Grain-oriented electrical steel sheet

Abstract

The grain-oriented electrical steel sheet includes: a base steel sheet; a forsterite film formed on a surface of the base steel sheet; and an insulating film formed on a surface of the forsterite film, wherein the base steel sheet includes, as a chemical composition, in terms of mass %, 0.80 to 7.00% of Si, in the surface of the base steel sheet, grains where the distance between grain boundaries of a grain is 3.0 mm or more and 13.0 mm or less in a rolling direction have an area ratio of 70% or more, a magnetic flux density B8 generated under a magnetizing force of 800 A/m is 1.88 T or more, when a sheet thickness is defined as t in a unit mm, an iron loss W17/50 is 13.1×t2−4.3×t+1.2 or less in a unit W/kg under a frequency of 50 Hz and a maximum magnetic flux density of 1.7 T, and a LvA200 Hz, which is a 200 Hz component of magnetostriction waveform is 60 to 78 dBA.

1 . A grain-oriented electrical steel sheet comprising:
 a base steel sheet;   a forsterite film formed on a surface of the base steel sheet; and   an insulating film formed on a surface of the forsterite film, wherein   the base steel sheet includes, as a chemical composition, in terms of mass %, 0.80 to 7.00% of Si,   in the surface of the base steel sheet, grains where the distance between grain boundaries of a grain is 3.0 mm or more and 13.0 mm or less in a rolling direction have an area ratio of 70% or more,   a magnetic flux density B8 generated under a magnetizing force of 800 A/m is 1.88 T or more,   when a sheet thickness of the base steel sheet is defined as t in a unit mm, an iron loss W17/50 is 13.1×t 2 −4.3×t+1.2 or less in a unit W/kg under a frequency of 50 Hz and a maximum magnetic flux density of 1.7 T, and   a LvA200 Hz, which is a 200 Hz component of magnetostriction waveform is 60 to 78 dBA.   
     
     
         2 . The grain-oriented electrical steel sheet according to  claim 1 , wherein
 in the surface of the base steel sheet, a plurality of linear strains extending in a direction intersecting a rolling direction is formed, and the plurality of linear strains has an interval of 3 to 10 mm in the rolling direction.   
     
     
         3 . The grain-oriented electrical steel sheet according to  claim 1 , wherein
 the base steel sheet has: a closure domain with a strip shape in an area percentage of 10% or less; and a main domain with a stripe shape having a width of 1.2 mm or less, each of which is observed in the surface.   
     
     
         4 . The grain-oriented electrical steel sheet according to  claim 1 , wherein
 when the magnetic flux density is 1.92 T or more and the sheet thickness is 0.18 to 0.23 mm, the W17/50 is 0.74 W/kg or less.   
     
     
         5 . The grain-oriented electrical steel sheet according to  claim 3 , wherein
 when the magnetic flux density is 1.92 T or more and the sheet thickness is 0.18 to 0.23 mm, the W17/50 is 0.74 W/kg or less.   
     
     
         6 . The grain-oriented electrical steel sheet according to  claim 2 , wherein
 the base steel sheet has: a closure domain with a strip shape in an area percentage of 10% or less; and a main domain with a stripe shape having a width of 1.2 mm or less, each of which is observed in the surface.   
     
     
         7 . The grain-oriented electrical steel sheet according to  claim 2 , wherein
 when the magnetic flux density is 1.92 T or more and the sheet thickness is 0.18 to 0.23 mm, the W17/50 is 0.74 W/kg or less.   
     
     
         8 . The grain-oriented electrical steel sheet according to  claim 6 , wherein
 when the magnetic flux density is 1.92 T or more and the sheet thickness is 0.18 to 0.23 mm, the W17/50 is 0.74 W/kg or less.