JP7405817B2 - Soft magnetic powder and dust core - Google Patents

Description

The present invention relates to soft magnetic powder and powder magnetic core.

Coil parts such as reactors are used in a variety of applications such as office automation equipment, solar power generation systems, and automobiles. A coil component has a coil attached to a core. A powder magnetic core is often used as this core.

A powder magnetic core is produced, for example, by forming an insulating layer around soft magnetic powder, adding a lubricant, and then press-molding the powder. The pressure during this pressure molding is quite high, from several tons to several tens of tons, and the soft magnetic powder is compacted.

Due to demands for improved energy exchange efficiency and low heat generation, powder magnetic cores are required to have magnetic properties that allow a large magnetic flux density to be obtained with a small applied magnetic field, and magnetic properties that minimize energy loss due to changes in magnetic flux density. Examples of magnetic properties related to magnetic flux density include magnetic permeability (μ). Magnetic properties related to energy loss include core loss (Pcv), also called core loss. Iron loss (Pcv) is expressed as the sum of hysteresis loss (Ph) and eddy current loss (Pe).

Patent No. 5929819 Japanese Patent Application Publication No. 2009-088502 Japanese Patent Application Publication No. 4586399

Research on reducing iron loss and improving magnetic permeability has been progressing for some time. For example, as in Patent Document 1, research is underway to find that low hysteresis loss can be obtained when crystal grains are coarse. Further, as in Patent Document 2, research is underway to reduce distortion of the crystal structure within the soft magnetic powder and increase magnetic permeability by subjecting the soft magnetic powder to heat treatment. Further, as in Patent Document 3, research is underway to suppress a decrease in saturation magnetic flux density by mixing 30% by mass or less of sendust with iron particles having an insulating coating formed on the surface as soft magnetic powder. However, in recent years, with the diversification of coil components, the demand for smaller size and higher performance of coil components has increased, and higher magnetic permeability and lower iron loss are further required.

The present invention has been made to solve the above problems, and its purpose is to provide soft magnetic powder and powder magnetic core that can reduce iron loss while maintaining good DC superimposition characteristics. It is in.

In order to achieve the above object, the soft magnetic powder of the present invention is a soft magnetic powder made by mixing pure iron powder and FeSiAl alloy powder, wherein the pure iron powder is water atomized powder and is smoothed. The FeSiAl alloy powder is a gas atomized powder, the particle size of the FeSiAl alloy powder is 13.0 μm or more and 31.8 μm or less, and the content of the pure iron powder contained in the soft magnetic powder is , 80 wt% or more and 95 wt% or less, and the content of the FeSiAl alloy powder is 5 wt% or more and 20 wt% or less.

Further, a dust core containing this soft magnetic powder is also an embodiment of the present invention.

According to the present invention, it is possible to obtain soft magnetic powder and powder magnetic core that can reduce iron loss while maintaining good DC superimposition characteristics.

2 is a graph showing the relationship between the amount of FeSiAl alloy powder added and iron loss, hysteresis loss, and eddy current loss. 2 is a graph showing the relationship between the amount of FeSiAl alloy powder added and DC superposition characteristics.

(Embodiment)
The soft magnetic powder and powder magnetic core of this embodiment will be explained. Note that the present invention is not limited to the embodiments described below.

A powder magnetic core is a magnetic material used in the core of coil components such as reactors installed in office automation equipment, solar power generation systems, automobiles, and the like. A powder magnetic core is produced by forming an insulating layer around soft magnetic powder and press-molding it to produce a powder compact. Then, a powder magnetic core is produced by heat-treating this powder compact.

The soft magnetic powder contains pure iron powder and FeSiAl alloy powder, and is made by mixing these powders. Pure iron powder is one that contains 99% or more of Fe. Pure iron powder consists of water atomized powder. That is, pure iron powder is produced by spraying water on Fe powder molten at high temperature to powder it, and then cooling and solidifying it. The content of pure iron powder contained in the soft magnetic powder is 80 wt% or more and 95 wt% or less.

Pure iron powder has been subjected to a smoothing treatment and is a powder in a smoothed state. A smoothed state refers to a state in which the irregularities on the surface of pure iron powder are leveled out, and a state in which the protrusions on the surface of pure iron powder are smooth, a state in which the entire surface is rounded, a state in which the surface is spherical, or a state in which the surface of pure iron powder is smooth. Contains state. The circularity of the smoothed pure iron powder is preferably 0.95 or more.

It is preferable to heat-treat the pure iron powder after smoothing it and before mixing it with the FeSiAl alloy powder. By performing this powder heat treatment, processing strain in the pure iron powder that occurs when smoothing treatment is performed can be removed by heat treatment. This powder heat treatment is performed in a non-oxidizing atmosphere, preferably in a reducing atmosphere such as hydrogen gas or a mixed gas of nitrogen and hydrogen, at a temperature of 900° C. or more and 1100° C. or less, preferably 950° C. or more and 1050° C. or less.

FeSiAl alloy powder is a powder containing iron, silicon, and aluminum. The FeSiAl alloy powder contains, for example, about 7 wt% to 11 wt% of Si and about 4 wt% to 8 wt% of Al with respect to Fe. The FeSiAl alloy powder may contain, for example, about 1 wt% to 3 wt% Ni with respect to Fe. Furthermore, the FeSiAl alloy powder may contain Co, Cr, or Mn.

The FeSiAl alloy powder consists of gas atomized powder. That is, FeSiAl alloy powder is produced by blowing gas onto FeSiAl alloy powder melted at high temperature to powder it, and then cooling and solidifying it. The content of the FeSiAl alloy powder contained in the soft magnetic powder is 5 wt% or more and 20 wt% or less.

The particle size of the FeSiAl alloy powder is preferably 13.0 μm or more and 31.8 μm or less, more preferably 13.0 μm or more and 19.5 μm or less. The particle size refers to the median diameter D50. By setting the particle size of the FeSiAl alloy powder within this range, it is possible to maintain good DC superimposition characteristics while reducing hysteresis loss and, ultimately, iron loss.

An insulating layer is formed around soft magnetic powder made of a mixture of pure iron powder and FeSiAl alloy powder. The insulating layer is made of an insulating material that is attached around the soft magnetic powder. As long as the insulating layer is attached around the soft magnetic powder, the manner in which the insulating material is attached does not matter. That is, the insulating material may be attached so as to cover the entire periphery of the soft magnetic powder, or may be attached so as to partially cover the soft magnetic powder so that a part of the surface of the soft magnetic powder is exposed. Further, the insulating material may be attached to the surface of each particle of the soft magnetic powder, or may be attached to the surface of the aggregate of the soft magnetic powder, or the insulating material may be attached to the surface of each particle of the soft magnetic powder, or the insulating material may be attached to the surface of the aggregate of the soft magnetic powder, or the insulating material may be attached to the surface of each particle of the soft magnetic powder, or it may be attached to the surface of the aggregate of the soft magnetic powder, or the insulating material may be attached to the surface of each particle of the soft magnetic powder. It may be attached.

As the insulating material, a silane coupling agent, a silicone oligomer, a silicone resin, or a mixture thereof can be used. That is, the silane coupling agent, the silicone oligomer, and the silicone resin may be used alone, or, for example, the silane coupling agent and the silicone oligomer, or the silane coupling agent and the silicone resin may be used as a mixture.

Further, the insulating layer may be a single layer or may be a plurality of layers. For example, the insulating layer may be composed of a plurality of layers divided into layers for each type, or may be composed of a single layer of an insulating material of one type or a mixture of two or more types. In this embodiment, an insulating layer containing a silane coupling agent and a silicone resin is formed around the soft magnetic powder.

As the silane coupling agent, aminosilane-based, epoxysilane-based, and isocyanurate-based silane coupling agents can be used, and in particular, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, tris -(3-trimethoxysilylpropyl)isocyanurate is preferred.

The amount of the silane coupling agent added is preferably 0.05 wt% or more and 1.0 wt% or less based on the soft magnetic powder. By adjusting the amount of the silane coupling agent added within this range, it is possible to improve the fluidity of the soft magnetic powder and to improve the density, magnetic properties, and strength properties of the molded powder magnetic core.

When a silane coupling agent is added as an insulating material, a mixture of soft magnetic powder and silane coupling agent is heated and dried. The drying temperature is preferably 25°C or higher and 200°C or lower. This is because if the drying temperature is lower than 25° C., the solvent may remain and the insulation coating may become incomplete. On the other hand, if the drying temperature is higher than 200° C., decomposition may progress and the insulating film may not be formed. Drying time is about 2 hours.

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

The amount of silicone resin added is 0.4 wt% or more and 3.0 wt% or less based on the soft magnetic powder. More preferably, it is 0.6 wt% or more and 2.0 wt% or less. If the amount of silicone resin added is small, the shrinkage effect that draws the soft magnetic powder together during heat treatment of the molded body will be weak, making it impossible to ensure high density and making it impossible to increase magnetic permeability. On the other hand, if the amount added is large, the insulating layer formed around the soft magnetic powder becomes too thick, making it impossible to ensure high density and making it impossible to increase magnetic permeability.

After adding the silicone resin, the mixture of soft magnetic powder and silicone resin is heated and dried. The drying temperature is preferably 100°C or higher and 250°C or lower. This is because if the drying temperature is lower than 100° C., the formation of the insulating film may be incomplete and eddy current loss may increase. On the other hand, if the drying temperature is higher than 250° C., the powder becomes inorganic and does not function as a binder, resulting in poor formation retention and a decrease in the density and magnetic permeability of the compact. Drying time is about 2 hours.

Examples of silicone oligomers include methyl-based and methylphenyl-based ones that have an alkoxysilyl group and no reactive functional group; epoxy-based, epoxymethyl-based, and mercapto-based ones that have an alkoxysilyl group and a reactive functional group; Mercaptomethyl, acrylicmethyl, methacrylmethyl, vinylphenyl, or alicyclic epoxy having a reactive functional group instead of an alkoxysilyl group can be used. In particular, a thick and hard insulating layer can be formed by using a methyl-based or methylphenyl-based silicone oligomer. Furthermore, in consideration of ease of forming an insulating layer, a methyl-based or methylphenyl-based material having a relatively low viscosity may be used.

The amount of silicone oligomer added is preferably 0.1 wt% or more and 2.0 wt% or less based on the soft magnetic powder. If the amount added is less than 0.1 wt%, it will not function as an insulating film, and magnetic properties will deteriorate due to increased eddy current loss. If the amount added is more than 2.0 wt%, the density of the powder magnetic core will decrease.

After adding the silicone oligomer, the mixture of soft magnetic powder and silicone oligomer is heated and dried. The drying temperature is preferably 25°C to 350°C. If the drying temperature is less than 25° C., the film formation will be incomplete, resulting in high eddy current loss and increased loss. On the other hand, if the drying temperature is higher than 350° C., the hysteresis loss increases due to oxidation of the powder, which increases the loss. Drying time is about 2 hours.

A lubricant is added to the soft magnetic powder around which an insulating layer is formed and mixed. Examples of the lubricant include stearic acid and its metal salts, ethylene bis stearamide, ethylene bis stearamide, and ethylene bis stearate amide.

After adding a lubricant, a desired mold is filled with soft magnetic powder and pressure molded to produce a powder compact. The pressure during molding is 10 to 20 tons/cm ² .

Thereafter, the produced powder compact is heat treated. This heat treatment is performed in a non-oxidizing atmosphere, preferably in a reducing atmosphere such as hydrogen gas or a mixed gas of nitrogen and hydrogen, at a temperature of 600°C or higher and at which the insulating layer formed around the soft magnetic powder is destroyed (e.g. , 900°C). A powder magnetic core is produced through this heat treatment.

(Example)
The present invention will be explained in more detail based on examples. Note that the present invention is not limited to the following examples.

First, as shown in Table 1, a plurality of pure iron powders and FeSiAl alloy powders were prepared.

Powders A and B shown in Table 1 (hereinafter, the powders listed in the types shown in Table 1 are referred to as Powder A, Powder B...Powder H) are pure iron powders, and A was produced by the water atomization method. Similarly to A, B is smoothed pure iron powder produced by water atomization. The smoothing process was performed using the high-speed airflow impingement method. The conditions for the smoothing treatment are a rotor rotation speed of 4800 rpm and a duration of 5 minutes.

Here, Table 2 shows the circularity of pure iron powder when the conditions of the smoothing treatment were changed. Condition 1 is a smoothing process for 5 minutes at a rotor rotation speed of 8000 rpm, Condition 2 is a smoothing process for 5 minutes at a rotor rotation speed of 6400 rpm, Condition 3 is a smoothing process for 10 minutes at a rotor rotation speed of 6400 rpm, and Condition 4 is a smoothing process for 5 minutes at a rotor rotation speed of 6400 rpm. Smoothing treatment was performed at several 4,800 rpm for 5 minutes.

As shown in Table 2 above, even under condition 4, where the number of rotations is the lowest, the circularity is 0.781 for D10 and 0.952 for D50. That is, by performing the smoothing treatment at a rotor rotation speed of 4800 rpm for 5 minutes, it is possible to obtain a pure iron powder having a high degree of circularity like the powder B described above.

Powders C to H shown in Table 1 are FeSiAl alloy powders. Powders C to G are FeSiAl alloy powders produced by gas atomization, and each powder has a different particle size as shown in Table 1. Powder H is a FeSiAl alloy powder produced by a pulverization method, and the production method is different from powders C to G.

(Comparison of types and amounts of FeSiAl alloy powder)
First, powder magnetic cores of Examples 1 to 3 and Comparative Examples 1 to 5 were produced. In Example 1, 1.0 wt% of alumina powder (primary particle size: 13 nm) was added and mixed with Powder B shown in Table 1, and the mixture was heat-treated at a temperature of 1000°C for 2 hours in an atmosphere with a hydrogen concentration of 5%. went. Then, 5 wt % of powder D, which had not been subjected to powder heat treatment, was added to and mixed with powder B after heat treatment to produce a composite powder.

After mixing powder B and powder D, 0.5 wt% of a silane coupling agent and 2.0 wt% of a silicone resin were added and mixed, and the mixture was dried at a temperature of 150° C. for 2 hours. For the purpose of eliminating agglomeration, the composite powder on which an insulating layer was formed was passed through a sieve with an opening of 500 μm, and 0.5 wt % of ethylene bicystearamide was added and mixed as a lubricant.

After mixing the lubricant, this powder was filled into a mold and pressure molded to obtain a green compact with an outer diameter of 20.85 mm, an inner diameter of 12.4 mm, and a height of 5.0 mm. Press molding was performed at a pressure of 12 tons/cm ² . After the powder compact was produced, the powder compact was heat-treated at a temperature of 600° C. for 2 hours in an atmosphere with a hydrogen concentration of 5%. In this way, the powder magnetic core of Example 1 was produced.

In Example 2, the manufacturing method and manufacturing conditions are the same as in Example 1, except that the amount of powder D added is 10 wt%. In Example 3, the manufacturing method and manufacturing conditions are the same as in Example 1, except that the amount of powder D added is 20 wt%.

Comparative Example 1 used powder A, which had not been smoothed, instead of powder B as the pure iron powder. Powder A was heat treated under the same conditions and method as the heat treatment of Powder B in Example 1. Further, unlike in Example 1, a powder magnetic core was produced using only powder A (pure iron powder) without mixing FeSiAl alloy powder. Other manufacturing methods and manufacturing conditions are the same as in Example 1.

Comparative Example 2 is similar to Example 1 in that Powder B was used as the pure iron powder, but differs in that FeSiAl alloy powder was not mixed. Other manufacturing methods and manufacturing conditions are the same as in Example 1.

Comparative Examples 3 and 4 differ from Example 1 only in the amount of powder D added. Comparative Example 3 added 25.0 wt%, and Comparative Example 4 added 30.0 wt%. Other manufacturing methods and manufacturing conditions are the same as in Example 1.

Comparative Example 5 differs from Example 1 in the type of FeSiAl alloy powder. That is, in Comparative Example 5, powder H produced by the pulverization method was used instead of powder D produced by the gas atomization method. Further, except that the amount of powder H added was 20 wt%, other manufacturing methods and manufacturing conditions were the same as in Example 1.

The density of each powder magnetic core produced in this way was measured. Density (g/cm ³ ) is apparent density. The outer diameter, inner diameter, and height of the powder magnetic core were measured, and from these values, the volume (cm ³ ) of each powder compact was calculated based on π×(outer diameter ² − inner diameter ² )×height. Then, the weight of the dust core was measured, and the density was calculated by dividing the measured weight by the calculated volume.

Further, each powder magnetic core was wound with a primary winding of 30 turns and a secondary winding of 30 turns using a copper wire of φ0.5 mm, and the iron loss and magnetic permeability were measured. The measurement conditions were a frequency of 20 kHz and a maximum magnetic flux density Bm of 200 mT. A BH analyzer (Iwatsu Keizoku Co., Ltd.: SY-8219) was used as the magnetic measurement device. Then, the hysteresis loss coefficient was calculated using the least squares method using the following equations (1) to (3) to finally calculate the hysteresis loss.

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

The magnetic permeability was calculated using an LCR meter (manufactured by Agilent Technologies, Inc.: 4284A) as the amplitude permeability when the maximum magnetic flux density Bm was set during the measurement of iron loss. The magnetic permeability was measured by measuring the initial magnetic permeability (0 A/m) when no magnetic field was applied without superimposing a direct current and the magnetic permeability (10 kA/m) when a magnetic field of 10 kA/m was applied.

The measurement results are shown in Table 3. Further, FIG. 1 shows a graph showing the relationship between the amount of FeSiAl alloy powder (powder D) added and iron loss, hysteresis loss, and eddy current loss in Examples 1 to 3 and Comparative Examples 2 to 4. FIG. 2 is a graph showing the relationship between the amount of FeSiAl alloy powder (powder D) added and the DC superimposition characteristics in Examples 1 to 3 and Comparative Examples 2 to 4.

First, Comparative Example 2 using Powder B that was smoothed as a pure iron powder had higher DC superimposition characteristics than Comparative Example 1 that used Powder A that had not been smoothed, and also had hysteresis loss and It was confirmed that both eddy current loss and iron loss were reduced. That is, it was confirmed that when the pure iron powder produced by the water atomization method was subjected to the smoothing treatment, the direct current superimposition characteristics increased, and all of the hysteresis loss, eddy current loss, and iron loss decreased.

Furthermore, in Examples 1 to 3, the DC superimposition characteristics were improved compared to Comparative Example 1 and maintained good values. In addition, the hysteresis loss, eddy current loss, and iron loss of Examples 1 to 3 tend to decrease as the amount of powder D added increases, and all of them are lower than those of Comparative Example 2. In particular, it was confirmed that the hysteresis loss of Examples 1 to 3 was lower than 1000 (kW/m ³ ), and lower than that of Comparative Example 2 in which no FeSiAl alloy powder was added.

Furthermore, when comparing Example 3 and Comparative Example 5, in which the same amount of FeSiAl alloy powder was added, Example 3 maintains a better DC superposition characteristic, and has lower hysteresis loss, eddy current loss, and iron loss. It is declining. As a result, it was confirmed that the FeSiAl alloy powder to be mixed with the pure iron powder is a gas atomized powder, which has good direct current superimposition characteristics and low iron loss.

Furthermore, it was confirmed that as the amount of powder D added was increased, hysteresis loss, eddy current loss, and iron loss were reduced. However, looking at the results of Comparative Examples 3 and 4, although the hysteresis loss, eddy current loss, and iron loss are reduced, the DC superposition characteristic is 32 or less, which is the same level as Comparative Example 1. Therefore, it was confirmed that when the amount of powder D added is 5.0 wt% or more and 20 wt% or less, hysteresis loss, eddy current loss, and iron loss can be reduced while maintaining good DC superimposition characteristics.

(Comparison of particle sizes of FeSiAl alloy powder)
Next, powder magnetic cores of Examples 4 to 6 and Comparative Example 6 were produced, and the density, iron loss, and magnetic permeability were measured using the same measurement conditions and method as above.

Examples 4 to 6 and Comparative Example 6 differ from Example 1 only in the particle size of the FeSiAl alloy powder. The particle size (D50) of Example 4 (powder C) was 31.8 μm, the particle size (D50) of Example 1 (powder D) was 19.5 μm, and the particle size (D50) of Example 5 (powder E) was 31.8 μm. ) is 16.4 μm, the particle size (D50) of Example 6 (powder F) is 13.0 μm, and the particle size (D50) of Comparative Example 5 (powder G) is 5.5 μm. Other manufacturing methods and manufacturing conditions are the same as in Example 1.

The measurement results are shown in Table 4.

As shown in Table 4, in Example 4 using FeSiAl alloy powder with a particle size of 31.8 μm, iron loss was reduced while maintaining a high initial magnetic permeability. Furthermore, as the particle size of the FeSiAl alloy powder becomes smaller, hysteresis loss increases and iron loss increases. In particular, in Comparative Example 6, the hysteresis loss was 900 (kW/m ³ ), and the iron loss also exceeded 1000 (kW/m ³ ). In particular, in Examples 3, 5, and 6, the DC superposition characteristic was 34, and the iron loss was also smaller than 940 (kW/m ³ ), confirming that it was possible to reduce the iron loss while maintaining good DC superposition characteristics. It was done. That is, it was confirmed that the particle diameter of the FeSiAl alloy powder is more preferably 13.0 μm or more and 19.5 μm or less.

(Comparison using different manufacturing methods)
Next, powder magnetic cores of Examples 7 to 9 were prepared in which the timing of mixing pure iron powder and FeSiAl alloy powder was changed, and the density, iron loss, and magnetic permeability were measured using the same measurement conditions and method as above. .

In Examples 7 to 9, Powder B, which is a pure iron powder, was first heat-treated under the same conditions as in Example 1. 0.5 wt% of a silane coupling agent and 2.0 wt% of a silicone resin were added and mixed to the heat-treated powder B, and the mixture was dried at a temperature of 150° C. for 2 hours. Then, Powder B on which an insulating layer was formed was passed through a sieve with an opening of 500 μm for the purpose of eliminating agglomeration, and 0.5 wt % of ethylene bicystearamide was added and mixed as a lubricant.

On the other hand, Powder D, which is a FeSiAl alloy powder, was not subjected to powder heat treatment, but 0.5 wt% of a silane coupling agent and 2.0 wt% of a silicone resin were added and mixed, and the mixture was dried at a temperature of 150°C for 2 hours. Ta. Then, Powder D on which an insulating layer was formed for the purpose of eliminating agglomeration was passed through a sieve with an opening of 500 μm, and 0.5 wt % of ethylene bicystearamide was added and mixed as a lubricant.

Then, Powder B and Powder D, each having an insulating layer formed thereon, were added and mixed in the amounts shown in Table 5 below. That is, in Example 7, the amount of powder D added was 5 wt%, in Example 8, the amount of powder D added was 10 wt%, and in Example 8, the amount of powder D added was 20 wt%. The subsequent steps are the same as in Example 1.

The measurement results are shown in Table 5.

As shown in Table 5, Examples 7 to 9 maintain good DC superimposition characteristics and have lower hysteresis loss, eddy current loss, and iron loss than Comparative Example 2 in which no FeSiAl alloy powder is added. It was confirmed that the reduction was achieved. Furthermore, as the amount of FeSiAl alloy powder added was increased, hysteresis loss, eddy current loss, and iron loss were reduced, and the same trends as shown in Table 3 were confirmed. In other words, whether the manufacturing method is to mix pure iron powder and FeSiAl alloy powder and then form an insulating layer, or the manufacturing method is to form an insulating layer on pure iron powder and FeSiAl alloy powder and then mix them. It was confirmed that the effects of the invention can be obtained.
(Comparison of different heat treatment temperatures for molded bodies)

Next, Examples 10 and 11 were prepared in which only the heat treatment temperature of the powder compact was changed from Example 1. In Example 10, the compact was heat-treated at 650°C, and in Example 11, the compact was heat-treated at 675°C.

On the other hand, Comparative Examples 7 and 8 were prepared in which only the heat treatment temperature of the compact was changed from Comparative Example 2. In Comparative Example 7, the compact was heat-treated at 650°C, and in Comparative Example 8, the compact was heat-treated at 675°C.

Furthermore, Comparative Examples 9 and 10 were prepared in which only the heat treatment temperature of the compact was changed from Comparative Example 5. In Comparative Example 9, the compact was heat-treated at 650°C, and in Comparative Example 10, the compact was heat-treated at 675°C.

Density, iron loss, and magnetic permeability were measured using the same measurement conditions and method as above. The results are shown in Table 6.

It was confirmed that Examples 1, 10, and 11 containing FeSiAl alloy powder (powder C), which is a gas atomized powder, maintained good eddy current loss even when the heat treatment temperature of the compact was increased. On the other hand, looking at Comparative Examples 2, 7, and 8 in which no FeSiAl alloy powder was added, and Comparative Examples 5, 9, and 10 in which pulverized FeSiAl alloy powder was added, it was found that when the heat treatment temperature was increased to 675°C, eddy current loss was confirmed to increase significantly.

Although this is speculation and is not limited to this, the following may be considered as the reason why Examples 1, 10, and 11 maintain good eddy current loss. Since the FeSiAl alloy powder (powder C), which is a gas atomized powder, is spherical, an insulating layer is easily formed uniformly on the powder surface. Generally, when an insulating layer is not formed uniformly and has thin parts, increasing the heat treatment temperature will destroy the insulating layer in these thin parts. Therefore, in Examples 1, 10, and 11, which contained a certain amount of powder with a uniform insulating layer formed, it is assumed that the thin part of the insulating layer was reduced and the insulating layer was not destroyed even when heat treated at a high temperature. do. On the other hand, the pulverized FeSiAl alloy powder (powder H) is angular, and it is difficult to form an insulating layer uniformly at these corner parts, resulting in thin parts, and the corner parts bite into other powders, resulting in poor insulation. This causes the layer to become thinner. Therefore, it is presumed that the insulating layer was more easily destroyed than the FeSiAl alloy powder, which is a gas atomized powder, and the eddy current loss increased. In the above example, the experiment was conducted using powder C, but it is assumed that the same results would be obtained for powders D to F.

(Other embodiments)
Although embodiments according to the present invention have been described in this specification, these embodiments are presented as examples and are not intended to limit the scope of the invention. The embodiments described above can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the scope of the invention. The embodiments and their modifications are included within the scope and gist of the invention as well as within the scope of the invention described in the claims and its equivalents.

Claims (3)

A soft magnetic powder made by mixing pure iron powder and FeSiAl alloy powder,
The pure iron powder is a water atomized powder and a smoothed powder,
The FeSiAl alloy powder is a gas atomized powder,
The particle size of the FeSiAl alloy powder is 13.0 μm or more and 31.8 μm or less,
The content of the pure iron powder contained in the soft magnetic powder is 80 wt% or more and 95 wt% or less, and the content of the FeSiAl alloy powder is 5 wt% or more and 20 wt% or less;
A soft magnetic powder characterized by The circularity of the smoothed pure iron powder is 0.95 or more;
The soft magnetic powder according to claim 1 , characterized by: Containing the soft magnetic powder of claim 1 or 2 ,
Features a powder magnetic core.

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