JP4325082B2 - Method for cleaning sintering jig for R-Fe-B permanent magnet and method for sintering R-Fe-B permanent magnet using sintering jig cleaned by the cleaning method - Google Patents
Method for cleaning sintering jig for R-Fe-B permanent magnet and method for sintering R-Fe-B permanent magnet using sintering jig cleaned by the cleaning method Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
- H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
- H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
- H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
- H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
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Description
【０００１】
【発明の属する技術分野】
本発明は、Ｒ化合物（ＲはＹを含む希土類元素：以下同じ）および／またはＲメタルが付着したＲ−Ｆｅ−Ｂ系永久磁石用焼結治具の穏和な条件での清浄方法、Ｒ−Ｆｅ−Ｂ系永久磁石用焼結治具に付着したＲ化合物および／またはＲメタルの簡易かつ効果的な除去方法、および該清浄方法によって清浄化された焼結治具を用いたＲ−Ｆｅ−Ｂ系永久磁石の焼結方法に関する。
【０００２】
【従来の技術】
Ｎｄ−Ｆｅ−Ｂ系永久磁石に代表されるＲ−Ｆｅ−Ｂ系焼結磁石は、所要組成の合金インゴットを粉砕して得られる合金粉末を磁場中で配向させつつプレス成形し、得られた成形体を焼結炉で焼結する工程を経て製造される。焼結工程は、例えば、Ｍｏを主成分とする台板上に成形体を載置して、さらに成形体が焼結工程前に酸化されたりしないように容器に収容した状態で１０００℃〜１２００℃の温度で行われる。この焼結の際、前記成形体のＲが液相となり、成形体表面に出てくる。液相になって出てきたＲはＲメタルとして治具に溶着する。溶着したＲメタルは、大気中の酸素や水分との反応によってＲ２Ｏ３やＲ（ＯＨ）３などのＲ化合物となり、治具表面に突起物や隆起物を形成する。これらの突起物や隆起物には、成形体からこぼれ落ちた合金粉末に起因するＲメタルやＲ化合物も含まれる。
Ｒ化合物やＲメタルからなる突起物や隆起物がある台板を用いて焼結工程を繰り返して行った場合、先に形成された突起物や隆起物を核にして付着物は次第に大きくなっていく。また、前記成形体は、焼結時に大きく収縮するため、成形体を、比較的大きな付着物と接触させたまま焼結を行うと、成形体の収縮が阻害され、該接触部から割れなどを生じさせてしまう。成形体がプレス時の磁場配向方向に２５％も収縮する場合もあるので、前記成形体の磁場配向方向を台板に対して平行にして成形体を載置すると、この問題はいっそう顕著となる。また、ＲメタルやＲ化合物が台板表面に残存していると、Ｒメタルが大気中の酸素や水分と反応してＲ２Ｏ３やＲ（ＯＨ）３などのＲ化合物となり、Ｒ化合物は焼結時に分解してＨ２Ｏを発生させる。発生したＨ２Ｏは、前記成形体と反応して、焼結体表面にＲ２Ｏ３やＲ（ＯＨ）３などのＲ化合物を生じさせてしまうため、できあがった磁石の磁気特性をも劣化させてしまうことになる。一方、Ｍｏを主成分とする台板を使用した場合、付着物を完全に除去しないまま再度焼結すると、付着物に含まれるＦｅは、焼結工程を繰り返し行うことでＭｏと反応し、台板表層部にＭｏ−Ｆｅの化合物を生成すると考えられる。このような化合物が生成した部分は、Ｆｅと反応していない台板部と比べて成形体（焼結体）との反応性が高く、ＲメタルやＲ化合物を溶着しやすくなっており、徐々に突起物や隆起物を成長させる。出願人は、特許第２７５４０９８号において、台板の付着物を除去することを目的として、焼結治具をショットブラストなどを行うことによって清浄する方法を提案した。
【０００３】
【発明が解決しようとする課題】
しかしながら上記のようなショットブラストなどを用いた機械的な方法だけでは、焼結治具の溶接部への付着物や焼結治具に溶着して形成された付着物のうち、比較的大きな付着物しか除去できず、付着物を完全に除去することは困難であった。特にＭｏ−Ｆｅの化合物がいったん形成されてしまった部分は非常に硬く、ショットブラストなどだけでは除去することは極めて困難であった。そのため、除去しきれなかった付着物を完全に除去するには、ショットブラストなどを行った後にやすりなどを用いて削り取るなどの処理が必要であった。しかしながら、このような処理を焼結治具に対して何回も行っていると、キズが入るので、焼結工程を繰り返しているうちに焼結治具表面が変形したり、ひび割れたりしてしまうなどの問題があった。したがって、機械的に清浄することによって焼結治具は繰り返して焼結工程において使用できるようにはなったものの、使用できる延べ回数には自ずと限度があり、より優れた清浄方法が望まれていた。
そこで本発明においては、Ｒ化合物および／またはＲメタルが付着したＲ−Ｆｅ−Ｂ系永久磁石用焼結治具の穏和な条件での清浄方法、Ｒ−Ｆｅ−Ｂ系永久磁石用焼結治具に付着したＲ化合物および／またはＲメタルの簡易かつ効果的な除去方法、および該清浄方法によって清浄化された焼結治具を用いたＲ−Ｆｅ−Ｂ系永久磁石の焼結方法を提供することを目的としている。
【０００４】
【課題を解決するための手段】
本発明者は、上記の点に鑑み、種々の検討を行った結果、Ｒ化合物やＲメタルが付着した焼結治具を機械的に清浄化処理する前に水素雰囲気中に存置すると、これらが水素を吸蔵し、水素化反応を起こして水素化合物を生成することによって膨張し、内部から脆化するので、穏和な機械的清浄化処理条件で焼結治具表面からこれらの付着物を極めて確実にかつ効果的に除去できることを知見した。
【０００５】
本発明は、かかる知見に基づきなされたもので、本発明のＲ−Ｆｅ−Ｂ系永久磁石用焼結治具の清浄方法は、請求項１記載の通り、Ｒ化合物および／またはＲメタルが付着したＲ−Ｆｅ−Ｂ系永久磁石用焼結治具を水素雰囲気中に存置した後、前記焼結治具を清浄化処理することを特徴とする。
また、本発明のその他の態様のＲ−Ｆｅ−Ｂ系永久磁石用焼結治具の清浄方法は、請求項２記載の通り、Ｒ−Ｆｅ−Ｂ系永久磁石用焼結治具に付着したＲ化合物および／またはＲメタルを水素雰囲気中で脆化した後、前記焼結治具を清浄化処理することを特徴とする。
また、請求項３記載の清浄方法は、請求項１または２記載の清浄方法において、前記焼結治具を構成する材料がＭｏを主成分とすることを特徴とする。
また、請求項４記載の清浄方法は、請求項３記載の清浄方法において、さらに焼結治具を構成する材料にＬａ２Ｏ３、ＺｒＯ２、ＴｉＣから選ばれる少なくとも一成分が添加されていることを特徴とする。
また、請求項５記載の清浄方法は、請求項１及至４のいずれかに記載の清浄方法において、前記焼結治具の表面に凹凸があることを特徴とする。
また、請求項６記載の清浄方法は、請求項５記載の清浄方法において、前記凹凸の表面粗度（Ｒａ）が０．１μｍ〜５００μｍであることを特徴とする。
また、請求項７記載の清浄方法は、請求項１及至６のいずれかに記載の清浄方法において、前記焼結治具が成形体を載置する台板であることを特徴とする。
また、本発明のＲ−Ｆｅ−Ｂ系永久磁石用焼結治具に付着したＲ化合物および／またはＲメタルの除去方法は、請求項８記載の通り、Ｒ化合物および／またはＲメタルが付着したＲ−Ｆｅ−Ｂ系永久磁石用焼結治具を水素雰囲気中に存置した後、Ｒ化合物および／またはＲメタルを除去することを特徴とする。
また、本発明のその他の態様のＲ−Ｆｅ−Ｂ系永久磁石用焼結治具に付着したＲ化合物および／またはＲメタルの除去方法は、請求項９記載の通り、Ｒ−Ｆｅ−Ｂ系永久磁石用焼結治具に付着したＲ化合物および／またはＲメタルを水素雰囲気中で脆化した後、除去することを特徴とする。
また、本発明のＲ−Ｆｅ−Ｂ系永久磁石の焼結方法は、請求項１０記載の通り、請求項１乃至７のいずれかに記載の清浄方法によって清浄化されたＲ−Ｆｅ−Ｂ系永久磁石用焼結治具を用いることを特徴とする。
【０００６】
【発明の実施の形態】
Ｒ化合物および／またはＲメタルが付着したＲ−Ｆｅ−Ｂ系永久磁石用焼結治具（以下「Ｒ−Ｆｅ−Ｂ系永久磁石用焼結治具」を単に「焼結治具」という）を水素雰囲気中に存置する方法としては、たとえば付着物が付いた焼結治具を水素炉内に収容する方法が挙げられる。
この場合、炉内の水素量は絶対圧で０．０５ＭＰａ〜０．５ＭＰａとすることが十分かつ均一な水素化、安全性、作業効率などの点で望ましい。
炉内の温度は、室温〜６００℃とすることが望ましい。炉内を加熱すれば、焼結治具も加熱されるので、焼結治具に付着したＲ化合物やＲメタルの水素吸蔵が活発に起こり、水素化反応が促進される。したがって、短時間のうちに水素がこれら付着物の内部にまで行き渡って体積膨張し、そのため、付着物内部でマイクロクラックが発生し、付着物を脆化させる。炉内の温度を６００℃よりも高くした場合、付着物の表層部が溶融し、溶着が進行するので望ましくない。炉内の温度が高いほど冷却に時間がかかるので、炉内の温度は４００℃以下とすることがより望ましい。なお、Ｒ−Ｆｅ−Ｂ系磁性合金粉末やその成形体などは水素との反応性に富み、反応熱を発生するので、焼結治具上にこれらを載置することによって、かかる反応熱を利用して焼結治具を加熱することもできる。
焼結治具の炉内への収容時間は３０分〜１０時間が望ましい。
【０００７】
焼結治具としては、具体的には、成形体を載置する台板、成形体を載置した台板を収容する焼結ケースや焼結パック、成形体を載置した台板を積載するために使用するスペーサーなどが挙げられる。
焼結治具の材質はＭｏを主成分とするものが望ましい。ステンレスやＦｅからなる焼結治具であってもよいが、Ｍｏは、Ｒに対する反応性が比較的低いのでＭｏとＲの反応物が付着しにくいこと、強度や靱性が高いので形状変形などが起こりにくいこと、熱伝導性が高く加熱されやすいので焼結温度や付着物の昇温が比較的速くなることなどの利点を有するからである。
また、Ｍｏを主成分とする焼結治具は、Ｍｏの他にＬａ２Ｏ３、ＺｒＯ２、ＴｉＣから選ばれる少なくとも一成分が添加された合金からなるものであってもよい。これらの成分が添加されることによって焼結治具の再結晶温度が上がるので、焼結時に硬化することがなく、衝撃などによっても割れたりすることが起こりにくくなるからである。
【０００８】
成形体を載置する台板は、その表面に凹凸があるものが望ましい。成形体に対する接触面積を減らすことにより、焼結時に成形体の変形や成形体と台板との溶着を抑制することができるからである。台板の凹凸の表面粗度（Ｒａ）は０．１μｍ〜５００μｍであることが望ましい。表面粗度がこれより小さいと、焼結時に台板と成形体が密着しすぎて両者が溶着するおそれがある。一方、表面粗度がこれより大きいと凹凸が大きすぎて凸部が成形体に食い込んでしまい、焼結時において成形体の収縮を阻害し、その結果、得られる焼結体に割れやひびなどを生じさせるおそれがある。とくにＶＣＭ（ボイスコイルモータ）やリニアモータに使用される磁石のように、大きくて重量がある磁石を製造するための成形体の場合、成形体への接触面積が少なく、かつ台板表面の凸部による焼結時の成形体の収縮の阻害を少なくするために、台板の表面粗度は２μｍ〜１０μｍが望ましい。
【０００９】
Ｒ化合物やＲメタルと水素との化学反応としては、たとえば以下の化学式で表される反応が考えられる。
Ｒ化合物やＲメタルが付着した焼結治具を水素雰囲気中に存置することによって、付着しているＲ化合物やＲメタルが水素を吸蔵して体積膨張することでこれらの中にマイクロクラックが発生して脆くなるので、焼結治具表面から剥離しやすくなる。したがって、これらは、たとえば、穏和な機械的清浄化処理条件で極めて簡易にかつ効果的に除去することができる。
清浄化処理の方法としては、ショットブラスト法、液化ホーミング法、バフ研磨法などの他、スチールウールやヘラなどを用いて手で擦り取るというような簡便な方法を採用することもできる。ショットブラスト法としては、砥粒にＡｌ２Ｏ３粒、ＳｉＯ２粒、ガラス粒などを使用することができ、砥粒の平均粒径としては２０μｍ〜１０００μｍが望ましい。ブラスト圧力としては１αＰａ〜５αＰａ（α＝９．８０６６５×１０４）が望ましい。ブラスト時間は３０秒〜３０分が望ましい。清浄化処理の後には、水やイソプロピルアルコールなどの有機溶媒を用いて焼結治具を洗浄してもよい。
なお、Ｒ化合物やＲメタルの除去手段は、治具自体を激しく傷つけるようなものでなければ前述の清浄化処理以外の手段も採用することができる。
【００１１】
上記の方法によって清浄化された焼結治具を用いて行う焼結方法は自体公知の方法を採用することができる。成形体の形状が長いものや、厚みが薄いものである場合、敷粉としてＡｌ２Ｏ３、ＳｉＯ２、ＺｒＯ２などの粉末やカーボン粉末を台板上に敷いて成形体を載置することが望ましい。これにより成形体に対する接触面を減らすことができ、焼結時に成形体の変形や成形体と台板との溶着を抑制することができるので都合がよい。
【００１２】
【実施例】
以下の実験例と比較例を各々５枚の台板を用いて行った。
実験例１：
（工程１）
組成がＮｄ：１４．５原子％、Ｄｙ：０．５原子％、Ｂ：７原子％、Ｆｅ：７８原子％である平均粒径が約３．５μｍの合金粉体を調製し、これを用いて、０．８ＭＡ／ｍの配向磁界で寸法１０ｍｍ×１０ｍｍ×３ｍｍの成形体（グリーン密度４．０ｇ／ｃｍ３、配向方向は３ｍｍの厚み方向）を作製した。前記合金粉末の調製方法は、以下のとおりである。
公知のストリップキャスト法を用い、上記組成の合金を高周波溶解によって溶融し、合金溶湯を形成した。この合金溶湯を１３５０℃に保持した後、単ロール法によって、合金溶湯をロール周速度約１ｍ／秒、冷却速度５００℃／秒、過冷度１８０℃の条件で急冷し、厚さ０．３ｍｍのフレーク状合金鋳塊を得た。
次に粗粉砕された原料合金を複数の原料パックに充填し、ラックに搭載した。この後、原料パックが搭載されたラックを水素炉の前まで搬送し、水素炉の内部へ挿入した。原料合金を水素炉内で加熱し、そして水素を吸蔵させて水素粉砕処理を行った。その後、水素炉内で室温程度にまで冷却された原料粉末を取り出し、これをジェットミルを用いて窒素ガス雰囲気中で微粉砕し、平均粒径が約３．５μｍの合金粉末を得た。
次にこの合金粉末に対してロッキングミキサー内で潤滑剤を０．３ｗｔ％添加・混合し、潤滑剤で合金粉末粒子の表面を被覆した。ここで、潤滑剤としては、脂肪酸エステルを石油系溶剤で希釈したもの、具体的には、脂肪酸エステルとしてカプロン酸メチルを、石油系溶剤としてイソパラフィンを用い、カプロン酸メチルとイソパラフィンとの重量比を１：９として希釈したものを用いた。このような操作は、液体潤滑剤で粉末粒子の表面を被覆することで、粉末の酸化を防止するとともにプレス時の配向性および粉末成形性（成形体の抜き出し易さ）を向上させるために行った。
寸法３００ｍｍ×２５０ｍｍ×１ｍｍのＭｏ板（Ｌａ２Ｏ３を１ｍａｓｓ％添加、Ｒａは２μｍ〜１０μｍ）を台板として使用し、前記の成形体を２０個、その１０ｍｍ×１０ｍｍの面が台板に接するように載置し、Ａｒ雰囲気中１１００℃で３時間の焼結を行った。その結果、台板表面上の成形体を載置していた部分にＲ化合物やＲメタルの突起物や隆起物が付着した。
（工程２）
上記の台板を水素炉内に収容し、炉内の温度を１００℃、水素圧（絶対圧）を０．１ＭＰａに維持して５時間存置した後、炉内を常温に戻してから台板を取り出した。
（工程３）
取り出した台板表面に、ブラスト圧力３αＰａ（α＝９．８０６６５×１０４）で、平均粒径が３００μｍ〜４００μｍのＡｌ２Ｏ３粒を砥粒として５分間噴射し、ショットブラストを行って台板を清浄した。
（結果）
全ての台板について、その表面の突起物や隆起物を完全に除去することができた。
【００１３】
実施例２：
実施例１によって清浄された台板を用いて、実施例１の工程１〜工程３を繰り返し行った。その結果、２００回繰り返してもどの台板の表面にも変化は見られなかった。
【００１４】
比較例１：
実施例１における工程２を省略する以外は実施例１と同じ処理を行った。その結果、どの台板にもその表面に突起物や隆起物が残り、これらを完全に除去することはできなかった。
【００１５】
比較例２：
比較例１で除去することができなかった突起物や隆起物をやすりを用いて削り取り、台板表面から突起物や隆起物を完全に除去した。この台板を用いて、実施例１の工程１→実施例１の工程３→やすりによる突起物や隆起物の除去、を繰り返して行った。その結果、１００回繰り返すまでにどの台板の表面にもひび割れが発生した。
【００１６】
上記の実験例と比較例から、実験例１の工程２にてＲ２Ｏ３やＲ（ＯＨ）３などのＲ化合物やＲメタルを脆化することで、これらを清浄化処理によって容易に除去することができること、その結果、焼結工程を繰り返し行っても台板表面を変形させたり、傷つけたり、ひび割れさせたりすることがないので、使用できる延べ回数を延長することができることが明らかになった。
【００１７】
【発明の効果】
本発明においては、焼結治具をショットブラストなどを行うことによって清浄化処理する前に水素雰囲気中に存置することによって、焼結治具に付着したＲ化合物やＲメタルに水素を吸蔵させる。その結果、Ｒ化合物やＲメタルが水素化反応を起こして水素化合物を生成することによって脆化し、焼結治具表面から剥離しやすくなる。よって、付着物を穏和な機械的清浄化処理条件で極めて簡易にかつ効果的に除去できるので、焼結工程を繰り返し行っても焼結治具表面を変形させたり、ひび割れさせたりすることがないので、使用できる延べ回数の延長を図ることができる。また、Ｒ化合物やＲメタルなどの付着物を除去した治具を用いることでこれらの付着物に起因する磁石の割れや磁石の磁気特性の劣化などを抑制することができる。また、治具に付着物が付いても早期にこれを除去することで、Ｍｏを主成分とする台板を使用した場合でも、台板表層部にＭｏ−Ｆｅの化合物を生成することを効果的に防止することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cleaning method under mild conditions of a sintering jig for an R—Fe—B permanent magnet to which an R compound (R is a rare earth element including Y; hereinafter the same) and / or an R metal is adhered, R— Simple and effective method for removing R compound and / or R metal adhering to a sintering jig for Fe-B permanent magnets, and R-Fe- using a sintering jig cleaned by the cleaning method The present invention relates to a sintering method for a B-based permanent magnet.
[0002]
[Prior art]
R-Fe-B sintered magnets represented by Nd-Fe-B permanent magnets were obtained by press-molding an alloy powder obtained by pulverizing an alloy ingot having a required composition in a magnetic field. It is manufactured through a step of sintering the compact in a sintering furnace. In the sintering process, for example, the molded body is placed on a base plate mainly composed of Mo, and further, the molded body is stored in a container so that the molded body is not oxidized before the sintering process. Performed at a temperature of ° C. During the sintering, R of the molded body becomes a liquid phase and comes out on the surface of the molded body. R that comes out in the liquid phase is welded to the jig as R metal. The welded R metal becomes an R compound such as R 2 O 3 or R (OH) 3 by reaction with oxygen or moisture in the atmosphere, and forms protrusions and protrusions on the jig surface. These protrusions and protrusions include R metal and R compound caused by alloy powder spilled from the compact.
When the sintering process is repeated using a base plate having protrusions and bumps made of R compound or R metal, the deposits gradually become larger with the protrusions and bumps formed earlier as the core. Go. In addition, since the molded body is greatly shrunk during sintering, if the molded body is sintered while being in contact with a relatively large deposit, the shrinkage of the molded body is inhibited, and cracks and the like are caused from the contact portion. It will cause it. Since the compact may shrink as much as 25% in the magnetic field orientation during pressing, this problem becomes even more pronounced when the compact is placed with the magnetic field orientation of the compact parallel to the base plate. . Further, when R metal or R compound remains on the surface of the base plate, R metal reacts with oxygen or moisture in the atmosphere to become R compound such as R 2 O 3 or R (OH) 3. Decomposes during sintering to generate H 2 O. The generated H 2 O reacts with the molded body to generate R compounds such as R 2 O 3 and R (OH) 3 on the surface of the sintered body, thus degrading the magnetic properties of the completed magnet. I will let you. On the other hand, when a base plate mainly composed of Mo is used, if it is sintered again without completely removing the deposits, Fe contained in the deposits reacts with Mo by repeating the sintering process, It is considered that a Mo—Fe compound is generated in the surface layer portion of the plate. The portion where such a compound is generated has a higher reactivity with the molded body (sintered body) than the base plate portion that does not react with Fe, and it is easy to weld R metal and R compound. Grow protrusions and bumps. In Japanese Patent No. 2754098, the applicant proposed a method of cleaning the sintering jig by performing shot blasting or the like for the purpose of removing deposits on the base plate.
[0003]
[Problems to be solved by the invention]
However, only mechanical methods using shot blasting as described above are relatively large among the deposits on the welded portion of the sintering jig and the deposits formed by welding to the sintering jig. Only the kimono could be removed, and it was difficult to completely remove the deposits. In particular, the portion where the Mo—Fe compound was once formed was very hard, and it was extremely difficult to remove it by shot blasting alone. For this reason, in order to completely remove the deposits that could not be removed, it was necessary to perform a process such as using a file after performing shot blasting. However, if such treatment is applied to the sintering jig many times, scratches will occur, and the sintering jig surface may be deformed or cracked while the sintering process is repeated. There was a problem such as. Therefore, although the sintering jig can be repeatedly used in the sintering process by mechanical cleaning, there is a limit to the total number of times that it can be used, and a better cleaning method has been desired. .
Therefore, in the present invention, a cleaning method under a mild condition of a sintering jig for an R—Fe—B permanent magnet to which an R compound and / or R metal is adhered, and a sintering treatment for an R—Fe—B permanent magnet. A simple and effective method for removing R compound and / or R metal adhering to a tool and a method for sintering an R-Fe-B permanent magnet using a sintering jig cleaned by the cleaning method The purpose is to do.
[0004]
[Means for Solving the Problems]
As a result of various studies in view of the above points, the present inventor found that when the sintering jig to which the R compound or R metal was adhered was placed in a hydrogen atmosphere before mechanical cleaning treatment, Occludes hydrogen, causes hydrogenation reaction to generate hydrogen compounds, expands, and embrittles from the inside, so these deposits are extremely reliable from the surface of the sintering jig under mild mechanical cleaning conditions. It was found that it can be removed efficiently and effectively.
[0005]
The present invention has been made on the basis of such knowledge, and the cleaning method for the sintering jig for R-Fe-B permanent magnets of the present invention has an R compound and / or an R metal adhering thereto as described in claim 1. The R-Fe-B permanent magnet sintering jig is placed in a hydrogen atmosphere, and then the sintering jig is cleaned.
Moreover, the cleaning method of the sintering jig for R—Fe—B permanent magnets according to another aspect of the present invention is attached to the sintering jig for R—Fe—B permanent magnets as described in claim 2. After the R compound and / or R metal is embrittled in a hydrogen atmosphere, the sintering jig is cleaned.
The cleaning method according to claim 3 is characterized in that, in the cleaning method according to claim 1 or 2, the material constituting the sintering jig contains Mo as a main component.
The cleaning method according to claim 4 is the cleaning method according to claim 3 , wherein at least one component selected from La 2 O 3 , ZrO 2 , and TiC is further added to the material constituting the sintering jig. It is characterized by that.
A cleaning method according to claim 5 is the cleaning method according to any one of claims 1 to 4, wherein the surface of the sintering jig is uneven.
The cleaning method according to claim 6 is the cleaning method according to claim 5, wherein the surface roughness (Ra) of the unevenness is 0.1 μm to 500 μm.
A cleaning method according to a seventh aspect is the cleaning method according to any one of the first to sixth aspects, wherein the sintering jig is a base plate on which the molded body is placed.
The method for removing the R compound and / or R metal adhering to the sintering jig for the R—Fe—B permanent magnet of the present invention has the R compound and / or R metal attached as described in claim 8. After the R-Fe-B permanent magnet sintering jig is placed in a hydrogen atmosphere, the R compound and / or R metal is removed.
The method for removing the R compound and / or R metal adhering to the sintering jig for the R—Fe—B permanent magnet according to another aspect of the present invention is the R—Fe—B system according to claim 9. The R compound and / or R metal adhering to the permanent magnet sintering jig is embrittled in a hydrogen atmosphere and then removed.
Moreover, the sintering method of the R—Fe—B permanent magnet of the present invention is the R—Fe—B system cleaned by the cleaning method according to claim 1 as described in claim 10. A permanent magnet sintering jig is used.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
R-Fe-B permanent magnet sintering jig with R compound and / or R metal attached (hereinafter, "R-Fe-B permanent magnet sintering jig" is simply referred to as "sintering jig") As a method for placing the material in a hydrogen atmosphere, for example, a method of accommodating a sintering jig with deposits in a hydrogen furnace can be mentioned.
In this case, the absolute amount of hydrogen in the furnace is preferably 0.05 MPa to 0.5 MPa in terms of sufficient and uniform hydrogenation, safety, work efficiency, and the like.
The temperature in the furnace is desirably room temperature to 600 ° C. If the inside of the furnace is heated, the sintering jig is also heated, so that hydrogen storage of the R compound and R metal adhering to the sintering jig occurs actively, and the hydrogenation reaction is promoted. Accordingly, hydrogen spreads to the inside of these deposits within a short period of time and expands in volume, so that microcracks are generated inside the deposits, and the deposits become brittle. When the temperature in the furnace is higher than 600 ° C., the surface layer portion of the deposit is melted and welding progresses, which is not desirable. The higher the temperature in the furnace, the longer the cooling takes. Therefore, the temperature in the furnace is more preferably 400 ° C. or lower. In addition, since R-Fe-B magnetic alloy powders and compacts thereof are rich in reactivity with hydrogen and generate reaction heat, the reaction heat can be reduced by placing them on a sintering jig. The sintering jig can also be heated by using it.
The housing time of the sintering jig in the furnace is desirably 30 minutes to 10 hours.
[0007]
Specifically, as the sintering jig, a base plate on which the molded body is placed, a sintering case and a sintered pack for housing the base plate on which the molded body is placed, and a base plate on which the molded body is placed are loaded. For example, spacers used for the purpose are described.
The sintering jig is preferably made of Mo as a main component. Sintering jigs made of stainless steel or Fe may be used, but Mo has relatively low reactivity with R, so that the reaction product of Mo and R is difficult to adhere, and because strength and toughness are high, shape deformation, etc. This is because it has the advantage that it does not easily occur and heat conductivity is high and it is easy to be heated, so that the sintering temperature and the temperature of the deposit are relatively fast.
The sintering jig mainly composed of Mo may be made of an alloy to which at least one component selected from La 2 O 3 , ZrO 2 and TiC is added in addition to Mo. The addition of these components increases the recrystallization temperature of the sintering jig, so that it does not harden during sintering and is less likely to crack due to impact or the like.
[0008]
As for the base plate which mounts a molded object, what has an unevenness | corrugation in the surface is desirable. This is because by reducing the contact area with the molded body, deformation of the molded body and welding between the molded body and the base plate can be suppressed during sintering. As for the surface roughness (Ra) of the unevenness | corrugation of a baseplate, it is desirable that they are 0.1 micrometer-500 micrometers. If the surface roughness is smaller than this, the base plate and the molded body are too closely adhered during sintering and both may be welded. On the other hand, if the surface roughness is larger than this, the irregularities are too large and the projections bite into the molded body, inhibiting the shrinkage of the molded body during sintering, and as a result, the resulting sintered body is cracked, cracked, etc. May be caused. In particular, in the case of a molded body for manufacturing a large and heavy magnet such as a magnet used in a VCM (voice coil motor) or linear motor, the contact area to the molded body is small and the surface of the base plate is convex. The surface roughness of the base plate is preferably 2 μm to 10 μm in order to reduce the inhibition of the shrinkage of the molded body during sintering by the part.
[0009]
As a chemical reaction between an R compound or R metal and hydrogen, for example, a reaction represented by the following chemical formula can be considered.
By placing a sintering jig with R compound or R metal attached in a hydrogen atmosphere, the adhering R compound or R metal absorbs hydrogen and expands in volume, thereby generating microcracks therein. Since it becomes brittle, it becomes easy to peel from the surface of the sintering jig. Thus, they can be removed very easily and effectively, for example, under mild mechanical cleaning conditions.
As a method for the cleaning treatment, a simple method such as scraping by hand with steel wool or a spatula can be adopted in addition to a shot blasting method, a liquefaction homing method, a buffing method, and the like. In the shot blasting method, Al 2 O 3 grains, SiO 2 grains, glass grains and the like can be used for the abrasive grains, and the average grain diameter of the abrasive grains is preferably 20 μm to 1000 μm. The blast pressure is preferably 1αPa to 5αPa (α = 9.80665 × 10 4 ). The blasting time is preferably 30 seconds to 30 minutes. After the cleaning treatment, the sintering jig may be cleaned using an organic solvent such as water or isopropyl alcohol.
As the means for removing the R compound and R metal, means other than the above-described cleaning treatment can be employed as long as the jig itself is not severely damaged.
[0011]
As a sintering method performed using the sintering jig cleaned by the above method, a method known per se can be adopted. If the shape of the compact is long or thin, place the compact by placing a powder of Al 2 O 3 , SiO 2 , ZrO 2 or the like on the base plate as a floor powder. Is desirable. Thereby, the contact surface with respect to a molded object can be reduced, and since a deformation | transformation of a molded object and welding with a molded object and a base plate can be suppressed at the time of sintering, it is convenient.
[0012]
【Example】
The following experimental examples and comparative examples were performed using five base plates each.
Experimental example 1:
(Process 1)
An alloy powder having a composition of Nd: 14.5 atomic%, Dy: 0.5 atomic%, B: 7 atomic%, Fe: 78 atomic% and an average particle diameter of about 3.5 μm was prepared and used. Thus, a molded body having a size of 10 mm × 10 mm × 3 mm (green density 4.0 g / cm 3 , the orientation direction is a thickness direction of 3 mm) was produced with an orientation magnetic field of 0.8 MA / m. The method for preparing the alloy powder is as follows.
Using a known strip casting method, an alloy having the above composition was melted by high frequency melting to form a molten alloy. After this molten alloy is maintained at 1350 ° C., the molten alloy is rapidly cooled at a roll peripheral speed of about 1 m / second, a cooling speed of 500 ° C./second, and a supercooling degree of 180 ° C. by a single roll method. A flaky alloy ingot was obtained.
Next, the coarsely pulverized raw material alloy was filled into a plurality of raw material packs and mounted on a rack. Thereafter, the rack loaded with the raw material pack was transported to the front of the hydrogen furnace and inserted into the hydrogen furnace. The raw material alloy was heated in a hydrogen furnace, and hydrogen was occluded to perform hydrogen pulverization. Thereafter, the raw material powder cooled to about room temperature in the hydrogen furnace was taken out and pulverized in a nitrogen gas atmosphere using a jet mill to obtain an alloy powder having an average particle size of about 3.5 μm.
Next, 0.3 wt% of a lubricant was added to and mixed with the alloy powder in a rocking mixer, and the surface of the alloy powder particles was coated with the lubricant. Here, as the lubricant, a fatty acid ester diluted with a petroleum solvent, specifically, methyl caproate as a fatty acid ester and isoparaffin as a petroleum solvent, the weight ratio of methyl caproate and isoparaffin is set. Diluted 1: 9 was used. Such an operation is performed in order to prevent powder oxidation by coating the surface of the powder particles with a liquid lubricant and to improve the orientation during pressing and the powder moldability (ease of extracting the molded product). It was.
A Mo plate of 300 mm × 250 mm × 1 mm size (1 mass% of La 2 O 3 added, Ra is 2 μm to 10 μm) is used as a base plate, 20 of the above-mentioned compacts, and the 10 mm × 10 mm surface is the base plate The samples were placed in contact with each other and sintered in an Ar atmosphere at 1100 ° C. for 3 hours. As a result, R compound and R metal protrusions and bumps adhered to the portion where the molded body on the surface of the base plate was placed.
(Process 2)
The above base plate is accommodated in a hydrogen furnace, the temperature in the furnace is maintained at 100 ° C., the hydrogen pressure (absolute pressure) is maintained at 0.1 MPa and left for 5 hours, and then the temperature in the furnace is returned to room temperature and then the base plate Was taken out.
(Process 3)
On the surface of the removed base plate, Al 2 O 3 grains having an average grain size of 300 μm to 400 μm are sprayed as abrasive grains at a blast pressure of 3αPa (α = 9.80665 × 10 4 ) for 5 minutes, and shot blasting is performed. The board was cleaned.
(result)
All the base plates were able to completely remove the protrusions and bumps on the surface.
[0013]
Example 2:
Using the base plate cleaned by Example 1, Steps 1 to 3 of Example 1 were repeated. As a result, no change was observed on the surface of any base plate even after repeating 200 times.
[0014]
Comparative Example 1:
The same process as in Example 1 was performed except that Step 2 in Example 1 was omitted. As a result, protrusions and bumps remained on the surface of any base plate, and these could not be completely removed.
[0015]
Comparative Example 2:
The protrusions and protrusions that could not be removed in Comparative Example 1 were scraped off using a file, and the protrusions and protrusions were completely removed from the surface of the base plate. Using this base plate, Step 1 of Example 1 → Step 3 of Example 1 → Removal of protrusions and protrusions by a file was repeated. As a result, cracks occurred on the surface of any base plate by repeating 100 times.
[0016]
From the above experimental examples and comparative examples, R compounds such as R 2 O 3 and R (OH) 3 and R metal are embrittled in Step 2 of Experimental Example 1 so that they can be easily removed by cleaning treatment. As a result, it is clear that even if the sintering process is repeated, the surface of the base plate is not deformed, damaged or cracked, so that the total number of usable times can be extended. It was.
[0017]
【The invention's effect】
In the present invention, hydrogen is occluded in the R compound or R metal adhering to the sintering jig by leaving the sintering jig in the hydrogen atmosphere before performing the cleaning treatment by shot blasting or the like. As a result, the R compound or the R metal undergoes a hydrogenation reaction to generate a hydrogen compound, and thus becomes brittle and easily peels from the surface of the sintering jig. Therefore, the deposits can be removed very easily and effectively under mild mechanical cleaning conditions, so that the surface of the sintering jig will not be deformed or cracked even if the sintering process is repeated. Therefore, the total number of times that can be used can be extended. Further, by using a jig from which deposits such as R compound and R metal are removed, it is possible to suppress the cracking of the magnet and the deterioration of the magnetic properties of the magnet caused by these deposits. In addition, even if an adhering material is attached to the jig, it can be removed at an early stage to produce a Mo-Fe compound on the surface of the base plate even when a base plate mainly composed of Mo is used. Can be prevented.
Claims (10)
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| JP2000163654A JP4325082B2 (en) | 1999-05-31 | 2000-05-31 | Method for cleaning sintering jig for R-Fe-B permanent magnet and method for sintering R-Fe-B permanent magnet using sintering jig cleaned by the cleaning method |
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| JP15106199 | 1999-05-31 | ||
| JP11-151061 | 1999-05-31 | ||
| JP2000163654A JP4325082B2 (en) | 1999-05-31 | 2000-05-31 | Method for cleaning sintering jig for R-Fe-B permanent magnet and method for sintering R-Fe-B permanent magnet using sintering jig cleaned by the cleaning method |
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| JP2002305122A (en) * | 2001-04-05 | 2002-10-18 | Sumitomo Special Metals Co Ltd | Method of manufacturing rare-earth sintered magnet |
| JP2002333282A (en) * | 2001-05-14 | 2002-11-22 | Tokyo Yogyo Co Ltd | Sintering setter and its producing method |
| JP4596131B2 (en) * | 2004-08-30 | 2010-12-08 | Ｔｄｋ株式会社 | Rare earth sintered magnet manufacturing method and sintered container |
| JP2019114714A (en) * | 2017-12-25 | 2019-07-11 | イビデン株式会社 | Manufacturing method of sintered magnet and receiver made of graphite |
| CN110957125B (en) * | 2019-12-24 | 2021-11-05 | 厦门钨业股份有限公司 | Sintering method of neodymium iron boron permanent magnet material and neodymium iron boron permanent magnet material |
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