Powder core manufacturing method

Abstract

A soft magnetic powder comprising a plurality of soft magnetic particles having an insulating film, the insulating film having an insulating layer containing phosphate, silica, or magnesia, and the insulating film having a plurality of cracks on the surface thereof.

Description

[Technical Field]

[0001] The present disclosure relates to a soft magnetic powder, a mixed powder, a powder core, a stator for a motor, a motor, and a method for manufacturing the powder core. This application claims priority from Japanese Patent Application No. 2024-094683 filed on June 11, 2024, the entire contents of which are incorporated herein by reference. [Background technology]

[0002] Conventionally, powder magnetic cores have been used as magnetic cores for electric devices such as motors and reactors. Powder magnetic cores are green compacts obtained by compressing soft magnetic powder having insulating films on the surfaces of soft magnetic particles. Patent Document 1 discloses a powder magnetic core used in motors.

[0003] Patent Documents 2 and 3 disclose motor recycling methods. They describe crushing a stator consisting of a magnetic core and a coil, separating the magnetic core and the coil, and sorting them by material. The magnetic core material described in Patent Documents 2 and 3 is an electromagnetic steel sheet such as a silicon steel sheet. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 031209 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-124841 [Patent Document 3] Japanese Patent Application Laid-Open No. 2012-147608 Summary of the Invention

[0005] The soft magnetic powder of the present disclosure includes a plurality of soft magnetic particles having an insulating film, the insulating film having an insulating layer containing phosphate, silica, or magnesia, and a plurality of cracks on the surface of the insulating film. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a cross-sectional view schematically showing a soft magnetic powder according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram showing the surface of an insulating film of a soft magnetic powder according to an embodiment. [Figure 3] FIG. 3 is an explanatory diagram of the mixed powder according to the embodiment. [Figure 4] FIG. 4 is a cross-sectional view schematically showing the mixed powder according to the embodiment. [Figure 5] FIG. 5 is a schematic perspective view showing an example of a powder magnetic core according to an embodiment. [Figure 6] FIG. 6 is a schematic perspective view showing another example of a powder magnetic core according to the embodiment. [Figure 7] FIG. 7 is a schematic perspective view showing yet another example of a powder magnetic core according to the embodiment. [Figure 8] FIG. 8 is a schematic perspective view of a stator for a motor according to the embodiment. [Figure 9] FIG. 9 is a schematic cross-sectional view of the motor according to the embodiment. [Figure 10] FIG. 10 is a schematic cross-sectional view showing an example of a crusher. [Figure 11] FIG. 11 is a graph showing the particle size distribution of the new powder and recycled powder of Sample No. 7 in Test Example 1. [Figure 12] FIG. 12 is a diagram schematically illustrating the insulating film of the recycled powder of Sample No. 8 in Test Example 2. [Figure 13] FIG. 13 is a partially enlarged view of a cross section of a dust core using new powder of Sample No. 8 in Test Example 2. [Figure 14] FIG. 14 is a partially enlarged view of a cross section of a dust core using recycled powder of Sample No. 1 in Test Example 2. [Figure 15] FIG. 15 is a partially enlarged view of a cross section of a dust core using recycled powder of Sample No. 8 in Test Example 2. [Figure 16]FIG. 16 is a graph showing the frequency distribution of Vickers hardness of each of the new powder and the recycled powder of Sample No. 1 in Test Example 3. [Figure 17] FIG. 17 is a graph showing the frequency distribution of Vickers hardness of the mixed powder of recycled powder and new powder of Sample No. 1 in Test Example 3. [Figure 18] FIG. 18 is a diagram showing the Fe2p3 spectra of the new powder and the recycled powder of Sample No. 7 in Test Example 4. [Figure 19] FIG. 19 is a diagram showing the Si2p spectra of the new powder and the recycled powder of Sample No. 7 in Test Example 4. [Figure 20] FIG. 20 is a partially enlarged view of a cross section of a dust core using new powder of Sample No. 1 in Test Example 5. [Figure 21] FIG. 21 is a partially enlarged view of a cross section of a dust core using recycled powder of Sample No. 1 in Test Example 5.

[0007] [Problem to be solved by this disclosure] It would be desirable to recover powder magnetic cores from used electrical equipment and recycle them. However, recycling of powder magnetic cores has not been carried out. Traditionally, powder magnetic cores have been manufactured using new soft magnetic powder as a raw material. New soft magnetic powder emits a large amount of carbon dioxide (CO2) during its manufacture. Therefore, it would be desirable to reduce the amount of new soft magnetic powder used, thereby reducing the CO2 emissions generated during the manufacture of powder magnetic cores, including the manufacture of soft magnetic powder.

[0008] An object of the present disclosure is to provide a soft magnetic powder that can reduce CO2 emissions generated during the production of a powder magnetic core.

[0009] [Effects of this disclosure] The soft magnetic powder of the present disclosure can reduce CO2 emissions generated during the production of powder magnetic cores.

[0010] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0011] (1) The soft magnetic powder of the present disclosure includes a plurality of soft magnetic particles having an insulating film, the insulating film having an insulating layer containing phosphate, silica, or magnesia, and a plurality of cracks on the surface of the insulating film.

[0012] The soft magnetic powder of the present disclosure is a recycled powder having multiple cracks on the surface of the insulating film. However, the term "soft magnetic powder" is sometimes used as a general term, and in such cases, it will be distinguished from "recycled powder." The soft magnetic powder of the present disclosure is obtained by pulverizing used powder cores. Powder cores are produced by compression molding soft magnetic powder having insulating films on the surfaces of soft magnetic particles. It has been confirmed that powder cores can be returned to powder by pulverization. In this case, it has been found that cracks may occur in the insulating film. These cracks are thought to be caused by the manufacturing history of the soft magnetic powder during the powder core manufacturing process, such as compression molding, and by impacts when pulverizing used powder cores. Recycled powder and new soft magnetic powder can be distinguished by the presence or absence of cracks in the insulating film. Hereinafter, in this disclosure, new soft magnetic powder that has never been used as a raw material for powder cores will be referred to as "new powder" to distinguish it from "recycled powder" obtained by pulverizing used powder cores. The above manufacturing history includes both the manufacturing history of dust cores using new powder as the raw material and the manufacturing history of dust cores using recycled powder as the raw material.

[0013] The CO2 emissions generated in the manufacturing process to obtain recycled powder are less than the CO2 emissions generated during the manufacturing of new powder. Therefore, by using the soft magnetic powder of the present disclosure as a raw material for powder magnetic cores, the CO2 emissions generated during the manufacturing of powder magnetic cores can be reduced.

[0014] In a powder magnetic core using the soft magnetic powder of the present disclosure as a raw material, even if the insulating film has cracks, as long as the insulating film does not peel off, electrical insulation between the soft magnetic particles is maintained by the insulating film. Therefore, a powder magnetic core using the soft magnetic powder of the present disclosure can reduce the increase in eddy current loss compared to a powder magnetic core using new powder.

[0015] The insulating film having the insulating layer easily maintains electrical insulation between adjacent soft magnetic particles in the powder magnetic core, thereby reducing eddy current loss in the powder magnetic core.

[0016] (2) In the soft magnetic powder of (1) above, the soft magnetic particles may have an average particle size of 20 μm (micrometers) or more and 400 μm or less, and the insulating film may have an average thickness of 40 nm (nanometers) or more and 500 nm or less.

[0017] When the average particle size of the soft magnetic particles is 20 μm or more, it is easy to increase the density of the powder magnetic core. When the average particle size of the soft magnetic particles is 400 μm or less, it is easy to reduce the eddy current loss of the powder magnetic core. When the average thickness of the insulating film is 40 nm or more, it is easy to reduce the eddy current loss of the powder magnetic core. When the average thickness of the insulating film is 500 nm or less, it is easy to improve the magnetic properties of the powder magnetic core.

[0018] (3) The soft magnetic powder of (1) or (2) above may have an average width of the cracks that is three times or less the average thickness of the insulating film, and the value obtained by dividing the average length of the cracks by the average width of the cracks may be 2 or more.

[0019] Even if the insulating film has cracks, as long as the cracks satisfy the above requirements, the insulating film tends to maintain sufficient electrical insulation between the soft magnetic particles in the powder magnetic core.

[0020] (4) In any one of the soft magnetic powders (1) to (3) above, the soft magnetic particles may have an average circularity of 0.35 or more and 0.5 or less.

[0021] Recycled powder obtained by pulverizing powder cores has soft magnetic particles with a lower circularity than new powder. The reason for the lower circularity of the soft magnetic particles is that the soft magnetic particles are plastically deformed by the molding pressure when they are compressed into a powder core. Soft magnetic powder with an average circularity of soft magnetic particles of 0.35 or more and 0.5 or less is considered to be recycled powder.

[0022] (5) In the soft magnetic powder of (4) above, the soft magnetic particles may have an average aspect ratio of 2.1 or more and 3.0 or less.

[0023] Recycled powder obtained by crushing dust cores has a larger aspect ratio of soft magnetic particles than new powder. Soft magnetic particles with an average aspect ratio of 2.1 or more and 3.0 or less are considered to be recycled powder.

[0024] (6) The soft magnetic powder of (4) or (5) above has a BET specific surface area of ​​0.1 m 2 / g or more 1.0m 2 / g or less.

[0025] The recycled powder made by crushing the powder core has a larger BET specific surface area than new powder. 2 / g or more 1.0m 2 / g or less is considered to be recycled powder.

[0026] (7) The soft magnetic powder according to any one of (1) to (6) above may have the following configuration: The soft magnetic particles have a composition in which the iron content is 99 mass% or more, and the peak of the frequency distribution of Vickers hardness is in the range of 115 Hv or more and 155 Hv or less.

[0027] Recycled powder obtained by crushing powder magnetic cores has soft magnetic particles with higher hardness than new powder of the same composition. The reason for the high hardness of soft magnetic particles is that the soft magnetic particles undergo work hardening when the powder magnetic core is crushed. When the iron content of the soft magnetic particles is 99% by mass or more, soft magnetic powder with a peak in the Vickers hardness frequency distribution in the range of 115 Hv to 155 Hv is considered to be recycled powder.

[0028] (8) The soft magnetic powder of any one of (1) to (7) above may have the following configuration: The soft magnetic particles contain iron, and have a peak in the range of 710 eV to 715 eV in an Fe2p3 spectrum measured by X-ray photoelectron spectroscopy.

[0029] Recycled powder obtained by crushing powder cores has a higher oxide content in the soft magnetic particles than new powder. When the soft magnetic particles contain iron, the iron oxide content increases. The reason for the increased iron oxide content is that powder cores are heat treated during their manufacturing process, and this heat treatment accelerates the oxidation of the iron contained in the soft magnetic particles, resulting in the production of iron oxide. Soft magnetic powder with a peak in the Fe2p3 spectrum between 710 eV and 715 eV is considered to be recycled powder.

[0030] (9) The soft magnetic powder according to any one of (1) to (8) above may have the following configuration: The insulating film contains silicon, and has a silica peak in the Si2p spectrum measured by X-ray photoelectron spectroscopy.

[0031] Recycled powder obtained by pulverizing powder cores has a higher oxide content in the insulating film than new powder. If the insulating film contains silicon, the silica content increases. The reason for the increased silica content is that powder cores are heat treated during their manufacturing process, and this heat treatment accelerates the oxidation of the silicon contained in the insulating film, increasing the amount of silica. Soft magnetic powders that have a silica peak in the Si2p spectrum are considered to be recycled powders.

[0032] (10) The mixed powder of the present disclosure includes a first soft magnetic powder and a second soft magnetic powder. The first soft magnetic powder is composed of a plurality of first soft magnetic particles having a first insulating film, and the first insulating film has a plurality of cracks on its surface. The second soft magnetic powder is composed of a plurality of second soft magnetic particles having a second insulating film, and the second insulating film has no cracks on its surface.

[0033] In the present disclosure, the mixed powder refers to a soft magnetic powder containing at least two or more types of soft magnetic powder. The first soft magnetic powder is a so-called recycled powder. The second soft magnetic powder is a new powder. By using the mixed powder of the present disclosure as a raw material for a powder magnetic core, it is possible to reduce CO2 emissions generated during the production of the powder magnetic core compared to using only the second soft magnetic powder, which is a new powder, as a raw material. Furthermore, by using the mixed powder of the present disclosure as a raw material for a powder magnetic core, it is possible to improve the magnetic properties of the powder magnetic core and reduce the eddy current loss of the powder magnetic core compared to using only the first soft magnetic powder, which is a recycled powder, as a raw material.

[0034] (11) In the mixed powder of (10) above, the mass ratio of the first soft magnetic powder to the total mass of the first soft magnetic powder and the second soft magnetic powder may be 1 mass % or more and less than 100 mass %.

[0035] By making the mass proportion of the recycled first soft magnetic powder 1% by mass or more, it is possible to reduce the amount of new second soft magnetic powder used, thereby reducing CO2 emissions. The greater the mass proportion of the first soft magnetic powder, the greater the CO2 reduction effect that can be expected. By making the mass proportion of the first soft magnetic powder less than 100% by mass, it is possible to improve the magnetic properties of the powder magnetic core by including new powder.

[0036] (12) The mixed powder of (10) or (11) above may have a frequency distribution of Vickers hardness that has two peaks including a first peak and a second peak.

[0037] As mentioned above, recycled powder has soft magnetic particles with higher hardness than virgin powder. A mixed powder with two peaks in the frequency distribution of Vickers hardness is considered to be a mixed powder of recycled and virgin powder. Using this mixed powder as a raw material for powder cores can reduce CO2 emissions generated during the production of powder cores, as mentioned above.

[0038] (13) The mixed powder of (12) above may have the following configuration: the composition of the first soft magnetic particles and the composition of the second soft magnetic particles each have an iron content of 99 mass% or more; the first peak is in the range of 115 Hv or more and 155 Hv or less; and the second peak is in the range of 90 Hv or more and 110 Hv or less.

[0039] In the frequency distribution of Vickers hardness, if the first peak is in the range of 115 Hv to 155 Hv, it is considered to be a mixed powder containing recycled powder. Furthermore, if the second peak is in the range of 90 Hv to 110 Hv, it is considered to be a mixed powder containing new powder. Using this mixed powder as a raw material for powder cores can reduce CO2 emissions generated during the production of powder cores, as mentioned above.

[0040] (14) The mixed powder of any one of (10) to (13) above may have the following configuration: It contains a powdered lubricant. The lubricant is a fatty acid amide or a metal soap. The particle diameter of the lubricant is 1 μm or more and 30 μm or less. The mass ratio of the lubricant to the total mass of the mixed powder is 0.1 mass% or more and 1.0 mass% or less.

[0041] The lubricant improves the lubricity of the mixed powder. By using a mixed powder containing the lubricant as a raw material for a powder magnetic core, the lubricity of the raw material during compression molding can be improved, making it easier to achieve a high density powder magnetic core.

[0042] (15) A powder magnetic core according to the present disclosure comprises the soft magnetic powder according to any one of (1) to (9) above, or the mixed powder according to any one of (10) to (14) above.

[0043] The powder magnetic core of the present disclosure contains so-called recycled powder, which allows for a reduction in the amount of new powder used.The powder magnetic core of the present disclosure uses the soft magnetic powder of the present disclosure or the mixed powder of the present disclosure as a raw material, which allows for a reduction in CO2 emissions generated during the production of the powder magnetic core.

[0044] (16) A motor stator according to the present disclosure includes the powder magnetic core according to (15) above and a coil.

[0045] The motor stator of the present disclosure includes the powder magnetic core of the present disclosure, and therefore can reduce CO2 emissions generated during production.

[0046] (17) A motor according to the present disclosure includes the motor stator and rotor described above in (16).

[0047] The motor of the present disclosure includes the motor stator of the present disclosure, and therefore can reduce CO2 emissions generated during manufacturing.

[0048] (18) A method for producing a powder magnetic core according to the present disclosure includes the steps of recovering used powder magnetic cores containing soft magnetic powder having insulating films on the surfaces of the soft magnetic particles, pulverizing the used powder magnetic cores to obtain recycled powder, compression-molding raw materials containing the recycled powder, and heat-treating the powder compact obtained in the compression-molding step.

[0049] The method for producing a powder magnetic core according to the present disclosure can produce recycled powder magnetic cores using recycled powder obtained by pulverizing used powder magnetic cores as a raw material. By using recycled powder as a raw material, the method for producing a powder magnetic core according to the present disclosure can reduce CO2 emissions generated during the production of the powder magnetic core.

[0050] (19) The method for producing a powder magnetic core according to (18) above may include a step of mixing a powdered lubricant with the raw material before the compression molding step. The lubricant is a fatty acid amide or a metal soap. The particle size of the lubricant is 1 μm or more and 30 μm or less. The mass ratio of the lubricant to the total mass of the raw material is 0.1 mass% or more and 1.0 mass% or less.

[0051] By mixing a lubricant into the raw material, the lubricity of the raw material during compression molding can be improved, making it easier to achieve a high density powder magnetic core.

[0052] (20) In the method for producing a powder magnetic core according to either (18) or (19) above, the step of obtaining the recycled powder may include a step of pulverizing the used powder magnetic core, classifying the pulverized product using a sieve, and a step of sorting the recycled powder using a magnet.

[0053] According to the above-described process for obtaining recycled powder, recycled powder of a predetermined particle size can be obtained by selection.

[0054] (21) The method for producing a powder magnetic core according to any one of (18) to (20) above may have the following configuration: In the step of obtaining the recycled powder, the used powder magnetic core is pulverized using a pulverizer equipped with a screen. The screen has a plurality of openings, each of which has a diameter of 1 mm or more and 15 mm or less.

[0055] By pulverizing the powder magnetic core using a pulverizer equipped with a screen, recycled powder can be easily obtained.

[0056] (22) In the method for producing a powder magnetic core according to any one of (18) to (21) above, the soft magnetic particles have an average particle size of 20 μm or more and 400 μm or less, and the insulating film has an average thickness of 40 nm or more and 500 nm or less.

[0057] When the average particle size of the soft magnetic particles is 20 μm or more, it is easy to increase the density of the powder magnetic core. When the average particle size of the soft magnetic particles is 400 μm or less, it is easy to reduce the eddy current loss of the powder magnetic core. When the average thickness of the insulating film is 40 nm or more, the insulating film is less likely to peel off when the powder magnetic core is pulverized. When the average thickness of the insulating film is 500 nm or less, the magnetic properties of the powder magnetic core can be improved.

[0058] (23) The method for producing a powder magnetic core according to any one of (18) to (22) above may have the following configuration: In the compression molding step, the raw material is compressed into a mold to form the green compact, and the temperature of the mold during compression is 30°C or higher and 100°C or lower.

[0059] By setting the temperature of the mold during compression within the above range, the raw material can be easily compression molded.

[0060] (24) The method for producing a powder magnetic core according to any one of (18) to (23) above may have the following configuration: The recycled powder has a plurality of cracks on the surface of the insulating film, the average width of the cracks is three times or less the average thickness of the insulating film, and the value obtained by dividing the average length of the cracks by the average width of the cracks is 2 or more.

[0061] If the cracks satisfy the above requirements, the electrical insulation between the soft magnetic particles by the insulating film is likely to be sufficiently maintained in the manufactured powder magnetic core.

[0062] (25) The method for producing a powder magnetic core according to any one of (18) to (24) above may further include a step of mixing the recycled powder with new soft magnetic powder before the compression molding step, where the raw material is a mixed powder of the recycled powder and the new soft magnetic powder.

[0063] By using a mixture of recycled and new powder as the raw material, CO2 emissions generated during the production of powder cores can be reduced compared to when only new powder is used as the raw material.In addition, compared to when only recycled powder is used as the raw material, the magnetic properties of the powder core can be improved and the eddy current loss of the powder core can be reduced.

[0064] (26) In the method for producing a powder magnetic core according to (25) above, the mass ratio of the recycled powder to the total mass of the recycled powder and the new soft magnetic powder is 1% by mass or more and less than 100% by mass.

[0065] By ensuring that the mass ratio of recycled powder is 1% by mass or more, it is possible to reduce the amount of new powder used, thereby expecting a reduction in CO2 emissions. The greater the mass ratio of recycled powder, the greater the CO2 reduction effect that can be expected. By ensuring that the mass ratio of recycled powder is less than 100% by mass, it is possible to expect an improvement in magnetic properties due to the inclusion of new powder.

[0066] [Details of the embodiments of the present disclosure] Specific examples of the soft magnetic powder, mixed powder, powder core, motor stator, motor, and method of manufacturing the powder core according to the present disclosure are described below. The same reference numerals in the drawings indicate the same items. The sizes of the components shown in each drawing are shown for the purpose of clarifying the description and do not necessarily represent the actual dimensional relationships. It should be noted that the present invention is not limited to these examples, but is defined by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0067] <Soft magnetic powder> A soft magnetic powder 1 according to an embodiment will be described with reference to FIGS. 1 and 2. As shown in FIG. 1, the soft magnetic powder 1 is a powder containing a plurality of soft magnetic particles 2 having an insulating film 3. One of the features of the soft magnetic powder 1 is that the surface of the insulating film 3 has a plurality of cracks 3c, as shown in FIG. 2. The soft magnetic powder 1 is a so-called recycled powder obtained by pulverizing used powder cores. The soft magnetic powder 1 is used as a raw material for powder cores.

[0068] [Soft magnetic particles] The soft magnetic particles 2 are made of, for example, iron or an iron-based alloy. The iron has a purity of, for example, 99% or more. Iron with a purity of 99% or more contains 99% or more by mass of iron. The iron-based alloy is, for example, at least one selected from an iron-silicon alloy (silicon steel), an iron-silicon-aluminum alloy (sendust), an iron-aluminum alloy, an iron-nickel alloy (permalloy), and an iron-cobalt alloy. The composition of the soft magnetic particles 2 in this example has an iron content of 99% or more by mass. Iron with a purity of 99% or more is softer than an iron-based alloy. Soft magnetic powder 1 containing soft magnetic particles 2 made of iron with a purity of 99% or more is easy to compact, making it easy to densify the powder core. Densifying the powder core can improve the magnetic properties of the powder core. The magnetic properties include, for example, relative permeability and saturation magnetic flux density. Iron-based alloys have higher electrical resistance than iron. The soft magnetic powder 1 containing the soft magnetic particles 2 formed from the iron-based alloy is likely to reduce eddy current loss that occurs when magnetic flux flows through a powder magnetic core.

[0069] <Average particle size> The average particle diameter of the soft magnetic particles 2 is, for example, 20 μm or more and 400 μm or less. The particle diameter is a value equivalent to the diameter of the particles when they are assumed to be spherical. The larger the particle diameter of the soft magnetic particles 2, the easier the soft magnetic particles 2 are to undergo plastic deformation. On the other hand, the smaller the particle diameter of the soft magnetic particles 2, the easier it is to reduce eddy current loss generated within the soft magnetic particles 2. When the average particle diameter of the soft magnetic particles 2 is 20 μm or more, the soft magnetic powder 1 is easily compression-molded, and the powder core is easily densified. By densifying the powder core, the magnetic properties of the powder core can be improved. When the average particle diameter of the soft magnetic particles 2 is 45 μm or more, the densification is easier, when it is 90 μm or more, the densification is even easier, when it is 150 μm or more, the densification is even easier, and when it is 200 μm or more, the densification is even easier. Furthermore, when the average particle diameter of the soft magnetic particles 2 is 400 μm or less, the eddy current loss of the powder core is easily reduced. If the average particle size of the soft magnetic particles 2 is 300 μm or less, eddy current loss can be more easily reduced. The average particle size of the soft magnetic particles 2 may be 45 μm or more and 300 μm or less, or may further be 90 μm or more and 300 μm or less.

[0070] The average particle size of the soft magnetic particles 2 can be determined as follows. The particle size distribution of the soft magnetic powder 1 is measured using a laser diffraction particle size distribution analyzer. The sum of the values ​​obtained by multiplying the measured particle sizes by their frequency is considered to be the average particle size of the soft magnetic particles 2. The frequency is the ratio of the number of particles in each particle size range to the total number of particles, expressed as a percentage. A particle size range is an individual division into a specified particle size range that divides the entire range from the minimum to the maximum particle size. For example, the range from greater than 15 μm to less than 25 μm is considered to be the 20 μm particle size range, the range from greater than 25 μm to less than 35 μm is considered to be the 30 μm particle size range, and the range from greater than 35 μm to less than 45 μm is considered to be the 40 μm particle size range. If the frequency of particles falling within the 20 μm particle size interval is 20%, the frequency of particles falling within the 30 μm particle size interval is 50%, and the frequency of particles falling within the 40 μm particle size interval is 30%, then the average particle size is (20 × 0.2) + (30 × 0.5) + (40 × 0.3) = 31 μm. In the above calculation example, for ease of understanding, the width of the particle size interval is set to 10 μm, but the width of the actual particle size interval is, for example, between 5 μm and 40 μm.

[0071] [Insulating film] The insulating film 3 covers the surface of the soft magnetic particles 2. The insulating film 3 electrically insulates adjacent soft magnetic particles 2 in the powder magnetic core. By providing the insulating film 3 on the surface of the soft magnetic particles 2, the electrical resistance of the powder magnetic core can be increased and the eddy current loss of the powder magnetic core can be reduced. The insulating film 3 is formed of, for example, a phosphate, an oxide of silicon, or an oxide of magnesium. The phosphate is, for example, zinc phosphate, iron phosphate, manganese phosphate, or calcium phosphate. The oxide of silicon is silicon monoxide (SiO) or silica (SiO2). The oxide of magnesium is magnesia (MgO).

[0072] The insulating film 3 may have a single-layer structure having only one type of insulating layer, or a multilayer structure having two or more types of insulating layers stacked together. The insulating film 3 may have an insulating layer containing phosphate, silica, or magnesia. An insulating film 3 having such an insulating layer easily maintains electrical insulation between the soft magnetic particles 2 in a powder magnetic core. An insulating layer containing phosphate has high adhesion to the soft magnetic particles 2. In addition, an insulating layer containing phosphate is easily deformed. An insulating film 3 having an insulating layer containing phosphate easily follows the deformation of the soft magnetic particles 2 when the soft magnetic powder 1 is compression-molded, and therefore is less likely to peel off. An insulating layer containing silica or magnesia is hard. An insulating film 3 having an insulating layer containing silica or magnesia is less likely to be damaged or become too thin when the soft magnetic powder 1 is compression-molded. When the insulating film 3 has a two-layer structure, it has a first insulating layer and a second insulating layer in this order. The first insulating layer is in contact with the surface of the soft magnetic particles 2. The second insulating layer is disposed on the first insulating layer and is in contact with the first insulating layer. For example, the first insulating layer contains phosphate or silica, and the second insulating layer contains one of phosphate, silica, and magnesia. Specifically, if the material of the first insulating layer is phosphate, the material of the second insulating layer is silica or magnesia. If the material of the first insulating layer is silica, the material of the second insulating layer is phosphate or magnesia. The insulating film 3 in this example has a two-layer structure in which the first insulating layer and the second insulating layer are stacked in order. In this example, the first insulating layer contains phosphate. The second insulating layer contains silica.

[0073] <Average thickness> Generally, the average thickness of the insulating film of a conventional soft magnetic powder is 20 nm or more and 30 nm or less. In contrast, the average thickness of the insulating film 3 of the soft magnetic powder 1 is, for example, 40 nm or more and 500 nm or less. The thicker the insulating film 3, the higher the electrical insulation between adjacent soft magnetic particles 2 in the powder core. The thinner the insulating film 3, the easier it is for the soft magnetic particles 2 to deform, making it easier to densify the powder core. Furthermore, the thinner the insulating film 3, the shorter the distance between adjacent soft magnetic particles 2, making it easier to increase the magnetic permeability of the powder core. When the average thickness of the insulating film 3 is 40 nm or more, it is easy to reduce the eddy current loss of the powder core. Furthermore, when the average thickness of the insulating film 3 is 40 nm or more, the insulating film 3 is less likely to peel off, making it easier to achieve the effect of reducing eddy current loss by the insulating film 3. When the average thickness of the insulating film 3 is 500 nm or less, it is easy to densify the powder core and increase the magnetic permeability of the powder core. Furthermore, if the average thickness of the insulating film 3 is 500 nm or less, the proportion of the soft magnetic particles 2 contained in the powder magnetic core will not be too small. This will improve the magnetic properties of the powder magnetic core. The average thickness of the insulating film 3 may be 50 nm to 400 nm, 80 nm to 350 nm, or even 100 nm to 300 nm. If the average thickness of the insulating film 3 is 50 nm to 400 nm, high magnetic properties are likely to be obtained. If the average thickness of the insulating film 3 is 80 nm to 350 nm, the variation in magnetic properties is likely to be small. If the average thickness of the insulating film 3 is 100 nm to 300 nm, the variation in magnetic properties is likely to be small and higher magnetic properties are likely to be obtained. The average thickness of the insulating film 3 may be 120 nm or more, 150 nm or more, or even 200 nm or more. If the insulating film 3 has a multilayer structure, the thickness of the insulating film 3 is the combined thickness of all the insulating layers that make up the insulating film 3.

[0074] The average thickness of the insulating film 3 can be determined as follows. A cross section of a powder magnetic core using the soft magnetic powder 1 as a raw material is observed under a microscope, and the observed image is subjected to image analysis. The microscope is a scanning electron microscope (SEM) or a transmission electron microscope (TEM), for example. 20 or more fields of view are observed. The magnification is, for example, 50,000 times or more and 200,000 times or less. The average thickness of the insulating film 3 in each field of view is determined by image analysis. In each field of view, the thickness of the insulating film 3 is measured at five or more locations and the average is determined. The average thickness of the insulating film 3 over all 20 or more fields of view is determined, and the average is taken as the average thickness of the insulating film 3.

[0075] <Cracked area> A soft magnetic powder 1 having multiple cracks 3c on the surface of the insulating film 3 can be said to be a recycled powder, not a new powder. New powder is unused soft magnetic powder in the state it was manufactured. Typically, new powder has almost no cracks or peeling in the insulating film. The multiple cracks 3c are generated when the powder core is crushed. Therefore, the presence or absence of multiple cracks 3c on the surface of the insulating film 3 can be used as an indicator to distinguish between recycled powder and new powder according to the embodiment.

[0076] As shown in Figure 2, the insulating film 3 of the soft magnetic powder 1 has multiple cracks 3c, but almost no peeling. Here, a "crack" is a portion where a streak-like crack (fissure) has occurred on the surface of the insulating film 3. A "peeling" is a portion where a portion of the insulating film 3 has peeled off in a planar manner. In a powder magnetic core using soft magnetic powder 1 as a raw material, it is required that the insulating film 3 maintain electrical insulation between adjacent soft magnetic particles 2. From this perspective, cracks and peeling can be distinguished. Here, a crack and a peeling are distinguished as follows: A "crack" is defined as a portion where the width of the portion where the insulating film 3 is absent is three times or less the thickness of the insulating film 3, and the value obtained by dividing the length of the portion where the insulating film 3 is absent by the width is two or more. A "peeling" is defined as a portion where the width of the portion where the insulating film 3 is absent is greater than the "crack," i.e., the width of the portion where the insulating film 3 is absent is more than three times the thickness of the insulating film 3.

[0077] In a powder magnetic core, even if the insulating film 3 has cracks 3c, electrical insulation between the soft magnetic particles 2 is maintained by the insulating film 3 as long as the insulating film 3 is not peeled off. If the average width of the cracks 3c is no more than three times the average thickness of the insulating film 3 and the value obtained by dividing the average length of the cracks 3c by the average width of the cracks 3c is 2 or more, electrical insulation between the soft magnetic particles 2 by the insulating film 3 is likely to be sufficiently maintained. The narrower the width of the cracks 3c, the less likely adjacent soft magnetic particles 2 are to come into direct contact, making it easier to maintain electrical insulation between the soft magnetic particles 2. The average width of the cracks 3c may be no more than twice the average thickness of the insulating film 3, or even no more than one time the average thickness of the insulating film 3.

[0078] For each crack 3c, the length is the distance of a curve from one end to the other end along the crack 3c when the surface of the insulating film 3 is viewed in plan. This curve is, for example, an approximate curve that passes through both ends of the crack 3c and at least five midpoints located between the ends. The midpoints are the points that bisect the width of the crack 3c. The average length of the crack 3c is calculated as the average value of the lengths of multiple cracks 3c. For each crack 3c, the width of the crack 3c is the maximum width of the gap between cracks perpendicular to the curve used to calculate the length. The average width of the crack 3c is calculated as the average value of the widths of multiple cracks 3c. The average length and average width of the crack 3c are calculated as the average values ​​of the lengths and widths of 10 or more cracks 3c, respectively.

[0079] [CO2 emissions] The CO2 emissions generated during the process of obtaining soft magnetic powder 1, which is a recycled powder, are less than those generated during the production of new powder. Therefore, using soft magnetic powder 1 as a raw material for powder cores can reduce the CO2 emissions generated during the production of powder cores. The main steps in the production process for new powder include transporting the raw materials, melting and pulverizing the raw materials, and insulating them. In contrast, the main steps in the production process for recycled powder include recovering the powder cores and crushing and classifying the powder cores.

[0080] <Mixed powder> A mixed powder 5 according to an embodiment will be described with reference to FIGS. 3 and 4. As shown in FIG. 3, the mixed powder 5 is a mixture of a first soft magnetic powder 1a and a second soft magnetic powder 1b. The "+" symbol in FIG. 3 indicates that two powders are mixed. As shown in FIGS. 3 and 4, the first soft magnetic powder 1a is composed of first coated particles 6a. The first coated particles 6a are composed of a plurality of first soft magnetic particles 2a each having a first insulating film 3a. The second soft magnetic powder 1b is composed of second coated particles 6b. The second coated particles 6b are composed of a plurality of second soft magnetic particles 2b each having a second insulating film 3b. The circled portion in the middle of FIG. 3 illustrates the surfaces of the first coated particles 6a and the second coated particles 6b. The first soft magnetic powder 1a has a plurality of cracks 3c on the surface of the first insulating film 3a. The second soft magnetic powder 1b has no cracks on the surface of the second insulating film 3b. The first soft magnetic powder 1a is a so-called recycled powder. Note that Fig. 4 does not show cracks 3c in the insulating film 3. The mixed powder 5 is used as a raw material for a dust core.

[0081] The first soft magnetic powder 1a corresponds to the soft magnetic powder 1 in the above-described embodiment. The first soft magnetic powder 1a and the second soft magnetic powder 1b have a basic structure in common in that they have an insulating film on the surface of the soft magnetic particles. The main difference between the first soft magnetic powder 1a and the second soft magnetic powder 1b is the presence or absence of cracks 3c in the insulating film 3. The first soft magnetic particles 2a and the second soft magnetic particles 2b are similar to the soft magnetic particles 2 of the soft magnetic powder 1 in terms of material, average particle diameter, etc., and the matters described in the above section [Soft Magnetic Particles] can be applied. The first insulating film 3a and the second insulating film 3b are similar to the insulating film 3 of the soft magnetic powder 1 in terms of material, average thickness, etc., and the matters described in the above section [Insulating Film] can be applied.

[0082] The mixed powder 5 contains a first soft magnetic powder 1a, which is a recycled powder, and a second soft magnetic powder 1b, which is a new powder. Therefore, by using the mixed powder 5 as a raw material for a powder core, it is possible to reduce CO2 emissions generated during the production of the powder core compared to using only new powder as a raw material. Furthermore, by using the mixed powder 5 as a raw material, it is possible to improve the magnetic properties of the powder core and reduce eddy current loss of the powder core compared to using only recycled powder as a raw material.

[0083] [Mass ratio of first soft magnetic powder] The mass proportion of the first soft magnetic powder 1a relative to the total mass of the first soft magnetic powder 1a and the second soft magnetic powder 1b is, for example, 1% by mass or more and less than 100% by mass. When the mass proportion of the first soft magnetic powder 1a is 1% by mass or more, the amount of new powder used can be reduced, thereby expected to reduce CO2 emissions. When the mass proportion of the first soft magnetic powder 1a is less than 100% by mass, the magnetic properties of the powder magnetic core can be expected to be improved by including new powder. The greater the mass proportion of the first soft magnetic powder 1a, the greater the CO2 reduction effect. The mass proportion of the first soft magnetic powder 1a may be, for example, 5% by mass or more, 10% by mass or more, 20% by mass or more, 40% by mass or more, 50% by mass or more, 70% by mass or more, or even 90% by mass or more.

[0084] [Lubricant] The mixed powder 5 may further contain a lubricant (not shown). The lubricant is a powdered solid lubricant. The lubricant improves the lubricity of the mixed powder 5. By using the mixed powder 5 containing the lubricant as a raw material for a powder core, the lubricity of the raw material during compression molding can be improved, making it easier to increase the density of the powder core.

[0085] The lubricant is, for example, a fatty acid amide or a metal soap. Examples of the fatty acid amide include stearic acid amide and ethylene bisstearic acid amide. Examples of the metal soap include metal stearates such as zinc stearate and lithium stearate. The particle diameter of the lubricant is, for example, 1 μm or more and 30 μm or less. The particle diameter of the lubricant is the particle diameter D50 at which the cumulative mass is 50% in the particle size distribution measured by a laser diffraction particle size analyzer. If the particle diameter of the lubricant is 1 μm or more and 30 μm or less, the lubricant is easily dispersed uniformly in the raw material. The particle diameter of the lubricant may be 5 μm or more and 25 μm or less. The mass ratio of the lubricant to the total mass of the mixed powder 5 is, for example, 0.1 mass% or more and 1.0 mass% or less. If the mass ratio of the lubricant is 0.1 mass% or more, the lubricity of the mixed powder 5 can be sufficiently improved. Therefore, the density of the powder magnetic core can be increased. If the mass proportion of the lubricant is 1.0 mass% or less, the proportion of soft magnetic powder contained in the powder magnetic core is less likely to decrease, thereby improving the magnetic properties of the powder magnetic core. The mass proportion of the lubricant may be 0.3 mass% or more and 0.6 mass% or less.

[0086] <Powder magnetic core> 5 to 7, a powder magnetic core 10 according to an embodiment will be described. The powder magnetic core 10 is made of the soft magnetic powder 1 or mixed powder 5 described above. As described above, the soft magnetic powder 1 and the first soft magnetic powder 1a of the mixed powder 5 are so-called recycled powders, and the powder magnetic core 10 contains recycled powder. The powder magnetic core 10 is a recycled powder core that uses recycled powder as at least a portion of the raw material.

[0087] In a powder core using new powder as a raw material, cracks or peeling of the insulating film are almost never observed. In contrast, in a powder core 10 using soft magnetic powder 1 and mixed powder 5 as raw materials, as described above, multiple cracks 3c are present on the surface of the insulating film 3 or first insulating film 3a. The presence of cracks 3c in the insulating film is one way of determining that the powder core 10 contains recycled powder.

[0088] Because the powder core 10 contains the soft magnetic powder 1 or the first soft magnetic powder 1a, which are recycled powders, the amount of new powder used can be reduced. Powder core 10 manufactured using recycled powder as a raw material can reduce CO2 emissions generated during the manufacture of the powder core 10. Powder core 10 made of soft magnetic powder 1 is made only of recycled powder and does not contain new powder, which is highly effective in reducing CO2 emissions. Powder core 10 made of mixed powder 5 contains second soft magnetic powder 1b, which is new powder, which can improve the magnetic properties of powder core 10 and reduce eddy current loss of powder core 10. The mass ratio of the recycled powder to the mass of powder core 10 is, for example, 1% by mass or more and 100% by mass or less.

[0089] The relative density of the powder core 10 is, for example, 85% or more. The higher the relative density of the powder core 10, the better the magnetic properties of the powder core 10. When the relative density of the powder core 10 is 85% or more, high magnetic properties are easily obtained. The powder core 10 having high magnetic properties contributes to improving the performance of electrical equipment such as motors and reactors. The relative density of the powder core 10 may be 90% or more, 93% or more, or even 95% or more. The upper limit of the relative density of the powder core 10 is not particularly limited, but is, for example, 99%. The relative density is the apparent density divided by the true density, expressed as a percentage. Here, the theoretical density of soft magnetic particles is taken as the true density.

[0090] The powder magnetic core 10 can have various shapes depending on the application. The powder magnetic core 10 can be used as a magnetic core for electric devices such as motors and reactors. The powder magnetic core 10a shown in FIG. 5 is an annular stator core used in the stator of an axial gap motor. The powder magnetic core 10a includes a yoke 20 and teeth 30. The yoke 20 and teeth 30 are integrally molded. The yoke 20 has an annular plate shape. A plurality of teeth 30 are equally spaced in an annular arrangement on the upper surface of the yoke 20. Each tooth 30 protrudes from the upper surface of the yoke 20. The teeth 30 have a cylindrical shape. In this example, there are 12 teeth 30. The teeth 30 in this example have a triangular prism shape. A coil (not shown) is attached to the outer periphery of each tooth 30. The number of teeth 30 is not particularly limited and can be appropriately determined depending on the specifications of the motor. The shape of the teeth 30 can be selected from any shape, such as a quadrangular prism, trapezoidal prism, or the like, in addition to a triangular prism.

[0091] The powder magnetic core 10b shown in FIG. 6 is a split core obtained by splitting the stator core described above with reference to FIG. 5 around the axis. The split core constitutes a part of the stator core. The stator core is formed by combining multiple split cores in an annular shape. The powder magnetic core 10b includes a fan-shaped yoke 20 and a triangular prism-shaped tooth 30 protruding from the top surface of the yoke 20. There is one tooth 30. In this example, the annular stator core is formed by combining 12 powder magnetic cores 10b.

[0092] The powder magnetic core 10c shown in FIG. 7 is another example of a split core obtained by splitting the stator core described above with reference to FIG. 5 around the axis. In the powder magnetic core 10c, three teeth 30 are arranged on one yoke 20. The yoke 20 has a fan-like shape. The teeth 30 have a triangular prism-like shape. In this example, a circular stator core is formed by combining four powder magnetic cores 10c.

[0093] The powder core 10 may include a resin mold (not shown). The resin mold covers at least a portion of the powder core 10. The resin mold is provided, for example, on a portion of the powder core 10 that comes into contact with the coil. The resin mold may be provided so as to cover the coil arranged on the powder core 10. In this case, the coil can be integrated with the powder core 10 by the resin mold.

[0094] <Motor stator> A motor stator 200 according to an embodiment will be described with reference to FIG. 8. Hereinafter, the motor stator may be simply referred to as a "stator." The stator 200 shown in FIG. 8 is used in an axial gap motor. The stator 200 includes a powder magnetic core 10 and a coil 210. The powder magnetic core 10 shown in FIG. 8 has the same configuration as the powder magnetic core 10a shown in FIG. 5. The coils 210 are arranged on each of the teeth 30.

[0095] <Motor> A motor 300 according to an embodiment will be described with reference to Fig. 9. The motor 300 includes a stator 200 and a rotor 250. The motor 300 shown in Fig. 9 is an axial gap motor in which the stator 200 and the rotor 250 are arranged facing each other in a direction along a rotation axis 330.

[0096] The rotor 250 is disposed so as to face the end faces of each tooth 30 of the stator 200. The rotor 250 includes a plurality of flat magnets 260 and an annular retaining plate 270 that supports these magnets 260. The end faces of each tooth 30 and each magnet 260 face each other at a predetermined interval in a direction along the rotation shaft 330. The retaining plate 270 is fixed to the rotation shaft 330 and rotates together with the rotation shaft 330. Each magnet 260 is embedded in the retaining plate 270. The plurality of magnets 260 are disposed at equal intervals around the rotation shaft 330. Each magnet 260 is magnetized in a direction along the rotation shaft 330. The magnetization directions of adjacent magnets 260 are opposite to each other.

[0097] Stator 200 and rotor 250 are housed in a cylindrical case 310. Disk-shaped plates 320 are attached to both ends of case 310. A through-hole is formed in the center of each plate 320, and a rotating shaft 330 passes through inside case 310. Stator 200 is fixed to case 310 by fitting the outer peripheral surface of yoke 20 into the inner peripheral surface of case 310. An annular bearing 340 that rotatably supports rotating shaft 330 is attached to the inner peripheral surface of yoke 20.

[0098] <Method of manufacturing powder magnetic cores> The powder magnetic core 10 can be manufactured by a method for manufacturing a powder magnetic core according to an embodiment. The method for manufacturing a powder magnetic core can manufacture a recycled powder by pulverizing used powder magnetic cores as a raw material. The method for manufacturing a powder magnetic core includes a recovery step, a pulverization step, a pressing step, and a heat treatment step. Each step will be described in detail below.

[0099] <Recovery process> The recovery process is a process for recovering used powder magnetic cores. Used powder magnetic cores contain soft magnetic powder with insulating films on the surfaces of the soft magnetic particles. The composition of the soft magnetic powder in used powder magnetic cores is basically the same as the composition of the soft magnetic powder 1 described above. Used powder magnetic cores may be powder magnetic cores that have never been recycled, or they may be powder magnetic cores that have been recycled at least once. A powder magnetic core that has never been recycled is a powder magnetic core manufactured using only new powder as a raw material. A recycled powder magnetic core is a powder magnetic core that contains recycled powder. Here, "used" does not necessarily mean that it has actually been used as an electrical device. Used powder magnetic cores may also be powder magnetic cores that have been manufactured as powder magnetic cores and then collected without being used as electrical equipment. In other words, anything that has been molded from soft magnetic powder into a powder magnetic core is considered a used powder magnetic core regardless of whether it has been used as an actual electrical device. Used powder magnetic cores may also be powder magnetic cores that have been collected as defective products during the production of powder magnetic cores.

[0100] The average particle diameter of the soft magnetic particles in the used powder magnetic core is, for example, 20 μm or more and 400 μm or less. The average particle diameter of the soft magnetic particles may be 45 μm or more and 300 μm or less, or even 90 μm or more and 300 μm or less. The average thickness of the insulating film in the used powder magnetic core is, for example, 40 nm or more and 500 nm or less. The average thickness of the insulating film may be 50 nm or more and 400 nm or less, 80 nm or more and 350 nm or less, or even 100 nm or more and 300 nm or less. Generally, the average thickness of the insulating film in conventional powder magnetic cores is 20 nm or more and 30 nm or less. In the manufacturing method for a powder magnetic core of the embodiment, the average thickness of the insulating film is set to 40 nm or more and 500 nm or less to prevent peeling of the insulating film when the powder magnetic core is pulverized in the pulverization step described below.

[0101] Used powder magnetic cores are collected from used electrical equipment. Used powder magnetic cores may still have accessories such as coils attached, or may remain covered in a resin mold. Therefore, there is no need to remove the coils or other accessories from the used powder magnetic cores, or to remove the resin mold.

[0102] <Crushing process> The pulverization process is a process in which used powder cores are pulverized to obtain recycled powder. The recycled powder is soft magnetic powder contained in used powder cores. In powder cores, adjacent soft magnetic particles are not metallurgically bonded to each other. The inventors discovered that when a powder core is pulverized, the soft magnetic particles separate from each other and become dispersed, i.e., powdered, and that the particle size of the powdered particles is substantially the same as the particle size of the soft magnetic powder contained in the powder core before pulverization. If the insulating film in a used powder core is thin, the insulating film may peel off due to the impact when the powder core is pulverized. If the insulating film is thick, cracks may occur in the insulating film when the powder core is pulverized, but peeling of the insulating film is unlikely to occur. If the average thickness of the insulating film before pulverization is 40 nm or more, the insulating film is unlikely to peel off when the powder core is pulverized.

[0103] The recycled powder can be configured in the same manner as the soft magnetic powder 1 of the embodiment described above. The average particle diameter of the recycled powder is, for example, 20 μm or more and 400 μm or less. The average particle diameter of the recycled powder is the average particle diameter of the soft magnetic particles including the insulating film. The thickness of the insulating film is on the order of tens to hundreds of nanometers, which is extremely thin compared to the particle diameter of the soft magnetic particles. Therefore, the average particle diameter of the recycled powder can be considered to be substantially the same as the average particle diameter of the soft magnetic particles. For the measurement method of the average particle diameter of the recycled powder, please refer to the above-mentioned section on "Average Particle Diameter." The average particle diameter of the recycled powder may be 45 μm or more and 300 μm or less, or even 90 μm or more and 300 μm or less. The average thickness of the insulating film in the recycled powder is, for example, 40 nm or more and 500 nm or less. The average thickness of the insulating film in the recycled powder may be 50 nm or more and 400 nm or less, 80 nm or more and 350 nm or less, or even 100 nm or more and 300 nm or less.

[0104] [Crusher] A known crusher can be used to crush the used powder magnetic cores. The crusher used may be, for example, a cutter crusher, a hammer crusher, or a chain crusher. A cutter crusher crushes the powder magnetic cores by scraping them off with a rotating blade. A hammer crusher crushes the powder magnetic cores by smashing them with a rotating hammer. A chain crusher crushes the powder magnetic cores by smashing them with a rotating chain.

[0105] The powder magnetic cores may be pulverized using a pulverizer equipped with a screen. An example of a pulverizer 100 will be described with reference to FIG. 10. FIG. 10 is a schematic diagram of the configuration of the pulverizer 100. The pulverizer 100 is a cutter-type pulverizer. The pulverizer 100 includes a pulverization chamber 110, a rotary blade 120, a fixed blade 130, and a screen 140. The pulverization chamber 110 has an inlet 111. Used powder magnetic cores 10 are fed into the pulverization chamber 110 through the inlet 111. The rotary blade 120 is disposed within the pulverization chamber 110. The rotary blade 120 is attached to a rotary shaft 121. A plurality of rotary blades 120 are attached in a line along the rotary shaft 121. The rotary blades 120 rotate as the rotary shaft 121 rotates. The fixed blade 130 is disposed within the pulverization chamber 110. A predetermined clearance is provided between the rotary blade 120 and the fixed blade 130. The powder magnetic core 10 is sheared by the rotary blade 120 and the fixed blade 130. The screen 140 is attached to the discharge outlet of the crushing chamber 110. The crushed material sheared by the rotary blade 120 and the fixed blade 130 is crushed and crushed between the rotary blade 120 and the screen 140.

[0106] The screen 140 is a plate having a plurality of openings 141. The powder cores 10 are pulverized to a size that can pass through the openings 141. As described above, when the powder cores 10 are pulverized, the soft magnetic particles break down into powder. The recycled powder 1 obtained by pulverizing the powder cores 10 is discharged through the openings 141. The shape of each opening 141 is, for example, circular. The diameter of each of the plurality of openings 141 can be selected appropriately depending on the size of the powder cores 10 to be pulverized. The diameter of each opening 141 is, for example, 1 mm or more and 15 mm or less. When the diameter of the openings 141 is 1 mm or more and 15 mm or less, the powder cores 10 are easily pulverized and the recycled powder 1 is easily obtained. The diameter of the openings 141 may be 2 mm or more and 10 mm or less.

[0107] When a used powder core 10 with a coil attached or resin molded is pulverized, the powder core 10 is pulverized to a particle size similar to that of the soft magnetic powder used as the raw material. In contrast, the coil and resin mold are pulverized to a size similar to the diameter of the openings 141 in the screen 140. The particle size of the recycled powder 1 obtained by pulverizing the powder core 10 is sufficiently smaller than the size of the pulverized coil and resin mold. Therefore, the recycled powder 1 and the pulverized coil and resin mold can be easily separated using a sieve. Furthermore, since the recycled powder 1 is attracted to a magnet, it may also be separated using a magnet.

[0108] The pulverization step may include a step of classifying the pulverized powder obtained by pulverizing the powder core 10 using a sieve, and a step of sorting the recycled powder 1 using a magnet. By performing the sieving step and the magnetic sorting step, only recycled powder 1 having a predetermined particle size can be selected and obtained.

[0109] <Pressing process> The pressing process is a process of compression molding raw materials including recycled powder. A green compact is obtained by compression molding raw materials including recycled powder. When the average particle diameter of the recycled powder is 20 μm or more and 400 μm or less, the recycled powder is easy to handle and compression mold. The higher the molding pressure when compressing the recycled powder, the higher the density of the powder magnetic core can be. The molding pressure is, for example, 500 MPa or more and 1500 MPa or less.

[0110] A step of mixing a lubricant with the raw material before the raw material is compression-molded may be included. By mixing a lubricant with the raw material, the lubricity of the raw material during compression molding can be improved, making it easier to increase the density of the powder magnetic core. The lubricant may be any of the lubricants described above in the section [Lubricant].

[0111] A step of mixing new powder with recycled powder may be included before the raw materials are compression-molded. Using a mixed powder containing new powder and recycled powder as the raw material can improve the magnetic properties of the powder core and reduce the eddy current loss of the powder core compared to using only recycled powder as the raw material. The mixed powder can have the same configuration as mixed powder 5 in the above-described embodiment. When using a mixed powder as the raw material, the mass ratio of the recycled powder to the total mass of the recycled powder and new powder is, for example, 1 mass% or more and less than 100 mass%. The mass ratio of the recycled powder in the mixed powder is maintained even after compression-molding. In other words, the mass ratio of the recycled powder in a powder core manufactured using the mixed powder as the raw material is the same as the mass ratio of the recycled powder in the mixed powder used as the raw material.

[0112] In the compression molding of raw materials, the raw materials are filled into a mold and compressed to form a green compact. The temperature of the mold during compression is, for example, 30°C or higher and 100°C or lower. By keeping the mold temperature within the above range, the raw materials can be easily compression molded. Furthermore, if the mold temperature is 100°C or lower, the lubricant is less likely to deteriorate.

[0113] <Heat treatment process> The heat treatment process is a process in which the compacted powder body is heat-treated after the pressing process. By heat-treating the compacted powder body, it is possible to remove the strain introduced into the soft magnetic particles by the compression molding, thereby improving the magnetic properties of the powder core. The heat treatment temperature is, for example, 300°C or higher and 900°C or lower. The lubricant disappears during the heat treatment.

[0114] [Test Example 1] The particle size distribution of the recycled powder obtained by crushing the powder magnetic core was investigated.

[0115] The dust core was manufactured using new powder as a raw material. The new powder was iron powder with an insulating film on the surface of soft magnetic particles made of iron. The soft magnetic particles had a composition in which the iron content was 99% by mass or more. The insulating film had a two-layer structure in which a first insulating layer, which was the inner layer, and a second insulating layer, which was the outer layer, were laminated in that order. The first insulating layer contained phosphate. The second insulating layer contained silica. In test example 1, nine new powders with different average particle sizes of the soft magnetic particles and average thicknesses of the insulating film were used as raw materials for the dust core.

[0116] The powder magnetic core is a circular stator core as shown in Figure 5. The outer diameter d of the stator core is approximately 52 mm. The thickness t of the stator core is approximately 19 mm. The thickness t of the stator core is the total thickness of the yoke and the teeth.

[0117] Powder magnetic cores were manufactured using each new powder as a raw material. Multiple powder magnetic cores were prepared for each new powder. Multiple powder magnetic cores using the same new powder as a raw material were pulverized using a pulverizer to obtain recycled powder. The pulverizer used was the SF-1 model manufactured by Sanriki Manufacturing Co., Ltd. This pulverizer was a cutter-type pulverizer equipped with a screen 140 shown in FIG. 10. Each of the multiple openings 141 formed in the screen 140 had a diameter of 5 mm. The rotation speed of the rotary blade was approximately 1000 rpm (revolutions per minute).

[0118] The particle size distribution of the recycled powder was measured using a laser diffraction particle size analyzer. The laser diffraction particle size analyzer used was an MT3300EX manufactured by Nikkiso Co., Ltd. The particle size distribution of the recycled powder was measured by averaging the particle size distributions of three samples taken from the recycled powder. The particle size distribution of the new powder was also measured before manufacturing the powder core. As with the recycled powder, the particle size distribution of the new powder was measured by averaging the particle size distributions of the three samples. The measured particle size distribution was based on mass. The particle diameters D10, D50, and D90 of the recycled and new powders were calculated. Particle diameter D10 is the particle diameter at 10% of the cumulative mass. Particle diameter D50 is the particle diameter at 50% of the cumulative mass. Particle diameter D90 is the particle diameter at 90% of the cumulative mass. The average particle diameter and average thickness of the insulating film of the new powder were also calculated. The results are shown in Table 1. The method for measuring the average particle size of new powder is the same as that described in the "Average Particle Size" section above. The method for measuring the average thickness of the insulating film is the same as that described in the "Average Thickness" section above. In Table 1, the "Particle Size" column indicates the average particle size. The "Film Thickness" column indicates the average thickness. In the "Type" column, "New" indicates new powder, and "Recycled" indicates "recycled powder." The "Particle Size Ratio" column in the "Particle Size Distribution" column indicates the value obtained by dividing the D50 of the recycled powder by the D50 of the new powder. The smaller the difference between the D50 of the recycled powder and the D50 of the new powder, the closer the particle size ratio value is to 1. A particle size ratio value between 0.9 and 1.1 indicates a small difference between the particle size of the recycled powder and the particle size of the new powder.

[0119] [Table 1]

[0120] As shown in Table 1, the particle size distribution of the recycled powder is nearly the same as that of the new powder for all of Samples No. 1 to No. 9. This shows that by pulverizing used dust cores, it is possible to pulverize them to a particle size similar to that of the soft magnetic powder used as the raw material.

[0121] The particle size distributions of the new powder and the recycled powder for sample No. 7 are shown in Figure 11. The horizontal axis of Figure 11 is particle diameter [μm], and the vertical axis is frequency [mass%]. The solid line graph shows the particle size distribution of the recycled powder, and the dashed line graph shows the particle size distribution of the new powder. As shown in the graph in Figure 11, the particle size distribution of the recycled powder and the particle size distribution of the new powder are nearly identical. This result also shows that by pulverizing a powder core, recycled powder with nearly the same particle size distribution as the new powder can be obtained.

[0122] [Test Example 2] Powder cores were manufactured using recycled powder and new powder, and the losses of these powder cores were evaluated.

[0123] Powder magnetic cores were manufactured using new powders of Samples No. 1 to No. 9, respectively, as described in Test Example 1, and powder magnetic cores were manufactured using recycled powders of Samples No. 1 to No. 9, respectively, as raw materials. The powder magnetic cores were manufactured as follows: 0.3 mass% of a lubricant was mixed with the raw materials. The lubricant was stearic acid amide. The lubricant particle diameter D50 was 25 μm. The raw materials were compression-molded to obtain a green compact. The molding pressure was approximately 850 MPa. The green compact was heat-treated. The heat treatment temperature was 600°C, and the holding time was 15 minutes. The manufactured powder magnetic cores were ring-shaped toroidal cores.

[0124] <Losses in powder magnetic cores> The loss of the powder core was measured. The loss of the powder core was measured as follows. A primary coil and a secondary coil were wound around the powder core. The primary coil had 300 turns, and the secondary coil had 30 turns. The iron loss when a current was passed through the primary coil to magnetize the powder core was measured using the secondary coil. The measured loss of the powder core was the iron loss W10 / 1k [W / kg] at a frequency of 1 kHz and a magnetic flux density of 1.0 T. Table 2 shows the iron loss W10 / 1k for each powder core using new powder and recycled powder for each sample. In Table 2, the value on the left side of the "Iron Loss W10 / 1k" column is the iron loss. The percentage value in the column to the right of "Iron Loss W10 / 1k" represents the ratio of the iron loss in the recycled powder to the iron loss in the new powder (100%). The density [g / cm] of each powder core was also measured. 3 The relative density [%] and relative magnetic permeability were calculated. These results are also shown in Table 2. The relative density is calculated based on the density of iron, 7.874 g / cm 3 " was calculated as the true density. The relative permeability was calculated as follows. Using a sample wound with a coil under the same conditions as in the loss measurement above, the DC BH characteristics were measured at a frequency of 10 Hz or less. The maximum permeability calculated from the initial magnetization curve was taken as the relative permeability.

[0125] [Table 2]

[0126] As shown in Table 2, the iron loss of the powder cores made with recycled powder generally increased compared to those made with new powder. In particular, the iron loss of sample No. 8, made with recycled powder, increased significantly by more than 300% compared to new powder. On the other hand, the iron loss of sample No. 9, made with recycled powder, increased very little compared to new powder. However, the relative permeability of sample No. 9 was low at approximately 130, indicating that its magnetic properties were inferior to those of the other samples. In contrast, the iron loss of the powder cores made with recycled powder in samples No. 1 to No. 7 increased by less than 50% compared to new powder, significantly reducing the increase in iron loss compared to sample No. 8. Furthermore, all of the powder cores made with recycled powder had a high relative permeability of 150 or higher. These results suggest that the increase in iron loss can be significantly reduced, particularly if the average thickness of the insulating film is 70 nm or greater.

[0127] <Evaluation of insulating films> The recycled powders of Samples No. 1 and No. 8 were observed using an SEM. The state of the insulating film on the surface of the soft magnetic particles was examined. The SEM magnification was 3000x. As shown in Figure 12, Sample No. 8 had cracks 3c in the insulating film 3, as well as many peeled areas 3f where the insulating film 3 had partially peeled off. The peeled areas 3f are indicated by hatching in Figure 12. On the other hand, Sample No. 1 had fine cracks in the insulating film 3, as shown in Figure 2. Sample No. 1 had many cracks 3c in the insulating film 3, but almost no major peeling of the insulating film 3 was observed. This suggests that the thicker the insulating film, the less likely it is to peel off when the powder core is crushed.

[0128] The length and width of cracks in the insulating film of the recycled powder of sample No. 1 were measured. SEM images of the surfaces of the two soft magnetic particles were obtained. Ten or more cracks were selected from the multiple cracks in each insulating film 3, and the length and width of each crack was measured using image analysis. The average length and width of the cracks were calculated. The aspect ratio was also calculated by dividing the average length of the cracks by the average width. The average length, average width, and aspect ratio of the cracks are shown below. Average crack length L = 1565 nm Average width of cracks: W = 100 nm Aspect ratio of the crack (L / W) = 15.6

[0129] Next, we investigated the state of the insulating film in the powder cores using the recycled powders of Sample No. 1 and Sample No. 8. We also investigated the state of the insulating film in the powder core using the new powder of Sample No. 8. The state of the insulating film was examined by observing the cross section of the powder core using a SEM at 1000x magnification. Figure 13 is a schematic enlarged cross section of the powder core using the new powder of Sample No. 8. As shown in Figure 13, in the powder core using the new powder, the entire surface of the soft magnetic particles 2 was covered with an insulating film 3. Figure 14 is a schematic enlarged cross section of the powder core using the recycled powder of Sample No. 1. As shown in Figure 14, although cracks 3c were present in the insulating film 3, almost no peeling of the insulating film 3 was observed. Figure 15 is a schematic enlarged cross section of the powder core using the recycled powder of Sample No. 8. As shown in Figure 15, there were many peeling areas 3f in the insulating film 3.

[0130] The reason why the iron loss of the powder core made with recycled powder in Sample No. 8 was significantly higher than that of the new powder is thought to be as follows. In the powder core made with new powder in Sample No. 8, as shown in Figure 13, the soft magnetic particles 2 are separated by the insulating film 3, maintaining electrical insulation between the soft magnetic particles 2. In contrast, in the powder core made with recycled powder in Sample No. 8, as shown in Figure 15, large peeling portions 3f are present in the insulating film 3, reducing electrical insulation between the soft magnetic particles 2. This is thought to be why the eddy current loss in the powder core made with recycled powder in Sample No. 8 was significantly higher. The reason why the increase in loss in the powder core made with recycled powder in Sample No. 1 was smaller than the increase in loss in the powder core made with recycled powder in Sample No. 8 is thought to be as follows. In the powder core made with recycled powder in Sample No. 1, as shown in Figure 14, cracks 3c are present in the insulating film 3, but electrical insulation between the soft magnetic particles 2 is maintained by the insulating film 3. Therefore, it is thought that the increase in eddy current loss was reduced in the recycled powder of sample No. 1.

[0131] [Test Example 3] The difference in hardness between new powder and recycled powder was investigated.

[0132] In Test Example 3, the frequency distribution of Vickers hardness was investigated for both new and recycled powders. For Sample No. 1 described in Test Example 1, the Vickers hardness of both new and recycled powders was measured using a micro-Vickers hardness tester. The soft magnetic particles contained 99% or more iron by mass. The micro-Vickers hardness tester used was a Mitutoyo HM-210. The frequency distribution of Vickers hardness was determined as follows: New and recycled powders were embedded in resin and polished to expose cross sections. More than 80 soft magnetic particles were randomly selected from each of the new and recycled powders, and the Vickers hardness of each soft magnetic particle was measured on its cross section to determine the frequency distribution of Vickers hardness. The frequency distributions of the Vickers hardness of the new and recycled powders are shown in Figure 16. Figure 16 shows the frequency distribution based on the number of particles. The horizontal axis of Fig. 16 is Vickers hardness [Hv] and the vertical axis is frequency [number of particles]. In Fig. 16, the hatched graph shows the frequency distribution of Vickers hardness of new powder, and the open graph shows the frequency distribution of Vickers hardness of recycled powder.

[0133] As shown in Figure 16, for new powder, the peak of the frequency distribution of Vickers hardness is in the range of 90 Hv to 110 Hv. On the other hand, for recycled powder, the peak of the frequency distribution of Vickers hardness is in the range of 115 Hv to 155 Hv. The peaks of the frequency distribution of Vickers hardness differ between new powder and recycled powder, and the Vickers hardness of the recycled powder is generally higher than that of new powder. One reason for the higher Vickers hardness of the recycled powder is thought to be that the soft magnetic particles are work-hardened when the powder core is crushed.

[0134] Based on the graph in FIG. 16, the frequency distribution of Vickers hardness of a mixed powder of recycled powder and virgin powder was calculated. FIG. 17 shows the frequency distribution of Vickers hardness of a mixed powder with a recycled powder fraction of 50%. The frequency distribution of Vickers hardness of the mixed powder shown in FIG. 17 has two peaks. The first peak is in the range of 115 Hv to 155 Hv, and the second peak is in the range of 90 Hv to 110 Hv. From this, if the frequency distribution of Vickers hardness has two peaks, including the first peak and the second peak, it is considered to be a mixed powder of recycled powder and virgin powder. If the recycled powder fraction is 35% or more and 75% or less, two peaks are likely to appear.

[0135] [Test Example 4] The oxides contained in the new and recycled powders were analyzed using X-ray photoelectron spectroscopy (XPS). The XPS device used was a Quantera SXM manufactured by ULVAC-PHI, Inc. The X-ray source was mono Al Kα radiation. The beam conditions were a beam diameter of 100 μm, a power of 100 W, and an acceleration voltage of 20 kV. The transmission energy was 55 eV (narrow scan) and 280 eV (wide scan).

[0136] For Sample No. 7 described in Test Example 1, the state of iron oxide contained in both the new powder and the recycled powder was analyzed. Figure 18 shows the Fe2p3 spectrum measured using an XPS device. The horizontal axis of Figure 18 represents binding energy [eV], and the vertical axis represents photoelectron intensity [c / s]. The solid line represents the Fe2p3 spectrum of the recycled powder, and the dashed line represents the Fe2p3 spectrum of the new powder.

[0137] As shown in Figure 18, the Fe2p3 spectrum of the new powder shows almost no peaks in the range of 710 eV to 715 eV, and no iron oxide is detected. On the other hand, the Fe2p3 spectrum of the recycled powder shows a peak in the range of 710 eV to 715 eV, and iron oxide is detected. The detected iron oxides include FeO, Fe2O3, Fe3O4, and Fe(OH)O. One possible reason for the detection of iron oxide in the recycled powder is that the heat treatment during the powder core manufacturing process causes the oxidation of the iron contained in the soft magnetic particles, resulting in the formation of iron oxide.

[0138] Next, we analyzed the state of silica contained in both the new and recycled powders of sample No. 7. Figure 19 shows the Si2p spectra measured using an XPS device. The horizontal axis of Figure 19 represents binding energy [eV], and the vertical axis represents photoelectron intensity [c / s]. The solid line represents the Si2p spectrum of the recycled powder, and the dashed line represents the Si2p spectrum of the new powder.

[0139] The silica peak is located in the Si2p range of 102 eV to 104 eV. As shown in Figure 19, the recycled powder has a peak at the silica position in the Si2p spectrum, and the peak intensity at the silica position is high, indicating that more silica is detected than in new powder. One possible reason why more silica is detected in the recycled powder is that the heat treatment during the powder core manufacturing process causes the oxidation of silicon contained in the insulating film to progress, increasing the amount of silica.

[0140] When the state of iron oxide contained in a mixed powder of recycled powder and new powder is analyzed by XPS, a peak is found in the range of 710 eV to 715 eV in the Fe2p3 spectrum, as shown in Figure 18. Furthermore, when the state of silica in the mixed powder is analyzed by XPS, two peaks, one due to the new powder and one due to the recycled powder, are detected in the range of 102 eV to 104 eV in the Si2p spectrum, as shown in Figure 19. Therefore, by analyzing the state of iron oxide by XPS, it is possible to determine whether recycled powder is present.

[0141] [Test Example 5] Other differences between virgin and recycled powders were investigated.

[0142] In Test Example 5, the average circularity, aspect ratio, and BET specific surface area of ​​the soft magnetic particles in the new powder and the recycled powder were examined.

[0143] For Sample No. 1 described in Test Example 1, the average circularity and aspect ratio of the soft magnetic particles in the new powder and recycled powder were investigated. Powder cores were manufactured using both the new powder and the recycled powder as raw materials. The powder cores were manufactured in the same manner as in Test Example 2. The cross-sections of the powder cores were observed using an SEM. The SEM magnification was 100x. Figure 20 is a schematic enlarged view of the cross-section of a powder core using the new powder of Sample No. 1. Figure 21 is a schematic enlarged view of the cross-section of a powder core using the recycled powder of Sample No. 1. In Figures 20 and 21, the black areas represent voids. The SEM images of the cross-sections of each powder core were analyzed to measure the circularity and aspect ratio of the soft magnetic particles 2. The image analysis software "ImageJ" was used for the image analysis. The average circularity was determined as follows: Circularity is calculated as 4πS / L where S is the area and L is the perimeter. 2The area and perimeter of 20 or more soft magnetic particles 2 were determined using ImageJ, and the circularity of each was calculated. The average circularity was obtained by calculating the average circularity value. The average aspect ratio was obtained by approximating the shape of the soft magnetic particles 2 to an ellipse using ImageJ, and then calculating the long and short diameters of the ellipse. The aspect ratio of each of 20 or more soft magnetic particles 2 was calculated by dividing the long diameter by the short diameter. The average aspect ratio was obtained by calculating the average aspect ratio. The average circularity of new powder of Sample No. 1 was 0.528, and the aspect ratio was 2.138. The average circularity of recycled powder of Sample No. 1 was 0.480, and the aspect ratio was 2.423.

[0144] Details of the ImageJ analysis procedure used in this study are as follows. The outline of each particle in the SEM observation image is drawn using a line (Windows Paint application). For the SEM image with the outline set, set the Threshold color in Color Threshold to B&W and create a binarized 8-bit image. Analyze the binarized image using Analyze Particles as a Tiff file with particles in white and boundaries in black. Check Pixel unticks to remove particles that are too small, such as particles smaller than 10 pixels.

[0145] Furthermore, for Samples No. 6 and No. 7 described in Test Example 1, the BET specific surface area of ​​each of the new powder and recycled powder was measured. The BET specific surface area measuring device used was a BELSORP-mini II manufactured by Microtrac-Bell Corporation. The BET specific surface area of ​​the new powder of Sample No. 6 was 0.014 m 2 / g, and the BET specific surface area of ​​the recycled powder is 0.032 m 2 The BET specific surface area of ​​the new powder of sample No. 7 was 0.035 m 2 / g, and the BET specific surface area of ​​the recycled powder is 0.520 m 2 / g.

[0146] The results of Test Example 5 reveal the following: The average circularity of the soft magnetic particles is smaller in the recycled powder than in the new powder. One possible reason for this is that the soft magnetic particles are plastically deformed by the pressure applied during the compaction of the powder core, resulting in a decrease in the circularity of the soft magnetic particles. From the comparison of the average circularity of the new powder and the average circularity of the recycled powder described above, if the average circularity of the soft magnetic particles is 0.5 or less, it is considered to be a recycled powder. The lower limit of the average circularity is, for example, 0.35 or more.

[0147] The aspect ratio of the soft magnetic particles is larger in recycled powder than in new powder. One possible reason for this is that the soft magnetic particles undergo plastic deformation when the powder core is pulverized, increasing the aspect ratio of the soft magnetic particles. Soft magnetic particles with an average circularity of 0.5 or less and an average aspect ratio of 2.1 or more are considered to be recycled powder. The upper limit of the average circularity is, for example, 3.0 or less.

[0148] When comparing the same samples, the BET specific surface area of ​​recycled powder is larger than that of new powder. This is thought to be due in part to cracks occurring in the insulating film when the powder core was crushed. When the average circularity of soft magnetic particles is 0.5 or less and the BET specific surface area is 0.1 m, 2 / g or more is considered to be recycled powder.

[0149] [Test Example 6] We estimated the amount of CO2 emissions generated during the production of powder magnetic cores.

[0150] In Test Example 6, the CO2 emissions when manufacturing 1 kg of powder magnetic cores were calculated for the following model case. The raw material for the soft magnetic particles was pure iron. The CO2 emissions per kWh of electricity was assumed to be 0.441 kg CO2 / kWh. This value was calculated using the CO2 emission coefficient for fiscal 2020 published by Tokyo Electric Power Company Energy Partner, Inc. on August 5, 2021 (see https: / / www.tepco.co.jp / ep / notice / news / 2021 / 1628675_8909.html). The CO2 emissions (kg CO2 / kg) were calculated for the case where new powder was used as the raw material for manufacturing powder magnetic cores, and for the case where recycled powder was used as the raw material for manufacturing powder magnetic cores.

[0151] CO2 emissions during the production of new powder = 0.96 kg CO2 / kg (A) The manufacturing process for new powder mainly involves transporting raw materials, melting and pulverizing the raw materials, and insulating treatment. "Raw material transportation" is the process of transporting raw materials to the factory. "Melting and pulverizing the raw materials" is the process of manufacturing pure iron powder. "Insulating treatment" is the process of coating the surface of pure iron powder with an insulating film.

[0152] CO2 emissions during the production of recycled powder = 0.032 kg CO2 / kg (B) The main steps in the manufacturing process for recycled powder include collecting powder cores and crushing and classifying them. "Collecting powder cores" involves collecting powder cores and transporting them to the factory. "Crushing and classifying powder cores" involves crushing and classifying the collected powder cores to obtain recycled powder.

[0153] CO2 emissions during the pressing process = 0.03 kg CO2 / kg (C) CO2 emissions during the heat treatment process = 0.14 kg CO2 / kg (D) CO2 emissions in subsequent processes = 0.03 kg CO2 / kg (E) Post-processing includes finishing the heat-treated powder magnetic cores, as well as packaging and shipping of the powder magnetic cores.

[0154] When manufacturing a dust core using new powder as the raw material, the CO2 emissions can be calculated by (A) + (C) + (D) + (E), which totals 1.16 kg CO2 / kg.

[0155] When manufacturing a dust core using recycled powder as the raw material, the CO2 emissions can be calculated by (B) + (C) + (D) + (E), which totals 0.232 kg CO2 / kg.

[0156] This calculation shows that when only recycled powder is used as a raw material, CO2 emissions can be reduced by approximately 80% compared to when only new powder is used as a raw material. Furthermore, this calculation also shows that when mixed powder is used as a raw material, CO2 emissions can be reduced by approximately 40% if the mass ratio of recycled powder is 50%. To reduce CO2 emissions by 10%, the mass ratio of recycled powder should be 12.5%.

[0157] [Note] This disclosure includes the following notes: (Appendix 1) a step of recovering used powder magnetic cores containing soft magnetic powder having insulating films on the surfaces of soft magnetic particles; pulverizing the used powder magnetic core to obtain recycled powder; and a step of compressing and molding the raw material containing the recycled powder, The amount of carbon dioxide emitted in the process from preparation of the raw materials to the compression molding is 10% to 80% less than when all of the raw materials are new powders. A method for manufacturing a powder magnetic core.

[0158] The method for producing a powder magnetic core in Appendix 1 can reduce CO2 emissions.

[0159] (Appendix 2) The soft magnetic particles are obtained by pulverizing a powder magnetic core containing a plurality of soft magnetic particles having an insulating film, and the soft magnetic particles are obtained by pulverizing a powder magnetic core containing a plurality of soft magnetic particles having an insulating film. Recycled powder.

[0160] (Appendix 3) A powder magnetic core obtained by compression molding raw materials containing the recycled powder described in Appendix 2.

[0161] The recycled powder in Supplementary Note 2 above may be the soft magnetic powder described in any one of (1) to (9) as an embodiment in the description of the embodiments of the present disclosure. Also, the recycled powder in Supplementary Note 2 may be the first soft magnetic powder contained in the mixed powder described in any one of (10) to (14) as an embodiment.

[0162] The powder magnetic core in Supplementary Note 3 above may be manufactured by further including the steps (18) to (26) described as embodiments in the description of the embodiments of the present disclosure. [Explanation of symbols]

[0163] 1. Soft magnetic powder (recycled powder) 1a First soft magnetic powder 1b Second soft magnetic powder 2 Soft magnetic particles 2a First soft magnetic particles 2b Second soft magnetic particles 3. Insulating film 3a First insulating film 3b Second insulating film 3f Peeling area, 3c Cracked area 5 Mixed powder 6a First coated particle 6b Second coated particle 10, 10a, 10b, 10c powder magnetic core 20 York 30 Teeth 100 Crusher 110 Grinding chamber, 111 Feeding port 120 rotary blade, 121 rotary shaft 130 Fixed blade 140 Screen, 141 Aperture 200 Motor stator (stator), 210 Coil 250 rotor, 260 magnet, 270 retaining plate, 300 motor 310 case, 320 plate, 330 rotating shaft, 340 bearing d: outer diameter, t: thickness

Claims

1. A process for recovering used compacted magnetic cores containing soft magnetic powder having an insulating film on the surface of soft magnetic particles, The process involves crushing the used compacted magnetic core to obtain recycled powder, A step of compressing and molding the raw material containing the recycled powder, The process includes a step of heat-treating the compacted powder obtained in the compression molding step, The average particle diameter of the soft magnetic particles is 20 μm or more and 400 μm or less. The average thickness of the insulating film is 40 nm or more and 500 nm or less. A method for manufacturing compacted magnetic cores.

2. Prior to the compression molding step, the process includes mixing a powdered lubricant into the raw material. The lubricant is a fatty acid amide or a metal soap. The particle size of the lubricant is 1 μm or more and 30 μm or less. The method for producing a compacted magnetic core according to claim 1, wherein the mass ratio of the lubricant to the total mass of the raw materials is 0.1% by mass or more and 1.0% by mass or less.

3. The method for producing a powdered magnetic core according to claim 1 or 2, wherein the step of obtaining the recycled powder includes the step of classifying the pulverized material obtained by crushing the used powdered magnetic core using a sieve, and the step of separating the recycled powder using a magnet.

4. In the process of obtaining the recycled powder, the used compacted magnetic core is crushed using a crusher equipped with a screen. The screen has a plurality of openings, The method for manufacturing a compacted magnetic core according to claim 1 or claim 2, wherein the diameter of each of the plurality of openings is 1 mm or more and 15 mm or less.

5. In the compression molding process, the compression molding of the raw material is performed by filling the raw material into a mold and compressing it to form the compacted powder. The method for manufacturing a powdered magnetic core according to claim 1 or claim 2, wherein the temperature of the mold during compression is 30°C or higher and 100°C or lower.

6. The recycled powder has a plurality of cracks on the surface of the insulating film, The average width of the crack is three times or less the average thickness of the insulating film. The method for manufacturing a compacted magnetic core according to claim 1 or claim 2, wherein the value obtained by dividing the average length of the cracked portion by the average width of the cracked portion is 2 or more.

7. Prior to the compression molding step, the process includes mixing new soft magnetic powder with the recycled powder. The method for producing a compacted magnetic core according to claim 1 or claim 2, wherein the raw material is a mixed powder of the recycled powder and the new soft magnetic powder.

8. The method for manufacturing a compacted magnetic core according to claim 7, wherein the mass ratio of the recycled powder to the total mass of the recycled powder and the new soft magnetic powder is 1% by mass or more and less than 100% by mass.

9. It comprises a plurality of soft magnetic particles having an insulating film, The insulating film has an insulating layer containing a phosphate, silica, or magnesia. The average particle diameter of the soft magnetic particles is 20 μm or more and 400 μm or less. The average thickness of the insulating film is 40 nm or more and 500 nm or less. The average circularity of the soft magnetic particles is 0.35 or more and 0.5 or less. Soft magnetic powder.

10. The soft magnetic powder according to claim 9, wherein the average aspect ratio of the soft magnetic particles is 2.1 or more and 3.0 or less.

11. BET specific surface area is 0.1 m² ２ / g or more 1.0m ２ The soft magnetic powder according to claim 9, wherein the amount is less than or equal to / g.

12. It comprises a plurality of soft magnetic particles having an insulating film, The insulating film has an insulating layer containing a phosphate, silica, or magnesia. The insulating film has a plurality of cracks on its surface, The average width of the crack is three times or less the average thickness of the insulating film. The value obtained by dividing the average length of the crack by the average width of the crack is 2 or more. Soft magnetic powder.

13. It comprises a plurality of soft magnetic particles having an insulating film, The insulating film has an insulating layer containing a phosphate, silica, or magnesia. The composition of the soft magnetic particles is such that the iron content is 99% by mass or more. The peak in the frequency distribution of Vickers hardness is within the range of 115 Hv to 155 Hv. Soft magnetic powder.

14. It comprises a plurality of soft magnetic particles having an insulating film, The insulating film has an insulating layer containing a phosphate, silica, or magnesia. The aforementioned soft magnetic particles contain iron, In the Fe2p3 spectrum measured by X-ray photoelectron spectroscopy, a peak is found in the range of 710 eV to 715 eV. Soft magnetic powder.

15. It comprises a plurality of soft magnetic particles having an insulating film, The insulating film has an insulating layer containing a phosphate, silica, or magnesia. The insulating film contains silicon, In the Si2p spectrum measured by X-ray photoelectron spectroscopy, a silica peak is observed. Soft magnetic powder.

16. The composition of the soft magnetic particles is such that the iron content is 99% by mass or more. The soft magnetic powder according to any one of claims 9 to 12, 14, and 15, wherein the peak of the frequency distribution of Vickers hardness is in the range of 115 Hv to 155 Hv.

17. It comprises a first soft magnetic powder and a second soft magnetic powder, The first soft magnetic powder consists of a plurality of first soft magnetic particles having a first insulating film, The surface of the first insulating film has a plurality of cracks, The second soft magnetic powder comprises a plurality of second soft magnetic particles having a second insulating film. The surface of the second insulating film is free of cracks. Mixed powder.

18. It comprises a first soft magnetic powder and a second soft magnetic powder, The first soft magnetic powder consists of a plurality of first soft magnetic particles having a first insulating film, The second soft magnetic powder comprises a plurality of second soft magnetic particles having a second insulating film. The frequency distribution of Vickers hardness has two peaks, including a first peak and a second peak. Mixed powder.

19. The composition of the first soft magnetic particles and the composition of the second soft magnetic particles each have an iron content of 99% by mass or more. The first peak is within the range of 115 Hv to 155 Hv, The mixed powder according to claim 18, wherein the second peak is in the range of 90 Hv to 110 Hv.

20. The mixed powder according to claim 17 or claim 18, wherein the mass ratio of the first soft magnetic powder to the total mass of the first soft magnetic powder and the second soft magnetic powder is 1% by mass or more and less than 100% by mass.

21. Contains a powdered lubricant, The lubricant is a fatty acid amide or a metal soap. The particle size of the lubricant is 1 μm or more and 30 μm or less. The mixed powder according to claim 17 or claim 18, wherein the mass ratio of the lubricant to the total mass of the mixed powder is 0.1% by mass or more and 1.0% by mass or less.

22. A soft magnetic powder according to any one of claims 9 to 15, or a mixed powder according to claim 17 or 18, Powder magnetic core.

23. The powdered magnetic core and coil as described in claim 22, Motor stator.

24. A motor comprising a stator and rotor as described in claim 23, Motor.

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