JPH0682577B2 - Fe-Si alloy dust core and method of manufacturing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a Fe—Si alloy powder magnetic core used for a noise filter, a choke coil of a switching power supply, and the like, and a method for manufacturing the same.

(Prior Art) Conventionally, powder magnetic core materials used for suppressing electromagnetic noise or for choke coils are pure iron powder, carbonyl iron powder, and Fe-S.
i-type (hereinafter referred to as permalloy), Fe-Si-Al alloy (hereinafter referred to as sendust) magnetic metal powder, water glass of insulating and adhesive, epoxy resin, etc. are added, molding pressure 1-15ton / It is known that after being press-molded with cm ² , it is manufactured through a process of heat treatment for removing compressive strain (edited by Powder and Powder Metallurgy Association, Magnetic Materials, (1970), Nikkan Kogyo Shimbun).

Pure iron dust cores are used for choke coils of switching power supplies of 50kHz or less, transformer cores of linking choke type power supply circuits, or noise suppression of circuits superposed with low frequency currents.

Permalloy dust cores are used for the secondary side smooth choke coil cores and noise suppression cores of switching power supplies in the 100 to 500kHz range, and sendust dust cores are also used in the same frequency range as permalloy dust cores. .

However, recently, along with the stricter regulation of high-frequency noise of electronic equipment and the demand for smaller and thinner equipment, there is an increasing demand for a dust core having higher magnetic permeability and excellent high-frequency characteristics than ever before.

The powder magnetic core insulates the powder particles with epoxy resin or water glass to eliminate direct contact between the powder particles to reduce eddy current loss in the high frequency region, and further densify by molding to achieve high magnetic permeability. Good frequency characteristics are obtained.

In order to obtain high magnetic permeability, it is sufficient to increase the packing density by high-pressure molding, but with the conventional sendust-based dust core, the powder is extremely hard, it is difficult to plastically deform, and high-pressure molding is difficult, and the life of the mold is remarkably high. It has a problem such as a decrease.

Permalloy dust core has higher magnetic permeability and superior high frequency characteristics than pure iron dust core, but it is expensive and does not have sufficient adhesion to the insulating layer, resulting in damage to the interlayer insulation between particles. However, there is a drawback that the frequency characteristic is significantly deteriorated.

(Problems to be Solved by the Invention) An object of the present invention is to have high permeability and excellent frequency characteristics,
An object of the present invention is to provide an inexpensive Fe-Si alloy powder magnetic core and a manufacturing method thereof.

(Means and Actions for Solving the Problems) From the above viewpoints, the present invention has studied the relationship between interlayer insulating properties and powder compressibility, which are factors of frequency characterization, and the composition of powder and magnetic properties. Fe produced by the water atomization method
-Si alloy powder forms a stable oxide film on the powder surface,
Moreover, it has been found that a powder magnetic core having excellent compressibility, high magnetic permeability and excellent frequency characteristics can be obtained, and it was developed based on this.

That is, the present invention is an alloy powder having an average particle size of 10 to 100 μm produced by a water atomizing method and having a composition of Si of 2 wt%.
~ 12%, oxygen 0.05 ~ 0.95%, the balance is essentially Fe
Fe-Si-based alloy powder magnetic core, characterized by using an alloy powder consisting of, and the composition of the alloy powder, Si is 2 to 12% by weight, oxygen to 0.05 to 0.95%, Al, Cr, The above Fe-Si alloy powder magnetic core contains Ti alone or in a combined amount of 3% or less, and the balance is substantially Fe.

Furthermore, an insulating and adhesive agent is added to the alloy powder, after molding, a method for producing a Fe-Si alloy powder magnetic core characterized by subjecting to hardening treatment, and similarly after molding, hardening treatment The method for producing a Fe—Si alloy powder magnetic core is characterized by performing heat treatment in an inert atmosphere in the temperature range of 500 ° C. to 950 ° C.

Hereinafter, the reasons for limitation of the present invention will be described.

Si in the composition of the alloy powder of the present invention is a basic component of the present alloy, and if Si is less than 2%, the electrical resistance is small and the eddy current loss in the high frequency range becomes large, so that the desired magnetic permeability cannot be obtained.
Further, if Si exceeds 12%, an intermetallic compound is formed, so that the powder becomes hard and the compressibility is impaired. Within that range,
The anisotropy constant and saturation magnetostriction are preferably 3.0 to 7.5%, which is small.

Oxygen is indispensable for forming an insulating film on the surface of powder. If it is less than 0.05%, a stable oxide film is not formed, and if it exceeds 0.95%, the film becomes too thick and the magnetic permeability decreases, resulting in Since the density of the powder also decreases, it was set to 0.05 to 0.95%.

Also, Al, Cr, Ti added as a selective component to the basic component,
It has a further effect because it forms a stable insulating film together with Si, but if it exceeds 3% in both cases of single addition and compound addition, the film becomes too thick and the compressibility of the powder is impaired. To do.

The particle size of the powder has a great influence on the magnetic permeability and the interlayer insulating property. When the average particle size is less than 10 μm, the magnetism of the powder itself deteriorates, and a high packing density cannot be obtained, so that the desired magnetic permeability cannot be obtained. On the other hand, if the particle size exceeds 100 μm, the friction between the powder particles becomes too large, the insulating layer is broken, and the high-frequency characteristics deteriorate, so the range was made 10 to 100 μm.

In the water atomizing method, the raw material is melted, and the molten metal is made to flow down from a nozzle in the form of a molten metal flow having a diameter of 2 to 20 mm, and high pressure water of 50 to 800 kg / cm ² is sprayed from the spray nozzle to the metal flow. It is made into particles and solidified as powder.

The powder obtained by this water atomization method has an excellent composition because the composition is easy to control and the desired component can be prepared, and because it is irregular in shape because it is quenched by water, it has excellent compressibility and demagnetizing field. Although the coefficient can be small, and the powder is oxidized by water, the thickness of the oxygen film, that is, the oxygen content of the alloy powder can be controlled by adjusting the atmosphere during spraying and adjusting the dissolved oxygen content of water. Therefore, a powder suitable for the dust core of the present invention can be manufactured.

In the water atomizing method, an atomizing nozzle is installed in the upper part of the spray tank, molten metal is dropped from the upper part of the tank as a fine stream, and high pressure water is collided from the nozzle to atomize it, so that the atmosphere in the spray tank is changed. When atomization is performed in the air, in the case of iron powder, the oxygen content of the powder becomes 3 to 5%.

When the tank is replaced with an inert gas such as nitrogen gas or argon gas, and water is poured into the tank to rapidly cool the powdered metal droplets, the oxygen content of the iron powder is reduced to 1%.
It can be reduced back and forth.

Furthermore, the water used for atomizing is previously Ar, N ₂
By bubbling gas such as or reducing the dissolved oxygen in the water by decompression treatment, the oxygen content of the iron powder can be reduced to 0.1% or less, and the oxygen content of the powder is changed by faring or changing. The amount can be controlled in the range of 0.05 to 0.95%.

The water atomized Fe-Si alloy powder produced in this manner is sieved to an average particle size of 10 to 100 μm, and water glass, epoxy resin, or heat treatment generally used as an insulating adhesive is applied. When applied, a heat-resistant resin, for example, a silicon-based resin, is added at about 1 to 10% by weight and mixed, and then formed into a desired shape by press forming at a forming pressure of about 1 to 15 ton / cm ² . After that, a hardening treatment and, if necessary, a heat treatment are carried out, and finally an insulating coating is applied to the surface to obtain a dust core.

Insulating / adhesive is added to Fe-Si alloy powder, and after molding, depending on the type of insulating / adhesive used and the application of the dust core,
Although a hardening treatment for hardening the molded body is performed by heating at about 100 ° C to 300 ° C, the hardening treatment may be omitted when the heat treatment described below is performed after the molding.

In order to improve the adhesion with the resin used as an insulating / adhesive agent, the Fe-Si alloy powder used as the raw material was added to the known Ti
It is desirable to perform surface treatment with a metal-based or Si-based organic metal coupling.

As described above, it is possible to manufacture a dust core having excellent electromagnetic characteristics by using the water atomized Fe-Si alloy powder, and it is possible to further improve the electromagnetic characteristics by heat-treating the press-molded magnetic core.

It is effective to perform the heat treatment in the temperature range of 500 ° C. to 950 ° C. in an inert atmosphere such as nitrogen or argon. This is not possible because the alloy powder is oxidized in the atmosphere as the atmosphere, and the characteristics of the oxygen film change in a reducing atmosphere such as hydrogen or decomposed ammonia gas. Therefore, a nitrogen or argon atmosphere is desirable.

If the temperature is less than 500 ° C, it is difficult to release the strain by molding, and if the temperature exceeds 950 ° C, the insulating film is broken and the powders sinter and the high frequency characteristics deteriorate. Therefore 500
The heat treatment at a temperature of ℃ to 950 ℃ can improve the electromagnetic characteristics by removing the strain of the magnetic core and adjusting the structure (formation of ordered lattice).

The heat treatment time is long at low temperature and short at high temperature, but is about 1 to 20 hours, preferably 1 to 5
It's time.

(Example) The Fe-Si alloy powder shown in Table 1 was manufactured by a water atomizing method and sieved to a predetermined average particle size. The oxygen content of the alloy powder was adjusted by using Ar gas as the atomizing atmosphere and bubbling cooling water and atomizing water with Ar gas.

Epoxy resin was added to these powders in an amount of 1.5% by weight to form a ring with an outer diameter of 20 mm, an inner diameter of 12 mm and a height of 8 mm at a pressure of 8 ton / cm.
After press-molded at ² performs cured for 2 hours at 0.99 ° C.,
The frequency characteristic of magnetic permeability was measured with an impedance meter.

In order to perform heat treatment, 1.0% by weight of water glass was added to the Fe-Si alloy powder, and the ring of the above size was pressed at a molding pressure of 8%.
It was press molded at ton / cm ² . The heat treatment was performed in an argon atmosphere.

The results of the characteristic evaluation are shown in Table 1.

Where μe10K is the permeability at 10kHz and μe10M / μe10K
Indicates the ratio of the magnetic permeability at 10 MHz and the magnetic permeability at 10 kHz, and was used as a guide for high frequency characteristics.

As is clear from Table 1, the magnetic cores 1 to 9 of the present invention have a powder oxygen content in the range of 0.05 to 0.95% and an average particle size of 10 to 10.
It is in the range of 0 μm, and the magnetic permeability at 10 kHz shows a high value of 70 or more. What is especially noteworthy is that the magnetic permeability at 10 MHz is the same as or higher than 10 kHz due to the high frequency characteristics.

In particular, the heat-treated magnetic cores 8 to 13 of the present invention maintain high magnetic permeability up to a high frequency range.

The comparative magnetic core 4, Sendust dust core 5, pure iron powder dust core 5, and Permalloy dust core 6 have higher magnetic permeability at 10 kHz than the magnetic cores 1 to 5 of the present invention, but have low permeability at 10 MHz and high frequency characteristics. to degrade.

Further, the comparative magnetic core 1 has a small particle size of the powder and the magnetism of the powder itself is poor, and the comparative magnetic core 2 has a large particle size and the insulating property in the high frequency region deteriorates.

When the Si content exceeds 12%, the powder of the comparative magnetic core 3 is hard, the packing density does not increase, and the magnetic permeability at 10 kHz is low.

Further, the comparative magnetic core 7 is manufactured by the gas atomizing method,
Since the powder has a spherical shape, the demagnetizing factor is large and the magnetic permeability is low. Furthermore, since the comparative magnetic core 8 has a thick oxide film, it has a low magnetic permeability. Since the comparative magnetic core 9 has a high annealing heat treatment temperature, the powder is sintered, so that the magnetic permeability in the low frequency region is high.
High frequency characteristics deteriorate. The comparative magnetic core 10 is a powder made by the carbonyl method and has good high frequency characteristics, but has a low absolute magnetic permeability.

FIG. 1 shows the magnetic cores 2 and 8 of the present invention shown in Table 1 in the same process as described above.
And changes in magnetic permeability of the comparative magnetic cores 4 and 5 and 10 with frequency. While the magnetic core 2 of the present invention shows high magnetic permeability even at 10 MHz or more, the comparative magnetic core begins to deteriorate from around 1 MHz. .

It can be seen that the magnetic core of the present invention has very good high frequency characteristics.

(Effects of the Invention) As described above, the present invention has a high magnetic permeability and excellent frequency characteristics, and has characteristics suitable as a noise filter and a choke coil for a power supply for high frequency and miniaturization of electronic devices. Is very effective.

[Brief description of drawings]

FIG. 1 is a table showing the frequency characteristics of magnetic permeability regarding the powder magnetic core of the present invention and the comparative powder magnetic core.

Claims (5)

[Claims] 1. The average particle size produced by the water atomizing method is 10 to 10.
100μm, composition is 2-12% (weight) of Si, 0.05 of oxygen
An Fe-Si based alloy powder magnetic core characterized by using an alloy powder containing ~ 0.95% and the balance being substantially Fe. 2. The composition of the alloy powder contains Si in an amount of 2 to 12% (by weight), oxygen in an amount of 0.05 to 0.95%, and Al, Cr, and Ti alone or in combination of 3% or less, and the balance is substantially contained. The Fe-Si alloy powder magnetic core according to claim 1, wherein the powder magnetic core is Fe. 3. The average particle size produced by the water atomizing method is 10 to 10.
100μm, composition is 2-12% (weight) of Si, 0.05 of oxygen
A method for producing a Fe-Si alloy powder magnetic core, comprising: adding an insulating and adhesive agent to an alloy powder containing 0.95% by weight and the balance being substantially Fe, followed by molding and hardening treatment. 4. The average particle size produced by the water atomizing method is 10 to 10.
100μm, composition is 2-12% (weight) of Si, 0.05 of oxygen
Insulating / adhesive agent is added to alloy powder containing 0.95% to 0.95%, the balance being substantially Fe, and heat-treated in a temperature range of 500 ° C to 950 ° C in an inert atmosphere after molding. Method for manufacturing Fe-Si alloy powder magnetic core. 5. The composition of the alloy powder contains Si in an amount of 2 to 12% (by weight), oxygen in an amount of 0.05 to 0.95%, and Al, Cr, and Ti alone or in combination of 3% or less, and the balance is substantially. 6. The method for producing an Fe—Si alloy powder magnetic core according to claim 4 or 5, which is Fe.