JPH05275227A - Manufacture of oxide magnetic material - Google Patents

Abstract

PURPOSE:To lessen the loss in the core of transformer by smashing, molding and sintering the material powder being mixed and prebaked. CONSTITUTION:Mn-Zn ferrite material powder is prebaked after being mixed, and then, the powder is smashed for 8-40hours with a ball mill made of zirconia. Next, it is molded and sintered. As the Mn-Zn ferrite material, Fe2O3 having content of 99% or more, MnCO3 having content of 99.5% or more, or ZnO having content of 99% or more is desirable. For the prebaking, it is desirable that it should be performed at 800-950 deg.C. Moreover, it is desirable that the sintering should be performed for about four hours at 1000-1200 deg.C in N2 gas atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a low loss magnetic material, and more particularly to a method for manufacturing a magnetic material used for a high frequency switching power supply.

[0002]

2. Description of the Related Art In recent years, the frequency of a switching power supply is 200 to 300 kH in order to miniaturize the power supply.
z is the mainstream, but there is a strong demand for further miniaturization,
High-performance devices that operate at higher frequencies are required for each power supply component. The magnetic material for a power transformer has a large magnetic flux density and a loss of electric energy, that is, the magnetic material when a coil is wound and a voltage is applied, as shown in the following formula 1 for downsizing. In order to reduce the core loss caused by the characteristics, it is required that hysteresis loss and eddy current loss are as small as possible.

[0003]

[Equation 1] A: Magnetic path cross-sectional area (cm ² ) E: Voltage (V) B: Magnetic flux density (mT) N: Number of coil turns f: Frequency (kHz)

Conventionally, an Mn-Zn oxide magnetic material has been used as a magnetic material for a switching power supply transformer up to 1 MHz band, but the core loss of the Mn-Zn oxide magnetic material cannot be said to be sufficiently small. is the current situation.
On the other hand, in order to further reduce the volume of the transformer core, the frequency used is becoming higher. Since the core loss increases as the frequency increases, it is urgent to reduce the loss of the transformer core as much as possible in order to meet this demand. An object of the present invention is to provide a method for producing an oxide magnetic material that solves the above problems.

[0005]

According to the present invention, in a method for producing manganese-zinc (Mn-Zn) ferrite, raw material powders are mixed and pre-fired powder is crushed with a zirconia ball for 8 to 40 hours. Then, the method is a method for producing an oxide magnetic material, which is characterized by forming and firing.

[0006]

The structure of the present invention will be described in detail below.
First, as an Mn-Zn ferrite raw material, iron oxide (Fe
₂ O ₃ ) is 99% or more, manganese carbonate [MnC
O ₃ , the raw material form of manganese oxide (MnO)] is 99.5.
%, Zinc oxide (ZnO) is preferably 99% or more. Of the above raw materials, MnCO ₃ is preferably stored in a dry place. The above raw material was mixed with Fe ₂ O ₃ at 53.
0 mol%, MnO 36.0 mol%, ZnO 11.0
Weigh it to be mol%. This is mixed with a ball mill or the like so as to be sufficiently uniform. The mixing is preferably a wet mixing method. Next, the mixture is dried and then pre-baked. The pre-baking temperature is preferably 800 to 950 ° C. Next, the obtained pre-baked powder is crushed for 8 to 40 hours using a zirconia ball. Zirconia balls have a great crushing effect,
Therefore, it is particularly preferable because the effect of improving the characteristics is great.
In addition, since the pre-fired powder is not sufficiently crushed for 8 hours or less, it is not effective in reducing the core loss of the sintered body. As a result, the eddy current loss becomes large and the overall core loss becomes large, which is not preferable. Then, after molding, sintering is performed. Sintering is 1000-1
It is preferable to carry out at 200 ° C. for about 4 hours. The sintering atmosphere is preferably N ₂ gas.

[0007]

EXAMPLES Examples of the present invention will be described below. F
53.0 mol% of e ₂ O ₃ and MnO (the raw material form is MnCO
₃ ) and ZnO are weighed so as to be 36.0 mol% and 11.0 mol%, and SiO ₂ is used as a grain boundary phase high resistance material.
Of 0.05% and CaO (the raw material form is CaCO ₃ ) of 0.1 mol% were added and wet mixed for 30 hours in an iron ball mill. At this time, 99% alcohol was used as the dispersion medium.

Next, the mud cloth was filtered, dried, and then pre-baked at 850.degree. Next, 100 g of the pre-baked powder, 1 kg of φ5 zirconia balls and 250 cc of alcohol were placed in a polypropylene pot (internal volume: about 1600 cc),
Rotation speed 130r. p. m. Was crushed under the conditions shown in Table 1. Next, after adding PVA (polyvinyl alcohol) as a powder binder (paste), it was molded at a pressure of 2.5 tons / cm ² so as to be φ30 × φ20 × 7t. The molded body is heated and degreased in the atmosphere at 480 ° C for 12 hours,
It was calcined in N ₂ gas at 30 ° C. for 4 hours. Heating rate is 2
The temperature was 00 ° C./H, and the cooling was furnace cooling. The shape of the obtained sintered body was φ25 × φ17 × 5t. The core loss of the sintered body was measured with a u function meter. The frequency was 1 MHz and the magnetic flux density was 0.05 tesla, and the measurement results are shown in Table 1. No. which is a comparative example. In contrast to Nos. 1 and 7, the sintered body produced by the method of the example has a core loss reduced by about 40%, and it is clear that the effect of the present invention is remarkable. The magnetic permeability μ was 2000 or more, and the saturation magnetic flux density 4πMs was 4900 or more.

[0009]

[Table 1] ─────────────────────────────────── Grinding time BET Average particle size PL (Core loss) 60 ° C No. (H) (m ² / g) (μm) (mw / cm ² ) ───────────────────────────────── ─── 1 ^* 0 2.33 0.51 1050 2 8 2.47 0.48 820 3 16 2.76 0.43 710 4 24 3.20 0.37 650 5 32 3.39 0.35 660 6 40 2.89 0.41 810 7 ^* 48 4.09 0.29 960 ────────── ───────────────────────── ^* : Comparative example

[0010]

As described above, according to the manufacturing method of the present invention, an oxide magnetic material of Mn-Zn ferrite having a significantly improved core loss can be obtained. The magnetic material obtained by the present invention is used as a core of a power transformer to reduce the size, thickness, weight and density of information equipment, communication equipment, office equipment, electronic measuring instruments, image equipment, audio equipment, etc. It is extremely useful industrially because it can be mounted.

Claims (1)

[Claims] 1. A method for producing manganese-zinc (Mn-Zn) ferrite, which comprises mixing raw material powders, crushing the pre-fired powder with a zirconia ball for 8 to 40 hours, and then molding and firing. A method for producing a characteristic oxide magnetic material.