JPH02290002A - Fe-si based alloy dust core and its manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an Fc-Si alloy dust core used for noise filters, choke coils of switching power supplies, etc., and a method for manufacturing the same.

(Prior art) Conventionally, powder magnetic core materials used for suppressing electromagnetic noise or for choke coils have been pure iron powder, carbonyl iron powder, Fe
- Ni-based alloy (hereinafter referred to as permalloy), Fe -
A magnetic metal powder containing Si-AΩ alloy (hereinafter referred to as Sendas 1) is added with water glass, epoxy resin, etc. as an insulating and tangent agent, and after press molding at a molding pressure of 1 to 15 Lon/cJ, compressive strain is applied. It is known that it is manufactured through a process of heat treatment to remove it (edited by Powder Metallurgy Association, Magnetic Materials, (1970), Kogyo Shimbunsha, H.).

Pure iron powder magnetic cores are used for choke coils in switching power supplies of 50kllz or less, transformer cores for linking choke type power supply circuits, or for suppressing noise in circuits where low frequency currents are superimposed.

Permalloy powder cores are used in the secondary smooth choke coil cores and noise suppression cores of switching power supplies in the 100-500kHz range, and Sendas 1 powder cores are also used in the same frequency range as permalloy powder cores. be done.

However, recently, with the tightening of high-frequency noise regulations for electronic devices and the demand for smaller, A'J-type devices, the demand for powder magnetic cores with higher magnetic permeability and excellent frequency characteristics has become stronger than ever. .

Powder magnetic cores are made by insulating powder particles with epoxy resin, water glass, etc. to eliminate direct contact between powder particles and reducing eddy current loss in the high frequency range. Furthermore, they are made denser by molding, and have high magnetic permeability. This provides good frequency characteristics.

In order to obtain high magnetic permeability, is it possible to increase the packing density by high-pressure molding?In the conventional Sendust-based powder magnetic core, the powder is extremely hard and difficult to plastically deform, making high-pressure molding difficult. There are problems such as a significant decrease in the lifespan of the

Permalloy powder magnetic cores have higher magnetic permeability than pure iron powder magnetic cores, have better high-frequency characteristics, are cheaper, and do not have sufficient adhesion with the insulating layer, causing the interlayer insulation between particles to break down. However, the disadvantage was that the frequency characteristics deteriorated significantly.

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

(Means and effects for solving the problem) From the above viewpoint, the present invention has been made by researching the relationship between interlayer insulation, powder compressibility, powder composition, etc., and magnetic properties, which are factors for frequency characteristics. F produced by water atomization method
The e-Si alloy powder was developed based on the discovery that it forms a stable oxide film on the powder surface, has excellent compressibility, and produces a dust core with high magnetic permeability and excellent frequency characteristics. It is something.

That is, the present invention is an alloy powder with an average particle size of 10 to 100 μm manufactured by a water atomization method, containing 2 to 12% by weight of Si and 0.05 to 0.95% of oxygen,
The Fc-Si alloy powder magnetic core is characterized by using an alloy powder in which the balance substantially consists of Fe, and the alloy powder has a composition of 2 to 12% by weight of Si and 0.5-1% of oxygen by weight.
The above-mentioned Fc contains 0.95%, 3% or less of AJ, Cr, and Ti singly or in combination, and the remainder is substantially Fe.
-Si-based alloy powder magnetic core.

Furthermore, a method for producing an Fe-Si alloy powder magnetic core, which is characterized in that an insulating and adhesive agent is added to the above-mentioned alloy powder, and after molding, a hardening treatment is performed; This is a method for producing a Fe-Si alloy powder magnetic core, which is characterized by carrying out heat treatment in an inert atmosphere at a temperature range of 500°C to 950°C, with or without applying.

The reasons for the limitations of the present invention will be explained below.

Si in the composition of the alloy powder of the present invention is a basic component of the present alloy, and if S1 is less than 2%, the electric resistance is small and eddy current loss in the high frequency range becomes large, making it impossible to obtain the desired magnetic permeability. Furthermore, if S exceeds 12%, intermetallic compounds are formed, which makes the powder hard and compressibility impaired. Even within that range, the anisotropy constant and saturation magnetostriction are small from 3.0 to 7.5.
% is preferred.

Oxygen is essential for forming an insulating film on the surface of powder, and 0. (If it is less than 15%, a stable oxide film will not be formed, and if it exceeds 0.95%, the film will become too thick, the magnetic permeability will decrease, and the density of the green compact will also decrease.
05 to 0.95%.

Also, AΩCr,T added as a selective component to the basic component
Although i is more effective because it forms a stable insulating film together with Si, 3
If it exceeds 3%, the film will become too thick and the compressibility of the powder will be impaired, so it should be set at 3% or less.

Powder particle size greatly affects magnetic permeability and interlayer insulation. If the average particle size is less than 10 mm, the magnetic properties of the powder itself will deteriorate, and a high packing density will not be obtained, making it impossible to obtain the desired magnetic permeability. On the other hand, if the particle size exceeds 1001 HIl, the friction between the powder particles becomes too large, the insulating layer is destroyed, and the high frequency characteristics deteriorate, so the range was set to 10 to 100 HIl.

In the water atomization method, raw materials are melted and the molten metal is made to flow down from a nozzle as a molten metal stream with a diameter of 2 to 20 mm.
High-pressure water of 50 to 800 kg/cat is injected from a spray nozzle to turn the metal stream into droplets and solidify them as powder.

The powder obtained by this water atomization method is easy to control the composition and can be made with the desired ingredients.Furthermore, since it is rapidly cooled by water, the powder has an irregular shape, so it has excellent compressibility and has excellent compressibility in the demagnetizing field. Although the powder is oxidized by water, the thickness of the oxide film, that is, the amount of oxygen in the alloy powder, can be controlled by adjusting the atmosphere during spraying and the amount of dissolved oxygen in the water. Therefore, powder suitable for the powder magnetic core of the present invention can be manufactured.

In the water atomization method, an atomizing nozzle is installed at the top of the spray tank, and the molten metal falls from the top of the tank as a trickle, and high-pressure water is collided with it from the nozzle to powder it, thereby reducing the atmosphere inside the spray tank. If atomization is performed in the atmosphere, the amount of oxygen in the powder will be 3 to 5% in the case of iron powder.

By replacing the inside of the tank with an inert gas such as nitrogen gas or argon gas, and then filling the tank with water to rapidly cool down the powdered metal droplets, the amount of oxygen in the iron powder can be reduced to 1%.
It can be reduced back and forth.

Furthermore, the water used for atomizing is arranged in Ar,
By bubbling gas such as N2 or reducing dissolved oxygen in water by decompression treatment, the amount of oxygen in iron powder can be reduced to 0 or 1.
% or less, and by changing the amount of dissolved acid cords, the amount of oxygen in the powder can be controlled within the range of 0.05 to 0.95%.

The water atomized FcSi alloy powder produced in this way is sieved to have an average particle size of 10 to 100 μm, and then treated with water glass, epoxy resin, which is commonly used as an adhesive that also serves as insulation, or when subjected to heat treatment. 1 to 1% by weight of heat-resistant resin, such as silicone resin, is added to
After adding about 0% and mixing, the molding pressure is 1 to 15 tons/
After molding into a desired shape by press molding or the like at approximately cJ, a hardening treatment and, if necessary, a heat treatment are performed, and finally an insulating coating is applied to the surface to form a powder magnetic core.

An insulation/adhesive is added to the Fe-Sj alloy powder, and after molding, it is heated to about 100°C to 300°C depending on the type of insulation/adhesive used and the purpose of the dust core to form a compact. Although a hardening treatment is performed to harden the material, the hardening treatment may be omitted if a heat treatment to be described later is performed after molding.

In addition, in order to improve the adhesion with the resin used as an insulator and adhesive, the raw material Fc-Sj alloy powder is surface-treated with known organic metal coupling such as Ti-based and Sj-based. It is desirable to keep it.

In this way, a powder magnetic core having excellent electromagnetic properties can be manufactured using the water atomized Fc-Si alloy powder, but the electromagnetic properties can also be improved by heat-treating the press-formed magnetic core.

It is effective to carry out the heat treatment at a temperature in the range of 500° C. to 950° C. in an inert atmosphere such as nitrogen or argon. It is not possible to use the atmosphere in the air because the alloy powder will oxidize, and in a reducing atmosphere such as hydrogen or decomposed ammonia gas, the characteristics of the oxide film will change. Therefore, a nitrogen or argon atmosphere is desirable.

If the temperature is less than 500°C, it will be difficult to release the strain caused by molding, and if it exceeds 950°C, the insulating film will be destroyed and the powders will sinter together, deteriorating the high frequency characteristics. Therefore, by heat treatment at a temperature of 500° C. to 950° C., it is possible to improve the electromagnetic properties by removing strain from the magnetic core and adjusting the structure (formation of a regular lattice).

The heat treatment time is longer at low temperatures and shorter at high temperatures, but is about 1 to 20 hours, preferably 1 to 20 hours.
It is 5 hours.

(Example) Fe-Sj alloy powders shown in Table 1 were produced by a water atomization method and sieved to a predetermined average particle size.

The amount of oxygen in the alloy powder was adjusted by changing the atomization atmosphere to Ar gas and bubbling cooling water and water for atomization with Ar gas.

Add 1.5% epoxy resin to these powders,
After press molding into a ring shape with an outer diameter of 20 m+n, an inner diameter of 12 mm, and a height of 8 cm at a molding pressure of 8 tons/cIll+, 15 (1
A curing treatment was performed at ℃ for 2 hours, and the frequency characteristics of magnetic permeability were measured using an impedance meter.

Further, in order to perform heat treatment, 1.0% by weight of water glass was added to the Fe-Sj alloy powder, and a ring of the above size was press-formed at a molding pressure of 8 ton/cJ.

The heat treatment was performed in an argon atmosphere.

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

Here μel. OK is lokllz magnetic permeability, and cz e IOM/μe I. OK is IOMllz
Permeability and l. It indicates the ratio of magnetic permeability at okllz and was used as a guide for high frequency characteristics.

As is clear from Table 1, in the magnetic cores 1 to 9 of the present invention, the oxygen content of the powder is in the range of 0.05 to 0.95%, the average particle size is in the range of 10 to 100 μm, and the transmission rate of 10 kHz is The magnetic coefficient shows a high value of 70 or more. Of particular note is the high frequency characteristics, with a magnetic permeability of 10 kHz at IOMI-1z.
It will be the same or, on the contrary, higher.

In particular, the magnetic cores 8 to 13 of the present invention that have been subjected to heat treatment maintain high magnetic permeability up to a high frequency range.

Sendust powder magnetic core of comparison magnetic core 4, pure iron powder powder magnetic core 5
Although the permalloy powder magnetic core 6 has a higher magnetic permeability at 10kHz than the magnetic cores 1 to 5 of the present invention, the magnetic permeability at 10MHz is low and the high frequency characteristics deteriorate.

Further, the comparative magnetic core 1 has a small powder particle size and has poor magnetic properties, and the comparative magnetic core 2 has a large particle size and has poor insulation properties in a high frequency range.

In addition, in the comparative magnetic core 3 in which the amount of Sl exceeds 12%, the powder is hard and the magnetic permeability at 10kHz, which increases the packing density, is also low.

Comparative magnetic core 7 was manufactured using the gas atomization method.
Because the powder has a spherical shape, the demagnetizing field coefficient increases, making it permeable.
rate is low. Furthermore, the comparative magnetic core 8 has a thick oxide film and thus has a low magnetic permeability. Comparative magnetic core 9 has a high annealing temperature, so
Since the powder is sintered, the magnetic permeability in the low frequency range increases, but the high frequency characteristics deteriorate. The comparative magnetic core IO is a powder made by the carbonyl method, and has good high frequency characteristics, but the absolute value of magnetic permeability is low.

Figure 1 shows magnetic cores 2 and 8 of the present invention shown in Table 1 in the same process as described above.
This figure shows the change in magnetic permeability of comparative magnetic cores 4 and 5 and IO with frequency. Inventive magnetic core 2 shows high magnetic permeability even at 10 MHz or higher, while comparative magnetic core has I MH
It begins to deteriorate near z.

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 high magnetic permeability and excellent frequency characteristics, and has characteristics suitable for increasing the frequency and miniaturizing electronic equipment as noise filters and choke coils for power supplies. The effect is large.

[Brief explanation of the drawing]

FIG. 1 is a chart 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 water atomization method is 10 to 100.
The composition is 2-12% (by weight) of Si and 0.0% of oxygen.
1. An Fe-Si based alloy powder magnetic core characterized by using an alloy powder containing 05 to 0.95% of Fe, the remainder being substantially Fe. 2. The composition of the alloy powder is 2 to 12% (by weight) of Si, 0.05 to 0.95% of oxygen, and further contains Al, Cr, and Ti.
2. The Fe-Si alloy powder magnetic core according to claim 1, which contains 3% or less of either alone or in combination, with the remainder being substantially Fe. 3. The average particle size produced by water atomization method is 10 to 100.
The composition is 2-12% (by weight) of Si and 0.0% of oxygen.
An Fe-Si alloy powder magnetic core is characterized in that an insulating and adhesive agent is added to an alloy powder containing 05 to 0.95% and the remainder is substantially Fe, and after molding, a hardening treatment is performed. Production method. 4. The average particle size produced by water atomization method is 10 to 100.
The composition is 2-12% (by weight) of Si and 0.0% of oxygen.
Adding an insulating and adhesive agent to an alloy powder containing 05 to 0.95% and the remainder substantially consisting of Fe, and after molding, heat treatment in an inert atmosphere at a temperature range of 500 to 950 °C. A method for producing a Fe-Si alloy powder magnetic core, characterized by: 5. The composition of the alloy powder is 2 to 12% (by weight) of Si, 0.05 to 0.95% of oxygen, and further contains Al, Cr, and Ti.
6. The method for producing an Fe-Si alloy powder magnetic core according to claim 4, wherein the Fe-Si alloy powder magnetic core contains 3% or less of either alone or in combination, with the remainder being substantially Fe.