Iron-based powder for powder magnetic core, powder magnetic core, and method for manufacturing powder magnetic core

Abstract

The present invention aims to provide an iron-based powder for a powder magnetic core, which has low iron loss and high insulation. The present invention is an iron-based powder for a powder magnetic core, wherein the central value of particle diameter calculated from the cumulative volume frequency of particles constituting the iron-based powder for a powder magnetic core is 150 μm or less, the cumulative volume frequency of the particles having an aspect ratio of 0.70 or less is 70% or less, and the central value of the aspect ratio calculated from the cumulative volume frequency is 0.60 or more.

Description

TECHNICAL FIELD

[0001] The present application relates to an iron-based powder for a powder magnetic core, a powder magnetic core, and a manufacturing method of a powder magnetic core. BACKGROUND

[0002] Compared with a melting method, a powder metallurgy method is high in dimensional accuracy even for manufacturing of a component of a complicated shape, and in addition, is low in waste of raw material, and thus is applied to manufacturing of various components. As a product manufactured by the powder metallurgy method, for example, a powder magnetic core can be cited. The powder magnetic core is a magnetic core manufactured by press-molding of a powder, and is used for a core and the like of an electric reactor and the like. In recent years, particularly in a hybrid vehicle, an electric vehicle, in order to downsize and improve a cruising distance, an electric reactor and the like having excellent magnetic properties are required, and the powder magnetic core used therefor is also required to have more excellent magnetic properties. Therefore, a powder magnetic core obtained by coating a powder of a ferromagnetic metal having a high magnetic flux density and a low iron loss with an insulating film and press-molding has been put into practical use.

[0003] In particular, in order to make the powder magnetic core low in iron loss, reduction of coercive force of a metal powder particle, or reduction of damage to an insulating film on a surface of a metal powder particle in a powder body obtained by press-molding can be cited. As a means thereof, a technique focusing on the shape of a metal powder particle has been proposed.

[0004] For example, in Patent Literature 1, it is disclosed that by using amorphous alloy particles having an average value of an aspect ratio (here, a major axis diameter / minor axis diameter) of 1 to 3, the filling rate at the time of powder molding becomes high because the particles are relatively close to a spherical shape, and a powder magnetic core having a high saturation magnetic flux density can be obtained.

[0005] In Patent Literature 2, it is also disclosed that by using nanocrystalline soft magnetic alloy particles having an aspect ratio (here, a major axis diameter / minor axis diameter) exceeding 1.0 and 2.6 or less, core loss in a high frequency region is reduced.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT LITERATURE

[0008] Patent Literature 1: Japanese Patent Application Laid-Open No. 2016-15357

[0009] Patent Literature 2: Japanese Patent Application Laid-Open No. 2015-167183 SUMMARY

[0010] However, in the technologies of Patent Literature 1 and Patent Literature 2, the number-based basis is adopted in the calculation of the average of the aspect ratio (here, the major axis diameter / minor axis diameter) of the particles, and the average of the aspect ratio (here, the major axis diameter / minor axis diameter) under such a basis, even if it is within a prescribed range, has a problem that it can include particles having an extremely small aspect ratio (here, the major axis diameter / minor axis diameter) and particles having an extremely large aspect ratio (here, the major axis diameter / minor axis diameter), and can result in a failure to obtain a target magnetic characteristic.

[0011] The present application solves the above-described problems, and aims to provide an iron-based powder for a powder magnetic core, which can realize a powder magnetic core having low iron loss and high insulation.

[0012] The present inventors have found that, with respect to a characteristic value of a powder, with the aspect ratio (i.e., the minor axis diameter / major axis diameter) of the ratio of the minor axis diameter to the major axis diameter of a projection image of a particle, focusing on the volume frequency of the aspect ratio distribution and the central value of the aspect ratio of the entire particles, and with both the cumulative volume frequency of particles having a prescribed aspect ratio and the central value of the aspect ratio of the entire particles as indices, a condition range related to these indices is set, whereby a powder magnetic core having low iron loss and high insulation can be produced. The present application is based on the above-described insight, and the gist thereof is as follows.

[0013] [1] An iron-based powder for a powder magnetic core,

[0014] The central value of the particle diameter calculated from the cumulative volume frequency of the particles constituting the above-described iron-based powder for a powder magnetic core is 150 μm or less,

[0015] The cumulative volume frequency of the aspect ratio of 0.70 or less of the above-described particles is 70% or less, and the central value of the aspect ratio calculated from the cumulative volume frequency is 0.60 or more.

[0016] [2] The iron-based powder for a powder magnetic core according to [1], wherein the maximum particle diameter of the above-described particles is 500 μm or less.

[0017] [3] The iron-based powder for a powder magnetic core according to [1] or [2], wherein the composition of components other than inevitable impurities is constituted by a soft magnetic powder represented by the composition formula: Fe a Si b B c P d Cu e M f

[0018] In the formula,

[0019] 79 at% ≤ a ≤ 84.5 at%,

[0020] 0 at% ≤ b < 6 at%,

[0021] ​0 at% < c < 10 at%,

[0022] 4 at% < d < 11 at%,

[0023] 0.2 at% < e < 1.0 at%,

[0024] 0 at% < f < 4 at%, and

[0025] a + b + c + d + e + f = 100 at%,

[0026] M is at least one element selected from the group consisting of Nb, Mo, Ni, Sn, Zr, Ta, W, Hf, Ti, V, Cr, Mn, C, Al, S, O, and N.

[0027] [4] The iron-based powder for a powder magnetic core according to any one of [1] to [3], wherein an insulating coating layer is provided on the surface of the particles constituting the iron-based powder for a powder magnetic core.

[0028] [5] A powder magnetic core, which is a pressure-molded body of the iron-based powder for a powder magnetic core according to any one of [1] to [4].

[0029] [6] A method for manufacturing a powder magnetic core, comprising the step of pressure-molding the iron-based powder for a powder magnetic core according to any one of [1] to [4] in a mold.

[0030] The reason why the powder magnetic core having low iron loss and high insulation can be produced by the iron-based powder for a powder magnetic core according to the present application is presumed as follows.

[0031] In the iron-based powder for a powder magnetic core according to the present application, the proportion of the particles having a very low aspect ratio is small, and the central value of the aspect ratio is large, so the unevenness of the surface of the particles that can be the pinning sites of the magnetic domain wall within one particle is reduced, and the movement of the magnetic domain wall is easy. Thus, the coercive force is reduced, and the hysteresis loss is reduced.

[0032] In addition, since the powder particles have a high aspect ratio, the destruction of the insulating coating layer of the powder particles in the powder body is reduced, and the conduction between the powder particles is also reduced, so the eddy current loss is reduced. Furthermore, the powder particles having a high aspect ratio have high fluidity, and the filling property into a mold is improved when the powder magnetic core is produced, and the rearrangement of the particles in the powder body is promoted when the powder is molded by pressure molding, and on the other hand, the friction between the mold and the particles is reduced. Thus, the movement of the powder on the wall surface of the mold is also easy, and the powder is easily densified, and a powder magnetic core having a high density can be produced. By the increase in the powder density, the reduction in the iron loss can be achieved.

[0033] The iron-based powder for a powder magnetic core according to the present application can provide a powder magnetic core having low iron loss and high insulation. DETAILED DESCRIPTION

[0034] Hereinafter, an embodiment of the present application will be described. The following description indicates a preferred embodiment of the present application, which does not limit the present application.

[0035] <Iron-based powder for powder magnetic core>

[0036] For the iron-based powder for powder magnetic core (hereinafter also referred to as "iron-based powder") as one embodiment of the present application, the central value of particle diameter calculated from the cumulative volume frequency of the constituent particles is 150 μm or less, the cumulative volume frequency of the particles having an aspect ratio of 0.70 or less is 70% or less, and the central value of the aspect ratio calculated from the cumulative volume frequency is 0.60 or more. Here, the "iron-based powder" means a metal powder containing 50% by mass or more of Fe.

[0037] [Central value of particle diameter]

[0038] For the iron-based powder of the present application, the central value D 50 of particle diameter calculated from the cumulative volume frequency of the constituent particles is 150 μm or less. When the central value D 50 of particle diameter is a fine particle of the above upper limit value or less, the flowability of the powder becomes high, the filling density to the mold is improved, and further the density of the powder magnetic core is improved, so that the iron loss can be sufficiently reduced. In addition, the fine particle can reduce the eddy current loss, and from this point of view, it is also advantageous in reducing the iron loss. The central value D 50 of particle diameter is preferably 100 μm or less. On the other hand, from the viewpoint of performing uniform resin coating on the powder, the central value D 50 of particle diameter can be 3 μm or more, and is preferably 5 μm or more.

[0039] The measurement of particle diameter and the method of calculating the central value D 50 of particle diameter from the cumulative volume frequency are as follows.

[0040] In the measurement of particle diameter, the powder to be the object is put into a solvent (for example, ethanol), and dispersed by ultrasonic vibration for 30 seconds or more, and the particle size distribution on a volume basis is measured by a laser diffraction type particle size distribution measuring machine using a laser diffraction-scattering method. From the obtained particle size distribution, the cumulative particle size distribution is calculated, and the particle diameter of the particle corresponding to 50% of the total volume of all particles is set as the central value D 50 , which is used as the representative value of the particle diameter of the powder.

[0041] [Aspect ratio]

[0042] The aspect ratio (A) in the present application is a value defined by the following (1) formula.

[0043] A = W / L...(1)

[0044] (here,

[0045] A is an aspect ratio,

[0046] W is a short axis diameter of one particle, in m,

[0047] L is a long axis diameter of one particle, in m.

[0048] The aspect ratio is determined as follows.

[0049] The powder to be measured is dispersed on a flat surface (e.g. the surface of a glass plate) using compressed air, and an image of each particle is captured using a microscope. The total number of particles in the powder to be measured is 1000 or more.

[0050] The captured image is analyzed using a computer, and for each particle projection image, the projected area, short axis diameter, and long axis diameter are measured. The long axis diameter is the maximum length that can be obtained in the projection image of the particle, and the short axis diameter is the maximum length in a direction orthogonal to the maximum length. The determination results are substituted into the above (1) to calculate the aspect ratio of each particle.

[0051] The diameter of a circle having the same area as the projected area of each particle (circle equivalent diameter) is calculated, and the volume of a sphere having the same diameter as the diameter is calculated. Thus, the aspect ratio and volume of each particle are obtained, the volume frequency of each aspect ratio can be calculated, and the cumulative volume frequency (volume ratio) of particles having an aspect ratio of 0.70 or less can be determined.

[0052] The aspect ratios of all particles in the powder to be measured are arranged in ascending order, and the central value of the particle corresponding to 50% of the total volume of all particles is set as A 50 Since the upper limit of the aspect ratio is 1 by definition, the central value of the aspect ratio is 1 or less.

[0053] In the iron-based powder of the present application, the cumulative volume frequency (volume ratio) of particles having an aspect ratio of 0.70 or less constituting the powder is 70% or less, and the central value A 50 of the aspect ratio calculated from the cumulative volume frequency is 0.60 or more. In the case where one or both of these conditions are not satisfied, the volume frequency of particles deformed from a spherical shape increases, the coercive force of the particles increases, and in addition, the destruction of the insulating coating of the particles also increases, resulting in an increase in the hysteresis loss of the powder core, the eddy current loss between particles, and ultimately the iron loss. It is preferable that the cumulative volume frequency of particles having an aspect ratio of 0.70 or less be 60% or less and the central value A 50 of the aspect ratio calculated from the cumulative volume frequency be 0.65 or more. The cumulative volume frequency of particles having an aspect ratio of 0.70 or less can also be 0%. In addition, the upper limit of the central value A 50 of the aspect ratio calculated from the cumulative volume frequency is 1, and can also be 1.

[0054] [Maximum particle diameter]

[0055] The iron-based powder of the present application preferably has a maximum particle diameter of 500 μm or less. By having a maximum particle diameter of 500 μm or less, the particle diameters of the powder particles as a whole are more uniform, the segregation of particles that are close in particle diameter and are aggregated with each other is prevented, the number of fine particles adhering to the surface of coarse particles is reduced, and fine particles enter the interstices between the particles formed by coarse particles, so that high densification, high strength, and thus low iron loss of the powder magnetic core can be achieved. On the other hand, from the viewpoint of uniform resin coating on the powder, the maximum particle diameter can be 10 μm or more. The maximum particle diameter is the maximum value of the particle diameter distribution when measured by a laser diffraction particle size distribution measuring machine, and the measurement conditions are the same as those of D 50 , described above. From the viewpoint of uniformity of the particles, the maximum particle diameter is preferably 2 times D 50 or less, and further preferably 1.5 times D a b c d e f

[0056] [Composition]

[0057] The iron-based powder of the present application preferably has a composition, excluding inevitable impurities, composed of a soft magnetic powder represented by the composition formula: Fe a Si b B c P d Cu e M f

[0058] (In the formula,

[0059] 79 at% ≤ a ≤ 84.5 at%,

[0060] 0 at% < b < 6 at%,

[0061] 0 at% < c ≤ 10 at%,

[0062] 4 at% < d ≤ 11 at%,

[0063] 0.2 at% ≤ e ≤ 1.0 at%,

[0064] 0 at% ≤ f ≤ 4 at%,

[0065] a + b + c + d + e + f = 100 at%,

[0066] M is at least one element selected from the group consisting of Nb, Mo, Ni, Sn, Zr, Ta, W, Hf, Ti, V, Cr, Mn, C, Al, S, O, and N

[0067] By such a composition, the crystallinity of the powder can be suppressed to 10% or less, and after heat treatment, nanocrystals of bcc Fe can be precipitated and the magnetic properties can be further improved.

[0068] The soft magnetic powder can contain inevitable impurities that are inevitably mixed from manufacturing processes and the like, but the above composition formula does not include the inevitable impurities.

[0069] Fe is an essential element that bears magnetism, and the proportion of Fe can be 79 at% or more, preferably 80 at% or more, and in addition, can be 84.5 at% or less, preferably 83.5 at% or less.

[0070] Si is an element that bears amorphous phase formation, and the proportion of Si can be less than 6 at% (including zero), preferably 2 at% or more, and in addition, more preferably 5.5 at% or less.

[0071] B is an element that bears amorphous phase formation, and the proportion of B can be 4 at% or more, preferably 5 at% or more, and in addition, can be 10 at% or less, preferably 9 at% or less.

[0072] P is an element that bears amorphous phase formation, and the proportion of P can exceed 4 at%, preferably exceed 5 at%, and in addition, can be 11 at% or less, preferably 10 at% or less.

[0073] Cu is an element that contributes to nanocrystallization, and the proportion of Cu can be 0.2 at% or more, preferably 0.3 at% or more, and in addition, can be 1.0 at% or less, preferably 0.9 at% or less.

[0074] In addition to the above elements, at least one element selected from the group consisting of Nb, Mo, Ni, Sn, Zr, Ta, W, Hf, Ti, V, Cr, Mn, C, Al, S, O, and N can be contained. The proportion of these elements can be 4 at% or less (including zero).

[0075] [Manufacture of Powder]

[0076] The iron-based powder of the present application can be manufactured using a water atomization method in which water or gas is sprayed to a molten metal to form a spray and is cooled and solidified, or a gas atomization method. Alternatively, it can be obtained by processing a powder obtained by a pulverization method or an oxide reduction method.

[0077] In the case of using the water atomization method or the gas atomization method, the aspect ratio can be made to be within the prescribed range by adjusting the gas in which water or gas is sprayed to be low pressure. Alternatively, the adjustment of the aspect ratio can also be performed by smoothing the surface of the particles or removing particles having a low circularity by classification using a sieve. For example, the surface of the particles of the powder obtained by the pulverization method, the oxide reduction method, or the water atomization method or the gas atomization method under normal pressure can be smoothed and / or particles having a low aspect ratio can be removed by classification using a sieve to obtain the iron-based powder of the present application.

[0078] In the case where the iron-based powder of the present application is a powder composed of a soft magnetic powder of a prescribed composition formula, the raw material can be adjusted so as to become the prescribed composition to be manufactured. For example, in the case of using the water atomization method or the gas atomization method, the raw material can be weighed so as to become the prescribed composition, dissolved to produce an alloy melt, and the alloy melt can be discharged from a nozzle, water or gas can be sprayed to form a spray and cooled and solidified, and the desired powder can be obtained by processing as the case can be.

[0079] [Insulating coating]

[0080] The iron-based powder for a powder magnetic core of the present application can have an insulating coating on the surface of the particles that constitute the iron-based powder for a powder magnetic core.

[0081] The insulating coating is not particularly limited, and can be an inorganic insulating coating or an organic insulating coating. One of them can be used, or two of them can be used.

[0082] As the inorganic insulating coating, a film containing an aluminum compound is preferred, and a film containing an aluminum phosphate is more preferred. The inorganic insulating coating can be a chemical conversion film.

[0083] As the organic insulating coating, an organic resin film is preferred. As the organic resin film, for example, an organic silicon resin, a phenol resin, an epoxy resin, a polyamide resin, a polyimide resin, or the like can be mentioned. They can be contained alone, or two or more of them can be contained at an arbitrary ratio. Among them, a film containing an organic silicon resin is more preferred.

[0084] The insulating coating can be a film of one layer, or can be a multilayer film composed of two or more layers. The multilayer film can be a multilayer film composed of the same kind of film, or can be a multilayer film composed of different kinds of films.

[0085] As the organic silicon resin, for example, SH805, SH806A, SH840, SH997, SR620, SR2306, SR2309, SR2310, SR2316, DC12577, SR2400, SR2402, SR2404, SR2405, SR2406, SR2410, SR2411, SR2416, SR2420, SR2107, SR2115, SR2145, SH6018, DC-2230, DC3037, QP8-5314, KR-251, KR-255, KR-114A, KR-112, KR-2610B, KR-2621-1, KR-230B, KR-220, KR-285, K295, KR-2019, KR-2706, KR-165, KR-166, KR-169, KR-2038, KR-221, KR-155, KR-240, KR-101-10, KR-120, KR-105, KR-271, KR-282, KR-311, KR-211, KR-212, KR-216, KR-213, KR-217, KR-9218, SA-4, KR-206, ES-1001N, ES-1002T, ES1004, KR-9706, KR-5203, KR-5221, and the like manufactured by Toray-Dow Corning Co., Ltd. can be mentioned, but are not limited to these. These can be used alone or two or more kinds can be used in any ratio.

[0086] As the aluminum compound, any compound containing aluminum can be used, and for example, phosphates, nitrates, acetates, hydroxides, and the like of aluminum can be mentioned. These can be used alone or two or more kinds can be used in any ratio.

[0087] The coating layer containing the aluminum compound can be a film in which the aluminum compound is the main component, or a film composed of the aluminum compound. The film can further contain a metal compound containing a metal other than aluminum. As the metal other than aluminum, for example, Mg, Mn, Zn, Co, Ti, Sn, Ni, Fe, Zr, Sr, Y, Cu, Ca, V, Ba, and the like can be mentioned. These can be used alone or two or more kinds can be used in any ratio. As the metal compound containing a metal other than aluminum, for example, phosphates, carbonates, nitrates, acetates, hydroxides, and the like can be mentioned. These can be used alone or two or more kinds can be used in any ratio. The metal compound is preferably soluble in a solvent such as water, and is more preferably a water-soluble metal salt.

[0088] When the content of phosphorus in the coating layer containing the phosphate or phosphorus oxide compound containing aluminum is set as P (mol), and the total content of all metal elements in the coating layer is set as M (mol), the ratio of P to M (P / M) is preferably 1 or more and less than 10. If P / M is 1 or more, chemical reactions on the surface of the iron-based powder at the time of coating layer formation proceed sufficiently, and the adhesion of the coating layer is improved, whereby the strength and insulation of the powder magnetic core can be further improved. On the other hand, if P / M is less than 10, no free phosphoric acid remains after the coating layer is formed, and corrosion of the iron-based powder can be sufficiently prevented. P / M is more preferably 1 to 5, and P / M is further preferably 2 to 3 from the viewpoint of effectively preventing variations and destabilization of the specific resistance.

[0089] In the coating layer containing the phosphate or phosphorus oxide compound containing aluminum, when the content of aluminum is set as A (mol), the ratio of A to M (A / M), which is the total content of all metal elements in the coating layer, is preferably more than 0.3 and 1 or less. If this range is satisfied, aluminum, which has high reactivity with phosphoric acid, is sufficiently present, and the remaining of unreacted free phosphoric acid can be suppressed. A / M is more preferably 0.4 or more, and further preferably 0.8 or more, and is preferably 1.0 or less.

[0090] The coating amount of the insulating coating layer is not particularly limited, but is preferably 0.01 to 10 mass%. If the coating amount is in the above range, a uniform coating layer can be formed, sufficient insulation can be ensured, and the proportion of the iron-based powder in the powder magnetic core can be ensured, and sufficient strength and magnetic flux density of the molded body can be obtained.

[0091] Here, the coating amount refers to a value defined by the following formula.

[0092] Coating amount (mass%) = (mass of the insulating coating layer) / (mass of the portion other than the insulating coating layer in the iron-based powder for powder magnetic cores) x 100

[0093] The iron-based powder for powder magnetic cores of the present application can contain a substance other than the above-described insulating film in at least one of the insulating coating layer, under the insulating coating layer, and on the insulating coating layer. As such a substance, a surfactant for improving wettability, a binder for inter-particle adhesion, an additive for adjusting pH, and the like can be given. The total amount of the substance is preferably 10 mass% or less with respect to the entire insulating coating layer.

[0094] The method of forming the insulating coating layer is not particularly limited, but is preferably formed by a wet process. As the wet process, for example, a method in which a treatment liquid for forming an insulating coating layer is mixed with the iron-based powder can be given.

[0095] The mixing method is not particularly limited, but a method in which the iron-based powder is mixed with the treatment solution by stirring in a tank of a super micronizer or a Henschel mixer, or the like, a method in which the iron-based powder is made to flow by a rolling flow type coating device or the like and supplied with the treatment solution to mix, or the like is preferred.

[0096] The supply of the solution to the iron-based powder can supply the entire amount before or immediately after the start of mixing, or can supply several times during mixing. Alternatively, a liquid droplet supply device, a sprayer, or the like can be used to continuously supply the treatment liquid during mixing.

[0097] The supply of the treatment liquid is not particularly limited, but is preferably performed using a sprayer. By using a sprayer, the treatment solution can be uniformly spread over the entire iron-based powder, and in addition, by adjusting the spraying conditions, the diameter of the sprayed droplets can be reduced to about 10 μm or less, as a result of which over-thickening of the coating can be prevented, and a uniform and thin insulating coating layer can be easily formed on the iron-based powder. On the other hand, stirring and mixing can be performed by a flow tank such as a flow granulator, a rolling granulator, or a stirring type mixer such as a Henschel mixer, which has the advantage of suppressing agglomeration of the powders with each other. From the viewpoint of forming a more uniform insulating coating layer on the iron-based powder, it is preferred to combine a flow tank or a stirring type mixer with the supply of the treatment solution using a sprayer. From the viewpoint of promoting drying of the solvent and promoting the reaction, it is advantageous to perform a heating treatment in the mixer or after mixing.

[0098] <Compression Powder Magnetic Core>

[0099] The compression powder magnetic core according to another embodiment of the present application is a compression powder magnetic core using the above-described iron-based powder for a compression powder magnetic core.

[0100] The manufacturing method of the compression powder magnetic core is not particularly limited, and any method can be used. For example, the compression powder magnetic core can be obtained by charging the iron-based powder of the present application into a mold and pressure forming into a desired size and shape. The iron-based powder preferably has an insulating coating film.

[0101] The pressure forming is not particularly limited, and any method can be used, for example, normal temperature forming, mold lubrication forming, or the like can be mentioned.

[0102] The forming pressure can be appropriately decided depending on the use, but from the viewpoint that if the forming pressure is increased, the compression powder density becomes higher and the magnetic characteristics improve, it is preferred to be 490 MPa or more, and more preferably 686 MPa or more.

[0103] A lubricant can be used at the time of press molding. The lubricant can be applied to the wall surface of the mold or added to the iron-based powder. By using the lubricant, it is possible to reduce the friction between the mold and the powder at the time of press molding, it is possible to further suppress the decrease in the density of the molded body, and it is also possible to reduce the friction at the time of taking out from the mold, it is possible to prevent the breakage of the molded body (the powder compact) at the time of taking out.

[0104] The lubricant is not particularly limited, and metal soaps such as lithium stearate, zinc stearate, calcium stearate, and the like, waxes such as fatty acid amides can be mentioned.

[0105] The powder compact obtained can be subjected to heat treatment. By performing the heat treatment, it is possible to expect effects such as the reduction in the hysteresis loss due to stress relief, the increase in the strength of the molded body, and the like. The heat treatment conditions can be appropriately decided, but the temperature is preferably 200°C to 700°C, and the time is preferably 5 minutes to 300 minutes. The heat treatment can be performed in any atmosphere such as in the atmosphere, in a non-active atmosphere, in a reducing atmosphere, in vacuum, and the like. It is also possible to provide a stage of maintaining at a certain temperature at the time of temperature increase or decrease in the heat treatment.

[0106] Example

[0107] Hereinafter, the present application will be further explained in detail by examples, but the present application is not limited by the examples.

[0108] The iron-based powder was produced according to the following procedure.

[0109] Fe78B9Si5P6Cu2non-crystalline soft magnetic alloy powder and Fe 81.3 Si3B9P6Cu 0.7 non-crystalline soft magnetic alloy powder. The produced powder was vacuum-dried to obtain a dried powder. 81.6 Si5B5P 7.5 Cu 0.4 Ni 0.5 non-crystalline soft magnetic alloy powder. The produced powder was vacuum-dried to obtain a dried powder.

[0110] The dried powder was classified to adjust the particle diameter and the aspect ratio. At the time of classification, an air classifier (manufactured by Seishin Enterprise Co., Ltd., LABO CLASSIFEL N-01) was used, and the dispersing plate was rotated at a speed of 1000 to 1650 rpm to perform classification. In addition, as comparative powders (Comparative Examples 1 and 8), powders produced by the water atomization method alone without performing classification using the air classifier were prepared.

[0111] The iron-based powder was evaluated as shown below.

[0112] The dry powder was dispersed on a glass surface, and 5000 particles were observed and photographed for each sample by a microscope (manufactured by Spectris Co., Ltd., Morphologi G3). The microscope used a lens with a magnification of 10 times. The cumulative volume frequency (volume ratio) of particles having an aspect ratio of 0.70 or less and the central value A, which is a representative value of the aspect ratio of the entire powder particles, were calculated from the calculated aspect ratio and volume frequency 50 In addition, using a laser diffraction particle size distribution measuring machine (manufactured by HORIBA, Ltd., LA-950V2), the soft magnetic alloy amorphous powder was put in ethanol as a solvent, and the particle diameter and volume frequency of the dry powder were measured after dispersion by ultrasonic vibration for 1 minute. The central value D, which is a representative value of the particle diameter of the entire powder particles, was calculated from the particle diameter and volume frequency 50 The maximum particle diameter is the maximum value of the particle size distribution when measured by the laser diffraction particle size distribution measuring machine.

[0113] The powder magnetic core was produced according to the following procedure.

[0114] The soft magnetic alloy amorphous powder was subjected to insulating coating by adding and mixing a solution for insulating coating, and a coated powder was produced. The solution used was a solution obtained by adding dimethylbenzene to dilute a silicone resin component at 60% by mass, and was used in an amount such that the resin became 3% by mass with respect to the soft magnetic alloy amorphous powder. After mixing, standing was performed for 10 hours in an atmospheric atmosphere in order to dry. After drying, heat treatment was performed at 150°C for 60 minutes in order to cure the resin.

[0115] Next, the coated soft magnetic alloy amorphous powder was filled in a mold coated with lithium stearate, and pressure molding was performed to produce a powder magnetic core (outer diameter 38 mmφ x inner diameter 25 mmφ x height 6 mm). The molding pressure was 1470 MPa, and 1-time molding was performed. In order to improve the strength of the molded body, after heating at 3°C / minute from room temperature in a furnace under a N2 atmosphere, heat treatment was performed at 400°C for 20 minutes. After heat treatment, after being taken out of the furnace under a N2 atmosphere, air cooling was performed to room temperature, and the obtained sample was used as the powder magnetic core.

[0116] The powder magnetic core was evaluated as shown below.

[0117] The powder density of each of the obtained powder magnetic cores was calculated. The powder density was calculated by measuring the mass of the powder magnetic core and dividing the mass by the volume calculated from the dimensions of the powder magnetic core.

[0118] A test sample was prepared by winding 100 turns on the primary side and 20 turns on the secondary side onto a fabricated powder core. Using a DC magnetization characteristic testing apparatus (METRON TECHNOLOGY RESEARCH CO.,LTD., SK-110 type), a hysteresis loop was plotted at a maximum magnetic flux density of 0.1T and 50Hz, and the area was used as the hysteresis loss. The measured hysteresis loss was set to 400 times, and the hysteresis loss at a magnetic flux density of 0.1T and a frequency of 20kHz was calculated. Additionally, using a high-frequency iron loss measuring apparatus (METRON TECHNOLOGY RESEARCH CO.,LTD.), the iron loss at 0.1T and 20kHz was measured. The difference between the measured iron loss and the aforementioned hysteresis loss was calculated as the eddy current loss.

[0119] The magnetic properties are evaluated as follows.

[0120] Iron loss is 250kW / m 3 Below...◎

[0121] Iron loss is 300kW / m 3 Below and above 250kW / m 3 ···〇

[0122] Iron loss exceeds 300kW / m 3 ···×

[0123] Table 1 shows the use of Fe 81.3 Si3B9P6Cu 0.7 The grading conditions, powder evaluation, and pressed magnetic core evaluation of comparative examples and embodiments of soft magnetic alloy amorphous powders.

[0124]

[0125] As shown in Table 1, when using D 50 The cumulative volumetric frequency (volume ratio) of particles smaller than 150 μm and with an aspect ratio of less than 0.70 is less than 70%, and the median aspect ratio is A. 50 In the case of powder with a particle size of 0.60 or higher, the iron loss of the pressed powder core is 300 kW / m. 3 As can be seen from the following, the powder used is an excellent iron-based powder for pressed magnetic cores.

[0126] Regarding iron loss, if we consider hysteresis loss and eddy current loss, the examples show lower and superior losses compared to the comparative examples. This is because the powders of the examples contain fewer particles with low aspect ratios (aspect ratios below 0.70), and A, which represents the overall aspect ratio of the powder, is lower. 50Also, the coercive force of the particles becomes low, and the hysteresis loss decreases. In addition, the destruction of the insulating coating on the surface of the particles when the powder is formed into a powder core is less, and the eddy current loss between the particles decreases.

[0127] wherein the cumulative volume frequency (volume ratio) of the particles having an aspect ratio of 0.70 or less is 60% or less, A 50 is 0.65 or more, D 50 In Examples 3 and 4, where the powder is 100 μm or less, the iron loss of the powder core is 250 kW / m 3 As shown below, the powder used is more excellent as an iron-based powder for a powder core.

[0128] Table 2 shows the classification conditions, evaluation of the powder, and evaluation of the powder core of the comparative example and the examples using Fe 81.6 Si5B5P 7.5 Cu 0.4 Ni 0.5 Table 2 shows the classification conditions, evaluation of the powder, and evaluation of the powder core of the comparative example and the examples using Fe

[0129]

[0130] As shown in Table 2, in the case of the powder of the examples where D 50 is 150 μm or less, the cumulative volume frequency (volume ratio) of the particles having an aspect ratio of 0.70 or less is 70% or less, and A 50 is 0.60 or more, the iron loss of the powder core is 300 kW / m 3 As shown below, the powder used is excellent as an iron-based powder for a powder core.

[0131] Regarding the iron loss, if the hysteresis loss and the eddy current loss are focused on, the examples are all lower and excellent compared to the comparative example. This is because the powder of the examples has fewer particles having a low aspect ratio of 0.70 or less, and A 50 Also, the coercive force of the particles becomes low, and the hysteresis loss decreases. In addition, the destruction of the insulating coating on the surface of the particles when the powder is formed into a powder core is less, and the eddy current loss between the particles decreases.

[0132] wherein the cumulative volume frequency (volume ratio) of the particles having an aspect ratio of 0.70 or less is 60% or less, A 50 is 0.65 or more, D 50 In Examples 7 and 8, where the powder is 100 μm or less, the iron loss of the powder core is 250 kW / m 3 As shown below, the powder used is more excellent as an iron-based powder for a powder core.

[0133] Industrial applicability

[0134] A powder magnetic core using the iron-based powder for powder magnetic cores of the present application has low iron loss and high insulation, and is highly useful.

Claims

1. An iron-based powder for a powder magnetic core, a central value of particle diameters calculated from a cumulative volume frequency of the particles constituting the iron-based powder for a powder magnetic core is 150 μm or less, a cumulative volume frequency of the particles having an aspect ratio of 0.70 or less is 70% or less, and a central value of the aspect ratio calculated from the cumulative volume frequency is 0.60 or more.

2. The iron-based powder for a powder magnetic core according to claim 1, wherein the maximum particle diameter of the particles is 500 μm or less.

3. The iron-based powder for a powder magnetic core according to claim 1, wherein The composition of the components other than the inevitable impurities is composed of soft magnetic powder represented by the composition formula: Fe a Si b B c P d Cu e M f ​ wherein, 79 at% ≤ a ≤ 84.5 at%, 0 at% < b < 6 at%, 0 at% < c ≤ 10 at%, 4 at% < d ≤ 11 at%, 0.2 at% ≤ e ≤ 1.0 at%, 0 at% ≤ f ≤ 4 at%, and a + b + c + d + e + f = 100 at%, M is at least one element selected from the group consisting of Nb, Mo, Ni, Sn, Zr, Ta, W, Hf, Ti, V, Cr, Mn, C, Al, S, O, and N. wherein, 4. The iron-based powder for a powder magnetic core according to claim 2, wherein The composition of the components other than the inevitable impurities is composed of soft magnetic powder represented by the composition formula: Fe a Si b B c P d Cu e M f ​ 79 at% ≤ a ≤ 84.5 at%, 0 at% < b < 6 at%, 0 at% < c ≤ 10 at%, 4 at% < d ≤ 11 at%, 0.2 at% ≤ e ≤ 1.0 at%, 0 at% ≤ f ≤ 4 at%, and a + b + c + d + e + f = 100 at%, M is at least one element selected from the group consisting of Nb, Mo, Ni, Sn, Zr, Ta, W, Hf, Ti, V, Cr, Mn, C, Al, S, O, and N. the surface of the particles constituting the iron-based powder for a powder magnetic core has an insulating coating.

5. The iron-based powder for a powder magnetic core according to any one of claims 1 to 4, wherein 6. A powder magnetic core, which is a pressure-molded body of the iron-based powder for a powder magnetic core according to any one of claims 1 to 5.

7. A method for manufacturing a powder magnetic core, comprising a step of charging the iron-based powder for a powder magnetic core according to any one of claims 1 to 5 into a mold and pressure-molding. ​

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