This grain-oriented electrical steel sheet is a grain-oriented electrical steel sheet including a base steel sheet and a tension coating, in which, when an average coating thickness of a flat surface coating portion is referred to as t1 (μm), a minimum coating thickness of a groove forming surface coating portion is referred to as t2.sub.Min (μm), and a maximum coating thickness of the groove forming surface coating portion is referred to as t2.sub.Max (μm), Expressions (1) and (2) are satisfied, and when a value of 0.95 times a distance D of the tension coating along a sheet thickness direction from a bottom surface position of the groove forming surface coating portion to a bottom surface position of the flat surface coating portion is referred to as an effective depth d (μm), Expression (3) is satisfied.

t2.sub.Min/t1≥0.4  (1)

t2.sub.Max/t1≤3.0  (2)

t2.sub.Max≤d/2  (3)

Grain-oriented electrical steel sheet having an aluminum borate coating able to impart larger tension that the past and a method for manufacturing grain-oriented electrical steel sheet are formed. The grain-oriented electrical steel sheet according to the present invention has a steel sheet and an insulating coating formed on the steel sheet and containing aluminum and boron, where the oxides contain crystalline oxides and a maximum value of an emission intensity ratio of boron with respect to aluminum at an interface between the insulating coating and the steel sheet, analyzed by glow discharge optical emission spectrometry, is 2.5 times or more and 4.0 times or less of the emission intensity ratio of boron with respect to aluminum in the insulating coating.

A grain oriented electrical steel sheet has a magnetic domain structure modified by strain introduction without a trace of treatment, in which noise generated when the grain oriented electrical steel sheet is used laminated on an iron core of a transformer is effectively reduced by: setting a magnetic flux density B.sub.8 to 1.92 T or higher; then setting a ratio of average magnetic domain width of treated surface after strain-introducing treatment W.sub.a to average magnetic domain width before strain-introducing treatment W.sub.0 as W.sub.a/W.sub.0<0.4; and setting a ratio of W.sub.a to average magnetic domain width of untreated surface W.sub.b as W.sub.a/W.sub.b>0.7; and further setting a ratio of average width of magnetic domain discontinuous portion W.sub.d in the untreated surface to average width of magnetic domain discontinuous portion in treated surface resulting from strain-introducing treatment W.sub.c as W.sub.d/W.sub.c>0.8; and setting W.sub.c<0.35 mm.

A grain oriented electrical steel sheet is subjected to a temperature holding treatment at a temperature T of 250-600° C. for 1-10 seconds in the primary recrystallization annealing and heated from temperature T to 700° C. at not less than 80° C./s and from 700° C. to a soaking temperature at not more than 15° C./s, wherein an oxygen potential from 700° C. to the soaking temperature is 0.2-0.4 and an oxygen potential during the soaking is 0.3-0.5 and an area ratio of secondary recrystallized grains is not less than 90% when an angle α deviated from {110}<001> ideal orientation is less than 6.5° and an area ratio is not less than 75% when a deviation angle is less than 2.5° and an average length [L] in the rolling direction is not more than 20 mm and an average value [β] of the angle β is 15.63×[β]+[L]<44.06.

A grain oriented electrical steel sheet comprising a grain oriented electrical steel sheet having a surface and a forsterite film formed on the surface of the steel sheet, wherein a total area percentage of defective parts scattered on the forsterite film is less than 1.5% relative to a surface area of the forsterite film when viewed from above the surface, and methods for evaluating a grain oriented electrical steel sheet comprising a grain oriented electrical steel sheet having a surface and a forsterite film formed on the surface of the steel sheet.

A pre-coating agent composition for a grain-oriednted electrical steel sheet, a grain-oriednted electrical steel sheet including the same, and a manufacturing method thereof are provided. Particularly, a pre-coating agent composition for a grain-oriednted electrical steel sheet including an acid containing boron (B); and a solvent, a grain-oriednted electrical steel sheet including the same, and a manufacturing method thereof are provided.

A method of manufacturing a grain oriented electrical steel sheet uses austenite (γ)-ferrite (α) transformation which develops excellent magnetic properties, uses T.sub.α calculated from equation (1) and performs the first pass of rough hot rolling at a temperature of (T.sub.α−100)° C. or higher with a rolling reduction of 30% or more, and further uses T.sub.γmax calculated from equation (2) and performs any one pass of finish hot rolling in a temperature range of (T.sub.γmax±50)° C. with a rolling reduction of 40% or more:
T.sub.α[° C.]=1383.98−73.29[% Si]+2426.33[% C]+271.68[% Ni]  (1)
T.sub.γmax[° C.]=1276.47−59.24[% Si]+919.22[% C]+149.03[% Ni]  (2)
where [% A] represents content of element “A” in steel (mass %).

When a steel material is processed to produce a grain-oriented electrical steel sheet, conditions of a decarburization annealing process and conditions of a process before the decarburization annealing are adjusted so that a difference in concentration of O, Si, Al, Mn and P between the front and back surfaces of the steel sheet after the decarburization annealing is within a given range with respect to an average concentration between the front and back surfaces, and hence the difference in concentration of each of O, Si and Mg between the front and back surfaces of the product sheet is within ±5%, the difference in concentration of one or more of Al, Mn and P between the front and back surfaces is within ±15% and the difference in the concentration of one or more of Ca and Ti between the front and back surfaces is within ±20%.

This grain-oriented electrical steel sheet includes a base steel sheet, a forsterite-based primary film disposed on a surface of the base steel sheet, and a phosphate-based tension-imparting film containing no chromium, which is disposed on a surface of the primary film. In a case where a Ti content and a S content are respectively expressed as XTi and XS, by mass %, the forsterite-based primary film satisfies Expression (1) and Expression (2). A strain-introduced magnetic domain control is performed on the grain-oriented electrical steel sheet.

0.10≤XTi/XS≤10.00   Expression (1)

XTi+XS≥0.10 mass %.   Expression (2)

[Problem] To provide: a coating liquid for forming an insulation coating for grain-oriented electrical steel sheets, which enables the achievement of excellent coating properties including high coating tension and excellent corrosion resistance even without using a chromium compound; a grain-oriented electrical steel sheet; and a method for producing a grain-oriented electrical steel sheet. [Solution] A coating liquid for forming an insulation coating for grain-oriented electrical steel sheets, which contains boric acid and hydrated silicate particles containing aluminum.