JP2004256877A - Dehydrogenation method, hydrogen atomizing method, and method for manufacturing rare-earth permanent magnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide techniques for shortening the length of time required for a dehydrogenation process, improving atomization in an atomizing step, and improving the magnetic properties of a magnet as a final product. <P>SOLUTION: As to a dehydrogenation method, a metal is disposed in an inert gas atmosphere and temperature inside a furnace is raised. After the inside of the furnace is formed into vacuum state, temperature is further raised. In an example 1 where the temperature inside the furnace is raised while making the atmosphere inside the furnace inert at first, dehydrogenation treatment is completed in a shorter time than in the case of a comparative example 1 wherein temperature raising is started after the inside of the furnace is formed into vacuum state; further, the precipitation of α-Fe is more suppressed than in the case of a comparative example 2 where dehydrogenation treatment is completed while keeping the inert gas atmosphere as such. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００６】
また、特許文献１および２に示された工程（Ｂ）では、吸水素の段階では炉内雰囲気をＨ_２とし、炉内圧力を２００Ｔｏｒｒ〜５０ｋｇ／ｃｍ^２として処理を行い、脱水素の段階では、炉内温度を１００℃以上に昇温させ、処理を行っている。
【０００７】
【発明が解決しようとする課題】
しかしながら、工程（Ａ）のように、脱水素の段階で炉内雰囲気をＡｒガスに置換し、６００℃で処理を行うと、金属間化合物が分解反応を起こし、硬度の高いα―Ｆｅが析出する。その結果、脱水素後に行われる微粉砕工程における粉砕性の低下や、最終的に得られる磁石の磁気特性が損なわれるという問題がある。
【０００８】
これに対し、表１の工程（Ｃ）に示すように、脱水素の処理を真空中で行うことにより、α―Ｆｅの析出を抑制する記述が既に提案されている（例えば、特許文献３。）。
【０００９】
【特許文献３】
特開平５−１０１９１８号公報
【００１０】
脱水素の処理を真空中で行うには、その前段の吸水素の段階で、炉内雰囲気を大気圧のＨ_２として処理を行っているため、水素吸収処理が完了した時点で真空ポンプを作動させ、炉内圧力を真空状態にしなければならない。このとき、このような処理を行う処理炉では、真空度に基づいた管理（炉の作動制御）を行っているのが一般的である。
このため、図１７に示すように、水素吸収処理の完了後、真空ポンプを作動させ、炉内が所定の真空度に到達した時点で、ヒータを作動させて炉内の加熱を開始する（図１７において（ｄ）の部分）わけであるが、吸水素完了直後の被処理粉末から排出される水素の量は多く、所定の真空度に到達するまでに時間が掛かる。また、ヒータを作動させて炉内の加熱を開始すると、所定の温度（例えば３２０℃付近）で、被処理粉末から水素が放出され、これによって炉内の真空度が低下する。これによってヒータの作動が停止されるとともに、所定の真空度に到達するまで真空ポンプが作動し（図１７において（ｅ）の部分）、ここでも時間を要することになる。その結果、炉内温度を最終的に予め設定した温度まで昇温させて脱水素処理を完了するまでに長い時間がかかり、水素粉砕工程全体が長時間化してしまうのである。
【００１１】
本発明は、このような技術的課題に基づいてなされたもので、脱水素処理の短時間化、微粉砕工程における粉砕性の向上、最終的に得られる磁石の磁気特性の向上を図ることのできる技術を提供することを目的とする。
【００１２】
【課題を解決するための手段】
本発明者は、不活性ガス雰囲気中で金属を加熱した後、雰囲気を真空状態とし、さらに加熱を行うことで、微粉砕工程における粉砕性、および最終的に得られる磁石の磁気特性を向上させつつ、短時間で脱水素処理が行えることを見出した。
これに基づいてなされた本発明の脱水素方法は、金属（合金を含む概念である）を不活性ガスが導入された雰囲気の炉内に配置し、炉内を第１の温度まで昇温させた後に炉内を所定以上の真空度とし、しかる後に、第１の温度より高い第２の温度まで炉内を昇温させることを特徴とする。
このとき、第１の温度は、金属中から水素が大量に放出される温度を上回る、例えば３３０〜４００℃とし、所定時間だけ維持するのが好ましい。また、炉内を第１の温度に維持している間に、炉内の真空引きを開始するのが好ましい。さらに、第１の温度で時間を維持することなく真空引きを開始し、所定以上の真空度にすることも可能である。
また、第２の温度についても、例えば４５０〜８００℃とし、所定時間だけ維持するのが好ましい。
【００１３】
本発明の水素粉砕方法は、金属に水素を吸収させる吸収工程と、水素が吸収された金属から水素を放出させる脱水素工程と、を備え、脱水素工程は、不活性ガスが導入された雰囲気下に金属を配置し、雰囲気の昇温を開始した後、雰囲気が所定の温度に至るまでの過程で雰囲気を所定の圧力以下に減圧させることを特徴とする。
このとき、雰囲気の減圧を開始するに際しては、雰囲気の温度を所定時間一定に保持した後に、減圧を開始するのが好ましい。このときの温度保持時間は、０．１〜５時間とし、保持温度は、例えば３３０〜４００℃の範囲内で設定することができる。
また、雰囲気が所定の温度に至った時点で、その雰囲気の温度を所定時間保持するのが好ましい。このときは、保持時間を２時間以上とし、保持温度は、例えば４５０〜８００℃の範囲内で設定することができる。
また、減圧後の所定の圧力は、ほぼ真空状態（例えば１．０×１０^−１Ｔｏｒｒ以下）とするのが好ましい。
【００１４】
ところで、吸収工程が実質的に水素からなる雰囲気下で終了する場合、この吸収工程の後、雰囲気中に導入するガスを水素から不活性ガスに切り替えた後に脱水素工程を行うのが好ましい。
【００１５】
本発明は、Ｒ−Ｔ−Ｂ（Ｒ＝Ｙを含む希土類元素の１種または２種以上、Ｔ＝ＦｅおよびＣｏの１種または２種、Ｂ＝ホウ素）系希土類永久磁石を製造する方法として捉えることもできる。この方法は、所定形態の原料合金の一部または全部に水素吸収および脱水素処理を施して水素粉砕物を得る工程と、水素粉砕物、または水素粉砕物を機械的な手段により粉砕した粉末を微粉砕して微粉砕粉末を得る工程と、微粉砕粉末を磁場中で所定形状に成形した後に焼結する工程と、を含む。そして、脱水素処理は、不活性ガスが導入された雰囲気下に配置した原料合金を、第１の温度まで昇温させた後、雰囲気の真空度を所定以上に高めるとともに、原料合金を第１の温度より高い第２の温度まで昇温させる。
このとき、原料合金は、最終的に得られる希土類永久磁石と実質的に一致する組成を有する合金とすることもできるし、Ｒ_２Ｆｅ_１４Ｂ化合物を主体とするＲ−Ｔ−Ｂ合金およびＲおよびＴを主体とするＲ−Ｔ合金を含むものとすることもできる。前者がシングル法、後者が混合法と称される製造方法を示している。なお、後者については、３種類以上の合金からなる場合をも含む。
【００１６】
ところで、上記したような水素吸収工程で行われる水素吸収反応は発熱反応であるが、温度上昇に伴って吸収水素量が低下すること、冷却等に要する時間が長くなり生産性の低下を招く。しかし、現状、水素吸収反応時の温度上昇を抑制し、かつ長時間を要することなく水素吸収を行うことのできる方法は見当たらない。
そのような方法について模索していた本発明者らは、水素吸収を、当初、水素ガスのみで開始した後に、水素濃度を低下させるために水素に対して不活性ガスを所定量混入させたところ、水素吸収による金属の発熱反応を抑えることができることを知見した。そして、その後に不活性ガスの混入を停止して、再度水素のみの雰囲気で水素吸収を継続したところ、長時間を要することなく水素吸収を完了できた。つまり、水素吸収処理において、水素の濃度を変化させることにより、短時間でかつ発熱反応を抑制した水素吸収処理を行うことができることを知見した。
このような知見に基づき、金属に水素を吸収させる方法として、金属を水素濃度（ａ）の水素雰囲気に晒し、所定の時期以降に水素雰囲気の水素濃度を水素濃度（ｂ）に低下させ、水素雰囲気を水素濃度（ｂ）に所定時間だけ維持した後に、水素濃度（ｃ）に上昇させることを特徴とすることもできる。
【００１７】
以上の水素吸収方法において、水素雰囲気は所定の処理室内に形成される。そして、典型的には、水素濃度（ａ）の水素雰囲気は、この処理室に水素ガスのみを導入することにより形成することができる。
また、水素濃度（ｂ）の水素雰囲気は、水素ガスが導入されている処理室に不活性ガスを導入することにより形成することができる。不活性ガスの導入により処理室内の水素濃度は低下する。
さらに、水素濃度（ｃ）の水素雰囲気は、処理室への不活性ガスの導入を停止するとともに水素ガスを導入することにより形成することができる。水素濃度（ｃ）は、水素濃度（ｂ）を超え、水素濃度（ａ）以下の範囲で選択することができる。
【００１８】
以上では水素吸収までを対象としたが、この方法は、前記の、金属に水素を吸収させる吸収工程と、水素が吸収された金属から水素を放出させる脱水素工程という基本的に２つの工程を有する水素粉砕方法に適用することもできる。すなわち、吸収工程では、実質的に水素からなる第１の雰囲気に金属を配置し、第１の雰囲気中に不活性ガスを供給することにより第２の雰囲気とし、さらに、第２の雰囲気への不活性ガスの供給を停止するとともに水素ガスを供給することにより実質的に水素からなる第１の雰囲気に戻すのである。
以上の特徴ある水素吸収工程を含む構成により、水素吸収工程における発熱反応を抑制し、かつ長時間を要することなく吸収工程を完了させることができるので、水素粉砕を効率よく行うことを可能とする。
【００１９】
また、第１の雰囲気中への不活性ガスの供給は、金属が水素の吸収を開始した直後から行うことが望ましい。発熱反応を有効に抑制するためである。
さらに、第２の雰囲気は、その水素濃度を９８〜９９．５％の範囲に制御することが望ましい。発熱反応を抑制しつつ水素吸収を進行させるためである。
【００２０】
以上の水素吸収方法ないし水素粉砕方法を適用したＲ−Ｔ−Ｂ（Ｒ＝Ｙを含む希土類元素の１種または２種以上、Ｔ＝ＦｅおよびＣｏの１種または２種、Ｂ＝ホウ素）系希土類永久磁石の製造方法を提供することもできる。この方法は、所定形態の原料合金の一部または全部を水素吸収および脱水素処理を施して水素粉砕物を得る工程と、水素粉砕物または水素粉砕物を機械的な手段により粉砕した粉末を微粉砕して微粉砕粉末を得る工程と、微粉砕粉末を所定形状に成形した後に焼結する工程とを含む。そして、脱水素処理では、不活性ガスからなる雰囲気下に配置した原料合金を、第１の温度まで昇温させた後、雰囲気の真空度を所定以上に高めるとともに、原料合金を第１の温度より高い第２の温度まで昇温させる。また、水素吸収処理では、原料合金を水素濃度（ａ）の水素雰囲気に晒し、所定の時期以降に水素雰囲気の水素濃度を水素濃度（ｂ）に低下させ、水素雰囲気を水素濃度（ｂ）に所定時間だけ維持した後に、水素濃度（ｃ）に上昇させる。
【００２１】
【発明の実施の形態】
以下、本発明の実施の形態について説明する。
本発明の脱水素方法は、金属を不活性ガス雰囲気の炉内に配置し、炉内を第１の温度まで昇温させた後に炉内を所定以上の真空度とし、しかる後に、第１の温度より高い第２の温度まで炉内を昇温させる。このように、不活性ガス中で炉内温度を昇温することで、金属に含まれる水素を効率的に放出させることができる。そして、不活性ガス中で、脱水素処理の最終処理温度まで昇温してしまうと、金属中にα―Ｆｅが析出してしまうため、これを防止するために炉内を真空状態とするのである。
このとき、第１の温度を、３３０℃以上とすることで、金属に含まれる水素が大量に放出される温度域（例えば３２０℃付近）において、雰囲気を不活性ガスとしておき、無用に真空引きすることを防ぐ。また、第１の温度を４００℃以下とすることで、不活性ガス雰囲気下でα―Ｆｅが合金中に析出するのを防ぐ。この第１の温度は、脱水素を促すため、所定時間、好ましくは０．５〜５時間だけ維持する。
そして、炉内を第１の温度に維持している間に、炉内の真空引きを開始する。炉内の真空度が１．０×１０^−１Ｔｏｒｒ以下となった時点で、炉内の昇温を再開し、第２の温度まで昇温させる。
第２の温度は、４５０〜８００℃とし、この温度を２時間以上保持するのが好ましい。このとき、炉内の真空状態を維持するため、炉内の真空引き（排気）は継続しておく。
【００２２】
金属を水素粉砕する場合、上記の脱水素方法を適用できる。
この場合、金属に水素を吸収させる水素吸収処理を経た後、上記の脱水素処理に移行する。
水素吸収処理においては、金属を、当初、水素濃度（ａ）の水素雰囲気に晒し、所定の時期以降に水素雰囲気の水素濃度を水素濃度（ｂ）に低下させるようにしても良い。もちろん、水素濃度（ａ）は、水素濃度（ｂ）より高い。水素濃度（ａ）は、例えば、実質的に水素ガスからなる雰囲気下で実現される。この雰囲気は、金属への水素吸収を促進するために、密閉容器内で形成することができる。このときの水素ガス圧は、０．０５〜２．５ｋｇｆ／ｃｍ^２の範囲とすることが望ましい。０．０５ｋｇｆ／ｃｍ^２未満で、水素吸収速度が遅くなり、十分な粉砕効果が得られず効率的な操業を妨げるのみならず安全性の面から０．０５ｋｇｆ／ｃｍ^２以上とすることが望ましい。また、２．５ｋｇｆ／ｃｍ^２を超えると水素との反応熱の増加が著しくなるためである。よって、水素ガス圧は０．２〜２．５ｋｇｆ／ｃｍ^２とするのが望ましい。なお、本明細書において、実質的に水素ガスからなるとは、水素以外の他のガスを意識的に含ませないことを意味する。例えば、工業的生産には９９．９９ｖｏｌ．％以上の純度を有する水素ガスが用いられている。この水素ガスは、Ｎ_２＜５０ｖｏｌ．ｐｐｍ、Ｏ_２＜１ｖｏｌ．ｐｐｍ程度の微量の不純物の含有を許容している。本明細書でいうところの実質的に水素ガスからなるとは、水素ガス以外のこのような微量ガス成分の含有を許容している。
【００２３】
水素濃度（ｂ）は、例えば水素濃度（ａ）の雰囲気が水素ガスのみから構成されている場合には所定量の不活性ガスを導入することにより形成できる。不活性ガスの導入により、水素吸収の程度を低減して反応熱の発生を抑制する。ただし、水素濃度（ｂ）が低くなると、水素吸収速度が低下して、水素吸収を完了するまでに要する時間が長くなる。したがって、水素吸収を迅速に完了させるためには、水素濃度を９８〜９９．５％の範囲とすることが望ましい。不活性ガスの導入は、金属が水素の吸収を開始した直後から行うのが望ましい。水素吸収による発熱反応を抑制するためである。なお、金属が水素の吸収を開始したことは、水素吸収処理を行う雰囲気の圧力の変化、具体的には圧力の低下を検知することにより知ることができる。
【００２４】
水素濃度（ｂ）による水素吸収処理を経たならば、次に水素吸収の雰囲気を水素濃度（ｃ）に上げる。水素濃度（ｂ）の雰囲気を得るために、不活性ガスを導入していたならば、その導入を停止し、水素吸収の雰囲気を水素ガスのみとすることにより、水素濃度（ｃ）の雰囲気を形成することができる。または、不活性ガスの導入量を、水素濃度（ｂ）のときよりも低減することによっても水素濃度（ｃ）の雰囲気を形成することができる。水素吸収がある程度進行すると、発熱反応が低減されるため、それに応じて水素濃度を高くする。
【００２５】
上記の、水素吸収処理が終了した後に、前記脱水素処理に移行するのである。この処理は、金属中に吸収された水素量を減少させること、具体的には水素化物を安定な価数状態とすることにより、その後の大気中におけるハンドリングの安定性を向上させることを目的として行われる。
このとき、水素吸収処理は、実質的に水素からなる雰囲気下で終了する。このため、吸収処理の後、雰囲気中に導入するガスを水素から不活性ガスに切り替えた後に脱水素工程が行われる。
【００２６】
本発明の脱水素方法は、Ｒ−Ｔ−Ｂ系希土類永久磁石の製造方法に適用することができる。Ｒ−Ｔ−Ｂ系合金は、特に粉砕し難い金属間化合物（Ｒ_２Ｆｅ_１４Ｂ）を含むため、水素粉砕方法が適用されている。図１は、本発明の希土類永久磁石の製造方法の工程の流れを示すものである。
はじめに、所定形態の原料合金の一部または全部を水素吸収および脱水素処理を施して水素粉砕し、水素粉砕物を得る。原料合金としては、鋳型を用いて得た鋳塊、ストリップキャスト法によるストリップ、その他のいかなる形態の合金をも対象とすることができる。ただし、水素吸収に供する合金のサイズが大きすぎると、水素吸収効率が低下する。１つの尺度として、鋳塊であれば厚さが３０ｍｍ以下とすることが望ましい。
【００２７】
Ｒ−Ｔ−Ｂ系希土類永久磁石は、最終的に得たい合金組成と一致する原料合金を用いて製造するシングル法と、最終的に得たい合金組成を構成する複数の合金を組み合わせる混合法とが知られている（図１は混合法による例である）。シングル法によりＲ−Ｔ−Ｂ系希土類永久磁石を製造する場合には、一般に、原料合金の全部を水素吸収および脱水素処理に供する。混合法によりＲ−Ｔ−Ｂ系希土類永久磁石を製造する場合には、複数の合金のうちの一部の合金に対して水素吸収および脱水素処理を施しても良いし、または複数の合金の全部について水素吸収および脱水素処理を施しても良い。
【００２８】
水素吸収および脱水素処理により粉砕された原料合金は、それぞれ必要に応じて粒径数百μｍ程度になるまで粗粉砕される。粗粉砕は、スタンプミル、ジョークラッシャー、ブラウンミル等の機械的粉砕手段を用い、不活性ガス雰囲気中にて行うことが望ましい。
水素吸収および脱水素処理による粉砕または上記粗粉砕後、微粉砕工程に移る。微粉砕は、主にジェットミルが用いられ、粒径数百μｍ程度の粗粉砕粉末が、平均粒径３〜５μｍになるまで行われる。ジェットミルは、高圧の不活性ガス（例えば窒素ガス）を狭いノズルより開放して高速のガス流を発生させ、この高速のガス流により粉体の粒子を加速し、粉体の粒子同士の衝突やターゲットあるいは容器壁との衝突を発生させて粉砕する方法である。
微粉砕で得られた粉末は、磁場中成形に供される。このとき、混合法を用いた場合、磁場中での成形に先立ち、粉末を混合して組成配合を行う。
加圧成形の際に、磁場を印加することにより結晶軸を配向させるが、微粉砕時に添加された潤滑剤が配向度の向上に寄与する。この磁場中成形は、１０〜１６ｋＯｅの磁場中で、１〜１．６ｔｏｎ／ｃｍ^２前後の圧力で行えばよい。
【００２９】
磁場中成形後、その成形体を真空または不活性ガス雰囲気中で焼結する。焼結温度は、組成、粉砕方法、粒度と粒度分布の違い等、諸条件により調整する必要があるが、１０００〜１１３０℃で１〜５時間程度焼結すればよい。
焼結後、得られた焼結体に時効処理を施すことができる。この工程は、保磁力Ｈｃｊを制御する重要な工程である。時効処理を二段に分けて行う場合には、８００℃近傍、６００℃近傍での所定時間の保持が有効である。８００℃近傍での熱処理を焼結後に行うと、保磁力Ｈｃｊが増大するため、混合法においては特に有効である。また、６００℃近傍の熱処理で保磁力Ｈｃｊが大きく増加するため、時効処理を一段で行う場合には、６００℃近傍の時効処理を施すとよい。
【００３０】
本発明が適用されるＲ−Ｔ−Ｂ系希土類永久磁石の組成は目的に応じ選択すればよいが、磁気特性に優れた希磁石を得るためには、焼結後の磁石組成において希土類元素Ｒ：２０〜４０ｗｔ％、ホウ素Ｂ：０．５〜４．５ｗｔ％、Ｔ（ＦｅおよびＣｏの１種または２種）：残部、となるような配合組成とすることが望ましい。ここで、希土類元素Ｒは、Ｙを含む希土類元素（Ｌａ，Ｃｅ，Ｐｒ，Ｎｄ，Ｓｍ，Ｅｕ，Ｇｄ，Ｔｂ，Ｄｙ，Ｈｏ，Ｅｒ，ＹｂおよびＬｕ）の１種または２種以上である。希土類元素Ｒの量が２０ｗｔ％未満であると、希土類永久磁石の主相となるＲ_２Ｆｅ_１４Ｂ相の生成が十分ではなく軟磁性を持つα−Ｆｅなどが析出し、保磁力Ｈｃｊが著しく低下する。一方、希土類元素Ｒが４０ｗｔ％を超えると主相であるＲ_２Ｆｅ_１４Ｂ相の体積比率が低下し、残留磁束密度Ｂｒが低下する。また希土類元素Ｒが酸素と反応し、含有する酸素量が増え、これに伴い保磁力発生に有効なＲ−ｒｉｃｈ相が減少し、保磁力Ｈｃｊの低下を招くため、希土類元素Ｒの量は２０〜４０ｗｔ％とする。Ｎｄは資源的に豊富で比較的安価であることから、希土類元素Ｒとしての主成分をＮｄとすることが好ましい。またＤｙは異方性磁界が大きく、保磁力Ｈｃｊを向上させる上で有効である。
【００３１】
また、ホウ素Ｂが０．５ｗｔ％未満の場合には高い保磁力Ｈｃｊを得ることができない。ただし、ホウ素Ｂが４．５ｗｔ％を超えると残留磁束密度Ｂｒが低下する傾向がある。したがって、上限を４．５ｗｔ％とする。望ましいホウ素Ｂの量は０．５〜１．５ｗｔ％である。
さらに、保磁力Ｈｃｊを改善するために、Ｍを加えてＲ−Ｔ−Ｂ−Ｍ系の希土類永久磁石とすることもできる。ここで、Ｍとしては、Ａｌ，Ｃｒ，Ｍｎ，Ｍｇ，Ｓｉ，Ｃｕ，Ｃ，Ｎｂ，Ｓｎ，Ｗ，Ｖ，Ｚｒ，Ｔｉ，Ｍｏ，Ｂｉ，ＡｇおよびＧａなどの元素を１種または２種以上添加することができるが、添加量が６ｗｔ％を超えると残留磁束密度Ｂｒが低下してくる。
【００３２】
【実施例】
＜検討実験１＞
ここで、上記の最終的な脱水素条件を検討するに先立ち、従来の、一般的に行われている方法により不活性ガス中で脱水素処理を行う場合と、特許文献３に記載された方法により真空中で脱水素処理を行った場合について、それぞれ処理温度による組成の違いを比較したので、その結果を示す。
原料合金として、主相合金として使用される合金、粒界相合金として使用される合金の、計２種類の合金を用いた。
主相合金は、３１ｗｔ％Ｎｄ−０．２％Ａｌ−１．１％Ｂ−ｂａｌ．Ｆｅの組成を有する、厚さ０．３５ｍｍのストリップキャスト合金を単ロール法により得た。この主相合金の金属間化合物は、Ｎｄ_２Ｆｅ_１４Ｂであり、残部はＮｄ−ｒｉｃｈ相となっている。
また、粒界相合金は、６０ｗｔ％Ｎｄ−５ｗｔ％Ｃｏ−０．１ｗｔ％Ｃｕ−０．２ｗｔ％Ａｌ−ｂａｌ．Ｆｅの組成を有する、厚さ９ｍｍの合金を、鉄製鋳型への鋳造により得た。この粒界相合金の金属間化合物は、Ｎｄ_２Ｆｅ_１７であり、残部はＮｄ−ｒｉｃｈ相となっている。
表２は、上記の原料合金を示すものである。
【００３３】
【表２】

【００３４】
得られた主相合金、粒界相合金を、それぞれ以下の条件（検討例１、検討例２）で、水素吸収処理、脱水素処理を経た後、その組成を解析した。
【００３５】
検討例１：不活性ガス中で脱水素処理を行った場合
［水素吸収処理］
（１）内容量６０Ｌの管状炉を用い、Ｍｏ製セッターに原料合金を８００ｇ入れ、炉内に設置した。このときの温度は室温である。
（２）炉内を真空ポンプにて１×１０^−１Ｔｏｒｒ以下（最高到達１×１０^−４Ｔｏｒｒ）まで排気した。
（３）炉内に水素ガスを導入、大気圧まで復圧させた。このとき、圧力低下を引き起こさないように水素ガスを供給し続けた。
（４）圧力低下が起こらなくなるまで水素を供給し続け、圧力低下が起こらなくなった時間で吸収終了とした。
［脱水素処理］
（５）水素吸収終了後、導入ガスをＡｒガスに切り替え、１気圧でＡｒガスをフローさせた。
（６）その直後、５℃／ｍｉｎで所定温度まで昇温、２時間保持した。このとき、保持した所定温度（以下、これを最終処理温度と適宜称する）は、２００、４００、５００、６００℃の４通りとした。
（７）２時間経過後、Ａｒガスを導入し、大気圧まで復圧した後、雰囲気を保ったまま急冷し、室温まで冷却した。
【００３６】
検討例２：真空中で脱水素処理を行った場合
（１）〜（４）の水素吸収処理：検討例１と同様。
（５）水素吸収終了後、導入ガスをＡｒガスに切り替え、１気圧でＡｒガスを０．５時間フローさせた（炉内の雰囲気をＡｒに変えた）。
（６）０．５時間後、真空ポンプにて１×１０^−１Ｔｏｒｒまで排気した。
（７）排気終了後、排気を継続したまま５℃／ｍｉｎで昇温した。途中、炉内圧力が１×１０^−１Ｔｏｒｒを超えることがあれば、１×１０^−１Ｔｏｒｒに到達するまで昇温を止めた。
（８）所定温度まで昇温後、２時間保持した。このとき、保持した所定温度は、２００、４００、５００、６００℃の４通りとした。
（９）２時間経過後、Ａｒガスを導入し、大気圧まで復圧した後、雰囲気を保ったまま急冷し室温まで冷却した。
【００３７】
さて、上記脱水素処理を経た、上記検討例１、検討例２の処理を経た原料合金（主相合金、粒界相合金）の状態をそれぞれＸ線回折によって確認した。
表３は、検討例１、検討例２によって得られた、主相合金中の金属間化合物（Ｎｄ_２Ｆｅ_１４Ｂ）の状態を示すものである。
【００３８】
【表３】

【００３９】
また、表４は粒界相合金の検討例１、検討例２の金属間化合物（Ｎｄ_２Ｆｅ_１４Ｂ）の状態を示すものである。
【００４０】
【表４】

【００４１】
また、表５は、検討例１、検討例２における、原料合金の金属間化合物以外の残部（Ｎｄ−ｒｉｃｈ相）の状態を示すものである。
【００４２】
【表５】

【００４３】
図２は、粒界相合金の検討例１におけるＸ線回折の測定結果を示すものであり、図３は、粒界相合金の検討例２のＸ線回折の測定結果を示すものである。なお、図３において、符号（ｆ）で示す曲線は、比較のために示した、検討例１の最終処理温度６００℃の結果である。
これらの結果から、不活性ガスをフローさせて脱水素処理を行った場合、表３に示したように、主相合金では、最終処理温度が２００、４００、５００℃では、α―Ｆｅの析出が認められないものの、６００℃の場合、α−Ｆｅの析出が認められる。
また、粒界相合金では、表４および図２に示したように、最終処理温度が２００、４００℃では、α―Ｆｅの析出が認められないものの、５００、６００℃の場合、α−Ｆｅの析出が認められる。
これに対し、真空中で脱水素処理を行った検討例２では、いずれの温度でもα―Ｆｅの析出が認められない。
【００４４】
また、主相合金、粒界相合金ともに、不活性ガス中で脱水素処理を行った検討例１では、表３、表４に示すように、最終処理温度が２００、４００℃のときに、表中でＮｄ_２Ｆｅ_１４ＢＨ、Ｎｄ_２Ｆｅ_１７Ｈと記載するように、金属間化合物の格子間に水素（Ｈ）が侵入（残留）している。
このことは、図２に示すように、２００、４００℃で金属間化合物による回折線が、５００、６００℃に比べ、低角側にシフトしており、金属間化合物の格子間に水素が侵入し、格子が膨張した結果であることからもわかる。またピークのシフトの大きさから、水素の残留量は、最終処理温度が２００℃のときより、４００℃のときのほうが少ないことがわかる。
これに対し、図３に示すように、真空中で脱水素処理を行った検討例２では、いずれの温度でも金属間化合物の格子間への水素（Ｈ）が侵入（残留）が認められない。
【００４５】
原料合金中の金属間化合物以外の残部（Ｎｄ−ｒｉｃｈ相）は、検討例１、検討例２ともに、表５に示すように２００、４００℃のときにＮｄＨ_３が存在し、５００、６００℃ではＮｄＨ_３より大気に対し安定なＮｄＨ_２となっている。これは図２、図３に示すように、２００℃のときにはＮｄＨ_３のピークが観察され、４００℃の時にはＮｄＨ_２とＮｄＨ_３の両方が存在するためにピーク幅が広がっていることからわかる。５００、６００℃においてはＮｄＨ_３のピークは観察されず、全てＮｄＨ_２となっている。
【００４６】
＜検討実験２＞
また、不活性ガス中で脱水素処理を行う場合、最終処理温度の保持時間の違いを比較した。
ここで、原料合金としては、検討例２と同様、主相合金として使用される合金、粒界相合金として使用される合金の、計２種類の合金を用いた。
得られた主相合金、粒界相合金を、それぞれ以下の条件（検討例３、検討例４）で、水素吸収処理、脱水素処理を経た後、その組成を解析した。
【００４７】
検討例３、４
［水素吸収処理］
（１）〜（４）、検討例２と同様
［脱水素処理］
（５）検討例２と同様、水素吸収終了後、導入ガスをＡｒガスに切り替え、１気圧でＡｒガスをフローさせた。
（６）その直後、５℃／ｍｉｎで所定温度まで昇温、２時間保持した。このとき、保持した所定温度（以下、これを最終処理温度と適宜称する）は、４００℃とした。
（７）最終処理温度を所定時間保持し、所定時間が経過した後、Ａｒガスを導入し、大気圧まで復圧した後、雰囲気を保ったまま急冷し、室温まで冷却した。このとき、最終処理温度の保持時間は、検討例３：検討例２と同様の２時間、検討例４：４時間とした。
【００４８】
上記検討例１、検討例２の処理を経た原料合金（粒界相合金）に対し、それぞれＸ線回折の測定を行った。
図４にその結果を示す。
この図４に示すように、検討例３よりも第１の温度での保持時間を長くした検討例４では、２８゜付近のＮｄＨ_３に対応するピーク強度が減少することから、ＮｄＨ_３の割合が減少していることが認められる。このＮｄＨ_３の減少分は、検討例１、２と同様にＮｄＨ_２になっている。また、金属間化合物であるＮｄ_２Ｆｅ_１７に対応するピークは、保持時間の延長により若干ではあるが高角側へのシフトが認められることから、残留水素量の低下による格子の収縮が起きていることがわかる。
【００４９】
これら検討実験１、２により、雰囲気を真空とすることでα―Ｆｅの析出が抑制され、また雰囲気温度を５００℃以上とすることで、大気に対してＮｄＨ_３より安定で、元合金中の酸素量の増加を抑制できるＮｄＨ_２を生成できることがわかる。
また、検討例３、４により、所定時間の温度保持により、残留水素量が低減できることがわかる。
【００５０】
＜実験例１＞
ここではまず、本発明を適用した場合と、特許文献３に記載された技術を適用した場合と、従来一般的に行われている手法を適用した場合との比較を行った。
原料合金として、主相合金として使用される合金、粒界相合金として使用される合金の、計２種類の合金を用いた。
主相合金は、３１ｗｔ％Ｎｄ−０．２％Ａｌ−１．１％Ｂ−ｂａｌ．Ｆｅの組成を有する、厚さ０．３５ｍｍのストリップキャスト合金を単ロール法により得た。
また、粒界相合金は、６０ｗｔ％Ｎｄ−５ｗｔ％Ｃｏ−０．１ｗｔ％Ｃｕ−０．２ｗｔ％Ａｌ−ｂａｌ．Ｆｅの組成を有する、厚さ９ｍｍの合金を、鉄製鋳型への鋳造により得た。
得られた主相合金、粒界相合金を、それぞれ以下の条件（実施例１、比較例１、比較例２）で、水素吸収処理、脱水素処理を経た後、粉砕した。
【００５１】
実施例１
［水素吸収処理］
（１）内容量６０Ｌの管状炉を用い、Ｍｏ製セッターに原料合金を８００ｇ入れ、炉内に設置した。このときの温度は室温である。
（２）炉内を真空ポンプにて１×１０^−１Ｔｏｒｒ以下（最高到達１×１０^−４Ｔｏｒｒ）まで排気した。
（３）炉内に水素ガスを導入、大気圧まで復圧させた。このとき、圧力低下を引き起こさないように水素ガスを供給し続けた。
（４）圧力低下が起こらなくなるまで水素を供給し続け、圧力低下が起こらなくなった時間で吸収終了とした。
［脱水素処理］
（５）水素吸収終了後、導入ガスをＡｒガスに切り替え、１気圧でＡｒガスをフローさせた。
（６）その直後、５℃／ｍｉｎで３５０℃まで昇温し、１時間温度を保持した。
（７）保持終了後、真空ポンプを用いて排気を行い、真空度が１．０×１０^−１Ｔｏｒｒ以下になるようにした。
（８）排気を継続したまま、５℃／ｍｉｎで５００℃まで昇温し、２時間保持した。
（９）２時間経過後、Ａｒガスを導入し、大気圧まで復圧した後、雰囲気を保ったまま急冷し室温まで冷却した。
【００５２】
比較例１：特許文献３に記載された工程に相当
（１）〜（４）の水素吸収処理：実施例１と同様。
（５）水素吸収終了後、導入ガスをＡｒガスに切り替え、１気圧でＡｒガスを０．５時間フローさせた（炉内の雰囲気をＡｒに変えた）。
（６）その後、真空ポンプにて１×１０^−１Ｔｏｒｒまで排気した。
（７）排気終了後、排気を継続したまま５℃／ｍｉｎで昇温した。途中、炉内圧力が１×１０^−１Ｔｏｒｒを超えることがあれば、１×１０^−１Ｔｏｒｒに到達するまで昇温を止めた。
（８）５００℃まで昇温後、２時間保持した。
（９）２時間経過後、Ａｒガスを導入し、大気圧まで復圧した後、雰囲気を保ったまま急冷し室温まで冷却した。
【００５３】
比較例２：従来一般的に行われていた工程に相当
（１）〜（４）の水素吸収処理：実施例１と同様。
（５）水素吸収終了後、導入ガスをＡｒガスに切り替え、１気圧でＡｒガスをフローさせた。
（６）その直後、５℃／ｍｉｎで５００℃まで昇温、２時間保持した。
（７）２時間経過後、雰囲気を保ったまま急冷し、室温まで冷却した。
【００５４】
以上の実施例１、比較例１、比較例２における、粒界相合金の、水素吸収処理終了時からの経過時間に対する炉体温度のプロファイルを図５に示す。また図６に、実施例１における脱水素処理時間に対する炉体温度および炉内圧力の変化プロファイルを示す。
図５に示すように、実施例１では、（ｇ）の部分で、前記（６）の工程での３５０℃で１時間保持し、およびその後の（７）の工程で真空引きを行っている。その結果、（８）の工程が完了するまでに５．５時間を要している。
比較例１では、（ｄ）の部分で、前記（６）の工程での１×１０^−１Ｔｏｒｒまでの真空引きを行っている。また、（ｅ）の部分では、（７）で真空引きを継続しつつ昇温している途中で、炉内圧力が１×１０^−１Ｔｏｒｒを上回ったために、昇温が止まっている。その結果、（８）の工程が完了するまでに、８．５時間を要している。
比較例２では、（６）の工程が完了するまでに、３．５時間余りを要している。
このように、実施例１によれば、脱水素処理を真空中で行う比較例１に比べれば、短時間で脱水素処理が終了していることがわかる。また、実施例１は、脱水素処理で炉内雰囲気をＡｒガスに置換する比較例２に比べると、脱水素処理に長時間を要しているものの、後述するように、実施例１により得られた永久磁石は、比較例２により得られた永久磁石を凌ぐ磁気特性を有している。
【００５５】
さて、上記脱水素処理を経た、上記実施例１、比較例１、比較例２の原料合金（主相合金、粒界相合金）をそれぞれ粉砕した。
これには、ディスクミルを用いて、機械粉砕を行ったのち、気流式粉砕機を用い微粉砕を行った。気流式粉砕機の粉砕圧は７ｋｇｆ／ｃｍ^２とした。
そして、得られた微粉の粒度分布はＳｙｍｐａｔｅｃ社製の乾式レーザー回折粒度分布計ＨＥＬＯＳ＆ＲＯＤＯＳを用いて測定した。微粉砕後の粒度分布を図７に、そのときの各粒径を表６に表す。
【００５６】
【表６】

【００５７】
図７において、主相合金については、比較例１、比較例２と顕著な差が認められなかったため、比較例１、比較例２の粒度分布を省略した。
粒界相合金（粉）は、実施例１に比べ、比較例２は、粒度が大きい。これについては、前述のα―Ｆｅの析出により粉砕性に悪影響が生じていることがわかる。
【００５８】
さて、上記の粉砕処理を経た、上記実施例１、比較例１、比較例２のそれぞれにおいて、主相合金微粉末と粒界相合金微粉末を混合し、その組成を３２ｗｔ％Ｎｄ−０．５％Ｃｏ−０．１％Ｃｕ−０．２％Ａｌ−ｂａｌ．Ｆｅとした。
そして、得られた混合微粉末を、１４ｋＯｅの配向磁界中、１．２ｔｏｎ／ｃｍ^２の圧力で横磁場成形した。得られた成形体を、１０３０℃・４時間（真空中）だけ焼結した後、８００℃×１時間、５８０℃ ×１時間の二段時効処理を施して、焼結体磁石を得た。得られた磁石の磁気特性を、Ｂ−Ｈトレーサを用い、室温にて測定した。その結果を表６に示した。
【００５９】
表６に示したように、実施例１は、磁気特性において、脱水素処理を真空中で行う比較例１に対しては、残留磁束密度Ｂｒに若干ではあるが優れ、保磁力ＨｃＪに関しては同等となっている。また、脱水素処理で炉内雰囲気をＡｒガスに置換する比較例２と比べると、実施例２は、残留磁束密度Ｂｒ、保磁力ＨｃＪともに凌いでいる。
【００６０】
以上のように、実施例１においては、比較例１に対しては脱水素処理の短時間化が図れ、比較例２に対しては磁気特性、粒度分布の面で優れていることが明らかである。つまり、従来よりも、磁気特性に優れる磁石を、短時間で、しかも微粉砕工程において優れた粉砕性で製造することができるのである。
【００６１】
＜実験例２＞
次に、脱水素処理で炉内を昇温する際の保持温度を変動させたときの、脱水素処理に要する時間、得られた焼結体磁石の磁気特性を比較した。
実施例２
原料合金としては、実施例１と同様、主相合金として使用される合金、粒界相合金として使用される合金の、計２種類の合金を用いた。
得られた主相合金、粒界相合金を、それぞれ以下の条件で、水素吸収処理、脱水素処理を経た後、粉砕した。
【００６２】
［水素吸収処理］
（１）〜（４）実施例１と同様。
［脱水素処理］
（５）水素吸収終了後、導入ガスをＡｒガスに切り替え、１気圧でＡｒガスをフローさせた。
（６）その直後、５℃／ｍｉｎで所定温度まで昇温し、１時間温度を保持した。このとき、前記の所定温度（保持温度）を、２５０、３００、３２０、３３０、３５０、３７５、４００、４５０、５００℃の９通りとした。
（７）所定温度での保持終了後、真空ポンプを用いて排気を行い、真空度が１．０×１０^−１Ｔｏｒｒ以下になるようにした。
（８）排気を継続したまま、５℃／ｍｉｎで５００℃まで昇温し、２時間保持した。
（９）２時間経過後、Ａｒガスを導入し、大気圧まで復圧した後、雰囲気を保ったまま急冷し室温まで冷却した。
【００６３】
以上の実施例２における、脱水素処理に要した時間を図８に示す。
図８に示すように、保持温度が３３０℃を下回った場合、脱水素に要する時間が長くなることがわかる。これは、３２０℃付近で大量に放出される水素を真空引きしているためである。
【００６４】
さて、上記脱水素処理を経た上記実施例２の原料合金（主相合金、粒界相合金）を、実験例１と同様、それぞれ粉砕した後、得られた主相合金微粉末と粒界相合金微粉末を混合して横磁場成形し、これにより得られた成形体を焼結、時効処理を施して、焼結体磁石を得た。得られた磁石の磁気特性を、Ｂ−Ｈトレーサを用い、室温にて測定した。得られた磁気特性のうち、残留磁束密度Ｂｒを図９に示す。
この図９に示すように、保持温度が４００℃を超えると、残留磁束密度Ｂｒが低下する傾向が見られる。これは、粒界相合金中の金属間化合物が分解し、α−Ｆｅが析出するために生じているためである。
【００６５】
このようにして、脱水素処理での保持温度を３３０〜４００℃の範囲内とすることで、脱水素に要する時間を短縮することができ、しかも磁気特性に優れた磁石を製造することができる。
【００６６】
＜実験例３＞
次に、脱水素処理で炉内を昇温する際の保持時間を変動させたときの、脱水素処理に要する時間を比較した。
実施例３
原料合金としては、実施例１と同様、主相合金として使用される合金、粒界相合金として使用される合金の、計２種類の合金を用いた。
得られた主相合金、粒界相合金を、それぞれ以下の条件で、水素吸収処理、脱水素処理を経た後、粉砕した。
【００６７】
［水素吸収処理］
（１）〜（４）実施例１と同様。
［脱水素処理］
（５）水素吸収終了後、導入ガスをＡｒガスに切り替え、１気圧でＡｒガスをフローさせた。
（６）その直後、５℃／ｍｉｎで３８０℃まで昇温し、０〜５時間の間の所定時間だけ温度を保持した。このとき、前記の保持時間は、０、０．５、１、２、３、５時間の６通りとした。
（７）所定温度での保持終了後、真空ポンプを用いて排気を行い、真空度が１．０×１０^−１Ｔｏｒｒ以下になるようにした。
（８）排気を継続したまま、５℃／ｍｉｎで５００℃まで昇温し、２時間保持した。
（９）２時間経過後、Ａｒガスを導入し、大気圧まで復圧した後、雰囲気を保ったまま急冷し室温まで冷却した。
【００６８】
以上の実施例３における、脱水素処理に要した時間を図１０に示す。
図１０に示すように、保持時間を０．５、１時間等とすることで、僅かながら脱水素に要する時間が減少している。しかし、保持時間が２時間を超えると、脱水素に要する時間が長くなることがわかる。これは、保持時間の延長分がそのまま脱水素に要する時間の延長に繋がっていることを示している。
これにより、脱水素の処理で所定の温度を保持した方が脱水素時間の短縮化が図れることがわかる。
【００６９】
＜実験例４＞
次に、脱水素処理の最終処理温度を変化させたときの、得られた焼結体磁石の磁気特性と酸素量を比較した。
実施例４
原料合金としては、実施例１と同様、主相合金として使用される合金、粒界相合金として使用される合金の、計２種類の合金を用いた。
得られた主相合金、粒界相合金を、それぞれ以下の条件で、水素吸収処理、脱水素処理を経た後、粉砕した。
【００７０】
［水素吸収処理］
（１）〜（４）実施例１と同様。
［脱水素処理］
（５）水素吸収終了後、導入ガスをＡｒガスに切り替え、１気圧でＡｒガスをフローさせた。
（６）その直後、５℃／ｍｉｎで昇温し、３５０℃で１時間温度を保持した。
（７）所定温度での保持終了後、真空ポンプを用いて排気を行い、真空度が１．０×１０^−１Ｔｏｒｒ以下になるようにした。
（８）排気を継続したまま、５℃／ｍｉｎで所定温度まで昇温し、２時間保持した。このとき、前記の所定温度（保持温度）としては、３５０、４００、５００、６００、７００、７５０、８００、８５０、９００℃の９通りとした。
（９）２時間経過後、Ａｒガスを導入し、大気圧まで復圧した後、雰囲気を保ったまま急冷し室温まで冷却した。
【００７１】
上記脱水素処理を経た上記実施例４の原料合金（主相合金、粒界相合金）を、実験例１と同様、それぞれ粉砕した後、得られた主相合金微粉末と粒界相合金微粉末を混合して横磁場成形し、これにより得られた成形体を焼結、時効処理を施して、焼結体磁石を得た。得られた磁石の磁気特性を、Ｂ−Ｈトレーサを用い、室温にて測定した。
得られた磁気特性と、得られた焼結体酸素量を表７に示す。
【００７２】
【表７】

【００７３】
この表７に示すように、４００℃以下、８５０℃以上では、焼結体酸素量が多く、磁気特性の劣化が認められる。４００℃以下はＮｄＨ_３により、また８５０℃以上ではＮｄ−ｒｉｃｈ相により、焼結体酸素量が多くなっているのである。
これにより、脱水素処理での最終処理温度は、４５０〜８００℃の範囲内とすることにより、磁気特性に優れる磁石を得ることができることがわかる。
【００７４】
＜実験例５＞
また、上記実験例１ではいわゆる２種の合金を原料合金とする、いわゆる混合法を用いたが、これに対し、最終組成物となる合金を原料合金としたいわゆるシングル法で焼結体磁石を作成した場合についても、従来技術との比較実証を行った。
原料合金としては、焼結体磁石を形成する最終組成物となる合金を用いた。
この合金は、２４ｗｔ％Ｎｄ−８％Ｄｙ−０．５％Ｃｏ−０．１％Ｃｕ−０．２％Ａｌ−１．０％Ｂ−ｂａｌ．Ｆｅの組成を有する、厚さ０．３５ｍｍのストリップキャスト合金を単ロール法により得た。
得られた合金を、それぞれ以下の条件（実施例５、比較例３）で、水素吸収処理、脱水素処理を経た後、粉砕した。
【００７５】
実施例５
［水素吸収処理］
（１）〜（４）実施例１と同様とした。
［脱水素処理］
（５）〜（９）実施例１と同様とした。
【００７６】
比較例３
［水素吸収処理］
（１）〜（４）実施例１と同様とした。
［脱水素処理］
（５）〜（７）比較例２と同様とした。
【００７７】
上記脱水素処理を経た上記実施例５、比較例３の原料合金を、実験例１と同様、の条件で機械粉砕、微粉砕した。
得られた微粉の粒度分布はＳｙｍｐａｔｅｃ社製の乾式レーザー回折粒度分布計ＨＥＬＯＳ＆ＲＯＤＯＳを用いて測定した。微粉砕後の粒度分布を図１１に、そのときの各粒径を表８に表す。
【００７８】
【表８】

【００７９】
図１１および表８に示すように、最終組成の合金を原料合金に用いた、つまりいわゆるシングル法を用いた場合にも、実施例１に対応した実施例５に比べ、比較例２に対応する比較例３は粒度が大きい。これについても、α―Ｆｅの析出が粉砕性に悪影響を及ぼしている。
【００８０】
さて、上記の粉砕処理を経た、上記実施例５、比較例３のそれぞれにおいて、得られた合金微粉末を、実施例１と同様、１４ｋＯｅの配向磁界中、１．２ｔｏｎ／ｃｍ^２の圧力で横磁場成形した。得られた成形体を、１０５０℃・４時間（真空中）だけ焼結した後、８００℃×１時間、５８０℃ ×１時間の二段時効処理を施して、焼結体磁石を得た。得られた磁石の磁気特性を、Ｂ−Ｈトレーサを用い、室温にて測定した。その結果を表８に示した。
【００８１】
この表８に示したように、脱水素処理で炉内雰囲気をＡｒガスに置換する比較例３と比べると、実施例３は、残留磁束密度Ｂｒ、保磁力ＨｃＪともに凌いでおり、磁気特性に優れていることが明らかである。
このように、シングル法においても、同様の効果が得られるのがわかる。
【００８２】
＜実験例６＞
また、脱水素処理だけでなく、水素吸収処理における条件を変化させた場合の検証も行った。
２４ｗｔ％Ｎｄ−８％Ｄｙ−０．５％Ｃｏ−０．１％Ｃｕ−０．２％Ａｌ−１．０％Ｂ−ｂａｌ．Ｆｅの組成を有する厚さ０．３５ｍｍのストリップキャスト合金を単ロール法により得た。
得られたストリップキャスト合金に、以下の３つの条件（実施例６、比較例４、比較例５）で水素吸収処理を行った。
【００８３】
実施例６
（１）容量６０Ｌの管状炉を用い、Ｍｏ製セッターに原料合金８００ｇを入れ炉内に設置した。このときの温度は室温である。なお、温度測定のために、炉芯管外部に熱伝対を設置した。
（２）炉内を真空ポンプにて１×１０^−１Ｔｏｒｒ以下（最高到達１×１０^−４Ｔｏｒｒ）まで排気した。
（３）水素ガスを導入して、炉内を０．１４ｋｇｆ／ｃｍ^２まで復圧し、一旦水素ガスの供給を中断した。
（４）ストリップキャスト合金に水素が吸収され始めたと判断したときに、炉内水素濃度が９９％程度となるまでＡｒガスのみを導入した。このときのＡｒは、１０Ｌ／ｍｉｎの流量で約５秒間導入した。炉内は０．８Ｌ−Ａｒ／６０Ｌ−Ｈ_２であるから、Ｈ_２濃度は９９％となる。なお、水素吸収の開始の判断は、炉内圧力の低下開始に基づいて行った。
（５）Ａｒガスの導入を中止し、水素ガスのみを再度供給開始した。水素ガスは、水素吸収を実行あらしめるために、炉内圧力が０．０５ｋｇｆ／ｃｍ^２以下にならないように供給した。
（６）水素の供給を行わなくても炉内の圧力低下が起こらなくなるときまで水素の供給を続けた。炉内の圧力低下が起こらなくなった時間を吸収終了時間とした。
【００８４】
比較例４
（１）実施例６と同様。
（２）実施例６と同様。
（３）水素ガスを導入して、炉内を０．１４ｋｇｆ／ｃｍ^２まで復圧した。その後も、炉内に圧力低下が生じないように水素ガスを供給した。
（４）水素の供給を行わなくても炉内の圧力低下が起こらなくなるまで水素の供給を続けた。炉内の圧力低下が起こらなくなった時間を吸収終了時間とした。
【００８５】
比較例５
（１）実施例６と同様。
（２）実施例６と同様。
（３）下記の比率による水素ガスおよびＡｒガスの混合ガスを導入して、炉内を０．１４ｋｇｆ／ｃｍ^２まで復圧した。その後も、炉内に圧力低下が生じないように混合ガスを供給した。水素ガス：Ａｒガス＝９：１（４）混合ガスの供給を行わなくても炉内の圧力低下が起こらなくなるときまで混合ガスの供給を続けた。炉内の圧力低下が起こらなくなった時間を吸収終了時間とした。
【００８６】
以上の実施例６、比較例４および比較例５における、水素ガスまたは混合ガスの導入開始からの経過時間と熱伝対により測定した温度変化（炉体の温度上昇分）の関係を図１２に示す。図１２に示すように、水素吸収開始から水素吸収終了まで水素ガスのみを導入した比較例４は、炉体温度の上昇が急速に行われ、かつ到達温度が高いことがわかる。また、水素吸収開始から水素吸収終了まで混合ガスのみを導入した比較例５は、炉体温度の上昇が緩やかで、かつ到達温度が低いことがわかる。これに対して、当初水素ガスを導入しつつ、所定のタイミングでＡｒガスを導入し、再度水素ガスを導入した実施例６は、比較例５に比べて短時間で水素吸収が終了していることがわかる。しかも、後述するように、実施例６により得られた永久磁石は、比較例４はもちろん、比較例５により得られた永久磁石を凌ぐ磁気特性を有している。なお、図１２において、実施例６〜比較例５によって吸収終了時間が異なるため、測定時間が異なっている。
【００８７】
次に、水素吸収が終了したストリップキャスト合金に脱水素処理を施した。脱水素条件は、実施例６〜比較例５ともに以下の通りである。
（１）水素吸収が終了した後、そのまま炉内導入ガスをＡｒガスに切り替え、Ａｒガスの導入と放出弁の開閉により、炉内圧力を０．１０〜０．１１ｋｇｆ／ｃｍ^２に維持する。
（２）そのままの状態で５℃／ｍｉｎで３５０℃まで昇温し、３５０℃にて１時間保持する。
（３）１時間後、真空ポンプにて１×１０^−１Ｔｏｒｒ以下まで炉内を排気する。
（４）排気終了後、さらに排気を継続したまま、５℃／ｍｉｎで５００℃まで昇温、２時間保持する。
（５）２時間経過後、Ａｒガスを導入し、大気圧まで復圧した後、雰囲気を保ったまま急冷し室温まで冷却する。
【００８８】
以上の水素吸収・脱水素処理を経た後に、気流式微粉砕機（日本ニューマチック製ＰＪＭ−１００ＮＰ）を用い、粉砕圧７ｋｇｆ／ｃｍ^２で微粉砕を行った。微粉砕の条件は、実施例６、比較例４、５とも同一である。
微粉砕によって得られた微粉末の粒度分布を、Ｓｙｍｐａｔｅｃ社製 乾式レーザー回折粒度分布計 ＨＥＬＯＳ＆ＲＯＤＯＳを用いて測定した。その結果を図１３に、そのときの各粒径を表９に示す。
【００８９】
次に、以上で得られた微粉末を、１４ｋＯｅ中の磁場中、１．２ｔｏｎ／ｃｍ^２の圧力で横磁場成形した。得られた成形体を１０５０℃・４時間（真空中）だけ焼結した後に、８００℃×１時間、５８０℃×１時間の二段時効処理を施して、焼結体磁石を得た。得られた磁石の磁気特性をＢ−Ｈトレーサにて室温で測定した。その結果を表９に示す。
図１３および表９に示すように、水素ガスのみで水素吸収を行った比較例４は、発熱反応による温度上昇が大きいために、脱水素後の粉砕が十分でない。そのために、微粉砕を行った後の粉末の粒度が大きく、磁気特性も劣っている。水素ガスとＡｒガスの混合ガスで水素吸収を行った比較例５は、微粉砕後の粒度、磁気特性は比較例４に比べて良好ではあるが、図１２に示したように、水素吸収までの時間が長い。以上に比べて本発明による実施例６は、水素ガスのみ水素吸収を行った比較例４に比べて発熱反応が抑制されているために、微粉砕後の粉末も微細で、かつ磁気特性は比較例４はもちろん比較例５を凌いでいる。しかも、図１２に示したように、水素ガスとＡｒガスの混合ガスで水素吸収を行う比較例５に比べて、短時間で水素吸収処理を完了できる。このように、実施例６は、磁気特性および水素吸収処理の短時間化という要求を兼備している。
【００９０】
【表９】

【００９１】
＜実験例７＞
３１ｗｔ％Ｎｄ−０．２％Ａｌ−１．１％Ｂ−ｂａｌ．Ｆｅの組成を有する厚さ０．３５ｍｍの主相合金形成用のストリップキャスト合金（以下、単にストリップ）を単ロール法により得た。また、６０ｗｔ％Ｎｄ−５％Ｃｏ−０．１％Ｃｕ−０．２％Ａｌ−ｂａｌ．Ｆｅの組成を有する厚さ９ｍｍの合金インゴット（以下、単にインゴット）を鉄製鋳型により鋳造することにより得た。得られたストリップ、インゴットに以下の条件で水素吸収処理を行った。
【００９２】
実施例７
ストリップ（主相形成用）およびインゴット（粒界相形成用）ともに、実施例６と同様の条件で水素吸収処理を行った。
【００９３】
比較例６
ストリップ（主相形成用）は実施例６、またインゴット（粒界相形成用）は比較例４と同様の条件で水素吸収処理を行った。
【００９４】
比較例７
ストリップ（主相形成用）は実施例６、またインゴット（粒界相形成用）を比較例５と同様の条件（水素ガスとＡｒガスの混合ガスを導入）で水素吸収処理を行った。
以上の実施例７、比較例６および比較例７で、インゴットの水素吸収における、水素ガスまたは混合ガスの導入開始からの経過時間と熱伝対により測定した温度変化（炉体の温度上昇分）の関係を図１４に示す。図１４に示すように、水素吸収開始から水素吸収終了まで水素ガスのみを導入した比較例６は、炉体温度の上昇が急速に行われ、かつ到達温度が高いことがわかる。また、水素吸収開始から水素吸収終了まで混合ガスのみを導入した比較例７は、炉体温度の上昇が緩やかで、かつ到達温度が低いことがわかる。これに対して、当初水素ガスを導入しつつ、所定のタイミングでＡｒガスを導入し、再度水素ガスを導入した実施例７は、比較例７に比べて短時間で水素吸収が終了していることがわかる。しかも、後述するように、実施例７により得られた永久磁石は、比較例６はもちろん、比較例７により得られた永久磁石を凌ぐ磁気特性を有している。
【００９５】
以上の水素吸収処理が終了した後に、実施例７、比較例６および比較例７について、実施例６と同様の条件で脱水素処理を行うことにより、粗粉砕粉末を得た。このインゴット粗粉砕粉末を、メッシュ分級し各粒径粉の割合を求めた。その結果を図１５に示すが、水素ガスのみを導入した比較例６は３ｍｍ以上の粗大粒が多く含まれることがわかる。
【００９６】
脱水素処理により得られた粗粉砕粉末を、気流式微粉砕機を用いて、微粉砕を行った。この粉砕条件は、実施例７、比較例６および比較例７ともに実施例６と同様である。ただし、比較例６の場合のみ、３ｍｍ以上の粗大粒子が多量に存在するため、気流粉砕前にディスク・ミルにて機械粉砕を施した。得られた粉砕粉末微粉の粒度分布はＳｙｍｐａｔｅｃ社製 乾式レーザー回折粒度分布計 ＨＥＬＯＳ＆ＲＯＤＯＳを用いて測定した。その結果を図１６に、そのときの各粒径を表１０に示す。
【００９７】
【表１０】

【００９８】
微粉砕された主相形成用合金粉と粒界相形成用合金粉とを、３２ｗｔ％Ｎｄ−０．５％Ｃｏ−０．１％Ｃｕ−０．２％Ａｌ−ｂａｌ．Ｆｅの組成となるように、混合した。この混合粉末を、１４ｋＯｅ中の磁場中、１．２ｔｏｎ／ｃｍ^２ の圧力で横磁場成形した。得られた成形体を１０５０℃×４時間（真空中）だけ焼結した後に、８００℃×１時間、５８０℃×１時間の二段時効処理を施して、焼結体磁石を得た。得られた磁石の磁気特性をＢ−Ｈトレーサにて室温で測定した。その結果を表１０に示した。実施例７による永久磁石は、比較例６はもちろん比較例７と同等の磁気特性を得ている。しかも、図１４に示したように、実施例７は、水素ガスとＡｒガスの混合ガスで水素吸収を行った比較例７に比べて短時間で水素吸収を完了できるから、生産効率の点からも優れている。このように、実施例７は、磁気特性および水素吸収処理の短時間化という要求を兼備している。
【００９９】
なお、以上の実験例１〜７では、Ｒ−Ｔ−Ｂ系希土類永久磁石について説明したが、本発明は他のいかなる金属についても適用できることはいうまでもない。
【０１００】
【発明の効果】
以上説明したように、本発明の脱水素方法によれば、短時間で、かつ粉砕性を損なう物質の析出を抑えて脱水素処理を行うことが可能となる。そして、本発明の水素粉砕方法によれば、脱水素処理を短時間で行いつつ、微粉砕工程における粉砕性を向上させることができる。また、本発明の希土類永久磁石の製造方法によれば、磁気特性に優れる磁石を、短時間で、しかも微粉砕工程において優れた粉砕性で製造することが可能となる。
【図面の簡単な説明】
【図１】本発明の希土類永久磁石の製造方法の工程の流れを示すものである。
【図２】不活性ガス中で脱水素処理を行い、最終処理温度を異ならせた場合に得られる合金のＸ線回折結果を示す図である。
【図３】真空中で脱水素処理を行い、最終処理温度を異ならせた場合に得られる合金のＸ線回折結果を示す図である。
【図４】最終温度保持時間を変えた場合に得られる合金のＸ線回折結果を示す図である。
【図５】脱水素処理時間に対し、炉体温度のプロファイルを示す図である。
【図６】実施例１において、脱水素処理時間に対する、炉体温度および炉内圧力のプロファイルを示す図である。
【図７】実験例１における、微粉砕後の粒径分布を示す図である。
【図８】保持温度に対する脱水素処理時間の関係を示す図である。
【図９】保持温度に対し、得られる磁石の残留磁束密度の関係を示す図である。
【図１０】保持時間に対する脱水素処理時間の関係を示す図である。
【図１１】実験例５における、微粉砕後の粒径分布を示す図である。
【図１２】実験例６における、水素吸収過程における炉体温度変化を示すグラフである。
【図１３】実験例６における、微粉砕後の粒度分布を示すグラフである。
【図１４】実験例７における、水素吸収過程における炉体温度変化を示すグラフである。
【図１５】実験例７における、水素粉砕後の重量比率を示すグラフである。
【図１６】実験例７における、微粉砕後の粒度分布を示すグラフである。
【図１７】真空中で脱水素処理を行う場合の、脱水素処理時間に対する炉体温度のプロファイルを示す図である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of dehydrogenating a metal (including an alloy) containing hydrogen, a method of pulverizing a metal with hydrogen, one or two kinds of rare earth elements R, Fe and Co, and a rare earth permanent magnet mainly containing boron B. About the manufacturing method of
[0002]
[Prior art]
Regarding a method of manufacturing an RTB-based permanent magnet, a method of pulverizing a raw material alloy by sequentially passing through a hydrogen absorption treatment and a dehydrogenation treatment for the purpose of improving magnet productivity and magnetic properties has been proposed. (For example, Patent Document 1 and Patent Document 2).
[0003]
[Patent Document 1]
Japanese Patent Publication No. 3-40082
[Patent Document 2]
Japanese Patent Publication No. 4-24401
[0004]
Conventionally, as shown in Table 1, in the generally performed step (A), the atmosphere in the furnace is changed to H at the stage of hydrogen absorption. ₂ And the treatment is performed at room temperature. In the dehydrogenation stage, the atmosphere in the furnace is replaced with an Ar gas (inert gas), and the temperature is raised to, for example, 600 ° C. to perform the processing.
[0005]
[Table 1]

[0006]
In the process (B) shown in Patent Documents 1 and 2, the furnace atmosphere is changed to H at the stage of hydrogen absorption. ₂ And the furnace pressure is 200 Torr to 50 kg / cm ² In the stage of dehydrogenation, the temperature in the furnace is raised to 100 ° C. or higher, and the process is performed.
[0007]
[Problems to be solved by the invention]
However, when the atmosphere in the furnace is replaced with Ar gas at the stage of dehydrogenation and the treatment is performed at 600 ° C. as in the step (A), the intermetallic compound undergoes a decomposition reaction, and α-Fe having high hardness precipitates. I do. As a result, there is a problem that the pulverizability in the fine pulverization step performed after the dehydrogenation is reduced and the magnetic properties of the finally obtained magnet are impaired.
[0008]
On the other hand, as shown in the step (C) in Table 1, a description has been already made to suppress the precipitation of α-Fe by performing the dehydrogenation treatment in a vacuum (for example, Patent Document 3). ).
[0009]
[Patent Document 3]
JP-A-5-101918
[0010]
In order to perform the dehydrogenation treatment in a vacuum, the atmosphere in the furnace is changed to an atmospheric pressure of H at the preceding stage of the hydrogen absorption. ₂ Therefore, when the hydrogen absorption treatment is completed, the vacuum pump must be operated to bring the furnace pressure into a vacuum state. At this time, in a processing furnace that performs such processing, management (operation control of the furnace) is generally performed based on the degree of vacuum.
For this reason, as shown in FIG. 17, after the hydrogen absorption process is completed, the vacuum pump is operated, and when the inside of the furnace reaches a predetermined degree of vacuum, the heater is operated to start heating the inside of the furnace (see FIG. 17). (Part (d) in FIG. 17), however, the amount of hydrogen discharged from the powder to be processed immediately after the completion of the hydrogen absorption is large, and it takes time to reach a predetermined degree of vacuum. Further, when heating the furnace is started by operating the heater, hydrogen is released from the powder to be processed at a predetermined temperature (for example, around 320 ° C.), thereby lowering the degree of vacuum in the furnace. As a result, the operation of the heater is stopped, and the vacuum pump is operated until the predetermined degree of vacuum is reached (portion (e) in FIG. 17), which also requires time. As a result, it takes a long time to finally raise the temperature in the furnace to a preset temperature and complete the dehydrogenation treatment, and the entire hydrogen crushing process becomes longer.
[0011]
The present invention has been made based on such technical problems, and aims to shorten the time of dehydrogenation treatment, improve the pulverizability in the fine pulverization step, and improve the magnetic properties of the finally obtained magnet. The aim is to provide technologies that can be used.
[0012]
[Means for Solving the Problems]
The inventor improved the pulverizability in the fine pulverization step, and the magnetic properties of the finally obtained magnet by heating the metal in an inert gas atmosphere, then setting the atmosphere to a vacuum state, and further heating. In addition, they have found that the dehydrogenation treatment can be performed in a short time.
According to the dehydrogenation method of the present invention based on this, a metal (which is a concept including an alloy) is placed in a furnace in an atmosphere into which an inert gas is introduced, and the furnace is heated to a first temperature. After that, the inside of the furnace is set to a predetermined degree of vacuum or more, and thereafter, the inside of the furnace is heated to a second temperature higher than the first temperature.
At this time, the first temperature is preferably higher than the temperature at which hydrogen is released from the metal in a large amount, for example, 330 to 400 ° C., and is preferably maintained for a predetermined time. Further, it is preferable to start evacuation of the furnace while maintaining the inside of the furnace at the first temperature. Further, it is possible to start evacuation without maintaining the time at the first temperature and to make the degree of vacuum equal to or higher than a predetermined value.
Also, the second temperature is preferably set to, for example, 450 to 800 ° C. and maintained for a predetermined time.
[0013]
The hydrogen crushing method of the present invention includes an absorption step of absorbing hydrogen in a metal and a dehydrogenation step of releasing hydrogen from the metal in which the hydrogen has been absorbed, wherein the dehydrogenation step is performed under an atmosphere in which an inert gas is introduced. The method is characterized in that a metal is arranged below, and after the temperature of the atmosphere is raised, the atmosphere is reduced to a predetermined pressure or less in a process until the atmosphere reaches a predetermined temperature.
At this time, when starting the decompression of the atmosphere, it is preferable to start the decompression after keeping the temperature of the atmosphere constant for a predetermined time. The temperature holding time at this time is set to 0.1 to 5 hours, and the holding temperature can be set within a range of, for example, 330 to 400 ° C.
Further, when the atmosphere reaches a predetermined temperature, it is preferable to maintain the temperature of the atmosphere for a predetermined time. At this time, the holding time is set to 2 hours or more, and the holding temperature can be set within a range of, for example, 450 to 800 ° C.
The predetermined pressure after the pressure reduction is substantially in a vacuum state (for example, 1.0 × 10 ^-1 (Torr or less).
[0014]
By the way, when the absorption step is completed in an atmosphere substantially composed of hydrogen, it is preferable that after the absorption step, the gas introduced into the atmosphere is switched from hydrogen to an inert gas, and then the dehydrogenation step is performed.
[0015]
The present invention relates to a method for producing a rare earth permanent magnet based on RTB (one or more rare earth elements including R = Y, one or two kinds of T = Fe and Co, B = boron). It can also be caught. This method includes a step of subjecting a part or the whole of a raw material alloy of a predetermined form to hydrogen absorption and dehydrogenation to obtain a hydrogen pulverized product; A step of obtaining a finely pulverized powder by pulverization, and a step of sintering the finely pulverized powder after shaping it into a predetermined shape in a magnetic field. Then, in the dehydrogenation treatment, after raising the temperature of the raw material alloy placed in the atmosphere into which the inert gas is introduced to the first temperature, the degree of vacuum in the atmosphere is increased to a predetermined level or more, and the raw material alloy is cooled to the first temperature. The temperature is raised to a second temperature higher than the second temperature.
At this time, the raw material alloy may be an alloy having a composition substantially identical to the finally obtained rare earth permanent magnet, ₂ Fe ₁₄ It may include an RTB alloy mainly composed of a B compound and an RT alloy mainly composed of R and T. The former shows a manufacturing method called a single method, and the latter shows a manufacturing method called a mixing method. In addition, about the latter, the case where it consists of three or more types of alloys is also included.
[0016]
By the way, the hydrogen absorption reaction performed in the above-described hydrogen absorption step is an exothermic reaction. However, the amount of absorbed hydrogen decreases as the temperature rises, and the time required for cooling or the like becomes longer, leading to a decrease in productivity. However, at present, there is no method capable of suppressing the temperature rise during the hydrogen absorption reaction and performing the hydrogen absorption without requiring a long time.
The present inventors who were searching for such a method, hydrogen absorption was initially started only with hydrogen gas, and then a predetermined amount of inert gas was mixed with hydrogen to reduce the hydrogen concentration. It has been found that an exothermic reaction of a metal due to hydrogen absorption can be suppressed. Then, after stopping the mixing of the inert gas and continuing the hydrogen absorption again in an atmosphere containing only hydrogen, the hydrogen absorption could be completed without requiring a long time. That is, in the hydrogen absorption process, it was found that by changing the concentration of hydrogen, the hydrogen absorption process in which the exothermic reaction was suppressed in a short time could be performed.
Based on such knowledge, as a method of absorbing hydrogen into a metal, the metal is exposed to a hydrogen atmosphere having a hydrogen concentration (a), and the hydrogen concentration in the hydrogen atmosphere is reduced to a hydrogen concentration (b) after a predetermined time. After maintaining the atmosphere at the hydrogen concentration (b) for a predetermined time, the atmosphere may be raised to the hydrogen concentration (c).
[0017]
In the above hydrogen absorption method, a hydrogen atmosphere is formed in a predetermined processing chamber. Typically, a hydrogen atmosphere having a hydrogen concentration (a) can be formed by introducing only hydrogen gas into this processing chamber.
Further, the hydrogen atmosphere of the hydrogen concentration (b) can be formed by introducing an inert gas into the processing chamber into which the hydrogen gas is introduced. The introduction of the inert gas reduces the hydrogen concentration in the processing chamber.
Further, the hydrogen atmosphere of the hydrogen concentration (c) can be formed by stopping the introduction of the inert gas into the processing chamber and introducing the hydrogen gas. The hydrogen concentration (c) can be selected in a range exceeding the hydrogen concentration (b) and not more than the hydrogen concentration (a).
[0018]
In the above, the process up to hydrogen absorption has been targeted. However, this method basically includes two steps of the above-described absorption step of absorbing hydrogen in a metal and the dehydrogenation step of releasing hydrogen from the metal in which hydrogen has been absorbed. The present invention can also be applied to a hydrogen pulverization method having the above. That is, in the absorption step, a metal is placed in a first atmosphere substantially composed of hydrogen, and an inert gas is supplied into the first atmosphere to form a second atmosphere. The supply of the inert gas is stopped and the supply of the hydrogen gas is performed to return to the first atmosphere substantially composed of hydrogen.
With the configuration including the above-described characteristic hydrogen absorption step, the exothermic reaction in the hydrogen absorption step can be suppressed, and the absorption step can be completed without requiring a long time, so that hydrogen pulverization can be performed efficiently. .
[0019]
The supply of the inert gas into the first atmosphere is desirably performed immediately after the metal starts absorbing hydrogen. This is because the exothermic reaction is effectively suppressed.
Further, it is desirable to control the hydrogen concentration of the second atmosphere in the range of 98 to 99.5%. This is for promoting the hydrogen absorption while suppressing the exothermic reaction.
[0020]
RTB (one or two or more rare earth elements including R = Y, one or two of T = Fe and Co, B = boron) to which the above hydrogen absorption method or hydrogen grinding method is applied A method for producing a rare earth permanent magnet can also be provided. In this method, a part or all of a raw material alloy in a predetermined form is subjected to a hydrogen absorption and dehydrogenation treatment to obtain a hydrogen pulverized product, and the hydrogen pulverized product or a powder obtained by pulverizing the hydrogen pulverized product by mechanical means is finely divided. A step of pulverizing to obtain a finely pulverized powder; and a step of forming the finely pulverized powder into a predetermined shape and then sintering. Then, in the dehydrogenation treatment, after raising the temperature of the raw material alloy placed in the atmosphere composed of the inert gas to the first temperature, the degree of vacuum of the atmosphere is increased to a predetermined level or more, and the raw material alloy is heated to the first temperature. Raise the temperature to a higher second temperature. In the hydrogen absorption treatment, the raw material alloy is exposed to a hydrogen atmosphere having a hydrogen concentration (a), and after a predetermined time, the hydrogen concentration in the hydrogen atmosphere is reduced to the hydrogen concentration (b), and the hydrogen atmosphere is reduced to the hydrogen concentration (b). After maintaining for a predetermined time, the hydrogen concentration (c) is increased.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
In the dehydrogenation method of the present invention, the metal is placed in a furnace in an inert gas atmosphere, and the inside of the furnace is heated to a first temperature, and then the inside of the furnace is set to a predetermined degree of vacuum. The inside of the furnace is heated to a second temperature higher than the temperature. As described above, by raising the furnace temperature in the inert gas, hydrogen contained in the metal can be efficiently released. If the temperature is raised to the final treatment temperature of the dehydrogenation treatment in an inert gas, α-Fe precipitates in the metal, so the furnace is evacuated to prevent this. is there.
At this time, by setting the first temperature to 330 ° C. or higher, the atmosphere is set as an inert gas in a temperature range (for example, around 320 ° C.) where a large amount of hydrogen contained in the metal is released, and unnecessary vacuuming is performed. To prevent Further, by setting the first temperature to 400 ° C. or less, α-Fe is prevented from being precipitated in the alloy in an inert gas atmosphere. This first temperature is maintained for a predetermined time, preferably 0.5 to 5 hours, to promote dehydrogenation.
Then, while the inside of the furnace is maintained at the first temperature, evacuation of the inside of the furnace is started. The degree of vacuum in the furnace is 1.0 × 10 ^-1 When the pressure becomes equal to or lower than Torr, the temperature in the furnace is restarted, and the temperature is raised to the second temperature.
It is preferable that the second temperature is 450 to 800 ° C., and this temperature is maintained for 2 hours or more. At this time, evacuation (evacuation) of the furnace is continued in order to maintain a vacuum state in the furnace.
[0022]
When metal is pulverized with hydrogen, the above-described dehydrogenation method can be applied.
In this case, the process proceeds to the above-described dehydrogenation treatment after the hydrogen absorption treatment for absorbing hydrogen into the metal.
In the hydrogen absorption treatment, the metal may be first exposed to a hydrogen atmosphere having a hydrogen concentration (a), and the hydrogen concentration in the hydrogen atmosphere may be reduced to the hydrogen concentration (b) after a predetermined time. Of course, the hydrogen concentration (a) is higher than the hydrogen concentration (b). The hydrogen concentration (a) is realized, for example, under an atmosphere substantially consisting of hydrogen gas. This atmosphere can be formed in a closed vessel to promote hydrogen absorption into the metal. The hydrogen gas pressure at this time is 0.05 to 2.5 kgf / cm. ² It is desirable to be within the range. 0.05kgf / cm ² If less than 0.05 kgf / cm, the hydrogen absorption rate becomes slow, a sufficient pulverizing effect cannot be obtained, and not only the efficient operation is prevented, but also from the viewpoint of safety. ² It is desirable to make the above. Also, 2.5kgf / cm ² This is because, if it exceeds 300, the heat of reaction with hydrogen will increase significantly. Therefore, the hydrogen gas pressure is 0.2 to 2.5 kgf / cm ² It is desirable that Note that, in this specification, substantially consisting of hydrogen gas means that a gas other than hydrogen is not intentionally included. For example, for industrial production, 99.99 vol. % Hydrogen gas is used. This hydrogen gas is N ₂ <50 vol. ppm, O ₂ <1 vol. A trace amount of impurities of about ppm is allowed. The term "consisting essentially of hydrogen gas" as used in the present specification allows the inclusion of such trace gas components other than hydrogen gas.
[0023]
The hydrogen concentration (b) can be formed, for example, by introducing a predetermined amount of an inert gas when the atmosphere having the hydrogen concentration (a) is composed only of hydrogen gas. The introduction of the inert gas reduces the degree of hydrogen absorption and suppresses the generation of reaction heat. However, when the hydrogen concentration (b) decreases, the hydrogen absorption rate decreases, and the time required to complete the hydrogen absorption increases. Therefore, in order to complete hydrogen absorption quickly, it is desirable that the hydrogen concentration be in the range of 98 to 99.5%. It is desirable to introduce the inert gas immediately after the metal starts absorbing hydrogen. This is for suppressing an exothermic reaction due to hydrogen absorption. The fact that the metal has started absorbing hydrogen can be known by detecting a change in the pressure of the atmosphere in which the hydrogen absorption treatment is performed, specifically, a decrease in the pressure.
[0024]
After the hydrogen absorption treatment based on the hydrogen concentration (b), the atmosphere for hydrogen absorption is raised to the hydrogen concentration (c). If an inert gas has been introduced in order to obtain an atmosphere with a hydrogen concentration (b), the introduction of the inert gas is stopped, and the atmosphere with a hydrogen concentration (c) is changed to an atmosphere for absorbing hydrogen with only hydrogen gas. Can be formed. Alternatively, the atmosphere having the hydrogen concentration (c) can be formed by reducing the amount of the inert gas introduced as compared with the case of the hydrogen concentration (b). When the hydrogen absorption progresses to some extent, the exothermic reaction is reduced, so that the hydrogen concentration is increased accordingly.
[0025]
After the above-described hydrogen absorption process is completed, the process shifts to the dehydrogenation process. The purpose of this treatment is to reduce the amount of hydrogen absorbed in the metal, specifically, to improve the stability of handling in the atmosphere by bringing the hydride into a stable valence state. Done.
At this time, the hydrogen absorption process ends in an atmosphere substantially consisting of hydrogen. Therefore, after the absorption treatment, the gas introduced into the atmosphere is switched from hydrogen to an inert gas, and then the dehydrogenation step is performed.
[0026]
The dehydrogenation method of the present invention can be applied to a method for producing an RTB-based rare earth permanent magnet. RTB-based alloys are particularly difficult to pulverize intermetallic compounds (R ₂ Fe ₁₄ In order to include B), a hydrogen grinding method is applied. FIG. 1 shows a process flow of a method for manufacturing a rare earth permanent magnet according to the present invention.
First, a part or all of the raw material alloy in a predetermined form is subjected to hydrogen absorption and dehydrogenation treatment and is hydrogen pulverized to obtain a hydrogen pulverized product. As the raw material alloy, an ingot obtained by using a mold, a strip formed by a strip casting method, and any other form of alloy can be used. However, if the size of the alloy used for hydrogen absorption is too large, the hydrogen absorption efficiency decreases. As one scale, in the case of an ingot, the thickness is desirably 30 mm or less.
[0027]
RTB-based rare earth permanent magnets are manufactured by a single method using a raw material alloy that matches the final desired alloy composition, and a mixed method that combines a plurality of alloys constituting the final desired alloy composition. Is known (FIG. 1 is an example by the mixing method). When manufacturing an RTB-based rare earth permanent magnet by the single method, generally, all of the raw material alloy is subjected to hydrogen absorption and dehydrogenation treatment. In the case of manufacturing an RTB-based rare earth permanent magnet by a mixing method, a part of the plurality of alloys may be subjected to hydrogen absorption and dehydrogenation treatment, or a plurality of alloys may be subjected to hydrogen absorption and dehydrogenation treatment. All may be subjected to a hydrogen absorption and dehydrogenation treatment.
[0028]
The raw material alloy pulverized by the hydrogen absorption and dehydrogenation treatments is coarsely pulverized to a particle size of about several hundred μm, if necessary. The coarse pulverization is desirably performed in an inert gas atmosphere by using mechanical pulverization means such as a stamp mill, a jaw crusher, and a brown mill.
After the pulverization by the hydrogen absorption and dehydrogenation treatment or the above coarse pulverization, the process proceeds to the fine pulverization step. The fine pulverization is mainly performed using a jet mill, and the coarse pulverized powder having a particle size of about several hundred μm is performed until the average particle size becomes 3 to 5 μm. In a jet mill, a high-pressure inert gas (for example, nitrogen gas) is released from a narrow nozzle to generate a high-speed gas flow, and the high-speed gas flow accelerates powder particles to cause collision of the powder particles. This is a method of crushing by generating collisions with a target or a container wall.
The powder obtained by the pulverization is subjected to molding in a magnetic field. At this time, when the mixing method is used, the powders are mixed and the composition is blended before molding in a magnetic field.
At the time of pressure molding, the crystal axis is oriented by applying a magnetic field, and the lubricant added at the time of pulverization contributes to the improvement of the degree of orientation. This molding in a magnetic field is performed in a magnetic field of 10 to 16 kOe in a range of 1 to 1.6 ton / cm. ² What is necessary is just to carry out by pressure of front and back.
[0029]
After compacting in a magnetic field, the compact is sintered in a vacuum or inert gas atmosphere. The sintering temperature needs to be adjusted according to various conditions such as the composition, the pulverizing method, the difference between the particle size and the particle size distribution, and the sintering may be performed at 1000 to 1130 ° C. for about 1 to 5 hours.
After sintering, the obtained sintered body can be subjected to an aging treatment. This step is an important step for controlling the coercive force Hcj. When the aging treatment is performed in two stages, it is effective to maintain the aging treatment at around 800 ° C. and around 600 ° C. for a predetermined time. When the heat treatment at around 800 ° C. is performed after sintering, the coercive force Hcj increases, which is particularly effective in the mixing method. Further, since the coercive force Hcj greatly increases by the heat treatment at around 600 ° C., when performing the aging treatment in one stage, it is preferable to perform the aging treatment at around 600 ° C.
[0030]
The composition of the RTB-based rare earth permanent magnet to which the present invention is applied may be selected according to the purpose. However, in order to obtain a rare magnet having excellent magnetic properties, the rare earth element R : 20 to 40 wt%, boron B: 0.5 to 4.5 wt%, and T (one or two of Fe and Co): the balance is desirable. Here, the rare earth element R is one or more of rare earth elements including Y (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu). When the amount of the rare earth element R is less than 20 wt%, R as the main phase of the rare earth permanent magnet ₂ Fe ₁₄ The formation of the B phase is not sufficient, and α-Fe or the like having soft magnetism precipitates, and the coercive force Hcj is significantly reduced. On the other hand, when the rare earth element R exceeds 40 wt%, the main phase R ₂ Fe ₁₄ The volume ratio of the B phase decreases, and the residual magnetic flux density Br decreases. Further, the rare-earth element R reacts with oxygen to increase the amount of oxygen contained therein, thereby reducing the R-rich phase effective for generating coercive force and lowering the coercive force Hcj. ４０40 wt%. Since Nd is abundant in resources and relatively inexpensive, it is preferable that the main component as the rare earth element R be Nd. Dy has a large anisotropic magnetic field and is effective in improving the coercive force Hcj.
[0031]
If the boron B content is less than 0.5 wt%, a high coercive force Hcj cannot be obtained. However, when boron B exceeds 4.5 wt%, the residual magnetic flux density Br tends to decrease. Therefore, the upper limit is set to 4.5 wt%. Desirable amount of boron B is 0.5-1.5 wt%.
Further, in order to improve the coercive force Hcj, M may be added to make a rare earth permanent magnet of RTBM type. Here, M is one or more elements such as Al, Cr, Mn, Mg, Si, Cu, C, Nb, Sn, W, V, Zr, Ti, Mo, Bi, Ag and Ga. It can be added, but when the amount exceeds 6 wt%, the residual magnetic flux density Br decreases.
[0032]
【Example】
<Examination experiment 1>
Here, prior to examining the above final dehydrogenation conditions, a case where dehydrogenation treatment is performed in an inert gas by a conventional and generally performed method and a method described in Patent Document 3 In the case where the dehydrogenation treatment was carried out in a vacuum, the difference in composition depending on the treatment temperature was compared, and the results are shown.
As the raw material alloy, a total of two kinds of alloys, an alloy used as a main phase alloy and an alloy used as a grain boundary phase alloy, were used.
The main phase alloy is 31 wt% Nd-0.2% Al-1.1% B-bal. A strip cast alloy having a composition of Fe and a thickness of 0.35 mm was obtained by a single roll method. The intermetallic compound of this main phase alloy is Nd ₂ Fe ₁₄ B, and the rest is in the Nd-rich phase.
The grain boundary phase alloy is 60 wt% Nd-5 wt% Co-0.1 wt% Cu-0.2 wt% Al-bal. An alloy having a composition of Fe and a thickness of 9 mm was obtained by casting in an iron mold. The intermetallic compound of this grain boundary phase alloy is Nd ₂ Fe ₁₇ And the remainder is in the Nd-rich phase.
Table 2 shows the above-mentioned raw material alloys.
[0033]
[Table 2]

[0034]
The obtained main phase alloy and grain boundary phase alloy were subjected to a hydrogen absorption treatment and a dehydrogenation treatment under the following conditions (Examination Examples 1 and 2), and then analyzed for their compositions.
[0035]
Study example 1: When dehydrogenation is performed in an inert gas
[Hydrogen absorption treatment]
(1) Using a tubular furnace having an internal capacity of 60 L, 800 g of the raw material alloy was put into a Mo setter and set in the furnace. The temperature at this time is room temperature.
(2) 1 × 10 inside the furnace with a vacuum pump ^-1 Torr or less (maximum 1 × 10 ^-4 Torr).
(3) Hydrogen gas was introduced into the furnace, and the pressure was restored to the atmospheric pressure. At this time, the supply of hydrogen gas was continued so as not to cause a pressure drop.
(4) Hydrogen was continuously supplied until the pressure drop did not occur, and the absorption was completed when the pressure drop did not occur.
[Dehydrogenation treatment]
(5) After completion of hydrogen absorption, the introduced gas was switched to Ar gas, and the Ar gas was allowed to flow at 1 atm.
(6) Immediately after that, the temperature was raised to a predetermined temperature at 5 ° C./min and kept for 2 hours. At this time, the held predetermined temperatures (hereinafter, appropriately referred to as final processing temperatures) were four types of 200, 400, 500, and 600 ° C.
(7) After a lapse of 2 hours, Ar gas was introduced, the pressure was restored to the atmospheric pressure, and then the mixture was rapidly cooled while maintaining the atmosphere, and cooled to room temperature.
[0036]
Study example 2: When dehydrogenation treatment is performed in a vacuum
Hydrogen absorption treatment of (1) to (4): Same as in Study Example 1.
(5) After completion of hydrogen absorption, the introduced gas was switched to Ar gas, and Ar gas was allowed to flow at 1 atm for 0.5 hours (the atmosphere in the furnace was changed to Ar).
(6) After 0.5 hour, 1 × 10 ^-1 Evacuated to Torr.
(7) After the evacuation, the temperature was raised at 5 ° C./min while the evacuation was continued. On the way, the furnace pressure is 1 × 10 ^-1 If it exceeds Torr, 1 × 10 ^-1 The heating was stopped until Torr was reached.
(8) After the temperature was raised to a predetermined temperature, the temperature was maintained for 2 hours. At this time, the held predetermined temperatures were four kinds of 200, 400, 500, and 600 ° C.
(9) After a lapse of 2 hours, Ar gas was introduced and the pressure was restored to the atmospheric pressure. Then, the atmosphere was maintained, and the mixture was rapidly cooled to room temperature.
[0037]
The states of the raw material alloys (main phase alloys and grain boundary phase alloys) that have undergone the above-described dehydrogenation treatment and have been subjected to the above-described examination examples 1 and 2 have been confirmed by X-ray diffraction.
Table 3 shows that the intermetallic compound (Nd) in the main phase alloy obtained in Study Example 1 and Study Example 2 was obtained. ₂ Fe ₁₄ The state of B) is shown.
[0038]
[Table 3]

[0039]
Table 4 shows the intermetallic compounds (Nd ₂ Fe ₁₄ The state of B) is shown.
[0040]
[Table 4]

[0041]
Table 5 shows the state of the remainder (Nd-rich phase) of the raw material alloy other than the intermetallic compound in Study Example 1 and Study Example 2.
[0042]
[Table 5]

[0043]
FIG. 2 shows the measurement results of X-ray diffraction in Study Example 1 of the grain boundary phase alloy, and FIG. 3 shows the measurement results of X-ray diffraction in Study Example 2 of the grain boundary phase alloy. Note that, in FIG. 3, the curve indicated by the symbol (f) is the result of the final processing temperature of 600 ° C. in Study Example 1 shown for comparison.
From these results, when the dehydrogenation treatment was performed by flowing the inert gas, as shown in Table 3, in the main phase alloy, when the final treatment temperature was 200, 400, or 500 ° C., α-Fe was deposited. However, at 600 ° C., precipitation of α-Fe is observed.
Further, in the grain boundary phase alloy, as shown in Table 4 and FIG. 2, at the final treatment temperature of 200 and 400 ° C., no precipitation of α-Fe was observed. Is observed.
On the other hand, in Study Example 2 in which the dehydrogenation treatment was performed in a vacuum, no precipitation of α-Fe was observed at any temperature.
[0044]
In addition, in Study Example 1 in which both the main phase alloy and the grain boundary phase alloy were subjected to dehydrogenation treatment in an inert gas, as shown in Tables 3 and 4, when the final treatment temperature was 200 or 400 ° C. Nd in the table ₂ Fe ₁₄ BH, Nd ₂ Fe ₁₇ As described as H, hydrogen (H) penetrates (remains) between lattices of the intermetallic compound.
This means that, as shown in FIG. 2, at 200 and 400 ° C., the diffraction line due to the intermetallic compound is shifted to a lower angle side than at 500 and 600 ° C., and hydrogen enters between lattices of the intermetallic compound. However, it can be seen from the result that the lattice is expanded. It can be seen from the magnitude of the peak shift that the residual amount of hydrogen is smaller when the final processing temperature is 400 ° C. than when the final processing temperature is 200 ° C.
On the other hand, as shown in FIG. 3, in Study Example 2 in which dehydrogenation treatment was performed in a vacuum, hydrogen (H) did not penetrate (remain) into the interstitial of the intermetallic compound at any temperature. .
[0045]
The balance (Nd-rich phase) other than the intermetallic compound in the raw material alloy was NdH at 200 and 400 ° C. as shown in Table 5 in both Study Example 1 and Study Example 2. ₃ Exist at 500 and 600 ° C. ₃ NdH more stable to atmosphere ₂ It has become. This is because, as shown in FIGS. ₃ Is observed, and at 400 ° C., NdH ₂ And NdH ₃ It can be seen from the fact that the peak width is wide due to the presence of both. NdH at 500 and 600 ° C ₃ No peak was observed, and all NdH ₂ It has become.
[0046]
<Examination experiment 2>
In the case of performing the dehydrogenation treatment in an inert gas, the difference in the retention time of the final treatment temperature was compared.
Here, as the raw material alloys, as in the case of Study Example 2, a total of two kinds of alloys, an alloy used as the main phase alloy and an alloy used as the grain boundary phase alloy, were used.
The obtained main phase alloy and grain boundary phase alloy were subjected to hydrogen absorption treatment and dehydrogenation treatment under the following conditions (Examination Example 3 and Examination Example 4), and then analyzed for their compositions.
[0047]
Study examples 3 and 4
[Hydrogen absorption treatment]
(1) to (4), similar to Study Example 2
[Dehydrogenation treatment]
(5) As in Study Example 2, after the end of hydrogen absorption, the introduced gas was switched to Ar gas, and Ar gas was allowed to flow at 1 atm.
(6) Immediately after that, the temperature was raised to a predetermined temperature at 5 ° C./min and kept for 2 hours. At this time, the held predetermined temperature (hereinafter, appropriately referred to as a final processing temperature) was 400 ° C.
(7) The final processing temperature was maintained for a predetermined time, and after the predetermined time had elapsed, Ar gas was introduced, the pressure was restored to the atmospheric pressure, and then the mixture was rapidly cooled while maintaining the atmosphere and cooled to room temperature. At this time, the holding time of the final treatment temperature was set to 2 hours, which was the same as that of Study example 3: Study example 2, and Study time 4: 4 hours.
[0048]
X-ray diffraction measurements were performed on the raw material alloys (grain boundary phase alloys) that had undergone the treatments of Study Example 1 and Study Example 2, respectively.
FIG. 4 shows the result.
As shown in FIG. 4, in Study Example 4 in which the holding time at the first temperature was made longer than in Study Example 3, NdH around 28 ° ₃ From the peak intensity corresponding to NdH ₃ It is recognized that the ratio of This NdH ₃ Is reduced by NdH as in the case of Study Examples 1 and 2. ₂ It has become. In addition, Nd which is an intermetallic compound ₂ Fe ₁₇ The peak corresponding to is slightly shifted to the higher angle side due to the extension of the retention time, indicating that the lattice shrinkage has occurred due to the decrease in the amount of residual hydrogen.
[0049]
According to these examination experiments 1 and 2, precipitation of α-Fe was suppressed by setting the atmosphere to a vacuum, and NdH ₃ NdH that is more stable and can suppress an increase in the amount of oxygen in the original alloy ₂ Can be generated.
In addition, it can be seen from examination examples 3 and 4 that the amount of residual hydrogen can be reduced by maintaining the temperature for a predetermined time.
[0050]
<Experimental example 1>
Here, first, a comparison was made between the case where the present invention was applied, the case where the technique described in Patent Document 3 was applied, and the case where a conventionally generally used method was applied.
As the raw material alloy, a total of two kinds of alloys, an alloy used as a main phase alloy and an alloy used as a grain boundary phase alloy, were used.
The main phase alloy is 31 wt% Nd-0.2% Al-1.1% B-bal. A strip cast alloy having a composition of Fe and a thickness of 0.35 mm was obtained by a single roll method.
The grain boundary phase alloy is 60 wt% Nd-5 wt% Co-0.1 wt% Cu-0.2 wt% Al-bal. An alloy having a composition of Fe and a thickness of 9 mm was obtained by casting in an iron mold.
The obtained main phase alloy and grain boundary phase alloy were subjected to a hydrogen absorption treatment and a dehydrogenation treatment under the following conditions (Example 1, Comparative Example 1, Comparative Example 2), and then pulverized.
[0051]
Example 1
[Hydrogen absorption treatment]
(1) Using a tubular furnace having an internal capacity of 60 L, 800 g of the raw material alloy was put into a Mo setter and set in the furnace. The temperature at this time is room temperature.
(2) 1 × 10 inside the furnace with a vacuum pump ^-1 Torr or less (maximum 1 × 10 ^-4 Torr).
(3) Hydrogen gas was introduced into the furnace, and the pressure was restored to the atmospheric pressure. At this time, the supply of hydrogen gas was continued so as not to cause a pressure drop.
(4) Hydrogen was continuously supplied until the pressure drop did not occur, and the absorption was completed when the pressure drop did not occur.
[Dehydrogenation treatment]
(5) After completion of hydrogen absorption, the introduced gas was switched to Ar gas, and the Ar gas was allowed to flow at 1 atm.
(6) Immediately thereafter, the temperature was raised to 350 ° C. at a rate of 5 ° C./min, and the temperature was maintained for 1 hour.
(7) After completion of the holding, evacuation is performed using a vacuum pump, and the degree of vacuum is set to 1.0 × 10 ^-1 Torr or less.
(8) With the evacuation continued, the temperature was raised to 500 ° C. at 5 ° C./min, and held for 2 hours.
(9) After a lapse of 2 hours, Ar gas was introduced and the pressure was restored to the atmospheric pressure. Then, the atmosphere was maintained, and the mixture was rapidly cooled to room temperature.
[0052]
Comparative Example 1: Corresponding to the process described in Patent Document 3
(1) to (4) Hydrogen absorption treatment: Same as in Example 1.
(5) After completion of hydrogen absorption, the introduced gas was switched to Ar gas, and Ar gas was allowed to flow at 1 atm for 0.5 hours (the atmosphere in the furnace was changed to Ar).
(6) After that, 1 × 10 ^-1 Evacuated to Torr.
(7) After the evacuation, the temperature was raised at 5 ° C./min while the evacuation was continued. On the way, the furnace pressure is 1 × 10 ^-1 If it exceeds Torr, 1 × 10 ^-1 The heating was stopped until Torr was reached.
(8) After the temperature was raised to 500 ° C., the temperature was maintained for 2 hours.
(9) After a lapse of 2 hours, Ar gas was introduced and the pressure was restored to the atmospheric pressure. Then, the atmosphere was maintained, and the mixture was rapidly cooled to room temperature.
[0053]
Comparative Example 2: Corresponding to a step generally performed conventionally
(1) to (4) Hydrogen absorption treatment: Same as in Example 1.
(5) After completion of hydrogen absorption, the introduced gas was switched to Ar gas, and the Ar gas was allowed to flow at 1 atm.
(6) Immediately after that, the temperature was raised to 500 ° C. at 5 ° C./min and kept for 2 hours.
(7) After a lapse of 2 hours, the mixture was rapidly cooled while maintaining the atmosphere, and cooled to room temperature.
[0054]
FIG. 5 shows the profile of the furnace body temperature with respect to the elapsed time from the end of the hydrogen absorption treatment of the grain boundary phase alloy in Example 1, Comparative Example 1, and Comparative Example 2 described above. FIG. 6 shows a change profile of the furnace body temperature and the furnace pressure with respect to the dehydrogenation processing time in Example 1.
As shown in FIG. 5, in Example 1, the portion (g) was held at 350 ° C. for 1 hour in the process (6), and the vacuum was drawn in the process (7) thereafter. . As a result, it takes 5.5 hours to complete the step (8).
In Comparative Example 1, in the portion of (d), 1 × 10 ^-1 A vacuum evacuation to Torr is performed. Further, in the part (e), the pressure in the furnace becomes 1 × 10 while the temperature is being increased while continuing the evacuation in (7). ^-1 The temperature has stopped rising due to exceeding Torr. As a result, it takes 8.5 hours to complete the step (8).
In Comparative Example 2, it took about 3.5 hours to complete the step (6).
As described above, according to Example 1, it is understood that the dehydrogenation processing is completed in a shorter time than in Comparative Example 1 in which the dehydrogenation processing is performed in a vacuum. Further, in Example 1, although a longer time was required for the dehydrogenation process than in Comparative Example 2 in which the atmosphere in the furnace was replaced with Ar gas in the dehydrogenation process, as described later, the dehydrogenation process was performed according to Example 1. The obtained permanent magnet has magnetic properties exceeding those of the permanent magnet obtained in Comparative Example 2.
[0055]
The raw material alloys (main phase alloy, grain boundary phase alloy) of Example 1, Comparative Example 1, and Comparative Example 2 having been subjected to the dehydrogenation treatment were each pulverized.
For this, mechanical pulverization was performed using a disk mill, and then fine pulverization was performed using an airflow type pulverizer. The pulverizing pressure of the air-flow type pulverizer is 7 kgf / cm ² And
The particle size distribution of the obtained fine powder was measured using a dry laser diffraction particle size distribution analyzer HELOS & RODOS manufactured by Sympatec. FIG. 7 shows the particle size distribution after the pulverization, and Table 6 shows the respective particle sizes at that time.
[0056]
[Table 6]

[0057]
In FIG. 7, as for the main phase alloy, no remarkable difference was observed from Comparative Examples 1 and 2, so that the particle size distributions of Comparative Examples 1 and 2 were omitted.
The grain boundary phase alloy (powder) has a larger particle size in Comparative Example 2 than in Example 1. Regarding this, it is understood that the above-mentioned precipitation of α-Fe adversely affects the pulverizability.
[0058]
Now, in each of Example 1, Comparative Example 1, and Comparative Example 2 having undergone the above-mentioned pulverization, the main phase alloy fine powder and the grain boundary phase alloy fine powder were mixed, and the composition was changed to 32 wt% Nd-0. 5% Co-0.1% Cu-0.2% Al-bal. Fe.
Then, the obtained mixed fine powder is placed in an orientation magnetic field of 14 kOe at 1.2 ton / cm. ² The transverse magnetic field was formed at a pressure of. The obtained compact was sintered at 1030 ° C. for 4 hours (in vacuum), and then subjected to a two-stage aging treatment at 800 ° C. × 1 hour and 580 ° C. × 1 hour to obtain a sintered body magnet. The magnetic properties of the obtained magnet were measured at room temperature using a BH tracer. Table 6 shows the results.
[0059]
As shown in Table 6, the magnetic properties of Example 1 were slightly better than Comparative Example 1 in which the dehydrogenation treatment was performed in vacuum, and the coercive force HcJ was equal to that of Comparative Example 1 which was slightly better. It has become. In addition, as compared with Comparative Example 2 in which the atmosphere in the furnace was replaced with Ar gas in the dehydrogenation treatment, Example 2 surpasses both the residual magnetic flux density Br and the coercive force HcJ.
[0060]
As described above, in Example 1, the time required for the dehydrogenation treatment was shortened with respect to Comparative Example 1, and it was clear that Comparative Example 2 was superior in terms of magnetic properties and particle size distribution. is there. In other words, it is possible to produce a magnet having better magnetic properties in a shorter time and with better pulverizability in the fine pulverization step than before.
[0061]
<Experimental example 2>
Next, when the holding temperature at the time of raising the temperature in the furnace during the dehydrogenation treatment was varied, the time required for the dehydrogenation treatment and the magnetic properties of the obtained sintered magnets were compared.
Example 2
As the raw material alloys, as in Example 1, two kinds of alloys were used in total: an alloy used as the main phase alloy and an alloy used as the grain boundary phase alloy.
The obtained main phase alloy and grain boundary phase alloy were subjected to hydrogen absorption treatment and dehydrogenation treatment under the following conditions, respectively, and then pulverized.
[0062]
[Hydrogen absorption treatment]
(1) to (4) Same as in the first embodiment.
[Dehydrogenation treatment]
(5) After completion of hydrogen absorption, the introduced gas was switched to Ar gas, and the Ar gas was allowed to flow at 1 atm.
(6) Immediately after that, the temperature was raised to a predetermined temperature at 5 ° C./min, and the temperature was maintained for 1 hour. At this time, the predetermined temperatures (holding temperatures) were set to nine values of 250, 300, 320, 330, 350, 375, 400, 450, and 500 ° C.
(7) After completion of holding at a predetermined temperature, evacuation is performed using a vacuum pump, and the degree of vacuum is set to 1.0 × 10 ^-1 Torr or less.
(8) With the evacuation continued, the temperature was raised to 500 ° C. at 5 ° C./min, and held for 2 hours.
(9) After a lapse of 2 hours, Ar gas was introduced and the pressure was restored to the atmospheric pressure. Then, the atmosphere was maintained, and the mixture was rapidly cooled to room temperature.
[0063]
FIG. 8 shows the time required for the dehydrogenation treatment in Example 2 described above.
As shown in FIG. 8, when the holding temperature is lower than 330 ° C., it can be seen that the time required for dehydrogenation becomes longer. This is because a large amount of hydrogen released around 320 ° C. is evacuated.
[0064]
The raw material alloys (main phase alloys and grain boundary phase alloys) of Example 2 that had been subjected to the above dehydrogenation treatment were each pulverized in the same manner as in Experimental Example 1, and the obtained main phase alloy fine powder and grain boundary phase were obtained. The alloy fine powder was mixed and subjected to transverse magnetic field molding, and the resulting compact was sintered and aged to obtain a sintered magnet. The magnetic properties of the obtained magnet were measured at room temperature using a BH tracer. FIG. 9 shows the residual magnetic flux density Br among the obtained magnetic characteristics.
As shown in FIG. 9, when the holding temperature exceeds 400 ° C., there is a tendency that the residual magnetic flux density Br decreases. This is because the intermetallic compound in the grain boundary phase alloy is decomposed and α-Fe is precipitated.
[0065]
By setting the holding temperature in the dehydrogenation treatment in the range of 330 to 400 ° C. in this manner, the time required for dehydrogenation can be reduced, and a magnet having excellent magnetic properties can be manufactured. .
[0066]
<Experimental example 3>
Next, the time required for the dehydrogenation treatment was compared when the holding time for raising the temperature inside the furnace in the dehydrogenation treatment was varied.
Example 3
As the raw material alloys, as in Example 1, two kinds of alloys were used in total: an alloy used as the main phase alloy and an alloy used as the grain boundary phase alloy.
The obtained main phase alloy and grain boundary phase alloy were subjected to hydrogen absorption treatment and dehydrogenation treatment under the following conditions, respectively, and then pulverized.
[0067]
[Hydrogen absorption treatment]
(1) to (4) Same as in the first embodiment.
[Dehydrogenation treatment]
(5) After completion of hydrogen absorption, the introduced gas was switched to Ar gas, and the Ar gas was allowed to flow at 1 atm.
(6) Immediately after that, the temperature was raised to 380 ° C. at a rate of 5 ° C./min, and the temperature was maintained for a predetermined time between 0 and 5 hours. At this time, the above-mentioned holding time was set to six patterns of 0, 0.5, 1, 2, 3, and 5 hours.
(7) After completion of holding at a predetermined temperature, evacuation is performed using a vacuum pump, and the degree of vacuum is set to 1.0 × 10 ^-1 Torr or less.
(8) With the evacuation continued, the temperature was raised to 500 ° C. at 5 ° C./min, and held for 2 hours.
(9) After a lapse of 2 hours, Ar gas was introduced and the pressure was restored to the atmospheric pressure. Then, the atmosphere was maintained, and the mixture was rapidly cooled to room temperature.
[0068]
FIG. 10 shows the time required for the dehydrogenation treatment in Example 3 described above.
As shown in FIG. 10, the time required for dehydrogenation is slightly reduced by setting the holding time to 0.5, 1 hour, or the like. However, it can be seen that when the holding time exceeds 2 hours, the time required for dehydrogenation becomes longer. This indicates that the extension of the holding time directly leads to the extension of the time required for dehydrogenation.
Thus, it can be understood that the dehydrogenation time can be shortened by maintaining the predetermined temperature in the dehydrogenation treatment.
[0069]
<Experimental example 4>
Next, when the final treatment temperature of the dehydrogenation treatment was changed, the magnetic properties and the oxygen amount of the obtained sintered magnet were compared.
Example 4
As the raw material alloys, as in Example 1, two kinds of alloys were used in total: an alloy used as the main phase alloy and an alloy used as the grain boundary phase alloy.
The obtained main phase alloy and grain boundary phase alloy were subjected to hydrogen absorption treatment and dehydrogenation treatment under the following conditions, respectively, and then pulverized.
[0070]
[Hydrogen absorption treatment]
(1) to (4) Same as in the first embodiment.
[Dehydrogenation treatment]
(5) After completion of hydrogen absorption, the introduced gas was switched to Ar gas, and the Ar gas was allowed to flow at 1 atm.
(6) Immediately thereafter, the temperature was raised at a rate of 5 ° C./min, and the temperature was maintained at 350 ° C. for 1 hour.
(7) After completion of holding at a predetermined temperature, evacuation is performed using a vacuum pump, and the degree of vacuum is set to 1.0 × 10 ^-1 Torr or less.
(8) With the evacuation continued, the temperature was raised to a predetermined temperature at 5 ° C./min and held for 2 hours. At this time, the predetermined temperatures (holding temperatures) were set to nine values of 350, 400, 500, 600, 700, 750, 800, 850, and 900 ° C.
(9) After a lapse of 2 hours, Ar gas was introduced and the pressure was restored to the atmospheric pressure. Then, the atmosphere was maintained, and the mixture was rapidly cooled to room temperature.
[0071]
The raw material alloys (main phase alloy and grain boundary phase alloy) of the above Example 4 which had been subjected to the above dehydrogenation treatment were each ground in the same manner as in Experimental Example 1, and the obtained main phase alloy fine powder and grain boundary phase alloy fine powder were obtained. The powder was mixed and subjected to transverse magnetic field molding. The resulting compact was sintered and aged to obtain a sintered magnet. The magnetic properties of the obtained magnet were measured at room temperature using a BH tracer.
Table 7 shows the obtained magnetic properties and the obtained sintered body oxygen amount.
[0072]
[Table 7]

[0073]
As shown in Table 7, below 400 ° C. and above 850 ° C., the amount of oxygen in the sintered body was large, and deterioration of magnetic properties was observed. NdH below 400 ° C ₃ At 850 ° C. or higher, the oxygen amount of the sintered body increases due to the Nd-rich phase.
Thus, it can be seen that a magnet having excellent magnetic properties can be obtained by setting the final treatment temperature in the dehydrogenation treatment in the range of 450 to 800 ° C.
[0074]
<Experimental example 5>
In the above-mentioned Experimental Example 1, a so-called mixed method was used in which so-called two kinds of alloys were used as raw material alloys. Also in the case where it was created, comparative verification with the conventional technology was performed.
As a raw material alloy, an alloy that was a final composition for forming a sintered magnet was used.
This alloy is composed of 24 wt% Nd-8% Dy-0.5% Co-0.1% Cu-0.2% Al-1.0% B-bal. A strip cast alloy having a composition of Fe and a thickness of 0.35 mm was obtained by a single roll method.
The obtained alloys were subjected to hydrogen absorption treatment and dehydrogenation treatment under the following conditions (Example 5, Comparative Example 3), and then pulverized.
[0075]
Example 5
[Hydrogen absorption treatment]
(1) to (4) Same as Example 1.
[Dehydrogenation treatment]
(5) to (9) Same as Example 1.
[0076]
Comparative Example 3
[Hydrogen absorption treatment]
(1) to (4) Same as Example 1.
[Dehydrogenation treatment]
(5) to (7) Same as Comparative Example 2.
[0077]
The raw material alloys of Example 5 and Comparative Example 3 after the dehydrogenation treatment were mechanically pulverized and finely pulverized under the same conditions as in Experimental Example 1.
The particle size distribution of the obtained fine powder was measured using a dry laser diffraction particle size distribution analyzer HELOS & RODOS manufactured by Sympatec. FIG. 11 shows the particle size distribution after the pulverization, and Table 8 shows the respective particle sizes at that time.
[0078]
[Table 8]

[0079]
As shown in FIG. 11 and Table 8, even when the alloy having the final composition was used as the raw material alloy, that is, when the so-called single method was used, Comparative Example 2 corresponded to Example 5 corresponding to Example 1. Comparative Example 3 has a large particle size. Also in this case, precipitation of α-Fe has an adverse effect on pulverizability.
[0080]
Now, in each of Example 5 and Comparative Example 3 having undergone the above-mentioned pulverization, the obtained alloy fine powder was subjected to an orientation magnetic field of 14 kOe in the same manner as in Example 1 at 1.2 ton / cm 2. ² The transverse magnetic field was formed at a pressure of. The obtained compact was sintered at 1050 ° C. for 4 hours (in vacuum), and then subjected to a two-stage aging treatment at 800 ° C. × 1 hour and 580 ° C. × 1 hour to obtain a sintered body magnet. The magnetic properties of the obtained magnet were measured at room temperature using a BH tracer. Table 8 shows the results.
[0081]
As shown in Table 8, as compared with Comparative Example 3 in which the atmosphere in the furnace was replaced with Ar gas in the dehydrogenation treatment, Example 3 surpassed both the residual magnetic flux density Br and the coercive force HcJ, and exhibited a magnetic property. It is clear that it is excellent.
Thus, it can be seen that the same effect can be obtained in the single method.
[0082]
<Experimental example 6>
In addition, not only the dehydrogenation treatment, but also the case where the conditions in the hydrogen absorption treatment were changed were verified.
24 wt% Nd-8% Dy-0.5% Co-0.1% Cu-0.2% Al-1.0% B-bal. A 0.35 mm thick strip cast alloy having an Fe composition was obtained by a single roll method.
The obtained strip cast alloy was subjected to a hydrogen absorption treatment under the following three conditions (Example 6, Comparative Example 4, and Comparative Example 5).
[0083]
Example 6
(1) A tubular furnace having a capacity of 60 L was used, and 800 g of the raw material alloy was placed in a Mo setter and set in the furnace. The temperature at this time is room temperature. In addition, a thermocouple was installed outside the furnace core tube for temperature measurement.
(2) 1 × 10 inside the furnace with a vacuum pump ^-1 Torr or less (maximum 1 × 10 ^-4 Torr).
(3) Hydrogen gas is introduced, and the inside of the furnace is 0.14 kgf / cm. ² Then, the supply of hydrogen gas was temporarily interrupted.
(4) When it was determined that hydrogen had begun to be absorbed into the strip cast alloy, only Ar gas was introduced until the hydrogen concentration in the furnace became about 99%. At this time, Ar was introduced at a flow rate of 10 L / min for about 5 seconds. 0.8L-Ar / 60L-H inside the furnace ₂ , So H ₂ The concentration is 99%. The determination of the start of hydrogen absorption was made based on the start of reduction in the furnace pressure.
(5) The introduction of Ar gas was stopped, and only the supply of hydrogen gas was started again. Hydrogen gas has a furnace pressure of 0.05 kgf / cm in order to perform hydrogen absorption. ² Supplied not to be below.
(6) The supply of hydrogen was continued until the pressure in the furnace did not drop even if the supply of hydrogen was not performed. The time when the pressure in the furnace did not drop was defined as the absorption end time.
[0084]
Comparative Example 4
(1) Same as in the sixth embodiment.
(2) Same as in the sixth embodiment.
(3) Hydrogen gas is introduced, and the inside of the furnace is 0.14 kgf / cm. ² Pressure was restored. Thereafter, hydrogen gas was supplied so as not to cause a pressure drop in the furnace.
(4) The supply of hydrogen was continued until the pressure in the furnace did not decrease even if the supply of hydrogen was not performed. The time when the pressure in the furnace did not drop was defined as the absorption end time.
[0085]
Comparative Example 5
(1) Same as in the sixth embodiment.
(2) Same as in the sixth embodiment.
(3) A mixed gas of hydrogen gas and Ar gas at the following ratio was introduced, and the inside of the furnace was 0.14 kgf / cm. ² Pressure was restored. Thereafter, the mixed gas was supplied so as not to cause a pressure drop in the furnace. Hydrogen gas: Ar gas = 9: 1 (4) Even if the mixed gas was not supplied, the supply of the mixed gas was continued until the pressure in the furnace did not decrease. The time when the pressure in the furnace did not drop was defined as the absorption end time.
[0086]
FIG. 12 shows the relationship between the elapsed time from the start of the introduction of the hydrogen gas or the mixed gas and the temperature change (increase in the temperature of the furnace body) measured by a thermocouple in Example 6, Comparative Example 4, and Comparative Example 5 described above. Show. As shown in FIG. 12, in Comparative Example 4 in which only hydrogen gas was introduced from the start of hydrogen absorption to the end of hydrogen absorption, it was found that the furnace body temperature was rapidly increased and the ultimate temperature was high. In Comparative Example 5 in which only the mixed gas was introduced from the start of hydrogen absorption to the end of hydrogen absorption, it can be seen that the furnace body temperature rose slowly and the temperature reached was low. On the other hand, in Example 6 in which Ar gas was introduced at a predetermined timing while hydrogen gas was initially introduced, and hydrogen gas was introduced again, hydrogen absorption was completed in a shorter time than in Comparative Example 5. You can see that. Moreover, as will be described later, the permanent magnet obtained in Example 6 has magnetic properties that are superior to those of Comparative Example 4 as well as the permanent magnet obtained in Comparative Example 5. In FIG. 12, since the absorption end time differs according to Example 6 to Comparative Example 5, the measurement time differs.
[0087]
Next, the strip cast alloy after the completion of the hydrogen absorption was subjected to a dehydrogenation treatment. The dehydrogenation conditions are as follows for all of Example 6 to Comparative Example 5.
(1) After the hydrogen absorption is completed, the gas introduced into the furnace is switched to Ar gas as it is, and the pressure inside the furnace is set to 0.10 to 0.11 kgf / cm by introducing Ar gas and opening and closing the discharge valve. ² To maintain.
(2) In this state, the temperature is raised to 350 ° C. at 5 ° C./min and maintained at 350 ° C. for 1 hour.
(3) After 1 hour, 1 × 10 ^-1 The inside of the furnace is evacuated to Torr or less.
(4) After the evacuation, the temperature is raised to 500 ° C. at 5 ° C./min for 2 hours while the evacuation is continued.
(5) After a lapse of 2 hours, Ar gas is introduced, the pressure is restored to the atmospheric pressure, and then the mixture is rapidly cooled down to room temperature while maintaining the atmosphere.
[0088]
After the hydrogen absorption and dehydrogenation treatment described above, a pulverizing pressure of 7 kgf / cm was obtained by using a pneumatic pulverizer (PJM-100NP manufactured by Nippon Pneumatic). ² And pulverized. The conditions of the fine pulverization are the same in Example 6 and Comparative Examples 4 and 5.
The particle size distribution of the fine powder obtained by the fine pulverization was measured using a dry laser diffraction particle size distribution analyzer HELOS & RODOS manufactured by Sympatec. FIG. 13 shows the results, and Table 9 shows the particle sizes at that time.
[0089]
Next, the fine powder obtained as described above was placed in a magnetic field of 14 kOe in a 1.2 ton / cm ² The transverse magnetic field was formed at a pressure of. After sintering the obtained molded body only at 1050 ° C. for 4 hours (in vacuum), a two-stage aging treatment at 800 ° C. × 1 hour and 580 ° C. × 1 hour was performed to obtain a sintered body magnet. The magnetic properties of the obtained magnet were measured at room temperature with a BH tracer. Table 9 shows the results.
As shown in FIG. 13 and Table 9, in Comparative Example 4 in which hydrogen was absorbed only with hydrogen gas, the temperature rise due to the exothermic reaction was large, so that pulverization after dehydrogenation was not sufficient. Therefore, the particle size of the powder after pulverization is large and the magnetic properties are inferior. In Comparative Example 5 in which hydrogen was absorbed with a mixed gas of hydrogen gas and Ar gas, the particle size and the magnetic characteristics after pulverization were better than those in Comparative Example 4, but as shown in FIG. Long time. In comparison with the above, in Example 6 according to the present invention, since the exothermic reaction was suppressed as compared with Comparative Example 4 in which only hydrogen gas was absorbed by hydrogen, the powder after pulverization was fine and the magnetic properties were comparatively low. Example 4 is of course superior to Comparative Example 5. Further, as shown in FIG. 12, the hydrogen absorption process can be completed in a shorter time than in Comparative Example 5 in which hydrogen is absorbed by a mixed gas of hydrogen gas and Ar gas. As described above, the sixth embodiment has both the magnetic characteristics and the demand for shortening the hydrogen absorption process.
[0090]
[Table 9]

[0091]
<Experimental example 7>
31 wt% Nd-0.2% Al-1.1% B-bal. A 0.35 mm thick strip cast alloy for forming a main phase alloy (hereinafter simply referred to as a strip) having a Fe composition was obtained by a single roll method. In addition, 60 wt% Nd-5% Co-0.1% Cu-0.2% Al-bal. An alloy ingot having a composition of Fe and having a thickness of 9 mm (hereinafter simply referred to as an ingot) was obtained by casting using an iron mold. The obtained strip and ingot were subjected to a hydrogen absorption treatment under the following conditions.
[0092]
Example 7
Both the strip (for forming the main phase) and the ingot (for forming the grain boundary phase) were subjected to the hydrogen absorption treatment under the same conditions as in Example 6.
[0093]
Comparative Example 6
The strip (for forming the main phase) and the ingot (for forming the grain boundary phase) were subjected to the hydrogen absorption treatment under the same conditions as in Example 6 and Comparative Example 4, respectively.
[0094]
Comparative Example 7
The strip (for forming the main phase) was subjected to the hydrogen absorption treatment in Example 6 and the ingot (for forming the grain boundary phase) under the same conditions as in Comparative Example 5 (introducing a mixed gas of hydrogen gas and Ar gas).
In the above Example 7, Comparative Example 6, and Comparative Example 7, the change in temperature (measured by the temperature rise of the furnace body) measured by the thermocouple and the elapsed time from the start of the introduction of the hydrogen gas or the mixed gas in the hydrogen absorption of the ingot. Is shown in FIG. As shown in FIG. 14, in Comparative Example 6 in which only hydrogen gas was introduced from the start of hydrogen absorption to the end of hydrogen absorption, it can be seen that the furnace body temperature was rapidly increased and the ultimate temperature was high. In Comparative Example 7, in which only the mixed gas was introduced from the start of hydrogen absorption to the end of hydrogen absorption, it can be seen that the furnace body temperature rises slowly and the temperature reached is low. On the other hand, in Example 7, in which Ar gas was introduced at a predetermined timing while hydrogen gas was initially introduced, and hydrogen gas was introduced again, hydrogen absorption was completed in a shorter time than in Comparative Example 7. You can see that. Moreover, as will be described later, the permanent magnet obtained in Example 7 has magnetic properties superior to those of Comparative Example 6 as well as the permanent magnet obtained in Comparative Example 7.
[0095]
After the above-mentioned hydrogen absorption treatment was completed, a roughly pulverized powder was obtained by subjecting Example 7, Comparative Example 6, and Comparative Example 7 to dehydrogenation treatment under the same conditions as in Example 6. This ingot coarsely pulverized powder was subjected to mesh classification to determine the ratio of each particle size powder. The results are shown in FIG. 15, and it can be seen that Comparative Example 6, in which only hydrogen gas was introduced, contained many coarse particles of 3 mm or more.
[0096]
The coarsely pulverized powder obtained by the dehydrogenation treatment was finely pulverized using an airflow type fine pulverizer. The pulverization conditions are the same as in Example 6 in Example 7, Comparative Example 6, and Comparative Example 7. However, only in the case of Comparative Example 6, since a large amount of coarse particles of 3 mm or more was present, mechanical pulverization was performed with a disk mill before airflow pulverization. The particle size distribution of the obtained fine powder was measured using a dry laser diffraction particle size distribution analyzer HELOS & RODOS manufactured by Sympatec. FIG. 16 shows the results, and Table 10 shows the particle sizes at that time.
[0097]
[Table 10]

[0098]
Finely pulverized alloy powder for forming a main phase and alloy powder for forming a grain boundary phase were mixed with 32 wt% Nd-0.5% Co-0.1% Cu-0.2% Al-bal. They were mixed so as to have a composition of Fe. This mixed powder was placed in a magnetic field of 14 kOe in 1.2 ton / cm ² The transverse magnetic field was formed at a pressure of. After sintering the obtained molded body only at 1050 ° C. × 4 hours (in vacuum), a two-stage aging treatment at 800 ° C. × 1 hour and 580 ° C. × 1 hour was performed to obtain a sintered body magnet. The magnetic properties of the obtained magnet were measured at room temperature with a BH tracer. Table 10 shows the results. The permanent magnet according to Example 7 has the same magnetic properties as Comparative Example 6 as well as Comparative Example 6. Moreover, as shown in FIG. 14, the seventh embodiment can complete the hydrogen absorption in a shorter time than the comparative example 7 in which the hydrogen absorption is performed by the mixed gas of the hydrogen gas and the Ar gas. Is also excellent. As described above, the seventh embodiment has both the magnetic characteristics and the demand for shortening the hydrogen absorption process.
[0099]
In the above-described Experimental Examples 1 to 7, the RTB-based rare earth permanent magnet has been described. However, it goes without saying that the present invention can be applied to any other metal.
[0100]
【The invention's effect】
As described above, according to the dehydrogenation method of the present invention, it is possible to perform the dehydrogenation treatment in a short period of time and while suppressing the deposition of the substance that impairs the pulverizability. And, according to the hydrogen pulverization method of the present invention, the pulverizability in the fine pulverization step can be improved while performing the dehydrogenation treatment in a short time. Further, according to the method for producing a rare earth permanent magnet of the present invention, it is possible to produce a magnet having excellent magnetic properties in a short time and with excellent pulverizability in a fine pulverization step.
[Brief description of the drawings]
FIG. 1 shows a process flow of a method for manufacturing a rare earth permanent magnet of the present invention.
FIG. 2 is a diagram showing an X-ray diffraction result of an alloy obtained when a dehydrogenation treatment is performed in an inert gas and a final treatment temperature is changed.
FIG. 3 is a view showing an X-ray diffraction result of an alloy obtained when a dehydrogenation treatment is performed in a vacuum and the final treatment temperature is changed.
FIG. 4 is a view showing an X-ray diffraction result of an alloy obtained when the final temperature holding time is changed.
FIG. 5 is a diagram showing a profile of a furnace body temperature with respect to a dehydrogenation treatment time.
FIG. 6 is a view showing a profile of a furnace body temperature and a furnace pressure with respect to a dehydrogenation treatment time in Example 1.
FIG. 7 is a diagram showing a particle size distribution after fine pulverization in Experimental Example 1.
FIG. 8 is a diagram showing a relationship between a holding temperature and a dehydrogenation treatment time.
FIG. 9 is a diagram showing a relationship between a holding temperature and a residual magnetic flux density of an obtained magnet.
FIG. 10 is a diagram showing a relationship between a retention time and a dehydrogenation treatment time.
FIG. 11 is a view showing a particle size distribution after fine pulverization in Experimental Example 5.
12 is a graph showing a furnace body temperature change in a hydrogen absorption process in Experimental Example 6. FIG.
FIG. 13 is a graph showing the particle size distribution after fine pulverization in Experimental Example 6.
FIG. 14 is a graph showing a furnace body temperature change in a hydrogen absorption process in Experimental Example 7.
FIG. 15 is a graph showing a weight ratio after hydrogen pulverization in Experimental Example 7.
FIG. 16 is a graph showing the particle size distribution after fine pulverization in Experimental Example 7.
FIG. 17 is a view showing a profile of a furnace body temperature with respect to a dehydrogenation processing time when performing a dehydrogenation treatment in a vacuum.

Claims (14)

A dehydrogenation method for releasing hydrogen from a metal containing hydrogen,
Placing the metal in a furnace where an inert gas atmosphere has been introduced,
After heating the inside of the furnace to a first temperature,
The inside of the furnace is set to a predetermined degree of vacuum,
Thereafter, the inside of the furnace is heated to a second temperature higher than the first temperature. The method according to claim 1, wherein the first temperature is maintained for a predetermined time. The dehydrogenation method according to claim 2, wherein evacuation of the furnace is started while the inside of the furnace is maintained at the first temperature. The dehydrogenation method according to any one of claims 1 to 3, wherein the first temperature is from 330 to 400 ° C. 5. The dehydrogenation method according to claim 1, wherein the second temperature is maintained for a predetermined time. The dehydrogenation method according to claim 5, wherein the second temperature is 450 to 800C. An absorption step of absorbing hydrogen into the metal,
A dehydrogenation step of releasing hydrogen from the metal in which hydrogen has been absorbed,
The dehydrogenation step,
After placing the metal under an atmosphere in which an inert gas has been introduced, and starting to raise the temperature of the atmosphere,
A hydrogen crushing method, wherein the atmosphere is reduced to a predetermined pressure or less in a process until the atmosphere reaches a predetermined temperature. The method according to claim 7, wherein the pressure of the atmosphere is started after the temperature of the atmosphere is maintained for a predetermined time. The hydrogen crushing method according to claim 7 or 8, wherein the temperature of the atmosphere is maintained for a predetermined time when the atmosphere reaches the predetermined temperature. The method according to claim 7, wherein the predetermined pressure is 1.0 × 10 ⁻¹ Torr or less. The method according to claim 7, wherein after the absorption step, which is completed in an atmosphere substantially composed of hydrogen, after the gas introduced into the atmosphere is switched from hydrogen to an inert gas, the dehydrogenation step is performed. 11. The hydrogen pulverization method according to any one of 10 above. A method for producing a rare earth permanent magnet based on RTB (one or more rare earth elements including R = Y, one or two kinds of T = Fe and Co, B = boron),
Performing a hydrogen absorption and dehydrogenation treatment on part or all of the raw material alloy in a predetermined form to obtain a hydrogen pulverized product;
A step of pulverizing the hydrogen pulverized product, or a powder obtained by pulverizing the hydrogen pulverized product by mechanical means to obtain a finely pulverized powder,
Sintering after shaping the pulverized powder into a predetermined shape in a magnetic field,
The dehydrogenation treatment,
After raising the temperature of the material alloy placed in the atmosphere in which the inert gas is introduced to the first temperature,
A method for manufacturing a rare-earth permanent magnet, wherein the degree of vacuum of the atmosphere is increased to a predetermined value or more, and the raw material alloy is heated to a second temperature higher than the first temperature. The raw material alloy is
The method for producing a rare-earth permanent magnet according to claim 12, wherein the alloy has a composition substantially identical to a finally obtained rare-earth permanent magnet. The raw material alloy is
A method for preparing a rare earth permanent magnet according to claim 12, characterized in that it comprises an R-T alloy mainly comprising R-T-B alloys and R and T composed mainly of R 2 _Fe 14 _B compound.

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