JPH0536516A - Manganese-zinc ferrite material, its manufacture and high frequency transformer - Google Patents

Abstract

PURPOSE:To reduce core loss with high frequency and increase core intensity even if material iron oxide contains a large amount of P by adding a predetermined amount of potassium. CONSTITUTION:A manganese-zinc ferrite material contains 52 to 54mol% of iron oxide when expressed in terms of Fe2O3, 28 to 38mol% of manganese oxide when expressed in terms of MnO, 8 to 20mol% of zinc oxide when expressed in terms of ZnO, 75 to 300ppm of P and 100 to 300ppm of potassium oxide when expressed in terms of metal. In addition 100 to 2000ppm of potassium compound expressed in terms of metal is mixed into a mixture of iron oxide containing 75 to 300ppm of P in a total amount, manganese oxide and zinc oxide, and this is granulated to be sintered in a mold. Thus loss can be reduced at a relatively high frequency region of 10kHz.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is particularly applicable to 10 to 500 kHz.
TECHNICAL FIELD The present invention relates to a manganese-zinc based ferrite material with low power loss and high core strength as a magnetic core for a power transformer that operates at a high frequency, a manufacturing method thereof, and a magnetic core for a high-frequency power transformer formed from the ferrite material.

[0002]

2. Description of the Related Art Manganese-zinc-based ferrite is widely used as a coil and transformer material for various communication equipments, consumer equipments, etc., but recently there is a tendency that a high frequency power source is used, and it is for that purpose. Performance as a transformer material has been required. Especially for switching power supplies, it is necessary to have a transformer material that can be used with a power of several tens of watts in the high frequency range of 10 kHz to 500 kHz. In addition to this, a stable transformer material for motor drive, signal amplification and oscillation is also required. It is said that. Until now, manganese-zinc-based low-loss ferrite has been used as a transformer material, but in the high frequency region of about 10 kHz to 500 kHz, power loss called core loss is large, and improvement in terms of core loss is required. There are various proposals for this purpose.

By the way, in the production of ferrite such as manganese-zinc-based ferrite, the raw material iron is iron chloride, and the iron oxide obtained by using it is mixed with oxides of manganese and zinc to form granules, which are then sintered. To obtain ferrite.

In such a case, impurities in the raw iron oxide have a great influence on magnetic properties such as core loss and magnetic permeability, and it is important to purify the iron chloride solution and regulate the amount of impurities. .

For example, in JP-A-2-30660, 30 to 37 mol% MnO and 10 to 15 mol% Z are used.
Low loss manganese-zinc based ferrite containing nO, P of 10 to 70 ppm, SiO ₂ of 100 to 300 ppm, Ca
O is regulated to 200 to 2000 ppm to reduce core loss in the high frequency range. Further, Japanese Patent Laid-Open No. 3-50124
In the publication, 51-54 mol% Fe ₂ O ₃ , 19-2
High magnetic permeability manganese-zinc ferrite containing 5 mol% ZnO, 0.01 to 0.15 wt% CaO, SiO ₂
0.02wt% or less, P 0.005wt% (50ppm)
Below, Cl is regulated to 0.01 to 0.12 wt% or less,
The magnetic permeability is improved.

However, a great amount of labor is required to purify the iron chloride solution so that the amount of P is 70 ppm or less, and the manufacturing equipment and manufacturing cost increase. However, as shown in these publications, the amount of P is 100 ppm or 150 ppm.
At low levels, low-loss ferrite causes a marked increase in core loss, and high-permeability ferrite causes a marked decrease in permeability.

On the other hand, especially in the case of low-loss ferrite, if the P content is regulated to 70 ppm or less, the bending strength becomes extremely low and the core strength is insufficient, so that many breakage accidents occur during magnetic core assembly.

[0008]

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a manganese-zinc based ferrite magnetic material having a high core strength and a low core loss in a high frequency range even if a large amount of P is contained in a raw iron oxide, and its production. A method and a magnetic core for a high frequency power transformer using the method.

[0009]

The above objects are achieved by the inventions (1) to (5) below. (1) 52 to 54 mol% of iron oxide in terms of Fe ₂ O ₃ ,
28 to 38 mol% of manganese oxide in terms of MnO and Zn
8 to 20 mol% zinc oxide in terms of O and 75 to 300 pp
A manganese-zinc-based ferrite material, characterized by containing P of m and an oxide of potassium of 100 to 2000 ppm in terms of metal.

(2) A mixture of iron oxide, manganese oxide, and zinc oxide containing 75 to 300 ppm of P in total,
Production of a manganese-zinc system ferrite material characterized in that the manganese-zinc system ferrite material according to the above (1) is obtained by mixing 100 to 2000 ppm of a potassium compound in terms of metal, granulating the mixture, and forming and sintering. Method.

(3) The method for producing a manganese-zinc ferrite material according to (2) above, wherein the sintering is performed at 1300 ° C. or higher.

(4) It is characterized by comprising the manganese-zinc system ferrite material described in (1) above or the manganese-zinc system ferrite material obtained by the manufacturing method described in (2) or (3) above. Magnetic core for high frequency power transformer.

(5) The magnetic core for a high frequency power transformer according to (4), which has an operating frequency of 10 to 500 kHz.

[0014]

In the present invention, addition of a predetermined amount of potassium realizes reduction of core loss at high P content and high core strength.

Conventionally, it has been known to add an alkali metal to manganese-zinc ferrite. For example, Japanese Patent Publication Sho 52-
In Japanese Patent No. 18726, addition of 0.06 to 0.04 wt% or less of Na ₂ O or K ₂ O aims to reduce ferrite noise of a magnetic head.

Further, in Japanese Patent Publication No. 48-6759,
0.032～0.7Wt% of NaCl, with the aim losses reduced by the addition of KCl, in JP-A 1-296602 and JP thereby achieving a loss reduction by the addition of 0.15 wt% or less of K ₂ O.

Further, in JP-A-61-242105 and JP-A-61-242104, K ₂ C of 0.3 wt% or less is also used.
O ₃ is added to improve the magnetic permeability of the high frequency power source core and reduce the loss.

However, none of them discloses the presence or absence of P and the content thereof, and it is certain that it is a low P content of 70 ppm or less in view of its magnetic characteristics. Therefore, the core strength represented by the transverse strength is low.

That is, the realization of both the reduction of core loss and the improvement of core strength by the addition of potassium with a high P content in the present invention was first discovered by the present inventors. Cannot be predicted from various publications disclosing the addition of the alkali metal. In addition,
The low loss due to the addition of potassium is realized by suppressing the abnormal grain growth during sintering that occurs when the amount of P is high. Furthermore, the grain system becomes uniform and at the same time the sintering temperature improves and the grain boundary strength increases. However, it is considered that the core strength represented by the transverse strength is improved.

[0020]

Specific Structure The specific structure of the present invention will be described in detail below. The manganese-zinc system ferrite material in the present invention contains iron oxide, manganese oxide and zinc oxide as main components.

There is no particular limitation on the amount ratio of these main components, but these main components are generally Fe, respectively.
₂ O ₃ in terms of 52 to 54 mol%, MnO converted 28 to 38 mol%, in particular 28 to 36 mol%, ZnO terms 8-20 mol%, it is preferable that the particularly about 11 to 18 mol%.
Outside this range, the loss increases and the Curie point becomes 100 ° C. or lower, or μa in the high frequency region decreases.

The P content in the ferrite material containing these main components is 75 to 300 ppm, particularly 80 to 200 ppm.
Is. If it is less than 75 ppm, when Dalai powder, mill scale or the like is used as the raw material iron, it will take an extraordinarily large amount of labor for refining iron chloride. In addition, the core strength is also reduced. On the other hand, when the P content is more than 300 ppm, the loss becomes too large and the effect of the present invention disappears.
Note that P generally exists at the grain boundary.

On the other hand, the ferrite material of the present invention contains K in the form of an oxide, especially K ₂ O.

The content is 10 in terms of metal.
It is set to 0 to 2000 ppm, particularly 200 to 2000 ppm, and further 300 to 1000 ppm. If it is less than 100 ppm, the loss is increased, and if it is more than 2000 ppm, the core strength is lowered and the loss is also increased. If the content is outside this range, the effect of the present invention disappears. Note that K ₂ O usually exists at grain boundaries.

It is preferable that one or more kinds of calcium oxide, silicon oxide, niobium oxide, bismuth oxide, indium oxide, vanadium oxide and the like are contained in such ferrite material. These are about 300 to 2000 ppm in terms of CaCO _{3 and} 1 in terms of SiO ₂ .
0 ~ 500ppm, 10-100 in Nb ₂ O ₅ conversion
About 0ppm, 0 in terms of Bi ₂ O ₃ or In ₂ O ₃
About ~1000ppm, 10~1000p in terms _of V ₂ O ₅
It is preferably about pm.

In the ferrite material containing such a component, the addition of potassium suppresses the growth of abnormal grains and regulates the grain size. When the particle diameters are uniform, the magnetic properties are improved, especially the residual magnetic flux density is decreased, the coercive force is decreased, and the hysteresis loss is decreased. Therefore, power loss, that is, core loss is reduced. In addition, the presence of P also assists the combined effect of potassium, increasing the sintered density and at the same time making the particle diameter uniform. As a result, the strength of the grain boundary is increased and the core strength is increased. In this case, the average crystal grain size is generally 10 to 3
It is about 0 μm.

With the ferrite material of the present invention, 30 to 120 ° C. at 50 ° C., sine wave 1000 kHz, 200 mT.
At 1200W ・ m ^-3 or less, especially 1000W ・ m ^-3 or less,
A low core loss of 400 to 700 W · m ^-3 can be obtained. Further, a magnetic permeability μa of 3500 to 8000 is obtained. A magnetic core for a power transformer formed of such a ferrite material has a frequency of 10 to 500 kHz,
It operates at a temperature of about 110 ° C., and its power is about 10 to 100 W. And 1000
A bending strength as high as N or more and up to 2000N can be obtained.

To produce the ferrite material and magnetic core of the present invention, first, as a main component, a usual iron oxide component,
A mixture of a manganese oxide component and a zinc oxide component is prepared.

These main components are mixed so that the final composition of the magnetic material is in the above-mentioned amount ratio, and are used as raw materials. At this time, the total P content in these mixtures was 70.
Restrict to ~ 300ppm.

Then, a potassium compound is added to these main components. The added amount corresponds to the composition ratio of the final component. Examples of the K compound include K ₂ CO ₃ , K _C 1 and K ₂
SO ₄ or the like can be used, but K ₂ SO ₄ or the like is preferable. Further, calcium carbonate, silicon oxide, niobium oxide, bismuth oxide and / or indium oxide, vanadium oxide and the like are added to the raw material mixture as raw materials for the trace components.

After mixing the main component and the added trace component in this way, the mixture is mixed with a spray dryer or the like for 80 to 20.
Granules with a diameter of about 0 μm. Then, a suitable binder, for example, polyvinyl alcohol, is added in a small amount, for example, 0.1 to 1.0 wt%, and the mixture is molded.

Next, this molded product is usually placed under atmospheric pressure for 8 hours.
Up to a predetermined temperature within the range of 00 to 1000 ° C, for example,
After rapid heating at a temperature rising rate of about 0 ° C./hr, the temperature is maintained for a certain time, preferably 1 hour or more. Then, in an atmosphere in which the oxygen concentration is controlled, the desired sintering temperature is increased to 50
Gradually heat at a temperature rising rate of 150 ° C / hr, and complete the sintering at that temperature.

The firing atmosphere at this time is preferably a nitrogen atmosphere in which the oxygen concentration is controlled to about 1 to 15%. Then, firing is usually performed in such an atmosphere at a predetermined temperature in the range of 1300 ° C. or higher, particularly 1350 to 1400 ° C.
It is carried out by holding for 1 to 4 hours.

In the cooling process after the completion of sintering in this way, the oxygen concentration is controlled in accordance with the temperature from the sintering temperature to about 1200 ° C., and thereafter, in an inert atmosphere such as a nitrogen atmosphere. It is preferable to carry out. The cooling rate is preferably about 500 to 700 ° C./hr. As described above, by setting a constant temperature state for a predetermined time, particularly 1 hour or more, at an appropriate temperature between 800 and 1000 ° C., and subsequently performing sintering in an atmosphere in which the oxygen concentration is controlled, a high frequency region is obtained. It is possible to obtain extremely high performance characteristics such as high magnetic permeability and low loss.

[0035]

EXAMPLES The present invention will be described in more detail below by showing specific examples of the present invention. Example 1 MnO (35 mol%), ZnO (11.5 mol%), F
e ₂ O ₃ (53.5 mol%) as a main component, CaCO ₃ (1000 ppm) and Nb ₂ O ₃ (250 pp as secondary components)
m), SiO ₂ (170ppm), V ₂ O ₅ (400ppm
), Was added. The total amount of P in the main component of Sample No. 1 for comparison was 150 ppm.

Further, SO ₄ was added to the sample No. 1 in an amount of 500 ppm and 1000 ppm in terms of K, to obtain sample Nos. 2 and 3 of the present invention.

Further, the sample No. 4 of the present invention in which the P amount of the sample No. 2 was 80 ppm and the P amount of the comparative sample No. 1 containing no K were set to 10 ppm, and the comparative sample No.
Got 5.

After mixing these, they are granulated with a spray drier to an average particle size of 150 μm, molded by adding a binder, and sintered at 1350 ° C. for 11 hours while controlling the oxygen atmosphere to give an outer diameter of 31 mm and an inner diameter of 19 mm. A toroidal core having a height of 8 mm was obtained. When the final composition was measured by fluorescent X-ray, it corresponded to the raw material composition.

Table 1 shows 100 kHz, 200 mT, 100 ° C.
Shows the power loss (core loss) and the bending strength.

[0040]

[Table 1]

From the results shown in Table 1, it can be seen that the core loss is reduced and the bending strength is improved according to the present invention.

Example 2 In Example 1, the change in core loss with temperature was measured. Fig. 2 shows the case of P150ppm, the case without K addition,
The results when K is added at 250 ppm, 500 ppm, and 1000 ppm are shown.

Further, in FIG. 2, P at K500 ppm
The relationship between the content and the core loss and the bending strength, and FIG. 3 shows the relationship between the K addition amount at P150 ppm and the core loss and the bending strength.

From these results, the effect of the present invention is clear.

[0045]

The manganese-zinc ferrite material of the present invention has a characteristic of low loss in a relatively high frequency range of 10 kHz to 500 kHz. Therefore, a transformer having an output of several W to several 10 W for OA equipment and the like. It is useful as a magnetic core, etc. And, such a feature is realized in a wide temperature range, and the core loss is sufficiently low at an actual operating temperature of about 80 to 110 ° C.

Such an effect is realized with a high P content of 75 to 300 ppm, and its merit in manufacturing is extremely great. Moreover, there is an advantage that the transverse strength is sufficient.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between temperature characteristics of core loss and the amount of K added at a P content of 150 ppm.

FIG. 2 is a graph showing a relationship between P content, core loss and bending strength.

FIG. 3 is a graph showing the relationship between the amount of K added, core loss, and bending strength.

Claims (5)

[Claims] 1. 52 to 54 mol% of iron oxide in terms of Fe ₂ O ₃ , 28 to 38 mol% of manganese oxide in terms of MnO, 8 to 20 mol% of zinc oxide in terms of ZnO, 75 to
A manganese-zinc-based ferrite material, which contains 300 ppm of P and 100 to 2000 ppm of metal oxide of potassium. 2. A mixture of iron oxide containing 75 to 300 ppm of P in total, manganese oxide and zinc oxide is mixed with 100 to 2000 ppm of a potassium compound in terms of metal, which is then granulated and sintered. A method for producing a manganese-zinc based ferrite material, comprising: obtaining the manganese-zinc based ferrite material according to claim 1. 3. The method for producing a manganese-zinc based ferrite material according to claim 2, wherein the sintering is performed at 1300 ° C. or higher. 4. A magnetic core for a high frequency power source transformer, comprising a manganese-zinc based ferrite material according to claim 1 or a manganese-zinc based ferrite material obtained by the manufacturing method according to claim 2 or 3. . 5. The magnetic core for a high frequency power transformer according to claim 4, wherein the operating frequency is 10 to 500 kHz.