Powdered magnetic core and method for manufacturing powdered magnetic core

Abstract

Provided is a powder magnetic core having excellent magnetic properties by reducing iron loss and a manufacturing method for the powder magnetic core. The powder magnetic core of the present invention contains FeSiAl alloy powder and an insulating resin coating the FeSiAl alloy powder, and in the case where the total of the weight of the FeSiAl alloy powder and the weight of Fe2O3 is 100 wt%, the proportion of the weight of Fe2O3 is 0.1 wt% or more.

Description

TECHNICAL FIELD

[0001] The present application relates to a powder magnetic core and a manufacturing method of a powder magnetic core. BACKGROUND

[0002] Reactors are used for various applications such as drive systems of hybrid cars, electric cars, and fuel cell cars. As a core of the reactor, for example, a powder magnetic core is used. The powder magnetic core is formed by pressure-molding a soft magnetic powder and an insulating film covering the soft magnetic powder.

[0003] Due to the improvement of energy exchange efficiency and the requirement of low heat generation, the powder magnetic core is required to have magnetic characteristics with small energy loss. The magnetic characteristics related to the energy loss specifically refer to iron loss (Pcv). The iron loss (Pcv) is represented by the sum of hysteresis loss (Phv) and eddy current loss (Pev).

[0004] [Related Art Documents]

[0005] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent No. 5027945 SUMMARY

[0007] [Problems to be Solved by the Invention]

[0008] Conventionally, when a strain is generated in the particles of the soft magnetic powder, the coercive force of the soft magnetic powder is increased, and the hysteresis loss is increased. Therefore, in order to remove the strain in the particles of the soft magnetic powder and reduce the coercive force, a heat treatment is performed on the molded body after the pressure molding at a high temperature, and the reduction of the hysteresis loss is achieved by removing the strain. However, in recent years, due to the diversification of the applications of the reactor, the reduction of the hysteresis loss is required.

[0009] An object of the present application is to provide a powder magnetic core and a manufacturing method of a powder magnetic core, which achieve excellent magnetic characteristics by reducing the iron loss.

[0010] [Technical Means to Solve the Problems]

[0011] The present inventors have conducted intensive studies, and as a result, have obtained the following insight: contrary to the above technical common sense, by performing an oxidation treatment on a part of the soft magnetic powder in the molded body, the soft magnetic powder is intentionally strained to a certain degree, and thus the reduction of the hysteresis loss, and further the reduction of the iron loss, can be achieved.

[0012] The powder magnetic core of the present application is a powder magnetic core including FeSiAl alloy powder and an insulating resin covering the FeSiAl alloy powder, wherein the proportion of Fe2O3 is 0.1 wt% or more, based on the total of the weight of the Fe2O3 and the weight of the FeSiAl alloy powder being 100 wt%.

[0013] Further, the manufacturing method of the powder magnetic core of the present application includes an insulating treatment step of covering an insulating resin on FeSiAl alloy powder; a molding step of molding the FeSiAl alloy powder subjected to the insulating treatment; and a heat treatment step of subjecting the FeSiAl alloy powder after molding to heat treatment in an oxidizing environment.

[0014] [Effects of the Invention]

[0015] According to the present application, it is possible to provide a powder magnetic core having excellent magnetic properties by reducing iron loss and a manufacturing method of a powder magnetic core. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 is a flowchart showing the manufacturing steps of the powder magnetic core of the embodiment.

[0017] Figure 2 is a graph showing the relationship between the proportion of the Fe2O3 layer and the iron loss, the hysteresis loss, and the eddy current loss.

[0018] Figure 3 is a graph showing the iron loss, the hysteresis loss, and the eddy current loss after heat treatment in an N2 environment and the iron loss, the hysteresis loss, and the eddy current loss after heat treatment in an N2 environment followed by heat treatment in the atmosphere. DETAILED DESCRIPTION

[0019] The present embodiment is a powder magnetic core in which an oxidized layer is formed on a part of soft magnetic powder in a press-molded body including the soft magnetic powder and an insulating resin covering the soft magnetic powder. The powder magnetic core is used as a magnetic body of an electric reactor, for example. Here, the layer includes a case where all the powder is covered and a case where a part of the powder is covered.

[0020] [Soft magnetic powder]

[0021] The soft magnetic powder used in the present embodiment is FeSiAl alloy powder in which iron, silicon, and aluminum are main components, i.e., so-called Sendust alloy powder. The average particle diameter (D50) of the soft magnetic powder can be, for example, 10 μm or more and 50 μm or less, and is preferably 15 μm or more and 25 μm or less. Further, in the present specification, the "average particle diameter" means D50, i.e., the median particle diameter, unless otherwise specified.

[0022] The soft magnetic powder is preferably one having a small surface area. That is, a high degree of sphericity is preferred. This is because, if the surface area is small, a uniform oxide layer can be formed efficiently with little oxygen. In addition, because the gap between the soft magnetic powders becomes small if the surface area becomes small, an increase in density and magnetic permeability can be achieved. As an index indicating a high degree of sphericity, in the case where the roundness of the soft magnetic powder is used, the roundness is preferably 0.95 or greater. Further, if the roundness is 0.98 or greater, this is more preferred.

[0023] The method of manufacturing the soft magnetic powder is not limited. However, as described above, a high degree of sphericity is preferred. The soft magnetic powder obtained by the gas atomization method becomes a substantially spherical particle. Therefore, the gas atomized powder formed by the gas atomization method can be used directly without processing.

[0024] In addition, among the crushed powder manufactured by the crushing method, the water atomized powder manufactured by the water atomization method, and the water gas atomized powder manufactured by the water gas atomization method, the particles on the surface are deformed in an irregular shape and have many irregularities. Therefore, in the case where these powders are used, processing that increases the average roundness of the particles is preferably performed. In this case, the average roundness of the particles can be increased by using a ball mill, mechanical alloying, a jet mill, a pulverizer, or a surface modification device to make the irregularities on the surface uniform.

[0025] [Manufacturing Process]

[0026] Figure 1 A flowchart showing the manufacturing process of the powder magnetic core of the present embodiment is shown in FIG. 1. As shown in FIG. 1, the manufacturing process of the powder magnetic core of the present embodiment has: (1) a powder heat treatment process, (2) an insulation treatment process, (3) a lubricant mixing process, (4) a molding process, and (5) a heat treatment process. Figure 1

[0027] (1) Powder Heat Treatment Process (Step S01)

[0028] The powder heat treatment process is a process of heat treating the soft magnetic powder. That is, the crystal structure of the FeSiAl alloy powder is changed by heat treating the FeSiAl alloy powder.

[0029] ​Specifically, the crystal structure of the FeSiAl alloy powder before the powder heat treatment is a bcc (body-centered cubic) structure including a regular structure DO3 structure and an irregular structure. Moreover, by performing the heat treatment on the FeSiAl alloy powder, the proportion of the irregular structure can be made to be a desired value. The proportion of the irregular structure and the DO3 structure can be calculated by X-ray diffraction using RieWeld analysis method. The difference between the irregular structure and the DO3 structure can be determined by the lattice constant calculated from the X-ray diffraction.

[0030] In the powder heat treatment step, heating is performed for 1 to 6 hours in a vacuum atmosphere, an inert gas atmosphere, i.e., a non-oxidizing atmosphere, or an atmospheric gas atmosphere. As the inert gas, H2and N2can be listed. As the heat treatment temperature, it is preferable to be 500°C or higher and 700°C or lower. By making the heat treatment temperature in the range, the proportion of the irregular structure in the crystal structure of the FeSiAl alloy powder can be made to be 14.6 wt% or more and 43.7 wt% or less, and thus reduction of the iron loss can be achieved.

[0031] Further, the coercive force of the FeSiAl alloy powder is preferably 0.43 A / cm or more and 1.81 A / cm or less. If the coercive force is in the range, reduction of the hysteresis loss can be achieved.

[0032] (2) Insulating treatment step (step S02)

[0033] The insulating treatment step is a step of forming an insulating film on the surface of the soft magnetic powder. That is, the insulating treatment step is performed by mixing an insulating resin in the soft magnetic powder, drying, and then sieving. As the insulating film, a silicone oligomer, a silicone resin, a silane coupling agent, or the like is used. Among them, a first layer insulating layer can be formed using a silicone oligomer or a silane coupling agent, and a second layer insulating layer can be formed using a silicone resin, and thus a two-layer insulating film can be formed. Hereinafter, the procedure of each material is described.

[0034] (a) Silicone oligomer mixing step

[0035] The silicone oligomer mixing step is a step of mixing a silicone oligomer to coat the surface of the heat-treated FeSiAl alloy powder. The silicone oligomer has an alkoxysilane group. The alkoxysilane group includes a methoxyl group, an ethoxyl group, and a methoxyl / ethoxyl group. As long as it is a silicone oligomer having an alkoxysilane group, a methyl group, a methylphenyl group, an epoxy group, an epoxy methyl group, a mercapto group, a mercapto methyl group, a methacrylate group, a methacrylate methyl group, a vinylphenyl group, and the like, which do not have a reactive functional group, can be used. In particular, by using a silicone oligomer of a methyl group or a methylphenyl group, a thick and hard insulating layer can be formed.

[0036] The addition amount of the silicone oligomer is preferably 0.1 wt% or more and 2.0 wt% or less with respect to the soft magnetic powder. When the addition amount is less than 0.1 wt%, the DC superimposition characteristics are sometimes deteriorated. When the addition amount is more than 2.0 wt%, the density is decreased, and thus there are cases where the initial permeability is decreased and the hysteresis loss is increased.

[0037] The drying temperature of the silicone oligomer layer is preferably 25°C or higher and 200°C or lower. This is because, when the drying temperature is lower than 25°C, the film formation becomes incomplete, and the eddy current loss is sometimes increased. On the other hand, when the drying temperature exceeds 200°C, decomposition occurs, and thus the film formation is sometimes difficult, and the density and the permeability of the molded body are sometimes decreased. The drying time is about several hours, for example, about 1 hour to 2 hours.

[0038] (b) silane coupling agent mixing step

[0039] The silane coupling agent mixing step is a step of mixing a silane coupling agent to coat the surface of the heat-treated FeSiAl alloy powder. The silane coupling agent can be, for example, an aminosilane type, an epoxy silane type, an isocyanurate type, an ethoxysilane type, a methoxysilane type, and particularly preferably 3-aminopropyl triethoxysilane, 3-glycidyloxypropyl trimethoxysilane, and tris-(3-trimethoxysilylpropyl) isocyanurate.

[0040] The addition amount of the silane coupling agent is preferably 0.25 wt% or more and 1.0 wt% or less. By making the addition amount of the silane coupling agent within the range, the standard deviation of the density, the magnetic characteristics, and the strength characteristics of the molded powder core can be improved.

[0041] The drying temperature of the silane coupling agent is preferably 25°C or higher and 200°C or lower. This is because, when the drying temperature is lower than 25°C, the solvent is sometimes left, and thus the coating film becomes incomplete. On the other hand, when the drying temperature exceeds 200°C, decomposition occurs, and thus the film formation is sometimes difficult. The drying time is about 2 hours.

[0042] (c) silicone resin mixing step

[0043] In the silicone resin mixing step, a prescribed amount of silicone resin is added to the FeSiAl alloy powder coated with the silicone oligomer or silane coupling agent, and dried at a prescribed temperature in an atmospheric environment. Through the silicone resin mixing step, a silicone resin layer is formed on the outside of the film formed by the silane coupling agent.

[0044] The silicone resin is a resin having a siloxane bond (Si-O-Si) in the main skeleton. By using a silicone resin, a film having excellent flexibility can be formed. The silicone resin can use a methyl-based, methylphenyl-based, propylphenyl-based, epoxy resin-modified, alkyd resin-modified, polyester resin-modified, rubber-based, or the like. Among these, in particular, in the case of using a methylphenyl-based silicone resin, a silicone resin layer having a small heating loss and excellent heat resistance can be formed.

[0045] The addition amount of the silicone resin is preferably 1.0 wt% or more and 3.0 wt% or less with respect to the soft magnetic powder. This is because, if the addition amount is less than 1.0 wt%, the function as an insulating film is not exerted, the eddy current loss increases, and thus there is a case where the magnetic characteristics decrease. Because, if the addition amount is more than 3.0 wt%, the core expands, and thus there is a case where the density of the molded body decreases, and the magnetic permeability decreases.

[0046] The drying temperature of the silicone resin is preferably 100°C or higher and 200°C or lower. This is because, if the drying temperature is lower than 100°C, the film formation becomes incomplete, and there is a case where the eddy current loss becomes high. On the other hand, because, if the drying temperature is higher than 200°C, it becomes inorganic, cannot exert the function as a binder, the shape retention property deteriorates, and there is a case where the density and the magnetic permeability of the molded body decrease. The drying time is about 2 hours.

[0047] (3) lubricant mixing step (step S03)

[0048] The lubricant mixing step is a step of adding a lubricant to the FeSiAl alloy powder subjected to the insulating film treatment and mixing. Through this step, the surface of the silicone resin layer is coated with the lubricant. By adding the lubricant to the soft magnetic powder, the sliding between the soft magnetic powders becomes good, and thus the density at the time of mixing can be improved, and the molding density can be made high. Furthermore, the reduction in the punching of the upper punch at the time of molding, and the generation of the longitudinal lines of the core wall surface due to the contact of the mold with the powder can be prevented.

[0049] As the lubricant, a wax such as stearic acid and a metal salt thereof, and ethylene bis is used. For example, ethylene bis stearamide, calcium stearate, lithium stearate, aluminum stearate, zinc stearate, and a mixture of these can be used. The addition amount of the lubricant is preferably 0.1 wt% or more and 0.6 wt% or less with respect to the soft magnetic powder.

[0050] (4) Forming step (step S04)

[0051] The forming step is a step of forming a formed body by pressure forming the soft magnetic powder on which the insulating film is formed on the surface. The pressure at the time of forming is 10 ton / cm 2 Hereinafter, 20 ton / cm 2 Hereinafter, it is preferable that the average be 15 ton / cm 2 or thereabouts.

[0052] (5) Heat treatment step (step S05)

[0053] The heat treatment step is a step of heat treating the formed body subjected to the forming step in an oxidizing environment. The heat treatment is also called annealing. The powder magnetic core is produced by the heat treatment step. The oxidizing environment is a gas containing oxygen, and also includes the atmosphere. By heat treating in the oxidizing environment, a Fe2O3 (hematite) layer is formed on the surface of the powder on which the insulating layer is formed. By forming the Fe2O3 layer, stress is generated in the inside of the powder, and slight strain is generated. Thus, an effect of reducing the hysteresis loss is obtained. It is presumed that this is because, if an oxide layer is formed on the surface of the powder, stress is applied to the powder, the width of the magnetic domain in the crystal becomes narrow, and the coercive force decreases.

[0054] In a case where the total of the weight of the FeSiAl alloy powder in the powder magnetic core and the weight of Fe2O3 is set to 100 wt%, the proportion of the weight of Fe2O3 can be relatively small, and it is preferable that it not become too large. For example, the proportion of the weight of Fe2O3 is preferably 0.1 wt% or more. In addition, the proportion of the weight of Fe2O3 is preferably 0.79 wt% or less. The temperature of the heat treatment is preferably 600°C or more and 900°C or less. The amount of oxygen in the oxidizing environment is preferably the same as the atmosphere.

[0055] If the heat treatment is performed in the atmosphere, the silicone resin rapidly reacts with oxygen, and it can become a cause of cracks. Therefore, first, the first heat treatment is performed in a nitrogen environment in which the atmosphere is purged with nitrogen, and the silicone resin is stabilized. Then, the second heat treatment is further performed in the atmosphere, and thus the Fe2O3 layer can also be produced. Thus, the generation of cracks can be prevented.

[0056] [Example]

[0057] (First Example)

[0058] The first example of the present embodiment will be described below. The sample used in the first example is produced in the following manner.

[0059] (1) Powder heat treatment

[0060] The FeSiAl powder having an average particle diameter (D50) of 21.0 μm obtained by the gas atomization method was subjected to powder heat treatment at a temperature of 700°C for 2 hours in a nitrogen atmosphere.

[0061] (2) Insulating treatment

[0062] The FeSiAl powder after the powder heat treatment was mixed with 0.5 wt% of silicone oligomer, and subjected to heat drying at 200°C for 2 hours, and then passed through a sieve having a mesh size of 250 μm. Then, the powder was mixed with 1.5% of silicone resin (methylphenyl-based), and subjected to heat drying at 150°C for 2 hours, and then passed through a sieve having a mesh size of 250 μm.

[0063] (3) Lubricant mixing treatment

[0064] After the insulating treatment, the powder was mixed with 0.5 wt% of ethylene bis (Acrawax (registered trademark)) as a lubricant, and subjected to heat drying at 150°C for 2 hours. Then, the powder was passed through a sieve having a mesh size of 250 μm.

[0065] (4) Shaping

[0066] The powder was shaped into an EER core shape using a mold under a condition of 12 ton / cm 2 The FeSiAl powder after the insulating treatment and the lubricant mixing treatment was subjected to press molding to form a shaped body in an EER core shape.

[0067] (5) Heat treatment

[0068] The shaped body was subjected to heat treatment at 750°C for 2 hours in the atmosphere, whereby a powder magnetic core of Sample 1 (Example 1) was produced. In addition, powder magnetic cores of Samples 2 and 3 (Examples 2 and 3) were produced under the same conditions except that the amount of the atmosphere was adjusted by flowing N2. In Sample 2, the flow rate of N2 was 0.5 L / min, and in Sample 3, the flow rate of N2 was 1.0 L / min.

[0069] On the other hand, a powder magnetic core of Sample 4 (Comparative Example 1) was produced by subjecting the shaped body to heat treatment in a nitrogen atmosphere in which the atmosphere was purged by flowing N2 at a flow rate of 4.0 L / min. In Comparative Example 1, only the environment of the heat treatment was different, and the other conditions were the same as in Examples 1, 2, and 3.

[0070] (Measurement results)

[0071] The proportion of DO3 structure and Fe2O3 in the crystal structure of the powder magnetic core, and the iron loss Pcv (hysteresis loss Ph and eddy current loss Pe) were measured for Examples 1 to 3 and Comparative Example 1 produced as described above. The DO3 structure as referred to herein corresponds to the FeSiAl alloy powder.

[0072] More specifically, in the powder magnetic core produced through the above processes (1) to (5), the proportions of the weight of the DO3 structure and the weight of Fe2O3 when the total of the weight of the DO3 structure and the weight of Fe2O3 is taken as 100 wt% are calculated by evaluating the crystal structure by X-ray diffraction of the shaped body. The X-ray diffraction device is a device manufactured by the company BRUKER (BRUKER D2 PHASER 2nd Gen, X-ray: Cu-Ka ray).

[0073] On the other hand, a reactor using the powder magnetic core produced through the above processes (1) to (5) as a core was produced, and measurement for calculating the iron loss Pcv was performed. That is, a winding of a copper wire of φ0.5 mm, 1st winding 16 turns, 2nd winding 8 turns was wound on the powder magnetic core, and measurement was performed using a BH analyzer (Rikoh Kogyo Co., Ltd.: SY-8219) as a magnetic measurement device. The measurement was performed under the conditions of a frequency of 100 kHz and a maximum magnetic flux density Bm of 100 mT, and hysteresis loss (Ph) and eddy current loss (Pe) were calculated. The calculation was performed by the following equations (1) to (3) and by the least squares method to calculate the hysteresis loss coefficient (Kh) and the eddy current loss coefficient (Ke) from the frequency curve of the loss.

[0074] Pcv = Kh x f + Ke x f 2 …(1)

[0075] Ph = Kh x f …(2)

[0076] Pe = Ke x f 2 …(3)

[0077] Pcv: iron loss

[0078] Kh: hysteresis loss coefficient

[0079] Ke: eddy current loss coefficient

[0080] f: frequency

[0081] Ph: hysteresis loss

[0082] Pe: eddy current loss

[0083] The measurement results described above are shown in Table 1 and Figure 2 .

[0084] [Table 1]

[0085]

[0086] Table 1 is a table showing the relationship of the proportion of Fe2O3to the iron loss (Pcv), the hysteresis loss (Ph), and the eddy current loss (Pe), Figure 2 is a graph corresponding to Table 1. First, in Comparative Example 1 in which the proportion of Fe2O3is 0%, the hysteresis loss (Ph) is 309 kw / m 3 , and the eddy current loss (Pe) is 227 kw / m 3 . In contrast, in Example 3, Example 2, and Example 1, as the proportion of Fe2O3increases, both the hysteresis loss (Ph) and the eddy current loss (Pe) decrease. In particular, the proportion of decrease in the hysteresis loss (Ph) becomes large. When Comparative Example 1 is compared with Example 1 in which the proportion of Fe2O3is 0.79 wt%, the hysteresis loss (Ph) decreases from 309 kw / m 3 to 101 kw / m 3 , a decrease of about 30%. Thus, the iron loss also decreases from 536 kw / m 3 to 291 kw / m 3 . When Comparative Example 1 is compared with Example 3 in which the proportion of Fe2O3is 0.10 wt%, the hysteresis loss (Ph) decreases from 309 kw / m 3 to 200 kw / m 3 , a decrease of about 65%. Thus, the iron loss also decreases from 536 kw / m 3 to 409 kw / m 3 . That is, if the proportion of Fe2O3is 0.1 wt% or more, the hysteresis loss (Ph) and the eddy current loss (Pe) decrease significantly. In addition, it is known that the hysteresis loss (Ph) and the eddy current loss (Pe) decrease significantly at 0.79 wt% or less. Furthermore, if Fe2O3is too much, the amount of FeSiAl alloy decreases, and thus the characteristics deteriorate.

[0087] (Second Embodiment)

[0088] Next, a second embodiment of the present embodiment will be described. The test sample used in the second embodiment is produced in the following manner.

[0089] (1) Powder heat treatment

[0090] A FeSiAl powder having an average particle diameter (D50) of 19.8 μm obtained by a gas atomization method is subjected to powder heat treatment at a temperature of 700°C for 2 hours in a nitrogen environment.

[0091] (2) Insulating treatment

[0092] For the FeSiAl powder after heat treatment of the powder, 1.0 wt% of a silane coupling agent (tetraethoxysilane) was mixed, heat-dried at 200°C for 2 hours, and then passed through a sieve with a mesh of 250 μm. Then, 1.5% of a silicone resin (methylphenyl-based) was mixed, heat-dried at 150°C for 2 hours, and then passed through a sieve with a mesh of 250 μm.

[0093] (3) Lubricant mixing treatment

[0094] After the insulation treatment, 0.5 wt% of ethylene bis (Acrawax (registered trademark)) was mixed as a lubricant, and heat-dried at 150°C for 2 hours. Then, it was passed through a sieve with a mesh of 250 μm.

[0095] (4) Shaping

[0096] The FeSiAl powder after the insulation treatment and the lubricant mixing treatment was shaped into an EER core shape using a mold under a room temperature condition at 12 ton / cm 2 The powder was pressure-molded to form a shaped body in the shape of an EER core.

[0097] The shaped body was heat-treated at 750°C for 2 hours in a nitrogen atmosphere, whereby a powder magnetic core of Sample 5 (Comparative Example 2) was produced. The flow rate of N2was 4 L / min. For this Sample 5, further heat treatment was performed at 750°C for 2 hours in the atmosphere, whereby a powder magnetic core of Sample 6 (Example 4) was produced.

[0098] (Measurement results)

[0099] For Comparative Example 2 and Example 4 produced as above, the proportions of DO3structure and Fe2O3in the crystal structure, and the iron loss Pcv(magnetic hysteresis loss Phand eddy current loss Pe) were measured. The measurement items, the measurement apparatus, and the measurement method of the second example were the same as those of the first example. The measurement results above are shown in Table 2 and Figure 3 .

[0100] [Table 2]

[0101]

[0102] Table 2 is a table showing the relationship between the proportion of Fe2O3and the iron loss (Pcv), Figure 3 is a graph corresponding to Table 2. In Figure 3 , the values of the magnetic hysteresis loss (Ph), the eddy current loss (Pe), and the iron loss (Pcv) are shown. First, in Comparative Example 2 in which the proportion of Fe2O3was 0%, the magnetic hysteresis loss (Ph) was 230 kw / m 3 , and the eddy current loss (Pe) was 147 kw / m 3On the other hand, in Example 4 where Fe2O3 is 0.51 wt%, the hysteresis loss (Ph) is reduced to 161 kw / m 3 , and the eddy current loss (Pe) is reduced to 132 kw / m 3 . In particular, the reduction ratio of the hysteresis loss (Ph) is large. Therefore, the iron loss (Pcv) is greatly reduced from 377 kw / m 3 to 293 kw / m 3 . This means that even in the powder magnetic core which has been subjected to heat treatment (annealing) once after press forming, by further subjecting to heat treatment in the atmosphere, i.e., oxygen environment, the reduction effect of the hysteresis loss (Ph) and the iron loss (Pcv) can be obtained.

[0103] [Other Embodiments]

[0104] The present application is not directly limited to the above-described embodiments, and the constituent elements can be modified and embodied in the implementation stage without departing from the gist thereof. In addition, various applications can be formed by suitable combination of the constituent elements disclosed in the above-described embodiments. For example, several constituent elements can be deleted from all the constituent elements shown in the embodiments. Further, the constituent elements in different embodiments can be suitably combined.

[0105] For example, the powder heat treatment step can not be performed. That is, even in the case where the powder is not subjected to heat treatment, the effect of reducing the iron loss can be obtained by heat treatment of the shaped body of the present application. However, the effect of reducing the iron loss can be obtained by the powder heat treatment, and therefore, by heat treatment of the shaped body of the present application, the advantage of further improving the effect of reducing the iron loss is obtained.

[0106] In addition, for example, the present application is not limited to the powder magnetic core of the reactor produced in the above-described Examples 1 to 4, but also includes an embodiment in which a choke coil is produced by winding a coil on the powder magnetic core. By this, the effect obtained in the above-described Examples 1 to 4 can be similarly obtained in the choke coil.

Claims

1. A dust core, characterized by comprises: FeSiAl alloy powder, and an insulating resin coating a surface of the FeSiAl alloy powder, an Fe2O3 layer being formed on a surface of the FeSiAl alloy powder on which an insulating layer is formed, the insulating resin is composed of one or two or more of a silicone oligomer, a silicone resin, and a silane coupling agent, the Fe2O3 layer is formed on the surface of the FeSiAl alloy powder so as to be adjacent to the insulating resin, the Fe2O3 layer has a configuration that imparts a compressive stress to an inside of the FeSiAl alloy powder, thereby reducing hysteresis loss, and a proportion of a weight of the Fe2O3 is 0.1 wt% or more and 0.79 wt% or less, in a case where a total of the weight of the FeSiAl alloy powder and the weight of the Fe2O3 is 100 wt%.

2. The dust core according to claim 1, characterized by: the FeSiAl alloy powder is an atomized powder.

3. The powder magnetic core according to claim 1, characterized by the FeSiAl alloy powder is a spheroidized powder.

4. The powder magnetic core according to any one of claims 1 to 3, characterized by, a circularity of the FeSiAl alloy powder is 0.95 or more.

5. A method of manufacturing a dust core, characterized by comprises: an insulating treatment step of coating a surface of FeSiAl alloy powder with an insulating resin; a molding step of molding the FeSiAl alloy powder subjected to the insulating treatment; and a heat treatment step of subjecting the FeSiAl alloy powder after the molding to heat treatment at 600°C or higher and 900°C or lower in an oxidizing atmosphere, the insulating resin is composed of one or two or more of a silicone oligomer, a silicone resin, and a silane coupling agent, in the heat treatment step, an Fe2O3 layer is formed so as to be adjacent to the insulating resin, and a stress is generated in an inside of the FeSiAl alloy powder by the Fe2O3 layer, thereby reducing hysteresis loss; a proportion of a weight of the Fe2O3 is 0.1 wt% or more and 0.79 wt% or less, in a case where a total of the weight of the FeSiAl alloy powder and the weight of the Fe2O3 is 100 wt%.

6. The production method of the powder magnetic core according to claim 5, characterized in that: the heat treatment step includes: a first heat treatment performed in a nitrogen atmosphere; and a second heat treatment performed after the first heat treatment and in an oxidizing atmosphere. comprises:

7. The method of producing a powder magnetic core according to claim 5 or 6, characterized by a powder heat treatment step of subjecting the FeSiAl alloy powder to heat treatment before the insulating treatment step. ​

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