JPS58135133A - Ferrite magnetic material - Google Patents

Abstract

PURPOSE:To obtain a ferrite magnetic material having improved magnetic permeability keeping low shrinkage, by mixing ferrite powder with glass powder, and baking the mixture at a temperature higher than the temperature to initiate the densification of the ferrite. CONSTITUTION:Ferrite powder having particle diameter of 5-50mum is mixed with 0.5-15wt% glass powder, and baked at or above the temperature to initiate the densification of the ferrite to obtain the objective ferrite material. Although a molded ferrite obtained by pressing ferrite powder in a mold contains a large number of voids, the number of the voids decreases and the molded ferrite shrinks by the diffusion between the atoms constituting the ferrite by heating the ferrite usually at 800-1,000 deg.C or above. According to the progress of densification, the ferrite acquires the functions of magnetic material and high strength. Since the ferrite particle is cated with glass in this process, a lower shrinkage can be achieved by carrying out the diffusion densification to a certain extent, and at the same time, terminating the diffusion at a desired stage.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a material made by mixing ferrite powder with glass powder and firing the mixture, and improves the magnetic properties by examining the particle size of the ferrite powder.

Ferrite magnetic materials manufactured by powder metallurgy are used in various devices as useful electronic components, and are contributing to the development of these devices.

However, since it is manufactured using a powder metallurgy method, 10
This is accompanied by a shrinkage of ~20%, resulting in large variations in the dimensions of the fired body. For this reason, when used as an electronic component, large dimensional variations occur even in one assembled product itself, which is an obstacle to improving the performance of the device. Therefore, in order to achieve a higher performance device, it is necessary to improve the dimensional accuracy of the ferrite, which is the object of the present invention.

Conventionally, in order to obtain high dimensional accuracy, efforts have been made by manufacturers to control the shrinkage rate to a constant value of 7#, but there are limits and high dimensional accuracy has not been achieved.

Further, efforts have been made to obtain high dimensional accuracy by reducing the large shrinkage ratio of 10 to 2096, but this is not sufficient.

In addition, as a method for manufacturing ferrite that achieves high dimensional accuracy,
A manufacturing method using a so-called molding method in which ferrite particles are solidified with a binder is known.

However, products made using this manufacturing method have very little difference in size from those made using kinkei, and although high dimensional accuracy can be achieved, the product strength is weak and its applications are limited.

The present invention aims to obtain a material with a low shrinkage rate, which is conventionally difficult, by adding glass powder to ferrite and firing it at a temperature above the point at which the ferrite starts to become densified, thereby achieving higher dimensional accuracy than K. At this time, the magnetic permeability of the low shrinkage material can be improved by carefully examining the ferrite particle size.

Conventional manufacturing methods in which magnetic materials and glass are mixed and heat treated include, for example,
In the cited example, hot pressing is performed, but in the present invention, a normal firing method can be used, so there is a significant difference in mass productivity. Furthermore, in the present invention, the ferrite is densified to a certain extent, whereas the cited example is different in that the glass and the magnetic material are simply solidified. Here, I would like to briefly touch on the densification of ferrite.A molded product made by pressing ferrite powder in a metal mold contains many pores, but usually 800 to 10 pores.
When heated to a temperature of 00° C. or higher, diffusion occurs between the atoms constituting the ferrite, and as a result, the number of pores decreases and the molded product contracts. As this densification progresses, the compact, which exhibits almost no magnetism, comes to function as a magnetic material and at the same time its strength increases. In the present invention, since the glass surrounds the ferrite particles, densification by diffusion at a certain degree progresses, and at the same time, the diffusion is stopped midway.
This achieves a lower shrinkage rate.

First, an example will be described in which a mixture of ferrite and glass powder, which is the basis of the present invention, has a low shrinkage rate.

Reference example Fe1O147,5Mg025. OZnO2α5 mo
Mixed powder consisting of tts remainder CuO at 900-1200℃
After calcination and finely pulverizing the powder to 2 to 5 μm, 10% by weight of amorphous glass powder with a softening point of 650°C and a particle size of 100 mm or less was added to the finely pulverized powder, and the powder was pulverized using a Raikai machine.
Mixed for an hour. After adding a PVA aqueous solution to the mixed powder and kneading it to granulate it, it was granulated in a mold with an outer diameter of 2 cm and an inner diameter of 10 cm.
A molded article was obtained to which on/- pressure was applied. Table 1 shows the characteristics of a sample obtained by firing a nucleic acid form at 1250° C. in the air, together with the characteristics of a sample subjected to the same treatment without adding glass powder.

Table IIN1 By adding glass in this manner, it is possible to obtain a material with a low shrinkage rate of 10 inches or less, which was not possible with the prior art. Moreover, the crushing strength is also greater than that of the ferrite solidified with resin, which is 100 to 30 W-.

Furthermore, when the fractured surface of the glass-added sample was mirror-polished and observed under a microscope, it was found that the structure consisted of glass surrounding ferrite particles.

Furthermore, the results of various studies with various addition amounts of glass10
It has been found that although a low shrinkage rate of '16 or less can still be obtained, the value of magnetic permeability changes depending on the IK added to the glass. As a result of further investigation into this point, it was found that the thicker the glass layer surrounding the ferrite particles, the lower the magnetic permeability.

In the present invention, the particle size of the ferrite powder is made larger than that of the above-mentioned reference example in order to maintain a low shrinkage rate and improve magnetic permeability.

Examples are shown below.

Example 1 A ferrite mixture with the same composition as in Reference Example 1 was calcined at the same temperature, then coarsely crushed and classified using an air classifier. A powder with a particle size of 20 to 25 μm was collected as a zero-class powder and used as a reference. Table 2 shows the properties of the same glass powder as in the example but with different amounts of addition and the same firing as in the reference example.

2nd Table of Contents IIIA Example 2 The same classified product as in Example 1 with a particle size in the range of 10 to 15 μm was collected, the same glass was added in different amounts, and the same firing was performed. ! Shown below.

As is clear from the examples shown in Table 3 and above, when the particle size of the ferrite particles is made larger than that of the reference example, it is possible to maintain a low shrinkage rate and improve the magnetic permeability. Note that as the particle size of ferrite increases, the formability deteriorates, so the upper limit was defined as 50 μm.

As described above, the material according to the present invention has a small shrinkage rate, achieves high dimensional accuracy, and contributes to further improving the performance of devices.

Although the magnetic permeability decreases somewhat by adding glass,
The magnetic permeability value required for ferrite is 5 to 20,000.
There are no limitations on the uses of the material of the present invention.

Agent 1) Naka Kotobuki l! 4.

Claims (1)

[Claims] ferrite powder with a particle size of 5 to 50 μm and a glass powder of 0.5 to 15% by weight to the powder are mixed and then fired at a temperature above which densification of 7 ferrite begins. Shrinkage rate soft magnetic ferrite material.