GRAIN-ORIENTED ELECTRICAL STEEL SHEET AND METHOD FOR MANUFACTURING SAME

Abstract

This grain-oriented electrical steel sheet includes a base steel sheet, a glass coating formed on the base steel sheet, and a tension-applied insulation coating formed on the glass coating, in which, in the base steel sheet, a plurality of linear strain regions that extend continuously or intermittently in a direction intersecting with a rolling direction are present, the plurality of linear strain regions are each 210 ?m or less in width in the rolling direction, the plurality of linear strain regions are parallel to each other, intervals of linear strain regions adjacent to each other in the rolling direction are 10 mm or less, and magnetostriction ?.sub.0-pb in a unit of ?m/m when the grain-oriented electrical steel sheet is excited up to 1.7 T and magnetostriction ?.sub.0-pa in a unit of ?m/m when the grain-oriented electrical steel sheet is heat-treated at 800? C. for 4 hours and then excited up to 1.7 T satisfy 0.02??.sub.0-pb??.sub.0-pa?0.20.

Claims

1. A grain-oriented electrical steel sheet comprising: a base steel sheet; a glass coating formed on the base steel sheet; and a tension-applied insulation coating formed on the glass coating, wherein, in the base steel sheet, a plurality of linear strain regions that extend continuously or intermittently in a direction intersecting with a rolling direction are present, the plurality of linear strain regions are each 210 ?m or less in width in the rolling direction, the plurality of linear strain regions are parallel to each other, intervals of linear strain regions adjacent to each other in the rolling direction are 10 mm or less, and magnetostriction ?.sub.0-pb in a unit of ?m/m when the grain-oriented electrical steel sheet is excited up to 1.7 T and magnetostriction ?.sub.0-pa in a unit of ?m/m when the grain-oriented electrical steel sheet is heat-treated at 800? C. for 4 hours and then excited up to 1.7 T satisfy the following expression (1),
0.02??.sub.0-pb??.sub.0-pa?0.20(1).

2. The grain-oriented electrical steel sheet according to claim 1, wherein the glass coating is formed of a structure including a Mg.sub.2SiO.sub.4 phase that is a primary phase and a MgAl.sub.2O.sub.4 phase, and in a cross section in a sheet thickness direction, when the glass coating is divided into three regions having an equal thickness in the sheet thickness direction, each region is designated as a 1/3 region, a 2/3 region, and a 3/3 region from a base steel sheet side toward a tension-applied insulation coating side, an area ratio of the MgAl.sub.2O.sub.4 phase in the 1/3 region is denoted by S1, an area ratio of the MgAl.sub.2O.sub.4 phase in the 2/3 region is denoted by S2, and an area ratio of the MgAl.sub.2O.sub.4 phase in the 3/3 region is denoted by S3, the S1, the S2, and the S3 satisfy the following expressions (2) to (4),
S1>S2>S3(2)
(S1+S2+S3)/3<0.50(3)
S3<0.10(4).

3. A method for manufacturing the grain-oriented electrical steel sheet according to claim 1, the method comprising: a hot rolling step of heating a steel piece to obtain a hot-rolled steel sheet by hot rolling; a hot-rolled sheet annealing step of performing hot-rolled sheet annealing on the hot-rolled steel sheet; a pickling step of pickling the hot-rolled steel sheet after the hot-rolled sheet annealing step; a cold rolling step of performing cold rolling once or a plurality of times with annealing therebetween on the hot-rolled steel sheet after the pickling step to obtain a cold-rolled steel sheet; a decarburization annealing step of performing decarburization annealing on the cold-rolled steel sheet; a final annealing step of applying and drying an annealing separating agent containing a MgO powder as a main component onto front and rear surfaces of the cold-rolled steel sheet after the decarburization annealing step, which is the base steel sheet, and performing final annealing to form glass coatings; a coating-forming step of forming tension-applied insulation coatings on the glass coatings to obtain a grain-oriented electrical steel sheet including the base steel sheet, the glass coatings formed on the base steel sheet, and the tension-applied insulation coatings formed on the glass coatings; and a magnetic domain segmentation step of irradiating surfaces of the tension-applied insulation coatings of the grain-oriented electrical steel sheet with an energy ray to form a plurality of linear strain regions on the base steel sheet, wherein, in the magnetic domain segmentation step, among the plurality of linear strain regions, intervals of linear strain regions adjacent to each other in a rolling direction are 10 mm or less, an energy ray power density Ip in a unit of W/mm.sup.2 that is defined by (P/S) using an energy ray output P in a unit of W and an energy ray irradiation cross-sectional area S in a unit of mm.sup.2 satisfies the following expression (5), an energy ray input energy Up in a unit of J/mm that is defined by P/Vs using the energy ray output P and an energy ray scanning velocity Vs in a unit of mm/sec satisfies the following expression (6), and a beam aspect ratio of the energy ray, which is defined by (dl/dc) using a diameter dl in a direction perpendicular to a beam scanning direction and a diameter dc in the beam scanning direction, in a unit of ?m, and the dl each satisfy the following expression (7) and the following expression (8),
250?Ip?2,000(5)
0.010<Up?0.050(6)
0.0010<dl/dc<1.0000(7)
10<dl<200(8).

4. The method for manufacturing the grain-oriented electrical steel sheet according to claim 3, wherein the energy ray is a laser beam.

5. The method for manufacturing the grain-oriented electrical steel sheet according to claim 4, wherein the laser beam is a fiber laser beam.

6. The method for manufacturing the grain-oriented electrical steel sheet according to claim 3, wherein the steel piece contains, by mass %, C: 0.010% to 0.200%, Si: 3.00% to 4.00%, sol. Al: 0.010% to 0.040%, Mn: 0.01% to 0.50%, N: 0.020% or less, S: 0.005% to 0.040%, P: 0.030% or less, Cu: 0% to 0.50%, Cr: 0% to 0.50%, Sn: 0% to 0.50%, Se: 0% to 0.020%, Sb: 0% to 0.500%, and Mo: 0% to 0.10%, and a remainder is Fe and impurities.

7. The method for manufacturing the grain-oriented electrical steel sheet according to claim 3, wherein the decarburization annealing step has a temperature raising process and a soaking process, in the temperature raising process, a temperature rising rate from 550? C. to 750? C. is set to 700 to 2,000? C./sec, an oxygen potential is set to 0.0001 to 0.0100, and the soaking process includes a first soaking process where an annealing temperature is set to 800? C. to 900? C. and an annealing time is set to 100 to 500 seconds in an atmosphere having an oxygen potential of 0.4 or more and 0.8 or less and a second soaking process where an annealing temperature is set to 850? C. or higher and 1,000? C. or lower and an annealing time is set to 5 seconds or longer and 100 seconds or shorter in an atmosphere having an oxygen potential of 0.1 or less.

8. The method for manufacturing the grain-oriented electrical steel sheet according to claim 3, the method further comprising, during the decarburization annealing step or after the decarburization annealing step: a nitriding treatment step of performing a nitriding treatment on the cold-rolled steel sheet.

9. A method for manufacturing the grain-oriented electrical steel sheet according to claim 2, the method comprising: a hot rolling step of heating a steel piece to obtain a hot-rolled steel sheet by hot rolling; a hot-rolled sheet annealing step of performing hot-rolled sheet annealing on the hot-rolled steel sheet; a pickling step of pickling the hot-rolled steel sheet after the hot-rolled sheet annealing step; a cold rolling step of performing cold rolling once or a plurality of times with annealing therebetween on the hot-rolled steel sheet after the pickling step to obtain a cold-rolled steel sheet; a decarburization annealing step of performing decarburization annealing on the cold-rolled steel sheet; a final annealing step of applying and drying an annealing separating agent containing a MgO powder as a main component onto front and rear surfaces of the cold-rolled steel sheet after the decarburization annealing step, which is the base steel sheet, and performing final annealing to form glass coatings; a coating-forming step of forming tension-applied insulation coatings on the glass coatings to obtain a grain-oriented electrical steel sheet including the base steel sheet, the glass coatings formed on the base steel sheet, and the tension-applied insulation coatings formed on the glass coatings; and a magnetic domain segmentation step of irradiating surfaces of the tension-applied insulation coatings of the grain-oriented electrical steel sheet with an energy ray to form a plurality of linear strain regions on the base steel sheet, wherein, in the magnetic domain segmentation step, among the plurality of linear strain regions, intervals of linear strain regions adjacent to each other in a rolling direction are 10 mm or less, an energy ray power density Ip in a unit of W/mm.sup.2 that is defined by (P/S) using an energy ray output P in a unit of W and an energy ray irradiation cross-sectional area S in a unit of mm.sup.2 satisfies the following expression (5), an energy ray input energy Up in a unit of J/mm that is defined by P/Vs using the energy ray output P and an energy ray scanning velocity Vs in a unit of mm/sec satisfies the following expression (6), and a beam aspect ratio of the energy ray, which is defined by (dl/dc) using a diameter dl in a direction perpendicular to a beam scanning direction and a diameter de in the beam scanning direction, in a unit of ?m, and the dl each satisfy the following expression (7) and the following expression (8),
250?Ip?2,000(5)
0.010<Up?0.050(6)
0.0010<dl/dc<1.0000(7)
10<dl<200(8).

10. The method for manufacturing the grain-oriented electrical steel sheet according to claim 4, wherein the steel piece contains, by mass %, C: 0.010% to 0.200%, Si: 3.00% to 4.00%, sol. Al: 0.010% to 0.040%, Mn: 0.01% to 0.50%, N: 0.020% or less, S: 0.005% to 0.040%, P: 0.030% or less, Cu: 0% to 0.50%, Cr: 0% to 0.50%, Sn: 0% to 0.50%, Se: 0% to 0.020%, Sb: 0% to 0.500%, and Mo: 0% to 0.10%, and a remainder is Fe and impurities.

11. The method for manufacturing the grain-oriented electrical steel sheet according to claim 5, wherein the steel piece contains, by mass %, C: 0.010% to 0.200%, Si: 3.00% to 4.00%, sol. Al: 0.010% to 0.040%, Mn: 0.01% to 0.50%, N: 0.020% or less, S: 0.005% to 0.040%, P: 0.030% or less, Cu: 0% to 0.50%, Cr: 0% to 0.50%, Sn: 0% to 0.50%, Se: 0% to 0.020%, Sb: 0% to 0.500%, and Mo: 0% to 0.10%, and a remainder is Fe and impurities.

12. The method for manufacturing the grain-oriented electrical steel sheet according to claim 4, wherein the decarburization annealing step has a temperature raising process and a soaking process, in the temperature raising process, a temperature rising rate from 550? C. to 750? C. is set to 700 to 2,000? C./sec, an oxygen potential is set to 0.0001 to 0.0100, and the soaking process includes a first soaking process where an annealing temperature is set to 800? C. to 900? C. and an annealing time is set to 100 to 500 seconds in an atmosphere having an oxygen potential of 0.4 or more and 0.8 or less and a second soaking process where an annealing temperature is set to 850? C. or higher and 1,000? C. or lower and an annealing time is set to 5 seconds or longer and 100 seconds or shorter in an atmosphere having an oxygen potential of 0.1 or less.

13. The method for manufacturing the grain-oriented electrical steel sheet according to claim 5, wherein the decarburization annealing step has a temperature raising process and a soaking process, in the temperature raising process, a temperature rising rate from 550? C. to 750? C. is set to 700 to 2,000? C./sec, an oxygen potential is set to 0.0001 to 0.0100, and the soaking process includes a first soaking process where an annealing temperature is set to 800? C. to 900? C. and an annealing time is set to 100 to 500 seconds in an atmosphere having an oxygen potential of 0.4 or more and 0.8 or less and a second soaking process where an annealing temperature is set to 850? C. or higher and 1,000? C. or lower and an annealing time is set to 5 seconds or longer and 100 seconds or shorter in an atmosphere having an oxygen potential of 0.1 or less.

14. The method for manufacturing the grain-oriented electrical steel sheet according to claim 6, wherein the decarburization annealing step has a temperature raising process and a soaking process, in the temperature raising process, a temperature rising rate from 550? C. to 750? C. is set to 700 to 2,000? C./sec, an oxygen potential is set to 0.0001 to 0.0100, and the soaking process includes a first soaking process where an annealing temperature is set to 800? C. to 900? C. and an annealing time is set to 100 to 500 seconds in an atmosphere having an oxygen potential of 0.4 or more and 0.8 or less and a second soaking process where an annealing temperature is set to 850? C. or higher and 1,000? C. or lower and an annealing time is set to 5 seconds or longer and 100 seconds or shorter in an atmosphere having an oxygen potential of 0.1 or less.

15. The method for manufacturing the grain-oriented electrical steel sheet according to claim 4, the method further comprising, during the decarburization annealing step or after the decarburization annealing step: a nitriding treatment step of performing a nitriding treatment on the cold-rolled steel sheet.

16. The method for manufacturing the grain-oriented electrical steel sheet according to claim 5, the method further comprising, during the decarburization annealing step or after the decarburization annealing step: a nitriding treatment step of performing a nitriding treatment on the cold-rolled steel sheet.

17. The method for manufacturing the grain-oriented electrical steel sheet according to claim 6, the method further comprising, during the decarburization annealing step or after the decarburization annealing step: a nitriding treatment step of performing a nitriding treatment on the cold-rolled steel sheet.

18. The method for manufacturing the grain-oriented electrical steel sheet according to claim 7, the method further comprising, during the decarburization annealing step or after the decarburization annealing step: a nitriding treatment step of performing a nitriding treatment on the cold-rolled steel sheet.

Description

EXAMPLES

[0193] Slabs having a chemical composition shown in Table 1 are manufactured. A hot rolling step is performed on these slabs. Specifically, the slabs are heated to 1350? C., and then hot rolling is performed on the slabs to manufacture hot-rolled steel sheets having a sheet thickness of 2.3 mm.

[0194] A hot-rolled sheet annealing step is performed on the hot-rolled steel sheets after the hot rolling step at an annealing temperature of 900? C. to 1200? C. for a holding time of 10 to 300 seconds.

[0195] After that, cold rolling is performed a plurality of times to obtain 0.17 to 0.27 mm cold-rolled steel sheets.

[0196] Decarburization annealing is performed on these cold-rolled steel sheets under conditions shown in Table 2A and Table 2B.

[0197] After the decarburization annealing, in test Nos. 11, 13, and 15, steel sheets are held at 700? C. to 850? C. for 10 to 60 seconds in a well-known nitriding treatment atmosphere (an atmosphere containing a gas having a nitriding ability such as hydrogen, nitrogen, or ammonia), and the N contents of the cold-rolled steel sheets after decarburization annealing are made to be 40 ppm or more and 1000 ppm or less.

[0198] A final annealing step is performed by applying an annealing separating agent containing magnesium oxide (MgO) as a main component to the surfaces of the steel sheets after a nitriding treatment in the test Nos. 11, 13, and 15 and after the decarburization annealing in the other test Nos. The final annealing temperature in the final annealing step is 1200? C., and the holding time at the final annealing temperature is 20 hours.

[0199] An insulation coating agent containing colloidal silica and phosphate as main components is applied to the surfaces (on glass coatings) of the steel sheets (grain-oriented electrical steel sheets) after cooling in the final annealing step and then baked to form tension-applied insulation coatings. A grain-oriented electrical steel sheet with each test number is manufactured by the above-described steps.

TABLE-US-00001 TABLE 1 Kind Slab (mass %, remainder: Fe and impurities) of steel C Si Mn P S sol. Al N Cu Cr Sn Se Sb Mo A 0.074 3.31 0.07 0.02 0.024 0.026 0.008 B 0.060 3.25 0.15 0.01 0.021 0.021 0.015 C 0.040 3.15 0.23 0.02 0.016 0.034 0.015 0.02 D 0.050 3.26 0.25 0.02 0.009 0.035 0.015 0.01 E 0.079 3.35 0.08 0.01 0.026 0.027 0.008 0.10 F 0.061 3.41 0.07 0.01 0.006 0.024 0.006 0.010 G 0.069 3.29 0.09 0.01 0.008 0.022 0.007 0.020 H 0.081 3.28 0.07 0.02 0.025 0.022 0.008 0.01

TABLE-US-00002 TABLE 2A Decarburization annealing step Temperature- raising process Temperature- First First Material 550? C. to 750? C. raising process soaking soaking First Second Second Second Kind temperature 550? C. to 750? C. soaking soaking soaking soaking soaking soaking Test of Thickness rising rate oxygen temperature time oxygen temperature time oxygen No. steel mm ? C./sec potential ? C. Sec potential ? C. Sec potential 1 A 0.27 800 0.0050 850 120 0.500 900 20 0.100 2 A 0.17 800 0.0002 850 120 0.500 900 20 0.100 3 A 0.17 800 0.0050 850 200 0.500 900 40 0.100 4 B 0.22 800 0.0002 850 200 0.600 900 40 0.100 5 B 0.22 800 0.0010 850 300 0.600 900 60 0.100 6 B 0.22 800 0.0090 850 300 0.600 900 60 0.050 7 C 0.22 1000 0.0010 850 400 0.700 900 80 0.050 8 D 0.22 1000 0.0002 850 400 0.700 900 80 0.050 9 A 0.27 1000 0.0006 850 480 0.700 900 90 0.100 10 A 0.17 1200 0.0008 810 140 0.430 930 15 0.010 11 E 0.27 1200 0.0040 820 120 0.420 930 15 0.010 12 D 0.17 1200 0.0090 820 120 0.500 930 15 0.010 13 B 0.17 1200 0.0010 830 120 0.500 930 15 0.010 14 E 0.27 1000 0.0006 900 200 0.500 1000 20 0.100 15 A 0.22 1000 0.0002 820 120 0.500 950 10 0.005 16 A 0.19 1000 0.0090 820 120 0.410 930 10 0.005 17 E 0.19 1000 0.0010 820 140 0.450 930 20 0.005 18 D 0.27 1900 0.0030 900 300 0.600 1000 60 0.100 19 H 0.19 1200 0.0003 830 120 0.420 950 10 0.010 20 E 0.27 1900 0.0010 900 400 0.700 1000 60 0.100 21 E 0.22 1200 0.0060 830 120 0.410 950 10 0.010 22 B 0.17 1900 0.0009 900 480 0.700 1000 80 0.100 23 A 0.22 1900 0.0010 900 480 0.700 1000 80 0.100 24 C 0.22 1900 0.0009 900 480 0.700 1000 80 0.100 25 D 0.17 400 0.0010 850 120 0.500 900 20 0.050 26 E 0.17 800 0.0030 950 120 0.500 900 40 0.050

TABLE-US-00003 TABLE 2B Decarburization annealing step Temperature- raising process Temperature- First First Material 550? C. to 750? C. raising process soaking soaking First Second Second Second Kind temperature 550? C. to 750? C. soaking soaking soaking soaking soaking soaking Test of Thickness rising rate oxygen temperature time oxygen temperature time oxygen No. steel mm ? C./sec potential ? C. Sec potential ? C. Sec potential 27 Q 0.17 1200 0.0020 800 120 0.600 900 60 0.050 28 A 0.17 1500 0.0002 850 60 0.600 900 80 0.050 29 B 0.17 1800 0.0006 850 600 0.700 900 90 0.050 30 C 0.17 1200 0.0003 850 120 0.300 1000 20 0.050 31 E 0.17 800 0.0040 850 120 0.900 1000 40 0.050 32 F 0.17 2000 0.0030 850 200 0.500 1000 60 0.050 33 B 0.22 2500 0.0010 850 200 0.500 1000 80 0.050 34 G 0.22 900 0.0090 850 200 0.500 1000 90 0.050 35 G 0.22 1500 0.0020 850 300 0.600 1000 60 0.050 36 E 0.22 1600 0.0006 850 300 0.600 800 10 0.050 37 A 0.22 1800 0.0030 850 300 0.700 800 120 0.050 38 F 0.22 1900 0.0002 900 120 0.700 800 60 0.200 39 D 0.22 1900 0.0003 900 120 0.600 800 40 0.050 40 D 0.27 1900 0.0002 900 200 0.600 900 20 0.050 41 B 0.27 1300 0.0009 900 200 0.600 900 120 0.050 42 B 0.27 1000 0.0003 900 300 0.500 900 10 0.200 43 E 0.27 1500 0.0030 900 300 0.500 900 10 0.200 44 E 0.27 1200 0.0030 900 400 0.600 1050 10 0.050 45 C 0.27 1200 0.0090 900 400 0.600 1050 80 0.200 46 A 0.27 1000 0.0080 900 480 0.700 1050 10 0.050 47 C 0.27 1800 0.0010 900 480 0.700 1050 80 0.200 48 D 0.27 1800 0.0200 900 480 0.700 1000 80 0.050 49 F 0.27 1800 0.0001 900 480 0.700 1000 80 0.050 50 A 0.22 1000 0.0090 820 120 0.410 930 10 0.005 51 A 0.22 1000 0.0090 820 120 0.410 930 10 0.005 52 C 0.22 1000 0.0090 820 120 0.410 930 10 0.005

[Analysis of Chemical Composition of Base Steel Sheet]

[0200] The chemical composition of the base steel sheet of the grain-oriented electrical steel sheet with each test number before magnetic domain segmentation obtained by the above-described method is obtained by the following method. First, the tension-applied insulation coating is removed from the grain-oriented electrical steel sheet with each test number. Specifically, the grain-oriented electrical steel sheet is immersed in a sodium hydroxide aqueous solution (80? C. to 90? C.) containing NaOH: 30 to 50 mass % and H.sub.2O: 50 to 70 mass % for 7 to 10 minutes. The grain-oriented electrical steel sheet after the immersion (the grain-oriented electrical steel sheet from which the tension-applied insulation coating has been removed) is washed with water. After the water washing, the grain-oriented electrical steel sheet is dried with a warm air blower for a little less than 1 minute.

[0201] Next, the glass coating is removed from the grain-oriented electrical steel sheet including no tension-applied insulation coating. Specifically, the grain-oriented electrical steel sheet is immersed in a hydrochloric acid aqueous solution (80? C. to) 90? C. containing 30 to 40 mass % of HCL for 1 to 10 minutes. Thereby, the glass coating is removed from the base steel sheet. The base steel sheet after the immersion is washed with water. After the water washing, the grain-oriented electrical steel sheet is dried with a warm air blower for a little less than 1 minute. The base steel sheet is taken out from the grain-oriented electrical steel sheet by the above-described step.

[0202] The chemical composition of the taken-out base steel sheet is obtained by a well-known component analysis method. Specifically, chips are generated from the base steel sheet using a drill, and the chips are collected. The collected chips are dissolved in an acid to obtain a solution. ICP-AES is performed on the solution to perform an elemental analysis of the chemical composition. Si in the chemical composition of the base steel sheet is obtained by a method specified in JIS G 1212: 1997 (Methods for Determination of Silicon Content). Specifically, when the above-described chips are dissolved in an acid, silicon oxide is precipitated as a precipitate. This precipitate (silicon oxide) is filtered out with filter paper, and the mass is measured, thereby obtaining the Si content. The C content and the S content are obtained by a well-known high-frequency combustion method (combustion-infrared absorption method). Specifically, the above-described solution is combusted by high-frequency heating in an oxygen stream, carbon dioxide and sulfur dioxide generated are detected, and the C content and the S content are obtained. The N content is obtained using a well-known inert gas melting-thermal conductivity method. The chemical composition of the base steel sheet is obtained by the above-described analysis method. The chemical composition of the steel sheet (base steel sheet) with each test number is as shown in Table 3. - in Table 3 indicates that the corresponding element content is less than the detection limit.

[Evaluation of Magnetic Characteristics]

[0203] While not shown in the table, a sample having a width of 60 mm and a length of 300 mm including the sheet width center position is collected from the grain-oriented electrical steel sheet with each test number. The length of the sample is set to be parallel to the rolling direction. The collected sample is held at 800? C. for 2 hours in a nitrogen atmosphere having a dew point of 0? C. or lower, and strains introduced at the time of sample collection are removed.

[0204] The magnetic flux density (T) is obtained by a single sheet magnetic characteristics test (SST test) in accordance with JIS C2556 (2015) using this sample. Specifically, a magnetic field of 800 A/m is applied to the sample, and the magnetic flux density (T) is obtained.

[0205] Furthermore, the iron loss W.sub.17/50 (W/kg) at a frequency set to 50 Hz and a maximum magnetic flux density set to 1.7 Tis measured in accordance with JIS C2556 (2015) using the sample.

TABLE-US-00004 TABLE 3 Kind Steel sheet (mass %, remainder: Fe and impurities) of steel C Si Mn P S sol. Al N Cu Cr Sr Se Sb Mo A 0.001 3.20 0.07 0.02 <0.002 <0.004 <0.002 B 0.001 3.15 0.15 0.01 <0.002 <0.004 <0.002 C 0.001 3.05 0.23 0.02 <0.002 <0.004 <0.002 0.02 D 0.001 3.15 0.25 0.02 <0.002 <0.004 <0.002 0.01 E 0.001 3.24 0.08 0.01 <0.002 <0.004 <0.002 0.10 F 0.001 3.30 0.07 0.01 <0.002 <0.004 <0.002 0.005 G 0.001 3.18 0.09 0.01 <0.002 <0.004 <0.002 0.020 H 0.001 3.17 0.07 0.02 <0.002 <0.004 <0.002 0.01

[0206] In addition, on the obtained grain-oriented electrical steel sheet with each test number (after the tension-applied insulation coating was formed), magnetic domain segmentation is performed by irradiating the surface of the steel sheet with an energy ray using a laser (fiber laser or pulsed laser) or an electron beam under conditions shown in Table 4A and Table 4B, and evaluation tests of the noise characteristics and the magnetic characteristics are performed. In addition, the overall thickness of the glass coating is measured by the above-described method, and then the area ratios $1, S2, and S3 of the MgAl.sub.2O.sub.4 phase in each region are also measured.

TABLE-US-00005 TABLE 4A Magnetic domain segmentation step Deviation angle with respect to direction Intervals Width of Laser/ perpendicular to in rolling linear Test electron Continuous/ Ip Up dl rolling direction direction strain No. beam intermittent W/mm.sup.2 J/mm dl/dc ?m ? mm ?m 1 Laser Continuous 320 0.004 0.0032 40 10 5 50 2 Laser Intermittent 438 0.012 0.0101 90 20 8 100 3 Laser Continuous 400 0.011 0.0061 70 5 4 80 4 Laser Continuous 333 0.017 0.0043 80 5 4 90 5 Laser Continuous 37 0.005 0.0015 150 10 5 160 6 Laser Intermittent 433 0.026 0.0171 160 8 3 170 7 Laser Continuous 450 0.045 0.0162 180 15 7 190 8 Laser Continuous 1300 0.033 0.0484 220 25 8 230 9 Laser Intermittent 84 0.080 0.0027 225 10 9 235 10 Laser Continuous 550 0.037 0.0030 95 5 4 105 11 Laser Continuous 283 0.043 0.0022 115 15 9 125 12 Laser Continuous 238 0.038 0.0025 140 28 8 150 13 Laser Intermittent 1800 0.045 0.0121 110 10 7 120 14 Laser Continuous 90 0.036 0.0028 235 20 6 245 15 Laser Continuous 253 0.038 0.0039 170 5 7 180 16 Laser Intermittent 1100 0.044 0.0085 130 0 6 140 17 Laser Intermittent 1533 0.042 0.0160 155 10 5 165 18 Laser Intermittent 250 0.056 0.0016 125 20 6 135 19 Laser Continuous 50 0.048 0.0009 210 8 5 220 20 Laser Continuous 2083 0.056 0.0241 170 5 5 180 21 Laser Continuous 2000 0.050 0.0241 190 0 6 200 22 Laser Continuous 2000 0.050 0.0241 190 3 12 200 23 Laser Continuous 3800 0.011 0.0064 40 5 4 50 24 Laser Continuous 2273 0.004 0.0073 40 3 3 50 25 Laser Continuous 500 0.044 0.0020 90 5 4 100 26 Laser Continuous 500 0.044 0.0020 90 5 4 100

TABLE-US-00006 TABLE 4B Magnetic domain segmentation step Deviation angle with respect to direction Intervals Width of Laser/ perpendicular to in rolling linear Test electron Continuous/ Ip Up dl rolling direction direction strain No. beam intermittent W/mm.sup.2 J/mm dl/dc ?m ? mm ?m 27 Laser Continuous 500 0.044 0.0020 90 5 4 100 28 Laser Continuous 500 0.044 0.0020 90 5 4 100 29 Laser Continuous 500 0.044 0.0020 90 5 4 100 30 Laser Continuous 500 0.044 0.0020 90 5 4 100 31 Laser Continuous 500 0.044 0.0020 90 5 4 100 32 Laser Continuous 500 0.044 0.0020 90 5 4 100 33 Laser Continuous 500 0.044 0.0020 90 5 4 100 34 Laser Continuous 500 0.044 0.0020 90 5 4 100 35 Laser Continuous 500 0.044 0.0020 90 5 4 100 36 Laser Continuous 500 0.044 0.0020 90 5 4 100 37 Laser Continuous 500 0.044 0.0020 90 5 4 100 38 Laser Continuous 500 0.044 0.0020 90 5 4 100 39 Laser Continuous 500 0.044 0.0020 90 5 4 100 40 Laser Continuous 500 0.044 0.0020 90 5 4 100 41 Laser Continuous 500 0.044 0.0020 90 5 4 100 42 Laser Continuous 500 0.044 0.0020 90 5 4 100 43 Laser Continuous 500 0.044 0.0020 90 5 4 100 44 Laser Continuous 500 0.044 0.0020 90 5 4 100 45 Laser Continuous 500 0.044 0.0020 90 5 4 100 46 Laser Continuous 500 0.044 0.0020 90 5 4 100 47 Laser Continuous 500 0.044 0.0020 90 5 4 100 48 Laser Continuous 500 0.044 0.0020 90 5 4 100 49 Laser Continuous 500 0.044 0.0020 90 5 4 100 50 Laser Continuous 1000 0.040 0.0009 100 5 6 110 51 Laser Continuous 1000 0.040 1.0000 100 5 6 110 52 Laser Continuous 1000 0.040 5.0000 100 5 6 110

[Evaluation of Noise Characteristics and Magnetostriction]

[0207] A sample having width of 100 mm and a length of 500 mm is collected from each grain-oriented electrical steel sheet. The length direction of the sample is made to correspond to the rolling direction RD, and the width direction is made to correspond to the sheet width direction TD.

[0208] From the sample, magnetostriction is measured by an AC magnetostriction measuring method using a magnetostriction measuring instrument. As the magnetostriction measuring instrument, an apparatus including a laser Doppler vibrometer, an exciting coil, an exciting power supply, a magnetic flux detecting coil, an amplifier, and an oscilloscope is used.

[0209] Specifically, an AC magnetic field is applied to the sample so that the maximum magnetic flux density in the rolling direction is 1.7 T and the frequency is 50 Hz. A change in the length of the sample caused by the expansion and contraction of the magnetic domains is measured with the laser Doppler vibrometer, and a magnetostriction signal is obtained. Fourier analysis is performed on the obtained magnetostriction signal to obtain an amplitude Cn of each frequency component fn (n is a natural number of 1 or more) of the magnetostriction signal. A magnetostriction rate level LVA (dB) represented by the following expression is obtained using an A correction coefficient an of each frequency component fn.

LVA=20?Log(?(?(?c?2??fn??n?Cn/?2).sup.2)/Pe0)

[0210] Here, ?c is an intrinsic acoustic resistance, and ?c is set to 400. Pe0 is the minimum audible sound pressure, and Pe0=2?10.sup.?5 (Pa) is used. As the A correction coefficient ?n, values shown in Table 2 of JIS C 1509-1 (2005) are used.

[0211] Based on the obtained magnetostriction rate level (LVA), the noise characteristics are evaluated according to the following criteria. When the magnetostriction rate level is less than 60 dBA, the grain-oriented electrical steel sheet is determined as excellent in terms of noise characteristics.

[0212] Furthermore, magnetostriction ?.sub.0-p (?m/m) is obtained from the magnetostriction signal. Specifically, from the length Lp (?m) of the test piece (steel sheet) at a magnetic flux density of 1.7 T and the length L.sub.0 (m) of the test piece at a magnetic flux density of 0 T under the above excitation conditions, ?.sub.0-p is calculated from (Lp?L.sub.0)/L.sub.0.

[0213] Furthermore, regarding the steel sheet on which the heat treatment has been performed at 800? C. for 4 hours, the magnetostriction ?.sub.0-p (?m/m) is measured in the same manner when the frequency is set to 50 Hz and the maximum magnetic flux density is set to 1.7 T. In addition, ?.sub.0-pb-?.sub.0-pa is obtained where ?.sub.0-pb indicates magnetostriction before the heat treatment and ?.sub.0-pa indicates magnetostriction after the heat treatment.

[0214] The results are shown in Table 5A, Table 5B, Table 6A, and Table 6B.

[Evaluation of Magnetic Characteristics]

[0215] A sample having a width of 60 mm and a length of 300 mm including the sheet width center position is collected from the grain-oriented electrical steel sheet with each test number. The length of the sample is set to be parallel to the rolling direction. The collected sample is held at 800? C. for 2 hours in a nitrogen atmosphere having a dew point of 0? C. or lower, and strains introduced at the time of sample collection are removed.

[0216] The magnetic flux density (T) is obtained by a single sheet magnetic characteristics test (SST test) in accordance with JIS C2556 (2015) using this sample. Specifically, a magnetic field of 800 A/m is applied to the sample, and the magnetic flux density (T) is obtained.

[0217] Furthermore, the iron loss W.sub.17/50 (W/kg) at a frequency set to 50 Hz and a maximum magnetic flux density set to 1.7 T is measured in accordance with JIS C2556 (2015) using the sample. In a case where the iron loss improvement ratio of 5.0% or more is satisfied, the iron loss improvement ratio is determined as excellent. The measurement results are shown in Table 6A and Table 6B.

[Coating Adhesion]

[0218] The coating adhesion (coating residual area ratio) of the grain-oriented electrical steel sheet is measured by the above-described method. When the coating residual area ratio is 50% or more, the coating adhesion is determined as acceptable (evaluation ?), and, when the coating adhesion is 90% or more, the coating adhesion is determined as excellent (evaluation ?). The evaluation results are shown in Table 6A and Table 6B:

TABLE-US-00007 TABLE 5A Overall Magnetostriction thickness of Area ratio of Mg.sub.2AlO.sub.4 phase Test ?.sub.0-pb ? glass coating (S1 + S1 > No. ?.sub.0-pa ?.sub.0-pb ?.sub.0-pa ?m S1 S2 S3 S2 + S3)/3 S2 > S3 1 ?0.82 ?0.81 0.01 2.2 0.60 0.12 0.01 0.24 ? 2 ?0.87 ?0.84 0.03 2.0 0.50 0.15 0.02 0.22 ? 3 ?0.89 ?0.78 0.11 3.4 0.65 0.16 0.00 0.27 ? 4 ?0.81 ?0.74 0.07 2.2 0.64 0.15 0.02 0.27 ? 5 ?0.89 ?0.88 0.01 3.0 0.67 0.20 0.02 0.30 ? 6 ?0.92 ?0.74 0.18 2.7 0.70 0.14 0.08 0.31 ? 7 ?0.87 ?0.78 0.09 2.6 0.62 0.16 0.05 0.28 ? 8 ?0.96 ?0.84 0.12 2.2 0.59 0.18 0.06 0.28 ? 9 ?0.91 ?0.90 0.01 3.5 0.57 0.19 0.07 0.28 ? 10 ?0.85 ?0.66 0.19 2.0 0.64 0.20 0.05 0.30 ? 11 ?0.86 ?0.84 0.02 2.1 0.48 0.25 0.04 0.26 ? 12 ?0.92 ?0.91 0.01 2.1 0.67 0.23 0.01 0.30 ? 13 ?0.91 ?0.73 0.18 2.7 0.64 0.19 0.06 0.30 ? 14 ?0.84 ?0.83 0.01 1.9 0.58 0.14 0.08 0.27 ? 15 ?0.89 ?0.81 0.08 2.9 0.67 0.18 0.09 0.31 ? 16 ?0.91 ?0.77 0.14 3.4 0.66 0.24 0.08 0.33 ? 17 ?0.84 ?0.69 0.15 2.9 0.54 0.15 0.04 0.24 ? 18 ?0.81 ?0.51 0.30 2.3 0.57 0.27 0.03 0.29 ? 19 ?0.94 ?0.78 0.16 2.4 0.54 0.22 0.01 0.26 ? 20 ?0.85 ?0.40 0.45 1.9 0.56 0.16 0.08 0.27 ? 21 ?0.91 ?0.71 0.20 3.1 0.59 0.18 0.00 0.26 ? 22 ?0.88 ?0.87 0.01 3.4 0.64 0.11 0.06 0.27 ? 23 ?0.89 ?0.51 0.38 3.2 0.67 0.19 0.07 0.31 ? 24 ?0.84 ?0.83 0.01 1.6 0.69 0.20 0.05 0.31 ? 25 ?0.95 ?0.76 0.19 2.5 0.41 0.43 0.19 0.34 x 26 ?0.84 ?0.67 0.17 1.8 0.43 0.45 0.12 0.33 x

TABLE-US-00008 TABLE 5B Overall Magnetostriction thickness of Area ratio of Mg.sub.2AlO.sub.4 phase Test. ?.sub.0-pb ? glass coating (S1 + S1 > No. ?.sub.0-pa ?.sub.0-pb ?.sub.0-pa ?m S1 S2 S3 S2 + S3)/3 S2 > S3 27 ?0.9 ?0.74 0.16 2.2 0.43 0.46 0.09 0.33 x 28 ?0.87 ?0.69 0.18 3.1 0.60 0.26 0.13 0.33 ? 29 ?0.89 ?0.73 0.16 3.1 0.65 0.32 0.17 0.38 ? 30 ?0.92 ?0.75 0.17 2.3 0.68 0.40 0.13 0.40 ? 31 ?0.86 ?0.71 0.15 1.6 0.53 0.26 0.15 0.31 ? 32 ?0.97 ?0.79 0.18 2.8 0.48 0.46 0.06 0.33 ? 33 ?0.91 ?0.76 0.15 2.5 0.61 0.41 0.19 0.40 ? 34 ?0.89 ?0.75 0.14 2.6 0.53 0.19 0.09 0.27 ? 35 ?0.88 ?0.74 0.14 3.1 0.54 0.29 0.06 0.30 ? 36 ?0.94 ?0.78 0.16 3.3 0.51 0.28 0.15 0.31 ? 37 ?0.81 ?0.65 0.16 2.6 0.63 0.22 0.16 0.34 ? 38 ?0.86 ?0.69 0.17 1.9 0.64 0.27 0.14 0.35 ? 39 ?0.94 ?0.80 0.14 2.4 0.68 0.19 0.14 0.34 ? 40 ?0.86 ?0.71 0.15 1.7 0.67 0.42 0.07 0.39 ? 41 ?0.87 ?0.73 0.14 2.7 0.70 0.60 0.40 0.57 ? 42 ?0.94 ?0.78 0.16 1.8 0.67 0.43 0.18 0.43 ? 43 ?0.93 ?0.78 0.15 2.1 0.69 0.43 0.14 0.42 ? 44 ?0.92 ?0.75 0.17 3.0 0.65 0.31 0.17 0.38 ? 45 ?0.9 ?0.74 0.16 2.5 0.67 0.34 0.19 0.40 ? 46 ?0.84 ?0.70 0.14 2.1 0.71 0.27 0.15 0.38 ? 47 ?0.86 ?0.71 0.15 2.4 0.68 0.26 0.18 0.37 ? 48 ?0.82 ?0.69 0.13 3.1 0.65 0.24 0.15 0.35 ? 49 ?0.88 ?0.69 0.19 1.6 0.72 0.23 0.11 0.35 ? 50 ?0.91 ?0.89 0.02 3.2 0.67 0.26 0.07 0.33 ? 51 ?0.92 ?0.70 0.22 2.6 0.68 0.23 0.08 0.33 ? 52 ?0.91 ?0.62 0.29 2.8 0.70 0.30 0.06 0.35 ?

TABLE-US-00009 TABLE 6A Magnetic characteristics Magnetic Iron loss Iron loss Coating Iron flux improvement improvement Noise residual Iron Test loss density ratio ratio characteristics area ratio loss/noise Coating No. W/kg T % 5% or more ? dB % balance evaluation 1 0.80 1.91 4.8 X 49 100 X ? 2 0.72 1.91 7.9 ? 47 99 ? ? 3 0.71 1.91 8.6 ? 50 98 ? ? 4 0.74 1.91 8.1 ? 52 98 ? ? 5 0.81 1.91 0.0 X 47 100 X ? 6 0.73 1.91 10.5 ? 57 94 ? ? 7 0.74 1.90 8.6 ? 53 96 ? ? 8 0.74 1.91 9.1 ? 60 95 X ? 9 0.80 1.92 4.8 X 49 98 X ? 10 0.69 1.90 11.6 ? 57 91 ? ? 11 0.79 1.91 6.0 ? 49 96 ? ? 12 0.81 1.91 3.8 ? 50 95 X ? 13 0.69 1.90 11.9 ? 58 93 ? ? 14 0.82 1.92 2.4 X 49 100 X ? 15 0.76 1.91 6.2 ? 49 97 ? ? 16 0.73 1.90 9.8 ? 57 96 ? ? 17 0.72 1.90 10.9 ? 59 95 ? ? 18 0.77 1.90 8.1 ? 60 96 X ? 19 0.78 1.91 0.0 ? 51 95 X ? 20 0.74 1.89 11.4 ? 63 92 X ? 21 0.68 1.90 12.8 ? 59 91 ? ? 22 0.76 1.91 2.6 X 55 100 X ? 23 0.71 1.90 12.3 ? 63 91 X ? 24 0.78 1.90 3.7 X 57 99 X ? 25 0.69 1.91 12.0 ? 57 50 ? ? 26 0.69 1.91 11.6 ? 58 60 ? ?

TABLE-US-00010 TABLE 6B Magnetic characteristics Magnetic Iron loss Iron loss Coating Iron flux improvement improvement Noise residual Iron Test loss density ratio ratio characteristics area ratio loss/noise Coating No. W/kg T % 5% or more ? dB % balance evaluation 27 0.69 1.91 11.2 ? 58 65 ? ? 28 0.69 1.91 10.9 ? 57 70 ? ? 29 0.69 1.91 11.8 ? 57 60 ? ? 30 0.69 1.91 11.3 ? 57 65 ? ? 31 0.69 1.91 11.6 ? 58 60 ? ? 32 0.70 1.91 10.7 ? 57 95 ? ? 33 0.73 1.91 10.3 ? 58 60 ? ? 34 0.72 1.91 10.6 ? 58 96 ? ? 35 0.73 1.91 10.3 ? 58 95 ? ? 36 0.72 1.91 10.7 ? 58 65 ? ? 37 0.72 1.91 10.6 ? 57 60 ? ? 38 0.73 1.91 10.1 ? 58 70 ? ? 39 0.73 1.91 10.4 ? 58 65 ? ? 40 0.76 1.91 9.6 ? 58 96 ? ? 41 0.76 1.91 9.5 ? 57 80 ? ? 42 0.76 1.91 9.1 ? 58 75 ? ? 43 0.76 1.91 9.2 ? 58 80 ? ? 44 0.76 1.91 9.2 ? 58 70 ? ? 45 0.76 1.91 10.0 ? 58 65 ? ? 46 0.76 1.91 9.8 ? 58 70 ? ? 47 0.76 1.91 9.0 ? 57 75 ? ? 48 0.76 1.91 9.2 ? 56 70 ? ? 49 0.76 1.91 9.4 ? 58 75 ? ? 50 0.78 1.90 3.7 ? 57 96 X ? 51 0.76 1.90 6.2 ? 60 97 X ? 52 0.75 1.90 7.4 ? 61 96 X ?

[0219] As is clear from Table 1 to Table 6B, in the steel sheets (invention examples) in which strain regions are preferably present and ?.sub.0-pb-?.sub.0-pa is within the scope of the present invention, itis possible to ensure a favorable iron loss/noise balance. Furthermore, in the steel sheets in which ?.sub.0-pb-?.sub.0-pa is within the scope of the present invention and it is possible to ensure a favorable iron loss/noise balance, in a case where the area ratio of the MgAl.sub.2O.sub.4 phase in the glass coating in each region satisfies the preferable relationship, the coating residual area ratio is sufficiently high, and favorable adhesion can also be satisfied.

[0220] On the other hand, in the steel sheets in which ?.sub.0-pb-?.sub.0-pa is outside the scope of the present invention and it is not possible to ensure a favorable iron loss/noise balance, the influence of the area ratio of the MgAl.sub.2O.sub.4 phase in the glass coating on the coating residual area ratio is not clear.

INDUSTRIAL APPLICABILITY

[0221] According to the present invention, it is possible to provide a grain-oriented electrical steel sheet having a favorable iron loss/noise balance and a method for manufacturing the same. In addition, according to a preferable aspect of the present invention, it is possible to provide a grain-oriented electrical steel sheet having a favorable iron loss/noise balance and also being excellent in terms of coating adhesion. Therefore, the industrial applicability is high.