The present invention relates to a grain-oriented electrical steel sheet and a method for manufacturing a grain-oriented electrical steel sheet.
Background technology
[0002]
Electrical steel sheets have a crystal structure whose main direction is {110} <001> and are often used as an iron core material for transformers. In particular, a material with a small iron loss is required in order to reduce energy loss. ing.
[0003]
Patent Document 1 discloses a method of irradiating a steel sheet surface after finish annealing with a laser beam to give local strain and thereby subdividing magnetic domains as a means for reducing iron loss of grain-oriented electrical steel sheets. ing.
Patent Document 2 discloses a magnetic domain subdivision means in which the effect does not disappear even after performing strain-removing annealing (stress-removing annealing) after iron core processing.
[0004]
On the other hand, since iron alloys containing iron and silicon have large magnetocrystalline anisotropy, the magnetic domain is subdivided when an external tension is applied, and the eddy current loss, which is the main element of iron loss, can be reduced. In particular, it is known that applying tension to a grain-oriented steel sheet containing 5% or less of silicon is effective in reducing the iron loss of the grain-oriented electrical steel sheet. This tension is applied by the coating formed on the surface.
[0005]
The directional electromagnetic steel sheet has a primary coating mainly composed of forsterite formed by the reaction between the oxide on the surface of the steel sheet and the annealing separator in the finish annealing step, and colloidal silica and phosphorus disclosed in Patent Document 3 and the like. A tension of about 10 MPa is applied when the plate thickness is 0.23 mm by the two-layer coating of the secondary coating mainly composed of amorphous material, which is generated by baking a coating liquid mainly composed of a phosphate.
[0006]
On the other hand, Patent Document 4 proposes a grain-oriented electrical steel sheet having a coating film mainly composed of aluminum borate crystals on the surface.
Prior art literature
Patent documents
[0007]
Patent Document 1: Japanese Patent Application Laid-Open No. 55-018566
Patent Document 2: Japanese Patent Application Laid-Open No. 62-86175
Patent Document 3: Japanese Patent Application Laid-Open No. 48-39338
Patent Document 4: Japanese Patent Application Laid-Open No. 6-65754
Outline of the invention
Problems to be solved by the invention
[0008]
In the case of the conventional coating as disclosed in Patent Document 3, a larger tension can be applied by increasing the coating amount, and although there is a possibility of improving the iron loss by improving the tension, the applied tension is improved. It is not preferable to make the coating thicker than the current one because it causes a decrease in the space factor. For this reason, there is a demand for a film that is thin and can apply a large tension to the steel sheet without causing a decrease in the space factor.
[0009]
In order for a certain film to become a high-tensile film, it is required that the Young's modulus of the film is high and the coefficient of thermal expansion is small. Generally, crystals have a higher Young's modulus than amorphous. The film made of aluminum borate described in Patent Document 4 has a higher Young's modulus than the conventional amorphous film made of silica and phosphate because the main constituent is a crystal. Since the coefficient of thermal expansion is also sufficiently low, it is possible to obtain a higher tension than the coating film as disclosed in Patent Document 3, coupled with the effect of Young's modulus.
[0010]
However, there is a demand for a film that can apply even greater tension. In order to realize a high-tensile film made of aluminum borate, it is necessary to sufficiently generate aluminum borate crystals in the film. Ideally, the tension film should be composed entirely of aluminum borate crystals, but in reality it is inevitable that elemental inhomogeneity within the film will occur due to element evaporation from the surface during baking. be. It is considered that if the element distribution is not appropriate, aluminum borate is not sufficiently formed and high tension cannot be obtained, but the relationship between the element distribution and tension has not been clarified so far.
[0011]
An object of the present invention is to provide a grain-oriented electrical steel sheet and a method for manufacturing grain-oriented electrical steel sheet having an aluminum borate film capable of applying a larger tension than before.
Means to solve problems
[0012]
The present inventor considered that in order to obtain a higher tension in the aluminum borate film, it is necessary to clarify the relationship between the element distribution and the tension in the film and clarify the conditions under which the high tension can be obtained. As a result of diligent studies, it was found that a high tension can be obtained when the amount of boron near the interface between the coating film and the steel sheet is large.
The present invention has been made based on the above findings, and the gist thereof is as follows.
[0013]
(1) Steel plate and
It has an insulating film made of an oxide containing aluminum and boron, which is provided on the steel sheet.
The oxide contains a crystalline oxide and contains
The maximum value of the emission intensity ratio of boron to aluminum at the interface between the insulating coating and the steel plate measured by glow discharge emission spectroscopy is 2.5 times or more the emission intensity ratio of boron to aluminum in the insulating coating. Directional electromagnetic steel plate that is 4.0 times or less.
(2) Applying a coating liquid containing a boron source and an aluminum source having a mass ratio of 1.8 to 2.6 in terms of Al 2O 3 / B 2O 3 to the surface of the steel sheet.
In an inert gas atmosphere with a dew point of 0 to 40 ° C and containing 0 to 25% by volume of hydrogen, the steel plate is heated to a predetermined temperature in the range of 450 to 600 ° C, with an average heating rate of 2 to 5 ° C / sec. After heating in, cool to 200 ° C or less at a cooling rate of 10 ° C / sec or more.
A grain-oriented electrical steel sheet having a temperature rise rate of 10 to 100 ° C./sec on average to 750 ° C. and heat treatment in a temperature range of 750 to 1000 ° C. for 20 to 120 seconds. Manufacturing method.
The invention's effect
[0014]
As described above, according to the present invention, by controlling the amount of boron in the vicinity of the interface between the insulating film and the steel sheet, a grain-oriented electrical steel sheet having an aluminum borate film capable of applying a larger tension than the conventional one can be obtained. Can be done.
A brief description of the drawing
[0015]
FIG. 1 is a glow discharge emission spectroscopic analysis chart of an insulating coating and a steel sheet in an example of a grain-oriented electrical steel sheet according to an embodiment of the present invention.
Embodiment for carrying out the invention
[0016]
A preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings below.
[0017]
<1. Directional electrical steel sheet ＞
Hereinafter, the grain-oriented electrical steel sheet according to this embodiment will be described. The grain-oriented electrical steel sheet according to the present embodiment has a steel sheet (base steel sheet) and an insulating film provided on the steel sheet and made of an oxide containing aluminum and boron.
[0018]
The steel sheet (base steel sheet) that can be used in this embodiment is not particularly limited as long as the secondary reconnection has been completed. As the steel sheet generally used as the base steel sheet, for example, a steel sheet having a forsterite primary film formed during finish annealing (secondary reconsolidation annealing) is a steel sheet that can be used in the present embodiment.
[0019]
As described above, an insulating film made of an oxide containing aluminum and boron is provided on the surface of the steel sheet. The oxide of the insulating film contains a crystalline oxide, and the emission intensity of boron with respect to aluminum at the interface between the insulating film and the steel plate, which is measured by glow discharge emission spectroscopy (GDS). The maximum value of the ratio B / Al is 2.5 times or more and 4.0 times or less the emission intensity ratio B / Al of boron with respect to aluminum in the insulating film. This improves the tension of the grain-oriented electrical steel sheet. Hereinafter, a detailed description will be given together with the idea of ​​the present inventor.
[0020]
The present inventor investigated and examined the improvement of the characteristics of the insulating film. As a result, it was found that a grain-oriented electrical steel sheet having a high tension can be obtained by controlling the amount of boron in the vicinity of the interface between the insulating film (tension film) and the steel sheet. Specifically, regarding the emission intensity ratio of boron to aluminum in the insulating coating, a high tension is applied when the maximum value at the interface between the insulating coating and the steel sheet is 2.5 times or more and 4 times or less the value in the insulating coating. It has been found that a grain-oriented electrical steel sheet having an insulating film that develops can be obtained.
[0021]
There are various methods for measuring the composition of the insulating coating in the depth direction, but since the insulating coating containing aluminum borate consists of boron, aluminum, and oxygen as components, a method by glow discharge emission spectroscopy that can easily measure these. Is appropriate. Specifically, the measurement results are processed as follows in order to quantify the element distribution in the insulating coating.
[0022]
After measuring the change in emission intensity with respect to the sputtering time for Al and B, the sputtering time dependence of the ratio B / Al (hereinafter referred to as B / Al value) of the emission intensity of both is obtained, as shown in FIG. It was clarified that high tension can be obtained when the maximum value (hereinafter B / Al peak) of the B / Al value near the interface between the insulating film and the steel plate (hereinafter referred to as the interface) is high. Here, in the GDS chart in FIG. 1, the interface is defined as the period from the vicinity of 0 to the rise of the emission intensity of iron (Fe) to a constant value. In FIG. 1, the region where the iron emission intensity is near 0 is the analytical value in the insulating coating, and the region where the iron emission intensity is non-zero and is almost constant is the analytical value in the steel sheet. be. Therefore, in the example shown in FIG. 1, the emission intensity of iron is approximately 100 seconds from the discharge time when the emission intensity of iron rises from the vicinity of 0 (near zero is a portion having an intensity of 5% or less of a constant value described later). 2 is a constant value (here, the "constant value" is the iron emission intensity value in the steel plate, and the change from the previous 1-second average value is 0.05% or less for the 1-second average value. Up to about 150 seconds, which is the value of the region), is the emission intensity corresponding to the interface where the composition changes from the coating component to the steel plate component. The B / Al peak defined in the present invention is the peak showing the highest value in this region. Therefore, in FIG. 1, the peak defined as the B / Al peak (Y) having a discharge time of about 120 seconds is the B / Al peak defined in the present invention, and the peak having a discharge time of about 10 seconds or about 190 seconds is the present invention. It does not correspond to the B / Al peak defined in. Table 1 shows an example of the measurement conditions of the glow discharge emission spectroscopic analysis method for obtaining the emission intensity of Fe, B, and Al.
[0023]
[table 1]

[0024]
In GDS, the ratio of the emission intensity of each element represents a value that correlates with the composition ratio of these elements in the portion of the sputtered sample. Therefore, by measuring and calculating the B / Al value measured from the insulating coating and the ratio of the B / Al peak near the interface between the insulating coating and the steel sheet, the vicinity of the interface between the insulating coating and the steel sheet compared with the insulating coating. It is possible to relatively observe the amount of boron in the steel.
[0025]
In the present invention, in order to obtain a directional electromagnetic steel plate having an aluminum borate film (insulating film) having excellent tension applying characteristics, a value obtained by dividing the emission intensity of boron measured as described above by the emission intensity of aluminum. Regarding (emission intensity), when the B / Al value in the insulating film is X and the maximum value of the B / Al peak is Y, Y / X is 2.5 or more and 4.0 or less. Here, the value of X is the entire region in which the change from the previous 1-second average value of the 1-second average B / Al value among the B / Al values ​​in the insulating coating is 0.001 or less. Is the average value of.
[0026]
A Y / X of 2.5 or more and 4.0 or less means that the B / Al value at the interface is larger than the B / Al value in the insulating coating, that is, based on the amount of Al. Then, it means that the amount of B at the interface is relatively larger than the amount of B in the insulating film. It is not clear why the tension increases when the Y / X value is appropriate, but it is presumed that a large amount of aluminum borate crystals are formed at the interface with the steel sheet of the insulating coating having a high coating tension. It is considered that high tension is developed. The reason for this is estimated as follows.
[0027]
Since boron oxide has a low melting point, it is considered that the molten boron oxide accelerates the diffusion of elements in the part of the insulating film where the amount of boric acid is large. It is presumed that if the element diffuses quickly, aluminum borate is likely to be formed, and it is considered that aluminum borate crystals are formed from a low temperature at the time of baking the insulating film, and as a result, the number of aluminum borate crystals increases. It is considered that when the number of aluminum borate crystals increases by the above mechanism, the film tension increases. In the present invention, in order to secure the amount of boric acid at the interface, the amount of B is used.Focusing on this, the B / Al value normalized by the amount of Al present in the insulating film was also specified, and the lower limit of the value was set to 2.5 times the value in the insulating film. However, if the B / Al peak is too high, the amount of unreacted boron at the interface increases, and in a moist atmosphere, moisture easily reaches the surface of the steel sheet, which may cause problems such as rusting. Further, if the B / Al peak is too high, the film tension may decrease. It is presumed that this is because if B accumulates too much at the interface, the presence of boron in the insulating coating becomes non-uniform, and aluminum borate crystals are not sufficiently formed in a part of the insulating coating, resulting in a decrease in coating tension. Will be done. Therefore, in the present invention, an upper limit is set for the value of the B / Al peak with respect to B / Al in the coating film, and good results can be obtained by increasing the value by 4.0 times.
[0028]
Y / X may be within the above range, but is preferably 2.6 or more, more preferably, in order to increase the number of aluminum borate crystals at the interface of the insulating coating with the steel sheet and further increase the coating tension. It is preferably 2.7 or more. Further, Y / X is preferably 3.8 or less, more preferably 3.5 or less, in order to suppress excessive boron at the interface of the insulating film with the steel sheet and suppress a decrease in film tension.
[0029]
If the insulating coating of the grain-oriented electrical steel sheet according to the present embodiment is too thick, the space factor of the grain-bearing steel sheet in the grain-oriented electrical steel sheet decreases. A thickness of 5% or less is preferable. More preferably 2, it is% or less. It should be noted that this film thickness is the total thickness of both sides of the steel plate, and for example, in the case of a base steel plate plate thickness of 0.23 mm, a preferable 5% or less is a total thickness of 11.5 μm or less on both sides, and per one side. It is 5.75 μm or less. Similarly, more preferably 2% or less is 4.6 μm or less in total on both sides, and 2.3 μm or less per one side. Further, from the viewpoint of applying tension, a sufficient effect cannot be obtained if the steel sheet is extremely thin, and 0.1 μm or more per surface of the steel sheet is preferable. The thickness of the steel plate is not particularly limited, and may be 0.10 mm or more and 0.35 mm or less as an example.
[0030]
<2. Manufacturing method of grain-oriented electrical steel sheet ＞
Next, the method for manufacturing the grain-oriented electrical steel sheet according to the present embodiment will be described. The method for manufacturing a directional electromagnetic steel plate according to the present embodiment is to apply a coating liquid containing a boron source and an aluminum source having a mass ratio of 1.8 to 2.6 in terms of Al 2O 3 / B 2O 3 to the surface of the steel plate. In an inert gas atmosphere containing 0 to 25% by volume of hydrogen at a dew point of 0 to 40 ° C., the steel plate is heated to a predetermined temperature in the range of 450 to 600 ° C., and the average heating rate is 2 to 5 ° C. After heating at / sec, it is cooled to 200 ° C or less at a cooling rate of 10 ° C / sec or more, and the steel plate is heated to 750 ° C at an average heating rate of 10 to 100 ° C / sec. , With heat treatment for 20-120 seconds in a temperature range of 750-1000 ° C.
[0031]
The present inventor examined the process conditions in detail for the means for realizing the insulating film as described above. As a result of the process study, in order to form an insulating film satisfying the above conditions, the mass ratio of aluminum oxide and boron oxide Al 2O 3 / B 2O 3 is 1.8 to 2 on the base steel sheet of the grain-oriented electrical steel sheet. After applying the coating liquid of 6.6, it was clarified that the temperature and atmosphere conditions of the heat treatment including the drying and baking temperature after the coating should be limited. This process consists of (i) diffusion of boron during temperature rise after drying of the coating solution and before crystallization of aluminum borate, (ii) nucleation of aluminum borate crystals, and (iii) growth of aluminum borate crystals.
Hereinafter, the method for manufacturing the grain-oriented electrical steel sheet according to the present embodiment will be described in detail while referring to the correspondence with the above processes (i) to (iii).
[0032]
First, prepare a base steel sheet to form an insulating film prior to each process. As the base steel sheet, a steel sheet as described above may be prepared. Specifically, a steel sheet having a forsterite primary film formed on the surface thereof is prepared by finish annealing by a conventionally known method. Just do it.
[0033]
Next, a coating liquid for forming an insulating film is applied to such a base steel sheet. The coating liquid contains a boron source and an aluminum source having a mass ratio of 1.8 to 2.6 in terms of Al 2O 3 / B 2O 3.
[0034]
As the boron source, orthoboric acid represented by H 3BO 3 is most preferable in terms of workability, price, etc., but metaboric acid represented by HBO 2, boron oxide represented by B 2O 3, or a mixture thereof. Can also be used.
[0035]
Examples of the aluminum source include aluminum oxide and aluminum oxide precursor compounds. Examples of the aluminum oxide precursor compound include aluminum oxide hydrate represented by Al 2O 3 · mH 2O such as boehmite, aluminum hydroxide, and various aluminum salts such as aluminum nitrate and aluminum chloride. Etc. are preferably used.
[0036]
Further, the boron source and the aluminum source in the coating liquid are included so that the mass ratio in terms of Al 2O 3 / B 2O 3 is 1.8 to 2.6. Thereby, the insulating film can be formed with an appropriate composition ratio. On the other hand, when the mass ratio is less than 1.8, the amount of boron in the insulating coating becomes too large, and as a result, boron accumulates too much at the interface, the presence of boron in the insulating coating becomes non-uniform, and insulation occurs. In some parts of the coating, the formation of aluminum borate crystals may not be sufficient and the coating tension may decrease. Further, when the mass ratio exceeds 2.6, the amount of aluminum source becomes too large, and as a result, the amount of boron in the vicinity of the interface between the insulating film and the base steel sheet is not sufficient, and the amount of aluminum borate crystals produced decreases. , The coating tension does not increase.
The mass ratio is preferably 1.9 or more and 2.4 or less, and more preferably 2.0 or more and 2.2 or less.
[0037]
These raw materials are dispersed in a dispersion medium to prepare a slurry as a coating liquid. Water is the best dispersion medium, but an organic solvent or a mixture thereof can be used as long as there is no particular problem in other steps. The solid content concentration of the slurry is appropriately selected depending on the workability and the like, and is not particularly limited.
[0038]
Further, by using a fine particle dispersion system called a so-called sol as an aluminum oxide precursor in this slurry, a thin, uniform, and good-adhesive insulating film may be obtained. This is particularly remarkable when there is no non-metal substance on the surface of the steel sheet and an insulating film is formed directly on the metal surface of the steel sheet.
[0039]
When a sol is used as the coating liquid, the above-mentioned boehmite sol and / or alumina sol as the aluminum oxide precursor is particularly suitable in terms of workability, price, and the like.
The coating liquid may contain components other than those described above as long as the effects of the present invention are not impaired.
[0040]
The obtained slurry (coating liquid) is applied to the surface of a grain-oriented electrical steel sheet whose finish annealing has been completed by a coater such as a roll coater, a dip method, spray spraying, electrophoresis, or a conventionally known method.
[0041]
The coating liquid before coating should be kept at a temperature of, for example, 20 ° C or higher and 40 ° C or lower in order to prevent precipitation of boric acid and excessive evaporation of water. If the temperature of the coating liquid is too low, boric acid precipitates in the coating liquid depending on the type and concentration of the boron source, and if the temperature is too high, the water content tends to decrease and normal coating cannot be performed. However, the desired coating may not be obtained.
[0042]
Next, in an inert gas atmosphere having a dew point of 0 to 40 ° C. and containing 0 to 25% by volume of hydrogen, the steel sheet is heated to a predetermined temperature in the range of 450 to 600 ° C., and the average heating rate is set to 2 to 5 ° C. Heat at / sec. In such a temperature range from room temperature to a predetermined temperature between 450 and 600 ° C., it is composed of a mixture of a boron compound and an aluminum compound formed on the base steel plate after heating, drying and drying of the coating liquid. The membranous material is heated.
[0043]
The reason for limiting the heating rate to a predetermined temperature in the range of 450 to 600 ° C. to 2 to 5 ° C./sec is to sufficiently diffuse boron in the above process (i). If the temperature rise rate is too fast, the diffusion of boron becomes insufficient, the target composition and amount of the water-soluble component cannot be obtained, and film defects due to bumping are likely to occur when the coating liquid is dried. On the other hand, if it is too late, the evaporation of boron progresses too much, and as a result, an insulating film having the desired composition cannot be obtained.
[0044]
The temperature reached by heating the steel sheet may be 450 ° C. or higher and 600 ° C. or lower, but is preferably 480 ° C. or higher and 530 ° C. or lower. As a result, it is possible to suppress the evaporation of boron and sufficiently diffuse the boron, and it is also possible to suppress the formation of unnecessary crystals.
[0045]
Further, examples of the inert gas in the atmosphere during heating include nitrogen and rare gases such as helium, argon, and xenon. Of these, nitrogen is preferable in order to control costs.
In addition, the atmosphere at the time of heating contains 0 to 25% by volume of hydrogen. As a result, oxidation between the steel sheet and the insulating film can be suppressed, and adhesion can be ensured. On the other hand, if the hydrogen content exceeds 25% by volume, there is no particular problem, but it is not preferable from the viewpoint of excessive cost.
[0046]
The dew point of the atmosphere during heating is 0 ° C or higher and 40 ° C or lower. If the dew point is less than 0 ° C., the tension of the insulating film cannot be sufficiently secured. Further, if the dew point exceeds 40 ° C., oxidation of the interface between the steel sheet and the insulating film is likely to occur, which causes a problem that the adhesion may be deteriorated. The dew point of the atmosphere at the time of heating is preferably 10 ° C. or higher and 30 ° C. or lower.
[0047]
Next, the steel sheet is heated at the above-mentioned temperature rise rate, and then cooled to 200 ° C. or lower at a cooling rate of 10 ° C./sec or more. Although the reason is not clear, it is presumed that such cooling treatment promotes nucleation of aluminum borate crystals in the above-mentioned process (ii). If the cooling temperature is not 200 ° C. or lower, or if the cooling rate is less than 10 ° C./sec, sufficient film tension cannot be obtained. The cooling temperature may be 200 ° C. or lower, but from the viewpoint of cost and required time, it is not preferable to make the cooling temperature excessively low, and it is preferably 100 ° C. or higher and 200 ° C. or lower. The cooling rate may be 10 ° C./sec or more, but if it is too fast, uniform cooling becomes difficult, so it is preferably 10 ° C./sec or more and 150 ° C./sec or less. Normally, cooling is performed immediately after heating at the above-mentioned heating rate.
[0048]
Next, the steel sheet is heated to 750 ° C. at an average temperature rise rate of 10 to 100 ° C./sec, and heat-treated in a temperature range of 750 to 1000 ° C. for 20 to 120 seconds. The coated steel sheet is dried as described above and then baked at 750 ° C. or higher to form an oxide film as an insulating film on the surface.
[0049]
Then, as described above, by raising the temperature of the steel sheet to 750 ° C. at an average heating rate of 10 to 100 ° C./sec, the evaporation of boron can be suppressed in the above-mentioned process (i). That is, in the temperature range of 600 ° C. or higher, the evaporation of boron is particularly liable to proceed, so that the temperature of the steel sheet is raised at a relatively high speed as described above. If the rate of temperature rise is slow, boron evaporates, making it impossible to obtain an insulating film with the desired composition. There is no problem even if the temperature rise rate is high, but even if it exceeds 100 ° C / sec, no improvement can be seen compared to the case of a lower temperature rise rate, and rapid temperature rise is the equipment cost. The practical upper limit of the heating rate is 100 ° C./sec because it can be a factor that pushes up the temperature. The rate of temperature rise is preferably 50 ° C./sec or more and 80 ° C./sec or less. It was
[0050]
The reason why it is necessary to heat-treat between 750 and 1000 ° C. for 20 to 120 seconds is that crystal growth of aluminum borate occurs and crystallization proceeds at 750 ° C. or higher in the above-mentioned process (iii). If the temperature and time are less than the above range, the crystallization of aluminum borate will be ten. It does not progress in minutes and sufficient tension cannot be obtained. Further, when the baking temperature (heat treatment temperature) is 750 ° C., the applied precursor may not become an oxide, and since the baking temperature is low, sufficient tension is not developed, which is not preferable.
[0051]
The heat treatment temperature may be within the above range, but is preferably 800 ° C. or higher and 950 ° C. or lower from the viewpoint of the balance between the effect of improving tension and the cost. The heat treatment time may be within the above range, but is preferably 50 seconds or more and 90 seconds or less.
When the temperature is raised above 750 ° C., the time from the time when the temperature exceeds 750 ° C. to the time when the temperature becomes lower than 750 ° C. is defined as the heat treatment time.
[0052]
The atmosphere during baking (during temperature rise and heat treatment) is preferably an inert gas atmosphere such as nitrogen, a reducing atmosphere such as a nitrogen-hydrogen mixed atmosphere, and an atmosphere containing air or oxygen excessively oxidizes the steel sheet excessively. Possibly unfavorable.
[0053]
Good results can be obtained at 0-40 ° C for the dew point of the atmospheric gas.
Alternatively, the atmosphere at the time of baking may be the same as the atmosphere at the time of drying the coating liquid.
[0054]
As described above, a grain-oriented electrical steel sheet having a high tension and having an insulating film as described above can be obtained.
Example
[0055]
The present invention will be described in more detail below based on examples, but the examples shown below are merely examples of the present invention, and the present invention is not limited to such examples.
[0056]
Example 1
A commercially available boric acid reagent and aluminum oxide (Al 2O 3) powder (average particle size: 0.4 μm) were mixed at the ratios shown in Table 2. Boric acid was weighed in terms of the equivalent of boron oxide (B 2O 3). Distilled water was added to this to prepare a slurry.
[0057]
The obtained slurry is applied to a unidirectional silicon steel sheet (with a forsterite primary coating) having a thickness of 0.23 mm and containing 3.2% of Si and having a forstellite primary coating, and has a coating mass of 4.5 g after baking. It was applied so as to be / m 2. Then, after drying and cooling under the conditions shown in Table 2, the temperature was raised to 750 ° C., and baking was performed at this temperature with a soaking time of 100 seconds to form an insulating film. The temperature reached by the steel sheet during drying was set to 500 ° C. The atmosphere at the time of drying, cooling, raising the temperature, and baking was a nitrogen atmosphere containing 10% hydrogen, and the dew point was 30 ° C.
[0058]
The sample on which the insulating film was formed was measured by X-ray diffraction, and the presence of crystalline aluminum borate was confirmed from the diffraction lines.
The coating on one side of the steel plate on which the insulating coating was formed was removed, and the coating tension was calculated from the bending of the steel plate. This tension is the tension of only the aluminum borate coating without the forsterite layer. An aqueous sodium hydroxide solution was used to remove the insulating film. Tension of 15 MPa or more was defined as high tension. From the results in Table 2, it can be seen that in the examples, an insulating film having high tension is obtained.
[0059]
[Table 2]

[0060]
Example 2
The boric acid reagent is equivalent to boron oxide (B 2O 3) to 45.3 g with respect to 100 g of commercially available aluminum oxide (Al 2O 3) powder (average particle size: 0.4 μm), and distilled water is added thereto to prepare a slurry. Made. Al 2O 3 / B 2O 3 is 2.2.
[0061]
This is applied to a unidirectional silicon steel sheet (with a forsterite primary coating) having a thickness of 0.23 mm and containing 3.2% of Si, and the coating weight after annealing is 4.5 g / m 2. It was applied so as to be. This is heated to 500 ° C at an average of 3 ° C / sec in a nitrogen atmosphere containing 10% by volume of hydrogen at a dew point of 30 ° C, cooled to 200 ° C at an average of 60 ° C / sec, and then cooled to a soaking temperature of 50 ° C / sec on average. The temperature was raised in 1 and baked under the conditions shown in Table 3 to form an insulating film.
[0062]
Similar to Example 1, the film on one side of the steel sheet on which the insulating film was formed was removed, and the film tension was calculated from the bending of the steel sheet. This tension is the tension of only the aluminum borate coating without the forsterite layer. An aqueous sodium hydroxide solution was used to remove the insulating film. Tension of 15 MPa or more was defined as high tension. From the results in Table 3, it can be seen that a high coating tension is obtained in the examples.
[0063]
[Table 3]

[0064]
Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person having ordinary knowledge in the field of technology to which the present invention belongs can come up with various modifications or modifications within the scope of the technical ideas described in the claims. , These are also naturally understood to belong to the technical scope of the present invention.
The scope of the claims
[Claim 1]
With steel plate
It has an insulating film made of an oxide containing aluminum and boron, which is provided on the steel sheet.
The oxide contains a crystalline oxide and contains
The maximum value of the emission intensity ratio of boron to aluminum at the interface between the insulating coating and the steel plate measured by glow discharge emission spectroscopy is 2.5 times or more the emission intensity ratio of boron to aluminum in the insulating coating. Directional electromagnetic steel plate that is 4.0 times or less.
[Claim 2]
Applying a coating liquid containing a boron source and an aluminum source with a mass ratio of 1.8 to 2.6 in terms of Al 2O 3 / B 2O 3 to the surface of the steel sheet,
In an inert gas atmosphere with a dew point of 0 to 40 ° C and containing 0 to 25% by volume of hydrogen, the steel plate is heated to a predetermined temperature in the range of 450 to 600 ° C, with an average heating rate of 2 to 5 ° C / sec. After heating in, cool to 200 ° C or less at a cooling rate of 10 ° C / sec or more.
A grain-oriented electrical steel sheet having a temperature rise rate of 10 to 100 ° C./sec on average to 750 ° C. and heat treatment in a temperature range of 750 to 1000 ° C. for 20 to 120 seconds. Manufacturing method.