JPH05267038A - Manufacture of oxide magnetic material - Google Patents

Abstract

PURPOSE:To obtain an oxide magnetic material having low loss by adding vanadium or a vanadium oxide before pre-baking, pre-baking and crushing a mixture, mixing a binder and press-molding and baking the whole. CONSTITUTION:Oxide powder containing 30-40mol% MnO, 5-15mol% ZnO and Fe2O3 as the remainder while containing 0.01-0.15wt.% CaO and 0.005-0.10wt.% SiO2 is prepared, A 0-1.0wt.% (0wt.% is not included) vanadium component is added to the oxide powder, and pre-baked at a temperature of 600-1100 deg.C. The pre-baked mixture is crushed by a ball mill, a binder is mixed, and the whole is press-molded and baked. Accordingly, oxide magnetic material powder having small loss in high frequency and sharp particle size distribution is acquired simply.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spinel type Mn-Zn type ferrite mounted on a switching power source,
In particular, it relates to a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, a switching power supply equipped with Mn-Zn ferrite has a drive frequency of at most 20.
The frequency was about 0 kHz, but in recent years, the drive frequency has been increasing with the demand for smaller size and lighter weight.

However, when the Mn-Zn type ferrite is used in a high frequency band, the heat generation due to the increase in the power loss of the ferrite becomes extremely large, and the function cannot be fully achieved. Therefore, conventionally, various elements such as silicon dioxide and calcium oxide have been added and mixed to reduce the loss.

[0004]

When manufacturing Mn-Zn ferrite, manganese oxide, zinc oxide,
The powdered ferric oxide raw material is weighed and mixed, then pre-baked, crushed, mixed with a binder, and further press-molded and baked to obtain a finished product.

By the way, if an attempt is made to promote the homogenization of the composition and the promotion of the densification in the firing step, the growth of crystal grains accompanied by abnormal grain growth occurs, and it is extremely difficult to uniformly control the structure. In addition, the weight of the raw material is reduced due to thermal decomposition, the volume is expanded due to the generation of gas, and the shrinkage of the raw material of the fine particles is significantly contracted. As a result, defects such as cracks and deformation occur in the product. Therefore, a method of solving the above-mentioned problems is taken by pre-baking once to homogenize the composition and control the powder particle size in the pre-baking stage.

Pre-baking is generally carried out in an air atmosphere or an inert atmosphere in a temperature range of 700 to 1200 ° C. in a tunnel type electric furnace, a rotary kiln or the like, but the particle size distribution of the pre-baked powder is generally It is known to be wide.

However, in the pre-fired powder having a wide particle size distribution, it is difficult to control the structure of the sintered body in the firing process which is a post-process, so that the crystal grain size cannot be made uniform and ferrite loss is increased. I will end up.

Although the structure can be controlled to some extent by the firing conditions, complication of the firing conditions is unavoidable, and the loss of ferrite cannot be fundamentally improved. In addition, the complicated firing conditions require a sufficient consideration for the selection of the firing furnace and cause a high cost.

An object of the present invention is to provide a manufacturing method capable of easily obtaining a low loss oxide magnetic material.

[0010]

According to the present invention, vanadium or vanadium oxide is added before pre-firing, which is a pre-step of the firing step, to add 0 to 1.0 wt% (0 (Not included), followed by preliminary calcination at 600 ° C. to 1100 ° C., pulverization, binder mixing, press molding, and calcination.

[0011]

With the oxide powder pre-calcined according to the present invention, a powder having a uniform particle size and a sharp particle size distribution can be obtained regardless of the amount of the powder to be treated. As a result, the sintered structure can be easily controlled, the firing conditions can be simplified, and the simplification of this step is very effective in terms of cost reduction.

In the oxide powder pre-calcined according to the present invention, a suitable crystal grain size can be set for each driving frequency, and by controlling the crystal grain size finely and uniformly,
It is possible to provide a low loss magnetic material having a small iron loss even when used at a high frequency of 00 kHz or more.

[0013]

EXAMPLES The present invention will be described below with reference to examples.

With reference to FIGS. 1 and 2, Samples 1 and 2 are
39.0 mol% of MnO and 8.0 as main components, respectively
It is a Mn-Zn-based ferrite containing mol% ZnO and the balance Fe ₂ O _3, and 0.025 wt% SiO ₂ and 0.043 wt% CaO as secondary components.

In Sample 1, vanadium oxide (V ₂ O ₅ ) was added to the oxide powder having the above composition so that the vanadium component was contained in an amount of 0.1% by weight, and then prebaked at 900 ° C. Sample 2 is a comparative sample, which was pre-baked at 900 ° C. without adding V ₂ O ₅ . Each sample is crushed with a ball mill and then mixed with a binder, press-molded, and baked.

FIG. 1 shows a frequency of 1 MHz and a maximum magnetic flux density of 50.
Is a graph showing the temperature characteristics of the power loss P _B at 0G. As is clear from FIG. 1, Sample 1 is superior in power loss to the ferrite of Sample 2 over the entire temperature range.

FIG. 2 shows a maximum magnetic flux density of 500 at a temperature of 60.degree.
6 is a graph showing frequency dependence of power loss P _B when G is set.

As is apparent from FIG. 2, Sample 1 is superior in power loss to the ferrite of Comparative Sample 2 in the entire frequency range.

Next, referring to FIG. 3, Samples 3 and 4 each contain 39.0 mol% MnO as the main component, 8.0 mol% ZnO, and the balance Fe ₂ O _3, and as the sub-components. 0.025 wt% SiO ₂ and 0.043 wt% C
It is a Mn-Zn ferrite containing aO.

Sample 3 is prepared by adding vanadium oxide (V ₂ O ₅ ) to the oxide powder having the above composition so as to contain 0.5% by weight as a vanadium component, and then pre-baking at 900 ° C.

Sample 4 is a comparative sample, which is a powder prefired at 900 ° C. without adding V ₂ O ₅ .

FIG. 3 is a graph showing the particle size distribution of the powder pre-fired at 900 ° C. It can be seen from FIG. 3 that the sample 3 has a sharper particle size distribution than the sample 4.

Referring to FIG. 3, each of the samples contained 39.0 mol% MnO and 8.0 mol% Zn as main components.
O and balance Fe ₂ O ₃ , 0.025
It is a Mn-Zn-based ferrite containing SiO ₂ in weight% and CaO in 0.043 weight%. For each sample, V ₂ O ₅ was added to the oxide powder having the above composition and pre-baked at 900 ° C., followed by ball mill grinding, binder mixing, press molding and baking.

FIG. 4 shows the relationship between the power loss P _B and the vanadium content at a temperature of 60 ° C., a frequency of 1 MHz and a maximum magnetic flux density of 500 G. From Figure 4, until a 1.0 wt% content of vanadium tends to decrease the power loss P _B, it can be seen that the power loss P _B exceeds 1.0% by weight drastically increases.

The increase in the power loss P _B level exceeding 1.0% by weight is due to the increase in the hysteresis loss due to the increase in the number of holes and the increase in the eddy current loss due to the crystal grain enlargement. It is thought to be because.

With reference to FIG. 5, each of the samples contained 39.0 mol% MnO and 8.0 mol% Zn as main components.
O, balance Fe ₂ O ₃ , 0.02
It is a Mn-Zn ferrite containing 5 wt% SiO ₂ and 0.043 wt% CaO. 0.5% by weight of vanadium component in the oxide powder having the above composition for each sample
After vanadium oxide (V ₂ O ₅ ) was added so as to be contained, pre-firing was performed at various temperatures, and then ball milling, binder mixing, press molding and firing were performed.

FIG. 5 shows the relationship between the power loss P _B at a temperature of 60 ° C., a frequency of 1 MHz and a maximum magnetic flux density of 500 G and the pre-baking temperature. As shown in FIG. 5, the P _B of the sample pre-fired in the temperature range of 600 ° C. to 1100 ° C. tends to decrease, but the power loss P _B occurs when pre-firing is performed at other temperatures.
It can be seen that

When the pre-baking temperature is 600 ° C. or lower,
The particle size distribution of powder cannot be made sharp. Therefore, it is very difficult to control the sintered structure, a uniform crystal grain size cannot be obtained, and both hysteresis loss and eddy current loss of ferrite increase, so that the power loss P _B is significantly deteriorated. On the other hand, when pre-baked at 1100 ° C. or higher, remarkable grain growth of powder occurs, and a dense sintered body cannot be obtained as it is.

It is possible to improve the sinterability by crushing in the subsequent step, but it becomes difficult to control the structure because the particle size distribution of the powder becomes wide, and the same problem as in the case of pre-baking at 600 ° C. or less occurs. ..

Referring to FIG. 6, Samples 5 and 6 each contain 39.0 mol% MnO as the main component, 8.0 mol% ZnO, and the balance Fe ₂ O _3, with 0 as a minor component. ．
It is a Mn-Zn-based ferrite containing 025 wt% SiO ₂ and 0.043 wt% CaO.

Sample 5 was prepared by adding vanadium oxide (V ₂ O ₅ ) to the oxide powder having the above composition so as to contain 0.1% by weight as a vanadium component, and then pre-baking at 900 ° C.
Then, pulverization, binder mixing, press molding and firing were performed.

Sample 6 is a comparative sample. After pre-baking the oxide powder having the above composition at 900 ° C., vanadium oxide (V ₂ O ₅ ) was added so as to be contained as 0.1% by weight as a vanadium component during pulverization. Then, binder mixing, press molding and firing were performed.

FIG. 6 shows a frequency of 1 MHz and a maximum magnetic flux density of 50.
Is a graph showing the temperature characteristics of the power loss P _B at 0G. It can be seen from FIG. 6 and Sample 5 that the power loss is superior to the ferrite of Sample 6 over the entire temperature range.

As is clear from the above description of each embodiment, 0 to 1.0% by weight (excluding 0) was added before the preliminary firing.
The low power loss P _B can be obtained by adding vanadium or a vanadium compound so as to contain the vanadium component of, and then pre-baking at 600 ° C. to 1100 ° C.

In the present invention, the production of the low loss magnetic material by adding V ₂ O ₅ has been described, but the vanadium compound targeted by the present invention is not limited in kind.
It does not have to contain an element that deteriorates the magnetic characteristics of ferrite. That is, the vanadium component may be contained in an amount of 0 to 1.0% by weight.

[0036]

As is apparent from the above examples, according to the present invention, vanadium or a vanadium compound is added so that the vanadium component is contained in an amount of 0 to 1.0% by weight before the preliminary firing. Then, by pre-baking at 600 ° C to 1100 ° C, a powder having a sharp particle size distribution can be obtained.

That is, according to the present invention, the sintered structure can be easily controlled, the firing conditions can be simplified, and the cost can be greatly reduced. In addition, the characteristics required for the switching power supply material are sufficiently satisfied, and the power loss P is maintained even at a high frequency of 200 kHz or more.
_It is possible to provide a low-loss oxide magnetic material in which _B is significantly reduced as compared with the conventional one. Therefore, it is possible to provide a material that is sufficiently suitable for reducing the size and weight of the switching power supply, as the material for the high frequency magnetic core.

[Brief description of drawings]

FIG. 1 is a diagram showing temperature characteristics of power loss P _B at a frequency of 1 MHz and a maximum magnetic flux density of 500 G.

FIG. 2 is a diagram showing frequency dependence of power loss P _B at a temperature of 60 ° C. and a maximum magnetic flux density of 500 G.

FIG. 3 is a diagram showing a particle size distribution of powder pre-fired at 900 ° C.

[Figure 4] Temperature 60 ℃, frequency 1MHz, maximum magnetic flux density 50
Is a diagram showing the relationship between the power loss P _B and the content of vanadium in 0G.

[Figure 5] Temperature 60 ℃, frequency 1MHz, maximum magnetic flux density 50
Is a diagram showing the relationship between the power loss P _B and the preliminary baking temperature at 0G.

FIG. 6 is a diagram showing temperature characteristics of power loss P _B at a frequency of 1 MHz and a maximum magnetic flux density of 500 G.

Claims (1)

[Claims] 1. A main component of 30 to 40 mol% of manganese oxide (MnO) and 5 to 15 mol% of zinc oxide (Zn).
O) and the balance ferric oxide (Fe ₂ O ₃ ) and 0.01 to 0.15% by weight of calcium oxide (C
aO) and 0.005 to 0.10% by weight of silicon dioxide (SiO ₂ ) in a magnetic powder of 0 to 1.0% by weight (0
% Of vanadium component is added so as to contain vanadium or a vanadium compound so as to obtain an added powder body, and the added powder body is pre-baked at a temperature of 600 ° C. to 1100 ° C. A second step of obtaining a fired body, and an oxide magnetic material is produced from the preliminary fired body by a powder metallurgy method.