JP3540438B2 - Magnet and manufacturing method thereof - Google Patents

Magnet and manufacturing method thereof Download PDF

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Publication number
JP3540438B2
JP3540438B2 JP14131995A JP14131995A JP3540438B2 JP 3540438 B2 JP3540438 B2 JP 3540438B2 JP 14131995 A JP14131995 A JP 14131995A JP 14131995 A JP14131995 A JP 14131995A JP 3540438 B2 JP3540438 B2 JP 3540438B2
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Prior art keywords
magnet
alloy
powder
infiltration
compact
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JPH08316014A (en
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弘一 矢島
確 竹渕
武司 永井
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TDK Corp
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TDK Corp
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    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01FMAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032Magnets 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
    • H01F1/04Magnets 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
    • H01F1/047Alloys characterised by their composition
    • H01F1/053Alloys characterised by their composition containing rare earth metals
    • H01F1/055Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H01F1/0571Alloys 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

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  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Hard Magnetic Materials (AREA)
  • Manufacturing Cores, Coils, And Magnets (AREA)

Description

【0001】
【産業上の利用分野】
本発明は、希土類磁石およびその製造方法に関する。
【0002】
【従来の技術】
高性能を有する希土類磁石としては、粉末冶金法によるSm−Co系磁石でエネルギー積32MGOeのものが量産されている。また、近年Nd2 Fe14B磁石等のR−T−B系磁石(TはFe、またはFeおよびCo)が開発されている。R−T−B系磁石は、Sm−Co系磁石に比べ原料が安価である。R−T−B系磁石は、従来のSm−Co系の粉末冶金プロセス(溶解→母合金鋳造→インゴット粗粉砕→微粉砕→成形→焼結→磁石)を適用して製造される焼結磁石と、磁石粉末を樹脂バインダや金属バインダで結合したボンディッド磁石とに大きく分類される。
【0003】
R−T−B系焼結磁石の製造方法には、1種類の原料合金を粉砕し、得られた粉末を成形して焼結する方法(特公昭61−34242号公報等)や、組成の相異なる2種類の合金粉末を混合して成形し、焼結する方法(特開昭61−81603号公報、特開昭63−93841号公報、特開平5−105915号公報等)などが挙げられる。
【0004】
しかし、焼結法では、一般的に成形体が焼結時に体積で30〜40%も収縮してしまう。この収縮は、粉末を成形する際の圧力を高くすることにより低減可能であるが、通常の磁石の要求寸法精度を満足するほどの変形量および収縮率に抑えることは困難である。このため、焼結後に所定の寸法および形状とするための研削が必要となり、コストアップの原因となっている。
【0005】
これに対し、R−T−B系ボンディッド磁石は、圧縮成形後の焼成が不要なため、磁石寸法は金型寸法とほぼ同じとなる。このため、寸法精度が高く、製造後に形状加工を必要としない。しかし、工業化されているR−T−B系のボンディッド磁石は、特公平1−54457号公報に示されるように、単ロール法等による急冷凝固を利用して得た多結晶粒子を用いるので等方性磁石となる。
【0006】
一方、異方性ボンディッド磁石用の磁石粉末としては、特公平4−20242号公報に示されるように、急冷凝固した粉末をホットプレスにより一軸性圧縮して高密度化した後、高温で一軸性塑性加工(ダイアップセット)を施して異方性化し、得られた異方性圧粉体を粉砕したものが提案されている。しかし、この異方性化プロセスは手間がかかり、生産コストが大幅に上昇してしまうので、異方性ボンディッド磁石としての生産は行なわれていないのが現状である。
【0007】
また、合金の水素吸蔵→脱水素による再結晶化という工程により、急冷凝固合金と同様な組織構造とし、かつ異方性を付与することも可能な方法も提案されている(特開平1−132106号公報)。しかし、この方法では、合金組成、水素吸蔵、脱水素などの条件の微小な変動により、磁石粒子の磁気的異方性が著しく低下したり、磁気的異方性にばらつきが生じたりしやすいので、安定性に欠けるという問題がある。
【0008】
また、急冷凝固を利用して得た磁石粒子や再結晶を利用した磁石粒子は、保磁力発生機構がピンニングタイプであるため着磁がしにくい。このため、着磁に要する磁界強度が極めて大きいという問題がある。
【0009】
ボンディッド磁石に異方性焼結磁石の粉砕粉を用いることも考えられるが、焼結体を粉砕すると保磁力や角形比が極端に劣化するため、磁石としての特性が得られない。この他、鋳造・熱間圧延プロセスで製造した磁石体の粉砕粉も異方性ボンディッド磁石の原料として提案されているが、焼結体を粉砕した場合と同様に、粉砕による保磁力の劣化が大きいため、実用材料とはなっていない。
【0010】
また、微粉の加圧成形→解砕→加熱→解砕という工程により集合粒度100〜1000μm の集合粉末とし、これをボンディッド磁石に適用する方法が提案されている(特開昭61−179801号公報)。同公報では、上記工程により、個々の結晶粒の周囲をNdに富んだ相が覆った集合粉末が得られるとしているが、上記工程では粒界相の制御が不十分になりやすく、このような組織構造を安定して実現することが難しい。
【0011】
また、焼結用の微粉を磁界中配向成形し、得られた成形体を通常の焼結磁石よりも低い温度で焼成することにより多孔質の焼結体を作り、これに樹脂を含浸させて異方性ボンディッド磁石とする方法も提案されている(特開昭59−219904号公報)。しかし、この方法も、粒界相を積極的には制御していないため、安定して高保磁力を得ることは難しい。
【0012】
また、特開平5−47528号公報には、Nd−Fe−B磁石粉末に焼結阻止剤または気化剤を混合するか、あるいは磁石粉末の表面を酸化した後、磁石粉末を磁界中で圧縮して圧粉体を作り、圧粉体を焼成して開放気孔を有する異方性焼成体を作り、400〜1000℃で熱処理後、開放気孔に樹脂を含浸して硬化する方法が記載されている。この方法も、粒界相を積極的には制御していないため、安定して高保磁力を得ることは難しい。
【0013】
ところで、上記した急冷凝固粉末は温間成形磁石にも適用できるが、温間成形磁石においても等方性であるということにかわりはない。
【0014】
【発明が解決しようとする課題】
本発明の目的は、保磁力が高い磁石粉末と、この磁石粉末を用いたボンディッド磁石および温間成形磁石とを、安価に提供することである。
【0015】
【課題を解決するための手段】
このような目的は、下記(1)〜()のいずれかの構成により達成される。
(1)R(Rは、Yを含む希土類元素の少なくとも1種である)、T(Tは、Feであるか、Co、NiおよびCuの少なくとも1種ならびにFeである)およびBを含有し、実質的にR214Bからなる相を含む成形体用合金と、Rを含み、R214BよりもRリッチな溶浸用合金とを用い、溶融した溶浸用合金を、成形体用合金の粉末の成形体に溶浸させて溶浸体を得、この溶浸体を粉砕して磁石粉末を得る工程を有する磁石の製造方法。
(2)実質的にR214B相(Rは、Yを含む希土類元素の少なくとも1種であり、Tは、Feであるか、Co、NiおよびCuの少なくとも1種ならびにFeである)からなる主相と、R214BよりもRリッチであり、前記主相を包囲する副相とを含む多結晶体であり、平均主相径が0.5〜10μ m、粒子径100〜500μm 、保磁力5 kOe以上である磁石粉末を含む磁石。
)前記磁石粉末をバインダで結合したボンディッド磁石である上記(2)の磁石。
)前記磁石粉末を温間成形した温間成形磁石である上記(2)の磁石。
)上記(1)の磁石の製造方法により製造されたものである上記(2)〜()のいずれかの磁石。

【0016】
【作用および効果】
本発明では、実質的にR214Bからなる相を有する粉末を磁界中で成形し、得られた成形体に、Rリッチな溶浸用合金を溶浸させて、溶浸体を製造する。この場合の溶浸とは、溶融した合金を成形体に染み込ませることである。液相の溶浸用合金は、成形体用合金の粉末に対して極めて濡れ性が良好であるため、短時間で成形体中の粒子間の空隙に充填される。このため、保磁力発生に重要なRリッチ相が溶浸体中において偏在しない組織構造が安定して得られる。しかも、溶浸の際には成形体用合金粉末は結晶成長せずその粒子径が維持されるので、R214B主相の径が小さな組織構造が安定して得られる。
【0017】
このようにして得られた溶浸体を粒子径100〜500μm 程度に粉砕すれば、焼結体を粉砕した場合と異なり保磁力の劣化が抑えられ、しかも、保磁力劣化防止効果のばらつきが小さくなる。このため、5 kOe以上の高保磁力を有する異方性磁石粉末が得られる。そして、この異方性磁石粉末をボンディッド磁石や温間成形磁石の製造に使用すれば、高保磁力の異方性ボンディッド磁石や異方性温間成形磁石が安定して得られる。
【0018】
【具体的構成】
以下、本発明の具体的構成について詳細に説明する。
【0019】
本発明では、成形体用合金と溶浸用合金とを用い、溶融した溶浸用合金を成形体用合金の粉末の成形体に溶浸することにより溶浸体を製造し、この溶浸体を粉砕して磁石粉末を得る。
【0020】
<成形体用合金>
成形体用合金は、R(Rは、Yを含む希土類元素の少なくとも1種である)、T(Tは、Feであるか、Co、NiおよびCuの少なくとも1種ならびにFeである)およびBを含有し、実質的にR214Bからなる相を含む。成形体用合金の具体的組成は、目的とする磁石特性に応じ、溶浸用合金の組成などを考慮して適宜決定すればよいが、好ましくは、
Rを26〜38重量%、
Bを0.9〜3重量%
含み、残部が実質的にTであるものとし、より好ましくは、
Rを27〜33重量%、
Bを1.0〜1.5重量%
含み、残部が実質的にTであるものとする。
【0021】
Rは、Y、ランタニドおよびアクチニドであるが、高残留磁束密度を得るためには好ましくはNdおよび/またはPrを用いる。これらの他に、Tb、Dy、La、Ce、Gd、Er、Ho、Eu、Pm、Tm、Yb、Y等の1種以上を用いてもよい。Nd+Prは、成形体用合金のRの50重量%以上、特に80重量%以上を占めることが好ましい。希土類元素の原料としては、ミッシュメタル等の混合物を用いることもできる。成形体用合金中のR含有量が少なすぎると鉄に富む相が析出して高保磁力が得られなくなり、R含有量が多すぎると高残留磁束密度が得られなくなる。
【0022】
214B系焼結磁石では、Rリッチ相が液相となって流動することにより焼結反応が進行するので、原料粉末を一般にR214BよりもRリッチとする。本発明では、成形体用合金粉末の成形体にRリッチな溶浸用合金を溶浸させることにより、成形体中の粒子周囲に保磁力発生のためのRリッチ相を形成するので、成形体用合金の組成をR214BよりもRリッチとする必要はない。逆に、成形体用合金のR比率が高すぎると、高残留磁束密度が得られなくなる。
【0023】
成形体用合金中のB含有量が少なすぎると高保磁力が得られなくなり、B含有量が多すぎると高残留磁束密度が得られなくなる。
【0024】
成形体用合金では、Fe+CoがTの50重量%以上、特に90重量%以上を占めることが好ましい。T中のFe+Coの比率が小さすぎると、磁石化したときに飽和磁化が小さくなり、高残留磁束密度が得られなくなる。
【0025】
また、成形体用合金では、Fe/(Fe+Co)が70重量%以上であることが好ましい。Feが少ないと磁石化したときに高残留磁束密度が得られなくなる。
【0026】
上記各元素の他、保磁力改善や耐食性改善などのために、Al、C、Si、Cr、Mn、Mg、Nb、Sn、W、V、Zr、Ti、Mo、Gaなどの元素を添加してもよいが、添加量が6重量%を超えると残留磁束密度の低下が問題となる。
【0027】
合金中には、これらの元素の他、酸素等の不可避的不純物や微量添加物などが含まれていてもよい。
【0028】
本発明では、成形体用合金粉末を磁界中で配向しながら成形するので、粉末化したときに単結晶粒子となるような結晶粒径であることが好ましいが、多結晶粒子であっても粒子内で結晶粒が配向していればよいので、平均結晶粒径は、例えば3〜600μm 程度の広い範囲から選択することができる。
【0029】
成形体用合金の粉末の平均粒子径は、好ましくは0.2〜20μm 、より好ましくは0.5〜10μm である。平均粒子径が小さすぎると粉末中の酸素量が多くなるため、溶浸用合金の使用量とのバランスによっては高保磁力が得られにくくなる。一方、平均粒子径が大きすぎると、保磁力の低下を招く。
【0030】
成形体用合金の粉末の製造方法は特に限定されず、鋳造合金を水素吸蔵粉砕などにより粉末化する方法や、還元拡散法等のいずれを用いてもよく、焼結磁石を粉砕して粉末化したもの、あるいは焼結磁石の研削屑を用いてもよい。磁界配向により異方性化された焼結磁石を粉砕あるいは研削すれば、配向された小径の結晶粒からなる多結晶粒子を得ることができるので、高残留磁束密度かつ高保磁力の溶浸体が得られる。
【0031】
<溶浸用合金>
溶浸用合金は、Rを含み、R214BよりもRリッチな合金である。
【0032】
溶浸用合金の融点は、好ましくは300℃以上、より好ましくは400℃以上であり、好ましくは800℃以下、より好ましくは700℃以下である。融点が低すぎると、成形時に潤滑剤やバインダとして用いるワックス等の有機物の分解温度との関係から、磁石中の残留炭素量が増加し、保磁力が低くなってしまう。また、成形体用合金粉末のもつ吸着水が抜けきらないうちに溶浸が始まることになり、この点からも保磁力低下を招く。一方、融点が高すぎると、磁石の主相となるR214B相の結晶粒が溶浸時に大きく成長してしまうので、好ましくない。
【0033】
溶浸用合金の組成は、必要とされる融点が得られるように、また、溶浸体を粉砕した磁石粉末の保磁力が高くなるように決定すればよく、特に限定されないが、Rに加え、M(Mは、Fe、Co、Ni、Cu、Al、Sn、GaおよびAgの少なくとも1種である)を含むことが好ましい。Rとしては、Nd、Pr、DyおよびCeの少なくとも1種、特にNd、PrおよびDyの少なくとも1種が好ましい。Mとしては、Fe、Co、CuおよびAlの少なくとも1種、特にFe、CoおよびCuの少なくとも1種がより好ましい。
【0034】
溶浸用合金のR含有量は、好ましくは40〜99重量%、より好ましくは60〜90重量%である。Rが少なすぎると融点を低くすることが難しくなり、また、磁石の保磁力向上効果も不十分となる。Rが多すぎるか、あるいはR単体であっても、やはり融点が高くなってしまう。なお、残部は実質的に上記Mであることが好ましい。ただし、Mの一部に替えて、B、Si、Cやその他の元素の少なくとも1種を添加してもよい。ただし、これらの元素の合計含有率は、溶浸用合金の3重量%以下とすることが好ましい。また、これらの他、酸素等の不可避的不純物や微量添加元素が含まれていてもよい。
【0035】
溶浸用合金はバルク状であってもよく、粉末状であってもよいが、溶浸用合金はR含有量が多く酸化されやすいため、好ましくはバルク状のものまたは粗粉を用いる。
【0036】
溶浸用合金の製造方法は特に限定されず、鋳造法や液体急冷法等のいずれを用いてもよい。
【0037】
<成形>
成形体用合金の粉末は、通常、焼結磁石製造の際の磁石粉末成形と同様にして圧縮成形する。異方性磁石粉末を製造するためには、磁界中で成形して成形体用合金の粉末を配向する。
【0038】
圧縮成形の際の成形圧力は特に限定されず、また、成形体の密度も特に限定されない。
【0039】
成形時の磁界強度は、通常、10 kOe以上、好ましくは15 kOe以上とする。成形時に印加する磁界は、直流磁界であってもパルス磁界であってもよく、これらを併用してもよい。本発明は、圧力印加方向と磁界印加方向とがほぼ直交するいわゆる横磁場成形法にも、圧力印加方向と磁界印加方向とがほぼ一致するいわゆる縦磁場成形法にも適用することができる。
【0040】
成形は、粉末の酸化を避けるために、通常、50℃以下で行なう。
【0041】
<溶浸>
溶浸は、溶浸用合金をその融点以上まで加熱することにより行なう。
【0042】
溶浸用合金の加熱手段は特に限定されず、電気炉や高周波加熱炉等のいずれを用いてもよいが、成形体も同時に加熱できる手段、例えば、電気炉を用いることが好ましい。成形体を溶浸用合金と同等の温度まで加熱することにより、成形体へ均一な溶浸ができる。
【0043】
具体的な溶浸方法は特に限定されない。例えば、溶浸用合金の融液に成形体を浸漬する方法や、融液を成形体に注ぐ方法、融液に成形体の一部を浸して成形体内に吸い取る方法などのいずれを用いてもよい。ただし、好ましくは、成形体と溶浸用合金とを接触させた状態で、溶浸用合金を溶融する方法を用いる。具体的には、成形体上に溶浸用合金を載置し、これを溶融することが好ましい。溶浸用合金の融液に成形体を浸漬する方法を用いてもよいが、この場合には、融液から引き上げた後に、成形体の表面全面で溶浸用合金が凝固するため、それを研削して除去する工程を設ける必要がある。これに対し、溶浸用合金を必要量だけ成形体上に載置して溶融すれば、溶浸後の成形体表面には溶浸用合金が残存しないか、あるいは成形体上面にわずかに残存するだけなので、工程を簡略化することができる。しかも、この方法では、溶融時に溶浸用合金は成形体以外と接触していないため、不純物の混入を防ぐことができる。
【0044】
成形体上に溶浸用合金を載置する方法を用いる場合、実用的には空隙の容積よりも少ない量の溶浸用合金を用いることが好ましい。なお、成形体の空隙率は、成形体用合金の組成と成形体密度とから算出することができる。具体的には、成形体の空隙に対し好ましくは10〜100容量%、より好ましくは40〜100容量%の溶浸用合金を用いる。溶浸用合金の使用量が少なすぎると、保磁力の高い磁石粉末が得にくくなる。一方、成形体の空隙よりも多量に使用した場合、磁気特性は向上せず、しかも、成形体表面に余剰の溶浸用合金が残存し、溶浸後に研削等の加工を施す必要が生じることがある。
【0045】
溶浸用合金を成形体上に載置する形態は特に限定されず、例えば、粗粉やインゴットの砕片を所定量秤量して載置してもよいが、好ましくは、溶浸用合金の粗粉を成形し、これを載置する。溶浸用合金を成形体とすることにより、使用量の管理が正確かつ容易となり、成形体への溶浸を均一に行なうことができる。なお、2色成形と同様にして、成形体用合金の粉末と溶浸用合金の粗粉とを、一体的に成形してもよい。
【0046】
液相の溶浸用合金は成形体用合金粉末に対する濡れ性が極めて良好であるため、溶融後、速やかに成形体に染み込む。したがって、溶浸するだけであれば融点以上まで加熱した後に温度保持を行なう必要はないが、保磁力および残留磁束密度を高めるためには、溶浸後、さらに昇温を続けて、溶浸用合金の融点より高い温度に保持する熱処理を行なうことが好ましい。この熱処理における保持温度は、溶浸用合金の融点によっても異なるが、好ましくは800℃以上、より好ましくは900℃以上である。ただし、磁石の主相となるR214B相の結晶粒成長を抑制するために、保持温度は1100℃以下とすることが好ましい。この熱処理において、温度保持を行なう時間は、好ましくは0.5〜8時間である。この時間が短すぎると熱処理による効果が不十分となり、長すぎるとR214B相の結晶粒成長が著しくなる。なお、この熱処理を施した後の溶浸体(溶浸後の成形体)は、空隙が残存している多孔質体であってもよく、空隙がほとんど残存していない状態であってもよい。
【0047】
なお、上記熱処理は、溶浸後にいったん降温してから行なってもよい。
【0048】
溶浸後、または上記熱処理後、時効処理を施してもよい。時効処理は、上記熱処理よりは保持温度が低い熱処理であり、時効処理により保磁力を向上させることができる。時効処理の際の保持温度は、好ましくは400〜800℃、より好ましくは500〜700℃である。また、温度保持時間は、好ましくは0.5〜4時間である。時効処理は、上記熱処理後、冷却した後に施すが、上記熱処理の降温過程において徐冷することにより、時効処理と同等の効果を得ることができる。
【0049】
なお、溶浸およびその後の熱処理は、溶浸用合金および成形体の酸化を防ぐために、真空中またはArガス等の不活性ガス雰囲気中で行なうことが好ましい。
【0050】
<溶浸体>
このようにして製造された溶浸体は、実質的にR214Bから構成される主相と、この主相を包囲する副相とを有する。主相は、一般に成形体用合金の粒子に基づくので、粒状であり、その周囲は比較的滑らかである。副相は、R214BよりもR比率の高いRリッチ相である。溶浸体中の副相の割合は、成形体密度によって異なるが、通常、20〜40体積%である。Coおよび/またはCuを含有する溶浸用合金を用いた場合、副相中にはR3 Co相および/またはRCu相が含まれ、溶浸用合金の組成によっては副相は実質的にこれらの相だけから構成される。
【0051】
溶浸用合金にFeが含まれていた場合には、R3 Co相のCoの少なくとも一部およびRCu相のCuの少なくとも一部がFeで置換されており、また、溶浸用合金にFeが含まれていなかった場合でも、主相からの拡散により、通常、このようなFeによる置換がみられる。
【0052】
また、溶浸用合金がCoおよびCuを含有するものであったときには、R3 Co相およびRCu相が含まれ、R3 Co相のCoの少なくとも一部がCuで置換されており、RCu相のCuの少なくとも一部がCoで置換されている。
【0053】
3 Co相およびRCu相は溶浸体の耐食性を向上させる効果を示し、RCu相の効果がより高い。そして、R3 Co相としてR3 (Co1-w-x Few Cux )相(0.01≦w≦0.3、0.01≦x≦0.3)を含み、かつRCu相としてR(Cu1-y-z Coy Fez )相(0.01≦y≦0.3、0.01≦z≦0.3)を含むときには、耐食性向上効果は著しく高くなる。溶浸体中におけるこれらの相の含有率は、それぞれ1〜30体積%であることが好ましい。そして、溶浸体中におけるこれらの相の合計含有率は、20〜40体積%であることが好ましい。すなわち、副相は、実質的にこれらの相だけから構成されることが好ましい。なお、このような場合でも、副相にはR酸化物相等の他の相が含まれるが、これら他の相の溶浸体中の比率は、5体積%程度以下である。溶浸体断面に現れるR3 Co相やRCu相の径は、通常、50μm 以下である。
【0054】
溶浸体の組成は、成形体用合金の組成、溶浸用合金の組成、これらの合金の比率などによって決定されるが、好ましくは、
Rを30〜60重量%、
Bを0.3〜6重量%
含むものとし、より好ましくは、
Rを35〜45重量%、
Bを0.6〜1.3重量%
含むものとする。なお、残部は、成形体用合金に由来するTおよび溶浸用合金に由来するMなどである。
【0055】
<粉砕>
溶浸体は、粉砕されて磁石粉末とされる。粉砕方法は特に限定されず、機械的粉砕法や水素吸蔵粉砕法などを適宜選択すればよく、これらを組み合わせて粉砕を行なってもよい。水素吸蔵粉砕法を利用する場合、水素は溶浸体に直接吸蔵させてもよく、機械的粉砕手段により溶浸体を砕いた後、吸蔵させてもよい。ただし、水素吸蔵粉砕を利用する場合、水素吸蔵により粒界の相構成が変化することがあり、これにより磁気特性が劣化するため、溶浸体の粉砕粉またはその成形体に対し、前述した時効処理を施すことが好ましい。
【0056】
磁石粉末の粒子径は特に限定されないが、ボンディッド磁石または温間成形磁石に適用する場合、好ましくは100〜500μm 、より好ましくは125〜250μm である。粒子径が小さすぎると、耐酸化性が不十分となり、また、保磁力の劣化が著しくなる。一方、粒子径が大きすぎると、ボンディッド磁石や温間成形磁石に適用する際に成形性が悪くなり、高充填率が得られなくなる。なお、この場合の粒子径とは、ふるい等による分級によってオーバーカットおよびアンダーカットされた粒子径の範囲を意味する。
【0057】
磁石粉末を構成する粒子は、通常、多結晶体であり、平均結晶粒径(平均主相径)は、好ましくは0.5〜10μm 、より好ましくは1〜5μm である。粉末中の酸素量を著しく増加させずに平均結晶粒径を0.5μm より小さくすることは、製法上実現が非常に困難である。一方、平均結晶粒径が10μm を超えていると、溶浸体の粉砕時や磁石粉末の成形時のストレスにより主相が破断される確率が高くなるため、保磁力の劣化を招きやすい。
【0058】
なお、本発明の磁石粉末は、通常、5 kOe以上の保磁力を有する。
【0059】
<ボンディッド磁石>
ボンディッド磁石は、磁石粉末をバインダで結合して作製する。本発明の磁石粉末は、プレス成形を用いるコンプレッションボンディッド磁石、あるいは射出成形を用いるインジェクションボンディッド磁石のいずれにも適用することができる。また、磁石粉末の成形体にバインダを含浸することによってもボンディッド磁石が得られる。バインダとしては、各種樹脂を用いることが好ましいが、金属バインダを用いてメタルボンディッド磁石とすることもできる。樹脂バインダの種類は特に限定されず、エポキシ樹脂やナイロン等の各種熱硬化性樹脂や各種熱可塑性樹脂から目的に応じて適宜選択すればよい。金属バインダの種類も特に限定されない。また、磁石粉末に対するバインダの含有比率や成形時の圧力等の各種条件にも特に制限はなく、通常の範囲から適当に選択すればよい。ただし、結晶粒の粗大化を防ぐために、高温の熱処理が必要な方法は避けることが好ましい。
【0060】
異方性ボンディッド磁石は、異方性磁石粉末を磁界中で成形して得た成形体にバインダを含浸させることにより作製できる。また、圧縮成形時や射出成形時に磁界を印加することによっても作製できる。
【0061】
<温間成形磁石>
温間成形磁石は、ホットプレス等を用いて磁石粉末を温間成形することにより作製する。温間成形条件は特に限定されず、温度、圧力等の各種条件は、通常の範囲、例えば400〜800℃程度、0.1〜3t/cm2 程度の範囲から適当に選択すればよい。異方性温間成形磁石を作製するためには、温間成形の初期段階(少なくとも磁石粉末のキュリー点未満)において磁界を印加すればよい。また、磁界中で仮成形後、磁界を印加せずに温間成形を行なってもよい。
【0062】
【実施例】
以下、本発明の具体的実施例を示し、本発明をさらに詳細に説明する。
【0063】
<実施例1:磁石粉末>
表1に示す磁石粉末を以下に示す方法で作製した。
【0064】
磁石粉末 No. 1−1〜1−8
まず、成形体用合金のインゴットを、Arガス雰囲気中での高周波溶解により鋳造した。インゴットの組成は、重量百分率で
(30Nd−3.5Dy)−1.1B−残部Fe
とした。このインゴットを窒素ガス雰囲気中で機械的粉砕した後、ジェットミルにより窒素ガス気流粉砕し、平均粒子径4.5μm の成形体用合金粉末とした。この成形体用合金粉末を、15 kOeの磁界中で、磁界方向と直交する方向に加圧して成形し、120mm×40mm×30mmの直方体状の成形体を得た。この成形体の密度は、5.00g/cm3 であった。
【0065】
次に、Arガス雰囲気中でアーク溶解により溶浸用合金を製造した。溶浸用合金の組成は、重量百分率で
12Co−17Cu−残部Fe
とした。
【0066】
次いで、成形体用合金粉末の成形体上に数ミリ角に砕いた溶浸用合金を載置し、真空中で1000℃にて2時間熱処理した後、急冷し、溶浸体とした。成形体中の空隙に対する溶浸用合金の容量比率を、表1に示す。冷却後、Ar雰囲気中で580℃にて1時間時効処理を施した。各溶浸体の平均結晶粒径(平均主相径)、密度、残留磁束密度Br、保磁力Hcj、最大エネルギー積(BH)max を、表1に示す。
【0067】
溶浸体を機械粉砕した後、分級し、粒子径125〜250μm の磁石粉末を得た。これらの磁石粉末の磁気特性を測定した。なお、磁石粉末No. 1−1および1−2では、溶浸体表面に残存している余剰の溶浸用合金を除去した後、粉砕した。
【0068】
磁石粉末 No. 1−9(比較例)
溶浸用合金を載置せずに上記成形体に上記熱処理を施し、その後、機械粉砕・分級して磁石粉末を得た。表1に溶浸体密度として示す値は、熱処理後の成形体の密度である。
【0069】
磁石粉末 No. 1−10(比較例)
通常の焼結磁石と同様に、密度4.20g/cm3 の成形体を1070℃で4時間焼成し、急冷後、600℃で1時間時効処理を施して焼結体を得、これを機械粉砕・分級して磁石粉末を得た。表1に溶浸体密度として示す値は、焼結体の密度である。
【0070】
磁石粉末 No. 1−11(比較例)
いわゆる2合金法により磁石体を作製し、これを粉砕・分級して磁石粉末を得た。まず、溶浸用合金を窒素ガス雰囲気中で機械的粉砕した後、ジェットミルにより窒素ガス気流粉砕し、平均粒子径3.0μm の粉末とした。この粉末と上記成形体用合金粉末とを、溶浸用合金粉末/成形体が重量比で0.3となるように混合した。次いで、磁石粉末No. 1−1と同様にして磁界中成形、熱処理および時効処理を行なって磁石体を得、これを粉砕・分級して磁石粉末とした。表1に溶浸体密度として示す値は、磁石体の密度である。
【0071】
これらの磁石粉末についても、上記と同様な測定を行なった。結果を表1に示す。
【0072】
【表1】

Figure 0003540438
【0073】
表1から、本発明の効果が明らかである。本発明の磁石粉末では、いずれも5kOe以上の保磁力が得られているのに対し、溶浸せずに作製されたNo. 1−9および1−10では保磁力が低い。No. 1−10は、No. 1−9よりも焼結が進んでおり、このため溶浸体の保磁力は高くなっているが、粉砕により保磁力が著しく低下している。No. 1−11は、粒界成分である溶浸用合金を通常の2合金法により混合したため、溶浸を利用する本発明とは異なり、粉砕により保磁力が著しく低くなってしまっている。
【0074】
<実施例2:磁石粉末>
成形体用合金粉末の平均粒子径および溶浸体に施す熱処理の条件を表2に示すものとし、これら以外は実施例1のNo. 1−3と同様にして磁石粉末を製造した。これらの磁石粉末について、実施例1と同様な測定を行なった。結果を表2に示す。
【0075】
【表2】
Figure 0003540438
【0076】
表2から、磁石粉末の平均主相径が10μm 以下であるとき、特に高い保磁力が得られることがわかる。
【0077】
<実施例3:磁石粉末>
溶浸用合金として表3に示す組成のものを用い、これ以外は実施例1のNo. 1−3と同様にして磁石粉末を製造した。これらの磁石粉末について、実施例1と同様な測定を行なった。結果を表3に示す。
【0078】
【表3】
Figure 0003540438
【0079】
表3から、Nd−Co−Cuにさらに他の元素を加えた4元系組成の溶浸用合金を用いた場合でも5 kOe以上の保磁力が得られることがわかり、Snを添加することにより保磁力の低下が特に抑えられることがわかる。
【0080】
<実施例4:異方性ボンディッド磁石>
上記実施例で製造した磁石粉末を、15 kOeの磁界中で磁界方向と平行に4t/cm2 の圧力を加えて成形した後、Ar雰囲気中で580℃にて1時間熱処理を施し、次いで、シリコン樹脂を含浸した。なお、磁石粉末の平均結晶粒径は、成形および熱処理により変化しなかった。得られたボンディッド磁石の密度および磁気特性を、表4に示す。
【0081】
【表4】
Figure 0003540438
【0082】
<実施例5:異方性温間成形磁石>
上記実施例で製造した磁石粉末を、15 kOeの磁界中で磁界方向と平行に4t/cm2 の圧力を加えて成形した後、650℃で0.5t/cm2 の圧力を30分間加えて温間成形した。得られた温間成形磁石の密度および磁気特性を、表5に示す。
【0083】
【表5】
Figure 0003540438
【0084】
以上の実施例の結果から、本発明の効果が明らかである。[0001]
[Industrial applications]
The present invention relates to a rare earth magnet and a method for manufacturing the same.
[0002]
[Prior art]
As a rare earth magnet having high performance, a Sm-Co based magnet manufactured by powder metallurgy and having an energy product of 32 MGOe is mass-produced. In recent years, NdTwo Fe14RTB-based magnets such as B magnets (T is Fe, or Fe and Co) have been developed. The raw material of the RTB-based magnet is less expensive than that of the Sm-Co-based magnet. The RTB-based magnet is a sintered magnet manufactured by applying a conventional Sm-Co-based powder metallurgical process (melting → master alloy casting → ingot coarse grinding → fine grinding → forming → sintering → magnet). And a bonded magnet in which magnet powder is bonded with a resin binder or a metal binder.
[0003]
A method for producing an RTB-based sintered magnet includes a method of pulverizing one kind of raw material alloy, molding and sintering the obtained powder (Japanese Patent Publication No. 61-34242, etc.), and a method of preparing a composition. A method in which two different types of alloy powders are mixed, molded and sintered (Japanese Patent Application Laid-Open Nos. 61-81603, 63-93841, 5-105915, etc.) and the like. .
[0004]
However, in the sintering method, the compact generally shrinks by 30 to 40% by volume during sintering. This shrinkage can be reduced by increasing the pressure at the time of molding the powder, but it is difficult to suppress the deformation amount and shrinkage ratio to satisfy the required dimensional accuracy of a normal magnet. For this reason, it is necessary to grind to a predetermined size and shape after sintering, which causes an increase in cost.
[0005]
On the other hand, since the RTB-based bonded magnet does not require firing after compression molding, the magnet dimensions are substantially the same as the mold dimensions. For this reason, dimensional accuracy is high, and shape processing is not required after manufacturing. However, an industrialized RTB-based bonded magnet uses polycrystalline particles obtained by using rapid solidification by a single roll method or the like, as shown in Japanese Patent Publication No. 1-54557. It becomes an isotropic magnet.
[0006]
On the other hand, as described in Japanese Patent Publication No. Hei 4-20242, as a magnetic powder for an anisotropic bonded magnet, a rapidly solidified powder is uniaxially compressed by a hot press to obtain a high density, and then a uniaxial Anisotropic green compacts obtained by performing plastic working (die-up set) to make them anisotropic and pulverizing the obtained anisotropic green compacts have been proposed. However, this anisotropic process is troublesome and greatly increases the production cost, so that at present, production as an anisotropic bonded magnet is not performed.
[0007]
Also, a method has been proposed in which the alloy has a structure similar to that of a rapidly solidified alloy and can be imparted with anisotropy by a process of storing hydrogen and recrystallizing by dehydrogenation (JP-A-1-132106). Publication). However, in this method, the magnetic anisotropy of the magnet particles is remarkably reduced or the magnetic anisotropy is likely to vary due to minute fluctuations in conditions such as the alloy composition, hydrogen storage, and dehydrogenation. However, there is a problem of lack of stability.
[0008]
Further, magnet particles obtained by using rapid solidification or magnet particles using recrystallization are hard to be magnetized because the coercive force generating mechanism is a pinning type. For this reason, there is a problem that the magnetic field strength required for magnetization is extremely large.
[0009]
It is also conceivable to use a ground powder of an anisotropic sintered magnet for the bonded magnet. However, when the sintered body is ground, the coercive force and the squareness ratio are extremely deteriorated, so that characteristics as a magnet cannot be obtained. In addition, pulverized powder of a magnet body produced by a casting and hot rolling process has also been proposed as a raw material of an anisotropic bonded magnet. Because it is large, it is not a practical material.
[0010]
In addition, a method has been proposed in which an aggregated powder having an aggregated particle size of 100 to 1000 μm is formed by a process of pressure molding of fine powder → crushing → heating → crushing and applied to a bonded magnet (Japanese Patent Application Laid-Open No. 61-179801). ). According to the same publication, the above-mentioned process provides an aggregated powder in which the individual crystal grains are covered with a phase rich in Nd. However, in the above-described process, the control of the grain boundary phase tends to be insufficient, and such It is difficult to achieve a stable organizational structure.
[0011]
In addition, fine powder for sintering is orientation-molded in a magnetic field, and the obtained compact is fired at a lower temperature than a normal sintered magnet to produce a porous sintered body, which is impregnated with a resin. A method using an anisotropic bonded magnet has also been proposed (JP-A-59-219904). However, also in this method, since the grain boundary phase is not actively controlled, it is difficult to stably obtain a high coercive force.
[0012]
Japanese Patent Application Laid-Open No. Hei 5-47528 discloses that a sintering inhibitor or a vaporizer is mixed with Nd-Fe-B magnet powder, or the surface of the magnet powder is oxidized and then the magnet powder is compressed in a magnetic field. A method is described in which a green compact is formed by heating, and the green compact is fired to form an anisotropic fired body having open pores, heat-treated at 400 to 1000 ° C., and impregnated with resin in the open pores and cured. . Also in this method, since the grain boundary phase is not actively controlled, it is difficult to stably obtain a high coercive force.
[0013]
By the way, the above-mentioned rapidly solidified powder can be applied to a warm compacted magnet, but it is still the same for a warm compacted magnet.
[0014]
[Problems to be solved by the invention]
An object of the present invention is to provide a magnet powder having a high coercive force, and a bonded magnet and a warm-formed magnet using the magnet powder at low cost.
[0015]
[Means for Solving the Problems]
Such a purpose is as follows (1) to (5This is achieved by any one of the above configurations.
(1) R (R is at least one rare earth element including Y), T (T is Fe, or at least one of Co, Ni and Cu, and Fe) and B , Substantially RTwo T14An alloy for a compact containing a phase consisting of B;Two T14Using an infiltrating alloy richer than B, the molten infiltrating alloy is infiltrated into a compact of the alloy powder to obtain an infiltrated body, and the infiltrated body is crushed. A method for producing a magnet, comprising a step of obtaining magnet powder.
(2) Substantially RTwo T14A main phase composed of a B phase (R is at least one kind of rare earth element including Y and T is Fe or at least one kind of Co, Ni and Cu and Fe);Two T14B is richer than B and contains a subphase surrounding the main phase.The average main phase diameter is 0.5 to 10 μm mA magnet containing magnet powder having a particle size of 100 to 500 μm and a coercive force of 5 kOe or more.
(3The above (2) which is a bonded magnet in which the magnet powder is bound by a binder)ofmagnet.
(4The above (2) which is a warm-formed magnet obtained by warm-forming the magnet powder.)ofmagnet.
(5The above (2) to () produced by the method for producing a magnet of the above (1).4) One of the magnets.

[0016]
[Action and effect]
In the present invention, substantially RTwo T14A powder having a phase consisting of B is molded in a magnetic field, and the obtained molded body is infiltrated with an R-rich infiltration alloy to produce an infiltrated body. Infiltration in this case refers to infiltration of the molten alloy into the compact. Since the liquid-phase infiltration alloy has extremely good wettability with respect to the powder of the compact alloy, it is filled in the voids between the particles in the compact in a short time. Therefore, a structure in which the R-rich phase important for generating the coercive force is not unevenly distributed in the infiltrated body can be stably obtained. In addition, during infiltration, the alloy powder for a compact does not grow and its particle diameter is maintained.Two T14A structure having a small diameter of the B main phase can be stably obtained.
[0017]
If the infiltrated body thus obtained is pulverized to a particle diameter of about 100 to 500 μm, the deterioration of the coercive force is suppressed unlike the case where the sintered body is pulverized, and the dispersion of the coercive force deterioration preventing effect is small. Become. Therefore, an anisotropic magnet powder having a high coercive force of 5 kOe or more can be obtained. If this anisotropic magnet powder is used for the production of a bonded magnet or a warm-formed magnet, an anisotropic bonded magnet or anisotropic warm-formed magnet having a high coercive force can be stably obtained.
[0018]
[Specific configuration]
Hereinafter, a specific configuration of the present invention will be described in detail.
[0019]
In the present invention, an infiltration body is manufactured by infiltrating a molten infiltration alloy into a molded body of an alloy powder for a molding body using an alloy for a molding body and an infiltration alloy. Is ground to obtain a magnet powder.
[0020]
<Molded alloy>
The alloys for compacts include R (R is at least one rare earth element including Y), T (T is Fe or at least one of Co, Ni and Cu, and Fe) and B And substantially RTwo T14B. The specific composition of the alloy for the compact may be appropriately determined in consideration of the composition of the alloy for infiltration, depending on the desired magnet properties, but is preferably
R is 26 to 38% by weight,
B is 0.9 to 3% by weight
And the remainder is substantially T, more preferably
R is 27 to 33% by weight,
B to 1.0 to 1.5% by weight
And the balance is substantially T.
[0021]
R is Y, lanthanide and actinide, but Nd and / or Pr are preferably used to obtain a high residual magnetic flux density. In addition to these, one or more of Tb, Dy, La, Ce, Gd, Er, Ho, Eu, Pm, Tm, Yb, and Y may be used. Nd + Pr preferably accounts for 50% by weight or more, particularly 80% by weight or more of R of the alloy for a compact. As a raw material of the rare earth element, a mixture such as misch metal can also be used. If the R content in the alloy for a compact is too low, a phase rich in iron will precipitate and a high coercive force cannot be obtained, and if the R content is too high, a high residual magnetic flux density cannot be obtained.
[0022]
RTwo T14In a B-based sintered magnet, since the sintering reaction proceeds when the R-rich phase turns into a liquid phase and flows, the raw material powder is generally mixed with R-phase.Two T14R is richer than B. In the present invention, the R-rich infiltration alloy is infiltrated into the compact of the alloy powder for a compact to form an R-rich phase for generating a coercive force around the particles in the compact. Alloy compositionTwo T14It is not necessary to make R richer than B. Conversely, if the R ratio of the alloy for a compact is too high, a high residual magnetic flux density cannot be obtained.
[0023]
If the B content in the alloy for a compact is too small, a high coercive force cannot be obtained, and if the B content is too large, a high residual magnetic flux density cannot be obtained.
[0024]
In the alloy for a compact, Fe + Co preferably accounts for 50% by weight or more, particularly 90% by weight or more of T. If the ratio of Fe + Co in T is too small, the saturation magnetization becomes small when magnetized, and a high residual magnetic flux density cannot be obtained.
[0025]
In the alloy for a compact, the ratio of Fe / (Fe + Co) is preferably 70% by weight or more. If Fe is small, a high residual magnetic flux density cannot be obtained when magnetized.
[0026]
In addition to the above elements, elements such as Al, C, Si, Cr, Mn, Mg, Nb, Sn, W, V, Zr, Ti, Mo, and Ga are added to improve coercive force and corrosion resistance. However, if the addition amount exceeds 6% by weight, a decrease in the residual magnetic flux density becomes a problem.
[0027]
The alloy may contain unavoidable impurities such as oxygen and trace additives in addition to these elements.
[0028]
In the present invention, since the alloy powder for a compact is compacted while being oriented in a magnetic field, it is preferable that the crystal powder has a crystal grain size such that it becomes a single crystal particle when powdered. The average crystal grain size can be selected from a wide range of, for example, about 3 to 600 μm, since the crystal grains need only be oriented within the range.
[0029]
The average particle size of the powder of the alloy for a compact is preferably 0.2 to 20 μm, more preferably 0.5 to 10 μm. If the average particle size is too small, the amount of oxygen in the powder increases, so that it is difficult to obtain a high coercive force depending on the balance with the amount of the infiltrating alloy used. On the other hand, if the average particle size is too large, the coercive force will decrease.
[0030]
The method of producing the powder of the alloy for the compact is not particularly limited, and any of a method of pulverizing the cast alloy by hydrogen absorption pulverization or a reduction diffusion method may be used. It is also possible to use the ground material or grinding dust of a sintered magnet. By grinding or grinding a sintered magnet that has been anisotropic by magnetic field orientation, polycrystalline particles consisting of oriented small-diameter crystal grains can be obtained, so that an infiltrated body with high residual magnetic flux density and high coercive force can be obtained. can get.
[0031]
<Infiltration alloy>
The infiltration alloy contains R, RTwo T14It is an R-rich alloy than B.
[0032]
The melting point of the alloy for infiltration is preferably 300 ° C. or higher, more preferably 400 ° C. or higher, preferably 800 ° C. or lower, more preferably 700 ° C. or lower. If the melting point is too low, the amount of residual carbon in the magnet increases and the coercive force decreases due to the relationship with the decomposition temperature of organic substances such as wax used as a lubricant and a binder during molding. In addition, infiltration starts before the adsorbed water of the alloy powder for a compact has been completely removed, and this also causes a decrease in coercive force. On the other hand, if the melting point is too high, the main phase of the magnet, RTwo T14This is not preferable because the crystal grains of the B phase grow greatly during infiltration.
[0033]
The composition of the alloy for infiltration may be determined so as to obtain the required melting point and to increase the coercive force of the magnet powder obtained by pulverizing the infiltrated body, and is not particularly limited. , M (M is at least one of Fe, Co, Ni, Cu, Al, Sn, Ga and Ag). R is preferably at least one of Nd, Pr, Dy and Ce, and particularly preferably at least one of Nd, Pr and Dy. As M, at least one of Fe, Co, Cu and Al, particularly at least one of Fe, Co and Cu, is more preferable.
[0034]
The R content of the alloy for infiltration is preferably 40 to 99% by weight, more preferably 60 to 90% by weight. If R is too small, it is difficult to lower the melting point, and the effect of improving the coercive force of the magnet becomes insufficient. Even if the amount of R is too large or R alone, the melting point will still be high. Preferably, the balance is substantially M. However, instead of part of M, at least one of B, Si, C and other elements may be added. However, the total content of these elements is preferably not more than 3% by weight of the alloy for infiltration. In addition, in addition to these, unavoidable impurities such as oxygen and a trace addition element may be contained.
[0035]
The infiltration alloy may be in a bulk form or a powder form. However, since the infiltration alloy has a high R content and is easily oxidized, a bulk form or coarse powder is preferably used.
[0036]
The method for producing the alloy for infiltration is not particularly limited, and any of a casting method, a liquid quenching method, and the like may be used.
[0037]
<Molding>
The powder of the alloy for the compact is usually compression-molded in the same manner as the molding of the magnet powder in the production of a sintered magnet. In order to produce the anisotropic magnet powder, the powder of the alloy for a compact is oriented in a magnetic field.
[0038]
The molding pressure during the compression molding is not particularly limited, and the density of the molded body is not particularly limited.
[0039]
The magnetic field strength during molding is usually at least 10 kOe, preferably at least 15 kOe. The magnetic field applied at the time of molding may be a DC magnetic field or a pulse magnetic field, and these may be used in combination. The present invention can be applied to a so-called horizontal magnetic field shaping method in which the pressure application direction and the magnetic field application direction are substantially orthogonal to each other, and to a so-called vertical magnetic field shaping method in which the pressure application direction and the magnetic field application direction substantially match.
[0040]
The molding is usually performed at 50 ° C. or less to avoid oxidation of the powder.
[0041]
<Infiltration>
Infiltration is performed by heating the alloy for infiltration to a temperature higher than its melting point.
[0042]
The means for heating the alloy for infiltration is not particularly limited, and any of an electric furnace, a high-frequency heating furnace and the like may be used. By heating the compact to the same temperature as the alloy for infiltration, uniform infiltration into the compact can be achieved.
[0043]
The specific infiltration method is not particularly limited. For example, any of a method of immersing the molded body in the melt of the infiltration alloy, a method of pouring the melt into the molded body, and a method of immersing a part of the molded body in the melt and sucking it into the molded body can be used. Good. However, preferably, a method of melting the infiltration alloy in a state where the compact and the infiltration alloy are in contact with each other is used. Specifically, it is preferable to place an infiltration alloy on a molded body and melt it. Although a method of immersing the molded body in the melt of the infiltration alloy may be used, in this case, the infiltration alloy is solidified over the entire surface of the molded body after being pulled out of the melt, so It is necessary to provide a step of grinding and removing. On the other hand, if the required amount of the infiltrating alloy is placed on the compact and melted, the infiltrating alloy does not remain on the compact after infiltration or remains slightly on the top of the compact. , The process can be simplified. In addition, according to this method, the infiltration alloy does not come into contact with anything other than the compact at the time of melting, so that contamination of impurities can be prevented.
[0044]
When the method of placing the infiltration alloy on the compact is used, it is practically preferable to use the infiltration alloy in an amount smaller than the void volume. The porosity of the compact can be calculated from the composition of the alloy for the compact and the density of the compact. Specifically, the infiltration alloy is preferably used in an amount of 10 to 100% by volume, more preferably 40 to 100% by volume, based on the voids of the compact. If the amount of the alloy for infiltration is too small, it becomes difficult to obtain magnet powder having a high coercive force. On the other hand, when used in a larger amount than the voids of the compact, the magnetic properties are not improved, and the excess alloy for infiltration remains on the surface of the compact, and it is necessary to perform processing such as grinding after infiltration. There is.
[0045]
The form in which the infiltration alloy is placed on the compact is not particularly limited. For example, coarse powder or crushed pieces of ingot may be weighed and placed in a predetermined amount. The powder is formed and placed. By using the alloy for infiltration as a molded body, the use amount can be controlled accurately and easily, and the molded body can be uniformly infiltrated. Note that, similarly to the two-color molding, the powder of the alloy for the compact and the coarse powder of the alloy for infiltration may be integrally molded.
[0046]
Since the liquid-phase infiltration alloy has extremely good wettability to the alloy powder for a compact, it immediately permeates the compact after melting. Therefore, if only infiltration is performed, it is not necessary to maintain the temperature after heating to the melting point or higher.However, in order to increase the coercive force and residual magnetic flux density, the temperature is further increased after infiltration, It is preferable to perform a heat treatment for maintaining the temperature higher than the melting point of the alloy. The holding temperature in this heat treatment varies depending on the melting point of the infiltration alloy, but is preferably 800 ° C. or more, more preferably 900 ° C. or more. However, R which is the main phase of the magnetTwo T14In order to suppress the crystal grain growth of the B phase, the holding temperature is preferably set to 1100 ° C. or lower. In this heat treatment, the time for maintaining the temperature is preferably 0.5 to 8 hours. If this time is too short, the effect of the heat treatment will be insufficient, and if it is too long, RTwo T14The phase B crystal grains grow remarkably. The infiltrated body after the heat treatment (the molded body after infiltration) may be a porous body in which voids remain, or may be a state in which voids hardly remain. .
[0047]
The heat treatment may be performed after the temperature is lowered once after the infiltration.
[0048]
After infiltration or after the heat treatment, aging treatment may be performed. The aging treatment is a heat treatment having a lower holding temperature than the above heat treatment, and the aging treatment can improve the coercive force. The holding temperature during the aging treatment is preferably 400 to 800 ° C, more preferably 500 to 700 ° C. The temperature holding time is preferably 0.5 to 4 hours. The aging treatment is performed after cooling after the heat treatment, but the same effect as the aging treatment can be obtained by gradually cooling in the temperature decreasing process of the heat treatment.
[0049]
The infiltration and the subsequent heat treatment are preferably performed in a vacuum or in an inert gas atmosphere such as Ar gas in order to prevent oxidation of the alloy for infiltration and the compact.
[0050]
<Infiltration body>
The infiltration body produced in this way has a substantially RTwo T14And a subphase surrounding the main phase. Since the main phase is generally based on particles of the compact alloy, it is granular and its surroundings are relatively smooth. The subphase is RTwo T14An R-rich phase having a higher R ratio than B. The proportion of the subphase in the infiltrated body varies depending on the density of the molded body, but is usually 20 to 40% by volume. When an infiltration alloy containing Co and / or Cu is used, RThree A Co phase and / or an RCu phase are contained, and depending on the composition of the infiltration alloy, the subphase is substantially composed of only these phases.
[0051]
When Fe is contained in the infiltration alloy, RThree At least a part of Co in the Co phase and at least a part of Cu in the RCu phase are replaced by Fe.Also, even when Fe is not contained in the infiltration alloy, diffusion from the main phase usually causes , Such substitution by Fe is observed.
[0052]
When the infiltration alloy contains Co and Cu, RThree Co phase and RCu phaseThree At least a part of Co in the Co phase is substituted by Cu, and at least a part of Cu in the RCu phase is substituted by Co.
[0053]
RThree The Co phase and the RCu phase show an effect of improving the corrosion resistance of the infiltrated body, and the effect of the RCu phase is higher. And RThree R as Co phaseThree (Co1-wx Few Cux ) Phase (0.01 ≦ w ≦ 0.3, 0.01 ≦ x ≦ 0.3), and R (Cu1-yz Coy Fez ) Phase (0.01 ≦ y ≦ 0.3, 0.01 ≦ z ≦ 0.3), the effect of improving the corrosion resistance is significantly increased. The content of each of these phases in the infiltration body is preferably 1 to 30% by volume. And the total content of these phases in the infiltration body is preferably 20 to 40% by volume. That is, it is preferable that the subphase is substantially composed of only these phases. Even in such a case, the subphase includes other phases such as the R oxide phase, but the ratio of these other phases in the infiltrated body is about 5% by volume or less. R appearing in cross section of infiltration bodyThree The diameter of the Co phase or the RCu phase is usually 50 μm or less.
[0054]
The composition of the infiltration body is determined by the composition of the alloy for the compact, the composition of the alloy for infiltration, the ratio of these alloys, etc., preferably,
R is 30 to 60% by weight,
0.3 to 6% by weight of B
And more preferably,
R is 35 to 45% by weight,
B to 0.6 to 1.3% by weight
Shall be included. The remainder is T derived from the alloy for the compact, M derived from the alloy for infiltration, and the like.
[0055]
<Pulverization>
The infiltrated body is pulverized into magnet powder. The pulverization method is not particularly limited, and a mechanical pulverization method, a hydrogen storage pulverization method, or the like may be appropriately selected, and pulverization may be performed by combining these methods. In the case of using the hydrogen absorbing and pulverizing method, hydrogen may be directly occluded in the infiltrated body, or may be occluded after the infiltrated body is crushed by a mechanical pulverizing means. However, when hydrogen storage grinding is used, the phase structure of the grain boundary may change due to hydrogen storage, which deteriorates the magnetic properties. Preferably, a treatment is applied.
[0056]
The particle size of the magnet powder is not particularly limited, but is preferably 100 to 500 μm, more preferably 125 to 250 μm when applied to a bonded magnet or a warm-formed magnet. If the particle size is too small, the oxidation resistance will be insufficient, and the coercive force will significantly deteriorate. On the other hand, if the particle diameter is too large, the moldability when applied to a bonded magnet or a warm-formed magnet is deteriorated, and a high filling rate cannot be obtained. The particle size in this case means the range of the particle size overcut and undercut by classification using a sieve or the like.
[0057]
The particles constituting the magnet powder are usually polycrystals, and the average crystal grain size (average main phase diameter) is preferably 0.5 to 10 μm, more preferably 1 to 5 μm. It is extremely difficult to reduce the average crystal grain size to less than 0.5 μm without significantly increasing the amount of oxygen in the powder due to the production method. On the other hand, if the average crystal grain size exceeds 10 μm, the probability that the main phase is broken by the stress at the time of pulverizing the infiltrated body or at the time of molding the magnet powder is increased, and thus the coercive force tends to deteriorate.
[0058]
The magnet powder of the present invention usually has a coercive force of 5 kOe or more.
[0059]
<Bonded magnet>
A bonded magnet is produced by combining magnet powder with a binder. The magnet powder of the present invention can be applied to either a compression bonded magnet using press molding or an injection bonded magnet using injection molding. A bonded magnet can also be obtained by impregnating a molded body of magnet powder with a binder. As the binder, various resins are preferably used, but a metal bonded magnet can also be used by using a metal binder. The type of the resin binder is not particularly limited, and may be appropriately selected from various thermosetting resins such as epoxy resin and nylon and various thermoplastic resins according to the purpose. The type of the metal binder is not particularly limited. In addition, there are no particular restrictions on various conditions such as the content ratio of the binder to the magnet powder and the pressure at the time of molding, and it may be appropriately selected from a normal range. However, it is preferable to avoid a method requiring high-temperature heat treatment in order to prevent coarsening of crystal grains.
[0060]
An anisotropic bonded magnet can be produced by impregnating a compact obtained by molding an anisotropic magnet powder in a magnetic field with a binder. It can also be produced by applying a magnetic field during compression molding or injection molding.
[0061]
<Warm formed magnet>
The warm-formed magnet is produced by warm-forming the magnet powder using a hot press or the like. Warm forming conditions are not particularly limited, and various conditions such as temperature and pressure are in a normal range, for example, about 400 to 800 ° C., 0.1 to 3 t / cm.Two What is necessary is just to select suitably from the range of a degree. In order to produce an anisotropic warm-formed magnet, a magnetic field may be applied in the initial stage of warm forming (at least below the Curie point of the magnet powder). After the temporary forming in a magnetic field, the warm forming may be performed without applying a magnetic field.
[0062]
【Example】
Hereinafter, specific examples of the present invention will be shown, and the present invention will be described in more detail.
[0063]
<Example 1: magnet powder>
The magnet powder shown in Table 1 was produced by the method shown below.
[0064]
Magnet powder No. 1-1 to 1-8
First, an ingot of an alloy for a compact was cast by high-frequency melting in an Ar gas atmosphere. The composition of the ingot is in percent by weight
(30Nd-3.5Dy) -1.1B-balance Fe
And The ingot was mechanically pulverized in a nitrogen gas atmosphere, and then pulverized with a jet mill in a stream of nitrogen gas to obtain an alloy powder for a compact having an average particle diameter of 4.5 μm. This alloy powder for compacts was pressed in a magnetic field of 15 kOe in a direction perpendicular to the direction of the magnetic field to form a compact having a rectangular parallelepiped shape of 120 mm × 40 mm × 30 mm. The density of this compact is 5.00 g / cmThree Met.
[0065]
Next, an infiltration alloy was manufactured by arc melting in an Ar gas atmosphere. The composition of the infiltration alloy is expressed as a percentage by weight.
12Co-17Cu-balance Fe
And
[0066]
Next, an infiltration alloy crushed into several millimeters square was placed on a compact of the alloy powder for a compact, and heat-treated in a vacuum at 1000 ° C. for 2 hours. Table 1 shows the volume ratio of the infiltrating alloy to the voids in the compact. After cooling, aging treatment was performed at 580 ° C. for 1 hour in an Ar atmosphere. Table 1 shows the average crystal grain size (average main phase diameter), density, residual magnetic flux density Br, coercive force Hcj, and maximum energy product (BH) max of each infiltrated body.
[0067]
The infiltrated body was mechanically pulverized and then classified to obtain a magnet powder having a particle diameter of 125 to 250 μm. The magnetic properties of these magnet powders were measured. In the case of magnet powder Nos. 1-1 and 1-2, pulverization was performed after removing excess infiltration alloy remaining on the surface of the infiltrated body.
[0068]
Magnet powder No. 1-9 (comparative example)
The compact was subjected to the heat treatment without placing the alloy for infiltration, and then mechanically pulverized and classified to obtain magnet powder. The value shown as the density of the infiltrated body in Table 1 is the density of the molded body after the heat treatment.
[0069]
Magnet powder No. 1-10 (comparative example)
As with ordinary sintered magnets, the density is 4.20 g / cmThree Was baked at 1070 ° C. for 4 hours, quenched, and then subjected to an aging treatment at 600 ° C. for 1 hour to obtain a sintered body, which was mechanically pulverized and classified to obtain a magnet powder. The value shown as the infiltration body density in Table 1 is the density of the sintered body.
[0070]
Magnet powder No. 1-11 (comparative example)
A magnet body was produced by a so-called two-alloy method, and this was pulverized and classified to obtain a magnet powder. First, the alloy for infiltration was mechanically pulverized in a nitrogen gas atmosphere, and then pulverized with a jet mill in a stream of nitrogen gas to obtain a powder having an average particle diameter of 3.0 μm. This powder and the alloy powder for a compact were mixed so that the weight ratio of the alloy powder for infiltration / the compact was 0.3 by weight. Next, a magnet body was obtained by performing molding in a magnetic field, heat treatment and aging treatment in the same manner as in the case of magnet powder No. 1-1, and this was ground and classified to obtain magnet powder. The value shown as the infiltration body density in Table 1 is the density of the magnet body.
[0071]
These magnet powders were also measured in the same manner as described above. Table 1 shows the results.
[0072]
[Table 1]
Figure 0003540438
[0073]
Table 1 clearly shows the effect of the present invention. In the magnet powder of the present invention, a coercive force of 5 kOe or more was obtained, whereas the coercive force of Nos. 1-9 and 1-10 produced without infiltration was low. No. 1-10 is more sintered than No. 1-9, so that the coercive force of the infiltrated body is high, but the coercive force is significantly reduced by pulverization. In No. 1-11, the alloy for infiltration, which is a grain boundary component, was mixed by an ordinary two-alloy method, so that unlike the present invention using infiltration, the coercive force was significantly reduced by pulverization.
[0074]
<Example 2: magnet powder>
Table 2 shows the average particle size of the alloy powder for the compact and the conditions of the heat treatment applied to the infiltrated body. Except for these, a magnet powder was produced in the same manner as in No. 1-3 of Example 1. The same measurement as in Example 1 was performed on these magnet powders. Table 2 shows the results.
[0075]
[Table 2]
Figure 0003540438
[0076]
Table 2 shows that particularly high coercive force is obtained when the average main phase diameter of the magnet powder is 10 μm or less.
[0077]
<Example 3: Magnet powder>
A magnet powder was manufactured in the same manner as in No. 1-3 of Example 1 except that the alloy for infiltration having the composition shown in Table 3 was used. The same measurement as in Example 1 was performed on these magnet powders. Table 3 shows the results.
[0078]
[Table 3]
Figure 0003540438
[0079]
From Table 3, it is found that a coercive force of 5 kOe or more can be obtained even when a quaternary composition infiltration alloy obtained by further adding other elements to Nd-Co-Cu is used. It can be seen that the decrease in coercive force is particularly suppressed.
[0080]
<Example 4: Anisotropic bonded magnet>
In a magnetic field of 15 kOe, the magnetic powder produced in the above example was placed in parallel with the magnetic field direction at 4 t / cm.Two , And heat-treated at 580 ° C. for 1 hour in an Ar atmosphere, and then impregnated with a silicon resin. The average crystal grain size of the magnet powder was not changed by the molding and the heat treatment. Table 4 shows the density and magnetic properties of the obtained bonded magnet.
[0081]
[Table 4]
Figure 0003540438
[0082]
<Example 5: Anisotropic warm formed magnet>
In a magnetic field of 15 kOe, the magnetic powder produced in the above example was placed in parallel with the magnetic field direction at 4 t / cm.Two After molding by applying pressure of 0.5 t / cm at 650 ° CTwo For 30 minutes to perform warm forming. Table 5 shows the density and magnetic properties of the obtained warm-formed magnet.
[0083]
[Table 5]
Figure 0003540438
[0084]
The effects of the present invention are apparent from the results of the above examples.

Claims (5)

R(Rは、Yを含む希土類元素の少なくとも1種である)、T(Tは、Feであるか、Co、NiおよびCuの少なくとも1種ならびにFeである)およびBを含有し、実質的にR214Bからなる相を含む成形体用合金と、Rを含み、R214BよりもRリッチな溶浸用合金とを用い、溶融した溶浸用合金を、成形体用合金の粉末の成形体に溶浸させて溶浸体を得、この溶浸体を粉砕して磁石粉末を得る工程を有する磁石の製造方法。Substantially containing R (R is at least one kind of rare earth element including Y), T (T is Fe or at least one kind of Co, Ni and Cu and Fe), and B, Using an alloy for compacts containing a phase consisting of R 2 T 14 B and an alloy for infiltration containing R and richer than R 2 T 14 B; A method for manufacturing a magnet, comprising the steps of infiltrating a molded body of an alloy powder to obtain an infiltrated body, and pulverizing the infiltrated body to obtain magnet powder. 実質的にR214B相(Rは、Yを含む希土類元素の少なくとも1種であり、Tは、Feであるか、Co、NiおよびCuの少なくとも1種ならびにFeである)からなる主相と、R214BよりもRリッチであり、前記主相を包囲する副相とを含む多結晶体であり、平均主相径が0.5〜10μ m、粒子径100〜500μm 、保磁力5 kOe以上である磁石粉末を含む磁石。A main phase substantially composed of an R 2 T 14 B phase (R is at least one kind of rare earth element including Y, and T is Fe or at least one kind of Co, Ni and Cu, and Fe). a phase, than R 2 T 14 B is R-rich, a subphase and the including polycrystalline body surrounding the main phase, the average main phase size 0.5~10Myu m, particle diameter 100~500μm And a magnet containing a magnet powder having a coercive force of 5 kOe or more. 前記磁石粉末をバインダで結合したボンディッド磁石である請求項2の磁石。 3. The magnet according to claim 2, wherein the magnet powder is a bonded magnet in which the magnet powder is bonded with a binder. 前記磁石粉末を温間成形した温間成形磁石である請求項2の磁石。The magnet according to claim 2, wherein the magnet is a warm-formed magnet obtained by warm-forming the magnet powder. 請求項1の磁石の製造方法により製造されたものである請求項2〜のいずれかの磁石。The magnet according to any one of claims 2 to 4 , which is manufactured by the method for manufacturing a magnet according to claim 1.
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