JP6191640B2 - Evaluation method and manufacturing method of non-oriented electrical steel sheet - Google Patents

Description

  The present invention relates to a method for evaluating a non-oriented electrical steel sheet capable of accurately and easily evaluating a non-oriented electrical steel sheet having good iron loss characteristics by punching, and manufacturing of the non-oriented electrical steel sheet using the evaluation method It is about the method.

  In general, it is known that magnetic properties of an electromagnetic steel sheet deteriorate when subjected to punching or the like. In particular, iron loss deterioration (increased iron loss) that increases iron loss results in increased costs due to energy loss of parts and products using the electrical steel sheet, so the amount of increase in iron loss due to punching is kept small. As a result, it is important to suppress the iron loss after punching (iron loss before punching + increase in iron loss by punching) to be small. That is, it is important to improve the iron loss characteristics by punching (the amount of iron loss increased by punching and the iron loss after punching).

  So far, various approaches have been taken experimentally or numerically to investigate the effects of punching and the like on iron loss increase.

  First, many examples of experimental approaches have been reported and will be omitted here.

  On the other hand, as a numerical analysis approach, non-patent document 1 and non-patent document 2 obtain the distribution of strain and stress generated in the electrical steel sheet from the numerical analysis result simulating shear punching, A case study of the relationship has been published.

  Further, Patent Document 1 and Patent Document 2 disclose a system that evaluates the iron loss of a magnetic body (steel plate or the like) in consideration of stress when the magnetic body (steel plate or the like) is processed.

  Further, although completely different from punching, in Patent Document 3 and Patent Document 4, in order to obtain a unidirectional electrical steel sheet having excellent iron loss characteristics, a part in which strain is introduced into the unidirectional electrical steel sheet by laser beam irradiation or the like. Disclosed is a method for evaluating iron loss characteristics using a value obtained by integrating the compressive residual stress in the region where the compressive residual stress exists for a two-dimensional distribution in the cross section perpendicular to the sheet width direction of the residual stress generated in the vicinity. Yes.

JP 2003-240831 A JP 2009-052914 A JP 2008-106288 A JP 2012-172215 A

Enomoto et al., “Electromagnetic steel plates for drive motors of hybrid / electric vehicles”, Nippon Steel Technical Report No. 378, pp. 51-54, 2003 Sugawara et al., “Development of estimation technique of magnetic property degradation due to punching of electrical steel sheet”, IEEJ Transactions A, Vol. 131, no. 7, pp. 567-574, 2011

  Generally, when an electromagnetic steel sheet having a lower iron loss as a material is applied to a part or product such as a motor or a transformer, the iron loss as a part or product can be kept low. However, the superiority or inferiority of the iron loss performance of the material may not match the superiority or inferiority of the iron loss performance of the assembled parts or products.

  One reason for this is the deterioration of iron loss in electrical steel sheets due to punching or the like. In addition, the influence on the iron loss characteristics due to the difference in the frequency band of the parts and products can be considered.

  Therefore, depending on the processing conditions of electromagnetic steel sheets and the use conditions of parts and products made of electromagnetic steel sheets, there will be electromagnetic steel sheets that minimize the iron loss of parts and products. The work to evaluate whether or not it is an appropriate electrical steel sheet taking into account the fact is that it takes a lot of man-hours and costs, such as making an evaluation after actually making a prototype.

  On the other hand, as described above, there are efforts to utilize numerical analysis (Non-Patent Documents 1 and 2, and Patent Documents 1 to 4), but each has the following problems.

  First, Non-Patent Documents 1 and 2 have two problems. One is the analysis accuracy of the punched end face shape in the numerical analysis simulating the punching process, and the other is the problem of the electromagnetic field analysis (electromagnetic field analysis) that is required after that.

  First, regarding the analysis accuracy of the punching end face shape, which is the first problem, the analysis results of the punching end face shape shown in Non-Patent Documents 1 and 2 show that the material (electrical steel sheet) is cut at an earlier stage than the actual one.・ It is judged that they have been separated, and it is difficult to say that the analysis accuracy is high.

  Specifically, in numerical analysis, the cutting edge of the punching tool is immediately broken in a state of being slightly pushed in the thickness direction. As a result, compared to the actual case, the shear plane length at the punched end face is short, and the “sag” is very small. By the way, as shown schematically in FIG. 1, who is a portion deformed so that the vicinity of the punching end surface hangs down in the punching direction or its deformation amount.

  For example, in FIG. 8 of Non-Patent Document 1, the shape and inclination of the left end, which is the punching end surface, are clearly different between the experiment and the analysis result, and there is a discrepancy in the size of anyone near the upper left end.

  Also, FIG. No. 11 discloses an analysis result in which fracture penetrates in the thickness direction when the punch bites into the material by 12/50 of the thickness, that is, 24% of the thickness. However, in actuality, the depth is about half of the plate thickness (in FIG. 3, about 2 of the plate thickness) as illustrated in FIG. 2 (schematic diagram of the cross section of the concavo-convex portion) and FIG. / 3) An uneven processed part for round caulking can be formed, and it is easily inferred from the numerical analysis that the punching fracture has occurred earlier than actual.

  In the numerical analysis results, when the fracture occurred earlier than the actual result, and when any of them was estimated to be small, it meant that the deformation state near the end face was underestimated, and not only the magnitude of the strain but also the strain was added. Since the size of the area, which is directly connected to the size of the stress generated / residual near the punched end face and the stress generation area, the analysis results shown in Non-Patent Documents 1 and 2 show the strain and stress distribution. It is hard to say that the analysis accuracy is high.

  Next, regarding electromagnetic field analysis performed subsequent to shear punching analysis, which is the second problem, based on the purpose of electromagnetic field analysis in Non-Patent Documents 1 and 2, when strain or stress is applied After referring to the basic data of the magnetic property change (deterioration), the magnetic property deterioration is predicted in consideration of the strain distribution and stress distribution after the shear punching.

  For this reason, for example, in Non-Patent Document 2, special attention is paid such that the element division of the electromagnetic field analysis is shared with that used in the punching analysis, and the strain and stress are easily referred to. Unlike analysis, element division is also performed in the thickness direction. If the punching shape is a rectangular rectangular plate, there is no problem in applying this analysis model. However, for example, when a complicated shape such as a motor core is punched, a large-scale three-dimensional analysis is required. Thus, analysis is practically impossible.

  Also, FIG. 12-FIG. Detailed data relating to the change in the magnetic properties of the electrical steel sheet when the stress level and plastic strain shown in FIG. It is not until these data are collected, organized, and made into a database that the electromagnetic field analysis can be performed for the first time. Conversely, the same electromagnetic field analysis cannot be applied to materials that do not have this database.

  On the other hand, as described above, Patent Document 1 and Patent Document 2 disclose a system that evaluates the iron loss of a magnetic material (steel plate, etc.) in consideration of stress when the magnetic material (steel plate, etc.) is processed. Has been. However, in Patent Documents 1 and 2, although the stress is obtained by analysis, there is no mention of the influence of processing strain. Further, in Patent Document 2, the stress that is unevenly distributed in the plate thickness direction found in the punched portion is not originally intended to take into account the characteristics, and is basically baked. It is clear that only a uniform stress in the thickness direction such as a fit is intended. There is no disclosure of a method for extracting and considering at least the strain and stress distribution distributed in the thickness direction after punching.

  In addition, as described above, in Patent Documents 3 and 4, in order to obtain a unidirectional electromagnetic steel sheet with excellent iron loss characteristics, residuals generated in the vicinity of a portion where strain is introduced into the unidirectional electromagnetic steel sheet by laser beam irradiation or the like. For a two-dimensional distribution of a stress in a cross section perpendicular to the plate width direction, a method of evaluating a value obtained by integrating a compressive residual stress in an area where the compressive residual stress exists is disclosed as an index. However, in Patent Documents 3 and 4, the value obtained by dividing the compressive residual stress by the area of action in the region of action, that is, the total compressive force, is used as an index, and the details will be shown in Examples described later. It is difficult to use as a comparison. The value of the generated compressive stress cannot be directly compared in absolute value between electrical steel sheets having different strength levels. Further, as clearly shown in FIG. This is because there is an index value or range within which the iron loss is minimized, and it is easily inferred that the appropriate range varies from material to material.

  As described above, the conventional method does not accurately evaluate strain and stress due to punching and the like, and in order to perform electromagnetic field analysis in consideration of the influence of such, a large amount of magnetization characteristic data is required. This is very complicated and difficult to apply to a practical punching shape.

  The present invention is limited to non-oriented electrical steel sheets among the electrical steel sheets, and overcomes the above-mentioned problems. Iron loss characteristics by punching (iron loss increase by punching, iron loss after punching) Provides a method for evaluating a non-oriented electrical steel sheet capable of accurately and easily evaluating and selecting a (small) non-oriented electrical steel sheet with good) and a method for producing a non-oriented electrical steel sheet using the evaluation method. It is for the purpose.

  In order to solve the above problems, the present invention has the following features.

  [1] A method for evaluating an increase in iron loss generated after processing a non-oriented electrical steel sheet using a predetermined index, and evaluating the quality of the iron loss characteristics of the non-oriented electrical steel sheet based on the evaluation result. The evaluation method for a non-oriented electrical steel sheet, wherein the index is one or both of an equivalent plastic strain distribution and a residual stress distribution whose value is determined from a numerical analysis result of processing.

[2] For the equivalent plastic strain ε _eq distribution, the index is the index Iε = ∫ε _eq dA obtained by integrating the region in the region where the equivalent plastic strain is generated, and the cut end face is related to the stress component σ in the magnetized direction. The index Iσ = ∫ (σ / σ _Y ) ds (where σ _Y is the relevant value) obtained by performing line integration in the region where the compressive stress is generated along an arbitrary line moving from the cutting end surface within the evaluation cross section. The method for evaluating a non-oriented electrical steel sheet according to [1] above, wherein the yield stress is a non-oriented electrical steel sheet.

  [3] The index Iσ is used as an evaluation index of the iron loss increase amount at the commercial frequency of the current, and the index Iε is used as an evaluation index of the iron loss increase amount in the high frequency band of the current [1] Or the evaluation method of the non-oriented electrical steel sheet according to [2].

  [4] None provided with an evaluation step of evaluating that the iron loss characteristic is good using the method for evaluating a non-oriented electrical steel sheet according to any one of [1] to [3]. A method for producing grain-oriented electrical steel sheets.

  In the present invention, a non-oriented electrical steel sheet having a good (small) non-oriented electrical steel sheet with good (small) iron loss characteristics due to processing (the amount of iron loss increased by processing and / or the amount of iron loss after processing) can be evaluated and selected easily and accurately Can do.

  That is, according to the present invention, the amount of increase in iron loss due to machining can be easily evaluated by numerical analysis. Therefore, for example, when the tensile test characteristics of a newly developed non-oriented electrical steel sheet are known, numerical analysis of processing can be performed, and the amount of iron loss deterioration can be predicted by the present invention. You can also grasp the superiority and inferiority. In addition, as the suitability of the non-oriented electrical steel sheet, it is possible to evaluate the frequency band of the applied part or product. In addition, it is possible to evaluate these before collecting data on the degree of influence on the stress and strain of the magnetization characteristics that require much man-hours.

  By utilizing the present invention, it becomes easy and accurate to narrow down suitable materials in selecting non-oriented electrical steel sheets when developing parts and products, and as a result, man-hours and development time can be reduced. On the other hand, in the development of materials for non-oriented electrical steel sheets, it can be used for evaluation as a simple evaluation index for newly developed materials, which also has the effect of increasing the efficiency of material development.

It is a schematic diagram of a punching end face shape. It is a cross-sectional schematic diagram of the uneven | corrugated | grooved part for round crimping. It is an example of an optical microscope photograph of a round caulking section. It is explanatory drawing of the processing influence investigation sample by a narrow strip. It is a measurement result of iron loss increase amount ΔW _15/50 . It is a measurement result of iron loss increase amount ΔW _10/400 . It is a figure which shows an example of the equivalent plastic strain distribution by a punching analysis result. It is a figure which shows an example of magnetization direction stress (sigma) _z (paper surface direction direction stress) distribution by a punching analysis result. It is a figure which shows the correlation with iron loss increase amount (DELTA) _{W15 / 50} and the line integral value (index _| index 8) of a compressive stress. It is a figure which shows the correlation with iron loss increase amount ( _{DELTA) W10 / 400} and the area integral (index _| index 3) of an equivalent plastic strain. It is a figure which shows the prediction precision of the iron loss increase amount (DELTA) _{W15 / 50} by the parameter _| index 1. FIG. It is a figure which shows the prediction precision of the iron loss increase amount ( _{DELTA) W 10/400 by} the _{parameter |} index 1. FIG. It is a figure which shows the prediction precision of the iron loss increase amount (DELTA) _{W15 / 50} by the parameter _| index 2. FIG. It is a figure which shows the prediction precision of the iron loss increase amount ( _{DELTA) W 10/400 by} the _{parameter |} index 2. FIG. It is a figure which shows the prediction precision of the iron loss increase amount (DELTA) _{W15 / 50} by the parameter _| index 3. FIG. It is a figure which shows the prediction precision of the iron loss increase amount ( _{DELTA) W 10/400 by} the _{parameter |} index 3. FIG. It is a figure which shows the prediction precision of the iron loss increase amount (DELTA) _{W15 / 50} by the parameter _| index 4. FIG. It is a figure which shows the prediction precision of the iron loss increase amount ( _{DELTA) W 10/400 by} the _{parameter |} index 4. FIG. It is a figure which shows the prediction precision of the iron loss increase amount (DELTA) _{W15 / 50} by the parameter _| index 5. FIG. It is a figure which shows the prediction precision of the iron loss increase amount ( _{DELTA) W 10/400 by} the _{parameter |} index 5. FIG. It is a figure which shows the prediction precision of the iron loss increase amount (DELTA) _{W15 / 50} by the parameter _| index 6. FIG. It is a figure which shows the prediction precision of the iron loss increase amount ( _{DELTA) W 10/400 by} the _{parameter |} index 6. FIG. It is a figure which shows the prediction precision of the iron loss increase amount (DELTA) _{W15 / 50} by the parameter _| index 7. FIG. It is a figure which shows the prediction precision of the iron loss increase amount ( _{DELTA) W 10/400 by} the _{parameter |} index 7. FIG. It is a figure which shows the prediction precision of the iron loss increase amount (DELTA) _{W15 / 50} by the parameter _| index 8. FIG. It is a figure which shows the prediction precision of the iron loss increase amount ( _{DELTA) W 10/400 by} the _{parameter |} index 8. FIG. It is the figure which performed the material comparison by evaluation parameter | Iσ |. It is the figure which performed the material comparison by evaluation parameter | index Iepsilon / t.

  The present invention newly finds an index that can easily predict the amount of increase in iron loss that occurs when a non-oriented electrical steel sheet is processed, and evaluates the superiority or inferiority of the iron loss characteristics of the non-oriented electrical steel sheet using the evaluation index. Is. That is, by processing, the equivalent plastic strain distribution and residual stress distribution generated with a non-uniform distribution in the thickness direction in the vicinity of the cutting end surface, which is the cutting surface, are calculated based on the numerical analysis of the processing, and the value is determined from the calculation result An index is used to evaluate the superiority or inferiority of iron loss characteristics of a non-oriented electrical steel sheet without performing electromagnetic field analysis.

  Here, a case where punching is applied as the processing means will be described as an example.

In the case of punching, first, a cross section perpendicular to the steel sheet surface for evaluating the equivalent plastic strain distribution and residual stress distribution is determined from the numerical analysis result of the punching. This section is hereinafter also referred to as “evaluation section”, and is a section perpendicular to the cut end surface and perpendicular to the steel plate surface. Here, as an evaluation index, with respect to the equivalent plastic strain ε _eq distribution, the index Iε = ε _eq dA integrated in the region where the equivalent plastic strain occurs, and / or the stress component σ in the magnetization direction The index Iσ = ∫ (σ), which is a line integral in a region where compressive stress is generated along an arbitrary line that moves away from the punching end surface within the evaluation cross section, starting from the punching end surface (cut end surface in the case of punching) / Σ _Y ) ds (where σ _Y is the yield stress of the non-oriented electrical steel sheet).

  In the above integration, A of dA is an area, and s of ds is a length. The frequency described below is the frequency of the excitation current.

As shown in the examples described later, the index Iε = ∫ε _eq dA is the iron loss increase ΔW _10/400 in the high frequency band (here, the iron loss increase at a magnetic flux density of 1.0 T and a frequency of 400 Hz). The index Iσ = ∫ (σ / σ _Y ) ds is the iron loss increase ΔW _15/50 in the commercial frequency band (here, the iron loss increase at a magnetic flux density of 1.5 T and a frequency of 50 Hz) It was found that the correlation was very high and the magnitude relationship was also consistent. Therefore, it is possible to evaluate superiority or inferiority in consideration of an increase in iron loss due to punching by using these indices alone or the sum of the amount of iron loss before punching and the amount of increase in iron loss due to punching.

Here, regarding the increase in iron loss in a high frequency band (here, 400 Hz), from the viewpoint of the skin effect, the strain having a characteristic distribution form in the surface layer portion of the material (here, equivalent plastic strain ε _eq ) Regarding the increase in iron loss at a commercial frequency (here, 50 Hz), the stress (here, the direction in which it is magnetized) has a characteristic distribution form even in the entire material cross section near the punched end face and near the center of the plate thickness. It was found that there is a high correlation with the compressive stress σ). Although the details will be described later with reference to FIG. 7, the equivalent plastic strain ε _eq is generated up to a deep position away from the punched end face in the surface layer portion of the material. Although details will be described later with reference to FIG. 8, the compressive stress σ acts to a position far from the punched end face in the approximate center of the plate thickness. Regarding the compressive stress σ, by using a value normalized by the yield stress σ _Y of each material, the steel sheets having different material strengths can be compared with each other. This is because the residual stress after plastic working usually has a higher absolute value for a material having a higher value depending on the material strength, particularly the yield stress σ _Y , unless special stress relaxation treatment is applied. Based on what remains.

  Regarding stress in the magnetized direction (especially compressive stress) and plastic strain, it causes a decrease in permeability and is closely related to an increase in iron loss. Keep it.

By the way, as described above, regarding evaluation with only two frequencies of the commercial frequency of 50 Hz and the relatively high frequency of 400 Hz, it is desirable to find an index that covers other frequency bands, but as described above, The amount of increase in iron loss at a certain frequency is correlated with the compressive stress σ having a characteristic near the center of the sheet thickness of the material and the equivalent plastic strain ε _eq having a characteristic near the surface layer of the material. A representative frequency is selected as the influence range of the above.

  Depending on the application environment of the parts and products, either the iron loss increase in the commercial frequency band or the iron loss increase in the high frequency band may be excellent, or both are excellent. In some cases, the index to be used may be determined according to each case.

  The absolute value | Iσ | of the index Iσ is 0.05 mm or less (| Iσ | ≦ 0.05 mm), and / or the value Iε / t obtained by dividing the index Iε by the thickness t for generalization is 0. If it is 033 mm or less (Iε / t ≦ 0.033 mm), the iron loss characteristic of the non-oriented electrical steel sheet may be evaluated as good.

  And as a manufacturing method of the non-oriented electrical steel sheet using said evaluation method, it is desirable to perform feedback as described below.

  That is, first, from a non-oriented electrical steel sheet manufactured by a predetermined method, a test piece for magnetic property evaluation illustrated in FIG. 4A (usually, the long side of the test piece is in the rolling direction and the sheet width direction). Are used to evaluate the magnetic characteristics, and the iron loss amount as the electromagnetic steel sheet is obtained. Usually, this process is frequently performed for each manufactured coil in order to guarantee the product quality of the electrical steel sheet. In addition, a tensile test that is not necessarily performed in general non-oriented electrical steel sheets is performed. For example, a tensile test piece such as JIS No. 5 (a magnetic steel sheet material from which the magnetic property evaluation test piece is cut out can be diverted, and the width direction of the plate is often used as the tensile direction) is cut out, and the tensile test is performed. Obtain mechanical properties and stress-strain curves of materials.

  Next, using the obtained stress-strain curve data, the analysis shown in the present invention is performed, and the evaluation indexes Iε and Iσ are obtained to predict the increase in iron loss due to punching.

  The present invention is characterized in that the evaluation judgment is made based on the total iron loss amount obtained by adding the iron loss increase amount obtained by the punching process or the iron loss amount before the punching process and the iron loss increase amount after the punching process. .

  In the evaluation judgment, the product specifications exchanged with the customer and the threshold value based on the accumulated evaluation results of the same standard products as the electrical steel sheet are set as predetermined criteria, and the amount of iron loss increased by punching or punching When the iron loss increase amount or the total iron loss amount is larger than the predetermined standard as compared with the total iron loss amount before and after the punching process, feedback is made to the manufacturing process. The feedback includes, for example, a method of adjusting the amount of the component to be added, optimizing the manufacturing conditions of the electrical steel sheet, for example, adjusting the conditions of the annealing temperature.

  The difference from the conventional manufacturing method is not only the evaluation of the iron loss amount of the electromagnetic steel sheet itself, but also the step of calculating the iron loss increase amount by punching and judging based on the iron loss increase amount. In the process, a criterion that uses an increase in iron loss due to punching is used.

  As a result, it is possible to suppress and control the amount of increase in iron loss due to machining, which has not been considered in the past, within a predetermined range. Also, if it is found that the iron loss has increased after the customer has processed the material or assembled it into a product such as a motor, the cause is a problem with the electromagnetic steel sheet itself or a defect in processing / manufacturing It can also be used as an effective means for investigating.

  Other than the manufacturing method itself, shipments such as comparing with the customer requirement level based on the evaluated increase in iron loss or total iron loss before and after punching, and changing the delivery destination as necessary It can also be used for destination determination.

  In the above description, the case where the punching process is applied has been described as an example, but the processing means is not limited to the punching process. As an example other than the punching process, there is a process by laser cutting, for example. Laser cutting generates plastic strain and residual stress in the magnetic steel sheet, which increases the amount of iron loss. However, the magnitude and distribution of the plastic strain and residual stress of the electromagnetic steel sheet by laser cutting are different from those in the case of punching. Therefore, the evaluation index may be appropriately selected according to the applied processing means. Although not illustrated, in the case of laser cutting, it is confirmed that the index 8 (Iσ) is appropriate among the indices shown in Table 1 described later. Also, the actual increase in iron loss is a problem in the case of mechanical cutting such as punching that increases the iron loss increase.

  This example illustrates the invention in more detail.

  In this embodiment, first, the amount of increase in iron loss due to punching of the non-oriented electrical steel sheet is actually measured, and then, based on the numerical analysis result of the punching process, the non-oriented electrical steel sheet is determined by eight index candidates. The amount of increase in iron loss due to punching was predicted and compared with actual measurements. Based on the comparative study, appropriate indicators were determined.

  First, the results of actual measurement and evaluation of the iron loss increase due to punching will be described.

  FIG. 4 is a diagram for explaining a method of actually measuring and evaluating the iron loss increase amount by punching. As shown to Fig.4 (a), the iron loss amount in the test piece of 30 mm width of a non-oriented electrical steel sheet is measured. Next, as shown in FIG.4 (b), this 30 mm width test piece is shear-punched, the three 10 mm width test pieces are produced, they are arranged side by side, and an iron loss amount is measured. And the increment (W2-W1) of the iron loss amount W2 in the three 10 mm width test pieces with respect to the iron loss amount W1 in the 30 mm width test piece is defined here as an iron loss increase amount ΔW due to punching.

  The test materials used were four types of non-oriented electrical steel sheets, A material, B material, C material, and D material, and the shear punching conditions were performed on a steel plate having a plate thickness of 0.35 mm with a clearance of 10 μm. The iron loss amount was measured under two conditions of 1.5T and 50 Hz and 1.0T and 400 Hz.

FIG. 5 shows the iron loss increase ΔW _15/50 at 1.5 T and 50 Hz, and FIG. 6 shows the iron loss increase ΔW _10/400 at 1.0 T and 400 Hz.

  From FIG. 5 and FIG. 6, it can be said that the A material has a large iron loss increase regardless of the frequency, and the D material has a small iron loss increase regardless of the frequency. Moreover, about B material, it turns out that the iron loss increase amount in high frequency 400Hz is small.

  Next, based on the numerical analysis result of the punching process, the amount of increase in iron loss due to the punching process is predicted and evaluated, and the result of comparison with the above actual measurement value is described.

  The details of the numerical analysis of the punching process are shown in detail in Non-Patent Document 2 described above as an example. Here, the basic conditions will be described mainly with respect to points different from Non-Patent Document 2. Was modeled as a two-dimensional plane distortion problem for punching of a non-oriented electrical steel sheet into a single plate having a thickness of 0.35 mm and a width of 30 mm. For numerical calculation, LS-DYNA which is elastoplastic deformation analysis software was used. As a physical property value of the material, a stress-strain relationship by a tensile test was used as input data. As an index (discriminant) of material breakage, the following (1) Cockcroft equation was used.

Note that the breakage threshold value C ₁ has a tensile total elongation of the test results basic to the values identified based on, as the tuning, who adjusted to match the experimental results punching, working to high accuracy of the analysis It was.

FIG. 7 is a diagram showing the shape after punching and the distribution of the equivalent plastic strain ε _eq from the numerical analysis result of punching. From FIG. 7, it can be seen that plastic strain is present in the upper and lower surfaces of the steel plate from the punched end surface (left end) to a relatively deep location. In FIG. 7, the direction in which the steel plate is magnetized is the direction perpendicular to the paper surface.

Similarly, in FIG. 8, the distribution of stress (negative value) on the compression side is particularly emphasized with respect to the stress σ _z in the direction in which the steel sheet is magnetized (here, the direction perpendicular to the paper surface) from the numerical analysis result of the punching process. It is the figure displayed as follows. The stress on the compression side of σ _z (compression stress) is high not only on the surface that strongly hits the die during punching (the lower surface side in FIG. 8), but also at the center of the plate thickness, especially at the center of the plate thickness, It can be seen that the compressive stress is generated at a position relatively far from the (left end).

Then, the eight indexes shown in Table 1 are prepared as index candidates based on the numerical analysis results, and the iron loss increase amounts ΔW _15/50 and ΔW _10/400 are predicted using the respective indexes, and the above-described actual measurement is performed. Comparison was made with the values.

FIG. 9 shows a value obtained by linearly integrating a value obtained by dividing the compressive stress σ _z by the yield stress σ _Y of the material, which has the highest correlation with the iron loss increase ΔW _15/50 (∫ (σ _z / σ _Y ) ds: The prediction result of iron loss increase amount ΔW _15/50 by index 8) is shown. 9 (a) is the same as FIG. 8 described above, FIG. 9 (b) measured values of the predicted values of the foregoing iron loss increase amount [Delta] W _15/50 core loss increase amount [Delta] W _15/50 by indicator 8 It is the figure compared with (FIG. 5).

  In FIG. 9B, the predicted value (vertical axis) is graphed by scaling the predicted value so that the predicted value of the A material matches the measured value (horizontal axis). The same applies to FIGS. 9 to 26 described below.

In FIG. 9B, the magnitude relationship in the actual measurement value (horizontal axis) matches the magnitude relationship in the predicted value (vertical axis) by the index 8, and the iron loss increase ΔW _15/50 of different steel types is good. It turns out that it can be predicted with accuracy.

Next, FIG. 10 shows the increase in the iron loss increase ΔW _10/400 based on the region integral value of the equivalent plastic strain ε _eq (） ε _eq dA: index 3), which had the highest correlation with the iron loss increase ΔW _10/400 . A prediction result is shown. FIG. 10A is the same as FIG. 7 described above, and FIG. 10B _shows the predicted value of the iron loss increase amount ΔW _10/400 according to the index 3 as the actual value of the iron loss increase amount ΔW _10/400 . It is the figure compared with (FIG. 6).

In FIG. 10 (b), the prediction result is that the two steel types (B material and D material) with small values are evaluated slightly higher, but the magnitude relationship of the iron loss increase amount ΔW _10/400 matches. I understand.

11 to FIG. 26, including the results of the above-described index 3 and index 8, the comparison between the predicted values of the iron loss increases ΔW _15/50 and ΔW _10/400 and the actual measured values by the eight index candidates. The comparison results (prediction accuracy) are summarized in Table 1.

Therefore, if index 8 is used for prediction of iron loss increase amount ΔW _15/50 and index 3 is used for prediction of iron loss increase amount ΔW _10/400 , the magnitude relationship between the predicted values and the actual measurement values are respectively calculated. It can be seen that the magnitude relationship matches.

From the viewpoint of the skin effect due to frequency, for the iron loss increase ΔW _10/400 when the frequency is relatively high, the equivalent plastic strain distribution that is particularly characterized by the distribution of the material surface layer is a representative index. I understand that. On the other hand, regarding the iron loss increase ΔW _15/50 at the commercial frequency, it is considered that the compression stress distribution, which is particularly characterized by the distribution in the central portion of the plate thickness, has become a representative index.

On the other hand, the index 1 is an index disclosed in Patent Document 3, but the magnitude relationship between the predicted value and the actual measurement value by the index 1 does not match, and the yield stress σ _Y of each steel type is taken into consideration as the index 2 Even so, the magnitude relationship between the measured values could not be predicted. For this reason, it turned out that it is a parameter | index unsuitable for the prediction of the iron loss increase amount by stamping.

In addition, index 4 showed a relatively good correlation with iron loss increase ΔW _15/50 and was one of the effective candidates, but it did not reach index 8 slightly in terms of prediction accuracy.

  The indices 5, 6, and 7 are also not suitable for predicting the amount of increase in iron loss due to punching because the magnitude relation in the predicted value does not sufficiently match the magnitude relation in the actual measurement value. I understood it.

  By the way, in this example, the importance of matching the magnitude relationship between the measured value of the iron loss increase and the magnitude relationship between the predicted values is emphasized. This is because of this.

  Finally, the results of the evaluation of the iron loss characteristics of the non-oriented electrical steel sheets (A material, B material, C material, D material) of the four steel types using the index 8 and the index 3 determined as appropriate indices. It is shown in FIG. 27 and FIG.

  Here, the index 8 of the iron loss increase amount in the commercial frequency band (that is, the index Iσ) indicates the absolute value, and the index 3 of the iron loss increase amount in the high frequency band (that is, the index Iε) The value divided by the plate thickness t is shown for conversion.

  Among the four steel types, D material having a small increase in iron loss regardless of frequency is found to be | Iσ | <0.05 mm and Iε / t = 0.033 mm. It can be said that it is one of the small materials.

  In addition, as described above, depending on the application environment of the part or product, there may be a case where either one of the characteristics of the iron loss increase amount in the commercial frequency band or the iron loss increase amount in the high frequency band is excellent, Since both of them need to be excellent, an index to be used may be determined according to each case.

Claims (2)

It is a method for evaluating an increase in iron loss generated after processing a non-oriented electrical steel sheet by a predetermined index, and evaluating the quality of the iron loss characteristics of the non-oriented electrical steel sheet based on the evaluation result,
The index is one of the equivalent plastic strain distribution and the residual stress distribution, the value of which is determined from the numerical analysis result of processing,
For the equivalent plastic strain εeq distribution, the index is an index Iε = ∫εeqdA obtained by region integration in a region where the equivalent plastic strain occurs, or for the residual stress distribution, the stress component σ in the magnetized direction. An index Iσ = ∫ (σ / σY) ds (Line integration is performed in a region where compressive stress is generated along an arbitrary line moving away from the cut end face within the evaluation cross section starting from the cut end face generated by processing. as here, ShigumaY is the yield stress of the non-oriented electrical steel sheets),
Evaluation of a non-oriented electrical steel sheet , wherein the index Iσ is used as an evaluation index for an increase in iron loss at a commercial frequency of current, and the index Iε is used as an evaluation index for an increase in iron loss at a high frequency band of current. Method. The manufacturing method of the non-oriented electrical steel sheet characterized by using the evaluation method of the non-oriented electrical steel plate of Claim 1 and evaluating an iron loss characteristic as favorable.

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