GRAIN-ORIENTED ELECTRICAL STEEL SHEET HAVING EXCELLENT INSULATION COATING ADHESION WITHOUT FORSTERITE COATING

Abstract

Provided is a grain-oriented electrical steel sheet including a base steel sheet, an intermediate layer which is disposed in contact with the base steel sheet and mainly includes silicon oxide, and an insulation coating which is disposed in contact with the intermediate layer and mainly includes phosphate and colloidal silica, in which the base steel sheet contains predetermined chemical composition, BN having an average particle size of 50 to 300 nm is present, when an emission intensity of B is measured using glow discharge emission analysis, predetermined conditions are satisfied, and a ratio of a major axis to a minor axis of BN is 1.5 or less.

Claims

1. A grain-oriented electrical steel sheet comprising: a base steel sheet; an intermediate layer which is disposed in contact with the base steel sheet and mainly includes silicon oxide; and an insulation coating which is disposed in contact with the intermediate layer and mainly includes phosphate and colloidal silica, wherein the base steel sheet contains, as a chemical compositions, by mass %: C: 0.085% or less; Si: 0.80 to 7.00%; Mn: 0.05 to 1.00%; acid-soluble Al: 0.010 to 0.065%; N: 0.0040% or less; S: 0.0100% or less; B: 0.0005 to 0.0080%; and a remainder of Fe and impurities, BN having an average particle size of 50 to 300 nm is present on a surface layer of the intermediate layer, when a total thickness of the base steel sheet and the intermediate layer is defined as d, a time until a sputtering depth reaches a position of d/100 from an outermost surface of the intermediate layer when an emission intensity of B is measured using glow discharge emission spectrometry (GDS) is defined as t(d/100), and a time until the sputtering depth reaches a position of d/10 from the outermost surface of the intermediate layer is defined as t(d/10), an emission intensity I.sub.B_t(d/100) of B at t(d/100) and an emission intensity I.sub.B_t(d/10) of B at t(d/10) satisfy the following Equation (1), and a ratio of a major axis to a minor axis of BN is 1.5 or less,
I.sub.B_t(d/100)>I.sub.B_t(d/10)  Equation (1).

2. The grain-oriented electrical steel sheet according to claim 1, wherein a number density of BN on the surface layer of the intermediate layer is 2×10.sup.6 pieces/mm.sup.2 or more.

Description

EXAMPLES

Example 1

[0178] Steel slabs A1 to A15 having the composition shown in Table 1-1 were heated to 1150° C. and subjected to hot rolling to obtain hot-rolled steel sheets having a sheet thickness of 2.6 mm, the hot-rolled steel sheets were subjected to hot-rolled sheet annealing in which annealing is performed at 1100° C. and subsequently at 900° C., and then cold-rolled once or cold-rolled a plurality of times with intermediate annealing interposed therebetween at 30° C. to obtain cold-rolled steel sheets having a final sheet thickness of 0.22 mm.

[0179] Steel slabs a1 to a13 having the composition shown in Table 1-1 were heated to 1150° C. and subjected to hot rolling to obtain hot-rolled steel sheets having a sheet thickness of 2.6 mm, the hot-rolled steel sheets were subjected to hot-rolled sheet annealing in which annealing is performed at 1100° C. and subsequently at 900° C., and then cold-rolled once or cold-rolled a plurality of times with intermediate annealing interposed therebetween at 30° C. to obtain cold-rolled steel sheets having a final sheet thickness of 0.22 mm.

TABLE-US-00001 TABLE 1-1 Steel slab chemical components (mass %) Slab (remainder is Fe and impurities) No. C Si Mn Al N S B A1 0.085 3.45 0.10 0.028 0.0040 0.008 0.0015 A2 0.031 1.21 0.10 0.029 0.0100 0.009 0.0020 A3 0.033 6.52 0.10 0.029 0.0100 0.007 0.0018 A4 0.041 3.45 0.08 0.028 0.0070 0.005 0.0019 A5 0.044 3.33 0.80 0.029 0.0060 0.004 0.0021 A6 0.052 4.52 0.12 0.020 0.0050 0.003 0.0016 A7 0.055 3.12 0.09 0.055 0.0017 0.001 0.0017 A8 0.061 2.81 0.09 0.030 0.0120 0.009 0.0018 A9 0.062 3.12 0.11 0.030 0.0040 0.001 0.0019 A10 0.071 2.92 0.13 0.030 0.0050 0.001 0.0021 A11 0.078 3.45 0.12 0.028 0.0110 0.010 0.0022 A12 0.055 3.44 0.10 0.027 0.0090 0.007 0.0006 A13 0.085 4.21 0.10 0.027 0.0080 0.006 0.0078 A14 0.082 3.45 0.11 0.031 0.0100 0.008 0.0025 A15 0.045 3.35 0.12 0.030 0.0060 0.009 0.0017 a1 0.092 3.45 0.12 0.029 0.0019 0.007 0.0002 a2 0.076 0.50 0.08 0.028 0.0028 0.007 0.0004 a3 0.065 8.00 0.09 0.028 0.0031 0.007 0.0004 a4 0.045 3.45 0.04 0.029 0.0021 0.009 0.0002 a5 0.061 3.35 1.21 0.029 0.0035 0.009 0.0006 a6 0.032 3.25 0.08 0.005 0.0038 0.006 0.0007 a7 0.012 3.12 0.07 0.082 0.0032 0.006 0.0009 a8 0.072 3.23 0.08 0.030 0.0051 0.009 0.0061 a9 0.043 3.45 0.10 0.027 0.0152 0.009 0.0003 a10 0.033 3.55 0.09 0.026 0.0012 0.012 0.0055 a11 0.039 3.15 0.08 0.026 0.0022 0.030 0.0002 a12 0.058 3.28 0.10 0.027 0.0019 0.007 0.0003 a13 0.021 3.19 0.13 0.028 0.0036 0.007 0.0152

[0180] The grain-oriented electrical steel sheets of Nos. B1 to B15 shown in Table 2 were manufactured as follows. Cold-rolled steel sheets having a final sheet thickness of 0.22 mm were subjected to decarburization annealing in which uniform heat treatment is performed at 860° C. in a moist atmosphere with the oxidation degree of 0.10, and then nitriding treatment (annealing that increases an amount of nitrogen in the steel sheets) is performed with ammonia gas. Subsequently, an annealing separator containing alumina as a main component was applied to the nitriding-treated steel sheets, and final annealing was performed at a temperature of 1200° C. for 20 hours in a hydrogen gas atmosphere. When the temperature was raised in the final annealing, the heating rate in the range of 1000 to 1100° C. was set to 5° C./hour. Further, after holding at 1200° C. for 20 hours, the temperature lowering rate in the range of 1200 to 1000° C. was set to 45° C./hour, and the temperature lowering rate in the range of 1000 to 600° C. was set to 25° C./hour. After the final annealing, excess alumina was removed from the steel sheets, and intermediate layer formation heat treatment was performed on the steel sheets from which excess alumina had been removed in an atmosphere of hydrogen: nitrogen of 75% by volume: 25% by volume and a dew point of −5° C. An aqueous coating solution mainly including colloidal silica and phosphate is applied onto the steel sheets after the intermediate layer formation heat treatment, and insulation coatings were formed by baking at a temperature of −5° C. for 30 seconds in an atmosphere of 75% by volume of hydrogen: 25% by volume of nitrogen to obtain products. The average particle size based on the number of the colloidal silica in the aqueous coating solution used was 100 nm.

[0181] Table 1-2 shows chemical compositions contained in the base steel sheets in the products. The compositions of the base steel sheets were measured using ICP-AES. Acid-soluble Al was measured by ICP-AES using a filtrate obtained by heat-decomposing samples with an acid. Further, C and S were measured using a combustion-infrared absorption method, and N was measured using an inert gas melting-thermal conductivity method.

[0182] The grain-oriented electrical steel sheets of Nos. b1 to b13 shown in Table 1-2 were manufactured as follows. Cold-rolled steel sheets having a final sheet thickness of 0.22 mm were subjected to decarburization annealing in which uniform heat treatment is performed at 860° C. in a moist atmosphere with an oxidation degree of 0.10, and then nitriding treatment (annealing to increase an amount of nitrogen in the steel sheets) was performed with ammonia gas. Subsequently, an annealing separator containing alumina as a main component was applied to the steel sheets after nitriding treatment, and final annealing was performed at a temperature of 1200° C. for 20 hours in a hydrogen gas atmosphere. When the temperature was raised in the final annealing, the heating rate in the range of 1000 to 1100° C. was set to 5° C./hour. Further, after holding at 1200° C. for 20 hours, the temperature lowering rate in the range of 1200 to 1000° C. was set to 100° C./hour, and the temperature lowering rate in the range of 1000 to 600° C. was 100° C./hour. After the final annealing, excess alumina was removed from the steel sheets, and intermediate layer formation heat treatment was performed on the steel sheets from which the excess alumina have been removed in an atmosphere of hydrogen: nitrogen of 75% by volume: 25% by volume and a dew point of −5° C. An aqueous coating solution mainly including colloidal silica and phosphate is applied onto the steel sheets after the intermediate layer formation heat treatment, and insulation coatings were formed by baking at a temperature of −5° C. for 30 seconds in an atmosphere of 75% by volume of hydrogen: 25% by volume of nitrogen to obtain products. The average particle size based on the number of the colloidal silica in the aqueous coating solution used was 100 nm.

[0183] Table 1-2 shows chemical compositions contained in the base steel sheets in the products. The compositions of the base steel sheets were measured using the same method as for steel Nos. B1 to B15.

[0184] The grain-oriented electrical steel sheet of steel No. b14 shown in Table 1-2 was manufactured as follows. A cold-rolled steel sheet having a final sheet thickness of 0.22 mm was subjected to decarburization annealing in which uniform heat treatment is performed at 850° C. in a moist atmosphere with an oxidation degree of 0.10, and then nitriding treatment (annealing to increase an amount of nitrogen in the steel sheet) was performed with ammonia gas. Subsequently, an annealing separator containing alumina as a main component was applied to the steel sheet after nitriding treatment, and final annealing was performed at a temperature of 1200° C. for 20 hours in a hydrogen gas atmosphere. When the temperature was raised in the final annealing, the heating rate in the range of 1000 to 1100° C. was set to 5° C./hour. Further, after holding at 1200° C. for 20 hours, the temperature lowering rate in the range of 1200 to 1000° C. was set to 200° C./hour, and the temperature lowering rate in the range of 1000 to 600° C. was set to 100° C./hour. After the final annealing, excess alumina was removed from the steel sheet, and the intermediate layer formation heat treatment was performed on the steel sheet from which the excess alumina has been removed in an atmosphere in which hydrogen: nitrogen was 75% by volume: 25% by volume and a dew point was −5° C. An aqueous coating solution mainly composed of colloidal silica and phosphate was applied onto the steel sheet after the intermediate layer formation heat treatment, and an insulation coating was formed by baking at a temperature of 800° C. for 30 seconds in an atmosphere of 75% by volume of hydrogen: 25% by volume of nitrogen to obtain a product. The average particle size based on the number of the colloidal silica in the aqueous coating solution used was 100 nm.

[0185] The grain-oriented electrical steel sheet of steel No. b15 shown in Table 1-2 was manufactured as follows. A cold-rolled steel sheet having a final sheet thickness of 0.22 mm was subjected to decarburization annealing in which uniform heat treatment is performed at 860° C. in a moist atmosphere with an oxidation degree of 0.10, and then nitriding treatment (annealing to increase an amount of nitrogen in the steel sheet) was performed with ammonia gas. Subsequently, an annealing separator containing alumina as a main component was applied to the steel sheet after nitriding treatment, and final annealing was performed at a temperature of 1200° C. for 20 hours in a hydrogen gas atmosphere. When the temperature was raised in the final annealing, the heating rate in the range of 1000 to 1100° C. was set to 5° C./hour. Further, after holding at 1200° C. for 20 hours, the temperature lowering rate in the range of 1200 to 1000° C. was set to 30° C./hour, and the temperature was kept at 1000° C. for 1 hour or more, and the temperature lowering rate in the range of 1000 to 600° C. was set to 50° C./hour. After the final annealing, excess alumina was removed from the steel sheet, and intermediate layer formation heat treatment was performed on the steel sheet from which the excess alumina has been removed in an atmosphere of 75% by volume of hydrogen: 25% by volume of nitrogen and a dew point of −5° C. An aqueous coating solution mainly composed of colloidal silica and phosphate was applied onto the steel sheet after the intermediate layer formation heat treatment, and an insulation coating was formed by baking at a temperature of 800° C. for 30 seconds in an atmosphere of 75% by volume of hydrogen: 25% by volume of nitrogen to obtain a product. The average particle size based on the number of the colloidal silica in the aqueous coating solution used was 100 nm.

TABLE-US-00002 TABLE 1-2 Chemical components (mass %) Steel Slab (remainder is Fe and impurities) No. No. C Si Mn Al N S B Examples B1 A1 0.080 3.45 0.10 0.028 0.0021 0.0021 0.0015 B2 A2 0.031 1.21 0.10 0.029 0.0031 0.0032 0.0020 B3 A3 0.001 6.52 0.10 0.029 0.0012 0.0012 0.0018 B4 A4 0.003 3.45 0.08 0.028 0.0010 0.0007 0.0019 B5 A5 0.005 3.33 0.80 0.029 0.0021 0.0005 0.0021 B6 A6 0.001 4.52 0.12 0.020 0.0019 0.0007 0.0016 B7 A7 0.002 3.12 0.09 0.055 0.0017 0.0008 0.0017 B8 A8 0.003 2.81 0.09 0.030 0.0006 0.0009 0.0018 B9 A9 0.007 3.12 0.11 0.030 0.0039 0.0051 0.0019 B10 A10 0.006 2.92 0.13 0.030 0.0022 0.0004 0.0021 B11 A11 0.012 3.45 0.12 0.028 0.0018 0.0092 0.0022 B12 A12 0.011 3.44 0.10 0.027 0.0019 0.0007 0.0006 B13 A13 0.002 4.21 0.10 0.027 0.0010 0.0081 0.0078 B14 A14 0.003 3.45 0.11 0.031 0.0009 0.0005 0.0025 B15 A15 0.001 3.35 0.12 0.030 0.0008 0.0005 0.0017 Comparative b1 a1 0.090 3.45 0.12 0.029 0.0008 0.0012 0.0002 examples b2 a2 0.008 0.50 0.08 0.028 0.0010 0.0014 0.0004 b3 a3 0.001 8.00 0.09 0.028 0.0009 0.0018 0.0004 b4 a4 0.002 3.45 0.04 0.029 0.0011 0.0022 0.0002 b5 a5 0.001 3.35 1.21 0.029 0.0019 0.0009 0.0006 b6 a6 0.012 3.25 0.08 0.005 0.0018 0.0010 0.0007 b7 a7 0.011 3.12 0.07 0.082 0.0018 0.0022 0.0009 b8 a8 0.001 3.23 0.08 0.030 0.0018 0.0018 0.0061 b9 a9 0.002 3.45 0.10 0.027 0.0018 0.0011 0.0003 b10 a10 0.001 3.55 0.09 0.026 0.0009 0.0025 0.0055 b11 a11 0.020 3.15 0.08 0.026 0.0018 0.0021 0.0002 b12 a12 0.010 3.28 0.10 0.027 0.0007 0.0012 0.0003 b13 a13 0.002 3.19 0.13 0.028 0.0018 0.0011 0.0152 b14 a14 0.002 3.28 0.12 0.028 0.0019 0.0012 0.0029 b15 a15 0.001 3.32 0.11 0.019 0.0009 0.0018 0.0112

[0186] <Magnetic Domain Control>

[0187] The magnetic domain control was performed on the product on which the insulation coating was formed using a mechanical method, a laser, or an electron beam. For some products, the cold-rolled sheets were grooved by etching or laser irradiation to control the magnetic domain.

[0188] <Precipitates>

[0189] Regarding the precipitates, the B compound observed up to 5 μm from the outermost surface of the intermediate layer perpendicular to the rolling direction of the steel sheet was analyzed using SEM-EDS to identify the particle size and the composition of BN. In addition, in the item of “presence or absence of BN precipitation” in Table 2, ∘ represents that one or more spherical BNs (BNs having a ratio of the major axis to the minor axis of 1.5 or less) were present in an observed visual field, and x represents that there were no spherical BN in the observed visual field.

[0190] <B Emission Intensity>

[0191] The emission intensity I.sub.B of B was measured using glow discharge emission spectrometry (GDS). I.sub.B_t(d/100) that is the emission intensity of B at t(d/100), and I.sub.B_t(d/10) that is the emission intensity of B at t(d/10) were obtained when a sputtering time during which the sputtering depth reached the position of d/100 from the outermost surface of the steel sheet excluding the insulation coating was defined as t(d/100), and a sputtering time during which the sputtering depth reached the position of d/10 from the outermost surface of the steel sheet excluding the insulation coating was defined as t (d/10), and I.sub.B_t(d/100)/I.sub.B_t(d/10) that is the ratio of them was written in the table.

<Coating Adhesion>

[0192] Coating adhesion was evaluated with a peeled area ratio at each diameter by forming the insulation coating on the steel sheet after final annealing and then winding the steel sheet around round bars having different diameters (20 mm, 10 mm, and 5 mm). The peeled area ratio is a ratio obtained by dividing an actually peeled area by a processed part area (an area in which the steel sheet is in contact with a round bar, which corresponds to a test width×a diameter of the round bar×n). If the peeling does not progress and the peeled area ratio is small even when the insulation coating is peeled off via a strong bending process, it can be evaluated that deterioration of transformer characteristics is small.

[0193] The coating adhesion was evaluated on a scale of 7 levels from A to G when a peeled area ratio of 0% is defined as A, more than 0% and less than 20% is defined as B, 20% or more and less than 40% is defined as C, 40% or more and less than 60% is defined as D, 60% or more and less than 80% is defined as E, 80% or more and less than 100% is defined as F, and 100% is defined as G. The evaluation of B or higher was evaluated as having good coating adhesion.

[0194] <Magnetic Characteristics>

[0195] <Magnetic Flux Density B8>

[0196] The magnetic flux density B8 (magnetic flux density when magnetized at 800 A/m) was measured with respect to the grain-oriented electrical steel sheet obtained using the above-mentioned manufacturing method through single sheet magnetic measurement (SST).

[0197] <Iron Loss W17/50>

[0198] A test piece (for example, a 100 mm×500 mm test piece) was prepared from the grain-oriented electrical steel sheet before and after the magnetic domain control, and the iron loss W17/50 (unit: W/kg), which is an energy loss per unit weight measured under excitation conditions at a magnetic flux density of 1.7 T and a frequency of 50 Hz, was measured.

[0199] Table 2 shows a precipitation state of BN of the grain-oriented electrical steel sheet (product), the results of GDS, the evaluation of the coating adhesion, and the magnetic characteristics. In the examples C1 to C15 within the scope of the present invention, grain-oriented electrical steel sheets having excellent coating adhesion and excellent magnetic characteristics have been obtained. In comparative examples c1 to c15 outside the scope of the present invention, either the coating adhesion or the magnetic characteristics were inferior.

TABLE-US-00003 TABLE 2 Magnetic characteristics Iron loss Coating adhesion W.sub.17/50 of Presence Average 20 mm φ 10 mm φ 5 mm φ Magnetic Iron magnetic or absence particle peeling peeling peeling flux loss domain Steel of BN size of I.sub.B.sub.—.sub.t(d/100)/ area area area density W.sub.17/50 control No. No. precipitation BN (nm) I.sub.B.sub.—.sub.t(d/10) ratio ratio ratio B8 (T) (W/kg) (W/kg) Miscellaneous Examples C1 B1 ∘ 120 1.3 A A B 1.946 0.87 0.62 C2 B2 ∘ 50 1.1 A B B 1.947 0.86 0.64 C3 B3 ∘ 80 1.6 A A B 1.953 0.87 0.66 C4 B4 ∘ 150 2.0 A A B 1.952 0.88 0.64 C5 B5 ∘ 300 4.5 A B B 1.944 0.85 0.63 C6 B6 ∘ 280 2.8 A A B 1.948 0.89 0.62 C7 B7 ∘ 200 1.9 A B B 1.956 0.87 0.63 C8 B8 ∘ 150 2.3 A A B 1.951 0.86 0.60 C9 B9 ∘ 130 1.9 A B B 1.951 0.87 0.61 C10 B10 ∘ 70 2.2 A B B 1.947 0.87 0.62 C11 B1 ∘ 90 2.3 A A B 1.945 0.85 0.64 C12 B12 ∘ 110 4.3 A A B 1.949 0.89 0.65 C13 B13 ∘ 250 5.5 A B B 1.956 0.86 0.64 C14 B14 ∘ 200 3.5 A A B 1.944 0.84 0.64 C15 B15 ∘ 100 1.5 A A B 1.954 0.85 0.60 Comparative c1 b1 x — 0.8 E E G 1.945 0.95 0.69 No BN Examples precipitation c2 b2 x — 0.7 G G G 1.944 0.97 0.71 No BN precipitation c3 b3 x — 0.9 E F G 1.945 0.99 0.72 No BN precipitation c4 b4 x — 0.5 G G G 1.948 0.97 0.71 No BN precipitation c5 b5 x — 0.9 D G G 1.945 0.99 0.72 No BN precipitation c6 b6 x — 0.9 D G G 1.947 0.96 0.70 No BN precipitation c7 b7 x — 0.9 C D G 1.946 0.94 0.68 No BN precipitation c8 b8 x — 15.0 C D G 1.945 0.93 0.68 No BN precipitation c9 b9 x — 0.5 D E G 1.944 0.94 0.68 No BN precipitation c10 b10 x — 1.3 D E G 1.943 1.03 0.75 No BN precipitation c11 b11 x — 0.9 C E G 1.942 1.04 0.76 No BN precipitation c12 b12 x — 0.9 B C G 1.922 1.06 0.77 No BN precipitation c13 b13 x — 5.0 E F G 1.946 0.96 0.70 No BN precipitation c14 b14 ∘ 30 1.2 A A B 1.946 0.92 0.73 c15 b15 ∘ 500 1.3 E F G 1.921 0.96 0.78

Example 2

[0200] First, a grain-oriented electrical steel sheet (product) was produced using the same method as in Example 1. Next, the magnetic domain control was performed for the product using a mechanical method, a laser, and an electron beam.

[0201] When the number density of BN was measured, the insulation coating was removed using sodium hydroxide from the grain-oriented electrical steel sheet obtained using the above-mentioned manufacturing method. Next, 10 visual fields were observed from the outermost surface of the intermediate layer having a cross-section perpendicular to the rolling direction of the steel sheet to 5 μm in a visual field of 4 μm in the sheet width direction×2 μm in the sheet thickness direction using SEM, and the number of BNs having a particle size of 50 nm or more and 300 nm or less was counted.

[0202] Also, using SEM-EDS, the average particle size was observed in 10 visual fields of 4 μm in the sheet width direction×2 μm in the sheet thickness direction, lengths of the major axes of the precipitates in the observed fields identified as BN using EDS were measured, and an average value thereof was taken as the average particle size.

[0203] Further, I.sub.B_t (d/100)/I.sub.B_t (d/10) was measured using the same method as described above.

[0204] Table 3 shows a precipitation state of BN of the grain-oriented electrical steel sheet (product), the results of GDS, the evaluation of coating adhesion, and the magnetic characteristics. In the examples D1 to D5 within the scope of the present invention, the coating adhesion was more excellent and the magnetic characteristics were also excellent.

TABLE-US-00004 TABLE 3 Magnetic characteristics Iron loss BN Coating adhesion W.sub.17/50 of Number 20 mm φ 10 mm φ 5 mm φ Magnetic Iron magnetic Magnetic density Average peeling peeling peeling flux loss domain domain Steel (pieces/ particle I.sub.B.sub.—.sub.t(d/100)/ area area area density W.sub.17/50 control control No. No. mm.sup.3) size (nm) I.sub.B.sub.—.sub.t(d/10) ratio ratio ratio B8 (T) (W/kg) (W/kg) method Examples D1 B1 2 × 10.sup.6 80 1.3 A A B 1.947 0.88 0.63 Laser irradiation groove D2 B2 4 × 10.sup.6 120 1.5 A A B 1.950 0.86 0.62 Laser irradiation groove D3 B3 3 × 10.sup.6 130 3.0 A A B 1.951 0.85 0.61 Gear groove D4 B4 2 × 10.sup.6 90 1.1 A A B 1.949 0.89 0.59 Etching groove D5 B5 3 × 10.sup.6 100 5.1 A A B 1.945 0.88 0.65 Electron beam

Example 3

[0205] Grain-oriented electrical steel sheets (products) were produced using the same method as in Examples 1 and 2. Next, the magnetic domain control was performed for the products using a mechanical method, a laser, and an electron beam.

[0206] For the grain-oriented electrical steel sheets (products), a precipitation mode of BN, I.sub.B_t (d/100)/I.sub.B_t(d/10), the coating adhesion, and the magnetic characteristics were measured. The results are shown in Table 4.

TABLE-US-00005 TABLE 4 Magnetic characteristics Iron loss GDS Coating adhesion W.sub.17/50 of Presence Average B emission 20 mm φ 10 mm φ 5 mm φ Magnetic Iron magnetic Magnetic or absence particle intensity peeling peeling peeling flux loss domain domain Steel of BN size of I.sub.B.sub.—.sub.t(d/100)/ area area area density W.sub.17/50 control control No. No. precipitation BN (nm) I.sub.B.sub.—.sub.t(d/10) ratio ratio ratio B8 (T) (W/kg) (W/kg) method Examples E1 B1 ∘ 70 18 A A B 1.951 0.87 0.61 Laser irradiation groove E2 B2 ∘ 120 12 A B B 1.952 0.86 0.62 Etching groove E3 B3 ∘ 300 16 A A B 1.949 0.87 0.63 Gear groove E4 B4 ∘ 250 15 A A B 1.952 0.88 0.62 Electron beam E5 B5 ∘ 200 17 A B B 1.948 0.86 0.60 Electron beam

[0207] In the examples E1 to E5 in which the ratio I.sub.B-t(d/100)/I.sub.B-t(d/10) of the emission intensity of B on the surface layer of the steel sheet to the emission intensity of B on a center of the steel sheet (on a side closer to the base steel sheet that the surface layer of the steel sheet) satisfies the above Equation (1), the coating adhesion and the magnetic characteristics were more excellent.

INDUSTRIAL APPLICABILITY

[0208] As described above, according to the present invention, the peeling of the insulation coating generated at the strong bending processing part of the steel sheet serving as the inner circumferential side of the iron core can be inhibited in the grain-oriented electrical steel sheet using BN as an inhibitor, and it is possible to stably provide a grain-oriented electrical steel sheet having excellent insulation adhesion, a low iron loss, and excellent manufacturability as a wound steel core. Therefore, the present invention is highly applicable in manufacturing the electrical steel sheets and in industries utilizing them.