Magnetic cores, magnetic components, and electronic devices

Abstract

The present invention provides a magnetic core having high magnetic permeability, high withstand voltage, and low voltage variation. The magnetic core contains magnetic powder. The total area ratio of the magnetic powder particles in a cross-section of the core is 75% or more and 90% or less. In the cross-section of the core, the magnetic powder particles are sequentially extracted from the cross-section in ascending order of particle size. The particles whose total area ratio is the smallest, exceeding 20% of the total area ratio of the magnetic powder particles, are designated as large-diameter particles. The large-diameter particles have an average roundness of 0.70 or more.

Description

Technical Field

[0001] The invention relates to a magnetic core, a magnetic component and an electronic device. Background Art

[0002] Patent Document 1 describes a core using a composite magnetic material obtained by further mixing an insulating binder into a mixed magnetic powder obtained by mixing iron-based crystalline alloy magnetic powder and iron-based amorphous alloy magnetic powder.

[0003] Patent Document 2 describes an inductor using a composite magnetic material in which individual particles contained in a mixed magnetic powder obtained by mixing Fe-Ni alloy magnetic powder with hard amorphous alloy magnetic powder are coated with a thermosetting resin.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2004-197218

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2004-363466 Summary of the Invention

[0008] Technical problem to be solved by the invention

[0009] An object of the present invention is to provide a magnetic core having high magnetic permeability, high withstand voltage, and small variations in withstand voltage.

[0010] Means for solving technical problems

[0011] In order to achieve the above object, the magnetic core of the present invention is a magnetic core containing magnetic powder.

[0012] The total area ratio of the magnetic powder particles in the cross section of the magnetic core is 75% or more and 90% or less.

[0013] In the cross section of the magnetic core, the particles of the magnetic powder are extracted in order from the largest particle size, and the extracted particles are defined as large-diameter particles when the total area ratio of the extracted particles is the minimum area ratio exceeding 20% of the total area ratio of the particles of the magnetic powder, and the average roundness of the large-diameter particles is greater than 0.70.

[0014] The magnetic core of the present invention has the above-mentioned features, and thus has high magnetic permeability, high withstand voltage, and small variations in withstand voltage.

[0015] In the cross section of the magnetic core, the average circularity of the large-diameter particles may be 0.80 or greater.

[0016] In a cross section of the magnetic core, the particle diameter of the large-diameter particles may be 5 μm or more and 50 μm or less.

[0017] In the cross section of the magnetic core, the average ellipticity of particles of the magnetic powder may be 0.90 or greater.

[0018] In the cross section of the magnetic core, the large-diameter particles may have an amorphous structure.

[0019] In a cross section of the magnetic core, the large-diameter particles may have a nano-heterostructure in which microcrystals having a grain diameter of 0.3 nm or more and less than 5 nm exist in an amorphous state.

[0020] In the cross section of the magnetic core, the large-diameter particles may have a structure composed of nanocrystals having a grain diameter of 5 nm to 50 nm.

[0021] The magnetic core may further contain resin.

[0022] The magnetic component of the present invention includes the above-mentioned magnetic core.

[0023] The electronic device of the present invention includes the above-mentioned magnetic core. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the Weibull plot.

[0025] Figure 2 This is an example of a diagram obtained by X-ray crystal structure analysis.

[0026] Figure 3 is by Figure 2 An example of a pattern obtained by performing peak shape fitting on the graph.

[0027] Figure 4A is a schematic diagram of the atomization device.

[0028] Figure 4B yes Figure 4A An enlarged schematic diagram of the main parts.

[0029] Explanation of symbols:

[0030] 1…Particle shape measurement results

[0031] 10…Atomization device

[0032] 20…Molten metal supply unit

[0033] 21…Molten Metal

[0034] 21a…Dripping molten metal

[0035] 30…Cooling section

[0036] 36…Coolant inlet

[0037] 38a1…outer convex part

[0038] 50…Coolant flow DETAILED DESCRIPTION

[0039] Hereinafter, a magnetic core according to an embodiment of the present invention will be described.

[0040] The magnetic core contains magnetic powder as a magnetic body. In addition, the magnetic powder may contain iron-based soft magnetic alloy powder described later.

[0041] Furthermore, the magnetic core may also contain a resin. The type and content of the resin are not particularly limited. Examples of the resin include thermosetting resins such as phenolic resin and epoxy resin. The resin content relative to the magnetic powder may be 1% to 5% by mass.

[0042] The total area ratio of the magnetic powder particles in the cross section of the magnetic core is 75% or more and 90% or less. Furthermore, the magnetic powder particles are extracted from the cross section of the magnetic core in ascending order of particle size. The particles whose total area ratio exceeds 20% of the total area ratio of the magnetic powder particles are defined as large-diameter particles. The average circularity of the large-diameter particles is 0.70 or more. The average circularity of the large-diameter particles may be 0.80 or more, 0.90 or more, or 0.95 or more.

[0043] The larger the total area ratio of the magnetic powder particles is, the easier it is to improve the relative magnetic permeability. The smaller the total area ratio of the magnetic powder particles is, the longer the distance between the magnetic powder particles is, and the resin is filled between the magnetic powder particles to form a resin layer. Therefore, the smaller the total area ratio of the magnetic powder particles is, the easier it is to improve the withstand voltage. Therefore, it was found that in order to comprehensively evaluate the withstand voltage and relative magnetic permeability, the withstand voltage × relative magnetic permeability can be used for evaluation. The higher the withstand voltage × relative magnetic permeability, the better and more excellent the balance between the withstand voltage and the relative magnetic permeability. In particular, in order to evaluate the influence of the difference in the shape of the magnetic powder particles on magnetic cores in which the total area ratio of the magnetic powder particles is approximately the same and the shapes of the magnetic powder particles are different, it is preferred to use the withstand voltage × relative magnetic permeability.

[0044] The inventors have discovered a method for further improving both the relative magnetic permeability and withstand voltage of magnetic cores using magnetic powder, improving the withstand voltage × relative magnetic permeability ratio, and reducing variations in the withstand voltage. Specifically, they discovered that controlling the average circularity of the large-diameter particles is more important than controlling the average circularity of the magnetic powder particles as a whole.

[0045] The magnetic core having the above characteristics has higher relative magnetic permeability and withstand voltage, higher withstand voltage × relative magnetic permeability, and smaller variations in withstand voltage compared to a magnetic core having substantially the same total area ratio of magnetic powder particles but not having the above characteristics.

[0046] The particle size distribution of the magnetic powder contained in the magnetic core can be measured by SEM observation. Specifically, for each particle of the magnetic powder contained in any cross-section of the magnetic core, the particle size (Heywood diameter) is calculated based on the SEM image. The magnification of the SEM observation is not particularly limited, as long as the particle size of the magnetic powder particles can be measured. In addition, the size of the observation range of the SEM observation is not particularly limited, and is set to a size that contains at least 500 particles of magnetic powder, preferably at least 1000 particles.

[0047] Then, within the aforementioned observation range defined in the cross section of the magnetic core, magnetic powder particles are extracted in order from the largest particle size, and the extracted particles whose total area ratio exceeds 20% of the total area ratio of the magnetic powder particles are defined as large-diameter particles. In other words, the magnetic powder particles contained in the aforementioned observation range defined in the cross section of the magnetic core are extracted, the magnetic powder particles are arranged in order from the largest particle size, and the areas are accumulated starting from the largest particle size particles, and the particles whose total area ratio exceeds 20% of the total area ratio of the magnetic powder particles in the aforementioned observation range are defined as large-diameter particles.

[0048] The definition of large-diameter particles will be further explained using a hypothetical example. In this hypothetical example, the area ratios of the magnetic powder particles, starting with the largest, are 10%, 7%, 5%, and 4%, respectively, while the area ratios of the other magnetic powder particles are all below 3%. In this case, when extracting the magnetic powder particles in order of particle size, 10%, 7%, and 5% of the particles are extracted. The total area ratio of the extracted particles is 17% when the 7% of particles are extracted, which is no more than 20%. Furthermore, when the 5% of particles are extracted, it is 22%, which is above 20%. Furthermore, when extracting less than 4% of particles, the total area ratio of the extracted particles increases even more. Therefore, the total area ratio when extracting the 5% of particles is 22%, the minimum area ratio exceeding 20%. In this case, the extracted particles, namely the 10%, 7%, and 5% of particles, are large-diameter particles.

[0049] It should be noted that the particle size of the large-diameter particles is not particularly limited. For example, it may be 1 μm or more and 150 μm or less, 3 μm or more and 100 μm or more, or 5 μm or more and 50 μm or less.

[0050] Furthermore, the D50 of the magnetic powder particles in the number-based particle size distribution in the cross-section of the magnetic core is also not particularly limited. For example, the D50 may be 0.1 μm to 100 μm, 0.5 μm to 50 μm, or 0.5 μm to 20 μm. It should be noted that the D50 is the particle size at which the cumulative value of the magnetic powder particle size is 50%.

[0051] The average circularity of the large-diameter particles in the magnetic core using the magnetic powder can be changed mainly by controlling the production method of the magnetic powder.

[0052] The roundness of the large-diameter particles contained in the magnetic core is calculated by 2×(π×S), where the area of the large-diameter particles in the cross section is S and the circumference of the large-diameter particles is L. 1 / 2 / L indicates.

[0053] The average circularity of the large-diameter particles is obtained by calculating the circularity of the large-diameter particles determined by the above method and averaging the calculated circularity.

[0054] The average ellipticity of the magnetic powder particles contained in the magnetic core is preferably 0.90 or greater, more preferably 0.95 or greater. The higher the average ellipticity of the magnetic powder particles, the higher the withstand voltage and the smaller the variation in withstand voltage.

[0055] The ellipticity of the magnetic powder particles is expressed as 4×S / (1×s×π), where the area of the magnetic powder particles in the cross section is S, the length of the major axis is l, and the length of the minor axis is s.

[0056] In general, when the particle is flat, the roundness is low. However, even when the particle is flat, the ellipse roundness is also high. On the other hand, even when the particle is in a depressed shape or a skewed shape, the roundness is sometimes not low. However, when the particle is in a depressed shape or a skewed shape, the ellipse roundness is low. It should be noted that, when the particle is in a shape with large concavoconvex, the roundness and the ellipse roundness are all low. That is, in order to evaluate whether the particle has been deformed beyond flatness from a perfect circle, for example, in order to evaluate whether the particle has a depression, a skew or a concavoconvex, it is sometimes preferred to use ellipse roundness.

[0057] Here, the flatness of the particles in the core rarely affects the withstand voltage characteristics. In contrast, the presence of deformations other than flatness—for example, whether the particles are concave, skew, or have large irregularities—is likely to affect the withstand voltage characteristics. This is because when voltage is applied, the fewer areas where the electric field is concentrated, the better the withstand voltage characteristics of the core. The number of areas where the electric field is concentrated is less dependent on the flatness of the particles and more dependent on whether the particles have deformations other than flatness.

[0058] The evaluation method for the variation in withstand voltage is not particularly limited. Hereinafter, an evaluation method using Weibull distribution will be described as an example of the evaluation method for the variation in withstand voltage.

[0059] According to the Weibull distribution, the failure rate λ(t) with respect to time t is expressed by the following equation (I): where m is the Weibull coefficient and α is called the scale parameter.

[0060] λ(t)=(m / α m )×t m-1 ···Formula (I)

[0061] Here, when m < 1, equation (I) indicates that the failure rate decreases over time. When m = 1, equation (I) indicates that the failure rate remains constant over time. When m > 1, equation (I) indicates that the failure rate increases over time. The following describes how to calculate the Weibull coefficient m.

[0062] The reliability (probability of no failure) R(t) of a product having the above-mentioned failure rate λ(t) is expressed by the following formula (II).

[0063] R(t)=exp{-(t / α) m Formula (II)

[0064] Furthermore, the unreliability (cumulative failure rate) F(t) is expressed by the following formula (III).

[0065] F(t)=1-R(t)=1-exp{-(t / α) m Formula (III)

[0066] Here, if the formula (III) is deformed, it becomes the following formula (IV).

[0067] ln[ln{1 / (1-F(t))}]=mlnt-mlnα···Formula (IV)

[0068] Here, if y=ln[ln{1 / (1-F(t))}] and x=lnt, then the equation is as shown in the following formula (V).

[0069] y=mx-mlnα···Formula (V)

[0070] That is, if y=ln[ln{1 / (1-F(t))}] is plotted against x=lnt, a straight line is formed, and the Weibull coefficient m can be calculated from its slope. This method is called Weibull plotting.

[0071] When m>1, the larger the Weibull coefficient m, the more rapidly the unreliability (cumulative failure rate) F(t) rises around a certain time t. In other words, the larger the Weibull coefficient m, the smaller the variation in the time until failure occurs among individual products.

[0072] Figure 1 The following diagram shows the outline of Weibull plot. Figure 1 In the case of m = 3, F(t) increases dramatically near a certain time t compared to the case of m = 1.5. In other words, when m is large, multiple products fail simultaneously near a certain time t, and the variation in the time until each product fails is small. It should be noted that in a Weibull plot, the further the line shifts to the right, the longer the time until each product fails.

[0073] The Weibull coefficient m can be determined by measuring the withstand voltage of multiple magnetic cores and performing a Weibull plot on the measurement results. The applied voltage when a voltage is applied to the magnetic core and a current of a specified magnitude flows is the withstand voltage. Then, the Weibull plot can be performed by setting the above-mentioned "time t" as "applied voltage V per unit length" and the above-mentioned "fault" as "current of a specified magnitude flowing". There are no particular restrictions on the method of Weibull plotting. In addition to the method of calculating m by plotting the test results on Weibull probability paper, computer programs that automatically perform Weibull plotting and calculate the Weibull coefficient m by inputting the test results have also become widely used in recent years.

[0074] As described above, when evaluating the variation in the withstand voltage using the Weibull distribution, the greater the Weibull coefficient m, the smaller the variation in the withstand voltage.

[0075] The composition of the magnetic powder is not particularly limited. As the magnetic powder, soft magnetic alloy powder may also be used. In addition, two or more magnetic powders having different particle sizes may be mixed as described above.

[0076] The magnetic core is composed of the formula (Fe (1-(α+β)) X1 α X2 β ) (1-(a+b+c+d+e+f)) M a B b P c Si d C e S f constitute,

[0077] X1 is one or more selected from Co and Ni,

[0078] X2 is one or more selected from Al, Mn, Ag, Zn, Sn, As, Sb, Cu, Cr, Bi, N, O and rare earth elements,

[0079] M is one or more selected from Nb, Hf, Zr, Ta, Mo, W, Ti and V,

[0080] 0≤a≤0.150

[0081] 0≤b≤0.200

[0082] 0≤c≤0.200

[0083] 0≤d≤0.200

[0084] 0≤e≤0.200

[0085] 0≤f≤0.0200

[0086] 0.100≤a+b+c+d+e≤0.300

[0087] α≥0

[0088] β≥0

[0089] 0≤α+β≤0.50

[0090] Iron-based soft magnetic alloy powder may be contained as the magnetic powder.

[0091] In the cross section of the magnetic core, the total area ratio of the iron-based soft magnetic alloy powder particles relative to the total area ratio of the magnetic powder particles may be 50% or more.

[0092] By containing the iron-based soft magnetic alloy powder particles having the above composition within the above range, the coercive force HcJ of the core is reduced, and the relative magnetic permeability of the core is likely to be further improved.

[0093] The total area ratio of the particles of the iron-based soft magnetic alloy powder may be 70% or more, or 90% or more.

[0094] The particles of the iron-based soft magnetic alloy powder may contain elements other than those mentioned above as inevitable impurities, for example, 0.1% by mass or less relative to 100% by mass of the particles of the iron-based soft magnetic alloy powder.

[0095] The iron-based soft magnetic alloy powder particles contained in the magnetic core of this embodiment preferably contain nanocrystals with a grain diameter of 5 nm to 50 nm and a bcc crystal structure. The inclusion of these nanocrystals in the iron-based soft magnetic alloy powder particles further reduces the HcJ of the magnetic core and improves the relative magnetic permeability.

[0096] Hereinafter, a method for manufacturing the magnetic core according to the present embodiment will be described.

[0097] First, the magnetic powder contained in the magnetic core is prepared. The method for producing the magnetic powder is not particularly limited. For example, atomization can be used. The type of atomization method is also arbitrary, and examples include water atomization and gas atomization. The following describes a method for producing a magnetic core containing iron-based soft magnetic alloy powder as the magnetic powder.

[0098] When the iron-based soft magnetic alloy powder obtained by the atomization method has an amorphous structure, heat treatment can be performed to precipitate nanocrystals with a bcc crystal structure and a grain diameter of 5 nm to 50 nm. This results in an iron-based soft magnetic alloy powder having a structure composed of nanocrystals. Heat treatment conditions, for example, are between 350°C and 800°C for 0.1 minute to 120 minutes. It should be noted that a single particle of iron-based soft magnetic alloy powder typically contains a large amount of nanocrystals. That is, the particle size of the iron-based soft magnetic alloy powder particles is different from the grain size of the nanocrystals. Furthermore, the crystal structure of the iron-based soft magnetic alloy powder can be confirmed using XRD or a transmission electron microscope. When evaluating the fine structure of the iron-based soft magnetic alloy powder in a magnetic core, it can be confirmed using bright field and selected area diffraction methods using a transmission electron microscope. When the iron-based soft magnetic alloy powder contains nanocrystals, the HcJ of the resulting magnetic core tends to be lower and the relative magnetic permeability tends to be higher. Furthermore, the fine structure of the iron-based soft magnetic alloy powder and the fine structure of the particles of the iron-based soft magnetic alloy powder may be the same.

[0099] Next, the microstructure of the iron-based soft magnetic alloy powder will be described.

[0100] In order to make the iron-based soft magnetic alloy powder contain nanocrystals, the iron-based soft magnetic alloy powder having an amorphous structure is usually heat-treated to precipitate the nanocrystals. Here, the amorphous structure refers to a structure with an amorphization rate X of 85% or more as shown in the following formula (1). Furthermore, the crystalline structure refers to a structure with an amorphization rate X of less than 85%.

[0101] X=100-(Ic / (Ic+Ia)×100)…(1)

[0102] Ic: integrated crystalline scattering intensity

[0103] Ia: Amorphous scattering integrated intensity

[0104] The amorphization ratio X is calculated by performing X-ray crystal structure analysis on the iron-based soft magnetic alloy powder using XRD to identify the phase. The peaks of crystallized Fe or its compound (Ic: integrated intensity of crystalline scattering, Ia: integrated intensity of amorphous scattering) are read and the crystallization ratio is calculated based on the peak intensities using the above formula (1). The calculation method is described in more detail below.

[0105] XRD was used to analyze the X-ray crystal structure of the iron-based soft magnetic alloy powder, and the following results were obtained: Figure 2 The peak shape is fitted using the Lorentz function of the following formula (2), and the following is obtained: Figure 3 The crystal component pattern α showing the integrated intensity of crystalline scattering is shown. c , Amorphous component pattern α showing the integrated intensity of amorphous scattering a , and the pattern α that combines them c+a The amorphization rate X is calculated from the integrated intensity of the crystalline scattering and the integrated intensity of the amorphous scattering of the obtained pattern using the above formula (1). It should be noted that the measurement range is the range of diffraction angle 2θ = 30° to 60°, in which the halo from the amorphous phase can be confirmed. Within this range, the error between the integrated intensity measured by XRD and the integrated intensity calculated using the Lorentz function is within 1%.

[0106]

[0107] h: peak height

[0108] u: peak position

[0109] w: half-peak width

[0110] b: background height

[0111] Generally speaking, the higher the amorphization rate X of the iron-based soft magnetic alloy powder, the lower the coercivity. Furthermore, after heat treatment, the iron-based soft magnetic alloy powder has a structure composed of nanocrystals, which tends to increase the saturation magnetic flux density of the magnetic core and reduce the coercivity compared to the case where the iron-based soft magnetic alloy powder has an amorphous structure. When using iron-based soft magnetic alloy powder with low coercivity to produce a magnetic core, the magnetic permeability of the magnetic core tends to increase.

[0112] The following describes a method for producing an iron-based soft magnetic alloy powder using a gas atomization method.

[0113] The inventors used Figure 4A and Figure 4B When the atomizing device shown above is used as the atomizing device, it is easy to produce an iron-based soft magnetic alloy powder having a large particle size, and further, it is easy to obtain an iron-based soft magnetic metal powder having an amorphous structure.

[0114] like Figure 4A As shown, the atomizing device 10 includes a molten metal supply portion 20 and a cooling portion 30 disposed vertically below the molten metal supply portion 20. In the figure, the vertical direction is a direction along the Z axis.

[0115] The molten metal supply unit 20 includes a heat-resistant container 22 for containing molten metal 21. In the heat-resistant container 22, raw materials of various metal elements weighed to form the final composition of the soft magnetic alloy powder are melted by a heating coil 24 to form molten metal 21. The temperature during melting, i.e., the temperature of molten metal 21, can be determined by taking into account the melting points of the raw materials of the various metal elements and can be set to, for example, 1200 to 1600°C.

[0116] The molten metal 21 is ejected from the ejection port 23 toward the cooling portion 30 as molten metal drops 21a. High-pressure gas is ejected from the gas ejection nozzle 26 toward the ejected molten metal drops 21a, and the molten metal drops 21a are converted into a large number of droplets that are transported toward the inner surface of the cylinder 32 along the flow of the gas.

[0117] The gas injected from the gas injection nozzle 26 is preferably an inert gas or a reducing gas. Examples of inert gases include nitrogen, argon, and helium. Examples of reducing gases include ammonia decomposition gas. However, if the molten metal 21 is a metal that is difficult to oxidize, the gas injected from the gas injection nozzle 26 may be air.

[0118] The molten metal 21a dripping toward the inner surface of the cylinder 32 collides with the coolant flow 50 formed into an inverted cone inside the cylinder 32, is further divided and miniaturized, and is cooled and solidified to form a solid alloy powder. The axis O of the cylinder 32 is inclined at a predetermined angle θ1 relative to the vertical line Z. The predetermined angle θ1 is not particularly limited, but is preferably 0 to 45 degrees. By setting it to such an angle range, it is easy to cause the molten metal 21a dripping from the nozzle 23 to be ejected toward the coolant flow 50 formed into an inverted cone inside the cylinder 32.

[0119] A discharge portion 34 is provided below the cylinder 32 along the axis O. This discharge portion 34 discharges the alloy powder contained in the coolant flow 50 together with the coolant to the outside. The alloy powder discharged along with the coolant is separated from the coolant in an external storage tank or the like and removed. The coolant is not particularly limited, and cooling water can be used.

[0120] In this embodiment, the dropping molten metal 21a collides with the coolant flow 50 formed into an inverted cone shape. Therefore, the flight time of the molten metal droplet 21a is shortened compared to the case where the coolant flow follows the inner surface 33 of the cylindrical body 32. The shortened flight time promotes the rapid cooling effect, and the amorphization rate X of the resulting iron-based soft magnetic alloy powder is improved. In addition, the shortened flight time makes the molten metal droplet 21a less susceptible to oxidation, thereby promoting the refinement of the resulting iron-based soft magnetic alloy powder and improving the quality of the iron-based soft magnetic alloy powder.

[0121] In this embodiment, the flow of the coolant in the coolant introduction portion (coolant discharge portion) 36 for introducing the coolant into the cylinder 32 is controlled to form the coolant flow into an inverted cone shape inside the cylinder 32 . Figure 4B The structure of the coolant introduction portion 36 is shown.

[0122] like Figure 4B As shown, an outer portion (outer space portion) 44 located radially outward of the cylinder 32 and an inner portion (inner space portion) 46 located radially inward of the cylinder 32 are defined by the frame 38. The outer portion 44 and the inner portion 46 are separated by the partition 40. In the passage portion 42 formed at the upper portion of the partition 40 in the direction of the axis O, the outer portion 44 and the inner portion 46 are connected, allowing the coolant to flow.

[0123] One or more nozzles 37 are connected to the outer portion 44, allowing the coolant to enter the outer portion 44 from the nozzles 37. In addition, a coolant ejection portion 52 is formed below the inner portion 46 in the direction of the axis O, and the coolant in the inner portion 46 is ejected (discharged) from this portion into the interior of the cylinder 32.

[0124] The outer circumferential surface of the frame 38 serves as the flow path inner circumferential surface 38b that guides the flow of the coolant within the inner portion 46. An outer convex portion 38a1 is formed at the lower end 38a of the frame 38, extending radially outward from the flow path inner circumferential surface 38b of the frame 38. Therefore, the annular gap between the tip of the outer convex portion 38a1 and the inner surface 33 of the barrel 32 serves as the coolant ejection portion 52. A flow path deflecting surface 62 is formed on the flow path-side upper surface of the outer convex portion 38a1.

[0125] like Figure 4B As shown, the radial width D1 of the coolant ejection portion 52 is narrower than the radial width D2 of the main portion of the inner portion 46 due to the outer convex portion 38a1. Since D1 is narrower than D2, the coolant that descends below the axis O inside the inner portion 46 along the flow path inner peripheral surface 38b then flows along the flow path deflecting surface 62 of the frame 38 and collides with the inner surface 33 of the cylinder 32 and is reflected. As a result, as shown in FIG. Figure 4A As shown, the coolant is ejected from the coolant ejection portion 52 into the interior of the cylinder 32 in an inverted cone shape, forming a coolant flow 50. It should be noted that when D1 = D2, the coolant ejected from the coolant ejection portion 52 forms a coolant flow along the inner surface 33 of the cylinder 32.

[0126] D1 / D2 is preferably less than 2 / 3, more preferably less than 1 / 2. In addition, D1 / D2 is preferably more than 1 / 10. It should be noted that, the smaller D1 / D2 is, the more the quenching effect is promoted, and there is a tendency that the amorphization rate X of the iron-based soft magnetic alloy powder obtained becomes larger. However, the smaller D1 / D2 is, the more the roundness of the iron-based soft magnetic alloy powder obtained decreases. That is, in order to take into account the quenching effect (the high amorphization rate X of the iron-based soft magnetic alloy powder) and the roundness of the iron-based soft magnetic alloy powder, it is necessary to appropriately adjust D1 / D2.

[0127] It should be noted that the coolant flow 50 flowing out of the coolant ejection portion 52 is an inverted conical flow that advances straight from the coolant ejection portion 52 toward the axis O, but may also be a swirling inverted conical flow.

[0128] Furthermore, the molten metal ejection rate, gas injection pressure, pressure within the cylinder 32, coolant ejection pressure, D1 / D2, and the like can be appropriately set according to the target soft magnetic alloy powder particle size. The molten metal ejection rate can be, for example, from 1 kg / min to 20 kg / min. The gas injection pressure can be, for example, from 0.5 MPa to 19 MPa. The pressure within the cylinder 32 can be, for example, from 0.5 MPa to 19 MPa. The coolant ejection pressure (pump pressure) can be, for example, from 0.5 MPa to 19 MPa.

[0129] The less the ejection amount of molten metal, the smaller the particle size, and the tendency of easily making the iron-based soft magnetic alloy powder with a structure consisting of amorphous. It should be noted that, in the structure consisting of amorphous, the nano heterogeneous structure including an amorphous structure consisting only of amorphous and a crystallite (a crystallite with a grain diameter of 0.3 nm or more and less than 5 nm) is present in the amorphous. Whether the iron-based soft magnetic alloy powder has an amorphous structure and whether it has a nano heterogeneous structure can be confirmed by bright field observation and selected area diffraction using a transmission electron microscope. When the iron-based soft magnetic alloy powder has a structure consisting of amorphous, it is easy to precipitate nano crystals by heat treatment.

[0130] As the gas injection pressure, the pressure inside the cylinder 32, and the coolant ejection pressure increase, the particle diameter decreases and the particle roundness also tends to decrease.

[0131] Furthermore, the heat treatment can also be used to precipitate nanocrystals in the iron-based soft magnetic alloy powder having an amorphous structure, thereby obtaining an iron-based soft magnetic alloy powder having a structure consisting of nanocrystals.

[0132] Regarding the particle size of the iron-based soft magnetic alloy powder, the particle size can be adjusted by changing the above-mentioned atomization conditions. In addition, the particle size can also be adjusted by adjusting the particle size using dry classification or wet classification. As dry classification methods, for example, sieving classification using a dry sieve and airflow classification can be cited. As wet classification methods, for example, classification methods such as classification using a wet filter and classification using centrifugal separation can be cited. That is, by adjusting the powder production conditions and classification method during atomization in the iron-based soft magnetic alloy powder produced by the above-mentioned atomization method, the particle size of the large-diameter powder in the cross section of the magnetic core can be adjusted, and the average roundness of the large-diameter powder can be controlled.

[0133] In sieving, powders are classified using dry sieving. In wet filtration, powders are dispersed in a dispersion medium and filtered through the filter. Generally, dry sieving tends to reduce the average roundness of large-diameter powders in the core cross-section. This means that irregularly shaped powder particles are more difficult to remove during dry sieving.

[0134] Furthermore, in sieving, the particle size of the iron-based soft magnetic alloy powder can be adjusted by, for example, changing the amount of powder added per sieving, the sieving time, and / or the mesh size. Furthermore, by increasing the number of times the powder passes through the mesh, it is easier to remove irregularly shaped powder particles.

[0135] Furthermore, by combining multiple iron-based soft magnetic alloy powders having different particle size distributions and / or roundnesses, it is possible to adjust the particle size and, in particular, the average roundness of the large-diameter powder in the core cross section. For example, it is possible to combine an iron-based soft magnetic alloy powder classified by dry sieving and an iron-based soft magnetic alloy powder classified by wet filtration.

[0136] Next, magnetic powder is produced. The above-mentioned iron-based soft magnetic alloy powder can be used directly as magnetic powder, or other powders can be mixed with the above-mentioned iron-based soft magnetic alloy powder to produce magnetic powder. The composition of the mixed powder is not particularly limited. For example, pure iron powder, carbonyl iron powder, permalloy powder, Fe-Si-based soft magnetic alloy powder, Fe-Si-Cr-based soft magnetic alloy powder, Fe-Co-based soft magnetic alloy powder, etc. can be mixed. In addition, iron-based soft magnetic alloy powders with different compositions can also be mixed. By controlling the particle size distribution of the various mixed magnetic powders, the filling rate of the magnetic powder in the final magnetic core can be controlled. In addition, an insulating coating can also be formed on the various magnetic powders.

[0137] When other powders are mixed with the iron-based soft magnetic alloy powder to produce magnetic powder, the proportion of the iron-based soft magnetic alloy powder in the magnetic powder may be 50 mass % or more, 70 mass % or more, or 90 mass % or more.

[0138] The number-based particle size distribution of magnetic powder before molding can also be confirmed using a Morphologi G3 (Malvern Panalytical). The Morphologi G3 is a device that disperses powder in air, projects the shape of individual particles, and evaluates them. Using an optical microscope or laser microscope, the shape of particles ranging from approximately 0.5 μm to several millimeters can be confirmed.

[0139] Because the Morphologi G3 can create and evaluate projections of a large number of particles at once, it can quickly evaluate the shapes of a large number of particles. Therefore, it is suitable for evaluating particle size distribution, etc., for soft magnetic alloy powders before molding. For example, it can create projections for approximately 20,000 soft magnetic alloy powder particles, automatically calculate the particle size and roundness of each particle, and calculate the average roundness of particles within a specific particle size range.

[0140] The number-based particle size distribution of the magnetic powder as determined by the Morphologi G3 does not match the number-based particle size distribution of the magnetic powder particles in the cross-section of the final magnetic core. The D50 and D90 values of the magnetic powder particles in the cross-section of the final magnetic core are somewhat smaller than the number-based D50 and D90 values determined by the Morphologi G3. This is because the magnetic powder particles are cut at random locations during the cutting of the core. In other words, even large particles may appear as small particles depending on the location of the cut.

[0141] However, there is a correlation between the number-based particle size distribution and circularity of the magnetic powder confirmed using the Morphologi G3 and the number-based particle size distribution and circularity of the magnetic powder particles in the cross-section of the resulting magnetic core. Therefore, by confirming the particle size distribution and circularity of the magnetic powder using the Morphologi G3, it is possible to predict the particle size distribution of the magnetic powder particles in the cross-section of the resulting magnetic core to a certain extent. In other words, it is easy to control the number-based particle size distribution and circularity of the magnetic powder before molding, and also to control the number-based particle size distribution and circularity of the magnetic powder particles in the cross-section of the resulting magnetic core.

[0142] The obtained magnetic powder is then molded to obtain a magnetic core. The molding method is not particularly limited. As an example, a method of obtaining a magnetic core by press molding will be described.

[0143] First, the magnetic powder and resin are mixed. By mixing the resin, a molded body with high strength can be easily obtained upon molding. The type of resin is not particularly limited. Examples include phenolic resins and epoxy resins. The amount of resin added is also not particularly limited. When adding resin, the amount can be from 1% to 5% by mass relative to the magnetic powder.

[0144] The mixture of magnetic powder and resin is granulated to obtain granulated powder. The granulation method is not particularly limited. For example, a blender can be used for granulation. The particle size of the granulated powder is not particularly limited.

[0145] The obtained granulated powder is pressurized to obtain a molded body. There is no particular limitation on the molding pressure. For example, the surface pressure can be 1 ton / cm 2 Above and 10ton / cm 2 The higher the molding pressure, the higher the relative magnetic permeability tends to be. However, when the particle size distribution of the magnetic powder is broad, the relative magnetic permeability can be improved even with a molding pressure lower than that of conventional press molding. This is because the resulting magnetic core is more dense.

[0146] The resin contained in the molded body can then be cured to obtain a magnetic core. The curing method is not particularly limited, and heat treatment can be performed under conditions that allow the resin used to cure.

[0147] There are no particular limitations on the use of the core. For example, it can be suitably used as a core for inductors, particularly power inductors. Furthermore, it can also be suitably used in inductors in which the core and coil are integrally formed.

[0148] Furthermore, the magnetic core or a magnetic component using the magnetic core can be suitably used in electronic devices.

[0149] In particular, the magnetic core has high magnetic permeability, high withstand voltage, and low voltage variation, making it suitable for use in fields requiring miniaturization, lightweighting, and high reliability. For example, it can be used in magnetic cores, magnetic components, and electronic devices used in hybrid vehicles, plug-in hybrid vehicles, and electric vehicles.

[0150] Example

[0151] Hereinafter, the present invention will be described in detail based on examples.

[0152] (Experimental Example 1)

[0153] The iron-based soft magnetic alloy powders A to F shown in Table 1 were prepared. First, Fe 0.735 Nb 0.030 B 0.090 Si 0.135 Cu0.100 Ingots of various materials are prepared and weighed in the form of a master alloy of a composition. Then, they are placed in a crucible arranged in a gas atomizer.

[0154] Next, the master alloy was placed in a heat-resistant container 22 located within the atomizing device 10. After the interior of the cylinder 32 was evacuated, the heat-resistant container 22 was heated by high-frequency induction using a heating coil 24 located outside the heat-resistant container 22. This melted and mixed the raw metals in the heat-resistant container 22, resulting in a molten metal (melt) at 1500°C.

[0155] The resulting molten metal was injected into the cylindrical body 32 of the cooling unit 30 at 1500°C. Argon gas was injected at the gas injection pressure listed in Table 1, thereby forming a large number of molten droplets. The molten metal ejection rate and the cooling water pump pressure were the same as those listed in Table 1. The molten droplets collided with the inverted conical cooling water flow formed by the cooling water supplied at the pump pressure listed in Table 1, becoming fine powder that was then recovered.

[0156] It should be noted that in Figure 4A 、 Figure 4B In the atomizing device 10 shown, the inner diameter of the inner surface of the cylinder 32 was set to 300 mm, the angle θ1 was set to 20 degrees, and D1 / D2 was set to the conditions described in Table 1.

[0157] Furthermore, heat treatment was performed at 550°C for 60 minutes. Classification was then performed according to the method shown in Table 1. In dry sieving, the powder was sieved in the air and classified. In wet filtration, the powder was dispersed using IPA as a dispersion medium, and the dispersion medium containing the powder was filtered through a filter.

[0158] In addition to the conditions listed in Table 1, the number-based particle size distribution of the iron-based soft magnetic alloy powder and the average roundness of the iron-based soft magnetic alloy powder with a particle size of D90 or greater were varied by varying the classification method and the mesh size of the sieve or filter. For iron-based soft magnetic alloy powders A and B, D10 was 2.0 to 4.0 μm, D50 was 7.0 to 12 μm, and D90 was 21 to 24 μm. For iron-based soft magnetic alloy powders C and D, D10 was 1.5 to 3.0 μm, D50 was 4.0 to 6 μm, and D90 was 8 to 15 μm. For iron-based soft magnetic alloy powders E and F, D10 was 3.0 to 8.0 μm, D50 was 15 to 25 μm, and D90 was 60 to 74 μm. Furthermore, the average circularity of the iron-based soft magnetic alloy powders with a D90 or greater in iron-based soft magnetic alloy powders A, C, and E was 0.60 to 0.65, and the average circularity of the iron-based soft magnetic alloy powders with a D90 or greater in iron-based soft magnetic alloy powders B, D, and F was 0.93 to 0.98. By ensuring that the number-based particle size distribution of each iron-based soft magnetic alloy powder and the average circularity of the iron-based soft magnetic alloy powder with a D90 or greater fall within the above ranges, the average particle size and average circularity of the large-diameter powder in the core cross section described in the tables below can be obtained.

[0159] It should be noted that the average roundness of D10, D50, D90, and D90 or more of each iron-based soft magnetic alloy powder is measured by observing the shape of 20,000 powder particles at a magnification of 10 times using Morphologi G3 (Malvern Panalytical). Specifically, a powder with a volume of 3cc is dispersed at an air pressure of 1 to 3bar, and a projection image obtained by a laser microscope is taken. Based on the particle size of each powder particle, the average roundness of D10, D50, D90, and D90 or more of the iron-based soft magnetic alloy powder is calculated based on the number of particles. It should be noted that the particle size of each powder particle is the Heywood diameter.

[0160] ICP analysis confirmed that the composition of the master alloy was substantially identical to that of the iron-based soft magnetic alloy powder.

[0161] The determination of whether each iron-based soft magnetic alloy powder was amorphous or crystalline was made. XRD was used to identify peaks due to crystallization, confirming that the powder was amorphous. Furthermore, each iron-based soft magnetic alloy powder was heat treated at 550°C for 1 hour, and XRD was again used to identify peaks due to crystallization. The crystallite diameter of the crystalline particles was found to be between 5 nm and 50 nm. This confirmed that all of the iron-based soft magnetic alloy powders contained nanocrystals.

[0162] Next, carbonyl iron powder was prepared as iron powder separately from the soft magnetic alloy powder. The volume-based particle size distribution of the carbonyl iron powder determined by laser diffraction showed D50 of 1.0 μm.

[0163] [Table 1]

[0164]

[0165] Next, a toroidal magnetic core and a cylindrical magnetic core were produced using the above-mentioned iron-based soft magnetic alloy powders A to F and carbonyl iron powder.

[0166] Iron-based soft magnetic alloy powder and carbonyl iron powder are mixed in the mass ratios listed in Tables 2 to 4 to obtain magnetic powder. Next, the magnetic powder and resin (phenolic resin) are mixed. The mixture is performed in such a manner that the amount of resin relative to the magnetic powder is the amount listed in Table 2. Next, a common planetary mixer is used as a stirrer to granulate the powder so as to obtain a granulated powder with a particle size of about 500 μm. Next, the obtained granulated powder is pressed under a surface pressure of 4 ton / cm 2 (392MPa)~8ton / cm 2 (784MPa) and the total area of the magnetic powder particles was adjusted to the total area of the magnetic powder particles described in Table 2. inner diameter A ring-shaped body with a height of 6.0 mm and a diameter of A cylindrical molded body with a height of 8.0 mm was formed. The obtained molded body was cured at 150°C to produce a toroidal core and a cylindrical core. These cores were produced in the number required for the test described below.

[0167] Total area ratio of magnetic powder particles

[0168] Cut the toroidal core with an arbitrary cross section and observe it using SEM at a magnification of 500 times. The observation range is the size of at least 1000 particles of magnetic powder. Then, calculate the total area ratio of the magnetic powder particles, that is, the total area ratio of the total area ratio of the particles of the iron-based soft magnetic alloy powder and the total area ratio of the particles of the carbonyl iron powder. It should be noted that when it is difficult to distinguish the particles of the magnetic powder and the resin layer at the above magnification, increase the magnification for observation. In this case, the total area of the observation range is made the same area. For example, when the magnification is magnified to 1000 times for observation, use 4 times the number of images in a way that the total area of the observation range is the same as when observing at 500 times.

[0169] Average ellipticity of magnetic powder particles

[0170] For the above observation range, the ellipticity of particles of all magnetic powders was calculated and averaged.

[0171] Average particle size and average roundness of large particles

[0172] The equivalent circular diameter (Heywood diameter) of all magnetic powder particles within the observation range was calculated to confirm the particle size distribution of the magnetic powder in the annular magnetic core. Then, within the observation range set as the cross-section of the magnetic core, the magnetic powder particles were extracted in order from the largest particle size, and the particles extracted when the total area ratio of the extracted particles was the smallest area ratio exceeding 20% of the total area ratio of the magnetic powder particles were defined as large-diameter particles. The average particle size and average circularity of the large-diameter particles were then calculated. Furthermore, in all experimental examples, the EDS composition diagram confirmed that all large-diameter particles were particles of any of the iron-based soft magnetic alloy powders A to F.

[0173] In addition, in all experimental examples, D50 of the magnetic powder in the cross section of the toroidal core was calculated and confirmed to be 1 μm or more and 100 μm or less.

[0174] Relative magnetic permeability

[0175] UEW wire was wound around a toroidal core, and relative permeability was measured at 100 kHz using a 4284A PRECISION LCR meter (Hewlett-Packard). The results were based on a comparative example produced under the same conditions, except that the average roundness of the large-diameter particles was too low due to the omission of iron-based soft magnetic alloy powders B, D, and F. A relative permeability of 1.04 times or greater compared to the comparative example was considered good.

[0176] Withstand voltage and m value

[0177] For 20 cylindrical cores, In-Ga electrodes were formed on two surfaces perpendicular to the thickness direction. Next, a voltage was applied using a source meter (THK-2011ADMPT manufactured by Tama Denso) and the voltage when a current of 1 mA flowed was measured. The withstand voltage of the cylindrical core was then determined by dividing this voltage by the thickness of the cylindrical core. The withstand voltage of the 20 cylindrical cores was averaged to obtain the value obtained as the withstand voltage of each experimental example. Furthermore, a Weibull plot was performed on the withstand voltage of the 20 cylindrical cores to calculate the m value for each experimental example. An m value of 3.0 or above was set as good.

[0178] Furthermore, except that the average roundness of the large-diameter particles was too low due to the absence of iron-based soft magnetic alloy powders B, D, and F, a comparative example was used as a benchmark. The withstand voltage of the comparative example was rated as good if it was 1.08 times or more higher.

[0179] Furthermore, in the evaluation of withstand voltage × relative magnetic permeability, a comparative example prepared under the same conditions was used as a benchmark, except that the average roundness of the large-diameter particles was too low due to the omission of iron-based soft magnetic alloy powders B, D, and F. The withstand voltage × relative magnetic permeability of the comparative example was rated as good if it was 1.2 times or more higher.

[0180] [Table 2]

[0181]

[0182] [Table 3]

[0183]

[0184] [Table 4]

[0185]

[0186] As shown in Tables 2 to 4, the Examples, in which the total area ratio of the magnetic powder particles was 75% or more and 90% or less, and the average circularity of the large-diameter particles was 0.70 or more, exhibited higher relative magnetic permeability and withstand voltage, and less variation in withstand voltage, compared to the Comparative Examples, which had substantially the same configuration except for the average circularity of the large-diameter particles being less than 0.70. Furthermore, the withstand voltage × relative magnetic permeability ratio of each Example was also good. It should be noted that in the above Examples, the withstand voltage of the cylindrical core was measured, and it was confirmed that the withstand voltage of the toroidal core was also comparable to that of the cylindrical core.

[0187] (Experimental Example 2)

[0188] Phosphate treatment was performed on the magnetic powders of Samples 19 to 24 to form an insulating coating. The coating thickness was 20 nm for the soft magnetic alloy powder and 10 nm for the carbonyl iron powder. The results of the evaluation, performed in the same manner as in Experimental Example 1, are shown in Table 5.

[0189] [Table 5]

[0190]

[0191] According to Table 5, even in the case where the insulating coating was formed, the same results as those in the case where the insulating coating was not formed were obtained.

[0192] (Experimental Example 3)

[0193] Samples 7a and 7b were prepared under the same conditions as Sample 7, except that the irregularly shaped particles contained in the carbonyl iron powder were removed by air classification. Samples 12a and 12b were prepared under the same conditions as Sample 12, except that the irregularly shaped particles contained in the carbonyl iron powder were removed by air classification. Removal of irregularly shaped particles increased the sphericity of the carbonyl iron powder and the average ellipticity of the magnetic powder particles. The results are shown in Table 6.

[0194] [Table 6]

[0195]

[0196] Table 6 shows that even when the irregular-shaped powder was removed, the same results as those obtained when the irregular-shaped powder was not removed were obtained. Furthermore, the higher the average ellipticity of the magnetic powder particles, the higher the withstand voltage and the m value.

[0197] (Experimental Example 4)

[0198] For sample number 43 of Experimental Example 1, the heat treatment conditions of powder A were changed to change the microstructure, and sample numbers 67, 70, and 72 were produced under the same conditions. In addition, for sample number 44 of Experimental Example 1, the heat treatment conditions of powders A and B were changed to change the microstructure, and sample numbers 68, 71, and 73 were produced under the same conditions. The results are shown in Table 7. It should be noted that the powders recorded as amorphous in the microstructure column of Table 7 have an amorphous structure. The powders recorded as nanocrystalline have a structure composed of nanocrystals. The powders recorded as heterogeneous structures have nanoheterogeneous structures. The powders recorded as crystalline have a structure composed of crystals with a grain diameter of 100 nm or more. In addition, the embodiments and comparative examples having the same crystalline state of the soft magnetic alloy powders are compared.

[0199] Furthermore, two types of powder A were prepared: a powder having a structure composed of nanocrystals by heat treatment at 550°C for 1 hour, and a powder having an amorphous structure without heat treatment. Furthermore, powder B was prepared without heat treatment to have an amorphous structure. Subsequently, the respective powders were blended in the blending ratios listed in Table 8 to produce Sample No. 69a and Sample No. 69. The results are shown in Table 8. Sample No. 69a and Sample No. 69 shared the fact that the mass ratio of the soft magnetic alloy powder having a structure composed of nanocrystals to the soft magnetic alloy powder having an amorphous structure was 70:30.

[0200]

[0201] Tables 7 and 8 show that the same results as those of Experimental Example 1 were obtained regardless of the crystal state of the powder. Furthermore, when the microstructure of powders A and B consisted of nanocrystals, the magnetic properties were the most excellent.

[0202] (Experimental Example 5)

[0203] In addition to the atomic ratio of Fe 0.78475 Nb 0.070 B 0.090 Si 0.020 P 0.030 C 0.005 S 0.00025 In addition to preparing ingots of various materials as master alloys of the composition, powder G was produced under the same conditions as powder A, and powder H was produced under the same conditions as powder B. Sample numbers 74 to 79 were produced under the same conditions as sample numbers 19 to 24, except that powder A was replaced with powder G and powder B was replaced with powder H. The results are shown in Table 9.

[0204] [Table 9]

[0205]

[0206] According to Table 9, the same results as those of Experimental Example 1 were obtained regardless of the composition of the powder.

Claims

1. A magnetic core, wherein: The magnetic core contains magnetic powder, The total area ratio of the magnetic powder particles in the cross section of the magnetic core is 75% or more and 90% or less. In the cross section of the magnetic core, the particles of the magnetic powder are extracted in order from the largest particle size, and the extracted particles whose total area ratio is the smallest area ratio exceeding 20% of the total area ratio of the particles of the magnetic powder are defined as large-diameter particles. The area of the large-diameter particles in the cross section is defined as S, the circumference of the large-diameter particles is defined as L, and the roundness of the large-diameter particles contained in the magnetic core is expressed as 2×(π×S). 1 / 2 / L indicates that the average roundness of the large-diameter particles is 0.80 or more, The area of the magnetic powder particles in the cross section is set to S, the length of the major axis is set to l, the length of the minor axis is set to s, the ellipticity of the magnetic powder particles is expressed as 4×S / (l×s×π), and the average ellipticity of the magnetic powder particles is greater than 0.

90.

2. The magnetic core according to claim 1, wherein In a cross section of the magnetic core, the large-diameter particles have a particle diameter of 5 μm or more and 50 μm or less.

3. The magnetic core according to claim 1, wherein In a cross section of the magnetic core, the large-diameter particles have an amorphous structure.

4. The magnetic core according to claim 1, wherein In a cross section of the magnetic core, the large-diameter particles have a nano-heterostructure in which microcrystals having a grain diameter of 0.3 nm or more and less than 5 nm exist in an amorphous phase.

5. The magnetic core according to claim 1, wherein In a cross section of the magnetic core, the large-diameter particles have a structure composed of nanocrystals having a grain diameter of 5 nm to 50 nm. The magnetic core according to claim 1 , wherein: It further contains resin.

7. A magnetic component, wherein: A magnetic core comprising the magnetic core according to any one of claims 1 to 6.

8. An electronic device, wherein: A magnetic core comprising the magnetic core according to any one of claims 1 to 6.

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