Grain-oriented electrical steel sheet and method for manufacturing the same

A grain-oriented electrical steel sheet, comprising:

• a base steel sheet, wherein the base steel sheet has a composition comprising, in mass %:
• Si:
• 0.50% to 7.00%;
• Mn:
• 0.05% to 1.00%;
• C:
• 0.005% or less,
• N:
• 0.0050% or less, and
• optionally comprising,
• acid-soluble Al:
• 0.0065% or less;
• S and Se:
• 0.001% or less in total;
• Bi:
• 0.010% or less;
• B:
• 0.0080% or less;
• Ti:
• 0.015% or less;
• Nb:
• 0.020% or less;
• V:
• 0.015% or less;
• Sn:
• 0.50% or less;
• Sb:
• 0.50% or less;
• Cr:
• 0.30% or less;
• Cu:
• 0.40% or less;
• P:
• 0.50% or less;
• Ni:
• 1.00% or less;
• Mo:
• 0.10% or less;
• and
• a remainder of Fe and impurities;
• an intermediate layer which is disposed on a surface of the base steel sheet, the intermediate layer comprising an Fe content of less than 30 atomic %, a P content of less than 5 atomic %, a Si content of 20 atomic % or more and less than 50 atomic %, an O content of 50 atomic % or more and less than 80 atomic %, and a Mg content of 10 atomic % or less;
• and
• an insulation coating which is disposed on a surface of the intermediate layer,
• wherein a final-annealed film is not present on a surface of the base steel sheet, and
• in a surface layer region,
• a Mn-depleted layer having a valley portion of a Mn content in which a Mn content is lower than an average Mn content of the base steel sheet in a region deeper than the surface layer region is provided, and
• a Mn-rich layer having a peak portion of a Mn content in which a Mn content is higher than that in the valley portion of the Mn content is provided in a region closer to a surface of the insulation coating than the Mn-depleted layer, and
• wherein:
• in a profile for a depth of a Mn standardized optical emission intensity calculated using the following Equations 1-1 and 1-2 from data of an optical emission intensity and a measurement time of Mn measured by a glow-discharge optical emission analysis for the grain-oriented electrical steel sheet, when a point having a maximum depth among points having a Mn standardized optical emission intensity of 0.9 is defined as a point A,
• the surface layer region is a region from the surface of the insulation coating to a depth of the point A,
• a point B at which the Mn standardized optical emission intensity is 0.50 or more and is the maximum is located in the surface layer region,
• a point C at which the Mn standardized optical emission intensity is the minimum is located between the point A and the point B in the surface layer region,
• the valley portion of the Mn content is a region having a depth of 0.1 μm before and after the point C,
• the peak portion of the Mn content is a region having a depth of 0.1 μm before and after the point B, and
• when an intermediate depth between the depth of the point B and the depth of the point C is defined as a boundary depth, and the Mn standardized optical emission intensity at the boundary depth is defined as a boundary Mn standardized optical emission intensity,
• the Mn-depleted layer is a region from the boundary depth to the depth of the point A, and
• the Mn-rich layer is present on the surface side of the insulation coating from the point B and is a region from a depth of a point having the same Mn standardized optical emission intensity as the boundary Mn standardized optical emission intensity to the boundary depth,
• depth of d μm of each of measurement points=(measurement depth after measurement end, unit μm)/(time until measurement end, unit seconds)×(measurement time of measurement point, unit seconds), Equation 1-1:
• Mn standardized optical emission intensity at depth of d μm=(optical emission intensity of Mn at depth of d μm)/(average optical emission intensity of Mn at depth of 25 μm to 30 μm). Equation 1-2: