JPH06151152A - Manufacture of mn-zn ferrite calcinated powder - Google Patents

Abstract

PURPOSE:To provide a manufacture of Mn-Zn ferrite calcinated powder so as to improve the formability for pressurizing formation, especially method for grinding the calcinated powder. CONSTITUTION:(1) DA is the grain diameter of the 50% of secondary grains before powdering and DB is the grain diameter of the 50% of the secondary grains after powdering. The ratio DB/DA is permitted to be in a range of 0.1 to 0.6 and the formability of the calcinated powder is improved so as to manufacture Mn-Zn ferrite calcinated powder. (2) The grain diameter DB of the 50% of the powdered secondary grains is permitted to be in a range of 0.5mum or more and 5mum or less and the Mn-Zn ferrite calcinated powder is manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing Mn-Zn ferrite calcined powder for improving moldability in pressure molding, and more particularly to a method for pulverizing calcined powder.

[0002]

2. Description of the Related Art Mn-Zn ferrite cores are used in power transformers and the like and are manufactured in large quantities. The manufacturing method is generally 800 to 120 after mixing raw materials.
Calcination is performed at about 0 ° C., and after crushing, it is granulated, molded, and fired.

In the molding process, a so-called pressure molding method such as uniaxial press molding is generally used in many cases as a molding method most suitable for mass production. The density of the molded body obtained by this method affects the density of the ferrite core after the subsequent firing, and generally, the higher the molded body density, the higher the sintered body density, and as a result, the product with excellent magnetic properties is obtained. can get. Therefore, in order to satisfy the properties required for the ferrite core, it is necessary to obtain a uniform molded product having a high density to some extent in the molding process.

However, in order to increase the compact density,
If the molding pressure is excessively increased, the mold may be damaged, the life of the mold may be shortened, and the density of the molded body tends to be non-uniform, which eventually causes a decrease in yield and an increase in cost. For this reason, it is desirable to achieve an appropriate compact density at the lowest possible compaction pressure during press molding. From such a viewpoint, conventionally, additives such as binders and plasticizers have been used to improve moldability. Have been devised (Japanese Patent Application No. 3-6).
1754, 61755).

However, changing the additive conditions of the additive causes problems such as a decrease in strength of the molded body and an inability to obtain an appropriate granulated powder during granulation.

[0006]

DISCLOSURE OF THE INVENTION The present invention does not rely on the conventional method of adding an additive but by controlling the pulverizing method of the calcined powder to obtain a ferrite calcined material having excellent formability. Intended to provide flour.

[0007]

In order to solve the above problems, the present invention pays attention to the relationship between the degree of pulverization of calcined powder and the formability, and 50% particle size D _{A of} secondary particles before pulverization and the ratio between the 50% particle size D _B of the secondary particles after grinding, the density of the molded body is increased when the specific range of the D _B / D _a, found that the moldability is improved, The present invention has been completed.

The gist of the present invention is as follows. (1) The ratio of 50% particle size D _A of secondary particles before crushing to 50% particle size D _B of secondary particles after crushing, D _B / D _A, is set to 0.
A method for producing a calcined powder of Mn-Zn ferrite, characterized in that the formability of the calcined powder is improved in the range of 1 to 0.6. (2) The 50% particle size D _B of the secondary particles after the pulverization is 0.
A method for producing a Mn—Zn-based ferrite calcined powder, which is in the range of 5 μm or more and 5 μm or less.

In the present invention, 50 of the calcined powder before and after crushing is used.
The% particle diameters D _A and D _B can be measured using a Microtrac, Coulter Counter, sedimentation method or the like. The density of the compact formed by molding the calcined powder with the same molding pressure is increased by using the calcined powder that is pulverized so that the value of D _B / D _A is in the range of 0.1 to 0.6. can do. When the value of D _B / D _A is larger than 0.6, the poor formability is considered to be related to the higher degree of aggregation of the calcined powder. Further, the value of D _B / D _A is 0.
When the ratio is 1 or less, the density of the compact decreases, and it is considered that a considerable amount of fine powder is generated during pulverization. In addition, the 50% particle size D _B of the secondary particles after pulverization is 0.5 μm.
When the thickness is 5 μm or less, a higher compact density can be obtained, and the effect of the present invention can be further brought out.

[0010]

EXAMPLES The present invention will be further described below based on examples. Fe ₂ O _3, the MnCO _3, ZnO, respectively 52 to 54 mol%, 35-38 mol% (MnO basis) were mixed at a ratio of 9-12 mol%, 800-110
After calcination at 0 ° C., ball mill pulverization was performed to produce Mn—Zn ferrite calcined powder having various particle sizes. The 50% particle size before and after pulverization at this time was measured by Microtrac. Further, PVA was added to these calcined powders for granulation, and then uniaxial pressing was performed at a pressure of ² ton / cm ² to form tablets having a diameter of 10 mm.

The density and the value of D _B / D _A of the obtained molded product are shown in Table 1. When D _B / D _A is ground to a range of 0.1 to 0.6, a molded product having a high density can be obtained.

_{Table 1} D _A (μm) D _B (μm) D _B / D _A compact density (g / cm ³ ) Example 1 4.13 2.29 0.55 3.06 Example 2 3.67 1.97 0.54 3.08 Example 3 2.94 1.53 0.52 3.06 Example 4 2. 57 1.00 0.39 3.07 Example 5 3.45 0.99 0.29 3.04 Comparative Example 1 3.38 2.09 0.62 2.95 Comparative Example 2 3.40 2.500 .74 2.95 Comparative Example 3 4.35 0.41 0.09 2.89

[0013]

As described above, according to the production method of the present invention, it is possible to provide a calcined powder of Mn-Zn ferrite having excellent formability. It is possible to prevent the generation of defective products due to non-uniformity, contribute to a decrease in yield and cost, and finally to manufacture an excellent ferrite core.

Claims (2)

[Claims] 1. _A ratio D _B / D _A of 50% particle size D _A of secondary particles before crushing and 50% particle size D _B of secondary particles after crushing,
A method for producing a Mn-Zn ferrite calcined powder, characterized in that the formability of the calcined powder is improved in the range of 0.1 to 0.6. 2. The 50% particle size D _B of the secondary particles after pulverization is 0.
The method for producing a Mn-Zn ferrite calcined powder according to claim 1, wherein the range is 5 μm or more and 5 μm or less.