JP2002294345A - Manufacturing method for grain oriented silicon steel sheet with very small iron loss after stress relieving annealing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a grain oriented silicon steel sheet with very small iron loss by applying sufficient tension to the steel sheet without impairing adhesivity of tension film even when stress relieving annealing is performed. SOLUTION: A coating layer of inorganic compound deposited by performing vapor phase deposition with the vapor deposition speed per one side being in a range of 0.02-50 nm/sec. in the atmosphere of >=0.1 atm. in the total pressure on the surface of the grain oriented silicon steel sheet in which generation of forsterite is suppressed or generated forsterite is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a grain-oriented electrical steel sheet having an extremely small iron loss after strain relief annealing suitable for use as an iron core material of a transformer or a generator.

[0002]

2. Description of the Related Art Si is contained and the crystal orientation is (110).
Grain-oriented electrical steel sheets oriented in the [001] direction or the (100) [001] direction have excellent soft magnetic properties and are therefore widely used as various iron core materials in the commercial frequency range. As a characteristic required for such a grain-oriented electrical steel sheet, it is generally important that iron loss represented by W _17/50 (W / kg), which is a loss when magnetized to 1.7 T at a frequency of 50 Hz, is low. .

In order to reduce iron loss, effective methods for reducing eddy current loss include a method of increasing electric resistance by containing Si, a method of reducing the thickness of a steel sheet, and a method of reducing a crystal grain size. On the other hand, as an effective method for reducing the hysteresis loss, there is a method of aligning the crystal orientation.

[0004] Of these methods, the method of increasing the electric resistance by containing Si has a limit because excessive addition of Si causes a decrease in the saturation magnetic flux density and causes an increase in the size of the iron core. The method of reducing the thickness has been limited because of the extreme increase in manufacturing costs. According to the method of aligning the crystal orientation, a product having an average deviation of the crystal from the rolling direction in the [001] direction of 3 ° or less can be obtained, but there is little room for further improvement.

Further, in recent years, the magnetic domain width has been artificially subdivided by a method such as locally introducing strain into the steel sheet surface by irradiating a plasma jet or a laser beam, or forming a groove in the steel sheet surface. Technology for reducing loss has been developed, and a significant iron loss reduction effect has been obtained. However,
There is a limit to the iron loss reduction effect of this technology.

On the other hand, separately from these, Japanese Patent Publication No. 52-24499
As disclosed in Japanese Patent Publication No. 7-9041, Japanese Patent Publication No. Hei 7-9041, Japanese Patent Publication No. Hei 5-87597, and Japanese Patent Publication No. Hei 6-37694, the roughness of the interface between the metal surface of the steel sheet and the non-metallic coating is reduced. As disclosed in the gazette, there has been proposed a method for reducing iron loss by performing a so-called crystal orientation emphasis treatment for leaving a crystal having a specific crystal orientation on a metal surface.
However, in order to reduce iron loss with these technologies, it is essential to apply strong tension to the steel sheet.
For that purpose, it was necessary to make a tension coating exist on the steel sheet surface. In other words, in the absence of the tension coating, the steel sheet surface was smooth, and conversely, the expansion of the magnetic domain width was promoted, leading to a significant deterioration of iron loss.

As a means for solving this problem, Japanese Patent Publication No. 52-24499 mentioned above discloses a method in which the surface of a steel sheet is mirror-polished by chemical polishing or electrolytic polishing, and the surface of the steel sheet is subjected to thin metal plating to oxidize or insulate the steel sheet surface. A method has been proposed to suppress magnetic defects due to deterioration of the steel sheet surface when the coating is applied and baked.However, if the metal plating has tension, the insulating coating is easily peeled off by the baking treatment. Even so, since the insulating coating was a normal phosphate-based non-tensile insulating coating, the effect of reducing iron loss was not so large. On the other hand, when the metal plating has no tension effect, the iron loss reduction effect is negligible, and in this case,
Even if an attempt is made to form a phosphate-based tension insulating film as the insulating film, it is difficult to improve magnetic properties because good film adhesion cannot be obtained. Therefore, this technology was never industrialized.

Japanese Patent Application Laid-Open No. 62-103374 discloses that, on the surface of a steel plate which has been smoothed by polishing, various oxides, borides, silicides, phosphides, sulfides and ground iron are mixed. A method in which a layer is formed by a CVD method and an insulating film is formed thereon is disclosed. However, this CVD method requires a high vacuum and is extremely costly. Has not been reached.

Further, Japanese Patent Publication No. 2-243770 discloses a method of forming a ceramic film by a sol-gel method. However, this method has a problem that a sufficient tension is applied because of poor adhesion to a steel sheet. No effect could be exerted on the steel sheet.

In addition, Japanese Patent Publication No. 56-4150 discloses that the surface of a steel sheet is subjected to chemical line polishing or electrolytic polishing to obtain a center line average roughness Ra.
A method is disclosed in which a ceramic thin film is formed on a smooth surface of 0.4 μm or less and a ceramic thin film is further formed thereon. Due to the difficulty of mass production and the slow deposition rate, it is not suitable for industrial production and has not yet been industrialized.

Also, Japanese Patent Application Laid-Open Nos. 3-47957 and 3-294465.
No. 3-294467, No. 3-294468, No. 3-294469 and No. 3-294470, the low-pressure plasma spraying method is applied to the smoothed ground iron surface or the metal plating surface thereon. A method for forming a film of oxide or silicide is disclosed. Further, Japanese Patent Application Laid-Open No. 10-245667 discloses a method for forming a tension film of oxide, nitride or carbide by using a plasma spraying method. However, with these methods,
Although an industrial deposition rate can be secured, a dense film cannot be formed due to the deposition of droplets, and the deposited surface is rough and easily peels off due to friction. Because of insufficient adhesion to oxide and silicide coatings formed by plasma spraying, desired magnetic properties could not be obtained, and large-scale decompression equipment was required. Has not been reached.

[0012]

As described above, recent trends in the technology for reducing iron loss of grain-oriented electrical steel sheets are to smooth the surface of the steel sheet during or after finish annealing or to perform crystal orientation emphasis treatment. After that, it is indispensable to form a tensile coating on the steel sheet surface. As a result, the film was peeled off, and as a result, tension could not be applied, and the effect of improving the magnetic properties could not be expected. Therefore, various measures have been taken to ensure the adhesion of the tension film, but when the adhesion is good,
Since the magnetic smoothing effect of the steel sheet surface is lost and the magnetic properties are also deteriorated, there is no industrial product manufactured by such a technology.

[0013] Further, the film formation by the gas phase is usually performed in a vacuum atmosphere, and not only the film formation speed is slow but also the installation of a vacuum chamber is indispensable. It was difficult. Furthermore, when the crystal orientation enhancement treatment is applied to the steel sheet surface, the adhesion of the tension coating is somewhat lessened than in the case of the smoothing treatment, but it is still far from the original adhesion, and the tension action is applied to the steel sheet. Because of insufficient transmission, a satisfactory iron loss reduction effect was not obtained.

[0014] The present invention advantageously solves the above-mentioned problems, and performs a smoothing process or a crystal orientation emphasizing process on the surface of a steel sheet, and further imparts tension to the steel sheet with a tension coating to greatly reduce iron loss. It is an object of the present invention to propose an advantageous method for manufacturing a grain-oriented electrical steel sheet that can exert a sufficient tension on the steel sheet without impairing the adhesion of the tension coating even when the reduction is intended.

[0015]

The development of the present invention will be elucidated below. Now, the present inventors have conducted a thorough study on the cause of peeling of the low-pressure plasma sprayed material or the ordinary plasma sprayed material described above. A) The coating is not a dense single layer but derived from droplets during spraying. Has a structure in which the granular coatings adhere to each other and have voids between the particles, and b) for this reason, the coating is broken from the voids of the coatings,
Alternatively, it was clarified that the coating was peeled off due to the oxidation of the steel sheet surface through the voids, or that the above-mentioned granular coating was peeled off due to surface irregularities.

The formation of voids between individual grains is due to a structure in which flat particles, which are smashed with semi-molten droplets on the surface of the steel sheet and are sequentially fixed, are piled up. It is considered that the formation of the joint causes a decrease in strength, and irregularities due to individual grains remain on the outermost surface. Further, it is considered that the oxidation of the steel sheet through the intergranular voids accelerates the exfoliation of the particles. To solve this problem,
Although it is thought that the coating should be deposited in a gaseous state, the conventionally known vacuum deposition method and gas phase synthesis method have drawbacks such as requiring a large-scale vacuum chamber, so that industrialization is extremely difficult. Have difficulty.

In view of the above findings, various film forming methods were examined. According to the thermal plasma evaporation method and the thermal plasma flash evaporation method, the coating material can be deposited in a plasma state, which is a kind of gaseous state, and the atmosphere can be easily removed. In addition, it is possible to operate under atmospheric pressure or a slightly reduced pressure atmosphere, and it is possible to form a dense coating layer with a small porosity on a grain-oriented electrical steel sheet without a forsterite coating. It turns out that it can be overcome.

In view of the above, the inventors of the present invention have received the above findings, and disclosed a method disclosed in Japanese Patent Application No. 11-287650, that is, a method for suppressing the formation of forsterite or removing the formed forsterite: On the surface of grain-oriented electrical steel sheets of 0.27 mm or less, the total pressure is 0.1 atm or more and the oxygen partial pressure is 0.
By forming a coating layer with an average thickness per side of 0.1 μm or more and 10 μm or less by vapor phase vapor deposition in a low oxidizing atmosphere of less than 1 atm, it has been found that a grain-oriented electrical steel sheet with extremely small iron loss can be manufactured. .

However, the coating of the grain-oriented electrical steel sheet manufactured by the technique disclosed in Japanese Patent Application No. 11-287650 may peel off after the strain relief annealing, and in this case, tension cannot be applied to the steel sheet. There is a problem that iron loss is greatly deteriorated. Here, “strain relief annealing” is performed by a customer for the purpose of removing the strain introduced in the iron core manufacturing process.
Annealing at 0 ° C. for about 3 hours.

Then, the inventors conducted further studies on the above-mentioned vapor deposition method to solve the above-mentioned problems, and found that the vapor deposition rate per one side was controlled to an appropriate range so that after the strain relief annealing, It is newly found that excellent film adhesion can be obtained, and as a result, a grain-oriented electrical steel sheet with extremely small iron loss can be manufactured. The present invention is based on the above findings.

That is, the gist of the present invention is as follows. 1. Suppress the generation of forsterite or remove the generated forsterite on the surface of grain-oriented electrical steel sheet, in an atmosphere with a total pressure of 0.1 atm or more, and set the deposition rate per side in the range of 0.02 to 50 nm / sec. A method for producing a grain-oriented electrical steel sheet having extremely small iron loss after strain relief annealing, wherein a coating layer of an inorganic compound is formed by performing vapor phase deposition.

2. 2. The method for producing a grain-oriented electrical steel sheet according to the above item 1, wherein the coating layer comprises one or more selected from oxides, nitrides and carbides.

3. 3. The method for producing a grain-oriented electrical steel sheet according to the above item 2, wherein the coating layer is a silicon compound.

4. 4. The method for producing a grain-oriented electrical steel sheet according to the above item 1, 2 or 3, further comprising forming a tension film and / or an insulating film after forming the coating layer.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. First, in the present invention, a grain-oriented electrical steel sheet in which forsterite generation is suppressed or the generated forsterite is removed is used. In a method for producing a grain-oriented electrical steel sheet that is subjected to finish annealing after applying an annealing separator containing magnesia as a main component, forsterite is generally formed on the steel sheet surface. However, forsterite formed on the surface of the steel sheet hinders direct bonding between the vaporized coating material and the ground iron. Therefore, in the present invention, forsterite generation is suppressed or the direction in which the generated forsterite is removed. It is necessary to use conductive magnetic steel sheets.

Means for suppressing the formation of forsterite are disclosed in JP-A-8-337823 and JP-A-59-96.
As shown in JP-A-278, a method mainly comprising alumina or silica or a mixture thereof with magnesia as an annealing separator, JP-A-64-62476, JP-A
As shown in Japanese Patent No. 104143, it is preferable to use a known method such as a method of adding chloride to an annealing separator containing magnesia as a main component. Further, as a means for removing forsterite, it is advantageous to use a method by pickling, electrolytic polishing or mechanical polishing.

Next, the steel sheet is subjected to vapor deposition. Unlike the ordinary vacuum vapor deposition method, the adhesion and uniformity between the coating layer and the ground iron in the vapor deposition phase, which is the main requirement of the technology of the present invention, is described. In order to increase the pressure, it is necessary to increase the pressure during vapor deposition. That is, in order to enhance the adhesion and uniformity of the coating layer,
The vapor deposition must be performed in an atmosphere in which the total pressure is 0.1 atm or more, preferably 0.8 atm or more. Although the upper limit of the total pressure is not particularly defined, a pressurized atmosphere of 1 atm or slightly is desirable from the viewpoint of suppressing the invasion of the atmosphere into the atmosphere.

Further, in the present invention, the vapor deposition rate per one side during the vapor phase vapor deposition is in the range of 0.02 to 50 nm / sec. When the deposition rate exceeds 50 nm / sec, the denseness of the coating layer is insufficient, not only the adhesion of the coating layer and the base iron after the stress relief annealing deteriorates, but also the tension is applied to the steel sheet by the peeling of the coating. If the deposition rate is less than 0.02 nm / sec, the effect of taking in a small amount of impurities present in the atmosphere between the steel sheet and the deposition layer becomes large, and the coating layer-ground This is because the adhesion of the iron after the stress relief annealing is deteriorated and good iron loss cannot be obtained.

The coating layer is made of an inorganic compound such as A1 ₂ O ₃ , Zr
O _2, oxides such as SiO _2, Si ₃ N _4, nitrides such as TiN, T
Carbides such as iC and SiC are desirable in terms of adhesion, and silicon compounds such as SiO ₂ , Si ₃ N ₄ and SiC are particularly preferred because of their excellent adhesion to ground iron. Also, a mixed layer of these may be used.

It is desirable to form a tension film and / or an insulating film after the vapor deposition. As a specific forming method, for example, a known insulating film using a phosphate or a chromate is used. As disclosed in JP-A-48-39338 and JP-A-50-79442,
A method in which a phosphate or a mixture of phosphate-silica is applied and baked, or a method in which an alumina borate film is formed as the film as described in JP-A-6-65754. Known methods such as,
Either method is suitable.

In addition, it is advantageous to apply a magnetic domain refining treatment to the steel sheet by introducing grooves or local strains, and the effect of imparting tension by the coating film is more effectively exerted. Furthermore, before vapor phase deposition, crystal orientation enhancement treatment on the steel sheet surface,
Performing a smoothing treatment by pickling, chemical polishing, electrolytic polishing, mechanical polishing, or the like is advantageous for reducing iron loss.

Although the thickness of the film to be formed is not particularly limited,
When the film to be formed is only a coating layer which is a vapor-deposited film, the thickness is preferably 0.1 μm or more and 10 μm or less,
When a tension film or an insulating film is formed on the coating layer, the total film thickness of the coating layer and the tension film, the total film thickness of the coating layer and the insulating film, or the thickness of the coating layer, the tension film, and the insulating film It is desirable that the total film thickness is 0.1 μm or more and 10 μm or less. If the thickness is less than 0.1 μm, the tension effect due to the coating is small, and if the thickness is 10 μm or more, iron loss is deteriorated due to a decrease in space factor.

The above is merely an example of the embodiment of the present invention, and various changes can be made within the scope of the claims.

[0034]

(Example 1) After forming a linear groove in the width direction of a steel sheet for magnetic domain refining, decarburizing annealing is performed, and an annealing separator containing 2% of magnesium chloride mixed with magnesia is applied. After that, a grain-oriented electrical steel sheet having a thickness of 0.23 mm, in which the formation of forsterite was suppressed by subjecting to secondary recrystallization annealing, was produced. Then, a SiC coating layer having a thickness of 0.07 μm on one side was formed on both sides of the steel sheet at various deposition rates shown in Table 1 by a high frequency-DC hybrid thermal plasma deposition method in an argon atmosphere of 1.0 atm. did. The deposition rate was adjusted by increasing or decreasing the supply of SiC powder, which is the starting material for the coating layer. Thereafter, a tension coating solution containing 60% colloidal silica and 40% magnesium phosphate as a main component was applied to the surface of the steel sheet, and baked at 800 ° C., so that the total thickness of the coating layer and the tension film was 1.0 μm. further,
800 ° C, 3 ° C
hr strain relief annealing. Table 1 shows the results obtained by examining the adhesion of the tension coating and the iron loss of the steel sheet with respect to the steel sheet after the strain relief annealing thus obtained.

The adhesion of the tension coating was evaluated by winding a steel sheet around cylinders having various diameters and determining the minimum diameter (minimum bending peel diameter) at which the coating did not peel. The iron loss of the steel sheet was measured by the Epstein method specified in JIS C 2550 (1992).

[0036]

[Table 1]

From the results shown in Table 1, the Examples (Nos. 1-2 to 1-5) in which the deposition rate was within the proper range were all excellent in the adhesion of the tension coating and small in iron loss of the steel sheet. I understand.

Example 2 A forsterite film of a grain-oriented electrical steel sheet having a thickness of 0.18 mm was removed by pickling.
A crystal orientation emphasis treatment for performing electropolishing in a NaCl aqueous solution was performed. Thereafter, in a 0.2 atm hydrogen-nitrogen mixed atmosphere, 1.0 μm of Zr per side was applied at various deposition rates shown in Table 2 by high frequency + DC hybrid thermal plasma deposition.
O ₂ coatings were applied on both sides. The deposition rate was adjusted by increasing or decreasing the supply of ZrO ₂ powder, which is the starting material for the coating layer. Next, a linear strain was applied to the steel sheet in the width direction by a gear for domain refining. Further, the grain-oriented electrical steel sheet thus manufactured was subjected to strain relief annealing at 800 ° C. for 3 hours.
Table 2 shows the results obtained by examining the adhesion of the tension coating and the iron loss of the steel sheet with respect to the steel sheet after the strain relief annealing thus obtained.

[0039]

[Table 2]

From the results shown in Table 2, it can be seen that Examples (Nos. 2-2 to 2-5) in which the deposition rate was within the proper range were all excellent in the adhesion of the tensile coating and small in iron loss of the steel sheet. I understand.

[0041]

As described above, according to the present invention, since the coating layer formed on the steel sheet without the forsterite coating can maintain good adhesion without peeling even after the strain relief annealing, it can be applied to the steel sheet. As a result, it is possible to stably obtain a grain-oriented electrical steel sheet with significantly reduced iron loss on an industrial scale.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C23C 30/00 C23C 30/00 C H01F 1/16 H01F 1/16 B (72) Inventor Michio Komatsubara Mizushima, Kurashiki-shi, Okayama Kawasaki-dori 1-chome (without address) Kawasaki Steel Corporation Mizushima Works F-term (reference) 4K026 AA03 AA22 BA01 BA12 BB05 CA18 DA02 EA01 EB11 4K029 AA02 AA24 BA43 BA55 BA56 BA58 BC05 BD03 CA01 EA01 FA01 GA03 GA03 4K03 A TA08 4K044 AA02 AB02 BA12 BA14 BA18 BB04 BC14 CA14 CA16 CA62 5E041 AA02 CA02

Claims (4)

[Claims] 1. A deposition rate per one side of 0.02 to 50 nm / in an atmosphere having a total pressure of 0.1 atm or more on a surface of a grain-oriented electrical steel sheet in which forsterite generation is suppressed or generated forsterite is removed. A method for producing a grain-oriented electrical steel sheet having extremely small iron loss after strain relief annealing, wherein a coating layer of an inorganic compound is formed by performing vapor deposition in a range of seconds. 2. The method for producing a grain-oriented electrical steel sheet according to claim 1, wherein the coating layer is made of one or more selected from oxides, nitrides and carbides. 3. The method for producing a grain-oriented electrical steel sheet according to claim 2, wherein the coating layer is a silicon compound. 4. The method according to claim 1, wherein after forming the coating layer, the tension coating and / or
4. The method for producing a grain-oriented electrical steel sheet according to claim 1, further comprising an insulating coating.