JP3960966B2 - Method for producing heat-resistant rare earth magnet - Google Patents
Method for producing heat-resistant rare earth magnet Download PDFInfo
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- JP3960966B2 JP3960966B2 JP2003411880A JP2003411880A JP3960966B2 JP 3960966 B2 JP3960966 B2 JP 3960966B2 JP 2003411880 A JP2003411880 A JP 2003411880A JP 2003411880 A JP2003411880 A JP 2003411880A JP 3960966 B2 JP3960966 B2 JP 3960966B2
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
- H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
- H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
- H01F41/0293—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets
Description
本発明は、用途面では車載用モータに適合し、材料面ではＤｙ等の希少金属を有効活用し
た、高耐熱性で且つ高性能な希土類磁石の製造方法に関する。
The present invention is compatible with the vehicle motor in applications plane, the material surface is used effectively rare metals such as Dy, a method of manufacturing a and high-performance rare earth magnets with high heat resistance.
Ｎｄ−Ｆｅ−Ｂ系希土類磁石は高いエネルギー積(ＢＨ)maxをもつ磁石として知られてお
り、ハードデスクドライブのボイスコイルモータ（ＶＣＭ）や磁気断層撮影装置（ＭＲＩ
）の磁気回路等に広く応用されている。一方、近年、環境問題の観点から脱ガソリン化に
向けて電気自動車や燃料電池車が開発され、特に、前者の生産台数は年々増加傾向にある
ために駆動用モータに適した磁石の需要が高まっている。
Nd-Fe-B rare earth magnets are known as magnets having a high energy product (BH) max, and are hard disk drive voice coil motors (VCM) and magnetic tomography devices (MRI).
) Is widely applied to magnetic circuits. On the other hand, in recent years, electric vehicles and fuel cell vehicles have been developed for degassing from the viewpoint of environmental problems, and in particular, the former production volume has been increasing year by year, so the demand for magnets suitable for drive motors has increased. ing.
電気自動車用の磁石においては高性能であると共に耐熱性が要求され、１００〜２００℃
における高温減磁を避けるために高保磁力型の磁石を選択して使用されている。この種の
磁石は、Ｎｄ2Ｆｅ14Ｂ主相と周囲のＮｄリッチ副相の組織を最適制御した上に、磁石中
にＮｄ元素よりも資源的に希少なＤｙ元素を数〜十質量％程度含有させることによって、
１．６〜２．４ＭＡ／ｍの保磁力Ｈcjが得られている。しかし、Ｎｄ−Ｆｅ−Ｂ系磁石は
残留磁束密度Ｂrと保磁力Ｈcjの値が相反する関係にあるために、磁石中のＤｙ元素の添
加量を増やしてＨcjを増加させるとＢrの減少を招き、これまで両者共に高い値を有する
希土類磁石は得られておらず、高性能（高Ｂr）型と耐熱（高Ｈcj）型とに分類されて生
産されている。
Magnets for electric vehicles are required to have high performance and heat resistance.
In order to avoid high-temperature demagnetization, a high coercivity type magnet is selected and used. In this type of magnet, the Nd 2 Fe 14 B main phase and the surrounding Nd-rich subphase structure are optimally controlled, and the Dy element, which is rarer in resources than the Nd element, is contained in the magnet in the order of several to about 10% by mass. By containing
A coercive force Hcj of 1.6 to 2.4 MA / m is obtained. However, since the residual magnetic flux density Br and the coercive force Hcj are in a contradictory relationship with each other in the Nd-Fe-B magnet, increasing the amount of Dy element added to the magnet to increase the Hcj results in a decrease in Br. So far, rare earth magnets having high values have not been obtained, and they are classified into high performance (high Br) type and heat resistant (high Hcj) type.
Ｂｒの低下を抑制しつつＨcjを向上させるには、焼結密度や各結晶粒の配向性を向上させ
る、添加元素を利用して結晶組織を微細化させる、等多くの報告があるが、Ｎｄよりも磁
気異方性が大きいＤｙやＴｂ等を主結晶内よりも結晶粒界に優先的に分布させるのが有効
である。焼結磁石を製作する際にＮｄ2Ｆｅ14Ｂを主とする合金と、Ｄｙ等を多く含む合
金若しくはＮｄ2Ｆｅ14Ｂ組成と若干異なる合金等を別々に製作し、各粉末を適正比率で
混合して成形焼結することによって保磁力を向上させる方法の発明が知られている（例え
ば、特許文献１、２）。また、異方性磁石粉末の製作において、Ｎｄ2Ｆｅ14Ｂを主とす
る合金粉末とＤｙ合金粉末を混合して熱処理することによって、前者の粉末表面にＤｙを
コーティングして保磁力を増加する方法の発明が知られている（例えば、特許文献３）。
In order to improve Hcj while suppressing a decrease in Br, there are many reports such as improving the sintered density and the orientation of each crystal grain, and using an additive element to refine the crystal structure. It is effective to preferentially distribute Dy, Tb, etc. having a larger magnetic anisotropy to the grain boundaries than in the main crystal. When manufacturing sintered magnets, an alloy mainly composed of Nd 2 Fe 14 B and an alloy containing a large amount of Dy or the like or an alloy slightly different from the composition of Nd 2 Fe 14 B are manufactured separately, and each powder is prepared in an appropriate ratio. Inventions for improving coercive force by mixing and sintering are known (for example,
耐熱性磁石を得るには、上記のように、室温での保磁力を大きくすることによって高温で
所望の保磁力を確保する方法以外に、モータ回転中の磁石温度の上昇を抑制する方法があ
る。Ｎｄ−Ｆｅ−Ｂ系焼結磁石はフェライト磁石やボンド磁石と比較して電気的に良導体
であるため、モータを毎分数千から１万回転で駆動した場合に磁石内部には渦電流が発生
し、結果的に磁石が発熱して温度上昇を生じる。この問題を回避するため、磁石内部に少
量の酸化物などの絶縁物質を含有して高電気抵抗とするＮｄ−Ｆｅ−Ｂ焼結磁石の発明が
知られている（例えば、特許文献４、５）。また、少量の酸素を含む雰囲気中で焼結を行
うことによって主成分のＮｄ２Ｏ３化合物を結晶粒界に存在させ、高電気抵抗とする磁石
の発明が知られている（例えば、特許文献６）。
In order to obtain a heat-resistant magnet, as described above, there is a method for suppressing an increase in magnet temperature during motor rotation, in addition to a method for ensuring a desired coercive force at a high temperature by increasing the coercive force at room temperature. . Since Nd-Fe-B sintered magnets are electrically better conductors than ferrite magnets and bonded magnets, eddy currents are generated inside the magnet when the motor is driven at several thousand to 10,000 revolutions per minute. As a result, the magnet generates heat and the temperature rises. In order to avoid this problem, an invention of a Nd—Fe—B sintered magnet containing a small amount of an insulating material such as an oxide inside the magnet and having a high electric resistance is known (for example,
上記の特許文献１、２には、略Ｎｄ2Ｆｅ14Ｂ組成の主合金とＮｄ-Ｄｙリッチ副合金を出
発原料として焼結することによって、Ｎｄリッチ粒界相にＤｙ元素等を多く分布させ、そ
の結果として残留磁束密度の低下を抑制しつつ保磁力を向上した焼結磁石が得られること
が開示されている。しかし、Ｄｙ等を多く含む合金製作に別途工数がかかること、該合金
は粘いために数ミクロンまで粉砕するには超急冷法や水素脆化する等、特殊な方法を用い
る必要があること、Ｎｄ2Ｆｅ14Ｂ組成合金よりも格段に酸化しやすいために一層の酸化
防止が必要であること、及び２つの合金の焼結と熱処理反応を厳密に制御する必要がある
こと等、製造面で多くの解決すべき課題がある。また、本方法によって得られる磁石にお
いては、現在、なお５〜１０質量％程度のＤｙが含有されるため、高保磁力型磁石は残留
磁束密度が低いものとなっている。
In
特許文献３には、Ｎｄ−Ｆｅ−Ｂ系磁石粉末と、Ｄｙ−Ｃｏ若しくはＴｂＨ2等の粉末と
を混合し高温で熱処理して、ＤｙやＴｂを磁石粉末表面にコーティングさせることによっ
て高保磁力の異方性磁石粉末を得ている。しかし、この方法でも、Ｄｙ−Ｃｏ若しくはＴ
ｂＨ2等の粉末における粉砕や酸化等の問題を解決できないこと、Ｄｙ−Ｃｏ若しくはＴ
ｂＨ2等の粉末を完全に反応終結させて消滅させ、主とする磁石粉末のみを得ることが難
しい。
In
Inability to solve problems such as crushing and oxidation in powders such as bH 2 , Dy-Co or T
It is difficult to obtain only the main magnet powder by completely terminating the reaction such as bH 2 and extinguishing it.
磁石使用状態での渦電流の発生を抑制して磁石温度の上昇を抑えるには、磁石の比抵抗を
上げることが有効である。例えば、従来のＮｄ−Ｆｅ−Ｂ系の焼結磁石あるいは熱間塑性
加工磁石の比抵抗は１〜２μΩ・ｍであり、同系のボンド磁石の１００分の１以下、絶縁
体であるフェライト焼結磁石とは比較にならないほど低い。Ｎｄ−Ｆｅ−Ｂ系磁石は、こ
れまで酸化を極力防止した製造工程によって作られた結果、磁石中の酸素含有量は約０．
３質量％程度に低減され、高いエネルギー積が実現している。これらの磁石に酸化物など
を加えて比抵抗を高めることが特許文献４〜６に開示されているが、保磁力及び残留磁束
密度など磁気性能が十分ではなく、車載用モータへの応用には難点がある。
Increasing the specific resistance of the magnet is effective for suppressing the generation of eddy current in the magnet use state and suppressing the increase of the magnet temperature. For example, the specific resistance of a conventional Nd—Fe—B sintered magnet or hot plastic working magnet is 1 to 2 μΩ · m. Low compared to magnets. Nd-Fe-B magnets have been manufactured by a manufacturing process that has prevented oxidation as much as possible, and as a result, the oxygen content in the magnets is about 0.
It is reduced to about 3% by mass and a high energy product is realized.
車用途に適する焼結磁石の改良においては、残留磁束密度の低下を抑えて保磁力を高める
と共に、渦電流による発熱とそれによる磁石温度の上昇を抑制することが重要である。ま
た、資源や価格面の観点からＤｙ等の希少元素の使用量を節減することも必要である。
In improving a sintered magnet suitable for a car application, it is important to suppress a decrease in residual magnetic flux density to increase a coercive force, and to suppress heat generation due to eddy current and a magnet temperature increase due thereto. In addition, it is necessary to reduce the use amount of rare elements such as Dy from the viewpoint of resources and price.
先に、本発明者らは、磁石表面にＰｒ，Ｄｙ，Ｔｂ，Ｈｏから選ばれる希土類金属の一種
又は二種以上を成膜して拡散することによって、わずかなこれらの希土類金属の含有量で
従来の焼結磁石と同等の保磁力を実現できるか、又は従来と同等の含有量においては保磁
力を著しく向上させることができる手段を見出し、これに関する発明を特許出願した（特
願２００３−１７４００３）。
First, the present inventors have formed a film of one or more kinds of rare earth metals selected from Pr, Dy, Tb, and Ho on the magnet surface and diffused them, so that the content of these rare earth metals is small. A means that can realize a coercive force equivalent to that of a conventional sintered magnet or can significantly improve the coercive force with a content equivalent to that of a conventional sintered magnet has been found, and a patent application for this has been filed (Japanese Patent Application No. 2003-174003). ).
本発明者らは、Ｎｄ−Ｆｅ−Ｂ系希土類磁石の比抵抗を高めるため上記発明の方法を元に
、詳細に調査実験を重ねた結果、磁石内に酸素を導入して比抵抗の高い結晶組織をつくり
出すことによって、高い磁気特性を維持した耐熱性希土類磁石の開発に成功した。
The present inventors have conducted detailed investigation experiments based on the method of the present invention in order to increase the specific resistance of the Nd-Fe-B rare earth magnet, and as a result, oxygen is introduced into the magnet to produce a crystal having a high specific resistance. By creating a structure, we succeeded in developing a heat-resistant rare earth magnet that maintains high magnetic properties.
すなわち、本発明は、（１）Ｍ（ただし、Ｍは、Ｔｂ及び／又はＤｙ）金属若しくはそれThat is, the present invention provides (1) M (where M is Tb and / or Dy) metal or
らの金属を含む合金又はそれらの金属の水素化物若しくは酸化物を、減圧槽内で原子、分Alloys containing these metals or hydrides or oxides of those metals in an
子、又はイオン化させて、酸素濃度が０．２５〜０．３質量％のＮｄ−Ｆｅ−Ｂ系磁石表Or Nd-Fe-B magnets having an oxygen concentration of 0.25 to 0.3% by mass
面にＭ金属が部分的に酸化した膜を成膜し、成膜と同時に、あるいは引き続いて酸素を含A film in which M metal is partially oxidized is formed on the surface, and oxygen is contained at the same time as the film formation or subsequently.
む雰囲気中で熱処理を行ってＭ元素と酸素を磁石表面から内部に拡散浸透させることによHeat treatment in an atmosphere to diffuse and penetrate M element and oxygen from the magnet surface to the inside.
り表面部から０．３μｍ以上の深さにＭ金属元素を拡散させ、拡散したＭ金属元素の含有M metal element is diffused from the surface to a depth of 0.3 μm or more, and the diffused M metal element is contained
量を０．０５〜５質量％、かつ磁石内の酸素含有量を０.４〜３質量％とすることを特徴The amount is 0.05 to 5% by mass, and the oxygen content in the magnet is 0.4 to 3% by mass.
とするＮｄ−Ｆｅ−Ｂ系耐熱性希土類磁石の製造方法である。This is a method for producing a Nd—Fe—B heat-resistant rare earth magnet.
また、本発明は、（２）前記成膜は、スパッタリング法により真空排気した減圧槽内にＡIn the present invention, (2) the film formation is performed in a vacuum chamber evacuated by a sputtering method.
ｒガスに１〜５容積％の酸素ガスを混合したガスを導入して行なうことを特徴とする上記The above process is performed by introducing a gas in which 1 to 5% by volume of oxygen gas is mixed with r gas.
（１）のＮｄ−Ｆｅ−Ｂ系耐熱性希土類磁石の製造方法、である。It is a manufacturing method of the Nd-Fe-B heat-resistant rare earth magnet of (1).
また、本発明は、（３）前記の酸素を含む雰囲気は、酸素濃度５０〜５０００ｐｐｍの不In the present invention, (3) the atmosphere containing oxygen is an oxygen concentration of 50 to 5000 ppm.
活性ガス雰囲気であることを特徴とする上記（１）のＮｄ−Ｆｅ−Ｂ系耐熱性希土類磁石An Nd—Fe—B heat-resistant rare earth magnet as described in (1) above, which is an active gas atmosphere
の製造方法、である。Manufacturing method.
また、本発明は、（４）拡散浸透したＭ金属元素が（Ｎｄ，Ｍ）Ｏ２系化合物として結晶
粒界に存在することを特徴とする上記（１）の耐熱性希土類磁石の製造方法、である。
また、本発明は、（５）前記酸素濃度が０．２５〜０．３質量％のＮｄ−Ｆｅ−Ｂ系磁石
は０．３〜８質量％のＭ元素を含有することを特徴とする上記（１）の耐熱性希土類磁石
の製造方法、である。
また、本発明は、（６）前記酸素濃度が０．２５〜０．３質量％のＮｄ−Ｆｅ−Ｂ系磁石
は、０．０１〜０．１質量％の不可避不純物を含む磁石であることを特徴とする上記（１
）の耐熱性希土類磁石の製造方法、である。 The invention also relates to (4) expansion Chihita watermarks M-metal elements (Nd, M) crystal as O 2 compound
(1) The method for producing a heat-resistant rare earth magnet according to (1) above, which exists at a grain boundary .
The present invention also provides (5) an Nd-Fe-B magnet having an oxygen concentration of 0.25 to 0.3% by mass.
Containing 0.3 to 8% by mass of M element, (1) heat-resistant rare earth magnet
Manufacturing method.
The present invention also provides: (6) Nd-Fe-B magnet having the oxygen concentration of 0.25 to 0.3% by mass.
Is a magnet containing 0.01 to 0.1% by mass of inevitable impurities (1)
) Heat-resistant rare earth magnets.
また、本発明は、（７）前記酸素濃度が０．２５〜０．３質量％のＮｄ−Ｆｅ−Ｂ系磁石The present invention also provides (7) an Nd-Fe-B magnet having the oxygen concentration of 0.25 to 0.3% by mass.
は、Ｍ元素を不可避不純物として以外含まない磁石であることを特徴とする上記（１）のIs a magnet which does not contain M element as an unavoidable impurity except for (1)
耐熱性希土類磁石の製造方法、である。A method for producing a heat-resistant rare earth magnet.
また、本発明は、（８）前記耐熱性希土類磁石は、磁石最表層のＭ元素の濃度が１００質In the present invention, (8) the heat-resistant rare earth magnet has a 100 elemental M element concentration in the outermost layer of the magnet.
量％であり、結晶粒界における磁石の表面側ほどＭ元素の濃度を濃くした構造であることThe structure is such that the concentration of the M element is increased toward the surface of the magnet at the grain boundary.
を特徴とする上記（１）の耐熱性希土類磁石の製造方法、である。(1) A method for producing a heat-resistant rare earth magnet according to the above (1).
本発明によれば、希土類磁石表面にＤｙ及び／又はＴｂ金属を成膜し、拡散して磁石内部
よりも表面部のＤｙ及び／又はＴｂ元素濃度を高くすることによって、従来の高保磁力型
磁石のように、原料に５〜１０質量％程度のＤｙなどを含有させて焼結しないでも、少な
いＤｙ及び／又はＴｂ金属含有量で高保磁力型磁石と同等以上の２ＭＡ／ｍ以上の保磁力
を出現させることができる。また、原料にＤｙなどを含有させて高保磁力とした磁石にこ
のような拡散処理をすれば保磁力をさらに大きくすることができる。さらに、表面部の比
抵抗を上げて５μΩ・ｍ以上とするために、磁石表面部に多くの酸素を含有させても、保
磁力はほとんど低減しないので、車載用モータに応用した場合、渦電流の防止と磁石温度
の上昇を抑制して耐熱性に優れた磁石を実現できる。
According to the present invention, a conventional high coercive force type magnet is formed by depositing Dy and / or Tb metal on the surface of a rare earth magnet and diffusing it to make the concentration of Dy and / or Tb element in the surface portion higher than inside the magnet. Thus, even if the raw material contains about 5 to 10% by mass of Dy or the like and does not sinter, it has a coercive force of 2 MA / m or more equivalent to or higher than that of a high coercive force type magnet with a small Dy and / or Tb metal content. Can appear. Further, if such a diffusion treatment is applied to a magnet having a high coercive force by containing Dy or the like in the raw material, the coercive force can be further increased. Furthermore, in order to 5μΩ · m or more to increase the specific resistance of the table surface, also contain a lot of oxygen in the magnet surface part, the coercive force is hardly reduced, when applied to automotive motor, vortex It is possible to realize a magnet having excellent heat resistance by preventing current and suppressing an increase in magnet temperature.
通常、同一質量又は体積の磁石を用いても、高温の磁石は磁気特性が低下するため、例え
ば、モータの代表特性であるトルクが小さくなる。結果として入力電力に対する機械出力
＝効率が低下する。しかし、本発明の方法で得られる磁石を用いれば、保磁力が大きい上
に、この温度上昇の抑制によって、磁石の磁気特性の低下度も小さくなるためにモータ効
率を上げることができる。
Normally, even when magnets having the same mass or volume are used, the magnetic characteristics of high-temperature magnets are reduced, and therefore, for example, torque, which is a typical characteristic of a motor, is reduced. As a result, the machine output with respect to the input power = the efficiency is lowered. However, if the magnet obtained by the method of the present invention is used , the coercive force is large, and by suppressing this temperature rise, the degree of decrease in the magnetic properties of the magnet is reduced, so that the motor efficiency can be increased.
Ｎｄ−Ｆｅ−Ｂ系磁石において、大きな保磁力を得るためには異方性磁界の大きい希土類
元素を含有元素として利用すること、及び磁石の内部組織を均一微細に制御することが特
に有効であることが知られている。Ｒを希土類元素とした場合に、Ｒ2Ｆｅ14Ｂ化合物の
中ではＮｄよりもＴｂ，Ｄｙが室温での異方性磁界が大きく、特に、ＴｂはＮｄのおよそ
３倍であることから保磁力向上にとって好適である。但し、これらの元素はいずれもＮｄ
よりも飽和磁化が小さいために、所望のエネルギー積を確保するためにはその添加量を極
力少なくする必要がある。さらに、これらの元素はＮｄ2Ｆｅ14Ｂ結晶のＮｄ元素と置換
すると磁束密度の低下が著しいために、結晶組織内ではなくＮｄリッチ粒界相に存在させ
るのが望ましい。
In order to obtain a large coercive force in an Nd—Fe—B magnet, it is particularly effective to use a rare earth element having a large anisotropic magnetic field as a contained element and to control the internal structure of the magnet uniformly and finely. It is known. When R is a rare earth element, in the R 2 Fe 14 B compound, Tb and Dy have a larger anisotropic magnetic field at room temperature than Nd. In particular, since Tb is approximately three times Nd, the coercive force. It is suitable for improvement. However, all of these elements are Nd
Since the saturation magnetization is smaller than that, it is necessary to reduce the addition amount as much as possible in order to secure a desired energy product. Further, when these elements are substituted with Nd elements of Nd 2 Fe 14 B crystals, the magnetic flux density is remarkably lowered. Therefore, it is desirable that these elements exist not in the crystal structure but in the Nd-rich grain boundary phase.
本発明では、Ｍ（但し、ＭはＴｂ及び／又はＤｙ）元素を磁石表面に成膜して拡散するこ
とによって、磁石全体においてはＭ元素を内部に薄く表面部に濃く分布させ、磁石内部組
織においては主結晶内よりも結晶粒界部にＭ元素を富化させることができる。
In the present invention, the M element (where M is Tb and / or Dy) is deposited on the surface of the magnet and diffused, so that the M element is thinly distributed inside and concentrated thickly on the surface in the entire magnet, In this case, the element M can be enriched in the grain boundary part rather than in the main crystal.
従来の焼結磁石内の結晶粒界相は、最近の研究（日本応用磁気学会誌、２６巻、１０６０
頁、２００２年）によれば、ＮｄＯ２化合物に類似して酸素が一部欠損した構造をもち、
化合物のＮｄ３＋イオンの大きな磁気異方性を利用して磁石の保磁力向上が果たされてい
る。従って、本発明においては、結晶粒界に浸透したＭ元素は金属としてではなく（Ｎｄ
，Ｍ）Ｏ２系化合物として結晶粒界に存在し、Ｎｄ３＋イオンよりもさらに大きいＭ３＋
イオンの複合効果によって保磁力が著しく増加することが推察できる。
Grain boundary phases in conventional sintered magnets have been studied recently (Journal of the Japan Society of Applied Magnetics, Vol. 26, 1060).
Page 2002) has a structure in which oxygen is partially deficient, similar to NdO 2 compounds,
The coercive force of the magnet is improved by utilizing the large magnetic anisotropy of the Nd 3+ ion of the compound. Therefore, in the present invention, the M element penetrating into the crystal grain boundary is not a metal (Nd
, M) O as 2 compounds present in the grain boundaries, a larger M 3+ than Nd 3+ ions
It can be inferred that the coercive force is remarkably increased by the combined effect of ions.
図１に、Ｔｂ金属をＡｒガスに酸素を混合した減圧槽内でスパッタリング法により成膜し
た後に少量の酸素雰囲気中で熱処理を行ったＮｄ−Ｆｅ−Ｂ系焼結磁石、即ち、実施例１
における本発明試料（４）のＥＰＭＡ（Ｘ線マイクロアナライザー）におけるＴｂ元素像
（ａ）、と不純物として０．０３％のＴｂを含んだ合金から出発した従来法によって製作
した比較例試料（１）のＥＰＭＡにおけるＴｂ元素像（ｂ）を示す。なお、酸素濃度の分
析はＥＰＭＡの画像濃淡差が小さいために割愛した。
FIG. 1 shows an Nd—Fe—B based sintered magnet formed by sputtering in a vacuum tank in which Tb metal is mixed with oxygen in Ar gas and then heat-treated in a small amount of oxygen atmosphere.
Comparative Example Sample (1) produced by a conventional method starting from an alloy containing 0.03% Tb as an impurity and Tb element image (a) in EPMA (X-ray microanalyzer) of sample (4) of the
本発明試料（４）の図１（ａ）に示す像においては、Ｔｂ元素は磁石表面部（又は表面近
傍）に濃く分布し、さらに最表層の結晶粒を除いた他の全ての結晶粒内にはほとんどＴｂ
元素は見られずに、磁石内部の深さ６０μｍ位まで結晶粒界に沿って拡散浸透しているこ
とがわかる。磁石の結晶粒界における、表面側ほどＴｂ元素濃度を濃くしたこの構造が、
少ないＴｂ含有量で保磁力が増加する証拠となっている。従って、従来の希土類磁石に含
有されている希少なＴｂやＤｙ等の希土類元素含有量を節減することが可能になる。
In the image shown in FIG. 1A of the sample (4) of the present invention, the Tb element is densely distributed on the magnet surface (or in the vicinity of the surface), and in all other crystal grains excluding the outermost crystal grains. Almost Tb
It can be seen that no element is seen, but diffuses and penetrates along the grain boundary to a depth of about 60 μm inside the magnet. This structure in which the Tb element concentration in the crystal grain boundary of the magnet is increased toward the surface side,
This is evidence that the coercive force increases with a small Tb content. Therefore, the rare earth element content such as rare Tb and Dy contained in the conventional rare earth magnet can be reduced.
一方、比較例試料（１）の図１（ｂ）に示す像においては、磁石内部に部分的にＴｂ元素
の濃淡が見られるが、総じてＴｂ元素は平均的に微量に分布している。また、図１（ａ）
より、成膜したＴｂ元素の拡散によっても、磁石最表面の１列目の結晶粒子を除く他の全
ての粒子は残存し、２列目の粒子も磁石粒としての大きな形態変化がないことがわかる。
On the other hand, in the image shown in FIG. 1B of the comparative example sample (1), the density of the Tb element is partially seen inside the magnet, but the Tb element is generally distributed in a trace amount on average. In addition, FIG.
As a result, even when the deposited Tb element is diffused, all other particles except the first row of crystal particles on the outermost surface of the magnet remain, and the second row of particles may not have a large change in shape as a magnet grain. Recognize.
（作用）
磁石表面にＭ元素を成膜後に熱処理を行うと、Ｍ元素は磁石内の浸透しやすい結晶粒界に
多く、主結晶内にはわずかに拡散浸透する。Ｍ元素の浸透する深さは３μｍ〜１０００μ
ｍ位であり、この浸透領域はＭ元素が富化したＭ−Ｎｄ−Ｏ成分の結晶粒界相と、Ｍ元素
が一部Ｎｄと置換したＮｄ−Ｍ−Ｆｅ−Ｂ成分の主結晶粒から成る。Ｍ元素が、従来の焼
結磁石のように磁石内部の主結晶内に均一に含まれると飽和磁化が低下し、残留磁束密度
も低下するため、本発明の磁石のようにＭ元素が結晶粒界に富化した構造をもつことによ
って保磁力の増加と残留磁束密度の低下を抑制することができる。
(Function)
When heat treatment is performed after depositing the M element on the magnet surface, the M element is often present in the crystal grain boundary where the magnet easily penetrates and slightly diffuses and penetrates into the main crystal. The penetration depth of M element is 3 μm to 1000 μm
This permeation region is from the grain boundary phase of the M-Nd-O component enriched with the M element and the main crystal grains of the Nd-M-Fe-B component in which the M element is partially substituted with Nd. Become. When the element M is uniformly contained in the main crystal inside the magnet as in a conventional sintered magnet, the saturation magnetization is reduced and the residual magnetic flux density is also reduced. Therefore, the element M is a crystal grain as in the magnet of the present invention. By having a structure enriched in the field, an increase in coercive force and a decrease in residual magnetic flux density can be suppressed.
また、酸素は、原料粉末に酸化物を添加する場合は酸化物のまま、或いは磁石成分の一部
と反応して他の酸化物として結晶粒界部に優先して析出する傾向がある。さらに、予め酸
化物を添加しない場合においても焼結や熱間での塑性加工、及び成膜や熱処理工程によっ
て、結晶粒界や磁石の表層部に高濃度の酸素を存在させることができる。これらの酸化物
や酸素による粒界絶縁効果によって、磁石の結晶粒界部と磁石表層部の比抵抗が著しく増
加し、車載用モータなどに使用した場合、磁石の高速回転中においても磁石内の渦電流の
防止と温度上昇の抑制が可能となり、高い保磁力を維持することが可能となる。
In addition, oxygen tends to be deposited in the form of an oxide in the raw material powder as it is, or reacts with a part of the magnet component to give priority to the crystal grain boundary as another oxide. Furthermore, even when no oxide is added in advance, a high concentration of oxygen can be present in the crystal grain boundaries and the surface layer of the magnet by sintering, hot plastic working, film formation, and heat treatment. Due to the grain boundary insulation effect of these oxides and oxygen, the specific resistance between the crystal grain boundary part and the magnet surface layer part of the magnet is remarkably increased. The eddy current can be prevented and the temperature rise can be suppressed, and a high coercive force can be maintained.
本発明においては、希土類元素と酸素との親和性の大きさに着眼し、酸素を積極的に活用
して、残留磁束密度の低下を抑制しつつ比抵抗を５μΩ・ｍ以上に上げることができた。
本発明によって、希少なＤｙ等の希土類元素含有量を節減しても高い保磁力と高残留磁束
密度を保有し、且つ渦電流による発熱を抑制した耐熱性の希土類磁石を提供することがで
きる。また、これにより希少なＤｙ等の資源問題の解決に寄与するものである。
In the present invention, it is possible to increase the specific resistance to 5 μΩ · m or more while focusing on the affinity between rare earth elements and oxygen and actively utilizing oxygen while suppressing the decrease in residual magnetic flux density. It was.
The present invention can provide a rare even saving the content of rare-earth element such as Dy possess high Iho force and high residual magnetic flux density, and the heat resistance of the rare-earth magnet that suppresses heat generation by eddy currents . This also contributes to the solution of rare resource problems such as Dy.
以下、本発明の耐熱性希土類磁石及びその製造方法を更に詳しく説明する。本発明で対象
とする磁石は、原料合金を数μｍの大きさに粉砕して成形、焼結してなる焼結磁石や、原
料粉末を熱間で成形した後にさらに成形品を熱間で塑性加工をした磁石等である。成分系
では、いわゆるＮｄ−Ｆｅ−Ｂ系磁石と称され、結晶組織はＮｄ２Ｆｅ１４Ｂ構造をもつ
数μｍの大きさの結晶粒の周囲を数ｎｍから数百ｎｍの厚さのＮｄリッチ相が取り囲んだ
構造をもつか、或いはＮｄ２Ｆｅ１４Ｂ構造をもつ数十〜数百ｎｍの大きさの結晶粒の集
合体から成る磁石である。これらの磁石には、磁気特性の調整のために通常添加される各
種の添加元素を含有していてもよい。保磁力を増加させるために０．３から８質量％程度
のＭ元素を含有しているものでもよい。さらに、０．０１〜０．１質量％程度の不可避的
な不純物が含まれていてもかまわない。
Hereinafter, the heat-resistant rare earth magnet of the present invention and the production method thereof will be described in more detail. The magnets that are the subject of the present invention are sintered magnets formed by pulverizing a raw material alloy to a size of several μm, forming, and sintering, and after forming raw material powder hot, further molding the molded product hot It is a processed magnet. In the component system, it is called a so-called Nd—Fe—B system magnet, and the crystal structure is Nd-rich with a thickness of several nanometers to several hundred nanometers around a crystal grain with a size of several μm having an Nd 2 Fe 14 B structure. The magnet is composed of an aggregate of crystal grains with a size of several tens to several hundreds of nanometers having a structure surrounded by phases or an Nd 2 Fe 14 B structure. These magnets may contain various additive elements that are usually added to adjust the magnetic properties. In order to increase the coercive force, it may contain about 0.3 to 8% by mass of M element. Furthermore, an inevitable impurity of about 0.01 to 0.1% by mass may be included.
磁石表面に供給して成膜する金属は、Ｎｄよりも磁気異方性が充分に大きく、且つ磁石中
の結晶粒界に優先的に拡散浸透することを目的とするため、Ｍ（Ｔｂ及び／又はＤｙ）金
属や、Ｍ金属を相当量含有する合金や化合物、例えば、Ｔｂ−Ｆｅ合金やＤｙ−Ｃｏ合金
、ＴｂＨ2などの水素化物、及びＴｂ２Ｏ３などの酸化物あるいはＴｂの一部が酸化した
Ｔｂ−Ｔｂ２Ｏ３複合合金等のＭ元素源を用いることができる。
The metal to be deposited on the magnet surface is sufficiently larger in magnetic anisotropy than Nd and has the purpose of preferentially diffusing and penetrating into the crystal grain boundaries in the magnet, so M (Tb and / or Or Dy) metals and alloys and compounds containing a substantial amount of M metal, for example, hydrides such as Tb-Fe alloy, Dy-Co alloy, TbH 2 , and oxides such as Tb 2 O 3 or a part of Tb. An M element source such as a Tb—Tb 2 O 3 composite alloy in which is oxidized can be used.
磁石表面に成膜したＭ元素源は、磁石表面に単に被覆されているだけでは保磁力の向上が
認められないため、少なくともＭ元素の一部が磁石内部に０．０５〜５質量％程度拡散し
て上記元素が富化した結晶粒界相を形成するようにすることが重要である。このため、通
常は成膜した後に５００〜１０００℃における熱処理を行ってＭ元素を拡散させる。
The M element source deposited on the magnet surface cannot be improved in coercive force simply by being coated on the magnet surface, so at least a part of the M element diffuses about 0.05 to 5% by mass inside the magnet. Thus, it is important to form a grain boundary phase enriched with the above elements. For this reason, normally, after film formation, heat treatment at 500 to 1000 ° C. is performed to diffuse the M element.
拡散処理によって浸透する上記のＭ元素の量と深さが保磁力の増加に影響する。例えば、
Ｎｄ−Ｆｅ−Ｂ系焼結磁石の結晶粒径はおよそ６〜１０μｍであるので、磁石最表面に露
出している結晶粒子の半径に相当する３μｍ以上の浸透深さが最低限必要である。これ未
満では主結晶粒を包むＮｄリッチ粒界相へのＭ元素の富化が不充分となり、保磁力の増加
がわずかなものとなる。浸透深さが３μｍを超えて約１０μｍ以上に深くなり、さらにＭ
元素が富化した粒界層の厚さが数十ｎｍ以上確保されると、保磁力が著しく増加するが、
過度に深く浸透すると主結晶のＮｄと置換する確率が多くなって残留磁束密度の低下を招
くため、拡散処理条件を調整して所望の磁気特性とする。
The amount and depth of the M element that penetrates by the diffusion treatment affects the increase in coercive force. For example,
Since the crystal grain size of the Nd—Fe—B based sintered magnet is approximately 6 to 10 μm, a penetration depth of 3 μm or more corresponding to the radius of the crystal particles exposed on the outermost surface of the magnet is required at a minimum. If it is less than this, the enrichment of the M element into the Nd-rich grain boundary phase surrounding the main crystal grains becomes insufficient, and the increase in coercive force becomes slight. The penetration depth exceeds 3 μm and becomes deeper than about 10 μm.
When the thickness of the grain boundary layer enriched with elements is ensured by several tens of nanometers or more, the coercive force is remarkably increased.
If it penetrates too deeply, the probability of substitution with Nd of the main crystal increases and the residual magnetic flux density decreases, so the diffusion treatment conditions are adjusted to obtain the desired magnetic characteristics.
このようにすることによって、例えば、磁石最表層のＭ元素の濃度は約１００質量％で、
Ｍ元素が拡散した結晶粒界相では数十質量％（磁石表面に近いほど高濃度）、Ｍ元素が拡
散した粒界相とＭ元素がほとんど拡散していない主相を平均化した数百μｍの領域で測定
すると数質量％となる。成膜した膜の一部が拡散処理後に拡散されずに磁石表面に残存し
ても構わないが、Ｍ元素を節減して十分な効果を得るためには、成膜したＭ元素を完全に
拡散させることが望ましい。
By doing so, for example, the concentration of M element on the outermost layer of the magnet is about 100% by mass,
The grain boundary phase in which M element is diffused is several tens of mass% (the concentration is higher as it is closer to the magnet surface), and the grain boundary phase in which M element is diffused and the main phase in which M element is hardly diffused are several hundred μm. It is several mass% when measured in the region of. A part of the deposited film may remain on the magnet surface without being diffused after the diffusion treatment, but in order to save M element and obtain a sufficient effect, the deposited M element is completely diffused. It is desirable to make it.
磁石全体に占めるＭ元素含有量は、残留磁束密度と保磁力のバランスによって決められる
。車用途向けに耐熱性を重視した場合に、従来の焼結磁石においては２ＭＡ／ｍ以上の保
磁力を得るために約８質量％以上のＤｙを含有する必要があったが、本発明では、Ｍ元素
を不純物程度にしか含まない磁石に拡散したＭ元素の含有量が５質量％未満において、Ｍ
元素の量及び拡散深さに応じて２ＭＡ／ｍ以上の保磁力を得ることができる。このことよ
り、残留磁束密度の低下が抑制され、且つ希少資源としてのＭ元素を節減することができ
る。
The M element content in the entire magnet is determined by the balance between the residual magnetic flux density and the coercive force. When heat resistance is important for car applications, the conventional sintered magnet needs to contain about 8% by mass or more of Dy in order to obtain a coercive force of 2 MA / m or more. When the content of M element diffused in a magnet containing only M element as an impurity is less than 5% by mass, M
A coercive force of 2 MA / m or more can be obtained depending on the amount of element and the diffusion depth. As a result, a decrease in residual magnetic flux density is suppressed, and the M element as a scarce resource can be saved.
磁石内の酸素は、ＮｄやＭ元素が富化した粒界相において一部酸化物の形態として、ある
いは磁石表面層が一部酸化した形態として存在する。これらの存在形態を問わず、酸素含
有量の下限値は５μΩ・ｍ以上の比抵抗を得るために、０．４質量％以上とすることが必
要である。この値未満では、磁石の比抵抗は５μΩ・ｍ未満となり、渦電流の抑制効果が
ない。酸素含有量が多いほど比抵抗が増加して、３質量％で１００μΩ・ｍを超え、耐熱
性が向上するが、３質量％を超えると磁石中の酸化物や酸素が濃縮した合金相の体積比率
が１０容積％以上となり、保磁力と残留磁束密度の低下が大きくなって高性能な磁石とし
て機能しがたくなる。従って、酸素の上限含有量は３質量％迄とすることが必要である。
Oxygen in the magnet, and the form of some oxides at the grain boundary phase Nd and M element-enriched, Oh Ru <br/> physician is present as a form magnet surface layer is partially oxidized. Regardless of the existence form, the lower limit value of the oxygen content needs to be 0.4% by mass or more in order to obtain a specific resistance of 5 μΩ · m or more. Below this value, the specific resistance of the magnet is less than 5 μΩ · m and there is no eddy current suppression effect. As the oxygen content increases, the specific resistance increases and exceeds 100 μΩ · m at 3% by mass, and the heat resistance is improved. When the oxygen content exceeds 3% by mass, the volume of the alloy phase in which the oxide and oxygen in the magnet are concentrated The ratio becomes 10% by volume or more, and the decrease in coercive force and residual magnetic flux density increases, making it difficult to function as a high-performance magnet. Therefore, the upper limit content of oxygen needs to be up to 3% by mass.
比抵抗については、従来のＮｄ−Ｆｅ−Ｂ磁石が１〜２μΩ・ｍであるため、例えば、車
用の駆動モータを毎分数千回転させた場合には磁石の表面温度が１５０℃以上になる場合
があるが、５μΩ・ｍ以上とすることによって磁石温度を１００〜１２０℃程度に抑える
ことができる。抵抗が上がるほど渦電流による温度上昇は小さくなるが、一般には、高抵
抗組成の磁石とするほど室温での磁気特性が低下するため、磁気特性とのバランスを考慮
して所望の比抵抗とすることが望ましい。
As for the specific resistance, since the conventional Nd-Fe-B magnet is 1 to 2 μΩ · m, for example, when the drive motor for a car is rotated several thousand revolutions per minute, the surface temperature of the magnet becomes 150 ° C. or more. In some cases, the magnet temperature can be suppressed to about 100 to 120 ° C. by setting it to 5 μΩ · m or more. As the resistance increases, the temperature rise due to eddy current decreases, but in general, the higher the resistance of the magnet, the lower the magnetic properties at room temperature. Therefore, the desired specific resistance is set in consideration of the balance with the magnetic properties. It is desirable.
酸素の具体的な導入方法は、従来一般的な０．２５〜０．３質量％程度の酸素濃度の磁石
を用いてスパッタリングを行う場合に、表面を一部酸化させたＴｂ又はＤｙ金属ターゲッ
トを使用する方法、あるいはＴｂなどの金属ターゲットを使用して減圧槽内に導入するＡ
ｒガスに1〜5容積％の酸素ガスを混合する方法が好ましく、これらの方法を用いることに
よって、磁石表面に上記金属が部分的に酸化した膜を設けることができる。酸素ガスを混
合する場合、Ａｒガスに対して１容積％未満の酸素では磁石の比抵抗がほとんど上がらな
い。５容積％超では、Ｍ元素の大部分が安定酸化物になって磁石内に浸透しにくくなる。
すなわち、酸素が足りない酸化物の方が浸透しやすい。また、スパッタ装置内の高周波コ
イルや試料保持具が酸化して電気的な障害を生む。この場合には、次の熱処理工程におい
てＭ元素成分と酸素が同時に磁石表層の膜から内部の一部に浸透するため、磁石内部全体
の酸素量をむやみに増やす必要がなく、従って、残留磁束密度の低下を小さくすることが
できる。
Specific methods for introducing oxygen, when performing sputtering with a magnet of the oxygen concentration in the conventional general about 0.25 to 0.3 wt%, the Tb or Dy metal target was partially oxidizing the surface Method of use or A introduced into a vacuum tank using a metal target such as Tb
A method in which 1 to 5% by volume of oxygen gas is mixed with r gas is preferable. By using these methods, a film in which the metal is partially oxidized can be provided on the magnet surface. Mixed with oxygen gas
In the case of combining them, the specific resistance of the magnet hardly increases with oxygen less than 1% by volume with respect to Ar gas . If it exceeds 5% by volume, most of the M element becomes a stable oxide and hardly penetrates into the magnet.
That is, an oxide that lacks oxygen is more likely to penetrate. In addition, the high frequency coil and the sample holder in the sputtering apparatus are oxidized to cause an electrical failure. In this case, in the next heat treatment step, the M element component and oxygen permeate into a part of the inside of the magnet surface layer at the same time, so there is no need to increase the amount of oxygen inside the magnet excessively. Can be reduced.
結晶粒界相は基本的に酸素が一部欠損した酸化物と考えられ、またＭ元素は酸素と強く結
びつく性質がある。成膜したＭ金属、あるいはＭと部分的に結びついた酸素は、熱処理に
よって磁石表面に留まるよりも磁石内部の酸化物に、あたかも吸引されるように結びつこ
うとして粒界相に浸透すると推測される。
The grain boundary phase is basically considered to be an oxide in which oxygen is partially lost, and the element M has a property of being strongly bonded to oxygen. It is speculated that the deposited M metal or oxygen partially bound to M penetrates the grain boundary phase as if it is attracted to the oxide inside the magnet rather than staying on the surface of the magnet by heat treatment. The
Ｍ金属を成膜した磁石の熱処理工程において、Ａｒガスなどの不活性ガス雰囲気中の酸素
濃度を５０〜５０００ｐｐｍ程度に上げることによって、磁石内に取り込まれる酸素量を
増やすことができる。５０ｐｐｍ未満の酸素濃度では磁石の比抵抗がほとんど上がらない
。５０００ｐｐｍ超の酸素濃度では、Ｍ元素の大部分が安定酸化物になって磁石内に浸透
しにくくなる。すなわち、酸素が足りない酸化物の方が浸透しやすい。磁石表面にＭ金属
が部分的に酸化した膜を設け、酸素濃度５０〜５０００ｐｐｍ程度の不活性ガス雰囲気中
で熱処理する方法では、磁石内部よりも表面部の酸素濃度を高くすることができるため、
酸素の導入による磁気特性の低下を抑制しながら、特に渦電流が集中して発生しやすい磁
石表面部のみの比抵抗を高めることができ、極めて有益な方法である。
In the heat treatment process of the magnet formed with the M metal film, the amount of oxygen taken into the magnet can be increased by increasing the oxygen concentration in an inert gas atmosphere such as Ar gas to about 50 to 5000 ppm. When the oxygen concentration is less than 50 ppm, the specific resistance of the magnet hardly increases. When the oxygen concentration exceeds 5000 ppm, most of the M element becomes a stable oxide and hardly penetrates into the magnet. That is, an oxide that lacks oxygen is more likely to penetrate. M metal on the magnet surface
Is provided with a partially oxidized film in an inert gas atmosphere with an oxygen concentration of about 50 to 5000 ppm.
In the method of heat treatment with , since the oxygen concentration of the surface portion can be higher than the inside of the magnet,
While suppressing the deterioration of magnetic properties due to the introduction of oxygen, it is possible to especially improve the specific resistance of the eddy current only magnet surface part prone to concentrate, is a very useful way.
Ｍ元素源の成膜手段としては、蒸着、スパッタリング、イオンプレーティング、レーザー
デポジションなどの物理的成膜法を用いて、Ｍ元素源を、減圧槽内で原子、分子、又はイ
オン化させて成膜する方法がより好適である。成膜手段としてスパッタリングの場合には
、減圧槽内で磁石試料を保持具と共に熱しておくか、又はスパッタリング時のＲＦ及びＤ
Ｃ出力を上げて成膜することによって成膜中の磁石を上記温度範囲、例えば８００℃位に
まで上昇させることができるため、実質的に成膜させながら同時に拡散を行うこともでき
る。
As a film forming means for the M element source, a physical film forming method such as vapor deposition, sputtering, ion plating, laser deposition, or the like is used, and the M element source is formed by atomizing, molecularly, or ionizing in a vacuum chamber. A film forming method is more preferable. In the case of sputtering as a film forming means, the magnet sample is heated together with a holder in a vacuum tank, or RF and D at the time of sputtering are used.
By increasing the C output and forming the film, the magnet during film formation can be raised to the above temperature range, for example, about 800 ° C., so that diffusion can be performed at the same time while substantially forming the film.
各種形状寸法を有する磁石表面の全部又は一部に上記のＭ元素の均一な膜を形成するには
、減圧槽内において複数のターゲットを用いて原子化、分子化させて磁石表面に３次元的
にＭ元素源を成膜させるスパッタリング法、又はＭ元素をイオン化させて、静電気的な吸
引による強被着特性を利用して成膜させるイオンプレーティング法が特に有効である。
In order to form a uniform film of the above-mentioned M element on all or part of the magnet surface having various shapes and dimensions, it is atomized and molecularized using a plurality of targets in a decompression tank and is three-dimensionally formed on the magnet surface. The sputtering method for forming a film of an M element source or the ion plating method for forming a film by ionizing the M element and utilizing strong adhesion characteristics by electrostatic attraction is particularly effective.
また、上記の作業における希土類磁石のプラズマ空間内の保持については、一個又は複数
個の磁石を線材や板材で回転自在に保持する方法や、複数個の磁石を皿状の容器に並べる
か、金網製の籠に装填して転動(tumbling)自在に保持する方法を採用することができる。
このような保持方法によって３次元的に磁石表面全体に均一な膜を形成することができる
。本発明の製造方法を実施するのに好適な三次元スパッタ装置の原理図は、先に出願の特
願２００３−１７４００３号に記載されている。
In addition, the holding of the rare earth magnets in the plasma space in the above-described operation can be performed by a method in which one or a plurality of magnets are rotatably held by a wire or plate, a plurality of magnets are arranged in a dish-like container, or a wire mesh It is possible to adopt a method of loading in a steel basket and holding it freely tumbling.
By such a holding method, a uniform film can be formed three-dimensionally on the entire magnet surface. A principle diagram of a three-dimensional sputtering apparatus suitable for carrying out the manufacturing method of the present invention is described in Japanese Patent Application No. 2003-174003 previously filed.
以下、本発明を実施例に従って詳細に説明する。
Ｎｄ13Ｆｅ78Ｃｏ1Ｂ8組成の合金インゴットから、ストリップキャスト法によって厚さ約
０．３ｍｍの合金薄片を製作した。次に、この薄片を容器内に充填し、５００ｋＰａの水
素ガスを室温で吸蔵させた後に放出させることによって、大きさ０．１〜０．２ｍｍの不
定形粉末を得て、引き続きジェットミル粉砕をして約３μｍの大きさの微粉末を製作した
。
Hereinafter, the present invention will be described in detail according to examples.
From an alloy ingot having a composition of Nd 13 Fe 78 Co 1 B 8 , an alloy flake having a thickness of about 0.3 mm was manufactured by strip casting. Next, this thin piece is filled in a container, and hydrogen gas of 500 kPa is occluded at room temperature and then released to obtain an amorphous powder having a size of 0.1 to 0.2 mm, followed by jet mill grinding. Thus, a fine powder having a size of about 3 μm was produced.
この微粉末約０．１ｇにステアリン酸カルシウムを０．０５質量％添加混合して金型に充
填し、１．２ＭＡ／ｍの磁界を加えてプレス成形をした。続いて、この成形体を真空炉に
装填して１０８０℃で１時間焼結をし、厚さ方向に異方性を有する幅３ｍｍ×長さ５ｍｍ
×厚さ１．５ｍｍの平板状磁石を製作した。これを比較例試料（１）とした。
About 0.1 g of this fine powder was added and mixed with 0.05% by weight of calcium stearate, filled in a mold, and press-molded by applying a magnetic field of 1.2 MA / m. Subsequently, the compact was charged in a vacuum furnace and sintered at 1080 ° C. for 1 hour, and the width was 3 mm × length was 5 mm having anisotropy in the thickness direction.
X A flat magnet having a thickness of 1.5 mm was manufactured. This was designated as a comparative sample (1).
次に、円環形状をしたＴｂ合金ターゲット一対を対向させてその中間に銅製の高周波コイ
ルを配置させた３次元スパッタ装置を用い、この平板状磁石表面へＴｂ金属を成膜した。
ターゲット金属は純度９９.９％のＴｂを用い、寸法形状は、外径８０ｍｍ、内径３０ｍ
ｍ、厚さ２０ｍｍの円環状とした。
Next, a Tb metal film was formed on the surface of the flat magnet using a three-dimensional sputtering apparatus in which a pair of Tb alloy targets having an annular shape were opposed to each other and a copper high-frequency coil was disposed between them.
The target metal is Tb with a purity of 99.9%. The dimensions are 80mm outer diameter and 30m inner diameter.
m and 20 mm in thickness.
実際の成膜作業は以下の手順で行った。上記の平板状磁石を直径０．３ｍｍのタングステ
ン線をコイル状に巻き回した内部に装入し、このコイルの一端をモータ軸に直結した治具
に取り付け、高周波コイルの中間に置かれるようセットした。スパッタ装置内を５×１０
-5Ｐａまで真空排気した後、Ａｒガスに２容積％の酸素ガスを混合したガスを導入して装
置内を３Ｐａに維持した。次に、ＲＦ出力３０ＷとＤＣ出力２Ｗを加えて５分間の逆スパ
ッタを行って磁石表面の酸化膜を除去した。続いて、ＲＦ出力６０ＷとＤＣ出力１２０Ｗ
を加えて磁石を６ｒｐｍで回転させ、Ａｒガスに２容積％の酸素ガスを混合したガスを流
しながら１５分間のスパッタを行い、厚さ４μｍの部分的に酸化したＴｂ膜を磁石表面全
体に形成した。ここで得られた磁石を比較例試料（２）とした。
The actual film forming operation was performed according to the following procedure. Insert the above flat magnet into a coil of tungsten wire with a diameter of 0.3 mm and attach one end of this coil to a jig directly connected to the motor shaft so that it is placed in the middle of the high frequency coil. did. Inside the sputter device is 5 × 10
After evacuating to -5 Pa, a gas in which 2% by volume of oxygen gas was mixed with Ar gas was introduced to maintain the inside of the apparatus at 3 Pa. Next, RF output 30 W and DC output 2 W were applied, and reverse sputtering was performed for 5 minutes to remove the oxide film on the magnet surface. Then, RF output 60W and DC output 120W
Is added, and the magnet is rotated at 6 rpm. Sputtering is performed for 15 minutes while flowing a gas in which 2% by volume of oxygen gas is mixed with Ar gas, and a partially oxidized Tb film having a thickness of 4 μm is formed on the entire surface of the magnet. did. The magnet obtained here was used as a comparative sample (2).
さらに、Ｔｂを成膜した磁石は、グローブボックスに設置した電気炉に装填し、酸素濃度
を１００ｐｐｍに維持したＡｒ雰囲気中で１段目を６００℃〜１０００℃で１０分間、２
段目を６００℃で３０分間の熱処理を行った。これらを表１に示すように１段目の処理温
度に応じて本発明試料（１）〜（５）とした。
Furthermore, the magnet on which Tb was formed was loaded in an electric furnace installed in a glove box, and the first stage was maintained at 600 ° C. to 1000 ° C. for 10 minutes in an Ar atmosphere in which the oxygen concentration was maintained at 100 ppm.
The stage was heat-treated at 600 ° C. for 30 minutes. As shown in Table 1, the samples of the present invention (1) to (5) were prepared according to the first stage treatment temperature.
各試料の磁気特性は、４．８ＭＡ／ｍのパルス着磁を印加した後に振動試料型磁力計を用
いて測定し、得られた値を初磁化曲線の傾きから求めた反磁界係数を用いて補正した。試
料中の酸素量はＬＥＣＯ社製のＲＯ−４１６ＤＲを用いて測定し、試料の比抵抗は四端子
法によって測定した。また、本発明試料（３）と比較例試料（１）を酸溶解してＩＣＰ分
析をした結果、Ｔｂ元素の含有量は前者が１．０２質量％で後者が０．０４質量％であり
、後者の含有量は不純物としての混入レベルであった。
The magnetic characteristics of each sample were measured using a vibrating sample magnetometer after applying a pulse magnetization of 4.8 MA / m, and the obtained value was determined using the demagnetizing factor obtained from the slope of the initial magnetization curve. Corrected. The amount of oxygen in the sample was measured using RO-416DR manufactured by LECO, and the specific resistance of the sample was measured by a four-terminal method. Moreover, as a result of acid-dissolving this invention sample (3) and comparative example sample (1) and performing ICP analysis, as for the content of Tb element, the former is 1.02 mass% and the latter is 0.04 mass%, The latter content was the level of contamination as an impurity.
表１に、各試料についての初段熱処理温度、磁気特性、酸素量、比抵抗の各値を示す。ま
た、図２は、酸素量と比抵抗、保磁力の関係を示すグラフである。表１及び図２から明ら
かなように、Ｔｂ金属を成膜して熱処理を行った本発明試料（１）〜（５）は、保磁力が
１．２２〜１．３５ＭＡ／ｍであり、いずれも比較例試料（１）及び（２）よりも保磁力
の増加が認められた。この理由は、Ｔｂ金属成分の磁石内への浸透によって、逆磁区が発
生しやすい焼結磁石表面部の結晶粒界にＴｂが高濃度に分布し、粒界相を磁気的に強化す
ることによって保磁力が向上したためと推察される。また、比較例試料（１）及び（２）
に対して本発明試料（１）〜（５）はいずれも酸素含有量が多く、比抵抗が５．５〜１１
．７μΩ・ｍであり、比較例試料（１）に対して約４〜８倍の比抵抗が得られた。
Table 1 shows the values of the first stage heat treatment temperature, magnetic characteristics, oxygen content, and specific resistance for each sample. FIG. 2 is a graph showing the relationship between oxygen content, specific resistance, and coercive force. As is clear from Table 1 and FIG. 2, the samples (1) to (5) of the present invention in which a Tb metal film was formed and heat-treated had a coercive force.
It was 1.22-1.35 MA / m, and in both cases, an increase in coercive force was recognized as compared with Comparative Samples (1) and (2). The reason for this is that Tb is distributed at a high concentration in the grain boundary of the surface of the sintered magnet where reverse magnetic domains are likely to occur due to the penetration of the Tb metal component into the magnet, and the grain boundary phase is magnetically strengthened. This is probably because the coercive force has improved. Comparative sample (1) and (2)
In contrast, the inventive samples (1) to (5) all have a high oxygen content and a specific resistance of 5.5 to 11.
. It was 7 μΩ · m, and a specific resistance approximately 4 to 8 times that of the comparative sample (1) was obtained.
実施例１と同じ平板状の焼結磁石を３次元スパッタ装置に取り付け、Ｄｙターゲットを使
用して磁石表面にＤｙ金属膜を成膜した。成膜作業は、実施例１と同様に逆スパッタを行
って磁石表面の酸化膜を除去した後、ＲＦ出力１２０ＷとＤＣ出力２００Ｗを加えてＡｒ
ガスに２容積％の酸素ガスを混合したガスを流しながら５〜４５分間のスパッタを行い、
４，６，１０，１４，２０μｍの各厚さの皮膜を形成した。続いて、酸素濃度を２００ｐ
ｐｍに維持したＡｒ雰囲気中で、９００℃で３０分間と６００℃で３０分間の熱処理を行
って、膜厚の小さい方から順に、本発明試料（６）〜（１０）とした。各試料は、磁気測
定後にＩＣＰ分析を行ってＤｙ含有量を測定した。
The same flat sintered magnet as in Example 1 was attached to a three-dimensional sputtering apparatus, and a Dy metal film was formed on the magnet surface using a Dy target. In the film forming operation, reverse sputtering is performed in the same manner as in Example 1 to remove the oxide film on the magnet surface.
Sputtering is performed for 5 to 45 minutes while flowing a gas in which 2% by volume of oxygen gas is mixed with the gas,
Films with thicknesses of 4, 6, 10, 14, and 20 μm were formed. Subsequently, the oxygen concentration is 200p.
Heat treatment was performed at 900 ° C. for 30 minutes and at 600 ° C. for 30 minutes in an Ar atmosphere maintained at pm, and samples of the present invention (6) to (10) were formed in order from the smallest film thickness. Each sample was subjected to ICP analysis after magnetic measurement to determine the Dy content.
一方、Ｎｄ13Ｆｅ78Ｃｏ1Ｂ8組成の合金においてＮｄの一部をＤｙで置換することによっ
て、Ｄｙ含有量の異なる合金インゴットを溶解した。なお、Ｄｙ含有量は上記で得られた
本発明試料（６）〜（１０）のＩＣＰ分析結果に従って、それぞれの含有量に合わせ込ん
だ。これらの合金を、ストリップキャスト法によって薄片化して、粉砕、成形、焼結をし
て、比較例試料（３）〜（７）とした。また、磁気特性、酸素含有量、比抵抗は実施例１
と同様に測定した。
On the other hand, alloy ingots having different Dy contents were melted by substituting a part of Nd with Dy in an alloy of Nd 13 Fe 78 Co 1 B 8 composition. In addition, Dy content was adjusted to each content according to the ICP analysis result of this invention sample (6)-(10) obtained above. These alloys were thinned by a strip cast method, pulverized, molded, and sintered to obtain comparative sample (3) to (7). In addition, magnetic characteristics, oxygen content, and specific resistance are shown in Example 1.
Was measured in the same manner.
表２に、各試料の酸素含有量と比抵抗を示す。表２より、比較例試料（３）〜（７）と本
発明試料（６）〜（１０）のＤｙ含有量はそれぞれほぼ一致して対応している。しかし、
比較例試料（３）〜（７）が従来の焼結法そのままの方法によって製作され、酸素含有量
が０．３〜０．４質量％と低いために比抵抗も小さいのに対して、本発明試料（６）〜（
１０）はＴｂ成膜後の熱処理時に磁石表面からＴｂの酸化膜中及びＡｒ雰囲気中の酸素を
磁石内部に拡散導入したことによって、比抵抗が１２．４〜１６．４μΩ・ｍであり、比
抵抗が約１０倍に増加した。なお、本発明試料の切断面のＥＰＭＡ画像観察から、酸素は
磁石内部よりも表面部に多く存在していることが観察された。このことより、磁石の比抵
抗は厳密には渦電流の集中する表面部のみが高抵抗となるため、磁石を高周波数で駆動す
る場合に有益な抵抗増加の手法と考えられる。また、いたずらに磁石内部の酸素含有量を
増やして磁気特性を下げる必要がない利点がある。
Table 2 shows the oxygen content and specific resistance of each sample. From Table 2, the Dy contents of the comparative example samples (3) to (7) and the present invention samples (6) to (10) correspond to correspond almost each other. But,
Comparative Samples (3) to (7) were produced by the conventional sintering method, and the specific resistance was small because the oxygen content was as low as 0.3 to 0.4% by mass. Invention samples (6) to (
10) removes oxygen in the Tb oxide film and Ar atmosphere from the magnet surface during heat treatment after Tb film formation.
By introducing diffusion into the magnet , the specific resistance was 12.4 to 16.4 μΩ · m, and the specific resistance increased about 10 times. From observation of the EPMA image of the cut surface of the sample of the present invention, it was observed that oxygen was present in the surface portion more than in the magnet. From this, the specific resistance of the magnet is strictly limited to only the surface portion where eddy currents are concentrated, which is considered to be a method of increasing resistance which is useful when the magnet is driven at a high frequency. In addition, there is an advantage that it is not necessary to increase the oxygen content in the magnet and lower the magnetic characteristics.
図３に、Ｄｙ含有量に対する、保磁力と残留磁束密度の関係を示す。図３より、酸素を１
．２５〜１．３３質量％含む本発明試料（６）〜（１０）の保磁力は、Ｄｙ含有量が同じ
場合、酸素を０．３３〜０．３８質量％しか含まない比較例試料（３）〜（７）のそれよ
りも大幅に増加し、４〜５質量％程度のＤｙ含有量においても２．０ＭＡ／ｍ以上の保磁
力が得られている。この結果より、従来の焼結磁石と同等の保磁力を得るために必要なＤ
ｙを節減することができ、希少な資源問題解消の一助となる。本発明試料（６）〜（１０
）での保磁力の増加理由は、Ｄｙ元素が結晶粒界に優先的に存在し、逆磁区の発生を抑制
しているためと考えられる。一方、残留磁束密度はほぼ同等であることが明らかになり、
この理由は、本発明試料（６）〜（１０）では酸素含有量が多いにもかかわらずＤｙ元素
が主結晶のＮｄを置換しにくいために残留磁束密度の低下が抑えられたためと推察される
。
FIG. 3 shows the relationship between the coercive force and the residual magnetic flux density with respect to the Dy content. From FIG. 3, oxygen is 1
. The coercive force of the present invention samples (6) to (10) containing 25 to 1.33 mass% has the same Dy content.
In the case of the comparative example samples (3) to (7) containing only 0.33 to 0.38% by mass of oxygen, it is 2.0 MA even at a Dy content of about 4 to 5% by mass. A coercive force of at least / m is obtained. From this result, it is necessary to obtain the same coercive force as that of a conventional sintered magnet.
y can be saved, which helps to solve rare resource problems. Invention samples (6) to (10
The reason for the increase in coercive force in (1) is presumably because the Dy element preferentially exists at the grain boundaries and suppresses the occurrence of reverse magnetic domains. On the other hand, it becomes clear that the residual magnetic flux density is almost the same,
The reason for this is presumed that in the samples (6) to (10) of the present invention, although the oxygen content was high, the Dy element was difficult to replace Nd of the main crystal, so that the decrease in residual magnetic flux density was suppressed. .
本発明の方法で得られるＮｄ−Ｆｅ−Ｂ系耐熱性希土類磁石は、高保磁力磁石としての通
常の用途はもちろん、特に、電気自動車や燃料電池車の駆動用モータ用の磁石として好適
に使用される。
The Nd—Fe—B heat-resistant rare earth magnet obtained by the method of the present invention is suitably used as a magnet for a motor for driving an electric vehicle or a fuel cell vehicle, as well as a normal use as a high coercive force magnet. The
Claims (8)
らの金属の水素化物若しくは酸化物を、減圧槽内で原子、分子、又はイオン化させて、酸
素濃度が０．２５〜０．３質量％のＮｄ−Ｆｅ−Ｂ系磁石表面にＭ金属が部分的に酸化し
た膜を成膜し、成膜と同時に、あるいは引き続いて酸素を含む雰囲気中で熱処理を行って
Ｍ元素と酸素を磁石表面から内部に拡散浸透させることにより表面部から０．３μｍ以上
の深さにＭ金属元素を拡散させ、拡散したＭ金属元素の含有量を０．０５〜５質量％、か
つ磁石内の酸素含有量を０.４〜３質量％とすることを特徴とするＮｄ−Ｆｅ−Ｂ系耐熱
性希土類磁石の製造方法。 M (provided that M is Tb and / or Dy) metal or an alloy containing these metals or a hydride or oxide of those metals in a vacuum chamber is atomized, moleculed, or ionized to produce an acid.
M metal partially oxidizes on the surface of the Nd-Fe-B magnet having an element concentration of 0.25 to 0.3% by mass.
Film was deposited, deposition and simultaneously or subsequently 0.3μm or more from the surface portion by diffusing penetration element M and oxygen by heat treatment in an atmosphere containing oxygen inside from the magnet surface
M metal element is diffused to a depth of 0.05 to 5% by mass,
A method for producing a Nd-Fe-B heat-resistant rare earth magnet , characterized in that the oxygen content in the magnet is 0.4-3 mass% .
酸素ガスを混合したガスを導入して行なうことを特徴とする請求項１記載のＮｄ−Ｆｅ−2. The Nd—Fe— according to claim 1, wherein a gas mixed with oxygen gas is introduced.
Ｂ系耐熱性希土類磁石の製造方法。A method for producing a B-based heat-resistant rare earth magnet.
とを特徴とする請求項１記載のＮｄ−Ｆｅ−Ｂ系耐熱性希土類磁石の製造方法。The method for producing a Nd—Fe—B heat-resistant rare earth magnet according to claim 1.
徴とする請求項１記載の耐熱性希土類磁石の製造方法。 Expansion Chihita watermarks M-metal elements (Nd, M) O 2 type method for producing a heat-resistant rare earth magnet according to claim 1, characterized by the presence in the crystal grain boundary as a compound.
元素を含有することを特徴とする請求項１記載の耐熱性希土類磁石の製造方法。The method for producing a heat-resistant rare earth magnet according to claim 1, comprising an element.
量％の不可避不純物を含む磁石であることを特徴とする請求項１記載の耐熱性希土類磁石2. The heat-resistant rare earth magnet according to claim 1, wherein the magnet contains an inevitable impurity in an amount of%.
の製造方法。Manufacturing method.
物として以外含まない磁石であることを特徴とする請求項１記載の耐熱性希土類磁石の製2. The heat-resistant rare earth magnet according to claim 1, wherein the magnet is not contained except as a product.
造方法。Manufacturing method.
おける磁石の表面側ほどＭ元素の濃度を濃くした構造であることを特徴とする請求項１記2. The structure according to claim 1, wherein the surface of the magnet has a structure in which the concentration of the M element is increased toward the surface side.
載の耐熱性希土類磁石の製造方法。The manufacturing method of the heat-resistant rare earth magnet of mounting.
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