JPH05205960A - Manufacture of ferrite magnet - Google Patents
Manufacture of ferrite magnetInfo
- Publication number
- JPH05205960A JPH05205960A JP4014800A JP1480092A JPH05205960A JP H05205960 A JPH05205960 A JP H05205960A JP 4014800 A JP4014800 A JP 4014800A JP 1480092 A JP1480092 A JP 1480092A JP H05205960 A JPH05205960 A JP H05205960A
- Authority
- JP
- Japan
- Prior art keywords
- discharge
- ferrite magnet
- pressure
- sintered
- magnetic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Landscapes
- Compounds Of Iron (AREA)
- Hard Magnetic Materials (AREA)
- Manufacturing Cores, Coils, And Magnets (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、フェライト磁石の製造
方法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a ferrite magnet.
【０００２】[0002]
【従来の技術】一般に焼結磁石の製造は、粉砕した原料
粉末を湿式または乾式で加圧成形し、その成形体を炉中
で焼結する方法で行われている。この方法では、焼結時
に長時間を要する、焼結の熱効率が低いなど生産性が悪
く、また焼結中に磁石物質の酸化・相変化などによる特
性の劣化が避け難い。そこで、このような欠点を解決す
る焼結磁石の製造方法として、特に希工類磁石の製造方
法において、特開昭63-51606号公報および特開平2-1981
05号公報に開示されている放電加熱による焼結方法が提
案されている。2. Description of the Related Art Generally, a sintered magnet is manufactured by a method in which a crushed raw material powder is pressure-molded by a wet or dry method and the molded body is sintered in a furnace. In this method, productivity is poor because it takes a long time during sintering and the thermal efficiency of sintering is low, and deterioration of properties due to oxidation and phase change of the magnet material during sintering is unavoidable. Therefore, as a method for manufacturing a sintered magnet that solves such a drawback, particularly in a method for manufacturing a rare-earth magnet, JP-A-63-51606 and JP-A-2-1981 have been used.
A sintering method by electric discharge heating disclosed in Japanese Patent Publication No. 05 has been proposed.
【０００３】[0003]
【発明が解決しようとする課題】しかしながら、放電加
熱をフェライト磁石の製造に適用しようとすると、磁粉
が絶縁体であるために放電が起こりにくい、異常粒成長
を起こして焼結組織が不均一となり磁気特性が低下する
などの問題があった。本発明の目的は、フェライト磁石
を放電加熱により、製造するに際して、異常粒成長の伴
なわない、磁気特性の優れたフェライト磁石の製造方法
を提案することである。However, when an attempt is made to apply discharge heating to the production of ferrite magnets, since the magnetic powder is an insulator, discharge is less likely to occur, abnormal grain growth occurs, and the sintered structure becomes nonuniform. There was a problem such as deterioration of magnetic properties. An object of the present invention is to propose a method for producing a ferrite magnet which is excellent in magnetic characteristics without abnormal grain growth when the ferrite magnet is produced by discharge heating.
【０００４】[0004]
【課題を解決するための手段】すなわち、本発明は、比
表面積が６〜12m2／ｇのフェライト磁粉を磁場中で加圧
成形し、該加圧下での雰囲気の圧力を１Torr以上、酸素
濃度20％以上とし、かつ交流を重畳した直流で放電焼結
することを特徴とするフェライト磁石の製造方法であ
る。That is, according to the present invention, a ferrite magnetic powder having a specific surface area of 6 to 12 m 2 / g is pressure-molded in a magnetic field, the atmosphere pressure under the pressure is 1 Torr or more, and the oxygen concentration is It is a method for manufacturing a ferrite magnet, which is characterized in that it is 20% or more and is subjected to discharge sintering with a direct current in which an alternating current is superposed.
【０００５】[0005]
【作 用】本発明によれば、フェライト磁石の製造にお
いて焼結に放電加熱を用いることが可能となり、同時に
異常粒成長を抑止して磁気特性の低下を有効に防ぐこと
が出来る。フェライト磁石の放電加熱においては、磁粉
が絶縁体であるために直流放電が起こりにくく、また一
旦放電が起こると放電箇所の温度上昇により電気抵抗が
下がるため、放電電流が局所に集中する傾向があった。
パルス放電により、直流放電を誘起する方法においても
同様の欠点があった。本発明によれば交流を重畳させた
直流を用いることで、交流成分により磁粉成形体全体に
放電を誘起した後、交流放電による全体の均一な温度上
昇と電離によって徐々に成形体全体に均一な直流放電を
起こさせることが出来る。[Operation] According to the present invention, discharge heating can be used for sintering in the production of a ferrite magnet, and at the same time, abnormal grain growth can be suppressed and deterioration of magnetic characteristics can be effectively prevented. In electric discharge heating of a ferrite magnet, direct current discharge is unlikely to occur because the magnetic particles are an insulator, and once discharge occurs, the electrical resistance decreases due to the temperature rise at the discharge location, so the discharge current tends to concentrate locally. It was
The method of inducing direct current discharge by pulse discharge has the same drawback. According to the present invention, by using a direct current superposed with an alternating current, after an electric discharge is induced in the whole magnetic powder molded body by an alternating current component, a uniform temperature rise and ionization of the whole due to the alternating current electric discharge make it uniform in the entire molded body. DC discharge can be generated.
【０００６】異常粒生成を起こす原因は、前述の放電電
流の局在の他に、成形体中の局部的な酸素濃度低下によ
る拡散の局部的な活発化、放電による加熱が磁粉表面に
集中するため局部的にあるいは全体として入熱が過大に
なり易いことが研究の結果明らかになった。本発明によ
れば、放電中の雰囲気の酸素濃度を20％以上とするので
成形体中の局部的な酸素濃度低下による異常粒成長を有
効に抑制することが出来る。また、放電による入熱を減
らすため雰囲気の圧力を下げると、成形体からの酸素の
脱離が起こり易いが、本発明では雰囲気の酸素濃度を20
％以上としているので、形状・材質に合わせて雰囲気圧
力を１Torrまで下げて入熱量を調整し、異常粒成長を防
ぐことが出来る。The causes of abnormal grain formation are, in addition to the above-mentioned localization of the discharge current, local activation of diffusion due to local decrease in oxygen concentration in the compact, and heating due to discharge is concentrated on the surface of the magnetic powder. As a result of research, it became clear that heat input tends to be excessive locally or as a whole. According to the present invention, the oxygen concentration in the atmosphere during discharge is set to 20% or more, so that abnormal grain growth due to a local decrease in oxygen concentration in the compact can be effectively suppressed. Further, when the pressure of the atmosphere is reduced to reduce heat input due to discharge, desorption of oxygen from the molded body is likely to occur, but in the present invention, the oxygen concentration of the atmosphere is set to 20
%, It is possible to prevent abnormal grain growth by adjusting the heat input by lowering the atmospheric pressure to 1 Torr according to the shape and material.
【０００７】更に、磁粉の比表面積を12m2／ｇ以下６m2
／ｇ以上とすることで、体積あたりの入熱量の大きな微
粉量を減らし異常粒成長を抑制することが出来る。比表
面積が12m2／ｇを超えると異常粒成長が発生し、６m2／
ｇ未満では成形の密度が低下し良好な焼結状態が得られ
ず磁気特性が低下する。磁粉の比表面積は熱処理や酸洗
処理で下げることが出来る他、粉砕機の種類、粉砕媒体
サイズ、粉砕力によっても変えることが出来る。Further, the specific surface area of the magnetic powder is 12 m 2 / g or less and 6 m 2
When the amount is / g or more, the amount of fine powder having a large heat input amount per volume can be reduced and abnormal grain growth can be suppressed. A specific surface area of 12m 2 / g by weight, abnormal grain growth occurs, 6 m 2 /
When it is less than g, the density of molding is lowered, a good sintered state cannot be obtained, and the magnetic properties are lowered. The specific surface area of the magnetic powder can be reduced by heat treatment or pickling treatment, and can also be changed by the type of pulverizer, pulverizing medium size, and pulverizing force.
【０００８】[0008]
【実施例】ボールミルで粉砕したストロンチウムフェラ
イト磁粉を用いて、内径25mmの絶縁性ダイと導電性パン
チからなる円柱型キャビティに30ｇの磁粉を充填して10
kOe の磁場中で350kgf/cm2の圧力で加圧成形した後、圧
力を保ったまま、13.56MHzの交流１kwを重畳させた直流
電圧を印加し、直流分２kVA の放電を２分間行った。磁
粉の比表面積、放電中の雰囲気と異常粒成長の有無なら
びに磁気特性の関係は表１の通りである。[Example] Using strontium ferrite magnetic powder crushed by a ball mill, 30 g of magnetic powder was filled in a cylindrical cavity composed of an insulating die with an inner diameter of 25 mm and a conductive punch, and 10
After press-molding in a magnetic field of kOe at a pressure of 350 kgf / cm 2 , a DC voltage with 13.56 MHz alternating current of 1 kw superimposed was applied while maintaining the pressure, and discharge of 2 kVA for a DC component was performed for 2 minutes. Table 1 shows the relationship between the specific surface area of the magnetic powder, the atmosphere during discharge, the presence or absence of abnormal grain growth, and the magnetic properties.
【０００９】[0009]
【表１】 [Table 1]
【００１０】本発明によれば異常粒成長を起こすことな
く高特性のフェライト磁石が得られている。According to the present invention, a high-performance ferrite magnet can be obtained without causing abnormal grain growth.
【００１１】[0011]
【発明の効果】本発明の放電加熱法を用いることによ
り、フェライト磁石の生産性と磁気特性を高めることが
できた。By using the discharge heating method of the present invention, the productivity and magnetic characteristics of ferrite magnets can be improved.
Claims (1)
粉を磁場中で加圧成形し、該加圧下での雰囲気の圧力を
１Torr以上、酸素濃度20％以上とし、かつ交流を重畳し
た直流で放電焼結することを特徴とするフェライト磁石
の製造方法。1. A ferrite magnetic powder having a specific surface area of 6 to 12 m 2 / g is pressure-molded in a magnetic field, the pressure of the atmosphere under the pressure is 1 Torr or more, the oxygen concentration is 20% or more, and an alternating current is superposed. A method for producing a ferrite magnet, characterized by performing direct-current discharge sintering.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4014800A JPH05205960A (en) | 1992-01-30 | 1992-01-30 | Manufacture of ferrite magnet |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4014800A JPH05205960A (en) | 1992-01-30 | 1992-01-30 | Manufacture of ferrite magnet |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH05205960A true JPH05205960A (en) | 1993-08-13 |
Family
ID=11871124
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP4014800A Pending JPH05205960A (en) | 1992-01-30 | 1992-01-30 | Manufacture of ferrite magnet |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH05205960A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002029829A (en) * | 2000-05-11 | 2002-01-29 | National Institute Of Advanced Industrial & Technology | Method for manufacturing sintered magnetoplumbite type ferrite magnet |
-
1992
- 1992-01-30 JP JP4014800A patent/JPH05205960A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002029829A (en) * | 2000-05-11 | 2002-01-29 | National Institute Of Advanced Industrial & Technology | Method for manufacturing sintered magnetoplumbite type ferrite magnet |
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