claim 6 , wherein

the slab further includes 0.05 wt % or less (excluding 0%) of Mn, 0.01 wt % or less (excluding 0%) of Al, 0.001 wt % or less (excluding 0%) of S and 0.001 wt % or less (excluding 0%) of N.

9 . The method of claim 6 , wherein:

the slab further includes 0.1 wt % or less (excluding 0%) of P, 0.05 wt % or less (excluding 0%) of Mo, 0.1 wt % or less (excluding 0%) of Sn and 0.05 wt % or less (excluding 0%) of Sb.

10 . The method of claim 6 , wherein:

the heating temperature in the heating of the slab is 1100 to 1350° C.

11 . The method of claim 6 , wherein:

the hot-rolled sheet-annealing includes the decarburization process.

12 . The method of claim 6 , wherein:

the hot-rolled sheet-annealing includes a first hot-rolled sheet-annealing at a temperature of 850 to 1000° C. and a dew-point temperature of 50 to 70° C. and a second hot-rolled sheet-annealing at a temperature of 1000 to 1200° C. and a dew-point temperature of 0° C. or less.

13 . The method of claim 12 , wherein:

the first hot-rolled sheet-annealing is performed for 10 to 300 seconds, and the second hot-rolled sheet-annealing is performed for 10 to 180 seconds.

14 . The method of claim 6 , wherein:

the process from the cold-rolling to the final-annealing is continuously performed.

15 . The method of claim 6 , wherein:

the process of the cold-rolling and the decarburization-annealing is repeated at least twice.

16 . The method of claim 6 , wherein:

the decarburization-annealing is performed at a temperature of 850 to 1000° C. and a dew-point temperature of 50 to 70° C.

17 . The method of claim 12 , wherein:

the final-annealing includes a first final-annealing at a temperature of 850 to 1000° C. and a dew-point temperature of 70° C. or less and a second final-annealing at a temperature of 1000 to 1200° C. under an atmosphere of H 2 50 volume % or more.

18 . The method of claim 17 , wherein:

the first final-annealing is performed for 10 to 180 seconds and the second final-annealing is performed for 10 to 600 seconds.