JP2023137624A - Dust core powder, method for manufacturing dust core powder, dust core, and method for manufacturing dust core - Google Patents

Abstract

To provide dust core powder to which further high heat treatment can be subjected and a method for manufacturing the same, and a dust core using the dust core powder and a method for manufacturing the same.SOLUTION: Dust core powder includes soft magnetic powder and tantalum alkoxide adhering to the surface of the soft magnetic powder. Such dust core powder can be manufactured using a manufacturing method including, after a tantalum adhesion step in which tantalum alkoxide is added to and mixed with soft magnetic powder, a heating step of heating the soft magnetic powder under an atmosphere at temperatures of 1,000°C or above.SELECTED DRAWING: Figure 1

Description

The present invention relates to a powder for a powder magnetic core and a powder magnetic core containing the powder for a powder magnetic core.

A coil, also called an inductor or reactor, is an electromagnetic component that converts electrical energy into magnetic energy for storage and release. Coils are also called reactors especially in power applications, and are used in various fields such as drive systems for hybrid vehicles, electric vehicles, and fuel cell vehicles, as well as office automation equipment, solar power generation systems, automobiles, and uninterruptible power supplies. .

A powder magnetic core is often used for the coil. A powder magnetic core is obtained by annealing a molded body obtained by compacting powder for a powder magnetic core. The dust core powder is a soft magnetic metal powder. Examples of soft magnetic powders include permalloy whose main component is iron (Fe-Ni alloy), Si-containing iron alloy (Fe-Si alloy), sendust alloy (Fe-Si-Al alloy), amorphous alloy, pure iron powder, etc. Can be mentioned.

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. Specifically, the magnetic property related to magnetic flux density is magnetic permeability (μ). Specifically, the magnetic property related to energy loss is iron loss (Pcv). Iron loss (Pcv) is expressed as the sum of hysteresis loss (Ph) and eddy current loss (Pe).

When distortion occurs in the crystals of soft magnetic powder, the coercive force increases due to the distortion, resulting in an increase in hysteresis loss. Therefore, one method for reducing hysteresis loss is heat treatment of soft magnetic powder at high temperatures. Heat treatment at high temperatures releases strain within the crystals of the soft magnetic powder, lowering the coercive force and reducing hysteresis loss.

Furthermore, as the magnetic domain width increases, eddy current loss increases. Therefore, one method for reducing eddy current loss is to insulate soft magnetic powder. By covering the soft magnetic powder with an insulating layer, the spaces between the soft magnetic powders are expanded, the magnetic domains are subdivided, and eddy current loss is reduced. Aluminum, titanium, zirconium, or silicone alkoxides have been proposed as the insulating material included in the insulating layer. Also, alkoxides of Fe, Ni, Mn, Mg, Li, Mo, Nb, Hf, Sc, or Zn have been proposed as insulating materials.

Japanese Unexamined Patent Publication No. 14601/1983 Japanese Patent Application Publication No. 2007-194273

The insulating layer also plays a role in preventing the soft magnetic powders from sintering together during heat treatment of the soft magnetic powders at high temperatures to reduce hysteresis loss. However, many of the insulating materials that have been proposed so far have not been able to cope with further high heat treatment in order to improve the hysteresis loss reduction effect. That is, in many insulating materials that have been proposed so far, if the heat treatment temperature is further increased, the soft magnetic powders sinter together, making it impossible to process them into powder magnetic cores.

The present invention has been proposed in order to solve the above-mentioned problems, and an object of the present invention is to provide a powder for powder magnetic core that enables heat treatment of soft magnetic powder at an even higher temperature, a method for producing the same, It is an object of the present invention to provide a powder magnetic core using this powder for powder magnetic core, and a method for manufacturing the same.

In order to achieve the above object, a powder for powder magnetic core according to an embodiment of the present invention includes soft magnetic powder and tantalum alkoxide that adheres to the surface of the soft magnetic powder. Soft magnetic powder with tantalum alkoxide attached to its surface is difficult to sinter even when exposed to high temperatures of 1000°C or higher, can be processed into powder magnetic cores, and has good resistance to intracrystalline distortion when subjected to high heat treatment at 1000°C or higher. This eliminates the hysteresis loss, reduces the hysteresis loss, and also subdivides the magnetic domain, reducing eddy current loss.

The tantalum alkoxide may be attached to the soft magnetic powder at a ratio of 0.25 wt% or more to 2.0 wt%. When the soft magnetic powder is within this range, the effect of reducing hysteresis loss is high.

The tantalum alkoxide may be attached to the soft magnetic powder at a ratio of 0.5 wt% or more to 1.5 wt%. When the magnetic powder is within this range, the effect of reducing hysteresis loss is particularly high.

The soft magnetic powder may have a powder particle size of 20 μm or less in terms of D50 in the particle size distribution. The soft magnetic powder whose diameter has been reduced in this way is difficult to uniformly disperse with the insulating material and is easily sintered. In addition, the soft magnetic powder whose diameter is reduced becomes more susceptible to oxidation due to the increased surface area, making it easier to sinter. Therefore, with the insulating materials that have been proposed so far, it has been difficult to perform high heat treatment at temperatures of 1000° C. or higher on soft magnetic powders whose diameters have been reduced in this way. However, even soft magnetic powder whose diameter is reduced in this way can be processed into a powder magnetic core by suppressing sintering.

The soft magnetic powder may be FeSi alloy powder.

A powder magnetic core containing these powders for powder magnetic cores is also one embodiment of the present invention. In this powder magnetic core, tantalum alkoxide may be modified into tantalum oxide and adhered thereto due to a reaction caused by heating.

In addition, in order to achieve the above object, the method for producing powder for powder magnetic core according to the embodiment of the present invention includes a tantalum adhesion step of adding and mixing tantalum alkoxide to soft magnetic powder, followed by an atmosphere at a temperature of 1000° C. or higher. The method further includes a heating step of heating the soft magnetic powder. With this manufacturing method, it is difficult to sinter even when exposed to high temperatures of 1000°C or higher, and can be processed as a powder magnetic core.In addition, it successfully eliminates intracrystalline distortion caused by high heat treatment of 1000°C or higher, reducing hysteresis loss. At the same time, it becomes possible to produce soft magnetic powder with finely divided magnetic domains and reduced eddy current loss.

It is also possible to further include a classification step of classifying the soft magnetic powder so that D50 in the particle size distribution is 20 μm or less, and to transfer the soft magnetic powder that has passed through the classification step to the tantalum adhesion step. This also benefits from a smaller diameter, and further reduces eddy current loss.

The present invention also includes a method for manufacturing a powder magnetic core, which includes, after the tantalum adhesion step in this manufacturing method, a molding step of press-molding the soft magnetic powder into a molded body of a predetermined shape, and a heat treatment step of annealing the molded body. This is one aspect.

According to the present invention, it is possible to process it as a powder magnetic core even by further high heat treatment, and it is also possible to reduce hysteresis loss and eddy current loss.

It is a graph in which the horizontal axis represents the amount of addition, and the vertical axis represents iron loss Pcv (kw/m ³ ), hysteresis loss Ph (kw/m ³ ), and eddy current loss Pe (kw/m ³ ).

Hereinafter, the powder for powder magnetic core and the powder magnetic core according to this embodiment will be explained in detail. Note that the present invention is not limited to the embodiments described below.

(Schematic configuration)
A powder magnetic core is a magnetic material used in the core of a coil, also called an inductor or reactor. A powder magnetic core is constructed by compacting powder for a powder magnetic core. This dust core powder has soft magnetic powder as its core. Powder for powder magnetic cores is produced through a tantalum adhesion step in which tantalum alkoxide is attached to the soft magnetic powder, and a post-tantalum adhesion heating step in which high heat treatment is performed after the tantalum adhesion step. The manufacturing process of the powder for powder magnetic core may include an insulation treatment process of forming a layer of a silane compound, a silicone resin, or both of these, as necessary. A powder magnetic core is produced through a molding process in which the powder for powder magnetic core is pressure-molded into a desired shape to form a molded body, and an annealing process in which the molded body is annealed.

(Soft magnetic powder)
Soft magnetic powder has iron as its main component. As the soft magnetic powder, pure iron powder, permalloy whose main component is iron (Fe-Ni alloy), Si-containing iron alloy (Fe-Si alloy), sendust alloy (Fe-Si-Al alloy), or two of these are used. A mixed powder of the above powders and the like can be mentioned.

Pure iron powder contains 99% or more of Fe. The Si-containing iron alloy may contain Co, Al, Cr, or Mn. When permalloy (Fe--Ni alloy) is used, the ratio of Ni to Fe is preferably 50:50 or 25:75, but other ratios may be used. For example, Fe-80Ni or Fe-36Ni may be used. In addition to Fe and Ni, Si, Cr, Mo, Cu, Nb, Ta, etc. may be included.

Examples of Fe-Si alloy powder include Fe-3.5%Si alloy powder and Fe-6.5%Si alloy powder, but the ratio of Si to Fe is other than 3.5% or 6.5%. It may be. Fe-Si-Al alloy is a ternary alloy consisting of iron, silicon, and aluminum. For example, Fe-Si-Al alloy contains about 6 wt% to 10 wt% of Si and about 4 wt% to 5 wt% of Al. However, about 1 wt% to 3 wt% of Ni may be included with respect to Fe, and Co, Cr, or Mn may also be included.

This soft magnetic powder may be produced by a pulverization method or an atomization method. The atomization method may be a water atomization method, a gas atomization method, or a water gas atomization method. The water atomization method is currently the most readily available and low cost. When the water atomization method is used, since the particle shape is distorted, the mechanical strength of the powder molded product obtained by pressure molding is easily improved, which is preferable. The gas atomization method is preferable because it can effectively reduce hysteresis loss.

This soft magnetic powder is preferably heat treated before the tantalum deposition step. This heat treatment is a pre-classification heat treatment, which makes it easier to crush the soft magnetic powder, and makes it easier to classify the soft magnetic powder into a desired particle size. The pre-classification heat treatment is preferably performed in a non-oxidizing atmosphere. As the non-oxidizing atmosphere, a low oxygen atmosphere such as an oxygen concentration of 0.01%, an inert gas atmosphere, or a reducing gas atmosphere is desirable. Examples of the inert gas include noble gases such as Ar and _N2 . Moreover, H ₂ etc. are mentioned as a reducing gas. The heating time is, for example, about 1 to 6 hours. In this pre-classification heat treatment step, the soft magnetic powder is preferably exposed to a temperature environment of 500°C or more and 700°C or less.

(tantalum alkoxide)
In the tantalum attachment step, tantalum alkoxide is attached to the surface of the soft magnetic powder. Tantalum alkoxide is represented by the general formula Ta(OR) ₅ , in which R is the same or different alkyl group, and the alkyl group has 1 or more carbon atoms. Examples of tantalum alkoxides include pentaethoxy tantalum, which is represented by the chemical formula Ta(OC ₂ H ₅ ) ₅ and has two carbon atoms in all alkyl groups. Examples of tantalum alkoxides include pentan-propoxy tantalum, which is represented by the chemical formula Ta(O-n-C ₃ H ₇ ) ₅ , and tantalum, which is represented by the chemical formula Ta(O-n-C ₄ H ₉ ) ₅ . Pent-n-butoxytantalum is mentioned.

Although this is speculation and is not limited to this mechanism, tantalum reduces hysteresis loss by repairing lattice defects in the crystals of the attached soft magnetic powder. This tantalum alkoxide is oxidized by heat treatment during the manufacturing process of the powder magnetic core, acts as an insulating layer, and also reduces eddy current loss. Furthermore, by adding tantalum as alkoxide to the soft magnetic powder, tantalum can be efficiently attached to the surface of the soft magnetic powder even in a trace amount, and it is difficult to aggregate even in a high temperature environment.

The amount of tantalum alkoxide added in the tantalum adhesion step is preferably 0.25 wt% or more and 2.0 wt% or less based on the soft magnetic powder, and particularly preferably 0.5 wt% or more and 1.5 wt% or less based on the soft magnetic powder. When the content is 0.25 wt% or more and 2.0 wt% or less, the effect of reducing hysteresis loss and eddy current loss is significant. When the content is 0.5 wt% or more and 1.5 wt% or less, the effect of reducing hysteresis loss becomes particularly large. For mixing, a planetary mixer with rotating blades in a container, a high-speed stirring granulator, or the like may be used. Unlike alumina, for example, tantalum alkoxide is liquid at room temperature (25° C.), and even if the amount added is small or the soft magnetic powder is small in diameter, it is easy to uniformly and highly disperse the tantalum alkoxide and the soft magnetic powder.

After the tantalum adhesion process, the process moves to a post-tantalum adhesion heating process. In the tantalum post-deposition heating step, the soft magnetic powder with tantalum alkoxide adhered to the surface is heat treated in a high temperature environment to release distortion within the crystals of the soft magnetic powder. It is necessary to expose the soft magnetic powder to a temperature environment of 380° C. or higher, but if tantalum alkoxide is added, the soft magnetic powder can also be exposed to a high temperature environment of 1000° C. or higher. A non-oxidizing atmosphere is also preferable for this heat treatment, for example, the soft magnetic powder is heat treated in a nitrogen atmosphere. It is exposed to a peak temperature of 1000° C. or higher, for example, for about 1 to 6 hours.

Even if soft magnetic powders are exposed to a temperature environment of 1000° C. or higher, when tantalum alkoxide is added, sintering of the soft magnetic powders can be suppressed. Therefore, when tantalum alkoxide is added, the benefits of reducing eddy current loss due to magnetic domain refinement to suppress sintering between soft magnetic powders and reducing hysteresis loss due to strain relief during high-temperature heat treatment can be achieved in the powder magnetic core. This can be achieved in a moldable state. In other words, since sintering between the soft magnetic powders is suppressed, after the tantalum alkoxide is attached, it can be transferred to an insulation treatment process as needed, and the powder for the dust core can be pressed into the desired shape. Can be molded to form a molded body.

When tantalum alkoxide is used, the soft magnetic powder preferably has a median diameter D50 of 20 μm or less in the particle size distribution. Before the tantalum adhesion process, the soft magnetic powder is heat-treated to crush the soft magnetic powder, and then goes through a classification process. By classifying with an air flow that takes advantage of different characteristics, it is possible to obtain particle sizes with a D50 of 20 μm or less in the particle size distribution.

When soft magnetic powder having a particle size in this range is used, the magnetic domains are easily segmented, and eddy current loss can be further reduced. On the other hand, soft magnetic powder having a particle size in this range has an increased surface area and is easily oxidized. Oxidized soft magnetic powder is easily sintered. However, when tantalum alkoxide is used, even when soft magnetic powder having a particle size in this range is exposed to a high temperature environment of 1000° C. or higher, the effect of suppressing sintering of the soft magnetic powder is exhibited.

(Insulation treatment process)
After going through the tantalum adhesion process and the tantalum post-deposition heating process, the soft magnetic powder is coated with an insulating layer to ensure electrical insulation between the particles of the soft magnetic powder and reduce eddy current loss in the dust core. . The insulating layer also has a binder function, improving shape retention during molding, further increasing the strength of the molded product after annealing, and improving the density of the soft magnetic powder, increasing the magnetic permeability of the powder magnetic core. raise.

The insulating layer may be attached so as to cover the entire surface of the soft magnetic powder, it may be attached so as to cover a part of the surface of the powder, or both of these aspects may be mixed. good. Further, the insulating powder may be attached to each particle of the soft magnetic powder, or may be attached to the surface of an aggregate of particles, or both of these modes may be mixed. When covering a part of the surface of particles or aggregates, the insulating resin may be dispersed and attached in dots, dispersed and attached in lumps, or a mixture of these modes. You can.

As the resin for the insulating layer, a silane compound, a silicone oligomer, a silicone resin, or a plurality of these can be used. The insulating layer may be a single layer or multiple layers. For example, the insulating layer may be composed of multiple layers divided into layers for each type, or may be a single layer of an insulating material of one type or a mixture of two or more types.

Silane compounds include silane compounds without functional groups and silane coupling agents. As the silane compound without a functional group, for example, alkoxysilanes such as ethoxy-based and methoxy-based alkoxysilanes can be used, and a more specific example is tetraethoxysilane. As the silane coupling agent, aminosilane type, epoxysilane type, isocyanurate type, etc. can be used, and more specifically, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, tris- (3-trimethoxysilylpropyl) isocyanurate is mentioned. The amount of the silane compound or silane coupling agent without a functional group to be 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 compound added within this range, it is possible to improve the fluidity of the soft magnetic powder and also to improve the density, magnetic properties, and strength properties of the molded powder magnetic core.

Silicone resin is a resin having a siloxane bond (Si--O--Si) as its main skeleton, and can form an insulating layer with excellent flexibility. As the silicone resin, typically, a 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 preferably 0.6 wt% or more and 2.5 wt% or less, and more preferably 0.8 wt% or more and 2.0 wt% or less, based on the soft magnetic powder. If the amount added is less than 0.6 wt%, it will not function as an insulating layer, and magnetic properties will deteriorate due to increased eddy current loss, and the silicone resin will not function as a binder, resulting in a decrease in strength. If the amount added is more than 2.5 wt%, the density of the powder magnetic core will decrease.

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 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 layer, 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.

In the insulation treatment process, first, a resin to be contained in the insulation layer and a soft magnetic powder are mixed together. The insulation treatment process includes a drying process by heating after the mixing process. In the drying step, although not particularly limited, it is preferable to expose the material to a temperature environment of 70° C. or more and 300° C. or less for about 2 hours. Note that if the drying temperature is less than 70°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 300° C., hysteresis loss increases due to oxidation of the powder, resulting in increased loss. The drying time is, for example, about 2 hours.

(molding process)
In the molding step, a molded body is formed by pressure molding the dust core powder produced through the insulation treatment step. The pressure during molding is 10 to 20 ton/cm ² , preferably about 12 to 15 ton/cm ² on average. In addition, if the lubricant addition process is performed prior to the molding process, the ejection pressure when releasing the upper punch during molding will be reduced, and the powder for the dust core will be prevented from sticking to the mold, which will improve the molding process. Improves body quality. Further, prior to the molding process, it is preferable to pass the soft magnetic powder through a sieve with a predetermined mesh size in order to eliminate agglomeration of the soft magnetic powder.

The lubricant coats the surface of the insulating layer coated with soft magnetic powder. Examples of the lubricant include, but are not limited to, stearic acid and its metal salts, ethylene bis stearamide, ethylene bis stearamide, ethylene bis stearate amide, and the like. The amount of lubricant added is preferably about 0.2 wt% to 0.8 wt% based on the soft magnetic powder. More preferably, the amount of lubricant added is about 0.3 wt% to 0.6 wt% based on the soft magnetic powder. By setting it within this range, the sliding between the soft magnetic powders can be further improved. The lubricant may be used when adding and mixing a silane compound, a silicone oligomer, a silicone resin, or a plurality of these in the insulation treatment process.

(Annealing process)
In the annealing process, the molded body that has undergone the molding process is heated to remove distortion. The heating environment is preferably 800° C. or higher in an inert atmosphere, a reducing atmosphere, an oxidizing atmosphere with adjusted oxygen concentration, or the air. Inert and reducing atmospheres are atmospheres with low amounts of reactive gases and filled with inert or neutral gases. The reactive gas is oxygen, water vapor, carbon dioxide, or the like. The inert gas is argon, helium, or the like. Neutral gases include nitrogen and ammonia. If the temperature is less than 800°C, the effect of strain removal will be limited.

As a result, powder for a powder magnetic core is produced based on the soft magnetic powder, and a powder magnetic core is produced based on the powder for a powder magnetic core. At the time when the production of the dust core is completed, the tantalum alkoxide may become tantalum oxide and adhere to the soft magnetic powder, or may be doped as tantalum into the soft magnetic powder.

Hereinafter, the present invention will be explained in more detail based on Examples. Note that the present invention is not limited to the following examples.

A powder for powder magnetic core was produced as follows, and a powder magnetic core was produced using this powder for powder magnetic core. Fe--Si alloy powder was used as the soft magnetic powder. This Fe--Si alloy powder contains 5.5 wt% Si. The Fe--Si alloy powder was dissolved by heating it in a nitrogen environment at 650° C. for 2 hours. After dissolving the Fe--Si alloy powder by heat treatment, it was sieved by classification treatment to select Fe--Si alloy powder having D50 of 20 μm or less in the particle size distribution.

The Fe--Si alloy powder selected by the classification process had a particle size distribution of D10 of 6.284 μm, D50 of 14.48 μm, D90 of 21.17 μm, and D100 of 32.72 μm. Further, the circularity of this Fe-Si alloy powder was 0.876 in the D10 range, 0.966 in the D50 range, and 0.985 in the D90 range in the particle size distribution. Further, the holding force Hc of the Fe-Si alloy powder was 3.32 A/cm. The particle size and circularity were calculated from 3000 samples using a particle image analyzer (manufactured by Malvern, device name: Morphologi G3S), and Fe-Si alloy powder was dispersed on a glass substrate. Photographs of the powder were taken using a microscope and each individual piece was automatically measured based on the image.

The Fe--Si alloy powder was transferred to a tantalum deposition process and a post-tantalum deposition heat treatment process. That is, 0.5 wt % of tantalum alkoxide was added to the Fe--Si alloy powder and mixed in a mortar. As the tantalum alkoxide, pentaethoxytantalum (hereinafter referred to as Ta(OC ₂ H ₅ ) ₅ ) represented by the chemical formula Ta(OC ₂ H ₅ ) ₅ was used. After adding and mixing Ta(OC ₂ H ₅ ) ₅ , the Fe-Si alloy powder was exposed to high heat at 1000° C. for 2 hours under nitrogen atmosphere. It should be noted that the temperature profile required a total of 10 hours, including the time to raise the temperature to the temperature range of 1000° C. for 2 hours and the time to lower the temperature.

Next, an insulation treatment step was carried out, in which 0.5 wt % silicone oligomer was added and mixed with the Fe--Si alloy powder, and the mixture was dried in an atmosphere at a temperature of 200° C. for 2 hours. 1.6 wt% silicone resin (solid content 50%) was added and mixed with the Fe--Si alloy powder that had passed through a sieve with an opening of 250 μm, and the mixture was dried in an atmosphere at a temperature of 150° C. for 2 hours.

In order to eliminate agglomeration, the powder for powder magnetic core was passed through a sieve with an opening of 250 μm, and 0.5 wt % of a lubricant (Acrawax (registered trademark)) was added. A mold was filled with powder for powder magnetic core to which a lubricant had been added, and press molding was performed to obtain a toroidal molded body having an outer diameter of 16.5 mm, an inner diameter of 11.0 mm, and a height of 5.0 mm. Press molding was performed at a pressure of 15 ton/cm ² . After the molded body was produced, the molded body was placed in an atmosphere with an oxygen concentration of 0.01% and fired at 850° C. for 2 hours. In this way, a powder magnetic core was produced.

In addition, various powders for powder magnetic cores and powder magnetic cores were produced. Various _{dust cores} are made by adding alumina powder _, Si(OC ₂ H ₅ ) _{4 , Nb} ( _{OC 2} H ₅ ) ₅ and Ti(On-C ₄ H ₉ ) ₄ were added and mixed. The powder cores were all identical except for the types of additives, including the amount added, mixing method, and exposure to 1000 °C and nitrogen atmosphere for 2 hours, with a total temperature profile time of 10 hours. Manufactured according to the manufacturing method, manufacturing conditions and composition.

Furthermore, Ta(OC ₂ H ₅ ) ₅ , alumina powder with an average primary particle diameter of 13 mm, Si(OC ₂ H ₅ ) ₄ , Nb(OC ₂ H ₅ ) ₅ and Ti(O-n-C ₄ H ₉ ) Powder magnetic cores having different heating temperatures after adding and mixing ₄ were prepared. In addition to 1000°C, 800°C and 900°C were added as heating temperatures. Regarding Ta(OC ₂ H ₅ ) ₅ and Si(OC ₂ H ₅ ) ₄ , the powder was not heat-treated after adding Ta(OC ₂ H ₅ ) ₅ and Si(OC ₂ H ₅ ) ₄ . A magnetic core was also fabricated.

Density of each powder magnetic core (g/cm ³ ), magnetic permeability μ0 at 0 A/m, magnetic permeability μ1 at 10 kA/m, iron loss Pcv (kW/m ³ ), hysteresis loss Ph (kW/m ³ ), and vortex Current loss Pe (kW/m ³ ) 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.

When measuring the magnetic permeability μ0 and μ1, a copper wire with a diameter of 0.5 mm was wound 17 turns around the powder magnetic core. When measuring the loss, a powder magnetic core was wound with 17 turns of a copper wire having a diameter of 0.5 mm as a primary winding, and 17 turns as a secondary winding. Then, by using an LCR meter (Agilent Technologies: 4284A), magnetic permeability μ0 and μ1 were calculated from the inductance of the magnetic field strength at 100 kHz and 1.0 V. In addition, iron loss Pcv (kW/m ³ ) was measured using a BH analyzer (Iwatsu Keizoku Co., Ltd.: SY-8219), which is a magnetic measurement device, under measurement conditions of a frequency of 100 kHz and a maximum magnetic flux density Bm of 100 mT. I did it.

Furthermore, hysteresis loss Ph (kW/m ³ ) and eddy current loss Pe (kW/m ³ ) were calculated from the measurement results of iron loss Pcv. The hysteresis loss Ph (kW/m ³ ) and the eddy current loss Pe (kW/m ³ ) are determined by calculating the hysteresis loss coefficient (Kh ), and calculated the eddy current loss coefficient (Ke).
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

Table 1 below shows Fe-Si alloy powder containing Ta(OC ₂ H ₅ ) ₅ , alumina powder, Si(OC ₂ H ₅ ) ₄ , Nb(OC ₂ H ₅ ) ₅ or Ti(O-n-C ₄ H ₉ ) Shows the state of heat treatment after adding and mixing ₄ . In Table 1, the circles indicate that sintering of the Fe--Si alloy powder is suppressed and the next insulation treatment process, molding process, and annealing process are possible. On the other hand, in Table 1, the x mark indicates that the Fe--Si alloy powders were sintered to such an extent that they could not proceed to the next insulation treatment process, molding process, and annealing process.

(Table 1)

Table 2 below shows Fe-Si alloy powder containing Ta(OC ₂ H ₅ ) ₅ , alumina powder, Si(OC ₂ H ₅ ) ₄ , Nb(OC ₂ H ₅ ) ₅ or Ti(O-n-C ₄ H ₉ ) Density of powder magnetic core (g/cm ³ ) of _{No. 4} , magnetic permeability μ0 at 0 A/m, magnetic permeability μ1 at 10 kA/m, iron loss Pcv (kW/m ³ ), hysteresis loss Ph (kW/m ³ ) and eddy current loss Pe (kW/m ³ ).

(Table 2)

As shown in Table 1, no sintering was observed in the Fe--Si alloy powder to which Ta(OC ₂ H ₅ ) ₅ was added and mixed when it was placed in a temperature environment of 1000° C. in the heat treatment step after adding tantalum. In the case of alumina powder, when heat treated at 1000° C., the Fe-Si alloy powder was sintered in some places, but it was possible to produce a powder magnetic core to the extent that various properties could be measured. On the other hand, in the case of Si(OC ₂ H ₅ ) ₄ , Nb(OC ₂ H ₅ ) ₅ and Ti(O-n-C ₄ H ₉ ) ₄ , when heat treated at 1000°C, the Fe-Si alloy powders sinter. Therefore, it was not possible to produce a powder magnetic core to the extent that various properties could be measured.

As shown in Table 2, in the case of alumina powder that can be heat treated at 1000°C, magnetic permeability μ0 at 0 A/m, magnetic permeability μ1 at 10 kA/m, iron loss Pcv (kW/m ³ ), hysteresis loss Ph (kW/ m ³ ) and eddy current loss Pe (kW/m ³ ) were all deteriorated compared to the alumina powder heat-treated at 900°C. In particular, the hysteresis loss Ph (kW/m ³ ) and eddy current loss Pe (kW/m ³ ) deteriorated significantly.

Due to the heat treatment at 1000° C., the alumina powder agglomerated and the Fe-Si alloy powder was sintered, and the magnetic domains were not subdivided and the eddy current loss Pe (kW/m ³ ) worsened. In particular, it was confirmed that since the median diameter D50 of the Fe--Si alloy powder was 20 μm or less, the Fe--Si alloy powder was oxidized and sintering was accelerated.

On the other hand, as shown in Table 2, in the case of Ta(OC ₂ H ₅ ) ₅ that can be heat-treated at 1000°C, the magnetic permeability μ0 at 0 A/m, the magnetic permeability μ1 at 10 kA/m, and the eddy current loss Pe (kW/m ³ ) became comparable to that at 900°C. Iron loss Pcv (kW/m ³ ) and hysteresis loss Ph (kW/m ³ ) were further improved when heat treated at 1000°C compared to when heat treated at 900°C.

By being able to perform the heat treatment at 1000°C, the strain in the crystals of the Fe--Si alloy powder was released, and the hysteresis loss was further improved. Furthermore, the altered substance from Ta(OC ₂ H ₅ ) ₅ to tantalum or tantalum oxide diffuses, suppressing lattice defects in the Fe--Si alloy powder and smoothing domain wall movement. Furthermore, even when heat treated at 1000°C, in the case of Ta(OC ₂ H ₅ ) ₅ , even Fe-Si alloy powder with a median diameter D50 of 20 μm or less does not sinter, and the eddy current loss Pe (kW/m ³ ) was good.

Next, powder magnetic cores were produced using powder for powder magnetic cores to which Ta(OC ₂ H ₅ ) ₅ was added in various amounts. These powder magnetic cores were also added with Ta(OC ₂ H ₅ ) ₅ in the tantalum addition step, and heated at 1000° C. in the post-tantalum addition heat treatment step. In the annealing process, it was exposed to a temperature environment of 930°C. Other than that, except for the difference in the amount of Ta(OC ₂ H ₅ ) ₅ added, each dust core powder and dust core were manufactured using the same manufacturing method, manufacturing conditions, and composition.

The amount of Ta(OC ₂ H ₅ ) ₅ added was varied in the range of 0.1 wt% to 2.20 wt% with respect to the Fe-Si alloy powder. Then, the density (g/cm ³ ), iron loss Pcv (kW/m ³ ), hysteresis loss Ph (kW/m ³ ), and eddy current loss Pe (kW/m ³ ) of each dust core were measured. The results are shown in Table 3.

(Table 3)

Also, based on Table 3, a diagram in which the horizontal axis represents the addition amount and the vertical axis represents iron loss Pcv (kW/m ³ ), hysteresis loss Ph (kW/m ³ ), and eddy current loss Pe (kW/m ³ ) I created a graph of 1. In Figure 1, the graph with a circle plot is the iron loss Pcv (kW/m ³ ), the graph with a triangle plot is the hysteresis loss Ph (kW/m ³ ), and the graph with a square plot is the vortex loss. Current loss Pe (kW/m ³ ).

As shown in Table 3 and FIG. 1, when the amount of Ta(OC ₂ H ₅ ) ₅ added to the Fe-Si alloy powder is 0.25 wt% or more and 2.0 wt%, the hysteresis loss Ph (kW It can be confirmed that the effect of reducing the eddy current loss Pe (kW/m ³ ) and eddy current loss Pe (kW/m ³ ) is high. Furthermore, when the amount of Ta(OC ₂ H ₅ ) ₅ added to the Fe-Si alloy powder is 0.5 wt% or more and 1.5 wt%, the effect of reducing hysteresis loss Ph (kW/m ³ ) is particularly high. It can be confirmed that it is high.

The embodiments and examples of the present invention have been presented as examples, and the present invention is not limited to the above embodiments and examples. The embodiments and examples 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, examples, and modifications thereof are included within the scope of the present invention.

Claims (10)

soft magnetic powder,
tantalum alkoxide adhering to the surface of the soft magnetic powder;
to have
Powder for powder magnetic cores featuring: The tantalum alkoxide is attached to the soft magnetic powder at a ratio of 0.25 wt% or more to 2.0 wt%;
The powder for powder magnetic core according to claim 1, characterized by: The tantalum alkoxide is attached to the soft magnetic powder at a ratio of 0.5 wt% or more to 1.5 wt%;
The powder for powder magnetic core according to claim 2, characterized in that: The soft magnetic powder has a powder particle size of 20 μm or less at D50 in the particle size distribution;
The powder for powder magnetic core according to any one of claims 1 to 3, characterized by: the soft magnetic powder is FeSi alloy powder;
The powder for powder magnetic core according to any one of claims 1 to 4, characterized by: Containing the powder for powder magnetic core according to any one of claims 1 to 5,
A powder magnetic core featuring: the tantalum alkoxide is altered and attached to tantalum oxide;
The powder magnetic core according to claim 6, characterized by: a tantalum adhesion step of adding and mixing tantalum alkoxide to soft magnetic powder;
After the tantalum adhesion step, a post-tantalum adhesion heating step of heating the soft magnetic powder in an atmosphere at a temperature of 1000° C. or higher;
including;
A method for producing powder for powder magnetic core, characterized by: further comprising a classification step of classifying the soft magnetic powder so that D50 in the particle size distribution is 20 μm or less,
transferring the soft magnetic powder that has undergone the classification step to the tantalum adhesion step;
The method for producing powder for powder magnetic core according to claim 8, characterized in that: After the tantalum adhesion step by the manufacturing method according to claim 8 or 9, a molding step of press-molding the soft magnetic powder into a molded body of a predetermined shape;
a heat treatment step of annealing the molded body;
including;
A method for producing a dust core characterized by:

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