JP5353399B2 - Indirect measurement method for coating tension of grain-oriented electrical steel sheet - Google Patents

Description

  The present invention relates to a simple indirect method for measuring the surface coating tension of a grain-oriented electrical steel sheet.

  Generally, a grain-oriented electrical steel sheet imparts tension to a steel sheet by applying a base film mainly composed of a forsterite film and an insulating coating in which a phosphate, colloidal silica, or the like is mixed. Such tension is applied to the rolling direction of the steel sheet in particular, and the main purpose is to stabilize the 180 ° magnetic domain structure by the magnetoelastic effect. By subdividing the 180 ° magnetic domain, iron loss characteristics and magnetic properties can be obtained. The deterioration of characteristics is minimized, and the effect of suppressing iron loss and magnetostrictive noise can be obtained. In addition, as a method for imparting tension to the grain-oriented electrical steel sheet to improve the iron loss characteristics, a method for improving the forsterite film (Patent Document 1) and a method by overcoating (Patent Document 2) are known. .

Japanese Patent Publication No.51-12451 Japanese Patent Publication No.53-28375

  In order to apply tension to the steel sheet for the purpose of suppressing deterioration of the iron loss characteristics and magnetic characteristics of the grain-oriented electrical steel sheet as described above, it is necessary to ensure a desired film tension. Therefore, it is very important to accurately measure the film tension value applied to the surface of a grain-oriented electrical steel sheet in order to accurately grasp the tension state and evaluate various properties such as iron loss of the steel sheet. It is.

  Conventionally, as described in Patent Document 2, as a means for measuring the film tension, a sample is cut out from a steel plate to be measured, and the film on one side is removed from the sample by pickling or the like and left. A method for measuring the amount of warpage of a sample due to the coating tension on one side of the plate is known. However, since the film tension is almost isotropic, the amount of warpage itself is also affected by the sample shape. Therefore, if the sample is not elongated in the rolling direction, it will be affected by the tension in the width direction, and the amount of warpage that can be measured will be reduced. It cannot be secured. That is, every time the film tension is measured, a sample having a certain shape (for example, 30 mm × 280 mm) is required, and thus there is a problem that sample preparation is troublesome in the conventional method. In addition, each time the coating film tension was measured, it took time to remove the single-sided film, and the work efficiency was also poor.

  In addition, in the method of obtaining the film tension from the amount of warpage of the sample, the absolute value of the amount of warpage is usually about 10 to 30 mm, the reading error of the measured value is as large as about 5%, and depending on the shape before removing the single-sided film The amount of warpage itself changes. In particular, in a product plate of a factory, the curved state due to coil annealing may not be completely corrected, and when correction is incomplete, the measured value inevitably fluctuates and becomes a large error factor. That is, since the measurement error becomes large in the measured amount of warpage of one sample, there is a problem in accuracy in the conventional method.

  As a means for solving the above-mentioned accuracy problem, there is a means for measuring the amount of warping of a plurality of samples (for example, 10 or more samples) and obtaining the film tension from the average value thereof. However, as described above, the preparation of the sample is complicated, and since it is a destructive inspection, the same sample cannot be measured a plurality of times. Therefore, an error factor (for example, the correction state described above) due to the difference in the sample collection position Difference) is inevitable.

  As a method for measuring the film tension, as described in Patent Document 2, magnetostriction measurement is performed under compressive stress, and the compressive stress value when the magnetostriction measurement value increases rapidly is proportional to the film tension. There is also a measurement method based on this knowledge. However, with this method, it is difficult to accurately apply the compressive stress, and it is also difficult to determine the film tension value accurately because the stress reading at the time when the magnetostriction amount suddenly increases appears. .

  This invention is made | formed in view of the said present condition, and it aims at providing the method of indirectly measuring the coating-film tension | tensile_strength of a grain-oriented electrical steel sheet highly accurately and simply.

  As a result of various studies on the method for measuring the film tension of the grain-oriented electrical steel sheet with high accuracy and simplicity as described above, the present inventors have given the magnetizing force in the direction perpendicular to the rolling direction of the steel sheet and the steel sheet. It has been found that there is a high correlation with the film tension, and that the film tension can be indirectly measured with high accuracy and simplicity by measuring the magnetizing force of the object to be measured, and the present invention has been completed.

The gist of the present invention is as follows.
(1) The relationship between the magnetizing force at a predetermined excitation magnetic flux density in the direction perpendicular to the rolling direction of the grain-oriented electrical steel sheet and the film tension applied to the steel sheet surface is obtained in advance, and the grain-oriented electrical steel sheet that is the object to be measured A grain-oriented electrical steel sheet that measures a magnetizing force at the predetermined exciting magnetic flux density in a direction perpendicular to the rolling, and determines a film tension of the object to be measured based on the relationship from an actual measurement value of the measured magnetizing force. Method for indirect measurement of the film tension.

(2) The indirect measurement method of the film tension of the grain-oriented electrical steel sheet according to (1), wherein the predetermined excitation magnetic flux density is in a range of 0.4 to 1.2 T.

  In the present invention, the film tension applied to the surface of the grain-oriented electrical steel sheet and the magnetization characteristics are obtained in advance from the relationship between the film tension measurement value obtained from the warpage measurement method and the like, and the magnetizing force is measured based on the relationship. Since the film tension is calculated from the value, the measurement error is small compared to the case where the film tension is directly obtained from the conventional warpage measurement method, and high-precision and simple indirect measurement is possible. Further, if the above relationship is obtained in advance, the work efficiency can be greatly improved since the subsequent measurements such as the one-side pickling removal required in the conventional warpage measurement method can be omitted.

It is a graph which shows the relationship between the exciting magnetic flux density of a perpendicular direction of rolling, and a magnetizing force before and after the film removal of a grain-oriented electrical steel sheet. It is a graph which shows the relationship between the film | membrane stress of the rolling direction of a grain-oriented electrical steel sheet, and the magnetizing force in the exciting magnetic flux density 1.0T of a rolling orthogonal direction. A graph plotting the coefficient of determination when the linear relationship between the magnetizing force and the film tension at a magnetic flux density of 0.1 to 1.2T in the direction perpendicular to the rolling applied to the grain-oriented electrical steel sheet is calculated by the least square method against the magnetizing force. It is. It is a graph when the value measured by the method of this invention and the conventional method is plotted about the relationship between the coating weight of an insulating film, and film tension.

The present inventors conducted the following experiment in order to obtain magnetic characteristics highly correlated with the film tension.
Prepare a product sheet of grain-oriented electrical steel sheet containing Si: 3.3mass%, Mn: 0.06mass%, Sb: 0.03mass%, with an undercoat and insulation coating, and first measure the excitation characteristics in the direction perpendicular to the rolling direction. did. Subsequently, the film (insulating coating and undercoat) was completely removed with sodium hydroxide, and the excitation characteristics were measured in the same manner as described above. By comparing the excitation characteristics before and after the film removal, the film tension relative to the excitation characteristics was measured. The impact was investigated.

  FIG. 1 shows changes in excitation characteristics before and after film removal. In FIG. 1, the vertical axis represents the excitation magnetic flux density (T) in the direction perpendicular to the steel sheet rolling, and the horizontal axis represents the magnetizing force (A / m). From the results of FIG. 1, it can be seen that when the excitation magnetic flux density is 1.3 T or more, no change is observed before and after the film removal. This means that it is affected only by the crystal orientation and not the film. On the other hand, when the excitation magnetic flux density is less than 1.3T, the excitation curve shifts to the left (low magnetization force side) by removing the film, and it can be seen that the magnetizing force required to excite to a constant magnetic flux density is significantly reduced. . That is, as a result of the above experiment, it was found that when the magnetic flux density in the direction perpendicular to the steel sheet rolling is less than 1.3 T, excitation in the direction perpendicular to the rolling becomes extremely difficult due to the presence of the coating.

Next, the following experiment was conducted in order to investigate the correlation between the magnetizing force and the film tension.
Prepare a grain-oriented electrical steel sheet having the same composition as above, with a base coating and various coating weights of insulation coating, and cut a sample 100 mm in the direction perpendicular to the rolling direction and 30 mm in the width direction from the product sheet. Excitation characteristics in the direction perpendicular to rolling were measured (sample number: 37). For samples after measurement, remove the coating (insulating coating and base coating) on one side of each sample by pickling, measure the amount of warpage of the sample after removal of the coating, and calculate the following formula (1) from the measured amount of warpage: From this, the film tension σ ′ of the sample was calculated.
Record
σ´ = Ed / 2R… (1) where R ≒ l × (2 / 2a)
In Eq. (1), E is the Young's modulus of the sample, d is the thickness of the sample (mm), R is the radius of curvature of the sample at the time of warpage (mm), l is the measured warp length (mm), and a is the warp Amount (mm). In the above, the amount of warpage was measured and the film tension was calculated with “E = 132 GPa” and “l = 250 mm”. The warpage measurement length means the length of the portion where the warpage is measured, excluding the clamping margin by the warpage amount measuring jig from the length in the direction perpendicular to the rolling direction of the sample.

Based on the above measurement and calculation results, the correlation between the film stress in the rolling direction of the steel sheet and the magnetizing force (H ₁₀ ) when the excitation magnetic flux density in the direction perpendicular to the rolling is 1.0 T was investigated. The survey results are shown in FIG. In FIG. 2, the vertical axis represents the film stress, a positive numerical value represents tension (tensile stress), a negative numerical value represents compressive stress, and the horizontal axis represents the magnetizing force. As shown in FIG. 2, a very high correlation was confirmed between the film stress value and the magnetizing force in the linear function obtained by the least square method, and the correlation coefficient R was 0.9883 (determination coefficient R ² = 0.9767). there were.

Furthermore, in order to confirm the influence of the excitation magnetic flux density on the above correlation, 20 samples were extracted from the steel sheet having the same composition as above, and the same experiment as described above was performed, so that the film stress and the magnetization at various excitation magnetic flux densities were obtained. The correlation with force was investigated, and each coefficient of determination R ² was determined. FIG. 3 shows magnetizing forces H ₁ , H ₂ , H ₄ , H ₆ , H ₈ , H ₁₀ , H _{12 at} excitation magnetic flux densities of 0.1T, 0.2T, 0.4T, 0.6T, 0.8T, 1.0T, and 1.2T. It plots the determined constant R ² for. From the results shown in FIG. 3, the coefficient of determination R ² between the film tension value and the magnetizing force is high in the range of the excitation magnetic flux density of 0.4 to 1.2 T, and the film is accurately measured by measuring the magnetizing force of the object to be measured. It can be seen that the tension can be determined.

  If the measurement is repeated many times for the same sample, the measurement value is averaged and the error factor can be reduced.For example, in the film tension measurement by the warpage measurement method, the sample must be destroyed by the measurement, The measurement cannot be repeated multiple times for the same sample. However, even if different samples are used, correlation with the magnetizing force using a large number of samples can reduce the error factor based on the same principle as the above-described averaging. Therefore, the film tension can be obtained with high accuracy by using the magnetization force of the object to be measured and the correlation.

In addition, as described above, considering that the amount of warping of the sample depends on the sample shape before removing the single-sided film, using a large number of samples can reduce measurement errors due to the sample shape before removing the single-sided film. Is beneficial. The coefficient of determination R ² between the film tension value and the magnetizing force depends on the number of samples. The larger the number of samples, the higher the coefficient of determination R ² .

  The mechanism showing a high correlation between the film tension and the magnetizing force during excitation in the direction perpendicular to the rolling direction is not necessarily clear, but is considered as follows. A grain-oriented electrical steel sheet is formed in the plane of a steel sheet by applying an insulating coating consisting of a base film mainly composed of a forsterite film and a phosphate and colloidal silica to a ground iron composed of giant crystal grains having Goss orientation. It becomes a product by applying tension. By applying tension to the steel sheet, the effect of reducing the iron loss by subdividing the 180 ° magnetic domains and the effect of strain caused by processing, etc. are reduced, and the effect of minimizing the iron loss and magnetostriction property deterioration is achieved. can get. By the way, the purpose of applying the tension is to stabilize the 180 ° magnetic domain structure by the magnetoelastic effect, particularly by applying tension in the rolling direction of the steel sheet. It has only a magnetic domain structure. Here, since the 180 ° magnetic domain structure has no magnetization component in the direction perpendicular to the rolling, it is necessary to collapse the 180 ° magnetic domain structure in order to magnetize in the direction perpendicular to the rolling, but the tension in the rolling direction is 180 ° as described above. Since the magnetic domain structure is stabilized, it is considered that the collapse becomes difficult and a large magnetizing force is required to magnetize. Therefore, it is estimated that a high correlation occurs between the film tension and the magnetizing force in the direction perpendicular to the rolling.

  In the present invention, the reason why the preferable range of the excitation magnetic flux density in the direction perpendicular to the rolling is 0.4 to 1.2 T is considered as follows. The direction perpendicular to the rolling direction of the grain-oriented electrical steel sheet having the Goss orientation is <110> in the crystal orientation. In the case of an experiment using a single crystal, magnetization proceeds to about 1.3 T with a magnetization force of about 5000 A / m. However, magnetization rotation is necessary for further magnetization. That is, in order to realize magnetization exceeding 1.3 T, magnetization rotation is required, but since the ease of magnetization rotation is determined by the crystal orientation, it is considered that the film tension is not affected. In addition, the magnetization characteristics on the low magnetic field side are such that the presence of fine grains having a crystal orientation other than the Goss orientation, or the presence of a locally strained part due to surface breakage, locally disturbs the 180 ° magnetic domain structure, Since the disordered portion is easily magnetized in the direction perpendicular to the rolling direction, the magnetizing force is reduced. For this reason, if the excitation magnetic flux density is too low, it is considered that the correlation is lowered due to the influence of fine grains other than the film tension and the strain region. In the case of a grain-oriented electrical steel sheet manufactured by a normal process, since the fine grains and the strained region are very small when viewed as a whole, there is no effect on the region where the excitation magnetic flux density is high.

  As described above, according to the present invention, by measuring the magnetization characteristic in the direction perpendicular to the rolling direction, it is possible to determine the film tension having a very high correlation with the stability of the 180 ° magnetic domain. In addition, the measurement method of the present invention has a measurement error of about 0.5%, which is smaller than that of the conventional warpage measurement method, and can eliminate work such as pickling removal on one side, so that the work efficiency can be remarkably improved.

Hereinafter, the present invention will be specifically described.
In the present invention, by applying an insulative coating in which a base film mainly composed of a forsterite film and a phosphate and colloidal silica are applied to a ground iron composed of giant crystal grains having a Goss orientation, a tension is applied in the plane of the steel sheet. It is related with the measuring method of the film tension of the grain-oriented electrical steel sheet made into a product by giving.

  The grain-oriented electrical steel sheet to be subjected to tension measurement can be manufactured by a known method, and the manufacturing method is not particularly limited. Although it does not specifically limit also about the basic component of the said steel plate, For example, besides containing Si: 2.0-4.0mass%, Mn: 0.03-0.50mass%, Sb: 0.10 mass% or less, Sn: Alloy elements such as 0.05 mass% or less and Ni: 0.3 mass% or less can be added. An insulating coating is applied to the surface of the steel sheet after the flattening annealing, but it is advantageous to apply a tension coating in which phosphate and colloidal silica are mixed in order to give a film tension to the steel sheet to obtain good iron loss.

  Prior to the measurement of the film tension of the object to be measured, a number of samples of the electromagnetic steel sheet with an insulating film are prepared for various film stresses, and the magnetizing force in the direction perpendicular to the rolling at a predetermined excitation magnetic flux density is measured. For each measured sample, after removing the single-sided coating (insulating coating and base coating) by pickling, the coating tension is calculated from the amount of warpage using the equation (1). Thereafter, a correlation between the measured value of the magnetizing force and the film tension is obtained. That is, in the present invention, regardless of the type of steel plate, the Young's modulus E and the plate thickness d, which are uniquely determined for each steel plate, are substituted into the equation (1) to calculate the film tension, The correlation with the film tension can be obtained.

  After obtaining the above correlation, the excitation characteristic (magnetizing force) in the direction perpendicular to the rolling is measured in order to determine the film tension of the object to be measured. The excitation magnetic flux density for measuring the magnetizing force is preferably selected in the range of 0.4 to 1.2T. More preferably, it is the range of 0.6-1.0T. When the steel types are the same, the film tension can be determined based on the same correlation. However, when the steel types are different in composition, orientation accumulation degree, fine grain existence frequency, etc., the correlation is obtained for each steel type. Note that the greater the number of samples for obtaining the correlation, the higher the measurement accuracy, and it is preferable to provide 10 or more samples for measurement.

  In addition, the correlation between the tension of the undercoat and the magnetizing force, and the correlation between the tension and the magnetizing force of the insulating coating are individually obtained, and the film tension of each of the undercoat and the insulating coating is determined based on these correlations. It is also possible.

  In order to obtain the correlation between the magnetizing force and the film tension, the film tension was measured by the warp measurement method by removing one side of the film (insulating coating and base film) in the above, but the method of measuring the film tension is limited to this. Instead, other measuring means may be used.

A grain-oriented electrical steel sheet (Young's modulus E = 132GPa) having only a forsterite undercoating with a thickness of 0.30 mm was prepared, and an insulating coating made of magnesium phosphate mixed with colloidal silica was baked at 850 ° C. to obtain a product. In the above, in order to obtain steel sheets having various film tensions, the basis weight of the insulating coating is 0 g / m ² , 2 g / m ² , 4 g / m ² , 6 g / m ² , 8 g / m ² , 10 g / m ² and 14 g / m ^2. Seven samples were prepared for each weight per unit area (n = 10). Thereafter, H ₁₀ , which is a magnetizing force (magnetizing force at an exciting magnetic flux density of 1.0 T) for exciting the magnetic flux density in the direction perpendicular to the rolling to 1.0 T, was measured for each sample. Subsequently, for each sample, the coating on one side (insulating coating and base coating) was removed by pickling, and then the coating tension was determined from the amount of warpage using the equation (1). From these data, the correlation relationship between the magnetizing force H ₁₀ and a coating tension, the film tension value corresponding to H ₁₀ measurements for each sample in the correlation, the film tension value of the sample (coating according to the present invention Measured tension).

  FIG. 4 shows the results of the film tension measurement according to the present invention, together with the results of the film measurement obtained directly from the measurement of the amount of warpage as a conventional example. In FIG. 4, the vertical axis represents the measured film tension in the steel sheet rolling direction, and the horizontal axis represents the coating weight per unit area. Usually, as the coating weight increases, the film tension increases in proportion to the weight, but as is apparent from FIG. The film tension value shows a clear proportional relationship with the coating weight per unit area. Moreover, the measurement error is reduced in the film measuring method according to the present invention as compared with the film measuring method based on the amount of warpage.

  In this example, the correlation between the magnetizing force and the film tension value was obtained using the sample itself that is the target of the tension measurement. However, a sample used only for obtaining the correlation was prepared separately, and the magnetization was measured. When calculating the tension measurement value from the force, the correlation obtained by these samples may be used.

  It becomes possible to indirectly measure the coating tension of the grain-oriented electrical steel sheet with high accuracy and simply.

Claims (2)

The relationship between the magnetizing force at a predetermined excitation magnetic flux density in the direction perpendicular to the rolling direction of the grain-oriented electrical steel sheet and the film tension applied to the surface of the steel sheet is determined in advance, and the direction perpendicular to the rolling direction of the grain-oriented electrical steel sheet to be measured is measured. Measuring the magnetizing force at the predetermined magnetic flux density in the direction, and determining the film tension of the object to be measured based on the relationship from the measured value of the measured magnetizing force. Indirect measurement method.   The indirect measurement method of the film tension of the grain-oriented electrical steel sheet according to claim 1, wherein the predetermined excitation magnetic flux density is in a range of 0.4 to 1.2T.

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