Method for manufacturing, rotary electric machine, and electrical steel

Abstract

To provide a proper stress state to an aluminum diffusion layer in which Al of an electrical steel is diffused.SOLUTION: There is disclosed a rotary electric machine: including an iron core formed by laminating an electric steel on one another; and a supporting member for supporting the iron core, the electrical steel including an aluminum diffusion layer and the supporting member being arranged so that an in-plane tensile stress is introduced in the aluminum diffusion layer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a manufacturing method, a rotating electric machine, and an electromagnetic steel sheet. [Background technology]

[0002] A technique is known in which a plating layer is formed on the surface of an electrical steel sheet by an aluminizing process (hot-dip aluminum plating process), and then a diffusion process is performed in a non-oxidizing atmosphere to create a state in which the Al concentration is gradient from the surface, thereby reducing loss in the electrical steel sheet (see, for example, Patent Documents 1 and 2).

[0003] In addition, a technique is known in which an Al-containing slurry is applied to the surface of an electrical steel sheet, followed by a diffusion treatment in a non-oxidizing atmosphere to create a gradient in the Al concentration from the surface, thereby reducing loss in the electrical steel sheet (see, for example, Patent Document 3).

[0004] Also, a technology is known in which a plating layer is formed on the surface of an electrical steel sheet by an aluminizing process, and then Al is penetrated by a long-term diffusion process at high temperature in an oxidizing atmosphere to realize a grain-oriented electrical steel sheet with an increased Al concentration, thereby reducing loss in the electrical steel sheet (see, for example, Patent Document 4). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] German Patent No. 102005004037 [Patent Document 2] European Patent Application Publication No. 1260598 [Patent Document 3] International Publication No. 2021 / 155280 Brochure [Patent Document 4] Special Publication No. 2018-509522 Summary of the Invention [Problem to be solved by the invention]

[0006] None of the above documents suggests that the stress state of an aluminum diffusion layer in which Al is diffused in an electrical steel sheet can affect characteristics such as core loss.

[0007] Therefore, in one aspect, an object of the present disclosure is to impart an appropriate stress state to an aluminum diffusion layer in which Al is diffused in an electrical steel sheet. [Means for solving the problem]

[0008] According to one aspect, the present invention relates to a magnetron having an iron core formed by laminating electromagnetic steel sheets; a support member for supporting the iron core, The electrical steel sheet includes an aluminum diffusion layer, The support member is disposed so as to introduce an in-plane tensile stress into the aluminum diffusion layer, thereby providing a rotating electric machine. Effect of the Invention

[0009] According to one aspect, the present disclosure makes it possible to impart an appropriate stress state to an aluminum diffusion layer in which Al is diffused in an electrical steel sheet. [Brief description of the drawings]

[0010] [Figure 1] 1 is a flowchart illustrating a flow of each process included in a manufacturing method according to the present embodiment. [Diagram 2] FIG. 2 is a diagram showing a cross-sectional structure of a steel material obtained by an aluminizing treatment. [Diagram 3] FIG. 2 is a diagram showing a cross-sectional structure of a steel material obtained by a diffusion treatment. [Figure 4] FIG. 2 is a plan view showing a schematic diagram of a steel material punched into a shape for a rotor core. [Diagram 5] FIG. 2 is a schematic diagram showing an example of a stress state of a part of a steel material. [Figure 6] FIG. 1 is an explanatory diagram of a method for calculating an Al penetration amount (part 1). [Figure 7]FIG. 13 is an explanatory diagram of a method for calculating the amount of Al penetration (part 2). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Each embodiment will be described in detail below with reference to the accompanying drawings. Note that the dimensional ratios in the drawings are merely examples and are not limited thereto, and shapes in the drawings may be partially exaggerated for convenience of explanation. In the following description, various substances may be specified by commonly known abbreviations or chemical symbols, such as aluminum being referred to as aluminum (or Al). In addition, hereinafter, when a phenomenon occurs in which the interatomic distance widens, it is expressed that tensile stress occurs in the direction of the widening.

[0012] Fig. 1 is a flow chart generally showing the flow of each step included in the manufacturing method according to the present embodiment. Fig. 2 is a diagram generally showing the cross-sectional structure of a steel material obtained by aluminizing treatment (steel material after aluminizing treatment).

[0013] The manufacturing method of this embodiment first includes a step (step S100) of preparing a steel material (base material) having a desired plate thickness. The steel material having the desired plate thickness can be obtained, for example, by rolling a material (for example, in the form of a steel slab or steel billet) obtained by casting or the like.

[0014] The desired thickness of the steel material is arbitrary, but may be, for example, 0.20 mm to 0.35 mm, and more preferably, 0.25 mm to 0.30 mm.

[0015] In this embodiment, the steel material is for an electromagnetic steel sheet, and preferably contains Si and Al. This is because adding Si and Al to the steel material reduces the crystal magnetic anisotropy and reduces the hysteresis loss. In addition, the addition of Si and Al increases the electrical resistance of the steel material, and therefore contributes to reducing the eddy current loss. Therefore, the addition of Si and Al leads to a reduction in the iron loss (hysteresis loss and eddy current loss) of the steel material. On the other hand, the excessive addition of Si and Al not only reduces the magnetic flux density, but also reduces the workability in the manufacturing process of the steel material (rolling, pressing, etc.). Note that the final product, for example, an electromagnetic steel sheet, can be pressed into a desired shape to form a rotor core, a stator core, etc. of a rotating electric machine. In consideration of such a contradictory matter, the steel material (base material) preferably contains Si in a range of more than 0.00 mass% and not more than 7.00 mass%, and Al in a range of more than 0.00 mass% and not more than 2.00 mass%.

[0016] Next, the manufacturing method of this embodiment includes an aluminum-containing layer forming step (step S102) of forming an aluminum-containing layer (see reference numeral 20 in FIG. 2) on the steel material. The aluminum-containing layer 20 can be formed, for example, by an aluminizing process. For example, the aluminum-containing layer is in the form of a plating layer having a thickness in the range of 2 μm or more and 30 μm or less. For example, a plating layer having a thickness in the range of 2 μm or more and 30 μm or less may be formed by gas wiping or the like.

[0017] In a modified example, the aluminum-containing layer may be formed by applying an aluminum-containing slurry instead of the aluminizing treatment, but the application of the aluminum-containing slurry has the disadvantage that it is difficult to cause Al to penetrate into the steel sheet in the subsequent diffusion treatment.

[0018] The aluminum-containing layer (plating layer) may be composed of only aluminum, for example, in the case of an aluminum-containing layer formed by sputtering or the like. Alternatively, the aluminum-containing layer (plating layer) may contain at least one of iron (Fe), silicon (Si), and manganese (Mn) in addition to aluminum. Preferably, the aluminum-containing layer (plating layer) contains Al, Fe, and Si. For example, the plating layer may contain Al in a range of 20% by mass or more and 100% by mass or less, Fe in a range of 0.00% by mass or more and 80% by mass or less, and Si in a range of 0.00% by mass or more and 15% by mass or less. The plating layer may be a single layer or a multilayer.

[0019] Next, the manufacturing method of this embodiment includes a diffusion treatment step (step S104) in which a diffusion treatment is performed on the steel material on which the aluminum-containing layer has been formed.

[0020] The diffusion treatment is a treatment for forming a state in which the Al concentration is gradient from the steel material surface based on the Al contained in the aluminum-containing layer. That is, the diffusion treatment forms an Al diffusion layer (see reference numeral 32 in FIG. 3 ) by diffusing the Al contained in the aluminum-containing layer from the steel material surface in the thickness direction. The Al diffusion layer may have a gradient (change gradient) of the Al concentration in a mode in which the Al concentration is higher toward the surface side in the thickness direction.

[0021] The diffusion process may be carried out under predefined temperature conditions for a predefined processing time (hereinafter also referred to as the "diffusion time").

[0022] The desired aluminum diffusion pattern is basically arbitrary as long as the Al diffusion layer has a gradient (change gradient) of the Al concentration.

[0023] The Al diffusion layer has an Al concentration gradient (change gradient) in which the Al concentration is higher toward the surface side in the thickness direction. Specifically, the Al concentration is highest at the surface of the Al diffusion layer and gradually decreases toward the center of the sheet thickness. In a modified example, the Al concentration may be approximately constant in the Al diffusion layer.

[0024] Next, the manufacturing method of this embodiment includes a tensile stress generating step (step S106) for introducing an in-plane tensile stress into the Al diffusion layer.

[0025] FIG. 4 is a plan view showing a steel material punched into a shape for a rotor core. Here, as an example, a steel material 70 punched into a shape for a rotor core will be described. Note that the steel material 70 has magnet holes 72, but the shape and arrangement of the magnet holes 72 are arbitrary, and the magnet holes 72 themselves may be omitted. FIG. 5 is a schematic diagram showing an example of a stress state of a part Q4 of the steel material 70. FIG. 5 shows a schematic example of a stress state occurring in a region within the range of radius r+dr and angle dθ.

[0026] The tensile stress is desirably generated along the direction in which the magnetic flux is formed, and may be generated in substantially all directions in any part Q4 of the steel material 70, as shown in FIG.

[0027] The method of generating the tensile stress is arbitrary, and for example, the tensile stress may be generated by an insulating film that may be formed on the Al diffusion layer, or may be generated by a support member (e.g., a nut or an end plate) in an assembled state as a rotating electric machine. In this case, the manufacturing method of the rotating electric machine includes a step of supporting the laminated core by the support member in a manner that generates the tensile stress. In this case, the laminated core is formed by laminating the steel material having the above-mentioned Al diffusion layer. The laminated core forms a rotor core, a stator core, or the like.

[0028] In this way, according to the manufacturing method of this embodiment, it is possible to generate tensile stress in an electrical steel sheet having an Al diffusion layer in which Al is diffused with a gradient (change gradient) of Al concentration. The effect of generating tensile stress will be described in detail with reference to the following examples. EXAMPLES

[0029] Next, some examples of steel materials actually processed by the inventors of the present invention using the manufacturing method according to this embodiment will be described.

[0030] The inventors of the present application prepared one type of steel material (represented as steel type C) having the component properties shown in Table 1 below, and performed processing based on the manufacturing method of this embodiment, resulting in the results shown in Table 2. Specifically, in Example 1 etc., a single sheet (rectangular shape with dimensions of 20×50 mm) test piece was cut out by laser from a steel plate having the chemical components shown in Table 1, and the test piece was subjected to an aluminizing treatment, resulting in the plating thickness shown in Table 2. Next, after the aluminizing treatment, a diffusion treatment was performed under the conditions shown in Table 2. Note that in Comparative Examples 6 to 8, the aluminizing treatment and the diffusion treatment were not performed.

[0031] In addition, all steel materials of steel type C contain 0 to 7.00 mass% Si, 0 to 1.00 mass% Mn, and 0 to 2.00 mass% Al. A base material with such a composition is preferable, but is not limited to this. In Table 2, mass% represents mass%.

[0032] [Table 1]

[0033] [Table 2]

[0034] [Table 3]

[0035] [Table 4]

[0036] [Table 5]

[0037] As a result, the results in Tables 3, 4, and 5 were obtained. Evaluation 1 in Tables 3 and 4 was evaluated by FE (Field Emission)-EPMA (Electron Probe Micro Analyzer) analysis. In Table 3, the symbol "" means "same as above." In this test, the type of coating and the coating temperature (coating) were the same in each of the examples and comparative examples in that they were oxides mainly made of aluminum and were equal to the temperature during the diffusion treatment. The iron loss in Evaluation 2 in Table 5 was the result of AC magnetic measurement, and the magnetic flux density in Evaluation 2 was the result of measurement using the initial magnetization curve of AC (50 Hz). The diffusion depth sheet thickness ratio is the value obtained by dividing the diffusion depth by the sheet thickness. In Table 5, the magnetic flux density represents the magnetic flux density (B50) at a magnetizing force of 5000 A / m, and the iron loss represents the iron loss (W10 / 400) at a frequency of 400 Hz and a magnetic flux density of 1.0 T. In addition, in Table 5, the iron loss reduction rate is a rate obtained by dividing the amount of reduction in iron loss from that of an untreated product by the iron loss of the untreated product.

[0038] In Table 4, the Al penetration amount / sheet thickness ratio is a value obtained by dividing the amount of aluminum penetration in the Al diffusion layer (hereinafter also referred to as "Al penetration amount") by the base material thickness when the amount of Al penetration is calculated based on the aluminum diffusion depth and the aluminum concentration at the center of the base material thickness (hereinafter also referred to as "center Al concentration"). Specifically, in this test, the amount of Al penetration was calculated as follows based on the aluminum diffusion depth, the surface Al concentration, and the center Al concentration. When the aluminum diffusion depth is less than the base plate thickness / 2, the amount of aluminum penetration = (surface aluminum concentration - center aluminum concentration) x aluminum diffusion depth x 1 / 2 In this case, the amount of Al penetration corresponds to the area S11 of the triangle indicated by the dashed line in Fig. 6. In this case, the three vertices of the triangle correspond to a position on the base material surface corresponding to the surface Al concentration, a position on the base material surface corresponding to the central Al concentration, and a position inward from the base material surface by the aluminum diffusion depth corresponding to the central Al concentration, as shown in Fig. 6. When the aluminum diffusion depth is greater than or equal to the thickness of the base material / 2, the amount of aluminum penetration is calculated as follows: (surface aluminum concentration + center aluminum concentration - base material aluminum concentration x 2) x aluminum diffusion depth x 1 / 2 In this case, the amount of Al penetration corresponds to the area S12 of a trapezoid indicated by a dashed line in Fig. 7. In this case, the four vertices of the trapezoid correspond to a position on the base material surface and corresponding to the surface Al concentration, a position on the base material surface and corresponding to the base material Al concentration, a position inward from the base material surface by the aluminum diffusion depth and corresponding to the central Al concentration, and a position inward from the base material surface by the aluminum diffusion depth and corresponding to the base material Al concentration, as shown in Fig. 7. The case where the aluminum diffusion depth is greater than or equal to the base material thickness / 2 corresponds to the case where the diffusion depth thickness ratio is 0.50 or greater in Table 3. The Al concentration in the base material corresponds to the base material composition in Table 2 (see also D0 in Figure 7). The base material thickness corresponds to the plate thickness in Table 2, and is the plate thickness excluding the coating thickness from the total thickness.

[0039] 6 and 7 show the Al concentration profile when an oxide layer is formed on the Al diffusion layer. In these figures, α1 represents the Al concentration in the insulating coating (oxide layer), and α2 represents the Al concentration on the surface of the Al diffusion layer.

[0040] The Al gradient thickness ratio is the gradient of the aluminum concentration change with respect to the change in the thickness direction in the Al diffusion layer. The Al gradient thickness ratio is the value obtained by dividing the Al gradient by the base material thickness. Specifically, in this test, the Al gradient was calculated as follows: Al gradient = (surface Al concentration - center Al concentration) / aluminum diffusion depth The thickness of the base material corresponds to the thickness in Table 2 and is the total thickness excluding the thickness of the coating.

[0041] Here, still referring to Tables 2, 3, 4, and 5, the case where a load is applied using the magnetic measurement method will be described.

[0042] In Tables 2 to 5, Examples 3 and after and Comparative Example 5 and after correspond to cases where load is applied by the magnetic measurement method. Comparative Example 6 and after correspond to cases where aluminizing treatment and diffusion treatment are not performed. In other words, Comparative Example 5 and after show the characteristics of the base material itself.

[0043] In this test, the load was applied in the tensile direction in order to confirm the effect of the tensile stress described above. The parameter value corresponding to the magnitude of the applied load when the load was applied is shown in "Introduced Stress" in Table 5. That is, in this test, the magnetic measurement was performed in a state where the tensile stress was applied.

[0044] Comparing Example 3 and onwards with Comparative Example 4 and onwards, it is found that the iron loss reduction rate is significantly greater when tensile stress is applied. It is also found that when aluminizing and diffusion treatments are performed, the iron loss reduction rate is significantly greater when tensile stress is applied, compared to when they are not (Comparative Example 6 and onwards). In Example 3 and onwards, the magnetic flux density reduction rate is within 25%, and the magnetic flux density reduction rate when tensile stress is applied is also good.

[0045] Therefore, it is preferable to form a laminated core (stator core or rotor core) of a rotating electric machine in a state in which a tensile stress is applied to the steel sheet having the above-mentioned Al diffusion layer. In this regard, the method of forming the state in which a tensile stress is applied is arbitrary, but the state in which a tensile stress is applied may be realized, for example, by a supporting process in which the laminated core is pressed in the axial direction by a supporting member such as a nut.

[0046] Alternatively, when a coating is applied to a steel sheet having an Al diffusion layer in addition to or instead of an oxide layer, the coating may be formed in such a manner that tensile stress is generated.

[0047] Here, in Examples 1 and 2, it is predicted that tensile stress occurs due to the difference in thermal expansion coefficient between the coating and the Al diffusion layer. In Comparative Examples 1 and 2, the coating is thin as shown in Table 3, and such tensile stress does not occur. Due to such differences, there is a significant difference in the iron loss reduction rate between Examples 1 and 2 and Comparative Examples 1 and 2, as shown in Table 5.

[0048] In addition, even in the steel plates according to Comparative Examples 1 and 2, a new insulating film may be provided separately to generate tensile stress in the Al diffusion layer. Alternatively, as described above, tensile stress may be generated in the laminated core by a supporting member such as a nut.

[0049] Although each embodiment has been described above in detail, the present invention is not limited to the specific embodiment, and various modifications and changes are possible within the scope of the claims. In addition, it is also possible to combine all or a plurality of the components of the above-described embodiments.

[0050] For example, in the above-described embodiment, the diffusion treatment may be performed immediately after the formation of the Al-containing layer, or may be performed after the formation of the Al-containing layer and processing such as pressing. Furthermore, the formation of the Al-containing layer may be achieved by deposition, sputtering, calorizing, shot peening, foil bonding, or the like, other than aluminizing or slurry. [Explanation of symbols]

[0051] 20 ··· Aluminum-containing layer (Aluminum-containing layer), 32 ··· Al diffusion layer (Aluminum diffusion layer)

Claims

1. an iron core formed by laminating electromagnetic steel sheets; a support member for supporting the iron core, The electrical steel sheet includes an aluminum diffusion layer, The supporting member is disposed so as to introduce an in-plane tensile stress into the aluminum diffusion layer.

2. The magnetic coil has an iron core formed by laminating electromagnetic steel sheets, The electromagnetic steel sheet is A coating on a surface of a base material; an aluminum diffusion layer; The coating is formed so as to introduce an in-plane tensile stress into the aluminum diffusion layer.

3. 3. The rotating electric machine according to claim 1, wherein the aluminum diffusion layer has an aluminum concentration that gradually decreases from the surface of the base material toward the center of the base material thickness.

4. A coating on a surface of a base material; an aluminum diffusion layer in which the aluminum concentration gradually decreases from the base material surface toward the center of the base material thickness; The coating is formed so as to introduce in-plane tensile stress into the aluminum diffusion layer.

5. An electrical steel sheet having an aluminum diffusion layer with tensile stress introduced into its plane.

6. The electrical steel sheet according to claim 4 or 5, wherein the aluminum diffusion layer has an aluminum concentration that gradually decreases from the surface of the base material toward the center of the base material thickness.

7. forming an aluminum diffusion layer on a steel material for an electrical steel sheet having an aluminum-containing layer formed on a surface thereof; A manufacturing method and a step of forming an insulating coating on a surface of a base material so as to introduce tensile stress into the aluminum diffusion layer.

8. forming an aluminum diffusion layer on a steel material for an electrical steel sheet having an aluminum-containing layer formed on a surface thereof; A step of laminating the steel material to form an iron core; and supporting the iron core on a supporting member so that tensile stress is introduced into the aluminum diffusion layer.

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