JP2001279460A - Manufacturing method for grain oriented silicon steel sheet extremely low in core loss - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method in which, while high tensile stress is applied on a steel sheet without deterioration the adhesive properties of a tension film, and high insulating properties can be maintained and to provide a grain oriented silicon steel sheet obtained in the same manufacturing method. SOLUTION: In this method, a grain oriented silicon steel sheet extremely low in core loss, is produced, in which the formation of forsterite is suppressed, or forsterite is removed. An organometallic compound having a hydrophilic group or an organic coupling group and further having a metallic coupling group is mixed with a water slurry or an aqueous for a substance to form the tensile film after baking solution of the raw material, this mixture is applied on a steel sheet, bucked and annealed to form the tension film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grain-oriented electrical steel sheet used for an iron core of a transformer or a generator, and more particularly to a grain-oriented electrical steel sheet having extremely low iron loss and a method of manufacturing the same.

[0002]

2. Description of the Related Art Si is contained and the crystal orientation is (11).
Grain-oriented electrical steel sheets oriented in the 0) [001] or (100) [001] direction have excellent soft magnetic properties and are therefore widely used as various iron core materials in the commercial frequency range. At this time, as a characteristic required for the magnetic steel sheet, it is important that the iron loss, which is generally expressed by W17 / 50 (W / kg), which is a loss when magnetized to 1.7 T at a frequency of 50 Hz, is low. It is. The iron loss is broken down into eddy current loss We and hysteresis loss Wh, and W17 / 50 = We + Wh.

[0003] In order to reduce iron loss, a method of increasing the electric resistance by containing effective Si to reduce eddy current loss,
There is a method of reducing the thickness of a steel sheet, a method of further reducing a crystal grain size, and a method of aligning crystal orientations effective for reducing hysteresis loss.

Of these, excessive inclusion of Si causes a decrease in saturation magnetic flux density and causes an increase in the size of the iron core, so there is a limit, and a method of reducing the thickness of a steel sheet causes an extreme increase in manufacturing cost. There was a limit. The method of aligning crystal orientations is as follows.
A product with a value of 97T has been obtained, leaving little room for further improvement.

Furthermore, in recent years, the magnetic domain width has been artificially reduced by a method such as locally introducing strain on the steel sheet surface by irradiating a plasma jet or a laser beam, or forming a groove on the steel sheet surface to reduce iron loss. A technology to reduce iron loss was developed, and a significant iron loss reduction effect was obtained. However, there is a limit to the iron loss reduction effect of this technology.

On the other hand, apart from these, Japanese Patent Publication No. 52-244
As disclosed in Japanese Unexamined Patent Publication No. 99-99, the roughness of the interface between the metal surface of a steel sheet and the non-metallic coating can be reduced.
No. 1, JP-B5-87597, and JP-B6-37694, a crystal orientation emphasis treatment is performed so that a crystal having a specific crystal orientation is particularly left on a metal surface. A method for reducing iron loss was proposed, and it was reported that the iron loss of the material was significantly reduced. However, in order to reduce iron loss with these technologies,
It is indispensable to give a strong tension to the steel sheet, and for that purpose, it was necessary to make a tension film exist on the surface of the steel sheet. That is, when the tension coating is not present, the surface of the steel sheet is smooth, and consequently the expansion of the magnetic domain width is promoted, and the iron loss is greatly deteriorated.

To solve this problem, Japanese Patent Publication No. 52-24499 mentioned above discloses that the surface of a steel sheet is mirror-finished by chemical polishing or electrolytic polishing, and the steel sheet surface is subjected to metal plating to oxidize the steel sheet surface. We have proposed a method of suppressing magnetic defects due to deterioration of the steel sheet surface when applying and baking an insulating coating.However, if the metal plating has tension, the insulating coating is easily peeled off by baking, and fortunately Even if it is avoided, there is a drawback that the plating layer diffuses into the steel sheet due to strain relief annealing before using the steel sheet and loses its effect.

Further, when the metal plating has no tension effect, the effect of reducing iron loss is very small.
Incidentally, when the insulating coating is a phosphate-based tension coating, the adhesion of the coating is not obtained at all, and there is no effect of improving the magnetic properties. Therefore, this technology was never industrialized.

Furthermore, Japanese Patent Application Laid-Open No. 62-103374 discloses that an extremely thin layer of a mixture of various oxides, borides, silicides, phosphides, sulfides and ground iron is provided on the surface of a steel plate which is smoothed by polishing. There is disclosed a method in which an insulating coating and baking layer is provided thereon. In this method, although the adhesion between the steel sheet and the insulating layer is excellent, the mirror smoothing effect of the steel sheet is mixed with the ground iron. Due to the existence of the ultra-thin layer, the magnetic layer was erased and the desired effect of the magnetic properties could not be obtained, so that it was not industrialized.

Further, Japanese Patent Publication No. 56-4150 discloses that the surface of a steel sheet is subjected to an average roughness R by chemical polishing or electrolytic polishing.
a: A method of forming a smooth surface of 0.4 μm or less and further applying a ceramic thin film thereon is disclosed. As a method of forming a ceramic thin film having good adhesion, chemical vapor deposition,
It is a vacuum deposition, it is difficult to mass-produce equipment, the deposition rate is slow, it is not suitable for industrial production, and it has not been industrialized.

Further, Japanese Patent Application Laid-Open No. 3-47957, Japanese Patent No. 294
465, 294466, 294467, 294468,
Japanese Patent Nos. 294469 and 294470 disclose a method of forming an oxide or silicide film on a smoothed ground iron surface or its metal plating surface by a low-pressure plasma spraying method. Although the film formation rate can be secured, the film is formed by the adhesion of droplets and a dense film cannot be formed.The formed surface is also rough and easily peels off due to friction. However, the adhesiveness to the material coating was not sufficient, and the desired magnetic properties could not be obtained, and large-scale decompression equipment was required, so that it was not industrialized.

On the other hand, JP-A-2-243770 discloses a method of forming a ceramic film by a sol-gel method such as a dehydration condensation reaction of a metal alkoxide. When applied to a film, the coating film may be cracked or peeled off, so that a plurality of coating treatments are required, and this method has not been industrially implemented. Further, Japanese Patent Application Laid-Open No. 3-130376 discloses a method in which a gel thin film is formed by a sol-gel method and then an insulating film is formed, but a uniform film cannot be formed on the sol-gel film. There is a problem that a partial insulation failure occurs. Japanese Patent Application Laid-Open No. 5-226134 also discloses an improved patent for the sol-gel method, but the problem relating to peeling has not been fundamentally solved. Further, JP-A-4-32
Japanese Patent No. 3382 discloses a technique in which a mixture of alkoxysilane and ceramics is applied and baked on forsterite to form a tension film, but when applied on a silicon steel sheet having no forsterite, it is completely peeled off. And cannot be used.

[0013]

As described above, the recent trend of the iron loss reduction technology for grain-oriented electrical steel sheets is to smooth the surface of the steel sheets during and after the finish annealing process or to perform crystal orientation emphasis treatment. It is indispensable to form a tension coating on the steel sheet surface after the steel sheet is formed.However, since the tension coating exerts a strong tension on the steel sheet surface, a strong shear stress acts on the interface between the steel sheet surface and the tension coating to inevitably form the coating. As a result, tension cannot be applied, and the magnetic properties deteriorate. On the other hand, various measures have been taken to ensure the adhesion of the tension coating, but when the adhesion is good, the magnetic smoothing effect on the steel sheet surface disappears, and the magnetic properties also deteriorate. As a result, none of these technologies has been industrially commercialized yet.

When the crystal orientation enhancement treatment is applied to the surface of the steel sheet, the contradiction of the conflicting requirements between the tension and the adhesion is somewhat relaxed as compared with the case of the smoothing treatment for the adhesion of the tension film. It is far from close adhesion, and a sufficient amount of reduction in iron loss cannot be obtained because the action of tension is not sufficiently transmitted to the steel sheet. Further, in the film formation by the sol-gel method, the thickness of the film can be obtained at most only about 0.5 μm in one treatment, so that the tension value is limited, and a sufficient iron loss reduction effect is obtained. I couldn't. Further, in general, the uniformity of the coating film quality was low on a steel sheet where forsterite did not develop, and there were many difficulties in the insulating properties.

According to the present invention, the unidirectional magnetic steel in which the formation of forsterite has been suppressed or the forsterite has been removed is subjected to pickling, smoothing treatment, and crystal orientation enhancement treatment as necessary, and further a tension coating is applied. Even in the above-mentioned technology, which applies tension to the steel sheet and greatly reduces iron loss, unidirectionality that can apply sufficient tension to the steel sheet and give high insulation without impairing the adhesion of the tension coating An object of the present invention is to propose a method for producing an electrical steel sheet and to industrially provide such a unidirectional electrical steel sheet having extremely low iron loss.

[0016]

The development of the present invention will be described below. The inventors have found that even if baking is performed using ceramics or colloidal ceramics as a main raw material of a tension coating and a hydrolyzate of a metal alkoxide as a binder, film formation and adhesion to a steel sheet are not achieved. In place of metal alkoxide, having a hydrophilic group or an organic bonding group, further baking using an organometallic compound having a metal bonding group as an adhesion improver,
The inventors have found that the formation of a thick film and good adhesion to a steel sheet can be easily obtained, and completed the present invention.

That is, the method of the present invention provides a unidirectional magnetic steel in which forsterite formation has been suppressed or forsterite has been removed, having a hydrophilic group or an organic bonding group,
Furthermore, an organometallic compound having a metal binding group is mixed with a raw material or a raw material solution of a substance that becomes a tension film after firing, applied to a steel plate, and then annealed to form a tension film. Provided is a method for producing a grain-oriented electrical steel sheet having low iron loss. Here, a manufacturing method in which the heat treatment in an oxidizing atmosphere at a temperature of 100 ° C. or more and 800 ° C. or less and the heat treatment in an inert gas or a reducing atmosphere at a temperature of 400 ° C. or more and 1200 ° C. or less is preferable. . Further, the metal binding group is an alkoxyl group and its hydrolysis group, acetoxy group, methoxycarbonyl group,
A production method that is one or more of a halogen group, the organometallic compound has a methoxy group as a metal binding group, a single or complex ethoxy group, or a silane coupling agent having a silanol group in which they are hydrolyzed, or A method for producing an oligomer, wherein the hydrophilic group is an amino group,
A carboxyl group, a hydroxyl group, a carbonyl group, one or more of a sulfo group, and an organic bonding group is a vinyl group, an epoxy group, a methacryl group, a methacryloxy group, a mercapto group,
A production method which is at least one of a ureido group, a glycidoxy group and a chloro group is preferred. Further, the organometallic compound has a production method having an amino group, a substance which becomes a tension film after firing, a production method mainly containing phosphate, chromic acid and colloidal silica, and a substance which becomes a tension film after firing, A production method containing boric acid and aluminum oxide as main components is preferred.

Hereinafter, the present invention will be described in detail. The method of the present invention is characterized in that an organic metal compound having a hydrophilic group or an organic bonding group and further having a metal bonding group is mixed with the raw material of the tension coating to be used. Here, it is considered that the metal binding group chemically bonds to the steel sheet and contributes to the adhesion of the coating. Further, it is considered that the organic bonding group and the hydrophilic group also chemically act on the tension film to contribute to the adhesion.

The metal binding group contained in the organometallic compound used in the present invention includes a methoxy group, an ethoxy group and the like.
In addition to an alkoxy group that produces an MO-Fe type metal bond by hydrolysis and its hydrolyzable group, an acyl group such as an acetoxy group, a lower alkoxycarbonyl group such as a methoxycarbonyl group, and a halogen group such as a chloro group are used. I can do it. M is a metal in the organometallic compound and can be selected from a single metal such as Al, Fe, Si, Ti, Zr, or two or more metals. Is more preferably Si. Further, as these organic Si compounds, those commercially available as silane coupling agents or oligomers thereof can also be used.

As the hydrophilic group, an amino group, a carboxyl group, a hydroxyl group, a carbonyl group, a sulfo group and the like can be used.

Next, as organic bonding groups, organic groups other than simple alkyl groups such as vinyl group, epoxy group, methacryl group, methacryloxy group, mercapto group, ureido group and glycidoxy group and halogen groups such as chloro group are effective. Suitable.

When the metal binding group has a hydrophilic property like an alkoxycarbonyl group such as a methoxycarbonyl group, a considerable effect can be obtained by itself. On the other hand, the effect of the present invention cannot be clearly obtained by using the metal binding group alone when the metal binding group also has the character as the organic binding group, but the reason has not been clarified so far.

The organometallic compound may have an alkyl group, an alkylene group, and the like in addition to the essential constituent groups described above.

The organometallic compound used in the present invention is not particularly limited as long as it has the above-mentioned functional group.
Having a chloro group and a vinyl group, vinyl trichlorosilane, an aminoalkyl trialkoxysilane having an alkoxyl group and an amino group, a γ-methacryloxyalkylalkoxysilane having an alkoxyl group and a methacryloxy group, a glycidoxy group and an alkoxyl group. Glycidoxyalkyl trialkoxysilanes, mercaptoalkyl trialkoxysilanes having a mercapto group and an alkoxyl group, titanate coupling agents having a group corresponding thereto, and trialcoholamine titanates having a hydroxyl group and an amino group. .

As a raw material for forming the tension film, a conventionally known raw material is used by making use of its characteristics. The following raw materials are applied as they are or as a solution or a dispersion of raw materials on a steel plate and annealed to obtain a tension film. Particles that become ceramics after baking, such as metal oxides, metal oxide hydrates, metal hydroxides, oxalates, carbonates, nitrates, sulfates, or composites thereof, are used as raw materials. Although the material of the ceramics is not limited, aluminum oxide, silicon oxide, titanium oxide, cordierite, mullite, spinel, zircon and the like are preferably used. These are often used as inorganic solutions, organic solutions, and inorganic-organic composite solutions. Specifically, a solution containing phosphoric acid-chromic acid-colloidal silica as a main component, chromic anhydride-
Liquid containing aluminum phosphate as the main component, chromic anhydride-
Liquid mainly composed of magnesium phosphate, chromic anhydride-
Liquid containing aluminum phosphate-colloidal silica as a main component, liquid containing chromic anhydride-magnesium phosphate-colloidal silica as a main component, aluminum oxide-boron oxide-based composite coating or alumina sol and boric acid-based coating obtained from aluminum borate coating And the like. Raw materials containing phosphoric acid-chromic acid-colloidal silica or aluminum oxide and boric acid are preferred, and aluminum oxide and boric acid are particularly preferred because they have high tension and can improve magnetic properties.

The mixing ratio of the above-mentioned organometallic compound to the raw material of the tension coating is not particularly limited.
In the mixture, the content is 10% by mass or less, and more preferably 0.05 to 3% by mass.

As the electromagnetic steel sheet used in the present invention, any known steel sheet can be used, and the recommended starting component composition is exemplified as follows. First, as a component of the steel sheet, Si is 1.5 to 7.0 mass%.
Desirably, it is contained. That is, Si is an effective component for increasing the electrical resistance of the product and reducing iron loss,
If Si exceeds 7.0% by mass, the hardness tends to be high, and production and processing tend to be difficult. If the amount is less than 1.5% by mass, transformation occurs during the secondary recrystallization annealing, and a stable secondary recrystallization structure cannot be obtained. Therefore, the lower limit is set to 1.5% by mass.

The crystal orientation can be further improved by containing 0.006% by mass or more of Al in the initial steel as an inhibitor element. The upper limit is 0.
If the amount exceeds about 06% by mass, the crystal orientation deteriorates again. Nitrogen has the same effect, and the upper limit is set to 100 ppm from the occurrence of blistering defects. Although the lower limit is not particularly defined, it is economically difficult to industrially lower the amount to less than about 20 ppm, and the lower limit is set to 20 ppm or more. Further, a step of performing a nitrogen increasing treatment after the primary recrystallization annealing is also advantageously applicable.
When the nitrogen increasing treatment is not performed, it is essential that the initial steel contains 0.01% by mass to 0.06% by mass in total of Se + S, and 0.02% by mass in order to precipitate as a Mn compound. It is necessary to contain -0.2% by mass of Mn. If the respective amounts are too small, the amount of precipitates for causing secondary recrystallization is too small, and if the amount is too large, solid solution before hot rolling becomes difficult. When the nitrogen increasing treatment is not performed, Mn is not necessarily required, but can be appropriately added for the purpose of improving the ductility of steel. In the steel, in addition to the above-mentioned elements, B, Bi, Sb, Mo, Te, and S, which are additional component elements suitable for manufacturing grain-oriented electrical steel sheets, are included.
n, P, Ge, As, Nb, Ni, Cr, Ti, Cu,
It is preferable to contain about 0.0005 to 2.0% by mass of an element selected from Pb, Zn and In alone or in combination. Below this, there is almost no effect, and when too much, the magnetic flux density is reduced. In addition, about 0.005 to 0.08 mass% of C can be added to the initial steel for the purpose of promoting recrystallization during hot rolling and improving magnetic properties.

Elements such as C, S, Se, and N are all
It has a detrimental effect on magnetic properties and particularly deteriorates iron loss. Therefore, in the product plate, C: 0.003% by mass or less, S, Se: 0.002% by mass or less, N: 0.002%
It is preferable to reduce it to not more than mass%.

The grain-oriented electrical steel sheet in which the formation of forsterite is suppressed can be manufactured by a known method such as a method in which a separating agent containing alumina as a main component in an annealing separating agent or a compound in which chloride is mixed with MgO. Preferably have smooth properties.
In addition, as a starting material, a small amount of forsterite remains when the base iron is partially exposed, and those where forsterite is formed by reacting with the annealing separator are removed by pickling or polishing. Can be used. It is recommended to perform magnetic domain refining by a method of forming grooves in the steel sheet by this stage in order to reduce iron loss. In addition, irrespective of the groove formation, any magnetic domain refining means such as strain or fine grain formation can be used together. Although the thickness is not necessarily limited, it is 0.15 to 0.30 m in order to maximize the ease of secondary recrystallization and the effect of reducing iron loss by this treatment.
A plate thickness of about m is appropriate.

Subsequently, iron loss can be reduced by smoothing treatment by pickling, chemical polishing, electrolytic polishing, or the like, or magnetic characteristics can be improved by crystal orientation enhancement treatment in which electrolysis is performed in an aqueous solution of a halogen compound. It is possible.

Next, the organometallic compound, which is the main feature of the present invention, is mixed with any ceramics, a raw material for a tension coating, or an organic solvent or an aqueous solution thereof, and coated on a steel sheet. A known method such as a spray method or a roll method can be applied as a coating method. As the metal binding group of the organometallic compound, a methoxy group or an ethoxy group is more preferred, and as the metal element in the organometallic compound, Si is more preferably used because it is stable and maintains adhesion and is thermally stable. Since the iron loss of the obtained electromagnetic steel sheet is low, the hydrophilic group is preferably an amino group. Commercially available silane coupling agents and those obtained by diluting the silane coupling agents and obtaining them as primers can be appropriately and effectively used for this purpose.

The formation of the tension film is performed at 100 ° C. or more and 800 ° C.
Heat treatment in the following oxidizing atmosphere,
The heat treatment is performed in combination with an inert gas at 0 ° C. or lower or a heat treatment in a reducing atmosphere. The order of the heat treatment may be performed in any order, but it is preferable that the heat treatment is performed in an oxidizing atmosphere and then in an inert or reducing atmosphere. The heat treatment time may be such that a tension film is formed.
To 120 seconds. Performing the heat treatment of the tension coating in an oxidizing atmosphere such as the air at a temperature of 100 ° C. or more and 800 ° C. or less is very effective for removing carbon in a steel sheet as described later. More preferably, the temperature is set to 120 to 200 ° C. Next, annealing at 400 ° C or higher and 1200 ° C or lower in a weakly reducing atmosphere, such as an inert gas such as nitrogen or a mixture of hydrogen, is recommended because it has the effect of suppressing the oxidative decomposition of metal bonding groups and completing the film formation. Is done. More preferably, the temperature is set to 600 to 900 ° C. At temperatures below the lower limits, effective removal of carbon and good film formation cannot be obtained. At temperatures above the upper limit, degradation due to oxidation of the adhered portion and partial melting of the steel sheet and film formation are undesirable.

Preferably, the drying and baking of the tension coating is performed by continuous annealing. If continuous annealing is used, the rate of temperature rise can be increased, so that a dense film with good adhesion can be formed even on a steel plate substantially free of foresterite. In addition, continuous annealing can reduce the amount of residual carbon in the sample. Some of the carbon in the organometallic compound mixed with the raw material may be absorbed into the steel after annealing, exceeding the allowable limit of 30 ppm for carbon in the steel. This is because if the heating rate is low, film formation starts from the outermost layer of the coating before carbon and organic substances are oxidized and released into the atmosphere, and the carbon is trapped inside the coating and eventually absorbed into the steel sheet. This is because In continuous annealing, carbon oxidation and film formation proceed in parallel, so it was found that carbon was effectively released without confinement of carbon. The heating rate is not particularly limited, but is preferably about 2 ° C./s or more, and 5 ° C./s
The above is more preferable. Although the line speed is not particularly limited, about 0.5 m / s is required to promote decarburization by relatively updating the surface gas of the steel sheet.
The above is preferred. Furthermore, 1.5 to 5 m / s is more preferable.

If the thickness of the tension coating is less than 0.5 μm, the effect of effectively applying tension to reduce iron loss is not sufficient, so that the thickness is preferably limited to 0.5 μm or more. More preferably, the thickness is 0.5 to 2 μm.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The forsterite film of a 0.22 mm-thick unidirectional electrical steel sheet that has been secondarily recrystallized using a separating agent mainly composed of MgO while forming fine grains for magnetic domain refining is removed by pickling, Further, a smoothing treatment was performed with a mixed solution of sulfuric acid and chromic acid until the average roughness of the steel sheet surface became about 0.10 μm.

A methoxy group as a metal binding group,
Using γ-methacryloxypropylmethyldimethoxysilane having a γ-methacryloxypropyl group as an organic bonding group as an organic metal compound, dissolve, mix and stir to a concentration of 1% by mass with respect to an equal mixture of ethanol and ion-exchanged water. Aluminum fine particles are made of organometallic compound 1
After applying 0 times mass suspension, apply coater and mail order speed 2m
/ S continuous annealing treatment at 120 ° C. for 12 seconds in the air and baking in a nitrogen atmosphere at 1020 ° C. for 45 seconds to make the film thickness per side 1.2 μm. A good coating was formed on the entire surface of the sample, and the magnetic properties of the obtained product were B8 = 1.911T, iron loss W17 / 50 = 0.62W /
kg.

2. P for MgO as an annealing separator
While suppressing formation of a forsterite film using a separating agent containing 0.3% by mass of bCl ₂ , grooves were formed in the steel sheet for domain refining, and a sheet thickness of 0.20 was subjected to secondary recrystallization.
mm oriented magnetic steel sheets were prepared. An aminopropyltriethoxysilane having an ethoxy group as a metal binding group and an amino group as a hydrophilic group is mixed with an aqueous solution comprising magnesium phosphate, colloidal silica, and chromic acid, and then coated with a coater roll and mixed with air and nitrogen at 300 ° C. Annealing in an atmosphere and continuous annealing in a nitrogen-hydrogen mixed atmosphere at 860 ° C. were continuously performed on the same line, and baked, so that the film thickness per side was 1.8 μm.

The magnetic properties of the obtained product were as follows: B8 = 1.91
3T, iron loss W17 / 50 = 0.54 W / kg.

(Comparative Example) Mg while forming fine grains for magnetic domain refinement
Plate thickness obtained by secondary recrystallization using a separating agent mainly composed of O
The forsterite film of the 22 mm grain-oriented electrical steel sheet was removed by pickling, and further subjected to a smoothing treatment with a mixed solution of sulfuric acid and chromic acid until the average roughness of the steel sheet surface became about 0.10 μm.

A tetraethoxysilane having only an ethoxy group as a metal binding group is dissolved and stirred at a concentration of 1% by mass in an equal mixture of ethanol and ion-exchanged water in this steel sheet, and fine particles of aluminum borate are further mixed with a binder. Of 1
After suspending 0 times, coater is applied and mail order speed 2m / s
Dried in air at 120 ° C for 12 seconds by continuous annealing
It was baked for 45 seconds in a nitrogen atmosphere at 1020 ° C., and the film thickness per one side was set to 1.2 μm. The coating partially peeled off, and the magnetic properties of the product were B8 = 1.913T, iron loss W
17/50 = 0.85 W / kg.

(Examples and Comparative Examples) Separately, the steel sheet is a grain-oriented electrical steel sheet (B8 = 1.
895T, W17 / 50 = 0.727 W / kg), after pickling off forsterite on the surface, removing various organometallic compounds shown in Table 1 into colloidal silica + phosphate on a material chemically polished in hydrofluoric acid. The mixture was mixed with a known chromic acid-based stock solution of a tension insulating coating, and the coating coverage, the thickness of the tension coating, and the iron loss were evaluated. The measurement of the present invention was performed under the following conditions. 1) Coating coverage: measured by observing the appearance of the formed tension coating. 2) Tension film thickness: Measured by electron microscope observation of film formation. 3) Iron loss: The loss [W17 / 50 (W / kg)] when magnetized to 1.7 T at a frequency of 50 Hz was measured.

[0043]

[Table 1]

[0044]

According to the present invention, the unidirectional magnetic steel in which the formation of forsterite has been suppressed or the forsterite has been removed is subjected to pickling, smoothing treatment, crystal orientation emphasis treatment if necessary, Even in the technology that significantly reduces iron loss by applying tension to the steel sheet by the coating, unidirectionality that can apply sufficient tension to the steel sheet and give high insulation without impairing the adhesion of the tension coating An object of the present invention is to propose a method for producing an electrical steel sheet and to industrially provide such a unidirectional electrical steel sheet having extremely low iron loss.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C22C 38/00 303 C22C 38/00 303U 38/60 38/60 (72) Inventor Mitsumasa Kurosawa Okayama 1-chome, Kawasaki-dori, Mizushima, Kurashiki (No address) Kawasaki Steel Corporation Mizushima Works F-term (reference) 4D075 BB28Z CA03 CA23 DB03 4K022 AA02 AA32 AA44 BA02 BA15 BA20 BA28 BA33 BA36 CA14 CA22 DA06 DB01 DB02 EA01 4K026 AA03 A BB05 BB10 CA16 CA18 CA22 CA23 CA37 CA41 DA02 DA11 EA07 EB11 4K033 AA02 PA04 PA05 PA09 RA04 TA04 5E041 AA02 AA11 BC01 BC05 CA02 HB09 HB11 HB14 NN18

Claims (9)

[Claims] 1. A tensile coating after sintering an organometallic compound having a hydrophilic group or an organic bonding group and further having a metal bonding group on unidirectional magnetic steel in which the formation of forsterite has been suppressed or the forsterite has been removed. After mixing with the raw material or the raw material solution of the substance to be applied and applying it on a steel plate,
A method for producing a grain-oriented electrical steel sheet having extremely low iron loss, comprising annealing to form a tension coating. 2. The method according to claim 1, wherein the formation of the tension film is carried out at a temperature of 100.degree.
Heat treatment in an oxidizing atmosphere at a temperature of 400 ° C. or less,
The method for producing a grain-oriented electrical steel sheet with extremely low iron loss according to claim 1, wherein the method is performed in combination with a heat treatment in an inert gas or a reducing atmosphere at a temperature of 00 ° C or less. 3. The one-way direction having extremely low iron loss according to claim 1, wherein the metal binding group is at least one of an alkoxyl group and a hydrolyzable group thereof, an acetoxy group, a methoxycarbonyl group, and a halogen group. Manufacturing method of conductive electrical steel sheet. 4. The method according to claim 1, wherein the organometallic compound is a silane coupling agent having a methoxy group or an ethoxy group as a metal binding group alone or in combination, or a silanol group obtained by hydrolyzing them, or an oligomer thereof. A method for producing a grain-oriented electrical steel sheet having extremely low iron loss according to claim 1. 5. The method according to claim 1, wherein the hydrophilic group is an amino group, a carboxyl group,
A hydroxyl group, a carbonyl group, one or more of a sulfo group, and an organic bonding group is one or more of a vinyl group, an epoxy group, a methacryl group, a methacryloxy group, a mercapto group, a ureido group, a glycidoxy group, and a chloro group. The method for producing a grain-oriented electrical steel sheet having extremely low iron loss according to any one of claims 1 to 4. 6. The method for producing a grain-oriented electrical steel sheet according to claim 1, wherein said organometallic compound has an amino group. 7. A material having a very low iron loss according to claim 1, wherein the substance which becomes a tension film after the sintering is mainly composed of phosphate, chromic acid, and colloidal silica. Manufacturing method of unidirectional electrical steel sheet. 8. The grain-oriented electrical steel sheet according to claim 1, wherein the substance which becomes a tension film after firing is mainly composed of boric acid and aluminum oxide. Manufacturing method. 9. An organometallic compound having a hydrophilic group or an organic bonding group and further having a metal bonding group, which is mixed with a raw material or a raw material solution of a substance which becomes a tension film after firing to form forsterite. An adhesion improver for a tension coating, characterized by improving the adhesion between a unidirectional magnetic steel which has been suppressed or forsterite removed and a tension coating.