JP2762531B2 - Ferrite magnetic body and method of manufacturing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-low shrinkage ferrite magnetic material obtained by binding and solidifying a highly crystalline ferrite magnetic powder with a glass material, and a method for producing the same. Kinds of ferrite magnetic materials are used as useful electronic components.

2. Description of the Related Art Most of the conventional methods for producing a ferrite magnetic material are mainly a powder metallurgy method, that is, a sintering method that requires steps of powder molding and high-temperature firing.

When a ferrite magnetic material is produced, the starting materials are mixed in a predetermined ratio, calcined under appropriate conditions, degassing and a certain amount of solid-phase reaction are advanced (this is called calcined powder), and then pulverized and formed. After the steps of graining and compacting, the compact is fully baked in an appropriate atmosphere at a temperature higher than the pre-baking temperature to obtain a polycrystalline ferrite sintered body having desired magnetic properties and mechanical strength. It has gained.

FIG. 2 shows a schematic diagram of the fine structure of this polycrystalline ferrite sintered body. In FIG. 2, 6 is a crystal grain, 7 is a grain boundary, 8 is a grain boundary pore, and 9 is a pore of the crystal grain 6.

The calcining temperature in the above process is set between 700 and 1000 ° C., at which the starting material of a predetermined blending ratio starts the solid-phase reaction, and the main calcining temperature for sufficient sintering is the material and composition of the calcined powder and the granules. Although it depends on the diameter and shape, it is usually a high temperature of 1000 to 1400 ° C. The firing atmosphere at this time depends on the required material,
An oxidizing atmosphere or a non-oxidizing atmosphere is selected depending on the composition.

A disadvantage of the ferrite sintering method is that sintering of the calcined powder compact in the main sintering step necessarily causes a dimensional change. In other words, after the final firing, usually 10-20%,
When it is large, it shrinks more, and the dimensional accuracy and yield of the sintered product are deteriorated. Therefore, post-processing, which is mechanical processing such as cutting and polishing, is required.

The above-mentioned shrinkage in the sintering process occurs for the following reasons.
That is, a compact obtained by simply pressing the calcined powder usually has a particle size of 2
The molding density is low due to the use of powder of about 5 μm or less, that is, there are still many voids although the powders are in contact with each other, and when heated at a temperature of 700 to 1000 ° C. or more, the contact portion between the calcined powders Interdiffusion of the atoms constituting the particles occurs, and the sintering phenomenon starts. As a result, the gap between the calcined powders decreases with the progress of sintering, and when it is large,
It shrinks by over 20%.

Therefore, it is important to make the temperature rise and fall during the main firing relatively slow in order to ensure that the sintering is exactly uniform and that the molded body is not subjected to thermal shock. As a result, the main calcination step may be as long as at least half a day or more in two days.

There have been many studies to improve the disadvantages of the ferrite sintering method. Among them, regarding the problem of shrinkage of the sintered body, various methods have been studied to reduce the shrinkage as much as possible and to control the shrinkage at a constant level. However, in order to ensure the performance and characteristics of ferrite, some shrinkage is avoided. The reality is that it cannot be done. For example, JP-A-58-135133
As described in JP-A-58-135606, after mixing ferrite calcined powder and glass powder,
When firing at a temperature at which ferrite densification (sintering) progresses, the glass powder added at this time covers the periphery of the ferrite particles, thereby partially suppressing ferrite densification and reducing the shrinkage of the sintered body. Can be obtained.
However, even in this case, since the calcined powder preparation temperature is lower than the final firing temperature of the compact afterwards, mutual diffusion occurs between the calcined powders that are still in direct contact during the final firing, and the compaction shrinkage phenomenon occurs. Was unavoidable and in fact shrank by a few percent.

Problems to be Solved by the Invention As described above, in the conventional ferrite sintered body, the more the sintering is performed in order to obtain the desired performance, the larger the shrinkage is, and conversely, if the shrinkage is suppressed, the performance is reduced. It is difficult to achieve both because they cannot be secured However, sintered ferrites are
It is widely used as a device material, and its performance and high dimensional accuracy are increasingly regarded as important.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned disadvantages of the prior art, and to provide a glass-bound ultra-low-shrinkage ferrite magnetic material having almost no shrinkage and excellent magnetic properties, and a method for manufacturing the same at a low cost. Things.

Means for Solving the Problems In order to solve the above problems, the ferrite magnetic material of the present invention comprises a highly crystalline ferrite magnetic powder having at least two types of particle size distributions, which has been sufficiently ferritized by high-temperature sintering. The mixture with the glass powder having a softening point lower than the temperature is heated at a temperature not lower than the softening temperature of the glass powder and not higher than the sintering temperature of the high crystalline ferrite magnetic powder to obtain a high crystalline ferrite magnetic powder. It is configured to be bound by a material.

Action Since the ferrite magnetic powder to be used has already been crystallized to near perfection by high-temperature firing, sintering between the highly crystalline ferrite magnetic powders hardly occurs in the subsequent heat treatment at a lower temperature. Simply, the glass powder mixed between the high crystalline ferrite magnetic powders is simply melted to bind the high crystalline ferrite magnetic powder. As a result, the porosity in the molded product does not change much before and after the heat treatment, so that a novel ferrite magnetic material having high dimensional accuracy close to the die molding dimensions and excellent magnetic properties can be obtained.

Furthermore, the heat treatment of the molded body does not expect sintering properties, and it is basically necessary to melt the glass powder as described above and flow between the high-crystalline ferrite magnetic powders and obtain a binding effect. It is much shorter than the main firing time of the method. For this reason, equipment costs and electricity costs are low, and the manufacturing method is simple, so that it can be manufactured at low cost.

Further, in the case of soft ferrite, it is desired to increase the resistance because it is necessary to minimize the eddy current loss of the ferrite itself. Since the high crystalline ferrite magnetic powder is electrically insulated, there is also obtained an advantage that the resistance value increases and the high frequency characteristics are improved.

Examples Hereinafter, examples of the present invention will be described.

That is, the present invention requires at least two components as shown in FIG.
High-crystalline ferrite magnetic powders 1 (hereinafter, referred to as coarse powder) and 2 (hereinafter, referred to as fine powder) having different particle size distributions are softened and melted at a firing temperature of the high-crystalline ferrite magnetic powders 1, 2 or lower. It is configured to be bound by a glass material 3 to be formed.

Specifically, two or more kinds of highly crystalline ferrite magnetic powders 1 and 2 having different particle size distributions and glass powder are mixed well,
After press-molding the granulated mixed granules, the glass powder mixed between the highly crystalline ferrite magnetic powders 1 and 2 in this compact is softened and melted to obtain the highly crystalline ferrite magnetic powders 1 and 2. A ferrite magnetic material obtained by simply bonding and solidifying 2 with a glass material 3. In the figure, 4 indicates voids, and 5 indicates pores in the highly crystalline ferrite magnetic powder 1.

The highly crystalline ferrite magnetic powders 1 and 2 used here are those which have sufficiently undergone a ferrite reaction by firing at a high temperature, and usually those fired at 1000 ° C. or higher are preferable.

If it is desired to obtain a soft magnetic ferrite, so the better the coercivity H _C highly crystalline ferrite magnetic powder 1 is less, but preferably as the size of the magnetic particles is large, whereas, the high crystalline ferrite magnetic powder 1 pack density Actually goes down to 10
A diameter of 0 to 200 μm is suitable. In the present invention,
The ferrite magnetic powder having at least two kinds of particle size distribution is used to increase the packing density (molding density) of the magnetic material, and the fine powder 2 having a small particle size is coarsely reduced in order to reduce the voids 4 as much as possible. It is configured to be combined with the powder 1. Particularly, a powder having a particle size of 5 μm or less is most effective.

Next, the softening temperature of the glass powder that binds the high-crystalline ferrite magnetic powders 1 and 2 may be lower than the firing temperature of the high-crystalline ferrite magnetic powders 1 and 2, but the application of the ferrite magnetic material according to the present invention is considered. The lower limit is 300 ° C from the viewpoint of heat resistance
It is desirable that this is the case. The amount of glass powder added to the high crystalline ferrite magnetic powders 1 and 2 is preferably 0.3 to 30% by weight.
If it is less than 0.3%, the binding effect of the high crystalline ferrite magnetic powders 1 and 2 is so small that mechanical strength cannot be secured. Meanwhile, 30%
When the amount of glass is larger, the binding force becomes sufficiently strong, but the amount of non-magnetism is increased, so that the magnetic properties of the ferrite magnetic material are remarkably deteriorated.

Since the main purpose of the heat treatment of the mixed molded body of the high crystalline ferrite magnetic powders 1 and 2 and the glass powder is to melt and infiltrate the glass powder, the heat treatment includes the holding time of the heat treatment and the time required for raising and lowering the temperature. Less than 3 hours is possible.

The heat treatment temperature may be basically higher than the softening temperature of the glass. However, as the temperature approaches the sintering temperature of the highly crystalline ferrite magnetic powders 1 and 2, especially at 800 ° C. or more, the binding effect of the glass material 3 increases. A favorable effect that the magnetic properties are excellent despite the low shrinkage was obtained.

 Hereinafter, specific examples will be described.

(Examples 1 to 10) A starting mixed granulated powder composed of 50 mol of Fe ₂ O ₃ , NiO 18 and ZnO 32 mol% was baked at 1320 ° C. for 6 hours.
A coarse powder of 0 μm and a fine powder of Ni-Zn soft ferrite of 5 μm or less were each prepared. As a result of X-ray analysis of this powder, a sharp spinel structure diffraction line unique to soft ferrite was obtained, and it was confirmed that the powder was a magnetic powder having extremely high crystallinity.

The composition ratio of the high crystalline ferrite magnetic powders 1 and 2 is based on 100 parts by weight of the magnetic powder 1 (coarse powder) and 30 parts by weight of the magnetic powder 2 (fine powder). A non-alkali lead borosilicate glass powder having a softening point (Td) of 370 ° C. and an average particle size of 1 μm was added to each of 0,0.5,1,3,5,10,3.
After adding and granulating by adding 0,40 wt% each, a ring-shaped molded product having an inner diameter of 7 mmφ, an outer diameter of 12 mmφ, and a thickness of 3 mm with different glass contents was produced at a pressure of 3 ton / cm.

Each of these molded products is individually set in an electric furnace,
Heat treatment was performed in the air to obtain a glass-bound ring-shaped ferrite core.

The material properties of the samples of Examples 1 to 10 are shown in Table 1 (Comparative Examples 1 and 2). Particle size of 5 to 20 μm as magnetic powder 2 (fine powder) in the same ferrite main firing powder as in Example 1 The magnetic powder 2 (fine powder) having a particle size of 20 to 50 μm and the magnetic powder 2 (fine powder) having 30 parts by weight (Comparative Example 2) were used in Example 1 respectively. The same glass powder was added in an amount of 5 wt%, mixed and granulated, and a ring-shaped molded product having the same size was produced in the same manner as in Example 1.

This molded product was placed in an electric furnace and heated at 1200 ° C. for 60 minutes in air to obtain a glass-containing type ring-shaped ferrite core.

 The material properties of this sample are shown in Table 1.

(Examples 11 to 15) The same ferrite main powder used in Example 1 was mixed with the same glass powder in an amount of 5 wt%, mixed and granulated.
Five ring-shaped molded articles having an inner diameter of 7 mm, an outer diameter of 12 mm, and a thickness of 3 mm were produced at a pressure of n / cm.

Place each of these molded products in an electric furnace one at a time
Heat treatment was performed in air at 000 ° C, 800 ° C, 600 ° C, and 450 ° C for 60 minutes to obtain a glass-bound ring-shaped ferrite core.

Table 2 shows the material properties of the samples of Examples 11 to 15 described above.

(Example 16) 5% by weight of a non-alkali lead borosilicate glass powder having a softening point (Ts) of 700 ° C and an average particle size of 1 µm was added to the same ferrite main firing powder used in Example 1, and mixed and formed. After granulation, 3ton / cm pressure, inner diameter 7mmφ, outer diameter 12mmφ, thickness 3cm
Was produced.

This molded product was heated in air at 1200 ° C. for 60 minutes to obtain a glass-bound ring-shaped ferrite core. This example
Table 2 shows the material properties of the 16 materials.

(Examples 17 to 28) A starting mixed granulated powder comprising Fe ₂ O ₃ 48, NiO 13, ZnO 34, and CuO 5 mol% was baked at 1320 ° C. for 6 hours, and crushed. A Ni-Zn-Cu soft ferrite main firing powder of 50 to 100 µm in coarse powder and 5 µm or less in fine powder was prepared. As a result of X-ray analysis of this powder, a sharp spinel structure diffraction line unique to soft ferrite was obtained, and it was confirmed that the powder was a magnetic powder having extremely high crystallinity.

The composition ratio of the high crystalline ferrite magnetic powders 1 and 2 is based on 100 parts by weight of the magnetic powder 1 (coarse powder) and 30 parts by weight of the magnetic powder 2 (fine powder). A non-alkali lead borosilicate glass powder having a softening point (Td) of 370 ° C. and an average particle size of 1 μm was respectively 0,0.1,0.3,0.5,1,1.
Add 3,5,10,30,40wt% each and mix and granulate, then 3ton / c
At a pressure of m ² , ring-shaped molded articles having an inner diameter of 7 mmφ, an outer diameter of 12 mmφ, and a thickness of 3 mm with different glass contents were produced.

Each of these molded products is individually set in an electric furnace,
Heat treatment was performed in the air for 1 minute to obtain a glass-bound ring-shaped ferrite core.

Table 3 shows the material properties of the samples of Examples 17 to 28.

In the above Examples and Comparative Examples, the initial magnetic permeability was measured according to the JIS standard (C2561). First, an insulating tape was wound around the above-mentioned ring-shaped ferrite core, and then the wire diameter was measured.
A sample was prepared by further winding an insulated copper wire of 0.26 mmφ all around. Next, this self-inductance was measured with a Maxwell bridge when the strength of the measured magnetic field was 0.8 (A / m) or less, and the initial magnetic permeability at a frequency of 1 (MHz) was calculated from this.

In addition, the saturation magnetic flux density is determined by JIS standard (C25
According to 61), the magnetic flux density at a magnetic field of 10 (Oe) was measured by the self-recording magnetometer method.

Furthermore, the shrinkage was measured by measuring the outer diameters of the ring-shaped molded product before the heat treatment and the ring-shaped ferrite core after the heat treatment, and calculating the dimensional shrinkage before and after the heat treatment. According to JIS standard (C2564), two thin wires were passed through the ring core once, and one of them was fixed. The tensile load at the moment when the core was broken was measured and determined.

Effect of the Invention As described above, according to the present invention, a glass-bound high-density low-shrinkage ferrite magnetic material has good dimensional accuracy, is a magnetic material having excellent magnetic properties, and can be manufactured at low cost. It can provide excellent effects as useful electronic components and materials used in various magnetic products.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a fine structure of a ferrite magnetic material according to the present invention, and FIG. 2 is a schematic diagram of a fine structure of a conventional typical sintered ferrite magnetic material. 1,2 ... High crystalline ferrite magnetic powder, 3 ... Glass material, 4 ... Void, 5 ... Pore.

Claims (5)

(57) [Claims] 1. A mixture of a highly crystalline ferrite magnetic powder having at least two kinds of particle size distributions which have been sufficiently ferritized by high-temperature sintering and a glass powder having a softening point lower than the sintering temperature. A ferrite magnetic material obtained by binding a highly crystalline ferrite magnetic powder with a glass material by a heat treatment at a temperature not lower than the softening temperature of the above and below the firing temperature of the highly crystalline ferrite magnetic powder. 2. The ferrite magnetic material according to claim 1, wherein the heat treatment temperature of the mixture of the high crystalline ferrite magnetic powder and the glass powder is 800 ° C. or higher and the firing temperature of the high crystalline ferrite magnetic powder or lower. 3. The ferrite magnetic material according to claim 1, wherein a soft magnetic powder having a particle size distribution of 5 μm or less is used as the highly crystalline ferrite magnetic powder. 4. The ferrite magnetic material according to claim 1, wherein the material ratio of the glass to the high crystalline ferrite magnetic powder is 0.3 to 30% by weight. 5. A mixture obtained by mixing and granulating a highly crystalline ferrite magnetic powder having at least two kinds of particle size distributions sufficiently ferritized by high-temperature firing and a glass powder having a softening point lower than the firing temperature. After heat molding, by a heat treatment at a firing temperature of the ferrite magnetic powder or less,
A method for producing a ferrite magnetic material in which a glass powder mixed in the compact is softened and melted to bind a highly crystalline ferrite magnetic powder with a glass material.