RU2821534C2 - Anisotropic electrical steel sheet - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, namely to sheet of anisotropic electrical steel used as material for iron core of transformers. Anisotropic electrical steel sheet comprises a main steel sheet, which is a silicon steel sheet, intermediate layer in contact with silicon steel sheet, and an insulating coating in contact with the intermediate layer. Intermediate layer is an oxide film with an average thickness of 2–500 nm, containing, at.%: 20–70 Si, 30–80 O, less than 20 Mg, less than 5 P and less than 20 Fe. Insulation coating is a phosphate-based coating with an average thickness of 0.1–10 mcm, containing, at.%: 5–30 P, 5–30 Si, 30–80 O, 1 or more and less than 25 Fe, less than 1.0 Cr, 0–10 Al, 0–10 Mg, 0–10 Mn, 0–10 Ni, 0–10 Zn, 0–10 V, 0–10 W, 0–10 Zr, 0–10 Co, 0–10 Mo, wherein total content of Al, Mg, Mn, Ni and Zn is 0.1–10, and the total content of V, W, Zr, Co and Mo is 0.1–10. Phosphate-based coating includes a first crystalline phosphorus oxide, the crystalline structure of which corresponds to the formula Fe₂P₂O₇, and a second crystalline phosphorus oxide, the crystalline structure of which corresponds to the formula Fe₇(P₂O₇)_4. Second crystalline phosphorus oxide includes at least one element selected from the group consisting of V, W, Zr, Co and Mo.

EFFECT: sheet has low magnetic losses and high adhesion of the insulating coating.

6 cl, 3 dwg, 21 tbl

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

[0001]

The present invention relates to an anisotropic electrical steel sheet. In particular, the present invention relates to an anisotropic electrical steel sheet having excellent insulating coating adhesion even without a forsterite film.

Priority is claimed to Japanese Patent Application No. 2021-090213, filed May 28, 2021, the contents of which are incorporated herein by reference.

BACKGROUND OF THE ART

[0002]

Anisotropic electrical steel sheet is mainly used in transformer. The transformer is continuously excited over a long period of time from installation to shutdown, so that continuous loss of energy occurs. Therefore, the energy loss that occurs when a transformer is magnetized by alternating current, i.e. magnetic loss, is the main parameter that determines the performance of a transformer.

[0003]

In order to reduce the magnetic loss of anisotropic electrical steel sheet, various methods have been developed. Examples of such methods include a method for highly aligning grains in a {110}<001> orientation called Goss orientation in a crystal structure, a method for increasing the content of a solid solution element such as Si which increases the electrical resistance of a steel sheet, and a method for reducing the thickness of a steel sheet .

[0004]

In addition, it is known that a method of applying tension to a steel sheet is effective in reducing magnetic loss. Thus, in most cases, in order to reduce magnetic loss, an insulating coating is formed on the surface of the anisotropic electrical steel sheet. This coating imparts tension to the anisotropic electrical steel sheet, and thereby reduces magnetic losses in a single steel sheet. In addition, this coating guarantees interlayer electrical insulation when anisotropic electrical steel sheets are used in laminated form, thereby reducing magnetic losses in the core.

[0005]

For example, as a coated anisotropic electrical steel sheet, a forsterite film, which is an oxide film including Mg, is formed on the surface of the base steel sheet, and then an insulating coating is formed on the surface of the forsterite film. In this case, the coating on the base steel sheet includes a forsterite film and an insulating coating. Both the forsterite film and the insulating coating have the function of providing electrical insulation and the function of applying tension to the base steel sheet.

[0006]

The forsterite film is formed during finishing annealing, in which secondary recrystallization in the steel sheet is caused by the reaction of an annealing separator containing mainly magnesium oxide (MgO) with silicon dioxide (SiO ₂ ) formed on the base steel sheet during decarburization annealing, at heat treatment at temperatures from 900 to 1200°C for 30 hours or more.

[0007]

The insulating coating is formed by applying a film-forming solution including, for example, phosphoric acid or phosphate, colloidal silica and chromic anhydride or chromate to the steel sheet after finishing annealing and subjecting it to baking and drying at 300-950°C for 10 seconds or more.

[0008]

In order for the coating to provide the functions of providing insulation and applying tension to the base steel sheet, sufficient adhesion between the coating and the base steel sheet is required.

[0009]

Generally, the above adhesion is mainly achieved by the anchoring effect caused by the roughness of the interface between the base steel sheet and the forsterite film. However, in recent years, it has been found that the roughness of the interface becomes an obstacle to the movement of the magnetic domain wall when the anisotropic electrical steel sheet is magnetized, and thus the roughness is also a factor that prevents the reduction of magnetic loss.

[0010]

For example, Patent Document 1 and Patent Document 2 disclose a technique for forming an insulating coating even in a state in which the surface of the base steel sheet has no forsterite and is made smooth to further reduce magnetic loss.

[0011]

In the method for producing an anisotropic electrical steel sheet disclosed in Patent Document 1, the forsterite film is removed by etching and the like, and then the surface of the base steel sheet is smoothed by chemical or electrolytic polishing. In the method for producing an anisotropic electrical steel sheet disclosed in Patent Document 2, the formation of a forsterite film itself is suppressed by using an annealing separator containing alumina (Al ₂ O ₃ ) for finishing annealing, and thereby the surface of the base steel sheet is smoothed.

[0012]

However, in the production methods disclosed in Patent Document 1 and Patent Document 2, there is a problem that the insulating coating is difficult to adhere to the surface of the base steel sheet (sufficient adhesion is not achieved) in the case where the insulating coating is formed in contact with surface of the main steel sheet (directly on the surface of the main steel sheet).

[0013]

For example, Patent Document 3 and Patent Document 4 disclose a technique for improving the adhesion of an insulating coating by controlling the state of the insulating coating or by controlling the state of an intermediate layer that is located between the base steel sheet and the insulating coating to ensure adhesion of the coating.

[0014]

In the anisotropic electrical steel sheet disclosed in Patent Document 3, the insulating coating has a layer containing crystalline phosphide. In the anisotropic electrical steel sheet disclosed in Patent Document 4, the intermediate layer has a local oxidation region, and the thickness of the intermediate layer in the region where the local oxidation region is included is 50 nm or more.

BACKGROUND DOCUMENTS

PATENT DOCUMENTS

[0015]

[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. S49-096920

[Patent Document 2] PCT International Patent Application No. WO2002/088403

[Patent Document 3] PCT International Patent Application No. WO2019/013353

[Patent Document 4] PCT International Patent Application No. WO2019/013350

SUMMARY OF THE INVENTION

PROBLEMS SOLVED BY THE INVENTION

[0016]

As described above, in order to reduce the magnetic loss of the anisotropic electrical steel sheet, it is effective to smooth the surface of the base steel sheet in the anisotropic electrical steel sheet. However, when the surface of the base steel sheet is made smooth, the adhesion of the insulating coating is deteriorated.

[0017]

In the techniques disclosed in Patent Document 1 and Patent Document 2, the adhesion of the coating is insufficient. In addition, although the adhesion of the coating is undoubtedly improved by the techniques disclosed in Patent Document 3 and Patent Document 4, it is preferable that in the anisotropic electrical steel sheet, the adhesion of the coating can be further improved.

[0018]

The present invention has been made in view of the above facts. It is an object of the present invention to provide an anisotropic electrical steel sheet having excellent insulating coating adhesion even without a forsterite film.

REMEDIES FOR SOLVING THE PROBLEM

[0019]

Aspects of the present invention are as follows.

(1) The anisotropic electrical steel sheet according to one aspect of the present invention includes:

a base steel sheet, which is a silicon steel sheet;

an intermediate layer in contact with the silicon steel sheet; And

an insulating coating in contact with the intermediate layer,

in which the intermediate layer is an oxide film satisfying:

20 at.% or more and 70 at.% or less Si content;

30 at.% or more and 80 at.% or less O content;

less than 20 at.% Mg content;

less than 5 at.% P content; And

less than 20 at.% Fe content, and

the average thickness of the oxide film is 2 nm or more and 500 nm or less,

wherein the insulating coating is a phosphate based coating satisfying:

5 at.% or more and 30 at.% or less P content;

5 at.% or more and 30 at.% or less Si content;

30 at.% or more and 80 at.% or less O content;

1 at.% or more and less than 25 at.% Fe content;

less than 1.0 at.% Cr content;

0 at.% or more and 10 at.% or less Al content;

0 at.% or more and 10 at.% or less Mg content;

0 at.% or more and 10 at.% or less Mn content;

0 at.% or more and 10 at.% or less Ni content;

0 at.% or more and 10 at.% or less Zn content;

0.1 at.% or more and 10 at.% or less of the total content of Al, Mg, Mn, Ni and Zn;

0 at.% or more and 10 at.% or less V content;

0 at.% or more and 10 at.% or less W content;

0 at.% or more and 10 at.% or less Zr content;

0 at.% or more and 10 at.% or less Co content;

0 at.% or more and 10 at.% or less Mo content; And

0.1 at.% or more and 10 at.% or less of the total content of V, W, Zr, Co and Mo, and

the average thickness of the phosphate-based coating is 0.1 µm or more and 10 µm or less, and

wherein the phosphate-based coating includes a first crystalline phosphorus oxide having a crystal structure of the formula Fe ₂ P ₂ O ₇ and a second crystalline phosphorus oxide having a crystal structure of the formula Fe ₇ (P ₂ O ₇ ) ₄ , and

the second crystalline phosphorus oxide includes at least one element selected from the group consisting of V, W, Zr, Co and Mo.

(2) In anisotropic electrical steel sheet according to item (1)

when the phosphate-based coating is divided along the thickness direction in a section whose cutting direction is parallel to the thickness direction into two equal regions, which are the internal region in contact with the oxide film and the surface region not in contact with the oxide film,

the proportion of the total area of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide that are included in the inner region may be greater than the proportion of the total area of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide that are included in the surface region.

(3) In an anisotropic electrical steel sheet according to item (1) or (2)

the proportion of the total area of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide that are included in the surface region may be 0% or more and 30% or less, and the proportion of the total area of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide that are included in the inner region , may be 3% or more and 50% or less.

(4) In the anisotropic electrical steel sheet according to any one of claims. (13),

when the inner region is divided along the sectional thickness direction into two equal regions, which are the first inner region in contact with the oxide film and the second inner region not in contact with the oxide film,

when the proportion of the first region is set as a percentage value obtained by dividing the area fraction of the second crystalline phosphorus oxide that is included in the first internal region by the total area fraction of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide that are included in the first internal region, and

when the proportion of the second region is set as a percentage value obtained by dividing the area fraction of the second crystalline phosphorus oxide that is included in the second internal region by the total area fraction of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide that are included in the second internal region,

the share of the second region may be greater than that of the first region.

(5) In the anisotropic electrical steel sheet according to any one of claims. (14),

said portion of the first region is 0% or more and 70% or less, and said portion of the second region may be 50% or more and 100% or less.

(6) In the anisotropic electrical steel sheet according to any one of claims. (15),

the diameter of the equivalent circle of the second crystalline phosphorus oxide may be on average 5 nm or more and 300 nm or less.

USEFUL EFFECTS OF THE INVENTION

[0020]

According to the above-described aspects of the present invention, it is possible to provide an anisotropic electrical steel sheet having excellent insulation coating adhesion even without a forsterite film.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]

Fig. 1 is a schematic cross-sectional view of an anisotropic electrical steel sheet in accordance with one embodiment of the present invention.

Fig. 2 is a schematic cross-sectional view of an anisotropic electrical steel sheet in accordance with one preferred embodiment of the present invention.

Fig. 3 is a flow chart illustrating a method for producing an anisotropic electrical steel sheet in accordance with one embodiment of the present invention.

OPTIONS FOR IMPLEMENTING THE INVENTION

[0022]

One preferred embodiment of the present invention will now be described in detail. However, the present invention is not limited only to the configuration that is disclosed in this embodiment, and various modifications are possible without departing from the spirit of the present invention. In addition, the limiting range described below includes its lower limit and its upper limit. However, a value expressed as "greater than" or "less than" is not included in this range. Unless otherwise specified, "%" of the amount of the corresponding elements expresses "wt.%" for the base steel sheet and "at.%" for the intermediate layer and insulating coating.

[0023]

Fig. 1 is a schematic cross-sectional view of an anisotropic electrical steel sheet in accordance with one embodiment of the present invention. As shown in FIG. 1, in a section whose cutting direction is parallel to the thickness direction, the anisotropic electrical steel sheet according to the embodiment does not include a forsterite film on the surface of the main steel sheet 1, but includes an intermediate layer 2 which mainly contains silicon oxide and which located on the surface of the main steel sheet 1 and includes an insulating coating 3 obtained from phosphate and colloidal silica, which is located on the intermediate layer 2.

[0024]

Specifically, the anisotropic electrical steel sheet according to an embodiment includes:

a base steel sheet, which is a silicon steel sheet;

an intermediate layer in contact with the silicon steel sheet; And

an insulating coating in contact with the intermediate layer,

in which the intermediate layer is an oxide film satisfying:

20 at.% or more and 70 at.% or less Si content;

30 at.% or more and 80 at.% or less O content;

less than 20 at.% Mg content;

less than 5 at.% P content; And

less than 20 at.% Fe content, and

the average thickness of the oxide film is 2 nm or more and 500 nm or less,

wherein the insulating coating is a phosphate based coating satisfying:

5 at.% or more and 30 at.% or less P content;

5 at.% or more and 30 at.% or less Si content;

30 at.% or more and 80 at.% or less O content;

1 at.% or more and less than 25 at.% Fe content;

less than 1.0 at.% Cr content;

0 at.% or more and 10 at.% or less Al content;

0 at.% or more and 10 at.% or less Mg content;

0 at.% or more and 10 at.% or less Mn content;

0 at.% or more and 10 at.% or less Ni content;

0 at.% or more and 10 at.% or less Zn content;

0.1 at.% or more and 10 at.% or less of the total content of Al, Mg, Mn, Ni and Zn;

0 at.% or more and 10 at.% or less V content;

0 at.% or more and 10 at.% or less W content;

0 at.% or more and 10 at.% or less Zr content;

0 at.% or more and 10 at.% or less Co content;

0 at.% or more and 10 at.% or less Mo content; And

0.1 at.% or more and 10 at.% or less of the total content of V, W, Zr, Co and Mo, and

the average thickness of the phosphate-based coating is 0.1 µm or more and 10 µm or less, and

wherein the phosphate-based coating includes a first crystalline phosphorus oxide having a crystal structure of the formula Fe ₂ P ₂ O ₇ and a second crystalline phosphorus oxide having a crystal structure of the formula Fe ₇ (P ₂ O ₇ ) ₄ , and

the second crystalline phosphorus oxide includes at least one element selected from the group consisting of V, W, Zr, Co and Mo.

[0025]

As described above, in the anisotropic electrical steel sheet according to the embodiment, the intermediate layer is not a forsterite film but a Si-based oxide film, and the insulating coating is a phosphate-based coating that includes a first crystalline phosphorus oxide and a second crystalline phosphorus oxide, which is the main technical features.

[0026]

Each feature is described in detail below. First, a phosphate coating of an anisotropic electrical steel sheet according to an embodiment will be described.

[0027]

<Phosphate based coating>

The phosphate-based coating is located on the outer surface of the layered structure of the anisotropic electrical steel sheet. The phosphate coating is formed on the base steel sheet at high temperature using a material having a lower coefficient of thermal expansion than the base steel sheet. During cooling, a difference in shrinkage occurs between the phosphate coating and the base steel sheet, and as a result, the phosphate coating applies tension to the base steel sheet. In the case where tension is applied to the base steel sheet in the anisotropic electrical steel sheet, the magnetic loss performance is greatly improved.

[0028]

In order for the phosphate coating to apply tension to the base steel sheet, it is important that the phosphate coating and the base steel sheet are bonded to each other. In the anisotropic electrical steel sheet according to the embodiment, to improve the adhesion of the coating, the composition and thickness of the phosphate coating is controlled, and a plurality of crystalline phosphorus oxides are included in the phosphate coating.

[0029]

The composition of the phosphate based coating is described below.

[0030]

In the anisotropic electrical steel sheet according to the embodiment, the phosphate-based coating includes essential elements and optional elements as necessary as a coating composition. In addition, it is preferable that the remainder, in addition to essential elements and optional elements, consists of impurities.

[0031]

In particular, phosphate based coating can satisfy the main elements:

5 at.% or more and 30 at.% or less P content;

5 at.% or more and 30 at.% or less Si content;

30 at.% or more and 80 at.% or less O content; And

1 at.% or more and less than 25 at.% Fe content.

In addition, a phosphate-based coating can satisfy optional elements:

0 at.% or more and 10 at.% or less Al content;

0 at.% or more and 10 at.% or less Mg content;

0 at.% or more and 10 at.% or less Mn content;

0 at.% or more and 10 at.% or less Ni content;

0 at.% or more and 10 at.% or less Zn content;

0.1 at.% or more and 10 at.% or less of the total content of Al, Mg, Mn, Ni and Zn;

0 at.% or more and 10 at.% or less V content;

0 at.% or more and 10 at.% or less W content;

0 at.% or more and 10 at.% or less Zr content;

0 at.% or more and 10 at.% or less Co content;

0 at.% or more and 10 at.% or less Mo content; And

0.1 at.% or more and 10 at.% or less of the total content of V, W, Zr, Co and Mo.

In addition, phosphate based coating can satisfy impurities:

less than 1.0 at.% Cr content.

[0032]

In most cases, the phosphate coating of anisotropic electrical steel sheet is formed by baking a film-forming solution including phosphate, colloidal silica and chromate. Chromate is included to improve corrosion resistance, chemical resistance and void suppression.

[0033]

On the other hand, the phosphate coating of an anisotropic electrical steel sheet according to an embodiment is formed by baking a film-forming solution including phosphate and colloidal silica but not including chromate. Thus, as described above, in the phosphate-based coating of the anisotropic electrical steel sheet according to the embodiment, the Cr content is limited to less than 1.0 at.%. This content is preferably 0.8 at.% or less, and more preferably 0.5 at.% or less.

[0034]

In the anisotropic electrical steel sheet according to the embodiment, limiting the Cr content in the phosphate-based coating to less than 1.0 at.% is one of the conditions for controlling the formation of the above-mentioned first crystalline phosphorus oxide and second crystalline phosphorus oxide in the phosphate-based coating. The conditions for the formation of these crystalline phosphorus oxides are described in detail below.

[0035]

P, Si, O and Fe, which are the main elements of the above-mentioned phosphate-based coating, are obtained from phosphate and colloidal silica contained in the film-forming solution, oxidation reaction during baking, elements diffusing from the base steel sheet, and the like. In addition, Al, Mg, Mn, Ni, Zn, V, W, Zr, Co and Mo, which are optional elements of the above phosphate coating, are obtained from the phosphate contained in the film-forming solution. For example, as the phosphate contained in the film-forming solution, at least one phosphate selected from the group consisting of Al, Mg, Mn, Ni, Zn, V, W, Zr, Co and Mo phosphates can be used. Preferably, at least one phosphate selected from the group consisting of Al, Mg, Mn, Ni and Zn phosphates may be used as the phosphate contained in the film-forming solution, and the phosphate-based coating may satisfy the condition of 0.1 at.% or more and 10 at.% or less of the total content of Al, Mg, Mn, Ni and Zn. For example, aluminum phosphate may be used as the phosphate contained in the film-forming solution, and the phosphate-based coating may satisfy the condition of 0.1 at.% or more and 10 at.% or less of Al content. In addition, at least one phosphate selected from the group consisting of Co, Mo, V, W and Zr can be used as the phosphate contained in the film-forming solution, and the phosphate-based coating can satisfy the condition of 0.1 at.% or more and 10 at.% or less of the total content of V, W, Zr, Co and Mo. In addition, the above-mentioned Cr is an impurity of the phosphate-based coating. The impurity comes from elements that come from the raw materials and the environment during the formation of the phosphate coating, or elements that diffuse from the base steel sheet. The lower limit of the impurity content is not particularly limited. Their content is preferably low, and may be 0%.

[0036]

In the anisotropic electrical steel sheet according to the embodiment, in order to improve coating adhesion, the phosphate-based coating composition may satisfy the above conditions. In particular, the Cr content in the phosphate-based coating is limited to less than 1.0 at.%.

[0037]

In addition, in the anisotropic electrical steel sheet according to the embodiment, in the phosphate-based coating composition (average coating composition), the P content is preferably more than 8 at.% and preferably less than 17 at.%, the Si content is preferably more less than 7 at.% and preferably less than 19 at.%, O content preferably greater than 58 at.% and preferably less than 66 at.%, Fe content preferably greater than 1 at.% and preferably less than 20 at.%. %, the Cr content is preferably less than 0.2 at.%, the Al content is preferably less than 10 at.% and preferably less than 3 at.%, the Mg content is preferably less than 10 at.% and preferably less than 3 at. .%, the Mn content is preferably less than 10 at.% and preferably less than 3 at.%, the Ni content is preferably less than 10 at.% and preferably less than 3 at.%, the Zn content is preferably less than 10 at.%. % and preferably less than 3 at.%, the total amount of Al, Mg, Mn, Ni and Zn is preferably 0.1 at.% or more, preferably more than 1 at.%, preferably less than 10 at.%, and preferably less than 3 at.%, the V content is preferably less than 3.0 at.% and preferably less than 2 at.%, the W content is preferably less than 3.0 at.% and preferably less than 2 at.%, the content Zr is preferably less than 3.0 at.% and preferably less than 2 at.%, Co content is preferably less than 3.0 at.% and preferably less than 2 at.%, Mo content is preferably less than 3.0 at.% and preferably less than 2 at.%, or the total amount of V, W, Zr, Co and Mo is preferably 0.1 at.% or more, preferably 0.2 at.% or more, preferably less than 3, 0 at.%, and preferably less than 2 at.%.

[0038]

To measure the composition of the phosphate coating, cross-sectional analysis can be performed using SEM-EDS (scanning electron microscope - energy dispersive X-ray spectroscopy) or TEM-EDS (transmission electron microscope - energy dispersive X-ray spectroscopy). The method for measuring the coating composition is described in detail below.

[0039]

The thickness of the phosphate based coating is described below.

[0040]

In the anisotropic electrical steel sheet according to the embodiment, in a section whose cutting direction is parallel to the thickness direction, the average thickness of the phosphate-based coating is 0.1 μm or more and 10 μm or less.

[0041]

When the average thickness of the phosphate-based coating is less than 0.1 μm, it is difficult to apply a predetermined tension to the base steel sheet. Thus, the average thickness is preferably 0.1 µm or more, and more preferably 0.5 µm or more.

[0042]

On the other hand, when the average thickness of the phosphate coating is more than 10 µm, cracks may occur in the phosphate coating during the formation process. Therefore, the average thickness is preferably 10 µm or less, and more preferably 5 µm or less.

[0043]

To measure the average thickness of the phosphate coating, linear cross-sectional analysis can be performed using SEM-EDS or TEM-EDS. The method for measuring average thickness is described in detail below.

[0044]

The crystalline phosphorus oxides contained in phosphate-based coatings are described below.

[0045]

In the anisotropic electrical steel sheet according to an embodiment, the phosphate-based coating includes a first crystalline phosphorus oxide whose crystal structure corresponds to the formula Fe ₂ P ₂ O ₇ and a second crystalline phosphorus oxide whose crystal structure corresponds to the formula Fe ₇ (P ₂ O ₇ ) ₄ .

[0046]

When the phosphate-based coating includes a first crystalline phosphorus oxide and a second crystalline phosphorus oxide, the adhesion of the coating is improved. The detailed cause is currently unclear, but the following mechanism is suggested. It appears that when crystalline phosphorus oxides are incorporated into an amorphous phosphate coating, the elasticity of the phosphate coating as a whole increases, the stress accumulated in the phosphate coating and the oxide film that is the intermediate layer are reduced without local concentration even under bending stress, in As a result, the phosphate-based coating becomes difficult to peel off. In particular, the second crystalline phosphorus oxide is believed to contribute significantly to the above effect.

[0047]

In order to form the first crystalline phosphorus oxide and the second crystalline phosphorus oxide in the phosphate-based coating, the following three conditions must be satisfied.

[0048]

(I) The intermediate layer is not a forsterite film, but a Si-based oxide film.

(II) The phosphate-based coating satisfies the condition of less than 1.0 at.% Cr content.

(III) Forming conditions are controlled during the formation of the phosphate-based coating.

Only when all three of these conditions are satisfied will both the first crystalline phosphorus oxide and the second crystalline phosphorus oxide be formed in the phosphate-based coating.

[0049]

First, as condition (I), it is important that the intermediate layer is not a forsterite film, but a Si-based oxide film. When the intermediate layer is a forsterite film, in addition to the fact that the coating adhesion problem does not initially occur, crystalline phosphorus oxides are not formed in the phosphate-based coating.

[0050]

The reason why crystalline phosphorus oxides do not form in the phosphate coating when the intermediate layer is a film of forsterite is currently unclear, but the following is speculated. For example, it appears that when the interlayer is a film of forsterite, the Fe content of the phosphate coating decreases, Fe continues to be in solid solution in the phosphate coating because the hydrogen content is low in the atmosphere during baking, and as a result in the phosphate coating Crystalline phosphorus oxides are not formed.

[0051]

Further, as condition (II), it is important that the Cr content of the phosphate-based coating is less than 1.0 at.%. When the Cr content in the phosphate-based coating is 1.0 at.% or more, the second crystalline phosphorus oxide in the phosphate-based coating is not formed even if the first crystalline phosphorus oxide is formed.

[0052]

The reason why the second crystalline phosphorus oxide is not formed in the phosphate-based coating when the Cr content of the phosphate-based coating is 1.0 at.% or more is currently not clear, but the following is speculated. When the Cr content in the phosphate-based coating is 1.0 at.% or more, (Fe, Cr) ₂ P ₂ O ₇ is formed in the phosphate-based coating. (Fe, Cr) ₂ P ₂ O ₇ tends to form preferentially. Thus, provided that (Fe, Cr) ₂ P ₂ O ₇ is formed in the phosphate coating, it is formed preferentially, and crystalline phosphorus oxide with the structure Fe ₇ (P ₂ O ₇ ) ₄ is difficult to form.

[0053]

On the other hand, when the Cr content in the phosphate-based coating is less than 1.0 at.%, (Fe, Cr) ₂ P ₂ O ₇ is not formed in the phosphate-based coating, and Fe ₂ P ₂ O ₇ is alternatively formed. However, Fe ₂ P ₂ O ₇ is not formed preferentially. Thus, provided that Fe ₂ P ₂ O ₇ is formed in the phosphate coating, crystalline phosphorus oxide with the structure Fe ₂ P ₂ O ₇ , as well as crystalline phosphorus oxide with the structure Fe ₇ (P ₂ O ₇ ) ₄ , is formed.

[0054]

Finally, as a condition (III), it is important that the molding conditions are controlled during the formation of the phosphate-based coating. When the molding conditions are not controlled during the formation of the phosphate-based coating, crystalline phosphorus oxide, especially the second crystalline phosphorus oxide, is not formed even if condition (I) and condition (II) are satisfied in the phosphate-based coating.

[0055]

In particular, as the molding conditions during the formation of the phosphate-based coating, it is important that the atmosphere and oxidation degree during baking are controlled, and the atmosphere, oxidation degree and cooling rate are controlled during cooling after baking. The production method will be described in detail below.

[0056]

The existence of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide can be confirmed using TEM. For example, electron beam diffraction is performed on a phosphate-based coating, the crystal structure of the crystal phase included in the area irradiated by the electron beam is identified from the electron beam diffraction pattern, and then it is confirmed whether the first crystalline phosphorus oxide whose crystal structure corresponds to the formula Fe ₂ is included P ₂ O ₇ , and a second crystalline phosphorus oxide, the crystal structure of which corresponds to the formula Fe ₇ (P ₂ O ₇ ) ₄ . The identification method for crystalline phosphorus oxide is described in detail below.

[0057]

In the anisotropic electrical steel sheet according to the embodiment, by simultaneously incorporating the first crystalline phosphorus oxide and the second crystalline phosphorus oxide into the phosphate-based coating, the adhesion of the coating is improved. Thus, the composition, morphology and size of crystalline phosphorus oxide are not particularly limited. However, in order to favorably improve the adhesion of the coating, it is preferable that the composition, morphology and size of crystalline phosphorus oxide satisfy the following characteristics.

[0058]

In the anisotropic electrical steel sheet according to the embodiment, it is preferable that the phosphate coating satisfies the condition of 0.1 at.% or more and 10 at.% or less of the total content of V, W, Zr, Co and Mo, and that the second crystalline the phosphorus oxide included at least one element selected from the group consisting of V, W, Zr, Co and Mo.

[0059]

When the phosphate-based coating satisfies the condition of 0.1 at.% or more and 10 at.% or less of the total content of V, W, Zr, Co and Mo, and when the above conditions (I) to (III) are satisfied, it is possible to form ( Fe, M) ₇ (P ₂ O ₇ ) ₄ as the second crystalline phosphorus oxide, the crystal structure of which corresponds to the formula Fe ₇ (P ₂ O ₇ ) ₄ . As used herein, the above-mentioned M corresponds to at least one element selected from the group consisting of V, W, Zr, Co and Mo.

[0060]

When (Fe, M) ₇ (P ₂ O ₇ ) ₄ is formed, and, for example, when elemental analysis is performed by irradiating the precipitates with an electron beam, the V, W, Zr, Co or Mo contained in the phosphate coating are detected as peak corresponding to an element in the EDS spectrum, and thus can be considered to be included as M in (Fe, M) ₇ (P ₂ O ₇ ) ₄ . In this case, the amount of second crystalline phosphorus oxides formed increases, and the influence of the individual second crystalline phosphorus oxides formed on the adhesion of the coating increases favorably. As a result, coating adhesion is significantly improved.

[0061]

Moreover, in the anisotropic electrical steel sheet according to the embodiment, it is preferable that in a section whose cutting direction is parallel to the thickness direction when the phosphate-based coating is divided into two equal regions, which are the inner region in contact with the oxide film and the surface region not in contact with the oxide film, the total area fraction of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide included in the inner region was greater than the total area fraction of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide included in the surface region.

[0062]

It appears that when the first crystalline phosphorus oxide and the second crystalline phosphorus oxide are more included in the internal region than in the surface region of the phosphate coating, the elasticity of the phosphate coating as a whole is favorably increased, stress is favorably reduced even under bending loads, resulting in which makes the phosphate-based coating difficult to peel off.

[0063]

For example, it is preferable that the proportion of the total area of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide that are included in the surface region is 0% or more and 30% or less, and the proportion of the total area of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide that included in the inner region was 3% or more and 50% or less.

[0064]

When the first crystalline phosphorus oxide and the second crystalline phosphorus oxide are more included in the inner region than in the surface region of the phosphate-based coating, and when the total area proportions of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide are within the above-mentioned ranges, the elasticity of the phosphate-based coating phosphate content generally favorably increases and coating adhesion improves to a greater extent.

[0065]

Moreover, in the anisotropic electrical steel sheet according to the embodiment, it is preferable that:

in a section whose cutting direction is parallel to the thickness direction, when the inner region is divided into two equal regions, which are the first inner region in contact with the oxide film and the second inner region not in contact with the oxide film,

when the proportion of the first region is set as a percentage value obtained by dividing the area fraction of the second crystalline phosphorus oxide that is included in the first internal region by the total area fraction of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide that are included in the first internal region, and

when the proportion of the second region is set as a percentage value obtained by dividing the area fraction of the second crystalline phosphorus oxide that is included in the second internal region by the total area fraction of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide that are included in the second internal region,

the share of the second region is greater than the share of the first region.

[0066]

When the second crystalline phosphorus oxide in the inner region is incorporated more into the second inner region than into the first inner region, the elasticity of the phosphate coating as a whole is favorably increased, the stress is favorably reduced even under bending loads, resulting in the phosphate coating becoming difficult to delaminate.

[0067]

For example, it is preferable that the proportion of the first region is 0% or more and 70% or less, and the proportion of the second region is 50% or more and 100% or less.

[0068]

When the second crystalline phosphorus oxide in the inner region is more included in the second inner region than in the first inner region, and when the proportion of the second region is within the above-mentioned range, the elasticity of the phosphate-based coating as a whole is further favorably increased, and the adhesion of the coating is improved to a greater extent.

[0069]

Fig. 2 is a schematic cross-sectional view of an anisotropic electrical steel sheet in accordance with one preferred embodiment of the present invention. In FIG. 2 shows the surface region 32, the inner region 31, the first inner region 31a and the second inner region 31b in the phosphate-based coating 3 (insulating coating 3).

[0070]

Moreover, in the anisotropic electrical steel sheet according to the embodiment, it is preferable that the diameter of the area-equivalent circle of the second crystalline phosphorus oxide is on average 5 nm or more and 300 nm or less.

[0071]

When the diameter of the area-equivalent circle of the second crystalline phosphorus oxide is within the above-mentioned range, the effect of the second crystalline phosphorus oxides on the adhesion of the coating is favorably increased. As a result, coating adhesion is significantly improved. The diameter of the area equivalent circle of the second crystalline phosphorus oxide is preferably 20 nm or more and 220 nm or less.

[0072]

The presence of V, W, Zr, Co or Mo in crystalline phosphorus oxide, the location and area fraction of crystalline phosphorus oxide, and the diameter of the equivalent area circle of crystalline phosphorus oxide can be measured using SEM-EDS or TEM-EDS. The measurement methods are described in detail below.

[0073]

Next, the oxide film that is the intermediate layer of the anisotropic electrical steel sheet according to the embodiment will be described.

[0074]

<Oxide Film>

The oxide film is located between the phosphate-based coating and the base steel sheet in the layer structure of the anisotropic electrical steel sheet. This oxide film is not a forsterite film, but is a Si-based oxide film, and has the function of adhering the phosphate-based coating to the base steel sheet.

[0075]

The composition of the oxide film is described below.

[0076]

In the anisotropic electrical steel sheet according to the embodiment, the phosphate-based coating includes essential elements and optional elements as required. In addition, it is preferable that the remainder, in addition to essential elements and optional elements, consists of impurities.

[0077]

In particular, the oxide film can satisfy the conditions for the main elements:

20 at.% or more and 70 at.% or less Si content; And

30 at.% or more and 80 at.% or less O content.

In addition, the oxide film may include constituent elements of the base steel sheet as optional elements, and the total amount thereof may be 0.1 at.% or more and 20 at.% or less.

In addition, the oxide film may satisfy the following conditions for impurities:

less than 20 at.% Mg content;

less than 5 at.% P content; And

less than 20 at.% Fe content.

[0078]

In general, in an anisotropic electrical steel sheet, a forsterite film (a film that mainly includes Mg ₂ SiO ₄ ) is formed as an intermediate layer by applying an annealing separator consisting mainly of MgO to the annealed decarburized steel sheet and then finishing annealing it steel sheet.

[0079]

When a forsterite film is formed, the adhesion of the coating is ensured by the anchoring effect that occurs due to the unevenness of the interface between the base steel sheet and the forsterite film. However, the interface roughness becomes an obstacle to the movement of the magnetic domain wall when the anisotropic electrical steel sheet is magnetized, which has a negative effect on the magnetic loss characteristics.

[0080]

In the anisotropic electrical steel sheet according to the embodiment, there is no forsterite film, and the interface between the intermediate layer and the main steel sheet is smooth. In addition to ensuring smoothness of the interface, the first crystalline phosphorus oxide and the second crystalline phosphorus oxide are formed in the phosphate-based coating by satisfying the above conditions (I) to (III) to improve the adhesion of the coating. As explained in the above condition (I), it is necessary to control the intermediate layer so that it is not a forsterite film, but a Si-based oxide film.

[0081]

Thus, as described above, in the oxide film (intermediate layer) of the anisotropic electrical steel sheet according to the embodiment, the Mg content is limited to less than 20 at.%. The Mg content is preferably 15 at.% or less, and more preferably 10 at.% or less. The conditions for the formation of not a forsterite film, but an oxide film (intermediate layer) are described in detail below.

[0082]

Si and O, which are the main elements of the above oxide film, are obtained from the constituent elements of the base steel sheet and the oxidation reaction during the formation of the oxide film. In addition, the above-mentioned Mg, P and Fe are oxide film impurities. These impurities are derived from elements that come from the raw materials and the environment, or elements that diffuse from the base steel sheet or phosphate coating. The lower limit of the impurity content is not particularly limited. Their content is preferably low, and may be 0%.

[0083]

In addition, in the anisotropic electrical steel sheet according to the embodiment, in the oxide film composition (average film composition), the Si content is preferably more than 26 at.% and preferably less than 44 at.%, the O content is preferably more than 38 at.%. % and preferably less than 68 at.%, the Mg content is preferably less than 20 at.%, the P content is preferably less than 5 at.%, or the Fe content is preferably less than 20 at.%.

[0084]

As with phosphate coating composition, cross-sectional composition analysis can be performed to measure oxide film composition using SEM-EDS or TEM-EDS. The method for measuring layer composition is described in detail below.

[0085]

The thickness of the oxide film is described below.

[0086]

In the anisotropic electrical steel sheet according to the embodiment, in a section whose cutting direction is parallel to the thickness direction, the average thickness of the oxide film is 2 nm more and 500 nm less.

[0087]

If the average thickness of the oxide film is less than 2 nm, the effect of thermal stress relaxation is insufficient. Thus, the average thickness is preferably 2 nm or more, and more preferably 5 nm or more.

[0088]

On the other hand, when the average thickness of the oxide film is more than 500 nm, the thickness becomes uneven and defects such as voids and cracks are formed in the film. Therefore, the average thickness is preferably 500 nm or less, and more preferably 400 nm or less.

[0089]

As with average phosphate coating thickness, linear cross-sectional analysis can be performed to measure average oxide film thickness using SEM-EDS or TEM-EDS. The method for measuring average thickness is described in detail below.

[0090]

Next, a base steel sheet of an anisotropic electrical steel sheet according to an embodiment will be described.

[0091]

<Main steel sheet>

The base steel sheet is the base material of anisotropic electrical steel sheet and is a silicon steel sheet. In the silicon steel sheet, the Si content can be 0.8 mass% or more and 7.0 mass% or less, and the crystal orientation can be controlled to be a {110}<001> orientation (Goss orientation).

[0092]

As used herein, the {110}<001> orientation means that the {110} plane of the crystal is aligned parallel to the rolled surface and the <001> axis of the crystal is aligned parallel to the rolling direction.

[0093]

The composition of silicon steel sheet is described below.

[0094]

In the anisotropic electrical steel sheet according to the embodiment, since the composition of the silicon steel sheet does not directly affect the existence of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide in the phosphate-based coating, the composition of the silicon steel sheet is not particularly limited. Next, the preferred composition of the silicon steel sheet for the anisotropic electrical steel sheet will be described in detail. "%" in the composition of the silicon steel sheet is "% by weight".

[0095]

The silicon steel sheet may include in its chemical composition essential elements, optional elements as required, and a remainder of Fe and impurities.

[0096]

In particular, a silicon steel sheet may include in its chemical composition, in wt.%,

0.8% or more and 7.0% or less Si,

0% or more and 1.00% or less Mn,

0% or more and 0.30% or less Cr,

0% or more and 0.40% or less Cu,

0% or more and 0.50% or less P,

0% or more and 0.30% or less Sn,

0% or more and 0.30% or less Sb,

0% or more and 1.00% or less Ni,

0% or more and 0.008% or less B,

0% or more and 0.15% or less V,

0% or more and 0.2% or less Nb,

0% or more and 0.10% or less Mo,

0% or more and 0.015% or less Ti,

0% or more and 0.010% or less Bi,

0% or more and 0.005% or less Al,

0% or more and 0.005% or less C,

0% or more and 0.005% or less N,

0% or more and 0.005% or less S,

0% or more and 0.005% or less Se, and

residue consisting of iron and impurities.

[0097]

In an embodiment, the silicon steel sheet may include Si as a main element (main alloying element).

[0098]

0.8% or more and 7.0% or less Si

Si (silicon) in the chemical composition of silicon steel sheet is an element effective in increasing electrical resistance and reducing magnetic loss. When the Si content is more than 7.0%, the steel sheet may easily crack during cold rolling, and rolling may be difficult to carry out. On the other hand, when the Si content is less than 0.8%, the electrical resistance may decrease and the magnetic loss of the product may increase. Thus, 0.8% or more and 7.0% or less of Si may be included. The lower limit of the Si content is preferably 2.0%, more preferably 2.5%, and even more preferably 2.8%. The upper limit of the Si content is preferably 5.0%, and more preferably 3.5%.

[0099]

In an embodiment, the silicon steel sheet may include impurities. Impurities correspond to elements that contaminate steel during its industrial production from ores and scrap that are used as raw materials for steel production, or from the environment of the production process, etc.

[0100]

Moreover, in an embodiment, the silicon steel sheet may include optional elements in addition to essential elements and impurities. For example, instead of a portion of Fe constituting the remainder, the silicon steel sheet may include optional elements such as Mn, Cr, Cu, P, Sn, Sb, Ni, B, V, Nb, Mo, Ti, Bi, Al, C , N, S or Se. Depending on the purpose, optional elements may be included. Thus, the lower limit of the content of the corresponding optional elements need not be limited, and the lower limit may be 0 mass%. Moreover, even though optional elements may be included as impurities, this does not affect the above effects.

[0101]

0% or more and 1.00% or less Mn

As with Si, Mn (manganese) is an element effective in increasing electrical resistance and reducing magnetic loss. In addition, Mn acts as an inhibitor by binding to S or Se. Thus, 1.00% or less Mn may be included. The lower limit of the Mn content is preferably 0.05%, more preferably 0.08%, and even more preferably 0.09%. The upper limit of the Mn content is preferably 0.50 mass%, and more preferably 0.20 mass%.

[0102]

0% or more and 0.30% or less Cr

As with Si, Cr (chromium) is an element effective in increasing electrical resistance and reducing magnetic loss. Thus, 0.30% or less Cr may be included. The lower limit of the Cr content is preferably 0.02%, and more preferably 0.05%. The upper limit of the Cr content is preferably 0.20%, and more preferably 0.12%.

[0103]

0% or more and 0.40% or less Cu

Cu (copper) is also an element effective in increasing electrical resistance and reducing magnetic loss. Thus, 0.40% or less Cu may be included. When the Cu content is more than 0.40%, the magnetic loss reduction effect may be saturated, and surface defects called “copper skin” may occur during hot rolling. The lower limit of the Cu content is preferably 0.05%, and more preferably 0.10%. The upper limit of Cu content is preferably 0.30%, and more preferably 0.20%.

[0104]

0% or more and 0.50% or less P

P(phosphorus) is also an element effective in increasing electrical resistance and reducing magnetic loss. Thus, 0.50% or less of P may be included. When the P content is more than 0.50%, the rollability of the silicon steel sheet may be deteriorated. The lower limit of the P content is preferably 0.005%, and more preferably 0.01%. The upper limit of the P content is preferably 0.20%, and more preferably 0.15%.

[0105]

0% or more and 0.30% or less Sn

0% or more and 0.30% or less Sb

Sn (tin) and Sb (antimony) are elements effective in stabilizing secondary recrystallization, and thereby developing the {110}<001> orientation. Thus, 0.30% or less Sn and 0.30% or less Sb may be included. When the Sn content or Sb content is more than 0.30%, the magnetic performance may deteriorate.

The lower limit of the Sn content is preferably 0.02%, and more preferably 0.05%. The upper limit of the Sn content is preferably 0.15%, and more preferably 0.10%.

The lower limit of the Sb content is preferably 0.01%, and more preferably 0.03%. The upper limit of the Sb content is preferably 0.15%, and more preferably 0.10%.

[0106]

0% or more and 1.00% or less Ni

Ni (nickel) is also an element effective in increasing electrical resistance and reducing magnetic loss. In addition, Ni is an element effective for controlling the metallographic structure of hot-rolled steel sheet, and thereby improving the magnetic performance. Thus, 1.00% or less Ni may be included. When the Ni content is more than 1.00%, secondary recrystallization may be unstable. The lower limit of the Ni content is preferably 0.01%, and more preferably 0.02%. The upper limit of Ni content is preferably 0.20%, and more preferably 0.10%.

[0107]

0% or more and 0.008% or less B

B (boron) is an element effective as an inhibitor in the form of BN. Thus, 0.008% or less B may be included. When the B content is more than 0.008%, magnetic performance may deteriorate. The lower limit of the B content is preferably 0.0005%, and more preferably 0.001%. The upper limit of the B content is preferably 0.005%, and more preferably 0.003%.

[0108]

0% or more and 0.15% or less V

0% or more and 0.2% or less Nb

0% or more and 0.015% or less Ti

V (vanadium), Nb (niobium) and Ti (titanium) are elements that act as inhibitors by binding to N, C, etc. Thus, 0.15% or less of V, 0.2% or less of Nb, and 0.015% or less of Ti may be included. When these elements remain in the final product (electrical steel sheet) and the V content exceeds 0.15%, the Nb content exceeds 0.2%, or the Ti content exceeds 0.015%, the magnetic performance may deteriorate.

The lower limit of the V content is preferably 0.002%, and more preferably 0.01%. The upper limit of the V content is preferably 0.10%, and more preferably 0.05%.

The lower limit of the Nb content is preferably 0.005%, and more preferably 0.02%. The upper limit of Nb content is preferably 0.1%, and more preferably 0.08%.

The lower limit of the Ti content is preferably 0.002%, and more preferably 0.004%. The upper limit of the Ti content is preferably 0.010%, and more preferably 0.008%.

[0109]

0% or more and 0.10% or less Mo

Mo (molybdenum) is also an element effective in increasing electrical resistance and reducing magnetic loss. Thus, 0.10% or less Mo may be included. When the Mo content is more than 0.10%, the rollability of the silicon steel sheet may be deteriorated. The lower limit of the Mo content is preferably 0.005%, and more preferably 0.01%. The upper limit of the Mo content is preferably 0.08%, and more preferably 0.05%.

[0110]

0% or more and 0.010% or less Bi

Bi (bismuth) is an element effective in stabilizing precipitates such as sulfides and the like, thereby improving the function of inhibitors. Thus, 0.010% or less Bi may be included. When the Bi content is more than 0.010%, the magnetic performance may deteriorate. The lower limit of the Bi content is preferably 0.001%, and more preferably 0.002%. The upper limit of Bi content is preferably 0.008%, and more preferably 0.006%.

[0111]

0% or more and 0.005% or less Al

Al (aluminium) is an element effective as an inhibitor when binding to N. Thus, 0.01 to 0.065% Al may be included before finishing annealing, for example, at the slab stage. However, when Al remains as an impurity in the final product (electrical steel sheet), and when the Al content is more than 0.005%, the magnetic performance may deteriorate. Thus, the Al content in the final product is preferably 0.005% or less. The upper limit of Al content in the final product is preferably 0.004%, and more preferably 0.003%. Herein, since Al is an impurity in the final product, the lower limit of its content is not particularly limited and is preferably low. Since it is industrially difficult to make the Al content of the final product 0%, the lower limit of the Al content of the final product may be more than 0% or 0.0005%. The above Al content means the acid-soluble Al content.

[0112]

0% or more and 0.005% or less C

0% or more and 0.005% or less N

C (carbon) is an element effective in controlling the primary recrystallization structure and improving magnetic performance. N (nitrogen) is an element that effectively acts as an inhibitor by binding to Al, B and the like. Thus, 0.02 to 0.10% C may be included before decarburization annealing, for example at the slab stage. In addition, 0.01 to 0.05% N may be included before finishing annealing, for example, in the post-nitriding annealing step. However, when these elements remain as impurities in the final product, and when the C content and N content are more than 0.005%, respectively, the magnetic performance may deteriorate. Thus, the C content and N content of the final product are preferably 0.005% or less, respectively. The C content and N content of the final product are preferably 0.004% or less, respectively, and more preferably 0.003% or less, respectively. Moreover, the total content of C and N in the final product is preferably 0.005% or less. Herein, since C and N are impurities in the final product, their content is not particularly limited and is preferably low. Since it is industrially difficult to make the C content and N content of the final product 0%, the C content and N content of the final product may be more than 0%, respectively, or 0.0005% or more, respectively.

[0113]

0% or more and 0.005% or less S

0% or more and 0.005% or less Se

S (sulfur) and Se (selenium) are elements that effectively act as an inhibitor by binding to Mn and the like. Thus, 0.005 to 0.050% S and 0 to 0.005% Se may be included before finishing annealing, for example at the slab stage. However, when these elements remain as impurities in the final product, and when the S content and Se content are more than 0.005%, respectively, the magnetic performance may deteriorate. Thus, the S content and Se content in the final product are preferably 0.005% or less, respectively. S content The Se content in the final product is preferably 0.004% or less, respectively, and more preferably 0.003% or less, respectively. Moreover, the total content of S and Se in the final product is preferably 0.005% or less. Herein, since S and Se are impurities in the final product, their content is not particularly limited and is preferably low. Since it is industrially difficult to make the S content and Se content of the final product 0%, the S content and Se content of the final product may be more than 0%, respectively, or 0.0005% or more, respectively.

[0114]

In an embodiment, the silicon steel sheet may optionally include, in wt.%, at least one element selected from the group consisting of:

0.05% or more and 1.00% or less Mn,

0.02% or more and 0.30% or less Cr,

0.05% or more and 0.40% or less Cu,

0.05% or more and 0.50% or less P,

0.02% or more and 0.30% or less Sn,

0.01% or more and 0.30% or less Sb,

0.01% or more and 1.00% or less Ni,

0.0005% or more and 0.008% or less B,

0.002% or more and 0.15% or less V,

0.005% or more and 0.2% or less Nb,

0.005% or more and 0.10% or less Mo,

0.002% or more and 0.015% or less Ti, and

0.001% or more and 0.010% or less Bi.

[0115]

The chemical composition of silicon steel can be measured using typical analytical methods. The method for measuring steel composition is described in detail below.

[0116]

Next, other features of the silicon steel sheet will be described.

[0117]

In the anisotropic electrical steel sheet according to the embodiment, it is preferable that the silicon steel sheet has a texture aligned with the {110}<001> orientation. When a silicon steel sheet is controlled to obtain Goss orientation, the magnetic performance is greatly improved.

[0118]

Moreover, the thickness of the silicon steel sheet is not particularly limited. In order to reduce magnetic loss, the thickness is on average preferably 0.35 mm or less, and more preferably 0.30 mm or less. The lower limit of the thickness of the silicon steel sheet is not particularly limited, but may be 0.10 mm in terms of equipment and cost.

[0119]

Moreover, it is preferable that the surface roughness of the silicon steel sheet (the roughness of the interface between the intermediate layer and the main steel sheet) is small. For example, with regard to the surface roughness of the silicon steel sheet, the arithmetic mean roughness (Ra) is preferably 0.5 μm or less, and more preferably 0.3 μm or less. The lower limit of the arithmetic mean roughness (Ra) of the base steel sheet is not particularly limited, but may be 0.1 μm because the magnetic loss reduction improving effect may be saturated when it is 0.1 μm or less.

[0120]

In the anisotropic electrical steel sheet according to the embodiment, due to the above-mentioned feature, the adhesion of the coating is excellent even without the forsterite film. Thus, the magnetic loss characteristics are significantly improved.

[0121]

Next, a method for measuring each feature of the anisotropic electrical steel sheet described above will be described in detail.

[0122]

<Measurement method for technical features>

First, the layer structure of the anisotropic electrical steel sheet described above can be identified, for example, by the following method.

[0123]

The test sample is cut from an anisotropic electrical steel sheet, and the layer structure of the test sample is observed using a scanning electron microscope (SEM) or transmission electron microscope (TEM). For example, a layer with a thickness of 300 nm or more can be observed using SEM, and a layer with a thickness less than 300 nm can be observed with TEM.

[0124]

Specifically, first a test piece is cut so that the cutting direction is parallel to the thickness direction (more specifically, the test piece is cut so that the section is parallel to the thickness direction and perpendicular to the rolling direction), and the structure of this section is observed using SEM with magnification at which each layer is included in the observed field of view. For example, when observing with a composite image of reflected electrons (COM image), it can be concluded how many layers the cross-section structure includes. For example, in a COMP image, the steel sheet may be depicted in a light color, the intermediate layer in a dark color, and the insulation coating in an intermediate color.

[0125]

In order to identify each layer in the cross-sectional structure, linear analysis is performed along the thickness direction using SEM-EDS, and a quantitative analysis of the chemical composition of each layer is performed. For example, the elements to be quantified are the five elements Fe, P, Si, O and Mg. The analysis device is not particularly limited. For example, SEM (NB5000 from Hitachi High-Tech Corporation), EDS (XFlash (r) 6|30 from Bruker AXS) and EDS analytical software (ESPRIT 1.9 from Bruker AXS) can be used.

[0126]

Based on the COMP image observation results and the SEM-EDS quantitative analysis results, the base steel sheet is evaluated as the region that is the layer located at the deepest position along the thickness direction, which has a Fe content of 80 at.% or more and an O content of 30 at.% or less, excluding measurement noise, and which has a linear segment (thickness) of 300 nm or more on the scan line in the linear analysis. Moreover, the area other than the base steel sheet is considered to be glass film and insulating coating.

[0127]

Regarding the region other than the main steel sheet identified above, based on the observation results of the COMP image and the quantitative analysis results by SEM-EDS, the phosphate coating is considered to be the region in which the Fe content is less than 80 at.%, the P content is 5 at.% or more, the Si content is 5 at.% or more, and the O content is 30 at.% or more, excluding measurement noise, and which has a linear segment (thickness) of 300 nm or more on the scan line in linear analysis . Moreover, the phosphate-based coating may include aluminum, magnesium, nickel, manganese, and the like derived from phosphate, in addition to the above four elements that are used to judge the phosphate-based coating.

[0128]

To determine an area that is a phosphate-based coating, precipitates, inclusions, voids, etc., which are contained in the coating are not considered as the purpose of evaluation, and the area that satisfies the quantitative analysis as a matrix is evaluated as being a phosphate-based coating . For example, when selections, inclusions, voids, etc. on the scan line in linear analysis are confirmed from the COMP image or linear analysis results, this area is not considered for evaluation, and the coverage is determined by the quantitative analysis results as a matrix. Precipitates, inclusions, and voids can be distinguished from the matrix by contrast in the COMP image, as well as by quantitative analysis of the constituent elements. When evaluating a phosphate-based coating, it is preferable that the evaluation be performed at a position that does not include highlights, inclusions, and voids in the scan line of the linear analysis.

[0129]

When a certain region excludes the base steel sheet and the phosphate-based coating identified above, and the line segment (thickness) on the linear analysis scan line corresponding to that region is 300 nm or more, that region is defined as an intermediate layer.

[0130]

The intermediate layer may satisfy the conditions of an Fe content of less than 80 at.%, a P content of less than 5 at.%, a Si content of 20 at.% or more, and an O content of 30 at.% or more. In addition, when the intermediate layer is not a forsterite film but an oxide film mainly containing silicon oxide, the intermediate layer can satisfy the condition of an Mg content of less than 20 at.%. In addition, the results of the quantitative analysis of the interlayer do not include the results of the analysis of precipitates, inclusions, voids, etc. contained in the intermediate layer, but represent the results of quantitative analysis as a matrix. When evaluating the interlayer, it is preferable that the evaluation be performed at a position that does not include highlights, inclusions, and voids in the scan line of the linear analysis.

[0131]

Identification of each layer and thickness measurement using the above-mentioned COMP image observation and SEM-EDS quantitative analysis are performed at five or more points while changing the observed field of view. Regarding the thicknesses of each layer obtained at a total of five or more points, the average value is calculated by eliminating the maximum value and minimum value from the measured values, and this average value is taken as the average thickness of each layer.

[0132]

In addition, if a layer in which the line segment (thickness) on the line analysis scan line is less than 300 nm is included in at least one of the five or more observed fields of view described above, that layer is observed in detail using TEM , and identification of the corresponding layer and thickness measurement are performed using TEM.

[0133]

The test piece, including the layer to be observed in detail using TEM, is cut with a focused ion beam (FIB) so that the cutting direction is parallel to the thickness direction (more specifically, the test piece is cut so that the section is parallel to the thickness direction and perpendicular to the rolling direction), and the structure of this section is observed (in a bright-field image) using scanning TEM (STEM) with magnification, which includes the corresponding layer in the observed field of view. In the case where each layer is not included in the observed field of view, the cross-sectional structure is observed in multiple continuous fields of view.

[0134]

In order to identify each layer in the cross-sectional structure, linear analysis is performed along the thickness direction using TEM-EDS, and a quantitative analysis of the chemical composition of each layer is performed. The elements to be quantified are the five elements Fe, P, Si, O and Mg. The analysis device is not particularly limited. For example, TEM (JEM-2100F from JEOL), EDS (JED-2300T from JEOL) and EDS analysis software (Analysis Station from JEOL) can be used.

[0135]

Based on the results of the TEM bright-field image observation described above and the TEM-EDS quantitative analysis results, each layer is identified, and the average thickness of each layer is measured. The method of evaluating each layer using TEM and the method of measuring the average thickness of each layer can be performed in accordance with the method of using SEM as described above.

[0136]

When the thickness of each layer identified by TEM is 5 nm or less, from the point of view of spatial resolution, it is preferable to use a TEM having a spherical aberration correction function. When the thickness of each layer is 5 nm or less, point analysis is performed, for example, at 2 nm intervals along the thickness direction, a line segment (thickness) of each layer is measured, and this line segment can be taken as the thickness of each layer. For example, when a TEM having a spherical aberration correction function is used, EDS analysis can be performed with a spatial resolution of approximately 0.2 nm.

[0137]

In the anisotropic electrical steel sheet according to the embodiment, the oxide film is in contact with the base steel sheet, and the phosphate-based coating is in contact with the oxide film. Therefore, in the case of identifying each layer according to the above criterion, layers other than the base steel sheet, oxide film and phosphate-based coating are not included.

[0138]

To measure the compositions of the phosphate and oxide film coating, quantitative analysis can be performed in detail using SEM-EDS or TEM-EDS in each area of the phosphate and oxide film coating identified above. For the above quantitative analysis, line analysis or point analysis can be carried out at multiple points in the target area. In quantitative analysis, the elements to be quantified may not be the five elements Fe, P, Si, O and Mg, but all the elements to be quantified. With respect to the phosphate and oxide coating compositions, the average composition can be measured in each region of the phosphate and oxide coating identified above.

[0139]

Further, the existence in the phosphate-based coating identified above of a first crystalline phosphorus oxide whose crystal structure corresponds to the formula Fe ₂ P ₂ O ₇ and a second crystalline phosphorus oxide whose crystal structure corresponds to the formula Fe ₇ (P ₂ O ₇ ) ₄ may be confirmed in the following way.

[0140]

Based on the identification results of the phosphate-based coating, a test piece including the phosphate-based coating is cut by FIB processing so that the cutting direction is parallel to the thickness direction (more specifically, the test piece is cut so that the cross-section is parallel to the thickness direction and perpendicular to the rolling direction) , and the structure of this cross-section is observed using TEM with magnification that includes the phosphate-based coating in the observed field of view.

[0141]

Wide area electron beam diffraction is performed on a phosphate coating in an observed field of view with an electron beam diameter less than 1/10 of the thickness of the phosphate coating or 200 nm, and the electron beam diffraction pattern is used to check whether any crystalline phase is included in area irradiated by the electron beam.

[0142]

In the case where it can be confirmed that the crystalline phase is included using the above electron beam diffraction pattern, the crystalline phase is confirmed in the bright field image, and spot analysis of the crystalline phase is performed using TEM-EDS. As a result of TEM-EDS spot analysis, when the chemical composition of the crystalline phase as an object contains Fe, P, and O in a total amount of 70 at.% or more and 100 at.% or less, and 10 at.% or less Si, the crystalline phase can be defined as the crystalline phase containing phosphorus. Therefore, the crystalline phase is defined as crystalline phosphorus oxide.

[0143]

As necessary, electron beam diffraction is performed on the crystal phase as an object by using a narrowed electron beam to obtain information only from the crystal phase as an object, and the crystal structure of the crystal phase as an object is identified from the electron beam diffraction pattern. This identification can be performed using a powder diffraction file (PDF) from the International Center for Diffraction Data (ICDD).

[0144]

From the results of the TEM-EDS spot analysis and electron beam diffraction described above, it can be determined whether the crystalline phase is the first crystalline phosphorus oxide, whose crystal structure corresponds to the formula Fe ₂ P ₂ O ₇ , or the second crystalline phosphorus oxide, whose crystal structure corresponds to the formula Fe ₇ ( P ₂ O ₇ ) ₄ .

[0145]

In addition to this, identification of whether the crystalline phase has the structure of Fe ₂ P ₂ O ₇ can be performed based on PDF: No. 01-072-1516. The identification of whether the crystalline phase has the structure of Fe ₇ (P ₂ O ₇ ) ₄ can be made based on PDF: No. 01-079-2259. In the case where the crystalline phase is identified based on the PDF described above, the identification can be performed with an interplanar distance tolerance of ±5% and an interplanar angle tolerance of ±3°.

[0146]

Confirmation (broad electron beam irradiation) of whether any crystalline phase is included in the electron beam irradiated region is performed sequentially along the thickness direction from the interface between the phosphate coating and the oxide film towards the outermost surface without a gap, and confirmation of the electron diffraction pattern The beam is repeated until it is confirmed that the crystalline phase is not included in the area irradiated by the electron beam.

[0147]

By repeating electron beam irradiation in the thickness direction, it is possible to determine whether or not crystalline phosphorus oxide is included in the phosphate-based coating, as well as the region where crystalline phosphorus oxide is contained in the phosphate-based coating. For example, it can be determined whether crystalline phosphorus oxide is included in the internal or surface region of the phosphate coating.

[0148]

The area fraction of crystalline phosphorus oxide can be obtained as follows. For example, the first crystalline phosphorus oxide and the second crystalline phosphorus oxide are identified by the above method, the crystalline phosphorus oxide identified above and the matrix are subjected to binarization, and then the area fraction of the crystalline phosphorus oxide can be obtained through image analysis. For example, the area percentage of the first crystalline phosphorus oxide included in the surface region is a percentage obtained by dividing the total area of the first crystalline phosphorus oxide by the total area of the surface region. As for image binarization for analysis, it can be done by manually coloring the crystalline phosphorus oxide in the photograph based on the above crystalline phosphorus oxide identification result.

[0149]

In addition, crystalline phosphorus oxide is observed as a black precipitate. In this way, the black precipitates and the matrix are binarized, and then the area fraction of the crystalline phosphorus oxide can be obtained by image analysis. The above area fraction represents the total area fraction of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide included in the observed field of view. Thus, the ratio (area ratio) between the first crystalline phosphorus oxide and the second crystalline phosphorus oxide can be obtained in advance, and the area ratio of the first crystalline phosphorus oxide and the area ratio of the second crystalline phosphorus oxide can be obtained using the above-described ratio and the above-described total area ratio.

[0150]

In addition, whether or not the second crystalline phosphorus oxide in the V, W, Zr, Co or Mo phosphate coating includes or not can be confirmed as follows. For example, the elements included in the second crystalline phosphorus oxide identified above, the crystal structure of which corresponds to the formula Fe ₇ (P ₂ O ₇ ) ₄ , can be qualitatively analyzed using TEM-EDS. Because the second crystalline phosphorus oxide is thermally unstable as a precipitate, its quantitative analysis is difficult. However, with the above qualitative analysis, it can be confirmed whether the second crystalline phosphorus oxide includes V, W, Zr, Co or Mo.

[0151]

In addition, the diameter of the equivalent circle of the second crystalline phosphorus oxide can be measured as follows. For example, the area equivalent circle diameters of at least five crystalline phosphorus oxides are obtained by analyzing images in each of five or more observed fields of view, the average value is calculated by removing the maximum value and the minimum value from the resulting area equivalent circle diameters, and the average value is taken for the average diameter of a circle of crystalline phosphorus oxide equivalent in area. As for image binarization for analysis, it can be done by manually coloring the crystalline phosphorus oxide in the photograph based on the above crystalline phosphorus oxide identification result.

[0152]

Then, the above-mentioned composition of the silicon steel sheet can be confirmed, for example, by the following method.

[0153]

For example, chemical composition can be measured using ICP-AES (Inductively Coupled Plasma Atomic Emission Spectrometer: Inductively Coupled Plasma Emission Spectrometry/Spectroscopy). In addition, the C and S contents can be measured by an infrared combustion absorption method, the N content can be measured by a thermal conductometric inert gas melting method, and the O content can be measured, for example, by a non-dispersive gas melting method. absorption in the infrared region of the spectrum during melting in a flow of inert gas.

[0154]

In the case where the anisotropic electrical steel sheet as a measurement sample has an oxide film, phosphate coating, etc. on its surface, the composition of the steel can be measured after removing the above-mentioned coating, layer or the like.

[0155]

For example, a coated anisotropic electrical steel sheet may be immersed in a hot alkaline solution. In particular, it is possible to remove the coating or the like. (oxide film, phosphate coating, etc.) from a silicon steel sheet by immersing the steel sheet in an aqueous solution of sodium hydroxide, which includes 20 wt.% NaOH and 80 wt.% H ₂ O, at a temperature of 80° C for 20 minutes, followed by rinsing with water and drying. In addition, the immersion time in the sodium hydroxide aqueous solution can be adjusted depending on the thickness of the coating and the like. on a silicon steel sheet.

[0156]

The texture of a silicon steel sheet can be measured using conventional analytical methods. For example, texture can be measured using X-ray diffraction (Laue method). The Laue method involves irradiating a steel sheet perpendicularly with an X-ray beam and analyzing the diffraction spots as they pass through or reflect. By analyzing these diffraction spots, it is possible to identify the crystal orientation at the point irradiated by the x-ray beam. In addition, by varying the irradiated point and analyzing diffraction spots at multiple points, it is possible to obtain the crystal orientation distribution. The Laue method is preferred for identifying the crystal orientation of a metallographic structure in which the grains are coarse.

[0157]

The surface roughness of a silicon steel sheet (the interface roughness between the intermediate layer and the main steel sheet) can be measured using a stylus-type surface roughness tester or a non-contact laser roughness tester. In the case where the silicon steel sheet has an oxide film, phosphate coating, etc. on its surface, the surface roughness can be measured after removing the above coating, layer or the like.

[0158]

Next, a method for producing an anisotropic electrical steel sheet according to an embodiment will be described.

[0159]

<Production method>

Fig. 3 is a flow chart illustrating a method for producing an anisotropic electrical steel sheet according to an embodiment of the present invention. In FIG. 3, blocks surrounded by a solid line belong to essential processes, and blocks surrounded by a dotted line belong to optional processes.

[0160]

The method for producing anisotropic electrical steel sheet according to the embodiment is not limited to the following method. The following production method is one case of producing an anisotropic electrical steel sheet according to an embodiment.

[0161]

The method for producing an anisotropic electrical steel sheet according to an embodiment is a method for producing an anisotropic electrical steel sheet without a forsterite film and includes the following processes.

(i) Hot rolling process for hot rolling a steel billet having a predetermined chemical composition to obtain a hot rolled steel sheet.

(ii) A cold rolling process for cold rolling a hot-rolled steel sheet one or more times with intermediate annealing in between to obtain a cold-rolled steel sheet.

(iii) A decarburization annealing process for decarburizing annealing a cold rolled steel sheet to obtain a decarburization annealed steel sheet.

(iv) An annealing separator coating process for applying the annealing separator to the decarburized annealed steel sheet and drying the annealing separator including Al ₂ O ₃ and MgO.

(v) A finish annealing process for finishing annealing a decarburized annealed steel sheet after applying an annealing separator to obtain a finish annealed sheet.

(vi) An anneal separator removal process for removing excess anneal separator from the surface of a finished annealed sheet by a method including water washing and/or etching.

(vii) An insulating coating forming process for forming an insulating coating on the surface of a finished annealed sheet.

[0162]

In addition, the method for producing anisotropic electrical steel sheet according to the embodiment may further include the following processes.

(a) Hot annealing process for hot annealing (hot strip) of hot rolled steel sheet.

(b) Hot pickling process for hot pickling of hot rolled steel sheet.

(c) Magnetic domain grinding process to carry out magnetic domain grinding.

[0163]

Each process is described in detail below.

[0164]

<Hot rolling process>

In the hot rolling process, a steel billet is hot rolled to obtain a hot rolled steel sheet, the steel billet including in its chemical composition, in wt.%,

0.020% or more and 0.10% or less C,

0.80% or more and 7.0% or less Si,

0.05% or more and 1.0% or less Mn,

0% or more and 0.050% or less of total S and Se content,

0.010% or more and 0.065% or less acid-soluble Al,

0.004% or more and 0.012% or less N,

0% or more and 0.30% or less Cr,

0% or more and 0.40% or less Cu,

0% or more and 0.50% or less P,

0% or more and 0.30% or less Sn,

0% or more and 0.30% or less Sb,

0% or more and 1.0% or less Ni,

0% or more and 0.008% or less B,

0% or more and 0.15% or less V,

0% or more and 0.20% or less Nb,

0% or more and 0.10% or less Mo,

0% or more and 0.015% or less Ti,

0% or more and 0.010% or less Bi, and

residue consisting of iron and impurities. In an embodiment, the steel sheet after the hot rolling process is referred to as hot rolled steel sheet.

[0165]

The method for producing a steel billet (slab) for use in the hot rolling process is not limited. For example, molten steel with a predetermined chemical composition can be obtained, and a slab can be manufactured using this molten steel. The slab can be produced using continuous casting. An ingot can be produced using molten steel and then a slab can be produced using blooming. In addition, the slab can be manufactured using other methods.

[0166]

The thickness of the slab is not particularly limited. The thickness of the slab can be, for example, 150-350 mm. The slab thickness is preferably 220-280 mm. A slab with a thickness of 10-70 mm, which is the so-called thin slab, can be used.

[0167]

The following explains the reasons for limiting the chemical composition of the steel billet. Hereinafter, "%" referring to the chemical composition is "% by weight".

[0168]

0.020% or more and 0.10% or less C

C (carbon) is an element that is effective in controlling the primary recrystallization structure, but which has a negative effect on the magnetic characteristics. Thus, C must be removed by decarburization annealing before finishing annealing. When the C content is more than 0.10%, the decarburization annealing time must be increased, which reduces the productivity. Therefore, the C content should be 0.10% or less. The C content is preferably 0.085% or less, and more preferably 0.070% or less.

[0169]

It is preferable that the C content be lower. However, taking into account industrial production performance and the magnetic characteristics of the product, the lower limit of the C content is essentially 0.020%.

[0170]

0.80% or more and 7.0% or less Si

Si (silicon) increases the electrical resistance of anisotropic electrical steel sheet, and thereby reduces magnetic losses. When the Si content is less than 0.80%, γ transformation occurs during finishing annealing, and the crystal orientation of the anisotropic electrical steel sheet is deteriorated. Therefore, the Si content should be 0.80% or more. The Si content is preferably 2.0% or more, and more preferably 2.50% or more.

On the other hand, when the Si content is more than 7.0%, cold workability deteriorates and cracks may be generated during cold rolling. Therefore, the Si content should be 7.0% or less. The Si content is preferably 5.0% or less, and more preferably 3.5% or less.

[0171]

0.05% or more and 1.0% or less Mn

Mn (manganese) increases the electrical resistance of anisotropic electrical steel sheet, and thereby reduces magnetic losses. In addition, Mn, when bound with S and/or Se, forms MnS and/or MnSe, which act as an inhibitor. When the Mn content is within the range of 0.05% or more and 1.0% or less, secondary recrystallization becomes stable. Therefore, the Mn content is 0.05% or more and 1.0% or less. The lower limit of the Mn content is preferably 0.08%, and more preferably 0.09%. The upper limit of the Mn content is preferably 0.50%, and more preferably 0.20%.

[0172]

0% or more and 0.050% or less total S and Se content

S (sulfur) and Se (selenium) are elements that react with Mn to form MnS or MnSe, which act as an inhibitor.

When the total amount of S and Se (S+Se) is more than 0.050%, the dispersion state of MnS and/or MnSe precipitation becomes uneven. In this case, the desired secondary recrystallization structure cannot be obtained, and the magnetic flux density may decrease. In addition, MnS remains in the steel after cleaning annealing, and hysteresis losses may increase. Therefore, the total amount of S and Se should be 0.050% or less.

The lower limit of the total amount of S and Se is not particularly limited, and may be 0%. The lower limit may be 0.003%, and may be 0.005%. When an inhibitor is used, the lower limit is preferably 0.015%.

[0173]

0.010% or more and 0.065% or less acid soluble Al

Acid-soluble Al (aluminum) is an element to form when combined with N AlN and/or (Al, Si)N, which acts as an inhibitor. When the amount of acid-soluble Al is less than 0.010%, the addition effect is not sufficiently obtained, and secondary recrystallization does not occur sufficiently. Therefore, the amount of acid-soluble Al should be 0.010% or more. The amount of acid-soluble Al is preferably 0.015% or more, and more preferably 0.020% or more.

[0174]

On the other hand, when the amount of acid-soluble Al is more than 0.065%, the dispersion state of AlN and/or (Al, Si)N precipitation becomes uneven, the desired recrystallization secondary structure cannot be obtained, and the magnetic flux density decreases. Therefore, the amount of acid-soluble Al (soluble Al) should be 0.065% or less. The amount of acid-soluble Al is preferably 0.055% or less, and more preferably 0.050% or less.

[0175]

0.004% or more and 0.012% or less N

N (nitrogen) is an element that, when combined with Al, forms AlN and/or (Al, Si)N, which act as an inhibitor. When the N content is less than 0.004%, the formation of AlN and/or (Al, Si)N becomes insufficient. Therefore, the N content should be 0.004% or more. The N content is preferably 0.006% or more, and more preferably 0.007% or more.

On the other hand, when the N content is more than 0.012%, bubbles (voids) may be formed in the steel sheet. Therefore, the N content should be 0.012% or less.

[0176]

The steel billet includes the above-mentioned elements in its chemical composition, and the remainder consists of Fe and impurities. However, in view of the effect on magnetic properties and the improvement of inhibitor functions by forming joints, the steel blank may include at least one of the optional elements as a replacement for a portion of Fe. For example, optional elements included as a replacement for the Fe portion may be Cr, Cu, P, Sn, Sb, Ni, B, V, Nb, Mo, Ti and Bi. However, optional elements may not be included, and the lower limits for their content may accordingly be 0%. Moreover, even though optional elements may be included as impurities, this does not affect the above effects. As used herein, impurities refer to elements that contaminate steel during its industrial production from the ores and scrap that are used as raw materials for steel production, or from the environment of the production process.

[0177]

0% or more and 0.30% or less Cr

0% or more and 0.40% or less Cu

0% or more and 0.50% or less P

0% or more and 0.30% or less Sn

0% or more and 0.30% or less Sb

0% or more and 1.00% or less Ni

0% or more and 0.008% or less B

0% or more and 0.15% or less V

0% or more and 0.2% or less Nb

0% or more and 0.10% or less Mo

0% or more and 0.015% or less Ti

0% or more and 0.010% or less Bi

Optional elements can be included as needed. Thus, the lower limit of the content of the corresponding optional elements need not be limited, and the lower limit may be 0 mass%.

[0178]

Next, the conditions for hot rolling the above-mentioned steel billet are explained.

The hot rolling conditions are not particularly limited. For example, the conditions are as follows.

The slab is heated before hot rolling. The slab is placed in a known heating furnace or a known holding furnace and heated. As one method, the slab is heated to 1280°C or less. For example, by setting the slab heating temperature to 1280°C or less, various problems caused by the heating temperature exceeding 1280°C can be avoided (when a special high-temperature heating furnace is required, the amount of scale in the melt increases rapidly, etc.). The lower limit of the slab heating temperature is not particularly limited. However, when the heating temperature is excessively low, hot rolling may become difficult and productivity may decrease. Thus, considering the performance, the heating temperature can be in the range of 1280°C or less. The lower limit of the slab heating temperature is preferably 1100°C. The upper limit of the slab heating temperature is preferably 1250°C.

[0179]

In addition to this, as another method, the slab is heated to a higher temperature of 1320°C or more. It is possible to stabilize secondary recrystallization by heating the slab to a higher temperature of 1320°C or higher and dissolving AlN and Mn(S, Se) and finely depositing them in subsequent processes.

The slab heating itself can be omitted, and hot rolling can be carried out after casting before the slab temperature decreases.

[0180]

The heated slab is hot rolled in a hot rolling mill to produce hot rolled steel sheet. The hot rolling mill includes, for example, a rough rolling mill and a finishing rolling mill located after the rough rolling mill. A rough rolling mill consists of rough rolling stands arranged in a row. Each roughing stand has a plurality of rolls arranged one above the other. In the same way, a finishing rolling mill includes finishing rolling stands arranged in a row. Each finishing rolling stand has a plurality of rolls located one above the other. The heated steel billet is rolled on a rough rolling wall and then on a finishing rolling mill to produce a hot rolled steel sheet.

The final temperature in the hot rolling process (the temperature of the steel sheet at the exit side of the finishing stand by which the steel sheet is finally rolled in the finishing rolling mill) can range from 700 to 1150°C. Hot rolled steel sheet is produced using the hot rolling process explained above.

[0181]

<Hot Annealing Process>

In the hot annealing process, if necessary, the hot rolled steel sheet produced by the hot rolling process is annealed (in a hot belt) to obtain a hot annealed sheet. In an embodiment, the steel sheet after the hot annealing process is referred to as hot annealed sheet.

[0182]

Hot annealing is carried out in order to homogenize the heterogeneous structure after hot rolling, control the precipitation of AlN, which is an inhibitor (provide fine precipitation) and control the second phase, solid dissolved carbon, etc. The annealing conditions may be known conditions suitable for the purpose. For example, to homogenize the heterogeneous structure after hot rolling, the hot-rolled steel sheet is kept at 750-1200°C (hot annealing furnace temperature) for 30-600 s.

Hot annealing is not always necessary. Hot annealing may be carried out as a result of consideration of the characteristics and production costs required for the final anisotropic electrical steel sheet.

[0183]

<Hot pickling process>

In the hot pickling process, if necessary, the hot rolled steel sheet after the hot rolling process or after the hot annealing process if performed, is pickled to remove surface scale. The etching conditions are not particularly limited, and known conditions can be suitably used.

[0184]

<Cold rolling process>

In the cold rolling process, the hot rolled steel sheet or annealed sheet after the process of hot rolling, hot annealing or hot pickling is cold rolled one or more times with intermediate annealing to obtain a cold rolled steel sheet. In an embodiment, the steel sheet after the cold rolling process is referred to as cold rolled steel sheet.

[0185]

The finishing cold rolling reduction ratio (cumulative cold rolling reduction ratio without intermediate annealing or cumulative cold rolling reduction ratio after intermediate annealing) is preferably 80% or more, and more preferably 90% or more. The upper limit of the reduction ratio in finishing cold rolling is preferably 95%.

[0186]

In this document, the finishing cold rolling reduction ratio (%) is defined as follows.

Reduction ratio during finishing cold rolling (%)=(1 - Thickness of steel sheet after finishing cold rolling/Thickness of steel sheet before finishing cold rolling) × 100

[0187]

<Decarburization Annealing Process>

In the decarburization annealing process, the cold-rolled steel sheet after the cold rolling process is subjected to magnetic domain refinement processing if necessary, and then subjected to decarburization annealing to accelerate primary recrystallization. In addition, decarburization annealing removes C, which negatively affects the magnetic performance, from the steel sheet. In an embodiment, the steel sheet after the decarburization annealing process is referred to as decarburization annealed sheet.

[0188]

For the above purposes, during decarburization annealing, the oxidation degree (PH ₂ O/PH ₂ ) of the annealing atmosphere (furnace atmosphere) should be from 0.01 to 0.15, the annealing temperature should be from 750 to 900°C, and the holding time should be from 10 to 600 s. The oxidation state of PH ₂ O/PH ₂ is defined as the ratio of the partial pressure of water vapor PH2O (atm) to the partial pressure of hydrogen PH2 (atm) in the atmosphere.

[0189]

When the oxidation degree (PH ₂ O/PH ₂ ) is less than 0.01, the decarburization rate slows down and the productivity drops. In addition to this, decarburization does not occur properly, and as a result, the magnetic performance after finishing annealing deteriorates. On the other hand, when the oxidation state is more than 0.15, iron-based oxides are formed, and as a result, it becomes difficult to smooth the interface after finishing annealing.

When the annealing temperature is less than 750°C, the decarburization rate slows down and the productivity drops. In addition to this, decarburization does not occur properly, and as a result, the magnetic performance after finishing annealing deteriorates. On the other hand, when the annealing heating temperature is more than 900°C, the grain size after primary recrystallization exceeds the favorable size, and as a result, the magnetic performance after finishing annealing is deteriorated.

When the holding time is less than 10 s, decarburization does not occur sufficiently. On the other hand, when the dwell time is more than 600 s, the performance decreases. In addition, the grain size after primary recrystallization exceeds the favorable size, and as a result, the magnetic performance after finishing annealing is deteriorated.

[0190]

Depending on the above-mentioned oxidation state (PH ₂ O/PH ₂ ), the heating rate to the annealing temperature in the heating step can be controlled. For example, in the case where induction heating is performed, the average heating rate may be 5-1000°C/s. Moreover, in the case where electrical heating is performed, the average heating rate may be 5-3000°C/s.

[0191]

In addition to this, nitriding treatment can be performed during the decarburization annealing process. In the nitriding treatment, the cold-rolled steel sheet may be annealed in an atmosphere including ammonia in at least one step before, during or after the above-mentioned holding. In the case where the heating temperature of the slab is lower, it is preferable that the nitriding treatment is carried out in a decarburization annealing process. With the additional nitriding treatment in the decarburization annealing process, an inhibitor such as AlN and (Al, Si)N is formed before secondary recrystallization in the finishing annealing process, and thus the secondary recrystallization can be stable.

[0192]

Although the conditions for the nitriding treatment are not particularly limited, it is preferable to conduct it so that the nitrogen content increases by 0.003% or more, preferably by 0.005% or more, and more preferably by 0.007% or more. When the nitrogen (N) content is more than 0.030%, these effects are saturated. Thus, the nitriding treatment can be carried out so that the content becomes 0.030% or less.

[0193]

Conditions for the nitriding treatment are not particularly limited, and known conditions can be suitably used.

For example, in the case where the nitriding treatment is carried out after decarburization annealing, such as holding at 750-900°C for 10-600 s at an oxidation degree (PH ₂ O/PH ₂ ) of 0.01-0.15, the nitriding treatment may be carried out in such a way that the cold-rolled steel sheet is not cooled to room temperature, but is maintained in a cooling stage in an atmosphere including ammonia. It is preferable that the oxidation state (PH ₂ O/PH ₂ ) in the cooling step is within the range of 0.0001-0.01. In addition, in the case where the nitriding treatment is carried out during decarburization annealing such as holding at 750-900°C for 10-600 s at an oxidation degree (PH ₂ O/PH ₂ ) of 0.01-0.15, ammonia can be included in atmospheric gas with the above oxidation state.

[0194]

<Applying Process of Annealing Separator>

In the process of applying the annealing separator, the decarburized annealed sheet after the decarburization annealing process (or the decarburized annealed sheet after the nitriding treatment) is optionally subjected to a magnetic domain refinement treatment, and then the annealing separator including Al ₂ O ₃ and MgO is applied to the decarburized annealed sheet. The applied annealing separator is then dried.

[0195]

In the case where the annealing separator includes MgO but does not include Al ₂ O ₃ , a forsterite film is formed on the steel sheet during the finishing annealing process. On the other hand, in the case where the annealing separator includes Al ₂ O ₃ but does not include MgO, mullite (3Al ₂ O ₃ ⋅2SiO ₂ ) is formed on the steel sheet. Mullite becomes an obstacle to the movement of the magnetic domain wall, and thus causes deterioration in the magnetic characteristics of the anisotropic electrical steel sheet.

[0196]

That is, in the method for producing anisotropic electrical steel sheet according to the embodiment, an annealing separator mainly including Al ₂ O ₃ and MgO is used as an annealing separator. By using an annealing separator comprising mainly Al ₂ O ₃ and MgO, a forsterite film is not formed on the surface of the steel sheet, and the surface of the steel sheet can be smoothed after finishing annealing. As used herein, that the annealing separator mainly includes Al ₂ O ₃ and MgO means that the total amount of Al ₂ O ₃ and MgO in the annealing separator is 50 mass% or more.

[0197]

For the annealing separator, the value of MgO/(MgO+Al ₂ O ₃ ), which is the mass fraction of MgO, should be 5-50%, and the amount of hydrate water should be 1.5 mass% or less.

When the MgO/(MgO+Al ₂ O ₃ ) value is less than 5%, mullite is formed in an excessive amount, and thus magnetic loss is deteriorated. On the other hand, when the MgO/(MgO+Al ₂ O ₃ ) value is more than 50%, forsterite is formed, and thus magnetic loss is deteriorated.

When the hydration water in the annealing separator is more than 1.5 mass%, the secondary recrystallization may become unstable, and it may be difficult to smooth the surface of the steel sheet because the surface of the steel sheet is oxidized (SiO ₂ is formed) during finishing annealing. The lower limit of the hydration water content is not particularly limited, but may be, for example, 0.1 mass%.

[0198]

The annealing separator is applied as an aqueous suspension or by electrostatic spraying. During the application process of the annealing separator, the annealing separator may further include nitrides, such as manganese nitride, iron nitride and chromium nitride, which decompose before secondary recrystallization during the finishing annealing process and which nitride the decarburized annealed sheet or the decarburized and nitrided sheet.

[0199]

<Finish annealing process>

The decarburized annealed sheet, after applying the above-mentioned annealing separator, is finish annealed to obtain a finish annealed sheet. When finishing annealing of the decarburized annealed sheet is carried out after applying the above-mentioned annealing separator, secondary recrystallization occurs and the crystal orientation is aligned to the {110}<001> orientation. In an embodiment, the steel sheet after the finish annealing process is referred to as a finish annealed sheet.

[0200]

During finishing annealing, when the atmosphere (furnace atmosphere) includes hydrogen, the oxidation state (PH ₂ O/PH ₂ ) should be 0.00010-0.2. In the case where the atmosphere consists of an inert gas (nitrogen, argon, etc.) without hydrogen, the dew point should be 0°C or less.

By adjusting the oxidation degree or dew point within the above range depending on the atmosphere, it is possible to ensure stable secondary recrystallization and increase the degree of orientation alignment.

[0201]

When the oxidation degree is less than 0.00010 in the case where the atmosphere includes hydrogen, the dense surface film of silica formed by decarburization annealing is reduced before secondary recrystallization in finishing annealing, and as a result, secondary recrystallization becomes unstable. On the other hand, when the oxidation state is more than 0.2, the dissolution of inhibitor such as AlN and (Al, Si)N is accelerated, and thus secondary recrystallization becomes unstable. In addition, when the dew point exceeds 0°C in the case where the atmosphere consists of an inert gas without hydrogen, the dissolution of inhibitor such as AlN and (Al, Si)N is accelerated, and thus secondary recrystallization becomes unstable. The lower limit of the dew point is not particularly limited, but may be, for example, -30°C.

[0202]

<Process of removing the annealing separator>

In the annealing separator removal process, excess annealing separator is removed from the surface of the steel sheet after the finish annealing (finish annealed sheet) by methods including water washing and/or pickling. Here, excess annealing separator means, for example, unreacted annealing separator that has not reacted with the steel sheet during finishing annealing.

[0203]

When the excess annealing separator is not sufficiently removed from the surface of the steel sheet, the fill factor decreases and the performance of the core deteriorates.

[0204]

In addition to the above water rinsing and etching, a scraper can be used to remove excess annealing separator. By using a scraper, excess annealing separator, which impairs wettability during the formation of the insulating coating, can be reliably removed.

[0205]

In addition, when etching is carried out to remove excess annealing separator, it can be carried out using an acid solution whose volume concentration is less than 20%. For example, it is preferable to use a solution containing less than 20% by volume in the sum of at least one of sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, perchloric acid, chromium oxide in aqueous solution, chromium sulfate, manganic acid, peroxosulfuric acid and peroxophosphoric acid. acids. It is more preferable to use a solution containing less than 10 vol.% of the listed components. The lower limit of the volume concentration is not particularly limited, but may be, for example, 0.1 vol%. By using the above solution, excess annealing separator can be effectively removed from the surface of the steel sheet. Herein, the above-mentioned vol.% may be a concentration based on volume at room temperature.

[0206]

Moreover, in the case where etching is performed, the solution temperature is preferably 20-80°C. By controlling the solution temperature to be within the above range, excess annealing separator can be effectively removed from the surface of the steel sheet.

[0207]

<Process of forming insulation coating>

In the process of forming the insulating coating, the finished annealed sheet, after removing the annealing separator, is subjected to processing to refine the magnetic domain if necessary, and then the insulating coating is formed on the surface of the finished annealed sheet. In an embodiment, the steel sheet after the insulating coating forming process is referred to as anisotropic electrical steel sheet.

[0208]

This coating imparts tension to the anisotropic electrical steel sheet, and thereby reduces magnetic losses in a single steel sheet. In addition, this coating guarantees interlayer electrical insulation when anisotropic electrical steel sheets are used in laminated form, thereby reducing magnetic losses in the core.

[0209]

The insulation coating is formed on the surface of the finished annealed sheet by applying an insulation coating solution that primarily includes at least one of phosphate or colloidal silica and does not contain chromate, baking it at 350-600°C, and then subjecting it to heat treatment at 800-1000°C.

[0210]

In addition, the above-mentioned insulating coating solution does not include chromate, but includes:

a first metal phosphate which is a phosphate of at least one metal selected from Al, Fe, Mg, Mn, Ni and Zn in an amount of 100 ppm. in solid equivalent;

a second metal phosphate, which is a phosphate of at least one metal selected from Co, Mo, V, W and Zr in an amount of 3-20 ppm. in solid equivalent;

colloidal silica in an amount of 35-125 parts. in solid equivalent; And

polymerization additive in an amount of 0.3-6.0 parts.

[0211]

Moreover, the average size of the primary particles of the above-mentioned colloidal silica is preferably 7-30 nm.

[0212]

Moreover, the above-mentioned polymerization additive is preferably at least one substance selected from the group consisting of nitrous acid, sodium nitrate, potassium nitrate, nitric acid, sodium nitrate, potassium nitrate, chlorous acid, sodium chloride, phosphonic acid, sodium phosphonate , triphosphoric acid, trisodium phosphate, polyphosphoric acid and sodium polyphosphate.

[0213]

Moreover, the above-mentioned insulating coating solution further includes preferably at least one substance selected from the group consisting of boric acid, sodium borate, titanium oxide, molybdenum oxide, pigments and barium titanate.

[0214]

When the baking temperature of the insulation coating is less than 350°C, the insulation coating solution drips while passing the steel sheet, causing poor appearance, and the insulation coating with sufficient adhesion is not obtained. When the baking temperature of the insulation coating is more than 600°C, because the heating rate is excessively high, only the outermost surface of the insulation coating is solidified, and the solidification of the inside is delayed, the formation of the coating becomes abnormal, and the adhesion of the coating becomes insufficient. When the heat treatment temperature after baking is less than 800°C, the formation of the coating becomes abnormal (insufficient curing) and the tension of the coating becomes insufficient. When the heat treatment temperature after baking is more than 1000°C, the phosphate is decomposed, the formation of the coating becomes abnormal, and the adhesion of the coating becomes insufficient.

[0215]

The atmospheric gas during heat treatment of the insulation coating should be a mixed gas containing 5-100 vol.% hydrogen and 95 to 0 vol.% nitrogen, and the oxidation degree (PH ₂ O/PH ₂ ) of the atmosphere should be 0.001-0.15 . The holding time at a temperature of 800-1000°C during heat treatment should be 10-120 s.

[0216]

After heat treatment under the above conditions, the steel sheet is cooled. The atmospheric gas during cooling after heat treatment should be a mixed gas containing 5-100 vol.% hydrogen and 95 to 0 vol.% nitrogen, and the oxidation degree (PH ₂ O/PH ₂ ) of the atmosphere should be 0.001-0.1 . The average cooling rate in the temperature range 800-500°C during cooling after heat treatment should be 5-45°C/s.

[0217]

Moreover, the oxidation degree of the atmosphere during cooling after heat treatment of the insulation coating changes to a smaller value than the oxidation degree of the atmosphere during heat treatment of the insulation coating. However, when the total amount of V, W, Zr, CO and MO in the phosphate-based coating satisfies the condition of 0.1 at.% or more and 10 at.% or less, the oxidation degree of the atmosphere during cooling after heat treatment of the insulation coating does not need to be changed to a lower value than the degree of oxidation of the atmosphere during heat treatment of the insulating coating.

[0218]

The atmospheric gas and oxidation degree during heat treatment of the insulation coating, the atmospheric gas, oxidation degree and cooling rate during cooling after heat treatment, and the change in atmospheric oxidation degree between heat treatment and cooling described above correspond to the above condition (III). To form the first crystalline phosphorus oxide and the second crystalline phosphorus oxide in the phosphate-based coating, condition (III) must be satisfied.

[0219]

<Magnetic domain grinding process>

A method for producing an anisotropic electrical steel sheet according to an embodiment may include a magnetic domain refining process, comprising conducting a magnetic domain refining process at a suitable timing (1) between the cold rolling process and the decarburization annealing process, (2) between the decarburization annealing process and process of applying the annealing separator, (3) between the process of removing the annealing separator and the process of forming the insulating coating, or (4) after the process of forming the insulating coating.

[0220]

By carrying out the magnetic domain refinement processing, the magnetic loss in the anisotropic electrical steel sheet can be reduced. In the case where the magnetic domain refining processing is carried out between the cold rolling process and the decarburization annealing process, between the decarburization annealing process and the annealing separator application process, or between the annealing separator removal process and the insulating coating forming process, the grooves can be formed linearly or pointwise in the direction , crossing the rolling direction, at a predetermined interval in the rolling direction. By forming the aforementioned grooves, the width of the 180-degree domains can be narrowed (the 180-degree domains can be ground).

[0221]

In the case where the magnetic domain refinement processing is carried out after the insulating coating forming process, stress deformation or grooves can be applied or formed linearly or pointwise in a direction intersecting the rolling direction at a predetermined interval in the rolling direction. When applying the above-mentioned stress deformation or when forming the above-mentioned grooves, the width of the 180-degree domains can be narrowed (the 180-degree domains can be refined).

[0222]

The above-mentioned stress deformation can be applied by irradiation with a laser beam, electron beam, or the like. The above groove may be formed by a mechanical groove forming method such as a gear wheel, a chemical groove forming method such as electrolytic etching, a thermal groove forming method such as laser irradiation, and the like. In the case where the insulating coating is damaged and performance such as electrical insulation is deteriorated due to the application of the above-mentioned stress deformation or the formation of the above-mentioned groove, the insulating coating can be formed again, and thus the damage can be eliminated.

Examples

[0223]

Next, the effects of one aspect of the present invention are described in detail with reference to the following examples. However, the conditions in the examples are exemplary conditions used to demonstrate the operation and effects of the present invention, so the present invention is not limited to these exemplary conditions. The present invention may use various types of conditions as long as these conditions do not depart from the scope of the present invention and achieve the object of the present invention.

[0224]

A steel slab, the chemical composition of which was controlled to match the composition of the silicon steel sheet shown in Table 1, was heated to 1150°C and then hot rolled to obtain a hot-rolled steel sheet with a thickness of 2.6 mm. After subjecting the hot-rolled steel sheet to hot annealing if necessary, it was cold-rolled one or more times with intermediate annealing to obtain a cold-rolled steel sheet having a final thickness of 0.22 mm. This cold-rolled steel sheet was subjected to decarburization annealing and then, while cooling, to a nitriding treatment in an ammonia-containing atmosphere. Known conditions were applied, starting with slab heating and ending with nitriding treatment.

[0225]

After the above-mentioned decarburization annealing, an annealing separator was applied to the sheet, followed by drying. The ratios of MgO and Al ₂ O ₃ (MgO/(MgO+Al ₂ O ₃ )) and the amount of hydrate water are shown in Tables 2-5. Meanwhile, the total amount of Al ₂ O ₃ and MgO in the annealing separator was 50 mass% or more. The annealed decarburized sheet, after applying the annealing separator, was finished annealed at 1200°C for 20 hours.

[0226]

The composition-controlled insulating coating solution was then applied, baked and heat-treated under the conditions shown in Tables 2-5. After the heat treatment, cooling was carried out under the conditions shown in Tables 2 to 5, and thereby an insulating coating was formed.

[0227]

In addition, after the process of forming the insulating coating, processing was carried out to refine the magnetic domains. Stress-strain or laser groove formation was used to refine the magnetic domains.

[0228]

For the obtained No. 1-73 anisotropic electrical steel sheets, the chemical composition of the silicon steel sheet, the average composition and average thickness of the intermediate layer, the average composition and average thickness of the insulating coating, and the state of crystalline phosphorus oxide in the insulating coating were evaluated based on the above method. The results are shown in Tables 1-17. In the tables, "first region" means "first interior region" and "second region" means "second interior region".

[0229]

In addition, magnetic losses and coating adhesion were assessed for the obtained sheets of anisotropic electrical steel No. 1-73.

[0230]

<Magnetic losses>

The samples were taken from the resulting anisotropic electrical steel sheet, and the magnetic loss W17/50 (W/kg) was measured under the conditions of an AC frequency of 50 Hz and an excited magnetic flux density of 1.7 T based on the Epstein test governed by JIS C2550-1 standard : 2000. When the magnetic loss of W17/50 was less than 0.68 W/kg, it was considered acceptable.

[0231]

<Coating adhesion>

Samples were taken from the resulting anisotropic electrical steel sheets, and the adhesion of the insulating coating was assessed by rolling the sample around a 20 mm or 15 mm diameter cylinder (180° bend) and measuring the area fraction of the coating remaining after reverse bending. When assessing the adhesion of the insulating coating, the presence or absence of peeling of the insulating coating was visually assessed. When the percentage of the remaining coating area not peeled off from the steel sheet was 90% or more, it was rated as “very good.” When this area fraction was 86% or more and less than 90%, it was rated as “good.” When this area fraction was 80% or more and less than 86%, it was rated as “insufficient.” When this area fraction was less than 80%, it was rated as “poor.” When the area percentage of coverage remaining was 86% or greater (the aforementioned "very good" and "good" ratings), it was considered acceptable in both 20 mm and 15 mm diameter test conditions.

The results are shown in Tables 18-21.

[0232]

As shown in Tables 1 to 21, in Examples of the present invention Nos. 1 to 73, the product characteristics satisfied the range of the present invention, and thus the coating adhesion was excellent. In addition, magnetic losses were excellent.

On the other hand, in Comparative Examples Nos. 1 to 73, at least one of the product characteristics did not meet the range of the present invention, so magnetic loss and/or coating adhesion were insufficient.

[0233]

[Table 1]

Production results Chemical composition of silicon steel sheet (in wt.%, with the remainder of Fe and impurities) Si Mn Cr Cu P Sn Sb Ni B V Nb Mo Ti Bi Al C N S Se Steel A 3.3 0.1 0.1 - 0.03 0.05 - - - - - - - - 0.001 0.001 0.001 0.001 - Steel B 2.7 0.2 - - - - - - - - - - - - 0.001 0.001 0.001 0.001 - Steel C 3.8 0.1 0.1 0.2 0.02 0.08 - - - - - - - - 0.001 0.001 0.001 0.001 0.001 Steel D 3.3 0.5 0.1 - - - - - - - - - - - 0.001 0.001 0.001 0.001 - Steel E 3.3 0.1 0.2 - - - - - - - - - - - 0.001 0.001 0.001 0.001 - Steel F 3.3 0.1 0.1 0.3 - - - - - - - - - - 0.001 0.001 0.001 0.001 - Steel G 3.3 0.1 0.1 - 0.2 - - - - - - - - - 0.001 0.001 0.001 0.001 - Steel N 3.3 0.1 0.1 - - 0.1 0.1 - - - - - - - 0.001 0.001 0.001 0.001 - Steel I 3.4 0.1 0.1 - - - - 0.3 - - - - - - 0.001 0.001 0.001 0.001 - Steel J 3.3 0.1 0.1 - - - - - 0.001 - - - - - 0.001 0.001 0.001 0.001 - Steel K 3.3 0.1 0.1 - - - - - - 0.002 - - - - 0.001 0.001 0.001 0.001 - Steel L 3.3 0.1 0.1 - - - - - - - 0.002 - - - 0.001 0.001 0.001 0.001 - Steel M 3.3 0.1 0.1 - - - - - - - - 0.05 - - 0.001 0.001 0.001 0.001 - Steel N 3.3 0.1 0.1 - - - - - - - - - 0.003 - 0.001 0.001 0.001 0.001 - Steel O 3.3 0.1 0.1 - - - - - - - - - - 0.001 0.001 0.001 0.001 0.001 -

* “-” in the table means that alloying elements were not intentionally added

[0234]

[Table 2]

Production conditions Annealing separator application Forming an insulating coating MgO/(MgO+Al ₂ O ₃ ) Hydration water Type of film-forming solution Heat treatment after baking Cooling after heat treatment Mixed atmospheric gas Atmospheric oxidation degree PH ₂ O/PH ₂ Excerpt Mixed atmospheric gas Atmospheric oxidation degree PH ₂ O/PH ₂ Cooling rate from 800°C to 500°C Hydrogen Nitrogen Temperature Time Hydrogen Nitrogen wt.% wt.% - about.% about.% - °C With about.% about.% - °C/s 1 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 2 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.03 15 3 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 4 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.03 15 5 Steel A 60 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 6 Steel A 100 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 7 Steel A 40 1.7 Not carried out due to excessive oxidation of the surface of the steel sheet - - - - - 8 Steel A 40 0.8 Without Cr 4 96 0.03 850 thirty 4 96 0.007 15 9 Steel A 40 0.8 Without Cr 75 25 0.0002 850 thirty 75 25 0.0002 15 10 Steel A 40 0.8 Without Cr 75 25 0.18 850 thirty 75 25 0.18 15 eleven Steel A 40 0.8 Without Cr 75 25 0.03 700 thirty 75 25 0.008 15 12 Steel A 40 0.8 Without Cr 75 25 0.03 850 5 75 25 0.008 15 13 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 50 14 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 15 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 16 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 17 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 18 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15

[0235]

[Table 3]

Production conditions Annealing separator application Forming an insulating coating MgO/(MgO+Al ₂ O ₃ ) Hydration water Type of film-forming solution Heat treatment after baking Cooling after heat treatment Mixed atmospheric gas Atmospheric oxidation degree PH ₂ O/PH ₂ Excerpt Mixed atmospheric gas Atmospheric oxidation degree PH ₂ O/PH ₂ Cooling rate from 800°C to 500°C Hydrogen Nitrogen Temperature Time Hydrogen Nitrogen wt.% wt.% - about.% about.% - °C With about.% about.% - °C/s 19 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 20 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 21 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 22 Steel A 40 0.8 Without Cr 75 25 0.03 800 thirty 75 25 0.008 15 23 Steel A 40 0.8 Without Cr 75 25 0.03 900 thirty 75 25 0.008 15 24 Steel A 40 0.8 Without Cr 75 25 0.03 950 thirty 75 25 0.008 15 25 Steel A 40 0.8 Without Cr 75 25 0.03 1000 thirty 75 25 0.008 15 26 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 27 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 28 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 29 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.016 15 thirty Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.023 15 31 Steel A 40 0.8 Without Cr 75 25 0.03 1000 120 75 25 0.008 15 32 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 4 96 0.007 15 33 Steel A 40 0.8 Containing Cr 75 25 0.03 850 thirty 75 25 0.008 15 34 Steel A 60 0.8 Containing Cr 75 25 0.03 850 thirty 75 25 0.008 15 35 Steel B 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 36 Steel C 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15

[0236]

[Table 4]

Production conditions Annealing separator application Forming an insulating coating MgO/(MgO+Al ₂ O ₃ ) Hydration water Type of film-forming solution Heat treatment after baking Cooling after heat treatment Mixed atmospheric gas Atmospheric oxidation degree PH ₂ O/PH ₂ Excerpt Mixed atmospheric gas Atmospheric oxidation degree PH ₂ O/PH ₂ Cooling rate from 800°C to 500°C Hydrogen Nitrogen Temperature Time Hydrogen Nitrogen wt.% wt.% - about.% about.% - °C With about.% about.% - °C/s 37 Steel D 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 38 Steel E 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 39 Steel F 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 40 Steel G 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 41 Steel N 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 42 Steel I 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 43 Steel J 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 44 Steel K 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 45 Steel L 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 46 Steel M 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 47 Steel N 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 48 Steel O 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 49 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 50 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 51 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 52 Steel A 40 0.8 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 53 Steel A thirty 0.5 Without Cr 75 25 0.01 850 thirty 75 25 0.008 15 54 Steel A 20 0.5 Without Cr 75 25 0.1 850 thirty 75 25 0.008 15

[0237]

[Table 5]

Production conditions Annealing separator application Forming an insulating coating MgO/(MgO+Al ₂ O ₃ ) Hydration water Type
film-forming solution Heat treatment after baking Cooling after heat treatment Mixed atmospheric gas Atmospheric oxidation degree PH ₂ O/PH ₂ Excerpt Mixed atmospheric gas Atmospheric oxidation degree PH ₂ O/PH ₂ Cooling rate from 800°C to 500°C Hydrogen Nitrogen Temperature Time Hydrogen Nitrogen wt.% wt.% - about.% about.% - °C With about.% about.% - °C/s 55 Steel A 50 0.6 Without Cr 75 25 0.1 850 thirty 75 25 0.008 15 56 Steel A 50 1.4 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 57 Steel A 5 0.7 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 58 Steel A 40 0.8 Without Cr 75 25 0.1 850 thirty 75 25 0.008 15 59 Steel A 40 0.8 Without Cr 75 25 0.01 850 thirty 75 25 0.008 15 60 Steel A thirty 0.5 Without Cr 75 25 0.06 850 thirty 75 25 0.06 10 61 Steel A thirty 0.5 Without Cr 75 25 0.03 850 thirty 75 25 0.004 40 62 Steel A thirty 0.5 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 63 Steel A thirty 0.5 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 64 Steel A thirty 0.5 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 65 Steel A thirty 0.5 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 66 Steel A thirty 0.5 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 67 Steel A thirty 0.5 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 68 Steel A thirty 0.5 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 69 Steel A thirty 0.5 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 70 Steel A thirty 0.3 Without Cr 75 25 0.008 800 10 75 25 0.004 15 71 Steel A 45 1.4 Without Cr 75 25 0.1 1000 110 75 25 0.01 15 72 Steel A thirty 0.5 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15 73 Steel A thirty 0.5 Without Cr 75 25 0.03 850 thirty 75 25 0.008 15

[0238]

[Table 6]

Production results Intermediate layer Insulation coating Composition (at.%) Average thickness
nm Composition (at.%) Si O Mg P Fe P Si O Fe Cr 1 Steel A 37 55 2 3 3 20 13 15 62.9 7 0.1 2 Steel A 38 54 2 3 3 18 13 14 62.9 7 0.1 3 Steel A 36 56 2 3 3 21 13 14 62.9 7 0.1 4 Steel A 37 55 2 3 3 23 13 15 62.9 7 0.1 5 Steel A 20 54 21 4 1 694 14 15 64.9 3 0.1 6 Steel A 21 46 28 4 1 1475 15 16 64.9 1 0.1 7 Steel A - - - - - - - - - - - 8 Steel A 37 55 2 3 3 22 13 14 62.9 7 0.1 9 Steel A 37 57 2 3 1 1 13 14 62.9 7 0.1 10 Steel A 24 37 2 5 32 39 13 14 62.9 7 0.1 eleven Steel A 37 55 2 3 3 eleven 13 14 62.9 7 0.1 12 Steel A 38 54 2 3 3 15 13 14 62.9 7 0.1 13 Steel A 39 53 2 3 3 23 13 14 62.9 7 0.1 14 Steel A 37 55 2 3 3 19 13 15 62.9 7 0.1 15 Steel A 36 56 2 3 3 20 13 15 62.9 7 0.1 16 Steel A 37 55 2 3 3 21 13 15 62.9 7 0.1 17 Steel A 37 55 2 3 3 20 13 15 62.9 7 0.1 18 Steel A 36 56 2 3 3 22 13 14 62.9 7 0.1

[0239]

[Table 7]

Production Results Intermediate layer Insulation coating Composition (at.%) Average thickness
nm Composition (at.%) Si O Mg P Fe P Si O Fe Cr 19 Steel A 36 56 2 3 3 18 13 14 62.9 7 0.1 20 Steel A 38 54 2 3 3 21 13 14 62.9 7 0.1 21 Steel A 37 55 2 3 3 20 13 14 62.9 7 0.1 22 Steel A 36 56 2 3 3 17 14 15 62.9 5 0.1 23 Steel A 38 54 2 3 3 25 12 13 61.9 10 0.1 24 Steel A 37 55 2 3 3 31 eleven 12 60.9 13 0.1 25 Steel A 37 55 2 3 3 37 9 10 59.9 18 0.1 26 Steel A 37 55 2 3 3 22 13 14 61.9 7 0.1 27 Steel A 36 56 2 3 3 21 13 14 63.4 7 0.1 28 Steel A 36 56 2 3 3 20 13 14 63.7 7 0.1 29 Steel A 37 55 2 3 3 21 13 14 63.7 7 0.1 thirty Steel A 36 56 2 3 3 19 13 14 63.7 7 0.1 31 Steel A 37 55 2 3 3 58 13 14 62.9 7 0.1 32 Steel A 38 54 2 3 3 20 13 14 62.9 7 0.1 33 Steel A 38 54 2 3 3 22 13 14 61.5 7 1.5 34 Steel A 21 53 21 4 1 702 14 15 63.5 3 1.5 35 Steel B 36 56 2 3 3 18 13 14 62.9 7 0.1 36 Steel C 38 54 2 3 3 22 13 14 62.9 7 0.1

[0240]

[Table 8]

Production Results Intermediate layer Insulation coating Composition (at.%) Average thickness
nm Composition (at.%) Si O Mg P Fe P Si O Fe Cr 37 Steel D 38 54 2 3 3 20 13 14 62.9 7 0.1 38 Steel E 37 55 2 3 3 19 13 14 62.9 7 0.1 39 Steel F 37 55 2 3 3 20 13 14 62.9 7 0.1 40 Steel G 36 56 2 3 3 21 13 14 62.9 7 0.1 41 Steel N 38 54 2 3 3 18 13 14 62.9 7 0.1 42 Steel I 36 56 2 3 3 21 13 14 62.9 7 0.1 43 Steel J 37 55 2 3 3 20 13 14 62.9 7 0.1 44 Steel K 36 56 2 3 3 19 13 14 62.9 7 0.1 45 Steel L 37 55 2 3 3 19 13 14 62.9 7 0.1 46 Steel M 37 55 2 3 3 21 13 14 62.9 7 0.1 47 Steel N 38 54 2 3 3 20 13 14 62.9 7 0.1 48 Steel O 36 56 2 3 3 18 13 14 62.9 7 0.1 49 Steel A 37 55 2 3 3 19 13 15 61.8 7 0.1 50 Steel A 36 56 2 3 3 20 13 15 61.9 7 0.1 51 Steel A 37 55 2 3 3 21 13 15 61.9 7 0.1 52 Steel A 37 55 2 3 3 20 13 15 61.9 7 0.1 53 Steel A 43 45 4 4 4 13 13 14 61.9 8 0.1 54 Steel A thirty 67 1 1 1 24 13 14 64.9 5 0.1

[0241]

[Table 9]

Production Results Intermediate layer Insulation coating Composition (at.%) Average thickness
nm Composition (at.%) Si O Mg P Fe P Si O Fe Cr 55 Steel A 27 53 16 2 2 31 14 15 60.9 7 0.1 56 Steel A 36 39 19 3 3 25 13 14 62.9 7 0.1 57 Steel A 36 57.5 0.5 3 3 20 13 14 62.9 7 0.1 58 Steel A 36 55 2 4 3 25 14 14 61.9 7 0.1 59 Steel A 36 58.5 2 0.5 3 15 13 14 62.9 7 0.1 60 Steel A 36 40 2 3 19 22 12 15 62.9 7 0.1 61 Steel A 36 58 2 3 1 18 13 14 62.9 7 0.1 62 Steel A 37 55 2 3 3 19 15 9 61.7 4 0.9 63 Steel A 36 56 2 3 3 20 9 18 63.6 2 0.1 64 Steel A 36 56 2 3 3 18 15 8 62.2 3 0.1 65 Steel A 37 55 2 3 3 21 9 17 63.2 2 0.1 66 Steel A 36 56 2 3 3 19 16 9 60.4 5 0.1 67 Steel A 36 56 2 3 3 20 9 18 60.7 3 0.1 68 Steel A 38 54 2 3 3 19 16 8 60.0 4 0.1 69 Steel A 36 56 2 3 3 19 10 18 60.1 2 0.1 70 Steel A 40 55 1 2 2 3 14 15 62.9 5 0.1 71 Steel A 33 57 3 2 5 490 14 15 58.9 9 0.1 72 Steel A 37 55 2 3 3 21 13 14 62.9 7 0.1 73 Steel A 38 54 2 3 3 21 13 14 62.9 7 0.1

[0242]

[Table 10]

Production Results Insulation coating Composition (at.%) Average thickness (µm) Al
(A) Mg
(A) Mn
(A) Ni
(A) Zn
(A) V
(b) W
(b) Zr
(b) Co
(b) Mo
(b) Total quantity(a) Total quantity (b) 1 Steel A 2 - - - - - - - - - 2.0 0.0 2 2 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 3 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 4 Steel A 2 - - - - - - - - - 2.0 0.0 2 5 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 6 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 7 Steel A - - - - - - - - - - - - - 8 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 9 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 10 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 eleven Steel A 2 - - - - 1 - - - - 2.0 1.0 2 12 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 13 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 14 Steel A - 2 - - - - - - - - 2.0 0.0 2 15 Steel A - - 2 - - - - - - - 2.0 0.0 2 16 Steel A - - - 2 - - - - - - 2.0 0.0 2 17 Steel A - - - - 2 - - - - - 2.0 0.0 2 18 Steel A 2 - - - - - 1 - - - 2.0 1.0 2

[0243]

[Table 11]

Production results Insulation coating Composition (at.%) Average thickness (µm) Al
(A) Mg
(A) Mn
(A) Ni
(A) Zn
(A) V
(b) W
(b) Zr
(b) Co
(b) Mo
(b) Total quantity(a) Total quantity (b) 19 Steel A 2 - - - - - - 1 - - 2.0 1.0 2 20 Steel A 2 - - - - - - - 1 - 2.0 1.0 2 21 Steel A 2 - - - - - - - - 1 2.0 1.0 2 22 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 23 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 24 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 25 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 26 Steel A 2 - - - - 2 - - - - 2.0 2.0 2 27 Steel A 2 - - - - 0.5 - - - - 2.0 0.5 2 28 Steel A 2 - - - - 0.2 - - - - 2.0 0.2 2 29 Steel A 2 - - - - 0.2 - - - - 2.0 0.2 2 thirty Steel A 2 - - - - 0.2 - - - - 2.0 0.2 2 31 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 32 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 33 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 34 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 35 Steel B 2 - - - - 1 - - - - 2.0 1.0 2 36 Steel C 2 - - - - 1 - - - - 2.0 1.0 2

[0244]

[Table 12]

Production results Insulation coating Composition (at.%) Average thickness (µm) Al
(A) Mg
(A) Mn
(A) Ni
(A) Zn
(A) V
(b) W
(b) Zr
(b) Co
(b) Mo
(b) Total quantity(a) Total quantity (b) 37 Steel D 2 - - - - 1 - - - - 2.0 1.0 2 38 Steel E 2 - - - - 1 - - - - 2.0 1.0 2 39 Steel F 2 - - - - 1 - - - - 2.0 1.0 2 40 Steel G 2 - - - - 1 - - - - 2.0 1.0 2 41 Steel N 2 - - - - 1 - - - - 2.0 1.0 2 42 Steel I 2 - - - - 1 - - - - 2.0 1.0 2 43 Steel J 2 - - - - 1 - - - - 2.0 1.0 2 44 Steel K 2 - - - - 1 - - - - 2.0 1.0 2 45 Steel L 2 - - - - 1 - - - - 2.0 1.0 2 46 Steel M 2 - - - - 1 - - - - 2.0 1.0 2 47 Steel N 2 - - - - 1 - - - - 2.0 1.0 2 48 Steel O 2 - - - - 1 - - - - 2.0 1.0 2 49 Steel A 0.1 2 - - - 1 - - - - 2.1 1.0 2 50 Steel A - - 2 - - 1 - - - - 2.0 1.0 2 51 Steel A - - - 2 - 1 - - - - 2.0 1.0 2 52 Steel A - - - - 2 1 - - - - 2.0 1.0 2 53 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 54 Steel A 2 - - - - 1 - - - - 2.0 1.0 2

[0245]

[Table 13]

Production results Insulation coating Composition (at.%) Average thickness (µm) Al
(A) Mg
(A) Mn
(A) Ni
(A) Zn
(A) V
(b) W
(b) Zr
(b) Co
(b) Mo
(b) Total quantity(a) Total quantity (b) 55 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 56 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 57 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 58 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 59 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 60 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 61 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 62 Steel A 9 - - - - 0.4 - - - - 9.0 0.4 2 63 Steel A 7 - - - - 0.3 - - - - 7.0 0.3 2 64 Steel A 9 - - - - 2.7 - - - - 9.0 2.7 2 65 Steel A 7 - - - - 1.7 - - - - 7.0 1.7 2 66 Steel A 9 - - - - 0.5 - - - - 9.0 0.5 2 67 Steel A 9 - - - - 0.2 - - - - 9.0 0.2 2 68 Steel A 9 - - - - 2.9 - - - - 9.0 2.9 2 69 Steel A 8 - - - - 1.8 - - - - 8.0 1.8 2 70 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 71 Steel A 2 - - - - 1 - - - - 2.0 1.0 2 72 Steel A 2 - - - - 1 - - - - 2.0 1.0 0.2 73 Steel A 2 - - - - 1 - - - - 2.0 1.0 9

[0246]

[Table 14]

Production Results Insulation coating Crystalline phosphorus oxide Presence of the first crystalline phosphorus oxide Second crystalline phosphorus oxide Total area fraction of the first and second crystalline phosphorus oxides Area fraction of the second crystalline phosphorus oxide in the internal region Availability Presence of V, W, Zr, Co or Mo Average diameter of an equivalent circle Surface area Inner area First area Second area - - - nm % area % area % % 1 Steel A Eat Eat - 34 0 6 21 48 2 Steel A Eat Eat Availability (V) 37 0 eleven 37 76 3 Steel A Eat Eat Availability (V) 38 0 25 64 93 4 Steel A Eat No - - 0 10 - - 5 Steel A No No - - - - - - 6 Steel A No No - - - - - - 7 Steel A - - - - - - - - 8 Steel A Eat No - - 0 8 - - 9 Steel A Eat Eat Availability (V) 36 0 26 63 94 10 Steel A Eat Eat Availability (V) 38 0 23 66 93 eleven Steel A Eat No - 35 0 26 - - 12 Steel A Eat No - 36 0 7 - - 13 Steel A Eat No - 33 0 23 - - 14 Steel A Eat Eat - 32 0 5 18 53 15 Steel A Eat Eat - 34 0 6 23 52 16 Steel A Eat Eat - 33 0 4 21 49 17 Steel A Eat Eat - 31 0 7 21 53 18 Steel A Eat Eat Availability (W) 36 0 24 67 95

[0247]

[Table 15]

Production results Insulation coating Crystalline phosphorus oxide Presence of the first crystalline phosphorus oxide Second crystalline phosphorus oxide Total area fraction of the first and second crystalline phosphorus oxides Area fraction of the second crystalline phosphorus oxide in the internal region Availability Average diameter of an equivalent circle Surface area Inner area First area Second area - - - nm % area % area % % 19 Steel A Eat Eat Availability (Zr) 33 0 23 64 93 20 Steel A Eat Eat Availability (Co) 32 0 22 64 92 21 Steel A Eat Eat Availability (Mo) 37 0 24 66 95 22 Steel A Eat Eat Availability (V) 26 0 14 71 94 23 Steel A Eat Eat Availability (V) 64 0 36 59 83 24 Steel A Eat Eat Availability (V) 108 18 51 54 82 25 Steel A Eat Eat Availability (V) 211 33 55 49 72 26 Steel A Eat Eat Availability (V) 32 0 33 77 100 27 Steel A Eat Eat Availability (V) 36 0 16 54 77 28 Steel A Eat Eat Availability (V) 36 0 9 43 64 29 Steel A Eat Eat Availability (V) 34 0 12 46 52 thirty Steel A Eat Eat Availability (V) 35 0 8 44 46 31 Steel A Eat Eat Availability (V) 307 62 67 55 62 32 Steel A Eat No - - 0 10 - - 33 Steel A Eat No - - 0 26 - - 34 Steel A No No - - - - - - 35 Steel B Eat Eat Availability (V) 35 0 23 64 96 36 Steel C Eat Eat Availability (V) 33 0 25 66 94

[0248]

[Table 16]

Production Results Insulation coating Crystalline phosphorus oxide Presence of the first crystalline phosphorus oxide Second crystalline phosphorus oxide Total area fraction of the first and second crystalline phosphorus oxides Area fraction of the second crystalline phosphorus oxide in the internal region Availability Presence of V, W, Zr, Co or Mo Average diameter of an equivalent circle Surface area Inner area First area Second area - - - nm % area % area % % 37 Steel D Eat Eat Availability (V) 34 0 24 64 93 38 Steel E Eat Eat Availability (V) 37 0 27 66 96 39 Steel F Eat Eat Availability (V) 32 0 26 67 97 40 Steel G Eat Eat Availability (V) 37 0 23 66 94 41 Steel N Eat Eat Availability (V) 36 0 24 63 95 42 Steel I Eat Eat Availability (V) 35 0 26 66 94 43 Steel J Eat Eat Availability (V) 36 0 25 63 94 44 Steel K Eat Eat Availability (V) 33 0 27 67 95 45 Steel L Eat Eat Availability (V) 33 0 23 64 96 46 Steel M Eat Eat Availability (V) 35 0 25 66 93 47 Steel N Eat Eat Availability (V) 36 0 24 65 96 48 Steel O Eat Eat Availability (V) 31 0 22 62 93 49 Steel A Eat Eat Availability (V) 33 0 23 64 91 50 Steel A Eat Eat Availability (V) 34 0 25 62 93 51 Steel A Eat Eat Availability (V) 34 0 22 65 90 52 Steel A Eat Eat Availability (V) 32 0 23 66 94 53 Steel A Eat Eat Availability (V) 34 0 26 66 94 54 Steel A Eat Eat Availability (V) 39 0 23 62 91

[0249]

[Table 17]

Production results Insulation coating Crystalline phosphorus oxide Presence of the first crystalline phosphorus oxide Second crystalline phosphorus oxide Total area fraction of the first and second crystalline phosphorus oxides Area fraction of the second crystalline phosphorus oxide in the internal region Availability Presence of V, W, Zr, Co or Mo Average diameter of an equivalent circle Surface area Inner area First area Second area - - - nm % area % area % % 55 Steel A Eat Eat Availability (V) 40 0 25 64 93 56 Steel A Eat Eat Availability (V) 38 0 24 63 91 57 Steel A Eat Eat Availability (V) 38 0 25 64 93 58 Steel A Eat Eat Availability (V) 38 0 24 62 91 59 Steel A Eat Eat Availability (V) 38 0 25 64 93 60 Steel A Eat Eat Availability (V) 38 0 26 67 94 61 Steel A Eat Eat Availability (V) 38 0 25 64 94 62 Steel A Eat Eat Availability (V) 35 0 eleven 48 73 63 Steel A Eat Eat Availability (V) 33 0 9 44 68 64 Steel A Eat Eat Availability (V) 42 0 27 67 94 65 Steel A Eat Eat Availability (V) 41 0 23 52 85 66 Steel A Eat Eat Availability (V) 36 0 eleven 42 76 67 Steel A Eat Eat Availability (V) 33 0 8 35 51 68 Steel A Eat Eat Availability (V) 44 0 28 68 95 69 Steel A Eat Eat Availability (V) 39 0 26 53 86 70 Steel A Eat Eat Availability (V) 26 0 23 52 87 71 Steel A Eat Eat Availability (V) 26 0 26 67 95 72 Steel A Eat Eat Availability (V) 39 0 31 67 95 73 Steel A Eat Eat Availability (V) 36 0 25 58 89

[0250]

[Table 18]

Evaluation results Note Magnetic losses W _17/50 (W/kg) Coating adhesion Cylinder with a diameter of 20 mm Cylinder with a diameter of 15 mm 1 Steel A 0.63 Very good Unsatisfactory Comparative example 2 Steel A 0.63 Very good good Example according to the invention 3 Steel A 0.63 Very good Very good Example according to the invention 4 Steel A 0.68 Unsatisfactory NG Comparative example 5 Steel A Not rated Not rated Not rated Comparative example 6 Steel A Not rated Not rated Not rated Comparative example 7 Steel A - - - Comparative example 8 Steel A 0.67 Unsatisfactory NG Comparative example 9 Steel A 0.68 NG NG Comparative example 10 Steel A 0.71 NG NG Comparative example eleven Steel A 0.68 good NG Comparative example 12 Steel A 0.68 Unsatisfactory NG Comparative example 13 Steel A 0.68 good NG Comparative example 14 Steel A 0.63 Very good Unsatisfactory Comparative example 15 Steel A 0.63 Very good Unsatisfactory Comparative example 16 Steel A 0.63 Very good Unsatisfactory Comparative example 17 Steel A 0.63 Very good Unsatisfactory Comparative example 18 Steel A 0.63 Very good Very good Example according to the invention

[0251]

[Table 19]

Evaluation results Note Magnetic losses W _17/50 (W/kg) Coating adhesion Cylinder with a diameter of 20 mm Cylinder with a diameter of 15 mm 19 Steel A 0.63 Very good Very good Example according to the invention 20 Steel A 0.63 Very good Very good Example according to the invention 21 Steel A 0.63 Very good Very good Example according to the invention 22 Steel A 0.63 Very good Very good Example according to the invention 23 Steel A 0.63 Very good Very good Example according to the invention 24 Steel A 0.63 Very good Very good Example according to the invention 25 Steel A 0.64 Very good good Example according to the invention 26 Steel A 0.63 Very good Very good Example according to the invention 27 Steel A 0.63 Very good Very good Example according to the invention 28 Steel A 0.63 Very good Very good Example according to the invention 29 Steel A 0.63 Very good Very good Example according to the invention thirty Steel A 0.64 Very good good Example according to the invention 31 Steel A 0.66 Very good good Example according to the invention 32 Steel A 0.67 Unsatisfactory NG Comparative example 33 Steel A 0.67 Very good Unsatisfactory Comparative example 34 Steel A Not rated Not rated Not rated Comparative example 35 Steel B 0.63 Very good Very good Example according to the invention 36 Steel C 0.63 Very good Very good Example according to the invention

[0252]

[Table 20]

Evaluation results Note Magnetic losses W _17/50 (W/kg) Coating adhesion Cylinder with a diameter of 20 mm Cylinder with a diameter of 15 mm 37 Steel D 0.63 Very good Very good Example according to the invention 38 Steel E 0.63 Very good Very good Example according to the invention 39 Steel F 0.63 Very good Very good Example according to the invention 40 Steel G 0.63 Very good Very good Example according to the invention 41 Steel N 0.63 Very good Very good Example according to the invention 42 Steel I 0.63 Very good Very good Example according to the invention 43 Steel J 0.63 Very good Very good Example according to the invention 44 Steel K 0.63 Very good Very good Example according to the invention 45 Steel L 0.63 Very good Very good Example according to the invention 46 Steel M 0.63 Very good Very good Example according to the invention 47 Steel N 0.63 Very good Very good Example according to the invention 48 Steel O 0.63 Very good Very good Example according to the invention 49 Steel A 0.63 Very good Very good Example according to the invention 50 Steel A 0.63 Very good Very good Example according to the invention 51 Steel A 0.63 Very good Very good Example according to the invention 52 Steel A 0.63 Very good Very good Example according to the invention 53 Steel A 0.63 Very good Very good Example according to the invention 54 Steel A 0.63 Very good Very good Example according to the invention

[0253]

[Table 21]

Evaluation results Note Magnetic losses W _17/50 (W/kg) Coating adhesion Cylinder with a diameter of 20 mm Cylinder with a diameter of 15 mm 55 Steel A 0.63 Very good Very good Example according to the invention 56 Steel A 0.63 Very good Very good Example according to the invention 57 Steel A 0.63 Very good Very good Example according to the invention 58 Steel A 0.63 Very good Very good Example according to the invention 59 Steel A 0.63 Very good Very good Example according to the invention 60 Steel A 0.63 Very good Very good Example according to the invention 61 Steel A 0.63 Very good Very good Example according to the invention 62 Steel A 0.63 Very good Very good Example according to the invention 63 Steel A 0.63 Very good Very good Example according to the invention 64 Steel A 0.64 Very good Very good Example according to the invention 65 Steel A 0.63 Very good Very good Example according to the invention 66 Steel A 0.63 Very good Very good Example according to the invention 67 Steel A 0.64 Very good Very good Example according to the invention 68 Steel A 0.64 Very good Very good Example according to the invention 69 Steel A 0.63 Very good Very good Example according to the invention 70 Steel A 0.64 Very good Very good Example according to the invention 71 Steel A 0.64 Very good Very good Example according to the invention 72 Steel A 0.65 Very good Very good Example according to the invention 73 Steel A 0.64 Very good Very good Example according to the invention

INDUSTRIAL APPLICABILITY

[0254]

According to the above-described aspects of the present invention, it is possible to provide an anisotropic electrical steel sheet having excellent insulation coating adhesion even without a forsterite film. Accordingly, the present invention has significant industrial applicability.

LIST OF REFERENCE SYMBOLS

[0255]

1 - Main steel sheet (silicon steel sheet)

2 - Intermediate layer (oxide film)

3 - Insulating coating (phosphate based coating)

31 - Inner area

31a - First interior area

31b - Second internal area

32 - Surface area

Claims (46)

1. An anisotropic electrical steel sheet containing: a base steel sheet, which is a silicon steel sheet; an intermediate layer in contact with the silicon steel sheet; And an insulating coating in contact with the intermediate layer, in which the intermediate layer is an oxide film satisfying: 20 at.% or more and 70 at.% or less Si content; 30 at.% or more and 80 at.% or less O content; less than 20 at.% Mg content; less than 5 at.% P content; And less than 20 at.% Fe content, and the average thickness of the oxide film is 2 nm or more and 500 nm or less, wherein the insulating coating is a phosphate based coating satisfying: 5 at.% or more and 30 at.% or less P content; 5 at.% or more and 30 at.% or less Si content; 30 at.% or more and 80 at.% or less O content; 1 at.% or more and less than 25 at.% Fe content; less than 1.0 at.% Cr content; 0 at.% or more and 10 at.% or less Al content; 0 at.% or more and 10 at.% or less Mg content; 0 at.% or more and 10 at.% or less Mn content; 0 at.% or more and 10 at.% or less Ni content; 0 at.% or more and 10 at.% or less Zn content; 0.1 at.% or more and 10 at.% or less of the total content of Al, Mg, Mn, Ni and Zn; 0 at.% or more and 10 at.% or less V content; 0 at.% or more and 10 at.% or less W content; 0 at.% or more and 10 at.% or less Zr content; 0 at.% or more and 10 at.% or less Co content; 0 at.% or more and 10 at.% or less Mo content; And 0.1 at.% or more and 10 at.% or less of the total content of V, W, Zr, Co and Mo, and the average thickness of the phosphate-based coating is 0.1 µm or more and 10 µm or less, and wherein the phosphate-based coating includes a first crystalline phosphorus oxide having a crystal structure of the formula Fe ₂ P ₂ O ₇ and a second crystalline phosphorus oxide having a crystal structure of the formula Fe ₇ (P ₂ O ₇ ) ₄ , and the second crystalline phosphorus oxide includes at least one element selected from the group consisting of V, W, Zr, Co and Mo. 2. Anisotropic electrical steel sheet according to claim 1, in which when the phosphate-based coating is divided along the thickness direction in a section whose cutting direction is parallel to the thickness direction into two equal regions, which are the internal region in contact with the oxide film and the surface region not in contact with the oxide film, the proportion of the total area of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide that are included in the inner region is greater than the proportion of the total area of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide that are included in the surface region. 3. Sheet of anisotropic electrical steel according to claim 2, in which the proportion of the total area of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide that are included in the surface region is 0% or more and 30% or less, and the proportion of the total area of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide that are included in the inner region, is 3% or more and 50% or less. 4. Sheet of anisotropic electrical steel according to claim 2 or 3, in which when the inner region is divided along the sectional thickness direction into two equal regions, which are the first inner region in contact with the oxide film and the second inner region not in contact with the oxide film, when the proportion of the first region is set as a percentage value obtained by dividing the area fraction of the second crystalline phosphorus oxide that is included in the first internal region by the total area fraction of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide that are included in the first internal region, and when the proportion of the second region is set as a percentage value obtained by dividing the area fraction of the second crystalline phosphorus oxide that is included in the second internal region by the total area fraction of the first crystalline phosphorus oxide and the second crystalline phosphorus oxide that are included in the second internal region, the share of the second region is greater than the share of the first region. 5. Sheet of anisotropic electrical steel according to claim 4, in which said share of the first region is 0% or more and 70% or less, and said share of the second region is 50% or more and 100% or less. 6. Sheet of anisotropic electrical steel according to any one of paragraphs. 1-5, in which the diameter of the equivalent circle of the second crystalline phosphorus oxide is on average 5 nm or more and 300 nm or less.