Method for processing electromagnetic steel sheet, motor, and method for manufacturing motor core

Abstract

The present invention provides a laser-based processing method for an electromagnetic steel sheet with a relatively thin plate thickness that does not cause deterioration of magnetic properties. In a method for processing an electromagnetic steel sheet by melting the electromagnetic steel sheet using a laser and processing the electromagnetic steel sheet into a predetermined shape, the scanning speed of the laser is set to 10,000 mm / min or more to perform the melting.

Description

Technical Field

[0001] The present invention relates to a method for processing an electromagnetic steel sheet, for example, a method for processing an electromagnetic steel sheet to give a desired shape. Further, the present invention relates to a motor having an iron core obtained by processing an electromagnetic steel sheet and a method for manufacturing the motor iron core. Background Art

[0002] In recent years, as represented by motors used in the aerospace field, wireless vacuum cleaners, etc., the demand for miniaturization of motors has been increasing. In order to maintain the output and aim for miniaturization, such small motors are being promoted to rotate at high speeds. Due to the high-speed rotation of the motor, the excitation frequency of the motor iron core becomes high. In addition, in order to compensate for the motor torque reduced due to the miniaturization of the motor, there is also a case where the number of poles of the rotor magnet is increased. On the other hand, the excitation frequency of the iron core is increasing day by day. As a core material for such a high-speed motor, low iron loss characteristics at high frequencies are required. As an effective means, it is well known to add a large amount of resistivity-increasing elements such as Si and Al or reduce the plate thickness.

[0003] On the other hand, it is well known that the addition of such a large amount of alloy elements and the thinning make the blanking process of the motor iron core difficult. In particular, in the case of aiming for miniaturization of the motor as described above, since the motor iron core is very small, poor blanking processability of the electromagnetic steel sheet as the core material reduces the blanking yield, and there are problems such as an increase in cost. In addition, since the hardness of electromagnetic steel sheets, amorphous, etc. with a high alloy addition amount is high, the wear of the die is severe, so the maintenance cost of the die becomes high, and the problem of reduced productivity is also becoming more prominent.

[0004] Therefore, for example, in the case of processing an electromagnetic steel sheet with a thin plate thickness and a large alloy amount, if laser processing that does not have a high productivity such as blanking based on a die is applied, it becomes a situation where advantages such as low cost can be exhibited compared to blanking based on a die. Against the background of the above situation, in Patent Document 1, a method for processing an electromagnetic steel sheet is proposed in which the steel sheet is melted by laser instead of using a die for blanking.

[0005] However, it is well known that laser-based processing involves heat input to the electromagnetic steel sheet and cooling, which introduces strain into the steel sheet, resulting in deterioration of the magnetic properties of the core material. The deterioration of the magnetic properties caused by the strain introduction of this laser is larger than that in the case of blanking, and thus there is a problem with laser-based processing as a method for manufacturing a motor iron core.

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2009-5539 Summary of the Invention

[0007] The present invention has been completed in view of the above problems, and in particular, provides a laser-based processing method that does not cause deterioration of magnetic properties with respect to electromagnetic steel sheets having a thin plate thickness.

[0008] The inventors investigated the influence of laser processing conditions on the properties of the core material and its mechanism, and even the conditions of electromagnetic steel sheets with little influence on magnetic properties caused by laser processing. As a result, it was found that there is an optimal range of conditions for the scanning speed, output of the laser, and even the plate thickness of the material, and thus the present invention was completed. The main structure of the present invention is as follows.

[0009] 1. A method for processing an electromagnetic steel sheet, which melts the electromagnetic steel sheet using a laser and processes the electromagnetic steel sheet into a specified shape. In the method for processing the electromagnetic steel sheet, the scanning speed of the laser is set to 10,000 mm / min or more to perform the melting.

[0010] 2. In the method for processing an electromagnetic steel sheet according to 1 above, the thickness of the electromagnetic steel sheet is 0.20 mm or less.

[0011] 3. In the method for processing an electromagnetic steel sheet according to 1 or 2 above, the output P (W) of the laser and the scanning speed s (mm / min) with respect to the plate thickness t (mm) of the electromagnetic steel sheet satisfy the following formula (1):

[0012] 500t + 50 ≤ P / s × 12000 ≤ 2000t + 100…(1).

[0013] 4. In the method for processing an electromagnetic steel sheet according to any one of 1 to 3 above, the laser is irradiated in pulses.

[0014] 5. In the method for processing an electromagnetic steel sheet according to any one of 1 to 4 above, the electromagnetic steel sheet has a composition containing C: 0.01% or less, Si: 2.0% or more and 7.0% or less, Al: 0.001% or more and 4.0% or less, and Mn: 0.5% or less by mass%.

[0015] 6. In the method for processing an electromagnetic steel sheet according to any one of 1 to 5 above, the electromagnetic steel sheet has a Si concentration distribution in which the Si concentration in the center layer in the plate thickness direction is lower than that in the steel sheet surface layer, and the difference between the Si concentration in the center layer in the plate thickness direction and the Si concentration in the steel sheet surface layer is 0.5 mass% or more and 5 mass% or less.

[0016] 7. In the method for processing an electromagnetic steel sheet according to any one of 1 to 6 above, the average content of Si in the plate thickness direction of the electromagnetic steel sheet is 6.2 mass% or more and 6.7 mass% or less.

[0017] 8. A motor uses an iron core, and the iron core is given an iron core shape by the processing method of the electromagnetic steel sheet described in any one of the above 1 to 7.

[0018] 9. A method for manufacturing a motor iron core includes a processing step of processing a plurality of electromagnetic steel sheets into an iron core shape and a stacking step of stacking the processed electromagnetic steel sheets. In the method for manufacturing the motor iron core, the thickness of the electromagnetic steel sheet is 0.20 mm or less, and in the processing step, laser fusing is performed by setting the scanning speed of the laser to 10,000 mm / min or more.

[0019] According to the present invention, laser processing of the electromagnetic steel sheet can be achieved without deteriorating the magnetic properties after processing. Therefore, in terms of magnetic properties, it is suitable for the iron core of a small and high-speed rotation drive type motor. On the other hand, by laser processing with a higher processing qualification rate than ordinary blanking processing, an electromagnetic steel sheet with a thin wall and a large alloy content, which is difficult to machine mechanically, can be provided. And as described above, by suppressing the introduction of strain into the electromagnetic steel sheet, the deterioration of magnetic properties is small, so a motor with excellent motor characteristics can be achieved. Description of the Drawings

[0020] Figure 1 It is a cross-sectional view of a motor including a stator core for an iron core manufacturing test (Example 1).

[0021] Figure 2 It is a cross-sectional view of a motor including a stator core for an iron core manufacturing test (Example 2). Detailed Description

[0022] In the processing method of the electromagnetic steel sheet (hereinafter also simply referred to as the steel sheet) of the present invention, it is important that when the electromagnetic steel sheet is fused using a laser and processed into a specified shape, the scanning speed of the laser is set to 10,000 mm / min or more. In the present invention, the laser is scanned along the contour line of a specified shape with respect to the electromagnetic steel sheet, and fusing is thereby performed at the contour line. Hereinafter, the conditions for this fusing will be described in sequence.

[0023] [Scanning speed of laser: 10,000 mm / min or more]

[0024] In the above-mentioned fusing process, the higher the scanning speed of the laser, the less energy is input into the processing of the steel plate, thereby suppressing the introduction of strain to the processing end face and also suppressing the deterioration of magnetic properties. In addition, a high scanning speed is also advantageous from the viewpoint of productivity, thus greatly contributing to the reduction of production costs. Specifically, taking the scanning speed of the laser: 10,000 mm / min as the boundary, if it is 10,000 mm / min or more, the cutting process of the electromagnetic steel plate can be carried out before the heat from the surface generated by the laser diffuses into the steel plate surface and the influence area on magnetic properties expands. If it is less than 10,000 mm / min, the heat from the surface generated by the laser diffuses into the steel plate surface, thereby increasing the influence on magnetic properties. Therefore, it is more effective to make the scanning speed of the laser 10,000 mm / min or more. Preferably, it is 15,000 mm / min or more.

[0025] In addition, although there is no particular limitation on the upper limit of the scanning speed of the laser, the faster the laser scanning speed, the more difficult it is to ensure the accuracy of the processing shape of the electromagnetic steel plate. Therefore, it is preferably 40,000 mm / min or less.

[0026] [Thickness of steel plate: 0.20 mm or less]

[0027] When the electromagnetic steel plate is used for the iron core of a motor, from the viewpoints of miniaturization of the motor, etc., a high-frequency low iron loss characteristic is required for the iron core material. Therefore, it is preferably a plate thickness effective for reducing eddy currents, that is, 0.20 mm or less. More preferably, it is 0.15 mm or less, and further preferably, it is 0.10 mm or less. Originally, if the plate thickness of the electromagnetic steel plate exceeds 0.20 mm, the workability of blanking is not very poor, so laser processing is not required, and blanking based on a die is more advantageous in terms of production cost. On the contrary, if the plate thickness is too thin, warping occurs after laser processing, resulting in poor shape, and there is a concern about causing defective conditions in the subsequent lamination process. Therefore, it is preferably 0.05 mm or more.

[0028] [Relationship between scanning speed and output of laser]

[0029] The strain introduced into the steel plate is determined by the balance between the output of the laser and the scanning speed. Therefore, from the viewpoint of magnetic properties, there is a preferred range for the output and scanning speed of the laser. For example, even if the laser output is high, if the scanning speed is fast, the energy input into the processing of the steel plate is also suppressed, thereby reducing the influence on magnetic properties. On the other hand, if the scanning speed is fast and the laser output is small, the incident energy is insufficient, resulting in problems such as deterioration of the shape of the processing end face and inability to ensure dimensional accuracy. Therefore, it is preferable to limit the relationship between the scanning speed and output of the laser. That is, it is preferable that the scanning speed s (mm / min) and output P (W) of the laser satisfy the following formula (1) with respect to the plate thickness t (mm) of the electromagnetic steel plate:

[0030] 500t + 50 ≤ P / s × 12000 ≤ 2000t + 100 ····· (1).

[0031] This is because (P / s × 12000) in formula (1) is an index of incident energy. To reliably fuse, it is preferably made above the lower limit (500t + 50). On the other hand, to prevent deterioration of the shape of the processed end face caused by unnecessary strain introduction into the steel plate, it is preferably below the upper limit (2000t + 100). Moreover, the range of these upper and lower limits depends on the plate thickness.

[0032] [Irradiate the laser in pulses]

[0033] As a method of suppressing the strain introduced into the steel plate during laser-based processing, applying pulsed laser is effective. This is because if pulsed laser is used, the heat-affected zone can be made smaller, thereby more effectively suppressing the introduction of strain.

[0034] [Composition of the electromagnetic steel sheet]

[0035] The electromagnetic steel sheet preferably has a composition containing C: 0.01 mass% or less, Si: 2.0 mass% or more and 7.0 mass% or less, Al: 0.001 mass% or more and 4.0 mass% or less, and Mn: 0.5 mass% or less. Here, as will be described later, the electromagnetic steel sheet also includes cases where, for example, the Si concentration varies in the plate thickness direction, but even in such cases of having such a concentration distribution, it is preferably within the above content range. In addition, the balance is preferably iron and inevitable impurities. Hereinafter, the reasons for adding each component will be described.

[0036] C: 0.01 mass% or less

[0037] If C exists excessively in the steel plate, magnetic aging will occur and the magnetic properties will deteriorate. Therefore, it is preferably 0.01 mass% or less. More preferably, it is 0.001% or less. The lower the lower limit, the more preferable, so there is no particular limitation.

[0038] Si: 2.0 mass% or more and 7.0 mass% or less

[0039] Al: 0.001 mass% or more and 4.0 mass% or less

[0040] Mn: 0.5 mass% or less

[0041] The above three elements are all for increasing the resistivity of the electromagnetic steel sheet and reducing the eddy current loss, and are preferably added in amounts of Si of 2.0% by mass or more, Al of 0.001% by mass or more, and Mn of 0.005% by mass or more. Moreover, if the addition amount of Si is less than 2.0%, there will originally be no difficulty caused by the blanking process using a die, so laser processing is not required. On the other hand, if all three elements are added excessively, the saturation magnetic flux density of the electromagnetic steel sheet will decrease, so they are respectively Si: 7.0% by mass or less, Al: 4.0% by mass or less, and Mn: 0.5% by mass or less. Here, the reason why the upper limit of the addition amount of Mn is significantly lower than that of the other two elements is that if Mn is added, the thermal expansion rate of the steel sheet increases, and thus the range of introduction of strain caused by laser processing becomes larger.

[0042] [Si concentration distribution]

[0043] The electromagnetic steel sheet preferably has a Si concentration distribution in which the Si concentration in the center layer in the plate thickness direction is lower than that on the steel sheet surface layer, and the difference between the Si concentration in the center layer in the plate thickness direction and the Si concentration on the steel sheet surface layer is 0.5% by mass or more and 5% by mass or less. That is, by having a distribution in which the Si concentration in the center layer in the plate thickness direction is lower than that on the steel sheet surface layer in the plate thickness direction of the steel sheet, eddy current loss can be suppressed, which is beneficial for reducing high-frequency iron loss. This is because the loss of eddy current is concentrated on the surface layer of the plate thickness due to the skin effect, so a high resistivity in the surface layer of the plate thickness will effectively play a role in reducing eddy current. In order to exert this effect, the Si concentration difference between the surface layer and the center layer of the steel sheet needs to be 0.5% by mass or more. On the other hand, if the Si concentration difference exceeds 5% by mass, the magnetostriction difference between the surface layer and the center layer becomes larger, and thus the hysteresis loss increases. Therefore, the Si concentration difference between the steel sheet surface layer and the center layer is preferably 0.5% by mass or more and 5% by mass or less. More preferably, it is 1.5% by mass to 3.5% by mass.

[0044] Here, regarding the above Si concentration difference, when the steel sheet is divided into three parts in the plate thickness direction, the layer from the front and back surfaces to 1 / 3 of the plate thickness is defined as the surface layer, and the layer of 1 / 3 of the plate thickness including the center part in the plate thickness direction sandwiched between them is defined as the center layer. The Si concentration of each layer is defined by the average value in the thickness direction. This concentration difference can be evaluated by using EPMA (Electron Probe Micro Analysis) to analyze the Si concentration distribution of the steel sheet cross-section, or can be determined from the results of wet analysis of a sample with a plate thickness of 1 / 3 obtained by chemically polishing one or both sides of the steel sheet.

[0045] [Other]

[0046] Other laser conditions, such as the diameter of the laser, the conditions of the assist gas, etc., are not limited, as long as they are carried out under conditions where the desired end face properties, etc. can be obtained. For example, in the case of processing an electromagnetic steel sheet into an iron core, if it is processed into a fine shape such as the front end of the teeth of the iron core, a relatively thin laser diameter is sufficient, and if it is necessary to suppress oxidation of the processed end face, the assist gas can be N2 or Ar instead of O2. In addition, regarding the laser processing apparatus, as long as the specified laser conditions are achieved, any processing apparatus and laser source can also be used.

[0047] In addition, the necessity of coating an insulating film on the steel sheet is the same as that of a normal electromagnetic steel sheet, and an insulating film having sufficient insulation can also be provided in advance on one or both sides of the steel sheet. In addition, the electromagnetic steel sheet used in the processing method of the electromagnetic steel sheet of the present invention is not particularly limited as long as it is a steel sheet that satisfies the above conditions. For example, it can also be a high alloy material or a composite steel. In addition, in order to obtain a Si concentration difference in the plate thickness direction, a siliconizing treatment including a CVD (chemical vapor deposition) process can also be carried out.

[0048] [Manufacturing method of motor iron core]

[0049] The processing method of the electromagnetic steel sheet of the present invention is particularly advantageously suitable for manufacturing a motor iron core. That is, in a manufacturing method of a motor iron core having a processing step of processing a plurality of electromagnetic steel sheets into an iron core shape and a stacking step of stacking the processed electromagnetic steel sheets, in the processing step, the scanning speed of the laser is made 10,000 mm / min or more to perform fusing based on the laser, thereby enabling the provision of a motor iron core suitable for the high efficiency of the motor. In addition, the stacking of the processed steel sheets in the stacking step can be carried out by fixing the steel sheets to each other by riveting, bonding, etc., and this method is not particularly limited.

[0050] In the present invention, not only the manufacturing cost is high, but also the equipment investment cost is high, but it has the advantage that it is not necessary to perform stress relief annealing after the formation of the above iron core. For example, if annealing is performed on a material with a Si concentration gradient, Si diffuses, and thus the Si concentration difference that is better for magnetic properties is impaired. Therefore, it is advantageous not to perform stress relief annealing.

[0051] Example 1

[0052] Anisotropic electromagnetic steel sheets with a thickness of 0.20 mm having a composition containing the components shown in Table 1 and the balance being iron and unavoidable impurities were used to manufacture Figure 1 a 2-pole 3-phase brushless DC motor having the cross-sectional shape shown, and its motor efficiency was evaluated. That is, under the conditions shown in Table 2, a laser was irradiated on the anisotropic electromagnetic steel sheet to perform according to Figure 1Fusing process the stator core shown in the figure, then stack multiple processed steel sheets and fix them to each other by impregnation bonding to obtain a laminated core with a thickness of 15 mm. In addition, all motor manufacturing conditions other than the laser conditions shown in Table 2 are the same.

[0053] Here, the evaluation of the motor characteristics is uniformly carried out under the driving conditions of 80000 rpm - 20 mNm by applying a PWM (pulse width modulation) sine wave with a driving voltage of 25.2V. In Table 2, the evaluation results of the motor efficiency are summarized together with the laser conditions. As shown in Table 2, it is considered that the motor efficiency is improved under the condition that the laser scanning speed is 10000 mm / min or more. In addition, when the laser scanning speed is 10000 mm / min or more and the laser output P (W) satisfies 500t + 50 ≤ P / s × 12000 ≤ 2000t + 100 with respect to the plate thickness t (mm) of the electromagnetic steel sheet, it is considered that the motor efficiency is improved to a greater extent. On the other hand, the maximum motor efficiency is obtained under the condition that the laser output is 150W and the scanning speed is 12000 mm / min. On the other hand, under the condition that the laser output is 100W and the scanning speed is 12000 mm / min, the electromagnetic steel sheet cannot be processed, so the motor cannot be manufactured.

[0054] [Table 1]

[0055] Table 1

[0056]

[0057] [Table 2]

[0058] Table 2

[0059]

[0060] Example 2

[0061] Use a non-oriented electromagnetic steel sheet with a composition containing the components shown in Table 3 and the remaining part being iron and inevitable impurities to manufacture Figure 2 a 4-pole 6-slot brushless DC motor with the cross-sectional shape shown in the figure, and evaluate its motor efficiency. That is, under the conditions shown in Table 4, irradiate the non-oriented electromagnetic steel sheet with laser to perform fusing process according to the shape of the stator core shown in Figure 2 the figure, then stack multiple processed steel sheets and fix them to each other by impregnation bonding to obtain a laminated core with a thickness of 20 mm. In addition, all motor manufacturing conditions other than the laser conditions shown in Table 4 are the same.

[0062] Here, when evaluating the motor characteristics, PWM sine wave energization with a drive voltage of 25.2 V is carried out uniformly under the drive conditions of 105000 rpm - 25 mNm. The evaluation results of the laser conditions, material conditions, and motor efficiency are summarized in Table 4. In Table 4, "continuous" in the laser oscillation mode column indicates the continuous oscillation laser condition, and "pulse" indicates the pulse oscillation with a pulse width of 30 μsec and an emission interval of 12 μm.

[0063] As shown in Table 4, under the condition that the laser scanning speed is lower than 10000 mm / min, the motor efficiency does not exceed 85% in any material. On the other hand, under the condition that the laser scanning speed is 10000 mm / min or more, the motor efficiency is significantly improved. The amount of improvement varies significantly depending on the material, and it is clear that the amount of improvement is larger in materials with a Si concentration distribution in the plate thickness direction. In addition, by making the laser condition pulse oscillation instead of continuous oscillation, a further improvement in motor efficiency can be observed.

[0064] [Table 3]

[0065] Table 3

[0066]

[0067]

Claims

1. A processing method of an electromagnetic steel sheet, which melts the electromagnetic steel sheet using a laser and processes the electromagnetic steel sheet into a specified shape. The processing method of the electromagnetic steel sheet is characterized in that the scanning speed of the laser is 10,000 mm / min or more and 40,000 mm / min or less, the melting is performed by making the output P (W) of the laser and the scanning speed s (mm / min) satisfy the following formula (1) with respect to the sheet thickness t (mm) of the electromagnetic steel sheet, 500t + 50 ≤ P / s × 12,000 ≤ 2,000t + 100…(1).

2. The processing method of the electromagnetic steel sheet according to claim 1, characterized in that the sheet thickness of the electromagnetic steel sheet is 0.20 mm or less.

3. The processing method of the electromagnetic steel sheet according to claim 1 or 2, characterized in that the laser is irradiated in a pulsed manner.

4. The processing method of the electromagnetic steel sheet according to any one of claims 1 to 3, characterized in that the electromagnetic steel sheet has a composition containing C: 0.01% or less, Si: 2.0% or more and 7.0% or less, Al: 0.001% or more and 4.0% or less, and Mn: 0.5% or less by mass%.

5. The processing method of the electromagnetic steel sheet according to any one of claims 1 to 4, characterized in that the electromagnetic steel sheet has a Si concentration distribution in which the Si concentration in the center layer in the sheet thickness direction is lower than that in the steel sheet surface layer, and the difference between the Si concentration in the center layer in the sheet thickness direction and the Si concentration in the steel sheet surface layer is 0.5 mass% or more and 5 mass% or less.

6. The processing method of the electromagnetic steel sheet according to any one of claims 1 to 5, characterized in that the average content of Si in the sheet thickness direction of the electromagnetic steel sheet is 6.2 mass% or more and 6.7 mass% or less.

7. A motor, characterized in that a core is used, and the core is given a core shape by the processing method of the electromagnetic steel sheet according to any one of claims 1 to 6.

8. A method for manufacturing a motor core, which has a processing step of processing a plurality of electromagnetic steel sheets into a core shape and a laminating step of laminating the processed electromagnetic steel sheets, the method for manufacturing the motor core is characterized in that the sheet thickness of the electromagnetic steel sheet is 0.20 mm or less, and in the processing step, the scanning speed of the laser is 10,000 mm / min or more and 40,000 mm / min or less, the melting based on the laser is performed by making the output P (W) of the laser and the scanning speed s (mm / min) satisfy the following formula (1) with respect to the sheet thickness t (mm) of the electromagnetic steel sheet, 500t + 50 ≤ P / s × 12,000 ≤ 2,000t + 100…(1).

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