JPH07278832A - Grain-oriented silicon steel sheet low in iron loss and its production - Google Patents

Abstract

PURPOSE:To produce a grain-oriented silicon steel sheet with the iron loss improved by forming a chemically stable coating film imparting a high tension to the steel sheet on the surface of the steel sheet. CONSTITUTION:A coating film consisting essentially of aluminum borate and borosilcate glass or a coating film consisting essentially of aluminum borate, iron borate and borosilicate glass is formed on the outermost surface of a steel sheet. A high tension is especially effectively imparted by the coating film contg. crystalline aluminum borate. A suspension contg. boric acid, an aluminum oxide precursor compd. and a silicon oxide precursor compd. is applied and baked at a specified temp. to form the oxide coating film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a unidirectional silicon steel sheet having reduced iron loss by having a coating film which is chemically stable and imparts a large tension to the steel sheet, and a method for producing the same.

[0002]

2. Description of the Related Art One-directional silicon steel sheets are (110), [0
[01] is mainly used as a magnetic iron core material, and a material having a small iron loss is required to reduce energy loss. As a means for reducing the iron loss of a unidirectional silicon steel sheet, there is a method of irradiating a laser beam on the surface of the steel sheet after finish annealing to give a local strain, and thereby subdividing the magnetic domain.
It is disclosed in Japanese Patent No. 26405. Further, there is a magnetic domain subdivision means which does not lose its effect even after strain relief annealing (stress relief annealing) after iron core processing is disclosed in, for example, JP-A-62-861.
No. 75 publication.

On the other hand, since iron alloys containing iron and silicon have large crystal magnetic anisotropy, application of external tension causes subdivision of magnetic domains, which reduces eddy current loss which is a main factor of iron loss. You can Therefore, it is effective to apply tension to the steel sheet in order to reduce the iron loss of the unidirectional silicon steel sheet containing 5% or less of silicon, and it is effective to apply the tension up to about 1.5 kgf / mm ^2. It is known that the loss can be reduced. This tension is usually applied by the film formed on the surface.

Conventionally, for unidirectional silicon steel sheets, a primary coating mainly composed of forsterite formed by a reaction between an oxide on the surface of the steel sheet and an annealing separator in the finish annealing step, and Japanese Patent Laid-Open No. 48-39338. 1.0 kgf / mm ² when the plate thickness is 0.23 mm due to the two-layer coating of the secondary coating formed by baking the coating liquid mainly containing colloidal silica and phosphate disclosed in Japanese Patent Publication No. Some tension is applied. Therefore, in the case of these existing coatings, there is still room for iron loss improvement by applying a larger tension, but increasing the applied tension by thickening the coating leads to a decrease in space factor, which is not preferable.

As another method for improving the iron loss of a unidirectional silicon steel sheet, the unevenness of the surface of the steel sheet after finish annealing and the internal oxide layer near the surface are removed to give a mirror finish, and the surface is made of metal. The method of plating is Japanese Patent Publication Sho 52-2
4499 discloses a method of further forming a tension film on the surface thereof, for example, JP-B-56-4150 and JP-A-6-61.
No. 1-201732, Japanese Patent Publication No. 63-54767, and Japanese Patent Application Laid-Open No. 2-213483. Even in these cases, the larger the tension applied to the steel sheet by the coating, the greater the iron loss improving effect.

From these things, a coating film which is excellent in adhesiveness, thin, and capable of imparting a large tension to a steel sheet has been desired. On the other hand, the present inventors have proposed a grain-oriented electrical steel sheet having aluminum borate as a main component, or a coating on which aluminum borate crystals and an amorphous oxide are mixed on the surface. However, in these coatings, the chemical stability may be slightly inferior, and particularly for a steel sheet that has been mirror-finished, an oxide layer is formed at the interface with the coating, depending on the manufacturing conditions, and good properties are obtained. In some cases, a unidirectional silicon steel sheet could not be obtained.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves these problems in the prior art and has a coating film which is chemically stable and imparts a large tensile force to the steel sheet.
An object of the present invention is to provide a unidirectional silicon steel sheet with reduced iron loss and a method for manufacturing the same.

[0008]

DISCLOSURE OF THE INVENTION The present invention is a unidirectional silicon steel sheet formed by forming a coating film containing aluminum borate and borosilicate glass as the main components on the outermost surface of the steel sheet on the surface of the steel sheet that has undergone finish annealing. Is the gist. Further, the gist is a low iron loss unidirectional silicon steel sheet having a coating film containing aluminum borate, iron borate, and borosilicate glass as the main components on the outermost surface of the steel sheet. Among them, aluminum borate is _{Al x B y O 3 (x} + y) / 2 (0.1 ≦ (y / x) ≦ 5)
The gist is a low iron loss unidirectional silicon steel sheet formed with the above-mentioned coating which is crystalline aluminum borate represented by the following chemical formula.

Further, as a manufacturing method thereof, a suspension containing boric acid, an aluminum oxide precursor compound, and a silicon oxide precursor compound is applied to the surface of the unidirectional silicon steel sheet on which finish annealing has been completed, and the temperature is 500 to 1350 ° C. Burn with
A method for producing a low iron loss unidirectional silicon steel sheet is characterized in that an oxide film is formed, and an oxide film is formed by a similar process using a suspension containing an iron compound. To do. Further, the gist of the method for producing a steel sheet is that the aluminum oxide precursor sol is used as the aluminum oxide precursor compound and the silicon oxide precursor sol is used as the silicon oxide precursor compound. Further, as a silicon oxide precursor sol, SiO ₂ · nH
Silica sol represented by the chemical formula of ₂ O or SiO _p (OH) _q , and / or colloidal silica, in particular, an alkyl silicate and / or an alkyl silicate hydrolyzate, which is a unidirectional silicon with low iron loss. The gist is the method of manufacturing a steel sheet.

[0010]

The unidirectional silicon steel sheet of the present invention has a coating film containing aluminum borate and borosilicate glass as the main components on the outermost surface. Conventionally, a film material having a small coefficient of thermal expansion is selected for applying tension to an electromagnetic steel sheet, and stress generated during cooling due to a difference in coefficient of thermal expansion from the steel sheet is used. However, it has been pointed out that not only the difference in thermal expansion coefficient, but also the Young's modulus of the coating material is a factor that influences the application of tension to the steel sheet.

Among the coating components of the present invention, it is presumed that aluminum borate satisfies the above requirements and brings a large amount of tension to the steel sheet. Al ₂ O ₃ —B ₂ O ₃ -based oxide generally called aluminum borate is 9Al ₂ O.
It has been found that there are two equilibrium phase compounds of ₃ · B ₂ O ₃ and 2Al ₂ O ₃ · B ₂ O ₃ , and they are effective in imparting tension to the steel sheet. However, aluminum borate
Depending on the production conditions, in addition to the above-mentioned two equilibrium phases, an intermediate composition of the two or a composition in the vicinity thereof may be taken.
This is because the two equilibrium phases have the same crystal structure and the lattice constants are almost the same, so that the substitution easily occurs between Al and B ion sites to form a metastable phase. .

[0012] As the composition ratio for forming such a metastable phase, 0.1 ≦ when expressed in _{Al x B y O 3 (x} + y) / 2
It was found that (y / x) ≦ 5, and it was confirmed that any of these had no problem and that the tension could be effectively applied. Among these, 0.1 ≦ (y / x) ≦ 2 is preferable, and 0.2 ≦ (y / x) ≦ 1 is more preferable as a composition particularly effective for imparting tension.
Usually, these aluminum borates often have a crystallite size of several nm to several tens of nm or more regardless of the composition, and are preferably crystalline in order to give a large tension. On the other hand, when aluminum borate does not have sufficient crystallinity and is in a state close to amorphous, the tension applied to the steel sheet is lower than that in the case of being crystalline, but the conventional coating Since a much larger tension can be applied as compared with the above, it can be used as a mode of the present invention without any trouble.

The film on the surface of the unidirectional silicon steel sheet of the present invention also contains borosilicate glass as a main component. This is generated by the reaction of boric acid in the coating liquid with the silicon oxide precursor and / or silicon in the steel plate component, but it is considered that it often exists as a matrix-like phase in the coating film. It reduces the micropores and the like that are found in the coating mainly composed of aluminum borate. It is estimated that this effect alleviates the problem of interfacial oxidation that occurs during baking.

The main components of borosilicate glass are boron and silicon, but there is no problem even if other components are mixed in. These may be inevitably mixed with other components in the coating film, impurities, or the like, or may be intentionally added to the coating liquid. As components, alkali metals, alkaline earth metals, transition metal elements and the like are generally used, but glass forming oxide elements, modifying oxide elements and the like are also conceivable. Among them, some elements such as Fe have the effect of increasing the chemical stability of the entire coating by being mixed in the glass, and the characteristics of the coating can be positively improved by adding them to the coating solution. .

The coating on the surface of the unidirectional silicon steel sheet of the present invention contains aluminum borate and borosilicate glass as main components, and the main component here is 50 in terms of volume ratio to the entire coating. % Or more. A more preferable content ratio is 70% or more as a volume ratio to the entire coating film. In the coating, the components other than the main component are not particularly limited,
Generally, it is a crystalline compound such as an alkali metal, an alkaline earth metal or a transition metal. In particular, the inclusion of a crystalline iron compound can significantly enhance the chemical stability of the coating.
Above all, by containing iron borate (Fe ₃ BO ₅ ) as a main component in the coating as in the case of aluminum borate and borosilicate glass, it is possible to impart a large tension to the steel sheet, chemically stabilize the coating, and suppress interfacial oxidation. A good coating having a large effect can be obtained.

The content ratio of aluminum borate and borosilicate glass, which are the main components in the coating, is such that aluminum borate has a volume relative to that of aluminum borate and borosilicate glass combined from the viewpoint that a larger coating tension can be obtained. The ratio is 60% or more, preferably 80% or more. Further, if the glass component is extremely small, the above-mentioned excellent coating properties cannot be obtained. Therefore, the preferable amount of the glass component is 5% or more, preferably 5% or more by volume ratio to the total amount of aluminum borate and borosilicate glass. It is 10% or more. When iron borate is contained, the content of each of the three main components is preferably 5% or more, and more preferably 10% or more, in terms of the volume ratio to the whole main component.

As an embodiment of the unidirectional silicon steel sheet of the present invention,
Although the above-mentioned coating is provided on the outermost surface of the steel sheet, the base material steel sheet on which the coating is formed is not particularly limited as long as secondary recrystallization is completed. Generally, a steel sheet generally used as a base material is a steel sheet having a forsterite primary coating formed during finish annealing (secondary recrystallization annealing), and the primary coating is removed by a method such as pickling. Then
Steel plate with exposed metal surface, or steel plate whose surface is further flattened by polishing, etc., finish annealing (secondary recrystallization annealing) under the condition that forsterite coating is not formed
And a steel plate whose metal surface is exposed or whose surface is further flattened. If the coating film of the unidirectional silicon steel sheet of the present invention is too thick, the space factor decreases, so that the coating film should be as thin as possible according to the purpose, and a thickness of 5% or less based on the steel sheet thickness is preferable. More preferably 2%
It is the following. Further, from the viewpoint of applying tension, if it is extremely thin, a sufficient effect cannot be obtained, and 0.1 μm or more is preferable.

Next, a method for suitably manufacturing the unidirectional silicon steel sheet of the present invention will be described below. A suspension containing boric acid, an aluminum oxide precursor compound, and a silicon oxide precursor compound is prepared. Boric acid is most preferably orthoboric acid represented by H ₃ BO ₃ in terms of workability and price, but H
Metaboric acid represented by BO ₂ , boron oxide represented by B ₂ O ₃ , or a mixture thereof can also be used. Not only aluminum oxide but also aluminum oxide hydrate such as boehmite represented by Al ₂ O ₃ .mH ₂ O, aluminum hydroxide and the like.

Various aluminum salts such as aluminum nitrate and aluminum chloride are also preferably used. Similarly, the silicon oxide precursor compound is also a general term for compounds that become silicon oxide after baking, and hydrates of silicon oxide, silicon oxyhydroxide, various silicon compounds and the like are preferably used.
A suspension (slurry) in which these raw materials are dispersed in a dispersion medium.
To make. Water is most suitable as the dispersion medium, but an organic solvent or a mixture thereof can be used unless there is any particular problem in other steps. Some of the raw materials may be dissolved at the time of making the slurry, but this is all right.

The slurry thus obtained is applied to the surface of the unidirectional silicon steel sheet which has been subjected to finish annealing by a conventionally known method such as a coater such as a roll coater, a dipping method, spraying, or electrophoresis. The steel sheet that has been subjected to finish annealing as used herein means: a steel sheet having a forsterite primary coating formed on its surface by performing finish annealing by a conventionally known method: a primary coating and incidentally formed Steel plate with internal oxide layer removed by immersion in acid:
Steel plate obtained by performing flattening annealing in hydrogen on the steel plate obtained in 1., or steel plate subjected to polishing such as chemical polishing or electrolytic polishing: Alumina powder or the like which is inactive against film formation, or trace amount of chloride It refers to a steel sheet, etc., to which a conventionally known annealing separator containing additives is applied and finish annealing is performed under the condition that a primary coating is not formed.

After the coated steel sheet is dried, 500 to 1350
An oxide film is formed on the surface by baking at ° C. The atmosphere during baking is an inert gas atmosphere such as nitrogen,
A reducing atmosphere such as a nitrogen-hydrogen mixed atmosphere is preferable, and an atmosphere containing air or oxygen may undesirably oxidize the steel sheet. There is no particular limitation on the dew point of the atmospheric gas. When the baking temperature is less than 500 ° C., the applied precursor may not become an oxide, and since the baking temperature is low, sufficient tension is not exhibited, which is not preferable. On the other hand, when the temperature exceeds 1350 ° C, it is not economical but not particularly disadvantageous, and more preferably 1250 ° C.
It is the following.

Another production method of the present invention is a method in which a suspension containing an iron compound in boric acid, an aluminum oxide precursor compound, and a silicon oxide precursor compound is used as a coating liquid. The iron compound used here can be used without any particular problem as long as it is a compound that becomes iron oxide after baking. For example, iron oxide, iron oxide hydroxide such as Fe ₂ O ₃ .aH ₂ O, and iron hydroxide. Of course, various iron compounds such as iron nitrate, iron chloride and iron sulfate can be preferably used. Among them, particularly, an iron compound that is soluble in the dispersion medium or an iron compound that is insoluble in the dispersion medium is preferably compound particles having a small particle size after dispersion. The particle size is preferably 1 μm or less, more preferably 0.5 μm.
μm or less. The steps after coating may be the same as those in the first manufacturing method using the mixed suspension of boric acid, aluminum oxide precursor compound, and silicon oxide precursor compound described above.

Of the above-mentioned slurries, a thin and uniform coating having good adhesion may be obtained by using a so-called sol fine particle dispersion system as the aluminum oxide precursor and the silicon oxide precursor. This is particularly remarkable when a non-metal substance does not exist on the surface and a film is directly formed on the metal surface. In this case, the fine particle dispersed sol described above or a sol containing a soluble component is preferably used. As the particle size of the sol used, if it is too fine, cracks during drying, peeling, etc., easily occur,
Since it becomes difficult to form a film having a predetermined thickness, it is preferably 1
It is at least 0 nm, more preferably at least 15 nm.

When a sol solution is used as the coating solution, the so-called boehmite sol and / or alumina sol described above as the aluminum oxide precursor has good workability,
Alternatively, it is particularly preferably used in terms of price. On the other hand, various kinds of silicon oxide precursor sols can be used, but silica sol represented by a chemical formula of SiO ₂ · nH ₂ O or SiO _p (OH) _q and / or colloidal silica is also workable. It is preferably used in terms of price. Among them, Si (O
An alkyl silicate of the chemical formula C _z H _{2z + 1} ) ₄ and / or its hydrolyzate is preferably used. Alkyl silicate is one kind of metal alkoxide, but its hydrolysis is relatively slow, and stable properties can be obtained as a precursor.

Alkyl silicate usually forms a hydroxide of silicon or a hydrate of silicon oxide by hydrolysis, but in the case of forming a kind of film, the hydrolysis of alkyl silicate is more preferable than using alkyl silicate as it is. There are cases in which it is preferable to use objects. In such a case, the precursor sol after hydrolysis is preferably used.
For this, there are several methods such as a method of preliminarily hydrolyzing and then mixing with other components, a method of parallelizing hydrolysis while mixing with other components, and adding aging if necessary, but In the invention, any of these is not a problem.

Among the preferred alkyl silicate compounds, those having a high hydrolysis rate and a small number of carbon atoms z are preferable, and z ≦ 3 is preferable, but a methyl silicate having z = 1 is a methyl produced by hydrolysis. Ethyl silicate with z = 2 is particularly preferably used because of the harmful nature of alcohol. Even when using a precursor sol of silicon oxide or aluminum oxide, it is possible to disperse the precursor sol in a dispersion medium, particularly water, as in the case of the slurry described above. In order to obtain particularly good dispersibility, pH control of the coating solution by addition of acid, alkali or the like is a technique often used, and the present invention can be carried out without any particular problems. Further, there is no problem in adding an extremely small amount of a surfactant or the like to improve the coating property on the steel sheet. The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0027]

【Example】

Example 1 Commercially available boric acid reagent, aluminum oxide powder (average particle size:
0.4 μm) and silicon oxide fine powder were weighed in the proportions shown in Table 1, and distilled water was added to this to prepare a slurry. A 0.2 mm-thick finish-annealed unidirectional silicon steel sheet containing 3.2% Si (forsterite
(After coating), so that one side is 4 g / m ² and dried, then 1000 in N ₂ atmosphere containing 3 vol% of H _2.
An oxide film was formed on the surface by baking at 5 ° C for 5 minutes.

From the results of chemical analysis, X-ray diffraction, electron microscope observation, etc., the obtained coating film was crystalline (2Al ₂ O ₃ .B
₂ O ₃ , or 9 Al ₂ O ₃ · B ₂ O ₃ ) containing aluminum borate, a glass phase containing boron and silicon as main components in a volume ratio of 50% or more, and also containing some unreacted silicon oxide. I found out that A winding test was conducted around a 20 mmφ cylinder so that the angle was 180 degrees, and the adhesion of the coating film evaluated from the peeling condition was extremely good. The chemical stability of the coating is evaluated by immersing the coated steel sheet in 100 ml of boiling distilled water as it is for 10 minutes, and by evaluating the weight change before and after that, for each composition, a weight of less than 5 mg per 50 cm ² steel sheet. It was a change. Further, the dissolution of the coating component into boiling distilled water was below the analytical detection limit for all compositions. Remove the coating on one side, the tension applied to the steel plate measured from the bending of the plate,
The magnetic properties are shown in Table 1. From the results in Table 1, it can be seen that the grain-oriented silicon steel sheets having significantly low iron loss are obtained.

[0029]

[Table 1]

Example 2 Commercial boric acid reagent, boehmite sol (average particle size: 100)
nm) and colloidal silica (average particle size: 15 nm) were mixed in a proportion corresponding to the solid content shown in Table 2, and distilled water was added to the mixture as needed to prepare a mixed sol. This was applied to a 0.2 mm thick unidirectional silicon steel sheet containing 3.2% of Si, aluminum oxide applied as an annealing separator, and subjected to mirror finishing at the same time as secondary recrystallization. After coating and drying so as to be ² , an oxide film was formed on the surface by baking at 850 ° C. for 3 minutes in an N ₂ atmosphere containing 10 vol% of H ₂ .

From the results of chemical analysis, X-ray diffraction, electron microscope observation, etc., the obtained coating film was crystalline (2Al ₂ O ₃ .B
₂ O _3, or _{9Al 2 O 3 · B 2 O} 3) aluminum borate of it was found to contain 50% or more glass phase in a volume ratio of the main component boron and silicon. The adhesion and chemical stability of the coating film evaluated in the same manner as in Example 1 were extremely good for all compositions. Tension applied to steel plate,
The magnetic properties are shown in Table 2. From the results in Table 2, it can be seen that the grain-oriented silicon steel sheets having extremely low iron loss are obtained. Further, when a cross section of the steel sheet on which the film was formed was polished and observed by SEM, no remarkable oxide layer was observed at the film-steel plate interface in any composition.

[0032]

[Table 2]

Example 3 Metaboric acid prepared by drying a commercially available boric acid reagent at 150 ° C., boehmite powder (average particle size / 50 nm), colloidal silica (average particle size: 15 nm), and FeOOH powder in solid content equivalent. The mixture was mixed in the proportions shown in Table 3, and distilled water was added to this to prepare a mixed sol. This was applied to a 0.2 mm-thick finish-annealed unidirectional silicon steel sheet (having a primary forsterite coating) containing 3.2% of Si on one side 4
After coating so as to be g / m ² and drying, an oxide film was formed on the surface by baking at 900 ° C. for 1 minute in an N ₂ atmosphere containing 1 vol% of H ₂ .

From the results of chemical analysis, X-ray diffraction, electron microscope observation, etc., the obtained coating film was crystalline (2Al ₂ O ₃ .B
₂ O ₃ , or 9Al ₂ O ₃ · B ₂ O ₃ ) aluminum borate, a glass phase containing boron and silicon as main components, and iron borate (Fe ₃ BO ₅ ) in a volume ratio of 50% or more. I understood it. The adhesion and chemical stability of the coating film evaluated in the same manner as in Example 1 were extremely good. Table 3 shows the tension applied to the steel sheet measured from the bending of the sheet after removing the coating on one surface and the magnetic properties. From the results in Table 3,
It can be seen that a unidirectional silicon steel sheet having a remarkably low iron loss was obtained in each case.

[0035]

[Table 3]

Example 4 Commercial boric acid reagent, boehmite sol (average particle size: 50 n
m), ethyl silicate was mixed in a proportion corresponding to the solid content shown in Table 4 (however, ethyl silicate is equivalent to the finally obtained oxide), and distilled water to which a trace amount of hydrochloric acid had been added was added and mixed. A sol was prepared. This is Si 3.2
%, Aluminum oxide applied as an annealing separator, and subjected to secondary recrystallization and mirror-finishing at a thickness of 0.2
mm unidirectional silicon steel plate coated on one side to 4 g / m ² and dried, then 8 in an N ₂ atmosphere containing 3 vol% of H _2.
An oxide film was formed on the surface by baking at 50 ° C. for 2 minutes.

From the results of chemical analysis, X-ray diffraction, electron microscope observation, etc., the obtained coating film was crystalline (2Al ₂ O ₃ .B
₂ O _3, or _{9Al 2 O 3 · B 2 O} 3 aluminum borate of) the glass phase consisting mainly of boron and silicon was found to contain 50% or more by volume ratio. Adhesion and chemical stability of the coating film evaluated in the same manner as in Example 1 around the 20 mmφ cylinder were extremely good. Table 4 shows the tension applied to the steel sheet measured from the bending of the sheet after removing the coating on one side and the magnetic properties. From the results in Table 4, it can be seen that the grain-oriented silicon steel sheets having extremely low iron loss are obtained. No significant oxide layer was observed at the film-steel plate interface.

[0038]

[Table 4]

[0039]

INDUSTRIAL APPLICABILITY According to the present invention, a unidirectional silicon steel sheet which is chemically stable by having a coating film of a specific component and whose iron loss is remarkably improved by its tension imparting effect,
And a method for manufacturing the same. In particular, it shows good characteristics for both steel sheets having a primary coating that has been conventionally used and mirror-finished steel sheets for the purpose of significantly reducing iron loss, and has an industrial effect from the viewpoint of versatility. It is enormous.

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[Procedure amendment]

[Submission date] May 16, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

Among the coating components of the present invention, it is presumed that aluminum borate satisfies the above requirements and brings a large amount of tension to the steel sheet. Al ₂ O ₃ —B ₂ O ₃ -based oxide generally called aluminum borate is 9Al ₂ O.
_{3 · 2 B 2 O 3,} 2Al 2 2 two equilibrium phases compound of O ₃ · B ₂ O ₃ is present, it was found to be effective in tensioning of the steel sheet. However, aluminum borate may have an intermediate composition of the two equilibrium phases or a composition in the vicinity thereof, depending on the production conditions. This is because the two equilibrium phases have the same crystal structure and the lattice constants are almost the same, so that the substitution easily occurs between Al and B ion sites to form a metastable phase. .

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction content]

From the results of chemical analysis, X-ray diffraction, electron microscope observation, etc., the obtained coating film was crystalline (2Al ₂ O ₃ .B
₂ O ₃ or 9 Al ₂ O ₃ · 2 B ₂ O ₃ ) contains aluminum borate, a glass phase containing boron and silicon as main components in a volume ratio of 50% or more, and also contains some unreacted silicon oxide. I found out. A winding test was conducted around a 20 mmφ cylinder so that the angle was 180 degrees, and the adhesion of the coating film evaluated from the peeling condition was extremely good. The chemical stability of the coating was evaluated by immersing the coated steel sheet in 100 ml of boiling distilled water for 10 minutes as it was, and evaluating the weight change before and after that, and for each composition, a weight of less than 5 mg per 50 cm ² steel sheet. It was a change. Further, the dissolution of the coating component into boiling distilled water was below the analytical detection limit for all compositions. Remove the coating on one side, the tension applied to the steel plate measured from the bending of the plate,
The magnetic properties are shown in Table 1. From the results in Table 1, it can be seen that the grain-oriented silicon steel sheets having significantly low iron loss are obtained.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0031

[Correction method] Change

[Correction content]

From the results of chemical analysis, X-ray diffraction, electron microscope observation, etc., the obtained coating film was crystalline (2Al ₂ O ₃ .B
₂ O _3, or _{9Al 2 O 3 · 2 B 2} O 3) aluminum borate of it was found to contain 50% or more glass phase in a volume ratio of the main component boron and silicon. The adhesion and chemical stability of the coating film evaluated in the same manner as in Example 1 were extremely good for all compositions. Table 2 shows the tension applied to the steel sheet and the magnetic properties. From the results in Table 2,
It can be seen that a unidirectional silicon steel sheet having a remarkably low iron loss was obtained in each case. Further, when a cross section of the steel sheet on which the coating was formed was polished and observed by SEM, no remarkable oxide layer was observed at the coating-steel sheet interface in any composition.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction content]

From the results of chemical analysis, X-ray diffraction, electron microscope observation, etc., the obtained coating film was crystalline (2Al ₂ O ₃ .B
₂ O ₃ or 9 Al ₂ O ₃ · 2 B ₂ O ₃ ) aluminum borate, a glass phase containing boron and silicon as main components, and iron borate (Fe ₃ BO ₅ ) in a volume ratio of 50% or more. I found out that The adhesion and chemical stability of the coating film evaluated in the same manner as in Example 1 were extremely good. Table 3 shows the tension applied to the steel sheet measured from the bending of the sheet after removing the coating on one surface and the magnetic properties. From the results in Table 3,
It can be seen that a unidirectional silicon steel sheet having a remarkably low iron loss was obtained in each case.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Name of item to be corrected] 0037

[Correction method] Change

[Correction content]

From the results of chemical analysis, X-ray diffraction, electron microscope observation, etc., the obtained coating film was crystalline (2Al ₂ O ₃ .B
₂ O _3, or _{9Al 2 O 3 · 2 B 2} O 3) aluminum borate of the glass phase consisting mainly of boron and silicon was found to contain 50% or more by volume ratio. 20 mmφ
The adhesiveness and the chemical stability of the coating film evaluated in the same manner as in Example 1 around the column were extremely good. Table 4 shows the tension applied to the steel sheet measured from the bending of the sheet after removing the coating on one side and the magnetic properties. From the results in Table 4, it can be seen that the grain-oriented silicon steel sheets having extremely low iron loss are obtained. No significant oxide layer was observed at the film-steel plate interface.

Claims (8)

[Claims] 1. A low iron loss unidirectional silicon steel sheet having a coating film containing aluminum borate and borosilicate glass as main components on the outermost surface of the steel sheet. 2. A low iron loss unidirectional silicon steel sheet having a coating film containing aluminum borate, iron borate, and borosilicate glass as a main component on the outermost surface of the steel sheet. Wherein aluminum borate is Al _x B _y O
The low iron loss unidirectional silicon steel sheet according to claim 1 or 2, which is a crystalline aluminum borate represented by a chemical formula of _{3 (x + y) / 2} (0.1≤ (y / x) ≤5). 4. A suspension containing boric acid, an aluminum oxide precursor compound, and a silicon oxide precursor compound is applied to the surface of the unidirectional silicon steel sheet on which finish annealing has been completed, and after drying,
A method for producing a low iron loss unidirectional silicon steel sheet, which comprises baking at a temperature of 500 to 1350 ° C. to form an oxide film. 5. A suspension containing boric acid, an aluminum oxide precursor compound, a silicon oxide precursor compound, and an iron compound is applied to the surface of the unidirectional silicon steel sheet that has been subjected to finish annealing, dried and then 500 to 1350 ° C. A method for producing a low iron loss unidirectional silicon steel sheet, which is baked at the above temperature to form an oxide film. 6. The method for producing a low iron loss unidirectional silicon steel sheet according to claim 4, wherein the aluminum oxide precursor compound is an aluminum oxide precursor sol and the silicon oxide precursor compound is a silicon oxide precursor sol. 7. The silicon oxide precursor sol is SiO ₂ .nH.
_The method for producing a low iron loss unidirectional silicon steel sheet according to any one of claims 4 to 6, which is silica sol represented by a chemical formula of ₂ O or SiO _p (OH) _q and / or colloidal silica. 8. The method for producing a low iron loss unidirectional silicon steel sheet according to claim 4, wherein the silicon oxide precursor sol is an alkyl silicate and / or an alkyl silicate hydrolyzate.