Grain-oriented electrical steel sheet, and manufacturing method therefor

Abstract

A method for manufacturing a grain-oriented electrical steel sheet, according to one embodiment of the present invention, comprises the steps of: manufacturing a hot rolled sheet by hot rolling a slab comprising, by wt %, 2.5-4.0% of Si, 0.03-0.09% of C, 0.015-0.040% of Al, 0.04-0.15% of Mn, 0.01% or less of S (excluding 0%) and 0.002-0.012% of N, and the balance of Fe and other inevitable impurities; cold rolling the hot rolled sheet to manufacture a cold rolled sheet; performing primary recrystallization annealing on the cold rolled sheet; and performing secondary recrystallization annealing on the cold rolled sheet for which the primary recrystallization annealing has been completed.

1 . A grain oriented electrical steel sheet, comprising:
 an electrical steel sheet base material containing, by wt %, 2.0 to 7.0% of Si and 0.01 to 0.07 wt % of Sb, and the balance of Fe and other inevitable impurities; and   an insulating coating layer positioned on the electrical steel sheet base material,   wherein the insulating coating layer includes pores having a particle size of 10 nm or more,   the electrical steel sheet base material has a subgrain boundary that exists in an area A within 1500 μm in an RD direction from a center of the pores and an area B within 50 to 100 μm from a surface of the electrical steel sheet base material toward an inside of the electrical steel sheet base material,   the subgrain boundary has an angle of 1° to 15° from crystal orientation of {110}<001>, and   an area fraction of the subgrain boundary in an ND cross section is 5% or less.   
     
     
         2 . The grain oriented electrical steel sheet of  claim 1 , wherein:
 in the subgrain boundary, a ratio y/z of a crystal grain length y in a TD direction to a crystal grain length z in the ND direction is 1.5 or less.   
     
     
         3 . The grain oriented electrical steel sheet of  claim 1 , wherein:
 a Goss crystal grain less than 1° from the crystal orientation of {110} <001> is included in an area B of 50 to 100 μm from the surface of the electrical steel sheet base material toward the inside of the electrical steel sheet base material, and   a ratio Ls/LG of an average particle size Ls of the subgrain boundary to the average particle size LG of the Goss crystal grain in the ND cross section is 0.20 or less.   
     
     
         4 . The grain oriented electrical steel sheet of  claim 1 , wherein:
 a fine grain interfacial layer exists from the surface of the electrical steel sheet toward the inside of the electrical steel sheet base material, and   the fine grain interfacial layer has an average grain diameter of 0.1 to 5 μm.   
     
     
         5 . The grain oriented electrical steel sheet of  claim 4 , wherein:
 the fine grain interfacial layer has a residual stress of −10 to −1000 MPa in the RD direction.   
     
     
         6 . The grain oriented electrical steel sheet of  claim 4 , wherein:
 a thickness of the fine grain interfacial layer is 0.1 to 5 μm.   
     
     
         7 . The grain oriented electrical steel sheet of  claim 1 , further comprising:
 a base coating layer between the electrical steel sheet base material and the insulating coating layer.   
     
     
         8 . The grain oriented electrical steel sheet of  claim 7 , wherein:
 a residual stress of the base coating layer in the RD direction is −50 to −1500 MPa.   
     
     
         9 . The grain oriented electrical steel sheet of  claim 7 , wherein:
 a thickness of the base coating layer is 0.1 to 15 μm.   
     
     
         10 . The grain oriented electrical steel sheet of  claim 1 , wherein:
 a residual stress of the insulating coating layer in the RD direction is −10 to −1000 MPa.   
     
     
         11 . The grain oriented electrical steel sheet of  claim 1 , wherein:
 a thickness of the insulating coating layer is 0.1 to 15 μm.   
     
     
         12 . The grain oriented electrical steel sheet of  claim 1 , wherein:
 the electrical steel sheet base material has a residual stress of 1 to 50 MPa in the RD direction.