JP2664336B2 - Low iron loss unidirectional silicon steel sheet having oxide-based composite coating and method for producing the same - Google Patents

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 providing a coating that imparts a large tension to the steel sheet, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Oriented silicon steel sheets are (110), [0
[01], and is widely used as a magnetic iron core material. In particular, a material having a small iron loss is required to reduce energy loss. As a means of reducing the iron loss of the unidirectional silicon steel sheet, the steel sheet surface after finish annealing is irradiated with a laser beam to give local strain,
Japanese Patent Application Laid-Open No. 58-26 discloses a method for subdividing magnetic domains.
No. 405. In addition, a magnetic domain refining means which does not lose its effect even after performing stress relief annealing (stress relief annealing) after iron core processing is disclosed in, for example, JP-A-62-86175.
No. 6,086,045.

On the other hand, an iron alloy containing iron and silicon has a large crystal magnetic anisotropy. Therefore, when an external tension is applied, the magnetic domain is subdivided and the eddy current loss which is a main element of iron loss is reduced. Can be. Therefore, it is effective to apply a tension to the steel sheet to reduce iron loss of a unidirectional silicon steel sheet containing 5% or less of silicon, and it is effective to apply a tension up to about 1.5 kgf / mm ² to effectively reduce iron loss. It is known that loss can be reduced. This tension is usually provided by a coating formed on the surface.

Conventionally, a unidirectional silicon steel sheet has a primary coating mainly composed of forsterite produced by a reaction between an oxide on the steel sheet surface and an annealing separator in a finish annealing step, and Japanese Patent Application Laid-Open No. 48-39338. A tension of about 1.0 kgf / mm ² is given by a two-layer coating of a secondary coating formed by baking a coating liquid mainly composed of colloidal silica and phosphate disclosed in Japanese Patent Application Laid-Open Publication No. H10-163,086. . Therefore, in the case of these existing coatings, although there is room for improving iron loss by applying a larger tension, an increase in the applied tension by increasing the thickness of the coating is not preferable because it results in a decrease in the space factor.

Further, as another method for improving iron loss of a grain-oriented silicon steel sheet, mirror finishing is performed by removing irregularities on the surface of the steel sheet after finish annealing and an internal oxide layer near the surface, and performing metal finishing on the surface. The method of plating is Japanese Patent Publication No. 52-2.
No. 4499, a method of forming a tension film on the surface is disclosed in, for example, Japanese Patent Publication No.
These are disclosed in Japanese Patent Application Laid-Open No. 1-2201732, Japanese Patent Publication No. 63-54767, Japanese Patent Application Laid-Open No. Hei 2-213488, and the like. In these cases as well, the greater the tension applied to the steel sheet by the coating, the greater the effect of improving iron loss. For these reasons, there has been a demand for a coating film having excellent adhesion and being thin and capable of applying a large tension to a steel sheet.

[0006]

SUMMARY OF THE INVENTION The present invention solves these problems in the prior art, and provides a unidirectional silicon steel sheet in which iron loss is reduced by providing a coating that imparts a large tension to the steel sheet, and It is an object of the present invention to provide a manufacturing method thereof.

[0007]

SUMMARY OF THE INVENTION The present invention provides a unidirectional silicon steel sheet having a magnesium oxide-aluminum oxide-silicon oxide composite coating on the surface, and a magnesium oxide-aluminum oxide-silicon oxide composite coating formed of a crystalline cordier. Unidirectional silicon steel sheet containing light and / or crystalline sapphirine, unidirectional silicon steel sheet having a magnesium oxide-aluminum oxide-silicon oxide-amorphous oxide-based composite coating on the surface, magnesium oxide-aluminum oxide-oxidation Unidirectional silicon containing silicon-amorphous oxide-based composite coating containing crystalline cordierite and / or crystalline saphirin and / or an amorphous phase containing at least one of silicon, boron and phosphorus as a component Steel sheet is the gist.

A suspension containing a magnesium oxide precursor compound, an aluminum oxide precursor compound, and a silicon oxide precursor compound is applied to the surface of the steel sheet that has been subjected to finish annealing, dried, and baked at a temperature of 500 to 1350 ° C. The gist is a manufacturing method for forming an oxide film. Further, the gist of the present invention is a production method in which the aluminum oxide precursor compound is an aluminum oxide precursor sol and the silicon oxide precursor compound is a silicon oxide precursor sol. Further, a suspension containing a magnesium oxide precursor compound, an aluminum oxide precursor compound, a silicon oxide precursor compound, boric acid and / or borate, phosphoric acid and / or phosphate is applied to the surface of the steel sheet after the finish annealing. The gist of the present invention is to provide a manufacturing method by drying and baking at a temperature of 500 to 1350 ° C. to form an oxide film. Further, the gist of the present invention is a production method in which the aluminum oxide precursor compound is an aluminum oxide precursor sol and the silicon oxide precursor compound is a silicon oxide precursor sol.

[0009]

The present invention will be described below in detail. The unidirectional silicon steel sheet of the present invention has a magnesium oxide-aluminum oxide-silicon oxide-based composite coating on its surface. Conventionally, a coating material having a small thermal expansion coefficient has been selected for applying tension to a silicon steel sheet, and a stress generated during cooling due to a difference in thermal expansion coefficient from the steel sheet has been used. However, it has been pointed out that not only the coefficient of thermal expansion but also the Young's modulus of the coating material is a factor that affects the application of tension to the steel sheet. Although it is impossible to clearly define the role of the coating components of the present invention, the aluminum oxide component has a relatively large Young's modulus, and the silicon oxide component has a relatively small coefficient of thermal expansion. It is speculated that a large tension is applied to the steel sheet by combining magnesium oxide with magnesium.

[0010] Magnesium oxide is only known as periclase as a crystal phase, but aluminum oxide has several crystal systems such as α-, γ-, δ-, θ-, Is not necessarily the same in each crystal system. However, the aluminum oxide of the present invention may be any of these. Further, the crystal does not necessarily have to have good crystallinity, and may be an amorphous substance having poor crystallinity, or a compound which is a precursor of the crystal. Silicon oxide is also known to have several types of crystal systems and amorphous phases. Among them, the amorphous phase called silica glass has a relatively small coefficient of thermal expansion and is particularly preferably used. Although crystalline SiO ₂ has a larger coefficient of thermal expansion than the amorphous phase, it is sometimes used from the viewpoint of improving the sticking resistance of the coating.

[0011] Further, by containing crystalline cordierite and / or crystalline saphirin in these films, it may be possible to impart a greater tension. Cordierite is a crystal represented by a chemical formula of 2MgO.2Al ₂ O ₃ .5SiO ₂ , and is presumed to give a high tension to a steel sheet due to its low thermal expansion coefficient and high Young's modulus. Sapphirine is 4MgO.5Al
A crystal represented by the chemical formula of ₂ O ₃ · 2SiO ₂ ,
For the same reason as in the case of cordierite, high tension is applied to the steel sheet.

Magnesium oxide in the composite coating of the present invention;
The proportion of aluminum oxide and silicon oxide can be in a relatively wide range, and can be any proportion. However, in order to maximize the characteristics of the composite coating, it is preferable that each component is contained at least 5% by weight, preferably 10% or more based on the whole coating. In addition, the amount of crystalline cordierite and saphirin can be any ratio, and by containing these compounds as much as possible, higher tension can be imparted, but the surface properties of the coating tend to deteriorate. Therefore, it is preferable to determine the optimum amount as needed. The preferred content of crystalline cordierite and sapphirine is 90% or less, more preferably 80% or less, and usually 5 to 7% by weight based on the entire coating.
It is selected from a range of about 5%.

The surface of another unidirectional silicon steel sheet of the present invention has a magnesium oxide-aluminum oxide-silicon oxide-amorphous oxide composite coating. The roles of the magnesium oxide component, aluminum oxide component and silicon oxide component are as described above, but the role of the amorphous oxide component is not so significant in imparting tension to the steel sheet, and the surface smoothness and the surface It is speculated that the adhesion to steel sheets has been greatly improved. Among them, it has been found that an amorphous phase containing at least one of silicon, boron and phosphorus as a component has a remarkable effect. Particularly when a glassy substance is formed, a remarkably great effect can be obtained. The content of silicon, boron, and phosphorus in the amorphous phase is 50% or more, and preferably 70% or more, in terms of the total weight of the respective oxides in terms of oxide.

The amorphous phase may contain a small amount of components other than silicon, boron and phosphorus.
Potential elements include Al, M
g, Fe as a base material component, and T as a primary coating component
i, Mn, S, Li, Na, K, Ca, Sr, B
a, V, Cr, Ni, Co, Cu and other alkali metals, alkaline earth metals, transition metal elements, or S
n, Pb, Bi, Sb and the like.

The content of the entire amorphous phase is not particularly limited. However, if the content is too large, the tension is not sufficiently applied to the steel sheet.
Or less, more preferably 70% or less. If the amount is too small, a sufficiently smooth coating surface and good adhesion may not be obtained in some cases. Therefore, it is desirable that the content be 5% by weight or more, more preferably 10% by weight or more, based on the whole coating. If the coating on the surface of the unidirectional silicon steel sheet of the present invention is too thick, the space factor is reduced, so that the coating is preferably as thin as possible according to the purpose. One guideline is 5% or less of the thickness of the steel sheet. More preferably, it is 2% or less of the thickness of the steel sheet. Further, from the viewpoint of imparting tension, if the thickness is extremely thin, a sufficient effect cannot be obtained, and the thickness is desirably 0.1 μm or more.

Hereinafter, a method for suitably producing the grain-oriented silicon steel sheet of the present invention will be described. One is to apply a suspension containing a magnesium oxide precursor compound, an aluminum oxide precursor compound, and a silicon oxide precursor compound to the surface of the steel sheet on which the finish annealing has been completed, and after drying, 500 to 1350 ° C.
This is a production method by baking at a temperature of 2 ° C. to form an oxide film.

The steel sheet which has been finish-annealed is a steel sheet which has been subjected to finish annealing by a conventionally known method and has a forsterite primary coating formed on the surface.
: Steel sheet obtained by immersing the primary coating and the accompanying oxide layer in acid to remove it, steel sheet obtained by flattening and annealing the steel sheet obtained in hydrogen, or chemical polishing, electrolytic polishing, etc. Polished steel sheet: A conventionally known annealed separator added with a minor additive such as an alumina powder or a chloride which is inert to the film formation, is applied under conditions that do not form a primary film. Includes steel sheets subjected to finish annealing.

The magnesium oxide precursor compound is a general term for compounds that become magnesium oxide after baking (heat treatment), and includes not only magnesium oxide but also various magnesium salts such as magnesium hydroxide, magnesium nitrate, and magnesium chloride. Point to. Similarly, after baking (heat treatment) of the aluminum oxide precursor compound
Is a general term for compounds that become aluminum oxide, and not only aluminum oxide but also Al ₂ O ₃ such as boehmite.
A hydrate of aluminum oxide, aluminum hydroxide, or various aluminum salts such as aluminum nitrate and aluminum chloride represented by nH ₂ O. The silicon oxide precursor compound is also a generic name of a compound that becomes silicon oxide after baking, and hydrates of silicon oxide, silicon oxyhydroxide, various silicon compounds, and the like are preferably used.

These raw materials are dispersed in a dispersion medium to prepare a suspension (slurry). The dispersion medium is most preferably water from the viewpoints of workability, cost and the like, but an organic solvent or a mixture thereof can be used unless there is any particular problem in other steps. Certain of the raw materials may dissolve at the time the slurry is made, but this is no problem.

The slurry thus obtained is applied to the surface of the unidirectional silicon steel sheet which has been finish-annealed by a conventionally known method such as a coater such as a roll coater, a dipping method, spraying or electrophoresis. After drying, 500
An oxide film is formed on the surface by baking at １３1350 ° C. The atmosphere at the time of baking is preferably a reducing atmosphere such as an inert gas atmosphere such as nitrogen or a nitrogen-hydrogen mixed atmosphere. An atmosphere containing air or oxygen is not preferable because it may oxidize the steel sheet. There is no particular limitation on the dew point of the atmospheric gas. If the baking temperature is lower than 500 ° C., the applied precursor may not become an oxide, and the baking temperature is low, so that sufficient tension is not developed, which is not preferable. On the other hand, when the temperature exceeds 1350 ° C., it is not economical, although there is no particular inconvenience, and the temperature is more preferably 1250 ° C. or less.

In the above-mentioned slurry, as the aluminum oxide precursor and the silicon oxide precursor compound, a fine particle dispersion system called a sol is used to obtain a thin and uniform compound.
In addition, a film having good adhesion may be obtained. This is particularly remarkable when a non-metallic substance does not exist on the surface and a film is formed directly on the metal surface. In such a case, the above-described sol containing fine particles or a sol containing a soluble component is preferably used. When a sol solution is used as the coating solution, the above-mentioned boehmite sol and / or alumina sol are particularly preferably used as the aluminum oxide precursor compound from the viewpoint of workability and cost. On the other hand, as the silicon oxide precursor sol, various sols can be used, and SiO ₂ .nH ₂ O or S
Silica sol represented by the chemical formula of iO _x · (OH) _y and / or colloidal silica also has workability,
It is preferably used in terms of price.

Among them, silicon sol is used as a silicon oxide precursor sol.
An alkyl silicate of the formula (OC _z H _{2z + 1} ) ₄ ,
And / or a hydrolyzate thereof is preferably used. Alkyl silicate is one type of metal alkoxide,
Hydrolysis is relatively slow and stable properties are obtained as a precursor. Alkyl silicate usually forms a hydroxide of silicon or a hydrate of silicon oxide by hydrolysis, but when a certain kind of film is formed, the hydrolyzate is used rather than using the alkyl silicate as it is. There are cases where it is preferable. In such a case, the precursor sol after hydrolysis is suitably used. For this, there are several methods, such as a method of mixing with other components after hydrolysis in advance, a method of performing hydrolysis while mixing with other components, and adding aging if necessary. In the present invention, there is no particular problem in either case.

Preferred alkyl silicate compounds are those having a high hydrolysis rate and a small number of carbon atoms z, preferably about z ≦ 3, and the methyl silicate having z = 1 is methyl silicate formed by hydrolysis. Ethyl silicates with z = 2 are particularly preferably used because of the harmful nature of alcohols. When 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 as described above, the magnesium oxide precursor compound is a magnesium oxide ultrafine powder prepared by a gas phase method or the like. It is preferable to use a fine powder prepared by a liquid phase method or the like, a dispersion system thereof, and soluble magnesium salts, thereby realizing uniform mixing at an extremely micro level.

In the case of using a precursor sol of aluminum oxide and silicon oxide, it is possible to use the precursor sol by dispersing it in a dispersion medium, particularly water, as in the case of the above-mentioned slurry. In order to obtain particularly good dispersibility, pH control of the coating solution by addition of an acid, an alkali or the like is a frequently used technique, and can be performed without any particular problem in the present invention.
In addition, there is no problem in adding a trace amount of a surfactant or the like for improving the applicability to the steel sheet. As another manufacturing method, a magnesium oxide precursor compound, an aluminum oxide precursor compound, a silicon oxide precursor compound, boric acid and / or borate, phosphoric acid and / or phosphate are applied to the surface of the steel sheet after finishing annealing. This is a production method in which a suspension containing the composition is applied, dried, and baked at a temperature of 500 to 1350 ° C. to form an oxide film.

As the boric acid and / or borate, H
Ortho boric acid represented by ₃ BO ₃ is most preferable in terms of price and the like, but metaboric acid represented by HBO ₂ and B ₂
Boron oxide represented by O ₃ or a mixture thereof can also be used. As the borate, alkali borates such as lithium borate and sodium borate, aluminum borate, zinc borate, barium borate, lead borate and the like are preferably used. As phosphoric acid and / or phosphate, phosphoric acid and orthophosphoric acid are particularly preferably used. Other phosphates include alkali phosphates such as lithium phosphate and sodium phosphate, alkaline earth phosphates such as magnesium phosphate and calcium phosphate, ammonium phosphate, aluminum phosphate, zinc phosphate and phosphorus. Barium phosphate, lead phosphate, iron phosphate, chromium phosphate and the like are preferably used.

In the second production method, similarly to the above-mentioned first production method, a thin, uniform and so-called sol is used as the aluminum oxide precursor and silicon oxide precursor compound by using a so-called sol. A film with good adhesion may be obtained. In such a case, the above-described sol containing fine particles or a sol containing a soluble component is preferably used. The compounding amount of boric acid and / or borate, phosphoric acid and / or phosphate can be selected from a wide range. However, in order not to impair the excellent feature of the present film that high tension is applied, oxidation is required. It is 50% by weight or less, preferably 30% by weight or less, of the total solid content (in terms of oxide) in terms of total material. Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.

[0027]

【Example】

Example 1 Commercially available magnesium oxide fine powder, aluminum oxide powder (α-Al ₂ O ₃ ), and silicon oxide powder were mixed in the proportions shown in Table 1, and distilled water was added thereto to prepare a slurry.
This was applied to a 0.2-mm-thick unidirectional silicon steel sheet (containing a forsterite primary coating) containing 3.2% of Si so as to have a thickness of 4 g / m ² on one side,
After drying, 800 in a N ₂ atmosphere containing 5 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, and the like, it was found that the obtained film was mainly composed of MgO, α-Al ₂ O ₃ , and a SiO ₂ -based amorphous phase. A winding test was performed around a 20 mmφ cylinder so that the angle was 180 degrees, and the adhesion of the coating evaluated from the peeling state was extremely good. The coating on one side was removed, and the applied tension to the steel sheet measured from the bending of the sheet and the magnetic properties are shown in Table 1. From the results shown in Table 1, it can be seen that unidirectional silicon steel sheets having remarkably low iron loss are obtained. The chemical stability of the film formed on the surface was also very good.

[0029]

[Table 1]

Example 2 Commercially available magnesium oxide fine powder, boehmite powder (average particle size: 100 nm), colloidal silica (average particle size: 15)
nm) was mixed at the ratio shown in Table 2 corresponding to the solid content, and distilled water was added as needed to prepare a mixed sol. This was coated on a 0.2 mm thick unidirectional silicon steel sheet containing 3.2% Si, coated with aluminum oxide as an annealing separator, and subjected to a mirror finishing treatment at the same time as secondary recrystallization. ^Two
After coating and drying so as to obtain an oxide film on the surface by baking at 1100 ° C. for 10 minutes in an N ₂ atmosphere containing 10 vol% of H ₂ .

Table 2 shows the constituent phases of the film measured from the results of chemical analysis, X-ray diffraction, electron microscope and the like. For some compositions in the table, the formation of cordierite was confirmed. The adhesion of the coating evaluated in the same manner as in Example 1 was extremely good. The coating on one side was removed, and the applied tension to the steel sheet measured from the bending of the sheet and the magnetic properties were also shown in Table 2. From the results shown in Table 2, it can be seen that unidirectional silicon steel sheets having significantly low iron loss were obtained. The chemical stability of the film formed on the surface was also very good.

[0032]

[Table 2]

Example 3 Commercially available magnesium oxide fine powder, boehmite powder (average particle size: 100 nm), ethyl silicate and boric acid reagent were mixed in the proportions shown in Table 3, and distilled water was added thereto to prepare a mixed sol. did. This was applied to a 0.2-mm-thick finish-annealed unidirectional silicon steel sheet (having a forsterite primary coating) containing 3.2% of Si so as to have a surface of 4 g / m ² and dried. after, N ₂ containing H ₂ 3 vol%
By baking at 850 ° C. for 3 minutes in an atmosphere, an oxide film was formed on the surface.

Table 3 shows the constituent phases of the coating film measured from the results of chemical analysis, X-ray diffraction, electron microscope and the like. No boron-containing crystalline phase is observed, indicating that the boron component exists as an amorphous phase. Example 1
The adhesion of the coating evaluated in the same manner as in Example 1 was extremely good. The coating on one side was removed, and the applied tension to the steel sheet and the magnetic properties measured from the bending of the sheet were also shown in Table 3. From the results shown in Table 3, it can be seen that unidirectional silicon steel sheets having significantly low iron loss were obtained. The chemical stability of the film formed on the surface was also very good.

[0035]

[Table 3]

Example 4 Commercially available magnesium oxide fine powder, boehmite powder (average particle size: 0.4 nm), ethyl silicate, boric acid reagent, and phosphoric acid were mixed in the proportions shown in Table 4, and distilled water was added thereto. To prepare a slurry. This was coated on a 0.2 mm thick unidirectional silicon steel sheet containing 3.2% Si, coated with aluminum oxide as an annealing separator, and subjected to a mirror finishing treatment at the same time as secondary recrystallization. ² so as coated, after drying, 950 ° C. in N ₂ atmosphere containing H ₂ 5 vol%,
An oxide film was formed on the surface by baking for 5 minutes.

Table 4 shows the constituent phases of the coating film measured from the results of chemical analysis, X-ray diffraction, electron microscope and the like. Boron and phosphorus components are present in an amorphous phase because no boron and phosphorus-containing crystalline phases are observed. I understand. The adhesion of the coating evaluated in the same manner as in Example 1 was extremely good. The coating on one side was removed, the applied tension to the steel sheet measured from the bending of the sheet, and the magnetic properties are also shown in Table 4. From the results in Table 4, it can be seen that the unidirectional silicon steel sheets having significantly low iron loss are obtained. The chemical stability of the film formed on the surface was also very good.

[0038]

[Table 4]

[0039]

According to the present invention, a coating of a specific component is provided,
It is possible to provide a unidirectional silicon steel sheet which is chemically stable and whose iron loss is remarkably improved by its tension imparting effect, and a method for producing the same. The present invention shows good properties especially for conventionally used steel sheets having a primary coating or mirror-finished steel sheets for the purpose of remarkably reducing iron loss. The effect is enormous.

Claims (8)

(57) [Claims] 1. A low iron loss unidirectional silicon steel sheet having a magnesium oxide-aluminum oxide-silicon oxide-based composite coating on the surface. 2. Magnesium oxide-aluminum oxide-
The silicon oxide-based composite coating is made of crystalline cordierite and / or
The low iron loss unidirectional silicon steel sheet according to claim 1 or a crystalline sapphirine. 3. A low iron loss unidirectional silicon steel sheet having a magnesium oxide-aluminum oxide-silicon oxide-amorphous oxide-based composite coating on the surface. 4. Magnesium oxide-aluminum oxide-
The silicon oxide-amorphous oxide-based composite coating is composed of crystalline cordierite and / or crystalline sapphirine, and / or
4. The low iron loss unidirectional silicon steel sheet according to claim 3, further comprising an amorphous phase containing at least one of silicon, boron and phosphorus as a component. 5. A suspension containing a magnesium oxide precursor compound, an aluminum oxide precursor compound, and a silicon oxide precursor compound is applied to the surface of the grain-oriented silicon steel sheet on which the finish annealing has been completed, dried, and then dried at 500 to 1350 ° C. A method for producing a low-iron-loss unidirectional silicon steel sheet which is baked at a temperature of 3 ° C. to form an oxide film. 6. The method for producing a low iron loss unidirectional silicon steel sheet according to claim 5, 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. A magnesium oxide precursor compound, an aluminum oxide precursor compound, a silicon oxide precursor compound, boric acid and / or borate, phosphoric acid and / or phosphoric acid, on the surface of the grain-oriented silicon steel sheet having been subjected to finish annealing. A method for producing a low iron loss unidirectional silicon steel sheet in which a suspension containing a salt is applied, dried, and baked at a temperature of 500 to 1350 ° C. to form an oxide film. 8. The method for producing a low iron loss unidirectional silicon steel sheet according to claim 7, wherein the aluminum oxide precursor compound is an aluminum oxide precursor sol, and the silicon oxide precursor compound is a silicon oxide precursor sol.