Compacted magnetic core, inductor, and method for manufacturing compacted magnetic core

Abstract

To provide a powder core, an inductor, and a method for manufacturing a powder core that can achieve high magnetic permeability and low loss. [Solution] The method for manufacturing a compacted magnetic core according to the present invention comprises the steps of: mixing magnetic powder and a thermosetting resin to granulate; compressing and molding the granules after granulation; and heat-treating the molded body after compression molding. The magnetic powder includes a first amorphous powder and a second amorphous powder, the mixing ratio of the first amorphous powder and the second amorphous powder is 30:70 to 95:5 by mass ratio, the average particle size of the first amorphous powder is larger than the average particle size of the second amorphous powder, the first crystallization start temperature of the first amorphous powder is lower than the first crystallization start temperature of the second amorphous powder, and nanocrystals are precipitated from at least the first amorphous powder during the heat treatment step.

Description

[Technical Field]

[0001] This disclosure relates to a compacted magnetic core, an inductor, and a method for manufacturing a compacted magnetic core. [Background technology]

[0002] In recent years, inductors have been used in a variety of electronic devices. In particular, inductors used in electronic devices such as personal computers are required to be miniaturized and to exhibit high inductance characteristics even when large currents are passed through them. Patent Document 1 discloses a method for manufacturing a compacted amorphous soft magnetic alloy that exhibits little decrease in magnetic permeability in the high-frequency range. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-175222 [Overview of the project] [Problems that the invention aims to solve]

[0004] As mentioned above, inductors are required to be miniaturized while also exhibiting high inductance characteristics even when large currents are passed through them. Therefore, the use of amorphous alloy powders and nanocrystalline alloy powders, which exhibit low loss characteristics, as magnetic materials for inductors has attracted attention. However, because these powders are hard, it is difficult to increase the packing density and thus difficult to increase the magnetic permeability.

[0005] In view of the above issues, the purpose of this disclosure is to provide a powder core, an inductor, and a method for manufacturing a powder core that can achieve high magnetic permeability and low loss. [Means for solving the problem]

[0006] The method for manufacturing a compressed powder magnetic core according to one aspect of the present disclosure includes a step of mixing a magnetic powder and a thermosetting resin and granulating, a step of compression-molding the granules after granulation, and a step of heat-treating the molded body after compression-molding. The magnetic powder includes a first amorphous powder and a second amorphous powder, the mixing ratio of the first amorphous powder and the second amorphous powder is 30:70 to 95:5 in terms of mass ratio, the average particle diameter d1 of the first amorphous powder is larger than the average particle diameter d2 of the second amorphous powder, the relationship between the first crystallization start temperature T1a of the first amorphous powder and the first crystallization start temperature T2a of the second amorphous powder satisfies T1a < T2a, and in the step of heat-treating, at least nanocrystals are precipitated from the first amorphous powder.

[0007] In the method for manufacturing a compressed powder magnetic core described above, the heat treatment temperature Th in the step of heat-treating may satisfy T1a - 50°C ≤ Th < T1b.

[0008] In the method for manufacturing a compressed powder magnetic core described above, the relationship between the second crystallization start temperature T1b of the first amorphous powder and the first crystallization start temperature T2a of the second amorphous powder may satisfy T2a < T1b.

[0009] In the method for manufacturing a compressed powder magnetic core described above, the ratio of the average particle diameter d1 of the first amorphous powder to the average particle diameter d2 of the second amorphous powder may satisfy 2 ≤ d1 / d2 ≤ 20.

[0010] In the method for manufacturing a compressed powder magnetic core described above, the mixing ratio of the first amorphous powder and the second amorphous powder may be 60:40 to 90:10 in terms of mass ratio.

[0011] In the method for manufacturing a compressed powder magnetic core described above, the difference between the first crystallization start temperature T1a of the first amorphous powder and the first crystallization start temperature T2a of the second amorphous powder may be 15°C or more.

[0012] In the method for manufacturing a compressed powder magnetic core described above, the amount of the thermosetting resin with respect to the total amount of the magnetic powder may be 0.2 mass% or more and 3.0 mass% or less in terms of mass ratio.

[0013] In the above method for manufacturing a compacted powder core, the first amorphous powder and the second amorphous powder may each be any one of an Fe—Si—B—P—Cu—Cr based alloy, an Fe—B—P—Cu—Cr based alloy, and an Fe—Si—B—Nb—Cu based alloy.

[0014] In the above method for manufacturing a compacted powder core, the composition formula of the first amorphous powder is, in terms of molar ratio, Fe , , ,

[0017] , ,

[0018] , , ,

[0016] Si b1 B c1 P x1 Cu y1 Cr z1 (where 80 at% ≤ a1 ≤ 90 at%, 0 at% ≤ b1 ≤ 3 at%, 3 at% ≤ c1 ≤ 18 at%, 0 at% ≤ x1 ≤ 17 at%, 0 at% ≤ y1 ≤ 1.2 at%, 0 at% ≤ z1 ≤ 3 at%), and the composition formula of the second amorphous powder is, in terms of molar ratio, Fe a2 Si b2 B c2 P x2 Cu y2 Cr z2 (where 75.4 at% ≤ a2 ≤ 85 at%, 0 at% ≤ b2 ≤ 9 at%, 4 at% ≤ c2 ≤ 12 at%, 4.5 at% ≤ x2 ≤ 12 at%, 0.3 at% ≤ y2 ≤ 1.2 at%, 0 at% ≤ z2 ≤ 3 at%).

[0015] In the above method for manufacturing a compacted powder core, the compression molding step may include a step of raising the temperature to a molding temperature of 200°C or lower.

[0016] In the above method for manufacturing a compacted powder core, in the heat treatment step, the nanocrystals may be precipitated so that the crystallinity is 40% or less. <00​​​​​The above-described method for manufacturing compacted magnetic cores may include a step in which the granulation step is performed by first forming an oxide film on the surface of the magnetic powder and then mixing it with a thermosetting resin.

[0019] The above-described method for manufacturing a compacted magnetic core further includes a third powder having a different composition from the second amorphous powder, wherein the average particle size d3 of the third powder is smaller than the average particle size d2 of the second amorphous powder, and the amount of the third powder relative to the total amount of the magnetic powder may be 30% by mass or less.

[0020] In the above-described method for manufacturing a compacted magnetic core, the average particle size d3 of the third powder may be 5 μm or less.

[0021] In the above-described method for manufacturing a compacted magnetic core, the third powder may be a crystalline powder.

[0022] In the above-described method for manufacturing a compacted magnetic core, the nanocrystals may be precipitated in the heat treatment step such that the degree of crystallinity is 1% or more and 70% or less.

[0023] A compacted magnetic core according to one aspect of this disclosure may be manufactured by any of the manufacturing methods described above.

[0024] A compacted magnetic core according to one aspect of the present disclosure comprises first and second particles which are at least partially nanocrystalline, the mixing ratio of the first particles to the second particles is 30:70 to 95:5 by mass ratio, the average particle size D1 of the first particles is greater than the average particle size D2 of the second particles, and the degree of crystallinity of the first particles is greater than the degree of crystallinity of the second particles.

[0025] In the compacted magnetic core described above, the second particle adjacent to the first particle may have a higher degree of crystallinity than the second particle not adjacent to the first particle.

[0026] The compacted magnetic core described above may have a crystallinity of 40% or less.

[0027] The compacted magnetic core described above further includes third particles having a different composition from the second particles, wherein the average particle size D3 of the third particles is smaller than the average particle size D2 of the second particles, and the amount of the third particles may be 30% by mass or less of the total amount of the first to third particles.

[0028] The compacted magnetic core described above may have an average particle size D3 of the third particles of 5 μm or less.

[0029] In the aforementioned compacted magnetic core, the third particle may be crystalline.

[0030] The powdered magnetic core described above may have a crystallinity of 1% to 70%.

[0031] An inductor according to one aspect of the present disclosure comprises the above-described powder core and coil. [Effects of the Invention]

[0032] This disclosure provides a powder core, an inductor, and a method for manufacturing a powder core that can achieve high permeability and low loss. [Brief explanation of the drawing]

[0033] [Figure 1] This is a perspective view showing an example of an inductor according to an embodiment. [Figure 2] This is an example of a SEM image of a cross-section of a compacted magnetic core according to the embodiment. [Figure 3] This is a flowchart illustrating the method for manufacturing a compacted magnetic core according to the embodiment. [Figure 4] These are the DSC curves obtained by differential scanning calorimetry (DSC) performed on the first amorphous powder and the second amorphous powder used in Experiment 1, under conditions of heating from room temperature at a rate of 10°C / min. [Modes for carrying out the invention]

[0034] Specific embodiments applying this disclosure will be described in detail below with reference to the drawings. However, this disclosure is not limited to the following embodiments. Also, for clarity, the following description and drawings have been simplified as appropriate. Furthermore, the multiple configuration examples described below can be implemented independently or in combination as appropriate. These multiple configuration examples have novel features that differ from each other. Therefore, these multiple configuration examples contribute to solving different purposes or problems and contribute to producing different effects.

[0035] <Inductor> The present disclosure will be described below with reference to the drawings. Figure 1 is a perspective view showing an example of an inductor according to this embodiment. As shown in Figure 1, the inductor 1 according to this embodiment comprises a powder core 10_1, 10_2 and a coil 13. The powder core 10_1 has a cavity that penetrates vertically through its central part and is arranged to surround the outside of the coil 13. The powder core 10_2 is provided inside the coil 13 and is arranged in the recess of the coil 13, which has a U-shaped cross-section.

[0036] For example, the inductor 1 shown in Figure 1 can be formed by placing a powdered magnetic core 10_2 in a recess of the coil 13, and then press-fitting a powdered magnetic core 10_1 from above. This allows for the formation of an inductor 1 in which the coil 13 is surrounded by powdered magnetic cores 10_1 and 10_2. In this specification, powdered magnetic cores 10_1 and 10_2 are collectively referred to as powdered magnetic core 10. Furthermore, the configuration of the inductor 1 shown in Figure 1 is just one example, and the powdered magnetic core 10 according to this embodiment may be used in inductors with configurations other than those shown in Figure 1. For example, the powdered magnetic core according to this embodiment may be a ring or annular shaped powdered magnetic core, or it may be a toroidal shaped inductor in which a coil is wound around the powdered magnetic core. The powdered magnetic core according to this embodiment will be described in detail below.

[0037] <Powder magnetic core> The compacted magnetic core according to this embodiment is a compacted magnetic core in which magnetic powder is bound via a binder layer. The magnetic powder used in the compacted magnetic core according to this embodiment is a soft magnetic powder containing iron, and the magnetic powder includes first particles and second particles. The average particle size D1 of the first particles is larger than the average particle size D2 of the second particles, and the mixing ratio of the first particles and the second particles is 30:70 to 95:5 by mass ratio. The first particles are the first amorphous powder described later, or particles obtained by nanocrystallizing at least a portion of the first amorphous powder. The second particles are the second amorphous powder described later, or particles obtained by nanocrystallizing at least a portion of the second amorphous powder. Furthermore, at least a portion of the first particles or the second particles is nanocrystallized. By having such a configuration, it is possible to provide a compacted magnetic core that can achieve miniaturization while achieving high magnetic permeability and low loss.

[0038] In the compacted magnetic core according to this embodiment, the average particle size D1 of the first particles is, for example, 10 μm or more and 50 μm or less, preferably 20 μm or more and 40 μm or less. The average particle size D2 of the second particles is, for example, 1 μm or more and 10 μm or less, preferably 2 μm or more and 6 μm or less. In this disclosure, the average particle size is the median diameter D50, and the average particle sizes D1 and D2 can be measured, for example, from a scanning electron microscope (SEM) image of the cross-section of the compacted magnetic core or using laser diffraction / scattering.

[0039] Figure 2 shows an example of a SEM image of a cross-section of a compacted magnetic core according to this embodiment. The compacted magnetic core shown in Figure 2 is a toroidal-shaped compacted magnetic core manufactured by the manufacturing method described later. As shown in Figure 2, the compacted magnetic core contains first particles 101 and second particles 102. In the example in Figure 2, the average particle size D1 of the first particles 101 is 30 μm, and the average particle size D2 of the second particles 102 is 3 μm. Because the small second particles 102 adequately fill the gaps between the large first particles 101, the compacted magnetic core has a high packing efficiency.

[0040] In this embodiment, the iron loss of the compacted magnetic core at 100 kHz and 100 mT is 3000 kW / m 3 Preferably, 2000 kW / m3 More preferably, 1500 kW / m 3 Further, more preferably 1000 kW / m 3 More preferably, 600 kW / m 3 The following applies:

[0041] In this embodiment, the iron loss of the compacted magnetic core at 1 MHz and 50 mT is 4000 kW / m 3 Preferably, 3000 kW / m 3 More specifically, 2000 kW / m 3 More preferably, 1500 kW / m 3 More preferably, 1200 kW / m 3 The following applies:

[0042] In this embodiment, the permeability μ' of the compacted magnetic core is 42 or higher, preferably 45 or higher, more preferably 50 or higher, and even more preferably 55 or higher. In this specification, unless otherwise specified, "permeability" refers to the value of the real component of the relative permeability.

[0043] In this embodiment, the crystallinity of the compacted magnetic core is 50% or less, more preferably 40% or less, even more preferably 35% or less, and particularly preferably 30% or less. Furthermore, the crystallinity of the compacted magnetic core is 1% or more, more preferably 3% or more, and even more preferably 5% or more. The crystallinity can be calculated, for example, by analyzing the measurement results of X-ray diffraction (XRD) using the whole powder pattern resolution method (WPPD). Compacted magnetic cores that satisfy the above crystallinity conditions exhibit high magnetic permeability and low iron loss.

[0044] The magnetic powder may further contain, in addition to the first and second particles, third particles having a different composition from the second particles. The average particle size D3 of the third particles is smaller than the average particle size D2 of the second particles, preferably 5 μm or less, more preferably 0.1 μm to 5 μm, and even more preferably 0.5 μm to 4 μm. The amount of the third particles is 30% by mass or less, preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, relative to the total amount of magnetic powder. The third particles are also preferably crystalline.

[0045] When the magnetic powder contains the third particle described above, the degree of crystallinity of the compacted magnetic core may be 70% or less, 60% or less, or 55% or less. A compacted magnetic core containing the third particle described above exhibits high permeability and low iron loss if the degree of crystallinity is 70% or less.

[0046] <Manufacturing method for compressed porcelain core> Next, the method for manufacturing a powdered magnetic core according to this embodiment will be described. Figure 3 is a flowchart illustrating the method for manufacturing a powdered magnetic core according to this embodiment.

[0047] As shown in Figure 3, when manufacturing a compacted magnetic core, the materials are first prepared (step S1). The materials for the compacted magnetic core according to this embodiment include magnetic powder and a binder. The magnetic powder includes a first amorphous powder and a second amorphous powder of soft magnetic properties containing iron, and the binder includes a thermosetting resin.

[0048] As the first amorphous powder and the second amorphous powder, powders with an alloy composition in which nanocrystalline phases of the α-Fe phase on the order of nanometers precipitate in the amorphous phase by appropriate heat treatment are used. For example, amorphous powder can be obtained by rapidly cooling and solidifying a suitable alloy molten metal by atomization to produce powder. As such alloys, Fe-Si-BPC-Cu, Fe-Si-B-Cu-Cr, Fe-Si-BP-Cu-Cr, Fe-BPC-Cu, Fe-Si-BP-Cu, Fe-BP-Cu, and Fe-Si-B-Nb-Cu systems can be used. The amorphous powder used is not particularly limited, but in this embodiment in particular, it is preferable to use Fe-BP-Cu alloy, Fe-Si-BP-Cu-Cr alloy, Fe-BP-Cu-Cr alloy, or Fe-Si-B-Nb-Cu alloy material.

[0049] In particular, the compositional formula of the first amorphous powder is expressed in terms of molar ratio of Fe a1 Si b1 B c1 P x1 Cu y1 Cr z1 When expressed as such, it is preferable that the following conditions are met: 80at%≦a1≦90at%, 0at%≦b1≦3at%, 3at%≦c1≦18at%, 0at%≦x1≦17at%, 0at%≦y1≦1.2at%, and 0at%≦z1≦3at%. Furthermore, the compositional formula of the second amorphous powder is expressed in terms of molar ratio as Fe a2 Si b2 B c2 P x2 Cu y2 Cr z2 When expressed as such, it is preferable that the following conditions are met: 75.4at%≦a2≦85at%, 0at%≦b2≦9at%, 4at%≦c2≦12at%, 4.5at%≦x2≦12at%, 0.3at%≦y2≦1.2at%, and 0at%≦z2≦3at%.

[0050] Furthermore, the method for producing amorphous powder is not limited to atomization; for example, powder obtained by crushing rapidly cooled thin strips may be used. In addition, among alloy compositions that become amorphous upon rapid cooling of the molten metal, metallic glass alloy powder having a glass transition temperature lower than the crystallization temperature of the amorphous phase may be used. Moreover, in the above alloy, 3 at% or less of Fe may be substituted with one or more elements from the group consisting of Co, Ni, Zn, Zr, Hf, Mo, Ta, W, Ag, Au, Pd, K, Ca, Mg, Sn, Ti, V, Mn, Al, S, C, O, N, Bi, and rare earth elements.

[0051] The first amorphous powder and the second amorphous powder can be produced by various manufacturing methods. For example, amorphous magnetic powder can be obtained by vacuum melting the raw materials for magnetic powder and then simultaneously pulverizing and rapidly cooling them using the water atomization method. The magnetic powder obtained in this way may be classified as needed to remove abnormally coarse powder particles.

[0052] The average particle size d1 of the first amorphous powder is greater than the average particle size d2 of the second amorphous powder. The ratio of the average particle size d1 of the first amorphous powder to the average particle size d2 of the second amorphous powder is preferably 2 ≤ d1 / d2 ≤ 20. The average particle size ratio d1 / d2 is more preferably 4 or greater, and even more preferably 6 or greater. The upper limit is more preferably 15 or less, and even more preferably 10 or less. When the average particle size ratio is in the range of 2 ≤ d1 / d2 ≤ 20, the second amorphous powder adequately fills the gaps in the first amorphous powder, thereby improving the packing efficiency of the compacted magnetic core.

[0053] For example, the average particle size d1 of the first amorphous powder is 10 μm or more and 50 μm or less, preferably 20 μm or more and 40 μm or less. The average particle size d2 of the second amorphous powder is 1 μm or more and 10 μm or less, preferably 2 μm or more and 6 μm or less. The average particle sizes d1 and d2 can be values ​​measured, for example, using laser diffraction / scattering.

[0054] The mixing ratio of the first amorphous powder and the second amorphous powder is 30:70 to 95:5 in terms of mass ratio, preferably 50:50 to 90:10, more preferably 60:40 to 90:10, still more preferably 60:40 to 80:20, and most preferably 70:30 to 80:20. By setting the mixing ratio of the first amorphous powder and the second amorphous powder to 30:70 to 95:5, the second amorphous powder appropriately fills the gaps between the first amorphous powders, and the packing ratio of the compacted magnetic core increases.

[0055] Also, the relationship between the first crystallization start temperature T1a of the first amorphous powder and the first crystallization start temperature T2a of the second amorphous powder satisfies T1a < T2a. The difference between T1a and T2a is preferably 15°C or more, more preferably 30°C or more. When the difference between T1a and T2a is 15°C or more, there is a wide range of temperature conditions under which only the first amorphous powder can be selectively nanocrystallized. That is, in the heat treatment process described later, it becomes easier to adjust the progress of nanocrystallization of the first amorphous powder and the second amorphous powder. In the present disclosure, in the DSC curve obtained by differential scanning calorimetry (DSC) performed under the condition of heating from room temperature at 10°C / min, the lowest temperature among the temperatures indicated by the intersection of the tangent line at the maximum slope on the low temperature side of the exothermic peak and the baseline is defined as the first crystallization start temperature. In the present invention, the exothermic peak of the first crystallization start temperature is a peak associated with the precipitation of bccFe (α-Fe phase) crystals.

[0056] In the present embodiment, the particle shapes of the first amorphous powder and the second amorphous powder are preferably closer to spherical. When an insulating film such as an oxide film is formed on the particle surface, if the sphericity of the particles is low, protrusions will occur on the particle surface, and when a molding pressure is applied, the stress from the surrounding particles will concentrate on the protrusions and the coating will be broken, and the insulation cannot be sufficiently maintained. As a result, the magnetic properties (especially loss) of the obtained compacted magnetic core may deteriorate. The sphericity of the particles can be controlled within a suitable range by adjusting the manufacturing conditions of the magnetic powder, for example, in the case of the water atomization method, the amount and water pressure of the high-pressure water jet used for atomization, the temperature and supply rate of the molten raw material, etc. Specific manufacturing conditions vary depending on the composition of the magnetic powder to be manufactured and the desired productivity.

[0057] The binder in the compacted magnetic core according to this embodiment constitutes a binder layer and has the function of binding the magnetic powders together. The binder includes a resin material. Preferably, the resin material is one that softens at around 100°C and acts as an insulating material and binder after compression molding. Furthermore, it is preferable to use a resin material that does not easily decompose during the heat treatment process of the molded body. Specifically, at least one selected from the group consisting of silicone resin, polyurethane resin, phenolic resin, polyimide resin, and epoxy resin can be used as the resin material. The mass ratio of the resin material to the total amount of magnetic powder is 0.2% by mass or more and 3.0% by mass or less, preferably 0.4% by mass or more and 2.0% by mass or less. By setting the mass ratio of the resin material to 0.2% by mass or more, the binding between magnetic powders is promoted and the strength of the compacted magnetic core can be increased. Also, by setting the mass ratio of the resin material to 3.0% by mass or less, the adhesion of resin to the molding die is reduced and manufacturing efficiency is increased, and the saturation magnetic flux density and permeability can be increased by relatively increasing the mass ratio of magnetic powder.

[0058] Furthermore, the binder may also contain low-melting-point glass. In this embodiment, the total amount of low-melting-point glass and resin material is less than 10% by volume relative to the magnetic powder of the compacted magnetic core. The low-melting-point glass can be phosphate-based, tin-phosphate-based, borate-based, silicate-based, borosilicate-based, barium silicate-based, bismuth oxide-based, germanate-based, vanadate-based, aluminophosphate-based, and telluride-based glass. It is preferable to use a material that improves insulation and bonding properties for the low-melting-point glass. In particular, in this disclosure, it is preferable to use a phosphate-based or tin-phosphate-based low-melting-point glass. The volume ratio of the low-melting-point glass to the magnetic powder is 0.5% by volume or more and 6% by volume or less, preferably 1.25% by volume or more and 3% by volume or less.

[0059] Next, the magnetic powder is coated with the resin material described above and granulated (Step S2). When coating (granulating) with the resin material, methods such as rolling granulation, spray drying, and agitation granulation can be used. Specifically, a resin layer can be formed on the surface of the magnetic powder by mixing the resin material dissolved in an organic solvent such as ethanol with the magnetic powder and drying it.

[0060] Next, the granulated material is compressed and molded (step S3). For example, compression molding can be performed by placing the granulated material into a mold, applying pressure, and then raising the temperature of the molded body to a predetermined temperature (e.g., 100-200°C) without further pressure to cure the resin.

[0061] The pressurization conditions are, for example, 5 ton / cm² at room temperature. 2 More than 15ton / cm 2 The following is possible:

[0062] In step S3, the mold into which the granules are introduced may be preheated to a predetermined preheating temperature. The preheating temperature can be, for example, 60°C to 200°C. In other words, it is preferable that the molding temperature be 60°C to 200°C. Setting the molding temperature to 60°C or higher promotes the deformation of the resin material and improves the fluidity of the powder. Therefore, even when the hardness of the first amorphous powder and the second amorphous powder is high and the compression moldability is poor, or when the amount of resin is small, the materials can be efficiently bound together. In addition, the density of the compacted magnetic core is improved, and excessive stress between the powders during compression molding is suppressed, thus preventing the deterioration of core loss. Furthermore, setting the molding temperature to 200°C or lower prevents deterioration of moldability due to a decrease in viscosity associated with the volatilization of the resin solvent and the start of the curing reaction, and also reduces the adhesion of resin to the molding die, thereby improving manufacturing efficiency.

[0063] Next, the molded body after compression molding is heat-treated (step S4). For example, the heat treatment is carried out by heating the molded body after compression molding at a heat treatment temperature Th in an inert atmosphere such as an Ar atmosphere using an image furnace or the like. The heat treatment temperature Th is set to a temperature at which nanocrystals are precipitated from at least the first amorphous powder in the molded body. That is, in the heat treatment step, nanocrystals are precipitated from only the first amorphous powder or from the first amorphous powder and the second amorphous powder. For example, the heat treatment temperature Th can be set to a temperature of T1a or higher. In this case, nanocrystals can be precipitated from the first amorphous powder. Even when the heat treatment temperature Th is set to a temperature of (T1a - 50°C) or higher, a part of the first amorphous powder can be nanocrystallized.

[0064] The heat treatment temperature Th is preferably a temperature that satisfies T1a - 50°C ≤ Th < T1b. When heat treatment is performed at a temperature that satisfies the above conditions, the heat generated during the nanocrystallization of the first amorphous powder is conducted and diffused to the surrounding particles (i.e., the second amorphous powder) where nanocrystallization is difficult to occur. Therefore, the nanocrystallization of the first amorphous powder can be promoted while suppressing overheating. For this reason, homogeneous nanocrystals can be stably precipitated while suppressing the precipitation of compound phases other than the α-Fe phase, and a dust core with high magnetic permeability and low iron loss can be obtained.

[0065] Note that the heat treatment temperature Th preferably satisfies T1a ≤ Th. When heat treatment is performed at a temperature of T1a or higher, the nanocrystallization of the first amorphous powder can be efficiently promoted, so that the dust core can be manufactured more quickly.

[0066] Furthermore, the heat treatment temperature Th is preferably a temperature that satisfies T2a - 50°C ≤ Th. When heat treatment is performed at a temperature of (T2a - 50°C) or higher, the second amorphous powder receives the heat of crystallization of the first amorphous powder, and nanocrystallization proceeds efficiently. Therefore, the heat treatment can be performed in a short time, and a dust core with high magnetic permeability and low iron loss can be stably obtained in a shorter time.

[0067] Note that the relationship between the second crystallization start temperature T1b of the first amorphous powder and the first crystallization start temperature T2a of the second amorphous powder preferably satisfies T2a - 50°C < T1b, and more preferably satisfies T2a < T1b. If T1b is less than or equal to (T2a - 50°C), there is no temperature that satisfies Th < T1b and T2a - 50°C ≤ Th. Therefore, there is no temperature condition that can efficiently nanocrystallize the second amorphous powder while preventing overheating of the first amorphous powder. On the other hand, when T2a < T1b is satisfied, since the temperature conditions that satisfy Th < T1b and T2a - 50°C ≤ Th are wide, it becomes easy to perform heat treatment efficiently.

[0068] Also, the heat treatment temperature Th preferably satisfies Th < T2a. When heat treatment is performed at T2a or higher, the nanocrystallization of the second amorphous powder is promoted more than necessary. At this time, due to the heat generated accompanying the nanocrystallization of the second amorphous powder, there is a possibility that the first amorphous powder may be overheated. Therefore, there is a possibility of causing excessive nanocrystallization of the first amorphous powder and precipitation of a compound phase other than the α-Fe phase. By setting the heat treatment temperature Th to be less than T2a, a dust core with high magnetic permeability and low iron loss can be obtained more stably.

[0069] In the present disclosure, in the DSC curve obtained by differential scanning calorimetry (DSC) performed under the condition of heating from room temperature at 10°C / min, the second lowest temperature among the temperatures indicated by the intersection of the tangent line at the maximum slope on the low temperature side of the exothermic peak and the baseline is defined as the second crystallization start temperature.

[0070] The compressed powder core manufactured by the above method includes first particles in which at least a part of the first amorphous powder is nanocrystallized and second particles in which at least a part of the second amorphous powder is nanocrystallized. Since the nanocrystallization of the first amorphous powder starts at a lower temperature than that of the second amorphous powder, the crystallinity of the first particles is greater than that of the second particles. Also, the second particles adjacent to the first particles have a higher crystallinity than the second particles not adjacent to the first particles. This is because the second amorphous powder adjacent to the first amorphous powder tends to be nanocrystallized earlier than the second amorphous powder not adjacent to the first amorphous powder due to the conduction of heat generated during the nanocrystallization of the first amorphous powder. The compressed powder core having these characteristics realizes high magnetic permeability and low iron loss.

[0071] Further, after nanocrystallizing the first amorphous powder, the heat treatment temperature Th may be further increased to precipitate nanocrystals from the second amorphous powder. In this case, by increasing the heat treatment temperature Th to (T2a - 50°C) or higher, a part of the second amorphous powder can be nanocrystallized.

[0072] When T2a < T1b is satisfied, after nanocrystallizing the first amorphous powder, it is preferable to increase the heat treatment temperature Th to a temperature satisfying T2a - 50°C ≤ Th < T1b, and more preferably to a temperature satisfying T2a - 50°C ≤ Th < T2a. Under such conditions, it is possible to promote the nanocrystallization of the second amorphous powder while suppressing the coarsening of the crystal particles and the precipitation of the compound phase of the first amorphous powder.

[0073] Furthermore, in the heat treatment process, it is preferable to precipitate nanocrystals such that the crystallinity of the compacted magnetic core is 50% or less, more preferably 40% or less. The crystallinity can be calculated, for example, by analyzing the measurement results of X-ray diffraction (XRD) using the whole powder pattern decomposition method (WPPD). By adjusting the heat treatment temperature and time to reduce the crystallinity of the compacted magnetic core to 50% or less, the coarsening of crystal particles and precipitation of compounds due to excessive heating can be suppressed, preventing a decrease in magnetic permeability and deterioration of losses. More preferably, by reducing it to 40% or less, more homogeneous nanocrystals can be obtained. Therefore, it is possible to increase the magnetic permeability of the compacted magnetic core and achieve low losses.

[0074] Furthermore, in the heat treatment process, it is preferable to precipitate nanocrystals such that the crystallinity of the compacted magnetic core is 1% or more, more preferably 3% or more, and even more preferably 5% or more. By making the crystallinity of the compacted magnetic core 1% or more, iron loss of the compacted magnetic core can be suppressed.

[0075] Furthermore, before the granulation process (step S2), a portion of the first amorphous powder or the second amorphous powder may be pre-crystallized into nanocrystals. For example, a portion of the first amorphous powder or the second amorphous powder can be nanocrystallized by heating it at a predetermined pretreatment temperature without pressurization. In this case, since the heat treatment is performed in powder form, the heat generated during nanocrystallization can be diffused, and excessive nanocrystallization can be suppressed. Also, because a portion is nanocrystallized, the heat treatment process after pressurization is less likely to result in heat distribution imbalances or thermal runaway, and compound precipitation and coarsening of crystal particles can be suppressed. Therefore, a compacted magnetic core with high magnetic permeability and low iron loss can be obtained.

[0076] The pretreatment temperature of the first amorphous powder can be, for example, (T1a-50°C) or higher and less than T1b. By setting the pretreatment temperature to (T1a-50°C) or higher, a portion of the first amorphous powder can be nanocrystallized. By setting the pretreatment temperature to less than T1b, compound precipitation and excessive nanocrystallization of the first amorphous powder can be suppressed. The pretreatment temperature of the second amorphous powder can be, for example, (T2a-50°C) or higher and less than T2b. By setting the pretreatment temperature to (T2a-50°C) or higher, a portion of the second amorphous powder can be nanocrystallized. By setting the pretreatment temperature to less than T2b, compound precipitation and excessive nanocrystallization of the second amorphous powder can be suppressed.

[0077] Furthermore, if a portion of the amorphous powder is nanocrystallized, the heat treatment in step S4 can be reduced. That is, the heat treatment temperature Th can be lowered, and the heat treatment time can be shortened. This makes it possible to suppress the degradation of the resin material associated with heat treatment.

[0078] Furthermore, an oxide film may be formed on the first amorphous powder or the second amorphous powder before the granulation process (step S2). For example, an oxide film can be formed on the amorphous powder by a mechanochemical method in which the oxide powder and the first amorphous powder or the second amorphous powder are mechanically mixed, a wet thin film fabrication method such as the sol-gel method, or a dry thin film fabrication method such as sputtering. Examples of oxide powders that can be used include the low-melting-point glass mentioned above, or metal oxide powders such as alumina, silica, magnesia, phosphorus oxide, boron oxide, iron oxide, and zinc oxide.

[0079] The mechanochemical method is a method of forming an oxide layer on the surface of magnetic powder by mixing magnetic powder and oxide powder while applying strong mechanical energy.

[0080] Thus, when an oxide film is pre-formed on the first amorphous powder or the second amorphous powder, a resin material is coated on top of the oxide film in step S2. By using oxide powder and resin material as a binder in this way, a thin and uniform insulating layer can be formed even with a small amount of binder added. In other words, in the compression molding process of step S3, the fluidity of the powder is promoted by the easily flowable resin component, the second amorphous powder can adequately fill the gaps between the first amorphous powders, and the pre-formed oxide film can more reliably suppress contact between powders without an insulating layer in between. Therefore, the packing efficiency and DC superposition characteristics of the compacted magnetic core can be improved.

[0081] The magnetic powder may further contain a third powder having a different composition from the second amorphous powder. The amount of the third powder is 30% by mass or less of the total amount of magnetic powder, preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less. The average particle size d3 of the third powder is smaller than the average particle size d2, preferably 5 μm or less, more preferably 0.1 μm or more and 5 μm or less, and even more preferably 0.5 μm or more and 4 μm or less.

[0082] The third powder can be amorphous or crystalline powder produced by atomization. Examples of amorphous powders include those with the same alloy composition as the first amorphous powder, or those with alloy compositions such as Fe-PB alloy, Fe-BP-Nb-Cr alloy, Fe-Si-B alloy, Fe-Si-BP alloy, Fe-Si-BP-Cr alloy, and Fe-Si-BPC alloy. Examples of crystalline powders include crystalline alloy powders and carbonyl iron powders, specifically various soft magnetic powders commonly used in inductors, such as Fe-Si, Fe-Si-Cr, Fe-Si-Al, Fe-Si-Al-Cl, Fe-Al-Cr, Fe-Ni, Fe-Co, and pure iron. The third powder is preferably a crystalline powder.

[0083] If the magnetic powder contains the third powder described above, nanocrystals may be precipitated during the heat treatment process so that the crystallinity of the compacted magnetic core is 70% or less, 60% or less, or 55% or less. If the magnetic powder contains the third particles described above, adjusting the heat treatment temperature and time to make the crystallinity of the compacted magnetic core 70% or less can suppress the coarsening of crystal particles and the precipitation of compounds due to excessive heating, thereby preventing a decrease in permeability and deterioration of losses. More preferably, by making it 60% or less, and even more preferably 55% or less, more homogeneous nanocrystals can be obtained. Therefore, the permeability of the compacted magnetic core can be increased and losses can be reduced. [Examples]

[0084] Next, embodiments of the present invention will be described.

[0085] <Experiment 1> Using the powder core manufacturing method described above (see Figure 3), powder cores for Examples 1-7 and Comparative Examples 1 and 2 were prepared. First, as the first amorphous powder, an Fe-BP-Cu system powder with an average particle size of 30 μm (median diameter D50) was prepared. As the second amorphous powder, an Fe-Si-BP-Cu-Cr system powder with an average particle size of 3 μm (median diameter D50) was used. The compositional formula of the first amorphous powder is, in terms of molar ratio, Fe 84.35 B 6.5 P 8.5 Cu 0.65 The compositional formula of the second amorphous powder is, in terms of molar ratio, Fe 77.9 Si6B 8.5 P6Cu 0.6 It was Cr1.

[0086] Figure 4 shows the DSC curves obtained by differential scanning calorimetry (DSC) performed on the first amorphous powder and the second amorphous powder under the condition of increasing the temperature from room temperature at 10°C / min. The first crystallization onset temperature T1a of the first amorphous powder was 380°C, and the second crystallization onset temperature T1b was 490°C. The first crystallization onset temperature T2a of the second amorphous powder was 440°C, and the second crystallization onset temperature T2b was 520°C.

[0087] Next, the first and second amorphous powders were pre-mixed in the mass ratios shown in Table 1A, and then coated with a resin material for granulation. At this time, epoxy resin was used as the resin material, and the mass ratio of the resin material to the magnetic powder was 0.4% by mass. Afterward, the granulated granules are placed in a mold preheated to 100°C and processed at a rate of 10 tonf / cm². 2 After pressurizing under these conditions, the resin was heated at 150°C for 2 hours to heat-cur the resin and obtain a molded body. At this time, the shape of the molded body was a toroidal shape with an outer diameter of 13 mm, an inner diameter of 8 mm, and a height of 5 mm. Finally, the molded bodies were heat-treated in an Ar atmosphere for 20 minutes at the heat treatment temperatures listed in Table 1A to produce the compacted magnetic cores of Comparative Examples 1 and 2 and Examples 1 to 7. The heat treatment was performed using an image furnace, and the heating rate to reach the predetermined heat treatment temperature was 100°C per minute.

[0088] For each sample prepared as described above, the density, permeability μ', iron loss Pcv, and crystal structure of the powder core were measured. Permeability μ' was determined using an impedance analyzer at a frequency of 20 kHz by winding a 10-turn copper wire winding onto the prepared toroidal powder core. Iron loss Pcv was determined by measuring the powder core using the two-coil method with a BH analyzer (manufactured by Iwasaki Communication Equipment Co., Ltd.). The measurement conditions were a 32-turn primary winding and a 10-turn secondary winding on the powder core, a frequency of 100 kHz, and a magnetic flux density of 100 mT. The crystal structure of the sample was analyzed by X-ray diffraction (XRD) on the surface of the sample.

[0089] The preparation conditions for each sample are shown in Table 1A, and the measurement results are shown in Table 1B. As shown in Table 1B, Examples 1-7, which used the second amorphous powder, had a higher density and a magnetic permeability μ' of 50 or more compared to Comparative Examples 1 and 2. Furthermore, while Comparative Example 2 showed precipitation of compounds in addition to α-Fe phase nanocrystals, compound precipitation was suppressed in Examples 1-7 even at high heat treatment temperatures. In addition, Examples 1-7 had lower iron loss and lower overall loss compared to Comparative Example 1.

[0090] [Table 1A]

[0091] [Table 1B]

[0092] The above results indicate that the compacted magnetic core made by mixing the first amorphous powder and the second amorphous powder exhibits better properties. Specifically, it is thought that the density of the compacted magnetic core improved as the second amorphous powder filled the gaps between the larger particle sizes of the first amorphous powder, and consequently, the permeability increased. Furthermore, it is thought that the heat generated during the nanocrystallization of the first amorphous powder diffused into the surrounding second amorphous powder, preventing excessive promotion of nanocrystallization and resulting in the formation of a homogeneous nanocrystalline structure and reduced iron loss. In addition, in Examples 5 to 7, there was a large amount of second amorphous powder surrounding the first amorphous powder, which suggests that the heat generated during the nanocrystallization of the first amorphous powder could diffuse efficiently, allowing for the production of compacted magnetic cores with good properties even under relatively high temperature conditions.

[0093] <Experiment 2> In Experiment 2, compacted magnetic cores of Examples 8-12 and Comparative Example 3 were prepared while varying the molding temperature. In Experiment 2, the preparation was the same as in Experiment 1, except that the molding temperature during compression molding was varied between 60 and 200°C, and the heat treatment temperature Th was fixed at 410°C. For each prepared sample, the density, packing efficiency, permeability μ', and iron loss Pcv of the compacted magnetic core were measured.

[0094] The packing efficiency of the compacted magnetic core was determined by comparing the volume of magnetic powder contained in the core with the total volume of the core measured by the Archimedes method. The volume of magnetic powder contained in the core was determined by subtracting the weight of the binder from the total weight of the core to find the weight of the magnetic powder contained in the core, and then dividing the weight of the magnetic powder by the true density of the magnetic powder.

[0095] The preparation conditions for each sample are shown in Table 2A, and the measurement results are shown in Table 2B. As shown in Table 2B, Examples 8-12 all had a filling efficiency exceeding 80%, and their magnetic permeability μ' was 50 or higher. In addition, the iron loss Pcv was 500 kW / m 3 The following favorable values ​​were observed. On the other hand, Comparative Example 3 was an example in which the molding temperature was set to room temperature, but molding could not be performed because the powder did not bind together during compression molding. This was because the hardness of the first amorphous powder and the second amorphous powder was high, making it difficult to deform the powder during compression molding, so strong binding between the powders could not be obtained, and the mass ratio of the resin material to the magnetic powder was low, resulting in insufficient flow of resin between the magnetic powders. From these results, it can be said that it is preferable to raise the molding temperature to 200°C or lower in the compression molding process.

[0096] [Table 2A]

[0097] [Table 2B]

[0098] <Experiment 3> In Experiment 3, compacted magnetic cores of Examples 13-16 were fabricated while varying the average particle size d2 of the second amorphous powder. In Experiment 3, the average particle size d2 was varied between 2 and 6 μm, the mixed mass ratio of the first amorphous powder to the second amorphous powder was fixed at 60:40, and the heat treatment temperature Th was fixed at 410°C, but the fabrication was the same as in Experiment 1. The average particle size ratio d1 / d2 with the first amorphous powder was between 5 and 15.

[0099] The preparation conditions for each sample are shown in Table 3A, and the measurement results are shown in Table 3B. As shown in Table 3B, Examples 13-16 all had a filling efficiency exceeding 75%, and their magnetic permeability μ' was 45 or higher. In addition, the iron loss Pcv was 500 kW / m 3 The following and favorable values ​​were observed.

[0100] [Table 3A]

[0101] [Table 3B]

[0102] <Experiment 4> In Experiment 4, compacted magnetic cores of Examples 17-22 were fabricated while varying the mixed mass ratio of the first amorphous powder and the second amorphous powder. The fabrication was the same as in Experiment 1, except that the mixed mass ratio was varied from 100:0 to 30:70 and the heat treatment temperature Th was fixed at 390°C.

[0103] The preparation conditions for each sample are shown in Table 4A, and the measurement results are shown in Table 4B. For comparison, the measurement results for Comparative Example 2 are also shown. As shown in Table 4B, Examples 17-22, in which the mixing mass ratio of the first amorphous powder to the second amorphous powder was 90:10 to 30:70, had a higher packing density and a higher magnetic permeability μ' of 50 or more than Comparative Example 2, in which the mixing mass ratio was 100:0. In addition, the iron loss Pcv was kept lower than in Comparative Example 2, at 600 or less.

[0104] [Table 4A]

[0105] [Table 4B]

[0106] Of the 17-22 examples, Examples 18 and 19, with a mixed mass ratio of 70:30-80:20, showed the highest packing efficiency. This indicates that by using a mixed mass ratio of 70:30-80:20 between the first amorphous powder and the second amorphous powder, the gaps in the first amorphous powder were most adequately filled by the second amorphous powder. In particular, the compacted magnetic core of Example 18 showed the highest permeability and lowest iron loss. This is thought to be because, in addition to the increased permeability due to the higher packing efficiency of the compacted magnetic core, the heat generated when the first amorphous powder nanocrystallized was efficiently diffused to the surroundings, forming a homogeneous nanocrystalline structure and resulting in lower iron loss.

[0107] <Experiment 5> As Experiment 5, compacted magnetic cores of Examples 23-25 ​​were fabricated while varying the mass ratio of resin material to magnetic powder. The fabrication was the same as in Experiment 1, except that the mass ratio was varied from 1% to 2% and the heat treatment temperature Th was set in the range of 390-400°C.

[0108] The preparation conditions for each sample are shown in Table 5A, and the measurement results are shown in Table 5B. As shown in Table 5B, all of Examples 23-25 ​​had high density and a magnetic permeability μ' of 55 or higher. In addition, the iron loss Pcv was 600 kW / m 3 The following and favorable values ​​were observed.

[0109] [Table 5A]

[0110] [Table 5B]

[0111] <Experiment 6> As Experiment 6, compacted magnetic cores of Examples 26-33 and Comparative Examples 4-6 were prepared. The procedure was the same as in Experiment 1, except that the type of magnetic powder was changed and the heat treatment temperature Th was set to a range of 390-410°C.

[0112] The preparation conditions for each sample are shown in Table 6A. As shown in Table 6A, the compacted magnetic cores of Examples 26 to 32 contain a third powder with a different composition from the second amorphous powder as magnetic powder. The compacted magnetic core of Example 33 substantially does not contain the third powder. The compacted magnetic core of Comparative Example 4 has an amount of the third powder that exceeds 30% by mass of the total amount of magnetic powder. The compacted magnetic core of Comparative Example 5 has an average particle size d3 of the third powder that is larger than the average particle size d2 of the second amorphous powder. The compacted magnetic core of Comparative Example 6 has a magnetic powder that does not contain amorphous powder and is composed only of the third powder.

[0113] The measurement results for each sample are shown in Table 6B. In Experiment 6, the iron loss Pcv was measured using a compacted magnetic core with a 32-turn primary winding and a 10-turn secondary winding, at a frequency of 1 MHz and a magnetic flux density of 50 mT. As shown in Table 6B, all of Examples 26-33 had high densities and permeability μ' of 42 or higher. Furthermore, the iron loss Pcv at a frequency of 1 MHz and a magnetic flux density of 50 mT was 4000 kW / m 3 The following and favorable values ​​were observed.

[0114] [Table 6A]

[0115] [Table 6B]

[0116] It should be noted that the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention. For example, in the manufacture of compacted magnetic cores, other magnetic powders may be added in addition to the first and second amorphous powders and the third powder. The proportion of such other magnetic powders is preferably 30% by mass or less of the total amount of magnetic powders. As such other magnetic powders, amorphous powders or crystalline alloy powders produced by atomization, or carbonyl iron powders can be used. For example, amorphous powders may have the same alloy composition as the first and second amorphous powders, or they may have different alloy compositions such as Fe-PB alloy, Fe-BP-Nb-Cr alloy, Fe-Si-B alloy, Fe-Si-BP alloy, Fe-Si-BP-Cr alloy, or Fe-Si-BPC alloy. Furthermore, examples of crystalline alloy powders include various soft magnetic powders commonly used in inductors, such as Fe-Si, Fe-Si-Cr, Fe-Si-Al, Fe-Si-Al-Cl, Fe-Al-Cr, Fe-Ni, Fe-Co, and pure iron.

[0117] This application claims priority based on Japanese Patent Application No. 2024-223936, filed on 19 December 2024, and incorporates all of its disclosures herein. [Explanation of symbols]

[0118] 1 Inductor 10, 10_1, 10_2 Powder magnetic core 13 coils 101 The first particle 102 The second particle

Claims

1. A process of mixing magnetic powder and thermosetting resin and granulating it, The process of compressing and molding the granules after granulation, The process includes a step of heat-treating the molded body after compression molding, The magnetic powder comprises a first amorphous powder and a second amorphous powder. The mixing ratio of the first amorphous powder and the second amorphous powder is 30:70 to 95:5 by mass ratio. The average particle size d1 of the first amorphous powder is larger than the average particle size d2 of the second amorphous powder. The relationship between the first crystallization start temperature T1a of the first amorphous powder and the first crystallization start temperature T2a of the second amorphous powder satisfies T1a < T2a. In the heat treatment step, at least nanocrystals are precipitated from the first amorphous powder. A method for manufacturing compacted magnetic cores.

2. The heat treatment temperature Th in the heat treatment step is T1a - 50°C ≤ Th < T1b. A method for manufacturing a compacted magnetic core according to claim 1.

3. The relationship between the second crystallization start temperature T1b of the first amorphous powder and the first crystallization start temperature T2a of the second amorphous powder satisfies T2a < T1b. A method for manufacturing a compacted magnetic core according to claim 1.

4. The ratio of the average particle size d1 of the first amorphous powder to the average particle size d2 of the second amorphous powder is 2 ≤ d1 / d2 ≤ 20. A method for manufacturing a compacted magnetic core according to claim 1.

5. The mixing ratio of the first amorphous powder and the second amorphous powder is 60:40 to 90:10 by mass. A method for manufacturing a compacted magnetic core according to claim 1.

6. The difference between the first crystallization start temperature T1a of the first amorphous powder and the first crystallization start temperature T2a of the second amorphous powder is 15°C or more. A method for manufacturing a compacted magnetic core according to claim 1.

7. The amount of the thermosetting resin relative to the total amount of the magnetic powder is 0.2% by mass or more and 3.0% by mass or less, in mass ratio. A method for manufacturing a compacted magnetic core according to claim 1.

8. The first amorphous powder and the second amorphous powder are any of the following: Fe-Si-B-P-Cu-Cr alloy, Fe-B-P-Cu-Cr alloy, and Fe-Si-B-Nb-Cu alloy. A method for manufacturing a compacted magnetic core according to claim 1.

9. The composition formula of the first amorphous powder is, in molar ratio, Fe ａ１ Si ｂ１ B ｃ１ P ｘ１ Cu ｙ１ Cr ｚ１ (However, 80at% ≤ a1 ≤ 90at%, 0at% ≤ b1 ≤ 3at%, 3at% ≤ c1 ≤ 18at%, 0at% ≤ x1 ≤ 17at%, 0at% ≤ y1 ≤ 1.2at%, 0at% ≤ z1 ≤ 3at%) where the composition formula of the second amorphous powder is, in terms of molar ratio, Fe ａ２ Si ｂ２ B ｃ２ P ｘ２ Cu ｙ２ Cr ｚ２ (where 75.4 at% ≤ a2 ≤ 85 at%, 0 at% ≤ b2 ≤ 9 at%, 4 at% ≤ c2 ≤ 12 at%, 4.5 at% ≤ x2 ≤ 12 at%, 0.3 at% ≤ y2 ≤ 1.2 at%, 0 at% ≤ z2 ≤ 3 at%) The method for manufacturing a compacted magnetic core according to claim 8.

10. The compression molding step includes a step of raising the temperature to a molding temperature of 200°C or lower. A method for manufacturing a compacted magnetic core according to claim 1.

11. In the heat treatment step, the nanocrystals are precipitated such that the degree of crystallinity is 40% or less. A method for manufacturing a compacted magnetic core according to claim 1.

12. The granulation step includes a step of preheating the first amorphous powder to nanocrystallize it, and then mixing it with the second amorphous powder and a thermosetting resin. A method for manufacturing a compacted magnetic core according to claim 1.

13. The granulation step includes a step of forming an oxide film on the surface of the magnetic powder in advance and then mixing it with a thermosetting resin. A method for manufacturing a compacted magnetic core according to claim 1.

14. The magnetic powder further comprises a third powder having a different composition from the second amorphous powder. The average particle size d3 of the third powder is smaller than the average particle size d2 of the second amorphous powder. The amount of the third powder relative to the total amount of the magnetic powder is 30% by mass or less. A method for manufacturing a compacted magnetic core according to claim 1.

15. The average particle size d3 of the third powder is 5 μm or less. The method for manufacturing a compacted magnetic core according to claim 14.

16. The third powder described above is a crystalline powder. The method for manufacturing a compacted magnetic core according to claim 14.

17. In the heat treatment step, the nanocrystals are precipitated such that the degree of crystallinity is 1% or more and 70% or less. The method for manufacturing a compacted magnetic core according to claim 14.

18. A compacted magnetic core manufactured by the manufacturing method described in any one of claims 1 to 17.

19. It contains first and second particles, at least partially of which are nanocrystalline, The mixing ratio of the first particle and the second particle is 30:70 to 95:5 by mass ratio. The average particle size D1 of the first particles is greater than the average particle size D2 of the second particles. The crystallinity of the first particle is greater than that of the second particle. Powder magnetic core.

20. The second particle adjacent to the first particle has a higher degree of crystallinity than the second particle not adjacent to the first particle. The compacted magnetic core according to claim 19.

21. The degree of crystallinity is 40% or less. The compacted magnetic core according to claim 19.

22. The present invention further comprises a third particle having a different composition from the second particle, The average particle size D3 of the third particle is smaller than the average particle size D2 of the second particle. The amount of the third particle is 30% by mass or less of the total amount of the first to third particles. The compacted magnetic core according to claim 19.

23. The average particle size D3 of the third particle is 5 μm or less. The compacted magnetic core according to claim 22.

24. The third particle is crystalline. The compacted magnetic core according to claim 22.

25. The degree of crystallinity is between 1% and 70%. The compacted magnetic core according to claim 22.

26. An inductor comprising a powdered magnetic core and a coil as described in claim 18.

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