Grain-oriented electromagnetic steel sheet and method for manufacturing grain-oriented electromagnetic steel sheet

Abstract

Provided is a grain-oriented electromagnetic steel sheet capable of exhibiting excellent magnetic characteristics and excellent iron loss characteristics as well as excellent noise characteristics. A grain-oriented electromagnetic steel sheet according to the present disclosure includes a base steel sheet, wherein, when the crystal orientation is measured by X-ray diffraction at measurement points arranged at a pitch of 2 mm in each of the rolling direction and a direction perpendicular to the rolling direction on the surface of the base steel sheet, the ratio R{211}<011> of the number of measurement points having an orientation difference of 15° or less from {211}<011> orientation to the total number of measurement points is 5% or less, the ratio R{110}<112> of the number of measurement points having an orientation difference of 15° or less from {110}<112> orientation to the total number of measurement points is 5% or less, the ratio R{110}<001> of the number of measurement points having an orientation difference of 15° or less from {110}<001> orientation to the total number of measurement points is at least 90%, and the high-angle boundary ratio RL=LI / La, which is the ratio of the total length LI of grain boundaries having an orientation difference of at least 15° to the total length La of grain boundaries, is 5-30%.

Description

Grain-oriented electrical steel sheet and manufacturing method thereof

[0001] The present disclosure relates to a grain-oriented electrical steel sheet and a method for manufacturing the same.

[0002] Grain-oriented electrical steel sheets are soft magnetic materials and are primarily used as iron core materials for transformers. Grain-oriented electrical steel sheets are primarily composed of crystal grains oriented in the {110}<001> direction (Goss-oriented grains). The size of the Goss-oriented grains is on the order of millimeters. Grain-oriented electrical steel sheets are manufactured by preferentially growing the Goss-oriented grains through a phenomenon called secondary recrystallization.

[0003] Grain-oriented electrical steel sheets are required to have excellent magnetic properties (high magnetic flux density and low iron loss). With regard to magnetic flux density, the higher the concentration of Goss-oriented grains, the better the magnetic flux density that can be obtained.

[0004] On the other hand, iron loss is expressed as the sum of hysteresis loss and eddy current loss. Hysteresis loss depends on crystal orientation, etc. Eddy current loss depends on sheet thickness, resistivity, magnetic domain size, etc. In order to reduce iron loss, it is effective to reduce hysteresis loss and eddy current loss. Increasing the degree of integration in the Goss orientation is known as a method for reducing hysteresis loss. Other known methods for reducing eddy current loss include increasing the content of elements that increase electrical resistance, such as Si, reducing the thickness of the steel sheet, and subdividing magnetic domains.

[0005] Recently, methods of reducing iron loss by reducing the sheet thickness have been investigated. However, reducing the sheet thickness increases the reduction ratio in cold rolling during the manufacturing process of grain-oriented electrical steel sheets. In this case, it may not be possible to consistently obtain excellent magnetic properties.

[0006] Therefore, means for improving the magnetic properties of grain-oriented electrical steel sheets even when the cold rolling reduction is high have been proposed, for example, in JP-A-6-145799 (Patent Document 1) and JP-A-7-62438 (Patent Document 2).

[0007] Patent Document 1 proposes a method for manufacturing grain-oriented electrical steel sheets by performing two cold rolling steps with intermediate annealing in between. Specifically, hot rolling is completed at 850°C or higher, and the steel sheet is immediately cooled and coiled at 600°C or lower. Then, prior to the first cold rolling step, the steel sheet is subjected to a carbide adjustment heat treatment in which the steel sheet is soaked for 2 to 10 seconds in a temperature range of 650 to 900°C. Patent Document 1 states that this allows for excellent magnetic flux density to be obtained even in thin grain-oriented electrical steel sheets.

[0008] Patent Document 2 proposes a method for manufacturing grain-oriented electrical steel sheet by performing two or more cold rolling steps with one intermediate annealing step in between. In Patent Document 2, the final cold rolling reduction is set to 89% or more. Furthermore, the steel sheet rolled to the final thickness is heat-treated to a temperature of 700°C or higher at a heating rate of 50°C / s or higher immediately before decarburization annealing. Patent Document 2 states that this makes it possible to obtain excellent magnetic flux density and excellent iron loss.

[0009] JP-A-6-145799 JP-A-7-62438

[0010] Excellent magnetic flux density and excellent core loss can also be obtained with the grain-oriented electrical steel sheets proposed in Patent Documents 1 and 2. However, excellent magnetic flux density and excellent core loss may also be obtained by other means.

[0011] Recently, there has been a growing demand for reduced noise and vibration in transformers. Therefore, grain-oriented electrical steel sheets are required to have not only excellent magnetic flux density and excellent core loss, but also excellent noise characteristics. Here, noise characteristics mean the ability to sufficiently reduce noise and vibration when the grain-oriented electrical steel sheet is installed in a transformer and in operation.

[0012] Magnetostriction of grain-oriented electrical steel sheets is cited as one of the factors that cause deterioration of noise characteristics (i.e., the generation of excessive noise and vibration). Magnetostriction here refers to vibrations observed in the rolling direction of grain-oriented electrical steel sheets, which are caused by slight changes in the outer shape of the grain-oriented electrical steel sheets due to changes in the strength of magnetization when the grain-oriented electrical steel sheets are excited with alternating current. The magnitude of magnetostriction is 10 －６Although it is an extremely small magnitude, the magnetostriction generates vibrations in the iron core, which then propagate to external structures such as the transformer tank, resulting in noise. The above-mentioned Patent Documents 1 and 2 do not consider noise characteristics.

[0013] An object of the present disclosure is to provide a grain-oriented electrical steel sheet that can provide excellent magnetic properties, excellent iron loss properties, and further excellent noise characteristics.

[0014] The grain-oriented electrical steel sheet of the present disclosure includes a base steel sheet, and the chemical composition of the base steel sheet is, in mass%, Si: 3.00 to 3.70%, Mn: 0.01 to 0.30%, N: 0.0001 to 0.0100%, C: 0.001 to 0.010%, sol. Al: 0-0.010%, one or more elements selected from the group consisting of S and Se: 0-0.010% in total, Ti: 0-0.010%, Ni: 0-0.50%, Cr: 0-0.50%, Cu: 0-0.50%, P: 0-0.05%, Mo: 0-0.05%, Sn: 0-0.30%, Sb: 0-0.30%, Bi: 0-0.0150%, Ta: 0-0.05%, Nb: 0-0.010%, V: 0-0.50%, B: 0-0.010%, Te: 0-0.0150%, and the balance being Fe and impurities. When the crystal orientation is measured by X-ray diffraction at measurement points arranged at 2 mm intervals in the rolling direction and in the direction perpendicular to the rolling direction on the surface of the base steel sheet, the ratio R of the number of measurement points whose orientation deviation from the {211}<011> orientation is 15° or less to all measurement points is ｛２１１｝＜０１１＞ is 5% or less, and the ratio R of the number of measurement points whose orientation deviation from the {110}<112> orientation is 15° or less to all measurement points ｛１１０｝＜１１２＞ is 5% or less, and the ratio R of the number of measurement points whose orientation deviation from the {110}<001> orientation is 15° or less to all measurement points ｛１１０｝＜００１＞ is 90% or more, and a high-angle grain boundary ratio RL=LI / La, which is the ratio of the total length LI of grain boundaries with a misorientation of 15° or more to the total length La of grain boundaries of crystal grains obtained from the misorientation at the measurement point, is 5% or more and 30% or less.

[0015] The method for producing a grain-oriented electrical steel sheet according to the present disclosure comprises, in mass %, Si: 3.00 to 3.70%, Mn: 0.01 to 0.30%, N: 0.0030 to 0.0150%, C: 0.010 to 0.100%, sol. Al: 0.010 to 0.050%, one or more elements selected from the group consisting of S and Se: 0.010 to 0.050% in total, Ti: 0 to 0.010%, Ni: 0 to 0.50%, Cr: 0 to 0.50%, Cu: 0 to 0.50%, P: 0 to 0.05%, Mo: 0 to 0.05%, Sn: 0 to 0.30%, Sb: 0 to 0.30%, Bi: 0 to 0.0200%, Ta: 0 to 0.05%, Nb: 0 to 0.010%, V: 0 to 0.50%, B: 0 to 0.010%, Te: 0 to The method includes a hot rolling process in which a slab consisting of 0.0200% Cu, and the balance being Fe and impurities, is hot-rolled to form a hot-rolled steel sheet; a hot-rolled sheet annealing process in which the hot-rolled steel sheet is annealed; a cold-rolling process in which the hot-rolled steel sheet after the hot-rolled sheet annealing process is cold-rolled to form a cold-rolled steel sheet; a decarburization annealing process in which the cold-rolled steel sheet is decarburized to form a decarburization-annealed steel sheet; a finish annealing process in which an annealing separator is applied to the decarburization-annealed steel sheet and then finish annealed; and an insulating coating formation process in which an insulating coating is formed on the surface of the finish-annealed sheet. In the cold rolling process, the cumulative reduction is set to 89% or more and 93% or less, and for the work rolls of the rolling stand that performs the first pass of cold rolling, the arithmetic mean roughness Ra (μm) in the axial direction of the work roll, the ten-point mean roughness Rzjis (μm), and the diameter Dw (mm) of the work roll satisfy the following formulas (1) and (2): 0.30≦Ra≦0.01Dw+3.08 (1) 3Ra≦Rzjis≦7Ra (2)

[0016] The grain-oriented electrical steel sheet of the present disclosure can achieve excellent magnetic properties, excellent iron loss properties, and further achieve excellent noise characteristics. The method for manufacturing the grain-oriented electrical steel sheet of the present disclosure can manufacture the above-mentioned grain-oriented electrical steel sheet.

[0017] Fig. 1 is a perspective view of a grain-oriented electrical steel sheet according to this embodiment, Fig. 2 is a schematic diagram of a tandem rolling mill used in a tandem rolling process, and Fig. 3 is a schematic diagram of a multi-stage rolling mill used in a reverse rolling process.

[0018] The present inventors have conducted research into grain-oriented electrical steel sheets that can provide excellent magnetic properties, excellent core loss properties, and also excellent noise characteristics, and as a result have made the following discoveries.

[0019] The present inventors first investigated and examined the reason why grain-oriented electrical steel sheets may not have sufficient magnetic flux density when cold-rolling reduction ratios are high. As a result, grain-oriented electrical steel sheets that did not have sufficient magnetic flux density contained not only Goss-oriented grains with {110}<001> orientation, but also excessive grains with {211}<011> orientation and {110}<112> orientation. It is believed that the growth of these {211}<011>-oriented grains and {110}<112>-oriented grains by secondary recrystallization reduces the number of Goss-oriented grains, resulting in a decrease in magnetic flux density.

[0020] Specifically, in the final annealing step in the manufacturing process of grain-oriented electrical steel sheets, the coiled cold-rolled steel sheet after the cold rolling step is annealed by batch processing. Since the cold-rolled steel sheet is in a coiled shape, the cold-rolled steel sheet is annealed for a long time while having a curvature. When secondary recrystallization occurs in a steel sheet having a curvature, it is thought that the deviation between the secondary recrystallization orientation and the matrix orientation increases depending on the curvature.

[0021] In the secondary recrystallization of grain-oriented electrical steel sheets, crystal orientation grains with a high proportion of Σ9 orientation grain boundaries tend to grow preferentially. Goss-oriented grains are more likely to form Σ9 orientation grain boundaries. On the other hand, {211}<011>-oriented grains and {110}<112>-oriented grains are less likely to form Σ9 orientation grain boundaries than Goss-oriented grains. Therefore, it is thought that {211}<011>-oriented grains and {110}<112>-oriented grains are less likely to grow during the final annealing process than Goss-oriented grains.

[0022] However, as described above, in the final annealing process, the cold-rolled steel sheet is in a coiled state. Therefore, as secondary recrystallization progresses, the nature of the grain boundaries of the crystal orientation grains changes depending on the curvature. Specifically, Goss-oriented grains are less likely to form Σ9-oriented grain boundaries, while {211}<011>-oriented grains and {110}<112>-oriented grains are less likely to form Σ9-oriented grain boundaries than Goss-oriented grains. As a result, it is believed that {211}<011>-oriented grains and {110}<112>-oriented grains are more likely to grow. This phenomenon becomes more pronounced as the cumulative reduction rate in the cold rolling process increases.

[0023] Based on the above findings, the inventors thought that excellent magnetic flux density could be obtained in a grain-oriented electrical steel sheet by reducing the proportion of {211}<011> oriented grains and {110}<112> oriented grains and increasing the proportion of Goss oriented grains. After further investigation, the inventors found that when the crystal orientation is measured by X-ray diffraction at measurement points arranged at 2 mm pitches in the rolling direction and in the direction perpendicular to the rolling direction on the surface of the base steel sheet of the grain-oriented electrical steel sheet, excellent magnetic flux density can be obtained if the following requirements A to C are met: (Requirement A) The proportion R of the number of measurement points whose orientation deviation from the {211}<011> orientation is 15° or less relative to all measurement points ｛２１１｝＜０１１＞ (Requirement B) The ratio R of the number of measurement points whose orientation deviation from the {110}<112> orientation is 15° or less to all measurement points ｛１１０｝＜１１２＞ (Requirement C) The ratio R of the number of measurement points whose orientation deviation from the {110}<001> orientation is 15° or less to all measurement points ｛１１０｝＜００１＞ is more than 90%.

[0024] As mentioned above, magnetic flux density is increased by increasing the number of Goss-oriented grains and minimizing the number of {211}<011>-oriented grains and {110}<112>-oriented grains. However, while excellent magnetic flux density can be obtained by satisfying requirements A to C, there are cases in which excellent core loss and noise characteristics cannot be obtained. This shows that in grain-oriented electrical steel sheets, improving magnetic flux density does not necessarily correlate with reducing core loss.

[0025] Therefore, the inventors further investigated means for reducing iron loss, and as a result, found that the presence of an appropriate number of high-angle grain boundaries in the microstructure improves iron loss.

[0026] The effect of grain boundaries on iron loss is not clear, but the following reasons are thought to be the cause. Auxiliary magnetic domains are formed where high-angle grain boundaries exist. The auxiliary magnetic domains disappear due to the tension of the insulating coating. When the auxiliary magnetic domains disappear, magnetostatic energy increases. To mitigate this increase in magnetostatic energy, the magnetic domain walls are subdivided. When the magnetic domain walls are subdivided, the iron loss generated when the domain walls move decreases. However, if there are excessive auxiliary magnetic domains, magnetostriction, which causes noise, increases.

[0027] Here, when the crystal orientation is measured by X-ray diffraction at measurement points arranged at 2 mm pitches in both the rolling direction and the direction perpendicular to the rolling direction on the surface of the base steel sheet of the grain-oriented electrical steel sheet, the ratio of the total length LI of grain boundaries with a misorientation of 15° or more to the total length La of the grain boundaries of the crystal grains obtained from the misorientation at the measurement points is defined as the large-angle grain boundary ratio RL (= LI / La). Note that misorientations of 1° or more are defined as grain boundaries.

[0028] If the high-angle grain boundary ratio RL is less than 5%, the proportion of high-angle grain boundaries is too low, and in this case, the auxiliary magnetic domains are too few, resulting in insufficient division of the magnetic domain walls and failure to obtain excellent core loss.

[0029] On the other hand, if the high-angle grain boundary ratio RL exceeds 30%, the proportion of high-angle grain boundaries becomes excessive. In this case, the auxiliary magnetic domains become excessive, hindering the movement of the magnetic domain walls. As a result, hysteresis loss increases. Furthermore, the excessive auxiliary magnetic domains increase magnetostriction. As a result, sufficient iron loss and excellent noise characteristics cannot be obtained.

[0030] If the high-angle grain boundary ratio RL is 5 to 30%, an appropriate number of high-angle grain boundaries and auxiliary magnetic domains are present. This results in finer magnetic domain walls and fewer auxiliary magnetic domains. As a result, excellent core loss and noise characteristics are obtained.

[0031] Based on the above findings, the inventors have completed the grain-oriented electrical steel sheet of the present embodiment having the following configuration.

[0032] The grain-oriented electrical steel sheet of the first embodiment includes a base steel sheet, and the chemical composition of the base steel sheet is, in mass%, Si: 3.00 to 3.70%, Mn: 0.01 to 0.30%, N: 0.0001 to 0.0100%, C: 0.001 to 0.010%, sol. Al: 0-0.010%, one or more elements selected from the group consisting of S and Se: 0-0.010% in total, Ti: 0-0.010%, Ni: 0-0.50%, Cr: 0-0.50%, Cu: 0-0.50%, P: 0-0.05%, Mo: 0-0.05%, Sn: 0-0.30%, Sb: 0-0.30%, Bi: 0-0.0150%, Ta: 0-0.05%, Nb: 0-0.010%, V: 0-0.50%, B: 0-0.010%, Te: 0-0.0150%, and the balance being Fe and impurities. When the crystal orientation is measured by X-ray diffraction at measurement points arranged at 2 mm intervals in the rolling direction and in the direction perpendicular to the rolling direction on the surface of the base steel sheet, the ratio R of the number of measurement points whose orientation deviation from the {211}<011> orientation is 15° or less to all measurement points is ｛２１１｝＜０１１＞ is 5% or less, and the ratio R of the number of measurement points whose orientation deviation from the {110}<112> orientation is 15° or less to all measurement points ｛１１０｝＜１１２＞ is 5% or less, and the ratio R of the number of measurement points whose orientation deviation from the {110}<001> orientation is 15° or less to all measurement points ｛１１０｝＜００１＞ is 90% or more, and a high-angle grain boundary ratio RL=LI / La, which is the ratio of the total length LI of grain boundaries with a misorientation of 15° or more to the total length La of grain boundaries of crystal grains obtained from the misorientation at the measurement point, is 5% or more and 30% or less.

[0033] The grain-oriented electrical steel sheet of the second embodiment is the grain-oriented electrical steel sheet of the first embodiment, in which the thickness of the base steel sheet is 0.19 mm or less.

[0034] The grain-oriented electrical steel sheet of the third embodiment is the grain-oriented electrical steel sheet of the first or second embodiment, and the chemical composition of the base steel sheet is, in mass %, Ti: 0.001 to 0.010%, Ni: 0.01 to 0.50%, Cr: 0.01 to 0.50%, Cu: 0.01 to 0.50%, P: 0.01 to 0.05%, Mo: 0.01 to 0.05%, Sn: 0. It contains one or more selected from the group consisting of: 0.01 to 0.30%, Sb: 0.01 to 0.30%, Bi: 0.0001 to 0.0150%, Ta: 0.01 to 0.05%, Nb: 0.001 to 0.010%, V: 0.01 to 0.50%, B: 0.001 to 0.010%, and Te: 0.0001 to 0.0150%.

[0035] The method for producing a grain-oriented electrical steel sheet of the first embodiment is the method for producing a grain-oriented electrical steel sheet of any one of the first to third embodiments, and includes a hot rolling process, a hot-rolled sheet annealing process, a cold rolling process, a decarburization annealing process, a finish annealing process, and an insulating coating forming process. In the hot rolling process, the grain-oriented electrical steel sheet is annealed to a concentration of, by mass%, 3.00 to 3.70% Si, 0.01 to 0.30% Mn, 0.0030 to 0.0150% N, 0.010 to 0.100% C, sol. A slab containing 0.010 to 0.050% Al, 0.010 to 0.050% in total of one or more selected from the group consisting of S and Se, 0 to 0.050% Ti, 0 to 0.010% Ni, 0 to 0.50% Cr, 0 to 0.50% Cu, 0 to 0.50% P, 0 to 0.05% Mo, 0 to 0.05% Sn, 0 to 0.30% Sb, 0 to 0.30% Bi, 0 to 0.0200% Ta, 0 to 0.05% Nb, 0 to 0.010% V, 0 to 0.50% B, 0 to 0.010% Te, and the balance being Fe and impurities, is hot-rolled to produce a hot-rolled steel sheet. In the hot-rolled sheet annealing step, the hot-rolled steel sheet is annealed. In the cold rolling process, the hot-rolled steel sheet after the hot-rolled sheet annealing process is cold-rolled to obtain a cold-rolled steel sheet. In the decarburization annealing process, the cold-rolled steel sheet is subjected to decarburization annealing to obtain a decarburization annealed steel sheet. In the finish annealing process, an annealing separator is applied to the decarburization annealed steel sheet, and then finish annealing is performed. In the insulating coating formation process, an insulating coating is formed on the surface of the finish annealed sheet. In the cold rolling process, the cumulative reduction is set to 89% or more and 93% or less, and the arithmetic mean roughness Ra (μm) in the axial direction of the work roll, the ten-point mean roughness Rzjis (μm), and the work roll diameter Dw (mm) of the work roll of the rolling stand that performs the first pass reduction of the cold rolling satisfy formulas (1) and (2). 0.30≦Ra≦0.01Dw+3.08 (1) 3Ra≦Rzjis≦7Ra (2)

[0036] The method for producing a grain-oriented electrical steel sheet of the second embodiment is the same as the method for producing a grain-oriented electrical steel sheet of the first embodiment, wherein in the decarburization annealing step, the decarburization annealing temperature is set to 750 to 950°C, and the average heating rate from 400°C to 750°C is set to 100°C / s or more and 3000°C / s or less.

[0037] The third embodiment of the method for manufacturing grain-oriented electrical steel sheet is the method for manufacturing grain-oriented electrical steel sheet of the first or second embodiment, and in the cold rolling process, cold rolling is started from the front end to the rear end of the hot-rolled steel sheet manufactured in the hot rolling process.

[0038] The grain-oriented electrical steel sheet of this embodiment will be described below. Note that "%" for elements means mass % unless otherwise specified.

[0039] [Configuration of grain-oriented electrical steel sheet] Fig. 1 is a perspective view of a grain-oriented electrical steel sheet according to this embodiment. In the figure, direction L refers to the rolling direction of the grain-oriented electrical steel sheet. Direction W refers to the direction perpendicular to the rolling of the grain-oriented electrical steel sheet (sheet width direction). Direction T refers to the normal direction of the rolled surface of the grain-oriented electrical steel sheet (sheet thickness direction). The rolled surface of the grain-oriented electrical steel sheet refers to the top or bottom surface of the grain-oriented electrical steel sheet.

[0040] Referring to FIG. 1 , the grain-oriented electrical steel sheet 1 according to this embodiment includes a base steel sheet 10. The grain-oriented electrical steel sheet 1 may further include a lower coating 11 and an insulating coating 12. When the grain-oriented electrical steel sheet 1 includes the lower coating 11 and the insulating coating 12, the lower coating 11 is formed on the base steel sheet 10. In FIG. 1 , the lower coating 11 is formed on the surface of the base steel sheet 10 in direct contact with the surface of the base steel sheet 10. The lower coating 11 is either a primary coating mainly composed of forsterite or an intermediate layer mainly composed of oxides such as silica and alumina. When emphasis is placed on reducing iron loss, the lower coating 11 is the primary coating. When emphasis is placed on punching workability, the lower coating 11 is the intermediate layer. The lower coating 11 is a well-known coating.

[0041] The insulating coating 12 is formed on the under-layer coating 11. As shown in Fig. 1 , the under-layer coating 11 and the insulating coating 12 may be formed on a pair of surfaces of the base steel sheet 10 (i.e., the front and back surfaces of the base steel sheet 10). The insulating coating 12 is a well-known insulating coating. The grain-oriented electrical steel sheet 1 may include the base steel sheet 10 and the insulating coating 12, but may not include the under-layer coating 11.

[0042] It is well known that grain-oriented electrical steel sheets may comprise a base steel sheet, an underlayer coating, and an insulating coating, or may comprise a base steel sheet and an insulating coating.

[0043] [Regarding Chemical Composition of Base Steel Sheet 10] The chemical composition of the base steel sheet 10 of the grain-oriented electrical steel sheet 1 contains the following elements.

[0044] Si: 3.00 to 3.70% Silicon (Si) increases the electrical resistance (specific resistance) of the steel sheet and reduces the iron loss of the grain-oriented electrical steel sheet 1. If the Si content is less than 3.00%, the above effect cannot be sufficiently obtained. On the other hand, if the Si content exceeds 3.70%, the steel sheet becomes embrittled. Therefore, the Si content is 3.00 to 3.70%. A preferred lower limit of the Si content is 3.05%, more preferably 3.10%, even more preferably 3.15%, even more preferably 3.20%, even more preferably 3.25%, and even more preferably 3.30%. A preferred upper limit of the Si content is 3.65%, even more preferably 3.60%, even more preferably 3.55%, and even more preferably 3.50%.

[0045] Mn: 0.01 to 0.30% Manganese (Mn) increases the resistivity of the steel sheet and reduces iron loss. Mn also improves the hot workability of the steel sheet and suppresses the occurrence of cracks during hot rolling. If the Mn content is less than 0.01%, the above effects cannot be sufficiently obtained. On the other hand, if the Mn content exceeds 0.30%, the magnetic flux density of the grain-oriented electrical steel sheet 1 decreases and iron loss also deteriorates. Therefore, the Mn content is 0.01 to 0.30%. A preferred lower limit of the Mn content is 0.02%, more preferably 0.03%, and even more preferably 0.05%. A preferred upper limit of the Mn content is 0.28%, more preferably 0.25%, even more preferably 0.20%, and even more preferably 0.15%.

[0046] N: 0.0001 to 0.0100% Nitrogen (N) forms nitrides and deteriorates the iron loss of the grain-oriented electrical steel sheet 1. If the N content exceeds 0.0100%, the iron loss of the grain-oriented electrical steel sheet 1 deteriorates significantly. Therefore, the N content is 0.0001 to 0.0100%. A preferred lower limit of the N content is 0.0002%, and more preferably 0.0005%. A preferred upper limit of the N content is 0.0090%, and more preferably 0.0050%, and even more preferably 0.0030%.

[0047] C: 0.001 to 0.010% Carbon (C) is an essential element in slabs to improve magnetic flux density. However, C is lost from the steel sheet during the manufacturing process of the grain-oriented electrical steel sheet 1. If more than 0.010% C remains in the finished grain-oriented electrical steel sheet 1, magnetic aging occurs, deteriorating the iron loss of the grain-oriented electrical steel sheet 1. A lower lower limit for the C content is preferable. However, excessive reduction in the C content increases manufacturing costs. Therefore, the lower limit for the C content is set to 0.001% or more. Therefore, the C content is 0.001 to 0.010%. A preferred lower limit for the C content is 0.002%, more preferably 0.003%. A preferred upper limit for the C content is 0.009%, more preferably 0.008%, and even more preferably 0.007%.

[0048] Sol. Al: 0 to 0.010% Acid-soluble aluminum (sol. Al) combines with N to form AlN during the manufacturing process of the grain-oriented electrical steel sheet 1, functioning as an inhibitor. However, if the sol. Al content exceeds 0.010%, Al-based inclusions remain in the steel sheet. In this case, the iron loss of the grain-oriented electrical steel sheet 1 deteriorates. Therefore, the sol. Al content is 0.010% or less. The sol. Al content may be 0%. In other words, the sol. Al content is 0 to 0.010%. The preferred lower limit of the sol. Al content is 0.001%. The preferred upper limit of the sol. Al content is 0.009%, more preferably 0.008%, and even more preferably 0.007%.

[0049] One or more elements selected from the group consisting of S and Se: 0 to 0.010% in total. Sulfur (S) and selenium (Se) combine with Mn during the manufacturing process to form fine MnS or MnSe, which act as inhibitors. Therefore, S and Se are essential elements in slabs. However, S and Se are lost from the steel sheet during the manufacturing process of grain-oriented electrical steel sheet 1. If the total content of one or more elements selected from the group consisting of S and Se in grain-oriented electrical steel sheet 1 exceeds 0.010%, MnS or MnSe will remain in the steel sheet. In this case, the iron loss of grain-oriented electrical steel sheet 1 will deteriorate. Therefore, the total content of one or more elements selected from the group consisting of S and Se is 0.010% or less. Note that the total content of one or more elements selected from the group consisting of S and Se may be 0%. In other words, the total content of one or more elements selected from the group consisting of S and Se is 0 to 0.010%. The preferred lower limit of the total content of one or more elements selected from the group consisting of S and Se is 0.001%. The preferred upper limit of the total content of one or more elements selected from the group consisting of S and Se is 0.008%, more preferably 0.006%, and even more preferably 0.004%.

[0050] The balance of the chemical composition of the grain-oriented electrical steel sheet 1 consists of Fe and impurities. Here, the impurities refer to substances that are mixed in from raw material ores, scrap, or the manufacturing environment when industrially manufacturing the base steel sheet 10 of the grain-oriented electrical steel sheet 1, and are acceptable within a range that does not adversely affect the grain-oriented electrical steel sheet 1 of this embodiment. Examples of impurities include Ca: 0-0.001%, Mg: 0-0.002%, Ce: 0-0.002%, O: 0-0.01%, As: 0-0.10%, Co: 0-0.10%, Zr: 0-0.003%, W: 0-0.10%, Hf: 0-0.02%, Sc: 0-0.02%, Sr: 0-0.02%, Zn: 0-0.02%, and P. The alloy contains one or more elements selected from the group consisting of b: 0-0.10%, Nd: 0-0.02%, REM: 0-0.02%, Ba: 0-0.02%, Cd: 0-0.02%, Pt: 0-0.02%, Au: 0-0.02%, Ga: 0-0.02%, Ge: 0-0.02%, Y: 0-0.02%, and La: 0-0.02%. When a plurality of these impurity elements are contained, the total content of the plurality of elements is 0-0.05%.

[0051] [Regarding Optional Elements] The chemical composition of the base steel sheet 10 of the grain-oriented electrical steel sheet 1 may further contain, in place of a portion of Fe, one or more elements selected from Ti: 0-0.010%, Ni: 0-0.50%, Cr: 0-0.50%, Cu: 0-0.50%, P: 0-0.05%, Mo: 0-0.05%, Sn: 0-0.30%, Sb: 0-0.30%, Bi: 0-0.0150%, Ta: 0-0.05%, Nb: 0-0.010%, V: 0-0.50%, B: 0-0.010%, and Te: 0-0.0150%. All of these elements are optional elements. Each element will be described below.

[0052] [Group 1: Ti] Ti: 0 to 0.010% Titanium (Ti) is an optional element and does not necessarily need to be contained. That is, the Ti content may be 0%. When contained, that is, when the Ti content exceeds 0%, Ti degrades the magnetic properties of the grain-oriented electrical steel sheet 1. When the Ti content exceeds 0.010%, the magnetic properties of the grain-oriented electrical steel sheet 1 are significantly degraded. Therefore, the Ti content is 0 to 0.010%. The Ti content is preferably as low as possible. However, excessive reduction of the Ti content increases manufacturing costs. Therefore, for normal industrial production, the preferred lower limit of the Ti content is 0.001%, more preferably 0.002%. The preferred upper limit of the Ti content is 0.009%, more preferably 0.008%, even more preferably 0.007%, and even more preferably 0.005%.

[0053] [Second Group: Ni, Cr, Cu, P, and Mo] Ni, Cr, Cu, P, and Mo are all optional elements. These elements change the microstructure formation behavior during the manufacturing process and improve the magnetic properties of the grain-oriented electrical steel sheet 1.

[0054] Ni: 0 to 0.50% Nickel (Ni) is an optional element and does not necessarily need to be contained. That is, the Ni content may be 0%. When Ni is contained, that is, when the Ni content exceeds 0%, Ni changes the microstructure formation behavior up to the final annealing process and promotes secondary recrystallization of Goss-oriented grains. As a result, the magnetic properties of the grain-oriented electrical steel sheet 1 are improved. Even if even a small amount of Ni is contained, the above effect can be obtained to some extent. However, if the Ni content exceeds 0.50%, secondary recrystallization may become unstable. Therefore, the Ni content is 0 to 0.50%. The preferred lower limit of the Ni content is 0.01%, more preferably 0.05%, and even more preferably 0.10%. The preferred upper limit of the Ni content is 0.40%, more preferably 0.30%, even more preferably 0.20%, and even more preferably 0.15%.

[0055] Cr: 0 to 0.50% Chromium (Cr) is an optional element and does not necessarily need to be contained. That is, the Cr content may be 0%. When chromium is contained, that is, when the Cr content exceeds 0%, Cr changes the microstructure formation behavior up to the final annealing process and promotes secondary recrystallization of Goss-oriented grains. As a result, the magnetic properties of the grain-oriented electrical steel sheet 1 are improved. Even if even a small amount of Cr is contained, the above effect can be obtained to some extent. However, if the Cr content exceeds 0.50%, Cr oxides are formed in the steel sheet. As a result, the iron loss of the grain-oriented electrical steel sheet 1 deteriorates. Therefore, the Cr content is 0 to 0.50%. The preferred lower limit of the Cr content is 0.01%, more preferably 0.05%, and even more preferably 0.10%. The preferred upper limit of the Cr content is 0.40%, more preferably 0.30%, even more preferably 0.20%, and even more preferably 0.15%.

[0056] Cu: 0 to 0.50% Copper (Cu) is an optional element and does not necessarily need to be contained. That is, the Cu content may be 0%. When copper is contained, that is, when the Cu content exceeds 0%, Cu changes the microstructure formation behavior up to the final annealing process and promotes secondary recrystallization of Goss-oriented grains. As a result, the magnetic properties of the grain-oriented electrical steel sheet 1 are improved. Even if even a small amount of Cu is contained, the above effects can be obtained to some extent. However, if the Cu content exceeds 0.50%, the hot workability of the steel sheet is reduced. Therefore, the Cu content is 0 to 0.50%. The preferred lower limit of the Cu content is 0.01%, more preferably 0.03%, and even more preferably 0.05%. The preferred upper limit of the Cu content is 0.40%, more preferably 0.30%, even more preferably 0.20%, and even more preferably 0.15%.

[0057] P: 0 to 0.05% Phosphorus (P) is an optional element and does not necessarily need to be contained. In other words, the P content may be 0%. When contained, that is, when the P content exceeds 0%, P changes the microstructure formation behavior up to the final annealing process and promotes secondary recrystallization of Goss-oriented grains. As a result, the magnetic properties of the grain-oriented electrical steel sheet 1 are improved. Even if even a small amount of P is contained, the above effect can be obtained to some extent. However, if the P content exceeds 0.05%, the workability of the steel sheet decreases. Therefore, the P content is 0 to 0.05%. The preferred lower limit of the P content is 0.01%. The preferred upper limit of the P content is 0.04%, more preferably 0.03%, and even more preferably 0.02%.

[0058] Mo: 0 to 0.05% Molybdenum (Mo) is an optional element and does not necessarily need to be contained. That is, the Mo content may be 0%. When contained, that is, when the Mo content exceeds 0%, Mo changes the microstructure formation behavior up to the final annealing process and promotes secondary recrystallization of Goss-oriented grains. As a result, the magnetic properties of the grain-oriented electrical steel sheet 1 are improved. Even if even a small amount of Mo is contained, the above effect can be obtained to some extent. However, if the Mo content exceeds 0.05%, the workability of the steel sheet decreases. Therefore, the Mo content is 0 to 0.05%. The preferred lower limit of the Mo content is 0.01%, more preferably 0.02%. The preferred upper limit of the Mo content is 0.04%, more preferably 0.03%.

[0059] [Third group: Sn, Sb, Bi, Ta, Nb, V, B, and Te] Sn, Sb, Bi, Ta, Nb, V, B, and Te are all optional elements. All of these elements function as inhibitors to stabilize secondary recrystallization.

[0060] Sn: 0 to 0.30% Tin (Sn) is an optional element and does not necessarily need to be contained. In other words, the Sn content may be 0%. When contained, Sn functions as an inhibitor and stabilizes secondary recrystallization during the manufacturing process of the grain-oriented electrical steel sheet 1. As a result, the magnetic properties of the grain-oriented electrical steel sheet 1 are improved. Even if even a small amount of Sn is contained, the above effect can be obtained to some extent. However, if the Sn content exceeds 0.30%, the magnetic properties of the grain-oriented electrical steel sheet 1 will actually deteriorate. Therefore, the Sn content is 0 to 0.30%. The preferred lower limit of the Sn content is 0.01%, more preferably 0.03%, and even more preferably 0.05%. The preferred upper limit of the Sn content is 0.25%, more preferably 0.20%, and even more preferably 0.15%.

[0061] Sb: 0 to 0.30% Antimony (Sb) is an optional element and does not necessarily need to be contained. That is, the Sb content may be 0%. When contained, Sb functions as an inhibitor and stabilizes secondary recrystallization during the manufacturing process of the grain-oriented electrical steel sheet 1. As a result, the magnetic properties of the grain-oriented electrical steel sheet 1 are improved. Even if even a small amount of Sb is contained, the above effect can be obtained to some extent. However, if the Sb content exceeds 0.30%, the magnetic properties of the grain-oriented electrical steel sheet 1 will actually deteriorate. Therefore, the Sb content is 0 to 0.30%. The preferred lower limit of the Sb content is 0.01%, more preferably 0.03%, and even more preferably 0.05%. The preferred upper limit of the Sb content is 0.25%, more preferably 0.20%, and even more preferably 0.15%.

[0062] Bi: 0 to 0.0150% Bismuth (Bi) is an optional element and does not necessarily need to be contained. In other words, the Bi content may be 0%. When contained, Bi functions as an inhibitor and stabilizes secondary recrystallization during the manufacturing process of the grain-oriented electrical steel sheet 1. As a result, the magnetic properties of the grain-oriented electrical steel sheet 1 are improved. Even if even a small amount of Bi is contained, the above effect can be achieved to some extent. However, if the Bi content exceeds 0.0150%, the magnetic properties of the grain-oriented electrical steel sheet 1 will actually deteriorate. Therefore, the Bi content is 0 to 0.0150%. The preferred lower limit of the Bi content is 0.0001%, more preferably 0.0005%, even more preferably 0.0010%, and even more preferably 0.0050%. The upper limit of the Bi content is preferably 0.0120%, more preferably 0.0100%, even more preferably 0.0070%, and still more preferably 0.0050%.

[0063] Ta: 0 to 0.05% Tantalum (Ta) is an optional element and does not necessarily need to be contained. That is, the Ta content may be 0%. When contained, Ta functions as an inhibitor and stabilizes secondary recrystallization during the manufacturing process of the grain-oriented electrical steel sheet 1. As a result, the magnetic properties of the grain-oriented electrical steel sheet 1 are improved. Even if even a small amount of Ta is contained, the above effect can be obtained to some extent. However, if the Ta content exceeds 0.05%, the magnetic properties of the grain-oriented electrical steel sheet 1 will actually deteriorate. Therefore, the Ta content is 0 to 0.05%. The preferred lower limit of the Ta content is 0.01%, and more preferably 0.02%. The preferred upper limit of the Ta content is 0.04%, and more preferably 0.03%.

[0064] Nb: 0 to 0.010% Niobium (Nb) is an optional element and does not necessarily need to be contained. That is, the Nb content may be 0%. When contained, Nb functions as an inhibitor and stabilizes secondary recrystallization during the manufacturing process of the grain-oriented electrical steel sheet 1. As a result, the magnetic properties of the grain-oriented electrical steel sheet 1 are improved. Even if even a small amount of Nb is contained, the above effect can be obtained to some extent. However, if the Nb content exceeds 0.010%, the magnetic properties of the grain-oriented electrical steel sheet 1 will actually deteriorate. Therefore, the Nb content is 0 to 0.010%. The preferred lower limit of the Nb content is 0.001%, and more preferably 0.003%. The preferred upper limit of the Nb content is 0.008%, and more preferably 0.006%.

[0065] V: 0 to 0.50% Vanadium (V) is an optional element and does not necessarily need to be contained. That is, the V content may be 0%. When contained, V functions as an inhibitor and stabilizes secondary recrystallization during the manufacturing process of the grain-oriented electrical steel sheet 1. As a result, the magnetic properties of the grain-oriented electrical steel sheet 1 are improved. Even if even a small amount of V is contained, the above effect can be obtained to some extent. However, if the V content exceeds 0.50%, the magnetic properties of the grain-oriented electrical steel sheet 1 will actually deteriorate. Therefore, the V content is 0 to 0.50%. The preferred lower limit of the V content is 0.01%, more preferably 0.05%, and even more preferably 0.10%. The preferred upper limit of the V content is 0.40%, more preferably 0.30%, and even more preferably 0.20%.

[0066] B: 0 to 0.010% Boron (B) is an optional element and does not necessarily need to be contained. In other words, the B content may be 0%. When contained, B functions as an inhibitor and stabilizes secondary recrystallization during the manufacturing process of the grain-oriented electrical steel sheet 1. As a result, the magnetic properties of the grain-oriented electrical steel sheet 1 are improved. Even if even a small amount of B is contained, the above effect can be obtained to some extent. However, if the B content exceeds 0.010%, the magnetic properties of the grain-oriented electrical steel sheet 1 will actually deteriorate. Therefore, the B content is 0 to 0.010%. The preferred lower limit of the B content is 0.001%, more preferably 0.002%, and even more preferably 0.003%. The preferred upper limit of the B content is 0.009%, more preferably 0.007%, and even more preferably 0.005%.

[0067] Te: 0 to 0.0150% Tellurium (Te) is an optional element and does not necessarily need to be contained. In other words, the Te content may be 0%. When contained, Te functions as an inhibitor and stabilizes secondary recrystallization during the manufacturing process of the grain-oriented electrical steel sheet 1. As a result, the magnetic properties of the grain-oriented electrical steel sheet 1 are improved. Even if even a small amount of Te is contained, the above effect can be achieved to some extent. However, if the Te content exceeds 0.0150%, the magnetic properties of the grain-oriented electrical steel sheet 1 will actually deteriorate. Therefore, the Te content is 0 to 0.0150%. The preferred lower limit of the Te content is 0.0001%, more preferably 0.0005%, even more preferably 0.0010%, and even more preferably 0.0050%. The upper limit of the Te content is preferably 0.0120%, more preferably 0.0100%, further preferably 0.0070%, and still further preferably 0.0050%.

[0068] [Method for Measuring the Chemical Composition of Grain-Oriented Electrical Steel Sheet 1] The chemical composition of the grain-orientated electrical steel sheet 1 of this embodiment can be measured by a known elemental analysis method. First, if the grain-orientated electrical steel sheet 1 has an underlayer coating 11 and an insulating coating 12 formed thereon, the underlayer coating 11 and the insulating coating 12 are removed by the following method. Specifically, the grain-orientated electrical steel sheet 1 with the insulating coating 12 is immersed in a high-temperature alkaline solution to remove the underlayer coating 11 and the insulating coating 12. The composition, temperature, and immersion time of the alkaline solution may be adjusted as appropriate. For example, the grain-orientated electrical steel sheet 1 with the insulating coating 12 is immersed in a high-temperature alkaline solution containing 30 to 50% by mass of NaOH + H ２ O: Immerse in a 50 to 70 mass % aqueous sodium hydroxide solution at 80 to 90°C for 5 to 10 minutes, rinse with water after immersion, and dry. This process removes the insulating coating 12 from the grain-oriented electrical steel sheet 1.

[0069] Furthermore, the grain-oriented electrical steel sheet 1 from which the insulating coating 12 has been removed and from which the underlayer coating 11 remains is immersed in high-temperature hydrochloric acid to remove the insulating coating 12. The concentration, temperature, and immersion time of the hydrochloric acid may be adjusted as appropriate. For example, the grain-oriented electrical steel sheet 1 from which the insulating coating 12 has been removed and from which the underlayer coating 11 remains is immersed in 30 to 40 mass % hydrochloric acid at 80 to 90°C for 1 to 5 minutes. After immersion, the grain-oriented electrical steel sheet 1 is rinsed with water and dried. Through the above steps, a base steel sheet 10 from which the insulating coating 12 and underlayer coating 11 have been removed is obtained.

[0070] The chemical composition of the obtained base steel sheet 10 is measured using a well-known elemental analysis method in accordance with JIS G0321:2017. Specifically, chips are collected from the grain-oriented electrical steel sheet 1. The collected chips are dissolved in acid to obtain a solution. ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry) is performed on the solution to perform elemental analysis of the chemical composition. The C content and S content are determined using a well-known high-frequency combustion method (combustion-infrared absorption method). The N content is determined using a well-known inert gas fusion-thermal conductivity method. For example, the chemical composition of the base steel sheet 10 can be analyzed using a component analysis device (product name: ICPS-8000) manufactured by Shimadzu Corporation.

[0071] The content of each element is determined by rounding off the measured value to the nearest significant digit based on the significant digits specified in this embodiment. For example, the Si content in this embodiment is determined as a value up to two decimal places. Therefore, the Si content is determined as a value up to two decimal places obtained by rounding off the measured value to two decimal places.

[0072] Similarly, the contents of elements other than the Si content in the grain-oriented electrical steel sheet 1 of this embodiment are also determined by rounding off the measured value to the smallest digit specified in this embodiment, and this is the content of the element.

[0073] Rounding off means rounding down if the fraction is less than 5, and rounding up if the fraction is 5 or more.

[0074] [Regarding the Underlayer Coating 11] As described above, the underlayer coating 11 may be a primary coating or an intermediate layer. The primary coating is made of forsterite (Mg ２ SiO ４ The primary coating is a well-known coating mainly composed of forsterite. The content of forsterite in the primary coating is 60% by mass or more. The primary coating is formed by annealing the surface of the base steel sheet 10 with an annealing separator containing magnesia and SiO ２ The lower coating 11 is formed by reaction with an oxide film such as SiO 2 or an element contained in the base steel sheet 10. Therefore, the lower coating 11 has a composition derived from the chemical composition of the annealing separator and the base steel sheet 10. For example, the lower coating 11 may be formed of a spinel (MgAl ２ O ４ ). When emphasis is placed on reducing iron loss, the lower coating 11 is the primary coating. On the other hand, the intermediate layer is a coating mainly composed of silica and alumina. More specifically, the total content of silica and alumina in the intermediate layer is 60% by mass or more. When emphasis is placed on punching workability, the lower coating 11 is the intermediate layer.

[0075] [Regarding the insulating coating 12] The insulating coating 12 is formed on the underlayer coating 11. When multiple grain-oriented electrical steel sheets 1 are stacked together, the insulating coating 12 ensures insulation between the stacked grain-oriented electrical steel sheets 1. The insulating coating 12 has a well-known configuration. Specifically, the insulating coating 12 contains at least one inorganic substance, such as a metal chromate salt, a metal phosphate salt, colloidal silica, a Zr compound, or a Ti compound. Preferably, the insulating coating 12 is a coating mainly composed of a phosphate compound. In other words, the insulating coating 12 contains a phosphate compound. When the insulating coating 12 is mainly composed of a phosphate compound, the content of the phosphate compound is 50% or more by mass.

[0076] Insulating coating 12 may contain, for example, one or more compounds selected from the group consisting of colloidal silica and polytetrafluoroethylene, together with the phosphate compound. The phosphate compound may be, for example, one or more compounds selected from the group consisting of sodium phosphate, aluminum phosphate, and magnesium phosphate.

[0077] [Regarding the Number Proportion of Specific Crystal Orientation] The grain-oriented electrical steel sheet 1 of this embodiment further satisfies the following requirements A to C when the crystal orientation is measured by X-ray diffraction at measurement points arranged at 2 mm pitches in the rolling direction and in the direction perpendicular to the rolling direction on the surface of the base steel sheet 10. (Requirement A) The ratio R of the number of measurement points whose orientation deviation from the {211}<011> orientation is 15° or less to all measurement points. ｛２１１｝＜０１１＞ (Requirement B) The ratio R of the number of measurement points whose orientation deviation from the {110}<112> orientation is 15° or less to all measurement points ｛１１０｝＜１１２＞ (Requirement C) The ratio R of the number of measurement points whose orientation deviation from the {110}<001> orientation is 15° or less to all measurement points ｛１１０｝＜００１＞ The following explains requirements A to C.

[0078] The crystal grains having the {211}<011> orientation and the crystal grains having the {110}<112> orientation have inferior magnetic properties compared to the Goss-oriented grains having the {110}<001> orientation. Therefore, it is preferable to have as few {211}<011> and {110}<112> orientation grains as possible.

[0079] Specifically, the ratio R of the number of measurement points whose orientation deviation from the {211}<011> orientation is 15° or less to all measurement points is ｛２１１｝＜０１１＞ If the ratio exceeds 5%, the {211}<011> oriented grains are in excess, resulting in poor magnetic properties.

[0080] Similarly, when the chemical composition of the base steel plate 10 satisfies the range of this embodiment, the ratio R of the number of measurement points whose orientation difference from the {110}<112> orientation is 15° or less to all measurement points is ｛１１０｝＜１１２＞ If the ratio exceeds 5%, the {110}<112> oriented grains are in excess, resulting in poor magnetic properties.

[0081] In addition, the ratio R of the number of measurement points whose misorientation from the {110}<001> orientation, which is the Goss orientation, to all measurement points is 15° or less. ｛１１０｝＜００１＞ If the ratio is less than 90%, the number of Goss-oriented grains will be too small, resulting in poor magnetic properties and possibly a decrease in noise characteristics.

[0082] If requirements A to C are satisfied, there will be a sufficient number of Goss-oriented grains and a sufficient number of {211}<011>-oriented grains and {110}<112>-oriented grains. This results in excellent magnetic properties. Specifically, excellent magnetic flux density.

[0083] Quantity ratio R ｛２１１｝＜０１１＞ The upper limit of the number ratio R is preferably 4%, and more preferably 3%. ｛２１１｝＜０１１＞ The lower limit of the number ratio R is preferably 1%, and more preferably 0%. ｛１１０｝＜１１２＞ The upper limit of the number ratio R is preferably 4%, and more preferably 3%. ｛１１０｝＜１１２＞ The lower limit of the number ratio R is preferably 1%, and more preferably 0%. ｛１１０｝＜００１＞The lower limit of the number ratio R is preferably 91%, more preferably 92%, even more preferably 93%, and even more preferably 94%. ｛１１０｝＜００１＞ The upper limit of the ratio is preferably 96%, more preferably 97%, and even more preferably 98%.

[0084] [Regarding the high-angle grain boundary ratio RL] Furthermore, in the grain-oriented electrical steel sheet 1 of this embodiment, the high-angle grain boundary ratio RL = LI / La, which is the ratio of the total length LI of grain boundaries with a misorientation of 15° or more to the total length La of the grain boundaries of the crystal grains obtained from the misorientations at the measurement points described above, is 5% or more and 30% or less.

[0085] As described above in requirements A to C, magnetic flux density is increased by increasing the number of Goss-oriented grains and minimizing the number of {211}<011>-oriented grains and {110}<112>-oriented grains in the crystal grains. However, although excellent magnetic flux density can be obtained by satisfying requirements A to C, it does not necessarily result in excellent iron loss. This shows that in grain-oriented electrical steel sheets, improved magnetic flux density does not necessarily correlate with reduced iron loss.

[0086] On the other hand, as mentioned above, the inventors' verification has shown that the presence of an appropriate number of high-angle grain boundaries improves iron loss. Specifically, auxiliary magnetic domains are formed where high-angle grain boundaries exist. If an appropriate number of auxiliary magnetic domains are formed, magnetic domain walls are subdivided, reducing iron loss.

[0087] If the high-angle grain boundary ratio RL is less than 5%, the proportion of high-angle grain boundaries is too low, and the auxiliary magnetic domains are too few. In this case, the magnetic domain walls are not sufficiently subdivided. As a result, a sufficiently low core loss cannot be obtained.

[0088] On the other hand, if the high-angle grain boundary ratio RL exceeds 30%, the ratio of high-angle grain boundaries becomes excessive, resulting in an excess of auxiliary magnetic domains. In this case, the movement of magnetic domain walls is hindered, and hysteresis loss increases instead. As a result, sufficiently low iron loss cannot be obtained. Furthermore, excessive auxiliary magnetic domains increase magnetostriction. Note that if the high-angle grain boundary ratio RL exceeds 30%, the magnetic flux density may decrease.

[0089] If the high-angle grain boundary ratio RL is 5 to 30%, an appropriate number of high-angle grain boundaries and auxiliary magnetic domains are present. This results in finer magnetic domain walls and suppresses the amount of excessive auxiliary magnetic domains. As a result, excellent iron loss and noise characteristics are obtained.

[0090] The lower limit of the high-angle grain boundary fraction RL is preferably 6%, more preferably 7%, more preferably 8%, even more preferably 10%, and even more preferably 12%. The upper limit of the high-angle grain boundary fraction RL is preferably 28%, more preferably 26%, even more preferably 24%, and even more preferably 22%.

[0091] [Method for Measuring Crystal Orientation at Measurement Point] The crystal orientation at the measurement point can be measured by the following method. X-ray diffraction is performed by the Laue method on the rolled surface of the grain-oriented electrical steel sheet 1. Specifically, one or more rectangular observation areas AR, each 250 mm in the rolling direction of the grain-oriented electrical steel sheet 1 and 60 mm in the direction perpendicular to the rolling direction, are measured from any point on the rolled surface of the grain-oriented electrical steel sheet 1. ｎ (n is a natural number) is selected. ｎ X-ray diffraction by the Laue method is performed on the specimen at measurement points spaced 2 mm apart in the rolling and width directions (3,906 measurement points) to obtain the crystal orientation at each measurement point. The spot diameter is 1 mm. Based on the crystal orientation obtained at each measurement point, the boundaries where the misorientation angle is between 1 and 180° are defined as grain boundaries. The regions surrounded by the grain boundaries are defined as crystal grains. The radiation source for X-ray diffraction by the Laue method is a W target, with a tube voltage of 40 kV and a tube current of 40 mA.

[0092] Each observation area AR ｎ Each time the measurement is completed, it is determined whether the total number of identified crystal grains is 100 or more. If the total number of crystal grains is less than 100, another observation area AR ｎ＋１ The X-ray diffraction is performed by selecting the crystal grains, and the measurement is completed when the total number of crystal grains reaches 100 or more.

[0093] Of all the measurement points for which measurement has been completed, the number of measurement points for which the misorientation from the {211}<011> orientation is 15° or less is calculated. Based on the total number of measurement points for which measurement has been completed and the number of measurement points for which the misorientation from the {211}<011> orientation is 15° or less, the number ratio R ｛２１１｝＜０１１＞ The percentage (%) is calculated using the following formula: ｛２１１｝＜０１１＞ = Number of measurement points with an orientation difference of 15° or less from the {211}<011> orientation / Total number of measurement points for which measurement has been completed × 100

[0094] Of all the measurement points for which measurement has been completed, the number of measurement points for which the misorientation from the {110}<112> orientation is 15° or less is calculated. Based on the total number of measurement points for which measurement has been completed and the number of measurement points for which the misorientation from the {110}<112> orientation is 15° or less, the number ratio R ｛１１０｝＜１１２＞ The percentage (%) is calculated using the following formula: ｛１１０｝＜１１２＞ = Number of measurement points with an orientation difference of 15° or less from the {110}<112> orientation / Total number of measurement points for which measurement has been completed × 100

[0095] Of all the measurement points for which measurement has been completed, the number of measurement points for which the misorientation from the {110}<001> orientation is 15° or less is calculated. Based on the total number of measurement points for which measurement has been completed and the number of measurement points for which the misorientation from the {110}<001> orientation is 15° or less, the number ratio R ｛１１０｝＜００１＞ The percentage (%) is calculated using the following formula: ｛１１０｝＜００１＞ = Number of measurement points with an orientation difference of 15° or less from the {110}<001> orientation / Total number of measurement points for which measurement has been completed × 100

[0096] Furthermore, all the observation areas AR for which measurement has been completed ｎ The total length of the grain boundaries of all the identified crystal grains is defined as La. Furthermore, the total length of the grain boundaries of all the identified crystal grains with a misorientation angle of 15° or more (high angle grain boundaries) is defined as LI.

[0097] For example, the first observation area AR １ After the measurement of the crystal orientation in the observation area AR is completed, if the number of identified crystal grains is 100 or more, １ All the crystal grains identified in are used to determine La and Li.

[0098] On the other hand, the observation area AR １ After the measurement is completed, if the number of identified crystal grains is less than 100, the second observation area AR ２ Then, the measurement is performed in the observation area AR ２ After the measurement is completed in the observation area AR １ and A.R. ２ If the total number of crystal grains identified in the observation area AR is 100 or more, １ and A.R. ２ All the crystal grains identified in are used to determine La and Li.

[0099] As described above, the observation area AR is kept constant until the total number of identified crystal grains reaches 100 or more. １ ~ A.R. ｎ Then, when the total number of crystal grains reaches 100 or more, all the observation areas AR for which measurement has been completed are counted. １ ~ A.R. ｎ La and LI are calculated using all the crystal grains identified in step 1. The calculated La and LI are used to calculate the high-angle grain boundary ratio RL (%) using the following formula: High-angle grain boundary ratio RL = LI / La × 100 Based on the crystal orientation at each measurement point, La and LI can be calculated using analysis software with the product name: OIM Analysis manufactured by TSL Solutions Co., Ltd.

[0100] At measurement points corresponding to grains or grain boundaries with a grain size of 1 mm or less, identifying the crystal orientation can be difficult, resulting in identification failure. Therefore, at such measurement points (hereinafter referred to as "failure measurement points"), the crystal orientation data of adjacent measurement points is substituted. Specifically, at the two measurement points (+X and -X) adjacent to the failure measurement point in the rolling direction and the two measurement points (+Y and -Y) adjacent to the failure measurement point in the width direction, the crystal orientation data is substituted in the order of priority: +X, -X, +Y, -Y. First, the crystal orientation data of the +X measurement point is substituted as the crystal orientation data of the failure measurement point. If the crystal orientation data of the +X measurement point is also defective, the crystal orientation data of the -X measurement point is substituted. As described above, the substitutable data is determined in order of priority. This method of substituting crystal orientation data is set as the "Clean up" function in the OIM Analysis described above. The X direction is, for example, the rolling direction, and the Y direction is, for example, the width direction.

[0101] [Advantages of the Grain-Oriented Electrical Steel Sheet 1 of the Present Embodiment] The grain-oriented electrical steel sheet 1 of the present embodiment satisfies requirements A to C, and has a high-angle grain boundary fraction RL of 5 to 30%. Therefore, excellent magnetic flux density can be obtained. Furthermore, after magnetic domain refinement treatment, excellent iron loss and noise characteristics can be obtained.

[0102] [Preferred Sheet Thickness of Base Steel Sheet 10 of Grain-Oriented Electrical Steel Sheet 1 of This Embodiment] There are no particular limitations on the sheet thickness of the base steel sheet 10 of the grain-oriented electrical steel sheet 1 of this embodiment. The sheet thickness of the base steel sheet 10 may be, for example, 0.17 to 0.22 mm, which is the same as that of base steel sheets of known grain-oriented electrical steel sheets.

[0103] The preferred thickness of the base steel sheet 10 is 0.19 mm or less. In the grain-oriented electrical steel sheet 1 of this embodiment, even if the thickness of the base steel sheet 10 is 0.19 mm or less, excellent magnetic flux density is obtained, and further, excellent iron loss and excellent noise characteristics are obtained after magnetic domain refining treatment.

[0104] [Other embodiments of the grain-oriented electrical steel sheet 1 of this embodiment] The grain-oriented electrical steel sheet 1 of this embodiment may further include a plurality of linear thermal strains each extending linearly and arranged in a direction perpendicular to the extending direction, or a plurality of grooves each extending linearly and arranged in a direction perpendicular to the extending direction.

[0105] The linear thermal strains or grooves are formed on the rolled surface of the grain-oriented electrical steel sheet 1 by a well-known magnetic domain refinement process. The linear thermal strains or grooves refine the magnetic domains of the grain-oriented electrical steel sheet 1. The grain-oriented electrical steel sheet 1 of this embodiment has excellent iron loss properties after the magnetic domain refinement process.

[0106] [Method for manufacturing the grain-oriented electrical steel sheet 1 of this embodiment] An example of a method for manufacturing the grain-oriented electrical steel sheet 1 of this embodiment will be described. The method for manufacturing the grain-oriented electrical steel sheet 1 described below is one example for manufacturing the grain-oriented electrical steel sheet 1 of this embodiment. Therefore, the grain-oriented electrical steel sheet 1 of this embodiment may be manufactured by a manufacturing method other than the manufacturing method described below. However, the manufacturing method described below is a preferred example of a method for manufacturing the grain-oriented electrical steel sheet 1 of this embodiment.

[0107] [Manufacturing Process Flow] An example of a method for manufacturing the grain-oriented electrical steel sheet 1 of this embodiment includes the following steps 1 to 6: (Step 1) Hot rolling step (Step 2) Hot-rolled sheet annealing step (Step 3) Cold rolling step (Step 4) Decarburization annealing step (Step 5) Finish annealing step (Step 6) Insulation coating formation step The hot-rolled sheet annealing step (Step 2) is an optional step. Therefore, the hot-rolled sheet annealing step may or may not be performed.

[0108] In the manufacturing method of this embodiment, the following manufacturing conditions are further satisfied in the cold rolling step (step 3) and the decarburization annealing step (step 4). (Condition 1) The cumulative reduction ratio RR of cold rolling in the cold rolling step is 89% or more and 93% or less. (Condition 2) For the work rolls of the rolling stand that performs the first pass of cold rolling, the arithmetic mean roughness Ra (μm) in the axial direction of the work roll, the ten-point mean roughness Rzjis (μm), and the work roll diameter Dw (mm) satisfy the following formulas (1) and (2): 0.30≦Ra≦0.01Dw+3.08 (1) 3Ra≦Rzjis≦7Ra (2) (Condition 3) Cold rolling is started from the front end to the rear end of the hot-rolled steel sheet manufactured in the hot rolling step. (Condition 4) During the temperature rise process in the decarburization annealing step, the average temperature rise rate HR in the range of 400° C. to 750° C. is set to 100° C. / sec or more and 3000° C. / sec or less.

[0109] Steps 1 to 6 will be described below.

[0110] [(Step 1) Hot Rolling Step] In the hot rolling step, a slab is hot rolled to produce a hot-rolled steel sheet. Here, the chemical composition of the prepared slab is adjusted so that the chemical composition of the grain-oriented electrical steel sheet 1 satisfies the range of this embodiment.

[0111] Specifically, the chemical composition of the slab is, in mass %, Si: 3.00 to 3.70%, Mn: 0.01 to 0.30%, N: 0.0030 to 0.0150%, C: 0.010 to 0.100%, sol. Al: 0.010 to 0.050%, one or more elements selected from the group consisting of S and Se: 0.010 to 0.050% in total, Ti: 0 to 0.010%, Ni: 0 to 0.50%, Cr: 0 to 0.50%, Cu: 0 to 0.50%, P: 0 to 0.05%, Mo: 0 to 0.05%, Sn: 0 to 0.30%, Sb: 0 to 0.30%, Bi: 0 to 0.0200%, Ta: 0 to 0.05%, Nb: 0 to 0.010%, V: 0 to 0.50%, B: 0 to 0.010%, Te: 0 to 0.0200%, and the balance being Fe and impurities.

[0112] The lower limit of the Si content is preferably 3.10%, more preferably 3.20%. The upper limit of the Si content is preferably 3.60%, more preferably 3.50%. The lower limit of the Mn content is preferably 0.02%, more preferably 0.05%. The upper limit of the Mn content is preferably 0.28%, more preferably 0.26%. The lower limit of the N content is preferably 0.0032%, more preferably 0.0034%. The upper limit of the N content is preferably 0.0120%, more preferably 0.0100%. The lower limit of the C content is preferably 0.012%, more preferably 0.014%. The upper limit of the C content is preferably 0.090%, more preferably 0.080%. The lower limit of the sol. Al content is preferably 0.012%, more preferably 0.014%. The upper limit of the Al content is preferably 0.048%, more preferably 0.046%. The lower limit of the total content of S and Se is preferably 0.012%, more preferably 0.014%. The upper limit of the total content of S and Se is preferably 0.048%, more preferably 0.046%. The lower limit of the Ti content is preferably 0.001%, more preferably 0.002%. The upper limit of the Ti content is preferably 0.008%, more preferably 0.006%. The lower limit of the Ni content is preferably 0.01%, more preferably 0.02%. The upper limit of the Ni content is preferably 0.40%, more preferably 0.30%, more preferably 0.20%. The lower limit of the Cr content is preferably 0.01%, more preferably 0.02%. The upper limit of the Cr content is preferably 0.40%, more preferably 0.30%, and even more preferably 0.20%. The lower limit of the Cu content is preferably 0.01%, and even more preferably 0.05%. The upper limit of the Cu content is preferably 0.40%, more preferably 0.30%, and even more preferably 0.20%. The lower limit of the P content is preferably 0.01%, and even more preferably 0.02%. The upper limit of the P content is preferably 0.04%, and even more preferably 0.03%.The lower limit of the Mo content is preferably 0.01%, more preferably 0.02%. The upper limit of the Mo content is preferably 0.04%, more preferably 0.03%. The lower limit of the Sn content is preferably 0.01%, more preferably 0.02%. The upper limit of the Sn content is preferably 0.25%, more preferably 0.20%. The lower limit of the Sb content is preferably 0.01%, more preferably 0.02%. The upper limit of the Sb content is preferably 0.25%, more preferably 0.20%, more preferably 0.15%. The lower limit of the Bi content is preferably 0.0001%, more preferably 0.0005%. The upper limit of the Bi content is preferably 0.0180%, more preferably 0.0150%, more preferably 0.0100%. The lower limit of the Ta content is preferably 0.01%, more preferably 0.02%. The upper limit of the Ta content is preferably 0.04%, more preferably 0.03%. The lower limit of the Nb content is preferably 0.001%, more preferably 0.002%. The upper limit of the Nb content is preferably 0.008%, more preferably 0.006%. The lower limit of the V content is preferably 0.01%, more preferably 0.05%. The upper limit of the V content is preferably 0.40%, more preferably 0.30%. The lower limit of the B content is preferably 0.001%, more preferably 0.002%. The upper limit of the B content is preferably 0.008%, more preferably 0.006%. The lower limit of the Te content is preferably 0.0001%, more preferably 0.0005%. The upper limit of the Te content is preferably 0.0150%, and more preferably 0.0100%.

[0113] In this manufacturing method, AlN is used as an inhibitor. Therefore, the Al content in the chemical composition of the slab is within the above-mentioned range. When a manufacturing method for grain-oriented electrical steel sheet using an inhibitor-less process is applied, the Al content in the slab is less than 0.010%.

[0114] Slabs are produced by the well-known steelmaking process, continuous casting process, or ingot making and blooming process. Slabs may be directly cast to thicknesses of up to 100 mm.

[0115] The hot rolling process using the prepared slab includes the following steps: (Step 11) Heating step (Step 12) Rough rolling step (Step 13) Finish rolling step Each of Steps 11 to 13 will be explained below.

[0116] [(Step 11) Heating Step] In the heating step, the slab is heated. For example, the slab is placed in a known heating furnace or a known soaking furnace and heated. The preferred heating temperature of the slab is 1100 to 1450°C.

[0117] [(Step 12) Rough Rolling Step] In the rough rolling step, rough rolling is performed on the heated slab to produce a rough bar (intermediate steel plate). Here, rough rolling means hot rolling the slab using a well-known rough rolling mill. The rough bar means an intermediate steel plate after the rough rolling step is completed and before the finish rolling step is started. In the rough rolling step, a rough rolling mill is used to apply a plurality of passes of reduction to the slab to produce a rough bar.

[0118] [(Step 13) Finish Rolling Step] In the finish rolling step, the rough bar produced in the rough rolling step is subjected to a known finish rolling to produce a hot-rolled steel sheet. Here, finish rolling means hot-rolling the rough bar using a known finish rolling mill. In the finish rolling step, a continuous rolling mill consisting of multiple tandem finishing rolling stands arranged in a row on a pass line is used to apply a rolling reduction to the rough bar by multiple passes to produce a hot-rolled steel sheet.

[0119] [(Step 2) Hot-rolled sheet annealing step] The hot-rolled sheet annealing step is an optional step. In other words, the hot-rolled sheet annealing step does not have to be performed. If performed, in the hot-rolled sheet annealing step, an annealing treatment is performed on the hot-rolled steel sheet produced in the hot rolling step. By performing the hot-rolled sheet annealing step, recrystallization occurs in the steel sheet structure, improving the magnetic properties.

[0120] In the hot-rolled sheet annealing step, it is sufficient to carry out well-known hot-rolled sheet annealing. The heating method of the hot-rolled steel sheet in the hot-rolled sheet annealing is not particularly limited, and a well-known heating method may be adopted. The hot-rolled sheet annealing temperature is, for example, 800 to 1200°C. The holding time at the hot-rolled sheet annealing temperature is, for example, 10 to 300 seconds. Note that when the hot-rolled sheet annealing step is carried out, the hot-rolled steel sheet may be subjected to pickling treatment after the hot-rolled sheet annealing step and before the cold-rolling step.

[0121] [(Step 3) Cold Rolling Step] In the cold rolling step, the produced hot-rolled steel sheet is cold-rolled to produce a cold-rolled steel sheet. As described above, the cold rolling step is carried out in one of the following two patterns: (Pattern 1) Tandem rolling is carried out, followed by reverse rolling. (Pattern 2) Only reverse rolling is carried out. The tandem rolling step and the reverse rolling step will be described.

[0122] [Tandem Rolling Process] In the tandem rolling process, cold rolling is performed using a tandem rolling mill. Fig. 2 is a schematic diagram of the tandem rolling mill. Referring to Fig. 2, the tandem rolling mill CM is disposed between a payoff reel (unwinding device) 21 and a tension reel (winding device) 22 from upstream to downstream.

[0123] The payoff reel 21 unwinds the wound hot-rolled steel sheet ST0. The tension reel 22 winds the intermediate steel sheet ST1 produced by the tandem rolling mill CM. The tandem rolling mill CM performs continuous rolling of the unwound hot-rolled steel sheet ST0 over a plurality of passes to produce the intermediate steel sheet ST1.

[0124] The tandem rolling mill CM is made up of multiple rolling stands CMS arranged in a row from upstream to downstream. １ ~CMS ｊ (j is a natural number of 2 or more). Each rolling stand CMS is equipped with a pair of work rolls WR1 extending horizontally. The pair of work rolls WR1 come into contact with the hot-rolled steel sheet to be cold-rolled, and cold-roll the hot-rolled steel sheet. The rolling stand CMS may be equipped with a plurality of backup rolls BR1. The backup rolls BR1 support the work rolls WR1 and suppress deflection of the work rolls WR1 during rolling.

[0125] In continuous rolling using a tandem rolling mill CM, when a hot-rolled steel sheet passes through each rolling stand CMS, the rolling is referred to as "one pass." Continuous rolling means that the hot-rolled steel sheet is rolled down in a plurality of passes using the tandem rolling mill CM. It is not necessary to roll down the hot-rolled steel sheet in all of the rolling stands CMS in the tandem rolling mill CM. For example, if there are six rolling stands CMS in the tandem rolling mill CM, １ ~CMS ６ In the case where the rolling stand CMS ６ In this case, when the hot rolled steel sheet is passed through without reduction, five passes of continuous rolling are carried out.

[0126] [Reverse Rolling Process] Fig. 3 is a schematic diagram of a multi-stage rolling mill used in the reverse rolling process. Referring to Fig. 3, in the reverse rolling process, a multi-stage rolling mill SM is used to perform reverse rolling with a plurality of passes on the intermediate steel sheet ST1 or the hot-rolled steel sheet ST0 after the tandem rolling process to produce a cold-rolled steel sheet ST2. In the following description, the intermediate steel sheet ST1 and the hot-rolled steel sheet ST0 will also be collectively referred to as the steel sheet ST.

[0127] The multi-stage rolling mill SM is, for example, a Sendzimir rolling mill. The multi-stage rolling mill SM is equipped with a pair of work rolls WR2 and a plurality of backup rolls BR2. In the multi-stage rolling mill SM, the pair of work rolls WR2 are supported by the plurality of backup rolls BR2, thereby minimizing deflection of the work rolls WR2. This makes it possible to achieve a high reduction. The pair of work rolls WR2 includes an upper work roll WR2U and a lower work roll WR2L. The lower work roll WR2L is disposed below the upper work roll WR2U.

[0128] Here, when a reduction is applied to the steel sheet ST as it passes through the multi-stage rolling mill SM, it is referred to as "one pass" reduction. In the case of reverse rolling, a reduction is applied to the steel sheet ST as it moves from upstream to downstream, and also as it moves from downstream to upstream. More specifically, one pass of reduction is applied to the steel sheet ST as it passes through the multi-stage rolling mill SM from upstream to downstream. Also, one pass of reduction is applied to the steel sheet ST as it passes through the same multi-stage rolling mill SM from downstream to upstream. In other words, when reduction is applied in both directions, two passes of reduction are applied to the steel sheet ST. Note that there are cases in which no reduction is applied to the steel sheet ST as it passes through the multi-stage rolling mill SM.

[0129] In the cold rolling step, either the above-mentioned tandem rolling and reverse rolling are carried out (pattern 1), or only reverse rolling is carried out (pattern 2) to produce a cold-rolled steel sheet.

[0130] [Manufacturing conditions in the cold rolling process] The cold rolling process satisfies the following conditions 1 to 3. (Condition 1) The cumulative reduction ratio RR of cold rolling in the cold rolling process is 89% or more and 93% or less. (Condition 2) For the work rolls of the rolling stand that performs the first pass of cold rolling, the arithmetic mean roughness Ra (μm), ten-point mean roughness Rzjis (μm), and work roll diameter Dw (mm) satisfy the following formulas (1) and (2): 0.30≦Ra≦0.01Dw+3.08 (1) 3Ra≦Rzjis≦7Ra (2) (Condition 3) Cold rolling is started from the front end to the rear end of the hot-rolled steel sheet manufactured in the hot rolling process. Conditions 1 to 3 will be explained below.

[0131] [Regarding Condition 1] The cumulative reduction rate RR of cold rolling in the cold rolling process is 89% or more and 93% or less. If the cumulative reduction rate RR is too low, {110}<112> oriented grains are generated in excess, and the generation of Goss oriented grains is excessively suppressed. If the cumulative reduction rate RR is too high, {211}<011> oriented grains are generated in excess, and the generation of Goss oriented grains is excessively suppressed. As a result, the produced grain-oriented electrical steel sheet 1 does not satisfy at least one of Requirements A to C. If the cumulative reduction rate RR is 89% or more and 93% or less, the cumulative reduction rate RR is in an appropriate range. In this case, the produced grain-oriented electrical steel sheet 1 satisfies Requirements A to C.

[0132] The preferred lower limit of the cumulative rolling reduction RR is 90%. The preferred upper limit of the cumulative rolling reduction RR is 92%.

[0133] [Regarding Formula (1) of Condition 2] For the work rolls of the rolling stand that performs the first pass reduction of cold rolling, the arithmetic mean roughness Ra (μm) in the axial direction of the work roll and the diameter Dw (mm) of the work roll satisfy Formula (1): 0.30≦Ra≦0.01Dw+3.08 (1)

[0134] The arithmetic mean roughness Ra of the work roll affects requirements A to C. If the arithmetic mean roughness Ra is too low, the strain introduced into the steel sheet is excessively small. In this case, {110}<112> oriented grains or {211}<011> oriented grains are generated in excess, and the generation of Goss oriented grains is excessively suppressed. As a result, the produced grain-oriented electrical steel sheet 1 does not satisfy at least one of requirements A to C.

[0135] On the other hand, if the arithmetic mean roughness Ra is too high relative to the work roll diameter Dw, excessive strain is introduced into the steel sheet surface layer. In particular, the reduction in the first pass of cold rolling has a significant effect on the shear texture of the steel sheet surface layer formed by hot rolling. If excessive strain is introduced into the steel sheet surface layer by the work rolls of the rolling stand that performs the reduction in the first pass of cold rolling, the development of texture is hindered. As a result, {110}<112> oriented grains or {211}<011> oriented grains are generated in excess, and the generation of Goss oriented grains is excessively suppressed. As a result, the manufactured grain-oriented electrical steel sheet 1 does not satisfy at least one of requirements A to C.

[0136] When the arithmetic mean roughness Ra satisfies the formula (1), the produced grain-oriented electrical steel sheet 1 satisfies requirements A to C.

[0137] The preferred lower limit of the arithmetic mean roughness Ra is 0.32 μm, and more preferably 0.34 μm. The preferred upper limit of the arithmetic mean roughness Ra is 0.01 Dw + 3.00, and more preferably 0.01 Dw + 2.90. The work roll diameter Dw is the arithmetic mean value of the diameters of a pair of work rolls.

[0138] [Regarding formula (2) of condition 2] In the work rolls of the rolling stand that performs the first pass reduction of cold rolling, the arithmetic mean roughness Ra (μm) in the axial direction of the work roll and the ten-point mean roughness Rzjis (μm) satisfy formula (2): 3Ra≦Rzjis≦7Ra (2)

[0139] The ten-point mean roughness Rzjis of a work roll is an index showing the local magnitude of unevenness on the work roll. In order for the high-angle grain boundary ratio RL to be within a certain range, Goss-oriented grains with slightly misaligned orientations must be adjacent to each other through secondary recrystallization. The ten-point mean roughness Rzjis affects the amount of local change in the steel sheet surface during cold rolling and affects the misalignment of adjacent Goss-oriented grains. In other words, the ten-point mean roughness Rzjis affects the high-angle grain boundary ratio RL.

[0140] If the ten-point mean roughness Rzjis is excessively low relative to the arithmetic mean roughness Ra of the work roll, the misorientation between adjacent Goss-oriented grains becomes excessively small. In this case, the high-angle grain boundary fraction RL becomes excessively small. On the other hand, if the ten-point mean roughness Rzjis is excessively high relative to the arithmetic mean roughness Ra of the work roll, the misorientation between adjacent Goss-oriented grains becomes excessively large. In this case, the high-angle grain boundary fraction RL becomes excessively large. If the ten-point mean roughness Rzjis satisfies formula (2), the high-angle grain boundary fraction RL is 5% or more and 30% or less.

[0141] The upper limit of the ten-point average roughness Rzjis is preferably 6.5 Ra, more preferably 6.0 Ra. The lower limit of the ten-point average roughness Rzjis is preferably 3.5 Ra, more preferably 4.0 Ra.

[0142] [Method of measuring arithmetic mean roughness Ra and ten-point mean roughness Rzjis] The arithmetic mean roughness Ra and ten-point mean roughness Rzjis of the work rolls of a rolling stand are determined by the following method.

[0143] Three arbitrary locations are selected as measurement locations on the surface of each work roll of a pair of work rolls. In other words, there are six measurement locations. On the surface of each work roll, the three measurement locations are arranged in a row in the axial direction of the work roll, with the measurement locations spaced 100 mm apart. At each measurement location, the arithmetic mean roughness Ra (μm) and ten-point mean roughness Rzjis (μm) are measured in the axial direction of the work roll in accordance with the method specified in JIS B 0601:2001. A contact-type roughness meter is used for the measurements. The conditions for calculating the roughness curve are as follows: Measuring force: 0.75 mN Stylus tip shape: 2 μmR60° Cutoff value λc: 0.8 mm Cutoff value λs: 2.5 μm Number of sections: 3 Measurement speed: 0.25 mm / sec Reference length: 0.8 mm Evaluation length: 16 mm A contact-type roughness meter, for example, SJ-210 manufactured by Mitutoyo Corporation, is used. The arithmetic mean value of the obtained arithmetic mean roughnesses at six locations is defined as the arithmetic mean roughness Ra (μm) of the work roll in the axial direction. The arithmetic mean value of the obtained ten-point mean roughnesses at six locations is defined as the ten-point mean roughness Rzjis (μm) of the work roll in the axial direction.

[0144] [Regarding Condition 3] In the manufacturing method of this embodiment, in the cold rolling step, cold rolling is started from the front end to the rear end of the hot-rolled steel sheet manufactured in the hot rolling step. That is, the rolling direction of the steel sheet at the start of cold rolling is made to coincide with the rolling direction of the steel sheet during hot rolling.

[0145] In the cold rolling process, if cold rolling is started from the front end to the rear end of the hot-rolled steel sheet produced in the hot-rolling process, the high-angle grain boundary fraction RL becomes 30% or less. Although the reason for this is not clear, the following reason is thought to be the case. If cold rolling is started from the front end to the rear end of the hot-rolled steel sheet produced in the hot-rolling process, it is thought that a suitable rolling structure that becomes a source of Goss orientation is formed in the shear deformation layer of the surface layer of the hot-rolled steel sheet produced in the hot-rolling process.

[0146] [(Step 4) Decarburization Annealing Step] In the decarburization annealing step, the cold-rolled steel sheet after the cold rolling step is subjected to decarburization annealing to induce primary recrystallization.

[0147] The decarburization annealing process includes the following steps: (Step 41) Heating step (Step 42) Decarburization step (Step 43) Cooling step

[0148] In the heating step (step 41), the steel sheet is heated to a desired temperature (ultimate temperature) between 750 and 950°C. In the decarburization step (step 42), the steel sheet is held at a decarburization annealing temperature of 750 to 950°C to perform decarburization annealing and induce primary recrystallization. In the cooling step (step 43), the steel sheet after the decarburization step is cooled by a known method. Note that the ultimate temperature and the decarburization annealing temperature may be the same temperature, or the ultimate temperature may be higher than the decarburization annealing temperature.

[0149] In this embodiment, in the heating step, the average heating rate HR is significantly increased in the temperature range of 400 to 750°C, which corresponds to the recrystallization temperature range of the steel sheet. This promotes the recrystallization of Goss-oriented grains. This increases the degree of concentration of Goss-oriented grains after secondary recrystallization. As a result, the magnetic properties of the grain-oriented electrical steel sheet can be improved.

[0150] Each step will be described in detail below.

[0151] [(Step 41) Heating Step] In the heating step, first, the cold-rolled steel sheet after the cold rolling step is loaded into a heat treatment furnace (decarburization annealing furnace). The atmosphere inside the heat treatment furnace is a nitrogen and hydrogen mixed gas atmosphere (non-oxidizing atmosphere) with a dew point of -50 to 0°C. In the heat treatment furnace for decarburization annealing in this embodiment, the cold-rolled steel sheet is heated to an arbitrary temperature between 750 and 900°C by, for example, high-frequency induction heating or electrical heating. The heating step satisfies the following condition 4. (Condition 4) The average heating rate HR in the temperature range of 400 to 750°C is 100°C / s or more and 3000°C / s or less.

[0152] [Regarding Condition 4] In the heating step, the average heating rate in the temperature range of the cold-rolled steel sheet from 400°C to 750°C is defined as the average heating rate HR (°C / sec).

[0153] Strain accumulates in the cold-rolled steel sheet produced by the cold rolling process. If the average heating rate HR is less than 100°C / s, the strain energy that serves as the driving force for recrystallization is released before the recrystallization begins. In this case, a sufficient amount of Goss-oriented grains cannot be generated in the cold-rolled steel sheet after primary recrystallization (i.e., the cold-rolled steel sheet after the decarburization annealing process).

[0154] When the average heating rate HR is 100°C / s or more, primary recrystallization occurs in a state where sufficient strain energy is accumulated in the cold-rolled steel sheet. Therefore, a sufficient amount of Goss-oriented grains can be generated in the cold-rolled steel sheet after primary recrystallization. Therefore, in the subsequent finish annealing process, many Goss-oriented grains remain when secondary recrystallization occurs. Therefore, the degree of accumulation of Goss-oriented grains after secondary recrystallization can be increased. As a result, the magnetic properties of the grain-oriented electrical steel sheet can be improved, and the variation in magnetic properties can also be suppressed.

[0155] The upper limit of the average heating rate HR is not particularly limited. However, even if the average heating rate HR is set to be faster than 3000° C. / s, the above-mentioned effect saturates. Therefore, the upper limit of the average heating rate HR is set to 3000° C. / s.

[0156] The lower limit of the average heating rate HR is preferably 150° C. / sec, and more preferably 200° C. / sec.

[0157] The average heating rate HR is measured by the following method. A plurality of thermometers are installed in a heat treatment furnace to measure the surface temperature of the steel sheet. The thermometers are arranged from upstream to downstream of the heat treatment furnace. The average heating rate HR (°C / sec) is calculated based on the temperature of the steel sheet measured by the thermometers and the time it takes for the steel sheet temperature to rise from 400°C to 750°C.

[0158] [(Step 42) Decarburization Step] In the decarburization step, the cold-rolled steel sheet after the heating step is held at the decarburization annealing temperature to perform decarburization annealing. This causes primary recrystallization to occur in the cold-rolled steel sheet. The atmosphere during the decarburization step may be a well-known atmosphere, for example, a non-oxidizing atmosphere containing hydrogen and nitrogen. The oxygen potential Po is, for example, 0.01 to 0.60. By performing decarburization annealing, carbon in the steel sheet is removed from the steel sheet, causing primary recrystallization to occur. The decarburization annealing temperature and the holding time at the decarburization annealing temperature are not particularly limited. The decarburization annealing temperature is, for example, 750 to 950°C. The holding time at the decarburization annealing temperature is, for example, 15 to 150 seconds.

[0159] [(Step 43) Cooling Step] In the cooling step, the cold-rolled steel sheet after the decarburization step is cooled to room temperature by a well-known method to obtain a decarburization-annealed steel sheet. The cooling method may be natural cooling or water cooling. Preferably, the cold-rolled steel sheet after the decarburization step is natural cooling. Through the above steps, a decarburization-annealed steel sheet is produced in the decarburization-annealing step.

[0160] [(Step 5) Finish Annealing Step] In the finish annealing step, an annealing separator is applied to a decarburization-annealed steel sheet, and the decarburization-annealed steel sheet to which the annealing separator has been applied is subjected to finish annealing to produce a finish annealed steel sheet. The finish annealing step includes the following steps: (Step 51) Annealing Separator Application Step (Step 52) Annealing Step Each step will be described below.

[0161] [(Step 51) Annealing Separator Application Step] In the annealing separator application step, an annealing separator is applied to the decarburized annealed steel sheet. Specifically, an aqueous slurry containing the annealing separator is applied to the decarburized annealed steel sheet. The aqueous slurry is prepared by adding water to the annealing separator and stirring the mixture.

[0162] The annealing separator may be one whose main component is magnesium oxide (MgO), or one whose main components are silica and alumina. "Main component" means that the annealing separator contains 60.0% or more by mass. The annealing separator may contain well-known additives other than MgO or silica and alumina. When emphasis is placed on reducing iron loss, the annealing separator should contain MgO as the main component. When emphasis is placed on punching workability, the annealing separator should contain silica and alumina as the main components.

[0163] In the annealing separator application process, an annealing separator in the form of an aqueous slurry is applied to the surface of the decarburized annealed steel sheet. The steel sheet with the annealing separator applied to its surface is wound into a coil. After the steel sheet is coiled, the annealing process is carried out.

[0164] [(Step 52) Annealing Step] The steel sheet after the annealing separator application step is subjected to an annealing step to induce secondary recrystallization. The final annealing step is performed by loading the coiled steel sheet into a heat treatment furnace. The manufacturing conditions for the annealing step are, for example, as follows. The atmosphere in the furnace during the annealing step is a well-known atmosphere.

[0165] Finish annealing temperature: 800 to 1200°C. Holding time at the finish annealing temperature: 5 to 60 hours. If the finish annealing temperature is less than 800°C, sufficient secondary recrystallization does not occur, and the precipitates used in the secondary recrystallization are not sufficiently purified. This results in poor magnetic properties of the produced grain-oriented electrical steel sheet. On the other hand, if the finish annealing temperature exceeds 1200°C, the effect on secondary recrystallization and purification is low, and problems such as steel sheet deformation occur. If the finish annealing temperature is 800 to 1200°C, assuming the above-mentioned holding time is appropriate, sufficient secondary recrystallization occurs and magnetic properties are improved. Furthermore, a primary coating is formed on the steel sheet surface. Using the above manufacturing process, the finish annealing process produces a finish-annealed steel sheet.

[0166] The final annealing process removes some of the elements in the chemical composition of the steel sheet. In particular, S, Al, N, and the like, which function as inhibitors, are largely removed. Furthermore, a lower coating (primary coating or intermediate layer) is formed on the surface of the grain-oriented electrical steel sheet after the final annealing process.

[0167] [(Step 6) Insulating Coating Forming Step] In the insulating coating forming step, an insulating coating (insulating coating) forming agent is applied to the finish annealed steel sheet. Further, the finish annealed steel sheet to which the insulating coating forming agent has been applied is subjected to a heat treatment. In this way, an insulating coating (insulating coating) is formed on the finish annealed steel sheet.

[0168] Specifically, a well-known insulating coating agent containing at least one inorganic substance, such as metal chromate salts, metal phosphate salts, colloidal silica, Zr compounds, and Ti compounds, is applied to the surface of a finish-annealed steel sheet (on the underlayer coating). The finish-annealed steel sheet to which the insulating coating agent has been applied is then baked. As a result, a well-known insulating coating is formed on the primary coating.

[0169] [Other Optional Steps] [Nitriding Step] The method for producing the grain-oriented electrical steel sheet 1 according to this embodiment may further include a nitriding step after the decarburization annealing step (step 4) and before the finish annealing step (step 5), if necessary. The nitriding step may be carried out under well-known conditions. The nitriding temperature is, for example, 700 to 850°C. The atmosphere in the nitriding furnace (nitriding atmosphere) is, for example, an atmosphere containing hydrogen, nitrogen, and a gas having nitriding ability, such as ammonia.

[0170] If the nitriding temperature is 700°C or higher, or 850°C or lower, nitrogen easily penetrates into the steel sheet during nitriding. Nitriding within this temperature range ensures a favorable amount of nitrogen inside the steel sheet. Therefore, fine AlN is favorably formed in the steel sheet before secondary recrystallization. As a result, secondary recrystallization favorably occurs during finish annealing. The time for which the steel sheet is held at the nitriding temperature is not particularly limited, but is, for example, 10 to 60 seconds.

[0171] [Magnetic Domain Refinement Treatment Step] The grain-oriented electrical steel sheet according to this embodiment may further be subjected to a magnetic domain refinement treatment step, if necessary, after the finish annealing step (step 5) or the insulating coating formation step (step 6). In the magnetic domain refinement treatment step, the surface (rolled surface) of the grain-oriented electrical steel sheet is irradiated with a laser beam that has a magnetic domain refinement effect to form linear thermal strain on the surface of the steel sheet, or to physically form grooves on the surface of the steel sheet. In this case, a grain-oriented electrical steel sheet with even better magnetic properties can be produced.

[0172] The grain-oriented electrical steel sheet 1 of this embodiment is manufactured by the above manufacturing process.

[0173] Hereinafter, aspects of the present invention will be described in detail with reference to examples. These examples are examples for confirming the effects of the manufacturing method of the grain-oriented electrical steel sheet according to the present embodiment, and are not intended to limit the present invention.

[0174] Grain-oriented electrical steel sheets shown in Table 3 (Tables 3A and 3B) were produced using slabs having the chemical compositions shown in Table 1 (Tables 1A, 1B, 1C, and 1D).

[0175] Specifically, the slabs shown in Table 1 (Table 1A, Table 1B, Table 1C, and Table 1D) were prepared.

[0176]

[0177]

[0178]

[0179]

[0180] The prepared slabs were subjected to a hot rolling process. Specifically, the slabs of each test number were heated to 1340°C in a heating furnace. The heated slabs were hot rolled to produce hot-rolled steel sheets having thicknesses (mm) shown in Table 3 (Table 3A, Table 3B).

[0181]

[0182]

[0183]

[0184]

[0185] The hot-rolled steel sheet after the hot rolling process was subjected to a hot-rolled sheet annealing process at a hot-rolled sheet annealing temperature of 900 to 1200°C for a holding time of 10 to 300 seconds. After the hot-rolled sheet annealing process, a cold-rolling process was carried out to produce a cold-rolled steel sheet having a sheet thickness (mm) shown in Table 3 (Table 3A, Table 3B). The conditions for the cold rolling process, namely, the cumulative reduction rate RR (%), the arithmetic mean roughness Ra (μm) of the work roll of the rolling stand for the first pass, the diameter Dw (mm) of the work roll of the rolling stand for the first pass, the ten-point mean roughness Rzjis (μm) of the work roll of the rolling stand for the first pass, the rolling direction of the first pass of cold rolling, and the cold rolling pattern, were as shown in Table 3 (Table 3A, Table 3B).

[0186] Here, in Table 3 (Table 3A, Table 3B), "T" in the "Evaluation" column of "Formula (1)" means that the arithmetic mean roughness Ra satisfies Formula (1), and "F" means that the arithmetic mean roughness Ra does not satisfy Formula (1). "Same direction" in the "Rolling direction of first pass" column means that cold rolling was started from the front end to the rear end of the hot-rolled steel sheet produced in the hot-rolling process, and "Opposite direction" means that cold rolling was started from the rear end to the front end of the hot-rolled steel sheet produced in the hot-rolling process. In the "Cold rolling pattern" column, "T+R" means that reverse rolling was performed after tandem rolling (i.e., Pattern 1 was performed as cold rolling), and "R" means that only reverse rolling was performed (i.e., Pattern 2 was performed as cold rolling).

[0187] The arithmetic mean roughness Ra and ten-point mean roughness Rzjis of the work rolls in the first pass of cold rolling were measured based on the above-mentioned [Method for measuring arithmetic mean roughness Ra and ten-point mean roughness Rzjis].

[0188] The cold-rolled steel sheet after the cold rolling process was subjected to a decarburization annealing process. Specifically, the atmosphere in the decarburization annealing furnace was a nitrogen and hydrogen mixed gas atmosphere (non-oxidizing atmosphere) with a dew point of -30°C. The average heating rate HR (°C / sec) in the temperature range of 400 to 750°C was as shown in Table 3 (Table 3A, Table 3B). After heating to a temperature of 800 to 950°C, the steel sheet was held at 800 to 950°C for 120 to 150 seconds. The oxygen potential Po in the atmosphere at this time was set to 0.01 to 0.60.

[0189] An annealing separator containing MgO as a main component was applied to the surface of the decarburized annealed steel sheet, and then the decarburized annealed steel sheet coated with the annealing separator was wound into a coil.

[0190] The coil was subjected to finish annealing to produce a finish annealed steel sheet. The finish annealing temperature was set to 1100 to 1200°C, and the holding time at the finish annealing temperature was set to 5 to 30 hours.

[0191] An insulating coating formation process was carried out on the steel sheets after the finish annealing process. Specifically, an insulating coating forming agent mainly composed of colloidal silica and phosphate was applied to the surface of the finish annealed steel sheets of each test number. The finish annealed steel sheets to which the insulating coating forming agent had been applied were then baked under the same conditions to form an insulating coating on the underlayer coating (primary coating). Grain-oriented electrical steel sheets of each test number were manufactured by the above manufacturing process.

[0192] The chemical composition of the grain-oriented electrical steel sheet of each test number was measured based on the above-mentioned [Method for measuring the chemical composition of grain-oriented electrical steel sheet 1]. As a result, the chemical compositions of the base steel sheets of the grain-oriented electrical steel sheets of each test number were as shown in Table 2 (Table 2A, Table 2B, Table 2C, Table 2D). The test equipment used was a component analyzer manufactured by Shimadzu Corporation (product name: ICPS-8000).

[0193]

[0194]

[0195] [Evaluation Tests] The following evaluation tests were carried out on the produced grain-oriented electrical steel sheets. (Test 1) Number Ratio R ｛２１１｝＜０１１＞ , number ratio R ｛１１０｝＜１１２＞ , and the number ratio R ｛１１０｝＜００１＞(Test 2) Measurement test of the high-angle grain boundary ratio RL (Test 3) Measurement test of magnetic flux density (Test 4) Iron loss evaluation test of grain-oriented electrical steel sheet after magnetic domain refinement treatment (Test 5) Magnetostriction evaluation test of grain-oriented electrical steel sheet after magnetic domain refinement treatment Tests 1 to 5 are described below.

[0196] [(Test 1) Number Ratio R ｛２１１｝＜０１１＞ , number ratio R ｛１１０｝＜１１２＞ , and the number ratio R ｛１１０｝＜００１＞ Based on the method described in the above [Method for measuring crystal orientation at measurement point], the number ratio R of grain-oriented electrical steel sheets of each test number was measured. ｛２１１｝＜０１１＞ (%), number ratio R ｛１１０｝＜１１２＞ (%) and number ratio R ｛１１０｝＜００１＞ The obtained values ​​are shown in Table 4 (Table 4A, Table 4B).

[0197]

[0198]

[0199] [(Test 2) Measurement test of high-angle grain boundary ratio RL] Based on the method described in [Method for measuring crystal orientation at measurement point] above, the high-angle grain boundary ratio RL (%) of the grain-oriented electrical steel sheet of each test number was determined. The obtained values ​​are shown as "LI / La (%)" in Table 4 (Table 4A and Table 4B).

[0200] [(Test 3) Magnetic Flux Density Measurement Test] A magnetic domain refining treatment was carried out by laser irradiation on the grain-oriented electrical steel sheets of each test number. In the magnetic domain refining treatment by laser irradiation, the irradiation pitch in the rolling direction was set to 4 mm intervals. The energy density Ua was set to 1.25 mJ / mm ２ It was decided.

[0201] A test piece was taken from the center of the sheet width of each grain-oriented electrical steel sheet of each test number after the magnetic domain refining treatment. The size of the test piece was 60 mm in the sheet width direction × 300 mm in the rolling direction × sheet thickness. In accordance with JIS C2556:2015, a magnetic field of 800 A / m was applied to the test piece by a single sheet magnetic property test (SST test), and the magnetic flux density B ８ The magnetic flux density B (T) was calculated. ８ "B" in Table 4 (Table 4A, Table 4B) ８ (T)" Magnetic flux density B８ If the magnetic flux density B is 1.921 T or more, it is determined that an excellent magnetic flux density is obtained. ８ When the value was less than 1.700T, it was determined that secondary recrystallization defects occurred, and Tests 1, 2, 4, and 5 were not carried out.

[0202] [(Test 4) Iron Loss Evaluation Test of Grain-Oriented Electrical Steel Sheet After Magnetic Domain Refinement Treatment] A test piece was taken from the center of the sheet width of the grain-orientated electrical steel sheet after magnetic domain refinement treatment. The size of the test piece was 100 mm x 500 mm x sheet thickness. In accordance with JIS C2556:2011, the iron loss W １７／５０ (W / kg) was calculated. １７／５０ The "W" in Table 4 (Table 4A, Table 4B) １７／５０ For each test number, it was determined that excellent iron loss was obtained under the following conditions: (1) When the plate thickness was 0.22 mm, the iron loss W １７／５０ (2) When the plate thickness is 0.19 mm, the iron loss W １７／５０ (3) When the plate thickness is 0.17 mm, the iron loss W １７／５０ is 0.625 W / kg or less.

[0203] [(Test 5) Magnetostriction Evaluation Test of Grain-Oriented Electrical Steel Sheets After Magnetic Domain Refinement Treatment] The magnetostriction of the grain-orientated electrical steel sheets of each test number was measured by the following method. The test specimens used were those obtained in Test 4 above. The magnetostriction measurement device was equipped with a laser Doppler vibrometer, an excitation coil, an excitation power supply, a magnetic flux detection coil, an amplifier, and an oscilloscope. Using the magnetostriction measurement device, magnetostriction was determined by an AC magnetostriction measurement method. Specifically, an AC magnetic field was applied to the test specimen so that the maximum magnetic flux density in the rolling direction was 1.700 T. The change in length of the sample due to expansion and contraction of the magnetic domains was measured with the laser Doppler vibrometer to obtain a magnetostriction signal. The obtained magnetostriction signal was subjected to Fourier analysis to determine the amplitude Cn of each frequency component fn (n is a natural number greater than or equal to 1) of the magnetostriction signal. The A correction coefficient αn of each frequency component fn was used to determine the magnetostriction rate level LVA (dB) expressed by the following equation: LVA=20×Log(√(Σ(ρc×2π×fn×αn×Cn / √2) ２ ) / Pe0) where ρc is the specific acoustic resistance, and ρc = 400. Pe0 is the minimum audible sound pressure, and Pe0 = 2 × 10 －５ (Pa) was used. The A correction coefficient αn was the value shown in Table 2 of JIS C 1509-1 (2005). The obtained magnetostriction velocity level LVA is shown in Table 4. If the obtained magnetostriction velocity level (LVA) was 58.04 dB or less, it was determined that excellent noise characteristics were obtained.

[0204] [Evaluation Results] With reference to Table 1 (Table 1A to Table 1D) and Table 2 (Table 2A to Table 2D), the grain-oriented electrical steel sheets of test numbers 1 to 47 satisfied requirements A to C, and had a high-angle grain boundary ratio RL (= LI / La) of 5 to 30%. Therefore, after the refinement treatment, they had excellent magnetic flux density B ８ Furthermore, after the magnetic domain refining process, excellent iron loss and noise characteristics were obtained.

[0205] On the other hand, in test numbers 48 to 53, condition 1 was not satisfied in the manufacturing process. Therefore, any of requirements A to C was outside the scope of the present invention. As a result, a sufficient magnetic flux density B ８ Furthermore, sufficient iron loss was not obtained, and sufficient noise characteristics were not obtained.

[0206] In test numbers 54 to 60, under manufacturing process condition 2, the arithmetic mean roughness Ra of the work roll in the first pass did not satisfy formula (1). Therefore, any of requirements A to C fell outside the scope of the present invention. As a result, a sufficient magnetic flux density B ８ In this case, sufficient core loss was not obtained, and sufficient noise characteristics were not obtained.

[0207] In test numbers 61 and 62, under manufacturing process condition 2, the ten-point average roughness Rzjis of the work roll in the first pass did not satisfy the upper limit of formula (2). Therefore, the high-angle grain boundary ratio RL (= LI / La) exceeded 30%. As a result, a sufficient magnetic flux density B ８ Furthermore, sufficient iron loss was not obtained, and furthermore, sufficient noise characteristics were not obtained.

[0208] In test number 63, under manufacturing process condition 2, the ten-point average roughness Rzjis of the work roll in the first pass did not satisfy the lower limit of formula (2). Therefore, the high-angle grain boundary ratio RL (= LI / La) was less than 5%. As a result, a sufficient magnetic flux density B ８ However, sufficient iron loss was not obtained.

[0209] Test No. 64 did not satisfy Condition 3 of the manufacturing process. Therefore, the high-angle grain boundary ratio RL (= LI / La) exceeded 30%. As a result, sufficient iron loss was not obtained, and furthermore, sufficient noise characteristics were not obtained.

[0210] Test numbers 65 and 66 did not satisfy condition 4 of the manufacturing process. ｛１１０｝＜００１＞ (Requirement C) was less than 90%. As a result, a sufficient magnetic flux density B ８ Furthermore, sufficient iron loss was not obtained, and furthermore, sufficient noise characteristics were not obtained.

[0211] In test number 67, the Si content of the slab and grain-oriented electrical steel sheet was too high, which caused the steel sheet to break during the manufacturing process, so an evaluation test was not carried out.

[0212] In test number 68, the Si content of the slab and grain-oriented electrical steel sheet was too low, and therefore sufficient iron loss could not be obtained even after the magnetic domain refinement treatment.

[0213] In test number 69, the Mn content in the slab and the base steel sheet of the grain-oriented electrical steel sheet was too high. ８ was less than 1.700T.

[0214] In test number 70, the Mn content in the slab and the base steel sheet of the grain-oriented electrical steel sheet was too low. ８ was less than 1.700T.

[0215] In test number 71, the N content of the slab was too high, and in test number 72, the N content of the slab was too low. ８ was less than 1.700T.

[0216] In test number 73, the C content of the slab was too high, and in test number 74, the C content of the slab was too low. ８ was less than 1.700T.

[0217] In test number 75, the sol. Al content of the slab was too high, and in test number 76, the sol. Al content of the slab was too low. ８ was less than 1.700T.

[0218] In test numbers 77 to 82, the total content of S and Se in the slab was outside the range of the present invention. ８ was less than 1.700T.

[0219] The embodiments of the present disclosure have been described above. However, the above-described embodiments are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiments, and can be implemented by appropriately modifying the above-described embodiments within the scope of the present disclosure.

[0220] 1 Grain-oriented electrical steel sheet 10 Base steel sheet 11 Lower layer coating 12 Insulating coating

Claims

1. It is a grain-oriented electrical steel sheet, Including the base steel plate, The chemical composition of the aforementioned base steel sheet is, in mass%, Si: 3.00-3.70%, Mn: 0.01 to 0.30%, N: 0.0001 to 0.0100%, C: 0.001 to 0.010%, Sol. Al: 0-0.010%, One or more selected from the group consisting of S and Se: total 0-0.010% Ti: 0 to 0.010%, Ni: 0 to 0.50%, Cr: 0 to 0.50%, Cu: 0 to 0.50%, P: 0-0.05%, Mo: 0 to 0.05%, Sn: 0 to 0.30%, Sb: 0 to 0.30%, Bi: 0 to 0.0150%, Ta: 0 to 0.05%, Nb: 0 to 0.010%, V: 0-0.50%, B: 0 to 0.010%, Te: 0 to 0.0150%, and, The remainder consists of Fe and impurities. When the crystal orientation is measured by X-ray diffraction at measurement points arranged at 2 mm intervals in the rolling direction and in the direction perpendicular to the rolling direction on the surface of the base steel sheet, The percentage of measurement points where the azimuth difference from the {211}<011> direction relative to all measurement points is 15° or less (R) ｛２１１｝＜０１１＞ The percentage is 5% or less. The percentage of measurement points where the azimuth difference from the {110} <112> direction relative to all measurement points is 15° or less (R) ｛１１０｝＜１１２＞ The percentage is 5% or less. The percentage of measurement points where the azimuth difference from the {110}<001> direction relative to all measurement points is 15° or less R ｛１１０｝＜００１＞ The percentage is over 90%, The ratio of the total length LI of grain boundaries with an orientation difference of 15° or more to the total length La of the grain boundaries of the crystal grains obtained from the orientation difference at the aforementioned measurement point, RL = LI / La, is 5% or more and 30% or less. Grain-oriented electrical steel sheet.

2. A grain-oriented electrical steel sheet according to claim 1, The thickness of the base steel plate is 0.19 mm or less. Grain-oriented electrical steel sheet.

3. A grain-oriented electrical steel sheet according to claim 1, The chemical composition of the aforementioned base steel sheet is, in mass%, Ti: 0.001 to 0.010%, Ni: 0.01-0.50%, Cr: 0.01-0.50%, Cu: 0.01 to 0.50%, P: 0.01-0.05%, Mo: 0.01-0.05%, Sn: 0.01-0.30%, Sb: 0.01 to 0.30%, Bi: 0.0001 to 0.0150%, Ta: 0.01-0.05%, Nb: 0.001 to 0.010%, V: 0.01-0.50%, B: 0.001 to 0.010%, and, Contains one or more selected from the group consisting of Te: 0.0001 to 0.0150%, Grain-oriented electrical steel sheet.

4. A method for manufacturing grain-oriented electrical steel sheets according to any one of claims 1 to 3, In mass percent, Si: 3.00-3.70%, Mn: 0.01 to 0.30%, N: 0.0030-0.0150%, C: 0.010-0.100%, Sol. Al: 0.010–0.050%, One or more selected from the group consisting of S and Se: 0.010 to 0.050% in total. Ti: 0 to 0.010%, Ni: 0 to 0.50%, Cr: 0 to 0.50%, Cu: 0 to 0.50%, P: 0-0.05%, Mo: 0 to 0.05%, Sn: 0 to 0.30%, Sb: 0 to 0.30%, Bi: 0-0.0200%, Ta: 0 to 0.05%, Nb: 0 to 0.010%, V: 0-0.50%, B: 0 to 0.010%, Te: 0 to 0.0200%, and, The remaining portion consists of a slab made of Fe and impurities, which is hot-rolled to form a hot-rolled steel sheet in a hot-rolling process. A hot-rolled steel sheet annealing step, A cold rolling step is performed to cold roll the hot-rolled steel sheet after the hot-rolled sheet annealing step to obtain a cold-rolled steel sheet. A decarburization annealing step is performed on the cold-rolled steel sheet to obtain a decarburized annealed steel sheet. A finish annealing process is performed on the decarburized annealed steel sheet by applying an annealing release agent and then performing finish annealing to obtain a finish annealed steel sheet. The process includes an insulating coating forming step of forming an insulating coating on the surface of the finished annealed steel sheet, In the aforementioned cold rolling process, The cumulative reduction rate should be between 89% and 93%. In a work roll of a rolling stand that performs the first pass of cold rolling, the axial arithmetic mean roughness Ra (μm), the ten-point mean roughness Rzjis (μm), and the diameter Dw (mm) of the work roll satisfy equations (1) and (2). A method for manufacturing grain-oriented electrical steel sheets. 0.30≦Ra≦0.01Dw+3.08 (1) 3Ra ≤ Rzjis ≤ 7Ra (2)

5. A method for manufacturing grain-oriented electrical steel sheets according to claim 4, In the aforementioned decarburization annealing process, The decarburization annealing temperature is set to 750-950°C. The average heating rate from 400°C to 750°C shall be between 100°C / second and 3000°C / second. A method for manufacturing grain-oriented electrical steel sheets.

6. A method for manufacturing grain-oriented electrical steel sheets according to claim 4, In the aforementioned cold rolling process, Cold rolling is started from the front end to the rear end of the hot-rolled steel sheet produced in the hot-rolling process. A method for manufacturing grain-oriented electrical steel sheets.