JPH06349625A - High-magnetic permeability oxide magnetic material and manufacure thereof - Google Patents

Abstract

PURPOSE:To inhibit the generation of the growth of abnormal grains at the time of firing of oxide powder by a method wherein spray calcined powder is used as raw calcinated powder for an Mn-Zn ferrite. CONSTITUTION:A high-magnetic permeability oxide magnetic material is formed into a constitution, wherein a composition consisting of 50 to 55mol% of Fe2O3, 20 to 35mol% of MnO and 15 to 30mol% of ZnO is used as the composition of the magnetic material, the crystal density of the magnetic material is 4.95g/cm<3> or higher, the mean crystal grain diameter of crystal grains constituting the magnetic material is 1.5mum or longer and the ratio of the crystal grains of a crystal grain diameter exceeding 150mum is set at 5% or lower of the whole crystal grains. A method of manufacturing this magnetic material is performed by a method wherein Fe, Mn and Zn are mixed in the form of a chloride solution, this solution is sprayed in a spray calcinating furnace to decompose thermally and after the obtained spray calcinated powder is used as oxide powder consisting of the composition consisting of the 50 to 55mol% of the Fe2O3, the 20 to 35mol% of the MnO and the 15 to 30mol% of the ZnO, the oxide powder is heat-treated at 200 to 1000 deg.C, is pulverized, granulated and molded and thereafter, is subjected to firing at 1330 deg.C or higher and at 1450 deg.C or lower. Thereby, the growth of abnormal grains is hardly caused even on a high-temperature and long-time firing condition and the high-magnetic permeability oxide magnetic material having a magnetic permeability of 10000 or higher can be stably obtained.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a high permeability oxide magnetic material for transformers and noise filters.

[0002]

2. Description of the Related Art Mn--Zn based ferrites are widely used in transformers and noise filters because of their high magnetic permeability. However, with the recent expansion of the frequency band under the noise law regulation and the increasing demand for miniaturization of component shapes, an excellent high-permeability Mn-Zn-based ferrite that can have a smaller and wider frequency band characteristic can be obtained. Development is needed. In order to increase the magnetic permeability, it is effective to increase the crystal grain size of ferrite and increase the density. For that purpose, baking at high temperature for a long time is required.

[0003]

However, under the conditions of firing at high temperature for a long time, abnormal grain growth often occurs during sintering, which rather deteriorates the characteristics and lowers the productivity. It is an object of the present invention to provide a method for stably obtaining an oxide magnetic material having a high magnetic permeability of 10,000 or more, with almost no abnormal grain growth even under high temperature and long-term firing conditions. is there.

[0004]

In order to solve the above problems, it is possible to suppress the occurrence of abnormal grain growth during firing by using a spray roasting powder as a raw material calcined powder of Mn-Zn ferrite. Found and completed the present invention.

The subject matter of the present invention is as follows. (1) Fe ₂ O ₃ 50 to 55 mol%, MnO 20
35 mol% and 15 to 30 mol% ZnO and the composition, crystal density of 4.95 g / cm ³ or more, an average grain diameter of 15μm or more, the proportion of crystal grains the crystal grain diameter exceeds 150μm of the total crystal grain A high-permeability oxide magnetic material having a content of 5% or less. (2) The ratio of the crystal grains having a sintered density of 5.0 g / cm ³ or more, an average crystal grain size of 25 μm or more, and a crystal grain size of more than 150 μm is 5% or less of the entire crystal grains (1).
The high-permeability oxide magnetic material described in 1. (3) Fe, Mn, and Zn are mixed in the form of a chloride solution, which is sprayed in a spray roasting furnace to be pyrolyzed, and Fe ₂ O is added.
_{3 After} forming an oxide powder having a composition of 50 to 55 mol%, MnO 20 to 35 mol% and ZnO 15 to 30 mol%, heat treating at 200 to 1000 ° C., and crushing, granulating and molding, and 1330 ° C. As described above, the method for producing a high-permeability oxide magnetic material, which is fired at 1450 ° C. or lower. In the present invention, the ratio of crystal grains having a crystal grain size of more than 150 μm is defined as the area ratio of the total cross-sectional areas of the crystal grains of more than 150 μm in the core cross-sectional area.

The present invention will be described in detail below. The composition of the ferrite material used in the present invention is F, which is the composition range of this type of material that is usually used as a high magnetic permeability material.
e ₂ O ₃ 50-55 mol%, MnO20～35 mol%, and ZnO 15 to 30 mole% is selected. In addition, Bi is effective in improving the magnetic permeability, if necessary.
₂ O ₃ , V ₂ O ₅ , InO, etc.
It may be contained. Furthermore, trace impurities that are unintentionally mixed, such as Si, P, Ni, Cr, and Al, which are initially contained in the raw material or mixed in the manufacturing process.
Impurities such as Cu, Mg, Ti, Na, Cl, and S may be contained in a trace amount that does not affect the characteristics. However, since P and Si have a great influence on the magnetic permeability, it is desirable to set them to 20 ppm and 100 ppm or less, respectively.

The firing temperature is 1330 ° C. or higher to increase the crystal grain size, but if necessary, 1380 ° C.
Abnormal grain growth does not occur even if firing is performed at a very high temperature as described above. In this case, it is possible to stably manufacture a material having a magnetic permeability of 10,000 or more, and exceeding 15,000 depending on conditions, with extremely high characteristics. is there.

In the present invention, as the raw material calcined powder, spray calcined powder is used instead of using the calcined powder obtained by mixing commonly used Fe ₂ O ₃ , MnO and ZnO, then calcining and pulverizing. Use flour. That is, Fe, Mn and Zn
Is mixed at a predetermined ratio in the form of a chloride solution, and the resulting liquid is sprayed in a spray roasting furnace to be pyrolyzed to obtain a mixed oxide powder of Fe, Mn, and Zn. 2 to do
0 to 1000 ° C, more preferably 400 to 800 ° C
Heat treatment for 1 to 4 hours to obtain an average primary particle diameter of 0.3 to 1.
A grain-grown material having a grain size of about 0 μm is used.

When a ferrite core is manufactured by using such a calcined powder, even if it is fired at a high temperature of 1330 ° C. or higher, abnormal grain growth does not occur, the density is high and the crystal grains are large and uniform. A sintered body having a good microstructure can be obtained. Specifically, the sintering density is 5.0 g / cm ³ or more, the average crystal grain size is 15 μm or more, preferably 20 μm or more, and the ratio of abnormal grains having a crystal grain size of more than 150 μm is 5% or less of the entire crystal grain. Consolidation is easily obtained. As a result, it is possible to stably manufacture a ferrite core having a magnetic permeability of 10,000 or more and, depending on conditions, 15,000 or more, which is extremely excellent.

The reason why a core having high characteristics is obtained when the spray roasted powder is used is considered as follows. Compared with the calcined powder produced by the conventional method, the particle size distribution is sharper and the chemical composition is uniform because it passes through the liquid phase. For this reason, local grain growth does not occur at the time of firing, the crystal grain size becomes a uniform fine structure, the number of pores is reduced, and a high-density sintered body can be obtained. In the calcined powder produced by the conventional method, the primary particles are combined by sintering to form secondary particles having a neck. The hard agglomerates cannot be removed even after molding, and voids are formed between the particles. The voids remain as pores even after sintering, and the density decreases. Further, since grain growth progresses more rapidly in the neck portion than in other portions, abnormal grain growth is likely to occur. On the other hand, since the spray roasted powder of the present invention is produced by a so-called build-up method, individual particles are present alone, and aggregation is weak,
A high-density molded body can be obtained without forming large voids.
As a result, the density of the sintered body increases. Further, since there is no neck portion, abnormal grain growth is unlikely to occur. Even after the heat treatment, the spray-roasted powder has a weak bond between the particles and can be crushed lightly. Therefore, fine powder is hardly generated and abnormal grain growth does not occur.

As described above, when the roasted powder of the present invention is used, the main causes of abnormal grain growth in the conventional case using the calcined powder are the non-uniformity of components and the formation of hard agglomerated particles. Existence,
Since all three points of existence of fine powder can be eliminated, abnormal grain growth does not occur even if firing is performed at high temperature for a long time, and it becomes possible to manufacture a high-density sintered body. In addition, when manufacturing the core
In the case of adopting a method in which only one or two components of e, Mn, and Zn are produced by the spray roasting method and then the remaining components are mixed, local grains due to non-uniformity of composition Since growth may occur and high characteristics may not be obtained, it is necessary to always contain three components.

[0012]

EXAMPLES The present invention will be further described below based on examples. By spray roasting, Fe ₂ O ₃ 53 mol%, MnO
An oxide mixed powder having a composition of 25 mol% and ZnO 22 mol% was produced. This was heat-treated at 800 ° C., then crushed, added with 1.0 wt% of PVA as a binder and granulated, and then molded into a ring shape having an outer diameter of 29 mm, an inner diameter of 18 mm, and a height of 7 mm. The compact was fired at 1330 to 1400 ° C. for 4 hours in a nitrogen atmosphere in which the oxygen concentration was controlled. Here, in the case of firing at 1380 ° C. or higher, in order to prevent evaporation of zinc, the molded body was embedded in calcined powder of the same composition and fired.

Table 1 shows the sintered density, the average crystal grain size, the ratio of abnormal grains having a crystal grain size of more than 150 μm (S ₁₅₀ ), 10 kHz, and room temperature permeability of the fired core thus obtained. In Comparative Example 1 in Table 1, after calcination powders of Fe ₂ O ₃ , Mn ₃ O ₄ , and ZnO were mixed, 1050
These are the characteristics of the core that was obtained by calcination at ℃ and crushing. In Comparative Example 2, the firing temperature was lowered (130
0 ° C.) is an example.

Table 1 Firing temperature Sintering density Average grain size S ₁₅₀ Permeability (℃) (g / cm ³ ) (μm) (%) Example 1 1330 5.0 16.0 0 8300 Example 2 1380 5.1 28.5 1.2 12500 Example 3 1400 5.1 43.5 1.5 16500 Comparative Example 1 1380 4.9 29.0 7.4 6200 Comparative Example 2 1300 4.9 11.00 4800 As is clear from Table 1, by using the spray roasted powder as the raw material calcined powder, it is possible to obtain a core having high sintering density, few abnormal grains, and high magnetic permeability.

[0015]

As described above, according to the present invention, since a material having a very high magnetic permeability can be easily obtained, it is possible to stably manufacture a transformer and a noise filter core having high characteristics. Above all extremely beneficial.

Claims (3)

[Claims] 1. Fe ₂ O ₃ 50 to 55 mol%, MnO
The composition is 20 to 35 mol% and ZnO 15 to 30 mol%, the crystal density is 4.95 g / cm ³ or more, the average crystal grain size is 15 μm or more, and the crystal grain ratio is more than 150 μm. 5% or less of a high magnetic permeability oxide magnetic material. 2. The ratio of crystal grains having a sintered density of 5.0 g / cm ³ or more, an average crystal grain size of 25 μm or more, and a crystal grain size of more than 150 μm is 5% or less of the entire crystal grains. The high-permeability oxide magnetic material described. 3. Fe, Mn and Zn are mixed in the form of a chloride solution, which is sprayed in a spray roasting furnace to be pyrolyzed.
₂ O ₃ 50-55 mol%, MnO 20-35 mol%
And ZnO 15 to 30 mol% and made into oxide powder, and then heat-treated at 200 to 1000 ° C. to be crushed,
A method for producing a high-permeability oxide magnetic material, which comprises firing at 1330 ° C. or higher and 1450 ° C. or lower after granulation and molding.