Method for predicting iron loss of grain-oriented electrical steel sheet and manufacturing system using the same

Abstract

To provide an iron loss prediction method of a grain-oriented electromagnetic steel sheet which can effectively perform magnetic domain subdivision processing by accurately predicting, before the magnetic domain subdivision processing, iron loss characteristics after the magnetic domain subdivision processing.SOLUTION: An approximate formula which is a correlation between an excitation current value obtained in advance when a grain-oriented electromagnetic steel sheet is excited to a predetermined magnetic flux density and an iron loss value after the magnetic domain refinement processing is performed on the grain-oriented electromagnetic steel sheet, and an excitation current value measured by exciting the grain-oriented electromagnetic electrical steel sheet which predicts iron loss to a predetermined magnetic flux density before the sheet is passed through a magnetic domain refinement processing apparatus are used.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for predicting iron loss of a grain-oriented electrical steel sheet subjected to a magnetic domain subdivision process capable of reducing transformer iron loss, and a manufacturing system using the same.

Background Art

[0002] A grain-oriented electrical steel sheet having a crystal structure in which the <001> direction, which is the easy magnetization axis of iron, is highly aligned in the rolling direction of the steel sheet is used as a core material for transformers. Although there are various characteristics required for the core of such a transformer, it is particularly important that the iron loss is small. From this viewpoint, the characteristic required for the grain-oriented electrical steel sheet as a core material is particularly important that the iron loss value is small.

[0003] Here, as a measure for reducing the iron loss value of the grain-oriented electrical steel sheet, subjecting the grain-oriented electrical steel sheet to a magnetic domain subdivision process can be mentioned. If the iron loss reaching the entire length of the coil can be predicted before such a magnetic domain subdivision process, it becomes possible to efficiently select a material for performing the magnetic domain subdivision process according to the order grade. And this leads to constructing an optimal production system.

[0004] Note that the iron loss distribution over the entire length of the coil can be grasped even at present by using a continuous iron loss meter. However, the correlation between the iron loss before the magnetic domain subdivision process and the iron loss after the magnetic domain subdivision process is small. Even if the iron loss before the process is small, the desired iron loss may not be obtained after the process, or even if the iron loss before the process is large, the iron loss after the process may achieve the target. That is, there was a problem in terms of accuracy in predicting the iron loss of the magnetic domain subdivision processed material in advance using a continuous iron loss meter.

[0005] Therefore, as a method for predicting the iron loss of a directionally electromagnetic steel sheet subjected to magnetic domain subdivision processing, Patent Document 1 discloses a method using the iron loss and magnetic flux density before the magnetic domain subdivision processing. In such Patent Document 1, it is found that there is a correlation between the magnetic flux density before the magnetic domain subdivision processing and the iron loss after the magnetic domain subdivision processing, and in order to further improve the accuracy, the iron loss before the magnetic domain subdivision processing is used.

[0006] In addition, Patent Document 2 discloses a method of quantifying the process variables of a product to predict the material value of the product. In such Patent Document 2, the quantization of the process variables is carried out to predict the material value of the product.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, as described above, since the relationship between the iron losses before and after the magnetic domain subdivision processing has a low correlation, even if the magnetic flux density before the magnetic domain subdivision processing is further used, there is a limit to accurately predicting the iron loss after the magnetic domain subdivision processing.

[0009] In addition, even if the process variables are quantized, errors will occur due to such quantization, and it is difficult to make predictions with the accuracy we require. In addition, the prior art does not disclose the specific process variables necessary for predicting the iron loss after the magnetic domain subdivision processing, and it is difficult to predict the iron loss after the magnetic domain subdivision processing with the accuracy we require using the above-mentioned Patent Documents 1 and 2.

[0010] The present invention has been made in view of the above circumstances, and before the magnetic domain subdivision treatment, by accurately predicting the iron loss characteristics after the magnetic domain subdivision treatment, an iron loss prediction method for a grain-oriented electrical steel sheet in which the magnetic domain subdivision treatment is efficiently performed, and a manufacturing system for realizing an optimal production system for the grain-oriented electrical steel sheet by using such an iron loss prediction method are provided.

Means for Solving the Problems

[0011] In order to achieve the above object, the inventors of the present invention first investigated the magnetic properties before the magnetic domain subdivision treatment that have a good correlation with the magnetic properties after the magnetic domain subdivision treatment. The investigation parameters were changes in iron loss, eddy current loss, and DC hysteresis loss before and after the magnetic domain subdivision treatment. Note that the iron loss and DC hysteresis loss were actually measured according to JIS C 2550-1, and the difference between the iron loss and the hysteresis loss was defined as the eddy current loss.

[0012] The relationships between the iron loss after the magnetic domain subdivision treatment and the iron loss, eddy current loss, and DC hysteresis loss before the magnetic domain subdivision treatment were respectively obtained, a linear approximation line was derived from such relationships, and the prediction accuracy of the linear approximation line was evaluated using the coefficient of determination (R 2 )(as described in Table 1). Note that the excitation magnetic flux density was 1.7 T, and when applying AC excitation, the excitation frequency was 50 Hz.

[0013]

Table 1

[0014] Table 1 shows the results of evaluating the correlation of each parameter, and it can be seen that the iron loss after the magnetic domain subdivision treatment shows a good correlation with the DC hysteresis loss before the magnetic domain subdivision treatment. That is, what is improved by the magnetic domain subdivision treatment is the eddy current loss, and the eddy current loss after the magnetic domain subdivision treatment becomes almost the same value as long as the magnetic domain subdivision treatment conditions are the same regardless of the value of the eddy current loss before the magnetic domain subdivision treatment. On the other hand, regarding the DC hysteresis loss, it is not improved by the magnetic domain subdivision treatment, and the superiority or inferiority does not change before and after the magnetic domain subdivision treatment. For the above reasons, it is considered that the iron loss after the magnetic domain subdivision process had a good correlation with the DC hysteresis loss before the magnetic domain subdivision process.

[0015] However, it is difficult to continuously measure the DC hysteresis loss over the entire length of the coil. Therefore, the inventors further searched for a factor that can be continuously measured over the entire length of the coil and has a good correlation with the DC hysteresis loss. As a result, a correlation was recognized between the magnetic flux density before the magnetic domain subdivision process and the value of the excitation current flowing when exciting the sample before the magnetic domain subdivision process, respectively, and the DC hysteresis loss. The correlation between the magnetic flux density before the magnetic domain subdivision process and the iron loss after the magnetic domain subdivision process was reproduced by the method of Patent Document 1.

[0016] The results are shown in Table 2. A better correlation was recognized between the relationship between the excitation current value before the magnetic domain subdivision process and the iron loss after the magnetic domain subdivision process than the relationship between the magnetic flux density B8 before the magnetic domain subdivision process and the iron loss after the magnetic domain subdivision process.

[0017]

Table 2

[0018] This is considered to be because the DC hysteresis loss decreases as the steel sheet becomes easier to magnetize, while the magnetic flux density has a correlation with the crystal orientation of the secondary recrystallized grains that affects the ease of magnetization, so a good coefficient of determination was obtained.

[0019] Furthermore, the reason why a better coefficient of determination was obtained with the excitation current is considered as follows. That is, the factors that affect the ease of magnetization are not only the crystal orientations that have a large correlation with the magnetic flux density. For example, the impurity content of the steel sheet also affects the ease of magnetization. On the other hand, since the excitation current is in a direct proportional relationship with the ease of magnetization, it includes the influence of all factors that affect the ease of magnetization. Therefore, it is considered that the excitation current obtained a better coefficient of determination than the magnetic flux density.

[0020] Note that if a search coil is used for the magnetic flux density and a current sensor is used for the excitation magnetic flux density, it is possible to continuously measure them over the entire length of the coil. In addition, in Patent Document 1, considering the magnetic wall spacing before the magnetic domain subdivision process as the cause of unacceptable variations in the relationship between the magnetic flux density and the iron loss, the iron loss before the magnetic domain subdivision process, which is correlated with the magnetic wall spacing, is introduced into the prediction formula to achieve high precision. However, such variations have not been completely eliminated. In contrast, the inventors of the present invention believe that unacceptable variations in the relationship between the magnetic flux density and the iron loss occur because the DC hysteresis loss varies due to causes other than the crystal orientation even at the same magnetic flux density. Therefore, the excitation current is adopted instead of the magnetic flux density to eliminate such variations.

[0021] In addition, as described above, before the magnetic domain subdivision process, since the iron loss characteristics after the magnetic domain subdivision process of the coil can be predicted, the productivity of the magnetic domain subdivision process line can be improved as follows. That is, the line speed, which greatly contributes to the productivity of the magnetic domain subdivision process line, is determined by the beam deflection speed of the magnetic domain subdivision process and the interval of the strain introduced linearly (line interval).

[0022] Here, when manufacturing high-grade products, since it is necessary to introduce sufficient strain into the steel sheet, it is necessary to narrow the line interval, and it is difficult to increase the line speed. On the other hand, in the case of general-purpose grade products, the amount of strain introduced into the steel sheet may be less than that of high-grade products, and since the line interval can be widened, the line speed can be increased. Furthermore, when the grade is lower, a further increase in speed becomes possible.

[0023] That is, if the eddy current loss cannot be predicted, production may exceed the order volume of the high-grade product. Thus, if production exceeds the order volume of the high-grade product, even if the product meets the high-grade standard, it may have to be sold as a general-purpose / low-grade product for which the line speed should have been increased, resulting in a decrease in productivity.

[0024] On the other hand, if the eddy current loss characteristics after the magnetic domain subdivision treatment can be predicted with high accuracy, overproduction of high-grade materials for which the line speed cannot be increased can be avoided, enabling efficient production of each grade according to the order volume. To confirm the above, Table 3 shows the production volumes before and after applying the relationship between the excitation current value before the magnetic domain subdivision treatment and the eddy current loss after the magnetic domain subdivision treatment.

[0025]

Table 3

[0026] Before applying the relationship between the excitation current value before the magnetic domain subdivision treatment and the eddy current loss after the magnetic domain subdivision treatment, 20% of the general-purpose grade material had characteristics that met the high-grade standard, and 30% of the low-grade material had characteristics that met the general-purpose grade or high-grade standard. On the other hand, when applying the relationship between the excitation current value before the magnetic domain subdivision treatment and the eddy current loss after the magnetic domain subdivision treatment, no extra high-grade material was included, and shipment according to the order grade became possible.

[0027] In addition, by applying the relationship between the excitation current value before the magnetic domain subdivision treatment and the eddy current loss after the magnetic domain subdivision treatment, the magnetic domain subdivision treatment conditions were optimized to the conditions suitable for the grade, and the productivity was significantly improved (by about 1.5 times).

[0028] From the above results, the importance of considering at least the predicted eddy current loss value and the order volume of each product specification when determining the manufacturing conditions of the magnetic domain subdivision treatment line became clear.

[0029] The present invention has been completed based on the above findings. That is, the gist of the present invention is as follows. 1. When predicting the iron loss after magnetic domain refinement treatment of a grain-oriented electromagnetic steel sheet before passing the grain-oriented electromagnetic steel sheet through a magnetic domain refinement treatment apparatus, an approximate formula which is a correlation between the excitation current value when the grain-oriented electromagnetic steel sheet is excited to a predetermined magnetic flux density, which has been obtained in advance, and the iron loss value after subjecting the grain-oriented electromagnetic steel sheet to magnetic domain refinement treatment, and an iron loss prediction method for a grain-oriented electromagnetic steel sheet using the excitation current value measured by exciting the grain-oriented electromagnetic steel sheet to a predetermined magnetic flux density before passing the grain-oriented electromagnetic steel sheet through a magnetic domain refinement treatment apparatus.

[0030] 2. The iron loss prediction method for a grain-oriented electromagnetic steel sheet according to 1 above, wherein the approximate formula is changed according to the steel sheet cross-sectional area.

[0031] 3. The iron loss prediction method for a grain-oriented electromagnetic steel sheet according to 1 or 2 above, wherein the approximate formula is changed according to the magnetic domain refinement treatment conditions.

[0032] 4. A manufacturing system for determining magnetic domain refinement treatment conditions by inputting the iron loss value predicted by the iron loss prediction method according to any one of 1 to 3 above and the order quantity for each product specification into a system for determining manufacturing conditions of a magnetic domain refinement treatment line.

Advantages of the Invention

[0033] According to the present invention, it becomes possible to accurately predict the iron loss value of the entire length of the coil after magnetic domain refinement treatment. Further, by using the method for predicting such an iron loss value, it becomes possible to realize an optimal production system for grain-oriented electromagnetic steel sheets.

Brief Description of the Drawings

[0034]

Figure 1

Embodiments for Carrying Out the Invention

[0035] Hereinafter, the constituent elements of the present invention will be described. Before the directionality electromagnetic steel sheet is passed through the magnetic domain refinement processing apparatus, when predicting the iron loss after the magnetic domain refinement processing of such a directionality electromagnetic steel sheet, an approximate formula that is a correlation between the excitation current value when the directionality electromagnetic steel sheet is excited to a predetermined magnetic flux density, which has been obtained in advance, and the iron loss value after the magnetic domain refinement processing of such a directionality electromagnetic steel sheet, and the excitation current value measured by exciting the directionality electromagnetic steel sheet to be predicted for iron loss to a predetermined magnetic flux density before passing it through the magnetic domain refinement processing apparatus are used.

[0036] Then, the present invention predicts the iron loss after the magnetic domain refinement processing of such a directionality electromagnetic steel sheet by applying the excitation current value measured by exciting the directionality electromagnetic steel sheet to be predicted for iron loss before passing it through the magnetic domain refinement processing apparatus to a predetermined magnetic flux density to the approximate formula. Therefore, in the present invention, it is important to derive in advance an approximate formula that is a correlation between the excitation current value when the directionality electromagnetic steel sheet before the magnetic domain refinement processing is excited to a predetermined magnetic flux density and the iron loss value after the magnetic domain refinement processing. First, the derivation method of such an approximate formula will be described.

[0037] The first is to cut out a plurality of samples of the directionality electromagnetic steel sheet before the magnetic domain refinement processing, perform magnetic measurement offline, and measure the excitation current value when excited to a predetermined magnetic flux density. Then, perform magnetic domain refinement processing on such samples and measure the iron loss offline. An approximate formula is obtained from the relationship between the measured excitation current value and the measured iron loss described above.

[0038] The second is to measure the excitation current value of the entire length of the coil with a continuous magnetic measurement device while continuously passing at least one or more coils before the magnetic domain refinement processing through the magnetic domain refinement processing apparatus. Next, cut out single plate samples from one or more locations randomly extracted from such a coil, and read the excitation current value of the cut-out location from the measurement data of the cut-out location in the measurement data of the excitation current value of the entire length of the coil. Then, perform magnetic domain refinement processing on the steel sheet at the cut-out location and measure the iron loss of such a steel sheet offline. An approximate expression is obtained from the relationship between the read excitation current value and the measured iron loss described above.

[0039] Thirdly, at least one pre-segmentation processing coil is continuously passed through the magnetic domain segmentation processing device, and the excitation current value of the entire length of the coil is measured by the continuous magnetic measurement device. Then, continuous magnetic domain segmentation processing is performed, single-plate samples are cut out from one or more randomly extracted locations, and the iron loss is measured offline. An approximate expression is obtained from the relationship between the measured excitation current value and the measured iron loss described above. Note that the excitation current value at the cutting position is read from the result of continuous measurement at that cutting position.

[0040] Fourthly, at least one pre-segmentation processing coil is continuously passed through the magnetic domain segmentation processing device, and the excitation current value of the entire length of the coil is measured by the continuous magnetic measurement device. Then, continuous magnetic domain segmentation processing is performed, and the iron loss is further measured by the continuous magnetic measurement device. And an approximate expression is obtained from the relationship between the excitation current value measured at the same randomly extracted position of such a measurement coil and the measured iron loss.

[0041] These four procedures may be performed independently to obtain an approximate expression according to the present invention, or a plurality of them may be combined to obtain such an approximate expression. Here, it is preferable to select a directional electromagnetic steel sheet or coil serving as a sample for obtaining the approximate expression to have the same Si content as the coil for determination. Furthermore, it is more preferable to select a coil with the same manufacturing process.

[0042] Even if such an approximate expression is created once, it is not continued to use the approximate expression. Instead, various data can be continuously acquired, and the approximate expression can be changed by limiting the measurement data to be used. For example, in order to prevent the occurrence of changes over time, it is possible to create and use an approximate expression limited to the data immediately before passing the plate.

[0043] In addition, if the approximate formula used in the present invention is obtained by linear approximation, sufficient accuracy can be obtained to achieve the effects of the present invention. However, it may also be obtained by methods other than linear approximation (for example, polynomial approximation, power approximation, moving average, etc.).

[0044] In the present invention, the predetermined magnetic flux density for exciting when obtaining the exciting current value is not particularly limited. However, if it is too high, it is difficult for effects other than crystal orientation to appear, while if it is too low, it is difficult for the influence of crystal orientation to appear. Therefore, in the present invention, the predetermined magnetic flux density for exciting is preferably in the range of 1.3 to 1.8 T.

[0045] Since the exciting current for exciting the steel sheet with the magnetic flux density changes depending on the cross-sectional area of the steel sheet, when the plate thickness and coil width are different, it is preferable in terms of prediction accuracy to create approximate formulas for each case and use them respectively.

[0046] In addition, when the magnetic domain subdivision processing conditions change, the reached iron loss after the magnetic domain subdivision processing changes. Therefore, when manufacturing under a plurality of magnetic domain subdivision processing conditions, it is preferable to create approximate formulas for each magnetic domain subdivision processing condition and use them respectively. The magnetic domain subdivision processing conditions are: I) type of beam (laser, plasma, electron beam, etc.), II) output, III) deflection speed, IV) irradiation line interval, etc.

[0047] The magnetic domain subdivision processing line is a process for manufacturing a plurality of product specifications on one line. When determining the manufacturing conditions of such a magnetic domain subdivision processing line, the manufacturing system of the present invention uses the predicted iron loss after magnetic domain subdivision processing of the total length of each coil and the current order quantity in a plurality of magnetic domain subdivision processing conditions.

[0048] Note that the iron loss guarantee value of each coil is the largest iron loss value in the coil. However, the present invention incorporates a process of removing a portion with a large iron loss partially in a subsequent process into the determination system, and can determine the magnetic domain subdivision processing conditions of each coil with the highest production efficiency.

[0049] There is a certain inevitable error in the approximate formula. Therefore, in the present invention, by incorporating the similarity of the approximate formula into the system, an error can be imparted to the predicted iron loss, and the occurrence of out-of-grade due to the error cause can be suppressed.

[0050] In the present invention, if the above-described factors are incorporated, the determination method of the magnetic domain subdivision processing conditions and the target coil is not particularly limited, but for example, the following procedure is exemplified.

[0051] First, the total order quantity is separated into high-grade, general-purpose grade, and low-grade, and by adjusting the irradiation conditions, coils capable of manufacturing high-grade are extracted. At this time, the production volume is set in consideration of the prediction accuracy.

[0052] Next, coils capable of realizing the general-purpose grade are extracted. At this time, it is preferable to limit and select the allowable magnetic domain subdivision processing conditions. That is, it is preferable not to select coils that cannot realize the general-purpose grade under magnetic domain subdivision processing conditions that reduce productivity more than necessary.

[0053] Finally, coils capable of realizing the low-grade are selected. Also at this time, the allowable magnetic domain subdivision processing conditions are limited and selected. It is preferable to select with stricter selection criteria than the general-purpose grade. If the order quantity cannot be processed at this stage, the selection criteria can be relaxed to select coils capable of realizing the general-purpose grade and the low-grade. At this stage, the coils not selected do not pass through the magnetic domain subdivision processing line

[0054] In the grain-oriented electrical steel sheet, grain-oriented electrical steel sheet coil, and their manufacturing methods described in this specification, any items not described in this specification can be based on known grain-oriented electrical steel sheets, known grain-oriented electrical steel sheet coils, and their manufacturing methods.

Example

[0055] Next, the present invention will be specifically described based on examples. The following examples show a preferred example of the present invention, and the present invention is not limited by these examples. The embodiments of the present invention can be appropriately changed within the scope that conforms to the gist of the present invention, and all of them are included in the technical scope of the present invention.

[0056] [Example 1] A plurality of non-segmented directional electromagnetic steel sheet coils with a plate thickness of 0.27 mm, which were not subjected to magnetic domain segmentation treatment and were manufactured by a known method, were prepared. The plate widths of such coils were three types: 500 mm (a), 750 mm (b), and 1000 mm (c). First, the coils were passed through a line equipped with a continuous magnetic measurement device, and the exciting current when excited to 1.7 T and the magnetic flux density B8 when magnetized at 800 A / m were measured over the entire length of the coils. Subsequently, magnetic domain segmentation treatment was performed on the entire length of such coils using a laser. At that time, the output was 1500 W, the deflection speed was 30 m / s, and the irradiation line interval was 3 to 10 mm. Next, samples were taken from each coil at a pitch of 100 m, and the iron loss characteristics after the magnetic domain segmentation treatment were evaluated. Also, from the exciting current and B8 measurement results collected by the continuous magnetic measurement device before the magnetic domain segmentation treatment, the exciting current and B8 at the location where the samples were taken were read. Using these data, the relationships between iron loss and exciting current and between iron loss and B8 were respectively derived.

[0057] Tables 4-1, 4-2, and 4-3 respectively show the results of evaluating the accuracy (coefficient of determination) of each approximate formula. As shown in Tables 4-1, 4-2, and 4-3, it can be seen that in all conditions, the relationship between exciting current and iron loss has better accuracy than the relationship between magnetic flux density and iron loss.

[0058]

Table 4-1

[0059]

Table 4-2

[0060]

Table 4-3

[0061] Next, after predicting the iron loss after the magnetic domain subdivision process of the strip coil using each approximate formula, the magnetic domain subdivision process was performed. By passing the strip through the continuous magnetic measurement device after the magnetic domain subdivision process, the iron loss distribution of the entire length of the coil after the magnetic domain subdivision process was actually measured. Thereafter, the predicted iron loss distribution of the entire length of the coil was compared with the actually measured iron loss distribution of the entire length of the coil, and the similarity was calculated.

[0062] This time, the similarity calculation was evaluated using the Euclidean distance: d. The predicted iron losses (a1, a2, a3, a4, ······, a i ) and the actually measured values (b1, b2, b3, b4, ······, b i ) at the same position in the longitudinal direction of the coil were used to calculate the difference for each according to the following formula, and the Euclidean distance: d shown in the following formula (1) was obtained. The similarity was expressed as 1 / (1 + d) such that the closer it was to 1, the closer the similarity, and the closer it was to 0, the farther away.

[0063]

Equation

[0064] The results are shown in Table 5-1, Table 5-2, and Table 5-3. It can be seen that those predicted by the method of the present invention show extremely high similarity.

[0065]

Table 5-1

[0066]

Table 5-2

[0067]

Table 5-3

[0068] [Example 2] A plurality of non-segmented directionally electromagnetic steel sheets with a plate thickness of 0.23 mm, which were produced by a known method, were prepared. The plate width was of one type, 1280 mm. First, cut plate samples were collected from a plurality of locations in the longitudinal direction of the coil. The continuous magnetic measurement device measures the entire length of the coil continuously during normal operation (online), but when not operating (offline), a single plate sample is set in the device, and the exciting current when excited to 1.5 T and the magnetic flux density B8 when magnetized at 800 A / m were measured. Next, the magnetic domain subdivision treatment was carried out offline using an electron beam. At that time, the output was 3000 W, the deflection speed was 60 m / s, and the irradiation line interval was 3 to 10 mm. Then, the iron loss characteristics after the magnetic domain subdivision treatment were evaluated offline. Using these data, the relationships between iron loss and exciting current, and between iron loss and B8 were respectively derived.

[0069] Using the iron loss values after the magnetic domain subdivision treatment predicted from the above-derived relationships (approximate formulas), when producing according to various virtual order acceptance ratios shown in Table 6, it was verified how much the production efficiency could be increased by adopting the method of the present invention.

[0070] First, the coil ratios capable of achieving high-grade, general-purpose, and low-grade were determined for each irradiation line interval (see Figure 1). Next, among the coils capable of achieving the high grade, the most productive ones (the starred ones on the high-grade line in Figure 1) were selected, and the high-grade candidate coils were determined by sequentially shifting to the conditions with lower productivity (in the direction of the white arrow within the high-grade area) until the required amount was reached. Furthermore, candidate coils for general-purpose and low-grade were selected in the same procedure. The production amounts verified by such a procedure are shown in Table 6 respectively.

[0071]

Table 6

[0072] When predicting the iron loss after the magnetic domain subdivision process using the approximate formula according to the present invention, the error can be minimized as much as possible, enabling more efficient production. It can be seen that the production volume increases in each case regardless of the order balance.

[0073] On the other hand, when predicting the iron loss after the magnetic domain subdivision process using the magnetic flux density, although the differentiation of each grade can be achieved compared to the case without prediction and the production volume increases, the prediction accuracy is inferior to that of the prediction using the present invention. Therefore, it can be seen that both the differentiation and the production volume are inferior compared to the present invention.

Claims

Claim 1 When predicting the iron loss after magnetic domain refinement treatment of a grain-oriented electromagnetic steel sheet before passing the grain-oriented electromagnetic steel sheet through a magnetic domain refinement treatment apparatus, an approximate formula which is a correlation between the excitation current value when the grain-oriented electromagnetic steel sheet is excited to a predetermined magnetic flux density and the iron loss value after subjecting the grain-oriented electromagnetic steel sheet to magnetic domain refinement treatment, obtained in advance, and the excitation current value measured by exciting the grain-oriented electromagnetic steel sheet to be predicted for iron loss to a predetermined magnetic flux density before passing the grain-oriented electromagnetic steel sheet through a magnetic domain refinement treatment apparatus are used for a method for predicting the iron loss of a grain-oriented electromagnetic steel sheet. Claim 2 The method for predicting the iron loss of a grain-oriented electromagnetic steel sheet according to claim 1, wherein the approximate formula is changed according to the cross-sectional area of the steel sheet. Claim 3 The method for predicting the iron loss of a grain-oriented electromagnetic steel sheet according to claim 1 or 2, wherein the approximate formula is changed according to the magnetic domain refinement treatment conditions. Claim 4 A manufacturing system that determines the magnetic domain refinement treatment conditions by inputting the iron loss value predicted by the iron loss prediction method according to claim 1 or 2 and the order quantity for each product specification into a system that determines the manufacturing conditions of a magnetic domain refinement treatment line. Claim 5 A manufacturing system that determines the magnetic domain refinement treatment conditions by inputting the iron loss value predicted by the iron loss prediction method according to claim 3 and the order quantity for each product specification into a system that determines the manufacturing conditions of a magnetic domain refinement treatment line.

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