WO2024262543A1 - Magnetic component and magnetic powder - Google Patents

Abstract

This magnetic component includes a magnetic powder, wherein the magnetic powder includes a metal portion, an oxide film, and at least one specific kind of particles. The specific particles contain Cu as a main component. The specific particles are present at the interface between the metal portion and the oxide film. The specific particles have a particle size of 3 to 70 nm.

Description

Magnetic parts and powders

The present invention relates to a magnetic component that includes magnetic powder, and to the magnetic powder used in the magnetic component.

Patent Document 1 discloses a soft magnetic powder including particles having a composition expressed by Fe _x Cu _a Nb _b (Si _1-y B _y ) _100-x-a-b , the particles including crystal grains and Cu segregated portions, the crystal grains having a grain size of 1.0 nm or more and 30.0 nm or less, and Cu segregated in the Cu segregated portions, and a dust core including this soft magnetic powder. Patent Document 2 discloses a nanocrystalline soft magnetic alloy having an alloy composition represented by Fe _100-a-b-c-d M _a Si _b B _c Cu _d , at least a portion of which contains crystal grains, the crystal grains having an average grain size of 50 nm or less, and a Cu segregation portion present in the nanocrystalline soft magnetic alloy at a position deeper than 2 nm from the surface of the nanocrystalline soft magnetic alloy, in which Cu elements are segregated, and a magnetic core using this nanocrystalline soft magnetic alloy. Furthermore, Patent Document 3 discloses an amorphous alloy ribbon having an alloy composition represented by Fe _100-a-b-c-d M _a Si _b B _c Cu _d , in which a Cu segregation portion is present on the surface side of the amorphous alloy ribbon, and in which Cu is segregated at a higher concentration in the Cu segregation portion than in the outermost surface portion of the amorphous alloy ribbon, and a magnetic core using a nanocrystalline soft magnetic alloy obtained by heat-treating the amorphous alloy ribbon to nanocrystallize it.

JP 2022-121260 A Patent No. 5429613 Patent No. 5339192

Magnetic components such as magnetic cores require high DC bias characteristics and low iron loss in order to be compact and handle large currents.

The present invention aims to provide magnetic components that meet the above requirements and magnetic powder that is suitable as a material for such magnetic components.

One aspect of the present invention provides a first magnetic component,
A magnetic component comprising a magnetic powder,
The magnetic powder includes a metal portion, an oxide film, and at least one specific particle,
The specific particles are mainly composed of Cu,
the specific particles are present at an interface between the metal portion and the oxide film,
The specific particles provide a magnetic component having a particle size of 3 to 70 nm.

In another aspect of the present invention, the first magnetic powder is
A magnetic powder comprising a metal portion, an oxide film, and at least one specific particle,
The specific particles are mainly composed of Cu,
the specific particles are present at an interface between the metal portion and the oxide film,
The specific particles provide a magnetic powder having a particle size of 3 to 70 nm.

The magnetic powder provided in the magnetic component of the present invention has the following characteristics: the magnetic powder comprises a metal portion, an oxide film, and at least one specific particle; the specific particle is mainly composed of Cu; the specific particle is present at the interface between the metal portion and the oxide film; the specific particle has a particle size of 3 to 70 nm. As a result, the magnetic component of the present invention has high DC superposition characteristics and also suppresses iron loss.

The object of the present invention will be appreciated and its configuration will be more completely understood by studying the following description of the best mode for carrying out the invention in conjunction with the accompanying drawings.

1 is a schematic cross-sectional view showing a portion of a magnetic component according to an embodiment of the present invention; FIG. 2 is a schematic cross-sectional view showing a part of a magnetic powder used as a material for the magnetic component of FIG. 1 . 1 is a scanning transmission electron microscope (STEM) image showing a portion of the magnetic powder of Example 7. In the figure, the locations where area analysis was performed are indicated as P1, P2, P3, and P4, respectively.

The present invention can be realized in various modifications and forms, but as an example, a specific embodiment as shown in the drawings will be described in detail below. The drawings and embodiments do not limit the present invention to the specific form disclosed herein, but include all modifications, equivalents, and alternative examples within the scope of the appended claims.

Referring to FIG. 1, the magnetic part 500 according to the embodiment of the present invention is a composite magnetic body in which magnetic powder 100 is dispersed within a hardened binder 600. In other words, the magnetic part 500 includes magnetic powder 100.

The magnetic powder 100 according to the embodiment of the present invention is an Fe-based soft magnetic alloy powder in which Fe is the main element and the main phase is an amorphous phase. The composition of the magnetic powder 100 will be described later. The magnetic powder 100 according to the embodiment can be used as a direct material for producing various magnetic parts and dust cores.

Referring to FIG. 2, the magnetic powder 100 of this embodiment is composed of a plurality of particles 110 that are amorphous and have a substantially spherical shape. Note that the present invention is not limited to this, and the particles 110 may have a shape other than substantially spherical. The surfaces of the particles 110 of this embodiment are not coated with glass or the like. Note that the present invention is not limited to this, and the surfaces of the particles 110 may be coated with glass or the like. In the magnetic powder 100 in which the surfaces of the particles 110 are coated with glass or the like, improved insulation resistance and improved flowability are achieved compared to the magnetic powder 100 in which the surfaces of the particles 110 are not coated with glass or the like.

Referring to FIG. 2, the particle 110 of this embodiment comprises a metal part 200, an oxide film 300, and at least one specific particle 400. That is, the magnetic powder 100 of this embodiment comprises a metal part 200, an oxide film 300, and at least one specific particle 400.

Referring to FIG. 2, the metal part 200 of this embodiment is mainly composed of Fe. The metal part 200 has a crystalline phase. More specifically, the metal part 200 has nanocrystals. These nanocrystals are generated by heat treating the magnetic powder 100 as described below. The metal part 200 is located deeper from the surface of the particle 110 than the oxide film 300.

Referring to FIG. 2, the oxide film 300 of this embodiment is a film whose main component is oxide. That is, the oxide film 300 is mainly composed of O. The proportion of O contained in the oxide film 300 is 35 at % or more. The oxide film 300 is located shallower from the surface of the particle 110 than the metal portion 200. The oxide film 300 forms the surface of the magnetic powder 100.

Referring to FIG. 2, the specific particle 400 of this embodiment is mainly composed of Cu. At least one of the specific particles 400 is located at the interface between the metal part 200 and the oxide film 300. In other words, the magnetic powder 100 contains at least one specific particle 400 located at the interface between the metal part 200 and the oxide film 300. In the radial direction of the particle 110, one surface of the specific particle 400 is in contact with the metal part 200, and the other surface of the specific particle 400 is in contact with the oxide film 300. The magnetic powder 100 may be configured such that at least one of the specific particles 400 is located at the interface between the metal part 200 and the oxide film 300, and at least another of the specific particles 400 is located inside the oxide film 300. This is preferable because the magnetic powder 100 is less likely to become magnetically saturated.

Referring to FIG. 2, the specific particles 400 of this embodiment have a particle size of 3 to 70 nm. Furthermore, if the particle size of the specific particles 400 is too small, the magnetic coupling between the particles 110 cannot be suppressed. For this reason, it is preferable that the specific particles 400 have a particle size of 5 nm or more. Cu, which is the main component of the specific particles 400, is conductive. Therefore, if the particle size of the specific particles 400 is too large, eddy currents tend to flow in the specific particles 400 due to the AC magnetic field, increasing eddy current loss. For this reason, it is preferable that the specific particles 400 have a particle size of 50 nm or less.

The concentration of Cu contained in the specific particles 400 of this embodiment is 40 at% or more. In addition, the concentration of Cu contained in the specific particles 400 is preferably 60 at% or more in order to suppress magnetic coupling between the particles 110.

Referring to FIG. 2, the aspect ratio of the specific particle 400 of this embodiment is greater than 1. Furthermore, when the specific particle 400 has an elliptical cross section, the surface of the particle 110 can be efficiently rendered nonmagnetic, so it is preferable that the aspect ratio of the specific particle 400 is 1.4 or greater.

In the magnetic powder 100 of this embodiment, the specific particles 400 exist independently without being directly bonded to each other. However, the present invention is not limited to this, and multiple specific particles 400 may be directly bonded to each other to form larger particles. This is preferable because the magnetic powder 100 is less likely to become magnetically saturated.

2, the occupancy rate Oc of specific particles 400 in this embodiment is 4 to 60%. Here, the occupancy rate Oc is a value obtained by the following formula (1) when particle 110 of magnetic powder 100 is viewed at a predetermined cross section, where Lb is the length of the interface between metal portion 200 and oxide film 300, and Li (i=1 to n) is the length along the interface between metal portion 200 and oxide film 300 for each of n specific particles 400 located on the interface between metal portion 200 and oxide film 300.
Formula (1): Oc=(ΣLi)/Lb*100
If the occupancy rate of the specific particles 400 is too small, the magnetic coupling between the particles 110 cannot be suppressed. For this reason, it is preferable that the occupancy rate of the specific particles 400 is 10% or more. Since Cu, which is the main component of the specific particles 400, is conductive, there is a possibility that an eddy current will flow in the specific particles 400 due to an AC magnetic field. However, by locating the specific particles 400 at intervals, it is possible to ensure insulation between the specific particles 400 and suppress an increase in eddy current loss. For this reason, it is preferable that the occupancy rate of the specific particles 400 is 50% or less.

The composition range of the magnetic powder 100 according to this embodiment is explained in more detail below.

1, magnetic powder 100 of the present embodiment is represented by the composition formula Fe _{a Sib} B _{c Pd} Cu _e M _f excluding inevitable impurities. In the composition formula Fe _a Sib _{B c Pd} Cu _e M _f , M is Cr and/or Nb, and 75.4 at%≦a≦86.4 at%, 0 at%≦b≦9 at%, 4 at%≦c≦13 at%, 3 at%≦d≦12 at%, 0.3 at%≦e≦1.0 at%, and 0 at%≦f≦5 at%.

In the magnetic powder 100 according to the present embodiment, the Fe element is the main element and is an essential element responsible for magnetism. The higher the Fe ratio, the higher the magnetic flux density Bs and the lower the raw material price. Furthermore, if the Fe ratio falls below 75.4 at%, Tx1 (described later) becomes higher and ΔT (described later) becomes smaller. This makes it difficult to heat treat the magnetic powder 100, and the magnetic properties after heat treatment deteriorate. Furthermore, if the Fe ratio exceeds 86.4 at%, the amorphousness decreases significantly and the soft magnetic properties deteriorate. In addition, the crystallinity of the magnetic powder 100 is suppressed to improve the amorphousness, and the soft magnetic properties of the magnetic powder 100 after heat treatment are improved, so the Fe ratio is more preferably in the range of 77.9 to 84.9 at%.

In the magnetic powder 100 according to this embodiment, the Si element is the element responsible for forming the amorphous phase. When the magnetic powder 100 contains Si, ΔT (described later) becomes large, and heat treatment can be performed stably. However, if the proportion of Si exceeds 9 at%, the amorphous forming ability decreases, and it becomes impossible to obtain a magnetic powder 100 having an amorphous phase as the main phase, so the proportion of Si is preferably 9 at% or less.

In the magnetic powder 100 according to this embodiment, the B element is an essential element responsible for forming the amorphous phase. If the proportion of B falls below 4 at%, it becomes difficult to form an amorphous phase by rapid cooling when producing the magnetic powder 100, and good magnetic properties cannot be obtained. Furthermore, if the proportion of B exceeds 13 at%, the melting point becomes high, which is unfavorable for manufacturing, and the ability to form an amorphous phase also decreases. For this reason, the proportion of B is preferably in the range of 4 to 13 at%.

In the magnetic powder 100 according to the present embodiment, the P element is an essential element responsible for forming the amorphous phase. By including P in the magnetic powder 100, it becomes easier to form a fine and uniform nanocrystalline structure, and good magnetic properties can be obtained. In addition, P has a high affinity with Cu, and can efficiently form specific particles 400 near the surface of the particle 110. However, if the proportion of P exceeds 12 at%, the balance with other metalloid elements becomes poor, and the ability to form an amorphous phase decreases. Also, if the proportion of P exceeds 12 at%, the saturation magnetic flux density Bs decreases significantly. Furthermore, if the proportion of P falls below 3 at%, the crystal grains tend to become large, and good magnetic properties cannot be obtained. For this reason, the proportion of P is preferably in the range of 3 to 12 at%.

In the magnetic powder 100 according to this embodiment, the Cu element is an essential element that contributes to the formation of the nanocrystalline phase. If the Cu ratio is below 0.3 at%, there is little cluster precipitation during heat treatment, making uniform nanocrystallization difficult. If the Cu ratio exceeds 1.0 at%, the amorphous forming ability decreases and the occupancy rate of the specific particles 400 becomes too large. For this reason, it is preferable that the Cu ratio is in the range of 0.3 to 1.0 at%. In particular, in order to improve the amorphous nature of the magnetic powder 100 and enable uniform nanocrystallization, and to make the size and occupancy rate of the specific particles 400 appropriate and to improve the soft magnetic properties after heat treatment, it is more preferable that the Cu ratio is 0.7 at% or less.

In the magnetic powder 100 of this embodiment, the proportion of M is 0 at% or more and 5 at% or less. Here, M is Cr and/or Nb.

The inclusion of Cr in the magnetic powder 100 of this embodiment makes it easier for an oxide film 300 to form on the surface of the particles 110 of the magnetic powder 100, improving corrosion resistance. Furthermore, the inclusion of Nb in the magnetic powder 100 of this embodiment inhibits the growth of bccFe (αFe) crystal grains during nanocrystallization, making it easier to form a fine nanocrystalline structure. However, the inclusion of Cr and Nb relatively reduces the proportion of Fe in the magnetic powder 100, so that the saturation magnetic flux density Bs of the magnetic powder 100 decreases, and the ability of the magnetic powder 100 to form an amorphous phase also decreases. Therefore, the proportion of M in the magnetic powder 100 needs to be 5 at% or less.

The magnetic powder 100 according to this embodiment is preferably one in which 3 at% or less of Fe is replaced with one or more elements selected from Co, Ni, Zn, Zr, Hf, Mo, Ta, W, Ag, Au, Pd, Na, K, Ca, Mg, Sn, Ti, V, Mn, Al, S, C, O, N, Bi and rare earth elements. This makes it possible to easily precipitate uniform nanocrystals in the magnetic powder 100 when the magnetic powder 100 is heat-treated, and also makes it possible to keep the adverse effects of the above elements in the magnetic powder 100 on the magnetic properties, etc., within an acceptable range.

The magnetic powder 100, magnetic component 500, and manufacturing method thereof in this embodiment will be described in more detail below.

The magnetic powder 100 of this embodiment can be produced by an atomization method such as a water atomization method or a gas atomization method. The magnetic powder 100 produced in this manner has a non-crystalline phase (amorphous phase) as the main phase and is composed of a plurality of particles 110 that are approximately spherical. The present invention is not limited to this, and the magnetic powder 100 may be composed of flakes formed by crushing an amorphous ribbon. In other words, the particles 110 that constitute the magnetic powder 100 of the present invention do not have to be approximately spherical. Even if the magnetic powder 100 is formed by crushing an amorphous ribbon in this manner, it can have a high saturation magnetic flux density Bs and a high relative magnetic permeability μ by having the configuration of the present invention.

In the powder production process using the atomization method, first, the raw materials are prepared. Next, the raw materials are weighed to obtain the specified composition and melted to produce a molten alloy. At this time, since the magnetic powder 100 of this embodiment has a low melting point, the power consumption required for melting can be reduced. Next, the molten alloy is discharged from a nozzle and is broken into alloy droplets using high-pressure gas or water, thereby producing fine magnetic powder 100.

In the above-mentioned powder production process, the gas used for fragmentation may be an inert gas such as argon or nitrogen. In addition, to improve the cooling rate, the alloy droplets immediately after fragmentation may be rapidly cooled by contacting them with a cooling liquid or solid, or the alloy droplets may be fragmented again to further refine them. When a liquid is used for cooling, for example, water or oil may be used. When a solid is used for cooling, for example, a rotating copper roll or a rotating aluminum plate may be used. However, the liquid or solid used for cooling is not limited to these, and various materials may be used.

Here, the quenching rate by the atomization method is 10 ³ K/s or more. If the quenching rate is less than 10 ³ K/s, the amount of precipitated initial crystals (mainly bccFe) increases, and accordingly, the amount of Cu precipitated in the metal part 200 increases. If the quenching rate is less than 10 ³ K/s, the composition of the amorphous phase in the magnetic powder 100 deviates from the desired composition, and the glass transition temperature Tg does not appear. In addition, if the quenching rate is less than 10 ³ K/s, the first crystallization start temperature Tx1 shifts to the high temperature side, or the temperature peak due to the first crystallization decreases. It is preferable that the quenching rate by the atomization method is 10 ⁴ K/s or more.

Furthermore, the magnetic powder 100 of the present invention preferably contains nanocrystals. Here, the magnetic powder 100 containing nanocrystals is obtained by subjecting the magnetic powder 100 to a heat treatment under predetermined heat treatment conditions as described below, thereby precipitating nanocrystals of bccFe (αFe).

When the magnetic powder 100 is heat-treated in a low-oxygen atmosphere mainly composed of an inert gas such as argon, it is crystallized two or more times. The temperature at which the first crystallization starts is called the first crystallization start temperature (Tx1), and the temperature at which the second crystallization starts is called the second crystallization start temperature (Tx2). The temperature difference between the first crystallization start temperature (Tx1) and the second crystallization start temperature (Tx2) is called ΔT = Tx2 - Tx1. The first crystallization start temperature (Tx1) is the exothermic peak of the precipitation of nanocrystals of αFe, and the second crystallization start temperature (Tx2) is the exothermic peak of the precipitation of compounds such as FeB and FeP. These crystallization start temperatures can be evaluated, for example, by performing a thermal analysis at a heating rate of about 10°C/min using a differential scanning calorimetry (DSC) device.

In order to precipitate αFe nanocrystals in the magnetic powder 100, it is desirable to perform heat treatment at a temperature equal to or lower than the second crystallization onset temperature (Tx2) so as to suppress the precipitation of the compound phase. Here, if ΔT is large, heat treatment under the specified heat treatment conditions becomes easier. Therefore, it is possible to obtain magnetic powder 100 with good soft magnetic properties by precipitating only αFe nanocrystals by heat treatment. In other words, by adjusting the elemental composition of magnetic powder 100 so as to increase ΔT and then performing heat treatment, the αFe nanocrystal structure contained in magnetic powder 100 becomes stable, and the iron loss of magnetic component 500 including magnetic powder 100 containing αFe nanocrystals is also reduced.

In order to produce magnetic powder 100 containing nanocrystals, the magnetic powder 100 produced by the above-mentioned powder production process is heat-treated as described above to precipitate αFe nanocrystals in the magnetic powder 100. As described above, this heat treatment must be performed at or below the second crystallization onset temperature (Tx2) so as not to precipitate a compound phase. In addition, this heat treatment is preferably performed at a temperature of 300°C or higher in a low-oxygen atmosphere mainly composed of an inert gas such as nitrogen or argon in order to form an oxide film 300 on the surface of the particles 110 of the magnetic powder 100.

The magnetic powder 100 produced by the above-mentioned powder production process can be used to manufacture the magnetic part 500. For example, the magnetic powder 100 can be molded into a predetermined shape and then heat-treated under predetermined heat treatment conditions to manufacture the magnetic part 500. The magnetic part 500 can also be used to manufacture magnetic parts such as transformers, inductors, motors, and generators. The method for manufacturing the magnetic part 500 of this embodiment using the magnetic powder 100 is described below.

The manufacturing method of the magnetic component 500 of this embodiment includes a step of producing a mixture of the magnetic powder 100 of this embodiment and the binder 600, a step of pressure-molding this mixture to produce a molded body, and a step of heat-treating this molded body.

First, in the process of producing a mixture of magnetic powder 100 and binder 600, the magnetic powder 100 of this embodiment is mixed with binder 600 having good insulating properties such as resin to obtain a mixture (granulated powder). When resin is used as binder 600, for example, silicone, epoxy, phenol, melamine, polyurethane, polyimide, or polyamideimide may be used. In order to improve insulating properties and binding properties, materials such as phosphates, borates, chromates, oxides (silica, alumina, magnesia, etc.), inorganic polymers (polysilane, polygermane, polystannane, polysiloxane, polysilsesquioxane, polysilazane, polyborazylene, polyphosphazene, etc.) may be used as binder 600 instead of or together with resin. In addition, multiple binders 600 may be used in combination, and a coating of two or more layers may be formed using different binders 600. In addition, since the manufacturing of magnetic part 500 includes a process of heat-treating the molded body as described above, it is preferable to use a binder 600 with high heat resistance. Generally, the amount of binder 600 is preferably about 0.1 to 10 wt%, and considering insulation and filling rate, about 0.3 to 6 wt% is preferable. However, the amount of binder 600 can be appropriately determined taking into consideration the powder particle size, applicable frequency, application, etc.

Next, in the process of producing a molded body by pressure molding the mixture, the granulated powder is pressure molded using a die to obtain a molded body. When pressure molding the granulated powder, in order to improve filling properties and suppress heat generation during nanocrystallization, powders such as Fe, FeSi, FeSiCr, FeSiAl, FeNi, and carbonyl iron powder that are softer than the magnetic powder 100 according to this embodiment may be mixed. Also, instead of or together with the above soft powder, any magnetic powder 100 having a particle size different from that of the magnetic powder 100 according to this embodiment may be mixed. In this case, the amount of the magnetic powder 100 mixed with the magnetic powder according to this embodiment is preferably 50 wt % or less.

Then, the molded body is subjected to a heat treatment under predetermined heat treatment conditions. This heat treatment causes αFe nanocrystals to precipitate in the magnetic powder 100. This heat treatment is similar to the heat treatment for the magnetic powder 100 described above, and must be performed at or below the second crystallization onset temperature (Tx2). In addition, in order to form an oxide film 300 on the surface of the particles 110 of the magnetic powder 100, this heat treatment is preferably performed at a temperature of 300°C or higher in a low-oxygen atmosphere mainly composed of an inert gas such as nitrogen or argon.

In the present embodiment, the magnetic part 500 is manufactured using magnetic powder 100 that has not been heat-treated as a raw material, but the present invention is not limited to this, and the magnetic part 500 may be manufactured using magnetic powder 100 that has been heat-treated in advance to precipitate αFe nanocrystals as a raw material. In this case, the magnetic part 500 can be manufactured by carrying out granulation and pressure molding in the same manner as in the manufacturing process of the magnetic part 500 described above.

The magnetic powder 100 of the present embodiment is used in the magnetic component 500 of the present embodiment, which is manufactured as described above, regardless of the manufacturing process. Similarly, the magnetic powder 100 of the present embodiment is used in the magnetic component 500 of the present embodiment.

The following describes the embodiment of the present invention in more detail with reference to several examples.

(Examples 1 to 39 and Comparative Examples 1 to 10)
As raw materials for the magnetic powders 100 of Examples 1 to 15, 24 to 28 and Comparative Examples 1 to 5, and 10 listed in Table 2 below, industrially pure iron, ferrosilicon, ferrophosphorus, ferroboron, ferrochrome, and electrolytic copper were prepared. The raw materials were weighed to obtain the alloy compositions of Examples 1 to 39 and Comparative Examples 1 to 10, and melted by high-frequency melting in an argon atmosphere to prepare molten alloys. Next, the prepared molten alloys were quenched by water atomization to prepare magnetic powders 100 with an average particle size of 3 to 15 μm. Similarly to the above, magnetic powders 100 with an average particle size of 15 to 65 μm were prepared for the magnetic powders 100 of Examples 16 to 23, 29 to 39 and Comparative Examples 6 to 9 listed in Table 2 below.

The magnetic powder 100 produced in Example 7 was heat-treated in an electric furnace in a low-oxygen atmosphere mainly composed of inert gas at a predetermined temperature between 375°C and 475°C for a predetermined time. In this heat treatment, the oxygen concentration in the treatment atmosphere was set to be in the range of 5 to 10,000 ppm, and the oxygen concentration at the start of the temperature rise was set to be higher than the oxygen concentration after a predetermined time had passed. This heat treatment also nano-crystallizes the magnetic powder 100.

A thin film sample was prepared from the magnetic powder 100 of Example 7 after heat treatment by the FIB (focused ion beam) method. The prepared thin film sample was observed with a scanning transmission electron microscope (STEM). In addition, elemental mapping analysis and area analysis were performed on the prepared thin film sample by energy dispersive X-ray spectroscopy (STEM-EDS). The results of the STEM observation and elemental mapping analysis are shown in Figure 3. The locations where area analysis was performed (P1, P2, P3, P4) are also shown in Figure 3, and the elemental analysis results for each location are shown in Table 1.

From FIG. 3, it was confirmed that the magnetic powder 100 of Example 7 has a plurality of specific particles 400 mainly composed of Cu. Also, from FIG. 3 and Table 1, it was confirmed that the P1 portion of the magnetic powder 100 of Example 7 contains a high concentration of Cu at 69.2 at%. Also, from FIG. 3, it was confirmed that the particle size of the particle at P1 is about 16 nm. Furthermore, from FIG. 3 and Table 1, it was confirmed that the P2 and P3 portions of the magnetic powder 100 of Example 7 contain high concentrations of O at 67.9 at% and 60.1 at%, respectively, while there is almost no Cu. In addition, from FIG. 3 and Table 1, it was confirmed that the P4 portion of the magnetic powder 100 of Example 7 contains a high concentration of Fe at 80.6 at%, while there is almost no Cu. From these results, it was confirmed that the magnetic powder 100 of Example 7 comprises a metal part 200 whose main component is Fe, an oxide film 300 whose main component is O, and a plurality of specific particles 400 whose main component is Cu, the specific particles 400 are present at the interface between the metal part 200 and the oxide film 300, and the particle size of the specific particles 400 is in the range of 3 to 70 nm.

The magnetic powder 100 before heat treatment according to Examples 1 to 39 produced by the above method was used to produce the magnetic parts (dust cores) 500 according to Examples 1 to 39 by the following method.

First, the magnetic powder 100 of Examples 1 to 39 and the binder (silicone resin) 600 were mixed so that the ratio of the binder 600 to the magnetic powder 100 was 3 wt%, and the mixture was sized using a stainless steel sieve with a mesh size of 500 μm to obtain granules. The granules were then filled into a mold, and the granules filled in the mold were molded using a hydraulic press at a molding pressure of 490 MPa. This produced a cylindrical molded body with an outer diameter of 13 mm and an inner diameter of 8 mm. The molded body was then heated to a predetermined temperature between 375°C and 475°C at a heating rate of 30°C/min in a low-oxygen atmosphere mainly composed of inert gas using an infrared heating device, and then held at the predetermined temperature for 20 minutes, and then air-cooled to room temperature to produce the magnetic parts (powder magnetic cores) 500 of Examples 1 to 39. In this heat treatment, the oxygen concentration in the treatment atmosphere was set to be in the range of 5 to 10,000 ppm, and the oxygen concentration at the start of the temperature rise was set to be higher than the oxygen concentration immediately before air cooling. This heat treatment also hardens the silicone resin, which is the binder 600, and nano-crystallizes the magnetic powder 100.

Furthermore, magnetic parts (dust cores) according to Comparative Examples 1 to 10 were produced using the powders of Comparative Examples 1 to 10 in a manner similar to that described above.

After cutting the powder magnetic cores 500 of Examples 1 to 39, CP (Cross Section Polisher) processing was performed, and thin film samples were prepared by the FIB (Focused Ion Beam) method. The thin film samples thus prepared were observed with a TEM to obtain multiple TEM images, and elemental analysis was performed using an EDX attached to the TEM. Based on these observation and analysis results, the particle size, aspect ratio, and Cu concentration of the specific particles 400 in the magnetic powder 100 constituting the powder magnetic cores 500 of Examples 1 to 39 were derived. Based on each of the obtained TEM images, the length Lb of the interface between the metal part 200 and the oxide film 300 and the length Li (i = 1 to n) along the interface between the metal part 200 and the oxide film 300 for each of the n specific particles 400 located on the interface between the metal part 200 and the oxide film 300 were derived, and the occupancy Oc was calculated using the above formula (1), and the average value of the obtained occupancy Oc was set as the occupancy Oc of the powder cores 500 of Examples 1 to 39. In addition, the particle size, aspect ratio, and Cu concentration of the specific particles in the powder constituting the powder cores of Comparative Examples 1 to 10 were derived using a method similar to the above method, and the occupancy Oc was calculated. These results are shown in Table 2.

From Table 2, it can be seen that in the powder magnetic cores 500 of Examples 1 to 28, the particle size of the specific particles 400 containing Cu as the main component is in the range of 3 to 70 nm, the concentration of Cu contained in the specific particles 400 is 40 at% or more, the aspect ratio of the specific particles 400 is greater than 1, and the occupancy rate of the specific particles 400 is in the range of 4 to 60%.

Also, from Table 2, it can be seen that the magnetic powders 100 of Examples 29 and 30 have 3 at% or less of Fe replaced with C, but in the powder cores 500 of Examples 29 and 30, the particle size of the specific particles 400 containing Cu as the main component is in the range of 3 to 70 nm, the concentration of Cu contained in the specific particles 400 is 40 at% or more, the aspect ratio of the specific particles 400 is greater than 1, and the occupancy rate of the specific particles 400 is in the range of 4 to 60%.

Furthermore, from Table 2, it can be seen that while the magnetic powder 100 of Example 31 has 3 at% or less of Fe replaced with Co, in the powder core 500 of Example 31, the particle size of the specific particles 400 containing Cu as the main component is in the range of 3 to 70 nm, the concentration of Cu contained in the specific particles 400 is 40 at% or more, the aspect ratio of the specific particles 400 is greater than 1, and the occupancy rate of the specific particles 400 is in the range of 4 to 60%.

In addition, from Table 2, it can be seen that the magnetic powder 100 of Example 32 has 3 at% or less of Fe replaced with Zn, but in the powder core 500 of Example 32, the particle size of the specific particles 400 mainly composed of Cu is in the range of 3 to 70 nm, the concentration of Cu contained in the specific particles 400 is 40 at% or more, the aspect ratio of the specific particles 400 is greater than 1, and the occupancy rate of the specific particles 400 is in the range of 4 to 60%.

In addition, from Table 2, it can be seen that the magnetic powders 100 of Examples 33 and 34 have 3 at% or less of Fe replaced with Sn, but in the powder cores 500 of Examples 33 and 34, the particle size of the specific particles 400 containing Cu as the main component is in the range of 3 to 70 nm, the concentration of Cu contained in the specific particles 400 is 40 at% or more, the aspect ratio of the specific particles 400 is greater than 1, and the occupancy rate of the specific particles 400 is in the range of 4 to 60%.

In addition, from Table 2, it can be seen that the magnetic powder 100 of Example 35 has 3 at% or less of Fe replaced with Ni, but in the powder core 500 of Example 35, the particle size of the specific particles 400 containing Cu as the main component is in the range of 3 to 70 nm, the concentration of Cu contained in the specific particles 400 is 40 at% or more, the aspect ratio of the specific particles 400 is greater than 1, and the occupancy rate of the specific particles 400 is in the range of 4 to 60%.

In addition, from Table 2, it can be seen that the magnetic powder 100 of Example 36 has 3 at% or less of Fe replaced with Mn, but in the powder core 500 of Example 36, the particle size of the specific particles 400 containing Cu as the main component is in the range of 3 to 70 nm, the concentration of Cu contained in the specific particles 400 is 40 at% or more, the aspect ratio of the specific particles 400 is greater than 1, and the occupancy rate of the specific particles 400 is in the range of 4 to 60%.

In addition, from Table 2, it can be seen that the magnetic powder 100 of Example 37 has 3 at% or less of Fe replaced with Al, but in the powder core 500 of Example 37, the particle size of the specific particles 400 containing Cu as the main component is in the range of 3 to 70 nm, the concentration of Cu contained in the specific particles 400 is 40 at% or more, the aspect ratio of the specific particles 400 is greater than 1, and the occupancy rate of the specific particles 400 is in the range of 4 to 60%.

In addition, from Table 2, it can be seen that the magnetic powder 100 of Example 38 has 3 at% or less of Fe replaced with Ti, but in the powder core 500 of Example 38, the particle size of the specific particles 400 containing Cu as the main component is in the range of 3 to 70 nm, the concentration of Cu contained in the specific particles 400 is 40 at% or more, the aspect ratio of the specific particles 400 is greater than 1, and the occupancy rate of the specific particles 400 is in the range of 4 to 60%.

In addition, from Table 2, it can be seen that the magnetic powder 100 of Example 39 has 3 at% or less of Fe replaced with O, but in the powder core 500 of Example 39, the particle size of the specific particles 400 mainly composed of Cu is in the range of 3 to 70 nm, the concentration of Cu contained in the specific particles 400 is 40 at% or more, the aspect ratio of the specific particles 400 is greater than 1, and the occupancy rate of the specific particles 400 is in the range of 4 to 60%.

On the other hand, from Table 2, it can be seen that the powder of Comparative Example 1 has an Fe content of less than 75.4 at% and the powder of Comparative Example 2 has an Fe content of more than 86.4 at%. However, in the powder cores of Comparative Examples 1 and 2, the particle size of the specific particles is less than 3 nm, the Cu concentration in the specific particles is less than 40 at%, and the occupancy rate of the specific particles is not within the range of 4 to 60%.

In addition, Table 2 shows that the powder of Comparative Example 3 has a Si content of more than 9 at%, but in the powder magnetic core of Comparative Example 3, the particle size of the specific particles is less than 3 nm, the Cu concentration in the specific particles is less than 40 at%, and the occupancy rate of the specific particles is not within the range of 4 to 60%.

Furthermore, from Table 2, it can be seen that the powder of Comparative Example 4 has a B content of less than 4 at% and the powder of Comparative Example 5 has a B content of more than 13 at%. However, in the powder cores of Comparative Examples 4 and 5, the particle size of the specific particles is less than 3 nm, the Cu concentration in the specific particles is less than 40 at%, and the occupancy rate of the specific particles is not within the range of 4 to 60%.

Furthermore, from Table 2, it can be seen that the powder of Comparative Example 6 has a P content of less than 3 at% and the powder of Comparative Example 7 has a P content of more than 12 at%; however, in the powder core of Comparative Example 6, the particle size of the specific particles is less than 3 nm and the Cu concentration in the specific particles is less than 40 at%, so the occupancy rate of the specific particles is not within the range of 4 to 60%, and in the powder core of Comparative Example 7, the particle size of the specific particles is more than 70 nm and so the occupancy rate of the specific particles is not within the range of 4 to 60%.

Furthermore, from Table 2, it can be seen that the powder of Comparative Example 8 has a Cu content of less than 0.3 at% and the powder of Comparative Example 9 has a Cu content of more than 1.0 at%; however, in the powder core of Comparative Example 8, the particle size of the specific particles is less than 3 nm, the Cu concentration in the specific particles is less than 40 at%, and the occupancy rate of the specific particles is not within the range of 4 to 60%, and in the powder core of Comparative Example 9, the particle size of the specific particles is more than 70 nm, and the occupancy rate of the specific particles is not within the range of 4 to 60%.

Furthermore, from Table 2, it can be seen that while the powder of Comparative Example 10 has an M content exceeding 5 at%, in the powder magnetic core of Comparative Example 10, the particle size of the specific particles is less than 3 nm, the Cu concentration in the specific particles is less than 40 at%, and the occupancy rate of the specific particles is not within the range of 4 to 60%.

For the produced powder cores 500 of Examples 1 to 15 and 24 to 28 and the powder cores of Comparative Examples 1 to 5 and 10, the DC superposition characteristics at 100 kHz were measured using an LCR meter connected to a dedicated DC bias power supply, and the retention rate R (%) was calculated. Here, the retention rate R is a value calculated by the following formula (2), where the measured value of L (or μ) at 0 kA/m is L0 (or μ0) and the measured value of L (or μ) at 8 kA/m is Lx (or μx).
Formula (2): R = Lx (or μx) / L0 (or μ0) * 100
Furthermore, for the powder magnetic cores 500 produced in Examples 1 to 15 and 24 to 28 and the powder magnetic cores in Comparative Examples 1 to 5 and 10, the iron loss Pcv (kW/m ³ ) under excitation conditions of 300 kHz and 50 mT was measured using a BH analyzer. These results are shown in Table 3.

From Table 3, it can be seen that in the powder magnetic cores 500 of Examples 1 to 15 and 24 to 28, the retention rate R was 70% or more, and the iron loss Pcv was 1250 kW/m3 ^or less.

On the other hand, from Table 3, it can be seen that in the powder magnetic cores of Comparative Examples 1 and 2 in which Fe is not within the range of 75.4 to 86.4 at%, the powder magnetic core of Comparative Example 3 in which Si exceeds 9 at%, the powder magnetic core of Comparative Example 4 in which B is less than 4 at%, the powder magnetic core of Comparative Example 5 in which B exceeds 13 at%, and the powder magnetic core of Comparative Example 10 in which M exceeds 5 at%, the retention rate R is less than 70% and the iron loss Pcv exceeds 1250 kW/ ^m3 .

From these findings, it can be seen that the powder magnetic cores 500 of Examples 1 to 15 and 24 to 28 have improved DC bias characteristics and reduced iron loss compared to the powder magnetic cores of Comparative Examples 1 to 5 and 10.

For the powder cores 500 produced in Examples 16 to 23 and 29 to 39 and the powder cores of Comparative Examples 6 to 9, the DC superposition characteristics at 100 kHz were measured using an LCR meter connected to a dedicated DC bias power supply, and the retention ratio R (%) was calculated using the above formula (2). In addition, for the powder cores 500 produced in Examples 16 to 23 and 29 to 39 and the powder cores of Comparative Examples 6 to 9, the iron loss Pcv (kW/m ³ ) under excitation conditions of 20 kHz and 100 mT was measured using a BH analyzer. These results are shown in Table 4.

From Table 4, it can be seen that in the powder magnetic cores 500 of Examples 16 to 23 and 29 to 39, the retention rate R was 70% or more, and the iron loss Pcv was 300 kW/m3 or ^less .

On the other hand, Table 4 shows that in the powder core of Comparative Example 6, in which P is less than 3 at%, and the powder core of Comparative Example 8, in which Cu is less than 0.3 at%, the retention rate R is less than 70%, and the iron loss Pcv exceeds 300 kW/m ^3. Also, Table 4 shows that in the powder core of Comparative Example 7, in which P exceeds 12 at%, and the powder core of Comparative Example 9, in which Cu exceeds 1.0 at%, the iron loss Pcv greatly exceeds 300 kW/m ³ .

From these findings, it can be seen that the powder magnetic cores 500 of Examples 16 to 23 and 29 to 39 have improved DC bias characteristics and reduced iron loss compared to the powder magnetic cores of Comparative Examples 6 to 9.

The present invention is based on Japanese Patent Application No. 2023-103003, filed with the Japan Patent Office on June 23, 2023, the contents of which are incorporated herein by reference.

Although the best mode for carrying out the present invention has been described, it will be clear to those skilled in the art that modifications can be made to the present invention without departing from the spirit of the present invention, and such modifications are within the scope of the present invention.

100 Magnetic powder 110 Particle 200 Metal part 300 Oxide film 400 Specific particle 500 Magnetic part (powder core)
600 Binder Lb Length Li Length

Claims (7)

A magnetic component comprising a magnetic powder,
The magnetic powder includes a metal portion, an oxide film, and at least one specific particle,
The specific particles are mainly composed of Cu,
the specific particles are present at an interface between the metal portion and the oxide film,
The specific particles have a particle size of 3 to 70 nm. A magnetic powder comprising a metal portion, an oxide film, and at least one specific particle,
The specific particles are mainly composed of Cu,
the specific particles are present at an interface between the metal portion and the oxide film,
The specific particles are magnetic powders having a particle size of 3 to 70 nm. The magnetic powder according to claim 2,
The concentration of Cu contained in the specific particles is 40 at % or more. The magnetic powder according to claim 2,
The aspect ratio of the specific particles is greater than 1. The magnetic powder according to claim 2,
The occupancy rate of the specific particles is 4 to 60%. A magnetic powder according to any one of claims 2 to 5,
The magnetic powder is represented by the composition formula Fe _a Si _b B _c P _d Cu _e M _f excluding inevitable impurities,
M is Cr and/or Nb;
A magnetic powder in which 75.4 at%≦a≦86.4 at%, 0 at%≦b≦9 at%, 4 at%≦c≦13 at%, 3 at%≦d≦12 at%, 0.3 at%≦e≦1.0 at%, and 0 at%≦f≦5 at%. The magnetic powder according to claim 6,
A magnetic powder in which 3 at % or less of the Fe is replaced with one or more elements selected from Co, Ni, Zn, Zr, Hf, Mo, Ta, W, Ag, Au, Pd, Na, K, Ca, Mg, Sn, Ti, V, Mn, Al, S, C, O, N, Bi and rare earth elements.

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