JP2012077363A - Method of producing powder for metallurgy, and method for production of powder magnetic core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing powders for metallurgy improving the density and strength of a powder magnetic core and having less environmental load, and to provide a method for production of the powder magnetic core.SOLUTION: The method of producing the powder for metallurgy includes: a step of covering the surface of a plurality of the first magnetic powders with a first binder; and a step of covering the surface of the first binder with a plurality of the second magnetic powders having a particle size smaller than that of the first magnetic powder. The binder is a silicone resin being a solid at room temperature, and the step of covering the surface of the plurality of the first magnetic powders with the binder is carried out while agitating the powders, and also includes a step of elevating the temperature of the silicone resin above the softening point thereof and after that a step of cooling below that point.

Description

  The present invention relates to a metallurgical powder manufacturing method, a powder magnetic core manufacturing method using the powder, and an electromagnetic component manufacturing method using the powder magnetic core.

  Conventionally, an inductor such as a choke coil has been used in a circuit that converts electric power, such as a switching power supply, for example, a DC-DC converter. Examples of the configuration of the inductor include a powder magnetic core obtained by heat-treating a powder compact formed by pressing magnetic powder with a press at a high temperature and a coil formed by winding a winding around the periphery of the powder magnetic core. . This magnetic powder has, for example, iron-based particles made of pure iron and an insulating film covering the surface. The dust core is required to have a magnetic characteristic that can obtain a large magnetic flux density by applying a small magnetic field and a magnetic characteristic that can react sensitively to an external magnetic field. In order to obtain a large magnetic flux density by applying a small magnetic field, it is necessary to improve the density and permeability of the dust core. In order to react sensitively to an external magnetic field, it is necessary to ensure insulation between magnetic powders and suppress energy loss of the dust core.

  In JP-A-7-254522 (Patent Document 1), it is an object to improve the magnetic permeability and its loss characteristics and to increase the mechanical strength in a powder magnetic core obtained by press-molding magnetic powder. As a solution, a method of manufacturing a dust core is described in which a mixing step of magnetic powder and silicone resin is provided twice, a heat treatment step is provided after each mixing step, and then a molding step and an annealing step are performed. Yes.

  In Patent Document 1, a silicone resin that is liquid at 25 ° C. or a solution in which a solid or liquid silicone resin is used at 25 ° C. is used.

Japanese Patent Laid-Open No. 7-254522

  Although the liquid silicone resin is used in the manufacturing method of the powder magnetic core described in Patent Document 1, it is difficult to uniformly coat the surface of the magnetic powder when the high viscosity liquid silicone resin is used, and the silicone is unevenly distributed. The problem that the density and intensity | strength of a powder magnetic core fall arises. When a low-viscosity liquid silicone resin is used, there is a problem that the insulating film is destroyed because the strength after the silicone resin is cured is low. This is because the low-viscosity liquid silicone resin has its terminal silanol group replaced with a less reactive alkoxyl group or the like for stabilization.

  Further, when a solid or liquid silicone is used in the form of a solution, the silicone resin is generally insoluble in water, and thus needs to be diluted with an organic solvent. Organic solvents have a problem of high environmental impact. Furthermore, since the solvent is vaporized after the silicone resin is diluted with an organic solvent and coated on the magnetic powder, there is a problem that a dense coating is difficult to obtain and the strength of the cured silicone resin is low.

  Accordingly, an object of the present invention is to provide a method for producing a metallurgical powder and a method for producing a powder magnetic core that improve density and strength and have a low environmental load.

In order to solve the above problems, a method for producing a metallurgical powder of the present invention includes:
Coating the first binder on the surfaces of the plurality of first magnetic powders;
Coating the surface of the first binder with a plurality of second magnetic powders having a particle size smaller than the particle size of the first magnetic powder. The binder is a silicone resin that is solid at room temperature,
The step of coating the binder on the surfaces of the plurality of first magnetic powders is performed while stirring the magnetic powder, and includes a step of raising the temperature to the softening temperature or higher of the silicone resin and a step of cooling to the softening temperature or lower. It was set as the manufacturing method of the metallurgical powder.

Thereby, a dense silicone film can be coated on the surface of the magnetic powder with a uniform thickness. Moreover, since an organic solvent is not used, a high-strength film can be formed. Furthermore, it can be set as the process with little load to an environment.
Further, by coating the binder only on the powder having a large particle diameter in advance, it is possible to prevent the second magnetic powder having a small particle diameter from aggregating when the first binder is coated. Furthermore, since a magnetic powder having a small particle diameter exists between large magnetic powders, the density can be improved.

  Preferably, in the metallurgical powder manufacturing method, the plurality of first magnetic powders and second magnetic powders include Fe—Si—Al alloys, Fe—Si alloys, Fe—Al alloys, and amorphous alloys. Use at least one.

  Thereby, since a magnetic powder does not carry out plastic deformation, the fracture | rupture of a silicone film can be prevented and a loss can be suppressed.

  Preferably, the metallurgical powder manufacturing method further includes a step of adding a second binder for reinforcing the compact during the step of coating the second magnetic powder, and the second binding. Water is used as a solvent for the agent.

  Thereby, the resin for molding is further provided, the strength of the molded body is improved, and the molded body can be easily held and transported.

  A powder magnetic core is manufactured by pressure-molding the metallurgical powder manufactured by the above process and heat-treating the molded body at a temperature equal to or higher than the sublimation temperature of the second binder.

  Thereby, a high-strength and high magnetic property powder magnetic core can be manufactured.

  An electromagnetic component is manufactured by winding a winding around the dust core.

  Thereby, an electromagnetic component having high strength and high magnetic properties can be manufactured.

  According to the metallurgical powder manufacturing method and the powder magnetic core manufacturing method of the present invention, it is possible to improve the density and strength and provide a metallurgical powder manufacturing method and a powder magnetic core manufacturing method with low environmental impact. it can.

  Hereinafter, the manufacturing method of the metallurgical powder, dust core, and electromagnetic component of the present invention will be described.

[Powder for metallurgy]
<Structure>
The metallurgical powder of the present invention includes a plurality of first magnetic powders, a first binder composed of a silicone resin coated on the surface thereof, and a plurality of second magnetic powders coated on the surface thereof. And a plurality of second magnetic powders having a particle size smaller than the particle size of the first magnetic powder.

(Magnetic powder)
The magnetic powder preferably has such a rigidity that it is not substantially deformed by the pressure applied when obtaining a molded body to be described later. For example, a magnetic powder having a Vickers hardness HV0.1 of 300 or more is suitable. Specific examples include Fe—Si—Al alloys, Fe—Si alloys, Fe—Al alloys, amorphous alloys, and the like. Of the Fe-Si-Al alloys, those containing 3 to 15% by mass of Si and 1 to 10% by mass of Al are suitable. Among Fe-Si alloys, those containing 3 to 15% by mass of Si are suitable. Of the Fe-Al alloys, those containing 1 to 10% by mass of Al are suitable. With such a magnetic powder, it is easy to obtain a fired body having predetermined electromagnetic characteristics. Other uses such as Fe-Ni alloys, Fe-B alloys, Fe-C alloys, Fe-N alloys, Fe-P alloys, Fe-Co alloys, Fe-Ni-Co alloys are also considered. It is done. The Vickers hardness HV0.1 is measured in accordance with JIS-Z2244, and “HV0.1” indicates that the load of the indenter during the test is 0.1 kgf. Specific examples of the Vickers hardness in each alloy system are about 500 for Fe-9.5Si-5.5Al, about 400 for Fe-6.5Si, and about 300 or more for Si-containing alloys of 4 mass% or more.

  The magnetic powder is composed of a first magnetic powder and a second magnetic powder having a particle size smaller than that of the first magnetic powder. The first magnetic powder and the second magnetic powder are preferably a combination in which the particle size distribution ranges do not overlap or a combination in which the distribution ranges are adjacent. By such a combination of coarse particles and fine particles, it is easy to obtain a molded body in which fine particles are filled in gaps between coarse particles. For example, the first magnetic powder preferably has a minimum particle size of about 40 μm and a maximum particle size of about 150 μm. Use of such coarse grains is effective in suppressing increase in eddy current loss when a dust core is used in a high frequency range of 1 kHz or higher. The maximum particle size of the second magnetic powder is preferably about 40 μm. However, for the convenience of handling fine particles, the minimum particle size of the second magnetic powder is preferably 1 μm or more. Further, the particle size ratio between the coarse particles and the fine particles is preferably about the average particle size of the fine particles: the average particle size of the coarse particles = 1: 2 to 1:10. Further, the mass blending ratio of coarse particles to fine particles is preferably about fine particles: coarse particles = 1: 1 to 1: 4. By setting it as such a particle size ratio or compounding ratio, it is easy to obtain a high-density molded body or fired body in which fine particles are filled in gaps between coarse particles.

  In addition, the magnetic powder is preferably obtained by the atomizing method, but any of those produced by the water atomizing method and those produced by the gas atomizing method can be used. Since the magnetic powder produced by the water atomization method has many irregularities on the particle surface, it is easy to obtain a high-strength fired body by meshing the irregularities. On the other hand, the magnetic powder produced by the gas atomization method is preferable because the particle shape is almost spherical, and there are few irregularities that break through the insulating layer. In addition, an insulating film such as a natural oxide film may be formed on the surface of the magnetic powder.

(First binder made of silicone resin)
The first binder made of silicone resin ensures insulation between the magnetic powders by covering the surface of the magnetic powders. When the metallurgical powder of the present invention is compressed to form a molded body, and then the molded body is fired, the binders are bonded and cured to retain the fired body. The step of coating the surface of the magnetic powder with the binder is performed by coating the magnetic powder and a silicone resin that is solid at room temperature at or above the softening temperature of the silicone resin.

  The object to be coated with the first binder made of silicone resin is the first magnetic powder. Thereby, aggregation of the fine particles generated at the time of resin coating can be suppressed. Moreover, when forming a molded object using the metallurgical powder of this invention, the state with which the fine particle was filled between coarse particles is implement | achieved frequently. In such a state, suppressing contact between the coarse particles is effective in reducing loss. Since the silicone resin film is formed only on the coarse particles, even if the fine particles are in direct contact with each other, it can be considered that there are equivalently slightly larger fine particles, so that the loss reduction effect can be sufficiently achieved. Can do. Thus, high density and low loss can be easily realized by coating only the first magnetic powder with the first binder made of silicone resin.

  The thickness of the first binder made of silicone resin is preferably 20 nm or more and 1 μm or less. By setting the lower limit value or more, the insulation between the magnetic powders is ensured, and the mechanical strength that is not destroyed by the applied pressure during metallurgical powder compression is ensured. By setting it to the upper limit value or less, the thickness of the coating is prevented from becoming too large, and when the metallurgical powder is formed into a molded body or a fired body, a predetermined density is secured and damage to the coating is suppressed.

(Second binder)
When the metallurgical powder is compressed into a molded body, the second binder is a resin for retaining the molded body, and is preferably a thermoplastic resin. Specific examples of the thermoplastic resin include acrylic alcohol, polyvinyl alcohol, polyvinyl butyral, polyethylene resin, and the like. The solvent for the second binder is preferably water.

<Manufacturing method>
The metallurgical powder of the present invention can be obtained by a production method mainly including resin mixing, cooling, and granulation.

(Mixed resin)
The magnetic powder is mixed with a solid silicone resin at room temperature. This mixing is preferably stirred with a mixer or the like. The blending amount of the silicone resin is preferably selected according to the specific surface area of the magnetic powder to be mixed. By determining the blending amount of the silicone resin according to the specific surface area of the magnetic powder, a silicone resin film having a predetermined thickness can be formed on the surface of the magnetic powder. The blending amount of the magnetic powder and the silicone resin may be, for example, such that the silicone resin is about 0.1 to 2.0% by mass with respect to the mixture of both, but is more preferably 0.3 to 1.0% by mass. The silicone resin is softened during mixing and coated on the magnetic powder. The softening of the silicone resin is performed by setting the temperature during mixing to be equal to or higher than the softening temperature of the silicone resin without using a solvent. In general, silicone resins that are liquid at room temperature may have a silanol group at the end of the composition replaced with an alkoxyl group having low reactivity in order to stabilize the liquid state. Therefore, there is a possibility that the strength cannot be increased when the molded body is fired. A liquid silicone resin having a high viscosity is difficult to uniformly coat a magnetic powder. When diluting a silicone resin with an organic solvent, there is a risk that the environmental burden will be high.

(cooling)
Usually, the mixed magnetic powder is cooled to below the softening temperature of the silicone resin. This cooling turns the silicone resin into a solid.

(Hoshigushi)
Usually, since the magnetic powder after cooling is partly bonded to each other via a silicone resin, it is preferable to perform “unraveling” to separate the bonding. The loosening operation is enough to lightly screen the magnetic powder after curing the silicone resin.

(Granulation)
The granulation is performed by mixing the first magnetic powder coated with the silicone resin, the second magnetic powder having a smaller particle diameter, and the molding resin with a mixer or the like. This mixing usually forms unit particles of granulated powder in which several magnetic powders are integrated with a molding resin. The molding resin is mixed with the magnetic powder by being diluted with water and sprayed.

  The mixture of the magnetic powder and the molding resin is preferably mixed so that the total amount of the molding resin to be added is 0.5 to 3.0% by mass of the mixture. By setting the resin content above this lower limit, the molded body can be sufficiently retained, and conversely by setting it to the upper limit or lower, the amount of resin in the mixture is set to an appropriate amount, so that the molded body has a high density. Can be

[Molded body]
<Structure>
The molded body of the present invention is obtained by pressure-molding the metallurgical powder into a predetermined shape. That is, in this molded body, the first magnetic powder coated with the silicone resin and the second magnetic powder having a smaller particle diameter are integrated with the molding resin. Since the magnetic powder used here is not substantially deformed by the pressure at the time of molding, the silicone coating coated on the surface of the magnetic powder is also prevented from being damaged. The shape of the molded body may be selected according to the shape of the magnetic core of the electromagnetic component.

<Manufacturing method>
Such a molded body is obtained by a method including a step of supplying metallurgical powder to a mold and a step of pressing the metallurgical powder in the mold to form a molded body.

  Here, the pressure for pressurizing the metallurgical powder is preferably about 500 MPa to 1200 MPa. By setting the lower limit value or more, a high-density molded body can be obtained. Moreover, the damage of the silicone film accompanying a deformation | transformation of a magnetic powder can be suppressed by setting it as below an upper limit. This pressurization may be performed at room temperature, but when a thermoplastic resin is used as the molding resin, it is preferably molded at a temperature equal to or higher than the glass transition temperature of the resin. This can improve the density and strength of the molded body.

[Dust core]
<Structure>
The dust core of the present invention is obtained by heat-treating the above molded body at a temperature higher than the sublimation temperature of the molding resin.

  As described above, in the metallurgical powder, the surface of the magnetic powder is coated with a binder made of silicone resin. This silicone film is modified by firing, becomes an amorphous body containing Si, C, and O, and becomes a binder that firmly integrates the magnetic powder.

<Manufacturing method>
Such a dust core can be obtained by subjecting the above-described molded body to a predetermined heat treatment. The heating temperature for this heat treatment is preferably 600 ° C to 1000 ° C. The heating time is preferably about 30 minutes to 2 hours. Many strains are introduced into the magnetic powder constituting the compact before firing. By heat-treating the molded body under the above conditions, the strain can be sufficiently removed. Further, by performing heat treatment under the above conditions, the molding resin disappears and the silicone resin coated on the surface of the magnetic powder is used as an amorphous binder containing Si, C, and O. In addition, the heat treatment atmosphere is preferably an inert gas atmosphere such as a nitrogen atmosphere or a reduced pressure atmosphere. Heat treatment in such an atmosphere is preferable in that it can prevent a decrease in the mass of the silicone resin and can reliably retain the shape of the dust core.

[Electromagnetic parts]
The electromagnetic component of the present invention includes a magnetic core and a coil. A magnetic core consists of a powder magnetic core mentioned above. Examples of the shape of the magnetic core include an E-type and an I-type core such as an annular shape and a rod shape. On the other hand, the coil is formed by winding a winding having a conductive wire provided with an insulating coating. As the cross-sectional shape of the winding, various shapes such as a circle and a rectangle can be used. For example, a round wire may be wound in a spiral shape to form a cylindrical coil, or a flat wire may be wound edgewise in a spiral shape to form a rectangular tube coil.

  This electromagnetic component may be configured by winding a winding around the outer periphery of the magnetic core, or may be configured by fitting an air-core coil formed in advance in a spiral shape into the outer periphery of the magnetic core.

  Specific examples of the electromagnetic component include a high frequency choke coil, a high frequency tuning coil, a bar antenna coil, a power choke coil, a power transformer, a switching power transformer, and a reactor.

  A metal powder was produced under the following conditions, a compact was molded, and the fired body was fired to produce a test piece of a dust core, and several characteristics of the test piece were evaluated.

<Preparation of test piece>
(Invention) Sample No. 1: Silicone resin coating only on coarse powder by heating and mixing First, magnetic powder obtained by gas atomization method with a composition of Fe-9.5 mass% Si-5.5 mass% Al and silicone resin powder Prepared. The maximum particle size of the magnetic powder used is 106 μm, and the average particle size is about 60 μm. YR3370 manufactured by Momentive was used as the silicone resin powder. This silicone resin has a softening point of 109 ° C. and a curing point of 200 ° C.

  Next, the magnetic powder was sieved and classified into two types: a fine particle having a particle size of 44 μm or less and a coarse particle having a minimum particle size of 44 μm and a maximum particle size of 106 μm. The mass ratio of fine particles to coarse particles is fine particles: coarse particles = 33: 67.

  Next, only the coarse particles of the magnetic powder and the silicone resin powder were heated while mixing with a stirring mixer to form a silicone resin film on the surface of the coarse particles. The temperature of the mixer during mixing was 150 ° C. The blending amount of the coarse particles and the silicone resin powder was such that the silicone resin powder was 0.5% by mass based on the total weight of the coarse particles and fine particles of the magnetic powder. At this time, the thickness of the silicone resin film is about 500 nm. As a stirring mixer, a super mixer manufactured by Kawata Corporation was used, the rotation speed of the mixer was 300 rpm, and the mixing time was 15 minutes. Thereafter, the obtained coarse particles with a silicone resin coating are sieved to loosen the particles.

  Subsequently, fine particles of magnetic powder and a molding resin diluted with water were added to the coarse particles on which the silicone resin film was formed, and granulated. Acrylic resin Q-736 manufactured by Chukyo Yushi Co., Ltd. was used as the molding resin. The granulation was carried out by rolling the magnetic powder while heating it using a dry bread granulator DPZ-01R manufactured by AS ONE, and adding a molding resin diluted with water by spraying. The magnetic powder sprayed with the molding resin solution is dried by heating to form a granulated powder in which a plurality of magnetic powders are bound. The temperature during granulation was 40 ° C. The blending amount of the magnetic powder and the molding resin was such that the molding resin was 1.0% by mass with respect to the total weight of the magnetic powder. The number of rotations during rolling was 300 rpm, and the granulation time was 60 minutes.

Next, the obtained granulated powder was supplied to a mold and compressed to obtain a molded body. The surface pressure during this pressure molding is 980 MPa. With this surface pressure, the magnetic powder is not substantially deformed during molding.
Then, the obtained molded body was subjected to a heat treatment at 800 ° C. for 1 hour in a nitrogen atmosphere to obtain a fired body to be the following sample No. 1. The obtained test piece made of the fired body has a ring shape and has an outer diameter of 34 mm, an inner diameter of 20 mm, and a thickness of 5 mm.

(Comparative product) Sample No. 2: Silicone resin coating on the entire magnetic powder Next, a magnetic powder similar to Sample No. 1 and a silicone resin powder similar to Sample No. 1 were prepared. Subsequently, the magnetic powder was mixed with the silicone resin powder as it was without classification. The amount of silicone resin was 0.5% by mass, which was the same as Sample No. 1. The mixing conditions are the same as for sample No. 1. Then, only the molding resin was added and granulated by the same method as in Sample No. 1, molded and heat-treated, and a fired body to be Sample No. 2 was produced. The size of the fired body specimen is the same as that of sample No. 1.

(Comparative product) Sample No. 3: Silicone resin powder mixing at room temperature Next, a magnetic powder similar to Sample No. 1 and a silicone resin powder similar to Sample No. 1 were prepared. Subsequently, the magnetic powder was classified in the same procedure as in Document No. 1, and the coarse particles and the silicone resin powder were mixed at room temperature. The amount of silicone resin was 0.5% by mass, which was the same as Sample No. 1. The mixing conditions other than the temperature are the same as for sample No. 1. Then, fine particles were added in the same manner as in Sample No. 1 and granulated, molded, and heat treated to produce a fired body to be Sample No. 2. The size of the fired body specimen is the same as that of sample No. 1.

(Comparative product) Sample No. 4: Silicone resin coating by dilution with an organic solvent Next, magnetic powder similar to Sample No. 1 and silicone resin powder similar to Sample No. 1 were prepared. Subsequently, the magnetic powder was classified by the same procedure as Sample No. 1. In order to form a silicone resin film on the surface of the coarse particles, a silicone resin dissolved in xylene was added to the coarse particles. The coating was performed by rolling the coarse particles while heating, and spraying a silicone resin dissolved in xylene. The amount of silicone resin was 0.5% by mass, which was the same as Sample No. 1. The temperature of the powder during coating was 60 ° C., the rotation speed during rolling was 300 rpm, and the coating time was 30 minutes.
Then, fine particles were added in the same manner as in Sample No. 1 and granulated, molded, and heat treated to produce a fired body to be Sample No. 3. The size of the fired body specimen is the same as that of sample No. 1.

<Evaluation>
About each sample produced as mentioned above, the characteristic value enumerated below was measured and the calcination object was evaluated. The evaluation results are summarized in Table 1 below.

≪Strength≫
The test force when the core was cracked by applying a load in the diameter direction to the sample was measured, and the crushing strength was calculated from the following formula.
(Formula) crushing strength = test force × [outer diameter− (outer diameter−inner diameter) / 2] / [thickness × {(outer diameter−inner diameter) / 2} 2]
An autograph manufactured by Shimadzu Corporation was used for the measurement. The compression speed of the autograph was 1 mm / s.

≪Magnetic characteristics≫
Winding was applied to the ring-shaped test piece to prepare a measuring member for measuring the magnetic properties of the test piece. For this measurement member, using a BH / μ analyzer SY-8258 made by Iwatsu Measurement Co., Ltd., the excitation magnetic flux density Bm: 1 kG (= 0.1 T), measurement frequency: 100 kHz, core loss W1 / 100k and AC initial permeability μiac It was measured.

≪Density≫
The outer diameter, inner diameter, thickness, and weight of each test piece were measured, and the density (g / cm ³ ) of the test piece was calculated. The outer diameter, inner diameter, and thickness were measured using a micrometer.

≪Evaluation results≫
From the results in Table 1, Sample No. 1 coated with a silicone resin by heating and mixing magnetic powder and silicone resin powder has higher strength than Sample No. 3 and Sample No. 4. This is because the dense silicone coating coated on the surface of the magnetic powder comes into contact during press molding, and the silicone coating is firmly bound by heat treatment. Sample No. 1 has a higher density and magnetic permeability than sample No. 2 in which the entire magnetic powder is coated with a silicone resin. This is because the generation of fine particle aggregates was suppressed by removing the fine particles during coating.

<Preparation of test piece>
The same magnetic powder as in Example 1 and the same silicone resin powder as in Example 1 were prepared. The magnetic powder was classified in the same procedure as in Example 1. Next, the coarse particles and the silicone resin powder were heated while being mixed with a stirring mixer to form a silicone resin film on the surface of the magnetic powder. The blending amount of the magnetic powder coarse particles and the silicone resin powder was such that the silicone resin powder was 0.1 to 2.0% by weight based on the total weight of the magnetic powder coarse particles and fine particles combined. The mixing conditions were the same as those of sample No. 1 in Example 1. Thereafter, similarly to Sample No. 1 in Example 1, the obtained coarse particles with a silicone resin coating were screened to loosen the particles.

Next, the coarse particles coated with the silicone resin and the fine particles are mixed and granulated, molded, and heat treated in the same manner as in Example 1 to produce the fired bodies to be the following samples No. 4 to No. did. The contents of the prepared test pieces are listed in Table 2 below. The dimensions of the test piece made of the fired body are the same as in Example 1.
(Invention) Sample No. 5: Coarse particles are coated with silicone resin, coating amount = 0.1% by weight
(Invention) Sample No. 6: Only coarse particles are coated with silicone resin, coating amount = 0.3% by weight
(Invention) Sample No.7: Coarse particles only coated with silicone resin, coating amount = 1.0% by weight
(Invention) Sample No.8: Coarse particles only coated with silicone resin, coating amount = 2.0% by weight

  About each test piece, the characteristic value similar to Example 1 was measured, and the sintered body was evaluated. The evaluation results are summarized in Table 2.

  From the results in Table 2, Samples No. 5 to No. 8 coated with silicone resin by heating and mixing coarse particles and silicone resin powder have higher strength than Sample No. 2 and Sample No. 3. Sample No. 5 with a small amount of coating has a slightly low strength, and sample No. 8 with a large amount of coating has a slightly low density and permeability.

  In addition, this invention is not necessarily limited to the Example mentioned above, In the range which does not deviate from the summary of this invention, it can change suitably.

  The metallurgical powder and dust core manufacturing method of the present invention are suitable for obtaining dust cores used in various inductors. The dust core and electromagnetic component of the present invention can be suitably used for a high-frequency choke coil, a high-frequency tuning coil, a bar antenna coil, a power choke coil, a power transformer, a switching power transformer, a reactor, and the like.

Claims (6)

Coating the first binder on the surfaces of the plurality of first magnetic powders;
Coating the surface of the first binder with a plurality of second magnetic powders having a particle size smaller than the particle size of the first magnetic powder. The binder is a silicone resin that is solid at room temperature,
The step of coating the surface of the plurality of first magnetic powders with a binder is performed while stirring, and includes a step of raising the temperature to a temperature higher than the softening temperature of the silicone resin and a step of cooling to a temperature lower than the softening temperature. Manufacturing method.   2. The metallurgy according to claim 1, wherein the plurality of first magnetic powders and second magnetic powders are at least one of an Fe—Si—Al alloy, an Fe—Si alloy, an Fe—Al alloy, and an amorphous alloy. For producing powder for use.   The method for producing a metallurgical powder according to claim 1 or 2, further comprising a step of introducing a second binder during the step of coating the second magnetic powder.   The method for producing a metallurgical powder according to claim 3, wherein the second binder is water as a solvent.   A powder magnetic core, wherein the metallurgical powder according to any one of claims 1 to 4 is molded by pressurization, and the compact is heat-treated at a temperature equal to or higher than a sublimation temperature of the second binder. Method.   A method for manufacturing an electromagnetic component, comprising: winding a winding around the dust core according to claim 5, and arranging a coil outside the magnetic core.