JP2015103719A - Powder-compact magnetic core, coil part, and method for manufacturing powder-compact magnetic core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder-compact magnetic core low in loss and high in hardness.SOLUTION: A powder-compact magnetic core comprises: soft magnetic particles; and an insulator layer interposed between the soft magnetic particles. The soft magnetic particles are made of an Fe-Si-Al based alloy. In a section of the powder-compact magnetic core, the maximum diameter/equivalent circle diameter is 1.0-1.3. The insulator layer includes Si and O and further, an oxide of at least one kind of alkali metals and Mg. Alternatively, a powder-compact magnetic core comprises: soft magnetic particles; and an insulator layer interposed between the soft magnetic particles. In the powder-compact magnetic core, the soft magnetic particles are made of an Fe-Si-Al based alloy; the content of oxygen is 500 ppm or less; and the insulator layer includes Si and O and further, an oxide of at least one kind of alkali metals and Mg.

Description

  The present invention relates to a dust core used for a magnetic core and the like, a coil component including the dust core, and a method for manufacturing the dust core. In particular, the present invention relates to a powder core having low loss and high strength.

  As a component provided in a circuit for converting energy, such as a switching power supply or a DC / DC converter, there is a magnetic component including a coil formed by winding a winding and a magnetic core in which the coil is disposed to form a closed magnetic circuit.

  Some of the magnetic cores utilize a powder magnetic core manufactured using a powder made of a soft magnetic material. As the powder magnetic core, for example, Patent Document 1 and Patent Document 2 show a powder magnetic core manufactured using soft magnetic particles made of Fe—Si—Al based alloy represented by Sendust as raw material powder. ing.

  The dust core of Patent Document 1 is made from coated particles comprising Fe—Si—Al-based alloy particles obtained by a gas atomization method or a water atomization method, and an insulating layer made of a silicate compound formed on the particle surface. Used for powder. And it is manufactured by pressurizing and compressing a composite material obtained by mixing a molding resin with a raw material powder, and subjecting the molded compact to a heat treatment. This heat treatment is performed in a nitrogen atmosphere when the particles are obtained by a gas atomizing method, and is performed in an air atmosphere when the particles are obtained by a water atomizing method.

  The dust core of Patent Document 2 heat-treats Fe-Si-Al-based alloy particles in an oxidizing atmosphere, and forms an insulating layer made of an oxide derived from alloy particles (mainly Al) on the surface of the alloy particles. The coated particles are used as raw material powder. And the compound which mixed the binder with this raw material powder is pressurized and compressed, and it heat-processes in an oxidizing atmosphere to the molded compression product, and is manufactured.

JP 2012-107330 A JP 2007-299871 A

  As interest in energy problems in recent years has increased, the characteristics required for dust cores have become stricter, and the development of dust cores with lower energy loss and higher strength is desired.

  The dust core of Patent Document 1 can ensure a certain degree of strength, and the dust core of Patent Document 2 can ensure a certain amount of low loss. However, the dust cores of Patent Document 1 and Patent Document 2 have room for further improvement in terms of both low loss and high strength.

  The present invention has been made in view of the above circumstances, and one of its purposes is to provide a powder magnetic core with low loss and high strength.

  Another object of the present invention is to provide a coil component including the above-described dust core.

  Another object of the present invention is to provide a method for producing the above-described dust core.

  The first dust core of the present invention includes a plurality of soft magnetic particles and an insulating layer interposed between the soft magnetic particles. The soft magnetic particles are made of an Fe—Si—Al alloy, and the maximum diameter / equivalent circle diameter in the cross section of the dust core is 1.0 or more and 1.3 or less. The insulating layer is made of an oxide containing Si and O, and at least one of alkali metal and Mg.

  The second dust core of the present invention includes a plurality of soft magnetic particles and an insulating layer interposed between the soft magnetic particles. The soft magnetic particles are made of an Fe—Si—Al-based alloy and have an oxygen content of 500 ppm or less. The insulating layer is made of an oxide containing Si and O, and at least one of alkali metal and Mg.

  The coil component of the present invention includes a coil formed by winding a winding and a magnetic core on which the coil is disposed. At least a part of the magnetic core is the dust core.

The first method for producing a dust core according to the present invention is produced using a coated soft magnetic powder comprising a plurality of coated soft magnetic particles whose outer periphery is coated with an insulating layer. The manufacturing method of the powder magnetic core of the present invention includes the following raw material preparation process, composite process, molding process, and heat treatment process.
In the raw material preparation step, the soft magnetic particles are Fe-Si-Al-based alloy, the maximum diameter / equivalent circle diameter in the projected area is 1.0 or more and 1.3 or less, the insulating layer is Si and O, A coated soft magnetic powder made of an oxide containing at least one of alkali metal and Mg is prepared.
In the composite process, a composite material including the coated soft magnetic powder and the molding resin material is produced.
In the molding step, the composite material is pressurized to produce a molded body.
In the heat treatment step, the molded body is subjected to a heat treatment in an oxidizing atmosphere to produce a magnetic core molded body in which the insulating layer is crystallized.

The second method for producing a dust core according to the present invention is produced using a coated soft magnetic powder comprising a plurality of coated soft magnetic particles whose outer periphery is coated with an insulating layer. The manufacturing method of the powder magnetic core of the present invention includes the following raw material preparation process, composite process, molding process, and heat treatment process.
The raw material preparation step is a Fe-Si-Al-based alloy having an oxygen content of 500 ppm or less, and an insulating layer made of an oxide containing Si and O, and further containing at least one of an alkali metal and Mg. Prepare a soft magnetic powder.
In the composite process, a composite material including the coated soft magnetic powder and the molding resin material is produced.
In the molding step, the composite material is pressurized to produce a molded body.
In the heat treatment step, the molded body is subjected to a heat treatment in an oxidizing atmosphere to produce a magnetic core molded body in which the insulating layer is crystallized.

  The dust core of the present invention has low loss and high strength.

  The coil component of the present invention is excellent in soft magnetic characteristics and strength.

  The method for producing a dust core of the present invention can produce a dust core with low loss and high strength.

It is a top view of the choke coil using the dust core concerning an embodiment.

<< Description of Embodiments of the Present Invention >>
The inventor has verified the loss and strength in a conventional dust core. As a result, as described above, when the raw material powder having the gas atomized soft magnetic particles and the insulating layer of the silicate compound on the surface is used as in Patent Document 1, the strength of the dust core is ensured to some extent as described above. Although it is easy, the strength may be inferior compared with the case of using water atomized soft magnetic particles. In addition, when using raw water powder with the water atomization method soft magnetic particles and the silicate compound insulating layer on the surface, iron loss is reduced compared to the case of using gas atomization method soft magnetic particles. Sometimes it was difficult. In many cases, the gas atomization method yields particles with less unevenness on the surface, whereas the water atomization method often yields particles with more unevenness on the surface. For this reason, the particles obtained by the gas atomization method tend to reduce the meshing of irregularities between particles such as those of the water atomization method, and it is difficult to increase the strength compared to the particles of the water atomization method. In addition, in the case of particles such as the water atomization method, the insulating layer formed on the surface of the soft magnetic particles may be deformed or damaged due to the engagement of the irregularities between the particles. It is considered that the iron loss can increase when the insulating layer is damaged and soft magnetic particles come into contact with each other. On the other hand, when an insulating layer made of an oxide derived from soft magnetic particles is provided as in Patent Document 2, since the insulating layer made of an oxide derived from soft magnetic particles is hard, the insulating layers are difficult to bond with each other and the strength is improved. I found it difficult.

  Therefore, the inventor has intensively studied a method for manufacturing a dust core having both low loss and high strength. As a result, as shown in a test example to be described later, soft magnetic particles made of an Fe-Si-Al-based alloy and an insulating layer made of a specific oxide are provided, and the soft magnetic particles have a specific shape and a specific shape. It was found that a powder magnetic core having both low loss and high strength can be obtained by preparing a raw material powder satisfying at least one of the oxygen contents and performing heat treatment in a specific atmosphere. The present invention is based on this finding. First, the contents of the embodiment of the present invention will be listed and described.

  (1) The first dust core according to the embodiment includes a plurality of soft magnetic particles and an insulating layer interposed between the soft magnetic particles. The soft magnetic particles are made of an Fe—Si—Al-based alloy, and the maximum diameter / equivalent circle diameter in the cross section is 1.0 or more and 1.3 or less. The insulating layer is made of an oxide containing Si and O, and at least one of alkali metal and Mg.

  According to said structure, while being excellent in intensity | strength, a loss can be made low. When the soft magnetic particles satisfy the maximum diameter / equivalent circle diameter, the shape is close to a sphere, and the insulating layer is less likely to be deformed or damaged during pressure forming during the manufacturing process. For this reason, the insulating layer is sufficiently interposed between the soft magnetic particles in the dust core so that the soft magnetic particles can be insulated from each other and the loss can be reduced. Further, since the insulating layer is made of the above oxide, the insulating layers are deformed and brought into close contact with each other at the time of pressure forming in the manufacturing process, and the insulating layer is crystallized and hardened in the subsequent heat treatment (firing) process. This is because the bond between the soft magnetic particles can be strengthened and the strength of the dust core can be increased.

  (2) The second dust core according to the embodiment includes a plurality of soft magnetic particles and an insulating layer interposed between the soft magnetic particles. The soft magnetic particles are made of an Fe—Si—Al-based alloy and have an oxygen content of 500 ppm or less. The insulating layer is made of an oxide containing Si and O, and at least one of alkali metal and Mg.

  According to said structure, while being excellent in intensity | strength, a loss can be made low. When the oxygen content of the soft magnetic particles is large, the loss tends to increase. Therefore, the loss can be reduced by satisfying the oxygen content of the soft magnetic particles. This is because the formation of fine oxide precipitates that significantly deteriorate the soft magnetic properties can be suppressed.

  (3) As one form of said 1st powder magnetic core, it is mentioned that oxygen content of a soft-magnetic particle is 500 ppm or less.

  According to said structure, while being excellent in intensity | strength, loss can be reduced further. When the soft magnetic particles satisfy the maximum diameter / equivalent circle diameter and satisfy the oxygen content, the particle shape becomes spherical, and damage to the insulating layer during pressure molding can be suppressed. At the same time, the generation of fine oxide precipitates that significantly deteriorate the soft magnetic properties can be suppressed. Therefore, the insulation between the particles can be maintained in a healthy state, and iron loss can be reduced and bonding between particles can be strengthened.

(4) As one form of said 1st and 2nd powder magnetic core, it is mentioned that an iron loss (W1 / 100k) is 300 kW / m < ³ > or less. This iron loss is a value when measured at at least a part of the ambient temperature range of 25 ° C. or higher and 150 ° C. or lower with an excitation magnetic flux density Bm of 0.1 T and a measurement frequency of 100 kHz.

  According to said structure, it can utilize suitably for the magnetic core of the coil components in various use temperature ranges.

(5) As one form of said 1st and 2nd powder magnetic core, said iron loss (W1 / 100k) is 300 kW / m < ² > or less, and crushing strength is 25 Mpa or more. The crushing strength is a value measured on the basis of “sintered bearing-crushing strength test method JIS Z 2507 (2000)”.

  According to said structure, it can utilize suitably for the magnetic core of the coil components calculated | required to have high intensity | strength.

  (6) As one form of the first and second powder magnetic cores, when the Si content in the soft magnetic particles is a mass% and the Al content is b mass%, 27 ≦ 2.5a + b ≦ 29, Satisfying 6 ≦ b ≦ 9.

  According to said structure, the energy loss of the powder magnetic core obtained using this soft-magnetic powder, especially the hysteresis loss in a high temperature environment (for example, 100 degreeC or more) can be reduced.

  (7) The coil component according to the embodiment includes a coil formed by winding a winding, and a magnetic core on which the coil is disposed. At least a part of the magnetic core is the first or second dust core.

  According to said structure, while being excellent in a soft magnetic characteristic, it is hard to damage. The present invention can be suitably used for coil parts that are arranged at locations that are susceptible to external influences such as vibration.

(8) The first dust core manufacturing method according to the embodiment is manufactured using a coated soft magnetic powder comprising a plurality of coated soft magnetic particles whose outer periphery is coated with an insulating layer. The manufacturing method of the powder magnetic core of the present invention includes the following raw material preparation process, composite process, molding process, and heat treatment process.
In the raw material preparation step, the soft magnetic particles are Fe-Si-Al-based alloy, the maximum diameter / equivalent circle diameter in the projected area is 1.0 or more and 1.3 or less, the insulating layer is Si and O, A coated soft magnetic powder made of an oxide containing at least one of alkali metal and Mg is prepared.
In the composite process, a composite material including the coated soft magnetic powder and the molding resin material is produced.
In the molding step, the composite material is pressurized to produce a molded body.
In the heat treatment step, the molded body is subjected to a heat treatment in an oxidizing atmosphere to produce a magnetic core molded body in which the insulating layer is crystallized.

  According to said structure, a low-loss and high intensity | strength powder magnetic core can be manufactured. This is because the specific coated soft magnetic powder is prepared in the raw material preparation step, and the heat treatment step is performed in an oxidizing atmosphere, whereby the insulation between the soft magnetic particles can be improved.

(9) The second method for producing a dust core according to the embodiment is produced using a coated soft magnetic powder comprising a plurality of coated soft magnetic particles whose outer periphery is coated with an insulating layer. The manufacturing method of the powder magnetic core of the present invention includes the following raw material preparation process, composite process, molding process, and heat treatment process.
The raw material preparation step is a Fe-Si-Al-based alloy having an oxygen content of 500 ppm or less, and an insulating layer made of an oxide containing Si and O, and further containing at least one of an alkali metal and Mg. Prepare a soft magnetic powder.
In the composite process, a composite material including the coated soft magnetic powder and the molding resin material is produced.
In the molding step, the composite material is pressurized to produce a molded body.
In the heat treatment step, the molded body is subjected to a heat treatment in an oxidizing atmosphere to produce a magnetic core molded body in which the insulating layer is crystallized.

  According to said structure, a low-loss and high intensity | strength powder magnetic core can be manufactured. This is because the specific coated soft magnetic powder is prepared in the raw material preparation step, and the heat treatment step is performed in an oxidizing atmosphere, whereby the insulation between the soft magnetic particles can be improved.

  (10) As one form of the manufacturing method of said 1st powder magnetic core, it is mentioned that the oxygen content of a soft-magnetic particle is 500 ppm or less.

  According to said structure, it is high intensity | strength and can manufacture a much lower powder dust core.

  (11) As one form of the manufacturing method of said 1st and 2nd powder magnetic core, heat processing temperature makes 600 degreeC or more 900 degrees C or less and oxygen concentration 0.1 volume% or more is mentioned. .

  According to said structure, it is effective in manufacturing a dust core with a low loss and high intensity | strength.

<< Details of Embodiment of the Present Invention >>
Details of embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to these illustrations, is shown by the claim, and intends that all the changes within the meaning and range equivalent to a claim are included.

[Dust core]
The dust core according to the embodiment includes a plurality of soft magnetic particles and an insulating layer interposed between the soft magnetic particles. The main features of this dust core are that the soft magnetic particles are made of Fe-Si-Al alloy, the insulating layer is made of a specific oxide, and (1) the shape of the soft magnetic particles is specified. (2) The soft magnetic particles have a low oxygen content, and have at least one of them. First, a dust core according to the embodiment will be described, and then a method for manufacturing the dust core and a coil component including the dust core will be described.

(Soft magnetic particles)
The kind of soft magnetic particles is Fe-Si-Al alloy. A typical example of the Fe—Si—Al engagement gold includes a composition containing 7.0% by mass to 11% by mass of Si, 3% by mass to 11% by mass of Al, with the balance being Fe and inevitable impurities. . The Fe—Si—Al-based alloy preferably contains 7.0 mass% or more and 9.5 mass% or less of Si and 4.0 mass% or more and 10.0 mass% or less of Al. If it does so, intensity | strength can be made high and the loss at normal temperature (about 25 degreeC) can be made low. In particular, the Fe—Si—Al-based alloy preferably satisfies 27 ≦ 2.5a + b ≦ 29 and 6 ≦ b ≦ 9 when the Si content is a mass% and the Al content is b mass%. . If it does so, in addition to being able to raise intensity | strength and reducing the loss at normal temperature, the loss at high temperature (100 degreeC or more) can also be reduced. More preferably, the Si content a and the Al content b in the Fe—Si—Al alloy satisfy 978/35 ≦ 18 / 7a + b ≦ 1023/35 and 6.6 ≦ b ≦ 8.4. The soft magnetic particles described in JP 2012-9825 A can be used as the soft magnetic particles.

As for the shape of the soft magnetic particles, the maximum diameter / equivalent circle diameter in the cross section of the dust core is 1.0 or more and 1.3 or less. If it does so, intensity | strength can be made high and the loss at normal temperature (about 25 degreeC) can be made low. The shape of the soft magnetic particles is particularly preferably a true sphere. A true sphere refers to a case where the maximum diameter / equivalent circle diameter is 1.0. The maximum diameter and the equivalent circle diameter of the soft magnetic particles are obtained as follows. First, the observation field of view of an arbitrary cross-section of the dust core is adjusted with a scanning electron microscope (SEM) so that the magnification is 100 to 1000 times, the number of observation fields is 2 or more, and the total observation area is 60000 μm ² or more. The observed image is analyzed with an image analyzer. Then, the maximum diameter, the equivalent circle diameter, and the maximum diameter / equivalent circle diameter of each soft magnetic particle are calculated, and the calculation results of the maximum diameter / equivalent circle diameter are averaged. The maximum diameter is the maximum length in the contour of each soft magnetic particle, and the equivalent circle diameter is the diameter of a circle having the same area as the area surrounded by the contour. The shape of the soft magnetic particles substantially maintains the shape of the soft magnetic particles prepared at the time of manufacture. This is because the soft magnetic particles themselves have high hardness and are not easily deformed during molding in the manufacturing process.

  The oxygen content of the soft magnetic particles is 500 ppm or less. If it does so, intensity | strength can be made high and the loss at normal temperature (about 25 degreeC) can be made low. The oxygen content of the soft magnetic particles is preferably as small as possible, and is preferably 400 ppm or less, more preferably 200 ppm or less, and particularly preferably 150 ppm or less. The oxygen content of the soft magnetic particles can be determined by an electron beam microanalyzer (EPMA). The oxygen content of the soft magnetic particles substantially maintains the oxygen content of the soft magnetic particles prepared at the time of manufacture.

  The average particle diameter of the soft magnetic particles is preferably 10 μm or more and 100 μm or less. Then, iron loss can be reduced. When the average particle size of the soft magnetic particles is 10 μm or more, an increase in hysteresis loss can be suppressed. On the other hand, when the average particle diameter of the soft magnetic particles is 100 μm or less, an increase in eddy current loss can be suppressed. The average particle diameter of the soft magnetic particles is the average value of equivalent circle diameters measured and calculated by the same measurement method as that for obtaining the above-described shape. The average particle diameter of the soft magnetic particles substantially maintains the average particle diameter of the soft magnetic particles prepared at the time of manufacture, similar to the shape of the soft magnetic particles described above.

(Insulating layer)
The insulating layer is interposed between the soft magnetic particles to ensure insulation between the soft magnetic particles. The insulating layer is usually formed so as to cover the outer peripheral surface of the soft magnetic particles. The insulating layer is made of a silicate compound containing Si and O, and at least one of alkali metal and Mg.

Examples of the silicate compound containing at least one of the alkali metal and Mg include potassium silicate (K ₂ SiO ₃ ), sodium silicate (Na ₂ SiO ₃ : water glass, also called sodium silicate), lithium silicate ( Li ₂ SiO ₃ ), magnesium silicate (MgSiO ₃ ) and the like. The content of each element in the insulating layer is such that Si is 10% by mass to 35% by mass, O is 20% by mass to 70% by mass, and the total amount of alkali metal and Mg is 5% by mass to 30% by mass. A range is preferred.

  The insulating layer may further contain Al in addition to the silicic acid compound. Although the form of Al to contain is not ask | required in particular, For example, the form contained as aluminum silicate, aluminate, etc. is mentioned. When the insulating layer contains sodium silicate and Al, the insulating property is excellent. When the insulating layer contains other silicate compounds such as potassium silicate, lithium silicate, magnesium silicate and Al, the heat resistance is excellent. When the insulating layer contains Al, the content of Al is preferably in the range of more than 0% by mass and 20% by mass or less.

  The insulating layer may contain a small amount of elements other than Si, Al, O, alkali metals, and Mg. Examples of elements other than Si, Al, O, alkali metal, and Mg include Fe, Ca, and the like. The content is preferably 20% by mass or less.

(Characteristic)
The dust core has low loss and high strength. The iron loss (W1 / 100 k) is, for example, 300 kW / m ³ or less. The iron loss (W1 / 100k) is a value measured at at least a part of the environmental temperature range of 25 ° C. or higher and 150 ° C. or lower with an excitation magnetic flux density Bm of 0.1T and a measurement frequency of 100 kHz. In other words, the dust core has a temperature at which the iron loss (W1 / 100k) is 300 kW / m ³ or less in an environmental temperature range of 25 ° C. or more and 150 ° C. or less. This iron loss (W1 / 100k) is preferably 200 kW / m ³ or less, and particularly preferably 180 kW / m ³ or less. In particular, when the iron loss (W1 / 100k) is low in a relatively high temperature range (for example, 100 ° C. or higher) in the environmental temperature range, it can be suitably used for a converter mounted on a hybrid vehicle that has been remarkably developed in recent years. On the other hand, the crushing strength is, for example, 25 MPa or more. The crushing strength is a value measured on the basis of “sintered bearing-crushing strength test method JIS Z 2507 (2000)”. The crushing strength is preferably 35 MPa or more, and more preferably 40 MPa or more.

[Production method of dust core]
The method for producing a dust core for producing the dust core includes a raw material preparation step, a composite step, a forming step, and a heat treatment step. The main feature of this method for producing a dust core is that a specific coated soft magnetic powder is prepared in the raw material preparation step and a specific heat treatment is performed in the heat treatment step. More specifically, in the raw material preparation step, a coated soft magnetic powder including a plurality of soft magnetic particles having at least one of the specific shape and the specific oxygen content described above and an insulating layer of a specific material is prepared. In the heat treatment step, heat treatment is performed in a specific atmosphere. Hereinafter, each process is demonstrated in order.

[Raw material preparation process]
As a raw material powder for the dust core, a coated soft magnetic powder including a plurality of coated soft magnetic particles including soft magnetic particles made of the above-described material and an insulating layer formed on the outer periphery thereof and made of the above-described material is prepared. The coated soft magnetic powder can be prepared, for example, by preparing a plurality of soft magnetic particles and coating the outer periphery of the soft magnetic particles with an insulating layer.

  The soft magnetic particles can be produced by a gas atomization method. Thereby, soft magnetic particles having a maximum diameter / equivalent circle diameter of 1.0 to 1.3, more preferably 1.0 to 1.1 in the projected area can be produced. The atmosphere for producing the soft magnetic particles is a low oxygen atmosphere with a low oxygen concentration. Thereby, soft magnetic particles having an oxygen content of 500 ppm or less can be produced. The atmosphere during the production of the soft magnetic particles is preferably an inert gas atmosphere (non-oxygen atmosphere). That is, by using a gas atomizing method and a low oxygen atmosphere (particularly a non-oxygen atmosphere), the maximum diameter / equivalent circle diameter in the projected area is 1.0 or more and 1.3 or less, and the oxygen content is 500 ppm or less. Soft magnetic particles can be produced. The average particle diameter of the soft magnetic particles is preferably 10 μm or more and 100 μm or less. The average particle diameter refers to a D50 (50%) particle diameter (a particle diameter corresponding to 50% of a mass-based cumulative distribution curve). A natural oxide film may be formed on the surface of the soft magnetic particles.

  Covering the outer periphery of the soft magnetic particles with, for example, an aqueous solution or water content of an alkali metal silicate while stirring the soft magnetic particles using a mixer or rolling the soft magnetic particles in a rotating container. This can be done by adding and mixing a solution such as a colloidal solution of magnesium silicate. It is preferable that the number of rotations of the mixer or the rotating container is 50 rpm or more and 500 rpm or less, and mixing is performed at a temperature of 30 ° C. or more and 100 ° C. or less for 10 minutes or more and 60 minutes or less. The solution is preferably added by spraying the solution at the above temperature. Then, after the sprayed solution is attached to the surface of the soft magnetic particles, the attached solution can be quickly dried to form a dense insulating layer. In the coated soft magnetic powder thus produced, since some of the soft magnetic particles are bonded to each other via an insulating layer, it is preferable to perform “unraveling” to separate the bonding. This loosening operation is sufficient to lightly screen the soft magnetic powder.

  The concentration of these solutions and the mass of the solid content in the solution with respect to the mass of the soft magnetic particles can be appropriately selected according to the desired thickness of the insulating layer. This is because the mass of the solid content can be roughly converted into the thickness of the insulating layer. Specifically, the concentration of the solution is 5% by mass or more and 50% by mass or less, and the addition amount of the solid content is 0.1% by mass or more and 3.0% by mass or less. For example, when the average particle size of soft magnetic particles is 50 μm, when the solid content is 0.1% by mass, an insulating layer having an average thickness of about 25 nm can be formed, and when the solid content is 1.0% by mass An insulating layer having an average thickness of about 750 nm can be formed. When the dust core is manufactured by setting the thickness of the insulating layer to 25 nm or more, sufficient insulation between particles can be secured, and by setting the thickness of the insulating layer to 750 nm or less, soft magnetism in the dust core is achieved. A sufficient amount of particles can be secured.

[Composite process]
A composite material including a raw material powder and a molding resin material is produced. The molding resin material retains its shape when the raw material powder is compressed into a compact. The material of the molding resin material is preferably a material that can achieve both the deformability during molding and the mechanical strength during molding. An example of the material is a thermoplastic resin. Specifically, acrylic resin, polyvinyl alcohol (PVA) resin, polyvinyl butyral (PVB) resin, polyethylene (PE) resin, and the like can be given. In particular, an acrylic resin is preferable from the viewpoint of both the deformability during molding and the mechanical strength during molding. This molding resin material substantially disappears during heat treatment of the molded body.

  The composite material can be produced by, for example, rolling the soft magnetic powder while heating it using a mixer or a dry pan granulator used when the insulating layer is coated on the soft magnetic particles, and diluting with water. This can be done by adding and mixing the molded resin material. When the same mixer as that used for coating the insulating layer is used, the insulating layer can be continuously coated and the mixed material can be produced. It is preferable that the rotational speed at the time of rolling is 50 rpm or more and 500 rpm or less, and the mixing is performed at a temperature of 30 ° C. or more and 100 ° C. or less for 10 minutes or more and 120 minutes or less. The molding resin material is preferably added by spraying the molding resin material at the above temperature as described above. Then, after the sprayed molding resin material is adhered to the surface of the coated soft magnetic particles, the adhered molding resin material is quickly dried, so that the molding resin material uniform on the outer periphery of the coated soft magnetic particles is obtained. Can be formed. The raw material powder to which the molding resin material is added is dried by heating to form a unit particle of a composite material in which a plurality of soft magnetic particles are integrated with the molding resin material.

  The amount of the molding resin material added to the raw material powder is preferably 0.5% by mass to 3.0% by mass with respect to the mass of the soft magnetic powder. By making the addition amount of the molding resin material 0.5 mass% or more, the molded body can be sufficiently retained. By making the addition amount 3.0% or less, the amount of resin in the mixture becomes an appropriate amount, and the amount of soft magnetic particles in the molded body and the molded body for magnetic core can be sufficiently secured. The amount of the resin material for molding is particularly preferably 0.5% by mass or more and 2.0% by mass or less.

[Molding process]
In the molding process, the composite material is pressurized to produce a molded body. The molded body can be manufactured by filling the composite material into a molding die capable of obtaining a predetermined shape and pressurizing the composite material in the mold. What is necessary is just to select the shape of a molded object according to the shape of the magnetic core of coil components.

  The pressure for pressurizing the composite material is preferably 500 MPa or more. By setting the pressure to 500 MPa or more, a high-density molded body can be obtained. The pressure is particularly preferably 800 MPa or more. The upper limit of the pressure can be appropriately selected as long as the soft magnetic particles are not substantially deformed and the insulating layer is not damaged. For example, the pressure is 2500 MPa or less.

[Heat treatment process]
The molded body is subjected to heat treatment to produce a molded body for a magnetic core in which the insulating layer is crystallized. The heat treatment removes strain introduced into the soft magnetic particles in the molding process and crystallizes the constituent material of the insulating layer.

  The heat treatment atmosphere is an oxidizing atmosphere. If it does so, the molded object for magnetic cores with a low loss and high intensity | strength can be manufactured. The oxygen concentration is preferably 0.1% by volume or more, and particularly preferably 5% by volume or more. By setting the oxygen concentration to 0.1% by volume or more, the insulating property between the soft magnetic particles can be improved. Examples of the oxygen concentration include 50% by volume or less, and further 25% by volume or less.

  The heat treatment temperature is preferably 600 ° C. or higher and 900 ° C. or lower, and particularly preferably 650 ° C. or higher and 800 ° C. or lower. The holding time of this heat treatment is preferably about 0.5 hours or more and 2 hours or less, and particularly preferably 1 hour or more and 2 hours or less.

  The oxygen content inside the soft magnetic particles in the obtained magnetic core molded body effectively maintains the oxygen content inside the soft magnetic particles in the raw material preparation step. This is because even if this heat treatment is performed at the above oxygen concentration, since the insulating layer is formed on the outer periphery of the soft magnetic particles, the oxidation of the soft magnetic particles themselves can be suppressed.

[Coil parts]
The above-described dust core and the dust core obtained by the above-described manufacturing method can be suitably used for the magnetic core of coil parts and its material. The coil component includes a coil formed by winding a winding, and a magnetic core on which the coil is disposed. An example of the winding is one having an insulating layer on the outer periphery of the conductor. Examples of the conductor include a wire made of a conductive material such as copper, copper alloy, aluminum, and aluminum alloy. Examples of the constituent material of the insulating layer include enamel, tetrafluoroethylene-hexafluoropropylene copolymer (FEP) resin, polytetrafluoroethylene (PTFE) resin, and silicon rubber. Known windings can be used. The form of the magnetic core typically includes a columnar body and an annular body. By combining a plurality of the above powder magnetic cores, columnar magnetic cores and annular magnetic cores of various sizes can be constructed. All of the magnetic core can be formed of the powder magnetic core, or only part of the magnetic core can be formed of the powder magnetic core. In the latter case, a magnetic core member made of another material such as an electromagnetic laminated steel sheet or a molded hardened body in which soft magnetic powder is dispersed in a resin may be combined. A magnetic core having a lower magnetic permeability than those dust cores and magnetic core members, in particular, a gap material made of a non-magnetic material or an air gap can be used.

  An example of this coil component is shown in FIG. A coil component 100 in FIG. 1 is a choke coil including an annular magnetic core 1 (magnetic core) and a coil 2 formed by winding a winding 2 w around the outer periphery of the magnetic core 1. The annular magnetic core 1 is composed of the dust core. In addition, examples of the coil 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.

[Function and effect]
According to the above-described dust core, low loss and high strength can be combined. In particular, in addition to low loss at room temperature, it also has low loss at high temperatures. According to the method for manufacturing a dust core described above, a dust core with low loss and high strength can be manufactured. Since the above-described coil component has a low-loss and high-strength powder magnetic core, it has a wide range of applications and can be used for various coil components.

<< Test Example 1 >>
A test piece of the powder magnetic core was prepared by preparing raw material powder → preparation of composite material → preparation of molded body → heat treatment, and the soft magnetic properties and strength were measured.

[Raw material preparation process]
(Preparation of soft magnetic powder)
Soft magnetic powders α to δ shown in Table 1 were prepared. The soft magnetic powders α to γ were prepared by dissolving an Fe—Si—Al alloy raw material in an Ar atmosphere and atomizing with nitrogen gas. The soft magnetic powders α to γ are powders that are not pulverized after being produced by a gas atomization method. The soft magnetic powder δ was prepared by dissolving a Fe—Si—Al alloy raw material in the air and atomizing with water to prepare a water atomized powder, and then pulverizing the water atomized powder in the air. Table 1 summarizes the composition, shape, oxygen content, and average particle size of the soft magnetic particles α to δ. The spherical shape shown in Table 1 means that the maximum diameter / equivalent circle diameter in the projected area of the soft magnetic particles is 1.0 or more and 1.3 or less, and the irregular shape means the maximum diameter / circle equivalent in the projected area. The diameter is out of the above range, that is, the maximum diameter / equivalent circle diameter in the projected area is more than 1.3.

  The soft magnetic powders α and γ have the relational expression (1) of 27 ≦ 2.5a + b ≦ 29 and 6 ≦ b ≦ 9, where the Si content is a mass% and the Al content is b mass%. Satisfies (2.5a + b = 28.05), and further satisfies the relational expression (2) of 978/35 ≦ 18 / 7a + b ≦ 1023/35 and 6.6 ≦ b ≦ 8.4 (18 / 7a + b≈ 28.66). On the other hand, the soft magnetic powders β and δ do not satisfy both the relational expressions (1) and (2) (2.5a + b = 29.25, 18 / 7a + b≈29.93).

(Insulation layer coating)
Next, an insulating layer made of the material shown in Table 1 was coated on the outer periphery of the particles of the soft magnetic powders α to δ as described below to produce a coated soft magnetic powder.

  The sodium silicate insulating layer (Sample Nos. 1, 2, 5, 6, 8 to 10) was formed by adding and mixing an aqueous sodium silicate solution while stirring the soft magnetic particles using a mixer. The concentration of the aqueous sodium silicate solution was 20% by mass. The soft magnetic particles and the aqueous solution were mixed so that the solid content of the aqueous solution was 1.2% with respect to the mass of the soft magnetic particles. The mixing conditions were a rotation speed of 300 rpm, a mixing temperature of 40 ° C., and a mixing time of 20 minutes. An insulating layer substantially composed of Si, O, and Na was formed on the surface of the soft magnetic particles during mixing. The thickness of the insulating layer was about 250 nm. Thereafter, the obtained coated soft magnetic powder was sieved to loosen the particles.

  The silicone resin insulation layers (Sample Nos. 3 and 4) were prepared by mixing soft magnetic powder and silicone resin using a mixer. The blending amount of the silicone resin with respect to the soft magnetic powder was set to 1.2% by mass. The mixing conditions were a rotation speed of 300 rpm, a mixing temperature of 40 ° C., and a mixing time of 20 minutes. The insulating layer had a thickness of about 250 nm. Thereafter, crushing was performed to separate the particles from each other.

The Al ₂ O ₃ insulating layer (sample No. 7) was formed by subjecting soft magnetic powder to heat treatment at 850 ° C. for 1 hour in an oxidizing atmosphere with an oxygen content of 20% by volume. The thickness of the insulating layer was about 200 nm.

[Composite process]
Next, a composite material including each coated soft magnetic powder and a molding resin material was produced. Here, using a dry bread granulator, the coated soft magnetic powder was rolled while being heated, and the molding resin material was added and mixed. As the molding resin material, an acrylic resin diluted with water was adjusted to 1.0 mass% with respect to the coated soft magnetic powder. The heating temperature was 40 ° C., the rotation speed was 300 rpm, and the mixing time was 1 hour.

[Molding process]
The obtained composite material was filled in a predetermined molding die, and the composite material in the die was pressed at a pressure of 980 MPa to produce a molded body.

[Heat treatment process]
The obtained molded body was heat-treated at 775 ° C. for 1 hour in the atmosphere shown in Table 1, and a test piece of a magnetic core molded body having an outer diameter of 34 mm, an inner diameter of 20 mm, and a thickness of 5 mm was produced as a sample. did. At this time, the insulating layer of sodium silicate was present on the particle surface as it was without being decomposed and crystallized, and the molding resin material was substantially lost. On the other hand, the insulating layer of the silicone resin became SiO ₂ insulating layer was vitrified.

[Evaluation]
About each sample produced as mentioned above, the iron loss (W1 / 100k) was measured as a soft magnetic characteristic, and the crumbling strength (MPa) was measured as an intensity | strength. The results are shown in Table 2.

(Soft magnetic properties)
The soft magnetic properties were measured by the following procedure. Winding was applied to the ring-shaped test piece to prepare a measurement member for measuring the soft magnetic properties of the test piece. About this measurement member, BH / μ analyzer SY-8258 manufactured by Iwatatsu Measurement Co., Ltd. was used. Here, each iron loss (W1 / 100k) when the excitation magnetic flux density Bm is 0.1 T, the measurement frequency is 100 kHz, and the environmental temperature is 25 ° C., 50 ° C., 75 ° C., 100 ° C., 125 ° C., 150 ° C. Was measured.

(Strength)
For the strength, the crushing strength was measured in accordance with “Sintered Bearing—Cavity Strength Test Method JIS Z 2507 (2000)”. Specifically, two plates are arranged on a ring-shaped test piece so as to face each other in the radial direction, the test piece is sandwiched between these plates, and a load is applied to one plate. And the maximum load when the said test piece broke was calculated | required, and this maximum load (n = 3 average) was evaluated as crushing strength (MPa).

[result]
In the raw material preparation step, from a soft magnetic particle having a spherical shape and an oxygen content of 500 ppm or less, an oxide containing Si and O, and at least one of an alkali metal and Mg (here, sodium silicate) Sample No. 1 was prepared by preparing a coated soft magnetic powder including an insulating layer and performing heat treatment in an oxidizing atmosphere (here, the amount of oxygen is 20% by volume). Both 1, 2 and 10 had both low loss and high strength. Specifically, Sample No. 1, 2 and 10 both have an iron loss (W1 / 100k) measured at least part of the environmental temperature range of 25 ° C. or more and 150 ° C. or less satisfying 300 kW / m ³ or less, and the crushing strength is 25 MPa or more. there were.

Sample No. No. 1 had an iron loss (W1 / 100 k) of 300 kW / m ³ or less in the entire environmental temperature range of 25 ° C. or more and 150 ° C. or less. Further, the iron loss (W1 / 100 k) at an environmental temperature of 50 ° C. or more and 150 ° C. or less was 250 kW / m ³ or less. Furthermore, the iron loss (W1 / 100 k) at an environmental temperature of 75 ° C. to 125 ° C. is 200 kW / m ³ or less, and the iron loss (W1 / 100 k) at an environmental temperature of 100 ° C. to 125 ° C. is 180 kW. / M ³ or less. Sample No. 1 can be suitably used over the entire temperature range from a low temperature range to a high temperature range, and is particularly suitable for use in a high temperature range. On the other hand, the crushing strength was 40 MPa or more, and the strength was very high.

Sample No. 2 has an iron loss (W1 / 100k) in an environmental temperature range of 25 ° C. or more and 50 ° C. or less of 300 kW / m ³ or less, and an iron loss (W1 / 100k) in an environmental temperature range of 25 ° C. or more and less than 50 ° C. Was 200 kW / m ³ or less. Sample No. 2 is particularly suitable for use in a low temperature range. On the other hand, the crushing strength was 40 MPa or more, and the strength was very high.

Sample No. No. 10 had an iron loss (W1 / 100 k) of 300 kW / m ³ or less, more preferably 250 kW / m ³ in an environmental temperature range of 50 ° C. or more and 150 ° C. or less. Moreover, the iron loss (W1 / 100k) in the environmental temperature of 100 degreeC or more and 125 degrees C or less was 200 kW / m < ³ > or less. Sample No. No. 10 can be suitably used over the entire temperature range from a low temperature range to a high temperature range, and is particularly suitable for use in a high temperature range. On the other hand, the crushing strength was 40 MPa or more, and the strength was very high.

On the other hand, sample No. 3-Sample No. None of 9 had both low loss and high strength, either low loss or high strength, or both low loss and high strength. Among them, sample No. 7 had a temperature at which the iron loss (W1 / 100 k) measured in any of the environmental temperature ranges from 25 ° C. to 150 ° C. was 300 kW / m ³ or less, but the crushing strength was as extremely low as 9 MPa. This is considered to be because the insulating layer is derived from soft magnetic particles, the insulating layer is hard, and the connection between the insulating layers is weak as described above with respect to the knowledge of the present inventors. Sample No. Although No. 8 was able to increase the crushing strength, the iron loss (W1 / 100 k) was extremely large in the entire environmental temperature range of 25 ° C. or more and 150 ° C. or less. Also, as described above with respect to the inventor's knowledge, the unevenness between the particles meshed with each other, so that the strength could be improved. However, the insulating layer was deformed or damaged, so that sufficient insulation between the particles could not be secured. It is thought that it was because of the reason.

  The dust core of the present invention can be used for magnetic cores of various coil components (for example, reactors, transformers, motors, choke coils, antennas, fuel injectors, ignition coils, etc.) and materials thereof. The method for producing a dust core of the present invention can be suitably used for producing the dust core. The coil component of the present invention can be used for a reactor, a transformer, a motor, a choke coil, an antenna, a fuel injector, an ignition coil, and the like.

100 Coil parts 1 Magnetic core 2 Coil 2w Winding

Claims (11)

A dust core comprising a plurality of soft magnetic particles and an insulating layer interposed between the soft magnetic particles,
The soft magnetic particles are
Made of Fe-Si-Al alloy,
The maximum diameter / equivalent circle diameter in the cross section of the dust core is 1.0 or more and 1.3 or less,
The insulating layer is a dust core made of an oxide containing Si and O, and at least one of an alkali metal and Mg. A dust core comprising a plurality of soft magnetic particles and an insulating layer interposed between the soft magnetic particles,
The soft magnetic particles are
Made of Fe-Si-Al alloy,
The oxygen content is 500 ppm or less,
The insulating layer is a dust core made of an oxide containing Si and O, and at least one of an alkali metal and Mg.   The dust core according to claim 1, wherein the soft magnetic particles have an oxygen content of 500 ppm or less. The iron loss (W1 / 100k) is 300 kW / m ³ or less at at least a part of the environmental temperature range of 25 ° C. or higher and 150 ° C. or lower when the excitation magnetic flux density Bm is 0.1 T and the measurement frequency is 100 kHz. The dust core according to any one of claims 1 to 3.   The dust core according to claim 4, wherein the crushing strength is 25 MPa or more. When the Si content in the soft magnetic particles is a mass% and the Al content is b mass%,
27 ≦ 2.5a + b ≦ 29
6 ≦ b ≦ 9
The powder magnetic core according to any one of claims 1 to 5, wherein: A coil formed by winding a winding, and a magnetic core on which the coil is disposed;
A coil component in which at least a part of the magnetic core is a dust core according to claim 1 or 2. A dust core manufacturing method for manufacturing a dust core using a coated soft magnetic powder comprising a plurality of coated soft magnetic particles having an insulating layer coated on an outer periphery of a soft magnetic particle,
The soft magnetic particles are Fe-Si-Al-based alloy, and the maximum diameter / equivalent circle diameter in the projected area is 1.0 or more and 1.3 or less, the insulating layer is made of Si and O, and an alkali metal And a raw material preparation step of preparing the coated soft magnetic powder made of an oxide containing at least one of Mg and Mg,
A composite process for producing a composite material comprising the coated soft magnetic powder and a molding resin material;
A molding step of pressing the composite material to produce a molded body;
A method of manufacturing a powder magnetic core, comprising: a heat treatment step in which the formed body is heat-treated in an oxidizing atmosphere to produce a formed body for a magnetic core in which the insulating layer is crystallized. A dust core manufacturing method for manufacturing a dust core using a coated soft magnetic powder comprising a plurality of coated soft magnetic particles having an insulating layer coated on an outer periphery of a soft magnetic particle,
The soft magnetic particles are an Fe-Si-Al-based alloy having an oxygen content of 500 ppm or less, and the insulating layer is made of an oxide containing Si and O, and at least one of an alkali metal and Mg. A raw material preparation step of preparing the coated soft magnetic powder,
A composite process for producing a composite material comprising the coated soft magnetic powder and a molding resin material;
A molding step of pressing the composite material to produce a molded body;
A method of manufacturing a powder magnetic core, comprising: a heat treatment step in which the formed body is heat-treated in an oxidizing atmosphere to produce a formed body for a magnetic core in which the insulating layer is crystallized.   The method for producing a dust core according to claim 8, wherein the soft magnetic particles have an oxygen content of 500 ppm or less.   11. The method for manufacturing a dust core according to claim 8, wherein the heat treatment step is performed at a heat treatment temperature of 600 ° C. or more and 900 ° C. or less and an oxygen concentration of 0.1 vol% or more.

Images