JP2023181663A - Iron-based soft magnetic powder - Google Patents

Abstract

To provide a powder from which a magnetic component having excellent magnetic properties can be obtained.SOLUTION: A soft magnetic powder comprises many particles 2. These particles 2 include particles having a diameter D2 of 50 μm or more. A ratio P2 calculated by the following formula is equal to or less than 50%: P2=(N2/N1)*100. In the formula, N1 represents the number of particles 2 having a diameter D2 of 50 μm or more. In this formula, N2 represents the number of particles 2 having a diameter D2 of 50 μm or more. The soft magnetic powder contains: a core 8; and 20 or more projections 10 that are attached to a surface of the core 8 and whose height is 1.0 μm or more, wherein an average height of the projections 10 that have a height of 1.0 μm or more is 10 μm or more.SELECTED DRAWING: Figure 2

Description

This specification discloses a soft magnetic powder whose main component is iron. This soft magnetic powder is suitable for powder magnetic cores, which are components such as reactors and inductances.

Reactors such as motors, inverters, and converters have magnetic cores. Inductances used in circuit boards and the like also have a magnetic core. There is a demand for large currents in reactors and inductances. From the viewpoint of increasing currents, there is a growing need for magnetic materials that are less susceptible to magnetic saturation with respect to currents. Furthermore, there is also a demand for miniaturization of reactors and inductances. From these viewpoints, powder magnetic cores are used for reactors and inductances. A powder magnetic core can be obtained by pressing metal powder. This metal powder consists of a large number of particles. Each particle has a core and an insulating film covering the core. This powder magnetic core is required to have magnetic properties that allow it to respond sensitively to changes in external magnetic fields.

Several improvements regarding the magnetic properties of dust cores have been proposed. JP2014-143286A discloses a soft magnetic powder containing Cr and Si. JP 2020-145405 A discloses a soft magnetic powder whose composition differs between the inside and the surface of the particle.

Japanese Patent Application Publication No. 2014-143286 JP2020-145405 Publication

Energy losses occur when powder magnetic cores are used in alternating magnetic fields. This energy loss is called "core loss." Core loss is the sum of hysteresis loss and eddy current loss. In the low frequency range, hysteresis loss is dominant. In the high frequency range, eddy current loss is dominant. If a powder with a thick insulating film is used, core loss of the powder magnetic core can be suppressed. However, this powder has poor filling properties. A dust core using this powder has insufficient saturation magnetization. This powder magnetic core does not meet the demands for large currents.

The applicant's intention is to provide a powder from which a magnetic member with excellent magnetic properties can be obtained.

The iron-based soft magnetic powder disclosed in this specification consists of a large number of particles. These particles include particles with a diameter of 50 μm or more. The ratio P2 calculated by the following formula is 50% or less.
P2 = (N2 / N1) * 100
In this formula, N1 represents the number of particles having a diameter of 50 μm or more. In this formula, N2 has a diameter of 50 μm or more and includes a core and 20 or more protrusions attached to the surface of the core and each having a height of 1.0 μm or more. It represents the number of particles whose protrusions have an average height of 10 μm or more and are 0 μm or more.

Preferably, the ratio P1 calculated by the following formula is 50% or more.
P1 = (N3 / N) * 100
In this formula, N represents the total number of particles, and N3 represents the number of particles whose circularity is 0.8 or more. Preferably, this ratio P1 is 80% or less.

Preferably, the ratio P3 calculated using the following formula is 20% or less.
P3 = (N4 / N1) * 100
In this formula, N1 represents the number of particles having a diameter of 50 μm or more. In this formula, N4 represents the number of particles having a diameter of 50 μm or more and the number of pores included in one cross section having a diameter of 0.1 μm or more is 2 or more.

Preferably, the ratio P4 calculated by the following formula is 50% or more.
P4 = (N1 / N) * 100
In this formula, N represents the total number of particles, and N1 represents the number of particles having a diameter of 50 μm or more.

Preferably, each particle has a main portion and an insulating coating covering all or part of the surface of the main portion. The material of this main part is an iron-based alloy. Preferably, the iron-based alloy is
Si: 2.0% by mass or more and 10.0% by mass or less,
Cr: 0.0% by mass or more and 10.0% by mass or less,
Al: 0.0% by mass or more and 10.0% by mass or less,
and B: 0.0% by mass or more and 10.0% by mass or less. The remainder is Fe and inevitable impurities.

The method for manufacturing a powder magnetic core disclosed in this specification includes:
A step of preparing an iron-based soft magnetic powder consisting of a large number of particles, including particles having a diameter of 50 μm or more, and having a ratio P2 calculated by the following formula of 50% or less,
and a step of pressurizing the powder.
P2 = (N2 / N1) * 100
In this formula, N1 represents the number of particles having a diameter of 50 μm or more. In this formula, N2 has a diameter of 50 μm or more and includes a core and 20 or more protrusions attached to the surface of the core and each having a height of 1.0 μm or more. It represents the number of particles whose protrusions have an average height of 10 μm or more and are 0 μm or more.

When this soft magnetic powder is pressurized, the particles are pressed against adjacent particles. Since the powder ratio P2 is 50% or less, this powder is less likely to be damaged by particles due to this pressing. A magnetic member with excellent magnetic properties can be obtained from this powder.

FIG. 1 is a projected view showing particles of iron-based soft magnetic powder according to one embodiment. FIG. 2 is a projection view of the particle of FIG. 1 shown with a first imaginary circle and a second imaginary circle. FIG. 3 is a cross-sectional view of the particle of FIG. 1. FIG. 4 is an enlarged view of a portion of the particles of FIG. 1. FIG. 5 is a projection view of the particles of FIG. 1 shown with a first imaginary circle. FIG. 6 is an enlarged view showing the pores of the particle of FIG. 3.

Hereinafter, preferred embodiments will be described in detail with appropriate reference to the drawings.

The iron-based soft magnetic powder according to this embodiment is a collection of many particles. This powder can be subjected to a pressing method that will be explained in detail later to obtain a molded body (for example, a powder magnetic core). In FIG. 1 a projection view of one particle 2 is shown. As is clear from FIG. 1, the particles 2 are strained. In other words, the contour 4 of the particle 2 has irregularities. This projection view is obtained by randomly selecting the viewing direction for the particle 2. The powder may include particles 2 having a shape close to a true sphere as well as distorted particles 2.

In FIG. 2, a first virtual circle 6 is shown. This first virtual circle 6 is the largest circle that can be drawn within the contour 4 of the particle 2. In other words, the first virtual circle 6 is the "maximum inscribed circle" defined by the "maximum inscribed circle center method". In this specification, the zone of the particle 2 surrounded by the first imaginary circle 6, that is, the inside of the largest inscribed circle, is referred to as the "core 8." A zone outside the first imaginary circle 6 of the particle 2, that is, a zone outside the maximum inscribed circle is referred to as a "protrusion 10." FIG. 2 shows a first protrusion 10a, a second protrusion 10b, a third protrusion 10c, a fourth protrusion 10d, a fifth protrusion 10e, and a sixth protrusion 10f. These protrusions 10 are attached to the core 8. In FIG. 2, the symbol D1 represents the diameter of the first virtual circle 6.

A second imaginary circle 12 is also shown in FIG. This second virtual circle 12 is the smallest circle that includes the outline 4 of the particle 2 inside it. In FIG. 2, the symbol D2 represents the diameter of the second virtual circle 12. This diameter D2 is referred to herein as the "diameter of particle 2."

In FIG. 3 a cross section of particle 2 is shown. The particle 2 has a main portion 14 and an insulating film 16. Insulating film 16 covers the surface of main portion 14 . In this embodiment, the insulating film 16 covers the entire surface of the main portion 14 . Therefore, the contour 4 of the particle 2 is also the contour of the insulating film 16. The insulating film 16 may cover a portion of the surface of the main portion 14. The particles 2 do not need to have the insulating film 16. From the viewpoint of suppressing core loss, it is preferable that the insulating film 16 covers the entire surface of the main portion 14. In FIG. 3, the reference numeral 18 represents a hole (detailed explanation will be given later).

The material of the main portion 14 is an iron-based alloy, which will be explained in detail later. A powder magnetic core obtained from a large number of particles 2 having the main portion 14 and the insulating film 16 has excellent magnetic properties. In this specification, a soft magnetic powder made of particles 2 whose main portion 14 is made of an iron-based alloy is referred to as an "iron-based soft magnetic powder" regardless of the material of the insulating film 16.

[Ratio P4]
In this specification, the ratio P4 is calculated using the following formula.
P4 = (N1 / N) * 100
In this formula, N represents the total number of particles 2, and N1 represents the number of particles 2 whose diameter D2 is 50 μm or more. From the viewpoint of efficiency in the pressing method for obtaining a molded body, the ratio P4 is preferably 50% or more, more preferably 60% or more, and particularly preferably 70% or more. The ratio P4 may be 100%.

The ratio P4 is calculated by laser diffraction/scattering particle size distribution measuring method. For this measurement method, for example, Microtrac Bell's "Particle Size Distribution Measuring Device MT3000II" is used. The particle size distribution of the powder is measured on a number basis, and the frequency of particles 2 having a diameter of 50 μm or more is confirmed.

[Ratio P2]
In FIG. 4, a part of the particle 2 is shown enlarged. FIG. 4 shows the vicinity of the first protrusion 10a. In FIG. 4, the reference numeral 20 represents the top of the first protrusion 10a. The top 20 is the point farthest from the first imaginary circle 6 on the outline 4a of the first protrusion 10a. The contour 4a of the first protrusion 10a is a part of the contour 4 of the particle 2. In FIG. 4, an arrow H1 represents the height of the first protrusion 10a. The height H1 is the distance from the top 20 to the first virtual circle 6. The shape of the contour 4 near the top 20 may be a curve (or straight line) or a corner.

FIG. 5 shows the height H1 of the first protrusion 10a, the height H2 of the second protrusion 10b, the height H3 of the third protrusion 10c, the height H4 of the fourth protrusion 10d, the height H5 of the fifth protrusion 10e, and A height H6 of the sixth protrusion 10f is shown. The method for determining the height H2 of the second protrusion 10b, the height H3 of the third protrusion 10c, the height H4 of the fourth protrusion 10d, the height H5 of the fifth protrusion 10e, and the height H6 of the sixth protrusion 10f is shown in FIG. This is the same as the method of determining the height H1 of the first protrusion 10a shown in 4. Each height H is the distance from the top 20 to the first virtual circle 6.

In this specification, the ratio P2 is calculated using the following formula.
P2 = (N2 / N1) * 100
In this formula, N1 represents the number of particles 2 whose diameter D2 is 50 μm or more. In this formula, N2 represents the number of particles 2 that satisfy all conditions 1-3 below.
Condition 1: Diameter D2 is 50 μm or more.
Condition 2: The number Np of protrusions 10 whose height H is 1.0 μm or more is 20 or more.
Condition 3: The average height Hp of the protrusions 10 whose height H is 1.0 μm or more is 10 μm or more.

In the particle 2 shown in FIG. 5, the height H1 of the first protrusion 10a, the height H2 of the second protrusion 10b, the height H3 of the third protrusion 10c, the height H5 of the fifth protrusion 10e, and the height H5 of the sixth protrusion 10f. The height H6 is 1.0 μm or more. Therefore, these protrusions 10 are targets for calculating the "number Np of protrusions 10" and the "average height Hp of protrusions 10." On the other hand, the height H4 of the fourth protrusion 10d is less than 1.0 μm. Therefore, the fourth protrusion 10d is not a target for calculating the "number Np of protrusions 10" and the "average height Hp of protrusions 10." The fine protrusions 10 that are included in this projection diagram and whose height is not measured but are clearly less than 1.0 μm are also included in the "Number of protrusions 10" and "Average height of protrusions 10". It is not subject to calculation of "Hp". Furthermore, the protrusions 10 that are attached to the core 8 but do not appear in this projection view are also not subject to calculation of the "number Np of protrusions 10" and the "average height Hp of the protrusions 10." For this particle 2, the average height Hp of the protrusions 10 is calculated using the following formula.
Hp = (H1 + H2 + H3 + H5 + H6) / 5

In the particle 2 that satisfies this condition 1-3, the contour 4 is distorted because the number of protrusions 10 having a large height H is large and the average height of the protrusions 10 is large. When this particle 2 is subjected to the pressurization method, the insulating film 16 of the adjacent particle 2 is damaged due to the large diameter D2. A powder magnetic core obtained from particles 2 with damaged insulating coating 16 has poor magnetic properties. Core loss is likely to occur in this powder magnetic core. From the viewpoint of magnetic properties, it is preferable that the number of particles 2 satisfying conditions 1-3 is small. From the viewpoint of magnetic properties, the ratio P2 is preferably 50% or less, more preferably 47% or less, and particularly preferably 45% or less. The ideal ratio P2 is 0%.

With powder having a ratio P2 of 50% or less, damage to the insulating film 16 can be suppressed even if the insulating film 16 is thin. Powder with a thin insulating film 16 has excellent filling properties. The powder magnetic core using this powder has a high density. This dust core has a large saturation magnetization. This powder magnetic core can meet the demands for large currents.

In calculating the ratio P2, the powder is classified using a sieve with an opening of 50 μm. Fifty particles 2 are randomly selected from the particles 2 remaining on the sieve and observed with a stereomicroscope. From the projected view of each particle 2, the diameter D2 of this particle 2 and the average size Sp of the projections 10 are measured, and the number N1 and number N2 are counted.

[Ratio P1]
In this specification, the ratio P1 is calculated using the following formula.
P1 = (N3 / N) * 100
In this formula, N represents the total number of particles 2, and N3 represents the number of particles 2 whose circularity Ro is 0.8 or more. Even if particles 2 with a large degree of circularity Ro are subjected to a pressurization method, the insulating coating 16 of adjacent particles 2 will not be easily damaged. A powder magnetic core obtained from a powder having a large ratio P1 of particles 2 with a circularity Ro of 0.8 or more has excellent magnetic properties. From this viewpoint, the ratio P1 is preferably 50% or more, more preferably 55% or more, and particularly preferably 60% or more.

The degree of circularity Ro is calculated using the following formula.
Ro = 4πS / ^L2
In this formula, S is the projected area of particle 2, and L is the length of the contour 4 of particle 2. The area S and the length L of the contour 4 are measured by image analysis. As a measuring device for image analysis, an image analysis device manufactured by Seishin Enterprise Co., Ltd. under the trade name "PITA-04" is exemplified.

Regardless of the size of the ratio P1, the damage suppression effect can be obtained by a small ratio P2. In other words, in this embodiment, setting the value of the ratio P1 is not an essential matter.

Even if the powder has a small ratio P1, damage to the insulating film 16 can be suppressed if the ratio P2 is sufficiently small. In the production of powder with a small ratio P1, the material yield is high. Therefore, a powder with a small ratio P1 can be obtained at low cost. From the viewpoint of cost, the ratio P1 is preferably 80% or less, more preferably 75% or less, and particularly preferably 70% or less.

[Ratio P3]
In FIG. 6, the holes 18 are shown enlarged. A third virtual circle 22 is also shown in FIG. This third imaginary circle 22 is the smallest circle that includes the outline 24 of the hole 18 inside thereof. In other words, the third virtual circle 22 is the "minimum circumscribed circle" defined by the "minimum circumscribed circle center method". In FIG. 6, the symbol D3 represents the diameter of the third imaginary circle 22. In this specification, this diameter D3 is referred to as the "diameter of the hole 18."

In this specification, the ratio P3 is calculated using the following formula.
P3 = (N4 / N1) * 100
In this formula, N1 represents the number of particles 2 whose diameter D2 is 50 μm or more. In this formula, N4 represents the number of particles 2 whose diameter D2 is 50 μm or more and the number Nv of pores 18 whose diameter D3 is 0.1 μm or more included in one cross section is 2 or more.

The ratio P3 correlates with the magnetic permeability of the dust core. From the viewpoint of the magnetic properties of the dust core, the ratio P3 is preferably 20% or more, more preferably 18% or less, and particularly preferably 15% or less. The ideal ratio P3 is 0%.

In calculating the ratio P3, the powder is classified using a sieve with an opening of 50 μm. A large number of particles 2 remaining on the sieve are embedded in the resin and polished. Fifty cross sections each having a diameter of 50 μm or more are randomly extracted from the cross sections of a large number of particles 2 appearing on the polished surface. In each of the 50 cross sections, the number of holes 18 having a diameter D3 of 0.1 μm or more is counted. The number of pores 18 having a diameter D3 of 0.1 μm or more in one cross section is defined as the number Nv in the particle 2. Holes 18 that do not appear in this cross section are not included in the number Nv.

[Material of main part]
As mentioned above, the material of the main portion 14 is an iron-based alloy. Iron-based alloys have excellent toughness. This powder is therefore suitable for the press method. A variety of soft magnetic iron-based alloys may be employed in the powder.

Preferably, the iron-based alloy is
Si: 2.0% by mass or more and 10.0% by mass or less,
Cr: 0.0% by mass or more and 10.0% by mass or less,
Al: 0.0% by mass or more and 10.0% by mass or less,
and B: 0.0% by mass or more and 10.0% by mass or less. Preferably, the remainder is Fe and unavoidable impurities.

[Material of insulating film]
The material of the film 16 is an insulating substance. The conductivity of the film 16 is lower than that of the main portion. A film 16 can be formed by oxidizing the surface of the main portion 14 . The material of the film 16 may be an organic substance. An example of the organic substance is a polymer of a mixture of titanium alkoxides and silicon alkoxides. Coating 16 may have two or more layers.

[Production method]
An atomization method, a pulverization method, etc. may be employed to produce this powder. As the atomization method, a gas atomization method, a disk atomization method, a water atomization method, a centrifugal atomization method, etc. are adopted. The gas atomization method and the disk atomization method are preferred from the viewpoint that the oxygen content and nitrogen content in the powder can be suppressed.

Typical voids 18 are gas pores resulting from gas atomization. Gas pores are generated when atomizing gas enters a droplet and solidifies. Helium gas, argon gas, and nitrogen gas are commonly used as inert gases for atomization. Since helium and argon are hardly absorbed by metals, gas pores are likely to occur in gas atomization using helium gas and argon gas. On the other hand, since nitrogen can be absorbed by metals, gas pores are less likely to occur in gas atomization using nitrogen gas. Furthermore, gas pores are less likely to occur even in disk atomization in which droplets are not formed using an inert gas. Preferred atomization methods from the viewpoint of obtaining powder with a small ratio P3 are gas atomization using nitrogen gas and disk atomization.

During atomization, protrusions 10 may attach to the core 8 before solidification of the molten metal is completed. Therefore, the material of the protrusion 10 is generally the same as the material of the core 8. This protrusion 10 is integral with the core 8. Protrusions 10 can also occur on the particles 2 due to other causes.

Preferably, the raw material powder obtained by atomization or the like is subjected to a jet mill treatment to obtain a powder. In the jet mill process, particles 2 collide with each other due to a high-speed jet stream. This collision shatters the protrusion 10. Therefore, a small ratio P2 can be achieved in powders obtained by jet milling. An example of an apparatus suitable for jet mill processing is the product name "MJM1" manufactured by Mtech Chemical Co., Ltd. The protrusions 10 may be crushed by a method other than jet milling.

The powder after jet milling may be annealed. The distortion caused in the particles 2 by jet milling can be removed by annealing. In annealing, the powder is held at a predetermined temperature (e.g., 600° C.) for a predetermined time (e.g., 5 hours) in an inert gas (e.g., argon gas) atmosphere, and then cooled in a furnace.

By subjecting the powder to heat treatment, the surface of the powder may be oxidized and an insulating film 16 may be generated. From the viewpoint of efficiency, it is preferable that the above-mentioned annealing be performed concurrently with this heat treatment. In this case, the atmosphere gas for annealing is the atmosphere (or part of it is the atmosphere).

[Magnetic member]
As a method for obtaining a powder magnetic core from this powder, a pressurization method can be mentioned. In the pressurization method, powder is put into a mold and pressurized. Thereby, a molded body is obtained. In pressurizing, a lubricant, a binder, etc. may be used. This compact is heat treated to obtain a powder magnetic core. Magnetic members other than powder magnetic cores can also be obtained from this powder by the pressing method.

The present specification is also directed to methods of manufacturing magnetic members. This manufacturing method is
A step of preparing an iron-based soft magnetic powder consisting of a large number of particles 2, including particles 2 having a diameter of 50 μm or more, and having a ratio P2 calculated by the following formula of 50% or less,
and compressing the powder.
P2 = (N2 / N1) * 100
In this formula, N1 represents the number of particles 2 having a diameter of 50 μm or more. In this formula, N2 has a diameter of 50 μm or more and includes a core 8 and 20 or more protrusions 10 that are attached to the surface of the core 8 and have a height of 1.0 μm or more. is 1.0 μm or more and the average height of protrusions is 10 μm or more.

Hereinafter, the effects of the soft magnetic powder according to Examples will be clarified, but the scope disclosed in this specification should not be interpreted to be limited based on the description of these Examples.

[Experiment 1]
[Example 1]
A raw material whose material was Alloy 3 shown in Table 1 below was prepared. A raw material powder was obtained by subjecting 30 kg of the raw material to gas atomization using argon gas. This raw material powder was classified using a sieve specified in "JIS Z 8801-1" so that the particle size was 20 μm or more and 150 μm or less. This powder was subjected to jet mill treatment using a jet mill device (the above-mentioned "MJM1") manufactured by Mtech Chemical Co., Ltd.
Compressed air pressure: 0.7MPa
Compressed air volume: 21m ³ /hour (350L/min)
Furthermore, this powder was annealed under the following conditions to obtain the soft magnetic powder of Example 1. Annealing removed the distortion caused by jet milling and also produced an insulating film. The material of this film was an iron-based oxide. The annealing conditions were as follows.
Atmosphere: Part of the atmosphere is replaced with argon gas (oxygen concentration: 500 ppm)
Heating start temperature: normal temperature (25℃)
Temperature increase rate: 0.16℃/s
Achieved temperature: 600℃
Holding time: 5 hours Cooling: Furnace cooling to room temperature

[Example 2-8]
Powders of Examples 2-8 were obtained in the same manner as in Example 1, except that the materials and atomizing gas were changed as shown in Table 2 below.

[Example 9-11]
Powders of Examples 9-11 were obtained in the same manner as in Example 1, except that the materials were as shown in Table 2 below, disk atomization was performed instead of gas atomization, and jet mill treatment was not performed.

[Comparative example 1-4]
A powder of Comparative Example 1-4 was obtained in the same manner as in Example 1 except that the materials and atomizing gas were as shown in Table 2 below, and the jet mill treatment was not performed.

[evaluation]
The powder was put into a mold and a pressure of 1520 MPa was applied to obtain a toroidal shaped molded body. The size of this molded body was as follows.
Outer diameter: 28mm
Inner diameter: 15mm
Height: 3mm

This compact was subjected to strain relief annealing to obtain a powder magnetic core. The annealing conditions were as follows.
Atmosphere: Argon gas (oxygen concentration: less than 1 ppm)
Heating start temperature: normal temperature (25℃)
Temperature increase rate: 0.16℃/s
Achieved temperature: 800℃
Holding time: 1 hour Cooling: Furnace cooling to room temperature The electrical resistance value of the powder core obtained from the powders of Example 1-11 and Comparative Example 1-4 was 1×10 ⁷ Ω・cm ³ or more. The insulation properties were sufficient.

The density and magnetic permeability μ' of this powder magnetic core were measured. A powder magnetic core with a large magnetic permeability μ' is less likely to cause core loss. Furthermore, grading was performed according to the following criteria. The results are shown in Table 2 below.
S: Magnetic permeability is 30 or more.
A: Magnetic permeability is 20 or more and less than 30.
B: Magnetic permeability is 15 or more and less than 20.
F: Magnetic permeability is less than 15.

[Experiment 2]
[Example 12-21]
Powders of Examples 12-21 were obtained in the same manner as in Example 1, except that the materials and atomizing gas were changed as shown in Table 3 below.

[Example 22-26]
Powders of Examples 22-26 were obtained in the same manner as in Example 1, except that the materials were as shown in Table 3 below, disk atomization was performed instead of gas atomization, and jet mill treatment was not performed.

[Comparative Example 5-9]
Powders of Comparative Examples 5-9 were obtained in the same manner as in Example 1 except that the materials and atomizing gas were as shown in Table 3 below and the jet mill treatment was not performed.

[evaluation]
A powder magnetic core was obtained in the same manner as in Experiment 1. The electric resistance value of the powder magnetic core obtained from the powder according to each of Example 12-26 and Comparative Example 5-9 was 1×10 ⁷ Ω·cm ³ or more, and the insulation property was sufficient.

The density and magnetic permeability μ' of this powder magnetic core were measured. Furthermore, grading was performed according to the following criteria. The results are shown in Table 3 below.
S: Magnetic permeability is 25 or more.
A: Magnetic permeability is 15 or more and less than 25.
B: Magnetic permeability is 10 or more and less than 15.
F: Magnetic permeability is less than 10.

[Experiment 3]
[Example 27-35]
Powders of Examples 27-35 were obtained in the same manner as in Example 1, except that the materials and atomizing gas were changed as shown in Table 4 below.

[Example 36-38]
Powders of Examples 36-38 were obtained in the same manner as in Example 1, except that the materials were as shown in Table 4 below, disk atomization was performed instead of gas atomization, and jet mill treatment was not performed.

[Comparative Example 10-13]
Powders of Comparative Examples 10-13 were obtained in the same manner as in Example 1 except that the materials and atomizing gas were as shown in Table 4 below and the jet mill treatment was not performed.

[evaluation]
A powder magnetic core was obtained in the same manner as in Experiment 1. The electric resistance value of the dust core obtained from the powder according to each of Examples 27-35 and Comparative Example 10-13 was 1×10 ⁷ Ω·cm ³ or more, and the insulation properties were sufficient.

The density and magnetic permeability μ' of this powder magnetic core were measured. Furthermore, grading was performed according to the following criteria. The results are shown in Table 4 below.
S: Magnetic permeability is 20 or more.
A: Magnetic permeability is 10 or more and less than 20.
B: Magnetic permeability is 5 or more and less than 10.
F: Magnetic permeability is less than 5.

As shown in Table 2-4, molded bodies with excellent magnetic properties can be obtained from the powders according to each example. From these evaluation results, the superiority of the present invention is clear.

The powder described above is suitable for various magnetic members.

2... Particle 4... First imaginary circle 6... Outline (of particle) 8... Core 10... Protrusion 12... Second imaginary circle 14... Main part 16... Film 18...Void 20...Top 22...Third virtual circle 24...Outline (of the pore)

Claims (7)

Consisting of many particles,
These particles include particles having a diameter of 50 μm or more,
Iron-based soft magnetic powder whose ratio P2 calculated by the following formula is 50% or less.
P2 = (N2 / N1) * 100
(In this formula, N1 represents the number of particles with a diameter of 50 μm or more.)
(In this formula, N2 has a diameter of 50 μm or more and includes a core and 20 or more protrusions that are attached to the surface of this core and have a height of 1.0 μm or more, and whose height is 1.0 μm or more.) .Represents the number of particles whose protrusions have an average height of 10 μm or more.) The soft magnetic powder according to claim 1, wherein the ratio P1 calculated by the following formula is 50% or more.
P1 = (N3 / N) * 100
(In this formula, N represents the total number of particles, and N3 represents the number of particles whose circularity is 0.8 or more.) The soft magnetic powder according to claim 2, wherein the ratio P1 is 80% or less. The soft magnetic powder according to claim 1 or 2, wherein the ratio P3 calculated by the following formula is 20% or less.
P3 = (N4 / N1) * 100
(In this formula, N1 represents the number of particles with a diameter of 50 μm or more.)
(In this formula, N4 represents the number of particles with a diameter of 50 μm or more and the number of pores included in one cross section with a diameter of 0.1 μm or more is 2 or more.) The soft magnetic powder according to claim 1 or 2, wherein the ratio P4 calculated by the following formula is 50% or more.
P4 = (N1 / N) * 100
(In this formula, N represents the total number of particles, and N1 represents the number of particles with a diameter of 50 μm or more.) Each particle has a main part and an insulating film covering all or part of the surface of the main part,
The soft magnetic powder according to claim 1 or 2, wherein the material of the main portion is an iron-based alloy. A step of preparing an iron-based soft magnetic powder consisting of a large number of particles, including particles having a diameter of 50 μm or more, and having a ratio P2 calculated by the following formula of 50% or less,
and A method for manufacturing a magnetic member, comprising the step of pressurizing the powder.
P2 = (N2 / N1) * 100
(In this formula, N1 represents the number of particles with a diameter of 50 μm or more.)
(In this formula, N2 has a diameter of 50 μm or more and includes a core and 20 or more protrusions that are attached to the surface of this core and have a height of 1.0 μm or more, and whose height is 1.0 μm or more.) .Represents the number of particles whose protrusions have an average height of 10 μm or more.)

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