JP2022001659A - Iron-based powder for dust core and dust core using the same - Google Patents

Abstract

To provide iron-based powder for a dust core capable of bring out a dust core having low iron loss and high insulation properties.SOLUTION: In iron-based powder for a dust core, the central value of the particle diameters calculated by volume frequency on accumulation of particles composing the iron-based powder for a dust core is 150 μm or lower, the volume frequency on accumulation in the circularity of 0.70 or lower in the particles is 30% or lower, and also, the central value of the circularity calculated by the volume frequency on accumulation is 0.80 or higher.SELECTED DRAWING: None

Description

The present invention relates to an iron-based powder for a dust core and a powder core using the iron-based powder.

Compared to the melting method, the powder metallurgy method is applied to the production of various parts because it has high dimensional accuracy even in the production of parts having complicated shapes and the waste of raw materials is small. Examples of the product manufactured by the powder metallurgy method include a dust core. The dust core is a magnetic core manufactured by pressure-molding powder, and is used for an iron core such as a reactor. In recent years, particularly in hybrid vehicles and electric vehicles, reactors and the like that are small in size and have excellent magnetic characteristics are required to improve the cruising range, and the dust cores used are also required to have better magnetic characteristics. There is. Therefore, a compact magnetic core in which a ferromagnetic metal powder having a high magnetic flux density and a low iron loss is coated with an insulating film and pressure-molded has been put into practical use.

In particular, in order to reduce the iron loss of the dust core, it is necessary to reduce the hysteresis loss and the eddy current loss that constitute the iron loss. As a means for that, a technique focusing on the circularity of the metal powder particles has been proposed.
For example, in Patent Document 1, the number fraction of particles having a circularity of 0.75 or more is 50% or more, and the fractional proportion of particles having a circularity of 0.65 or less is 15% or less, and is equivalent to a circle. It is disclosed that the coercive force is reduced and the hysteresis loss is reduced by using the iron-based powder having an average diameter of 50 μm or more.
In Patent Document 2, by using a powder having a maximum value of the circularity of particles of 0.5 or more and an average value of 0.2 or more, the fluidity when the powder is filled in a mold is improved. It is disclosed to improve soft magnetic properties.

Japanese Unexamined Patent Publication No. 2009-200325 Japanese Unexamined Patent Publication No. 2019-21906

However, if the number fraction of the particles having a circularity of a certain value or less is set to a certain value or less as in the technique of Patent Document 1, there are cases where there are many particles having an extremely low circularity, and the target maintenance is performed. Problems such as the inability to obtain magnetic force may occur.
Just by specifying the maximum value of 0.5 or more and the average value of 0.2 or more for the circularity of the particles as in the technique of Patent Document 2, the fluidity of the powder correlates with the void ratio of the dust core. The low circularity particles that affect it are not fully considered and are insufficient for improving fluidity.

An object of the present invention is to provide an iron-based powder for a dust core that can solve the above problems and provide a powder core having low iron loss and high insulating properties.

The present inventors pay attention to the circularity distribution of the volume frequency of the entire powder particles and the median value of the circularity as the characteristic values of the powder, and the cumulative volume frequency of the particles having a predetermined circularity and the circularity of the entire particles. It was found that it is possible to produce a dust core having low iron loss and high insulating property by setting the condition range for these indexes using the two as the median value of. The present invention is based on the above findings, and its gist structure is as follows.

[1] The median particle size of the iron-based powder for the dust core, which is calculated by the cumulative volume frequency of the particles constituting the iron-based powder for the powder magnetic core, is 150 μm or less, and the particles have the same particle size. An iron-based powder for a dust core having a cumulative volume frequency of 0.70 or less and a median circularity of 0.80 or more calculated by the cumulative volume frequency of 30% or less.
[2] The iron-based powder for a compact magnetic core according to [1], wherein the maximum particle size of the particles is 500 μm or less.
[3] The composition of the components excluding unavoidable impurities is the composition formula; Fe _a Si _b B _c P _d Cu _e M _f.
(During the ceremony,
79 at% ≤ a ≤ 84.5 at%,
0 at% ≤ b <6 at%,
0 at% <c ≤ 10 at%,
4at% <d≤11at%,
0.2 at% ≤ e ≤ 1.5 at%,
0 at% ≤ f ≤ 4 at%, and a + b + c + d + e + f = 100 at%.
M is at least one element selected from the group consisting of Nb, Mo, Ni, Sn, Zr, Ta, W, Hf, Ti, V, Cr, Mn, C, Al, S, O and N).
The iron-based powder for a compact magnetic core according to [1] or [2], which comprises the soft magnetic powder indicated by.
[4] The iron-based powder for a dust core according to any one of [1] to [3], which has an insulating coating on the surface of the particles.
[5] A dust core made of the iron-based powder for the powder core according to any one of [1] to [4].

The following can be presumed as the reason why the iron-based powder for a dust core of the present invention can produce a powder core having low iron loss and high insulation.
In the iron-based powder for a dust core of the present invention, since the proportion of particles having extremely low circularity is small and the median circularity of the entire powder particles is large, it can be a pinning site of a magnetic wall in one particle. The unevenness on the surface of the powder particles is reduced, and the domain wall can be easily moved. As a result, the coercive force is reduced, so that the hysteresis loss is reduced.
Further, since the powder particles are close to a spherical shape, the destruction of the insulating coating of the powder particles in the green compact is reduced, and the conduction between the powder particles is also reduced, so that the eddy current loss is reduced. Furthermore, the powder particles that are close to a spherical shape have high fluidity, improve the filling property into the mold when producing the dust core, and rearrange the particles in the powder even during powder molding by pressure molding. While promoting, the friction between the mold and the particles is reduced. Therefore, the powder can be easily moved on the wall surface of the mold and can be easily consolidated, and a high-density powder magnetic core can be produced. Reduction of iron loss can be achieved by increasing the powder density.

According to the iron-based powder for a dust core of the present invention, a powder core having low iron loss and high insulating property is provided.

Hereinafter, embodiments of the present invention will be described. The following description shows a preferred embodiment of the present invention and does not limit the present invention in any way.

<Iron-based powder for compaction core>
The iron-based powder for a compact magnetic core (hereinafter, also referred to as “iron-based powder”) according to an embodiment of the present invention has a median particle size of 150 μm or less calculated by the cumulative volume frequency of the constituent particles. The cumulative volume frequency of the particles having a circularity of 0.70 or less is 30% or less, and the median circularity calculated by the cumulative volume frequency is 0.80 or more. Here, the "iron-based powder" refers to a metal powder containing 50% by mass or more of Fe.

[Median particle size]
In the iron-based powder of the present invention, the median value D _{50 of the} particle size calculated by the cumulative volume frequency of the constituent particles is 150 μm or less. When the median particle size D ₅₀ is smaller than the above upper limit, the fluidity of the powder is higher, the filling density in the mold is improved, and the density of the dust core is improved, and iron is used. The loss can be sufficiently reduced. Further, the fine particles can reduce the eddy current loss, which is also advantageous for reducing the iron loss. The median particle size D ₅₀ is preferably 100 μm or less. On the other hand, the median particle size D ₅₀ can be 3 μm or more, preferably 5 μm or more, from the viewpoint of uniformly coating the powder with a resin.

The method for calculating the _{median particle size D 50} from the particle size measurement and the cumulative volume frequency is as follows.
To measure the particle size, the target powder is put into a solvent (for example, ethanol), dispersed by ultrasonic vibration for 30 seconds or longer, and then measured by a laser diffraction type particle size distribution measuring machine using a laser diffraction / scattering method. Measure the particle size distribution based on the volume of the particles. The cumulative particle size distribution is calculated from the obtained particle size distribution, and the particle size of the particles corresponding to 50% of the total volume of all particles is set _{as the median D 50 and} used as a representative value of the particle size of the corresponding powder.

（ここで、
Ｃは、円形度であり、
Ａは、１粒子の投影面積であって、単位はｍ²であり、
Ｐは、１粒子の粒子周囲長さであって、単位はｍである。） [Circularity]
The circularity (C) in the present invention is a value defined by the following equation (1).

(here,
C is circularity
A is the projected area of one particle, and the unit is m ² .
P is the peripheral length of one particle, and the unit is m. )

The measurement of circularity shall be as follows.
The powder to be measured is dispersed on a flat surface (for example, the surface of a glass plate) with compressed air, for example, and an image of each particle is taken with a microscope. The total number of particles in the powder to be measured shall be 1000 or more.
The captured image is analyzed by a computer, and the projected area and perimeter of each particle are measured. Substituting the measurement result into the above equation (1), the circularity of each particle is calculated.
The diameter of a circle having the same area as the projected area of each particle (circle equivalent diameter) is calculated, and the volume of a sphere having the same diameter as the diameter is calculated. As a result, the circularity and volume of each particle can be obtained, the volume frequency at each circularity can be calculated, and the cumulative volume frequency (volume ratio) of particles having a circularity of 0.70 or less can be obtained.

The circularity of all particles in the powder to be measured is arranged in ascending order, and the median circularity of particles corresponding to 50% of the total volume of all particles is defined as C ₅₀ . Since the upper limit of the circularity is 1 according to the definition, the median circularity is 1 or less. Since the average value of circularity is greatly affected by the value of particles having a large circularity, the median value C ₅₀ of circularity is used in the present invention as an index indicating the circularity of the entire powder.

In the iron-based powder of the present invention, the cumulative volume frequency (volume ratio) of the particles constituting the powder having a circularity of 0.70 or less is 30% or less, and the median circularity calculated by the cumulative volume frequency C ₅₀ is 0.80 or more. When one or both of these conditions are not satisfied, the coercive force of the particles increases due to the high volume frequency of the particles that deviate from the spherical shape and have an irregular shape, and the insulating coating of the particles is also destroyed. The increase causes a hysteresis loss of the dust core and an increase in eddy current loss between particles, and finally the iron loss also increases. Preferably, the cumulative volume frequency with a circularity of 0.70 or less is 20% or less, and the median circularity C ₅₀ calculated from the cumulative volume frequency is 0.85 or more. The cumulative volume frequency with a circularity of 0.70 or less may be 0%. _{Further, the upper limit of the median value C 50} of the circularity calculated by the cumulative volume frequency is 1, and may be 1.

[Maximum particle size]
The iron-based powder of the present invention preferably has a maximum particle size of 500 μm or less. By setting the maximum particle size to 500 μm or less, the more the particle size of the entire powder particles becomes uniform to some extent, the more particles with similar particle sizes gather closer together to prevent segregation of the particles and the fine particles adhering to the surface of the coarse particles. As the number decreases and fine particles enter into the gaps between the particles created by the coarse particles, the powder magnetic core can be made denser and stronger, leading to lower iron loss. On the other hand, the maximum particle size can be 10 μm or more from the viewpoint of uniformly coating the powder with a resin. Maximum particle size is the maximum value of the particle size distribution when measured by a laser diffraction particle size distribution analyzer, the measurement conditions are the same as the above measurement of D _50. From the viewpoint of particle homogenization, the maximum particle size is preferably 2 times or less, more preferably 1.5 times or less of _{D 50.}

[Ingredient composition]
The iron-based powder of the present invention has a component composition excluding unavoidable impurities.
Composition formula: Fe _a Si _b B _c P _d Cu _e M _f
(During the ceremony,
79 at% ≤ a ≤ 84.5 at%,
0 at% ≤ b <6 at%,
0 at% <c ≤ 10 at%,
4at% <d≤11at%,
0.2 at% ≤ e ≤ 1.5 at%,
0 at% ≤ f ≤ 4 at%,
a + b + c + d + e + f = 100 at%,
M is at least one element selected from the group consisting of Nb, Mo, Ni, Sn, Zr, Ta, W, Hf, Ti, V, Cr, Mn, C, Al, S, O and N).
It is preferably composed of the soft magnetic powder represented by. With such a composition, the crystallinity of the powder can be suppressed to 10% or less, and nanocrystals of bccFe can be precipitated after the heat treatment to further improve the magnetic properties.
The soft magnetic powder may contain unavoidable impurities that are inevitably mixed in from the manufacturing process or the like, but the above composition formula excludes unavoidable impurities.

Fe is an essential element responsible for magnetism, and the proportion of Fe can be 79 at% or more and 84.5 at% or less, preferably 80 at% or more, and 83.5 at% or less.

Si is an element responsible for forming an amorphous phase, and the proportion of Si can be less than 6 at% (including zero), preferably 2 at% or more, and more preferably 5.5 at% or less. Is.

B is an element responsible for forming an amorphous phase, and the proportion of B can be 4 at% or more and 10 at% or less, preferably 5 at% or more, and preferably 9 at% or less.

P is. It is an element responsible for forming an amorphous phase, and the proportion of P can be more than 4 at% and 11 at% or less, preferably more than 5 at%, and preferably 10 at% or less.

Cu is an element that contributes to nanocrystallization, and the proportion of Cu can be 0.2 at% or more and less than 1.5 at%, preferably 0.3 at% or more, and preferably 1 It is 0.0 at% or less.

In addition to the above elements, at least one element selected from the group consisting of Nb, Mo, Ni, Sn, Zr, Ta, W, Hf, Ti, V, Cr, Mn, C, Al, S, O and N can be used. It may be included. The proportion of these elements can be 4 at% or less (including zero).

[Manufacturing of powder]
The iron-based powder of the present invention can be produced by using a water atomizing method or a gas atomizing method in which water or gas is sprayed onto a molten metal to form a spray and cooled and solidified. Alternatively, it can also be obtained by processing the powder obtained by the pulverization method or the oxide reduction method.
When the water atomizing method or the gas atomizing method is used, the circularity can be set within a predetermined range by adjusting the water or the gas to which the gas is blown to a low pressure. Alternatively, the circularity can be adjusted by smoothing the surface of the particles or by classifying the particles with a sieve to remove particles having a low circularity. For example, smoothing the particle surface of the powder obtained by the pulverization method, the oxide reduction method, the normal high-pressure water atomization method or the gas atomization method, and / or classifying with a sieve to obtain particles having a low circularity. It can also be removed to obtain the iron-based powder of the present invention.

When the iron-based powder of the present invention is a powder composed of a soft magnetic powder having a predetermined composition formula, it can be produced by adjusting the raw materials so as to have a predetermined composition. For example, when the water atomizing method or the gas atomizing method is used, the raw materials are weighed so as to have a predetermined composition and melted to prepare a molten alloy, and the molten alloy is discharged from a nozzle and sprayed with water or gas to form a spray. Can be cooled and solidified, and optionally processed to obtain the desired powder.

[Insulation coating]
The iron-based powder for a dust core of the present invention can be provided with an insulating coating on the surface of the particles constituting the iron-based powder for a dust core.

The insulating coating is not particularly limited, and may be an inorganic insulating coating or an organic insulating coating. Either one of these may be used or both may be used.
As the inorganic insulating coating, a coating film containing an aluminum compound is preferable, and a coating film containing aluminum phosphate is more preferable. The inorganic insulating coating may be a chemical conversion film.
As the organic insulating coating, an organic resin coating is preferable. Examples of the organic resin film include silicone resin, phenol resin, epoxy resin, polyamide resin, and polyimide resin. These may be contained alone, or two or more kinds may be contained in an arbitrary ratio. Above all, a film containing a silicone resin is more preferable.
The insulating coating may be a single-layer coating or a multilayer coating consisting of two or more layers. The multilayer coating may be a multilayer coating composed of the same type of coating or a multilayer coating composed of different types of coatings.

Examples of the silicone resin include SH805, SH806A, SH840, SH997, SR620, SR2306, SR2309, SR2310, SR2316, DC12577, SR2400, SR2402, SR2404, SR2405, SR2406, SR2410, SR2411, manufactured by Toray Dow Corning Co., Ltd. SR2416, SR2420, SR2107, SR2115, SR2145, SH6018, DC-2230, DC3037, QP8-5314, and KR-251, KR-255, KR-114A, KR-112, KR-2610B manufactured by Shin-Etsu Chemical Co., Ltd. , KR-2621-1, KR-230B, KR-220, KR-285, K295, KR-2019, KR-2706, KR-165, KR-166, KR-169, KR-2038, KR-221, KR -155, KR-240, KR-101-10, KR-120, KR-105, KR-271, KR-282, KR-311, KR-221, KR-212, KR-216, KR-213, KR 217, KR-9218, SA-4, KR-206, ES-1001N, ES-1002T, ES1004, KR-9706, KR-5203, KR-5221 and the like, but are not limited thereto. These may be used alone or in any ratio of two or more.

As the aluminum compound, any compound including aluminum can be used, and examples thereof include aluminum phosphates, nitrates, acetates, and hydroxides. These may be used alone or in any ratio of two or more.
The coating containing the aluminum compound may be a coating mainly composed of the aluminum compound, or may be a coating made of the aluminum compound. The coating may further contain a metal compound containing a metal other than aluminum. Examples of metals other than aluminum include Mg, Mn, Zn, Co, Ti, Sn, Ni, Fe, Zr, Sr, Y, Cu, Ca, V, Ba and the like. These may be used alone or in any ratio of two or more. Examples of the metal compound containing a metal other than aluminum include phosphates, carbonates, nitrates, acetates, hydroxides and the like. These may be used alone or in any ratio of two or more. The metal compound is preferably soluble in a solvent such as water, and more preferably a water-soluble metal salt.

When the phosphorus content in the coating containing an aluminum-containing phosphate or phosphoric acid compound is P (mol) and the total content of all metal elements in the coating is M (mol), the ratio of P to M ( It is preferable that P / M) is 1 or more and less than 10. When the P / M is 1 or more, the chemical reaction on the surface of the iron-based powder at the time of coating formation proceeds sufficiently, and the adhesion of the coating is improved, thereby further improving the strength and insulating property of the dust core. Can be made to. On the other hand, when the P / M is less than 10, free phosphoric acid does not remain after the coating is formed, and the corrosion of the iron-based powder can be sufficiently prevented. The P / M is more preferably 1 to 5, and the P / M is further preferably 2 to 3 from the viewpoint of effectively preventing the variation and instability of the specific resistance.

In a coating containing an aluminum-containing phosphate or phosphoric acid compound, when the aluminum content is A (mol), A with respect to M (mol), which is the total content of all metal elements in the coating. The ratio (A / M) of is preferably more than 0.3 and 1 or less. Within this range, aluminum having high reactivity with phosphoric acid is sufficiently present, and the residual unreacted free phosphoric acid can be suppressed. The A / M is more preferably 0.4 to 1.0, still more preferably 0.8 to 1.0.

The amount of the insulating coating is not particularly limited, but is preferably 0.01 to 10% by mass. When the coating amount is within the above range, a uniform coating can be formed, sufficient insulating properties can be ensured, and the proportion of the iron-based powder in the dust core can be secured. Sufficient molded body strength and magnetic flux density can be obtained.
Here, the covering amount refers to a value defined by the following equation.
Coverage (mass%) = (mass of insulation coating) / (mass of iron-based powder for dust core excluding insulation coating) x 100

The iron-based powder for a compact magnetic core of the present invention may contain a substance different from the above-mentioned insulating coating in at least one of the insulating coating under the insulating coating and above the insulating coating. Examples of such a substance include a surfactant for improving wettability, a binder for binding between particles, an additive for adjusting pH, and the like. The total amount of the substance with respect to the entire insulation coating is preferably 10% by mass or less.

The method for forming the insulating coating is not particularly limited, but it is preferably formed by wet treatment. Examples of the wet treatment include a method of mixing a treatment liquid for forming an insulating coating and an iron-based powder.
The mixing method is not particularly limited, but a method of stirring and mixing the iron-based powder and the treatment solution in a tank such as an attritor or a Henschel mixer, a rolling flow type coating device, or the like, the iron-based powder is made into a fluid state, and the treatment solution is prepared. A method of supplying and mixing is preferable.
The whole amount of the solution to the iron-based powder may be supplied before or immediately after the start of mixing, or may be supplied in several batches during mixing. Alternatively, the treatment liquid may be continuously supplied during mixing by using a droplet supply device, a spray, or the like.
The supply of the treatment liquid is not particularly limited, but it is preferably performed by using a spray. By using a spray, the treatment solution can be evenly sprayed over the entire iron-based powder, and the spray conditions can be adjusted to reduce the diameter of the spray droplets to about 10 μm or less, resulting in excess coating. This is because it can be prevented from becoming thick and a uniform and thin insulating coating can be easily formed on the iron-based powder. On the other hand, stirring and mixing can also be performed by a flow tank such as a flow granulator or a rolling granulator, or a stirring type mixer such as a Henshell mixer, and these have the advantage of suppressing aggregation of powders. Have. From the viewpoint of forming a more uniform insulating coating on the iron-based powder, it is preferable to combine a flow tank or a stirring type mixer with the supply of the treatment solution by spraying. It is advantageous to perform heat treatment in the mixer or after mixing from the viewpoint of accelerating the drying of the solvent and accelerating the reaction.

<Powder core>
The dust core according to another embodiment of the present invention is a powder core made by using the iron-based powder for the powder core.
The method for producing the dust core is not particularly limited, and any method can be used. For example, a dust core can be obtained by charging the iron-based powder of the present invention into a mold and pressure-molding the iron-based powder so as to have a desired size and shape. The iron-based powder preferably has an insulating coating.

The pressure molding is not particularly limited, and any method can be used, and examples thereof include a room temperature molding method and a mold lubrication molding method.
The molding pressure can be appropriately determined according to the intended use, but is preferably 490 MPa or more, more preferably 686 MPa or more, from the viewpoint that if the molding pressure is increased, the powder density increases and the magnetic properties are improved. ..

A lubricant can be used for pressure molding. The lubricant may be applied to the wall surface of the mold or added to the iron-based powder. By using a lubricant, it is possible to reduce the friction between the mold and the powder during pressure molding, further suppressing the decrease in the density of the molded body, and the friction when extracting from the mold. Can also be reduced, and cracking of the molded body (compact magnetic core) at the time of taking out can be prevented.
The lubricant is not particularly limited, and examples thereof include metal soaps such as lithium stearate, zinc stearate and calcium stearate, and waxes such as fatty acid amides.

The obtained dust core may be heat-treated. By performing the heat treatment, effects such as reduction of hysteresis loss due to strain removal and increase of molded body strength can be expected. The heat treatment conditions can be appropriately determined, but the temperature is preferably 200 to 700 ° C. and the time is preferably 5 to 300 minutes. The heat treatment can be performed in any atmosphere such as the atmosphere, the inert atmosphere, the reducing atmosphere, and the vacuum. It is also possible to provide a step of maintaining a constant temperature when the temperature is raised or lowered during the heat treatment.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to Examples.

The iron-based powder was prepared by the following procedure.
Amorphous soft magnetic alloy powder with composition Fe ₈₁ Si ₃ B ₉ P ₆ Cu ₁ and soft magnetic alloy amorphous powder with composition Fe _81.3 Si ₂ B ₇ P ₉ Cu _0.5 Sn _0.2 are manufactured by quenching solidification by water atomization method. did. A dry powder was obtained from the produced powder by vacuum drying.
The dry powder was classified and the particle size and circularity were adjusted. An air flow classifier (Laboclassile N-01 manufactured by Seishin Enterprise Co., Ltd.) was used for classifying, and the dispersion plate was rotated at a speed of 1000 to 1650 rpm for classifying. Further, as comparative powders (Comparative Example 1 and Comparative Example 8), powders prepared only by the water atomization method without performing classification by an air flow classifier were prepared.

The evaluation of the iron-based powder was as follows.
The dry powder was dispersed on a glass surface, and 5000 particles per sample were observed and photographed with a microscope (Moforogi G3 manufactured by Spectris Co., Ltd.). A lens with a magnification of 10 times was used for the microscope. From the calculated circularity and volume frequency, the cumulative volume frequency (volume ratio) of particles having a circularity of 0.70 or less and the median value C ₅₀ , which is a representative value of the circularity of the entire powder particles, were calculated. In addition, the particle size and volume frequency of the dry powder were measured by using a laser diffraction type particle size distribution measuring machine (LA-950V2 manufactured by HORIBA, Ltd.) to put the soft magnetic alloy amorphous powder into the solvent ethanol for 1 minute. It was measured after dispersion by sonic vibration. _{From the particle size and volume frequency, the median value D 50} , which is a representative value of the particle size of the entire powder particles, was calculated. The maximum particle size is the maximum value of the particle size distribution when measured by a laser diffraction type particle size distribution measuring machine.

The dust core was created by the following procedure.
The soft magnetic alloy amorphous powder was coated with insulation by adding and mixing a solution for insulating coating to obtain a coating powder. The solution used was a solution obtained by diluting silicone resin (resin content 60% by mass) by adding xylene, and the amount of resin to be 3% by mass with respect to the soft magnetic alloy amorphous powder was used. After mixing, it was allowed to stand in an air atmosphere for 10 hours for drying. After drying, heat treatment was performed at 150 ° C. for 60 minutes to cure the resin.
Next, these coated soft magnetic alloy amorphous powders were filled in a mold coated with lithium stearate and pressure-molded to obtain a powder magnetic core (outer diameter 38 mmφ x inner diameter 25 mmφ x height 6 mm). The molding pressure was 1470 MPa, and molding was performed once. Was heat treated for 20 minutes at 400 ° C. After heating at 3 ° C. / min from room temperature in a furnace under a N ₂ atmosphere for strength improvement of the shaped body. After the heat treatment _{, the sample was taken out from the furnace in an N 2} atmosphere and then air-cooled to room temperature, and the obtained sample was used as a dust core.

The evaluation of the dust core was as follows.
The dust density of each of the obtained dust cores was determined. The dust density was calculated by measuring the mass of the dust core and dividing the mass by the volume calculated from the dimensions of the powder core.
The prepared powder magnetic core was wound in 100 turns on the primary side and 20 turns on the secondary side to prepare a sample for measurement. A hysteresis loop was drawn at a maximum magnetic flux density of 0.1 T and 50 Hz using a DC magnetization characteristic test device (SK-110 type manufactured by Metron Giken Co., Ltd.), and the area was defined as a hysteresis loss. The measured hysteresis loss was multiplied by 400 to calculate the hysteresis loss at a magnetic flux density of 0.1 T and a frequency of 20 kHz. In addition, iron loss at 0.1 T and 20 kHz was measured using a high-frequency iron loss measuring device (manufactured by Metron Giken Co., Ltd.). The difference between the measured iron loss and the above-mentioned hysteresis loss was calculated as an eddy current loss.
The magnetic characterization is as follows.
Iron loss is 250kW / m ³ or less ... ◎
Iron loss is 300 kW / m ³ or less 250 kW / m over ³ ... 〇 Iron loss is over 300 kW / m ³ ... ×

Table 1 shows the classification conditions, the evaluation of the powder, and the evaluation of the dust core for the comparative examples and the examples using the soft magnetic alloy amorphous powder having _{the composition of Fe 81} Si ₃ B ₉ P ₆ Cu _1.

As shown in Table 1, D ₅₀ is 150 μm or less, the cumulative volume frequency (volume ratio) with a circularity of 0.70 or less is 30% or less, and the median circularity C ₅₀ is 0.80. When the powder of the above-mentioned examples is used, the iron loss of the dust core is 300 kW / m ³ or less, and it can be seen that the used powder is excellent as the iron-based powder for the powder core.
Focusing on the hysteresis loss and the eddy current loss with respect to the iron loss, the examples were both low and excellent as compared with the comparative examples. This is because the powder of the example has fewer low circularity particles with a circularity of 0.70 or less, C ₅₀ indicating the circularity of the entire powder is also high, and many particles are close to spherical, so that the coercive force of the particles is large. It can be said that this is because the hysteresis loss is reduced because the value is low, and the vortex current loss between the particles is reduced because the insulation coating on the particle surface is less damaged when the dust core is used.
Among them, in Examples 3 and 4 in which a powder having a cumulative volume frequency (volume ratio) of 0.70 or less of circularity of 20% or less, C ₅₀ of 0.85 or more, and D ₅₀ of 100 μm or less was used, the dust core was used. It can be seen that the iron loss of the core is 250 kW / m ³ or less, and the powder used is more excellent as the iron-based powder for the compact magnetic core.

Table 2 shows the classification conditions, the evaluation of the powder, and the evaluation of the dust core for comparative examples and examples using the soft magnetic alloy amorphous powder having a _{composition of Fe 81.3} Si ₂ B ₇ P ₉ Cu _0.5 Sn _0.2.

As shown in Table 2, _{Examples in which D 50} is 150 μm or less, the cumulative volume frequency (volume ratio) of circularity 0.70 or less is 30% or less, and C ₅₀ is 0.80 or more. When the powder of the above is used, the iron loss of the powder magnetic core is 300 kW / m ³ or less, and it can be seen that it is excellent as the iron-based powder for the powder magnetic core.
Focusing on the hysteresis loss and the eddy current loss in the iron loss, the examples were both low and excellent as compared with the comparative examples. This is because the powder of the example has fewer low circularity particles with a circularity of 0.70 or less, C ₅₀ indicating the circularity of the entire powder is also high, and many particles are close to spherical, so that the coercive force of the particles is large. It can be said that this is due to the fact that the hysteresis loss is reduced because the value is low, and the destruction of the insulating coating on the particle surface when the dust core is used is also reduced, and the eddy current loss between the particles is reduced.
Above all, when the powders of Examples 7 and 8 having a circularity of 0.70 or less, a volume ratio of 20% or less, a C ₅₀ of 0.85 or more, and a D ₅₀ of 100 μm or less are used, the iron loss of the dust core Is 250 kW / m ³ or less, and it can be seen that it is even more excellent as an iron-based powder for a compact magnetic core.

The powder magnetic core using the iron-based powder for the powder magnetic core of the present invention has low iron loss and high insulating properties, and is highly useful.

Claims (5)

The median particle size of the iron-based powder for the dust core, which is calculated by the cumulative volume frequency of the particles constituting the iron-based powder for the dust core, is 150 μm or less, and the circularity of the particles is 0. An iron-based powder for a dust core having a cumulative volume frequency of .70 or less of 30% or less and a median circularity of 0.80 or more calculated by the cumulative volume frequency. The iron-based powder for a dust core according to claim 1, wherein the maximum particle size of the particles is 500 μm or less. The composition of the components excluding unavoidable impurities is the composition formula; Fe _a Si _b B _c P _d Cu _e M _f.
(During the ceremony,
79 at% ≤ a ≤ 84.5 at%,
0 at% ≤ b <6 at%,
0 at% <c ≤ 10 at%,
4at% <d≤11at%,
0.2 at% ≤ e ≤ 1.5 at%,
0 at% ≤ f ≤ 4 at%, and a + b + c + d + e + f = 100 at%.
M is at least one element selected from the group consisting of Nb, Mo, Ni, Sn, Zr, Ta, W, Hf, Ti, V, Cr, Mn, C, Al, S, O and N).
The iron-based powder for a compact magnetic core according to claim 1 or 2, which comprises the soft magnetic powder represented by. The iron-based powder for a dust core according to any one of claims 1 to 3, which has an insulating coating on the surface of the particles. A dust core made of the iron-based powder for the powder core according to any one of claims 1 to 4.