Coated soft magnetic alloy particles, powder magnetic core, magnetic application component, and method for producing coated soft magnetic alloy particles

Abstract

The present invention relates to a coated soft magnetic alloy particle (1) characterized by comprising a soft magnetic alloy particle (10) containing an amorphous phase and a first film (20) coating the surface of the soft magnetic alloy particle (10), the first film (20) having at least one compound selected from inorganic compounds having a crystal structure of hexagonal, trigonal or monoclinic crystal and a layered silicate mineral; and an average smoothness ζ_ave of the outer peripheral profile of a cross section thereof is 0.92 to 1.00.

Description

Technical Field

[0001] This invention relates to coated soft magnetic alloy particles, pressed magnetic cores, magnetic application components, and methods for manufacturing coated soft magnetic alloy particles. Background Technology

[0002] Magnetic application components such as motors, reactors, inductors, and various coils require high-efficiency operation and operation under high current. Therefore, the soft magnetic materials used in the iron cores (powder cores) of these components require low iron loss and high saturation flux density. Generally, iron loss includes hysteresis loss and eddy current loss, but in order to drive at high frequencies in the context of miniaturization of magnetic application components, powder cores with low eddy current loss are desirable.

[0003] Powder-pressed magnetic cores contain at least soft magnetic particles made of soft magnetic materials, and may also include binders and lubricants as needed. The higher the resistance between the soft magnetic materials contained in the powder-pressed magnetic core, the less eddy current loss it can reduce.

[0004] In addition, the higher the space filling rate of the soft magnetic material in the pressed powder core, the higher the permeability of the coil and the higher the saturation magnetic flux density, so it is preferred.

[0005] To maximize saturation magnetic flux density and minimize iron loss, nanocrystalline materials containing an amorphous phase are suitable for use in soft magnetic materials. Methods for manufacturing nanocrystalline materials include atomization (Patent Document 1) and pulverization (Patent Document 2).

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: International Publication No. 2019 / 031463

[0009] Patent Document 2: Japanese Patent Application Publication No. 2018-50053 Summary of the Invention

[0010] However, the method described in Patent Document 1 has the problem that the average particle size of the nanocrystalline materials that can be produced is small and the saturation magnetic flux density is low.

[0011] The method described in Patent Document 2 involves manufacturing soft magnetic particles by pulverizing a thin strip made using a liquid quenching method. While the liquid quenching method increases saturation magnetic flux density due to its rapid cooling rate, the soft magnetic particles are flat rather than spherical. Therefore, when forming the soft magnetic particles into pressed magnetic cores, a problem arises where the space filling rate of the soft magnetic particles decreases.

[0012] In addition, when soft magnetic particles are manufactured by crushing thin strips, unevenness (edges) is formed on the surface of the flat-shaped soft magnetic particles.

[0013] Furthermore, if the space filling rate of the soft magnetic particles in the pressed powder core is low, the following problems will occur: the magnetic permeability of the pressed powder core will decrease, and the contact area between the soft magnetic particles will decrease. During molding, the stress will be concentrated at the contact points between the soft magnetic particles, resulting in increased iron loss.

[0014] The present invention was made to solve the above-mentioned problems, and its purpose is to provide soft magnetic alloy particles that can improve the space filling rate of soft magnetic particles while reducing iron loss when making pressed magnetic cores.

[0015] The coated soft magnetic alloy particles of the present invention are characterized by comprising: soft magnetic alloy particles containing an amorphous phase and a first coating covering the surface of the soft magnetic alloy particles, wherein the first coating has at least one compound selected from inorganic compounds and layered silicate minerals having a crystal structure of hexagonal, trigonal or monoclinic crystals; and the average smoothness ζ_ave of the outer periphery of its cross section is 0.92 to 1.00.

[0016] The powder-pressed magnetic core of the present invention is characterized in that it contains coated soft magnetic alloy particles of the present invention.

[0017] The magnetic application component of the present invention is characterized in that it comprises coated soft magnetic alloy particles of the present invention or pressed powder magnetic core of the present invention.

[0018] The method for manufacturing coated soft magnetic alloy particles of the present invention is characterized by performing the following steps: preparing soft magnetic alloy particles, and mixing the soft magnetic alloy particles with at least one compound selected from inorganic compounds and layered silicate minerals having a crystal structure of hexagonal, trigonal or monoclinic crystals, and processing by mechanical fusion method, thereby forming a first coating on the surface of the soft magnetic alloy particles.

[0019] According to the present invention, it is possible to provide soft magnetic alloy particles that can improve the space filling rate of soft magnetic particles while reducing iron loss when making pressed magnetic cores. Attached Figure Description

[0020] Figure 1 This is a cross-sectional view schematically illustrating an example of a coated soft magnetic alloy particle of the present invention.

[0021] Figure 2 This is an illustration of the average smoothness of the particles.

[0022] Figure 3 This is a cross-sectional schematic diagram of the coating device used in the mechanical fusion process.

[0023] Figure 4 This is a perspective view schematically representing an example of a coil as a component used in magnetic applications.

[0024] Figure 5 This is an electron microscope image of the coated soft magnetic alloy particles of sample number 2.

[0025] Figure 6 This is an electron microscope image of the soft magnetic alloy particles in sample number 6.

[0026] Figure 7 This is an electron microscope image of the coated soft magnetic alloy particles of sample number 1. Detailed Implementation

[0027] The following describes the coated soft magnetic alloy particles, pressed magnetic core, magnetic application component, and manufacturing method of the coated soft magnetic alloy particles of the present invention.

[0028] However, the present invention is not limited to the following configurations, and can be appropriately modified and applied without changing the spirit of the invention. It should be noted that configurations obtained by combining two or more of the preferred configurations of the present invention described below are also part of the present invention.

[0029] [Coated soft magnetic alloy particles]

[0030] Figure 1 This is a cross-sectional view schematically illustrating an example of a coated soft magnetic alloy particle of the present invention.

[0031] Figure 1 The coated soft magnetic alloy particle 1 shown has a soft magnetic alloy particle 10, a first coating 20 covering the surface of the soft magnetic alloy particle 10, and a second coating 30 covering the surface of the first coating.

[0032] The surface of the soft magnetic alloy particles 10 has irregularities (edges), but these irregularities are filled in by the first coating 20 and become smooth. In addition, the surface of the coated soft magnetic alloy particles 1 becomes smooth after the second coating 30 is formed on the surface of the first coating 20.

[0033] The average smoothness ζ_ave of the cross-section of the coated soft magnetic alloy particles of the present invention is 0.92 to 1.00. The average smoothness will be explained with reference to the accompanying drawings.

[0034] Figure 2 This is an illustration of the average smoothness of the particles.

[0035] Figure 2The left side represents the cross-sectional shape of particle 40. Lop represents the total perimeter of the outline of particle 40. The total perimeter Lop is obtained by manually analyzing the total perimeter II using image analysis software (e.g., WinROOF2018: manufactured by Mitani Corporation).

[0036] Let the major axis of the particle be 'a', and the diameter orthogonal to 'a' be 'b'. Additionally, let the image area of ​​the particle be 'Sp'.

[0037] exist Figure 2 To the right of particle 40, an ellipse with the same aspect ratio λ and area Sp as the two-dimensional projection image of particle 40 is depicted by dashed lines. The lengths of the major axis a′ and minor axis b′ in the ellipse are themselves different from those of the major axis a and minor axis b.

[0038] Let the total circumference of the ellipse be Loe.

[0039] Then, the ratio of Loe to Lop = Loe / Lop is used as the smoothness ζ.

[0040] For this smoothness ζ, it is 1 if the particle is a circle or ellipse without bumps, but less than 1 if its surface has bumps.

[0041] The smoothness ζ of any 20 particles in an electron microscope image of coated soft magnetic alloy particles is measured, the average value is taken, and the average smoothness ζ_ave is calculated.

[0042] Then, if the average smoothness ζ_ave is 0.92 to 1.00, it is determined that the particles have high surface smoothness. The average smoothness ζ_ave of the coated soft magnetic alloy particles is 0.92 or more, preferably 0.94 or less.

[0043] If coated soft magnetic alloy particles with high average smoothness are used, space formation caused by the unevenness of the particle surface is less likely to occur. Therefore, when making soft magnetic alloy particles into pressed magnetic cores, the space filling rate of the soft magnetic alloy particles can be improved, and iron loss can be reduced.

[0044] Soft magnetic alloy particles are particles containing an amorphous phase. Furthermore, soft magnetic alloy particles are preferably nanocrystalline materials possessing an amorphous phase. Nanocrystalline materials are materials primarily composed of fine grains with an average grain size of 30 nm or less.

[0045] The average grain size of the crystals contained in soft magnetic alloy particles is related to the coercivity, which exhibits a maximum relative to the average grain size. For example, a maximum occurs around 50 nm to 100 nm. Since the coercivity has a strong correlation with the -6th power of the average grain size on the grain size side smaller than the grain size where the maximum occurs, reducing the grain size is effective in reducing the coercivity.

[0046] Nanocrystalline materials can be obtained by crystallizing amorphous phases. Since amorphous phases are metastable phases, crystal nuclei can be generated and grown by heating at temperatures above the crystallization initiation temperature and maintaining the temperature for a long time.

[0047] For example, in Fe-based nanocrystalline materials, to form an amorphous phase, it is preferable to replace Fe with at least one element selected from, for example, B, P, C, and Si. Furthermore, to promote crystal nucleation, it is preferable to replace Fe with Cu.

[0048] Furthermore, in order to suppress grain growth and generate a large number of fine grains, Fe can be replaced with at least one element selected from, for example, Nb, Mo, Zr, Hf, Ta and W.

[0049] To adjust saturation magnetization and magnetostriction, Fe can be replaced with at least one element selected from Ni and Co.

[0050] Since the types and amounts of solute elements that can be dissolved in Fe are limited, if the crystallization of the amorphous phase proceeds, the solute elements diffuse into the amorphous phase, thus increasing the thermal stability of the amorphous phase. Therefore, an amorphous phase remains even after crystallization.

[0051] The presence of an amorphous phase can be confirmed by obtaining local electron beam diffraction patterns using a transmission electron microscope. Due to its high precision, the nanobeam deflection method is preferred. Alternatively, the presence of an amorphous phase can be confirmed by observing the presence or absence of a halo pattern originating from an amorphous structure near 2θ = 44°, based on the X-ray diffraction pattern obtained using the θ-2θ method with an X-ray diffraction apparatus.

[0052] The chemical composition of the soft magnetic alloy particles described above is not particularly limited, but metallic materials with Fe as the main component are preferred. Specifically, pure iron-based soft magnetic materials (electromagnetic soft iron), Fe-based alloys, Fe-Si-based alloys, Fe-Ni-based alloys, Fe-Al-based alloys, Fe-Si-Al-based alloys, Fe-Si-Cr-based alloys, Fe-Ni-Si-Co-based alloys, or Fe-based amorphous alloys are more preferred. Examples of Fe-based amorphous alloys include Fe-Si-B and Fe-Si-B-Cr-C alloys. One or more of the above-mentioned metallic materials can be used.

[0053] In addition, soft magnetic alloy particles preferably have Fe a Si b B c C d P e Cu f Sn g M1 h M2 iThe chemical composition is indicated.

[0054] In the above chemical composition, a+b+c+d+e+f+g+h+i = 100 (molar parts).

[0055] A portion of Fe can be replaced by M1, which is one or more elements from Co and Ni. In this case, M1 is preferably less than 30 atomic percent of the total chemical composition. Therefore, M1 satisfies 0 ≤ h ≤ 30.

[0056] A portion of Fe can be replaced by M2, which is one or more elements selected from Ti, Zr, Hf, Nb, Ta, Mo, W, Cr, Al, Mn, Ag, V, Zn, As, Sb, Bi, Y, and rare earth elements. In this case, M2 preferably accounts for less than 5 atomic percent of the overall chemical composition. Therefore, M2 satisfies 0 ≤ i ≤ 5.

[0057] It should be noted that a portion of Fe can be replaced by both M1 and M2. The total of Fe, M1, and M2 satisfies 79 ≤ a + h + i ≤ 86.

[0058] The proportion of Si satisfies 0 ≤ b ≤ 5, preferably 0 ≤ b ≤ 3.

[0059] The proportion of B satisfies 4 ≤ c ≤ 13.

[0060] The proportion of C satisfies 0 ≤ d ≤ 3. More preferably, it is 0.1 ≤ d ≤ 3.

[0061] In addition, the combined ratio of B and C satisfies 5 ≤ ​​c + d ≤ 14.

[0062] The proportion of P satisfies 1 ≤ e ≤ 10.

[0063] The proportion of Cu satisfies 0.4 ≤ f ≤ 2.

[0064] The proportion of Sn satisfies 0.3 ≤ g ≤ 6.

[0065] In addition, when the total of the above chemical components is set to 100% by weight, the soft magnetic alloy particles may further contain less than 0.1% by weight of sulfur (S).

[0066] The first coating has at least one compound selected from inorganic compounds and layered silicate minerals having a crystal structure of hexagonal, trigonal or monoclinic crystals.

[0067] The first coating is preferably an inorganic compound having the property of being able to peel off in layers.

[0068] Examples of inorganic compounds with hexagonal, trigonal, or monoclinic crystal structures include hexagonal boron nitride (h-BN), zirconium disulfide (ZrS2), vanadium disulfide (VS2), niobium disulfide (NbS2), molybdenum disulfide (MoS2), tungsten disulfide (WS2), rhenium disulfide (ReS2), tungsten selenide (WSe), molybdenum selenide (MoSe), niobium selenide (NbSe), graphite, cadmium chloride (CdCl2), and cadmium iodide (CdI2).

[0069] Among them, molybdenum disulfide (MoS2) is preferred.

[0070] Examples of layered silicate minerals include mica, biotite, marine mudstone, illite, lepidolite, zinc scintillation, talc, and pyrophyllite.

[0071] The aforementioned inorganic compounds and layered silicate minerals exhibit the property of layered peeling or brittle fracture under stress. Therefore, when mixed with soft magnetic alloy particles and stress is applied, fragments that are caught and peeled or broken by the protrusions on the surface of the soft magnetic alloy particles fill the depressions on the surface of the particles. Through further mixing and stress application, particles with a smooth surface are formed, with the surface of the soft magnetic alloy particles coated by a first film.

[0072] The first coating functions as an insulating film for the soft magnetic alloy particles. By improving the insulation of the soft magnetic alloy particles, the interparticle resistance increases, thus reducing eddy current losses.

[0073] The coated soft magnetic alloy particles preferably further have a second coating on a surface having an oxide layer and being coated with the first coating.

[0074] By coating the soft magnetic alloy particles with a second film, the interparticle resistance of the soft magnetic alloy particles can be increased, and eddy currents can be further reduced.

[0075] The oxide included in the second coating is preferably an oxide containing silicon, and more preferably silicon dioxide (SiO2). That is, the second coating preferably contains silicon oxide. Silicon dioxide has high insulation resistance and high coating strength, and is therefore preferred as the second coating.

[0076] The average particle size of the soft magnetic alloy particles is preferably above 10 μm, and more preferably below 50 μm.

[0077] Furthermore, the average thickness of the first coating is preferably 50 nm or more, and more preferably 400 nm or less. If the average thickness of the first coating is 50 nm or more, it can effectively smooth the surface roughness of the soft magnetic alloy particles. If the average thickness of the first coating is too thick, the magnetic interaction between the soft magnetic alloy particles is suppressed; therefore, it is preferable that the average thickness of the first coating is 400 nm or less.

[0078] In addition, the average thickness of the second film is preferably 10 nm or more, and more preferably 300 nm or less.

[0079] Furthermore, the average particle size of the coated soft magnetic alloy particles is preferably 10 μm or more, and more preferably 55 μm or less.

[0080] The average particle size of soft magnetic alloy particles and the average particle size of coated soft magnetic alloy particles can be determined using a laser diffraction-scattering particle size and particle size distribution measuring device.

[0081] [Method for manufacturing coated soft magnetic alloy particles]

[0082] First, prepare soft magnetic alloy particles.

[0083] Such soft magnetic alloy particles can be made, for example, as follows.

[0084] Raw materials (soft magnetic alloys) weighed to a specified chemical composition are heated and melted to form a molten liquid, which is then cooled to obtain a thin ribbon. For manufacturing ribbons containing an amorphous phase, a cooling solidification method and conditions with a rapid cooling rate are preferred.

[0085] Stress is applied to the obtained thin strip to produce pulverized powder. Grinding methods such as pin mills, hammer mills, feather mills, sample mills, ball mills, and stamping mills are not particularly limited.

[0086] Near-spherical particles can also be produced by simultaneously applying shear and compressive stress to the pulverized powder to induce plastic deformation. The pulverizer is not particularly limited, but a high-speed rotary pulverizer, such as one with a mixing system (manufactured by Nara Machinery Manufacturing Co., Ltd.), is preferred. By applying stress to the contact points between the soft magnetic alloy particles and causing multiple particles to aggregate into a single particle, soft magnetic alloy particles that are closer to spherical in shape can be obtained, and are therefore preferred.

[0087] In addition, commercially available powders can be prepared as soft magnetic alloy particles [e.g., Fe-based amorphous alloy powder (manufactured by Epson Atmix Corporation)].

[0088] For soft magnetic alloy particles, it is preferable to use two sieves with different sieve diameters to remove coarse particles and fine particles respectively, so that the particle size is consistent.

[0089] Next, a first film is formed on the surface of the soft magnetic alloy particles.

[0090] In forming the first coating, soft magnetic alloy particles are mixed with at least one compound selected from inorganic compounds and layered silicate minerals having crystal structures of hexagonal, trigonal or monoclinic crystals (hereinafter also referred to as the first coating compound) and processed by mechanical fusion.

[0091] In the mechanical fusion process, soft magnetic alloy particles and a first coating compound are introduced into a container and mixed while mechanical impact is applied.

[0092] Figure 3 This is a cross-sectional schematic diagram of the coating device used in the mechanical fusion process.

[0093] Figure 3 The coating device 51 shown has a cylindrical chamber 52, configured such that a blade 53 rotates within the chamber 52 as indicated by arrow 54. A workpiece 55 (soft magnetic alloy particles and a first coating compound) is placed into the chamber 52, and in this state, the workpiece 55 is processed by rotating the blade 53.

[0094] Examples of coating devices as described above include powder processing devices (NOB, NOB-MINI) manufactured by Hosokawa Micron Corporation.

[0095] Through this treatment, the unevenness of the surface of the soft magnetic alloy particles is filled by the first coating compound, and the surface of the first coating becomes a smooth surface.

[0096] As a preferred condition for obtaining a smooth surface, the amount of the first coating compound can be such that it is sufficient to fill the unevenness of the surface of the soft magnetic alloy particles. The amount of the first coating compound relative to 100% by weight of the soft magnetic alloy particles is preferably 0.30% by weight or more, more preferably 0.60% by weight or more.

[0097] Furthermore, the average particle size of the first coating compound is preferably 500 nm or less.

[0098] Furthermore, it is preferable to rotate the blades in the coating device at a speed of, for example, 1 rpm to 10,000 rpm. Additionally, it is preferable to set the processing time to 1 minute to 60 minutes.

[0099] Through the above steps, the coated soft magnetic alloy particles of the present invention can be manufactured.

[0100] After the first coating is formed, a fine crystalline structure can be generated by heating the soft magnetic alloy particles above the first crystallization initiation temperature. The first crystallization initiation temperature refers to the temperature at which a crystalline phase with a body-centered cubic structure begins to form when the amorphous phase, which has the chemical composition constituting the soft magnetic alloy particles, is heated from room temperature. The first crystallization initiation temperature depends on the heating rate; the faster the heating rate, the higher the first crystallization initiation temperature, and the slower the heating rate, the lower the first crystallization initiation temperature. If a crystalline phase with a body-centered cubic structure is sufficiently formed, the saturation magnetic flux density increases, and the coercivity decreases.

[0101] Next, it is preferable to further perform a step of forming a second film having oxides on the surface of the first film.

[0102] There are no particular limitations on the method for forming the second coating, but the sol-gel method can be used to form a uniform and strong coating.

[0103] Furthermore, the amount of compound constituting the second coating (hereinafter also referred to as the compound for the second coating) is preferably 0.10% by weight or more, and preferably 0.50% by weight or less, relative to 100% by weight of the soft magnetic alloy particles.

[0104] The process of forming the second coating can be carried out, for example, by mixing a solution containing a compound for the second coating or its precursor with coated soft magnetic alloy particles having the first coating formed, and then heating and drying.

[0105] [Powder-pressed magnetic core]

[0106] The pressed powder magnetic core of the present invention comprises the coated soft magnetic alloy particles of the present invention.

[0107] The pressed powder magnetic core of the present invention can be used in magnetic application components such as motors, reactors, inductors, and various coils.

[0108] Powder-pressed magnetic cores are manufactured by mixing a binder material dissolved in a solvent with coated soft magnetic alloy particles, filling the mixture into a mold, and applying pressure. The resin constituting the binder material is not particularly limited; it can be a thermosetting resin such as epoxy resin, phenolic resin, or silicone resin, or a mixture of thermoplastic and thermosetting resins. The molded powder-pressed magnetic core can be heated after drying excess solvent to improve its mechanical strength.

[0109] The conditions for powder pressing can be the same as those known in the past, but it is preferred, for example, to perform powder pressing at a temperature of 250°C or below, a pressure of 0.1 MPa or above, and a pressure of 800 MPa or below.

[0110] To mitigate the strain introduced by the coating soft magnetic alloy particles due to the pressure during molding, heat treatment can be performed. For example, heat treatment at a temperature of 300°C to 450°C can easily mitigate strain, provided that the resin burns or volatilizes without adversely affecting the magnetic properties.

[0111] The powder-coated magnetic core of the present invention uses the coated soft magnetic alloy particles of the present invention, thus increasing the space filling rate of the soft magnetic particles. Therefore, it is possible to form a coil with high permeability and high saturation magnetic flux density.

[0112] [Magnetic Application Components]

[0113] The magnetic application components of the present invention comprise the coated soft magnetic alloy particles of the present invention or the pressed powder magnetic core of the present invention.

[0114] Examples of magnetic application components include motors, reactors, inductors, and various coils. For instance, a coil in which a wire is wound around a powder-coated magnetic core can be cited.

[0115] Figure 4 This is a perspective view schematically representing an example of a coil as a component used in magnetic applications.

[0116] Figure 4 The coil 100 shown includes: a pressed powder core 110 containing coated soft magnetic alloy particles of the present invention, and a primary winding 120 and a secondary winding 130 wound around the pressed powder core 110. Figure 4 In the coil 100 shown, a primary winding 120 and a secondary winding 130 are double-wound on a ring-shaped powder core 110.

[0117] The structure of the coil is not limited to Figure 4 The structure of the coil 100 shown is as follows. For example, a coil can be wound on a powder core having a ring shape. Alternatively, it can have a structure comprising a body containing coated soft magnetic alloy particles of the present invention and a coil conductor embedded in the body.

[0118] Because the coil, which is the magnetic application component of this invention, has a high space filling rate of soft magnetic particles in the pressed powder core, it becomes a coil with high permeability and high saturation magnetic flux density.

[0119] Example

[0120] The following describes embodiments of the present invention in more detail. It should be noted that the present invention is not limited to these embodiments.

[0121] [Example 1]

[0122] To meet the chemical composition formula Fe 84.2 Si1B9C1P3Cu 0.8The raw materials were weighed using the Sn1 method. The total weight of the raw materials was 150g. The Fe raw material was MAIRON (99.95% purity) manufactured by Toho Zinc Co., Ltd. The Si raw material was granular silicon (99.999% purity) manufactured by High Purity Chemical Research Institute Co., Ltd. The B raw material was granular boron (99.5% purity) manufactured by High Purity Chemical Research Institute Co., Ltd. The C raw material was powdered graphite (99.95% purity) manufactured by High Purity Chemical Research Institute Co., Ltd. The P raw material was blocky iron phosphide Fe3P (99% purity) manufactured by High Purity Chemical Research Institute Co., Ltd. The Cu raw material was flake copper (99.9% purity) manufactured by High Purity Chemical Research Institute Co., Ltd. The Sn raw material was granular tin (99.9% purity) manufactured by High Purity Chemical Research Institute Co., Ltd.

[0123] The above-mentioned raw materials were filled into an alumina crucible (U1 material) manufactured by TEP Corporation and heated to 1300°C using induction heating, held for 1 minute to dissolve. The dissolution atmosphere was argon. The molten material obtained from dissolving the raw materials was poured into a copper mold and cooled to solidify, yielding a master alloy. The master alloy was crushed into pieces approximately 3mm to 10mm in size using a jaw crusher. Next, the crushed master alloy was processed into a thin strip using a single-roller liquid quenching device. Specifically, 15g of the master alloy was filled into a quartz nozzle and heated to 1200°C in an argon atmosphere using induction heating to dissolve it. The molten material obtained from dissolving the master alloy was supplied to the surface of a copper cooling roller, resulting in a thin strip with a thickness of 15μm to 25μm and a width of 1mm to 4mm. The outlet gas pressure was 0.015MPa. The orifice diameter of the quartz nozzle was 0.7mm. The circumferential speed of the cooling roller was 50m / s. The distance between the cooling roller and the quartz nozzle was 0.27mm.

[0124] The obtained thin strip was pulverized using a sample mill (SAM) manufactured by Nara Machinery Manufacturing Co., Ltd. The SAM was rotated at 15,000 rpm.

[0125] The powder obtained by SAM grinding was spheroidized using a high-speed rotary pulverizer. The high-speed rotary pulverizer used was the NHS-0 type mixing system manufactured by Nara Machinery Co., Ltd. The rotation speed was 13,000 rpm, and the processing time was 30 minutes.

[0126] The spheroidized powder was passed through a 38μm mesh sieve to remove large particles remaining on the sieve. Next, the powder was passed through a 20μm mesh sieve to remove fine particles and recover the soft magnetic alloy particles remaining on the sieve.

[0127] Next, the first coating is formed on the soft magnetic alloy particles according to the following steps.

[0128] 0.24 g of molybdenum disulfide particles were mixed with 40 g of the soft magnetic alloy particles that were screened and recovered as described above. The amount of molybdenum disulfide was 0.60% by weight relative to 100% by weight of the soft magnetic alloy particles.

[0129] The average particle size of molybdenum disulfide particles is less than 500 nm.

[0130] The above-mentioned mixed powder was processed by mechanical fusion to form a first coating. The apparatus used was a Hosokawa Micron Corporation NOB-MINI, with the rotation speed set to 6000 rpm and the processing time set to 30 minutes.

[0131] Then, the soft magnetic alloy particles are heat-treated at a temperature 20°C higher than the initial crystallization temperature of the soft magnetic alloy particles to generate nanocrystals from the amorphous phase.

[0132] The heat treatment furnace used was an infrared annealing furnace (RTA) manufactured by ADVANCE RIKO, Inc. The heat treatment atmosphere was argon, and the infrared lamp base was carbon. A 2g sample was placed on a 4-inch diameter carbon base, and then another 4-inch diameter carbon base was placed on top of it. A control thermocouple was inserted into a thermocouple insertion hole formed on the lower carbon base. The heating rate was 400°C / min. The holding time at the heat treatment temperature was 1 minute. Cooling was performed naturally, reaching below 100°C in approximately 30 minutes.

[0133] The initial crystallization temperature was determined using a differential scanning calorimeter (DSC404F3, Netsch). The sample was heated from room temperature to 650°C at a rate of 20°C / min, and the pyrolysis at each temperature was measured. Platinum was used for the sample container. Argon (99.999%) was used at a flow rate of 1 L / min. The sample volume ranged from 15 mg to 20 mg. The first crystallization initiation temperature was defined as the intersection of the tangent line of the DSC curve below the temperature at which pyrolysis begins and the tangent line of the maximum slope of the rising pyrolysis peak caused by the crystallization reaction.

[0134] The coated soft magnetic alloy particle was designated as sample number 1.

[0135] Next, a second coating was formed on the surface of the coated soft magnetic alloy particles of sample number 1. 8.5 g of isopropanol, 8.5 g of 9% ammonia, and 1.14 g of 30% PLYSURF AL (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., a phosphate ester type anionic surfactant) were mixed with 30 g of the coated soft magnetic alloy particles of sample number 1.

[0136] Next, a mixture of 7.9 g of isopropanol and 2.1 g of TEOS (silicon oxynitride membrane) was mixed in three portions, 1.0 g each time, and filtered through filter paper. The sample recovered from the filter paper was washed with acetone, heated and dried at 80°C for 60 minutes, and then heat-treated at 140°C for 30 minutes to form a second coating, thus obtaining coated soft magnetic alloy particles.

[0137] The coated soft magnetic alloy particle was designated as sample number 2.

[0138] As shown in Table 1, by changing the composition of the first and second coatings, coated soft magnetic alloy particles were prepared, resulting in coated soft magnetic alloy particles with sample numbers 3, 4, and 5.

[0139] In addition, soft magnetic alloy particles that did not form the first and second coatings were designated as sample number 6. It should be noted that, in the description of the determination method shown below, particles of sample number 6 are also treated as coated soft magnetic alloy particles.

[0140] The average smoothness ζ_ave, saturation magnetic flux density Bs, coercivity Hc, and powder volume resistivity of the prepared samples were measured, and the results are shown in Table 1. The measurement methods are as follows.

[0141] The method for determining the average smoothness of coated soft magnetic alloy particles is as described in this instruction manual. Figure 2 As described above, WinROOF2018 (manufactured by Mitani Shoji Co., Ltd.) was used as the image analysis software.

[0142] The method for measuring saturation magnetic flux density Bs is as follows.

[0143] The saturation magnetization Ms was determined using a vibrating sample magnetization analyzer (VSM). A capsule used for powder analysis was filled with coated soft magnetic alloy particles and compacted so that the particles did not move when a magnetic field was applied.

[0144] The apparent density ρ was determined using a hydrometer. The displacing gas was He.

[0145] The saturation magnetic flux density Bs is calculated using the following equation (1) based on the values ​​of the saturation magnetization Ms measured by VSM and the apparent density ρ measured by hydrometer.

[0146] Bs=4π·Ms·ρ···(1)

[0147] Coercivity Hc was measured using a coercivity meter K-HC1000 manufactured by Tohoku Special Steel Co., Ltd. Soft magnetic alloy particles were filled into capsules used for powder testing and compacted so that the particles did not move when a magnetic field was applied.

[0148] The volume resistivity of the powder was measured using the MCP-PD51 powder resistivity measuring unit manufactured by Mitsubishi Chemical Analytech Co., Ltd., under a pressure of 60 MPa.

[0149] Electron micrographs showing the soft magnetic alloy particles (particles of sample number 6) before the formation of the first and second coatings, and the coated soft magnetic alloy particles (particles of sample number 2) after the formation of the first and second coatings. Also shown are electron micrographs showing only the soft magnetic alloy particles after the formation of the first coating (particles in the fabrication process of sample number 1).

[0150] Figure 5 This is an electron microscope image of the coated soft magnetic alloy particles from sample number 2. Figure 6 This is an electron microscope image of the soft magnetic alloy particles in sample number 6. Figure 7 This is an electron microscope image of the coated soft magnetic alloy particles of sample number 1.

[0151] Compare Figure 5 and Figure 6 It can be seen that by forming the first and second coatings, the surface of the soft magnetic alloy particles becomes smooth.

[0152] In addition, from Figure 7 It can be seen that by forming the first coating, the surface of the soft magnetic alloy particles becomes smooth.

[0153] [Table 1]

[0154]

[0155] In Table 1, the sample numbers marked with * are comparative examples outside the scope of this invention. In sample numbers 4 and 5, only a silicon dioxide film was applied, and no molybdenum disulfide film equivalent to the first film was applied. However, this silicon dioxide film is regarded as the second film and is recorded in Table 1.

[0156] As shown in Table 1, among the samples 1, 2, and 3 that fall within the scope of this invention, the average smoothness ζ_ave is above 0.92, the saturation magnetic flux density is high, and the coercivity is low. Furthermore, in samples 2 and 3, the powder volume resistivity is high.

[0157] Sample number 4 has high coercivity and low powder volume resistivity.

[0158] Sample No. 5 has a high volume resistivity but low saturation magnetic flux density and high coercivity.

[0159] The powder in sample number 6 has a low volume resistivity.

[0160] [Example 2]

[0161] The sample prepared in Example 1 was processed into a ring-shaped pressed powder magnetic core. The weight of a mixed powder consisting of 70% by weight of coated soft magnetic alloy particles and 30% by weight of iron powder with an average particle size of 5 μm was set to 100% by weight. 1.5% by weight of phenolic resin PC-1 and 3.0% by weight of acetone were mixed in a mortar.

[0162] After acetone is evaporated in an explosion-proof oven at 80°C for 30 minutes, the sample is filled into a mold and thermoformed at 60MPa pressure and 180°C to form a ring shape with an outer diameter of 8mm and an inner diameter of 4mm to produce a pressed powder magnetic core.

[0163] Next, the filling rate Pr of the powder-pressed magnetic core is determined. The outer diameter φo and inner diameter φi of the powder-pressed magnetic core are measured at three points using vernier calipers and the average value is calculated. The thickness t of the magnetic core is measured at three points using a micrometer, and the volume Vc of the powder-pressed magnetic core is calculated using equation (2).

[0164] The weight m of the sample was determined by an electronic balance, and the filling density ρc of the pressed powder core was calculated using equation (3).

[0165] The apparent density of the mixed powder is set as ρm, and the filling rate Pr of the pressed powder core is calculated using equation (4).

[0166]

[0167]

[0168]

[0169] The relative initial permeability of the pressed powder core was determined using a Keysight Technologies E4991A impedance analyzer and a 16454A magnetic material testing fixture.

[0170] To measure iron loss, copper wire was wound around a powder-coated magnetic core. The diameter of the copper wire was 0.26 mm. Both the primary winding used for excitation and the secondary winding used for detection had 20 turns, implementing double-wire winding. The frequency condition was 100 kHz, resulting in a maximum magnetic flux density of 20 mT.

[0171] Table 2 shows the fill rate Pr, relative initial permeability, and iron loss of the annular powder cores of each sample prepared in Example 1. It should be noted that the correspondence between Example 1 and Example 2 is as follows: Sample 1 → Sample 7, Sample 2 → Sample 8, Sample 3 → Sample 9, Sample 4 → Sample 10, Sample 5 → Sample 11, Sample 6 → Sample 12.

[0172] [Table 2]

[0173]

[0174] In Table 2, the sample numbers marked with * are comparative examples outside the scope of this invention.

[0175] As shown in Table 2, among the samples 7, 8 and 9 that fall within the scope of this invention, the pressed powder magnetic core has a high fill rate Pr (space fill rate), a high relative initial permeability, and low iron loss.

[0176] Samples 10, 11, and 12 all have low filler ratios (Pr) and relatively low initial permeability in their powder-pressed magnetic cores. Consequently, samples 10 and 12 exhibit high iron losses.

[0177] Symbol Explanation

[0178] 1. Coated soft magnetic alloy particles

[0179] 10 Soft magnetic alloy particles

[0180] 20 First membrane

[0181] 30 Second membrane

[0182] 40 particles

[0183] 51 covered device

[0184] 52 chambers

[0185] 53 blades

[0186] 54. Arrow indicating the direction of blade rotation.

[0187] 55. Subjected material (soft magnetic alloy particles and compound for first coating)

[0188] 100 Coil (Magnetic Application Component)

[0189] 110 Powder-pressed magnetic core

[0190] 120 One-time winding

[0191] 130 Secondary winding

Claims

1. A pressed powder magnetic core, characterized in that, It comprises a binder and coated soft magnetic alloy particles, said coated soft magnetic alloy particles having: Soft magnetic alloy particles containing amorphous phases, and The first coating has at least one compound selected from inorganic compounds and layered silicate minerals having a crystal structure of hexagonal, trigonal or monoclinic crystals, and covers the surface of the soft magnetic alloy particles. Furthermore, the first coating covers the unevenness of the surface of the soft magnetic alloy particles. The average smoothness ζ_ave of the outer periphery of the cross-section of the coated soft magnetic alloy particles is 0.92 to 1.

00.

2. The pressed powder magnetic core according to claim 1, wherein the coated soft magnetic alloy particles further have a second coating, the second coating having an oxide and coating the surface of the first coating.

3. The pressed powder magnetic core according to claim 2, wherein, The second coating comprises silicon dioxide.

4. The pressed powder magnetic core according to any one of claims 1 to 3, wherein, The soft magnetic alloy particles have Fe... a Si b B c C d P e Cu f Sn g M1 h M2 i The chemical composition is indicated. M1 is one or more elements selected from Co and Ni. M2 is one or more elements selected from Ti, Zr, Hf, Nb, Ta, Mo, W, Cr, Al, Mn, Ag, V, Zn, As, Sb, Bi, Y, and rare earth elements. It satisfies 79≤a+h+i≤86, 0≤b≤5, 4≤c≤13, 0≤d≤3, 5≤c+d≤14, 1≤e≤10, 0.4≤f≤2, 0.3≤g≤6, 0≤h≤30, 0≤i≤5 and a+b+c+d+e+f+g+h+i=100 (molar parts).

5. The pressed powder magnetic core according to any one of claims 1 to 3, wherein, The first coating contains molybdenum disulfide.

6. The pressed powder magnetic core according to any one of claims 1 to 3, wherein, The adhesive material comprises resin.

7. A magnetic application component, characterized in that, The powder core comprising any one of claims 1 to 6.

8. A method for manufacturing a pressed powder magnetic core, characterized in that, Coated soft magnetic alloy particles are manufactured using the following method: the coated soft magnetic alloy particles are mixed with a binder material and then shaped. The method for manufacturing the coated soft magnetic alloy particles includes the following steps: The process of preparing soft magnetic alloy particles, and The process of mixing the soft magnetic alloy particles with at least one compound selected from inorganic compounds and layered silicate minerals having a crystal structure of hexagonal, trigonal or monoclinic crystals, and processing the mixture by mechanical fusion, thereby forming a first coating on the surface of the soft magnetic alloy particles. The unevenness of the surface of the soft magnetic alloy particles is filled by the first coating. The average smoothness ζ_ave of the outer periphery of the cross-section of the coated soft magnetic alloy particles is 0.92 to 1.

00.

9. The method for manufacturing a pressed powder magnetic core according to claim 8, wherein, The manufacturing method of the coated soft magnetic alloy particles further includes a step of forming a second coating with oxides on the surface of the first coating.

10. The method for manufacturing a pressed powder magnetic core according to claim 8 or 9, wherein, The adhesive material comprises resin.

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