JP2000216016A - Dust core and coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a coil, which is excellent in DC superposition characteristics, by a method wherein alloy powder formed by adding a specified amount of Mn to a specified amount of an Si-Fe alloy is used to remarkedly raise the DC superposition characteristics of a dust core. SOLUTION: A starting material is formed in a composition of about 1 to about 10 wt.% of Si and about 0.1 to about 5 wt.% of Mn with the remnant of Fe. Alloy powder is formed by powdering an ingot made by a high-frequency furnace from the starting material or is formed by an atomizing method and the composition of the alloy powder is made uniform. Moreover, this alloy powder is subjected to heat treatment according to the need, then a binder is mixed with the alloy powder and the mixture is press-molded into a desired form using a metal mold. Then this molded material is subjected to distortion removal heat treatment according to the need. In such a way, a dust core is formed by an increase in a saturation magnetization and of low-coercive force ferromagnetic powder. A winding wire is executed on this dust core to form a coil. Thereby, a coil, which is excellent in DC superposition characteristics, is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a dust core and a coil used for a choke coil or the like.

[0002]

2. Description of the Related Art Soft magnetic ferrite cores and dust cores are used in choke coils used at high frequencies. Among them, the soft magnetic ferrite core has a disadvantage that the saturation magnetic flux density is small. On the other hand, a dust core manufactured by molding a ferromagnetic metal powder has a higher saturation magnetic flux density than a soft magnetic ferrite core.
It has the advantage of excellent DC superimposition.

Further, in response to recent demands for downsizing of electronic components accompanying downsizing of electronic devices, operating currents have been increasingly increased. Along with this, there is a strong demand for powder magnetic cores to be used with improved magnetic permeability in high magnetic fields.

Generally, in order to improve the DC superposition characteristics of a coil, it is essential to select a magnetic core having a high saturation magnetization, that is, to select a magnetic core which is not magnetically saturated at a high magnetic field.

Therefore, a material having a necessarily high saturation magnetization is indispensable. Pure iron is well known as such a high saturation magnetization material. This pure iron is widely used as a dust core material.

However, a dust core made of pure iron has only a superposition characteristic lower than that of a sendust-based dust core whose material has a saturation magnetization of about half. This is presumably because pure iron has a higher coercive force due to its high magnetic anisotropy than sendust, and a large eddy current loss due to the low electric resistance of the material.

[0007] In order to remedy this disadvantage, Si, A
It is widely known that by manufacturing an alloy using l or the like as an additional element, magnetic anisotropy can be reduced and electrical resistance can be improved.

[0008]

However, according to the results of studies by the present inventors, when viewed as a dust core material,
No matter how the alloy powder of any of the additive elements produced the dust core, the improvement of the superposition characteristics was not remarkable. It is considered that the reason for this is that there is no composition for reducing the magnetic anisotropy in the alloy system, so that the coercive force is high and the saturation magnetization with high material confidence cannot be used effectively.

Accordingly, an object of the present invention is to provide a dust core made of a ferromagnetic powder having a high saturation magnetization and a low coercive force in view of the above-mentioned problems, thereby providing excellent DC superposition characteristics. Is to provide a coil.

[0010]

Means for Solving the Problems The inventors of the present invention have repeatedly studied alloy compositions to achieve the above object, and have found that
It has been found that by using an alloy powder obtained by adding 0.1 wt% to 5 wt% of Mn to a SiFe alloy of 10 wt% to 10 wt%, the DC superposition characteristics of the dust core are remarkably improved.

This is because Si, which is known as a magnetic steel sheet material,
This is because the coercive force of the alloy powder was reduced by adding Mn to Fe, and it is presumed that reduction of magnetic anisotropy is involved.

Here, the reason why the SiFe alloy system is selected is that Si can significantly reduce the magnetic anisotropy of Fe by adding a small amount of Si as compared with Al. Also, S
In the iFe alloy system, the amount of Si is 6.5%, the magnetostriction is minimum, and 6.5% SiFe has the lowest coercive force value in the present alloy system.

However, when the alloy powder was used, its coercive force value could not be said to be low. This is probably because the effect of magnetic anisotropy is more pronounced in powder than in bulk. In other words, it is considered that the crystal magnetic anisotropy, which is another component of the magnetic anisotropy, is not zero.

The present inventors have found that by adding Mn, SiF
It has been found that the coercive force value of the e-alloy powder is reduced. This is considered to be the effect of reducing the magnetic anisotropy described above. Thereby, it is considered that the coercive force value of the magnetic core was also reduced, and as a result, a high magnetic permeability when the DC current was superimposed was achieved.

That is, the present invention relates to a dust core obtained by compression-molding a powder obtained by mixing a ferromagnetic metal powder and a binder, wherein the ferromagnetic metal powder contains 1 wt% to 10 wt%
i, a dust core, which is an alloy composition powder with 0.1 wt% to 5 wt% Mn and the balance Fe.

Further, the present invention is a coil formed by winding the dust core.

[0017]

Embodiments of the present invention will be described below.

The starting material has a composition of 1% by weight to 10% by weight.
Si, 0.1% by weight to 5% by weight Mn, the balance being Fe,
The metal powder may be produced by pulverizing an ingot produced by high frequency melting or by an atomizing method, as long as the composition is uniform.

The alloy powder is heat-treated if necessary, then mixed with a binder and pressed into a desired shape using a mold. Next, the compact is subjected to a strain relief heat treatment as required, whereby a dust core according to the embodiment of the present invention is manufactured.

Here, the reason why the amount of Si is specified is that if the amount of Si is less than 1%, the effect of Mn addition is not obtained, and if the amount of Si exceeds 10%, the saturation magnetization is significantly reduced and the effect of Mn addition is lost. If the Mn content is less than 0.1%, the effect of addition is not obtained, and if it exceeds 5%, the saturation magnetization is significantly reduced.
This is because the effect of n addition is lost.

[0021]

The present invention will be described below with reference to examples.

(Example 1) 1.5% Si, 1.0% Mn,
An alloy ingot having a balance of Fe composition was produced by high frequency melting. This ingot was ground to 150 μm or less using a jaw crusher and a roll mill. Next, the pulverized powder was placed in a container made of Fe and placed in a furnace at 1000 ° C. × 2.
After keeping in a hydrogen atmosphere for a time, the furnace was cooled as it was. next,
After removing this powder from the furnace, the powder was removed from the furnace using a sieve.
It was classified to μm. Next, 3.0 wt% of a silicone resin was mixed with the classified powder, and the outer diameter was 20 mm and the inner diameter was 10 m.
m at room temperature at 10 ton / cm ² ,
A toroidal dust core was obtained.

The dust core was heat-treated at 170 ° C. for 2 hours in the air to cure the binder. Next, in order to remove the distortion during powder compaction,
After heat treatment in hydrogen at 0 ° C. for 2 hours, winding was performed and HP
DC superimposition characteristics were measured with a 4284A precision meter manufactured by FUJIFILM Corporation.

The magnetic permeability μ was calculated from the measured inductance value. The superimposed DC magnetic field Hm (Oe) was calculated from the superimposed DC current value. FIG. 1 shows the relationship between the DC magnetic field and the magnetic permeability based on these results.

As a comparative example, the starting material was a 6.5% SiFe alloy (with no Mn added), and powder was produced from an ingot just as in Example 1 of the present invention, and heat treatment, binder mixing, and molding were performed. The direct current superimposition characteristics of the dust core prepared by performing the heat treatment were measured. The results are shown in FIG.

As is apparent from FIG. 1, the dust core according to Example 1 of the present invention has improved DC superposition characteristics as compared with the comparative example.

(Example 2) The amount of Mn was set at 0, 0.1, 0.5, 1.0, 2.5, 2.5 while the amount of Si was fixed at 6.5%.
Ingots having compositions of 0, 7.5 and 10.0% were produced by high frequency melting. Next, the powder was subjected to heat treatment, sieving, binder mixing, core production, and heat treatment in the same manner as in Example 1, and then these cores were wound with 80 turns on the primary side and 30 turns on the secondary side. TRF-
The DC magnetic characteristics of the cores, which were the powder magnetic cores, were measured by a 5A DC recording magnetometer.

Of the measurement results, the applied magnetic field 200 (O
FIG. 2 shows the values of the magnetic flux density B200 and the coercive force Hc with respect to the amount of Mn added in e).

As can be seen from FIG.
It can be seen that at 1% or more, an increase in the magnetic flux density B and a decrease in the coercive force Hc are achieved. Also, when the Mn addition amount exceeds 5%, the value of the magnetic flux density B becomes lower than that of the comparative example, and it can be seen that the effect of the Mn addition is substantially lost. Where M
The reason why the magnetic flux density B is improved by adding n is that a large magnetization can be obtained in a low magnetic field by reducing the coercive force Hc.

Next, a winding was applied to the core, which was a dust core, and the DC bias characteristics were measured by a 4284A precision meter made by HP. Among the measured values, the applied magnetic field 40 (O
FIG. 3 shows the result obtained by calculating the magnetic permeability μ in e).

FIG. 3 shows that the permeability is improved when the amount of Mn is 0.1 to 5% and when Mn is not added.

[0032]

As described above, according to the dust core of the present invention, 1 wt% to 10 wt% of Si and the remaining Fe are 0.1% by weight.
By manufacturing a dust core using an alloy powder to which 1 wt% to 5 wt% Mn is added, it becomes possible to manufacture a coil having excellent DC superimposition characteristics.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a DC superposed magnetic field and a magnetic permeability μ of a dust core in Example 1 and Comparative Example of the present invention.

FIG. 2 is a diagram showing the relationship between the magnetic flux density B and the coercive force Hc with respect to the amount of Mn added to a dust core in Example 2 of the present invention.

FIG. 3 is a diagram showing the relationship between the amount of Mn added to a dust core and the magnetic permeability μ in Example 2 of the present invention.

Continued on the front page F term (reference) 4K018 AA26 CA07 KA44 5E041 AA02 AA11 AA19 BB03 CA02 CA10 HB05 NN01

Claims (2)

[Claims] 1. A dust core obtained by compression-molding a powder obtained by mixing a ferromagnetic metal powder and a binder, wherein the ferromagnetic metal powder contains 1% by weight to 10% by weight Si, 0.1% by weight A dust core, which is an alloy composition powder containing 5 wt% Mn and the balance Fe. 2. A coil obtained by winding the dust core according to claim 1.