JP4682584B2 - Soft magnetic metal powder for dust core and dust core - Google Patents

Description

  The present invention relates to a soft magnetic metal powder for a dust core and a dust core having a high magnetic flux density and a low iron loss produced using the soft magnetic metal powder.

In response to the goal of reducing CO ₂ emissions at the Kyoto Conference in 1997, in recent years, technology development for reducing fossil fuel consumption and product development in response to it have been widely conducted. For example, in Japan, fossil fuel consumption by power generation accounts for a significant proportion of CO ₂ emissions. To reduce this, the development of distributed power sources such as solar cells and fuel cells has been It is being pursued energetically in parallel with the promotion of computerization.
Similarly, for automobiles that account for a significant proportion of CO ₂ emissions, fossil fuel reduction technologies are being developed through hybridization.

By the way, in these techniques, the technique of once converting the energy obtained by motive power or sunlight into electric power and converting it again into the target form of energy is widely adopted. This is because the power is not only easily controlled energy but also easily converted into another form of energy.
Therefore, improving power conversion efficiency is extremely important for improving energy efficiency with new technologies.

  There are various elements in the power conversion circuit, and their characteristics and control methods strongly influence the efficiency. Among them, one that has a strong influence on the efficiency is a magnetic element composed of a coil and an iron core typified by a transformer and a reactor. Since these elements are elements that always operate in the conversion circuit, even a slight improvement in efficiency often greatly affects the improvement in the efficiency of the entire conversion circuit. Therefore, this element is always required to improve efficiency.

  In addition, since such a magnetic element has a structure in which an iron core is wound, it is often larger and heavier than a semiconductor element or the like. The large number of winding portions directly leads to an increase in manufacturing cost as well as weight and shape. Therefore, the demand for downsizing is great as well as efficiency improvement.

In order to improve the above two problems, various developments have been widely performed.
To describe the details of the development, it is possible to increase the magnetic permeability and magnetic flux density, which can reduce the number of windings and reduce the size of the iron core, and to reduce the iron loss that directly leads to improved efficiency. These are properties that strongly depend on the iron core even in the magnetic element. Therefore, improvement of the iron core material is a very important issue that cannot be avoided for improving the characteristics of the magnetic element. In particular, in a power conversion circuit, the current is often converted into an alternating current having a frequency of about 1 kHz to 50 kHz and then converted into a target output. Therefore, it is extremely important to improve the characteristics in such a frequency range.

In general, laminated iron cores produced by laminating soft ferrite cores, electromagnetic steel plates, electromagnetic iron plates and the like are widely used as iron cores of magnetic elements.
Among these, the laminated iron core has a feature that it has a high magnetic permeability, a high magnetic flux density can be easily obtained, and is relatively inexpensive. However, on the other hand, when the frequency of the alternating current to be used is increased, the eddy current inside the steel plate generated due to the alternating magnetic field induced by the current increases rapidly, and accordingly the heat generation and core loss of the iron core, There is a problem that so-called iron loss increases rapidly.

On the other hand, the soft ferrite core has a problem that the iron loss is small but the saturation magnetic flux density is low. In a magnetic element using an iron core having a low saturation magnetic flux density, the iron core may cause magnetic saturation when a large current flows. When magnetic saturation occurs, not only does the function as a magnetic element fail, but in the worst case, there is a risk of causing the converter circuit to run away.
As the output of the conversion circuit has increased, the current flowing through the magnetic element has also increased. Recently, the low saturation magnetic flux density of the soft ferrite core has been a big problem.
In view of the above background, there has been a strong demand for the development of a new core material to replace the laminated core and the soft ferrite core in order to further improve the efficiency of the conversion circuit.

  In view of such a background, a powder magnetic core produced by pressing a mixed powder obtained by appropriately adding a binder such as a resin to a soft magnetic metal powder has begun to attract attention. This is because the dust core has the following two merits. That is, one is that powder is used as a raw material, and furthermore, a material having excellent insulation properties such as resin is used as a binder, so that generation of eddy current can be suppressed, and as a result, iron loss can be reduced as compared with a laminated core. Is possible. Furthermore, since a soft magnetic metal is used as a raw material, an iron core having a higher saturation magnetic flux density than that of soft ferrite and hardly causing magnetic saturation can be obtained.

In view of these features, dust cores are attracting a great deal of attention as an iron core material that replaces magnetic steel sheets and soft ferrite.
However, there is a problem that the iron loss of the dust core is still large in the frequency range used in the conversion circuit, and the permeability and magnetic flux density are not sufficient. In order to use a dust core as a new iron core material that can be replaced with a magnetic steel sheet or soft ferrite, it is essential to improve the magnetic flux density of the dust core and reduce the iron loss.

In order to achieve the above-mentioned problem of the dust core, that is, the goal of reducing iron loss and improving magnetic flux density, several techniques have been proposed.
For example, it is widely known that the magnetic flux density of a dust core increases with an increase in the density of the compact, but based on this finding, technological development for improving the density of the compact core is widely conducted. ing.

On the other hand, the iron loss of the dust core is largely divided into hysteresis loss and eddy current loss. Among these, several techniques have been proposed to reduce eddy current loss.
For example, a method for controlling the particle size of the soft magnetic metal powder (for example, Patent Document 1), a method for mixing the soft magnetic metal powder and an insulating substance such as resin (for example, Patent Document 2), and the like can be mentioned.
On the other hand, various studies have been made to reduce hysteresis loss. In the first place, the hysteresis loss becomes prominent in the dust core due to the fact that enormous processing strain is applied to the soft magnetic metal powder when the soft magnetic metal powder is pressed and formed into a dust core. Therefore, it has been pointed out that it is effective to reduce the strain applied to the soft magnetic metal powder by annealing the molded body after pressure molding to reduce the hysteresis loss (for example, non-patent document). 1). In particular, annealing at 600 ° C. or higher is said to be effective. However, since the resin used to reduce eddy current loss is generally inferior in heat resistance, when annealing is performed to reduce hysteresis loss, the insulating material is decomposed, resulting in a significant deterioration in insulation. End up. As a result, there is a problem that it is very difficult to achieve both reduction in eddy current loss and reduction in hysteresis loss.

In order to solve such problems, several techniques have been proposed in the past.
For example, several techniques have been proposed in which the surface of a soft magnetic metal powder is treated with a material containing phosphoric acid or chromic acid to form an insulating film having excellent heat resistance (for example, Patent Document 3).
However, when the inventors investigated this technique, it was found that these materials deteriorated when annealed at 550 ° C. or higher, resulting in loss of insulation. Therefore, it was confirmed that it is difficult to reduce both hysteresis loss and eddy current loss.
As a similar technique, several methods using a silicone resin having relatively excellent heat resistance among resins have been proposed (for example, Patent Document 4).
However, since the silicone resin is also thermally decomposed at 500 ° C. or higher, it has been found that the insulation is lost when annealed at 500 ° C. or higher. Therefore, it is difficult to reduce both hysteresis loss and eddy current loss by this technique.

Therefore, we intended to maintain insulation even after strain relief annealing by coating the surface of the metal powder with a material with higher heat resistance, for example, a high melting point oxide such as SiO ₂ or Al ₂ O ₃ . Several technologies have been proposed. For example, Patent Document 5 discloses a technique in which a finely divided powder such as an oxide and a resin are mixed with a soft magnetic metal powder and then pressure-molded to obtain a sample having high insulation even after annealing. Yes.
However, as a result of testing by the inventors, simply mixing the fine powder causes the fine powder to be in a non-uniformly dispersed state, resulting in a location where sufficient insulation cannot be obtained, and as a result, sufficient before annealing. Insulation could not be obtained, and it was found that when annealed, the insulation was further reduced, and it was difficult to reduce iron loss.

Further, Patent Document 6 introduces a technique for obtaining high-purity iron powder having an insulating film for producing a dust core from a high-purity iron powder coated with silica sol.
Therefore, the inventors also tested this technique. As a result, the silica sol film has poor adhesion to high-purity iron powder, and the film peels off by pressure molding, so the dust core obtained by this method is also the case where the above-described oxide powder is used. Similarly, it has been found that sufficient insulation cannot be obtained.

In addition, several technologies have been proposed that intentionally oxidize soft magnetic metal powder to form an insulating layer with excellent heat resistance on the surface and maintain insulation even after strain relief annealing ( For example, Patent Document 7).
However, the inventors have tested that the insulating film formed in this way loses insulation during annealing because the oxide layer decomposes into soft magnetic metal and oxygen due to thermal equilibrium reaction during annealing. It turned out that iron loss reduction was difficult to achieve.

Several techniques have been proposed to avoid the problem of insufficient adhesion when using oxide powder or the like. For example, in Patent Document 8, by using a technique that imparts a strong shearing force such as mechanofusion, an oxide particle is mechanically embedded on the surface of the soft magnetic metal powder to be attached and insulated with excellent heat resistance. There is shown a method of obtaining a soft magnetic metal powder having an insulating coating excellent in heat resistance by forming a coating and further applying an insulating coating thereon with a phosphoric acid-based material.
However, as a result of testing by the inventors, it has been found that it is extremely difficult to embed oxide particles uniformly on the surface of the metal powder, and it is not possible to obtain sufficiently satisfactory insulation.

  Patent Document 9 introduces a technique of mixing a soft magnetic metal powder and a silicon-containing powder and then heat-treating the silicon to diffuse the soft magnetic metal powder. In this technique, an insulating layer is formed on the surface. As a result, an insulating coating excellent in heat resistance could not be obtained.

Furthermore, several techniques for producing soft magnetic metal powders in which silicon is added as a prealloy as an alloy component have been disclosed (for example, Patent Document 10 and Patent Document 11). These are techniques using the feature that silicon is easily concentrated on the surface. In other words, silicon is concentrated on the surface during atomization and subsequent heat treatment, and further oxidized to form an insulating film with excellent heat resistance on the surface of the soft magnetic metal powder. By carrying out the treatment, an attempt is made to obtain a soft magnetic metal powder having an insulating film excellent in heat resistance. These publications point out that silicon concentrated on the surface of metal powder is presumed to exist as an oxide, and that this silicon oxide layer is present as a base, which improves the insulation after the insulation coating process. Has been.
Therefore, the inventors conducted tests according to these methods. As a result, it was confirmed that the insulating properties of the soft magnetic metal powder obtained by this technique were improved to some extent as compared with other conventional techniques. However, the insulation is still insufficient, and furthermore, the density of the green compact is reduced due to the increase in hardness of the soft magnetic metal powder due to the addition of silicon. As a result, a sufficient magnetic flux density cannot be obtained. It turned out to be.

Furthermore, Patent Document 12 discloses a powder having a two-layer insulating layer obtained by coating the surface of a soft magnetic metal powder with a high-resistance substance, and further treating the surface of the high-resistance substance with a phosphoric acid-based chemical conversion treatment liquid. A method of obtaining a soft magnetic compact having a high specific resistance and a high density has been proposed.
However, this technique has a problem that heat treatment cannot be performed at a temperature of 600 ° C. or higher because the phosphoric acid-based film is deteriorated at a high temperature.
In addition, when the inventors tested, it was found that when annealing at 400 ° C. or higher, the specific resistance was significantly reduced, and it was difficult to achieve the intended aim.

By the way, the inventors have previously developed a soft magnetic metal powder whose surface is covered with a material composed of a silicone resin and an insulating powder having excellent heat resistance as a solution to the above-mentioned problem, and Patent Document 13 Disclosed in.
However, even with this technique, it was difficult to obtain a sufficiently satisfactory insulation.

JP 58-147106 A JP-A-62-71202 JP-A-6-260319 JP 2004-103778 A JP-A-11-238613 Japanese Patent Laid-Open No. 9-180924 Special Table 2001-510286 JP 2003-332116 A Japanese Patent Laid-Open No. 2-97603 JP 2003-297624 A JP 2003-142310 A JP 2001-85211 A JP 2003-303711 A Horie et al .: Journal of Japan Society of Applied Magnetics, Vol.22, No.2, P.45 (1998)

The present invention advantageously solves the above-described problems, and provides a soft magnetic metal powder for a powder magnetic core having a low iron loss and a high magnetic flux density. Specifically, a highly compressible metal is provided. A first object is to provide a soft magnetic metal powder having a powder as a raw material and coated with a heat-resistant insulating coating thereon.
A second object of the present invention is to provide a dust core produced from the soft magnetic metal powder as described above, having a high magnetic flux density and low iron loss.

Now, as a result of earnest research to solve the above problems, the inventors do not directly coat the soft magnetic metal powder, which is a raw material, with a silicone resin, but first cause an oxide to exist on the surface of the raw material powder, Next, an insulating material having excellent heat resistance such as an oxide is present thereon, and further a bond strengthening treatment is performed by heating or the like, so that the two parts are firmly fixed to each other, thereby pressing the powder. As a result, when the powder magnetic core was produced, the insulative property was greatly improved.
The present invention is based on the above findings.

That is, the gist configuration of the present invention is as follows.
(1) On the entire surface or part of the surface, the surface of the atomized alloy powder having an oxide of an alloy component formed by oxidation in the process of manufacturing by the atomizing method is formed on the surface of the atomized alloy powder from among oxides, carbonates and sulfates. An alloy powder having a structure in which at least one selected insulating layer is coated and a silicone resin layer is further coated thereon, and the surface of the atomized alloy powder and the insulating layer are bonded to each other in a non-oxidizing atmosphere. A soft magnetic metal powder for a dust core, which is fixed by a bond strengthening process comprising a heat treatment in a range of ˜1200 ° C. for 20 to 240 minutes .

(2) Oite above (1), the alloy powder, characterized in that Fe-Si alloy powder, selected from among the Fe-Al alloy powder and Fe-Ni alloy powder is either, Soft magnetic metal powder for dust cores.

(3) Oite above (1) or (2), an insulating layer, Mg, Ca, Sr, Ba , Ti, Zr, Co, Ni, Al, oxides of metal elements Si, carbonates and sulphates A soft magnetic metal powder for a dust core, wherein the soft magnetic metal powder is one or more selected from the above.

( 4 ) A magnetic flux density characterized by being obtained by filling the mold with the soft magnetic metal powder according to any one of (1) to ( 3 ) above and performing an annealing treatment after pressure molding. High dust core with low iron loss.

( 5 ) A dust core having high magnetic flux density and low iron loss, characterized in that in ( 4 ) above, the annealing treatment is a treatment at 600 ° C. or higher for 30 minutes or longer in a non-oxidizing atmosphere.

According to the present invention, a soft magnetic metal powder having excellent compressibility and high insulation can be obtained.
Therefore, by using the soft magnetic metal powder as a raw material, a dust core having a high magnetic flux density and a low iron loss can be obtained.

Hereinafter, the present invention will be specifically described.
FIG. 1 shows a typical coating structure of soft magnetic metal powder according to the present invention. In the figure, reference numeral 1 is an atomized alloy powder, which is a raw material, and 2 is an oxide formed on the surface thereof. Such an oxide, as shown in FIG. In addition, it may be formed on the entire surface of the atomized alloy powder 1 or may be formed in an island shape on a part of the surface of the atomized alloy powder 1 as shown in FIG. No. 3 is an insulating layer of the same kind or different kind from the oxide 2 formed on the surface of the atomized alloy powder 1 having the alloy component oxide 2 on the entire surface or part of the surface as described above, and 4 A silicone resin layer further coated thereon.

  In the present invention, after the surface of the atomized alloy powder 1 having the alloy component oxide 2 on the entire surface or a part of the surface is coated with, for example, the insulating layer 3, the bonding strengthening treatment for increasing the bonding strength is performed. It is characterized by where it is applied.

Conventionally, since the insulating coating layer 3 was directly coated on the surface of the atomized alloy powder 1 without interposing the oxide 2, the bonding force between the alloy powder 1 and the insulating layer 3 was extremely small. For this reason, the insulating coating is peeled off during the pressure molding, and as a result, the insulating property after the strain relief annealing is forced to be lowered.
On the other hand, in the soft magnetic metal powder of the present invention, the insulating layer 3 is strongly fixed to the oxide 2 formed by concentrating the components in the atomized alloy powder by the bond strengthening treatment. The oxide 2 is formed by concentrating the components in the alloy, and the interface between the alloy powder 1 and the oxide 2 becomes continuous, so that the bonding force between the oxide 2 and the alloy powder 1 becomes extremely high. . Further, since the oxide 2 and the insulating layer 3 are bonded through a bonding strengthening process, the insulating layer 3 is finally strongly bonded to the alloy powder 1 through the oxide 2.

  By adopting such a structure, the insulation coating will not be peeled off even by stress acting on the powder surface during pressure molding, and the produced powder magnetic core will be subjected to strain relief annealing at a temperature of 600 ° C or higher. It still shows high insulation. Therefore, it is possible to reduce both hysteresis loss and eddy current loss, which has been difficult in the past, and thus a dust core with very low iron loss can be obtained.

  Moreover, in the case of the technique which coat | covered only the conventional silicone resin, the insulation fall by decomposition | disassembly of the silicone resin had arisen at the temperature of 600 degreeC or more. However, in the present invention, a two-layer insulating film that is strongly bonded to the alloy powder under the silicone resin and exhibits higher heat resistance and insulation is formed, so that the silicone resin is heated by heating at a temperature of 600 ° C. or higher. Even if the decomposition of the material proceeds slightly, the insulation between the alloy powders is maintained by the lower insulating film, so that a sufficiently satisfactory insulation is ensured.

In the technique using the conventional Fe-Si alloy powder, as an insulating layer on the surface, it is necessary to play a role of oxide 2 and the insulating layer 3 as described above. Therefore, it is necessary to contain a relatively large amount of silicon in the soft magnetic metal powder, which causes a decrease in compressibility, and as a result, a magnetic flux density is inevitably reduced.
However, in the present invention, a large amount of silicon is contained in the metal powder by coating the insulating layer 3 on the oxide 2 derived from the soft magnetic metal powder raw material and further performing a bond strengthening treatment. Therefore, it became possible to obtain the insulation equivalent to the prior art using Fe-Si alloy powder. As a result, since a large amount of silicon is not included, a decrease in compressibility is prevented, and thus a high magnetic flux density can be obtained.

Hereinafter, each component will be described in detail.
(Alloy powder)
As the alloy powder used in the present invention, any alloy powder may be used as long as it is ferromagnetic and an oxide insulating layer is formed on the surface at the time of production by an atomizing method. Typical alloy powders include Fe-Si based alloy powder containing 0.005 to 1.0 mass% Si, Fe-Al based alloy powder containing 3 to 20 mass% Al, Fe-Ni containing 20 to 80 mass% Ni. Based alloy powder and the like. Needless to say, in addition to the basic components described above, these alloy powders may contain other elements as long as they do not adversely affect the compressibility and magnetic properties of the dust core. In addition, the alloy powder in the present invention is not limited to the above, but as described above, any alloy powder that is ferromagnetic and has an oxide insulating layer formed on the surface at the time of fabrication by an atomizing method can be used. Fits.

Among the above-described alloy powders, particularly when silicon is added as an alloy component, the magnetic anisotropy is reduced as compared with pure iron powder, so that the magnetic permeability and magnetic flux density are increased. In addition, since silicon easily diffuses to the powder surface, it has the property of being easily concentrated on the surface. The silicon concentrated on the surface is easily oxidized by oxygen in the air, etc., and easily changes to silica having excellent insulating properties. Therefore, the powder to which silicon is added is characterized by excellent magnetic properties and high insulation properties. Therefore, as the alloy powder in the present invention, Fe—Si based alloy powder is particularly suitable. In this case, if the Si amount is less than 0.005 mass%, sufficient insulation cannot be obtained. On the other hand, if it exceeds 1.0 mass%, there arises a problem that compressibility is lowered and magnetic permeability and magnetic flux density are lowered. More preferably, it is the range of 0.01 mass% or more and 0.5 mass% or less.
Moreover, there is no restriction | limiting in particular about the particle size of alloy powder, What is necessary is just to determine suitably according to the use and required characteristic of a powder magnetic core.

(Oxide on the surface of the alloy powder)
This oxide is actively formed in the process of manufacturing the alloy powder by the atomizing method. Conventionally, in the production of atomized powder, it was usual to avoid the formation of such oxides as much as possible, but in the present invention, the surface of the alloy powder is oxidized by actively oxidizing the surface, contrary to this. Alternatively, an oxide is partially formed. When the alloy powder is Fe-Si alloy, SiO ₂ is formed on the surface, when it is Fe-Al alloy, Al ₂ O ₃ is formed on the surface, and when it is Fe-Ni alloy, NiO is formed on the surface. Is done.
In addition, the amount of the oxide is determined by the manufacturing conditions in the atomizing method (for example, a medium used for pulverization during atomization [for example, a method using water], adjustment of oxygen concentration in the atmosphere in which atomization is performed, heating after atomization, or medium The drying conditions [temperature, time, atmosphere], etc.) can be controlled as appropriate.
Here, the preferred amount of oxide varies somewhat depending on the amount of the alloy component contained in the powder. For example, in the case of a film shape, the thickness is preferably about 0.5 to 1000 nm.

  In the oxide formed in this way, the component concentration change at the interface between the raw material powder and the oxide becomes continuous, so when the component concentration changes discontinuously as in the case of adhesion, for example. In comparison, the adhesion with the raw material powder is extremely excellent.

(Insulating layer)
In the present invention, the insulating layer may be made of any material as long as it has higher insulating properties than the above-described oxide and can be subjected to bond strengthening treatment with the oxide. Among them, a material having excellent insulating properties and excellent heat resistance is particularly suitable for achieving the purpose of forming an insulating film having excellent heat resistance, which is the final object of the present invention.

Examples of such insulating materials include oxides, carbonates and sulfates of metal elements such as Mg, Ca, Sr, Ba, Ti, Zr, Co, Ni, Al, and Si, which have high insulating properties. Examples include salt. In the present invention, these may be used alone or in combination.
Moreover, you may use what becomes the raw material and precursor of these materials. Examples of such a solution include a solution in which an oxide is hydrated, such as alumina sol, silica sol, and titania sol, or a solution in which a precursor such as the above metal complex solution or alkoxide solution is dispersed and dissolved. Moreover, you may use the thing of the state in which several forms were mixed, such as the form which disperse | distributed the powder to the solution. Of course, other forms than those listed here may be used as long as an insulating layer is finally formed.

  As a method of forming such an insulating layer, for example, a method of coating the material by adding an insulating material to the above-described alloy powder having an oxide, and a vapor deposition method such as CVD or PVD. Examples thereof include a method of coating, or a method of combining a plurality of these methods. Of course, methods other than those described here may be used.

Among the above methods, the method of coating the raw material powder with an insulating material is easy to adjust the coating component, the coating amount of the coating component, the thickness of the coating layer, etc., so that a desired insulating film can be obtained reliably. Therefore, it is preferable.
Examples of such mixing means include a mixing process using a mixing device such as an attritor, a Henschel mixer, or a ball mill.

  Further, as the material of the insulating layer, a solution in which an oxide is hydrated, such as the above-mentioned alumina sol, silica sol, or titania sol, or a solution in which a precursor such as a metal complex solution or alkoxide solution is dispersed or dissolved is used. Compared with the case where powder is used as a raw material, the insulating layer can be formed in a dense and uniform state. By forming such an insulating layer, the obtained powder finally shows a high insulating property, which is particularly suitable in the present invention. Furthermore, in the case of a solution in which the oxide is hydrated, if the moisture in the molecule is scattered by heating, an insulating film excellent in heat resistance that does not easily reduce weight or volume even when heated is formed. Is more preferable.

  In the present invention, the amount of the insulating layer forming substance added to the alloy powder is preferably about 0.01 to 5.0 mass%. This is because when the amount added is less than 0.01 mass%, the amount added is too small, so that the coating becomes non-uniform, it is difficult to obtain sufficient insulation, and the strength is further reduced. On the other hand, if it exceeds 5.0 mass%, the ratio of the raw material powder in the powder magnetic core is decreased, and accordingly, the magnetic flux density is decreased accordingly.

Now, in this invention, in order to improve the adhesiveness of an above-mentioned oxide and an insulating layer, a joint reinforcement | strengthening process is performed. By performing this treatment, an oxide having excellent heat resistance and an insulating layer are firmly fixed, and at the same time, an insulating coating composed of three parts can be reliably obtained in the finally obtained soft magnetic metal powder. become. Therefore, this process is extremely important in the present invention.
In addition to the fact that the method using heat treatment for this treatment allows flexible material design by utilizing known knowledge, the local reaction is less than the method using mechanical method or chemical reaction. Since it is difficult to occur, it is easy to obtain a uniform state in the entire treated powder, industrial production is easy, and the entire device is simple, and the soft magnetic metal powder of the present invention is produced. It is extremely effective as a bond strengthening treatment method for achieving this.
In this regard, when a method of applying a strong shearing force such as mechanofusion is used as a bond strengthening treatment, unevenness is likely to occur in the degree of treatment, so an insulating layer should be uniformly formed on the surface of the metal powder as described above. Is extremely difficult to achieve sufficiently satisfactory insulation. In addition, the compressibility is lowered due to processing strain, and the powder is spheroidized by processing. Therefore, the sample formed from this powder becomes extremely brittle and is difficult to handle practically.

The conditions such as processing temperature, time, and atmosphere during such heat treatment vary depending on the combination of materials used, but the melting point of the raw material powder and the insulating material, the diffusion coefficient of the materials between and within each material. The amount of each component typified by oxygen, the particle size of the material, the amount of insulating material added, etc. may be taken into consideration. For example, when the alloy powder is Fe—Si alloy powder and the coating material is a high melting point material such as Al ₂ O ₃ or SiO ₂ , the temperature is preferably about 500 ° C. or more and 1200 ° C. or less. This is because if the treatment temperature is less than 500 ° C, the material diffusion becomes insufficient, so the effect of improving the adhesion is small. On the other hand, if it exceeds 1200 ° C, the diffusion between the raw material powders becomes remarkable and the powders sinter. Because. In order to pulverize the material once sintered, it is necessary to apply a huge force to pulverize the material. When such a huge force acts, the insulating layer quality once bonded to the raw material powder falls off, and the effect of improving the insulation becomes insufficient. In addition, work hardening takes place because the processing force is added to the powder by a huge force. Since the green compact density of a sample obtained by molding such powder is extremely low, a decrease in magnetic flux density is inevitable.
Moreover, what is necessary is just to determine suitably also according to a use also about time. It is preferably 20 to 240 minutes.

  Furthermore, the atmosphere in such heat treatment may be an oxidizing atmosphere such as air or oxygen atmosphere, an inert atmosphere such as nitrogen gas or argon gas, a reducing atmosphere such as hydrogen gas, ammonia gas or RX gas, or a vacuum depending on the application. You may choose from the appropriate. Further, the atmosphere may be switched during the heat treatment. In the case where the atmosphere is oxidizing, the metal may be oxidized during the bond strengthening treatment, resulting in a decrease in magnetic properties and compressibility. Therefore, in the present invention, it is more preferable to carry out in an inert or reducing atmosphere or a non-oxidizing atmosphere such as under vacuum. The water vapor dew point may be adjusted as necessary.

  In addition, it is preferable that the heat processing temperature here is higher than the annealing temperature of the molded object mentioned later. If the temperature is low, not only does the strengthening treatment become insufficient, but the unreacted part during the bond strengthening treatment reacts when the molded body is annealed, and at this time, gas is generated and the molded body is destroyed, which is not preferable. Therefore, the heat treatment temperature for strengthening the bond is preferably about +10 to + 150 ° C. with respect to the annealing temperature of the molded body. Especially preferably, it is the range of + 50- + 150 degreeC.

  When the heat bond strengthening treatment as described above is performed, the oxide 2 and the insulating layer 3 shown in FIG. 1 are formed of an oxide or a metal salt, the bond is stronger than when the metal and the oxide are bonded. can get. This is because the diffusion of oxygen contained in the oxide by thermal energy proceeds more easily than the diffusion of metal atoms, so that the exchange of oxygen occurs first, and then the diffusion of the metal component is simply caused by the diffusion of oxygen. This is because the state is accelerated as compared with the case of the metal-oxide, and as a result, the diffusion of the entire component is accelerated. Particularly in the case of oxides, this phenomenon is remarkable, which is particularly advantageous.

In addition, it is preferable that an oxide and an insulating layer have especially heat resistance among the insulating films comprised from three parts according to this invention. If the heat resistance of this portion is low, the desired heat resistance may not be obtained even if the heat resistance of the silicone resin layer is sufficiently high. Here, having heat resistance means that insulation is maintained even after soft magnetic metal powder is used as a powder magnetic core and the powder magnetic core is annealed. Therefore, any substance that satisfies this condition may be used, and the index used for evaluation is not particularly limited.
Among them, the weight loss rate Δm can be easily measured, and it can be well matched with the case of evaluating the insulation after molding into a powder magnetic core and annealing, so the heat resistance of oxide and insulating layer is especially evaluated It is suitable as an index to perform.

As a method for evaluating the weight reduction rate Δm of the oxide and the insulating layer, there are a method of taking out and measuring the substance alone of the covering portion, and a method of measuring the whole soft magnetic metal powder having the oxide and the insulating layer. Of course, you may measure by methods other than these.
When taking it out as a single unit, the metal part of the soft magnetic metal powder is dissolved with acid, alkali or other soluble substance, and the residue is taken out. Only the concentrated part where mechanical energy is given to the soft magnetic metal powder is separated. And a method in which only a metal part is electrically dissolved using an electrode formed by pressure molding at a low pressure that does not cause destruction of the concentrated part.
The weight reduction rate Δm is calculated from the relationship Δm = Ma / Mb, where Mb is the mass before heating and Ma is the mass when heated in an inert gas atmosphere.
In the present invention, when the weight after heating to 800 ° C. in N ₂ gas is Ma and the weight before heating is Mb, a preferable Δm is 0.3 or more and 1.0 or less. Especially preferably, it is 0.5 or more and 1.0 or less, More preferably, it is 0.7 or more and 1.0 or less.

In the present invention, in the soft magnetic metal powder obtained by the above procedure, the total element concentration of the surface oxide and the insulating layer is Cs (at%), and the total concentration of main elements at a depth of 10 μm from the outer surface is Cb ( at%), Cs / Cb is preferably 1.5 or more. When Cs / Cb is less than 1.5, sufficient insulation cannot be obtained when a dust core is formed because of insufficient concentration on the surface.
Measurement of Cs and Cb may be performed by a surface analyzer (AES) using Auger electron spectroscopy. The area of the part to be measured may be appropriately determined according to the particle size of the raw material powder to be used. For example, in the case of a powder having a particle size of about 30 to 100 μm, a square part with a side of about 5 to 30 μm is used. You should evaluate. In order to improve the accuracy of the measurement value, Cs / Cb is preferably measured for a plurality of particles. A preferable measurement number is 5 or more and 15 or less.

Further, in the present invention, the oxide and the insulating layer are preferably present uniformly over the entire surface of the alloy powder, and the form is preferably as shown in FIG. If the distribution of the oxide 2 and the insulating layer 3 becomes non-uniform, the insulation of the powder magnetic core obtained by press-molding the soft magnetic metal powder according to the present invention is lowered before annealing, and further lowered after annealing. This is not preferable.
Such an oxide and an insulating layer, when mapping the insulating film component by AES, when the total measurement area is Sa, and the area where the element of the insulating film component exists is St, St / Sa is 0.1 or more, It is preferable to set it to 1.0 or less. When this value is less than 0.1, there are too few portions where the insulating coating exists, and the dust core produced from the soft magnetic metal powder of the present invention cannot obtain sufficient insulation. A preferable range of St / Sa is 0.3 or more and 1.0 or less, and more preferably 0.5 or more and 1.0 or less.
The area of the measurement target portion may be appropriately determined depending on the particle size of the raw material powder to be used. For example, when a powder having a particle size of about 30 to 100 μm is targeted, a square portion having a side of about 5 μm to 30 μm. You can evaluate with. In order to improve the accuracy of this measurement value, St / Sa is preferably measured for a plurality of particles. The preferred number of measurements is 5 or more and 15 or less as in the case of Cs / Cb. As for St / Sa, when evaluating Cs, it is preferable to evaluate it together because efficient evaluation can be performed.

  Furthermore, the total thickness of the oxide and the insulating layer is preferably about 0.5 nm to 4000 nm. Especially preferably, it is the range of 1-1000 nm. The total thickness of the oxide and the insulating layer is defined by the distance between the outermost surface of the raw metal portion and the outermost surface of the insulating layer by cutting a cross section of the soft magnetic metal powder. The distance is the length between the perpendicular line on the outermost surface of the metal part and the intersection point 1 of the outermost surface of the metal, the perpendicular line drawn through the intersection point 1, and the intersection point 2 on the outermost surface part of the insulating layer. Defined by It is preferable to arrange a plurality of measurement points so that the outer periphery of one particle is evenly divided. The number of divisions is preferably 100 or more. This is repeated for a plurality of particles, and the average value of the results measured at each point is defined as the total thickness S of the oxide and the insulating layer, and the dispersion value is defined as the variation V of the total thickness of the oxide and the insulating layer.

  The ratio V / S between the total thickness S of the oxide and the insulating layer and the variation V of the total thickness of the oxide and the insulating layer is preferably 0.0 or more and 0.90 or less. Particularly preferably, it is 0.0 or more and 0.50 or less, and more preferably 0.0 or more and 0.40 or less. When V / S exceeds 0.90, the film becomes very thin after pressure molding, and there is a place where the distance between the soft magnetic metal powder particles is not sufficiently separated inside the compact, so that the dust core is sufficiently insulated. It is not preferable because the property cannot be obtained. In addition, the inside of the oxide and the insulating layer is preferably dense. When the oxide and insulating layer are observed from the cross section, the area of the oxide and the entire insulating layer is defined as Ca, and the area of the void portion existing inside the coating portion of the oxide and the insulating layer is defined as Cp. / Ca is preferably 0.0 or more and less than 0.3. Particularly preferably, it is 0.0 or more and less than 0.1. When Cp / Ca is large, the strength of the coating portion of the oxide and the insulating layer becomes weak, so that the coating portion is destroyed during pressure molding. As a result, the thickness variation of the insulating coating increases, and the insulating property of the dust core produced by press-molding the soft magnetic metal powder decreases. In addition, the size of the oxide and insulating layer near the powder surface viewed from the cross-sectional side of the soft magnetic metal powder and the filling state inside the soft magnetic metal powder can be observed by embedding and polishing the soft magnetic metal powder in a resin. What is necessary is just to evaluate using the observation result by the scanning electron microscope (SEM) of a sample.

  The soft magnetic metal powder thus obtained is further coated with a silicone resin having excellent heat resistance to form the outermost layer. Thereby, the insulation of a powder magnetic core improves further and also improves to a molded object strength. This silicone resin is excellent in adhesiveness as compared with other resins that can be coated, and is also excellent in heat resistance and insulation.

  The silicone resin in the present invention refers to a polyorganosiloxane containing a trifunctional (T unit) or tetrafunctional (Q unit) siloxane unit in the molecule. Such a silicone resin is characterized in that it has a higher crosslink density and a cured product is harder than silicone oil or silicone rubber, and is suitable for the present invention. By the way, silicone resins are roughly classified into straight silicone resins whose components are composed only of silicone, and silicone-modified organic resins that are copolymers of silicone components and organic resins. In the present invention, any of them is used. It doesn't matter. Straight silicone resins are roughly classified into MQ resins and DT resins, and any of them may be used in the present invention. Examples of the silicone-modified organic resin include alkyd modification, epoxy modification, polyester modification, acrylic modification, and phenol modification, and any of them may be used in the present invention. Silicone resins include a type that cures when heated and a type that cures even at room temperature. Any of these types may be used in the present invention. There are several types of curing reactions for silicone resins. For example, the mechanism of curing thermosetting silicone resins can be broadly divided into those based on dehydration condensation reactions, addition reactions, and peroxide reactions. The curing mechanism can be distinguished by deoxime reaction and dealcoholization reaction. The silicone resin used in the present invention only needs to be cured by any of the above curing reactions.

  Examples of the silicone resin used in the present invention include SH805, SH805, SH806A, SH840, SH997, SR620, SR2306, SR2309, SR2310, SR2316, DC12577, SR2400, SR2402, SR2404, SR2405 manufactured by Toray Dow Corning Silicone. , SR2406, SR2410, SR2411, SR2416, SR2420, SR2107, SR2115, SR2145, SH6018, DC6-2230, DC3037, DC3074, QP8-5314, manufactured by Shin-Etsu Chemical, KR251, KR255, KR114A, KR112, KR2610B, KR2621-1 , KR230B, KR220, KR220L, KR285, K295, KR300, KR2019, KR2706, KR165, KR166, KR169, KR2038, KR221, KR155, KR240, KR101-10, KR120, KR105, KR271, KR282, KR311, KR211, KR212, KR211, KR212 , KR213, KR217, KR9218, SA-4, KR206, KR5206, ES1001N, ES1002T, ES1004, KR9706, KR5203, KR5221, X-52-1435, and the like. Of course, silicone resins other than those listed here may be used. Moreover, you may use the silicone resin which modified these substances or these raw material substances. Furthermore, you may use the silicone resin which mixed the 2 or more types of silicone resin from which a kind, molecular weight, and a functional group differ in a suitable ratio.

  When the silicone resin constituting the outermost layer is added to or coated on the soft magnetic metal powder, the powdered material may be mixed, or the silicone resin is dissolved in a solvent and the solution is brought into contact with the soft magnetic metal powder. It may be mixed or coated. In the case of preparing a solution, any solvent may be used as long as it can dissolve the silicone resin. Examples of such materials include alcohol solvents such as ethanol and methanol, ketone solvents such as acetone and methyl ethyl ketone, aromatic solvents such as benzene, toluene, xylene, phenol, and benzoic acid. Examples include petroleum solvents such as ligroin and kerosene. An aromatic solvent that easily dissolves the silicone resin is particularly preferred. If the silicone resin is soluble, water may be used. The concentration of the solution may be determined in consideration of ease of construction and drying time. Furthermore, in order to control the viscosity, thixotropy and leveling properties of the silicone resin solution, the drying time after application, the time until the resin is cured, the curing temperature of the resin and the crosslink density during curing, etc. Additives may be added. Examples of such additives include metal soaps such as metal stearates that control the curing of the silicone resin, and surfactants such as perfluoroalkyl. When added as a solvent, segregation of the silicone resin can be prevented. Therefore, even if the amount added is the same, the insulation of the powder magnetic core is improved compared to the case where powder is used. Is preferably added.

  In addition, the addition of the silicone resin constituting the outermost layer may be added first in total, or may be added in the middle of stirring. Moreover, you may spray through a spray nozzle at the time of stirring. When the silicone resin solution used in the present invention is sprayed and added through a spray nozzle, the silicone resin solution used in the present invention is added uniformly to the soft magnetic metal powder, and the film is also uniform. For stirring and mixing, an attritor, a Henschel mixer, a ball mill, a fluidized granulator, a rolling granulator or the like is generally used. Agitation using a fluidized tank as in a fluidized granulator or a rolling granulator is preferable because aggregation of powders is suppressed. Further, it is particularly preferable to spray the silicone resin solution used in the present invention on the fluidized tank through spraying, since the effect of the spray spraying and the effect using the fluidized tank are combined and a more uniform coating can be obtained. Heat treatment may be performed during or after mixing for the purpose of accelerating the drying of the solvent or curing the silicone resin.

  In the present invention, the addition amount of the silicone resin constituting the outermost layer is the solid content of the silicone resin with respect to the soft magnetic metal powder (solid content = the amount of added solution−the amount of solvent in the solution) with respect to the soft magnetic metal powder. It is preferable to set it as about 0.01-5 mass%. If the added amount is less than 0.01 mass%, the amount of the silicone resin is too small, so that the coating of the raw material powder becomes non-uniform, and the effect of improving the insulation becomes insufficient. On the other hand, if it exceeds 5 mass%, Since the ratio of the raw material powder is remarkably reduced, the magnetic flux density is lowered, which is not preferable.

The soft magnetic metal powder with an insulation coating produced by the above method is pressure-molded using a mold or the like after a lubricant or the like is added as necessary. Examples of the lubricant include metal soaps such as lithium stearate, zinc stearate, and calcium stearate, and waxes such as fatty acid amides. Mold lubrication in which a lubricant is applied to the mold surface without adding a lubricant to the soft magnetic metal powder may be used.
The molding pressure may be appropriately determined according to the application, but is preferably about 490 to 1960 MPa. When the molding pressure is less than 490 MPa, the density of the molded body is lowered, resulting in a problem that the magnetic flux density is lowered. On the other hand, when the molding pressure is more than 1960 MPa, the mold wear during molding becomes remarkable, which is not practical.

In order to release the strain applied to the iron-based powder during pressurization and reduce the hysteresis loss after the above molding, it is particularly preferable to anneal the molded body while maintaining it at a temperature of 600 ° C. or higher. A particularly preferable annealing temperature is 800 ° C. or higher. For the reasons described above, the annealing temperature is preferably about −10 ° C. to −150 ° C. from the temperature during the bond strengthening treatment. Particularly preferred is -50 ° C to -150 ° C. The annealing time is preferably 30 minutes or longer. Annealing atmosphere is an inert atmosphere such as Ar or N _2, be a non-oxidizing atmosphere such as a reducing atmosphere or vacuum, such as hydrogen preferable. What is necessary is just to determine suitably the dew point of water vapor | steam according to a use etc. The temperature rise rate and temperature drop rate during annealing are 20 ° C / min or less in order to prevent the insulation coating from being destroyed due to the difference in thermal expansion coefficient and the occurrence of thermal distortion in the metal structure of the soft magnetic metal powder due to rapid cooling. It is preferable to set the degree. Further, a step of holding at a constant temperature may be provided when the temperature is raised or lowered.

Example 1
As the raw material powder, seven types of alloy powders shown in Table 1 manufactured by the atomizing method were used. Table 1 shows the components, particle size distribution, and powder characteristics (apparent density) of each alloy powder.
In addition, surface analysis was performed by AES to measure surface components. The measurement conditions of AES were PHISICAL ELECTONICS PHI MODEL 660, acceleration voltage: 10 kV, sample current amount: 0.2 μA, measurement area: 20 μm square, sample tilt angle: 30 °. The detected elements and element concentrations (at%) are also shown in Table 1. It was confirmed that oxides were formed on the surface of the alloy powder containing elements other than iron (Fe) such as silicon (Si) and oxygen (O).
In addition, this invention is effective with respect to the metal powder which shows all ferromagnetism. Therefore, of course, the present invention is effective even for metal powder exhibiting ferromagnetism that is not in the examples.

Next, an insulating layer was formed. Here, the materials shown in Table 2 were used. After preparing a solution having a concentration of 10 mass%, the solution was coated with a rolling fluidized bed. In the powder form, an insulating material having excellent heat resistance was added to the raw material powder, and then mixed for 10 minutes with a Henschel mixer. Furthermore, the bond reinforcement | strengthening process by the heat processing shown collectively in Table 2 was performed. After the bond strengthening treatment, classification was performed with a sieve having an opening of 180 μm to obtain the soft magnetic metal powder of the present invention. The powder was separately examined for changes in weight in an inert atmosphere with a thermobalance, and Δm was calculated from the results.
The results are also shown in Table 2.

For the powder obtained as described above, Cs / Cb and St / Sa were determined using AES. The measurement conditions of AES were PHI MODEL 660 manufactured by PHISICAL ELECTONICS, with acceleration voltage: 10 kV, sample current amount: 0.2 μA, measurement area: square of 20 μm square, sample tilt angle: 30 °. After measuring the surface, Cb was measured under the same conditions after sputtering the above measurement area with an ion gun in the depth direction of 10 μm. Table 2 shows the elements used in the evaluation of Cs / Cb and St / Sa, the number of measurement points, and the measured average values and variances. When St was confirmed, the distribution of oxygen atoms was also investigated. In any result, the oxygen concentration distribution was consistent with the element distribution used for the St / Sa evaluation. Thus, it was found that the atoms observed on the surface exist in the form of insulating oxides having excellent heat resistance such as SiO ₂ , Al ₂ O ₃ , TiO ₂ , and ZrO ₂ .

  Moreover, after embedding 5 g of soft magnetic metal powder in the resin, the polished sample which was polished with the resin so that the cross section of the powder could be observed was observed with a scanning electron microscope (SEM) and confirmed within an observation field of 1 mm square. For all the powders, the distribution and average value of the distribution and size of the concentrated portion of the material portion with excellent heat resistance and insulation at the surface concentrated portion and the filling rate Cp / Ca inside the concentrated portion Asked. These values are calculated using the results of continuously observing the outer peripheral portion of the particles at a magnification of 100,000. Table 2 also shows the number of powders in the field of view and their measurement results.

  The outermost layer made of silicone resin was formed on the soft magnetic metal powder having the insulating layer formed as described above. SR2400 from Toray Dow Corning was used as the silicone resin. For coating, a solution in which the resin was made of xylene with a concentration of 5 mass% was used. The coating of the silicone resin on the soft magnetic metal powder was performed by a rolling fluidized tank type coating apparatus. Addition of the silicone resin solution is performed by spraying the coating material so that the solid content is the amount shown in Table 2 with respect to the powder in the fluid state using a spray after the raw material powder is fluidized in the apparatus container. It was done by doing. After completion of spraying, keep the fluid state for 20 minutes for drying to obtain a soft magnetic metal powder coated with a coating material on the raw material powder, and further heating in air at 250 ° C for 60 minutes The silicone resin was cured by heating to obtain a soft magnetic metal powder sample.

The soft magnetic metal powder thus obtained was filled into a mold and pressure-molded to obtain a ring sample for measurement (outer diameter: 38 mm, inner diameter: 25 mm, height: 6.2 mm). The molding pressure was 980 MPa. The lubrication at the time of pressurization was mold lubrication in which a lubricant solution in which zinc stearate was dispersed in water was applied to the mold surface. Further, some samples were annealed at the temperatures shown in Table 2 for 60 minutes in an N ₂ gas atmosphere. Table 2 shows the soft magnetic metal powder and silicone resin used, the solid content addition amount of the silicone resin, the lubricant addition amount during molding, the molding pressure, and the annealing temperature of the molded body sample.

Using the sample obtained as described above, the green density, specific resistance, magnetic flux density, and iron loss were measured. The green density was calculated by measuring the dimensions and weight of the sample and using the values. The specific resistance was measured by the four probe method. The energizing current was 1A. The crushing strength was measured in accordance with the method defined in “JIS Z 2507 as“ crushing strength test method for sintered oil-impregnated bearing ””. The magnetic flux density was evaluated by a magnetic flux density B _10k at a magnetic field H = 10 kA / m using a coil in which a formal coated conductor of φ0.6 mm was used as a ring sample on the primary side: 100 turns and the secondary side: 20 turns. Iron loss was evaluated under the conditions of frequency: 200 Hz to 10 kHz and magnetic flux density Bm = 0.2 T using a coil with a Φ0.6 mm formal coated conductor on the primary side: 40 turns and secondary side: 40 turns. did. For iron loss, the frequency: 5 kHz, magnetic flux density: 0.2 T (W _{2 / 5k} ), and for other values, the measured values are shown in Table 2.

  As shown in Table 2 in comparison with the examples and comparative examples, the metal powder according to the present invention, in which the oxide and the insulating layer were formed, the bond strengthening treatment was performed, and the outermost layer was formed with the silicone resin, It can be seen that the specific resistance is high and the iron loss is low as compared with the comparative example which does not have a three-layer structure or is not subjected to the bond strengthening treatment (Examples 1-1 to 1-9 and Comparative Examples). 1-1 to 1-5). In particular, when a solution such as a sol is used, St / Sa, which is an index representing the uniformity of the oxide and the insulating layer, is improved as compared with the case where powder is used. Examples 1-4 and 1-5 show that the thickness S is improved and the dispersion V and V / S values of S are also reduced, resulting in high specific resistance and reduced iron loss. And a comparison between Examples 1-18 and 1-19.

Comparing Examples 1-1 to 1-2 and Examples 1-3 to 1-8, even if the amount of silica sol added is the same, the amount of oxygen is large, and an oxide composed of iron and oxygen is formed on the surface. It can be seen that in Examples 1-3 to 1-8 using the formed powder 2, the value of St / Sa is higher, and the oxide and the insulating layer are uniformly formed. In addition, the latter has higher specific resistance and lower iron loss than the former. Thus, it is understood that the characteristics can be further improved by using a powder having a large amount of oxygen. Further, when the bond strengthening treatment temperature is lower than the compact annealing temperature, the specific resistance tends to decrease and the iron loss tends to increase, and it is understood that the bond strengthening treatment temperature is preferably higher than the compact annealing temperature. In addition, after preparing the composition similar to Example 1-10, the heat processing in air | atmosphere was performed as a joint reinforcement | strengthening process. As a result, the green density is 5.80 Mg / m ³ , the specific resistance is 10 μΩm, the magnetic flux density is 0.45 T, and the iron loss is 220 W / kg. The magnetic flux density is lower than that of Example 1-10 and the iron loss is larger. Oops. This shows that when heat treatment is performed as the bond strengthening treatment, it is preferably performed in a non-oxidizing atmosphere.

  In addition, when using powder 5 in which an oxide centered on silicon and oxygen is formed on the surface because it contains silicon, the value of Cs / Ct is high, and an insulating material with excellent heat resistance is not covered later. Even though oxides were formed on the surface, Comparative Examples 1-6 and 1-7, in which either the insulating layer or the outermost layer was omitted, had low specific resistance and high iron loss. Further, the green density was lower than that of the other examples in which the formation conditions of the insulating layer or the outermost layer were similar, and the magnetic flux density was also reduced. From this, it can be seen that the present invention having an insulating coating composed of three parts according to the present invention is effective for obtaining high magnetic flux density and low iron loss.

  In Examples 1-38 and 1-39, 0.2 mass% of Si was added to Permalloy 45 (45% Ni) and Alpalm (16% Al), respectively, and the powder was used to form an oxide on the surface. Is the result of As in the other examples, the present invention is found to be effective for Ni and Al alloy powders.

Example 2
SR2400, SR2410, SH805 from Toray Dow Corning Co., Ltd. and KR220L, KR300, X-52-1435, ES1004 from Shin-Etsu Chemical were prepared as silicone resins. Next, these were made into a solution having a concentration of 5 mass% with xylene (water only when X-52-1435 was used). Using this solution, a silica core was coated on a powder in which silica was concentrated under the conditions of Example 1-6 and Example 1-11, and a dust core was prepared. Table 3 shows the types of silicone resin used, the coating amount, the molding pressure, the annealing temperature, and the properties measured by the same procedure as in Example 1.

  As shown in Table 3, it can be seen that even if any silicone resin is used, good characteristics are exhibited. It can also be seen that good characteristics are exhibited even when the lubrication method and the amount added are changed.

Example 3
The powder obtained in Example 1-11 was pressure molded at a molding pressure of 490 to 1960 MPa. Moreover, the annealing temperature was changed about some samples. Table 4 shows the results of evaluation of these characteristics.

  As shown in Table 4, it can be seen that the present invention is effective in any case.

Example 4
In Example 4, the powder and silica shown in Table 5 were added in the same amount as shown in Table 5 and then premixed, followed by mechanochemical treatment using a Hosokawa Micron mechanofusion system to perform bond strengthening treatment. went. The processing amount per time was 1.0 kg / ch, the processing time was 10 minutes, and the rotation speed was 2,600 rpm. At this time, the rotational power was 1.2 kW ± 0.05 kW.
After the treatment, the formation of the outermost layer made of silicone resin and the production of a molded body sample and heat treatment were performed in the same manner as in the other examples, and the characteristics were evaluated.
The obtained results are also shown in Table 5.

  As shown in Table 5, during the mechanofusion treatment, the compressibility decreased due to processing strain added to the iron powder. As a result, the green compact density and magnetic flux density decreased compared to Examples 1-20, which had the same composition and were subjected to heat-strengthening bonding treatment. It can be seen that the loss has been realized.

  According to the present invention, a soft magnetic metal powder having excellent compressibility and high insulation and a soft magnetic metal powder having a high magnetic flux density and a low iron loss can be obtained. As a result, a laminated core is obtained. As a result, a dust core can be obtained as an alternative to the soft ferrite core.

It is sectional drawing of the alloy powder which provides the insulation coating comprised by three parts according to this invention, (a) is the case where an oxide is formed in the whole surface of the atomized alloy powder, (b) is the surface of the atomized alloy powder. This is a case where an oxide is partially formed in an island shape.

Explanation of symbols

1 Atomized alloy powder 2 Oxide 3 Insulating layer 4 Silicone resin layer

Claims (5)

At least selected from oxides, carbonates and sulfates on the surface of the atomized alloy powder having an oxide of an alloy component formed by oxidation in the process of manufacturing by an atomizing method on the entire surface or a part of the surface An alloy powder having a structure in which a kind of insulating layer is further coated and a silicone resin layer is further coated thereon, and the surface of the atomized alloy powder and the insulating layer are heated to 500 to 1200 ° C. in a non-oxidizing atmosphere. A soft magnetic metal powder for a dust core, which is fixed by a bond strengthening process comprising a heat treatment in a range of 20 to 240 minutes . Oite to claim 1, the alloy powder, characterized in that Fe-Si alloy powder, selected from among the Fe-Al alloy powder and Fe-Ni alloy powder is any one, for dust core Soft magnetic metal powder. Oite to claim 1 or 2, one of insulating layers, picked Mg, Ca, Sr, Ba, Ti, Zr, Co, Ni, Al, oxides of metal elements Si, from among the carbonates and sulphates Alternatively, a soft magnetic metal powder for a dust core, characterized by comprising two or more kinds. A soft magnetic metal powder according to any one of claims 1 to 3 is filled in a mold, subjected to pressure forming, and then subjected to an annealing treatment, characterized by high magnetic flux density and low iron loss. Powder magnetic core. 5. The dust core according to claim 4, wherein the annealing treatment is a treatment at 600 ° C. or higher for 30 minutes or longer in a non-oxidizing atmosphere, and the magnetic flux density is high and the iron loss is low.

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