JP2000232014A - Manufacture of composite magnetic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide composite magnetic materials related to a metallic system power core with high performance to be used for a choke coil with a low core loss, high magnetic permeability, and satisfactory DC superimposing characteristics. SOLUTION: This composite magnetic material is obtained through compression molding the mixture of a magnetic powder with insulating materials, and then subjecting it to heat treatment. In this case, the heat treatment is carried out twice, and if the first heat treatment oxidizing atmosphere is defined as P1, and the second heat treatment oxidizing atmosphere is defined as P2, the relation P1>P2 is satisfied. Thus, a method for manufacturing the composite magnetic powder having low core loss and superior DC superimposing characteristics can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-performance metal-based composite magnetic material used for a choke coil and the like, and more particularly to a method for producing a composite magnetic material used as a soft magnetic material for a magnetic core.

[0002]

2. Description of the Related Art In recent years, miniaturization of electric and electronic devices has been progressing.
A small and highly efficient magnetic material is required, and a ferrite core or a dust core is used as a choke coil used at a high frequency. Among them, the ferrite core has a disadvantage that the saturation magnetic flux density is small. On the other hand, a dust core manufactured by molding a metal magnetic powder has an extremely large saturation magnetic flux density as compared with soft magnetic ferrite, which is advantageous for miniaturization. It cannot be said that the loss is superior to that of ferrite. Therefore, in a core used for a choke coil or an inductor, a large core loss causes a large temperature rise of the core, and thus it is difficult to reduce the size.

The core loss of a dust core usually consists of hysteresis loss and eddy current loss, but eddy current loss increases in proportion to the square of the frequency and the square of the size at which the eddy current flows. The generation of eddy currents is suppressed by covering an electrically insulating resin or the like. On the other hand, the hysteresis loss usually requires applying a molding pressure of 5 ton / cm ² or more in order to increase the molding density of the dust core.
For this reason, the strain increases as the magnetic material and the magnetic permeability deteriorates, and the hysteresis loss increases. In order to avoid this, a heat treatment is performed after molding to release the strain as necessary.However, if a high-temperature heat treatment is required, the magnetic powder is insulated and the powders are bonded together. Insulating fixers were indispensable to maintain the quality.

Almost organic resins such as epoxy resins, phenolic resins, and vinyl chloride resins conventionally used as binders for dust cores or silicate water glasses as inorganic binders are disclosed in Japanese Patent Application Laid-Open No. 1-215902. Alumina cement described in JP-A-6-299114, a silicone resin described in JP-A-6-342714, and a silicone resin described in JP-A-8-45724 and a mixture of organic titanium and the like. Proposed.

In order to ensure DC superimposition characteristics, a conventional magnetic core made of ferrite or the like has a number
By providing a gap of 00 μm, a decrease in the inductance L value at the time of DC superposition is reduced. However, such a wide gap is a source of beat noise,
Leakage flux from the gaps caused a significant increase in copper losses in the windings, especially at high frequencies. On the other hand, a dust core is used without a gap because of its low magnetic permeability, and therefore, copper loss due to beat noise and leakage magnetic flux is small.

[0006]

However, in order to improve the magnetic properties, it is essential to further increase the density of the dust core, but the insulating properties of the magnetic powder surface are easily broken, resulting in an increase in eddy current loss. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide a composite magnetic material which eliminates the above-mentioned conventional disadvantages, has a low core loss, has a high magnetic permeability, and has good DC superimposition characteristics.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a composite magnetic material obtained by subjecting a mixture comprising a magnetic powder and an insulating material to compression molding and then subjecting the mixture to heat treatment. The manufacturing method satisfies the relationship of P1> P2 when the first heat treatment oxygen atmosphere P1 and the second heat treatment oxygen atmosphere P2 are provided.
Here, assuming that the first heat treatment temperature T1 and the second heat treatment temperature T2, it is preferable that the relationship of T1 <T2 is satisfied.

According to the present invention, it is possible to obtain a composite magnetic material having a high magnetic permeability with a low core loss even at a high frequency and a good DC superposition characteristic.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION
A composite magnetic material obtained by compression-molding a mixture of a magnetic powder and an insulating material and then performing a heat treatment, wherein the heat treatment is performed two or more times to form a first heat treatment oxygen atmosphere P1 and a second heat treatment oxygen atmosphere P2, A method for producing a composite magnetic material, characterized by satisfying a relationship of P1> P2.
By doing so, the magnetic powder metal surface in the molded body is oxidized and insulated during the first heat treatment, but the eddy current loss is surely reduced even in the high-density molding, for unknown reasons.

According to a second aspect of the present invention, when the first heat treatment temperature T1 and the second heat treatment temperature T2 are set, T1 <T
2. The method for producing a composite magnetic material according to claim 1, wherein the relationship of 2 is satisfied. By doing so, heat treatment is performed at a low temperature when the oxygen partial pressure is high, and at a high temperature when the oxygen partial pressure is low, thereby forming an insulating film for the first time and performing a strain relief heat treatment in the second heat treatment. It is considered that the hysteresis loss can be reliably reduced.

According to a third aspect of the present invention, 1% ≦ P1 ≦ 3
3. The method for producing a composite magnetic material according to claim 1, wherein 0% and P2 ≦ 1%. Although it depends on the magnetic powder used, 1% ≦ P1 ≦ 30% is considered to be an oxygen partial pressure suitable for forming an insulating film on the metal surface, and P2 ≦ 1% is 2%.
This is considered to be a preferable oxygen partial pressure at which the magnetic properties are not degraded during the heat treatment for strain relief in the second heat treatment.

According to a fourth aspect of the present invention, there is provided the method according to the fourth aspect, wherein
3. The method according to claim 1, wherein ≦ 500 ° C., 500 ° C. ≦ T2 ≦ 900 ° C.
By doing so, it is considered that the C component contained in the organic binder, the lubricant, and the like surely flies during the first heat treatment, so that the insulation in the molded body is ensured and the eddy current loss can be further reduced. .

According to a fifth aspect of the present invention, there is provided a composite magnetic material obtained by compression-molding a mixture comprising a magnetic powder A and a spacing material B, wherein the magnetic powders A are adjacent to each other by the spacing material B. The distance δ satisfies the relationship of 10 ⁻³ ≦ δ / d ≦ 10 ^{−1 for} at least 70% of the entire magnetic powder, where d is the average particle size of the magnetic powder. 2. A method for producing a composite magnetic material according to item 1. By controlling using the spacing material B to secure the minimum necessary space length between the magnetic powders A, the width of the magnetic space distribution can be narrowed as a whole, and excellent magnetic permeability can be maintained while maintaining high magnetic permeability. Superimposition characteristics can be realized.

[0015] The invention according to claim 6 is characterized in that, as the magnetic powder A, Fe-based, FeSi-based, FeAlSi-based, FeNi
Magnetic powder containing at least one of ferromagnetic materials of the system, permendur, amorphous, and nano-microcrystalline.
2. The method for producing a composite magnetic material according to claim 1, wherein the average particle size of the composite magnetic material is 100 μm or less. These metallic magnetic materials have both high saturation magnetic flux density and high magnetic permeability, and can be easily obtained with atomized powder, pulverized powder and the like, and a high-performance composite magnetic material can be obtained. Further, when the average particle size of the magnetic powder A is 100 μm or less, it is effective in reducing eddy current.

Hereinafter, an embodiment of the present invention will be described.

(Embodiment 1) The metal magnetic powder is FeAlS
Atomized powder having an average particle size of 50 μm of an i-based alloy, Si-9%, Al-5%, and the balance Fe was used.

Mixing Step 2 parts by weight of butyral resin as a binder and 100 parts of ethanol as a solvent for dissolving the binder are added to 100 parts by weight of the metal magnetic powder.
Parts by weight were mixed with a mixing stirrer.

Granulation Step After the mixing step, the solvent is degassed and dried from the mixture.
The dried mixture was pulverized and granulated in order to ensure fluidity that can be introduced into a molding machine to produce granulated powder. Further, stearic acid 0.1 part by weight was added as a lubricant in order to improve the fluidity of the granulated powder.

Forming Step The granulated powder is pressed by a uniaxial press under a pressure of 12 t / cm ² for 3 seconds, and has an outer diameter of 25 mm, an inner diameter of 15 mm and a thickness of about 1 mm.
A 0 mm toroidal shaped body was obtained.

Heat treatment step Thereafter, a sample was prepared under heat treatment conditions shown in (Table 1). Note that the temperature holding time was 0.5 hour for all heat treatments.

The magnetic permeability, core loss, and DC superposition of the sample thus obtained were measured. The permeability is L
The core loss was measured at a frequency of 10 kHz with a CR meter, the core loss was measured at a measurement frequency of 50 kHz with a measurement magnetic flux density of 0.1 T using an AC B-H curve measuring instrument, and the DC superposition characteristic was 1600 A / The magnetic permeability at the time of m is shown.

The evaluation results are shown in (Table 1).

[0024]

[Table 1]

Here, the choke coil for harmonic distortion countermeasures has a current measurement frequency of 50 kHz, a measured magnetic flux density of 0.1 T, a core loss of 1000 kW / m ³ or less, a magnetic permeability of 60 or more,
The selection criterion is 70% or more for DC superposition.

As shown in Table 1, if the heat treatment is performed twice and the first heat treatment oxygen concentration P1 and the second heat treatment oxygen concentration P2 are satisfied, the one satisfying the relationship of P1> P2 has a low loss. I understand that. In addition, the first heat treatment temperature T
Assuming that the first and second heat treatment temperatures are T2, it is more preferable to satisfy the relationship of T1 <T2. Also, 1% ≦ P1 ≦ 30
%, And P2 ≦ 1% is more preferably satisfied. 150 ℃ ≦
It is found that it is more preferable to satisfy T1 ≦ 500 ° C. and 500 ° C. ≦ T2 ≦ 900 ° C.

Even if the conventional dust core is insulated on the surface of the metal powder with a binder or an oxide film before molding, the insulating property is destroyed in the process of high-density molding, so that the eddy current loss increases. It is considered that the loss could not always be reduced. According to the present invention, an oxide film is formed on the surface of the metal powder at the first heat treatment in the state of a high-density compact, and the heat treatment for strain removal is ensured by the second heat treatment, so that eddy current loss and hysteresis loss can be reliably reduced. We think that the loss has been reduced. Although it depends on the magnetic powder used, 1% ≦ P1 ≦ 30% is considered to be the oxygen partial pressure suitable for forming an insulating film on the metal surface, and P2 ≦ 1% is the magnetic pressure during the strain removal heat treatment in the second heat treatment. This is considered to be a preferable oxygen partial pressure that does not deteriorate the characteristics.
In addition, it is considered that this has the effect of preventing the C component and the like contained in the organic binder, the lubricant, and the like from flying during the first heat treatment in an oxidizing atmosphere, thereby preventing deterioration of magnetic characteristics. Needless to say, even if the third and subsequent heat treatments are performed after the second heat treatment, this effect is not impaired as long as the heat treatment temperature is not higher than T2.

(Embodiment 2) The metal magnetic powder is FeAlS
Average grain size of i-based alloy, Si-9%, Al-5%, balance Fe
Using atomized powder with a diameter of 70μm as a spacing material
Al with a particle size of 5 μm_TwoO _ThreeWas used.

Mixing Step With 100 parts by weight of the metallic magnetic powder, 2 parts by weight of butyral resin as a binder and 1 part by weight of a spacing material were mixed by a mixing stirrer.

Granulation Step After the mixing step, the solvent is degassed and dried from the mixture.
The dried mixture was pulverized and granulated in order to ensure fluidity that can be introduced into a molding machine to produce granulated powder. Further, stearic acid 0.1 part by weight was added as a lubricant in order to improve the fluidity of the granulated powder.

Forming Step This granulated powder is adjusted by δ /
By changing d, a toroidal shaped body having an outer diameter of 25 mm, an inner diameter of 15 mm, and a thickness of about 10 mm was obtained.

Heat Treatment Step The heat treatment temperature is T1 = 400 ° C., P1 = 20%, T2 = 7
Each holding time was set to 0.5 hour so that 00 and P2 ≦ 0.01%.

The magnetic permeability, core loss, and DC bias of the sample thus obtained were measured. The permeability is L
The core loss was measured at a frequency of 10 kHz with a CR meter, the core loss was measured at a measurement frequency of 50 kHz with a measurement magnetic flux density of 0.1 T using an AC B-H curve measuring instrument, and the DC superposition characteristic was 1600 A / The magnetic permeability at the time of m is shown.

The evaluation results are shown in (Table 2).

[0035]

[Table 2]

Here, the choke coil for harmonic distortion countermeasures has a current measurement frequency of 50 kHz, a measured magnetic flux density of 0.1 T, a core loss of 1000 kW / m ³ or less, a magnetic permeability of 60 or more,
The selection criterion is 70% or more for DC superposition. Note that δ /
d is a value obtained by using SIMS and XMA and satisfying 70% or more in both cases.

As is clear from the results of Table 2, in order to achieve both good DC bias characteristics and magnetic permeability, 10 ⁻³ ≦
It can be seen that it is more preferable to satisfy the relationship of δ / d ≦ 10 ⁻¹ .

Here, generally, the true magnetic permeability of the magnetic powder is expressed as μ
Assuming that r and the effective magnetic permeability of the magnetic core are μe, the following equation is obtained.

Μe ≒ μr / (1 + μr · δ / d) The lower limit of δ / d is determined by the minimum necessary DC superposition characteristic, and the upper limit of δ / d is determined by the required magnetic permeability. In order to realize good characteristics, 10 ⁻³ ≦ δ / d ≦ 10 ⁻¹ .

According to the present invention, the type of the spacing material, the particle size,
By changing the particle size distribution and the like, it is possible to control δ to control the magnetic permeability and the DC bias characteristics of the composite magnetic material. Not only inorganic materials but also organic materials and metals can be used as the spacing material. Needless to say, the magnetic permeability and the DC superimposition characteristics of the composite magnetic material can be controlled by a combination thereof.

(Embodiment 3) Pure magnetic metal powder used has purity of 99.6%, Fe-Al-Si has Sendust composition of 9% Si, 5% Al, balance Fe, Fe-S
i is Si-3.5%, balance Fe, Fe-Ni is Ni-7
8.5%, balance Fe, permendur is Co-50
%, The balance being Fe atomized powder, Fe-based amorphous powder is Fe-Si-B alloy, nano-microcrystalline magnetic powder is Fe-
A ribbon was prepared from the Si-B-Cu alloy by a liquid quenching method and then pulverized to obtain a powder.

Mixing Step 1.5 parts by weight of a silicone resin as a binder were mixed with 100 parts by weight of the metal magnetic powder using a mixing stirrer.

Granulation Step After the mixing step, the solvent is degassed and dried from the mixture.
The dried mixture was pulverized and granulated in order to ensure fluidity that can be introduced into a molding machine to produce granulated powder. Further, 0.1 part by weight of zinc stearate was added as a lubricant in order to improve the fluidity of the granulated powder.

Forming Step This granulated powder is pressed under a uniaxial press with a pressing force of 15 t / cm ² for 3 seconds, and has an outer diameter of 25 mm, an inner diameter of 15 mm and a thickness of about 1 mm.
A 0 mm toroidal shaped body was obtained.

Heat Treatment Step The heat treatment temperature is T1 = 350 ° C., P1 = 20%, T2 = 6
Each holding time was 0.5 hour so that 00, P2 ≦ 0.005%.

Samples were prepared using soft magnetic powder having an average particle size as shown in Table 3. The magnetic permeability, core loss, and direct current superposition of the sample thus obtained were measured. The magnetic permeability is measured at a frequency of 10 kHz with an LCR meter, the core loss is measured at a measurement frequency of 50 kHz with a measurement magnetic flux density of 0.1 T using an AC B-H curve measuring instrument, and the DC superposition characteristic is measured at a measurement frequency of 50 kHz. Magnetic field is 1600
The magnetic permeability at A / m is shown.

The evaluation results are shown in (Table 3).

[0048]

[Table 3]

Here, the choke coil for harmonic distortion countermeasures has a current measurement frequency of 50 kHz, a measured magnetic flux density of 0.1 T, a core loss of 1000 kW / m ³ or less, a magnetic permeability of 60 or more,
The selection criterion is 70% or more for DC superposition.

From the results shown in Table 3, it can be seen that all the soft magnetic materials show good characteristics. In addition, even if the magnetic powder or the composition ratio is other than the examples, the magnetic powder A may be Fe-based, Fe-Si-based, Fe-Al-Si-based, Fe-N
Needless to say, a mixed powder containing at least one of i-type, permendur, amorphous, and nano-crystalline ferromagnetic materials, or an alloy or a solid solution has the same effect. These metallic magnetic materials have a high saturation magnetic flux density and a high magnetic permeability, and have the same effects irrespective of the production method such as the atomized powder method, the pulverized powder method, and the super-quenching method. In addition, other magnetic materials,
It goes without saying that the same effect is obtained regardless of the powder shape such as a spherical shape and a flat shape. Since the eddy current loss increases in proportion to the square of the frequency and the square of the size of the eddy current flowing, if the surface of the magnetic powder is covered with an insulator, the eddy current depends on the particle size of the metal magnetic powder. Therefore, the average particle size is preferably 100 μm or less.

[0051]

As is apparent from the above description, the present invention can provide a composite magnetic material having low core loss, high magnetic permeability, and good DC superimposition characteristics.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Fujii 1006 Kazuma Kadoma, Kazuma, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. (reference) 4K018 AA24 AA26 AA30 BB04 CA12 DA21 DA35 FA08 KA43 KA61 5E041 AA02 AA04 AA07 AA11 BD03 CA02 HB05 HB11 NN06 NN17 NN18

Claims (6)

[Claims] 1. A composite magnetic material obtained by subjecting a mixture comprising a magnetic powder and an insulating material to compression molding and then performing a heat treatment, wherein the heat treatment is performed twice or more, wherein the first heat treatment oxygen concentration P1, A method for producing a composite magnetic material, wherein a relationship of P1> P2 is satisfied when a second heat treatment oxygen concentration is P2. 2. The method of manufacturing a composite magnetic material according to claim 1, wherein a relationship of T1 <T2 is satisfied when a first heat treatment temperature T1 and a second heat treatment temperature T2 are satisfied. 3. The method for producing a composite magnetic material according to claim 1, wherein 1% ≦ P1 ≦ 30% and P2 ≦ 1%. 4. 150 ° C. ≦ T1 ≦ 500 ° C., 500 ° C. ≦
3. The method for producing a composite magnetic material according to claim 1, wherein T2 ≦ 900 ° C. 5. A composite magnetic material obtained when a mixture comprising a magnetic powder A and a spacing material B is compression-molded, wherein a distance δ between adjacent magnetic powders A by the spacing material B is equal to or less than a value of the magnetic powder. Assuming that the average particle size is d, 10 ⁻³ ≦
2. The method for producing a composite magnetic material according to claim ¹ , wherein the relationship of δ / d ≦ 10 ⁻¹ is satisfied by 70% or more of the whole magnetic powder. 6. The magnetic powder A may be Fe-based, FeSi
System, FeAlSi system, FeNi system, permendur,
The magnetic powder A contains at least one of an amorphous and nano-crystalline ferromagnetic material, and has an average particle diameter of 100 μm.
A method for producing a composite magnetic material according to claim 1 below.