JP2003243215A - Composite magnetic material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite magnetic material that can contribute to the compactness of an electromagnetic part such as a choke coil and be used in a high frequency range, and has superior magnetic characteristics. <P>SOLUTION: This composite magnetic material uses a metal powder wherein Si content is ≥1 wt.% and ≤8 wt.%, and a remaining part is made of Fe or an inevitable impurity, or another metal powder wherein Si content is ≥1 wt.% and ≤8 wt.%, more than one kind of element selected from a group of Al, Cr, Mo, V, Mn, Ti, Nb, Ta, Zr, Hf, and W is included at ≥0.01 wt.% and ≤5 wt.%, total quantity of the Si and the selected more than one kind of element is ≥1 wt.% and ≤10 wt.%, and a remaining part is made of Fe and an inevitable impurity. After it is heated in a nitrogen atmosphere before annealing, it is annealed at a high temperature in a non-acidic atmosphere. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite magnetic material used in inductors, choke coils, transformers, etc. of electronic equipment.

[0002]

2. Description of the Related Art As electronic devices are made smaller and thinner, it is strongly required that parts and devices used therein be made smaller and thinner. On the other hand, LSIs such as CPUs have become highly integrated, and the power supply circuit supplied to them has several amps.
A current of several tens of amperes may be supplied. Therefore, also in inductors such as choke coils used for these, there is a demand for miniaturization and a reduction in inductance due to DC superposition is required to be small. Further, the operating frequency has become higher, and it is required that the eddy current loss at high frequency is low. That is, it is required to supply an inductor that can be used with a large current and a high frequency, and that is as small and thin as possible.

Ferrite soft magnetic materials and metallic magnetic materials are examples of magnetic materials used for inductors such as choke coils. However, since the ferrite soft magnetic material has a lower saturation magnetic flux density than the metal magnetic material, the inductance is largely decreased due to magnetic saturation, and the DC superposition characteristic is poor. Therefore, a gap is normally provided in the vertical direction that obstructs the magnetic path of the core, and the apparent magnetic permeability is lowered before use. However, such a gap becomes a source of noise noise. Further, since the saturation magnetic flux density remains low even if the magnetic permeability is lowered, there is a problem that the direct current superposition characteristic is worse than that of the metallic magnetic material.

On the other hand, the metallic magnetic material has a remarkably large saturation magnetic flux density and a good direct current superposition characteristic as compared with the ferrite material, but its electric resistance is low, so that it has a large eddy current loss in a high frequency range of several hundreds kHz to MHz and remains as it is. I can not use it.
Therefore, it is used as a so-called dust core, which is made into a powder, is subjected to insulation treatment between powder particles, and is pressure-molded to form a core. In order to obtain good magnetic properties, it is necessary to increase the filling rate of the metal magnetic powder, which is several ton / cm.
^It is necessary to perform high-pressure molding at ² to ²⁰ ton / cm ² .
At this time, the magnetic characteristics are remarkably deteriorated by the processing strain introduced at the time of molding. Therefore, in order to improve the magnetic properties, annealing after forming is performed for the purpose of releasing strain.

[0005]

Generally, in metal materials, the recovery is a phenomenon that occurs at a temperature of ½ or more of the melting point, and at least 600 ° C. or more is preferable in order to sufficiently release the strain in an Fe-rich composition alloy. Needs to be annealed at 700 ° C. or higher. However, most organic resins such as epoxy resin, phenol resin, vinyl chloride resin, etc., which are conventionally used as insulating binders for dust cores, have low heat resistance when subjected to high temperature heat treatment to release strain. It cannot be used because it is decomposed, and it is necessary to use an inorganic insulating binder. As the inorganic insulating binder, water glass, polysiloxane resin (Japanese Patent Laid-Open No. 6-299)
No. 114) has been proposed, but the heat resistance temperature is 5
Since it is 00 ° C to 600 ° C, it is difficult to anneal at higher temperatures.

The present invention solves the above-mentioned problems in the prior art and provides a composite magnetic material capable of annealing at high temperature and having excellent magnetic properties.

[0007]

In order to achieve this object, the invention described in claim 1 of the present invention is
The content of Si is 1 wt% or more and 8 wt% or less, the balance is added to the magnetic metal powder consisting of Fe and unavoidable impurities, the insulating binder is added, and further pressure-molded into a molded body in a nitriding atmosphere. It is a composite magnetic material characterized by being annealed in a non-oxidizing atmosphere after heat treatment. With this configuration, it is possible to perform annealing at high temperature and to provide a composite magnetic material with excellent magnetic properties. The effect of becoming

The invention according to claim 2 of the present invention is
Si content is 1 wt% or more and 8 wt% or less, and
Al, Cr, Mo, V, Mn, Ti, Nb, Ta, Z
One or more elements selected from the group consisting of r, Hf, and W are 0.0
1 wt% or more and 5 wt% or less, and the total amount of Si and one or more elements selected from the above group is 1 wt% or more and 10 wt% or more.
The following is added to the metallic magnetic powder, the balance of which is Fe and unavoidable impurities, with an insulating binder added, and further pressure-molded to obtain a molded body, which is then heat-treated in a nitriding atmosphere and then changed to a non-oxidizing atmosphere. The composite magnetic material is characterized by being annealed by means of the above-mentioned structure. With this structure, the effect of forming a nitride layer is improved, whereby annealing at a high temperature is possible, and a composite material having more excellent magnetic properties than the invention of claim 1. It is possible to provide the magnetic material.

The invention according to claim 3 of the present invention is
A heat treatment is applied to the metal magnetic powder according to claim 1 or 2 in a nitriding atmosphere, an insulating binder is added, and pressure molding is performed to obtain a molded body, which is annealed in a non-oxidizing atmosphere. With this structure, the same effects as those of the first and second aspects of the invention can be obtained even when the magnetic metal powder is heat-treated in a powder state and then pressure-molded and annealed.

The invention according to claim 4 of the present invention is
The composite magnetic material according to any one of claims 1 to 3, wherein a heat treatment temperature in a nitriding atmosphere is 500 to 1000 ° C, and a more stable nitride layer is formed by heat treatment at a predetermined temperature. In addition, it is possible to obtain the effect that the eddy current loss of the magnetic material can be reduced.

The invention according to claim 5 of the present invention is
Annealing temperature in non-oxidizing atmosphere is 700 to 1000 ° C
The composite magnetic material according to any one of claims 1 to 3, which is further annealed at a predetermined temperature to sufficiently release processing strain during formation and reduce eddy current loss. The effect that it becomes possible is obtained.

The invention according to claim 6 of the present invention is
The average particle size of the metal magnetic powder is 1 to 100 μm.
The composite magnetic material according to any one of items 1 to 5, and by having a predetermined average particle diameter, it is possible to increase the molding density and reduce the eddy current loss of the magnetic material. can get.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. The metal magnetic powder used in the present invention has a Si content of 1 wt% or more and 8 wt% or less, and the balance of Fe and inevitable impurities. S in the present invention
The role of i is the following two points. One point is to improve the soft magnetic characteristics, reduce magnetic anisotropy and magnetostriction constant,
It also has the effect of increasing electrical resistance and reducing eddy current loss. The second point is to enable high temperature annealing. As a result of earnest studies, it was found that high temperature annealing can be performed by using the metal magnetic powder of the present invention and performing heat treatment in a nitriding atmosphere as a pre-annealing step. The reason is not clear, but it is guessed as follows. It is considered that the insulating material reacts with and diffuses with the metal magnetic powder as a cause of the loss of interparticle insulation during high temperature annealing. Si has a strong affinity with nitrogen and produces stable nitrides. Therefore, a heat treatment is performed in a nitriding atmosphere to form a nitride layer on the powder surface. The formed nitride layer suppresses the diffusion of the insulating material into the powder. The amount of Si added is preferably 1 wt% or more and 8 wt% or less. 1 wt
If it is less than%, the above effect is small and high temperature annealing cannot be performed. When it is more than 8 wt%, the saturation magnetization is largely lowered and the direct current superposition characteristic is deteriorated. Furthermore, in the metal magnetic powder of the present invention, Al, Cr, Mo, V, Mn, Ti, Nb, Ta, which have a strong affinity for nitrogen as a nitride layer forming element,
Si containing one or more elements selected from the group of Zr, Hf, and W.
It is also possible to add them together. The addition amount of one or more selected from the above group is 0.01 wt% or more and 5 wt% or more.
It is preferable that the amount is less than or equal to 10 wt%. If it is less than 0.01 wt%, the effect of forming a nitride layer is poor, and if it is more than 5 wt%, or Si
When the total amount of the above is more than 10 wt%, the saturation magnetization is greatly reduced and the direct current superposition characteristic is deteriorated.

The insulating binder in the present invention is preferably one which forms an insulating oxide, such as a silane-based, titanium-based or chromium-based coupling agent, a silicone resin,
Further, oxide powders such as SiO ₂ , TiO ₂ , Al ₂ O _{3 and the} like can be mentioned, but more preferable are silane-based, titanium-based, chromium-based coupling agents and silicone resins, which are inexpensive and have good dispersibility.

The heat treatment in the nitriding atmosphere in the present invention is a heat treatment in a nitriding gas atmosphere such as nitrogen gas or ammonia gas, and may be carried out before the annealing. It may be carried out in the powder state and thereafter, after the molding or annealing, or after the molding. It may be annealed after performing. The heat treatment temperature is preferably 500 to 1000 ° C. Fifty
If the temperature is lower than 0 ° C, the nitriding rate is slow and it is not preferable. 1000
If the temperature exceeds ℃, when heat treatment is performed in a nitriding atmosphere after molding, the insulation between the metal magnetic powder particles cannot be obtained and eddy current loss increases. Further, when heat treatment is performed in a powder state in a nitriding atmosphere, if the treatment temperature is 1000 ° C. or less, sintering does not occur or is slightly sintered, so that it can be easily crushed, but 1000 ° C. If it exceeds the above range, the sintering proceeds, the crushing becomes difficult, and the powder particle size becomes coarse, resulting in a large eddy current loss, which is not preferable.

The annealing treatment in the present invention is for releasing the processing strain during molding. The atmosphere during annealing is preferably non-oxidizing, and examples thereof include an inert gas such as argon gas and helium gas, a reducing gas such as hydrogen gas, and a vacuum atmosphere. Further, annealing can be performed in a nitrogen gas atmosphere, and in this case, the nitriding treatment and the annealing treatment can be performed in the same manner. Annealing temperature is 700
The temperature is preferably 1000 ° C. If the temperature is lower than 700 ° C., the strain release is not sufficient, and if the temperature is higher than 1000 ° C., the insulation between the metal magnetic powder particles cannot be obtained and the eddy current loss increases.

The particle size of the metal magnetic powder used in the present invention is preferably 1.0 μm or more and 100 μm or less. If the powder particle size is smaller than 1.0 μm, the molding density will be low and the magnetic permeability will be reduced, such being undesirable. If the powder particle size is larger than 100 μm, eddy current loss at high frequencies becomes large, which is not preferable. More preferably 50 μm
The following is recommended.

Specific embodiments of the present invention will be described below with reference to tables.

(Embodiment 1) With the composition shown in (Table 1), a metal magnetic powder having an average particle diameter of about 12 μm was prepared. 1.2 parts by weight of silicone resin was added to and mixed with the prepared powder to prepare a compound. Using the obtained compound, pressure molding was performed at 12 ton / cm ² to prepare a toroidal core, and heat treatment and annealing treatment were performed in a nitriding atmosphere under the conditions shown in (Table 1). The obtained samples were evaluated for DC superimposition and core loss. Regarding the direct current superposition, the magnetic permeability at an applied magnetic field of 50 Oe and a frequency of 100 kHz was measured and evaluated by an LCR meter. The core loss is measured with an AC B-H curve measuring device at a frequency of 100k.
The measurement was performed at Hz and a measured magnetic flux density of 0.1T. The results are shown in (Table 1).

[0020]

[Table 1]

(Embodiment 2) The metal magnetic powder used in Example 1 was heat-treated in a nitriding atmosphere under the conditions shown in (Table 2), and then a silane coupling agent was added to the powder.
A compound was prepared by adding 0 parts by weight and mixing. Using the obtained compound, pressure molding was performed at 12 ton / cm ² to prepare a toroidal core, and annealing treatment was performed under the conditions shown in (Table 2). DC superimposition on the obtained sample,
The core loss was evaluated. For DC superimposition,
The magnetic permeability at an applied magnetic field of 50 Oe and a frequency of 100 kHz was measured and evaluated with an LCR meter. AC loss is core B
The measurement was performed using a -H curve measuring machine at a measurement frequency of 100 kHz and a measurement magnetic flux density of 0.1T. The results are shown in (Table 2).

[0022]

[Table 2]

From (Table 1) and (Table 2), the content of Si is 1 wt% or more and 8 wt% or less, the balance is metallic magnetic powder consisting of Fe and unavoidable impurities, or the content of Si is 1
% to 8 wt% and Al, Cr, M
0.01 wt% or more and 5 w of one or more elements selected from the group of o, V, Mn, Ti, Nb, Ta, Zr, Hf, and W
Nitrogen is annealed before annealing by using a metallic magnetic powder containing t% or less, the total amount of Si and one or more elements selected from the above group is 1 wt% or more and 10 wt% or less, and the balance being Fe and inevitable impurities. It can be seen that high temperature annealing is possible by heat treatment in an atmosphere, and the obtained composite soft magnetic material of the present invention exhibits good DC superposition characteristics and low core loss.

(Embodiment 3) The composition is 94.9% Fe-
A metal magnetic powder having 5.0% Si-0.1% Mn and an average particle size shown in (Table 3) was prepared. 1.2 parts by weight of silicone resin was added to and mixed with the prepared powder to prepare a compound. 12 ton / c using the obtained compound
A toroidal core was prepared by pressure molding at m ² and heat-treated in nitrogen gas at 750 ° C. for 30 minutes, and then annealed in argon gas at 900 ° C. for 30 minutes. The obtained samples were evaluated for initial magnetic permeability and core loss. The initial permeability was measured and evaluated with an LCR meter at a frequency of 100 kHz. The core loss was measured using an AC BH curve measuring instrument at a measurement frequency of 100 kHz and a measurement magnetic flux density of 0.1T. The results are shown in (Table 3).

[0025]

[Table 3]

From Table 3, it can be seen that a low loss is exhibited at a particle size of 1 to 100 μm, preferably 1 to 50 μm.

[0027]

As described above, according to the present invention, the content of Si is 1 wt% or more and 8 wt% or less, and the balance is added to the metallic magnetic powder consisting of Fe and unavoidable impurities, and further, The composite magnetic material is characterized in that it is pressed into a compact, heat-treated in a nitriding atmosphere, and then annealed in a non-oxidizing atmosphere.

According to the present invention, it becomes possible to provide a composite magnetic material which can be annealed at a high temperature and has excellent magnetic characteristics.

Continued front page    F-term (reference) 4K018 AA26 AB01 AC01 BA15 BA16                       BB04 BC01 BC28 BC29 BC30                       BD01 FA08 GA02 KA44                 5E041 AA02 AA19 BB03 CA02 CA03                       HB11 NN01 NN04 NN06 NN18

Claims (6)

[Claims] 1. A molded body is obtained by adding an insulating binder to a metal magnetic powder having a Si content of 1 wt% or more and 8 wt% or less and the balance being Fe and inevitable impurities, and further press-molding the metal magnetic powder. A composite magnetic material characterized by being heat-treated in a nitriding atmosphere and then annealed in a non-oxidizing atmosphere. 2. The content of Si is 1 wt% or more and 8 wt% or less, and Al, Cr, Mo, V, Mn, Ti, N
0.01 wt% or more and 5 wt% or less of one or more elements selected from the group of b, Ta, Zr, Hf, and W, and the total amount of Si and one or more elements selected from the above group is 1 wt% or more. An insulating binder is added to a metal magnetic powder containing 10 wt% or less and the balance being Fe and unavoidable impurities, and the mixture is pressure-molded to obtain a molded body, which is heat-treated in a nitriding atmosphere and then non-oxidizing. A composite magnetic material characterized by being annealed in an atmosphere. 3. The magnetic metal powder according to claim 1 or 2 is heat treated in a nitriding atmosphere, an insulating binder is added, and pressure molding is performed to obtain a molded body, which is annealed in a non-oxidizing atmosphere. A composite magnetic material characterized in that 4. The heat treatment temperature in a nitriding atmosphere is 500.
The composite magnetic material according to claim 1, wherein the composite magnetic material has a temperature of ˜1000 ° C. 5. 5. The annealing temperature in a non-oxidizing atmosphere is 70.
It is 0-1000 degreeC, The composite magnetic material as described in any one of Claims 1-3. 6. The average particle size of the magnetic metal powder is 1 to 100 μm.
The composite magnetic material according to claim 1, wherein