Grain-oriented electrical steel sheet, and method for manufacturing grain-oriented electrical steel sheet

Abstract

We provide a oriented electrical steel sheet that obtains excellent magnetic properties, excellent iron loss properties, and also obtains excellent noise properties. The oriented electrical steel sheet according to the present disclosure comprises a base steel sheet, and when the crystal orientation is measured by X-ray diffraction at measurement points arranged at a pitch of 2 mm in each direction of the rolling direction and the direction perpendicular to the rolling direction on the surface of the base steel sheet, the ratio of the number of measurement points R{211} with an orientation difference of 15° or less from the {211} orientation for all measurement points is 5% or less, the ratio of the number of measurement points R{110} with an orientation difference of 15° or less from the {110} orientation is 5% or less, the ratio of the number of measurement points R{110} with an orientation difference of 15° or less from the {110} orientation is 90% or more, and the ratio of the large angle grain boundary RL = LI / La, which is the ratio of the total length LI of the grain boundary with an orientation difference of 15° or more to the total length La of the grain boundary of the crystal grain, is 5% or more and 30% or less.

Description

Technology Field

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

[0002] Grained electrical steel sheets are soft magnetic materials and are mainly used as core materials for transformers. Grained electrical steel sheets are mainly {110} called Goss orientation <001> It consists of oriented grains (Goss orientation grains). The size of the Goss orientation grains is on the order of millimeters. By preferentially growing the Goss orientation grains through a phenomenon called secondary recrystallization, oriented electrical steel sheets are manufactured.

[0003] In grain-oriented electrical steel sheets, excellent magnetic properties (high magnetic flux density and low iron loss) are required. Regarding magnetic flux density, the higher the density of Goss orientation grains, the better the magnetic flux density obtained.

[0004] Meanwhile, 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. To reduce iron loss, it is effective to reduce hysteresis loss and eddy current loss. As a method to reduce hysteresis loss, it is known to increase the degree of integration in the Goss orientation. In addition, as a method to reduce eddy current loss, it is known to increase the content of elements that increase electrical resistance, such as Si, reduce the thickness of the steel sheet, or subdivide the magnetic domains.

[0005] Recently, methods to reduce iron loss by thinning the sheet thickness are being considered. However, thinning the sheet thickness increases the reduction ratio during cold rolling in the manufacturing process of oriented electrical steel sheets. In this case, excellent magnetic properties may not be stably obtained.

[0006] Therefore, even when the reduction rate of cold rolling is high, means to improve the magnetic properties of oriented electrical steel sheets are proposed, for example, in Japanese Patent Publication No. Hei 6-145799 (Patent Document 1) and Japanese Patent Publication No. Hei 7-62438 (Patent Document 2).

[0007] Patent Document 1 proposes a method for manufacturing a oriented electrical steel sheet by performing two cold rollings with intermediate annealing in between. Specifically, hot rolling is terminated at 850°C or higher, and the steel sheet is immediately cooled and coiled at 600°C or lower. After that, prior to the first cold rolling, a cracking carbide control heat treatment is performed on the steel sheet for 2 to 10 seconds in a temperature range of 650 to 900°C. Patent Document 1 states that, by doing so, excellent magnetic flux density is obtained even for a thin oriented electrical steel sheet.

[0008] Patent Document 2 proposes a method for manufacturing a 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 ratio is set to 89% or more. Additionally, the steel sheet rolled to the final sheet thickness is heat-treated at a temperature of 700°C or higher at a heating rate of 50°C / s or more immediately before decarburization annealing. Patent Document 2 states that excellent magnetic flux density and excellent iron loss can be obtained by doing so. Prior art literature

[0009] Japanese Patent Publication No. Hei 6-145799 Japanese Patent Publication No. Hei 7-62438 The problem to be solved

[0010] Excellent magnetic flux density and excellent iron loss are obtained in the oriented electrical steel sheets proposed in Patent Document 1 and Patent Document 2. However, excellent magnetic flux density and excellent iron loss may be obtained by other means.

[0011] Recently, there has also been a demand for the reduction of noise and vibration in transformers. Therefore, oriented electrical steel sheets are required to possess excellent noise characteristics, along with excellent magnetic flux density and iron loss. Here, noise characteristics refer to properties that allow for sufficient reduction of noise and vibration when the oriented electrical steel sheet is mounted in a transformer and in operation.

[0012] Magnetostriction of grain-oriented electrical steel can be cited as one of the factors that degrade noise characteristics (i.e., factors causing excessive noise and vibration). The magnetostriction referred to here means the vibration observed in the rolling direction of the grain-oriented electrical steel, caused by a slight change in the external shape of the sheet accompanying a change in magnetization intensity when the sheet is energized by alternating current. The magnitude of the magnetostriction is 10 -6 Although the order is very small, the magnetic deformation causes vibrations in the iron core, which propagate to external structures such as the transformer tank and become noise. In the aforementioned Patent Document 1 and Patent Document 2, no examination regarding noise characteristics has been conducted.

[0013] The object of the present disclosure is to provide a oriented electrical steel sheet in which excellent magnetic properties, excellent iron loss properties, and excellent noise properties are obtained. means of solving the problem

[0014] The oriented electrical steel sheet of the present disclosure comprises 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 to 0.010%, one or more selected from the group consisting of S and Se: total 0 to 0.010%, 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 0.0150%, Ta: 0 to 0.05%, Nb: 0 to 0.010%, V: 0 to 0.50%, B: 0 to 0.010%, Te: 0 to 0.0150%, and the remainder consists of Fe and impurities. When the crystal orientation by X-ray diffraction is measured at measurement points arranged at a 2 mm pitch in each direction of the rolling direction and the direction orthogonal to the rolling direction on the surface of the base steel sheet, {211} for all measurement points <011> R is the ratio of the number of measurement points with an bearing difference of 15° or less from the bearing. {211}<011> This is 5% or less, and {110} for all measurement points <112> R is the ratio of the number of measurement points with an bearing difference of 15° or less from the bearing. {110}<112> 5% or less, and {110} for all measurement points <001> R is the ratio of the number of measurement points with an bearing difference of 15° or less from the bearing. {110}<001> This is 90% or more, and the angle-of-magnitude grain boundary ratio RL = LI / La, which is the ratio of the total length LI of grain boundaries with an orientation difference of 15° or more to the total length La of grain boundaries obtained from the orientation difference at the measurement point, is 5% or more and 30% or less.

[0015] The method for manufacturing a oriented electrical steel sheet of 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 selected from the group consisting of S and Se: total 0.010 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%, The method comprises a hot rolling process for hot rolling a slab composed of 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 remainder being Fe and impurities, to produce a hot-rolled steel sheet; a hot-rolled sheet annealing process for annealing the hot-rolled steel sheet; a cold rolling process for cold rolling the hot-rolled steel sheet after the hot-rolled sheet annealing process to produce a cold-rolled steel sheet; a decarburization annealing process for decarburizing the cold-rolled steel sheet to produce a decarburized annealed steel sheet; a finishing annealing process for applying an annealing separator to the decarburized annealed steel sheet and then performing finishing annealing; and an insulating film forming process for forming an insulating film on the surface of the finishing annealed sheet. In the cold rolling process, the cumulative reduction rate is set to 89% or more and 93% or less, and in the work roll of the rolling stand that performs the first pass of cold rolling, the arithmetic mean roughness Ra (㎛) in the axial direction of the work roll, the 10-point average roughness Rzjis (㎛), and the diameter Dw (mm) of the work roll satisfy Equations (1) and (2).

[0016] 0.30≤Ra≤0.01Dw+3.08 (1)

[0017] 3Ra≤Rzjis≤7Ra (2) Effects of the invention

[0018] In the oriented electrical steel sheet of the present disclosure, excellent magnetic properties and excellent iron loss properties are obtained, and excellent noise properties are also obtained. The method for manufacturing the oriented electrical steel sheet of the present disclosure can manufacture the oriented electrical steel sheet described above. Brief explanation of the drawing

[0019] FIG. 1 is a perspective view of a oriented electrical steel sheet according to the present embodiment. Figure 2 is a schematic diagram of a tandem rolling mill used in a tandem rolling process. Figure 3 is a schematic diagram of a multi-stage rolling mill used in a reverse rolling process. Specific details for implementing the invention

[0020] The inventors conducted an investigation into oriented electrical steel sheets that obtain excellent magnetic properties, excellent iron loss properties, and also excellent noise properties. As a result, the following findings were obtained.

[0021] The inventors initially investigated and examined the causes of cases where the magnetic flux density of a oriented electrical steel sheet is not sufficiently obtained when the reduction rate of cold rolling is high. As a result, in the oriented electrical steel sheet where a sufficient magnetic flux density was not obtained, {110} <001> Not only Goth's defense particles having a defense, but also {211} <011> Crystal grains having orientation, and {110} <112> Oriented grains were present in excess. These {211} <011> Directional particles and {110} <112> It is thought that as the orientation particles grow through secondary recrystallization, the Gos orientation particles are reduced, and as a result, the magnetic flux density is lowered.

[0022] Specifically, in the finishing annealing process during the manufacturing process of oriented electrical steel sheets, coil-shaped cold-rolled steel sheets after the cold rolling process are annealed by batch processing. At this time, since the cold-rolled steel sheets are in coil shape, they are annealed for a long time while having curvature. It is thought that if secondary recrystallization occurs in a steel sheet with curvature, the misalignment between the secondary recrystallization orientation and the matrix orientation increases depending on the curvature.

[0023] In the secondary recrystallization of grain-oriented electrical steel sheets, grains with a high proportion of Σ9-corresponding orientation boundaries tend to grow preferentially. Goss orientation grains tend to form Σ9-corresponding orientation boundaries. Meanwhile, {211} <011> Directional particles and {110} <112> Compared to Goss orientation particles, orientation particles find it difficult to form Σ9 corresponding orientation grain boundaries. Therefore, {211} <011> Directional particles and {110} <112> It is thought that orientation particles are difficult to grow during the finishing annealing process compared to Goss orientation particles.

[0024] However, as mentioned above, in the finishing annealing process, the cold-rolled steel sheet is in the form of a coil. Therefore, accompanied by the progression of secondary recrystallization, the properties of the grain boundaries of the crystal orientation grains change according to the curvature. Specifically, it becomes difficult for Goss orientation grains to form Σ9 corresponding orientation grain boundaries, and on the other hand, {211} <011> Directional particles and {110} <112> Compared to Goss orientation particles, the difficulty of forming Σ9 corresponding orientation grain boundaries is alleviated for orientation particles. As a result, {211} <011> Directional particles and {110} <112> It is believed that orientation grains become more likely to grow. This phenomenon becomes more pronounced as the cumulative reduction rate in the cold rolling process increases.

[0025] Based on the above findings, the inventors have, in a oriented electrical steel sheet, {211} <011> Directional particles and {110} <112> It was thought that excellent magnetic flux density could be obtained by lowering the ratio of orientation particles and increasing the ratio of Goss orientation particles. Furthermore, upon further investigation, the inventors discovered that excellent magnetic flux density is obtained when the crystal orientation is measured by X-ray diffraction at measurement points arranged at a pitch of 2 mm in the rolling direction and the direction perpendicular to the rolling direction, respectively, on the surface of the base steel sheet of the oriented electrical steel sheet, if the following requirements A to C are satisfied.

[0026] (Requirement A)

[0027] {211} for all measurement points <011> R is the ratio of the number of measurement points with an bearing difference of 15° or less from the bearing. {211}<011> This is 5% or less.

[0028] (Requirement B)

[0029] {110} for all measurement points <112> R is the ratio of the number of measurement points with an bearing difference of 15° or less from the bearing. {110}<112> It is 5% or less.

[0030] (Requirement C)

[0031] {110} for all measurement points <001> R is the ratio of the number of measurement points with an bearing difference of 15° or less from the bearing. {110}<001> This is over 90%.

[0032] As described above, regarding the grains, the number of Goss orientation grains is increased as much as possible, and {211} <011> Directional particles and {110} <112> By minimizing the number of orientation particles, the magnetic flux density is increased. However, although excellent magnetic flux density is obtained by satisfying requirements A to C, there were cases where excellent iron loss and excellent noise characteristics were not obtained. This indicates that, in oriented electrical steel sheets, an improvement in magnetic flux density is not necessarily correlated with a reduction in iron loss.

[0033] Therefore, the inventors further investigated means for reducing iron loss. As a result, the inventors discovered that the presence of an appropriate amount of large-angle grain boundaries in the microstructure improves iron loss.

[0034] Although the influence of grain boundaries on iron loss is not entirely clear, the following reasons are considered. At locations where large-angle grain boundaries exist, auxiliary domains are formed. These auxiliary domains are extinguished by the tension exerted by the insulating film. When auxiliary domains are extinguished, static energy increases. To mitigate this increase in static energy, magnetic domain walls become subdivided. Subdividing magnetic domain walls reduces iron loss generated during domain wall movement. However, if auxiliary domains become excessive, magnetic strain, which causes noise, increases.

[0035] Here, when crystal orientation is measured by X-ray diffraction at measurement points arranged at a pitch of 2 mm in the rolling direction and the direction perpendicular to the rolling direction, respectively, on the surface of the base steel sheet of a oriented electrical steel sheet, the ratio of the total length Ll of grain boundaries with an orientation difference of 15° or more to the total length La of grain boundaries obtained from the orientation difference at the measurement points is defined as the large angle grain boundary ratio RL (=Ll / La). In addition, an orientation difference of 1° or more is defined as a grain boundary.

[0036] If the ratio of large angle grain boundaries RL is less than 5%, the ratio of large angle grain boundaries is excessively low. In this case, there are excessively few auxiliary domains. Consequently, the subdivision of magnetic domain walls becomes insufficient, and excellent iron loss is not obtained.

[0037] On the other hand, if the ratio of large angle grain boundaries RL exceeds 30%, the ratio of large angle grain boundaries becomes excessive. In this case, auxiliary domains become excessive, and the movement of magnetic domain walls is hindered. As a result, hysteresis loss actually increases. In addition, as auxiliary domains become excessive, magnetic strain increases. As a result, sufficient iron loss is not obtained, and excellent noise characteristics are not obtained.

[0038] When the ratio of large angle grain boundaries RL is 5 to 30%, a suitable amount of large angle grain boundaries exists, and a suitable amount of auxiliary magnetic domains also exists. As a result, magnetic domain walls are subdivided, and auxiliary magnetic domains are reduced. Consequently, excellent iron loss is obtained, and excellent noise characteristics are obtained.

[0039] Based on the above findings, the inventors have completed a oriented electrical steel sheet of the present embodiment having the following configuration.

[0040] The first type of oriented electrical steel sheet comprises 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 to 0.010%, one or more selected from the group consisting of S and Se: total 0 to 0.010%, 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 0.0150%, Ta: 0 to 0.05%, Nb: 0 to 0.010%, V: 0 to 0.50%, B: 0 to 0.010%, Te: 0 to 0.0150%, and the remainder consists of Fe and impurities. When the crystal orientation by X-ray diffraction is measured at measurement points arranged at a 2 mm pitch in each direction of the rolling direction and the direction orthogonal to the rolling direction on the surface of the base steel sheet, {211} for all measurement points <011> R is the ratio of the number of measurement points with an bearing difference of 15° or less from the bearing. {211}<011> This is 5% or less, and {110} for all measurement points <112> R is the ratio of the number of measurement points with an bearing difference of 15° or less from the bearing. {110}<112> 5% or less, and {110} for all measurement points <001> R is the ratio of the number of measurement points with an bearing difference of 15° or less from the bearing. {110}<001> This is 90% or more, and the angle-of-magnitude grain boundary ratio RL = Ll / La, which is the ratio of the total length Ll of grain boundaries with an orientation difference of 15° or more to the total length La of grain boundaries obtained from the orientation difference at the measurement point, is 5% or more and 30% or less.

[0041] The second type of oriented electrical steel sheet is the first type of oriented electrical steel sheet, and the thickness of the base steel sheet is 0.19 mm or less.

[0042] The third type of oriented electrical steel sheet is the first or second type of oriented electrical steel sheet, 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: 0.01 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, It contains one or more selected from the group consisting of Te: 0.0001 to 0.0150%.

[0043] The method for manufacturing a first type of oriented electrical steel sheet is a method for manufacturing a oriented electrical steel sheet of any one of the first to third types, and comprises a hot rolling process, a hot-rolled sheet annealing process, a cold rolling process, a decarburization annealing process, a finishing annealing process, and an insulating film forming process. In the hot rolling process, 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 selected from the group consisting of S and Se: total 0.010 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 A slab composed of 0.05%, Nb: 0 to 0.010%, V: 0 to 0.50%, B: 0 to 0.010%, Te: 0 to 0.0200%, and the remainder being Fe and impurities is hot-rolled to produce a hot-rolled steel sheet. In the hot-rolled sheet annealing process, 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 produce a cold-rolled steel sheet. In the decarburization annealing process, decarburization annealing is performed on the cold-rolled steel sheet to produce a decarburized annealed steel sheet. In the finishing annealing process, an annealing separator is applied to the decarburized annealed steel sheet, and then finishing annealing is performed. In the insulating film formation process, an insulating film is formed on the surface of the finishing annealed sheet.In the cold rolling process, the cumulative reduction rate is set to 89% or more and 93% or less, and in the work roll of the rolling stand that performs the first pass of cold rolling, the arithmetic mean roughness Ra (㎛) in the axial direction of the work roll, the 10-point average roughness Rzjis (㎛), and the diameter Dw (mm) of the work roll satisfy Equations (1) and (2).

[0044] 0.30≤Ra≤0.01Dw+3.08 (1)

[0045] 3Ra≤Rzjis≤7Ra (2)

[0046] The method for manufacturing a second type of oriented electrical steel sheet is the method for manufacturing a first type of oriented electrical steel sheet, and in the decarburization annealing process, 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 / second or more and 3000°C / second or less.

[0047] The method for manufacturing a third type of oriented electrical steel sheet is a method for manufacturing a first or second type of oriented electrical steel sheet, and in the cold rolling process, cold rolling is initiated from the front end of the hot-rolled steel sheet produced in the hot rolling process toward the rear end.

[0048] The oriented electrical steel sheet of the present embodiment is described below. In addition, "%" regarding elements refers to mass% unless otherwise specified.

[0049] [Regarding the composition of grain-oriented electrical steel sheets]

[0050] FIG. 1 is a perspective view of a oriented electrical steel sheet according to the present embodiment. In the drawing, direction L refers to the rolling direction of the oriented electrical steel sheet. Direction W refers to the rolling direction perpendicular to the oriented electrical steel sheet (sheet width direction). Direction T refers to the normal direction of the rolled surface of the oriented electrical steel sheet (sheet thickness direction). In addition, the rolled surface of the oriented electrical steel sheet refers to the upper surface or lower surface of the oriented electrical steel sheet.

[0051] Referring to FIG. 1, the oriented electrical steel sheet (1) according to the present embodiment comprises a base steel sheet (10). The oriented electrical steel sheet (1) may also comprise a lower layer film (11) and an insulating film (12). When the oriented electrical steel sheet (1) comprises a lower layer film (11) and an insulating film (12), the lower layer film (11) is formed on the base steel sheet (10). In FIG. 1, the lower layer film (11) is formed on the surface of the base steel sheet (10) by directly contacting the surface of the base steel sheet (10). The lower layer film (11) is either a primary film mainly composed of forsterite or an intermediate layer mainly composed of oxides such as silica and alumina. When the reduction of iron loss is important, the lower layer film (11) is made into a primary film. When punching processability is important, the lower film (11) is made into an intermediate layer. The lower film (11) is a well-known film.

[0052] An insulating film (12) is formed on a lower film (11). As shown in FIG. 1, the lower film (11) and the insulating film (12) may be formed on a pair of surfaces of the base steel plate (10) (i.e., the surface and back surface of the base steel plate (10). The insulating film (12) is a well-known insulating film. The oriented electrical steel plate (1) may have a base steel plate (10) and an insulating film (12), and may not have a lower film (11).

[0053] In addition, it is well known that oriented electrical steel sheets may be provided with a base steel sheet, a lower layer film, and an insulating film, or with a base steel sheet and an insulating film.

[0054] [Regarding the chemical composition of the base steel plate (10)]

[0055] The chemical composition of the base steel sheet (10) of the oriented electrical steel sheet (1) contains the following elements.

[0056] Si: 3.00 to 3.70%

[0057] Silicon (Si) increases the electrical resistance (resistivity) of the steel sheet, thereby reducing the iron loss of the oriented electrical steel sheet (1). If the Si content is less than 3.00%, the above effect is not sufficiently obtained. On the other hand, if the Si content exceeds 3.70%, the steel sheet becomes embrittled.

[0058] Therefore, the Si content is 3.00 to 3.70%.

[0059] The preferred lower limit of the Si content is 3.05%, more preferably 3.10%, more preferably 3.15%, more preferably 3.20%, more preferably 3.25%, and more preferably 3.30%.

[0060] The preferred upper limit of the Si content is 3.65%, more preferably 3.60%, even more preferably 3.55%, and even more preferably 3.50%.

[0061] Mn: 0.01 to 0.30%

[0062] Manganese (Mn) increases the resistivity of the steel sheet and reduces iron loss. Mn also increases 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 are not sufficiently obtained. On the other hand, if the Mn content exceeds 0.30%, the magnetic flux density of the oriented electrical steel sheet (1) decreases, and iron loss also deteriorates.

[0063] Therefore, the Mn content is 0.01 to 0.30%.

[0064] The preferred lower limit of the Mn content is 0.02%, more preferably 0.03%, and even more preferably 0.05%.

[0065] The 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%.

[0066] N: 0.0001 to 0.0100%

[0067] Nitrogen (N) forms nitrides, which degrade the iron loss of the oriented electrical steel sheet (1). If the N content exceeds 0.0100%, the iron loss of the oriented electrical steel sheet (1) degrades significantly.

[0068] Therefore, the N content is 0.0001 to 0.0100%.

[0069] The preferred lower limit of the N content is 0.0002%, and more preferably 0.0005%.

[0070] The preferred upper limit of the N content is 0.0090%, more preferably 0.0050%, and even more preferably 0.0030%.

[0071] C: 0.001 to 0.010%

[0072] Carbon (C) is an essential element in slabs because it improves magnetic flux density. However, C is removed from the steel sheet during the manufacturing process of the oriented electrical steel sheet (1). If more than 0.010% of C remains in the oriented electrical steel sheet (1) that is the product, magnetic aging occurs, and the iron loss of the oriented electrical steel sheet (1) deteriorates.

[0073] It is preferable for the lower limit of the C content to be low. However, excessive reduction of the C content increases manufacturing costs. Therefore, the lower limit of the C content is set to 0.001% or higher.

[0074] Therefore, the C content is 0.001 to 0.010%.

[0075] The preferred lower limit of the C content is 0.002%, and more preferably 0.003%.

[0076] The preferred upper limit of the C content is 0.009%, more preferably 0.008%, and even more preferably 0.007%.

[0077] sol.Al: 0 to 0.010%

[0078] Acid-soluble aluminum (sol.Al) combines with N to form AlN during the manufacturing process of the oriented electrical steel sheet (1) and functions 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 oriented electrical steel sheet (1) deteriorates.

[0079] Therefore, the sol.Al content is 0.010% or less. Also, the sol.Al content may be 0%. That is, the sol.Al content is 0 to 0.010%.

[0080] The preferred lower limit of the sol.Al content is 0.001%.

[0081] The preferred upper limit of the sol.Al content is 0.009%, more preferably 0.008%, and even more preferably 0.007%.

[0082] One or more selected from the group consisting of S and Se: 0 to 0.010% in total

[0083] Sulfur (S) and selenium (Se) combine with Mn during the manufacturing process to form fine MnS or MnSe, which are inhibitors. Therefore, S and Se are essential elements in the slab. However, S and Se escape from the steel sheet during the manufacturing process of the oriented electrical steel sheet (1). If the total content of one or more selected from the group consisting of S and Se in the oriented electrical steel sheet (1) exceeds 0.010%, MnS or MnSe remains in the steel sheet. In this case, the iron loss of the oriented electrical steel sheet (1) deteriorates.

[0084] Accordingly, the total content of one or more selected from the group consisting of S and Se is 0.010% or less. In addition, the total content of one or more selected from the group consisting of S and Se may be 0%. That is, the total content of one or more selected from the group consisting of S and Se is 0 to 0.010%.

[0085] The preferred lower limit of the total content of one or more selected from the group consisting of S and Se is 0.001%.

[0086] The preferred upper limit of the total content of one or more selected from the group consisting of S and Se is 0.008%, more preferably 0.006%, and even more preferably 0.004%.

[0087] The remainder of the chemical composition of the oriented electrical steel sheet (1) consists of Fe and impurities. Here, impurities refer to those that are incorporated from raw materials such as ore, scrap, or the manufacturing environment when the base steel sheet (10) of the oriented electrical steel sheet (1) is manufactured industrially, and are allowed within a range that does not have an adverse effect on the oriented electrical steel sheet (1) of this embodiment. Impurities are, for example, Ca: 0 to 0.001%, Mg: 0 to 0.002%, Ce: 0 to 0.002%, O: 0 to 0.01%, As: 0 to 0.10%, Co: 0 to 0.10%, Zr: 0 to 0.003%, W: 0 to 0.10%, Hf: 0 to 0.02%, Sc: 0 to 0.02%, Sr: 0 to 0.02%, Zn: 0 to 0.02%, Pb: 0 to 0.10%, Nd: 0 to 0.02%, REM: 0 to 0.02%, Ba: 0 to 0.02%, Cd: 0 to 0.02%, Pt: 0 to 0.02%, Au: 0 to It contains one or more selected from the group consisting of 0.02%, Ga: 0 to 0.02%, Ge: 0 to 0.02%, Y: 0 to 0.02%, and La: 0 to 0.02%. When multiple of these impurity elements are contained, the total content of the multiple elements is 0 to 0.05%.

[0088] [For Optional Elements]

[0089] The chemical composition of the base steel sheet (10) of the oriented electrical steel sheet (1) may also contain, instead of some of Fe, one or more selected from 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 0.0150%, Ta: 0 to 0.05%, Nb: 0 to 0.010%, V: 0 to 0.50%, B: 0 to 0.010%, and Te: 0 to 0.0150%. All of these elements are optional elements.

[0090] Each element is explained below.

[0091] [1st Army: Ti]

[0092] Ti: 0 to 0.010%

[0093] Titanium (Ti) is an optional element and does not need to be contained. That is, the Ti content can be 0%.

[0094] When contained, that is, when the Ti content exceeds 0%, Ti degrades the magnetic properties of the oriented electrical steel sheet (1). When the Ti content exceeds 0.010%, the magnetic properties of the oriented electrical steel sheet (1) are significantly degraded.

[0095] Therefore, the Ti content is 0 to 0.010%.

[0096] It is desirable for the Ti content to be as low as possible. However, excessive reduction of the Ti content increases manufacturing costs. Therefore, in the case of normal industrial production, the desirable lower limit of the Ti content is 0.001%, and more preferably 0.002%.

[0097] 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%.

[0098] [Group 2: Ni, Cr, Cu, P, and Mo]

[0099] Ni, Cr, Cu, P, and Mo are all arbitrary elements. All of these elements change the structure formation behavior during the manufacturing process, thereby improving the magnetic properties of the oriented electrical steel sheet (1).

[0100] Ni: 0 to 0.50%

[0101] Nickel (Ni) is an optional element and does not need to be contained. That is, the Ni content can be 0%.

[0102] When 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 orientation grains. As a result, the magnetic properties of the oriented electrical steel sheet (1) are improved. Even if Ni is contained in small amounts, the above effect is obtained to some extent.

[0103] However, if the Ni content exceeds 0.50%, secondary recrystallization may become unstable.

[0104] Therefore, the Ni content is 0 to 0.50%.

[0105] The preferred lower limit of the Ni content is 0.01%, more preferably 0.05%, and even more preferably 0.10%.

[0106] 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%.

[0107] Cr: 0 to 0.50%

[0108] Chromium (Cr) is an optional element and does not need to be included. That is, the Cr content can be 0%.

[0109] When contained, that is, when the Cr content is greater than 0%, Cr changes the microstructure formation behavior up to the final annealing process and promotes secondary recrystallization of Goss orientation grains. As a result, the magnetic properties of the oriented electrical steel sheet (1) are improved. Even if Cr is contained in small amounts, the above effect is obtained to some extent.

[0110] However, if the Cr content exceeds 0.50%, Cr oxide is formed in the steel sheet. Because of this, the iron loss of the oriented electrical steel sheet (1) deteriorates.

[0111] Therefore, the Cr content is 0 to 0.50%.

[0112] The preferred lower limit of the Cr content is 0.01%, more preferably 0.05%, and even more preferably 0.10%.

[0113] 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%.

[0114] Cu: 0 to 0.50%

[0115] Copper (Cu) is an optional element and does not need to be included. That is, the Cu content can be 0%.

[0116] When contained, that is, when the Cu content is greater than 0%, Cu changes the microstructure formation behavior up to the final annealing process and promotes secondary recrystallization of Goss orientation grains. As a result, the magnetic properties of the oriented electrical steel sheet (1) are improved. Even if only a small amount of Cu is contained, the above effect is obtained to some extent.

[0117] However, if the Cu content exceeds 0.50%, the hot workability of the steel sheet decreases.

[0118] Therefore, the Cu content is 0 to 0.50%.

[0119] The preferred lower limit of the Cu content is 0.01%, more preferably 0.03%, and even more preferably 0.05%.

[0120] 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%.

[0121] P: 0 to 0.05%

[0122] Phosphorus (P) is an optional element and does not need to be present. That is, the P content can be 0%.

[0123] When contained, that is, when the P content is greater than 0%, P changes the microstructure formation behavior up to the final annealing process and promotes secondary recrystallization of Goss orientation grains. As a result, the magnetic properties of the oriented electrical steel sheet (1) are improved. Even if P is contained in small amounts, the above effect is obtained to some extent.

[0124] However, if the P content exceeds 0.05%, the workability of the steel sheet decreases.

[0125] Therefore, the P content is 0 to 0.05%.

[0126] The preferred lower limit of the P content is 0.01%.

[0127] The preferred upper limit of the P content is 0.04%, more preferably 0.03%, and even more preferably 0.02%.

[0128] Mo: 0 to 0.05%

[0129] Molybdenum (Mo) is an optional element and does not need to be included. That is, the Mo content can be 0%.

[0130] 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 orientation grains. As a result, the magnetic properties of the oriented electrical steel sheet (1) are improved. Even if Mo is contained in small amounts, the above effect is obtained to some extent.

[0131] However, if the Mo content exceeds 0.05%, the workability of the steel sheet decreases.

[0132] Therefore, the Mo content is 0 to 0.05%.

[0133] The preferred lower limit of the Mo content is 0.01%, and more preferably 0.02%.

[0134] The preferred upper limit of the Mo content is 0.04%, and more preferably 0.03%.

[0135] [Group 3: Sn, Sb, Bi, Ta, Nb, V, B and Te]

[0136] Sn, Sb, Bi, Ta, Nb, V, B, and Te are all arbitrary elements. All of these elements function as inhibitors and stabilize secondary recrystallization.

[0137] Sn: 0 to 0.30%

[0138] Tin (Sn) is an optional element and does not need to be contained. That is, the Sn content can be 0%.

[0139] When included, Sn functions as an inhibitor and stabilizes secondary recrystallization during the manufacturing process of the oriented electrical steel sheet (1). As a result, the magnetic properties of the oriented electrical steel sheet (1) are improved. Even if only a small amount of Sn is included, the above effect is obtained to some extent.

[0140] However, if the Sn content exceeds 0.30%, the magnetic properties of the oriented electrical steel sheet (1) are actually degraded.

[0141] Therefore, the Sn content is 0 to 0.30%.

[0142] The preferred lower limit of the Sn content is 0.01%, more preferably 0.03%, and even more preferably 0.05%.

[0143] The preferred upper limit of the Sn content is 0.25%, more preferably 0.20%, and even more preferably 0.15%.

[0144] Sb: 0 to 0.30%

[0145] Antimony (Sb) is an optional element and does not need to be present. That is, the Sb content can be 0%.

[0146] When included, Sb functions as an inhibitor and stabilizes secondary recrystallization during the manufacturing process of the oriented electrical steel sheet (1). As a result, the magnetic properties of the oriented electrical steel sheet (1) are improved. Even if only a small amount of Sb is included, the above effect is obtained to some extent.

[0147] However, if the Sb content exceeds 0.30%, the magnetic properties of the oriented electrical steel sheet (1) are actually degraded.

[0148] Therefore, the Sb content is 0 to 0.30%.

[0149] The preferred lower limit of the Sb content is 0.01%, more preferably 0.03%, and even more preferably 0.05%.

[0150] The preferred upper limit of the Sb content is 0.25%, more preferably 0.20%, and even more preferably 0.15%.

[0151] Bi: 0 to 0.0150%

[0152] Bismuth (Bi) is an optional element and does not need to be present. That is, the Bi content can be 0%.

[0153] When included, Bi functions as an inhibitor and stabilizes secondary recrystallization during the manufacturing process of the oriented electrical steel sheet (1). As a result, the magnetic properties of the oriented electrical steel sheet (1) are enhanced. Even if only a small amount of Bi is included, the above effect is obtained to some extent.

[0154] However, if the Bi content exceeds 0.0150%, the magnetic properties of the oriented electrical steel sheet (1) are actually degraded.

[0155] Therefore, the Bi content is 0 to 0.0150%.

[0156] 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%.

[0157] The preferred upper limit of the Bi content is 0.0120%, more preferably 0.0100%, even more preferably 0.0070%, and even more preferably 0.0050%.

[0158] Ta: 0 to 0.05%

[0159] Tantalum (Ta) is an optional element and does not need to be contained. That is, the Ta content can be 0%.

[0160] When included, Ta functions as an inhibitor and stabilizes secondary recrystallization during the manufacturing process of the oriented electrical steel sheet (1). As a result, the magnetic properties of the oriented electrical steel sheet (1) are enhanced. Even if only a small amount of Ta is included, the above effect is obtained to some extent.

[0161] However, if the Ta content exceeds 0.05%, the magnetic properties of the oriented electrical steel sheet (1) are actually degraded.

[0162] Therefore, the Ta content is 0 to 0.05%.

[0163] The preferred lower limit of the Ta content is 0.01%, and more preferably 0.02%.

[0164] The preferred upper limit of the Ta content is 0.04%, and more preferably 0.03%.

[0165] Nb: 0 to 0.010%

[0166] Niobium (Nb) is an optional element and does not need to be contained. That is, the Nb content can be 0%.

[0167] When contained, Nb functions as an inhibitor and stabilizes secondary recrystallization during the manufacturing process of the oriented electrical steel sheet (1). As a result, the magnetic properties of the oriented electrical steel sheet (1) are enhanced. Even if Nb is contained in small amounts, the above effect is obtained to some extent. However, if the Nb content exceeds 0.010%, the magnetic properties of the oriented electrical steel sheet (1) are actually degraded.

[0168] Therefore, the Nb content is 0 to 0.010%.

[0169] The preferred lower limit of the Nb content is 0.001%, and more preferably 0.003%.

[0170] The preferred upper limit of the Nb content is 0.008%, and more preferably 0.006%.

[0171] V: 0 to 0.50%

[0172] Vanadium (V) is an optional element and does not need to be contained. That is, the V content can be 0%.

[0173] When included, V functions as an inhibitor and stabilizes secondary recrystallization during the manufacturing process of the oriented electrical steel sheet (1). As a result, the magnetic properties of the oriented electrical steel sheet (1) are improved. Even if V is included in small amounts, the above effect is obtained to some extent.

[0174] However, if the V content exceeds 0.50%, the magnetic properties of the oriented electrical steel sheet (1) are actually degraded.

[0175] Therefore, the V content is 0 to 0.50%.

[0176] The preferred lower limit of the V content is 0.01%, more preferably 0.05%, and even more preferably 0.10%.

[0177] The preferred upper limit of the V content is 0.40%, more preferably 0.30%, and even more preferably 0.20%.

[0178] B: 0 to 0.010%

[0179] Boron (B) is an optional element and does not need to be contained. That is, the B content can be 0%.

[0180] When included, B functions as an inhibitor and stabilizes secondary recrystallization during the manufacturing process of the oriented electrical steel sheet (1). As a result, the magnetic properties of the oriented electrical steel sheet (1) are improved. Even if only a small amount of B is included, the above effect is obtained to some extent.

[0181] However, if the B content exceeds 0.010%, the magnetic properties of the oriented electrical steel sheet (1) are actually degraded.

[0182] Therefore, the B content is 0 to 0.010%.

[0183] The preferred lower limit of the B content is 0.001%, more preferably 0.002%, and even more preferably 0.003%.

[0184] The preferred upper limit of the B content is 0.009%, more preferably 0.007%, and even more preferably 0.005%.

[0185] Te: 0 to 0.0150%

[0186] Tellurium (Te) is an optional element and does not need to be contained. That is, the Te content can be 0%.

[0187] When included, Te functions as an inhibitor and stabilizes secondary recrystallization during the manufacturing process of the oriented electrical steel sheet (1). As a result, the magnetic properties of the oriented electrical steel sheet (1) are enhanced. Even if Te is included in small amounts, the above effect is achieved to some extent. However, if the Te content exceeds 0.0150%, the magnetic properties of the oriented electrical steel sheet (1) actually decrease.

[0188] Therefore, the Te content is 0 to 0.0150%.

[0189] 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%.

[0190] The preferred upper limit of the Te content is 0.0120%, more preferably 0.0100%, even more preferably 0.0070%, and even more preferably 0.0050%.

[0191] [Method for measuring the chemical composition of the oriented electrical steel sheet (1)]

[0192] The chemical composition of the oriented electrical steel sheet (1) of this embodiment can be measured by a well-known component analysis method.

[0193] First, when a lower layer film (11) and an insulating film (12) are formed on a oriented electrical steel sheet (1), the lower layer film (11) and the insulating film (12) are removed by the following method. Specifically, the oriented electrical steel sheet (1) having the insulating film (12) is immersed in a high-temperature alkaline solution to remove it. The composition of the alkaline solution, the temperature, and the immersion time can be adjusted appropriately. For example, the oriented electrical steel sheet (1) having the insulating film (12) is immersed in an aqueous sodium hydroxide solution of NaOH: 30 to 50 mass% + H2O: 50 to 70 mass% at 80 to 90°C for 5 to 10 minutes, and after immersion, it is washed with water and dried. By this process, the insulating film (12) is removed from the oriented electrical steel sheet (1).

[0194] Additionally, the oriented electrical steel sheet (1), from which the insulating film (12) has been removed and the lower film (11) remains, is immersed in high-temperature hydrochloric acid to remove it. The concentration, temperature, and immersion time of the hydrochloric acid can be adjusted appropriately. For example, the oriented electrical steel sheet (1), from which the insulating film (12) has been removed and the lower film (11) remains, is immersed in 30 to 40 mass% hydrochloric acid at 80 to 90°C for 1 to 5 minutes. After immersion, the oriented electrical steel sheet (1) is washed with water and dried. Through the above process, a base steel sheet (10) from which the insulating film (12) and the lower film (11) have been removed is obtained.

[0195] The chemical composition of the obtained base steel sheet (10) is measured using a well-known component analysis method in accordance with JIS G0321:2017. Specifically, cutting material is collected from a oriented electrical steel sheet (1). The collected cutting material is dissolved in acid to obtain a solution. ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometry) is performed on the solution to conduct elemental analysis of the chemical composition. The C content and S content are determined by the well-known high-frequency combustion method (combustion-infrared absorption method). The N content is determined by the well-known inert gas melt-thermal conductivity method. For example, the chemical composition of the base steel sheet (10) can be analyzed by using a component analysis device (product name: ICPS-8000) manufactured by Shimadzu Corporation.

[0196] In addition, the content of each element is rounded to the nearest whole number of decimal places of the measured value based on the significant figures specified in this embodiment. For example, the Si content of this embodiment is specified to the nearest whole number of decimal places. Accordingly, the Si content is the value to the nearest whole number of decimal places obtained by rounding the third decimal place of the measured value.

[0197] Likewise, for the element content other than the Si content of the oriented electrical steel sheet (1) of the present embodiment, the value obtained by rounding the last digit of the numerical value up to the minimum number of digits specified in the present embodiment is used as the element content.

[0198] Also, rounding means discarding the last digit if it is less than 5, and rounding up if it is 5 or more.

[0199] [Regarding the lower film (11)]

[0200] As described above, the lower film (11) may be a primary film or an intermediate layer. The primary film is a well-known film mainly composed of forsterite (Mg2SiO4). The content of forsterite in the primary film is 60% or more by mass%. The primary film is formed by the reaction of an annealing separator containing magnesia with an oxide film such as SiO2 on the surface of the base steel plate (10) or with elements contained in the base steel plate (10) during final annealing. Therefore, the lower film (11) has a composition derived from the chemical composition of the annealing separator and the base steel plate (10). For example, the lower film (11) contains spinel (MgAl2O4). When the reduction of iron loss is important, the lower film (11) is made into a primary film. Meanwhile, the intermediate layer is a film mainly composed of silica and alumina. More specifically, the intermediate layer has a total content of silica and alumina of 60% or more by mass. When punching processability is important, the lower film (11) is used as the intermediate layer.

[0201] [Regarding the insulating film (12)]

[0202] An insulating film (12) is formed on a lower film (11). The insulating film (12) ensures insulation between the oriented electrical steel sheets (1) stacked together when a plurality of oriented electrical steel sheets (1) are used in a stacked manner. The insulating film (12) has a well-known composition. Specifically, the insulating film (12) contains at least one of the following inorganic materials: metal chromate salt, metal phosphate salt, colloidal silica, Zr compound, Ti compound, etc. Preferably, the insulating film (12) is a film mainly composed of a phosphoric acid compound. That is, the insulating film (12) contains a phosphoric acid compound. When the insulating film (12) is mainly composed of a phosphoric acid compound, the content of the phosphoric acid compound is 50% or more by mass%.

[0203] The insulating film (12) may contain, for example, one or more selected from the group consisting of colloidal silica and polytetrafluoroethylene together with a phosphoric acid compound. The phosphoric acid compound consists of, for example, one or more selected from the group consisting of sodium phosphate, aluminum phosphate, and magnesium phosphate.

[0204] [Regarding the ratio of the number of specific determination directions]

[0205] In the directional electrical steel sheet (1) of the present embodiment, when the crystal orientation is measured by X-ray diffraction at measurement points arranged at a pitch of 2 mm in each direction of the rolling direction and the direction perpendicular to the rolling direction on the surface of the base steel sheet (10), the following requirements A to C are satisfied.

[0206] (Requirement A)

[0207] {211} for all measurement points <011> R is the ratio of the number of measurement points with an bearing difference of 15° or less from the bearing. {211}<011> This is 5% or less.

[0208] (Requirement B)

[0209] {110} for all measurement points <112> R is the ratio of the number of measurement points with an bearing difference of 15° or less from the bearing. {110}<112> It is 5% or less.

[0210] (Requirement C)

[0211] {110} for all measurement points <001> R is the ratio of the number of measurement points with an bearing difference of 15° or less from the bearing. {110}<001> This is over 90%.

[0212] Requirements A through C will be explained below.

[0213] {211} <011> Crystal grains with orientation, and {110} <112> The oriented grains are {110} <001> Compared to Goss-oriented particles with orientation, the magnetic properties are inferior. Therefore, {211} <011> Defense particles, and {110} <112> It is preferable to have as few defense particles as possible.

[0214] Specifically, {211} for all measurement points <011> R is the ratio of the number of measurement points with an bearing difference of 15° or less from the bearing. {211}<011> If this exceeds 5%, {211} <011> There is an excess of orientation particles. As a result, magnetic properties are reduced.

[0215] Likewise, in the case where the chemical composition of the base steel plate (10) satisfies the range of this embodiment, {110} for all measurement points <112> R is the ratio of the number of measurement points with an bearing difference of 15° or less from the bearing. {110}<112> If it exceeds 5%, {110} <112> There is an excess of orientation particles. As a result, magnetic properties are reduced.

[0216] Also, {110} which is the Gothic orientation for the entire measurement point <001> R is the ratio of the number of measurement points with an bearing difference of 15° or less from the bearing. {110}<001> If this is less than 90%, the number of Goss defense particles is excessively low. As a result, magnetic properties are reduced. In addition, noise characteristics may deteriorate.

[0217] If requirements A through C are satisfied, there are sufficiently many Goss defense particles, and also {211} <011> Directional particles and {110} <112> The number of orientation particles is sufficiently small. As a result, excellent magnetic properties are obtained. Specifically, excellent magnetic flux density is obtained.

[0218] Number ratio R {211}<011> The desirable upper limit of is 4%, and more preferably 3%.

[0219] Number ratio R {211}<011>The desirable lower limit of is 1%, and more preferably 0%.

[0220] Number ratio R {110}<112> The desirable upper limit of is 4%, and more preferably 3%.

[0221] Number ratio R {110}<112> The desirable lower limit of is 1%, and more preferably 0%.

[0222] Number ratio R {110}<001> The preferred lower limit of is 91%, more preferably 92%, even more preferably 93%, and even more preferably 94%.

[0223] Number ratio R {110}<001> The desirable upper limit of is 96%, more preferably 97%, and even more preferably 98%.

[0224] [Grain boundary ratio R L About

[0225] In the directional electrical steel sheet (1) of the present embodiment, the ratio of the total length LI of the grain boundary with an orientation difference of 15° or more to the total length La of the grain boundary obtained from the orientation difference at the measurement point described above, the large angle grain boundary ratio RL = LI / La, is 5% or more and 30% or less.

[0226] As described in requirements A to C above, the crystal grains are made to have as many Goss orientation grains as possible, and {211} <011> Directional particles and {110} <112> By minimizing the number of orientation particles, the magnetic flux density is increased. However, while excellent magnetic flux density is obtained by satisfying requirements A to C, it cannot be said that excellent iron loss is necessarily obtained. This indicates that, in oriented electrical steel sheets, an improvement in magnetic flux density is not necessarily correlated with a reduction in iron loss.

[0227] Meanwhile, as described above, the presence of an appropriate amount of large-angle grain boundaries, as verified by the inventors, improves iron loss. Specifically, auxiliary magnetic domains are formed at locations where large-angle grain boundaries exist. When an appropriate amount of auxiliary magnetic domains is formed, the magnetic domain walls are subdivided, and iron loss is reduced.

[0228] If the ratio of large angle grain boundaries RL is less than 5%, the ratio of large angle grain boundaries is excessively low, and there are excessively few auxiliary domains. In this case, the subdivision of magnetic domain walls is insufficient. As a result, sufficiently low iron loss is not obtained.

[0229] On the other hand, if the ratio of large angle grain boundaries RL exceeds 30%, the ratio of large angle grain boundaries becomes excessive, and as a result, auxiliary magnetic domains also become excessive. In this case, the movement of magnetic domain walls is inhibited, and hysteresis loss actually increases. As a result, sufficiently low iron loss is not obtained. In addition, if auxiliary magnetic domains become excessive, magnetic strain increases. Also, if the ratio of large angle grain boundaries RL exceeds 30%, magnetic flux density may decrease.

[0230] When the ratio of large angle grain boundaries RL is 5 to 30%, an appropriate amount of large angle grain boundaries exists, and an appropriate amount of auxiliary magnetic domains also exists. As a result, the magnetic domain walls are subdivided, and an excessive amount of auxiliary magnetic domains is suppressed. Consequently, excellent iron loss is obtained, and excellent noise characteristics are also obtained.

[0231] The preferred lower limit of the large angle grain boundary ratio RL is 6%, more preferably 7%, more preferably 8%, more preferably 10%, and more preferably 12%.

[0232] The preferred upper limit of the large angle grain boundary ratio RL is 28%, more preferably 26%, even more preferably 24%, and even more preferably 22%.

[0233] [Method for measuring the determined orientation at the measurement point]

[0234] The determination orientation at the measurement point can be measured by the following method.

[0235] X-ray diffraction by the Laue method is performed on the rolled surface of the oriented electrical steel sheet (1). Specifically, from any point on the rolled surface of the oriented electrical steel sheet (1), one or more rectangular observation areas AR are formed, each 250 mm in the rolling direction of the oriented electrical steel sheet (1) and 60 mm in the direction perpendicular to the rolling direction. n Select (n is a natural number). Observation area AR n For this, X-ray diffraction by the Laue method is performed at measurement points spaced 2 mm apart in the rolling direction and width direction (3906 measurement points) to obtain the crystal orientation of each measurement point. At this time, the spot diameter is set to 1 mm. Based on the crystal orientation obtained at each measurement point, the boundary where the orientation difference angle is 1 to 180° is defined as the crystal grain boundary. The region surrounded by the crystal grain boundary is defined as the crystal grain. In addition, the X-ray source for X-ray diffraction by the Laue method is a W target, the tube voltage is 40 kV, and the tube current is 40 mA.

[0236] AR for each observation area n Whenever a measurement is completed in, it is determined whether the total number of specified grains is 100 or more. If the number of grains is less than 100, another observation area AR n＋1 Select and perform the X-ray diffraction described above. When the total number of crystal grains reaches 100 or more, the measurement is completed.

[0237] Among all measurement points where measurement has been completed, {211} <011> Calculate the number of measurement points where the bearing difference from the bearing is 15° or less. The total number of completed measurement points and {211} <011> Based on the number of measurement points with an bearing difference of 15° or less from the bearing, the number ratio R {211}<011> Calculate (%) using the following formula.

[0238] Number ratio R {211}<011>={211} <011> Number of measurement points with a bearing difference of 15° or less from the bearing / Total number of completed measurement points × 100

[0239] Among all measurement points where measurement has been completed, {110} <112> Calculate the number of measurement points where the bearing difference from the bearing is 15° or less. The total number of completed measurement points and {110} <112> Based on the number of measurement points with an bearing difference of 15° or less from the bearing, the number ratio R {110}<112> Calculate (%) using the following formula.

[0240] Number ratio R {110}<112> ={110} <112> Number of measurement points with a bearing difference of 15° or less from the bearing / Total number of completed measurement points × 100

[0241] Among all measurement points where measurement has been completed, {110} <001> Calculate the number of measurement points where the bearing difference from the bearing is 15° or less. The total number of completed measurement points and {110} <001> Based on the number of measurement points with an bearing difference of 15° or less from the bearing, the number ratio R {110}<001> Calculate (%) using the following formula.

[0242] Number ratio R {110}<001> ={110} <001> Number of measurement points with a bearing difference of 15° or less from the bearing / Total number of completed measurement points × 100

[0243] In addition, AR of all observation areas where measurements have been completed n The total length of the grain boundaries of all specified grains is defined as La. Additionally, among all specified grain boundaries, the total length of the grain boundaries with an orientation difference of 15° or more (large angle grain boundaries) is defined as LI.

[0244] For example, after the measurement of crystal orientation in the first observation area AR1 is completed, if the number of specified crystal grains is 100 or more, La and LI are calculated using all specified crystal grains in the observation area AR1.

[0245] Meanwhile, after the measurement in observation area AR1 is completed, if the number of identified grains is less than 100, a second measurement is performed in observation area AR2. Then, after the measurement in observation area AR2 is completed, if the total number of identified grains in observation areas AR1 and AR2 is 100 or more, La and LI are calculated using all the grains identified in observation areas AR1 and AR2.

[0246] As described above, until the total number of specified grains reaches 100 or more, observation areas AR1 to AR n Continue measurements in. Then, when the total number of grains reaches 100 or more, all observation areas AR1 to AR where measurements have been completed n Using all specified grains, La and LI are calculated.

[0247] Using the obtained La and LI, the large angle grain boundary ratio RL(%) is calculated by the following formula.

[0248] Large angle grain boundary ratio RL = LI / La × 100

[0249] Based on the determined orientation of each measurement point, La and LI can be obtained by using OIM Analysis, a product manufactured by TSL Solutions Co., Ltd., as analysis software.

[0250] In addition, at measurement points corresponding to grains or grain boundaries with a grain size of 1 mm or less, it is difficult to identify the crystal orientation, and identification failures may occur. Therefore, at such measurement points (hereinafter referred to as defective measurement points), the crystal orientation data of adjacent measurement points is substituted. Specifically, for two measurement points (+X and -X) adjacent to the defective measurement point in the rolling direction, and two measurement points (+Y and -Y) adjacent to the said measurement point in the width direction, the crystal orientation data is substituted in the order of +X, -X, +Y, and -Y. First, the crystal orientation data of the +X measurement point is substituted as the crystal orientation data of the defective 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 data that can be substituted is determined in order of priority. Furthermore, this method of substituting crystal orientation data is set as a "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.

[0251] [Effect of the oriented electrical steel sheet (1) of this embodiment]

[0252] The oriented electrical steel sheet (1) of this embodiment satisfies requirements A to C, and the large angle grain boundary ratio RL is 5 to 30%. Therefore, excellent magnetic flux density is obtained. In addition, excellent iron loss and excellent noise characteristics are obtained after magnetic domain subdivision treatment.

[0253] [Preferred plate thickness of the base steel plate (10) of the directional electrical steel plate (1) of the present embodiment]

[0254] The thickness of the base steel plate (10) of the oriented electrical steel plate (1) of the present embodiment is not particularly limited. For example, the thickness of the base steel plate (10) may be 0.17 to 0.22 mm, which is equivalent to the base steel plate of a well-known oriented electrical steel plate.

[0255] The preferred plate thickness of the base steel plate (10) is 0.19 mm or less. In the oriented electrical steel plate (1) of the present embodiment, even if the plate thickness of the base steel plate (10) is 0.19 mm or less, excellent magnetic flux density is obtained, and excellent iron loss and excellent noise characteristics are obtained after magnetic domain subdivision treatment.

[0256] [Another form of the oriented electrical steel sheet (1) of this embodiment]

[0257] In the directional electrical steel sheet (1) of the present embodiment, a plurality of linear thermal deformations, each extending linearly and arranged in a direction perpendicular to the extension direction, or a plurality of grooves, each extending linearly and arranged in a direction perpendicular to the extension direction, may also be formed.

[0258] Linear thermal deformation or grooves are formed on the rolled surface of the oriented electrical steel sheet (1) by a known magnetic domain subdivision treatment. The linear thermal deformation or grooves subdivide the magnetic domains of the oriented electrical steel sheet (1). In the oriented electrical steel sheet (1) of this embodiment, excellent iron loss is obtained after the magnetic domain subdivision treatment.

[0259] [Method for manufacturing the oriented electrical steel sheet (1) of the present embodiment]

[0260] An example of a method for manufacturing a oriented electrical steel sheet of the present embodiment is described. The method for manufacturing the oriented electrical steel sheet (1) described below is an example for manufacturing the oriented electrical steel sheet (1) of the present embodiment. Accordingly, the oriented electrical steel sheet (1) of the present embodiment may be manufactured by a manufacturing method other than the method described below. However, the manufacturing method described below is a preferred example of the method for manufacturing the oriented electrical steel sheet (1) of the present embodiment.

[0261] [Manufacturing Process Flow]

[0262] An example of a method for manufacturing a oriented electrical steel sheet (1) of the present embodiment includes the following processes 1 to 6.

[0263] (Process 1) Hot Rolling Process

[0264] (Process 2) Hot-rolled plate annealing process

[0265] (Process 3) Cold Rolling Process

[0266] (Process 4) Decarburization Annealing Process

[0267] (Process 5) Final Annealing Process

[0268] (Process 6) Insulation film formation process

[0269] In addition, the hot-rolled plate annealing process (Process 2) is an optional process. Therefore, the hot-rolled plate annealing process may or may not be performed.

[0270] In the manufacturing method of the present embodiment, the following manufacturing conditions are also satisfied in the cold rolling process (Process 3) and the decarburization annealing process (Process 4).

[0271] (Condition 1)

[0272] The cumulative reduction rate RR of cold rolling in the cold rolling process is 89% or more and 93% or less.

[0273] (Condition 2)

[0274] In a work roll of a rolling stand that performs the first pass of cold rolling, the arithmetic mean roughness Ra (㎛) in the axial direction of the work roll, the 10-point average roughness Rzjis (㎛), and the diameter Dw (mm) of the work roll satisfy equations (1) and (2).

[0275] 0.30≤Ra≤0.01Dw+3.08 (1)

[0276] 3Ra≤Rzjis≤7Ra (2)

[0277] (Condition 3)

[0278] Cold rolling is initiated from the front end to the rear end of a hot-rolled steel sheet produced in a hot-rolling process.

[0279] (Condition 4)

[0280] In the heating process of the decarburization annealing process, the average heating rate HR in the range of 400℃ to 750℃ is set to 100℃ / sec or more and 3000℃ / sec or less.

[0281] Processes 1 to 6 will be described below.

[0282] [(Process 1) Hot Rolling Process]

[0283] In the hot rolling process, hot rolling is performed on a slab to produce a hot-rolled steel sheet. Here, the chemical composition of the prepared slab is adjusted so that the chemical composition of the oriented electrical steel sheet (1) satisfies the range of this embodiment.

[0284] 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 selected from the group consisting of S and Se: total 0.010 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: 0 to 0.0200%, and the remainder consists of Fe and impurities.

[0285] The preferred lower limit of the Si content is 3.10%, and more preferably 3.20%.

[0286] The preferred upper limit of the Si content is 3.60%, and more preferably 3.50%.

[0287] The preferred lower limit of the Mn content is 0.02%, and more preferably 0.05%.

[0288] The preferred upper limit of the Mn content is 0.28%, and more preferably 0.26%.

[0289] The preferred lower limit of the N content is 0.0032%, and more preferably 0.0034%.

[0290] The preferred upper limit of the N content is 0.0120%, and more preferably 0.0100%.

[0291] The preferred lower limit of the C content is 0.012%, and more preferably 0.014%.

[0292] The preferred upper limit of the C content is 0.090%, and more preferably 0.080%.

[0293] The preferred lower limit of the sol.Al content is 0.012%, and more preferably 0.014%.

[0294] The preferred upper limit of the sol.Al content is 0.048%, and more preferably 0.046%.

[0295] The preferred lower limit of the total content of S and Se is 0.012%, and more preferably 0.014%.

[0296] The preferred upper limit of the total content of S and Se is 0.048%, and more preferably 0.046%.

[0297] The preferred lower limit of the Ti content is 0.001%, and more preferably 0.002%.

[0298] The preferred upper limit of the Ti content is 0.008%, and more preferably 0.006%.

[0299] The preferred lower limit of the Ni content is 0.01%, and more preferably 0.02%.

[0300] The preferred upper limit of the Ni content is 0.40%, more preferably 0.30%, and even more preferably 0.20%.

[0301] The preferred lower limit of the Cr content is 0.01%, and more preferably 0.02%.

[0302] The preferred upper limit of the Cr content is 0.40%, more preferably 0.30%, and even more preferably 0.20%.

[0303] The preferred lower limit of the Cu content is 0.01%, and more preferably 0.05%.

[0304] The preferred upper limit of the Cu content is 0.40%, more preferably 0.30%, and even more preferably 0.20%.

[0305] The preferred lower limit of the P content is 0.01%, and more preferably 0.02%.

[0306] The preferred upper limit of the P content is 0.04%, and more preferably 0.03%.

[0307] The preferred lower limit of the Mo content is 0.01%, and more preferably 0.02%.

[0308] The preferred upper limit of the Mo content is 0.04%, and more preferably 0.03%.

[0309] The preferred lower limit of the Sn content is 0.01%, and more preferably 0.02%.

[0310] The preferred upper limit of the Sn content is 0.25%, and more preferably 0.20%.

[0311] The preferred lower limit of the Sb content is 0.01%, and more preferably 0.02%.

[0312] The preferred upper limit of the Sb content is 0.25%, more preferably 0.20%, and even more preferably 0.15%.

[0313] The preferred lower limit of the Bi content is 0.0001%, and more preferably 0.0005%.

[0314] The preferred upper limit of the Bi content is 0.0180%, more preferably 0.0150%, and even more preferably 0.0100%.

[0315] The preferred lower limit of the Ta content is 0.01%, and more preferably 0.02%.

[0316] The preferred upper limit of the Ta content is 0.04%, and more preferably 0.03%.

[0317] The preferred lower limit of the Nb content is 0.001%, and more preferably 0.002%.

[0318] The preferred upper limit of the Nb content is 0.008%, and more preferably 0.006%.

[0319] The preferred lower limit of the V content is 0.01%, and more preferably 0.05%.

[0320] The preferred upper limit of the V content is 0.40%, and more preferably 0.30%.

[0321] The preferred lower limit of the B content is 0.001%, and more preferably 0.002%.

[0322] The preferred upper limit of the B content is 0.008%, and more preferably 0.006%.

[0323] The preferred lower limit of the Te content is 0.0001%, and more preferably 0.0005%.

[0324] The preferred upper limit of the Te content is 0.0150%, and more preferably 0.0100%.

[0325] In this manufacturing method, AlN is used as an inhibitor. Therefore, the Al content in the chemical composition of the slab is within the range described above. When applying the method for manufacturing oriented electrical steel sheets by the inhibitorless method, the Al content in the slab becomes less than 0.010%.

[0326] Slabs are manufactured by well-known steelmaking processes, continuous casting processes, or ingot and bloom rolling processes. Slabs may be made by direct casting and have a thickness of 100 mm or less.

[0327] The hot rolling process using a prepared slab includes the following processes.

[0328] (Process 11) Heating Process

[0329] (Process 12) Rough Rolling Process

[0330] (Process 13) Finishing Rolling Process

[0331] Hereinafter, each process 11 to 13 will be described.

[0332] [(Process 11) Heating Process]

[0333] In the heating process, the slab is heated. For example, the slab is loaded into a known heating furnace or a known cracking furnace and heated. The preferred heating temperature of the slab is 1100 to 1450°C.

[0334] [(Process 12) Rough Rolling Process]

[0335] In the rough rolling process, rough rolling is performed on a heated slab to produce a jova (intermediate steel plate). Here, rough rolling refers to hot rolling a slab using a well-known rough rolling mill. A jova refers to the intermediate steel plate after the completion of the rough rolling process and before the start of the finishing rolling process. In the rough rolling process, a rough rolling mill is used to apply a reduction of multiple passes to the slab to produce the jova.

[0336] [(Process 13) Finishing Rolling Process]

[0337] In the finishing rolling process, a well-known finishing rolling is performed on a piece of steel produced by the roughing rolling process to produce a hot-rolled steel sheet. Here, finishing rolling means hot-rolling a piece of steel using a well-known finishing rolling mill. In the finishing rolling process, a continuous rolling mill consisting of a tandem type of multiple finishing rolling stands arranged in a row on a pass line is used to apply a number of passes of reduction to the piece of steel to produce a hot-rolled steel sheet.

[0338] [(Process 2) Hot-rolled Plate Annealing Process]

[0339] The hot-rolled sheet annealing process is optional. In other words, the hot-rolled sheet annealing process is not required. If performed, the annealing process involves treating the hot-rolled steel sheet produced in the hot-rolling process. By performing the hot-rolled sheet annealing process, recrystallization occurs in the steel sheet structure, thereby enhancing magnetic properties.

[0340] In the hot-rolled sheet annealing process, it is sufficient to perform a well-known hot-rolled sheet annealing. The heating method of the hot-rolled steel sheet during hot-rolled sheet annealing is not particularly limited, and any 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. In addition, if the hot-rolled sheet annealing process is performed, pickling treatment may be performed on the hot-rolled steel sheet after the hot-rolled sheet annealing process and before the cold rolling process.

[0341] [(Process 3) Cold Rolling Process]

[0342] In the cold rolling process, cold rolling is performed on the manufactured hot-rolled steel sheet to produce a cold-rolled steel sheet. As described above, the cold rolling process is performed in one of the following two patterns.

[0343] (Pattern 1) After performing tandem rolling, reverse rolling is performed.

[0344] (Pattern 2) Perform only reverse rolling

[0345] Explain the tandem rolling process and the reverse rolling process.

[0346] [Tandem Rolling Process]

[0347] In the tandem rolling process, cold rolling is performed using a tandem rolling mill.

[0348] FIG. 2 is a schematic diagram of a tandem rolling mill. Referring to FIG. 2, the tandem rolling mill (CM) is positioned between a payoff reel (rewinding device) (21) and a tension reel (winding device) (22) from upstream to downstream.

[0349] The payoff reel (21) unwinds the wound hot-rolled steel sheet (ST0). The tension reel (22) winds the intermediate steel sheet (ST1) manufactured by the tandem rolling mill (CM).

[0350] The tandem rolling mill (CM) performs continuous rolling with a number of passes on the repeated hot-rolled steel sheet (ST0) to produce an intermediate steel sheet (ST1).

[0351] The tandem rolling mill (CM) comprises a plurality of rolling stands (CMS1 to CMS) arranged in a line from upstream to downstream. j Each rolling stand (CMS) is equipped with a pair of work rolls (WR1) that extend horizontally. The pair of work rolls (WR1) come into contact with a hot-rolled steel sheet to be cold-rolled and cold-roll the hot-rolled steel sheet. The rolling stand (CMS) may also be equipped with a plurality of backup rolls (BR1). The backup rolls (BR1) support the work rolls (WR1) and suppress the sagging of the work rolls (WR1) during rolling.

[0352] In continuous rolling using a tandem rolling mill (CM), the process of rolling a hot-rolled steel sheet at each rolling stand (CMS) as it passes through is referred to as "1-pass rolling." Continuous rolling means rolling through multiple passes using a tandem rolling mill (CM). Furthermore, it is not necessary to roll the hot-rolled steel sheet at every rolling stand (CMS) within the tandem rolling mill (CM). For example, in the case where six rolling stands (CMS1 to CMS6) are arranged within the tandem rolling mill (CM), if the hot-rolled steel sheet is passed through rolling stand (CMS6) without being rolled, it is considered that five passes of continuous rolling have been performed.

[0353] [Reverse Rolling Process]

[0354] FIG. 3 is a schematic diagram of a multi-stage rolling mill used in a 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 number of passes on an intermediate steel sheet (ST1) or a hot-rolled steel sheet (ST0) after a 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) are collectively referred to as steel sheets (ST).

[0355] 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 sagging of the work rolls (WR2) is suppressed to the maximum extent by supporting the pair of work rolls (WR2) with the plurality of backup rolls (BR2). By doing so, high reduction can be achieved. The pair of work rolls (WR2) includes an upper work roll (WR2U) and a lower work roll (WR2L). The lower work roll (WR2L) is positioned below the upper work roll (WR2U).

[0356] Here, when a reduction is applied to the steel plate (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, reduction is applied when the steel plate (ST) moves from upstream to downstream, and also when the steel plate (ST) moves from downstream to upstream. More specifically, when the steel plate (ST) passes through the multi-stage rolling mill (SM) from upstream to downstream, one-pass reduction is applied to the steel plate (ST). Additionally, when the steel plate (ST) passes through the same multi-stage rolling mill (SM) from downstream to upstream, one-pass reduction is applied to the steel plate (ST). That is, when reduction is applied in a reciprocal manner, two-pass reduction is applied to the steel plate (ST). In addition, there are cases where no compression is applied to the steel plate (ST) when it passes through the multi-stage rolling mill (SM).

[0357] In the cold rolling process, either the above tandem rolling and reverse rolling (Pattern 1) or only reverse rolling (Pattern 2) is performed to manufacture a cold-rolled steel sheet.

[0358] [Manufacturing conditions in the cold rolling process]

[0359] In the cold rolling process, the following conditions 1 to 3 are satisfied.

[0360] (Condition 1)

[0361] The cumulative reduction rate RR of cold rolling in the cold rolling process is 89% or more and 93% or less.

[0362] (Condition 2)

[0363] In a work roll of a rolling stand that performs the first pass of cold rolling, the arithmetic mean roughness Ra (㎛) in the axial direction of the work roll, the 10-point average roughness Rzjis (㎛), and the diameter Dw (mm) of the work roll satisfy equations (1) and (2).

[0364] 0.30≤Ra≤0.01Dw+3.08 (1)

[0365] 3Ra≤Rzjis≤7Ra (2)

[0366] (Condition 3)

[0367] Cold rolling is initiated from the front end to the rear end of a hot-rolled steel sheet produced in a hot-rolling process.

[0368] Conditions 1 through 3 will be explained below.

[0369] [Regarding Condition 1]

[0370] The cumulative reduction rate RR of cold rolling in the cold rolling process is 89% or more and 93% or less.

[0371] If the cumulative reduction rate RR is too low, {110} <112> As defense particles are generated in excess, the generation of Gos defense particles is excessively suppressed. If the cumulative reduction rate is excessively high, {211} <011> The formation of orientation particles is excessive, and the formation of Gos orientation particles is excessively suppressed. As a result, in the manufactured orientational electrical steel sheet (1), at least one of requirements A to C is not satisfied.

[0372] If the cumulative reduction rate RR is 89% or more and 93% or less, the cumulative reduction rate RR is within an appropriate range. In this case, requirements A to C are satisfied in the manufactured oriented electrical steel sheet (1).

[0373] The preferred lower limit of the cumulative reduction rate RR is 90%. The preferred upper limit of the cumulative reduction rate RR is 92%.

[0374] [Regarding Equation (1) of Condition 2]

[0375] In the work roll of a rolling stand that performs the first pass 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 Equation (1).

[0376] 0.30≤Ra≤0.01Dw+3.08 (1)

[0377] The arithmetic mean roughness Ra of the work roll affects requirements A through C. If the arithmetic mean roughness Ra is too low, the deformation introduced into the steel plate is excessively small. In this case, {110} <112> Directional particles, or {211} <011> As a result, an excess of orientation particles is generated, and the generation of Gos orientation particles is excessively suppressed. Consequently, in the manufactured orientational electrical steel sheet (1), at least one of requirements A to C is not satisfied.

[0378] On the other hand, if the arithmetic mean roughness Ra is excessively high with respect to the work roll diameter Dw, the deformation introduced into the surface layer of the steel sheet becomes excessive. In particular, the reduction in the first pass of cold rolling has a significant influence on the shear texture of the steel sheet surface layer formed during hot rolling. If the deformation introduced into the surface layer of the steel sheet by the work roll of the rolling stand performing the reduction in the first pass of cold rolling becomes excessive, it hinders the development of the texture. Therefore, {110} <112> Directional particles, or {211} <011> Antagonal particles are generated in excess, and the generation of Goss antagonal particles is excessively suppressed. As a result, in the manufactured oriented electrical steel sheet (1), at least one of requirements A to C is not satisfied.

[0379] When the arithmetic mean roughness Ra satisfies Equation (1), requirements A to C are satisfied in the manufactured oriented electrical steel sheet (1).

[0380] The preferred lower limit of the arithmetic mean roughness Ra is 0.32 μm, and more preferably 0.34 μm.

[0381] The preferred upper limit of the arithmetic mean roughness Ra is 0.01Dw+3.00, and more preferably 0.01Dw+2.90.

[0382] In addition, the diameter Dw of the work roll is the arithmetic mean of the diameters of a pair of work rolls.

[0383] [Regarding Equation (2) of Condition 2]

[0384] In the work roll of the rolling stand that performs the first pass of cold rolling, the arithmetic mean roughness Ra (㎛) in the axial direction of the work roll and the 10-point average roughness Rzjis (㎛) satisfy Equation (2).

[0385] 3Ra≤Rzjis≤7Ra (2)

[0386] The 10-point average roughness Rzjis of a work roll is an indicator representing the local size of irregularities on the work roll. For the large angle grain boundary ratio RL to be within a certain range, Goss orientation grains that are slightly misaligned from each other must undergo secondary recrystallization and become adjacent to one another. The 10-point average roughness Rzjis influences the amount of local variation in the surface layer of the steel sheet during cold rolling and affects the misalignment of neighboring Goss orientation grains. In other words, the 10-point average roughness Rzjis influences the large angle grain boundary ratio RL.

[0387] If the 10-point average roughness Rzjis is excessively low compared to the arithmetic mean roughness Ra of the work roll, the orientational misalignment of neighboring Goss-oriented grains becomes excessively small. In this case, the large angle grain boundary ratio RL becomes excessively small. On the other hand, if the 10-point average roughness Rzjis is excessively high compared to the arithmetic mean roughness Ra of the work roll, the orientational misalignment of neighboring Goss-oriented grains becomes excessively large. In this case, the large angle grain boundary ratio RL becomes excessively large.

[0388] If the 10-point average illuminance Rzjis satisfies Equation (2), the large angle grain boundary ratio RL becomes 5% or more and 30% or less.

[0389] The preferred upper limit of the 10-point average illuminance Rzjis is 6.5Ra, and more preferably 6.0Ra. The preferred lower limit of the 10-point average illuminance Rzjis is 3.5Ra, and more preferably 4.0Ra.

[0390] [Regarding the measurement methods of arithmetic mean illuminance Ra and 10-point average illuminance Rzjis]

[0391] The arithmetic mean roughness Ra and 10-point average roughness Rzjis of the work rolls of the rolling stand are obtained by the following method.

[0392] On the surface of each work roll of a pair of work rolls, any three points are designated as measurement points. That is, there are six measurement points. On the surface of each work roll, the three measurement points are arranged in a line along the axial direction of the work roll, and the spacing between each measurement point is 100 mm. At each measurement point, the arithmetic mean roughness Ra (㎛) and the 10-point average roughness Rzjis (㎛) are measured along the axial direction of the work roll in accordance with the method specified in JIS B 0601:2001. The roughness meter used for measurement is a contact-type roughness meter. The conditions for calculating the roughness curve are as follows.

[0393] Measuring force: 0.75 mN

[0394] Stylus tip shape: 2㎛R60°

[0395] Cut-off value λc: 0.8mm

[0396] Cut-off value λs: 2.5㎛

[0397] Number of intervals: 3

[0398] Measurement speed: 0.25 mm / sec

[0399] Standard length: 0.8mm

[0400] Evaluation length: 16mm

[0401] For example, the contact type illuminance meter uses the Mitsutoyo SJ-210 product.

[0402] The arithmetic mean value of the arithmetic mean roughness of the six obtained locations is set as the arithmetic mean roughness Ra (㎛) in the axial direction of the work roll. In addition, the arithmetic mean value of the 10-point average roughness of the six obtained locations is set as the 10-point average roughness Rzjis (㎛) in the axial direction of the work roll.

[0403] [Regarding Condition 3]

[0404] In the manufacturing method of the present embodiment, in the cold rolling process, cold rolling is initiated from the front end to the rear end of a hot-rolled steel sheet produced in the hot rolling process. That is, the rolling direction of the steel sheet at the start of cold rolling is aligned with the rolling direction of the steel sheet during hot rolling.

[0405] In the cold rolling process, when cold rolling is initiated from the front end to the rear end of a hot-rolled steel sheet produced in the hot rolling process, the large angle grain boundary ratio RL becomes 30% or less. The reason for this is not clear, but the following reason can be considered. It is thought that when cold rolling is initiated from the front end to the rear end of a hot-rolled steel sheet produced in the hot rolling process, 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.

[0406] [(Process 4) Decarburization Annealing Process]

[0407] In the decarburization annealing process, decarburization annealing is performed on the cold-rolled steel sheet after the cold rolling process to induce primary recrystallization.

[0408] The decarburization annealing process includes the following processes.

[0409] (Process 41) Temperature increase process

[0410] (Process 42) Decarburization Process

[0411] (Process 43) Cooling Process

[0412] In the heating process (Process 41), the steel plate is heated to any temperature (reached temperature) from 750 to 950°C. In the decarburization process (Process 42), the steel plate is maintained at a decarburization annealing temperature of 750 to 950°C to perform decarburization annealing and induce primary recrystallization. In the cooling process (Process 43), the steel plate after the decarburization process is cooled by a known method. Additionally, the reached temperature and the decarburization annealing temperature may be the same temperature, or the reached temperature may be higher than the decarburization annealing temperature.

[0413] In this embodiment, during the heating process, the average heating rate HR in the temperature range of 400 to 750°C, which corresponds to the recrystallization temperature range of the steel sheet, is significantly accelerated. This promotes the recrystallization of Goss orientation grains. As a result, the degree of integration into the Goss orientation after secondary recrystallization can be increased. Consequently, the magnetic properties of the oriented electrical steel sheet can be improved.

[0414] The details of each process are explained below.

[0415] [(Process 41) Temperature Increase Process]

[0416] In the heating process, first, the cold-rolled steel sheet after the cold rolling process is loaded into a heat treatment furnace (decarburization annealing furnace). In addition, the atmosphere inside the heat treatment furnace is set to an atmosphere of a mixed gas of nitrogen and hydrogen with a dew point of -50 to 0°C (non-oxidizing atmosphere). In the heat treatment furnace for decarburization annealing in this embodiment, the cold-rolled steel sheet is heated to any temperature of 750 to 900°C by, for example, high-frequency induction heating or electric current heating. The heating process satisfies the following condition 4.

[0417] (Condition 4)

[0418] The average heating rate HR in the temperature range of 400℃ to 750℃ is set to 100℃ / sec or more and 3000℃ / sec or less.

[0419] [Regarding Condition 4]

[0420] In the heating process, the average heating rate of the cold-rolled steel sheet in the temperature range of 400°C to 750°C is defined as the average heating rate HR (°C / sec).

[0421] Deformation accumulates in cold-rolled steel sheets produced by the cold rolling process. If the average heating rate HR is less than 100°C / sec, the deformation energy that serves as the driving force for recrystallization is released before recrystallization begins. In this case, a sufficient amount of Goss orientation 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).

[0422] When the average heating rate HR is 100°C / sec or higher, primary recrystallization occurs when sufficient deformation energy is accumulated in the cold-rolled steel sheet. Consequently, a sufficient amount of Goss orientation particles can be generated in the cold-rolled steel sheet after primary recrystallization. Consequently, a large amount of Goss orientation particles remain when secondary recrystallization occurs during the subsequent finishing annealing process. Consequently, the degree of accumulation of Goss orientation after secondary recrystallization can be increased. As a result, the magnetic properties of the oriented electrical steel sheet can be improved, and fluctuations in magnetic properties can also be suppressed.

[0423] In addition, the upper limit of the average heating rate HR is not specifically limited. However, even if the average heating rate HR is faster than 3000℃ / sec, the above effect saturates. Therefore, the upper limit of the average heating rate HR is 3000℃ / sec.

[0424] The preferred lower limit of the average heating rate HR is 150℃ / sec, and more preferably 200℃ / sec.

[0425] The average heating rate HR is measured by the following method. A plurality of thermometers are installed inside the heat treatment furnace to measure the surface temperature of the steel plate. The plurality of thermometers are arranged from the upstream to the downstream of the heat treatment furnace. Based on the temperature of the steel plate measured by the thermometers and the time taken for the steel plate temperature to rise from 400°C to 750°C, the average heating rate HR (°C / sec) is calculated.

[0426] [(Process 42) Decarburization Process]

[0427] In the decarburization process, the cold-rolled steel sheet after the heating process is held at the decarburization annealing temperature to perform decarburization annealing. This induces primary recrystallization in the cold-rolled steel sheet. The atmosphere during the decarburization process is sufficient if it is a known atmosphere, for example, a non-oxidizing atmosphere containing hydrogen and nitrogen. The oxygen potential Po is set to, for example, 0.01 to 0.60. By performing decarburization annealing, carbon in the steel sheet is removed from the steel sheet, and primary recrystallization is induced. 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.

[0428] [(Process 43) Cooling Process]

[0429] In the cooling process, the cold-rolled steel sheet after the decarburization process is cooled to room temperature by a known method to become a decarburized annealed steel sheet. The cooling method may be air cooling or water cooling. Preferably, the cold-rolled steel sheet after the decarburization process is air-cooled. Through the above process, a decarburized annealed steel sheet is manufactured in the decarburization annealing process.

[0430] [(Process 5) Final Annealing Process]

[0431] In the finishing annealing process, an annealing separator is applied to a decarburized annealed steel plate, and finishing annealing is performed on the decarburized annealed steel plate coated with the annealing separator to manufacture a finishing annealed steel plate.

[0432] The final annealing process includes the following processes.

[0433] (Process 51) Annealing Separator Application Process

[0434] (Process 52) Annealing Process

[0435] The following describes each process.

[0436] [(Process 51) Annealing Separator Application Process]

[0437] In the annealing separator application process, an annealing separator is applied to a decarburized annealed steel plate. Specifically, an aqueous slurry containing an annealing separator is applied to the decarburized annealed steel plate. The aqueous slurry is prepared by adding water to the annealing separator and stirring.

[0438] The annealing separator may be composed mainly of magnesium oxide (MgO), or may be composed mainly of silica and alumina. "Main component" means that it constitutes 60.0% or more by mass in the annealing separator. The annealing separator may contain known additives other than MgO or other than silica and alumina.

[0439] When the reduction of iron loss is important, the annealing separator is composed mainly of MgO. When punching processability is important, the annealing separator is composed mainly of silica and alumina.

[0440] 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 shape. After the steel sheet is coiled, an annealing process is performed.

[0441] [(Process 52) Annealing Process]

[0442] After the annealing separator application process, an annealing process is performed on the steel sheet to induce secondary recrystallization. The final annealing process is performed by loading the coil-shaped steel sheet into a heat treatment furnace. The manufacturing conditions for the annealing process are, for example, as follows. In addition, the atmosphere inside the furnace during the annealing process is a well-known atmosphere.

[0443] Finish annealing temperature: 800 to 1200℃

[0444] Holding time at finishing annealing temperature: 5 to 60 hours

[0445] If the finishing annealing temperature is less than 800°C, sufficient secondary recrystallization is not achieved, and purification to remove precipitates used in secondary recrystallization is insufficient. Consequently, the magnetic properties of the manufactured oriented electrical steel sheet are reduced. On the other hand, if the finishing annealing temperature exceeds 1200°C, the effects on secondary recrystallization and purification are low, and problems such as deformation of the steel sheet occur. If the finishing annealing temperature is between 800°C and 1200°C, provided that the holding time is appropriate, sufficient secondary recrystallization is achieved, and the magnetic properties are improved. Additionally, a primary film is formed on the surface of the steel sheet.

[0446] Through the above manufacturing process, a finished annealed steel sheet is manufactured in the finishing annealing process.

[0447] Furthermore, through the finishing annealing process, each element of the steel sheet's chemical composition is removed to a certain extent from the steel sheet. In particular, elements such as S, Al, and N, which function as inhibitors, are removed significantly. Additionally, a lower film (primary film or intermediate layer) is formed on the surface of the oriented electrical steel sheet after the finishing annealing process.

[0448] [(Process 6) Insulating Film Formation Process]

[0449] In the insulation film formation process, an insulation film forming agent is applied to the finishing annealed steel plate. Additionally, heat treatment is performed on the finishing annealed steel plate to which the insulation film forming agent has been applied. By doing so, an insulation film is formed on the finishing annealed steel plate.

[0450] Specifically, a known insulating film-forming agent containing at least one of inorganic materials such as metal chromate salts, metal phosphate salts, colloidal silica, Zr compounds, and Ti compounds is applied to the surface (above the lower film) of a finishing annealed steel sheet. Then, baking is performed on the finishing annealed steel sheet coated with the insulating film-forming agent. By doing so, a known insulating film is formed on the primary film.

[0451] [Any other processes]

[0452] [Nitriding Process]

[0453] The method for manufacturing the oriented electrical steel sheet (1) according to the present embodiment may also, if necessary, perform a nitriding treatment process after the decarburization annealing process (Process 4) and before the finishing annealing process (Process 5). The nitriding treatment process may be performed under known conditions. The nitriding treatment temperature is, for example, 700 to 850°C. The atmosphere inside the nitriding treatment furnace (nitriding treatment atmosphere) is an atmosphere containing a gas having nitriding ability, such as hydrogen, nitrogen, and ammonia.

[0454] If the nitriding treatment temperature is 700°C or higher, or 850°C or lower, nitrogen is likely to penetrate into the steel sheet during the nitriding treatment. If the nitriding treatment is performed within this temperature range, the amount of nitrogen inside the steel sheet can be preferably secured. Consequently, fine AlN is preferably formed in the steel sheet prior to secondary recrystallization. As a result, secondary recrystallization is preferably manifested during the final annealing. In addition, the time for holding the steel sheet at the nitriding treatment temperature is not particularly limited, but is, for example, 10 to 60 seconds.

[0455] [Text Detail Processing Process]

[0456] The oriented electrical steel sheet according to the present embodiment may also undergo a magnetic domain refinement treatment process after the final annealing process (Process 5) or the insulating film formation process (Process 6), if necessary. In the magnetic domain refinement treatment process, a laser light having a magnetic domain refinement effect is irradiated onto the surface (rolled surface) of the oriented electrical steel sheet to form linear thermal deformation on the surface of the steel sheet or to physically form grooves on the surface of the steel sheet. In this case, an oriented electrical steel sheet with even better magnetic properties can be manufactured.

[0457] By the above manufacturing process, the directional electrical steel sheet (1) of the present embodiment is manufactured.

[0458] The embodiments of the present invention will be specifically described below by way of examples. These examples are merely illustrative of the method for manufacturing a oriented electrical steel sheet according to the present embodiment and do not limit the present invention.

[0459] Example 1

[0460] Using slabs having the chemical composition shown in Table 1 (Table 1A, Table 1B, Table 1C, Table 1D), the oriented electrical steel sheets shown in Table 3 (Table 3A and Table 3B) were manufactured.

[0461] Specifically, the slabs shown in Table 1 (Table 1A, Table 1B, Table 1C, Table 1D) were prepared.

[0462] [Table 1A]

[0463]

[0464] [Table 1B]

[0465]

[0466] [Table 1C]

[0467]

[0468] [Table 1D]

[0469]

[0470] A hot rolling process was performed on the prepared slabs. Specifically, the slabs of each test number were heated to 1340°C in a heating furnace. Hot rolling was performed on the heated slabs to produce hot-rolled steel sheets with the plate thickness (mm) shown in Table 3 (Table 3A, Table 3B).

[0471] [Table 2A]

[0472]

[0473] [Table 2B]

[0474]

[0475] [Table 2C]

[0476]

[0477] [Table 2D]

[0478]

[0479] For the hot-rolled steel sheet after the hot rolling process, a hot-rolled sheet annealing process was carried out at a hot-rolled sheet annealing temperature of 900 to 1200°C for a holding time of 10 to 300 seconds.

[0480] After the hot-rolled sheet annealing process, a cold rolling process was performed to produce a cold-rolled steel sheet with a thickness (mm) as shown in Table 3 (Table 3A, Table 3B). The conditions for the cold rolling process, such as the cumulative reduction rate RR (%), the arithmetic mean roughness Ra (μm) of the work roll of the first-pass rolling stand, the diameter Dw (mm) of the work roll of the first-pass rolling stand, the 10-point average roughness Rzjis (μm) of the work roll of the first-pass rolling stand, the rolling direction of the first-pass cold rolling, and the cold rolling pattern, were as shown in Table 3 (Table 3A, Table 3B).

[0481] Here, in Table 3 (Table 3A, Table 3B), “T” in the “Evaluation” column of the “Equation (1)” column means that the arithmetic mean roughness Ra satisfies Equation (1), and “F” means that the arithmetic mean roughness Ra satisfies Equation (1). In the “Rolling Direction of the First Pass” column, “Same Direction” means that cold rolling is started from the front end of the hot-rolled steel sheet produced in the hot-rolling process toward the rear end, and “Opposite Direction” means that cold rolling is started from the rear end of the hot-rolled steel sheet produced in the hot-rolling process toward the front end. In the “Cold Rolling Pattern” column, “T+R” means that reverse rolling was performed after tandem rolling (i.e., that Pattern 1 was performed as cold rolling), and “R” means that only reverse rolling was performed (i.e., that Pattern 2 was performed as cold rolling).

[0482] In addition, the arithmetic mean roughness Ra and 10-point average roughness Rzjis of the work roll of the first cold rolling pass were measured based on the [Measurement method for arithmetic mean roughness Ra and 10-point average roughness Rzjis] described above.

[0483] A decarburization annealing process was performed on the cold-rolled steel sheet after the cold rolling process. Specifically, the atmosphere of the decarburization annealing furnace was a mixed gas atmosphere of nitrogen and hydrogen with a dew point of -30°C (non-oxidizing atmosphere). The average heating rate HR (°C / sec) in the temperature range of 400 to 750°C was set as shown in Table 3 (Table 3A, Table 3B). After heating to a temperature of 800 to 950°C, the temperature was maintained at 800 to 950°C for 120 to 150 seconds. At this time, the oxygen potential Po in the atmosphere was set to 0.01 to 0.60.

[0484] An annealing separator composed mainly of MgO was applied to the surface of the decarburized annealed steel sheet. Subsequently, the decarburized annealed steel sheet coated with the annealing separator was wound into a coil shape.

[0485] Finish annealing was performed on the coil to manufacture 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.

[0486] An insulating film formation process was performed on the steel sheets after the final annealing process. Specifically, an insulating film forming agent composed mainly of colloidal silica and phosphate was applied to the surface of the final annealed steel sheets of each test number. Subsequently, baking was performed on the final annealed steel sheets coated with the insulating film forming agent under the same conditions to form an insulating film on the lower film (primary film). Through the above manufacturing process, the oriented electrical steel sheets of each test number were manufactured.

[0487] In addition, the chemical composition of the oriented electrical steel sheet for each test number was measured based on the [method for measuring the chemical composition of the oriented electrical steel sheet (1)] described above. As a result, the chemical composition of the base steel sheet of the oriented electrical steel sheet for each test number was as shown in Table 2 (Table 2A, Table 2B, Table 2C, Table 2D). In addition, a component analysis device manufactured by Shimadzu Seisakusho (product name: ICPS-8000) was used as the test device.

[0488] [Table 3A]

[0489]

[0490] [Table 3B]

[0491]

[0492] [Evaluation Test]

[0493] The following evaluation tests were conducted on the manufactured oriented electrical steel sheets.

[0494] (Test 1) Count ratio R {211}<011> , count ratio R {110}<112> , and count ratio R {110}<001> measurement test

[0495] (Test 2) Measurement test of large angle grain boundary ratio RL

[0496] (Test 3) Magnetic Flux Density Measurement Test

[0497] (Test 4) Iron loss evaluation test of oriented electrical steel sheets after domain refinement treatment

[0498] (Test 5) Magnetostriction evaluation test of oriented electrical steel sheets after domain refinement treatment

[0499] Tests 1 through 5 will be described below.

[0500] [(Test 1) Count ratio R {211}<011> , count ratio R {110}<112> , and count ratio R {110}<001> [Measurement Test]

[0501] Based on the method described in the [Method for Measuring Determination Orientation at a Measurement Point] above, the number ratio R of oriented electrical steel sheets for each test number {211}<011> (%), count ratio R {110}<112> (%), and count ratio R {110}<001> (%) was calculated. The obtained values ​​are shown in Table 4 (Table 4A, Table 4B).

[0502] [Table 4A]

[0503]

[0504] [Table 4B]

[0505]

[0506] [(Test 2) Large angle grain boundary ratio R L [Measurement Test]

[0507] Based on the method described in the [Method for Measuring the Determination Orientation at the Measurement Point] above, the large angle grain boundary ratio RL(%) of the oriented electrical steel sheet for each test number was calculated. The obtained values ​​are shown in “LI / La(%)” in Table 4 (Table 4A, Table 4B).

[0508] [(Test 3) Magnetic Flux Density Measurement Test]

[0509] For the oriented electrical steel sheets of each test number, magnetic domain refinement treatment by laser irradiation was performed. In the magnetic domain refinement treatment by laser irradiation, the irradiation pitch in the rolling direction was set to a spacing of 4 mm. In addition, the energy density Ua was 1.25 mJ / mm² 2 did it.

[0510] Test specimens were taken from the center of the plate width of the oriented electrical steel sheet of each test number after magnetic domain subdivision treatment. The dimensions of the test specimens were 60 mm in the plate width direction × 300 mm in the rolling direction × plate thickness. In accordance with JIS C2556:2015, a magnetic field of 800 A / m was applied to the test specimens by a single-plate magnetic property test (SST test) to determine the magnetic flux density B8(T). The obtained magnetic flux density B8 is shown in “B8(T)” in Table 4 (Table 4A, Table 4B). If the magnetic flux density B8 is 1.921T or higher, it was determined that an excellent magnetic flux density was obtained. Furthermore, if the magnetic flux density B8 is less than 1.700T, it was determined that a secondary recrystallization defect occurred, and Tests 1, 2, 4, and 5 were not performed.

[0511] [(Test 4) Iron loss evaluation test of oriented electrical steel sheets after domain refinement treatment]

[0512] A test specimen was taken from the center of the plate width of the oriented electrical steel sheet after domain refinement treatment. The dimensions of the test specimen were 100mm × 500mm × plate thickness. In accordance with JIS C2556:2011, using the test specimen, the iron loss W at a frequency of 50Hz and a maximum magnetic flux density of 1.700T was calculated. 17 / 50 (W / kg) was calculated. The obtained iron loss W 17 / 50 "W" in Table 4 (Tables 4A, 4B) 17 / 50 (W / kg) is shown in

[0513] For each test number, it was determined that excellent iron loss was obtained under the following conditions.

[0514] (1) Iron loss W when plate thickness is 0.22mm 17 / 50 This is 0.703W / kg or less.

[0515] (2) Iron loss W when plate thickness is 0.19mm 17 / 50 This is 0.669W / kg or less.

[0516] (3) Iron loss W when plate thickness is 0.17mm 17 / 50 This is 0.625W / kg or less.

[0517] [(Test 5) Magnetostriction evaluation test of oriented electrical steel sheets after domain refinement treatment]

[0518] The magnetostriction of the oriented electrical steel sheet of each test number was measured by the following method. As the test specimen, the test specimen taken from Test 4 above was used. The magnetostriction measuring 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.

[0519] Using the above-described magnetostriction measuring device, magnetostriction was determined by the alternating current magnetostriction measurement method. Specifically, an alternating current magnetic field was applied to the test specimen such that the maximum magnetic flux density in the rolling direction was 1.700 T. The change in the length of the sample due to the stretching of the magnetic domains was measured using a laser Doppler vibrometer to obtain a magnetostriction signal. The obtained magnetostriction signal was Fourier analyzed to determine the amplitude Cn of each frequency component fn (where n is a natural number greater than or equal to 1) of the magnetostriction signal. Using the A correction factor αn of each frequency component fn, the magnetostriction rate level LVA (dB) was calculated, expressed by the following equation.

[0520] LVA=20×Log(√(Σ(ρc×2π×fn×αn×Cn / √2) 2 ) / Pe0)

[0521] Here, ρc is the specific acoustic resistance, and ρc was set to 400. Pe0 is the minimum audible sound pressure, and Pe0 = 2 × 10⁻⁶ -5(Pa) was used. The A correction factor αn was the value listed in Table 2 of JIS C 1509-1 (2005).

[0522] The obtained magnetostriction rate level LVA is shown in Table 4. If the obtained magnetostriction rate level (LVA) is 58.04 dB or less, it was determined that excellent noise characteristics were obtained.

[0523] [Evaluation Results]

[0524] Referring to Table 1 (Tables 1A to 1D) and Table 2 (Tables 2A to 2D), the oriented electrical steel sheets of test numbers 1 to 47 satisfied requirements A to C, and the large angle grain boundary ratio RL (=LI / La) was 5 to 30%. Therefore, excellent magnetic flux density B8 was obtained after the domain refinement treatment. In addition, excellent iron loss and excellent noise characteristics were obtained after the domain refinement treatment.

[0525] Meanwhile, in test numbers 48 to 53, condition 1 was not satisfied in the manufacturing process. Consequently, any of requirements A to C fell outside the scope of the present invention. As a result, a sufficient magnetic flux density B8 was not obtained. Furthermore, sufficient iron loss was not obtained, and sufficient noise characteristics were not obtained.

[0526] In test numbers 54 to 60, under condition 2 of the manufacturing process, the arithmetic mean roughness Ra of the first pass work roll did not satisfy Equation (1). Consequently, any of requirements A to C fell outside the scope of the present invention. As a result, sufficient magnetic flux density B8 was not obtained, sufficient iron loss was not obtained, and sufficient noise characteristics were not obtained.

[0527] In test numbers 61 and 62, under manufacturing process condition 2, the 10-point average roughness Rzjis of the first pass work roll did not satisfy the upper limit of Equation (2). Consequently, the large angle grain boundary ratio RL (=LI / La) exceeded 30%. As a result, a sufficient magnetic flux density B8 was not obtained. Furthermore, sufficient iron loss was not obtained, and sufficient noise characteristics were not obtained.

[0528] In test number 63, under manufacturing process condition 2, the 10-point average roughness Rzjis of the first pass work roll did not satisfy the lower limit of Equation (2). Consequently, the large angle grain boundary ratio RL (=LI / La) was less than 5%. As a result, although a sufficient magnetic flux density B8 was obtained, sufficient iron loss was not obtained.

[0529] In test number 64, condition 3 of the manufacturing process was not satisfied. As a result, the large angle grain boundary ratio RL (=LI / La) exceeded 30%. Consequently, sufficient iron loss was not obtained, and sufficient noise characteristics were not obtained.

[0530] In test numbers 65 and 66, manufacturing process condition 4 was not satisfied. Therefore, the number ratio R {110}<001> (Requirement C) was less than 90%. As a result, sufficient magnetic flux density B8 was not obtained. In addition, sufficient iron loss was not obtained, and sufficient noise characteristics were not obtained.

[0531] In test number 67, the Si content of the slab and the oriented electrical steel sheet was too high. As a result, the steel sheet fractured during the manufacturing process. Therefore, the evaluation test was not conducted.

[0532] In test number 68, the Si content of the slab and the oriented electrical steel sheet was too low. As a result, insufficient iron loss was obtained after the magnetic domain refinement treatment.

[0533] In test number 69, the Mn content in the base steel sheets of the slab and oriented electrical steel sheet was too high. As a result, the magnetic flux density B8 was less than 1.700T.

[0534] In test number 70, the Mn content in the base steel sheets of the slab and oriented electrical steel sheet was too low. As a result, the magnetic flux density B8 was less than 1.700T.

[0535] 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. For this reason, the magnetic flux density B8 was less than 1.700T.

[0536] 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. As a result, the magnetic flux density B8 was less than 1.700T.

[0537] 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. As a result, the magnetic flux density B8 was less than 1.700T.

[0538] In test numbers 77 to 82, the total content of S and Se in the slab was outside the range of the present invention. Therefore, the magnetic flux density B8 was less than 1.700T.

[0539] The embodiments of the present disclosure have been described above. However, the embodiments described above are merely examples for carrying out the present disclosure. Accordingly, the present disclosure is not limited to the embodiments described above, and may be carried out by appropriately modifying the embodiments described above within the scope without departing from the spirit thereof. Explanation of the symbols

[0540] 1: Grain-oriented electrical steel sheet 10: Base steel plate 11: Lower layer membrane 12: Insulating film

Claims

Claim 1 It is a grain-oriented electrical steel sheet, comprising a base steel sheet, wherein 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 to 0.010%, one or more selected from the group consisting of S and Se: total 0 to 0.010%, 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 0.0150%, Ta: 0 to 0.05%, Nb: 0 to 0.010%, V: 0 to 0.50%, B: 0 to 0.010%, Te: 0 to 0.0150%, and the remainder being Fe and impurities, and when the crystal orientation by X-ray diffraction is measured at measurement points arranged at a 2mm pitch in each direction of the rolling direction and the direction orthogonal to the rolling direction on the surface of the base steel sheet, {211} for all measurement points <011> R is the ratio of the number of measurement points with an bearing difference of 15° or less from the bearing. {211}<011> This is 5% or less, and {110} for all measurement points <112> R is the ratio of the number of measurement points with an bearing difference of 15° or less from the bearing. {110}<112> 5% or less, and {110} for all measurement points <001> R is the ratio of the number of measurement points with an bearing difference of 15° or less from the bearing. {110}<001> A oriented electrical steel sheet having a ratio of 90% or more, and a large angle grain boundary ratio RL = LI / La, which is the ratio of the total length LI of grain boundaries with an orientation difference of 15° or more to the total length La of grain boundaries obtained from the orientation difference at the measurement point, wherein the ratio is 5% or more and 30% or less. Claim 2 In claim 1, the oriented electrical steel sheet having a plate thickness of 0.19 mm or less of the base steel sheet. Claim 3 In claim 1, 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: 0.01 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 A oriented electrical steel sheet containing one or more types selected from the group consisting of 0.0150%. Claim 4 A method for manufacturing a grain-oriented electrical steel sheet as described in any one of claims 1 to 3, comprising, 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 selected from the group consisting of S and Se: total 0.010 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 A hot rolling process for hot rolling a slab comprising 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 remainder being Fe and impurities, to produce a hot-rolled steel sheet; a hot-rolled sheet annealing process for annealing the hot-rolled steel sheet; a cold rolling process for cold rolling the hot-rolled steel sheet after the hot-rolled sheet annealing process to produce a cold-rolled steel sheet; a decarburization annealing process for performing decarburization annealing on the cold-rolled steel sheet to produce a decarburized annealed steel sheet; a finishing annealing process for performing finishing annealing after applying an annealing separator to the decarburized annealed steel sheet; and an insulating film forming process for forming an insulating film on the surface of the finishing annealed sheet. A method for manufacturing a oriented electrical steel sheet, comprising a process, wherein in the cold rolling process, the cumulative reduction rate is set to 89% or more and 93% or less, and in a work roll of a rolling stand that performs the first pass of cold rolling, the arithmetic mean roughness Ra (㎛) in the axial direction of the work roll, the 10-point average roughness Rzjis (㎛), and the diameter Dw (mm) of the work roll satisfy Equations (1) and (2). 0.30≤Ra≤0.01Dw+3.08 (1)3Ra≤Rzjis≤7Ra (2) Claim 5 A method for manufacturing an oriented electrical steel sheet according to claim 4, wherein in the decarburization annealing process, the decarburization annealing temperature is set to 750 to 950°C and the average heating rate from 400°C to 750°C is 100°C / second or more and 3000°C / second or less. Claim 6 A method for manufacturing an oriented electrical steel sheet according to claim 4, wherein in the cold rolling process, cold rolling is initiated from the front end to the rear end of the hot-rolled steel sheet produced in the hot rolling process.

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