RU2823712C2 - Sheet of anisotropic electrical steel and method of its production - Google Patents

Abstract

FIELD: various technological processes.

SUBSTANCE: invention relates to anisotropic electrical steel sheet and method of its production. Anisotropic electrical steel sheet comprises a base steel sheet, a glass coating formed on the base steel sheet, and an insulating coating with tension formed on the glass coating, wherein the base steel sheet has a plurality of linear deformation areas, which are arranged continuously or periodically in a direction intersecting with the rolling direction, each of the plurality of linear deformation regions has width of 210 mcm or less in the rolling direction, the plurality of linear deformation regions are parallel to each other, intervals of linear deformation areas adjacent to each other in rolling direction are 10 mm or less, and magnetostriction λ_0-pb in mcm/m at excitation of anisotropic electrical steel sheet to 1.7 T and magnetostriction λ_0-pa in mcm/m during heat treatment of anisotropic electrical steel sheet at 800 °C for 4 hours and subsequent excitation to 1.7 T satisfy condition 0.02≤λ_0-pb – λ_0-pa≤0.20.

EFFECT: providing a sheet of anisotropic electrical steel, having a favourable balance of magnetic losses/noise and adhesion of the coating.

8 cl

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

[0001]

The present invention relates to an anisotropic electrical steel sheet and to a method for producing the same.

Priority is claimed on Japanese Patent Application No. 2021-053619, filed on March 26, 2021, the contents of which are incorporated herein by reference.

PRIOR ART

[0002]

Anisotropic electrical steel sheets are soft magnetic materials, and are mainly used as core materials for transformers. Therefore, anisotropic electrical steel sheets are required to have magnetic characteristics such as high magnetization performance and low magnetic loss.

Magnetic loss is the loss of power consumed as heat energy when the core is excited by an alternating magnetic field, and should be as small as possible from the viewpoint of energy conservation. The degree of magnetic loss is affected by the magnetization coefficient, sheet thickness, coating tension, amount of impurities, electrical resistivity, grain size, magnetic domain size, etc. Although many technologies have been developed for anisotropic electrical steel sheets, research and development on reducing magnetic loss is still ongoing to improve energy efficiency.

[0003]

For example, Patent Document 1 discloses a method for producing an anisotropic electrical steel sheet, including a step of irradiating the surface of the anisotropic electrical steel sheet with a focused beam of a continuous laser while scanning the anisotropic electrical steel sheet in a direction inclined with respect to the rolling direction, and a step of repeated irradiation while shifting the portions to be scanned by the continuous laser beams at predetermined intervals, wherein when the average power of the continuous laser beams is denoted as P (W), the scanning speed is denoted as Vc (mm/s), the predetermined intervals are denoted as PL (mm), and the average irradiation energy density Ua is denoted as Ua=P/(Vc × PL) (mJ/mm ² ), the magnetic domains are controlled by irradiation with laser beams such that the conditions of 1.0 mm≤PL≤3.0 mm and 0.8 mJ/mm ² are satisfied. ≤Ua≤2.0 mJ/mm ² .

Patent Document 1 shows that magnetic loss can be reduced in both directions, L direction and C direction, of an anisotropic electrical steel sheet, while easily achieving high productivity.

[0004]

In addition, Patent Document 2 discloses a method for producing an anisotropic electrical steel sheet in which linear closure domains are formed approximately perpendicular to the rolling direction of the steel sheet at approximately constant intervals by scanning and irradiating with continuously oscillating laser beams to improve magnetic loss characteristics.

Patent Document 2 shows that when the laser is in the TEM ₀₀ mode, in which the intensity profile of the laser beam in the cross section perpendicular to the beam propagation direction has a maximum intensity near the center of the optical axis, and the focused diameter d [mm] of the beam in the rolling direction, the linear scanning speed V [mm/s] of the laser beam and the average power P [W] of the laser are in the ranges of 0 < d≤0.2 and 0.001≤P/V≤0.012, it is possible to obtain an anisotropic electrical steel sheet having reduced magnetic loss.

[0005]

In addition, Patent Document 3 discloses a method for producing an anisotropic electrical steel sheet in which the surface of the anisotropic electrical steel sheet is irradiated with a laser beam at regular intervals to improve magnetic characteristics.

In Patent Document 3, it is shown that the laser is a Q-switched pulse oscillatory _CO2 laser, the irradiation beam shape is an ellipse whose main axis is located in the sheet width direction, the irradiation power density of the laser pulse is set equal to or less than the membrane damage threshold on the surface of the steel sheet, thereby suppressing the formation of a laser irradiation mark, and the long axis length of the elliptical beam is set equal to or greater than the irradiation interval of the pulse beam in the sheet width direction, whereby continuous pulse beams are superimposed on the surfaces of the steel sheet, a cumulative irradiation energy large enough to improve magnetic characteristics is transmitted, and effective magnetic domain control can be obtained by suppressing laser irradiation marks.

[0006]

In this regard, in recent years, there has been a growing demand for reducing noise and vibration in electromagnetic equipment such as transformers, and the anisotropic electrical steel sheets used for transformer cores need to be a material suitable for not only low magnetic loss but also low noise or low vibration. It is believed that one of the causes of noise or vibration of transformers in materials is the magnetostriction of the anisotropic electrical steel sheets. The magnetostriction referred to in this paper refers to the vibration that occurs in the rolling direction of the anisotropic electrical steel sheet caused by a slight change in the external shape of the anisotropic electrical steel sheet combined with a change in the magnetization intensity when the anisotropic electrical steel sheet is excited by an alternating current. The magnitude of this magnetostriction is on the order of 10 ^-6 and is extremely small, but this magnetostriction generates vibration in the cores, the vibration spreads to the external structure such as the transformer tank and turns into noise.

[0007]

The laser irradiation of anisotropic electrical steel sheet proposed in the above-described Patent Documents 1 to 3 is effective in reducing magnetic loss, but there is a problem that the closure domain formed by the laser irradiation increases magnetostriction, resulting in deterioration of noise performance.

[0008]

Regarding such a problem, Patent Document 4, for example, discloses an anisotropic electrical steel sheet having low magnetic loss, which produces low noise when included in a transformer.

Patent Document 4 shows that when closure domain regions whose width in the rolling direction periodically changes are formed on the surface of a steel sheet, each of the closure domain regions satisfies the conditions that the ratio (Wmax/Wmin) of the maximum width Wmax to the minimum width Wmin in the rolling direction on the surface of the steel sheet is 1.2 or more and 2.2 or less, the average width Wave in the rolling direction on the surface of the steel sheet is 80 μm or more and 200 μm or less, the maximum depth D in the sheet thickness direction is 32 μm or more, and the value of (Wave × D)/s is 0.0007 mm or more and 0.0016 mm or less, a more favorable magnetic loss/noise balance can be realized than in the prior art.

[0009]

In addition, Patent Document 5 describes an anisotropic electrical steel sheet in which local deformations are introduced in a direction intersecting the rolling direction at periodic intervals in the rolling direction, in which linear portions of a closing domain are formed near the deformations in a demagnetized state, magnetic domains having a length in the rolling direction of 1.2 mm or more are present, extended in the rolling direction from the portion of the closing domain, and, furthermore, in regions along the portions of the closing domain in the case where 1.8 or more magnetic domains per millimeter are formed on average, and the linear intervals of the portions of the closing domain are denoted by s (mm), the width of the portion of the closing domain w (mm) and the depth of the portion of the closing domain in the sheet thickness direction h (μm) satisfy the relationships of 4 mm≤s≤1.5 mm and hw/s≤0.9 μm.

Patent Document 5 suggests that the index of the magnitude of the introduced deformation, represented by the expression hw/s, affects magnetic loss and noise.

[0010]

However, as a result of the present inventors' research, it was found that the improvement in noise performance in the methods described in Patent Documents 4 and 5 is insufficient in terms of the excellent magnetic loss/noise balance that has been sought in recent years. In addition, it was found that magnetic domain control also damages the coating that is formed on the surface of the steel sheet to impart insulation properties and tension to the anisotropic electrical steel sheets, and thus deteriorates the adhesion of the coating.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0011]

[Patent Document 1] Japanese Patent No. 4669565

[Patent Document 2] Japanese Patent No. 4510757

[Patent Document 3] Japanese Patent No. 3361709

[Patent Document 4] Japanese Patent No. 6060988

[Patent Document 5] Japanese Patent No. 6176282

DISCLOSURE OF INVENTION

PROBLEMS SOLVED BY THE INVENTION

[0012]

As described above, traditionally, anisotropic electrical steel sheets in which the magnetic loss characteristics and noise characteristics are simultaneously improved sufficiently in view of the coating adhesion, as well as the production methods thereof, have not been disclosed.

The object of the present invention is to provide an anisotropic electrical steel sheet having excellent magnetic loss characteristics and noise characteristics (in which the magnetic loss improvement ratio due to magnetic domain segmentation is large and the noise is small when the anisotropic electrical steel sheet is included in a transformer, i.e. the magnetic loss/noise balance is excellent), and a method for producing the same. Preferably, the object is to provide an anisotropic electrical steel sheet having excellent magnetic loss characteristics and noise characteristics, and further having excellent coating adhesion.

MEANS TO SOLVE THE PROBLEM

[0013]

The inventors of the present invention studied magnetic domain control conditions for obtaining an anisotropic electrical steel sheet having an excellent balance between magnetic loss characteristics and noise characteristics (magnetic loss/noise balance). As a result, for the energy beam irradiation conditions for magnetic domain control, it was found that when the shape of the energy beam on the irradiated surface is controlled, the input energy is set relatively large, and the specific power is set relatively low, the magnetic loss/noise balance becomes favorable. However, it was found that in these steel sheets, peeling of the coating is possible at the portion irradiated with the energy beams as a starting point.

[0014]

In an anisotropic electrical steel sheet, an irradiated portion is rapidly heated and rapidly cooled by irradiation with an energy beam (laser beam, electron beam, etc.). As a result, residual deformation occurs from the surface near the irradiated portion to the inside of the steel sheet, and a deformation region (residual deformation region) is formed. Peeling off of the coating may occur at the portion irradiated with energy beams as a starting point. The reason for this is considered to be that not only the coating at the irradiated portion is damaged, but also the residual deformation near the irradiated portion causes peeling of the coating. Taking this into account, the inventors of the present invention attempted to adjust the irradiation conditions of energy beams to such a degree of deformation that a favorable magnetic loss/noise balance can be maintained. As a result, it was found that when the width or the intervals of the formation of the deformation regions are in suitable ranges by adjusting the irradiation conditions of energy beams, a favorable magnetic loss/noise balance can be obtained.

In addition, the inventors of the present invention attempted to quantitatively estimate the amount of deformation depending on the amount of magnetostriction in an anisotropic electrical steel sheet that was irradiated with energy beams with a high input energy at a low power density. As a result, it was found that favorable adhesion of the coating can be ensured by adjusting the amount of change in magnetostriction before and after a specific heat treatment so that it is in a certain range.

In addition, the inventors of the present invention conducted intensive research on the modification of the coating, paying attention to the relationship between the structure of the composite phase forming the coating and the adhesion of the coating. As a result of these studies, it was found that more favorable adhesion of the coating can be ensured by retaining the MgAl ₂ O ₄ phase formed in the coating in the lower part of the glass coating.

[0015]

The present invention has been made taking into account the above observations. The essence of the present invention is as follows.

[1] An anisotropic electrical steel sheet according to one aspect of the present invention includes a base steel sheet, a glass coating formed on the base steel sheet, and a tension-type insulating coating formed on the glass coating, the base steel sheet having a plurality of linear deformation regions that are continuously or periodically arranged in a direction intersecting with the rolling direction, each of the plurality of linear deformation regions having a width of 210 μm or less in the rolling direction, the plurality of linear deformation regions being parallel to each other, the intervals of the linear deformation regions adjacent to each other in the rolling direction being 10 mm or less, and a magnetostriction λ _0-pb in μm/m upon excitation of the anisotropic electrical steel sheet of up to 1.7 T and a magnetostriction λ _0-pa in μm/m upon heat treatment of the anisotropic electrical steel sheet at 800°C for 4 hours and subsequent excitation up to 1.7 T satisfy the following expression (1).

0.02≤λ _0-pb - λ _0-pa ≤0.20 (1)

[2] In the anisotropic electrical steel sheet according to item [1], the glass coating is formed by a structure including _{the Mg2SiO4} phase, which is a primary phase, and _{the MgAl2O4} phase, and in the cross section in the sheet thickness direction, when the glass coating is divided into three regions having the same thickness in the sheet thickness direction, each region is designated as a 1/3 region, a 2/3 region, and a 3/3 region from the side of the base steel sheet toward the side of the insulating coating with tension, the area ratio of the _MgAl2O4 phase in the _1/3 region is designated as S1, the area ratio of the _MgAl2O4 phase in the _2/3 region is designated as S2, and the area ratio of the _MgAl2O4 phase in the _3/3 region is designated as S3, S1, S2, and S3 can satisfy the following expressions (2) to (4).

S1 > S2 > S3 (2)

(S1+S2+S3)/3<0.50 (3)

S3<0.10 (4)

[3] A method for producing an anisotropic electrical steel sheet according to another aspect of the present invention is a method for producing an anisotropic electrical steel sheet according to [1] or [2], comprising a hot rolling step comprising heating a steel billet to obtain a hot rolled steel sheet by hot rolling, a hot rolled steel sheet annealing step for annealing the hot rolled steel sheet, a pickling step for pickling the hot rolled steel sheet after the annealing step of the hot rolled sheet, a cold rolling step for cold rolling once or a plurality of times while annealing therebetween the hot rolled steel sheet after the pickling step to obtain a cold rolled steel sheet, a decarburization annealing step for decarburization annealing the cold rolled steel sheet, a finish annealing step of applying and drying an annealing release agent containing MgO powder as a main component, onto a front and a rear surfaces of a cold-rolled steel sheet after the decarburization annealing step, which is a base steel sheet, and performing finish annealing to form glass coatings, a coating forming step of forming tension insulating coatings on the glass coatings to obtain an anisotropic electrical steel sheet including the base steel sheet, glass coatings formed on the base steel sheet, and tension insulating coatings formed on the glass coatings, and a magnetic domain segmentation step of irradiating the surfaces of the tension insulating coatings of the anisotropic electrical steel sheet with an energy beam to form a plurality of linear deformation regions on the base steel sheet, wherein in the magnetic domain segmentation step, among the plurality of linear deformation regions, the intervals of the linear deformation regions adjacent to each other in the rolling direction are 10 mm or less, the power density of the energy beams Ip (W/ ^mm2 ), which is defined as (P/S) using the output power of the energy beams P (W) and the cross-sectional area of the energy beams S ( ^mm2 ), satisfies the following expression (5), the input energy of the energy beam Up (J/mm), which is defined as P/Vs using the output energy of the beam P and the scanning speed of the energy beam Vs (mm/sec), satisfies the following expression (6), and

the aspect ratio of the energy beam, which is defined as (dl/dc) using the diameter dl in the direction perpendicular to the beam scanning direction and the diameter dc in the beam scanning direction (in μm), satisfies the following expression (7), and dl satisfies the following expression (8).

250≤Ip≤2000 (5)

0.010 < Up≤0.050 (6)

0.0010 < dl/dc < 1.0000 (7)

10 < dl < 200 (8)

[4] In the method for producing anisotropic electrical steel sheet according to paragraph [3], the energy beam may be a laser beam.

[5] In the method for producing anisotropic electrical steel sheet according to paragraph [4], the laser beam may be a fiber laser beam.

[6] In the method for producing anisotropic electrical steel sheet in accordance with any of paragraphs. [3] - [5] The steel workpiece may contain in its chemical composition, in wt.%, C: 0.010% - 0.200%, Si: 3.00% - 4.00%, soluble Al: 0.010% - 0.040%, Mn: 0.01% - 0.50%, N: 0.020% or less, S: 0.005% - 0.040%, P: 0.030% or less, Cu: 0% - 0.50%, Cr: 0% - 0.50%, Sn: 0% - 0.50%, Se: 0% - 0.020%, Sb: 0% - 0.500%, and Mo: 0% - 0.10%, as well as a remainder including Fe and impurities.

[7] In the method for producing anisotropic electrical steel sheet in accordance with any of paragraphs. [3] - [6] the decarburization annealing step may include a temperature raising process and a holding process, in the temperature raising process, the temperature raising rate from 550°C to 750°C may be set to 700-2000°C/s, the oxygen potential may be set to 0.0001-0.0100, and the holding process may include a first holding process with an annealing heating temperature of 800°C - 900°C, an annealing time of 100-500 s and an atmosphere having an oxygen potential of 0.4 or more and 0.8 or less, and a second holding process with an annealing heating temperature of 850°C or higher and 1000°C or lower, an annealing time of 5 s or more and 100 s or less and an atmosphere having an oxygen potential of 0.1 or less.

[8] The method for producing an anisotropic electrical steel sheet according to any one of paragraphs [3] to [7] may further include, during the decarburization annealing step or after the decarburization annealing step, a step of nitriding treatment of the cold-rolled steel sheet.

BENEFICIAL EFFECTS OF THE INVENTION

[0016]

According to the above-described aspects of the present invention, it is possible to provide an anisotropic electrical steel sheet having a favorable magnetic loss/noise balance, as well as a method for producing the same. In addition, according to a preferred aspect of the present invention, it is possible to provide an anisotropic electrical steel sheet having a favorable magnetic loss/noise balance, as well as excellent coating adhesion.

EMBODIMENTS OF THE PRESENT INVENTION

[0017]

An anisotropic electrical steel sheet according to one embodiment of the present invention (anisotropic electrical steel sheet according to the present embodiment) includes a base steel sheet having a predetermined chemical composition, a glass coating formed on the base steel sheet, and a tension-type insulating coating formed on the glass coating.

In addition, a plurality of linear deformation regions (residual deformation) are formed in the base steel sheet, which are continuously or discontinuously arranged in a direction intersecting with the rolling direction, substantially parallel to each other. The width of each linear deformation region (width in the rolling direction) is 210 μm or less, and the intervals in the rolling direction of adjacent linear deformation regions of the plurality of linear deformation regions are each 10 mm or less.

[0018]

Next, an anisotropic electrical steel sheet according to the present embodiment will be described.

[0019]

<Base steel sheet>

(Chemical composition)

The anisotropic electrical steel sheet according to the present embodiment is largely characterized by deformation regions (linear deformation regions) and a composite phase in a glass coating, and the base steel sheet in the anisotropic electrical steel sheet is not limited in terms of a chemical composition, which may be in a well-known range. For example, in order to obtain the characteristics that are generally required for anisotropic electrical steel sheets, the chemical composition preferably contains the following. In the present embodiment, "%" referring to the chemical composition means "mass %" unless otherwise expressly stated.

[0020]

C: 0.010% or less

C (carbon) is an element effective for stepwise controlling the microstructure of the steel sheet until the decarburization annealing step is completed. However, when the C content exceeds 0.010 mass%, the magnetic characteristics of the anisotropic electrical steel sheet, which is the product sheet, deteriorate. Therefore, in the base steel sheet of the anisotropic electrical steel sheet according to the present embodiment, the C content is preferably set to 0.010 mass% or less. The C content is more preferably 0.005 mass% or less. The C content is preferably as low as possible; however, when the C content is reduced to less than 0.0001%, the effect of controlling the microstructure is saturated and the production cost increases. Therefore, the C content can be set to 0.0001% or more.

[0021]

Si: 3.00% - 4.00%

Si (silicon) is an element that improves the magnetic loss performance by increasing the electrical resistance of the anisotropic electrical steel sheet. When the Si content is less than 3.00%, a sufficient effect of reducing the eddy current loss cannot be obtained. Therefore, the Si content is preferably set to 3.00% or more. The Si content is more preferably 3.10% or more, and even more preferably 3.20% or more.

On the other hand, when the Si content exceeds 4.00%, the anisotropic electrical steel sheet becomes brittle and its passability deteriorates significantly. In addition, the workability of the anisotropic electrical steel sheet deteriorates, and the steel sheet may break during rolling. Therefore, the Si content is preferably set to 4.00% or less. The Si content is more preferably 3.80% or less, and even more preferably 3.70% or less.

[0022]

Mn: 0.01% - 0.50%

Mn (manganese) is an element that combines with S to form MnS. These precipitates act as an inhibitor (normal grain growth inhibitor) and cause secondary recrystallization in steel. Mn is also an element that further improves the hot workability of steel. When the Mn content is less than 0.01%, it becomes impossible to obtain the above effect sufficiently. Therefore, the Mn content is preferably set to 0.01% or more. The Mn content is more preferably 0.02% or more.

On the other hand, when the Mn content exceeds 0.50%, secondary recrystallization does not develop, and the magnetic properties of steel deteriorate. Therefore, in the base steel sheet of the anisotropic electrical steel sheet according to the present embodiment, the Mn content is preferably set to 0.50% or less. The Mn content is more preferably 0.20% or less, and still more preferably 0.10% or less.

[0023]

N: 0.010% or less

N (nitrogen) is an element that bonds with Al to form AlN, which functions as an inhibitor. However, when the N content exceeds 0.010%, the magnetic characteristics are deteriorated due to the inhibitor remaining excessively in the base steel sheet. Therefore, in the base steel sheet of the anisotropic electrical steel sheet according to the present embodiment, the N content is preferably set to 0.010% or less. The N content is more preferably 0.008% or less.

On the other hand, the lower limit of the N content is not particularly determined; however, when the N content decreases to less than 0.001 mass%, the production cost increases. Therefore, the N content may be set to 0.001% or more.

[0024]

Soluble Al: 0.020% or less,

Soluble Al (acid-soluble aluminum) is an element that bonds with N to form AlN, which functions as an inhibitor during the production of anisotropic electrical steel sheet. However, when the content of soluble Al exceeds 0.020%, the magnetic characteristics deteriorate due to the inhibitor remaining excessively in the base steel sheet. Therefore, in the base steel sheet of the anisotropic electrical steel sheet according to the present embodiment, the content of soluble Al is preferably set to 0.020% or less. The content of soluble Al is more preferably 0.010% or less, and still more preferably less than 0.001%. The lower limit of the content of soluble Al is not particularly defined; however, when the content of soluble Al decreases to less than 0.0001%, the production cost increases. Therefore, the content of soluble Al can be set to 0.0001% or more.

[0025]

S: 0.010% or less

S (sulfur) is an element that bonds with Mn to form MnS, which functions as an inhibitor in the manufacturing steps. However, when the S content exceeds 0.010%, the magnetic characteristics are deteriorated due to the excessively remaining inhibitor. Therefore, in the main steel sheet of the anisotropic electrical steel sheet according to the present embodiment, the S content is preferably set to 0.010% or less. The S content in the anisotropic electrical steel sheet is preferably as low as possible. For example, the S content is less than 0.001%. However, when the S content in the anisotropic electrical steel sheet decreases to less than 0.0001%, the manufacturing cost increases. Therefore, the S content in the anisotropic electrical steel sheet may be 0.0001% or more.

[0026]

P: 0.030% or less

P (phosphorus) is an element that deteriorates the machinability during rolling. When the P content is 0.030% or less, it is possible to suppress excessive deterioration in the machinability during rolling and prevent fracture during production. From this viewpoint, the P content is preferably set to 0.030% or less. The P content is preferably 0.020% or less, and is further preferably 0.010% or less.

The lower limit of the P content may be 0%; however, the sensitivity limit of chemical analysis is 0.0001%, and thus the lower limit of the P content in practical steel sheets is 0.0001%. In addition, P is also an element having the effect of improving texture and improving magnetic properties. In order to obtain this effect, the P content can be set to 0.001% or more, or 0.005% or more.

[0027]

Residue: iron and impurities.

The chemical composition of the base steel sheet in the anisotropic electrical steel sheet according to the present embodiment contains the above-described elements, and the remainder may be Fe and impurities. However, for the purpose of improving magnetic characteristics and the like, Cu, Cr, Sn, Se, Sb, and Mo may be additionally contained in the ranges to be shown below. These elements may also be contained as impurities.

In addition, even when, for example, any one or more of W, Nb, Ti, Ni, Bi, Co and V are contained in a total amount of 1.0% or less as elements other than those specified, the effect of the anisotropic electrical steel sheet according to the present embodiment is not weakened.

Here, impurities are elements that are included from ore or waste as a raw material, production environment, etc. during industrial production of a base steel sheet, and may be contained in such amounts that they do not adversely affect the performance of the anisotropic electrical steel sheet according to the present embodiment.

[0028]

Cr: 0% - 0.50%

Cr (chromium) is an element that contributes to increasing the filling level of the Goss orientation in the secondary recrystallization structure to improve the magnetic characteristics. In order to obtain the above effect, the Cr content is preferably set to 0.01% or more, more preferably 0.02% or more, and still more preferably 0.03% or more.

On the other hand, when the Cr content exceeds 0.50%, Cr oxide is formed and the magnetic characteristics are deteriorated. Therefore, the Cr content is preferably set to 0.50% or less. The Cr content is more preferably 0.30% or less, and still more preferably 0.10% or less.

[0029]

Sn: 0% - 0.50%

Sn (tin) is an element that contributes to improving magnetic characteristics by controlling the primary recrystallization structure. In order to obtain the effect of improving magnetic characteristics, the Sn content is preferably set to 0.01% or more. The Sn content is preferably 0.02% or more, and even more preferably 0.03% or more.

On the other hand, when the Sn content exceeds 0.50%, the secondary recrystallization becomes unstable and the magnetic characteristics deteriorate. Therefore, the Sn content is preferably set to 0.50% or less. The Sn content is more preferably 0.30% or less, and still more preferably 0.10% or less.

[0030]

Cu: 0% - 0.50%

Cu (copper) is an element that contributes to increasing the filling level of the Goss orientation in the secondary recrystallization structure. Cu is an optional element in the base steel sheet according to the present embodiment. Therefore, the lower limit of its content is 0%; however, in order to obtain the above-described effect, the content of Cu is preferably set to 0.01% or more. The content of Cu is more preferably 0.02% or more, and still more preferably 0.03% or more.

On the other hand, when the Cu content exceeds 0.50%, the steel sheet becomes brittle during hot rolling. Therefore, in the base steel sheet of the anisotropic electrical steel sheet according to the present embodiment, the Cu content is preferably set to 0.50% or less. The Cu content is more preferably 0.30% or less, and still more preferably 0.10% or less.

[0031]

Se: 0% - 0.020%

Se (selenium) is an element having the effect of improving magnetic characteristics. Therefore, Se may be contained. In the case where Se is contained, its content is preferably set to 0.001% or more in order to reliably obtain the effect of improving magnetic characteristics. The content of Se is preferably 0.003% or more, and more preferably 0.006% or more.

On the other hand, when the Se content exceeds 0.020%, the adhesion of the glass coating deteriorates. Therefore, the Se content is preferably set to 0.020% or less. The Se content is more preferably 0.015% or less, and still more preferably 0.010% or less.

[0032]

Sb: 0% - 0.500%

Sb (antimony) is an element having the effect of improving magnetic properties. Therefore, Sb may be contained. In the case where Sb is contained, its content is preferably set to 0.005% or more in order to reliably obtain the effect of improving magnetic properties. The content of Sb is more preferably 0.010% or more, and still more preferably 0.020% or more.

On the other hand, when the Sb content exceeds 0.500%, the adhesion of the glass coating is significantly deteriorated. Therefore, the Sb content is preferably set to 0.500% or less. The Sb content is more preferably 0.300% or less, and still more preferably 0.100% or less.

[0033]

Mo: 0% - 0.10%

Mo (molybdenum) is an element having the effect of improving magnetic characteristics. Therefore, Mo may be contained. When Mo is contained, its content is preferably set to 0.01% or more in order to reliably obtain the effect of improving magnetic characteristics. The content of Mo is more preferably 0.02% or more, and still more preferably 0.03% or more.

On the other hand, when the Mo content exceeds 0.10%, the cold rollability is deteriorated, and there is a possibility that the base steel sheet may break. Therefore, the Mo content is preferably set to 0.10% or less. The Mo content is more preferably 0.08% or less, and even more preferably 0.05% or less.

[0034]

As described above, it is shown that the chemical composition of the base steel sheet in the anisotropic electrical steel sheet according to the present embodiment contains the above-described essential elements with the remainder consisting of Fe and impurities, or the chemical composition contains the above-described essential elements and further contains one or more optional elements with the remainder consisting of Fe and impurities.

[0035]

The chemical composition of the base steel sheet in the anisotropic electrical steel sheet according to the present embodiment can be measured after removing the glass coating and the tension insulating coating formed on the surface.

Specifically, the anisotropic electrical steel sheet is immersed in an aqueous solution of sodium hydroxide (with a temperature of 80°C to 90°C) containing NaOH: 30-50 wt.% and _H2O : 50-70 wt.% for 7-10 min, as a result of which the insulating coating is removed under tension.

The anisotropic electrical steel sheet from which the insulation coating has been removed under tension is washed with water and dried with warm air for slightly less than 1 min. The dried anisotropic electrical steel sheet (anisotropic electrical steel sheet without the insulation coating under tension) is immersed in an aqueous solution of hydrochloric acid (with a temperature of 80°C - 90°C) containing 30-40 wt.% HCl for 1-10 min, whereby the glass coating is removed.

After immersion, the base steel sheet is washed with water and dried with warm air for just under 1 minute.

The base steel sheet can be extracted from the anisotropic electrical steel sheet through the above-described step.

The chemical composition of such a base steel sheet is obtained by a known method of component analysis. Specifically, chips are obtained from the base steel sheet using a drill, these chips are collected and dissolved in acid to obtain a solution. The elemental analysis of the chemical composition of this solution is performed using ICP-AES.

Here, Si in the chemical composition of the base steel sheet is obtained by the method specified in JIS G 1212 (1997) (Methods for Determining Silicon Content). Specifically, when the above-described chips are dissolved in acid, silicon oxide precipitates, this precipitate (silicon oxide) is filtered with filter paper, and its mass is measured, resulting in the Si content.

The C content and the S content are obtained by a well-known high-frequency combustion method (infrared absorption combustion method). Specifically, the above solution is burned by high-frequency heating in an oxygen flow, the resulting carbon dioxide and sulfur dioxide are determined, and the C content and the S content are obtained as a result.

The N content is obtained using the method of determining the specific thermal conductivity by melting in an inert gas.

[0036]

(Deformation areas)

In a base steel sheet included in an anisotropic electrical steel sheet according to the present embodiment, there are a plurality of linear deformation regions (residual deformation regions) formed by irradiation with energy rays.

A plurality of linear deformation regions extend in the direction intersecting with the rolling direction on the surface of the base steel sheet, these regions are parallel to each other (in actual production, a deviation of approximately 5° is allowed), their width in the rolling direction is 210 μm or less, and the gaps between them in the rolling direction are 10 mm or less. When the deformation regions are created as described above, a favorable balance of magnetic loss/noise can be obtained.

The locations where deformation exists can be analyzed using the X-ray diffraction residual deformation measurement method (see, e.g., K. Iwata, et.al., J. Appl. Phys. 117. 17A910 (2015)). In addition, when the energy beam irradiation mark can be confirmed on the surface of the steel sheet, the irradiation mark can be determined as the deformation region.

[0037]

In addition, it is known that, especially in the case where these deformations (residual deformations) are compressive deformations in the rolling direction and tensile deformations in the sheet thickness direction, regions magnetized in the sheet thickness direction, which are called closure domains, are formed in the regions where the deformation is present (strain regions).

[0038]

In the present embodiment, the fact that the linear deformations extend in the direction intersecting with the rolling direction indicates that the extension directions of the deformation regions are within a range of 30° or less in terms of the angle of deviation from the direction perpendicular to the rolling direction. When the extension direction deviates from this angular range, the effect of segmenting the magnetic domains of the steel sheet by 180° becomes weak, and a sufficient effect of reducing magnetic loss cannot be obtained.

The deformation region may be continuously present in a linear form or may extend discontinuously in one direction (for example, in a dotted form), but is preferably continuous from the viewpoint of reducing magnetic loss. The linear deformation regions are formed by irradiating with an energy beam. The type of the energy beam is not particularly limited, but a laser beam or an electron beam, which are generally used in practice, is preferable. In the case of irradiating with an electron beam, it is necessary to bring the atmosphere during the electron beam irradiation to a vacuum having a certain pressure or less, which creates concerns about increasing the cost of production.

In addition, when the intervals in the rolling direction of a plurality of linear deformation regions adjacent to each other are more than 10 mm, the effect of segmenting the magnetic domains at an angle of 180° becomes weak, and the effect of reducing the magnetic loss becomes insufficient. Therefore, the intervals between adjacent linear deformation regions in the rolling direction are set to 10 mm or less. It is preferable that these intervals are substantially equal.

When the irradiation pitch becomes small, the magnetic loss generally becomes small; however, when the irradiation pitch becomes excessively small, the magnetic effect of domain segmentation is saturated, the eddy current loss rarely decreases, the increase in hysteresis loss due to deformation becomes large, and the magnetic loss deteriorates. In addition, there are cases where the noise performance deteriorates. Therefore, the intervals between adjacent regions of linear deformation in the rolling direction are preferably set to 3 mm or more.

Here, the interval in the rolling direction between adjacent deformation regions is the distance between the center of the linear deformation region and the center of the adjacent linear deformation region in the rolling direction.

The length of the deformation in the width direction of the sheet is not limited, but the deformation is preferably formed from one end to the other end of the base steel sheet in the width direction. In the case where the steel sheet is irradiated with an energy beam intermittently (intermittently), during the irradiation of the steel sheet with an energy beam in the width direction at specific pitches, the major axis (length along the width direction) d0 of the part irradiated with the energy beam and the length d1 along the width direction between the parts not irradiated with the energy beams, each of which is enclosed between two parts irradiated with the energy beams, must satisfy the condition d1≤3×d0. d0 may be in the range of 50 μm to 50 mm.

[0039]

In addition, when the proportion of deformation regions on the surface of the base steel sheet becomes excessively large, the deformations in the entire base steel sheet increase, the overall hysteresis loss increases, the magnetic loss deteriorates, and the noise performance deteriorates. Therefore, the widths of the deformation regions are set to 210 μm or less. These widths are preferably 200 μm or less, more preferably 150 μm or less, and still more preferably 100 μm or less.

[0040]

In addition, in the anisotropic electrical steel sheet according to the present embodiment, the state associated with deformation is determined by the amount of change in magnetostriction after performing a certain heat treatment. Specifically, the magnetostriction λ _0-pb when the anisotropic electrical steel sheet is excited to 1.7 T and the magnetostriction λ _0-pa when the anisotropic electrical steel sheet is heat treated at 800°C for 4 hours and then excited to 1.7 T satisfy the following expression (1).

0.02≤λ _0-pb - λ _0-pa ≤0.20 (µm/m) (1)

In the case where expression (1) is satisfied, it becomes possible to guarantee a favorable magnetic loss/noise balance.

In essence, this expression is considered as an expression that evaluates the deformation caused in the base steel sheet by irradiation with energy rays, as well as its distribution and the state of lattice defects that determine the deformations, etc. When the deformation caused by heat treatment at 800°C for 4 hours ensures magnetostriction in the range of expression (1), it becomes possible to realize a favorable balance of magnetic loss/noise.

The fact that the change in magnetostriction before and after the heat treatment is less than 0.02 μm/m means that an appropriate amount of deformation has not yet been introduced during the energy ray irradiation, or a deformation state has been formed in which it is difficult to achieve strain relief by heat treatment. In this case, a favorable magnetic loss/noise balance cannot be obtained. On the other hand, the fact that the change in magnetostriction before and after the heat treatment is more than 0.20 μm/m means that an excessive amount of deformation has been introduced during the energy ray irradiation, or a deformation state has been formed in which stress relief by heat treatment occurs too easily. In this case, a favorable magnetic loss/noise balance cannot be obtained either.

[0041]

<Glass coating>

In the anisotropic electrical steel sheet according to the present embodiment, a glass coating is formed on the surface of a base steel sheet.

The glass coating is an inorganic coating containing magnesium silicate as a main component. The glass coating is formed by the reaction between the annealing release agent containing magnesium oxide (MgO) applied to the surface of the base steel sheet and the component on the surface of the base steel sheet during finish annealing, has a composition derived from the annealing release agent and the component of the base steel sheet, and is formed from a structure including an _Mg2SiO4 phase that is the primary phase (50% of the area or more) and _{an MgAl2O4} phase. There are cases where, in addition to these phases _, approximately 1% or less of sediment may be contained.

[0042]

The area (area fraction) occupied by each phase is determined from the oxide composition obtained by an energy-dispersive X-ray analyzer attached to a scanning electron microscope while observing the cross section of the glass coating. The area in which Mg, Al and O are present and the Al concentration is 5% or more is regarded as the _MgAl2O4 phase, and the area in which the Si concentration is 5% or more is regarded as _{the Mg2SiO4} phase _.

[0043]

In the anisotropic electrical steel sheet according to the present embodiment, the composite phase that forms the glass coating preferably has a predetermined structure. Specifically, in a cross section in the thickness direction of the anisotropic electrical steel sheet, when the glass coating is divided into 3 regions having an equal thickness in the sheet thickness direction, each region being designated as a 1/3 region, a 2/3 region, and a 3/3 region from the side of the base steel sheet toward the surface of the steel sheet, and an area ratio of the MgAl ₂ O ₄ phase in the 1/3 region being designated as S1, an area ratio of the MgAl ₂ O ₄ phase in the 2/3 region being designated as S2, and an area ratio of the MgAl ₂ O ₄ phase in the 3/3 region being designated as S3, the following formulas (2) to (4) are preferably satisfied.

When observing the cross section at the front end of the glass coating, serious unevenness or individual island regions are also observed. In the present embodiment, a sufficient length of 20 mm or more in the direction parallel to the surface of the steel sheet is observed, the distance between the position where the glass coating penetrates most deeply into the base steel sheet and the outermost surface of the steel sheet in the sheet thickness direction at the location where the glass coating is present is defined as the total thickness of the glass coating, and the thicknesses of the 1/3 region, the 2/3 region and the 3/3 region are determined. In addition, when calculating the area ratio of the MgAl ₂ O ₄ phase in each region, the total area of the individual regions, which serves as a denominator, is the "region that is the glass coating" including the island region. Thus, in the 1/3 region which is the front region of the glass coating, the "region representing the glass coating" is likely to have a highly irregular shape or a separate island region, and there is a considerable amount of the Fe phase in the same thickness range; however, when calculating the area ratio of the _MgAl2O4 phase _, the Fe phase region is not included in the area (total area) which serves as the denominator. Therefore, the total area of the 1/3 region is usually smaller than the total area of the 2/3 region or the 3/3 region.

S1 > S2 > S3 (2)

(S1+S2+S3)/3<0.50 (3)

S3<0.10 (4)

In the case where expressions ( ₂ ) to (4) are satisfied, it means that the _MgAl2O4 phase, which is a mixed phase, is unevenly distributed in the glass coating on the side of the base steel sheet.

[0044]

In the _1/3 region, the _MgAl2O4 phase is a composite phase that improves the adhesion of the coating. In the glass coating, the 1/3 region is the region connected to the base steel sheet. The boundary between the glass coating and the base steel sheet has a complex uneven shape, which is also commonly called the "root". Due to this shape, the glass coating and the base steel sheet are firmly connected due to the so-called anchor effect. Therefore, even when _{the MgAl2O4} phase is present in this region to a certain extent in a mixed form, the formation of cracks that can act as a starting point for peeling of the coating is less likely.

Therefore, it is preferable that _{the MgAl2O4} phase is unevenly distributed in the 1/3 region of the glass coating. From the viewpoint of adhesion, even in the 1/3 region, a form in which _{the MgAl2O4} phase is distributed on the side of the base steel sheet as unevenly as possible is preferable, and a form in which the _MgAl2O4 phase _is unevenly distributed (only) at the boundary between the glass coating and the base steel sheet is one of the most preferable forms.

[0045]

On the other hand, in the 3/3 region, the _MgAl2O4 phase is a composite phase whose formation should be avoided. When _{the MgAl2O4 phase} is present in the 3/3 region of the glass coating, the _MgAl2O4 phase becomes a starting point for the formation of cracks, and the adhesion of the coating is significantly deteriorated. Therefore, S3< _0.10 is preferable, S3< _0.05 is more preferable, and S3=0 is the most preferable form. In addition, when the proportion of _{the MgAl2O4} phase as a whole becomes 0.50 or more, the starting point is formed between the _MgAl2O4 phase and the _Mg2SiO4 phase. Therefore, the area ratio (S1+ _S2 +S3)/3 _{of the MgAl2O4} phase in the glass coating is preferably less than 0.50, and more preferably 0.30 or less.

[0046]

When the primary coating has such a shape, it becomes possible to obtain more favorable coating adhesion in a steel sheet having the above-described deformations (change in magnetostriction due to heat treatment), while providing a favorable magnetic loss/noise balance. The reason for this is not clear, but is presumably described below.

In the anisotropic electrical steel sheet according to the present embodiment, a favorable balance of magnetic loss/noise is realized under the irradiation condition of an energy beam with a high input energy at a low power density, but peeling of the coating from the laser irradiated portion is also likely to occur. This suggests that the strains that are generated in the anisotropic electrical steel sheet according to the present embodiment are different from the strain distributions that have been conventional so far. Therefore, when a stress acts on the anisotropic electrical steel sheet, it is expected that a higher peeling stress than before acts at the interface between the base steel sheet and the glass coating in the deformation regions. It is believed that this peeling stress is weakened by the MgAl ₂ O ₄ phase unevenly distributed in the glass coating on the side of the base steel sheet. It is unclear whether this weakening occurs because the stress generated by the uneven distribution of different types of phases weakens the peel stress attributed to residual stress, or because the uneven distribution of different types of phases itself has a large peel stress resistance force. However, when considering the fact that the effect of improving the adhesion of the coating by the uneven distribution of the _MgAl2O4 phases, which is described in the present embodiment, has _a significant effect in magnetic domain control materials having the strains shown in the present embodiment, this combination is considered to have a particularly preferable interaction.

In addition, it can be considered that not only the energy beam irradiation conditions but also the possibility that the uneven distribution of _{the MgAl2O4} phase in the glass coating itself qualitatively affects the deformation in the energy beam irradiated part makes the magnetic loss/noise balance more preferable. As for the clarification of the effect of the interaction between stress and the shape of the glass coating on the magnetic loss/noise balance or adhesion, a detailed analysis is expected in the future.

[0047]

The anisotropic electrical steel sheet according to the present embodiment is an anisotropic electrical steel sheet in which a favorable balance of magnetic loss/noise is realized under the condition of irradiation with an energy beam with a high input energy at a low power density, but sufficient coating adhesion can be obtained. Specifically, when the anisotropic electrical steel sheet is wound on a round rod with a diameter of 20 mm and bent back, the area ratio of the remaining coating becomes 90-100%. This area ratio of the remaining coating becomes an index that indicates whether the coating adhesion is favorable or poor. The area ratio of the remaining coating is preferably 95% or more.

[0048]

The area proportion of the remaining coating is estimated by conducting a bending adhesion test. A flat specimen of 80 mm × 80 mm taken from an anisotropic electrical steel sheet with a coating is wrapped around a round rod of 20 mm in diameter and then pulled out to a flat state, the area of the coating that has not peeled off from this steel sheet (glass coating and/or insulating coating with tension) is measured, and the value obtained by dividing the area of the non-peeled coating by the area of the steel sheet is determined as the area proportion of the remaining coating (%). For example, the area of the non-peeled coating can be measured by placing a transparent film with a grid pitch of 1 mm on the test specimen.

[0049]

<Insulation coating with tension>

In the anisotropic electrical steel sheet according to the present embodiment, an insulating coating is formed on the surface of the glass coating with tension.

The tension insulating coating imparts electrical insulation properties to the anisotropic electrical steel sheet, thereby reducing the eddy current loss and improving the magnetic loss of the anisotropic electrical steel sheet. In addition, according to the tension insulating coating, in addition to the electrical insulation properties described above, various characteristics such as corrosion resistance, heat resistance and slip resistance can be obtained.

In addition, the tension insulation coating has the function of applying tension to the anisotropic electrical steel sheet. When tension is applied to the anisotropic electrical steel sheet to facilitate the movement of the domain walls in the anisotropic electrical steel sheet, the magnetic loss of the anisotropic electrical steel sheet can be improved.

The tension-type insulating coating may be a known coating which is formed, for example, by applying a film-forming solution containing a metal phosphate and silica as the main components to the surface of a glass coating and baking it.

[0050]

<Thickness of base steel sheet: 0.17mm to 0.30mm>

The thickness of the base steel sheet in the anisotropic electrical steel sheet according to the present embodiment is not limited, but is preferably 0.17-0.30 mm in consideration of not only low magnetic loss but also application in transformer cores requiring low noise and low vibration. Since the sheet thickness is smaller, a more favorable effect of reducing eddy current loss can be obtained and a more favorable magnetic loss can be obtained, and thus the preferred upper limit of the thickness of the base steel sheet is 0.30 mm. However, special equipment becomes necessary to manufacture a base steel sheet with a thickness of less than 0.17 mm, which is undesirable from a production perspective such as an increase in cost. Therefore, the preferred lower limit of the sheet thickness from an industrial point of view is 0.17 mm.

[0051]

<Production method>

The anisotropic electrical steel sheet according to the present embodiment can be produced by a production method comprising the following steps.

(i) A hot rolling step comprising heating a steel blank and hot rolling it to produce a hot rolled steel sheet,

(ii) the annealing stage of hot rolled steel sheet,

(iii) a step of pickling the hot rolled steel sheet after the step of annealing the hot rolled steel sheet,

(iv) a step of cold rolling one or more times (two or more) the hot rolled steel sheet after a pickling step with annealing therebetween to obtain a cold rolled steel sheet,

(v) the stage of decarburization annealing of cold rolled steel sheet,

(vi) a finishing annealing step comprising applying and drying a separating annealing agent containing MgO powder as a main component onto the front and back surfaces of the cold-rolled steel sheet, which is the base steel sheet, after the decarburization annealing step and performing finishing annealing to form a glass coating,

(vii) a step of forming tension-type insulating coatings on the glass coating to obtain an anisotropic electrical steel sheet comprising a base steel sheet, glass coatings formed on the base steel sheet, and tension-type insulating coatings formed on the glass coatings, and

(viii) a magnetic domain segmentation step comprising irradiating the surfaces of the insulating coatings with tension in the anisotropic electrical steel sheet with an energy beam to form a plurality of regions of linear deformation on the base steel sheet.

In the method for producing an anisotropic electrical steel sheet according to the present embodiment, the conditions at the magnetic domain segmentation stage, in particular the deformation state, and the conditions at the decarburization annealing stage, in particular the form of the MgAl ₂ O ₄ phase in the glass coating, are controlled.

These stages will be described in detail below. In the following description, when the conditions at each stage are not described, each stage can be performed by appropriately applying the known conditions.

[0052]

<Chemical composition of steel blank>

The chemical composition of the steel blank that undergoes the heating step is not limited; however, in order to obtain the characteristics that are generally required for anisotropic electrical steel sheets, the chemical composition preferably contains the following. In the following description, unless otherwise explicitly stated, "%" means "mass%". The steel blank is, for example, a slab.

[0053]

C: 0.010% - 0.200%

C (carbon) is an element having the effect of improving the magnetic flux density. However, when the C content in the steel workpiece exceeds 0.200 mass%, the steel undergoes a phase transformation in the secondary recrystallization annealing (that is, in the finish annealing), the secondary recrystallization proceeds insufficiently, and favorable magnetic flux density and magnetic loss characteristics cannot be obtained. Therefore, the C content in the steel workpiece is preferably set to 0.200 mass% or less. The C content is preferably as low as possible from the viewpoint of reducing the magnetic loss. From the viewpoint of reducing the magnetic loss, the C content is more preferably 0.150% or less, and still more preferably 0.100% or less.

On the other hand, when the C content in the steel blank is less than 0.010%, it is impossible to obtain the effect of improving the magnetic flux density. Therefore, the C content in the steel blank is set to 0.010 mass% or more. The C content is preferably 0.040% or more, and more preferably 0.060% or more.

[0054]

Si: 3.00% - 4.00%

Si (silicon) is an extremely effective element for increasing the electrical resistance (resistivity) of steel and reducing the eddy current loss that constitutes a part of the magnetic loss. When the Si content in a steel workpiece is less than 3.00%, the steel undergoes a phase transformation in the secondary recrystallization annealing, the secondary recrystallization does not proceed sufficiently, and favorable magnetic flux density and magnetic loss characteristics cannot be obtained. Therefore, the Si content in the steel workpiece is preferably set to 3.00% or more. The Si content in the steel workpiece is more preferably 3.10% or more, and still more preferably 3.20% or more.

On the other hand, when the Si content exceeds 4.00 mass%, the steel sheet becomes brittle and its passability through production stages is significantly impaired. Therefore, the Si content of the steel blank is preferably set to 4.00% or less. The Si content of the steel blank is more preferably 3.80% or less, and still more preferably 3.60% or less.

[0055]

Soluble Al: 0.010% - 0.040%

Soluble Al (acid-soluble aluminum) is a major inhibitory element among compounds called inhibitors that affect secondary recrystallization in an anisotropic electrical steel sheet, and is an essential element from the viewpoint of causing secondary recrystallization in the base steel sheet according to the present embodiment. When the content of soluble Al in the steel blank is less than 0.010%, AlN functioning as an inhibitor is insufficiently formed, secondary recrystallization becomes insufficient, and magnetic loss characteristics are not improved. Therefore, in the steel blank, the content of soluble Al is preferably set to 0.010% or more. The content of soluble Al is more preferably 0.015% or more, and still more preferably 0.020%.

On the other hand, when the content of soluble Al exceeds 0.040%, the embrittlement of the steel sheet becomes significant. Therefore, the content of soluble Al in the steel blank is preferably set to 0.040% or less. The content of soluble Al is more preferably 0.035% or less, and still more preferably 0.030% or less.

[0056]

Mn: 0.01% - 0.50%

Mn (manganese) is an important element that forms MnS, which is one of the main inhibitors. In the case where the Mn content in the steel workpiece is less than 0.01%, the absolute amount of MnS required to cause secondary recrystallization is insufficient. Therefore, the Mn content in the steel workpiece is preferably set to 0.01% or more. The Mn content is more preferably 0.03% or more, and still more preferably 0.06% or more.

On the other hand, when the Mn content in the steel workpiece exceeds 0.50%, the steel undergoes a phase transformation in the secondary recrystallization annealing, the secondary recrystallization does not proceed sufficiently, and favorable magnetic flux density and magnetic loss characteristics cannot be obtained. Therefore, the Mn content in the steel workpiece is set to 0.50% or less. The Mn content is more preferably 0.40% or less, and still more preferably 0.30% or less.

[0057]

N: 0.020% or less

N (nitrogen) is an element that reacts with acid-soluble Al to form AlN, which functions as an inhibitor. When the N content in a steel workpiece exceeds 0.020%, bubbles (voids) are formed in the steel sheet during cold rolling, the strength of the steel sheet increases, and the passability during production deteriorates. Therefore, the N content in the steel workpiece is preferably set to 0.020% or less. The N content is more preferably 0.015% or less, and still more preferably 0.010% or less. If AlN is not used as an inhibitor, the lower limit of the N content may include 0%. However, since the sensitivity limit of chemical analysis is 0.0001 mass%, the practical lower limit of the N content in actual steel sheets is 0.0001 mass%. On the other hand, in order to form AlN which functions as an inhibitor, the N content in the steel workpiece is preferably 0.001 mass% or more, and more preferably 0.005 mass% or more.

[0058]

S: 0.005% - 0.040%

S (sulfur) is an important element that reacts with Mn to form MnS, which is an inhibitor. In the case where the S content in the steel workpiece is less than 0.005%, a sufficient inhibitor effect cannot be obtained. Therefore, the S content in the steel workpiece is preferably set to 0.005% or more. The S content is more preferably 0.010% or more, and still more preferably 0.020% or more.

On the other hand, when the S content in the steel billet exceeds 0.040%, S causes hot brittleness, making hot rolling extremely difficult. Therefore, the S content in the steel billet is preferably set to 0.040% or less. The S content is more preferably 0.035% or less, and still more preferably 0.030% or less.

[0059]

P: 0.030% or less

P (phosphorus) is an element that deteriorates the machinability during rolling. When the P content is 0.030% or less, it is possible to suppress excessive deterioration in the machinability during rolling and prevent fracture during production. From this viewpoint, the P content is preferably set to 0.030% or less. The P content is preferably 0.020% or less, and is further preferably 0.010% or less.

The lower limit of the P content may be 0%; however, the sensitivity limit of chemical analysis is 0.0001%, and thus the lower limit of the P content in practical steel sheets is 0.0001%. In addition, P is also an element having the effect of improving texture and improving magnetic properties. In order to obtain this effect, the P content can be set to 0.001% or more, or 0.005% or more.

[0060]

Residue: iron and impurities.

The chemical composition of the steel blank used for producing the anisotropic electrical steel sheet according to the present embodiment contains the above-described elements, and the remainder is Fe and impurities. However, for the purpose of improving magnetic characteristics and the like, Cu, Cr, Sn, Se, Sb, and Mo may be additionally contained in the ranges to be shown below.

Here, impurities are elements that are included from ore or waste as a raw material, production environment, etc. during industrial production of a base steel sheet, and may be contained in such amounts that they do not adversely affect the performance of the anisotropic electrical steel sheet according to the present embodiment.

[0061]

Cu: 0% - 0.50%

Cu (copper) is an element that contributes to increasing the filling level of the Goss orientation in the secondary recrystallization structure and contributes to improving the adhesion of the glass coating. In the case of obtaining the above effect, the content of Cu is preferably set to 0.02% or more. The content of Cu is more preferably 0.03% or more.

On the other hand, when the Cu content exceeds 0.50%, the steel sheet becomes brittle during hot rolling. Therefore, the Cu content in the steel blank is preferably set to 0.50% or less. The Cu content is more preferably 0.30% or less, and still more preferably 0.10% or less.

[0062]

Cr: 0% - 0.50%

Cr (chromium), similar to Sn which will be described later and Cu, is an element which contributes to increasing the filling level of the Goss orientation in the secondary recrystallization structure to improve the magnetic characteristics, and also contributes to improving the adhesion of the glass coating. In order to obtain the above-described effects, the content of Cr is preferably set to 0.02% or more, and more preferably 0.03% or more.

On the other hand, when the Cr content exceeds 0.50%, Cr oxide is formed and the magnetic characteristics are deteriorated. Therefore, the Cr content is preferably set to 0.50% or less. The Cr content is more preferably 0.30% or less, and still more preferably 0.10% or less.

[0063]

Sn: 0% - 0.50%

Sn (tin) is an element having the effect of improving magnetic characteristics. Therefore, Sn may be contained. When Sn is contained, its content is preferably set to 0.005% or more in order to reliably obtain the effect of improving magnetic characteristics. In view of satisfying both magnetic characteristics and coating adhesion, the content of Sn is preferably 0.02% or more, and more preferably 0.03% or more.

On the other hand, when the Sn content exceeds 0.50%, the adhesion of the glass coating is significantly deteriorated. Therefore, the Sn content is preferably set to 0.50% or less. The Sn content is more preferably 0.30% or less, and still more preferably 0.10% or less.

[0064]

Se: 0% - 0.020%

Se (selenium) is an element having the effect of improving magnetic characteristics. Therefore, Se may be contained. In the case where Se is contained, its content is preferably set to 0.001% or more in order to reliably obtain the effect of improving magnetic characteristics. In view of satisfying both magnetic characteristics and coating adhesion, the content of Se is more preferably 0.003% or more, and still more preferably 0.006% or more.

On the other hand, when the Se content exceeds 0.020%, the glass coating is significantly deteriorated. Therefore, the upper limit of the Se content is preferably set to 0.020%. The Se content is more preferably 0.015% or less, and still more preferably 0.010% or less.

[0065]

Sb: 0% - 0.500%

Sb (antimony) is an element having the effect of improving magnetic characteristics. Therefore, Sn may be contained. When Sb is contained, its content is preferably set to 0.001% or more in order to reliably obtain the effect of improving magnetic characteristics. In view of satisfying both magnetic characteristics and plating adhesion, the content of Sb is more preferably 0.005% or more, and still more preferably 0.010% or more.

On the other hand, when the Sb content exceeds 0.500%, the glass coating is significantly deteriorated. Therefore, the upper limit of the Sb content is preferably set to 0.500%. The Sb content is more preferably 0.300% or less, and still more preferably 0.100% or less.

[0066]

Mo: 0% - 0.10%

Mo (molybdenum) is an element having the effect of improving magnetic characteristics. Therefore, Mo may be contained. When Mo is contained, its content is preferably set to 0.01% or more in order to reliably obtain the effect of improving magnetic characteristics. The content of Mo is more preferably 0.02% or more, and still more preferably 0.03% or more.

On the other hand, when the Mo content exceeds 0.10%, the cold rollability is deteriorated, and there is a possibility that the base steel sheet may break. Therefore, the Mo content is preferably set to 0.10% or less. The Mo content is more preferably 0.08% or less, and even more preferably 0.05% or less.

[0067]

<Hot rolling stage>

In the hot rolling stage, a steel billet having a predetermined chemical composition is heated and then hot rolled to obtain a hot rolled steel sheet. The heating temperature of the steel billet is preferably set in the range of 1100°C to 1450°C. The heating temperature is more preferably 1300°C to 1400°C.

The hot rolling conditions are not particularly limited, and can be set according to the circumstances based on the required characteristics. The thickness of the hot rolled steel sheet is preferably in the range of, for example, 2.0 mm or more and 3.0 mm or less.

[0068]

<Hot rolled sheet annealing stage>

The annealing stage of hot rolled sheet is the annealing stage of the hot rolled steel sheet produced in the hot rolling stage, in order to obtain a hot rolled and annealed steel sheet. When such annealing is performed, the structure of the steel sheet undergoes recrystallization, and it becomes possible to realize good magnetic properties.

In the annealing step of the hot-rolled sheet according to the present embodiment, the hot-rolled steel sheet produced in the hot rolling step can be annealed according to a known method to obtain a hot-rolled and annealed steel sheet. The means for heating the hot-rolled steel sheet during the annealing are not particularly limited, and a known heating method can be used. In addition, the annealing conditions are also not particularly limited, and the hot-rolled steel sheet can be annealed, for example, in a temperature range of 900°C to 1200°C for a time of 10 s to 5 min.

[0069]

<Cold rolling stage>

In the cold rolling stage, cold rolling is performed, including a plurality of passes, on a hot rolled and annealed steel sheet after annealing the hot rolled sheet to obtain a cold rolled steel sheet having a thickness of 0.17-0.30 mm. Cold rolling may be cold rolling that is performed once (without intermediate annealing), or may be performed multiple times including intermediate annealing, wherein the cold rolling is stopped and intermediate annealing is performed at least once before the final pass of the cold rolling stage.

In the case where intermediate annealing is performed, the cold-rolled steel sheet is preferably held at a temperature of 1000°C to 1200°C for 5 seconds or more and 180 seconds or less. The annealing atmosphere is not particularly limited. The number of times of intermediate annealing is preferably 3 or less in consideration of the production cost.

In addition, pickling of the hot rolled and annealed steel sheet surface can be performed before the cold rolling stage.

[0070]

In the cold rolling step according to the present embodiment, the hot rolled and annealed steel sheet can be cold rolled according to a known method to obtain a cold rolled steel sheet. For example, it is possible to make the final rolling reduction be in the range of 80% or more and 95% or less. In the case where the final rolling reduction is less than 80%, there is an increased possibility that the Goss nucleus having the {110}<001> orientation with a high degree of integration in the rolling direction cannot be obtained, which is undesirable. On the other hand, in the case where the final rolling reduction exceeds 95%, there is an increased possibility that the secondary recrystallization becomes unstable in the subsequent finish annealing step, which is undesirable. When the final rolling reduction is in the above-described range, Goss nuclei in which the {110}<001> orientation has a high degree of integration in the rolling direction can be obtained, and the instability of secondary recrystallization can be suppressed.

The final rolling reduction is the cumulative cold rolling reduction, and is the cumulative cold rolling reduction after finish annealing when annealing is performed.

[0071]

<Decarburizing annealing stage>

The _{decarburization} annealing step is an important step to control the state of _MgAl2O4 phase in the glass coating. In the case of forming the above-described state of the presence of _{the MgAl2O4 phase} in the process of increasing the temperature in the decarburization annealing stage, which includes the temperature increasing process and the holding process, it is necessary that the temperature increasing rate from 550°C to 750°C be 700-2000°C/s, the oxygen potential be 0.0001-0.0100, and the holding process include a first holding process with an annealing temperature of 800°C - 900°C and an annealing duration of 100-500 s in an atmosphere with an oxygen potential of 0.4 or more and 0.8 or less, and a second holding process with an annealing temperature of 850°C - 1000°C and an annealing duration of 5-100 s in an atmosphere with an oxygen potential of 0.1 or less.

The second holding process (second heat treatment) may be performed after a single temperature reduction after the first holding process (first heat treatment), or may be performed continuously without reducing the temperature after the first heat treatment.

[0072]

The reason why the state of _{the MgAl2O4} phase in the glass coating becomes preferable as described above when the decarburization annealing is carried out in the range described above is unclear, but is presumably as follows.

The glass coating is formed by the reaction between MgO applied to the surface of the steel sheet before the finish annealing as an annealing release agent and Si contained in the base steel sheet. As the reaction proceeds during the finish annealing, the boundary between the glass coating and the base steel sheet becomes the base steel sheet, and finally, the leading end of the glass coating on the side of the base steel sheet acquires such a complicated uneven shape as the "root" described above.

In this process, the _MgAl2O4 phase is formed by the reaction between _MgO and Al in the base steel sheet, and two formation routes are roughly assumed. One route is the case where the MgO in the annealing separating agent and the Al which comes from the base steel sheet directly react with each other. The other route is the case where the MgO in the annealing separating agent first reacts with the Si in the base steel sheet to form the _Mg2SiO4 phase, and then _{the Mg2SiO4} phase further reacts with Al to become _{the MgAl2O4} phase. In the former case _{, the MgAl2O4} phase is considered to occur at a relatively early stage of the glass coating formation process. On the other hand, in the latter case, since Mg and O are fixed as an oxide with Si, the formation of _{the MgAl2O4} phase is considered to occur at a relatively late stage of the glass coating formation process. If we take into account the fact that the formation of the glass coating containing _{the Mg2SiO4} phase as the primary phase ultimately occurs when the oxidized region passes into the base steel sheet, it can be considered that the _MgAl2O4 phase formed at a relatively early stage remains on the surface of the glass coating. On the other hand, it is considered that _{the MgAl2O4 phase ,} which is formed at a relatively late stage, is located on the side of the boundary between the glass coating and the base steel sheet. Taking this into account, it can be assumed that the MgO present on the surface of the base steel sheet preferably reacts predominantly with _Si in the finish annealing to maintain the _MgAl2O4 phase that is formed in the glass coating on the side of the base steel sheet.

It is considered that the decarburization annealing conditions of the present embodiment become conditions for forming a sufficient amount of _SiO2 on the surface of the steel sheet for which the decarburization annealing step has been completed. Thus, when the surface of the steel sheet for which the decarburization annealing step has been completed is covered with a sufficient amount of _SiO2 , in the case where a separating annealing agent containing MgO as a main component is further applied to the surface and the reaction of the separating annealing agent is started in the finish annealing, MgO preferably forms a _Mg2SiO4 phase in the initial stage of the reaction. As a result _, the state of having _{a MgAl2O4} phase in the glass coating becomes preferable. On the contrary, in the case where the above-described decarburization annealing conditions are not satisfied because a sufficient amount of _SiO2 is not present on the surface of the steel sheet for which the decarburization annealing step has been completed, in the case where the reaction of the annealing separating agent starts in the finish annealing, MgO directly reacts with the Al-containing base steel sheet in the initial stage of the reaction and forms a _MgAl2O4 phase. As a result _, the state of having _{the MgAl2O4 phase} in the glass coating does not become preferable.

[0073]

Due to the above-described thermal history in the decarburization annealing step, the glass coating which is formed on the surface of the base steel sheet thereafter takes a preferable shape, and it becomes possible to produce an anisotropic electrical steel sheet having a favorable magnetic loss/noise balance and more excellent coating adhesion by controlling magnetic domains under suitable laser processing conditions.

[0074]

<Nitriding stage>

The nitriding treatment can be carried out during the decarburization annealing stage or after the decarburization annealing stage and before the finish annealing stage, which will be described below.

For example, in the nitriding step, the cold-rolled steel sheet after the holding process in the decarburization annealing step is held at a temperature of approximately 700°C to 850°C in a nitriding treatment atmosphere (containing a gas having a nitriding ability, such as hydrogen, nitrogen or ammonia). It is preferable to carry out nitriding of the steel sheet so that the N content in the cold-rolled steel sheet reaches 40 to 1000 ppm. When the N content in the cold-rolled steel sheet after nitriding is less than 40 ppm, AlN is not sufficiently precipitated in the cold-rolled steel sheet, and there is a possibility that AlN will not act as an inhibitor. Therefore, in the case where AlN is used as an inhibitor, the N content in the cold-rolled steel sheet after nitriding is preferably set to 40 ppm or more.

On the other hand, when the N content in the cold-rolled steel sheet exceeds 1,000 ppm, AlN is excessively present in the steel sheet even after secondary recrystallization is completed in the finish annealing. Such AlN causes deterioration in magnetic loss. Therefore, the N content in the cold-rolled steel sheet after nitriding is preferably set to 1,000 ppm or less.

[0075]

<Final annealing stage>

In the finishing annealing stage, a predetermined annealing release agent is applied to the cold-rolled steel sheet obtained in the decarburization annealing stage or further subjected to nitriding, and then finishing annealing is performed. Finish annealing is usually performed for a long time in the state of the steel sheet being wound into a coil. Therefore, before finishing annealing, an annealing release agent is applied to the cold-rolled steel sheet and dried to prevent the seizure between the inner and outer parts of the sheet in the coil.

As the annealing release agent to be applied, an annealing release agent containing MgO as the main component (e.g. containing 80 mass% or more of MgO) is used. Using the annealing release agent containing MgO as the main component makes it possible to form a glass coating on the surface of the base steel sheet. In the case where MgO is not the main component, the primary coating ( _glass coating) is not formed. The reason for this is that the primary coating is a compound _{of Mg2SiO4} or _MgAl2O4 , and the Mg required for the formation reaction is insufficient.

Finish annealing can be performed under conditions such as raising the temperature to 1150-1250°C in an atmospheric gas containing hydrogen and nitrogen, and then annealing the cold rolled steel sheet for 10-60 hours.

[0076]

<Stage of formation of the insulating coating>

In the insulating coating formation stage, the insulating coating with tension is formed on one or both surfaces of the cold-rolled steel sheet after the finish annealing. The conditions for forming the insulating coating with tension are not particularly limited, and the film-forming liquid can be applied and dried in a known manner using a known insulating coating forming liquid. When the insulating coating with tension is formed on the surface of the steel sheet, the magnetic properties of the anisotropic electrical steel sheet can be further improved.

The surface of the steel sheet on which the insulating coating (tensioned insulating coating) is to be formed may be a surface on which an optional pretreatment such as degreasing treatment with alkali, etc., or pickling with hydrochloric acid, sulfuric acid, phosphoric acid, etc., has been performed before the film-forming liquid is applied, or may be a finish-annealed surface on which no pretreatment has been performed.

The tension-type insulation coating which is formed on the surface of the glass coating (which is formed on the base steel sheet on the glass coating) is not particularly limited as long as the tension-type insulation coating can be used as an insulation coating of anisotropic electrical steel sheets, and a known insulation coating can be used. As such an insulation coating, composite insulation coatings containing an inorganic substance as a main component and further containing an organic substance can be used. Here, the composite insulation coating is an insulation coating containing at least any inorganic substance such as a metal salt of chromic acid, a metal phosphate, colloidal silica, a Zr compound or a Ti compound as a main component, in which fine particles of an organic resin are dispersed. In particular, from the viewpoint of reducing the environmental burden during production, which is increasingly in demand in recent years, an insulation coating using metal phosphate, a binder of Zr or Ti, or their carbonate or ammonium salts as a raw material is preferably used.

[0077]

<Stage of magnetic domain segmentation>

In the magnetic domain segmentation step, the surface of the insulation coating is irradiated with an energy beam under tension, thereby introducing a plurality of linear deformations extending in a direction intersecting with the rolling direction into the surface of the base steel sheet. In the magnetic domain segmentation step, regions (deformation regions) are formed in the base steel sheet in which a plurality of linear deformations (thermal deformations generated by rapid heating by irradiation with energy beams and subsequent rapid cooling) substantially parallel to each other are formed at predetermined intervals in the rolling direction, and the intervals (that is, intervals of deformation regions adjacent to each other) are set to 10 mm or less in the rolling direction.

When the intervals of multiple linear deformation regions in the rolling direction are more than 10 mm, the effect of improving magnetic loss is insufficient. Therefore, deformations (residual deformations) are formed by irradiating the tension insulation coating with an energy beam in each rolling direction at intervals of 10 mm or less.

The type of energy beam is not particularly limited. It is possible to use a laser beam or an electron beam, which are commonly used in practice.

In the case of using laser irradiation, a continuous laser or a pulsed laser may be used, but a continuous laser is preferable. In addition, of the laser beam and the electron beam, the laser beam is preferable. The reason for this is that a vacuum environment is required in the electron beam irradiation stage, which increases the production cost. Therefore, in the present embodiment, magnetic domain segmentation is performed using a laser beam. The laser beam is, for example, a fiber laser beam.

[0078]

In addition, as described above, in order to obtain anisotropic electrical steel sheet that has both low magnetic loss and low noise and excellent coating adhesion, deformations are introduced into the base steel sheet.

In particular, the insulating coating with tension is irradiated with an energy beam so that the power density of the energy beam Ip, which is defined as P/S using the output power of the energy beam P (W) and the cross-sectional area of the energy beam S (mm ² ), satisfies the following expression (5), and the input energy of the energy beam (J/mm), which is defined as P/Vs using the output of the energy beam P and the scanning speed of the energy beam Vs (mm/s), satisfies the following expression (6).

[0079]

250≤Ip≤2000 Expression (5)

0.010 < Up≤0.050 Expression (6)

[0080]

When Ip is less than 250, not enough energy is supplied, and the magnetic domain segmentation effect (magnetic loss reduction effect) cannot be obtained. Therefore, the Ip value is 250 or more. Ip is preferably 500 or more.

On the other hand, when Ip becomes greater than 2000, excessive thermal deformation occurs beyond the magnetic domain segmentation effect, resulting in deterioration of noise performance. Therefore, the value of Ip is 2000 or less. It is preferably 1750 or less, and more preferably 1500 or less.

In addition, when Up is less than 0.010, the irradiation effect cannot be achieved sufficiently, and the magnetic loss is not improved. On the other hand, when Up is greater than 0.050, the noise performance is deteriorated.

[0081]

In addition, in the method for producing an anisotropic electrical steel sheet according to the present embodiment, when irradiated with an energy beam, the aspect ratio of the beam is adjusted so as to satisfy the following expression (7), wherein the aspect ratio of the beam is determined by the expression (dl/dc) using the diameter dl in the direction perpendicular to the scanning direction of the beam (scanning direction) and the diameter dc in the scanning direction of the energy beam in μm.

[0082]

0.0010 < dl/dc < 1.0000 (7)

[0083]

When the beam aspect ratio is 0.0010 or less, heat is generated during beam irradiation, the energy input efficiency is reduced, and a sufficient magnetic domain segmentation effect (magnetic loss reduction effect) cannot be obtained. Therefore, the beam aspect ratio is more than 0.0010.

On the other hand, when the beam aspect ratio is 1.0000 or more, heat is not generated when the beam is irradiated; however, residual stress is generated instead, and the noise reduction effect cannot be obtained. Therefore, the beam aspect ratio is less than 1.0000. The beam aspect ratio is preferably less than 0.0500, and more preferably less than 0.0050.

[0084]

In addition, the diameter dl of the energy beam (in µm) in the direction perpendicular to the beam scanning direction satisfies the following expression (8).

[0085]

10 < dl < 200 (8)

[0086]

In a normal laser light source, it is difficult to set the beam diameter to 10 μm or less. Therefore, dl has a value greater than 10.

On the other hand, when dl becomes 200 or more, excessive thermal deformation occurs beyond the magnetic domain segmentation effect, resulting in deterioration of noise performance. Therefore, the value of dl is less than 200. The value of dl is preferably less than 150, and more preferably less than 100.

[0087]

In the method for producing an anisotropic electrical steel sheet according to the present embodiment, as described above, irradiation is performed with an energy beam having a relatively high Ip value in a state where the beam aspect ratio is small. Such irradiation is not usually performed. The reason for this is that it is considered that a decrease in the beam aspect ratio causes dispersion of the irradiation energy and weakens the effect of increasing Ip.

However, the present inventors have discovered for the first time that the above-described irradiation conditions are preferable as a result of studies based on new data that control of the spatial distribution of deformations is important in terms of simultaneously reducing magnetic losses and noise.

[Examples]

[0088]

Slabs having the compositions shown in Table 1 were obtained. These slabs were subjected to a hot rolling step. Specifically, the slabs were heated to 1350°C and then hot rolled to produce hot rolled steel sheets with a thickness of 2.3 mm.

The annealing stage of hot-rolled steel sheets was performed after the hot rolling stage at an annealing temperature of 900°C to 1200°C for a holding time of 10 to 300 s.

After that, cold rolling was performed many times to obtain cold rolled steel sheets with a thickness of 0.17-0.27 mm.

Decarburization annealing of these cold rolled steel sheets was carried out under the conditions shown in Table 2A and Table 2B.

After the decarburization annealing in Tests Nos. 11, 13 and 15, the steel sheets were held at 700°C to 850°C for 10 to 60 s in a known nitriding atmosphere (an atmosphere containing a gas having a nitriding ability such as hydrogen, nitrogen or ammonia), and the N content of the cold rolled steel sheets after the decarburization annealing was 40 ppm or more and 1000 ppm or less.

The finish annealing step was performed by applying an annealing release agent containing magnesium oxide (MgO) as the main component to the surfaces of the steel sheets after nitriding in Tests Nos. 11, 13 and 15 and after decarburization annealing in other tests. The finish annealing temperature in the finish annealing step was 1200°C, and the holding time at the finish annealing temperature was 20 hours.

The insulating coating containing colloidal silica and phosphate as the main components was applied to the surfaces (glass coatings) of steel sheets (anisotropic electrical steel sheets) after cooling in the finishing annealing stage, and then baked to form tension-type insulating coatings. The anisotropic electrical steel sheet for each test was produced through the above-described stages.

[0089]

[Table 1] Type of steel Slab (wt.%, residue: iron and impurities) C Si Mn P S Soluble Al N Cu Cr Sn Se Sb Mo A 0.074 3.31 0.07 0.02 0.024 0.026 0.008 - - - - - - B 0,060 3.25 0.15 0.01 0,021 0,021 0,015 - - - - - - C 0,040 3.15 0.23 0.02 0,016 0.034 0,015 0.02 - - - - - D 0,050 3.26 0.25 0.02 0,009 0.035 0,015 - 0.01 - - - - E 0,079 3.35 0.08 0.01 0.026 0.027 0,008 - - 0.10 - - - F 0.061 3.41 0.07 0.01 0.006 0.024 0.006 - - - 0,010 - - G 0.069 3.29 0.09 0.01 0,008 0.022 0,007 - - - - 0,020 - H 0.081 3.28 0.07 0.02 0.025 0.022 0,008 - - - - - 0.01

[0090]

[Table 2A] Test No. Material Decarburizing annealing stage Type of steel Thickness Temperature increase rate from 550°C to 750°C Oxygen potential with temperature increase from 550°C to 750°C First holding temperature Duration of the first exposure Oxygen potential of the first exposure Second exposure temperature Duration of the second exposure Oxygen potential of the second exposure mm °C/s °C With °C With 1 A 0.27 800 0,0050 850 120 0,500 900 20 0,100 2 A 0.17 800 0.0002 850 120 0,500 900 20 0,100 3 A 0.17 800 0,0050 850 200 0,500 900 40 0,100 4 B 0.22 800 0.0002 850 200 0,600 900 40 0,100 5 B 0.22 800 0,0010 850 300 0,600 900 60 0,100 6 B 0.22 800 0,0090 850 300 0,600 900 60 0,050 7 C 0.22 1000 0,0010 850 400 0,700 900 80 0,050 8 D 0.22 1000 0.0002 850 400 0,700 900 80 0,050 9 A 0.27 1000 0,0006 850 480 0,700 900 90 0,100 10 A 0.17 1200 0,0008 810 140 0,430 930 15 0,010 11 E 0.27 1200 0,0040 820 120 0,420 930 15 0,010 12 D 0.17 1200 0,0090 820 120 0,500 930 15 0,010 13 B 0.17 1200 0,0010 830 120 0,500 930 15 0,010 14 E 0.27 1000 0,0006 900 200 0,500 1000 20 0,100 15 A 0.22 1000 0.0002 820 120 0,500 950 10 0,005 16 A 0.19 1000 0,0090 820 120 0,410 930 10 0,005 17 E 0.19 1000 0,0010 820 140 0,450 930 20 0,005 18 D 0.27 1900 0,0030 900 300 0,600 1000 60 0,100 19 H 0.19 1200 0,0003 830 120 0,420 950 10 0,010 20 E 0.27 1900 0,0010 900 400 0,700 1000 60 0,100 21 E 0.22 1200 0,0060 830 120 0,410 950 10 0,010 22 B 0.17 1900 0,0009 900 480 0,700 1000 80 0,100 23 A 0.22 1900 0,0010 900 480 0,700 1000 80 0,100 24 C 0.22 1900 0,0009 900 480 0,700 1000 80 0,100 25 D 0.17 400 0,0010 850 120 0,500 900 20 0,050 26 E 0.17 800 0,0030 950 120 0,500 900 40 0,050

[0091]

[Table 2B] Test No. Material Decarburizing annealing stage Type of steel Thickness Temperature increase rate from 550°C to 750°C Oxygen potential with temperature increase from 550°C to 750°C First holding temperature Duration of the first exposure Oxygen potential of the first exposure Second exposure temperature Duration of the second exposure Oxygen potential of the second exposure mm °C/s °C With °C With 27 C 0.17 1200 0,0020 800 120 0,600 900 60 0,050 28 A 0.17 1500 0.0002 850 60 0,600 900 80 0,050 29 B 0.17 1800 0,0006 850 600 0,700 900 90 0,050 30 C 0.17 1200 0,0003 850 120 0,300 1000 20 0,050 31 E 0.17 800 0,0040 850 120 0,900 1000 40 0,050 32 F 0.17 2000 0,0030 850 200 0,500 1000 60 0,050 33 B 0.22 2500 0,0010 850 200 0,500 1000 80 0,050 34 G 0.22 900 0,0090 850 200 0,500 1000 90 0,050 35 G 0.22 1500 0,0020 850 300 0,600 1000 60 0,050 36 E 0.22 1600 0,0006 850 300 0,600 800 10 0,050 37 A 0.22 1800 0,0030 850 300 0,700 800 120 0,050 38 F 0.22 1900 0.0002 900 120 0,700 800 60 0,200 39 D 0.22 1900 0,0003 900 120 0,600 800 40 0,050 40 D 0.27 1900 0.0002 900 200 0,600 900 20 0,050 41 B 0.27 1300 0,0009 900 200 0,600 900 120 0,050 42 B 0.27 1000 0,0003 900 300 0,500 900 10 0,200 43 E 0.27 1500 0,0030 900 300 0,500 900 10 0,200 44 E 0.27 1200 0,0030 900 400 0,600 1050 10 0,050 45 C 0.27 1200 0,0090 900 400 0,600 1050 80 0,200 46 A 0.27 1000 0,0080 900 480 0,700 1050 10 0,050 47 C 0.27 1800 0,0010 900 480 0,700 1050 80 0,200 48 D 0.27 1800 0,0200 900 480 0,700 1000 80 0,050 49 F 0.27 1800 0,0001 900 480 0,700 1000 80 0,050 50 A 0.22 1000 0,0090 820 120 0,410 930 10 0,005 51 A 0.22 1000 0,0090 820 120 0,410 930 10 0,005 52 C 0.22 1000 0,0090 820 120 0,410 930 10 0,005

[0092]

[Analysis of chemical composition of base steel sheet]

The chemical composition of the base steel sheet in the anisotropic electrical steel sheet for each test before magnetic domain segmentation was obtained in the following manner. First, the insulating coating is removed from the anisotropic electrical steel sheet under tension. Specifically, the anisotropic electrical steel sheet is immersed in an aqueous solution of sodium hydroxide (with a temperature of 80°C to 90°C) containing NaOH: 30-50 wt% and _H2O : 50-70 wt% for 7-10 min. The anisotropic electrical steel sheet after immersion (the anisotropic electrical steel sheet from which the insulating coating has been removed under tension) is washed with water. After washing, the anisotropic electrical steel sheet is dried with a stream of warm air for less than one minute.

Then, the glass coating is removed from the anisotropic electrical steel sheet. Specifically, the anisotropic electrical steel sheet is immersed in an aqueous solution of hydrochloric acid (80°C - 90°C) containing 30-40 mass% HCl for 1-10 min. In this way, the glass coating is removed from the base steel sheet. The base steel sheet is washed with water after immersion. After washing, the anisotropic electrical steel sheet is dried with a stream of warm air for less than one minute. The base steel sheet can be removed from the anisotropic electrical steel sheet by the above-described step.

The chemical composition of the extracted base steel sheet is obtained by a known method of component analysis. Specifically, chips are obtained from the base steel sheet by a drill, and these chips are collected. The collected chips are dissolved in acid to obtain a solution. Elemental analysis of the chemical composition of this solution is performed by ICP-AES. Si in the chemical composition of the base steel sheet is obtained by the method specified in JIS G 1212: 1997 (Determination methods for silicon content). Specifically, when the above-described chips are dissolved in acid, silicon oxide precipitates. This precipitate (silicon oxide) is filtered with filter paper, and its mass is measured, thereby obtaining the Si content. The C content and the S content are obtained by a well-known high-frequency combustion method (infrared absorption combustion method). Specifically, the above solution is combusted by high-frequency heating in an oxygen flow, the carbon dioxide and sulfur dioxide generated are determined, and the C content and S content are obtained as a result. The N content is obtained by using the method for determining the specific thermal conductivity by melting in an inert gas. The chemical composition of the base steel sheet is obtained by the above analysis method. The chemical composition of the steel sheet (base steel sheet) for each test is shown in Table 3. "-" in Table 3 means that the content of the corresponding element is lower than the measurement limit.

[0093]

[Evaluation of magnetic characteristics]

Although not shown in the table, a specimen of 60 mm in width and 300 mm in length including the position of the center of the sheet width is taken from the anisotropic electrical steel sheet of each test. The length of the specimen is set parallel to the rolling direction. The taken specimen is kept at 800°C for 2 hours in a nitrogen atmosphere having a dew point of 0°C or lower, and the stresses introduced during the sampling are removed.

The magnetic flux density (T) is determined by the single sheet magnetic performance test (SST) in accordance with JIS C2556 (2015) using this specimen. Specifically, a magnetic field of 800 A/m is applied to the specimen, and the magnetic flux density (T) is determined.

In addition, the magnetic loss W _17/50 (W/kg) at 50Hz and maximum magnetic flux density of 1.7T is measured in accordance with JIS C2556 (2015) using this sample.

[0094]

[Table 3] Type of steel Steel sheet (wt.%, balance: iron and impurities) C Si Mn P S Soluble Al N Cu Cr Sn Se Sb Mo A 0,001 3.20 0.07 0.02 < 0.002 < 0.004 < 0.002 - - - - - - B 0,001 3.15 0.15 0.01 < 0.002 < 0.004 < 0.002 - - - - - - C 0,001 3.05 0.23 0.02 < 0.002 < 0.004 < 0.002 0.02 - - - - - D 0,001 3.15 0.25 0.02 < 0.002 < 0.004 < 0.002 - 0.01 - - - - E 0,001 3.24 0.08 0.01 < 0.002 < 0.004 < 0.002 - - 0.10 - - - F 0,001 3.30 0.07 0.01 < 0.002 < 0.004 < 0.002 - - - 0,005 - - G 0,001 3.18 0.09 0.01 < 0.002 < 0.004 < 0.002 - - - - 0,020 - H 0,001 3.17 0.07 0.02 < 0.002 < 0.004 < 0.002 - - - - - 0.01

[0095]

In addition, on the anisotropic electrical steel sheet obtained in each test (after forming the tension insulating coating), magnetic domain segmentation is performed by irradiating the surface of the steel sheet with an energy beam using a laser (fiber laser or pulsed laser) or an electron beam under the conditions shown in Table 4A and Table 4B, and tests are performed to evaluate the noise and magnetic characteristics. In addition, the total thickness of the glass coating is measured in the above-described manner, and then the area ratios S1 _, S2, and S3 of the _MgAl2O4 phase in each region are also measured.

[0096]

[Table 4A] Test No. Magnetic domain segmentation stage Laser/Electron Beam Continuous/intermittent Ip Up dl/dc dl Angle of deviation relative to the direction perpendicular to the rolling direction Intervals in the rolling direction Linear deformation width W/ ^mm2 J/mm microns ° mm microns 1 Laser Continuous 320 0.004 0.0032 40 10 5 50 2 Laser Intermittent 438 0,012 0,0101 90 20 8 100 3 Laser Continuous 400 0,011 0.0061 70 5 4 80 4 Laser Continuous 333 0,017 0,0043 80 5 4 90 5 Laser Continuous 37 0,005 0,0015 150 10 5 160 6 Laser Intermittent 433 0.026 0,0171 160 8 3 170 7 Laser Continuous 450 0.045 0,0162 180 15 7 190 8 Laser Continuous 1300 0.033 0,0484 220 25 8 230 9 Laser Intermittent 84 0,080 0.0027 225 10 9 235 10 Laser Continuous 550 0.037 0,0030 95 5 4 105 11 Laser Continuous 283 0.043 0.0022 115 15 9 125 12 Laser Continuous 238 0.038 0.0025 140 28 8 150 13 Laser Intermittent 1800 0.045 0,0121 110 10 7 120 14 Laser Continuous 90 0.036 0.0028 235 20 6 245 15 Laser Continuous 253 0.038 0.0039 170 5 7 180 16 Laser Intermittent 1100 0.044 0.0085 130 0 6 140 17 Laser Intermittent 1533 0.042 0,0160 155 10 5 165 18 Laser Intermittent 250 0.056 0,0016 125 20 6 135 19 Laser Continuous 50 0.048 0,0009 210 8 5 220 20 Laser Continuous 2083 0.056 0,0241 170 5 5 180 21 Laser Continuous 2000 0,050 0,0241 190 0 6 200 22 Laser Continuous 2000 0,050 0,0241 190 3 12 200 23 Laser Continuous 3800 0,011 0.0064 40 5 4 50 24 Laser Continuous 2273 0.004 0,0073 40 3 3 50 25 Laser Continuous 500 0.044 0,0020 90 5 4 100 26 Laser Continuous 500 0.044 0,0020 90 5 4 100

[0097]

[Table 4B] Test No. Magnetic domain segmentation stage Laser/Electron Beam Continuous/
intermittent Ip Up dl/dc dl Angle of deviation relative to the direction perpendicular to the rolling direction Intervals in the rolling direction Linear deformation width W/ ^mm2 J/mm microns ° mm microns 27 Laser Continuous 500 0.044 0,0020 90 5 4 100 28 Laser Continuous 500 0.044 0,0020 90 5 4 100 29 Laser Continuous 500 0.044 0,0020 90 5 4 100 30 Laser Continuous 500 0.044 0,0020 90 5 4 100 31 Laser Continuous 500 0.044 0,0020 90 5 4 100 32 Laser Continuous 500 0.044 0,0020 90 5 4 100 33 Laser Continuous 500 0.044 0,0020 90 5 4 100 34 Laser Continuous 500 0.044 0,0020 90 5 4 100 35 Laser Continuous 500 0.044 0,0020 90 5 4 100 36 Laser Continuous 500 0.044 0,0020 90 5 4 100 37 Laser Continuous 500 0.044 0,0020 90 5 4 100 38 Laser Continuous 500 0.044 0,0020 90 5 4 100 39 Laser Continuous 500 0.044 0,0020 90 5 4 100 40 Laser Continuous 500 0.044 0,0020 90 5 4 100 41 Laser Continuous 500 0.044 0,0020 90 5 4 100 42 Laser Continuous 500 0.044 0,0020 90 5 4 100 43 Laser Continuous 500 0.044 0,0020 90 5 4 100 44 Laser Continuous 500 0.044 0,0020 90 5 4 100 45 Laser Continuous 500 0.044 0,0020 90 5 4 100 46 Laser Continuous 500 0.044 0,0020 90 5 4 100 47 Laser Continuous 500 0.044 0,0020 90 5 4 100 48 Laser Continuous 500 0.044 0,0020 90 5 4 100 49 Laser Continuous 500 0.044 0,0020 90 5 4 100 50 Laser Continuous 1000 0,040 0,0009 100 5 6 110 51 Laser Continuous 1000 0,040 1,0000 100 5 6 110 52 Laser Continuous 1000 0,040 5,0000 100 5 6 110

[0098]

[Noise and magnetostriction performance assessment]

A specimen having a width of 100 mm and a length of 500 mm is taken from each sheet of anisotropic electrical steel. The length direction of the specimen corresponds to the rolling direction RD, and the width direction corresponds to the sheet width direction TD.

The magnetostriction of the sample is measured by measuring the magnetostriction of alternating current using a magnetostriction measuring device. The magnetostriction measuring device is a device including a laser Doppler vibrometer, an excitation coil, an excitation power supply, a magnetic flux detection coil, an amplifier and an oscilloscope.

Specifically, an alternating magnetic field is applied to the specimen so that the maximum magnetic flux density in the rolling direction is 1.7 T, and the frequency is 50 Hz. The change in the specimen length caused by the expansion and contraction of magnetic domains is measured by a laser Doppler vibrometer, and a magnetostriction signal is obtained. Fourier analysis of the obtained magnetostriction signal is performed to obtain the amplitude Cn of each frequency component fn (n is a natural number equal to or greater than 1) of the magnetostriction signal. The magnetostriction level LVA (dB), represented by the following expression, is obtained by using the correction factor αn of each frequency component fn.

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

Here ρc is the proper acoustic resistance, set equal to 400. Pe0 is the minimum audible sound pressure, set equal to Pe0=2 × 10 ^-5 (Pa). The values given in Table 2 of the JIS C 1509-1 (2005) standard are used as the correction factor αn.

Based on the obtained magnetostriction level (LVA), the noise performance is evaluated according to the following criteria. When the magnetostriction level is less than 60 dBA, the anisotropic electrical steel sheet is considered to be excellent in terms of noise performance.

[0099]

In addition, the magnetostriction λ _0-p (μm/m) is obtained from the magnetostriction signal. Specifically, from the length Lp (μm) of the test specimen (steel sheet) at the magnetic flux density of 1.7 T and the length L ₀ (m) of the test specimen at the magnetic flux density of 0 T under the above-mentioned excitation conditions, λ _0-p is calculated by the formula (Lp-L ₀ )/L ₀ .

In addition, for the steel sheet subjected to heat treatment at 800°C for 4 hours, the magnetostriction λ _0-p (μm/m) is measured in the same way at a frequency of 50 Hz and a maximum magnetic flux density of 1.7 T. In addition, the value of λ _0-pb - λ _0-pa is obtained, where λ _0-pb means the magnetostriction before heat treatment, and λ _0-pa means the magnetostriction after heat treatment.

These results are shown in Tables 5A, 5B, 6A, and 6B.

[0100]

[Evaluation of magnetic characteristics]

A specimen having a width of 60 mm and a length of 300 mm including the position of the center of the sheet width is taken from the anisotropic electrical steel sheet of each test. The length of the specimen is set parallel to the rolling direction. The taken specimen is kept at 800°C for 2 hours in a nitrogen atmosphere having a dew point of 0°C or lower, and the stresses introduced during the sampling are removed.

The magnetic flux density (T) is determined by the single sheet magnetic performance test (SST) in accordance with JIS C2556 (2015) using this specimen. Specifically, a magnetic field of 800 A/m is applied to the specimen, and the magnetic flux density (T) is determined.

In addition, the magnetic loss W _17/50 (W/kg) at a frequency of 50Hz and a maximum magnetic flux density of 1.7T is measured according to JIS C2556 (2015) using this sample. When the improvement rate of magnetic loss is 5.0% or more, it is determined to be excellent. The measurement results are shown in Table 6A and Table 6B.

[0101]

[Coating adhesion]

The coating adhesion (remaining coating area ratio) of the anisotropic electrical steel sheet is measured in the above manner. When the remaining coating area ratio is 50% or more, the coating adhesion is judged to be acceptable (rating ), and when the coating adhesion is 90% or more, it is defined as excellent (rating ). The evaluation results are shown in Table 6A and Table 6B.

[0102]

[Table 5A] Test No. Magnetostriction Full thickness of glass coating Area fraction of the Mg ₂ AlO ₄ phase λ _0-pa λ _0-pb λ _0-pb - λ _0-pa S1 S2 S3 (S1+S2+S3)/3 S1 > S2 > S3 microns 1 -0.82 -0.81 0.01 2,2 0.60 0.12 0.01 0.24 2 -0.87 -0.84 0.03 2.0 0.50 0.15 0.02 0.22 3 -0.89 -0.78 0.11 3.4 0.65 0.16 0,00 0.27 4 -0.81 -0.74 0.07 2,2 0.64 0.15 0.02 0.27 5 -0.89 -0.88 0.01 3.0 0.67 0.20 0.02 0.30 6 -0.92 -0.74 0.18 2.7 0.70 0.14 0.08 0.31 7 -0.87 -0.78 0.09 2.6 0.62 0.16 0.05 0.28 8 -0.96 -0.84 0.12 2,2 0.59 0.18 0.06 0.28 9 -0.91 -0.90 0.01 3.5 0.57 0.19 0.07 0.28 10 -0.85 -0.66 0.19 2.0 0.64 0.20 0.05 0.30 11 -0.86 -0.84 0.02 2.1 0.48 0.25 0.04 0.26 12 -0.92 -0.91 0.01 2.1 0.67 0.23 0.01 0.30 13 -0.91 -0.73 0.18 2.7 0.64 0.19 0.06 0.30 14 -0.84 -0.83 0.01 1.9 0.58 0.14 0.08 0.27 15 -0.89 -0.81 0.08 2.9 0.67 0.18 0.09 0.31 16 -0.91 -0.77 0.14 3.4 0.66 0.24 0.08 0.33 17 -0.84 -0.69 0.15 2.9 0.54 0.15 0.04 0.24 18 -0.81 -0.51 0.30 2,3 0.57 0.27 0.03 0.29 19 -0.94 -0.78 0.16 2.4 0.54 0.22 0.01 0.26 20 -0.85 -0.40 0.45 1.9 0.56 0.16 0.08 0.27 21 -0.91 -0.71 0.20 3.1 0.59 0.18 0,00 0.26 22 -0.88 -0.87 0.01 3.4 0.64 0.11 0.06 0.27 23 -0.89 -0.51 0.38 3.2 0.67 0.19 0.07 0.31 24 -0.84 -0.83 0.01 1.6 0.69 0.20 0.05 0.31 25 -0.95 -0.76 0.19 2.5 0.41 0.43 0.19 0.34 × 26 -0.84 -0.67 0.17 1.8 0.43 0.45 0.12 0.33 ×

[0103]

[Table 5B] Test No. Magnetostriction Full thickness of glass coating Area fraction of Mg ₂ AlO ₄ phase λ _0-pa λ _0-pb λ _0-pb - λ _0-pa S1 S2 S3 (S1+S2+S3)/3 S1 > S2 > S3 microns 27 -0.9 -0.74 0.16 2,2 0.43 0.46 0.09 0.33 × 28 -0.87 -0.69 0.18 3.1 0.60 0.26 0.13 0.33 29 -0.89 -0.73 0.16 3.1 0.65 0.32 0.17 0.38 30 -0.92 -0.75 0.17 2,3 0.68 0.40 0.13 0.40 31 -0.86 -0.71 0.15 1.6 0.53 0.26 0.15 0.31 32 -0.97 -0.79 0.18 2.8 0.48 0.46 0.06 0.33 33 -0.91 -0.76 0.15 2.5 0.61 0.41 0.19 0.40 34 -0.89 -0.75 0.14 2.6 0.53 0.19 0.09 0.27 35 -0.88 -0.74 0.14 3.1 0.54 0.29 0.06 0.30 36 -0.94 -0.78 0.16 3.3 0.51 0.28 0.15 0.31 37 -0.81 -0.65 0.16 2.6 0.63 0.22 0.16 0.34 38 -0.86 -0.69 0.17 1.9 0.64 0.27 0.14 0.35 39 -0.94 -0.80 0.14 2.4 0.68 0.19 0.14 0.34 40 -0.86 -0.71 0.15 1.7 0.67 0.42 0.07 0.39 41 -0.87 -0.73 0.14 2.7 0.70 0.60 0.40 0.57 42 -0.94 -0.78 0.16 1.8 0.67 0.43 0.18 0.43 43 -0.93 -0.78 0.15 2.1 0.69 0.43 0.14 0.42 44 -0.92 -0.75 0.17 3.0 0.65 0.31 0.17 0.38 45 -0.9 -0.74 0.16 2.5 0.67 0.34 0.19 0.40 46 -0.84 -0.70 0.14 2.1 0.71 0.27 0.15 0.38 47 -0.86 -0.71 0.15 2.4 0.68 0.26 0.18 0.37 48 -0.82 -0.69 0.13 3.1 0.65 0.24 0.15 0.35 49 -0.88 -0.69 0.19 1.6 0.72 0.23 0.11 0.35 50 -0.91 -0.89 0.02 3.2 0.67 0.26 0.07 0.33 51 -0.92 -0.70 0.22 2.6 0.68 0.23 0.08 0.33 52 -0.91 -0.62 0.29 2.8 0.70 0.30 0.06 0.35

[0104]

[Table 6A] Test No. Magnetic characteristics Noise characteristics Proportion of area of remaining coverage Balance magnetic losses/noise Coverage assessment Magnetic losses Magnetic flux density Magnetic Loss Improvement Factor Magnetic Loss Improvement Factor W/kg Tl % 5% or more 0 dB % 1 0.80 1.91 4.8 X 49 100 × 2 0.72 1.91 7.9 47 99 3 0.71 1.91 8.6 50 98 4 0.74 1.91 8.1 52 98 5 0.81 1.91 0,0 X 47 100 × 6 0.73 1.91 10.5 57 94 7 0.74 1.90 8.6 53 96 8 0.74 1.91 9.1 60 95 × 9 0.80 1.92 4.8 X 49 98 × 10 0.69 1.90 11.6 57 91 11 0.79 1.91 6.0 49 96 12 0.81 1.91 3.8 50 95 × 13 0.69 1.90 11.9 58 93 14 0.82 1.92 2.4 X 49 100 × 15 0.76 1.91 6.2 49 97 16 0.73 1.90 9.8 57 96 17 0.72 1.90 10.9 59 95 18 0.77 1.90 8.1 60 96 × 19 0.78 1.91 0,0 51 95 × 20 0.74 1.89 11.4 63 92 × 21 0.68 1.90 12.8 59 91 22 0.76 1.91 2.6 X 55 100 × 23 0.71 1.90 12.3 63 91 × 24 0.78 1.90 3.7 X 57 99 × 25 0.69 1.91 12.0 57 50 26 0.69 1.91 11.6 58 60

[0105]

[Table 6B] Test No. Magnetic characteristics Noise characteristics Remaining Coverage Area Proportion Balance magnetic losses/noise Coverage assessment Magnetic losses Magnetic flux density Magnetic Loss Improvement Factor Magnetic Loss Improvement Factor W/kg Tl % 5% or more 0 dB % 27 0.69 1.91 11.2 58 65 28 0.69 1.91 10.9 57 70 29 0.69 1.91 11.8 57 60 30 0.69 1.91 11.3 57 65 31 0.69 1.91 11.6 58 60 32 0.70 1.91 10.7 57 95 33 0.73 1.91 10.3 58 60 34 0.72 1.91 10.6 58 96 35 0.73 1.91 10.3 58 95 36 0.72 1.91 10.7 58 65 37 0.72 1.91 10.6 57 60 38 0.73 1.91 10.1 58 70 39 0.73 1.91 10.4 58 65 40 0.76 1.91 9.6 58 96 41 0.76 1.91 9.5 57 80 42 0.76 1.91 9.1 58 75 43 0.76 1.91 9.2 58 80 44 0.76 1.91 9.2 58 70 45 0.76 1.91 10.0 58 65 46 0.76 1.91 9.8 58 70 47 0.76 1.91 9.0 57 75 48 0.76 1.91 9.2 56 70 49 0.76 1.91 9.4 58 75 50 0.78 1.90 3.7 57 96 × 51 0.76 1.90 6.2 60 97 × 52 0.75 1.90 7.4 61 96 ×

[0106]

As can be seen from Tables 1 to 6B, in the steel sheets (examples of the present invention) in which deformation regions are preferably present and the value of λ _0-pb - λ _0-pa conforms to the present invention, a favorable balance of magnetic loss/noise can be ensured. Furthermore, in the steel sheets in which the value of λ _0-pb - λ _0-pa conforms to the present invention and a favorable balance of magnetic loss/noise can be ensured, in the case where the area ratio of the MgAl ₂ O ₄ phase in the glass coating in each region satisfies the preferred ratio, the area ratio of the remaining coating is sufficiently high, and favorable adhesion can also be obtained.

On the other hand, in steel sheets in which the value of λ _0-pb - λ _0-pa does not conform to the present invention and it is impossible to ensure a favorable magnetic loss/noise balance, the influence of the area ratio of the MgAl ₂ O ₄ phase in the glass coating on the area ratio of the remaining coating is not clear.

INDUSTRIAL APPLICABILITY

[0107]

According to the present invention, it is possible to provide an anisotropic electrical steel sheet having a favorable magnetic loss/noise balance, and a method for producing the same. In addition, according to a preferred aspect of the present invention, it is possible to provide an anisotropic electrical steel sheet having a favorable magnetic loss/noise balance, and also excellent coating adhesion. Therefore, the industrial applicability is high.

Claims (45)

1. A sheet of anisotropic electrical steel containing: base steel sheet; a glass coating formed on a base steel sheet; and a tension-bonded insulating coating formed on a glass coating, in which a plurality of regions of linear deformation are present in the base steel sheet, which extend continuously or discontinuously in a direction intersecting with the rolling direction, each of the plurality of linear deformation regions has a width of 210 μm or less in the rolling direction, a plurality of linear deformation regions are parallel to each other, the intervals of the linear deformation regions adjacent to each other in the rolling direction are 10 mm or less, wherein the base steel sheet has a chemical composition containing in wt. %: C: 0.010 or less, Si: 3.00-4.00, Mn: 0.01-0.50, N: 0.010 or less, sol. Al: 0.020 or less, S: 0.010 or less, P: 0.030 or less, Cr: 0-0.50, Sn: 0-0.50, Cu: 0-0.50, Se: 0-0.020, Sb: 0-0.500, Mo: 0-0.10 and the balance of Fe and impurities, and the magnetostriction λ _0-pb (μm/m) when the anisotropic electrical steel sheet is excited to 1.7 T, and the magnetostriction λ _0-pa (μm/m) when the anisotropic electrical steel sheet is heat treated at 800°C for 4 hours and then excited to 1.7 T, satisfy the following expression (1), 0.02≤λ _0-pb - λ _0-ra ≤0.20 (1). 2. A sheet of anisotropic electrical steel according to claim 1, wherein the glass coating is formed from a structure comprising a Mg ₂ SiO ₄ phase, which is a primary phase, and a MgAl ₂ O ₄ phase, and in the cross section in the sheet thickness direction, when the glass coating is divided into 3 regions having an equal thickness in the sheet thickness direction, each region is designated as a 1/3 region, a 2/3 region and a 3/3 region from the base steel sheet side toward the tension insulating coating side, and the area ratio of _{the MgAl2O4} phase in the 1/3 region is designated as S1, the area ratio of the _MgAl2O4 phase in the _2/3 region is designated as S2 and the area ratio of the _MgAl2O4 phase in the _3/3 region is designated as S3, S1, S2 and S3 satisfy the following expressions (2)-(4): S1>S2>S3 (2), (S1+S2+S3)/3<0.50 (3), S3<0.10 (4). 3. A method for producing a sheet of anisotropic electrical steel according to paragraph 1 or 2, comprising: a hot rolling step comprising heating the steel blank to obtain a hot rolled steel sheet by hot rolling; a hot rolled steel sheet annealing stage for annealing the hot rolled steel sheet; a pickling step for pickling the hot rolled steel sheet after the annealing step of the hot rolled steel sheet; a cold rolling step for cold rolling the hot rolled steel sheet one or more times after a pickling step with annealing therebetween to obtain a cold rolled steel sheet; a decarburization annealing step for decarburization annealing the cold rolled steel sheet; a finishing annealing step comprising applying and drying an annealing release agent containing Mgo powder as a main component onto the front and back surfaces of the cold-rolled steel sheet, which is the base steel sheet, after the decarburization annealing step and performing finishing annealing to form a glass coating; a coating forming step for forming tension insulating coatings on the glass coatings to obtain an anisotropic electrical steel sheet comprising a base steel sheet, glass coatings formed on the base steel sheet, and tension insulating coatings formed on the glass coatings; and a magnetic domain segmentation stage comprising irradiating the surfaces of the insulating coatings with tension in the anisotropic electrical steel sheet with an energy beam to form a plurality of linear deformation regions on the base steel sheet, in which at the stage of segmentation of magnetic domains among the plurality of linear deformation regions, the intervals of the linear deformation regions adjacent to each other in the rolling direction are 10 mm or less, the power density of the energy beam Ip (W/ ^mm2 ), which is defined as (P/S) using the output power of the energy beam P (W) and the cross-sectional area of the energy beam S ( ^mm2 ), satisfies the following expression (5), the input energy of the energy beam Up (J/mm), which is defined as P/Vs using the output power of the energy beam P and the scanning speed of the energy beam Vs (mm/s), satisfies the following expression (6), and the aspect ratio of the energy beam, which is defined as (d1/dc) using the diameter d1 in the direction perpendicular to the beam scanning direction (in μm) and the diameter dc in the beam scanning direction (in μm), satisfies the following expression (7), and d1 satisfies the following expression (8), 250≤Ip≤2000 (5), 0.010<Up≤0.050 (6), 0.0010<d1/dc<1.0000 (7), 10<d1<200 (8). 4. A method for producing an anisotropic electrical steel sheet according to claim 3, wherein the energy beam is a laser beam. 5. A method for producing an anisotropic electrical steel sheet according to claim 4, wherein the laser beam is a fiber laser beam. 6. A method for producing anisotropic electrical steel sheet according to any of paragraphs 3-5, wherein the steel workpiece contains, in mass%, C: 0.010-0.200, Si: 3.00-4.00, soluble Al: 0.010-0.040, Mn: 0.01-0.50, N: 0.020 or less, S: 0.005-0.040, P: 0.030 or less, Cu: 0-0.50, Cr: 0-0.50, Sn: 0-0.50, Se: 0-0.020, Sb: 0-0.500, and Mo: 0-0.10, and a remainder including Fe and impurities. 7. A method for producing anisotropic electrical steel sheet according to any of paragraphs 3-6, in which the decarburizing annealing step comprises a temperature raising process and a holding process, in the process of increasing the temperature, the rate of temperature increase from 550°C to 750°C is set to 700-2000°C/s, the oxygen potential is set to 0.0001-0.0100, and the soaking process includes a first soaking process in which the annealing temperature is set to 800-900°C and the annealing time is set to 100-500 s in an atmosphere having an oxygen potential of 0.4 or more and 0.8 or less, and a second soaking process in which the annealing temperature is set to 850°C or higher and 1000°C or lower and the annealing time is set to 5-100 s in an atmosphere having an oxygen potential of 0.1 or less. 8. A method for producing anisotropic electrical steel sheet according to any one of paragraphs 3-7, further comprising during the decarburization annealing stage or after the decarburization annealing stage: nitriding stage for nitriding cold rolled steel sheet.