JPS6238411B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a composite (cermet type ferrite) of a magnetic material of metal or alloy and ferrite. Recently, there has been a strong tendency for γ-Fe ₂ O ₃ in magnetic recording media, which has been widely used up until now, to be gradually replaced by magnetic alloy powder or vapor-deposited magnetic alloy film. Accordingly, the conventional main magnetic head materials, such as single crystal ferrite and high-density ferrite, are being replaced by amorphous magnetic materials or ultra-quenched sendust alloys. The main reason is that the saturation magnetic flux density of ferrite is approximately 5000
6,000 Gauss, which is far below the 8,000 to 10,000 Gauss value required for alloy magnetic recording tape heads. In this way, the saturation magnetic flux density of soft magnetic spinel ferrite, which has been conventionally used as head material, is significantly lower than that of metallic magnetic materials, but spinel ferrite has high electrical resistance not seen in metallic magnetic materials. rate and has excellent wear resistance. Therefore, if it were possible to develop a material that combines the excellent properties of ferrite and metal or alloy magnetic materials, it would be extremely promising as a head material compatible with alloy tapes. In addition, if a material with the above characteristics can be obtained, it can be applied to materials other than head materials, such as cores for transformers of switching power supplies that switch at high frequencies, cores for chiyoke coils, etc., and it can be used to miniaturize these parts. , which can greatly contribute to higher performance.
The range of applications is extremely wide. By the way, as is well known, cermet, which is a composite material of metal and oxide, is widely used as a structural material. However, there have been no published research reports on composite materials of magnetic materials such as metals or alloys and ferrite, which is a ferromagnetic oxide, and only a small number of patent applications have been published (Japanese Patent Application Laid-Open No. No. 50-9798, Japanese Patent Publication No. 51-20594
(Japanese Patent Publication No. 53-91397). Of course, there are no examples of these composite magnetic materials being put into practical use. this is,
This seems to be because the difference between the high vacuum atmosphere for producing magnetic materials such as metals and alloys and the oxidizing atmosphere for producing ferrite is so significant that it is difficult to combine them. The present inventors first developed a Sendust alloy (Fe
-Al/Si alloy) powder and ferrite powder were mixed and sintered in various atmospheres, but it was not possible to obtain a material with excellent magnetic and electrical properties. As described above, it is not possible to obtain a highly practical material by simply mixing and firing the alloy magnetic material and ferrite. The present invention was made in view of these technical circumstances, and its purpose is to create a composite material of ferrite, which has excellent magnetic and electrical properties, and a magnetic material such as metal or alloy. The purpose is to provide a manufacturing method. The present inventors decided to refer to a composite of ferrite and a magnetic material such as a metal or an alloy as a "cermet-type ferrite," and conducted systematic basic research on it in an attempt to develop a new and useful composite material. As a result, the inventors discovered that a cermet-type ferrite with excellent magnetic and electrical properties could be produced by the method described in detail below, leading to the completion of the present invention. be. That is, the present invention provides a method for producing cermet-type ferrite, in which 1 to 10% by weight of B ₂ O ₃ is added to a mixture of spinel-type ferrite powder and magnetic metal powder or magnetic alloy powder, and the mixture is fired at a temperature of 600 to 800°C. , and the sintered body thus obtained,
This is a method for manufacturing cermet-type ferrite in which the material is placed in a closed container under reduced pressure or vacuum conditions of 5 mmHg or less, and reheated to a temperature of 450 to 570°C to adjust its maximum magnetic flux density and electrical resistivity. The first feature of the invention is that 1 to 10% by weight of boric anhydride (B ₂ O ₃ ) is added and sintered at 600 to 800°C. When ferrite powder is mixed with magnetic material powder of metal or alloy and fired, at least
It cannot be sintered sufficiently unless it is heated to 900°C or higher. When sintered at such high temperatures, the electrical resistivity is quite low, making it particularly unsuitable as a high-frequency material. However, a small amount
When B ₂ O ₃ is added and fired, a well-sintered sample with excellent magnetism can be obtained by firing at 600 to 800°C, as shown in FIG. FIG. 1 shows the change in maximum magnetic flux density when carbonyl iron powder is mixed with magnetite powder, which is a type of ferrite, and 3% by weight of B ₂ O ₃ is added and fired. In the figure, 0% on the horizontal axis indicates that the composition of the sample is entirely magnetite, and 100% on the horizontal axis indicates that the entire sample is carbonyl iron. Further, in the same figure, curve A is the case where the firing temperature is 600°C, curve B is the case when the firing temperature is 700°C, and curve C is the case when the firing temperature is 800°C. When B ₂ O ₃ is added, the lower the firing temperature, the more the maximum magnetic flux density tends to increase.
However, when the firing temperature is lower than 500°C, a decrease in sintered density is observed, and mechanical strength also decreases. This is the reason why the sintering temperature is set in the range of 600 to 800°C in the present invention. Thus, the significance of the effect that the addition of B ₂ O ₃ has on lowering the firing temperature cannot be predicted at all from conventional knowledge. It is also surprising that the effect of adding B ₂ O ₃ is remarkable even when the amount added is as small as 1% by weight. However, when the amount of B ₂ O ₃ added exceeds 10% by weight, the maximum magnetic flux density becomes even lower.
This is the reason why the amount of B ₂ O ₃ added in the present invention is limited to 1 to 10% by weight. Furthermore,
Low melting point oxides other than B ₂ O ₃ , such as PbO,
We also experimented with Bi ₂ O ₃ , P ₂ O ₅ , GeO, etc.
It has been confirmed that there is no significant effect like B ₂ O ₃ . It has also been revealed that adding B ₂ O ₃ to lower the firing temperature significantly improves the electrical resistivity. Figure 2 shows that magnetite powder is mixed with carbonyl iron powder in the same way as in Figure 1, and B ₂ O ₃
The graph shows the change in electrical resistivity when 3% by weight of the following was added and fired. In the figure, curves A, B, and C are for firing temperatures of 600°C, 700°C, and 800°C, respectively. As is clear from the figure, adding B ₂ O ₃ and lowering the firing temperature can increase the electrical resistivity, thus making it possible to use it in a higher frequency range. From the above, it is more preferable for the sintering temperature to be on the low temperature side for both magnetic properties and electrical properties, and within the above temperature range, about 600 to 700°C is particularly preferable. When firing a sample, the atmosphere is also important. That is, when producing cermet-type ferrite by adding B ₂ O ₃ , if the molded product is fired in air as usual, the pressure of the atmosphere is reduced to a range of 2 to 5 mmHg using a vacuum pump. . It has been confirmed that if the degree of pressure reduction is outside the above range, the metal will be excessively oxidized and the ferrite will be excessively reduced. Incidentally, Figures 1 and 2 are the results of an experiment conducted by heating in a reduced pressure atmosphere of 2 mmHg. However, when adding a small amount of B ₂ O ₃ and hot pressing (pressure firing) under high pressure,
The atmosphere may be argon, nitrogen, or oxygen. This is because, under high pressure, the influence of the atmospheric gas is limited to the surface layer of the sample, making it difficult to diffuse deep into the interior of the sample. In the present invention, spinel-type ferrite powder,
Powder of magnetic metal or magnetic alloy is mixed. As the spinel ferrite, for example, magnetite, manganese ferrite, nickel ferrite, zinc ferrite, copper ferrite, or a composite ferrite of these can be used. As the magnetic metal, for example, iron, nickel, cobalt, etc. can be used, and as the magnetic alloy, iron- Nickel alloy, iron-silicon alloy, iron-aluminum-silicon alloy, etc. can be used. The materials of the spinel ferrite, magnetic metal, and magnetic alloy are not particularly limited. Also,
Their mixing ratio is also arbitrary. The mixing ratio may be determined to satisfy the magnetic and electrical properties required by the use of the sintered body. For example, when magnetite powder and carbonyl iron powder are used as raw materials, the content of carbonyl iron is preferably about 40 to 80% by weight, as shown in FIGS. 1 and 2. 40
If it is less than 800° C. by weight, the maximum magnetic flux density will be reduced, and if it exceeds 80% by weight, the electrical resistivity will be extremely low. The second feature of the invention is that the sample obtained by firing by the above method is sealed in a glass tube, etc., and reheated to adjust the maximum magnetic flux density and electrical resistivity of the sample. be. At this time, the atmosphere inside the glass tube or the closed container is set to a reduced pressure or vacuum state of 5 mmHg or less, and is maintained at a constant temperature in the temperature range of 450 to 570° C. for a long period of time. Then,
As shown in FIG. 3, the maximum magnetic flux density (curve D) gradually increases and the electrical resistivity (curve E) gradually decreases as time passes. Figure 3 shows the experimental results when a cermet-type ferrite consisting of carbonyl iron, magnetite, and B ₂ O ₃ was held at 550°C and reheated. When the heating holding time extends to 10 hours or more, both the tendency for the maximum magnetic flux density to increase and the tendency for the electrical resistivity to decrease become remarkable. This change in properties is due to the precipitation of metallic iron inside the sample, and this has been confirmed from the results of X-ray analysis. Therefore, when the time of holding at 550°C reaches about 100 hours, the precipitation of iron in the sample is almost completed, and both the maximum magnetic flux density and the electrical resistivity converge to a certain value. As detailed above, the method for producing cermet-type ferrite of the present invention is completely new, and the magnetic and electrical properties of the obtained cermet-type ferrite are determined by the respective characteristics of the component metal and ferrite. It will be a combination of the following. Figure 4 shows that the carbonyl iron content is 60% by weight.
A sample containing 40% by weight of magnetite and 5% by weight of B ₂ O ₃ was heated at 600°C under a reduced pressure of 5 mmHg.
This shows the relationship between magnetic strength and temperature when fired. A rapid change in magnetization strength is observed at approximately 580°C and approximately 770°C. The former corresponds to the Curie temperature of magnetite, and the latter corresponds to the Curie temperature of iron. From this, it can be seen that the cermet-type ferrite produced by the method of the present invention is a composite having the characteristics of iron and ferrite, respectively. Next, the manufacturing method of the present invention will be explained in more detail with reference to Examples. Example 1 Commercially available pure magnetite (Fe ₃ O ₄ ) powder with an average particle size of about 2 microns and carbonyl iron powder with a particle size of about 3 microns were weighed at a weight ratio of 1:3, and the total mass B ₂ O ₃ corresponding to 3% by weight of
was added and molded into a round bar shape with a diameter of 10 mm and a length of 20 mm using a mold. The molding pressure at that time was 1 ton/cm ²
It was hot. This was carried out at 900°C in a reduced pressure atmosphere of 3mmHg.
℃ for 15 minutes and quenched. The maximum magnetic flux density of the cermet type ferrite obtained in this way is 9000
Gauss, coercive force was 2 oersted, electrical resistivity was 5 x 10 ^-3 ohm cm, and specific gravity was 6.6. Further, the maximum magnetic flux density when the magnetite in Example 1 is replaced with another ferrite (other conditions are exactly the same) is shown in the following table. From this table,
It can be seen that the maximum magnetic flux density further increases when zinc ferrite is contained.

[Table] Example 2 Manganese ferrite powder and carbonyl iron powder were mixed at a weight ratio of 2:3, and
Add 5% B ₂ O ₃ by weight, raise the temperature to 800°C while applying 200 mega-pounds of pressure, and maintain the temperature at 5%.
After holding for a minute, it was cooled. The atmosphere used at this time was argon gas. The specific gravity of the sample thus obtained was 7.0, the maximum magnetic flux density was 10200 Gauss,
The electrical resistivity was 1×10 ⁻³ Ω·cm. Example 3 The sample obtained in Example 1 was sealed in a glass tube, and the pressure inside the tube was reduced to 2 mmHg using a vacuum pump. 500 of this
When heated and held at ℃ for 70 hours, the maximum magnetic flux density was
11500 Gauss and an electrical resistivity of 3×10 ^-4 Ω·cm was obtained. As detailed above, according to the present invention, it is possible to produce a cermet type ferrite which is extremely useful industrially and has a significantly higher maximum magnetic flux density than conventional ferrites.

[Brief explanation of the drawing]

Figure 1 shows carbonyl iron, magnetite and a small amount of
A graph showing the maximum magnetic flux density at each firing temperature in the cermet type ferrite of the present invention made of B ₂ O ₃ ,
Figure 2 is a graph showing the measurement results of the electrical resistivity, Figure 3 is a graph showing the change in maximum magnetic flux density and electrical resistivity when cermet type ferrite is reheated at 550℃, and Figure 4 is a graph showing the change in electric resistivity when cermet type ferrite is reheated at 550°C. It is a graph showing the temperature dependence of the magnetization strength of ferrite.

Claims (1)

[Claims] 1. 1 to 10 B ₂ O ₃ is added to a mixture of spinel-type ferrite powder and magnetic metal powder or magnetic alloy powder.
1. A method for producing cermet-type ferrite, which comprises adding cermet-type ferrite at a temperature of 600 to 800°C. 2 Add 1 to 10 B ₂ O ₃ to a mixture of spinel-type ferrite powder and magnetic metal powder or magnetic alloy powder.
The sintered body obtained by adding % by weight and firing at a temperature of 600 to 800°C is placed in a closed container under reduced pressure or vacuum of 5 mmHg or less, and reheated to a temperature of 450 to 570°C, and its maximum magnetic flux is A method for producing cermet-type ferrite characterized by adjusting density and electrical resistivity.