JP2018190799A - Soft magnetic material, powder magnetic core using soft magnetic material, reactor using powder magnetic core, and manufacturing method of powder magnetic core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soft magnetic material in which DC superposition characteristics are improved by reducing loss, when silicon oligomer is used for forming an insulation coat, and to provide a powder magnetic core using the soft magnetic material, a reactor using the powder magnetic core, and a manufacturing method of powder magnetic core.SOLUTION: In a soft magnetic material having soft magnetic powder, and an insulation coat covering the surface of the soft magnetic powder, hardness of the soft magnetic powder is 300 MPa or less, and the insulation coat is silicon oligomer covering the outside of the soft magnetic powder. When the insulation coat is formed using silicon oligomer having strong mechanical coupling force and capable of forming a thick insulation coat, a uniform insulation coat can be formed in the case of powder magnetic core, and good DC superposition characteristics can be realized.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a soft magnetic material, a powder magnetic core using the soft magnetic material, a reactor using the powder magnetic core, and a method for manufacturing the powder magnetic core.

  Reactors are used as part of the power supply system for motors, inverters, and converters. A powder magnetic core is used as the core of this reactor. The dust core is formed by press-molding a powder composed of a metal powder and an insulating film covering the metal powder.

  The powder magnetic core is required to have a magnetic characteristic capable of obtaining a large magnetic flux density with a small applied magnetic field and a magnetic characteristic such that an energy loss due to a change in the magnetic flux density is small, due to demands for improving energy exchange efficiency and low heat generation. Specifically, the magnetic characteristic relating to the magnetic flux density is the magnetic permeability (μ). Specifically, the magnetic characteristics relating to energy loss are iron loss (Pcv). The iron loss (Pcv) is represented by the sum of hysteresis loss (Ph) and eddy current loss (Pe).

JP 2008-305823 A JP 2010-001561 A JP 2012-129217 A

  The dust core using soft magnetic powder is required to improve the magnetic flux density as described above. For this purpose, it is necessary to increase the density of the dust core. For this reason, compacting is performed at a high pressure, but at that time, many distortions are generated in the particles of the soft magnetic powder. This distortion increases the coercive force of the dust core and increases hysteresis loss. When the hysteresis loss increases, the loss as a whole increases, and the saturation magnetic flux density decreases, so that the direct current superimposition characteristics deteriorate.

  Therefore, for the purpose of removing distortion generated in the particles of the soft magnetic powder, a method in which the periphery of the soft magnetic powder is covered with an insulating coating and a high heat treatment temperature is employed is employed. At that time, if an insulating coating of the powder magnetic core having a weak mechanical coupling force is used, it is crushed together with the soft magnetic powder at the time of molding, and the insulating coating is damaged or torn. Moreover, the thin film of the insulating coating film is easily destroyed or lost by thermal decomposition in the heat treatment process, and the dielectric breakdown is likely to occur between the soft magnetic powders.

  Uses a silicone oligomer that has a strong mechanical bonding force and can form a thick insulating film against soft magnetic powder, thereby increasing the heat treatment temperature while ensuring insulation between soft magnetic powders. Has been studied. However, the effect could not be obtained depending on the kind of soft magnetic powder combined with the silicone oligomer.

  An object of the present invention is to provide a soft magnetic material with reduced loss and improved direct current superposition characteristics, a dust core using a soft magnetic material, and a dust core when a silicone oligomer is used in forming an insulating film. It is in providing the used reactor and the manufacturing method of a powder magnetic core.

  In order to achieve the above object, a soft magnetic material of the present invention is a soft magnetic material having a soft magnetic powder and an insulating coating covering the surface of the soft magnetic powder, and the hardness of the soft magnetic powder is 300 MPa. The insulating film is a silicone oligomer that covers the outside of the soft magnetic powder.

  The addition amount of the silicone oligomer may be 0.15 to 1.25 wt% with respect to the soft magnetic powder.

  The soft magnetic powder may be an Fe—Ni alloy or an Fe—Si alloy.

  In the Fe—Si alloy powder, the ratio of Si to Fe may be 1.5% or more and 6.5% or less.

  The silicone oligomer may be a methyl or methylphenyl silicone oligomer.

  A dust core using the soft magnetic material and a reactor in which a coil is wound around the dust core are also one embodiment of the present invention.

  According to the present invention, it is possible to achieve a high heat treatment temperature in the heat treatment step by using a soft magnetic powder obtained by covering a soft magnetic powder having a hardness of 300 MPa or less with a silicone oligomer. Thereby, distortion in the soft magnetic powder can be removed, hysteresis loss can be reduced, and saturation magnetic flux density can be increased. As a result, it is possible to provide a dust core with low loss and excellent direct current superposition characteristics and a method for manufacturing the same.

It is a flowchart which shows the manufacturing method of the powder magnetic core which concerns on one Embodiment of this invention. It is a figure which shows the correlation of the increase amount of the powder hardness and magnetic permeability which concern on one Embodiment of this invention. It is a graph which shows the iron loss of the comparative example 1 and Example 1 in a 1st characteristic. It is a graph which shows the direct current superposition characteristic of comparative example 1 and Example 1 in the 1st characteristic. It is a graph which shows the iron loss of the comparative example 2 and Example 2 in a 2nd characteristic. It is a graph which shows the direct current superposition characteristic of comparative example 2 and Example 2 in the 2nd characteristic. It is a graph which shows the iron loss of the comparative example 3 and Example 3 in a 3rd characteristic. It is a graph which shows the direct current superposition characteristic of comparative example 3 and Example 3 in the 3rd characteristic. It is a graph which shows the iron loss of the comparative example 4 and Example 4 in a 4th characteristic. It is a graph which shows the direct current superposition characteristic of comparative example 4 and Example 4 in the 4th characteristic.

[1. Embodiment]
[1-1. Constitution]
The soft magnetic powder material of the present embodiment includes a soft magnetic powder and a silicone oligomer layer that covers the surface of the soft magnetic powder. In this embodiment, the hardness of the soft magnetic powder is 300 MPa or less. In the present embodiment, a silicone oligomer layer is formed by mixing a silicone oligomer with a soft magnetic powder. The soft magnetic powder on which the silicone oligomer layer is formed is pressure-molded into a predetermined shape to produce a molded body. The shape of the molded body can be various shapes such as toroidal, I-type, U-type, θ-type, E-type, and EER-type. The powder magnetic core is molded by heat-treating the molded body arranged in a predetermined shape. The soft magnetic powder before forming the silicone oligomer layer and the inorganic insulating powder may be mixed, and the inorganic insulating powder may be uniformly adhered to the surface of the soft magnetic powder in advance.

(Magnetic powder)
As the magnetic powder used in the present embodiment, a magnetic powder having a hardness of 300 MPa or less is used. For the hardness, one magnetic powder having an average particle diameter of 30 to 40 μm is pressed, and the pressure value when the powder is deformed by 10% is defined as the hardness of the powder. For the hardness measurement, a MCT series micro compression tester manufactured by Shimadzu Corporation was used. In the present specification, the “average particle diameter” refers to D50, that is, the median diameter unless otherwise specified.

  As the type of magnetic powder used in the present embodiment, various powders can be used as long as the hardness is 300 MPa or less. For example, permalloy (Fe—Ni alloy), Si-containing iron alloy (Fe—Si alloy), pure iron powder, etc., which are soft magnetic powders containing iron as a main component, are used as the magnetic powder. The iron alloy may further contain Co, Cr, or Mn. When using permalloy (Fe—Ni alloy), the ratio of Ni to Fe is preferably 50:50 or 25:75, but may be other ratios. For example, Fe-80Ni and Fe-36Ni may be used. In addition to Fe and Ni, Si, Cr, Mo, Cu, Nb, Ta, or the like may be included. Examples of the Fe-Si alloy powder include Fe-3.5% Si alloy powder and Fe-6.5% Si alloy powder, but the ratio of Si to Fe is other than 3.5% or 6.5%. It may be 1.5% or more and 6.5% or less. Pure iron powder contains 99% or more of Fe. The soft magnetic powder is not limited to one type but may be a mixed powder of two or more types.

  The average particle diameter (D50) of the soft magnetic powder is preferably 20 μm to 150 μm. As the magnetic powder, those produced by a gas atomizing method, a water atomizing method or a water gas atomizing method can be used. The soft magnetic powder by the gas atomization method is a substantially spherical particle. Therefore, it can be used as it is without being processed. The soft magnetic powder produced by the water atomization method is non-spherical particles having irregularities formed on the surface thereof. In this case, it is desirable that the average circularity of the particles be 0.90 or more by leveling the surface irregularities using a ball mill, mechanical alloying, jet mill, attritor or surface modification device.

(Inorganic insulating powder)
The inorganic insulating powder that uniformly adheres to the surface of the soft magnetic powder is at least one of alumina powder, magnesia powder, silica powder, titania powder, and zirconia powder, which is an inorganic insulating powder having a melting point of 1000 ° C. or higher. preferable. The inorganic insulating powder having a melting point of 1000 ° C. or higher is used as a material for the powder magnetic core by sintering the inorganic insulating powder by heat applied in the heat treatment process performed for the purpose of removing distortion due to the pressure applied during the molding described later. This is to prevent it from becoming unusable.

  The specific surface area of the inorganic insulating powder is preferably 65 to 130 m <2> / g (7 to 200 nm in terms of particle diameter), more preferably 100 to 130 m <2> / g (7 to 50 nm in particle diameter). The larger the specific surface area of the inorganic insulating powder, the smaller the particle size. When the particle diameter is smaller, the inorganic insulating powder enters between the soft magnetic powders without any gaps, and a dense insulating coating is formed, thereby reducing the strain at the time of forming the dust core. On the other hand, when the specific surface area of the inorganic insulating powder is too large, the particle diameter becomes too small and the production becomes difficult.

  The addition amount of the inorganic insulating powder is 0.2 to 2.0 wt% with respect to the soft magnetic powder. If it is less than this, insulation performance cannot fully be exhibited, and eddy current loss may increase remarkably at high heat treatment temperatures. On the other hand, if it is more than this, the insulation performance can be exhibited, but the molding density is lowered, and there may be a problem that the magnetic properties other than the eddy current loss are deteriorated. When these problems do not occur, it is not always necessary to uniformly deposit the inorganic insulating powder on the surface of the soft magnetic powder.

(Insulation coating)
The magnetic powder contained in the soft magnetic powder material is covered with two types of insulating coatings having insulating properties. That is, with the soft magnetic powder as the center, the first insulating film is formed on the outer side, and the second insulating film is formed on the outer side of the first insulating film.

  The first insulating film is a silicone oligomer layer. The first insulating film is formed of a silicone oligomer layer solidified by adding a predetermined amount of a silicone oligomer to the magnetic powder and performing drying at a predetermined temperature in an air atmosphere.

  Silicone oligomers can be methyl-based or methylphenyl-based having alkoxysilyl groups and no reactive functional groups, and epoxy-based, epoxymethyl-based, mercapto-based, mercapto-based compounds having alkoxysilyl groups and reactive functional groups. Methyl-based, acrylmethyl-based, methacrylmethyl-based, vinylphenyl-based, alicyclic epoxy-based compounds having a reactive functional group without having an alkoxysilyl group can be used. In particular, a thick and hard insulating layer can be formed by using a methyl or methylphenyl silicone oligomer. In view of the ease of the silicone oligomer layer forming step, methyl or methylphenyl having a relatively low viscosity may be used. More specifically, silicone oligomers comprising alkoxysilanes, organopolysiloxanes, alkoxysiloxanes, or methoxy functional methyl-phenyl-polysiloxanes, which are relatively low viscosity silicone oligomers, can be used.

  The molecular weight of the silicone oligomer is preferably 100 to 4000. When the molecular weight is less than 100, it is likely to be destroyed or lost by thermal decomposition in the heat treatment step, and the dielectric breakdown is likely to occur between the soft magnetic powders. On the other hand, if the molecular weight is larger than 4000, the film thickness becomes too thick and the magnetic properties are deteriorated.

  The addition amount of the silicone oligomer is preferably 0.15 to 3.5 wt% with respect to the soft magnetic powder, and 0.5 to 1.25 wt% when the soft magnetic powder is Fe—Ni alloy powder. It is more preferable that When the soft magnetic powder is Fe-Si alloy powder or pure iron powder, it is more preferably 0.15 to 3.5 wt%. If the addition amount is less than 0.15 wt%, it does not function as an insulating film, and eddy current loss increases, resulting in deterioration of magnetic characteristics. When the addition amount is more than 3.5 wt%, the core expands to lower the density of the molded body and lower the magnetic permeability.

  The second insulating film is a silicone resin layer. The second insulating film is formed of a silicone resin layer solidified by adding a predetermined amount of a silicone resin to a magnetic powder on which a silicone oligomer layer is formed, and drying in an air atmosphere at a predetermined temperature. Is done.

  The silicone resin is a resin having a siloxane bond (Si—O—Si) as a main skeleton. By using a silicone resin, a film excellent in flexibility can be formed. As the silicone resin, methyl, methylphenyl, propylphenyl, epoxy resin-modified, alkyd resin-modified, polyester resin-modified, rubber or the like can be used. Among these, in particular, when a methylphenyl-based silicone resin is used, it is possible to form a silicone resin layer with little heat loss and excellent heat resistance.

  The addition amount of the silicone resin is preferably 0.8 to 1.6 wt% with respect to the soft magnetic powder. If the addition amount is less than 0.8 wt%, it does not function as an insulating film, and eddy current loss increases, resulting in a decrease in magnetic properties. When the addition amount is more than 1.6 wt%, the core expands to lower the density of the molded body and lower the magnetic permeability. By appropriately adjusting the amount of the silicone resin added to the silicone oligomer, it is possible to form a strong insulating film having a high insulating performance, and particularly the weight ratio of the silicone resin to the silicone oligomer is 1: 0.8 to 1: 3. In case, strength and insulation performance are excellent.

[1-2. Manufacturing method of powder magnetic core]
The manufacturing method of the powder magnetic core of the present embodiment includes the following steps. This process is shown in the flowchart of FIG.
(1) An inorganic insulating powder adhering step (step 1) in which an inorganic insulating powder is mixed with an inorganic insulating powder to the soft magnetic powder.
(2) A silicone oligomer layer forming step (step 2) in which a silicone oligomer layer is formed by mixing a silicone oligomer with a soft magnetic powder having an inorganic insulating powder adhered to the surface.
(3) A silicone resin layer forming step of forming a silicone resin layer by mixing a silicone resin with the soft magnetic powder having the silicone oligomer layer formed thereon (step 3).
(4) A molding step (step 4) in which the soft magnetic powder that has undergone the above-described step is subjected to pressure molding treatment to produce a molded body.
(5) A heat treatment process (step 5) in which the molded body that has undergone the molding process is heat treated at 600 ° C. or higher.
Hereafter, each process is demonstrated concretely.

(1) Inorganic insulating powder adhering step In the inorganic insulating powder adhering step, soft magnetic powder and inorganic insulating powder are mixed. Mixing is performed using a mixer (W type, V type), a pot mill or the like, and at this time, mixing is performed so that internal strain does not enter the powder. As described above, the inorganic insulating powder layer can be adhered to the surface of the soft magnetic powder. By attaching the inorganic insulating powder to the surface of the soft magnetic powder, the soft magnetic powder can be insulated and the heat treatment temperature can be increased.

  The inorganic insulating powder may be attached in the form of dots dispersed on the surface of the soft magnetic powder, or in the case of being dispersed and attached in a lump on the surface of the soft magnetic powder. The case where it adheres, forming the layer of an inorganic insulating powder so that the surface or a part of surface may be covered is included. In addition to being attached to the surface of the soft magnetic powder, a case where it is mixed with a silicone oligomer layer formed on the outside of the soft magnetic powder and dispersed in the silicone oligomer layer is also included. In addition, depending on conditions, such as stirring time by a mixer, it may not disperse | distribute in a silicone oligomer layer.

(2) Silicone oligomer layer forming step In the silicone oligomer layer forming step, a predetermined amount of silicone oligomer is added to the soft magnetic powder, and drying is performed at a predetermined temperature in the air atmosphere. A silicone oligomer layer is formed outside the soft magnetic powder by the silicone oligomer layer forming step.

  The drying temperature of the silicone oligomer layer is preferably 25 ° C to 350 ° C, and more preferably 200 ° C to 350 ° C when the soft magnetic powder is an Fe-Ni alloy powder. When the soft magnetic powder is Fe-Si alloy powder or pure iron powder, 25 ° C to 350 ° C is more preferable. When the drying temperature is less than 25 ° C., film formation is incomplete and eddy current loss increases. On the other hand, when the drying temperature is higher than 350 ° C., the powder is oxidized to increase the hysteresis loss, and the density and magnetic permeability of the compact are reduced. The drying time is about several hours, for example, about 1 to 2 hours.

  In the case where the inorganic insulating powder adhering step is not provided, the silicone oligomer layer forming step adds a predetermined amount of the silicone oligomer to the soft magnetic powder and performs drying at a predetermined temperature in the air atmosphere. A silicone oligomer layer is formed on the surface of the soft magnetic powder by the silicone oligomer layer forming step.

(3) Silicone resin layer forming step In the silicone resin layer forming step, a predetermined amount of silicone resin is added to the soft magnetic powder on which the silicone oligomer layer is formed, and dried at a predetermined temperature in an air atmosphere. A silicone resin layer is formed outside the silicone oligomer layer by the silicone resin layer forming step.

  The drying temperature of the silicone resin layer is preferably 100 ° C to 400 ° C, and more preferably 200 ° C to 300 ° C when the soft magnetic powder is an Fe-Ni alloy powder. When the soft magnetic powder is an Fe—Si alloy powder, 100 ° C. to 400 ° C. is more preferable. When the soft magnetic powder is pure iron powder, 100 ° C. to 300 ° C. is more preferable. When the drying temperature is lower than 100 ° C., film formation is incomplete and eddy current loss increases. On the other hand, when the drying temperature is higher than 300 ° C., the powder is oxidized to increase the hysteresis loss, and the density and magnetic permeability of the compact are reduced. The drying time is about 2 hours.

  By such a mixing step, granulated powder (hereinafter also referred to as a composite magnetic material) that is a mixture of magnetic powder and resin can be obtained.

(4) Molding step In the molding step, a compact is formed by pressure molding soft magnetic powder having an insulating coating formed on the surface. The pressure during molding is 10 to 20 ton / cm2, and the average is 15 ton /
About cm 2 is preferable.

(5) Heat treatment step In the heat treatment step, the temperature at which the insulating coating coated with the soft magnetic powder is destroyed at 600 ° C. or higher in a N 2 gas or N 2 + H 2 gas non-oxidizing atmosphere with respect to the molded body that has undergone the molding step. The powder magnetic core is produced by performing heat treatment below (for example, 950 ° C.). The reason why the heat treatment is performed at a temperature lower than the temperature at which the insulating film is broken is to release distortion in the molding process and prevent the insulating film coated around the soft magnetic powder from being broken by the heat during the heat treatment. On the other hand, if the heat treatment temperature is increased too much, the insulating film coated with the soft magnetic powder is broken, and the eddy current loss is greatly increased due to the deterioration of the insulating performance. This causes a problem that the magnetic characteristics are deteriorated.

[1-3. Action / Effect]
(A) [corresponding to claim 1]
The dust core of this embodiment is formed by covering the periphery of a magnetic powder having a hardness of 300 MPa or less with an insulating coating derived from a silicone oligomer. Table 1 shows the hardness of various soft magnetic powders, the reduction rate μ1 (10 kA / m) of the magnetic permeability of the dust core using various soft magnetic powders and a silane coupling agent, various soft magnetic powders and oligomers. 5 is a graph showing an increase rate of the magnetic permeability decrease rate μ2 (10 kA / m) of the dust core using the magnetic permeability decrease rate μ2 with respect to the permeability decrease rate μ1. In addition, the calculation method of the reduction rate of the magnetic permeability was calculated from the following formula 1.
[Formula 1]
Permeability decrease rate μ = μ (10kA / m) / μ (0) (1)
μ (0): Permeability when no magnetic field is applied
μ (10kA / m): Magnetic permeability when a magnetic field of 10kA / m is applied

[Table 1]

  In Table 1, the presence / absence of the effect of each soft magnetic powder was evaluated as “◯” with an increase rate of 1.10 or more as effective, and “×” with an increase rate of less than 1.10 as ineffective. Moreover, FIG. 2 which shows the correlation of the hardness of soft-magnetic powder and an increase rate from Table 1 was created.

  From Table 1 and FIG. 2, the dust core in which an insulating coating with a silicone oligomer is formed around a soft magnetic powder having a hardness of 300 or less is compared with a dust core in which an insulating coating with a silane coupling agent is formed. The permeability at a magnetic field of 10 kA / m is improved. When the rate of increase in magnetic permeability at a magnetic field of 10 kA / m is calculated as (permeability decrease rate μ2 when using a silicone oligomer) / (permeability decrease rate μ1 when using a silane coupling agent), The increase rate is 1.1 or more. On the other hand, in the dust core using the FeSiAl powder having a hardness of 386, the dust core formed with the silicone oligomer insulating film has a magnetic field of 10 kA compared with the dust core formed with the insulating film using the silane coupling agent. The permeability at / m is improved, but the rate of increase is limited. For example, the increase rate is 1.1 or less. From FIG. 2, it can be seen that the lower the hardness of the powder, the larger the increase rate, which is the difference in magnetic permeability due to the difference in the insulating coating. Furthermore, the straight line in the figure is an approximate straight line calculated from each plot data. According to this approximate straight line, it can be seen that when the hardness of the powder is 300 or less, the permeability increase rate is 10% or more at a magnetic field of 10 kA / m.

  That is, when an insulating coating having a weak mechanical coupling force by a silane coupling agent or the like is formed on a soft magnetic powder having a hardness of 300 or less, a soft magnetic powder having a shape close to a sphere due to the pressure during the pressing step Crushed and deformed. For example, as for the shape of the powder, a part of the surface of the sphere becomes a flat surface or an ellipsoid. If the shape of the soft magnetic powder is a sphere, the soft magnetic powders face each other at one point on the surface of the powder when the powder magnetic core is formed. In this case, the distance between the plurality of soft magnetic powders is substantially the same, and an insulating film having a uniform thickness exists between the plurality of soft magnetic powders. On the other hand, when the deformed parts of the deformed powder are opposed to each other, there is a possibility that the parts are opposed at a plurality of points or the crushed parts are opposed to each other. In this case, the distance between the plurality of soft magnetic powders varies, and there are insulation coatings of various thicknesses between the plurality of soft magnetic powders, resulting in variations in the thickness of the insulation coating. In the dust core, if there is a portion with a thin insulating coating, it is magnetized from that portion, leading to deterioration of the DC superposition characteristics. On the other hand, when a silicone oligomer is used that has a strong mechanical bonding force and can form a thick insulating film, when the insulating film is formed, a soft magnetic powder is formed between the soft magnetic powders. It is possible to form a uniform insulating film, and it is possible to realize good DC superposition characteristics. On the other hand, when FeSiAl powder is used as the soft magnetic powder, since the hardness of FeSiAl itself is high, the FeSiAl powder is not deformed by the pressure during the pressurizing process, and even when a powder magnetic core is used, There is an insulating coating of uniform thickness. This is largely the same whether the insulating coating is made of a silane coupling agent or a silicone oligomer. This is considered to be the reason why the permeability increase rate at a magnetic field of 10 kA / m does not increase significantly when an insulating layer made of a silicone oligomer is formed on FeSiAl powder. As described above, by using a soft magnetic material in which the periphery of a magnetic powder having a hardness of 300 MPa or less is covered with an insulating coating derived from a silicone oligomer, the loss of the dust core can be reduced and the direct current superposition characteristics can be improved.

[1-4. Example]
Examples of the present invention will be described below with reference to Tables 2 to 9 and FIGS.
(1) Measurement items As measurement items, permeability and iron loss (loss) were measured by the following methods. The magnetic permeability was calculated from the inductance at 20 kHz and 1.0 V by applying a primary winding (20 turns) to the produced dust core and using an impedance analyzer (Agilent Technology: 4294A).

  The iron loss is obtained by applying a primary winding (20 turns) and a secondary winding (3 turns) to the dust core, and using a BH analyzer (Iwatori Measurement Co., Ltd .: SY-8232), which is a magnetic measurement instrument, The iron loss (Pcv) was measured under the conditions of a frequency of 50 kHz and a maximum magnetic flux density Bm = 0.1T. And hysteresis loss (Ph) and eddy current loss (Pe) were calculated from the iron loss. This calculation was performed by calculating the hysteresis loss coefficient (Kh) and the eddy current loss coefficient (Ke) from the frequency curve of the iron loss by the following method (1) to (3) by the least square method.

Pcv = Kh × f + Ke × f ² (1)
Phv = Kh × f (2)
Pev = Ke × f ² (3)
Pcv: Iron loss Kh: Hysteresis loss coefficient Ke: Eddy current loss coefficient f: Frequency Phv: Hysteresis loss Pev: Eddy current loss

In this example, the average particle diameter and the circularity of each powder are the average values of 3000 pieces using the following apparatus. The powder is dispersed on a glass substrate, and a powder photograph is taken with a microscope. Each shot was automatically measured from the image.
Company name: Malvern
Device name: morphologic G3S

[First characteristic comparison (Influence on direct current superposition characteristics due to difference in insulating coating: Fe-4.5Si alloy powder)]
In the first characteristic comparison, Example 1 and Comparative Example 1 are created and compared with respect to the influence on the direct current superposition characteristics by the insulating coating when Fe-4.5Si alloy powder is used as the soft magnetic powder.

(2) Sample preparation method The Fe-4.5Si alloy powders used in Example 1 and Comparative Example 1 were those shown in Table 2 below. The sample was produced as follows. In the following description, “wt%” indicates a weight ratio with respect to the soft magnetic powder.
[Table 2]

(A) As Example 1, 0.75 wt% of alumina powder, which is an inorganic insulating powder, was mixed with the soft magnetic powder shown in Table 2. Thereafter, 0.5 wt% of a silicone oligomer was mixed with the soft magnetic powder to which the alumina powder was adhered, and heat-dried at 150 ° C. for 1 hour in an air atmosphere to form an insulating coating. As Comparative Example 1, 1.25 wt% of alumina powder, which is an inorganic insulating powder, was mixed with the soft magnetic powder shown in Table 2. Thereafter, 0.5 wt% of a silane coupling agent was mixed with the soft magnetic powder to which the alumina powder was adhered to form an insulating coating.
(B) Methylphenyl silicone resin (product name: SILRES (registered trademark) REN60) was mixed with 1.4 wt% of the soft magnetic powder of Example 1 and Comparative Example 1 on which an insulating film was formed, In Example 1, heat drying was performed at 150 ° C. and in Comparative Example 1 at 200 ° C. for 2 hours.
(C) 30 th meshes (aperture 500 μm) were passed through for the purpose of crushing the lump generated after heat drying. Then, 0.4 wt% of zinc stearate was mixed as a lubricant.
(D) The soft magnetic powder with the insulating coating formed by the above process was filled in a toroidal container having an outer diameter of 17 mm, an inner diameter of 11 mm, and a height of 8 mm, and a molded body was produced at a molding pressure of 15 ton / cm ² .
(F) Finally, the compact was heat-treated in a nitrogen atmosphere at a heat treatment temperature of 850 ° C. for 2 hours to produce a dust core.

Table 3 is a table showing the magnetic characteristics of the dust cores of Example 1 and Comparative Example 1.
[Table 3]

  The magnetic permeability is the amplitude magnetic permeability, and was calculated from the inductance of the strength of each magnetic field at 20 kHz and 1.0 V by using the impedance analyzer described above. “Μ0” in Table 3 represents the initial permeability when DC is not superimposed, that is, when the magnetic field strength is 0 H (A / m). “Μ (10 kA / m)” in Table 3 indicates the rate of decrease in magnetic permeability when the strength of the magnetic field is 10 (kA / m). From Table 3, FIG. 3 showing the iron loss of Comparative Example 1 and Example 1 and FIG. 4 showing the DC superposition characteristics of Comparative Example 1 and Example 1 were prepared.

  From Table 3 and FIG. 3, Example 1 which uses the silicone oligomer with a strong mechanical bond strength as an insulating film is compared with the comparative example 1 which uses the silane coupling agent with a weak mechanical bond force, and iron loss ( Pcv) is reduced. The iron loss (Pcv) is the sum of hysteresis loss (Phv) and eddy current loss (Pev), but the insulating film of silicone oligomer particularly acts to reduce hysteresis loss (Phv).

  Moreover, from Table 3 and FIG. 4, Example 1 which uses the silicone oligomer with a strong mechanical bonding force as an insulating film is magnetic field compared with the comparative example 1 using a silane coupling agent with a weak mechanical bonding force. The rate of increase in magnetic permeability when the strength of 10 is 10 (kA / m) is 1.14 from 68.8 / 60.1.

  As described above, the hysteresis loss is reduced by covering the periphery of the Fe-4.5Si alloy powder with a hardness of 300 MPa or less with the insulating film of the silicone oligomer layer, and as a result, the powder compact with excellent low DC loss characteristics and low loss. A magnetic core and a manufacturing method thereof can be provided.

[Second characteristic comparison (Influence on direct current superposition characteristics due to difference in insulating coating: Fe-1.5Si alloy powder)]
In the second characteristic comparison, Example 2 and Comparative Example 2 are created and compared with respect to the influence of the insulating coating on the DC superposition characteristics when Fe-1.5Si alloy powder is used as the soft magnetic powder.

(3) Sample preparation method The Fe-1.5Si alloy powders used in Example 2 and Comparative Example 2 were those shown in Table 4 below.
[Table 4]

(A) As Example 2, 0.75 wt% of alumina powder as inorganic insulating powder was mixed with the soft magnetic powder shown in Table 4. Thereafter, 1.0 wt% of the silicone oligomer was mixed with the soft magnetic powder to which the alumina powder was adhered, and heat-dried at 150 ° C. for 1 hour in an air atmosphere to form an insulating coating. Further, as Comparative Example 1, 0.75 wt% of alumina powder, which is an inorganic insulating powder, was mixed with the soft magnetic powder shown in Table 4. Thereafter, 1.0 wt% of a silane coupling agent was mixed with the soft magnetic powder to which the alumina powder was adhered to form an insulating coating.
(B) Thereafter, as in Example 1 and Comparative Example 1, a silicone resin insulating film was formed, and zinc stearate was mixed as a lubricant. Then, the same toroidal container as in Example 1 and Comparative Example 1 was filled, and a molded body was produced at a molding pressure of 15 ton / cm ² . Finally, the compact was heat treated in a nitrogen atmosphere at a heat treatment temperature of 800 ° C. for 2 hours to produce a dust core.

Table 5 is a table showing the magnetic characteristics of the dust cores of Example 2 and Comparative Example 2.
[Table 5]

  From Table 5 and FIG. 5, as in the case of the Fe-4.5Si alloy powder, Example 2 using a silicone oligomer having a strong mechanical bonding force as the insulating film uses a silane coupling agent having a low mechanical bonding force. Compared with the comparative example 2, the iron loss (Pcv) is reduced. The iron loss (Pcv) is the sum of hysteresis loss (Phv) and eddy current loss (Pev), but the insulating film of silicone oligomer particularly acts to reduce hysteresis loss (Phv).

  In addition, from Table 5 and FIG. 6, Example 2 using a silicone oligomer having a strong mechanical bonding force as an insulating film was compared with Comparative Example 2 using a silane coupling agent having a low mechanical bonding force. The rate of increase in the magnetic permeability when the strength is 10 (kA / m) is 1.23 from 61.6 / 50.0.

  As mentioned above, the hysteresis loss is reduced by covering the periphery of the Fe-1.5Si alloy powder having a hardness of 300 MPa or less with the insulating film of the silicone oligomer layer, and as a result, the powder compact that has low loss and excellent DC superposition characteristics. A magnetic core and a manufacturing method thereof can be provided.

[Third characteristic comparison (Influence on direct current superposition characteristics due to difference in insulating coating: Fe-6.5Si alloy powder)]
In the third characteristic comparison, Example 3 and Comparative Example 3 are created and compared with respect to the influence on the DC superposition characteristics by the insulating coating when Fe-6.5Si alloy powder is used as the soft magnetic powder.

The Fe-6.5Si alloy powders used in Example 3 and Comparative Example 3 were those shown in Table 6 below.
[Table 6]

(A) As Example 3, 0.75 wt% of alumina powder, which is an inorganic insulating powder, was mixed with the soft magnetic powder shown in Table 6. Thereafter, 1.0 wt% of the silicone oligomer was mixed with the soft magnetic powder to which the alumina powder was adhered, and heat-dried at 150 ° C. for 1 hour in an air atmosphere to form an insulating coating. As Comparative Example 3, 1.25 wt% of alumina powder, which is an inorganic insulating powder, was mixed with the soft magnetic powder shown in Table 6. Thereafter, 0.5 wt% of a silane coupling agent was mixed with the soft magnetic powder to which the alumina powder was adhered to form an insulating coating.
(B) Thereafter, as in Example 1 and Comparative Example 1, a silicone resin insulating film was formed, and zinc stearate was mixed as a lubricant. Then, the same toroidal container as in Example 1 and Comparative Example 1 was filled, and a molded body was produced at a molding pressure of 15 ton / cm ² . Finally, the compact was heat-treated in a nitrogen atmosphere at a heat treatment temperature of 850 ° C. for 2 hours to produce a dust core.

Table 7 is a table showing the magnetic characteristics of the dust cores of Example 3 and Comparative Example 3.
[Table 7]

  From Table 7 and FIG. 7, Example 3, which uses a silicone oligomer with a strong mechanical bonding force as the insulating coating, uses a silane coupling agent with a low mechanical bonding force, as in the case of Fe-4.5Si alloy powder. Compared with the comparative example 3, the iron loss (Pcv) is reduced. The iron loss (Pcv) is the sum of hysteresis loss (Phv) and eddy current loss (Pev), but the insulating film of silicone oligomer particularly acts to reduce hysteresis loss (Phv).

  Moreover, from Table 7 and FIG. 8, Example 3 which uses the silicone oligomer with a strong mechanical bonding force as an insulating film is magnetic field compared with the comparative example 3 which uses a silane coupling agent with a weak mechanical bonding force. The rate of increase in magnetic permeability when the strength of 10 is 10 (kA / m) is 1.12 from 68.7 / 61.2.

  As mentioned above, the hysteresis loss is reduced by covering the periphery of the Fe-6.5Si alloy powder with a hardness of 300 MPa or less with the insulating film of the silicone oligomer layer, and as a result, the powder compact that has low loss and excellent DC superposition characteristics. A magnetic core and a manufacturing method thereof can be provided.

[Fourth characteristic comparison (Influence on direct current superposition characteristics due to difference in insulating coating: Fe-Ni alloy powder)]
In the fourth characteristic comparison, Example 4 and Comparative Example 4 are created and compared with respect to the influence on the DC superposition characteristics by the insulating coating when Fe—Ni alloy powder is used as the soft magnetic powder.

The Fe—Ni alloy powders used in Example 4 and Comparative Example 4 were those shown in Table 8 below.
[Table 8]

(A) As Example 4, 0.5 wt% of alumina powder as inorganic insulating powder was mixed with the soft magnetic powder shown in Table 8. Thereafter, 1.0 wt% of the silicone oligomer was mixed with the soft magnetic powder to which the alumina powder was adhered, and heat-dried at 150 ° C. for 1 hour in an air atmosphere to form an insulating coating. Further, as Comparative Example 4, 0.75 wt% of alumina powder, which is an inorganic insulating powder, was mixed with the soft magnetic powder shown in Table 6. Thereafter, 0.5 wt% of a silane coupling agent was mixed with the soft magnetic powder to which the alumina powder was adhered to form an insulating coating.
(B) Thereafter, as in Example 1 and Comparative Example 1, a silicone resin insulating film was formed, and zinc stearate was mixed as a lubricant. Then, the same toroidal container as in Example 1 and Comparative Example 1 was filled, and a molded body was produced at a molding pressure of 15 ton / cm ² . Finally, the compact was heat-treated in a nitrogen atmosphere for 2 hours at a heat treatment temperature of 600 ° C. for Comparative Example 4 and 850 ° C. for Example 1 to produce a dust core.

Table 9 is a table showing the magnetic characteristics of the dust cores of Example 4 and Comparative Example 4.
[Table 9]

  From Table 9 and FIG. 9, Example 4 which uses the silicone oligomer with a strong mechanical bond strength as an insulating film uses the silane coupling agent with a weak mechanical bond strength similarly to the case of Fe-4.5Si alloy powder. Compared with the comparative example 4, the iron loss (Pcv) is reduced. The iron loss (Pcv) is the sum of hysteresis loss (Phv) and eddy current loss (Pev), but the insulating film of silicone oligomer particularly acts to reduce hysteresis loss (Phv).

  Moreover, from Table 9 and FIG. 10, Example 4 which uses the silicone oligomer with a strong mechanical bonding force as an insulating film is magnetic field compared with the comparative example 4 using a silane coupling agent with a weak mechanical bonding force. The rate of increase in magnetic permeability when the strength of 10 is 10 (kA / m) is 1.21 from 71.7 / 59.2.

  As described above, the hysteresis loss is reduced by covering the periphery of the Fe-Ni alloy powder with a hardness of 300 MPa or less with the insulating coating of the silicone oligomer layer, and as a result, the dust core has excellent DC superposition characteristics with low loss. And a manufacturing method thereof.

(Conclusion)
From the above first to fourth characteristic comparisons, it is possible to form a uniform insulating film by covering the periphery of a soft magnetic powder having a hardness of 300 MPa or less with an insulating film of a silicone oligomer layer, regardless of the type of powder. This makes it possible to create a dust core having good direct current superposition characteristics.

[2. Other Embodiments]
The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment.

Claims (8)

A soft magnetic material having a soft magnetic powder and an insulating coating covering the surface of the soft magnetic powder,
The soft magnetic powder has a hardness of 300 MPa or less,
The insulating coating is a silicone oligomer that coats the outside of the soft magnetic powder;
Soft magnetic material characterized by The addition amount of the silicone oligomer is 0.15 to 1.25 wt% with respect to the soft magnetic powder,
The soft magnetic material according to claim 1.   The soft magnetic material according to claim 1 or 2, wherein the soft magnetic powder is Fe-Ni alloy powder or Fe-Si alloy powder.   4. The soft magnetic material according to claim 3, wherein a ratio of Si to Fe is 1.5% or more and 6.5% or less in the Fe—Si alloy powder. 5. The silicone oligomer is a methyl or methylphenyl silicone oligomer;
The soft magnetic material according to any one of claims 1 to 4, wherein:   A dust core using the soft magnetic material according to any one of claims 1 to 5.   A reactor in which a coil is wound around the dust core according to claim 6. A step of mixing a silicone oligomer with a soft magnetic powder having a hardness of 300 MPa or less and drying to form a silicone oligomer layer;
A step of mixing a silicone resin with the soft magnetic powder having the silicone oligomer layer formed thereon and drying to form a silicone resin layer;
A molding step for producing a compact by subjecting the soft magnetic powder that has undergone each of the above steps to pressure molding, and
A heat treatment step of heat-treating the molded body that has undergone the molding step at 600 ° C. or higher;
The manufacturing method of the powder magnetic core which has this.

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