JP7603759B2 - Soft magnetic powder and dust cores - Google Patents

Description

The present invention relates to soft magnetic powder and a dust core containing this soft magnetic powder.

Coil components such as reactors are used in a variety of applications, including office equipment, solar power generation systems, and automobiles. Coil components have a coil attached to a core. Powder magnetic cores are often used for this core.

Powder cores contain soft magnetic powder and an insulating layer formed around the soft magnetic powder. The soft magnetic powder with the insulating layer formed on it is compressed under high pressure of several tons to several tens of tons to create a compact. This compact is then subjected to a heat treatment known as annealing to create a powder core.

Due to requirements for improved energy exchange efficiency and low heat generation, powder magnetic cores are required to have magnetic properties that minimize energy loss when the magnetic flux density changes. The magnetic property related to energy loss is specifically iron loss (Pcv). Iron loss (Pcv) is expressed as the sum of hysteresis loss (Ph) and eddy current loss (Pe).

Patent No. 5929819 JP 2017-098426 A

Research has been conducted to reduce hysteresis loss. For example, as in Patent Document 1, research has been conducted to show that low hysteresis loss can be obtained when the crystal grains are coarse. In addition, as in Patent Document 2, research has been conducted to show that eddy current loss can be reduced by separating the core and coil by a certain distance or more. However, in recent years, the applications of coil components have become more diverse, and there is an even greater demand for reducing hysteresis loss and eddy current loss, i.e., reducing iron loss.

The present invention has been made to solve the above problems, and its purpose is to provide a soft magnetic powder and a dust core that can reduce hysteresis loss and eddy current loss and can reduce iron loss.

As a result of intensive research, the inventors discovered that by attaching a compound formed by bonding Nb and glass to the surface of soft magnetic powder containing Fe-Si alloy powder, the crystal structure of the surface of the Fe-Si alloy powder can be restored to a regular structure by the Nb, thereby reducing hysteresis loss. They also discovered that the glass acts as an insulating coating, reducing eddy current loss.

The present invention has been made based on the above findings, and is characterized in that the soft magnetic powder of the present invention comprises an Fe-Si alloy powder and an insulating layer, a compound formed by bonding Nb and phosphate glass adheres to a surface of the Fe-Si alloy powder, the insulating layer is formed on the surface of the Fe-Si alloy powder to which the compound formed by bonding Nb and phosphate glass adheres , the average particle size of the Fe-Si alloy powder is 13.76 μm or more in terms of median size D50, the amount of the compound added is 0.2 wt % or more and 0.6 wt % or less with respect to the Fe-Si alloy powder, and the Nb content in the compound is 0.090 wt % or more and 0.27 wt % or less .

A dust core containing this soft magnetic powder is also an aspect of the present invention.

The present invention makes it possible to obtain soft magnetic powder and dust cores that can reduce hysteresis loss and eddy current loss and can reduce iron loss.

1 is a graph showing hysteresis loss in Example and Comparative Examples 1 and 2. FIG. 4 is a diagram showing the relationship between the average particle size of the soft magnetic powder and hysteresis loss. FIG. 4 is a diagram showing the relationship between the average particle size of the soft magnetic powder and eddy current loss. FIG. 4 is a diagram showing the relationship between the average particle size of the soft magnetic powder and iron loss. FIG. 1 is a diagram showing the relationship between the amount of a compound in which Nb and phosphate glass are combined and hysteresis loss. FIG. 1 is a diagram showing the relationship between the amount of a compound formed by combining Nb with phosphate glass and eddy current loss. FIG. 1 is a diagram showing the relationship between the amount of a compound in which Nb and phosphate glass are combined and iron loss.

The soft magnetic powder and powder magnetic core according to this embodiment will be described in detail. Note that the present invention is not limited to the embodiment described below.

Powder cores are magnetic materials used in the cores of coil parts installed in office equipment, solar power generation systems, automobiles, etc. Powder cores are made of soft magnetic powder. A compound of niobium (hereafter referred to as Nb) and glass adheres to the surface of the soft magnetic powder. In addition, the soft magnetic powder to which the compound formed by combining Nb and glass adheres is coated with an insulating layer. The soft magnetic powder coated with this insulating layer is pressure-molded to produce a compact, which is then heat-treated to produce the powder core.

As the soft magnetic powder, Fe-Si alloy powder containing Si with iron as the main component is used. Examples of Fe-Si alloy powder include Fe-5.5%Si alloy powder containing 5.5 wt% Si relative to Fe, and Fe-6.5%Si alloy powder containing 6.5 wt% Si relative to Fe, but the ratio of Si to Fe may be other than 5.5% or 6.5%. The Fe-Si alloy powder may also contain Co, Al, Cr, or Mn. The particle size (median size D50) of the Fe-Si alloy powder is preferably 13.76 μm or more. By making the particle size 13.76 μm or more, the effect of reducing hysteresis loss by adhering Nb is significantly manifested.

The Fe-Si alloy powder is preferably heat-treated in a non-oxidizing atmosphere such as a vacuum atmosphere or an inert gas atmosphere, or in the air, before the compound formed by bonding Nb and glass is attached. Examples of inert gas include _H2 and _N2 . The heat treatment temperature is preferably 500°C or higher and 700°C or lower. By heat-treating the Fe-Si alloy powder in a temperature range of 500°C or higher and 700°C or lower, the hysteresis loss is reduced. The heat treatment time is about 2 hours.

A compound formed by bonding Nb and glass is attached to the surface of the Fe-Si alloy powder. This compound may be attached to the surface of each particle of the Fe-Si alloy powder, or to the surface of the particle aggregate, or both of these forms may be mixed. In addition, the compound formed by bonding Nb and glass may be attached so as to cover the entire surface of the particle or particle aggregate, or may be attached so as to cover a portion of the surface of the particle or particle aggregate.

This is speculation and the mechanism is not limited to this, but it is believed that Nb attached to the surface of the Fe-Si alloy powder reduces hysteresis loss by repairing lattice defects in the crystals of the Fe-Si alloy powder. It is also believed that phosphate glass attached to the surface of the Fe-Si alloy powder acts as an insulating coating, reducing eddy current loss.

By combining Nb with glass, which has a high affinity for metals, it is possible to efficiently attach Nb to the surface of Fe-Si alloy powder even in the case of a small amount of Nb. If a mixture of Nb powder and resin is added to Fe-Si alloy powder, the resin may adhere to the surface of the Fe-Si alloy powder, and Nb may not adhere. In other words, just because the mixture is attached does not necessarily mean that Nb is attached. The surface of Fe-Si alloy powder to which Nb is not attached is not repaired, and it may not be possible to effectively reduce hysteresis loss. In order to increase the possibility of attaching Nb to the surface of Fe-Si alloy powder, it is necessary to increase the Nb content in the mixture.

On the other hand, when a compound is formed by bonding Nb and glass as in the present invention, this compound also contains Nb, so Nb adheres to the surface of the Fe-Si alloy powder. Therefore, compared to the case of a mixture with Nb, Nb can be adhered to the surface of the Fe-Si alloy powder more efficiently.

Glass with a melting point of 900°C or less can be used. For example, well-known glass such as phosphate glass can be used. By setting the melting point at 900°C or less, the glass softens during heat treatment of the powder compact, and spreads more easily over the surface of the Fe-Si alloy powder. For example, when the heat treatment temperature of the powder compact is 650°C and the melting point of the glass is 900°C, and there is a large difference between the heat treatment temperature and the melting point of the glass, it is possible to soften the glass by adjusting the heat treatment time.

The amount of the compound formed by combining Nb and glass is preferably 0.1 wt% or more and 0.6 wt% or less relative to the Fe-Si alloy powder. The amount of Nb contained in this compound is preferably 0.045 wt% or more and 0.27 wt% or less. By keeping the amount of the compound added and the Nb content in the compound within this range, hysteresis loss can be reduced.

More preferably, the amount of the compound formed by combining Nb and glass is 0.2 wt% or more and 0.6 wt% or less relative to the Fe-Si alloy powder. The Nb content in this compound is also preferably 0.09 wt% or more and 0.27 wt% or less. By keeping the amount of the compound added and the Nb content in the compound within this range, not only can hysteresis loss be reduced, but eddy current loss can also be reduced, resulting in reduced iron loss.

After adding the compound formed by bonding Nb and glass, heat treatment is performed in a nitrogen atmosphere. The heat treatment temperature is preferably 350°C to 800°C. The heat treatment time is about 10 hours, but may be changed as appropriate depending on the heat treatment temperature. When adding the compound formed by bonding Nb and glass, a known binder such as an acrylic binder may be added. The binder evaporates during this heat treatment, and may not adhere to the surface of the Fe-Si alloy powder, or may remain as a residue.

An insulating layer is formed on the outside of the Fe-Si alloy powder to which the compound formed by bonding Nb and glass is attached. That is, when the compound formed by bonding Nb and glass is attached so as to cover the entire surface of the particle or particle aggregate, an insulating layer is formed on the surface of the compound formed by bonding Nb and glass, and when the compound formed by bonding Nb and glass is attached so as to cover only a portion of the surface of the particle or particle aggregate, a portion of the insulating layer is also formed on the surface of the Fe-Si alloy powder.

The insulating material constituting the insulating layer includes a silane coupling agent, a silicone oligomer, a silicone resin, or a mixture of these. The insulating layer may be a single layer or multiple layers. For example, the insulating layer may be composed of multiple layers divided by type, or may be a single layer of one type or a mixture of two or more types of insulating material.

As the silane coupling agent, aminosilane, epoxysilane, and isocyanurate silane coupling agents can be used, with 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, and tris-(3-trimethoxysilylpropyl)isocyanurate being particularly preferred. The amount of silane coupling agent added is preferably 0.10 wt% or more and 1.0 wt% or less relative to the Fe-Si alloy powder. By adding the amount of silane coupling agent within this range, the fluidity of the soft magnetic powder can be improved, and the density, magnetic properties, and strength properties of the molded powder core can be improved.

After adding the silane coupling agent, the mixture of Fe-Si alloy powder and silane coupling agent is heated and dried. The drying temperature is preferably 25°C to 200°C. If the drying temperature is lower than 25°C, the solvent may remain and the insulating coating may be incomplete. On the other hand, if the drying temperature is higher than 200°C, decomposition may progress and the insulating coating may not be formed. The drying time is about 2 hours.

Silicone oligomers that can be used include methyl-based and methylphenyl-based ones that have an alkoxysilyl group but no reactive functional group, epoxy-based, epoxymethyl-based, mercapto-based, mercaptomethyl-based, acrylic methyl-based, methacrylic methyl-based, and vinylphenyl-based ones that have an alkoxysilyl group and a reactive functional group, and alicyclic epoxy-based ones that have a reactive functional group instead of an alkoxysilyl group. In particular, by using methyl-based or methylphenyl-based silicone oligomers, a thick and hard insulating layer can be formed. In addition, methyl-based and methylphenyl-based ones, which have a relatively low viscosity, may be used in consideration of the ease of forming the insulating layer.

The amount of silicone oligomer added is preferably 0.1 to 2.0 wt% of the Fe-Si alloy powder. If the amount added is less than 0.1 wt%, it will not function as an insulating coating, and eddy current loss will increase, resulting in reduced magnetic properties. If the amount added is more than 2.0 wt%, it will result in a decrease in the density of the powder core.

After the silicone oligomer is added, the mixture of Fe-Si alloy powder and silicone oligomer is heated and dried. The drying temperature is preferably 25°C to 350°C. If the drying temperature is below 25°C, the film will not be formed completely, leading to high eddy current loss and increased loss. On the other hand, if the drying temperature is above 350°C, the powder will oxidize, resulting in high hysteresis loss and increased loss. The drying time is approximately 2 hours.

Silicone resin is a resin that has a siloxane bond (Si-O-Si) in its main skeleton. By using silicone resin, it is possible to form a coating with excellent flexibility. Silicone resins that can be used include methyl-based, methylphenyl-based, propylphenyl-based, epoxy resin-modified, alkyd resin-modified, polyester resin-modified, and rubber-based silicone resins. Among these, when using methylphenyl-based silicone resins in particular, it is possible to form an insulating layer with little loss on heating and excellent heat resistance.

The amount of silicone resin added is preferably 0.8 to 2.0 wt% relative to the Fe-Si alloy powder. If the amount added is less than 0.8 wt%, it will not function as an insulating coating, and eddy current loss will increase, resulting in reduced magnetic properties. If the amount added is more than 2.0 wt%, it will result in a decrease in the density of the powder core.

After adding the silicone resin, the mixture of Fe-Si alloy powder and silicone resin is heated and dried. The drying temperature is preferably 100°C to 200°C. If the drying temperature is lower than 100°C, the formation of the insulating coating will be incomplete, which may result in high eddy current loss. On the other hand, if the drying temperature is higher than 200°C, the powder will become inorganic and will not function as a binder, resulting in poor shape retention and a decrease in the density and magnetic permeability of the molded body. The drying time is approximately 2 hours.

When forming the insulating layer, moisture may be added. Examples of moisture include water and ethanol. The moisture is added after mixing the soft magnetic powder with a silane coupling agent, silicone resin, etc., or at the initial stage of heating and drying the silane coupling agent, silicone resin, etc. The moisture is added by dispersing it in a mist or spray form, or by dripping it as fine droplets. Adding moisture improves the hydrolysis and condensation reactions required for the silane coupling agent, etc., and improves the strength of the core. The moisture evaporates when heated and dried, and does not remain in the insulating layer.

A lubricant is added to the Fe-Si alloy powder with an insulating layer formed around it, and the powder core is produced through a pressure molding process and a compact heat treatment process. Examples of lubricants include stearic acid and its metal salts, as well as ethylene bis stearamide, ethylene bis stearamide, and ethylene bis stearate amide.

The pressure molding process is a process for producing a powder compact by pressure molding the Fe-Si alloy powder on which the insulating layer has been formed. First, the Fe-Si alloy powder is filled into a die, and then pressure is applied at 10 to 20 ton/ ^cm2 to form a powder compact.

In the compact heat treatment process, the powder compact is heat treated in a non-oxidizing atmosphere such as nitrogen gas, hydrogen gas, a mixture of nitrogen and hydrogen, or a low-oxygen atmosphere such as 0.01% oxygen, at a temperature of 650°C or higher and lower than the temperature at which the insulating layer formed around the Fe-Si alloy powder is destroyed (for example, 900°C). A powder magnetic core is produced through the heat treatment.

The present invention will be described in more detail with reference to the following examples. Note that the present invention is not limited to the following examples.

First, soft magnetic powders of Example 1 and Comparative Examples 1 and 2 were prepared, and dust cores were prepared using each soft magnetic powder. Example 1 and Comparative Examples 1 and 2 differ in the presence or absence of phosphate glass on the surface of the soft magnetic powder and the type of metal bonded to the phosphate glass. Specifically, Example 1 has a compound formed by bonding Nb and phosphate glass attached to the surface of the soft magnetic powder, while Comparative Example 1 does not add a compound formed by bonding Nb and phosphate glass, and Comparative Example 2 has a compound formed by bonding Sn and phosphate glass attached. The rest of the process and conditions were the same for all the soft magnetic powders. The soft magnetic powders and dust cores of Example 1 and Comparative Examples 1 and 2 were prepared as follows:

First, Fe-5.5% Si alloy powder was prepared. The Fe-5.5% Si alloy powder was heat-treated in a nitrogen atmosphere at 650°C for 2 hours.

In Example 1, 0.3 wt% of a compound formed by combining Nb and phosphate glass and 0.75 wt% of an acrylic binder were added to the heat-treated Fe-5.5% Si alloy powder. In Comparative Example 2, 0.3 wt% of a compound formed by combining Sn and phosphate glass and 0.75 wt% of an acrylic binder were added. Then, in Example 1 and Comparative Example 2, heat treatment was performed for 10 hours at a temperature of 380°C in a nitrogen atmosphere. On the other hand, in Comparative Example 1, phosphate glass combined with metals such as Nb and Sn was not added, and Nb and phosphate glass were not attached to the surface of the Fe-5.5% Si alloy powder. In other words, in Comparative Example 1, the following process was performed without performing this process.

After that, 0.5 wt% of silicone oligomer was mixed with the Fe-5.5% Si alloy powder and dried in air at 200°C for 2 hours. The Fe-5.5% Si alloy powder was passed through a sieve with 250 μm openings in order to eliminate agglomeration. 1.6 wt% of silicone resin with a solid content of 50% was mixed with the sieved Fe-5.5% Si alloy powder and dried in air at 150°C for 2 hours, and the Fe-5.5% Si alloy powder was passed through a sieve with 250 μm openings in order to eliminate agglomeration. As a result, in Example 1 and Comparative Example 2, a layer of silicone oligomer was formed on the outside of the Fe-5.5% Si alloy powder to which the compound of Nb or Sn and phosphate glass was attached, and further, a layer of silicone resin was laminated on the outside of the layer of silicone oligomer. On the other hand, in Comparative Example 1, a layer of silicone oligomer was formed on the surface of the Fe-5.5% Si alloy powder, and a layer of silicone resin was further laminated on the outside of the silicone oligomer layer.

Then, 0.5 wt% of a lubricant (Acrawax (registered trademark)) was mixed. The soft magnetic powder to which the lubricant was added was filled into a metal mold and press-molded to obtain each powder compact having an outer diameter of 16.5 mm, an inner diameter of 11.0 mm, and a height of 5.0 mm. The pressure of the press molding was 15 ton/ ^cm2 . Each powder compact was heat-treated at 850°C for 2 hours in a nitrogen atmosphere.

A 20-turn primary winding and a 20-turn secondary winding were wound with φ0.5 mm copper wire around the powder magnetic cores of Example 1 and Comparative Examples 1 and 2 produced as described above, and the hysteresis loss was measured. The measurement conditions were a frequency of 100 kHz and a maximum magnetic flux density Bm = 100 mT. The magnetic measuring device used was a BH analyzer (Iwatsu Measurement Co., Ltd.: SY-8219). The hysteresis loss coefficient and eddy current loss coefficient were calculated using the least squares method using the following equations (1) to (3), to calculate the hysteresis loss, eddy current loss, and iron loss.

Pcv =Kh×f+Ke×f2...(1)
Ph = Kh×f...(2)
Pe=Ke×f2...(3)
Pcv: Iron loss Kh: Hysteresis loss coefficient Ke: Eddy current loss coefficient f: Frequency Ph: Hysteresis loss Pe: Eddy current loss

The results of the measured hysteresis loss are shown in Table 1 and Fig. 1. Fig. 1 is a graph showing the hysteresis loss of Example 1 and Comparative Examples 1 and 2.

As shown in Table 1 and Figure 1, it was confirmed that Example 1, in which a compound of Nb and phosphate glass was added, had a reduced hysteresis loss compared to Comparative Example 1, in which no glass was added, and Comparative Example 2, in which a compound of Sn and phosphate glass was added. This is presumably because the crystal structure of the surface of the Fe-5.5%Si alloy powder became a regular structure by attaching Nb to the surface of the Fe-5.5%Si alloy powder. Therefore, it was confirmed that the hysteresis loss was reduced by attaching a compound of Nb and phosphate glass to the surface of the Fe-Si alloy powder.

Next, soft magnetic powders of Examples 2 to 5 and Comparative Examples 3 to 8 were prepared, and dust cores were made using each soft magnetic powder, and the hysteresis loss, eddy current loss, and iron loss were measured. As shown in Table 2 below, Examples 2 to 5 and Comparative Examples 3 to 8 differ in the particle size of the Fe-5.5% Si alloy powder used as the soft magnetic powder.

In Examples 2 to 5 and Comparative Examples 3 to 8, the Fe-5.5% Si alloy powder prepared as soft magnetic powder was heat-treated in a nitrogen atmosphere at 650°C for 2 hours. Heat treatment was performed. The heat-treated Fe-5.5% Si alloy powder was then sieved to obtain Fe-5.5% Si alloy powder with the particle size (median size D50) shown in Table 2 below.

In addition, in Examples 2 to 5 and Comparative Example 3, 0.3 wt% of a compound of Nb and phosphate glass and 0.75 wt% of an acrylic binder were added to the Fe-5.5% Si alloy powder classified in the same manner as in Example 1, and the compound of Nb and phosphate glass was adhered to the surface of the Fe-5.5% Si alloy powder. On the other hand, in Comparative Examples 4 to 8, like Comparative Example 1, no phosphate glass was added. The rest of the samples were produced using the same process and conditions as Example 1 and Comparative Examples 1 and 2.

The results of the above measurements are shown in Table 2 and Figures 2 to 4. Figure 2 shows the relationship between the average particle size of the soft magnetic powder and hysteresis loss. Figure 3 shows the relationship between the average particle size of the soft magnetic powder and eddy current loss. Figure 4 shows the relationship between the average particle size of the soft magnetic powder and iron loss.

As shown in Table 2 and Figures 2 and 3, it was confirmed that adding a compound formed by combining Nb and phosphate glass reduces not only hysteresis loss but also eddy current loss, and as a result, as shown in Figure 4, it was confirmed that iron loss is reduced. This is presumably because phosphate glass adheres to the surface of the Fe-5.5% Si alloy powder and acts as an insulating coating, thereby reducing eddy current loss.

However, looking at Comparative Example 3, which has an average particle size of 5.527 μm, it was confirmed that the effect of reducing hysteresis loss was difficult to obtain, despite the addition of a compound in which Nb and phosphate glass were combined, as in Examples 2 to 5. This is speculation and is not limited to this mechanism, but in the case of fine powder with an average particle size of 5.527 μm, it is difficult to increase the density in the first place, and the density tends to decrease. Therefore, it is thought that the impact of the increase in hysteresis loss due to the decrease in density had a greater effect than the hysteresis loss reduction effect due to the repair of the crystal structure by Nb.

In addition, when comparing Comparative Example 3 and Comparative Example 8, both of which have an average particle size of 5.527 μm, it was confirmed that, although eddy current loss was reduced in Comparative Example 3, hysteresis loss worsened. This is also speculation, and the mechanism is not limited to this, but it is believed that the density was reduced by adding glass compared to Comparative Example 8, which did not contain glass, resulting in an increase in hysteresis loss. Therefore, it was confirmed that the effect of reducing hysteresis loss can be obtained by making the average particle size 13.76 μm or more.

Finally, soft magnetic powders were prepared for Examples 6 to 14 and Comparative Examples 9 to 29, and dust cores were produced using each soft magnetic powder. Fe-5.5% Si alloy powder was also prepared as the soft magnetic powder for Examples 6 to 14 and Comparative Examples 9 to 29. However, the Fe-Si alloy powder was heat-treated and sieved so that the average particle size (median size D50) of the Fe-5.5% Si alloy powder was one type with a mean particle size of 13.76 μm.

As shown in Tables 3 to 5 below, the amount of compound formed by combining Nb and phosphate glass is different, with 0.3 wt% added. Furthermore, with regard to the heat treatment atmosphere after the compacts were produced, the powder cores of Examples 6 to 8 and Comparative Examples 9 to 15 were heat treated in a nitrogen atmosphere, the powder cores of Examples 9 to 11 and Comparative Examples 16 to 22 were heat treated in a 0.01% low-oxygen atmosphere, and the powder cores of Examples 12 to 14 and Comparative Examples 23 to 29 were heat treated in a hydrogen atmosphere. The rest of the powder cores were produced using the same process and conditions as Example 1 and Comparative Examples 1 and 2.

Then, the hysteresis loss, eddy current loss, and iron loss were calculated using the magnetic measuring device. The results are shown in Tables 3 to 5 and Figures 5 to 7. Table 3 shows the results of Examples 6 to 8 and Comparative Examples 9 to 15 in which the compacts were heat-treated in a nitrogen atmosphere. Table 4 shows the results of Examples 9 to 11 and Comparative Examples 16 to 22 in which the compacts were heat-treated in a low-oxygen atmosphere. Table 5 shows the results of Examples 12 to 14 and Comparative Examples 23 to 29 in which the compacts were heat-treated in a hydrogen atmosphere. The Nb content shown in each table was derived from the analysis of a compound in which Nb and phosphate glass were combined, which revealed that the Nb content was 45%. Figure 5 shows the relationship between the amount of Nb and phosphate glass combined compound and hysteresis loss. Figure 6 shows the relationship between the amount of Nb and phosphate glass combined compound and eddy current loss. Figure 7 shows the relationship between the amount of Nb and phosphate glass combined compound and iron loss.

As shown in Tables 4 to 6 and Figures 4 to 6, when a trace amount of a compound formed by combining Nb and phosphate glass is added at 0.01 wt%, the hysteresis loss and eddy current loss increase, but when the amount added is increased from that amount, the hysteresis loss and eddy current loss decrease, and when 0.1 wt% (Nb content of 0.0450 wt%) is added, the hysteresis loss becomes smaller than 700 (kW/m ³ ). It was also confirmed that when 0.2 wt% (Nb content of 0.0900 wt%) is added, the eddy current loss is also reduced, and the iron loss is lower than 1000 (kW/m ³ ). This tendency was the same regardless of the atmosphere in which the molded body was heat-treated.

On the other hand, when the amount of the compound in which Nb and phosphate glass are combined is more than 0.6 wt% (Nb content is 0.2700 wt%), hysteresis loss increases and iron loss begins to increase. This is a conjecture and is not limited to this mechanism, but it is thought that when the amount added is large, Nb not only repairs but also causes distortion in the crystal structure, so hysteresis loss increases. Therefore, it was confirmed that the amount of the compound in which Nb and phosphate glass are combined is preferably 0.1 wt% to 0.6 wt% (Nb content is 0.0450 wt% to 0.2700 wt%). It was also confirmed that this result is the same whether the heat treatment atmosphere of the molded body is nitrogen, oxygen, or hydrogen.

Other Embodiments
In this specification, an embodiment of the present invention has been described, but this embodiment is presented as an example and is not intended to limit the scope of the invention. The above-mentioned embodiment can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. The embodiment and its modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and gist of the invention.

Claims (2)

Fe-Si alloy powder and an insulating layer,
A compound formed by bonding Nb and phosphate glass is attached to the surface of the Fe-Si alloy powder,
the insulating layer is formed on a surface of the Fe-Si alloy powder to which a compound formed by bonding the Nb and the phosphate glass is attached ,
The average particle size of the Fe—Si alloy powder is 13.76 μm or more in terms of median diameter D50,
The amount of the compound added is 0.2 wt % or more and 0.6 wt % or less with respect to the Fe-Si alloy powder,
The content of Nb in the compound is 0.090 wt % or more and 0.27 wt % or less ;
A soft magnetic powder characterized by: Contains the soft magnetic powder according to claim 1 ;
A powder magnetic core characterized by:

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