JP4288637B2 - Method for producing rare earth alloy powder for permanent magnet - Google Patents

Description

【０００１】
【発明の属する技術分野】
この発明は、永久磁石用希土類系合金粉末の製造方法の改良に係り、特に、各種モータ、アクチュエータ等に適した希土類系ボンド磁石並びに焼結磁石に用いられる永久磁石用希土類系合金粉末の製造方法に関する。
【０００２】
【従来の技術】
希土類系永久磁石用合金粉末の金属組織制御法として、HDDR(Hydrogenation-Disproportionation‐Desorption‐Recombination)処理法と呼ばれるものがある。HDDR処理とは、水素化(Hydrogenation)、不均化(Disproportionation)、脱水素化(Desorption)、および再結合(Recombination)を順次実行するプロセスである。
【０００３】
このHDDR処理で合金磁石粉末を製造するには、R‐T‐(M)‐B系原料合金(RはYを含む希土類元素、TはFeまたはFeとCoとの混合物、Mは添加元素、Bはボロンで一部又は全量をCで置換可能)のインゴットまたは粉末をH₂ガス雰囲気またはH₂ガスと不活性ガスとの混合雰囲気中で温度500℃〜1000℃に保持し、それによって上記合金のインゴットまたは粉末に水素を吸蔵させた後、H₂分圧13Pa以下の真空雰囲気またはH₂分圧13Pa以下の不活性ガス雰囲気になるまで温度500℃〜1000℃で脱水素処理し、次いで冷却する。
【０００４】
HDDR処理法によって希土類系永久磁石用合金粉末を製造する方法は、例えば特開平1-132106号公報、特開平2-4901号公報に開示されている。当該水素雰囲気での熱処理法で製造されたR‐T‐(M)‐B合金磁石粉末は大きな保磁力を有しており、組成および処理条件の選択によっては磁気的な異方性を有する。
【０００５】
このような性質を有するのは、金属組織が実質的に0.1〜1μmの非常に微細な結晶の集合体となるためである。より詳細には、上記HDDR処理によって得られる極微細結晶の粒径が正方晶R₂T₁₄B系化合物相の単磁区臨界粒径に近いために高い保磁力を発揮し、しかも、極微細結晶粒が結晶方位をある程度、揃えて集合しているためである。
【０００６】
HDDR処理法は、大きな反応熱を伴う固相‐気相の化学反応であるために、処理条件等の制御がきわめて困難であるという欠点を有している。特に処理量が多いときほど温度及び雰囲気の制御が困難になり、安定して優れた磁気特性を得ることが難しい。また、水素化・不均化反応と、その逆反応である脱水素・再結合反応を同一処理設備で連続して行うため、それぞれの処理条件を最適にすることが困難であった。
【０００７】
特開平5-166617号公報では、脱水素・再結合反応を安定的に進行させるため、また水素放出時の安全性を考慮して、水素化・分解反応と脱水素・再結合反応をそれぞれ独立で処理し、R‐T‐(M)‐B系合金の塊状物または粉末に熱処理で行う方法が提案されている。
【０００８】
特開平7-316717号、特開平7-316753号公報には、均一微細な組織を持ち、保磁力の温度係数の小さい磁石粉末を得るために、750℃以下の温度域で水素化・分解反応を起こさせた中間原料が示されている。低温域で水素化・分解反応を行わせて冷却し、制御された形状と大きさを持つ中間生成相を有する原料を得、前記原料に、脱水素・再結合処理を施すことで、生成する主相の結晶粒径を小さく均一にできることが提示されている。
【０００９】
【発明が解決しようとする課題】
発明者等は、HDDR処理において、原料合金の組成と処理条件のみの調整で、比較的簡単に磁気的な異方性と高い保磁力を有する磁粉が得られることに興味を持ち、特に磁気的な異方性が得られるメカニズムの解明に鋭意努力を重ねてきた。その結果大きな磁気的異方性を得るためには、反応速度や中間生成組織が重要であることを知見した。すなわち、実際の処理条件では、水素中における特定温度域の昇温速度が重要であることを見出し、特開平6-128610号や特開平7-54003号公報に示した。
【００１０】
また、水素化・分解反応後の合金のミクロ組織には、これまで知られていたR水素化物相、T相、T‐B系化合物(Fe₂B)相以外に、R₂T₁₄B化合物相及びこの相と整合する正方晶(Fe₃Bと思われる)が存在する場合に大きな磁気的異方性が得られることを知見し、特開平9-256001号に示した。
【００１１】
HDDR法における磁気異方性の起源は、前記公報にも示したように、母合金の結晶方位の維持にあり、その遺伝子としてR₂T₁₄B化合物相及びこの相と整合する正方晶(Fe₃Bと思われる)が機能している。厳密には雰囲気の水素分圧によって変わるが、600〜750℃の範囲で水素化・分解反応が進行すると、これら2相は残存することができずに分解し、脱水素処理後の磁気的異方性が低下、残留磁化が小さくなる。この現象を避けるために、特開平6-128610号や特開平7-54003号公報に示したような、特定温度範囲の昇温速度を一定レベル以上に維持するか、この温度域を通過した後に水素を導入するなどの方法が採られる。
【００１２】
前記知見内容に基づき、特開平5-166617号公報に示された方法をみると、冷却時に水素雰囲気において600〜750℃の範囲を通過するため、R₂T₁₄B化合物相及びこの相と整合する正方晶(Fe₃Bと思われる)の分解反応が進行して磁気的な異方性が失われ、大きな残留磁化を得ることはできない。
【００１３】
この現象を回避するため、特開平5-166617号公報では、水素雰囲気での冷却速度を50℃/min以上と規定しているが、処理量が増すに従い、大きな冷却速度を得ることが困難となり、前記規定は工業的に実施することは極めて困難である。
【００１４】
また、特開平7-316717号、特開平7-316753号公報に示された方法では、低温域の処理ではR₂T₁₄B化合物相及びこの相と整合する正方晶(Fe₃Bと思われる)の分解反応を回避できる可能性があるが、処理温度が低温であるために水素化・分解反応に多大な時間を要する。
【００１５】
この発明は、R‐T‐(M)‐B系原料合金のHDDR処理に際して、脱水素処理を行うだけで安定して高い保磁力と大きな残留磁化を持つ、希土類系ボンド磁石並びに焼結磁石が得られる永久磁石用希土類系合金粉末を、工業的に製造すること、すなわち安定的にかつ多量に生産できる製造方法を確立することを目的としている。また、この発明は、所要の脱水素処理を行うだけで安定して高い保磁力と大きな残留磁化を持つ、中間生成物として取扱いが良好な永久磁石用希土類系原料合金を提供することを目的とする。
【００１６】
【課題を解決するための手段】
発明者は、HDDR処理において大きな磁化を維持したまま、粉末状態で大きな保磁力を得ることが可能な処理方法を目的に種々検討したところ、HDDR処理磁粉の磁気特性が、水素化・分解反応後の組織と、脱水素・再結合反応の反応速度に大きく影響を受ける、すなわち、HDDR処理における脱水素時の水素放出速度の変化が再結合反応速度の変化となって、結果的に磁性粉末の磁気特性に大きく影響すること、よってその脱水素時の反応速度を制御することで高い保磁力が得られることを知見した。
【００１７】
また、発明者は、安定的にかつ多量にHDDR処理できる方法を目的に、脱水素時の反応速度の制御方法について検討した結果、最初の脱水素化処理にて被処理物の水素濃度が所定値に達した時点で一旦同処理を終了し、その後二度目の脱水素化処理を施す方法によっても連続的処理と同様の高い保磁力が得られることを知見した。
【００１８】
発明者は、前記の前段、後段の2段階処理について、さらに鋭意検討した結果、最初の脱水素化処理を特定条件で終了させることにより、二度目の同処理において、大量に処理できかつ大きな磁化を維持したまま、粉末状態で大きな保磁力が得られること、すなわち、一度目の処理による中間生成物の原料合金を造り置きしておくことが可能で、その後二度目の処理で前記中間生成物の原料合金を一度に大量に処理でき、高磁気特性を有するHDDR処理粉末が得られることを知見し、この発明を完成した。
【００１９】
すなわち、この発明による希土類系合金粉末の製造方法は、Ｒ_２Ｔ_１４Ｂ（ＢはＣで一部又は全量置換可能）型の化合物相が５０ｖｏｌ％以上を占める合金からなる鋳塊または粉末を、水素化及び不均化処理し、さらに脱水素化及び再結合処理するに際し、最初の脱水素化処理にて被処理物の水素濃度が次式の範囲に達した時点で一旦同処理を終了して冷却し、その後二度目の脱水素化処理を施すことを特徴とする。
０．０００７２５×Ｃ _Ｒ ≦Ｃ _Ｈ ≦０．０１２０×Ｃ _Ｒ
但し、Ｃ _Ｈ は合金中の水素濃度（ｗｔ％）、Ｃ _Ｒ は合金中の希土類Ｒ成分濃度（ｗｔ％）。
【００２０】
また、この発明によるHDDR処理おける最初の脱水素化処理として、雰囲気の制御、例えば不活性ガス流気中及び/又は真空排気による雰囲気の全圧によって調節される方法などにより、
(A) 脱水素化の反応速度を0.1wt%/h〜5.0wt%/hの範囲で進行させ、反応開始から被処理物の水素濃度C_Hが次の(1)式の範囲に達するまで実施する方法、
(B) 脱水素化の反応速度を0.01wt%/h〜0.2wt%/hの範囲で進行させ、反応開始から被処理物の水素濃度C_Hが次の(2)式の範囲に達するまで実施する方法、
を提案する。
0.000725×C_R≦C_H≦0.00750×C_R (1)式
0.00700×C_R≦C_H≦0.0120×C_R (2)式
但し、C_Hは合金中の水素濃度(wt%)、
C_Rは合金中の希土類R成分濃度(wt%)。
【００２１】
また、この発明によるHDDR処理おける二度目の脱水素化処理として、
(C) 雰囲気の制御により脱水素化の反応速度を0.01wt%/h〜0.2wt%/hの範囲で進行させる方法、
(D1) 第1段階は、雰囲気の制御により反応開始から被処理物の水素濃度C_Hが前記(1)式の範囲に達するまでであり、第2段階は、水素濃度C_Hが0.01wt%以下となるまで実施する方法、
(D2) 第1段階は、水素放出速度が0.1wt%/h〜5.0wt%/h、雰囲気の制御により反応開始から被処理物の水素濃度C_Hが前(1)式の範囲に達するまでであり、第2段階は、水素放出速度が0.01wt%/h〜0.20wt%/hであり、水素濃度C_Hが0.01wt%以下となるまで実施する方法、
(E) 真空中または不活性ガス雰囲気中で、温度650〜1000℃に15分〜4時間保持した後に冷却し、水素濃度を0.01wt%以下とする方法、
を提案する。
【００２２】
この発明において、上記脱水素化処理方法の好ましい構成例を示すと、(A)方法で処理されて所定の水素濃度となった中間生成物は、上記の(C)方法あるいは(E)方法にて二度目の脱水素化処理されることが好ましい。また、(A)方法後の中間生成物の水素濃度に応じて、二度目の脱水素化処理として2段階で処理する(D1)又は(D2)方法を採用することができる。さらに(B)方法で処理された中間生成物は、上記の2段階で処理する(D1)又は(D2)方法により二度目の脱水素化処理が実施されることが好ましい。また、(B)方法で処理された中間生成物を(E)方法で処理することもできる。
【００２３】
さらに、この発明によるHDDR処理おける二度目の脱水素化処理を行うための昇温方法として、雰囲気を全圧50kPa〜1000kPaである不活性ガス雰囲気とする方法、雰囲気を水素分圧100Pa以上であり、かつ600〜750℃の範囲の温度領域を10℃/min以上の速度で昇温する方法、を提案する。
【００２５】
【発明の実施の形態】
この発明は、HDDR処理法による永久磁石用希土類系合金粉末の製造方法において、脱水素・再結合反応を2回に分けて行うもので、最初の脱水素化処理によって得られた、中間生成物の希土類系原料合金を別途実施する2度目の脱水素化処理を施して目的の希土類系合金粉末を得るもので、量産規模で実施できることを特徴としている。
【００２６】
この発明について、以下に、対象とする合金組成、水素化・不均化処理の好ましい実施条件、最初の脱水素化処理の好ましい実施条件、中間生成物の希土類系原料合金の性状、2度目の脱水素化処理の好ましい実施条件の順に詳述する。
【００２７】
合金組成
この発明の対象とする合金組成は、R₂T₁₄B(BはCで一部又は全量置換可能)型の化合物相が50vol%以上を占める合金であり、また種々の添加元素Mを含有し得る。希土類元素Rは、Yを含むいずれの希土類元素を含有することも制限しないが、Rのうち少なくともNdまたはPrの一方、あるいはその両方を含む必要がある。また、Dy、Tb、Hoのうち、1種以上を含有することは、最終的に得られる磁石材料の保磁力を高める効果があり、好ましい。
【００２８】
Rの量は、10〜20at%が望ましく、より好ましくは11〜15at%である。R量が10at%未満では保磁力が低下し、20at%を越えると強磁性相の比率が低下し、磁化が小さくなる。
【００２９】
Tは、鉄属元素であり、Fe、Co、Niが該当する。CoをFeと置換して添加すると、キュリー点が上昇する効果以外に、HDDR処理における磁気的な異方性をより得やすくなり、高い磁化が得られる。Coの添加はTのうち50%まで可能で、50%を越えると磁化が低下するので好ましくない。Niは、小量の添加では異方性の向上に効果があるが、磁化を下げるのでTの5%以下の添加が望ましい。
【００３０】
Tの量は、67〜85at%が望ましく、67at%未満ではR₂T₁₄B化合物相の比率が低下して磁化が小さくなり、85at%を越えると磁気的にソフトの相が生成し、保磁力が低下する。
【００３１】
Bは、その一部をCで置換することができ、また、全量Cで置換することも可能である。Bの量は、4〜10at%が良く、4at%未満では磁気的にソフトの相が生成して保磁力が低下し、10at%を越えるとR₂T₁₄B化合物相の比率が低下して磁化が小さくなる。
【００３２】
必要に応じて添加する添加元素Mは、磁気的な異方性を高めたり、保磁力を高めることを目的に添加される。異方性向上に効果のある元素として、Ga、Zr、Hf等が良く知られており、保磁力を高める元素としてCu、Al等がある。このほか、Si、Ti、V、Cr、Mn、Zn、Ge、Nb、In、Sn、Ta、W、Pbなどを添加含有させることができる。
【００３３】
添加元素Mは、1種または2種以上を組み合わせて添加することが可能である。Mの添加量は、前記効果を目的として添加する場合、5at%以下にすることが望ましい。添加量が5at%を越えると、磁性に寄与しない相が増加して磁化が低下する。
【００３４】
水素化条件
水素化温度は、650℃未満であると、水素化・不均化反応が充分に進行せず、950℃を超える、後述の雰囲気水素分圧の範囲内では水素化・不均化反応が生じない条件となるため、水素化温度範囲は650〜950℃が望ましい。
【００３５】
水素化時の水素分圧は、10kPa未満では反応の進行が不充分で、高い保磁力を発現することができず、また1000kPaを超えると、装置に高い耐圧構造が要求され、またHDDR処理して得た合金粉末の磁気特性上のメリットが特に認められないことから、水素分圧範囲は10〜1000kPaが望ましい。
【００３６】
前記処理温度並びに水素分圧条件は、必ずしも一定に維持する必要はなく、途中で変更しても良いし、連続的に変化させても良い。
【００３７】
なお、高い磁気異方性を有する高磁化の磁粉を得るには、さらに処理温度を750℃以上に限定し、昇温速度を10℃/min以上で700℃以上の温度域まで昇温することが好ましい。
【００３８】
また、特にバルク状原料合金を得るためには、真空中または不活性ガス中で昇温して、温度が750℃以上に達してから水素を導入する方法を用いることで、クラック等の欠陥の少ない原料合金が得られる。
【００３９】
水素濃度調整処理、最初の脱水素処理
水素化・不均化反応処理の終了時点で、処理装置内の水素ガスを追い出す、Ar置換処理を行う。この時、雰囲気の水素分圧は徐々に低下するので、水素放出反応の最初期の反応は始まっている。
【００４０】
Ar置換処理は、引き続き行う水素放出処理の安全性を確保するためにも有用であり、大きな残留磁化を得るためには所定時間行うことが好ましい。なお、後続の工程も含め、Arに換えてHeやNe等の希ガスを使用することができる。ガス種は使用する装置や工程での至便性やコストなどで適宜選択するとよい。
【００４１】
Ar置換の処理時間は、短時間では大きな残留磁化が得られず、長すぎると保磁力が小さくなる。このAr置換処理の時間は、処理量、処理装置の内容積等で決定される。なお、等方性の磁粉を得る場合は、当該処理は必須ではない。
【００４２】
この発明において、最初の脱水素化処理にて合金の水素濃度を特定の範囲に調整することにより、得られる中間生成物は、取扱いが良好となり、所要の二度目の脱水素処理を行うだけで、安定して高い保磁力と大きな残留磁化を持つ希土類系原料合金が得られる。これを実現するには、この発明の目的とする、より優れた保磁力と残留磁化を両立させかつ処理量の増大や時間の短縮などの生産性が得られるように考慮して、中間生成物合金が特定の水素濃度となるように、最初の脱水素化処理方法に、前記(A)又は(B)方法を選定し、次に該方法と合金の水素濃度に応じて、二度目の脱水素化処理を前記(C)方法(D1)又は(D2)方法、(E)方法より適宜選定するものである。従って、後述する種々の脱水素化処理の条件や中間生成物の好ましい性状(限定条件)などは、最初と二度目の脱水素化処理方法の選定と処理後の合金の水素濃度の程度などによって相対的に変動することになる。
【００４３】
この発明において、最初の脱水素処理には、(A)脱水素化の反応速度を0.1wt%/h〜5.0wt%/hの範囲で進行させ、反応開始から被処理物の水素濃度C_Hが次の(1)式の範囲に達するまで実施する方法、(B)脱水素化の反応速度を0.01wt%/h〜0.2wt%/hの範囲で進行させ、反応開始から被処理物の水素濃度C_Hが次の(2)式の範囲に達するまで実施する方法が好ましい。
0.000725×C_R≦C_H≦0.00750×C_R (1)式
0.00700×C_R≦C_H≦0.0120×C_R (2)式
但し、C_Hは合金中の水素濃度(wt%)、
C_Rは合金中の希土類R成分濃度(wt%)。
【００４４】
Ar置換処理に引き続き、最初の脱水素・再結合反応工程として、不活性ガス流気または真空排気、あるいは減圧下での不活性ガス流気の雰囲気で、水素放出速度0.1〜5.0wt%/hの範囲で、所定水素濃度になるまで熱処理を行い脱水素処理を実施する。水素化、Ar置換、最初の脱水素処理の一例を図示すると、図1Aの如くのヒートパターンとなる。
【００４５】
前記(A)方法の処理によって得られる原料合金の水素濃度C_Hは、0.00750×C_Rを超える範囲に脱水素処理を行っても磁気特性上のメリットは認められず、また前記処理方法で水素濃度C_Hを0.000725×C_R未満の範囲に制御すると、保磁力の向上効果が失われるため、好ましくない。
【００４６】
(A)方法の処理で前記水素濃度の範囲に至るまでの水素放出速度が、0.1wt%/h未満では、脱水素処理して得られる磁粉の保磁力が低くなるため好ましくない。また、水素放出速度が5.0wt%/hを超える処理は、処理量を極度に小さくするなど、実現に困難が伴うため好ましくない。
【００４７】
最初の脱水素処理を前記(B)方法で実施する場合、具体的に水素濃度調整処理として、前記Ar置換処理における処理時間を調節することで所定水素濃度の原料合金を得ることができる。原料合金中の水素濃度C_Hが、0.00700×C_R未満では脱水素処理を行って得られる磁性粉末の保磁力が低下し、また0.0120×C_Rを超えると冷却過程において、異方性発現の核となるR₂Fe₁₄B化合物相が失われ、残留磁化が低下するため、好ましくない。
【００４８】
Ar置換並びに最初の脱水素処理は、650℃〜1000℃の温度範囲で行う。650℃未満では、R水素化物が分解しないか、分解しても非常に長時間を要し、実用性が乏しい。一方、1000℃を越えると、再結合したR₂Fe₁₄B化合物相が粒成長を起こし、粗大になって保磁力が低下するためである。
【００４９】
最初の脱水素処理における水素放出速度を実現する具体的方法として、減圧Ar処理を行うことが好ましい。脱水素処理では、雰囲気の水素分圧が水素放出速度に効果的に作用するが、多量処理においては水素放出量が多大になるため、ボイル‐シャルルの法則に則り、雰囲気の全ガス分子量を制御する必要がある。実処理では雰囲気置換が効率的に行われないとミクロな原料粉末表面近傍に水素分圧の高い領域が生じ、水素放出速度を低下させてしまう。
【００５０】
この現象を回避するには、減圧状態で充分な量の雰囲気ガスを流気する方法が簡単で効果的である。実際には、ロータリーポンプ等のガス排気手段で雰囲気ガスを排気しながら、Arガスを導入し、炉内の総圧を100Pa〜10kPaの範囲の一定値に維持する方法を用いることができる。この雰囲気下で、R水素化物から水素ガスが放出できる条件が維持される。
【００５１】
前記の水素放出速度を0.1〜5.0wt%/hあるいは0.01wt%/h〜0.2wt%/hとする方法は、上記の減圧Ar処理以外に種々の方法を採用できる。例えば、特開平2-4901号公報などに示された、真空排気による方法や、単に大気圧や加圧条件でArガス等を流気する方法、また特許第2838615号公報に示したような、密閉系で水素吸蔵合金を用いて系内の水素分圧を制御する方法等が挙げられる。
【００５２】
いずれの脱水素処理方法を採用する場合においても、その水素放出速度が最終的に得られる磁粉の磁気特性に大きな影響を及ぼすことから、例えば、使用設備の有効内容積と真空排気能力とのバランスから処理量を決定する方法や、炉内総圧を調節する方法、Ar流気量を調節する方法などの種々の方法により、水素放出速度を調整する。
【００５３】
なお、処理時間は、処理量及び設備要因によって影響を受けるが、より好ましい処理時間は、2分〜60分である。
【００５４】
この最初の脱水素処理において、温度条件、雰囲気条件は、必ずしも一定である必要はなく、処理の途中で変更しても良い。また、連続的に変化させても良い。処理温度は、必ずしも水素化条件と同じにする必要はなく、独立に決定すればよい。
【００５５】
最初の脱水素処理後の冷却は、冷却速度、雰囲気総圧などは特に限定されない。生産効率を高める観点から、Ar等の不活性ガスで加圧して強制冷却を行っても良い。
【００５６】
中間生成物
中間生成物上述の最初の脱水素処理を完了することにより、少なくともＲ_２Ｔ_１４Ｂ（ＢはＣと一部又は全量置換可能）型の化合物相を含有する合金からなる鋳塊及び/又は粉末であり、含有水素濃度Ｃ_Ｈが下記（３）式の範囲にある永久磁石用希土類系原料合金を得ることができる。この希土類系原料合金は、所要の２度目の脱水素処理を行うだけで安定して高い保磁力と大きな残留磁化を持つもので、中間生成物として取扱いが良好であること特徴とする。
０．０００７２５×Ｃ _Ｒ ≦Ｃ _Ｈ ≦０．０１２０×Ｃ _Ｒ （３）式
【００５７】
この中間生成物である塊状物または粉末の希土類系原料合金の水素濃度C_Hは、0.000725×C_R未満では脱水素処理を行っても従来技術に比べて保磁力を向上させる効果が小さく、脱水素工程を別工程で行う効果が得られないため好ましくない。また、水素濃度C_Hが0.0120×C_Rを超える場合は、原料合金製造時、特に冷却時に水素化・分解反応が進行して磁気的異方性を得るための核となるR₂T₁₄B化合物相及びこの相と整合する正方晶(Fe₃Bと思われる)が失われ、その結果得られる磁粉の残留磁化が低下するので好ましくない。
【００５８】
上記希土類系原料合金が、2度目の脱水素工程を経て磁気的な異方性を持つ磁性粉末となるには少なくとも、再結合の核として、元の結晶方位を維持しているR₂T₁₄B化合物相が存在する必要がある。
【００５９】
この発明の好ましい希土類系原料合金においては、R化合物が全て水素化物とはなり得ない水素濃度であるため、水素化物でないRの少なくとも一部は、再結合の核として、R₂T₁₄B化合物相を形成していることが必須である。R₂T₁₄B化合物相が存在しない場合、脱水素処理を行って製造された磁粉は磁気的に等方的となり、磁化が小さくなるため好ましくない。
【００６０】
また、R水素化物相、T‐B化合物相、T相の3相は、脱水素・再結合時に新たなR₂T₁₄B化合物相を生成するために必須である。前記3相のうちR水素化物相がない場合は、脱水素処理を行ったときに軟磁性化合物を生成したり、軟磁性のT相が残存して保磁力が低下する。T-B相がない場合は軟磁性R‐T化合物相が析出して保磁力が劣化する。T相がない場合は強磁性でないR‐T‐B化合物が生成して磁化が低下するため好ましくない。従って、この発明の最初の脱水素処理を終了した好ましい希土類系原料合金には、R水素化物相、T‐B系化合物相、T相及びR₂T₁₄B化合物相の、少なくとも4相が共存する組織を有することが必須である。
【００６１】
上記のR水素化物相、T相及びR₂T₁₄B化合物相が存在していることは、粉末X線回折法や、熱分析法によって比較的容易に観察できるが、T‐B系化合物相は、その存在量が僅かであることから粉末X線回折法では明瞭に観察できない場合もある。透過電子顕微鏡及び電子線回折法を用いれば、前記4相をすべて確認することができる。
【００６２】
R水素化物相、T‐B系化合物相、T相及びR₂T₁₄B化合物相の、少なくとも4相から構成される希土類系原料合金の結晶粒径は、各相が0.01〜1μmの範囲であることが好ましい。
【００６３】
希土類系原料合金に粒径が1μmを超える結晶が存在する場合、その結晶は脱水素処理によっても1μm以下に微細化することはできず、結果的に当該結晶は著しく小さい保磁力を持つため、好ましくない。なお、粒径が1μmを超えるような結晶は、水素化・不均化反応が不十分なために未反応で残存するR₂T₁₄B化合物であることが多い。又上記各相の結晶粒径を0.01μm未満とすることは、技術的に困難でまた得られる磁性粉末の磁気特性上のメリットがないため、結晶粒径の下限は0.01μm以上とした。
【００６４】
2度目の脱水素処理
上述の性状からなる希土類系原料合金を、再度、所定の脱水素処理することにより、安定して高い保磁力と大きな残留磁化を有し、高性能のボンド磁石並びに焼結磁石を得るのに適した永久磁石用希土類系合金粉末が得られる。
【００６５】
2度目の脱水素処理には、(C)雰囲気の制御により脱水素化の反応速度を0.01wt%/h〜0.2wt%/hの範囲で進行させる方法、(D1)第1段階は、雰囲気の制御により反応開始から被処理物の水素濃度C_Hが前記(1)式の範囲に達するまでであり、第2段階は、水素濃度C_Hが0.01wt%以下となるまで実施する方法、(D2)第1段階は、水素放出速度が0.1wt%/h〜5.0wt%/h、雰囲気の制御により反応開始から被処理物の水素濃度C_Hが前(1)式の範囲に達するまでであり、第2段階は、水素放出速度が0.01wt%/h〜0.20wt%/hであり、水素濃度C_Hが0.01wt%以下となるまで実施する方法、(E)真空中または不活性ガス雰囲気中で、温度650〜1000℃に15分〜4時間保持した後に冷却し、水素濃度を0.01wt%以下とする方法、が好ましい。
【００６６】
(E)方法において、処理温度が650℃未満ではR水素化物が分解しないか、分解しても非常に長時間を要し、実用性が乏しい。一方、1000℃を越えると再結合したR₂Fe₁₄B相が粒成長を起こし、粗大になって保磁力が低下する。当該処理のヒートパターンの一例を示すと、図1Bのとおりである。なお、処理温度は、必ずしも一定に保持する必要はなく、処理の途中で変更しても、連続的に変化させても良い。
【００６７】
脱水素処理では、R水素化物が水素を解離する必要があるが、化学平衡から見積もられるR水素化物の水素解離条件は、例えば、Nd水素化物では、温度650℃では水素分圧3Pa以下であり、温度800℃では水素分圧100Pa以下、温度850℃では水素分圧1000Pa以下であり、水素放出反応を進行させるためにはこの条件が実現されていることが必要である。この範囲外では、水素放出反応が進行せず、R₂Fe₁₄B相が再結合しないため、磁粉の保磁力が低くなり好ましくない。
【００６８】
脱水素処理においては、原料合金から水素が放出されるが、放出された水素を含めて前記水素分圧範囲であることが必要である。水素分圧を前記範囲に維持するには、雰囲気をArガスなどの不活性ガスで流気しながら処理する方法がある。雰囲気ガスを流気することにより、雰囲気中の水素分圧が上昇して水素放出反応が停止することを防止でき、安定した水素放出速度を実現できる。
【００６９】
Arガスなどの不活性ガスを流気する場合、雰囲気の総圧が大気圧(0.1MPa)である場合と、不活性ガス導入とポンプによる排気を同時に行って雰囲気の総圧を0.1MPa未満に維持する場合と、雰囲気ガスの供給量と排出量を調整して雰囲気の総圧を0.1MPaを越える条件で行う場合がある。水素分圧を前記範囲に維持するには、雰囲気を真空排気し続ける方法がある。
【００７０】
原料合金の処理量に対して、熱処理装置の内容積が充分大きい場合は、雰囲気ガスを流気せず、封入する方法でも脱水素は可能であるが、この場合でも、水素放出が充分に行われるためには、水素が放出された時点で水素分圧が前記範囲内であることが必要である。しかし、封入状態で処理する方法は、処理量に制限を受けるため、好ましい方法とはいえない。なお、処理雰囲気は、脱水素処理中に変更しても良いし、連続的に変化させても良い。
【００７１】
前記の(E)方法の脱水素処理後の冷却は、水素分圧が100Pa以下であれば、冷却速度、雰囲気総圧などは特に限定されない。生産効率を高める観点から、Ar等の不活性ガスで加圧して強制冷却を行っても良い。
【００７２】
次に二度目の脱水素処理方法として、(C)方法について説明する。希土類系原料合金中の水素濃度C_Hが前記(1)式の範囲となる原料合金を用いる場合は、水素放出速度が0.01〜0.2wt%/hとなるように脱水素処理を行うことが望ましい。水素放出速度が0.01wt%/h未満では、脱水素処理に多大な時間を要して好ましくない。一方、0.2wt%/hを越えると得られる磁粉の保磁力が低下する。
【００７３】
また、二度目の脱水素処理方法として、2段階処理を行う(D1),(D2)方法について説明する。(D1)と(D2)方法とは実質的に同様方法であるが、(D1)は水素濃度で、(D2)は水素放出速度で各段階を規定している。原料合金中の水素濃度C_Hが前記(2)式の範囲となる原料合金を用いる場合は、前記水素放出速度で脱水素処理を行っても良いが、高い保磁力が得られない。そこで、例えば真空排気法で、より大きな水素放出速度で脱水素処理を行った場合は、高い保磁力と大きな残留磁化が得られる。
【００７４】
さらに、優れた磁気特性を得るためには、脱水素処理の途中で処理雰囲気を変更するなどの方法で、水素濃度の変化に応じて水素放出速度を多段階に変化させることが好ましい。すなわち、脱水素・再結合反応の全体を一様な雰囲気で処理しても、前半の反応速度が大きく、後半は小さくなるが、この発明では雰囲気操作により積極的に水素放出速度を変えるように処理を行う。
【００７５】
この発明の二度目の脱水素処理において、前半を第1段階、後半を第2段階とし、第1段階で大きな水素放出速度とすれば、高い保磁力と大きな残留磁化が得られ、引き続き第2段階の反応速度を先より小さくすることで残留磁化を低下させずにさらに高い保磁力が得られる。第2段階の水素放出速度の方が大きい場合は、磁性粉末の水素濃度が0.01wt%以下であっても保磁力の向上効果は認められない。
【００７６】
前記の(D1),(D2)方法において、第1段階と第2段階との切替時期は、原料合金の水素濃度C_Hが前記(1)式の範囲にあるときに行うことが好ましい。前記切替時期が、水素濃度C_H＜0.000725×C_Rの場合、保磁力の向上効果が認められない。また、水素濃度C_H＞0.007500×C_Rの場合は、保磁力が向上しないだけでなく、第2段階の処理に多大な時間を要するため好ましくない。
【００７７】
上記の第1段階が終了した時点で一旦600℃以下まで冷却し、改めて昇温して第2段階の処理を行うこともできる。また、第1段階が終了した時点で一旦室温付近まで冷却し、取り出して別の設備を用いて第2段階の脱水素熱処理を行うこともできる。
【００７８】
水素放出速度は、第1段階では0.1〜5.0wt%/hの水素濃度変化となるようにする。0.1wt%/h未満では高い保磁力が得られない。一方、5.0wt%/hを超える場合も高い保磁力が得られない。
【００７９】
水素放出速度は、第2段階では0.01〜0.2wt%/hの水素濃度変化となるようにする。0.01wt%/h未満では処理に多大な時間を要して好ましくない。一方、0.2wt%/hを超える場合は保磁力を向上させる効果が認められない。
【００８０】
水素放出速度は、脱水素処理の温度、雰囲気の圧力、雰囲気の水素分圧、雰囲気ガスの流量、雰囲気ガス排気速度、真空排気速度等を適宜変更することで調整可能であるが、さらに、処理物の量を変えることでも調整が可能である。このことを利用して、水素化処理から最初の脱水素処理までを比較的小スケールの設備で小規模に行って前述の希土類系原料合金を製造し、二度目の脱水素処理を大スケールで行う方法を採ることが可能となる。また逆に、水素処理から最初の脱水素処理までを大スケールで行い、二度目の脱水素処理を小スケールで行う方法をとることが可能となる。
【００８１】
なお、この発明における水素放出速度とは、得られる磁性粉末の水素濃度が0.01wt%以下となるまでの速度を示し、水素濃度が0.01wt%に達して以降の水素放出反応は除外する。また、水素放出後の脱水素温度及び雰囲気を維持する場合の処理時間も除外する。
【００８２】
また、この発明において、水素放出速度は、脱水素・再結合反応の反応速度を示しており、水素放出速度の表示は、被処理物中の水素濃度の単位時間当たりの変化率で表すこととする。
【００８３】
脱水素処理における水素放出速度の制御は、雰囲気の全圧制御で行うことが簡単で効果的である。例えば、二度目の脱水素処理の第1段階では、処理装置内に1〜20l/min程度のArガスを導入しながら、ロータリーポンプ等の真空排気装置で排気を行うと、処理装置内の全圧を1〜5kPa程度に調節することができ、0.1〜5.0wt%/hの水素放出速度を得ることができる。
【００８４】
前記条件は、処理装置の内容積、原料合金の処理量、ポンプの排気能力等で設定すべき数値は異なる。また、ガス導入回路に取り付けた流量調節弁や、排気回路の流量調節弁を調節して、雰囲気ガス導入量、排気量を任意に変えることもできる。
【００８５】
減圧状態を全圧で制御するために、ガス導入弁または真空排気弁を圧力計からの信号に基づいて開閉動作を行わせる方法も適用できる。例えば、二度目の脱水素処理の第2段階では、処理装置内に1〜20l/min程度のArガスを導入・放出させ、大気圧下のAr流気処理とすることで、0.01〜0.2wt%/hの水素放出速度を得ることができる。
【００８６】
前記条件は、処理装置の内容積、原料合金の処理量等で設定すべき数値は異なる。水素放出速度は、雰囲気の全圧及びガス流量によって制御することができる。一般に雰囲気の全圧が同一であれば、雰囲気ガスの導入・排気量が大きい方が水素放出速度が大きい。ガス流量が同じであれば、全圧が低いほど水素放出速度が大きい。
【００８７】
処理量が増えた場合、放出される水素の絶対量は処理量に比例するため、より効果的な脱水素処理を行う必要があるが、この場合、雰囲気全圧で水素放出速度を制御した方が制御幅が大きく、2段階の脱水素処理の効果がより顕著に現れる。
【００８８】
もちろん、上記の脱水素時の水素放出速度の制御方法は、必ずしも全圧制御で行う必要はない。例えば、特許第2838615号に示した、水素吸蔵合金を用いたシステムにおいて、水素吸蔵合金の温度を制御することで処理装置内と水素貯蔵装置内とで水素分圧に差を付ける方法では、処理装置内と水素貯蔵装置内との差圧の大きさで水素放出速度を制御することができる。
【００８９】
二度目の脱水素処理の昇温過程における雰囲気は、原料の合金の水素濃度C_Hが前記(2)式の範囲の場合、脱水素処理における昇温過程でも水素放出反応が進行し、この速度が磁性粉末の磁気特性に影響を与える場合がある。従って、脱水素処理温度に到達するまで、水素放出反応の進行をできるだけ抑えた方が、高い磁気特性を得るための処理条件の制御が容易で、優れた磁気特性を得ることができる。
【００９０】
上記の昇温過程を、水素分圧100Pa以上の水素分庄とすると、600〜750℃の温度域を通過するときに水素化・分解反応が進行し、結晶配向の核となるべきNd₂Fe₁₄B相が失われ、その結果得られる磁性粉末の残留磁化が小さくなるので好ましくない。
【００９１】
昇温過程の雰囲気全圧が50kPa未満では、昇温中に水素放出反応が進行してしまい、水素放出速度の制御が十分行えずに低保磁力となったり、残留磁化が小さくなったりするため好ましくない。一方、1000kPa以上の雰囲気全圧は、設備側の対応が困難になるため好ましくない。
【００９２】
従って、二度目の脱水素処理の昇温過程の雰囲気は、水素分圧100Pa未満、雰囲気全圧50〜1000kPaの範囲が好ましい。なお、原料合金の水素濃度C_Hが0.00700×C_R未満の場合についても、前記条件で昇温することもできる。
【００９３】
二度目の脱水素処理において、水素分圧100Pa以上の雰囲気で昇温する場合は、600〜750℃の温度範囲を昇温速度10℃/min以上の速度で通過させる必要がある。昇温速度が10℃/min未満であると、水素化・分解反応が進行し、結晶配向の核となるべきNd₂Fe₁₄B相が失われ、その結果得られる磁性粉末の残留磁化が小さくなるので好ましくない。
【００９４】
この発明において、脱水素処理時間についての限定は特に行わない。脱水素処理により、水素濃度が0.01wt%以下となった後、引き続き温度及び雰囲気を保持しても、磁気特性に対する影響は殆ど認められないためである。
【００９５】
しかし、まだ未解明ではあるが、残存水素が磁粉の耐候性や経時変化に影響を及ぼす可能性がないとは言えず、その場合は残存水素濃度をさらに下げる必要があるかもしれない。この場合は、処理時間を延長する方法や、処理量が多い場合には最終的に真空排気を行う方法が効果的である。特に、処理温度が高い場合は、水素放出後の必要以上の長時間保持によって結晶粒成長が起こり、保磁力が低下傾向となるため、長時間処理は好ましくない。
【００９６】
【実施例】
実施例1
ここでは(A)方法+(C)方法を実施した。まず、28.0Nd-61.2Fe-9.1Co-0.6Ga-0.1Zr-1.0B(wt%)の組成のインゴットを用意し、Ar中1100℃24時間の均質化処理を行い、さらに0.1MPa、10l/minの水素ガス流気中で300℃2時間の水素脆化処理を行い、冷却した後、目開き425μmのふるいで整粒して母合金粉末とした。
【００９７】
この母合金粉末500gを、開口部寸法80×200mmのSUS310S製容器に充填し、インコネル製炉心管を有する管状熱処理炉に装填し、水素化・不均化処理、最初の脱水素処理を行った。
【００９８】
処理条件は、0.1MPaの水素雰囲気中(5l/min流気)で840℃まで15℃/minで昇温し、その温度で2時間保持した後、温度を維持しながら10l/minのArガスで5分間Ar置換を行い、引き続き同温度でArガスを20l/min導入しながらロータリーポンプにより炉内を真空排気し、炉内圧力を6kPaに所定時間維持する減圧Ar処理を行った。所定時間経過後、真空排気を止め、雰囲気圧力を大気圧まで復圧し、10l/minのArを流気しながら冷却した。
【００９９】
前記製造方法において、C_R=28.0であるから、水素濃度C_Hは0.020≦C_H≦0.210(wt%)の範囲がこの発明の範囲である。この時の水素放出速度、得られた原料合金の水素濃度と磁気特性を表1に示す。
【０１００】
この時の得られた原料合金の破断面を、走査電子顕微鏡で観察したところ、結晶粒径はおよそ0.2μmでほぼ均一であった。
【０１０１】
また、粉末X線回折法による相同定によれば、水素濃度C_Hが前記範囲の原料合金については、NdH₂、Fe、Nd₂Fe₁₄Bの3相の回折ピークが確認された。水素濃度が0.020wt%未満の原料合金では、Nd₂Fe₁₄B相以外の回折ピークは殆ど観察されなかった。
【０１０２】
次に、前記処理で得られた原料合金粉末各20gを、開口部寸法30×50mmのSUS310S製容器に充填し、管状熱処理炉に装填し、大気圧(0.1MPa)でArガスを10l/min導入しながら800℃、150分の熱処理を行った。冷却は、引き続きArガスを流気しながら行った。
【０１０３】
この脱水素処理により得られた磁粉の水素濃度と磁気特性を、横軸に前記原料合金の部分脱水素処理時間を採って図2に示す。また、前記原料合金の水素濃度を横軸として図3に示す。なお、水素分析値は不活性ガス抽出法で測定した結果である。
【０１０４】
図3によれば、いずれの組成の合金においても、原料合金中の水素濃度が0.020〜0.210wt%であるときに、大きな残留磁化と高い保磁力が同時に得られていることが判る。
【０１０５】
【表１】

【０１０６】
実施例2
ここでは(B)方法+(D)方法を実施する。実施例1と同じ母合金粉末500gを、開口部寸法80×250mmのSUS310S製容器に充填し、インコネル製炉心管を有する管状熱処理炉に装填し、水素化処理を行った。
【０１０７】
処理条件は、0.1MPaの水素雰囲気中(5l/min)で840℃まで15℃/minで昇温し、その温度で2時間保持した後、温度を維持しながら10l/minのArガスで所定時間Ar置換による水素濃度調整を行い、引き続きArガスを20l/min導入しながら冷却した。
【０１０８】
前記処理で得られた原料合金の水素濃度と構成相、磁気特性を表2に示す。この時の原料合金の破断面を、走査電子顕微鏡で観察したところ、結晶粒径はおよそ0.2μmでほぼ均一であった。
【０１０９】
次に、前記処理で得られた原料合金100gを、開口部寸法60×100mmのSUS310S製容器に充填し、管状熱処理炉に装填して二度目の脱水素処理を行った。前記原料合金を、大気圧(0.1MPa)でArガスを10l/min導入しながら820℃まで昇温し、同温度で保持して5l/minのArガスを導入しながら炉内を真空排気して全圧を4.0kPaに維持し、10分間処理した後、真空排気を止め、Arガスで大気圧まで復圧して、Arを5l/min流気しながら行った。
【０１１０】
前記の製造方法において、C_R=28.0であるから、水素濃度C_Hは0.196≦CH≦0.336(wt%)の範囲がこの発明の範囲である。この脱水素処理により得られた磁性粉末の磁気特性を表3に示す。表3には、脱水素処理における減圧Ar流気処理終了時及び脱水素処理終了後の推定水素濃度も示す。
【０１１１】
表3によれば、原料合金中の水素濃度が0.196〜0.336wt%であるときに、大きな残留磁化と高い保磁力が同時に得られていることが判る。
【０１１２】
【表２】

【０１１３】
【表３】

【０１１４】
比較例1
実施例1で用いた、平均粒径が425μm以下のの母合金粉末500gを、開口部寸法80×200mのSUS310S製容器に充填し、インコネル製炉心管を有する管状熱処理炉に装填し、水素化処理を行った。処理条件は、0.1MPaの水素雰囲気中(5l/min流気)で840℃まで15℃/minで昇温し、その温度で2時間保持した後、水素雰囲気中で冷却した。
【０１１５】
この時得られた原料合金の水素濃度は、0.37wt%であった。また、粉末X線回折法による相同定によれば、NdH₂、Fe₂B、Feの3相は確認できたが、Nd₂Fe₁₄B相は認められなかった。この時の原料合金の破断面を、走査電子顕微鏡で観察したところ、結晶粒径はおよそ0.2μmでほぼ均一であった。
【０１１６】
次に、前記処理で得られた原料合金粉末100gを、開口部寸法60×100mmのSUS310S製容器に充填し、管状熱処理炉に装填し、大気圧(0.1MPa)でArガスを10l/min導入しながら800℃、100分の熱処理を行った。冷却は、引き続きArガスを流気しながら行った。この脱水素処理により得られた磁粉の磁気特性を、図4に減磁曲線で示す。なお、図4には、比較のために実施例1の場合の結果の一例を併記する。
【０１１７】
図4によれば、実施例に比較して明らかに残留磁化が小さく、優れた磁気特性を得るためには、最初の脱水素処理で得られた原料合金は、この発明による水素濃度及び相構成を有することが必要であることが判る。
【０１１８】
比較例2
実施例1で用いた平均粒径425μm以下のの母合金粉末500gを、開口部寸法80×200mのSUS310S製容器に充填し、インコネル製炉心管を有する管状熱処理炉に装填し、水素化処理を行った。処理条件は、0.1MPaの水素雰囲気中(5l/min流気)で800℃まで15℃/minで昇温し、その温度で1時間保持した後、水素雰囲気中で冷却した。
【０１１９】
この際得られた原料合金の水素濃度は、0.24wt%であった。また、粉末X線回折法による相同定によれば、NdH₂、Fe₂B、Fe、Nd₂Fe₁₄B相の4相は確認できた。この時の原料合金の破断面を、走査電子顕微鏡で観察したところ、結晶粒径はおよそ0.2μmの部分と3μmを超える部分が混在していた。
【０１２０】
次に、前記処理で得られた原料合金粉末100gを、開口部寸法60×100mmのSUS310S製容器に充填し、管状熱処理炉に装填し、大気圧(0.1MPa)でArガスを10l/min導入しながら800℃、100分の熱処理を行った。冷却は、引き続きArガスを流気しながら行った。
【０１２１】
この脱水素処理により得られた磁粉の磁気特性を、図4に減磁曲線で示す。なお、図4には、比較のために実施例1の場合の結果の一例を併記する。図4によれば、比較例2の結果は、実施例1に比較して明らかに低い保磁力を示すことが判る。
【０１２２】
実施例3
ここでは(A)方法+(C)方法を実施した。まず、26.9Nd-2.5Dy-60.1Fe-9.0Co-0.4Ga-0.1Zr-1.0B(wt%)の組成のインゴットを用意し、Ar中1100℃24時間の均質化処理を行い、さらに0.1MPa、10l/minの水素ガス流気中で300℃2時間の水素脆化処理を行い、冷却した後、目開き425μmのふるいで整粒して母合金粉末とした。
【０１２３】
この母合金粉末500gを、開口部寸法80×200mmのSUS310S製容器に充填し、インコネル製炉心管を有する管状熱処理炉に装填し、水素化処理と最初の脱水素処理を行った。
【０１２４】
処理条件は、0.1MPaの水素雰囲気中(5l/min流気)で810℃まで15℃/minで昇温し、その温度で2時間保持した後、温度を維持しながら10l/minのArガスで5分間Ar置換を行い、引き続き同温度でArガスを20l/min導入しながらロータリーボンプにより炉内を真空排気し、炉内圧力を6kPaに所定時間維持する減圧Ar処理を15分間行った後、真空排気を止め、雰囲気圧力を大気圧まで復圧し、10l/minのArを流気しながら冷却した。
【０１２５】
この際得られた原料合金の水素濃度は0.11wt%であった。粉末X線回折法による相同定によれば、NdH₂、Fe₂B、Fe、Nd₂Fe₁₄Bの4相の回折ピークが確認された。
【０１２６】
次に、前記処理で得られた原料合金粉末30gを、開口部寸法30×45mmのSUS310S製容器に充填し、管状熱処理炉に装填し、大気圧(0.1MPa)でArガスを10l/min導入しながら800℃にて所定時間の熱処理を行った。冷却は、引き続きArガスを流気しながら行った。
【０１２７】
この二度目の脱水素処理により得られた磁粉の磁気特性並びに水素濃度を、横軸に熱処理時間を採って図5に示す。図5によれば、水素濃度が0.01wt%以下となったときに優れた磁気特性が得られることが判る。
【０１２８】
実施例4
ここでは(A)方法+(C)方法を実施した。実施例3で用いた原料合金粉末60gを、開口部寸法30×45mmのSUS310S製容器に充填し、管状熱処理炉に装填し、種々の雰囲気で780℃にて所定時間の熱処理を行った。処理時間は、最終的に水素濃度が0.01wt%以下となるように設定した。冷却は、Arガスを流気しながら行った。
【０１２９】
この脱水素処理の処理条件と、得られた磁粉の磁気特性並びに水素濃度を、表4に示す。表4によれば、水素放出速度が0.01〜0.2wt%/hの範囲にあるときに、特に優れた磁気特性が得られることが判る。
【０１３０】
【表４】

【０１３１】
実施例5
26.9Nd-2.5Dy-55.6Fe-13.5Co-0.4Ga-0.1Zr-1.0B(wt%)の組成のインゴットを用意し、Ar中1100℃24時間の均質化処理を行い、さらに0.3MPaの水素ガス中で2時間保持して水素脆化処理を行った後、目開き150μmのふるいで整粒して母合金粉末とした。
【０１３２】
この母合金粉末500gを、開口部寸法15×250mm、深さ50mmのSUS310S製容器に充填し、この容器48個を内熱型熱処理炉に装填し、母合金粉末24kgの水素化処理、最初の脱水素処理を行った。
【０１３３】
処理条件は、0.2MPaの水素雰囲気中で860℃まで15℃/minで昇温し、その温度で2時間保持した後、温度を維持しながら150l/minのArガスで15分間、Ar置換を行い、引き続き同温度でArガスを5l/min導入しながらロータリーポンプにより炉内を真空排気し、炉内圧力を4kPaに所定時間維持する減圧Ar処理を25分間行った後、真空排気を止め、雰囲気圧力を大気圧まで復圧し、10l/minのArを流気しながら冷却した。
【０１３４】
この際得られた原料合金の水素濃度は0.13wt%であった。粉末X線回折法による相同定によれば、NdH₂、Fe₂B、Fe、Nd₂Fe₁₄Bの4相の回折ピークが確認された。
【０１３５】
次に、前記処理で得られた原料合金粉末を、開口部寸法60×100mmのSUS310S製容器に所定量充填して管状熱処理炉に装填し、種々の雰囲気で810℃にて所定時間の熱処理を行った。処理時間は、水素濃度が0.01wt%以下となるように設定した。冷却は、Arガスを流気しながら行った。この脱水素処理の処理条件と、得られた磁粉の磁気特性並びに水素濃度を表5に示す。
【０１３６】
表5によれば、この発明による脱水素処理は、同処理時の処理量、雰囲気、処理時間の組み合わせを種々選択できることが判る。
【０１３７】
【表５】

【０１３８】
実施例6
実施例4と同様にして得た原料合金粉末50kgを、開口部寸法250×250mm、深さ50mmのSUS310S製容器6ヶに充填し、内熱型熱処理炉に装填して脱水素処理を行った。
【０１３９】
脱水素処理の雰囲気は、Arガスを5l/min導入しながら真空排気を行う方法により、雰囲気の圧力はおよそ1.5kPaとした。処理は850℃で60分保持した後、雰囲気をArガスで0.25MPaまで加圧して撹拌する方法で強制冷却した。
【０１４０】
処理後、処理容器内の種々部分に位置する磁粉をサンプリングし、VSMにて磁気特性を評価した。その結果を表6に示す。表6によれば、この発明の処理は、多量処理でも均質な磁気特性が得られていることが判る。
【０１４１】
【表６】

【０１４２】
実施例7
実施例2で得られた原料合金Sと同様の原料合金100gを、開口部寸法60×100mmのSUS310S製容器に充填し、管状熱処理炉に装填して脱水素処理を行った。
【０１４３】
前記原料合金を、大気圧(0.1MPa)でArガスを10l/min導入しながら820℃まで昇温し、同温度で保持して、5l/minのArガスを導入しながら炉内を真空排気して全圧を4.0kPaに維持し、所定時間処理した後、真空排気を止め、Arガスで大気圧まで復圧して、Arを5l/min流気しながら120分間の熱処理を行った。冷却は、引き続きArガスを流気しながら行った。
【０１４４】
この脱水素処理により得られた磁粉の水素濃度と磁気特性を、減圧Ar流気の時間を横軸として図6に示す。また、減圧Ar流気終了時の推定水素濃度を横軸として図7に示す。図7によれば、減圧脱水素終了時の原料合金中の水素濃度が0.020〜0.210wt%であるときに、大きな残留磁化と高い保磁力が同時に得られていることが判る。
【０１４５】
比較例3
実施例2で用いた、平均粒径425μm以下の母合金粉末500gを、開口部寸法80×200mmのSUS310S製容器に充填し、インコネル製炉心管を有する管状熱処理炉に装填し、水素化処理を行った。処理条件は、0.1MPaの水素雰囲気中(5l/min流気)で840℃まで15℃/minで昇温し、その温度で2時間保持した後、水素雰囲気中で冷却した。冷却速度は、840℃〜500℃の間で、およそ55℃/minであった。
【０１４６】
この時得られた原料合金の水素濃度は、0.37wt%であった。また、粉末X線回折法による相同定によれば、NdH₂、Fe₂B、Feの3相は確認できたが、Nd₂Fe₁₄B相は認められなかった。
【０１４７】
次に、前記処理で得られた原料合金粉末100gを、開口部寸法60×100mmのSUS310S製容器に充填し、管状熱処理炉に装填して脱水素処理を行った。
【０１４８】
前記原料合金を、大気圧(0.1MPa)でArガスを10l/min導入しながら820℃まで昇温し、同温度で保持して、5l/minのArガスを導入しながら炉内を真空排気して全圧を4.0kPaに維持し、所定時間処理した後、真空排気を止め、Arガスで大気圧まで復圧して、Arを5l/min流気しながら100分間の熱処理を行った。冷却は、引き続きArガスを流気しながら行った。
【０１４９】
この脱水素処理により得られた磁粉の水素濃度と磁気特性を、減圧Ar流気の時間を横軸として図8に示す。また、減圧Ar流気終了時の推定水素濃度を横軸として図9に示す。図8、図9の結果は、この発明の実施例7の図6、図7に比較して、明らかに残留磁化が低いことが判る。
【０１５０】
比較例4
実施例2で得たものと同様の原料合金100gを、開口部寸法60×100mmのSUS310S製容器に充填し、管状熱処理炉に装填し、大気圧(0.10MPa)下でArガスを10l/min導入しながら820℃、150分の熱処理を行った。冷却は、引き続きArガスを流気しながら行った。
【０１５１】
この脱水素処理により得られた磁粉の磁気特性を、表7に示す。表7の結果は、表4に比較して、明らかに保磁力、残留磁化共に低いことが判る。
【０１５２】
【表７】

【０１５３】
実施例8
ここでは(B)方法+(D)方法を実施した。実施例2で用いたものと同等の原料合金100gを、開口部寸法60×100mmのSUS310S製容器に充填し、インコネル製炉心管を有する管状熱処理炉に装墳し、種々の条件で脱水素処理を行った。
【０１５４】
処理温度は、830℃で一定とし、Arガス流量及び雰囲気全圧を調整して水素放出速度を種々に変化させた。昇温は、0.10MPaのAr流気(5l/min)中で15℃/minの昇温速度で行い、所定時間、所定条件の脱水素処理後、0.10MPaのAr流気(5l/min)中で冷却した。
【０１５５】
この時の脱水素処理条件と、得られた磁粉の磁気特性を表4に示す。なお、前記処理と同様の処理条件で第1段階脱水素処理まで行って冷却した原料粉末の水素分析値を、表8の処理中の減圧Ar処理後の水素濃度推定値として表中に併記する。
【０１５６】
表8によれば、第1段階の水素放出反応における水素濃度変化速度が、0.1〜5.0wt%/h、第2段階の水素放出反応における水素濃度変化速度が0.01〜0.2wt%/hで、且つ第2段階の水素濃度変化速度が第1段階の水素濃度変化速度より小さい値であれば、高い保磁力が得られることが判る。
【０１５７】
【表８】

【０１５８】
実施例9
実施例2で用いたものと同等の原料合金No.3及びNo.4を用い、開口部寸法60×100mmのSUS310S製容器に充填し、インコネル製炉心管を有する管状熱処理炉に装填し、昇温時の雰囲気を種々に変えて脱水素処理を行った。
【０１５９】
脱水素処理の条件は、820℃において、5l/minのArガスを導入しながら炉内を真空排気して全圧を4.0kPaに維持し、10分間保持した後、真空排気を止め、Arガスで大気圧まで復圧して、Arを5l/min流気しながら100分間の熱処理を行った。冷却は、引き続きArガスを流気しながら行った。
【０１６０】
昇温時の雰囲気は、イ:5l/minのArガスを導入しながら炉内を真空排気して全圧を4.0kPaに維持する、ロ:0.10MPaで5l/minのArガスを流気する、ハ:0.10MPaで5l/minのH₂ガスを流気する、という3種の方法を試みた。昇温速度は、すべて15℃/minとした。
【０１６１】
得られた磁性粉末の磁気特性の評価結果を、図10には原料合金No.3の結果を、図11には原料合金No.4の結果を減磁曲線で示す。図10、図11によれば、0.10MPaのAr流気中で昇温した場合が最も優れた磁気特性を示すことが判る。原料合金の水素濃度が小さい図11では、昇温時の雰囲気の影響が小さくなることが判る。
【０１６２】
実施例10
実施例9で行った脱水素処理において、昇温速度を変化させた。この時、原料合金はNo.3を用い、昇温速度以外の処理条件はすべて実施例9と同一とした。昇温速度は、5℃/min、10℃/min、15℃/min、20℃/minの4条件で行った。
【０１６３】
得られた磁性粉末の減磁曲線を、図12〜図14に示す。図12及び図13では昇温速度の影響は小さいのに対し、図14に示した、水素雰囲気での昇温においては、5℃/minの昇温速度で残留値化が大幅に低下している。水素中の昇温では、昇温速度を10℃/min以上にすることが好ましいことが判る。
【０１６４】
【発明の効果】
この発明は、R‐T‐(M)‐B系原料合金のHDDR処理に際して、脱水素化処理を前半、後半の二度に分けて処理することを特徴とし、実施例に明らかなように、最初の脱水素化処理を特定条件で終了させることにより、二度目の同処理において、大量に処理できかつ大きな磁化を維持したまま、粉末状態で大きな保磁力を有する永久磁石用希土類系合金粉末が得られる。
【０１６５】
この発明は、所要の脱水素処理を二度に分けて行うだけで安定して高い保磁力と大きな残留磁化を持つ、中間生成物として取扱いが良好な永久磁石用希土類系原料合金を提供できる。
【０１６６】
この発明は、脱水素処理を別工程とすることで、脱水素処理用の設備は大幅に簡略化でき、多量処理が容易になり、原料工程を含めた全体の生産能率が大幅に向上する。また、二度目の脱水素工程の水素放出速度を多段階に変化させることで、残留磁化を低下させることなく、高保磁力化ができる。
【図面の簡単な説明】
【図１】 Aはこの発明による水素化処理から最初の脱水素処理までの処理条件例を示すヒートパターン図であり、Bはの発明による2度目の脱水素処理条件例を示すヒートパターン図である。
【図２】 A,B,Cは、実施例1における減圧Ar流気時間と、処理後の磁性粉末の水素濃度(wt%)、残留磁化Jr(T)、保磁力HcJ(MA/m)との関係を示すグラフである。
【図３】 A,B,Cは、実施例1における原料合金粉末の水素濃度と、処理後の磁性粉末の水素濃度(wt%)、残留磁化Jr(T)、保磁力HcJ(MA/m)との関係を示すグラフである。
【図４】実施例1、比較例1及び比較例2における外部磁界Hex(MA/m)と磁化J(T)との関係を示すグラフである。
【図５】 A,B,Cは、実施例3における脱水素処理時間と、処理後の磁性粉末の水素濃度(wt%)、残留磁化Jr(T)、保磁力HcJ(MA/m)との関係を示すグラフである。
【図６】 A,B,Cは、実施例7における減圧Ar流気時間と、処理後の磁性粉末の水素濃度(wt%)、残留磁化Jr(T)、保磁力HcJ(MA/m)との関係を示すグラフである。
【図７】 A,B,Cは、実施例7における減圧Ar流気処理終了時の推定水素濃度と、処理後の磁性粉末の水素濃度(wt%)、残留磁化Jr(T)、保磁力HcJ(MA/m)との関係を示すグラフである。
【図８】 A,B,Cは、比較例3におけ減圧Ar流気時間と、処理後の磁性粉末の水素濃度(wt%)、残留磁化Jr(T)、保磁力HcJ(MA/m)との関係を示すグラフである。
【図９】 A,B,Cは、比較例3における減圧Ar流気処理終了時の推定水素濃度と、処理後の磁性粉末の水素濃度(wt%)、残留磁化Jr(T)、保磁力HcJ(MA/m)との関係を示すグラフである。
【図１０】実施例9における原料合金No.3の外部磁界Hex(MA/m)と磁化J(T)との関係を示すグラフである。
【図１１】実施例9における原料合金No.4の外部磁界Hex(MA/m)と磁化J(T)との関係を示すグラフである。
【図１２】実施例10における減圧Ar中昇温した原料合金No.Rの外部磁界Hex(MA/m)と磁化J(T)との関係を示すグラフである。
【図１３】実施例10における減圧Ar流気中昇温した原料合金No.Rの外部磁界Hex(MA/m)と磁化J(T)との関係を示すグラフである。
【図１４】実施例10における水素中昇温した原料合金No.Rの外部磁界Hex(MA/m)と磁化J(T)との関係を示すグラフである。[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an improvement in a method for producing a rare earth alloy powder for permanent magnets, and in particular, a method for producing a rare earth alloy powder for permanent magnets used in rare earth bond magnets and sintered magnets suitable for various motors and actuators.To the lawRelated.
[0002]
[Prior art]
As a method for controlling the microstructure of rare earth based permanent magnet alloy powder, there is a method called HDRD (Hydrogenation-Disproportionation-Desorption-Recombination) treatment. The HDDR process is a process for sequentially executing hydrogenation, disproportionation, desorption, and recombination.
[0003]
In order to produce alloy magnetic powder by this HDDR treatment, R-T- (M) -B-based raw material alloy (R is a rare earth element containing Y, T is a mixture of Fe or Fe and Co, M is an additive element, (B can be partially or completely replaced by boron with C) Ingot or powder of H₂Gas atmosphere or H₂After maintaining the temperature between 500 ° C. and 1000 ° C. in a mixed atmosphere of gas and inert gas, thereby allowing the ingot or powder of the above alloy to store hydrogen, H₂Vacuum atmosphere with partial pressure of 13 Pa or less or H₂Dehydrogenation treatment is performed at a temperature of 500 ° C. to 1000 ° C. until an inert gas atmosphere having a partial pressure of 13 Pa or less, and then cooled.
[0004]
Methods for producing rare earth based permanent magnet alloy powders by the HDDR treatment method are disclosed in, for example, Japanese Patent Laid-Open Nos. 1-132106 and 2-4901. The RT- (M) -B alloy magnet powder produced by the heat treatment in the hydrogen atmosphere has a large coercive force, and has magnetic anisotropy depending on the selection of composition and processing conditions.
[0005]
The reason for having such a property is that the metal structure becomes an aggregate of very fine crystals of substantially 0.1 to 1 μm. More specifically, the grain size of the ultrafine crystal obtained by the above HDDR treatment is tetragonal R₂T₁₄This is because it is close to the single-domain critical grain size of the B-based compound phase and thus exhibits a high coercive force, and the ultrafine crystal grains are assembled with a certain degree of crystal orientation.
[0006]
Since the HDDR processing method is a solid-gas phase chemical reaction with a large reaction heat, it has a drawback that it is extremely difficult to control processing conditions. In particular, as the amount of treatment increases, it becomes more difficult to control the temperature and atmosphere, and it is difficult to stably obtain excellent magnetic characteristics. In addition, since the hydrogenation / disproportionation reaction and the reverse reaction, dehydrogenation / recombination reaction, are continuously performed in the same processing equipment, it is difficult to optimize each processing condition.
[0007]
In Japanese Patent Laid-Open No. 5-166617, the hydrogenation / decomposition reaction and the dehydrogenation / recombination reaction are independent from each other in order to allow the dehydrogenation / recombination reaction to proceed stably and in consideration of safety during hydrogen release. A method has been proposed in which a mass or powder of RT- (M) -B alloy is processed by heat treatment.
[0008]
In JP-A-7-316717 and JP-A-7-316753, in order to obtain a magnet powder having a uniform and fine structure and a small temperature coefficient of coercive force, a hydrogenation / decomposition reaction in a temperature range of 750 ° C. or lower The intermediate raw material that caused the reaction is shown. Cool by hydrogenation / decomposition reaction in a low temperature range to obtain a raw material having an intermediate product phase having a controlled shape and size, and generate the raw material by subjecting it to dehydrogenation / recombination treatment It has been proposed that the crystal grain size of the main phase can be made small and uniform.
[0009]
[Problems to be solved by the invention]
The inventors are interested in the fact that magnetic powder having magnetic anisotropy and high coercive force can be obtained relatively easily by adjusting only the composition of the raw material alloy and the processing conditions in the HDDR processing, and in particular magnetically. Efforts have been made to elucidate the mechanism that provides the desired anisotropy. As a result, in order to obtain a large magnetic anisotropy, it was found that the reaction rate and the intermediate structure are important. That is, under actual processing conditions, it was found that the rate of temperature rise in a specific temperature range in hydrogen was important, and it was shown in JP-A-6-1281010 and JP-A-7-54003.
[0010]
In addition, the microstructure of the alloy after the hydrogenation / decomposition reaction includes R hydride phase, T phase, TB compound (Fe₂B) In addition to phase, R₂T₁₄B compound phase and tetragonal crystal (Fe_ThreeIt was found that a large magnetic anisotropy can be obtained in the presence of B)), and disclosed in JP-A-9-256001.
[0011]
The origin of magnetic anisotropy in the HDDR method is the maintenance of the crystal orientation of the master alloy, as shown in the above-mentioned publication.₂T₁₄B compound phase and tetragonal crystal (Fe_ThreeB) is functioning. Strictly speaking, it varies depending on the hydrogen partial pressure of the atmosphere, but when the hydrogenation / decomposition reaction proceeds in the range of 600 to 750 ° C, these two phases cannot be left and decompose and become magnetically different after dehydrogenation. The directivity is lowered and the residual magnetization is reduced. In order to avoid this phenomenon, as shown in JP-A-6-1281010 and JP-A-7-54003, the heating rate in a specific temperature range is maintained above a certain level, or after passing through this temperature range. A method such as introducing hydrogen is adopted.
[0012]
Based on the contents of the above knowledge, when looking at the method disclosed in JP-A-5-166617, it passes through a range of 600 to 750 ° C. in a hydrogen atmosphere at the time of cooling.₂T₁₄B compound phase and tetragonal crystal (Fe_ThreeB)), the magnetic anisotropy is lost, and a large remanent magnetization cannot be obtained.
[0013]
In order to avoid this phenomenon, in Japanese Patent Laid-Open No. 5-166617, the cooling rate in a hydrogen atmosphere is defined as 50 ° C./min or more. However, as the processing amount increases, it becomes difficult to obtain a large cooling rate. The above regulations are extremely difficult to implement industrially.
[0014]
Further, in the method disclosed in JP-A-7-316717 and JP-A-7-316753, R in the low temperature region treatment₂T₁₄B compound phase and tetragonal crystal (Fe_ThreeB) may be avoided, but the hydrogenation / decomposition reaction takes a long time because the processing temperature is low.
[0015]
The present invention relates to rare earth bond magnets and sintered magnets that stably have high coercive force and large remanent magnetization by simply performing dehydrogenation during the HDR processing of RT- (M) -B based alloy. The object is to industrially produce the obtained rare earth alloy powder for permanent magnets, that is, to establish a production method capable of producing a stable and large quantity. Another object of the present invention is to provide a rare earth-based raw material alloy for permanent magnets that has a stable and high coercive force and a large remanent magnetization and can be handled as an intermediate product simply by performing the required dehydrogenation treatment. To do.
[0016]
[Means for Solving the Problems]
The inventor has conducted various studies for the purpose of processing methods capable of obtaining a large coercive force in a powder state while maintaining a large magnetization in the HDDR processing. The dehydrogenation / recombination reaction rate is greatly influenced by the structure of the hydrogen, that is, the change in the hydrogen release rate during dehydrogenation in the HDDR process becomes the change in the recombination reaction rate, resulting in the magnetic powder It has been found that a high coercive force can be obtained by controlling the reaction rate during dehydrogenation, which greatly affects the magnetic properties.
[0017]
In addition, the inventors have studied a method for controlling the reaction rate during dehydrogenation for the purpose of stable and large-scale HDR processing, and as a result, the hydrogen concentration of the object to be treated is predetermined in the first dehydrogenation treatment. It was found that the same coercive force as that in the continuous treatment can be obtained by the method of once ending the treatment when reaching the value and then performing the second dehydrogenation treatment.
[0018]
The inventor has further intensively studied the above-described two-stage processing at the former stage and the latter stage, and as a result, the first dehydrogenation process is terminated under specific conditions, so that the second process can be processed in a large amount and has a large magnetization. In the powder state, a large coercive force can be obtained, that is, it is possible to leave a raw material alloy of an intermediate product by the first treatment, and then the intermediate product in the second treatment. The present invention was completed by discovering that it was possible to process a large amount of raw material alloy at a time and to obtain an HDDR-treated powder having high magnetic properties.
[0019]
    That is, the manufacturing method of the rare earth alloy powder according to the present invention is R₂T₁₄An ingot or powder made of an alloy in which a compound phase of B (B can be partially or wholly replaced by C) type is 50 vol% or more is subjected to hydrogenation and disproportionation treatment, and further dehydrogenation and recombination treatment. At that time, the hydrogen concentration of the material to be treated is reduced by the first dehydrogenation treatment.Range of the following formulaOnce this process is reached,CoolThen, the second dehydrogenation treatment is performed.
0.000725 × C _R ≦ C _H ≦ 0.0120 × C _R
However, C _H Is the hydrogen concentration in the alloy (wt%), C _R Is the rare earth R component concentration (wt%) in the alloy.
[0020]
In addition, as the first dehydrogenation process in the HDDR process according to the present invention, it is possible to control the atmosphere, for example, a method adjusted by the total pressure of the atmosphere in an inert gas flow and / or vacuum exhaust,
(A) The reaction rate of dehydrogenation proceeds in the range of 0.1 wt% / h to 5.0 wt% / h._HIs carried out until it reaches the range of the following equation (1),
(B) The reaction rate of dehydrogenation proceeds in the range of 0.01 wt% / h to 0.2 wt% / h, and the hydrogen concentration C of the workpiece from the start of the reaction_HIs carried out until it reaches the range of the following equation (2),
Propose.
0.000725 × C_R≦ C_H≦ 0.00750 × C_R    (1 set
0.00700 × C_R≦ C_H≦ 0.0120 × C_R    (2) Formula
However, C_HIs the hydrogen concentration in the alloy (wt%),
C_RIs the concentration of rare earth R component in the alloy (wt%).
[0021]
In addition, as the second dehydrogenation process in the HDRR process according to the present invention,
(C) a method of allowing the reaction rate of dehydrogenation to proceed in the range of 0.01 wt% / h to 0.2 wt% / h by controlling the atmosphere,
(D1) The first stage is to control the hydrogen concentration C_HUntil the range of the formula (1) is reached, the second stage is the hydrogen concentration C_HIs carried out until 0.01 wt% or less,
(D2) In the first stage, the hydrogen release rate is 0.1 wt% / h to 5.0 wt% / h._HUntil the range of the previous equation (1) is reached, the second stage is that the hydrogen release rate is 0.01 wt% / h to 0.20 wt% / h, and the hydrogen concentration C_HIs carried out until 0.01 wt% or less,
(E) A method of cooling after holding at a temperature of 650 to 1000 ° C. for 15 minutes to 4 hours in a vacuum or in an inert gas atmosphere so that the hydrogen concentration is 0.01 wt% or less,
Propose.
[0022]
In this invention, when a preferred configuration example of the dehydrogenation treatment method is shown, the intermediate product treated by the method (A) and having a predetermined hydrogen concentration is added to the method (C) or (E). The second dehydrogenation treatment is preferable. In addition, depending on the hydrogen concentration of the intermediate product after the method (A), the method (D1) or (D2) in which treatment is performed in two stages can be adopted as the second dehydrogenation treatment. Further, the intermediate product treated by the method (B) is preferably subjected to a second dehydrogenation treatment by the method (D1) or (D2) in which the intermediate product is treated in the above two steps. Further, the intermediate product treated by the method (B) can also be treated by the method (E).
[0023]
Furthermore, as a method of raising the temperature for performing the second dehydrogenation process in the HDDR process according to the present invention, a method of setting the atmosphere to an inert gas atmosphere having a total pressure of 50 kPa to 1000 kPa, and the atmosphere has a hydrogen partial pressure of 100 Pa or more. And a method of raising the temperature in the range of 600 to 750 ° C. at a rate of 10 ° C./min or more is proposed.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
This invention is a method for producing rare earth alloy powders for permanent magnets by the HDDR treatment method, in which the dehydrogenation and recombination reactions are carried out in two steps. The intermediate product obtained by the first dehydrogenation treatment The target rare earth-based alloy powder is obtained by performing a second dehydrogenation treatment separately for the rare earth-based raw material alloy, and is characterized by being able to be carried out on a mass production scale.
[0026]
Regarding the present invention, the target alloy composition, preferred conditions for the hydrogenation / disproportionation treatment, preferred conditions for the first dehydrogenation treatment, properties of the rare earth-based material alloy of the intermediate product, the second time The details will be described in the order of preferred conditions for the dehydrogenation treatment.
[0027]
Alloy composition
The alloy composition targeted by this invention is R₂T₁₄An alloy in which a compound phase of B (B can be partially or wholly substituted by C) type accounts for 50 vol% or more, and may contain various additive elements M. The rare earth element R is not limited to containing any rare earth element including Y, but it is necessary to include at least one of Nd and Pr or both of R. In addition, it is preferable that one or more of Dy, Tb, and Ho are contained because of the effect of increasing the coercive force of the finally obtained magnet material.
[0028]
The amount of R is desirably 10 to 20 at%, more preferably 11 to 15 at%. If the amount of R is less than 10 at%, the coercive force decreases, and if it exceeds 20 at%, the ratio of the ferromagnetic phase decreases and the magnetization decreases.
[0029]
T is an iron group element and corresponds to Fe, Co, and Ni. When Co is substituted for Fe and added, in addition to the effect of increasing the Curie point, it becomes easier to obtain magnetic anisotropy in the HDDR process, and high magnetization can be obtained. Co can be added up to 50% of T, and if it exceeds 50%, the magnetization decreases, which is not preferable. Ni is effective in improving anisotropy when added in a small amount, but it is desirable to add 5% or less of T because it lowers the magnetization.
[0030]
The amount of T is preferably 67-85at%, and if it is less than 67at%, R₂T₁₄The ratio of the B compound phase decreases to decrease the magnetization, and if it exceeds 85 at%, a magnetically soft phase is generated and the coercive force is decreased.
[0031]
A part of B can be substituted with C, or the entire amount can be substituted with C. The amount of B is preferably 4 to 10 at%, and if it is less than 4 at%, a magnetically soft phase is generated and the coercive force is reduced.₂T₁₄The ratio of the B compound phase is lowered and the magnetization is reduced.
[0032]
The additive element M added as necessary is added for the purpose of increasing the magnetic anisotropy or increasing the coercive force. Ga, Zr, Hf, and the like are well known as elements that are effective in improving anisotropy, and Cu, Al, and the like are elements that increase the coercive force. In addition, Si, Ti, V, Cr, Mn, Zn, Ge, Nb, In, Sn, Ta, W, Pb, and the like can be added and contained.
[0033]
The additive element M can be added alone or in combination of two or more. The amount of M added is desirably 5 at% or less when added for the purpose described above. When the addition amount exceeds 5 at%, phases that do not contribute to magnetism increase and magnetization decreases.
[0034]
Hydrogenation conditions
When the hydrogenation temperature is less than 650 ° C, the hydrogenation / disproportionation reaction does not proceed sufficiently, and the hydrogenation / disproportionation reaction occurs within the range of the atmospheric hydrogen partial pressure described below, exceeding 950 ° C. Therefore, the hydrogenation temperature range is preferably 650 to 950 ° C.
[0035]
If the hydrogen partial pressure during hydrogenation is less than 10 kPa, the progress of the reaction is insufficient, and high coercive force cannot be expressed. Since the merit on the magnetic properties of the alloy powder obtained in this way is not particularly recognized, the hydrogen partial pressure range is preferably 10 to 1000 kPa.
[0036]
The treatment temperature and the hydrogen partial pressure condition are not necessarily maintained constant, and may be changed in the middle or may be changed continuously.
[0037]
In order to obtain highly magnetized magnetic particles having high magnetic anisotropy, the processing temperature is further limited to 750 ° C or higher, and the temperature rising rate is increased to 10 ° C / min or higher to a temperature range of 700 ° C or higher. Is preferred.
[0038]
In particular, in order to obtain a bulk material alloy, by using a method in which the temperature is increased in vacuum or in an inert gas and hydrogen is introduced after the temperature reaches 750 ° C. or higher, defects such as cracks can be obtained. Less raw material alloys can be obtained.
[0039]
Hydrogen concentration adjustment process, first dehydrogenation process
At the end of the hydrogenation / disproportionation reaction process, an Ar replacement process is performed to expel hydrogen gas in the processing apparatus. At this time, since the hydrogen partial pressure in the atmosphere gradually decreases, the initial reaction of the hydrogen releasing reaction has started.
[0040]
The Ar substitution treatment is useful for ensuring the safety of the subsequent hydrogen release treatment, and is preferably performed for a predetermined time in order to obtain a large residual magnetization. Including the subsequent steps, a rare gas such as He or Ne can be used instead of Ar. The gas type may be appropriately selected depending on the convenience and cost in the apparatus and process to be used.
[0041]
When the Ar replacement treatment time is short, large remanent magnetization cannot be obtained, and if it is too long, the coercive force becomes small. The Ar replacement processing time is determined by the processing amount, the internal volume of the processing apparatus, and the like. In addition, when obtaining isotropic magnetic powder, the said process is not essential.
[0042]
In this invention, by adjusting the hydrogen concentration of the alloy to a specific range in the first dehydrogenation treatment, the intermediate product obtained can be handled well, and only by performing the required second dehydrogenation treatment. A rare earth-based material alloy having a stable high coercive force and a large remanent magnetization can be obtained. In order to achieve this, the intermediate product, which is the object of the present invention, is considered so as to achieve both excellent coercive force and remanent magnetization and to obtain productivity such as increased throughput and reduced time. The method (A) or (B) is selected as the first dehydrogenation treatment method so that the alloy has a specific hydrogen concentration, and then the second dehydration is performed according to the method and the hydrogen concentration of the alloy. The raw material treatment is appropriately selected from the method (C) (D1) or (D2) and the method (E). Therefore, the conditions for various dehydrogenation treatments described later and preferred properties of the intermediate products (limitation conditions) depend on the selection of the first and second dehydrogenation treatment methods and the degree of hydrogen concentration in the alloy after treatment. It will fluctuate relatively.
[0043]
In this invention, in the first dehydrogenation treatment, the reaction rate of (A) dehydrogenation proceeds in the range of 0.1 wt% / h to 5.0 wt% / h, and the hydrogen concentration C of the object to be treated from the start of the reaction._H(B) The reaction rate of the dehydrogenation is advanced in the range of 0.01 wt% / h to 0.2 wt% / h, and from the start of the reaction, Hydrogen concentration C_HIs preferably performed until it reaches the range of the following formula (2).
0.000725 × C_R≦ C_H≦ 0.00750 × C_R    (1 set
0.00700 × C_R≦ C_H≦ 0.0120 × C_R    (2) Formula
However, C_HIs the hydrogen concentration in the alloy (wt%),
C_RIs the concentration of rare earth R component in the alloy (wt%).
[0044]
Following Ar replacement treatment, as the first dehydrogenation / recombination reaction step, hydrogen release rate 0.1-5.0wt% / h in atmosphere of inert gas flow or vacuum exhaust or inert gas flow under reduced pressure In this range, heat treatment is performed until a predetermined hydrogen concentration is reached, and dehydrogenation is performed. An example of hydrogenation, Ar replacement, and initial dehydrogenation is shown in a heat pattern as shown in FIG. 1A.
[0045]
Hydrogen concentration C of the raw material alloy obtained by the treatment of the method (A)_HIs 0.00750 × C_REven if the dehydrogenation treatment is performed over the range above, no merit in magnetic properties is observed, and the hydrogen concentration C_H0.000725 × C_RControl within the range below is not preferable because the effect of improving the coercive force is lost.
[0046]
If the hydrogen release rate up to the range of the hydrogen concentration by the treatment of the method (A) is less than 0.1 wt% / h, the coercive force of the magnetic powder obtained by the dehydrogenation treatment is lowered, which is not preferable. In addition, treatment with a hydrogen release rate exceeding 5.0 wt% / h is not preferable because it is difficult to realize, for example, extremely reducing the treatment amount.
[0047]
When the first dehydrogenation treatment is performed by the method (B), a raw material alloy having a predetermined hydrogen concentration can be obtained by adjusting the treatment time in the Ar substitution treatment as a hydrogen concentration adjustment treatment. Hydrogen concentration C in raw alloy_HIs 0.00700 × C_RIf it is less than 1, the coercive force of the magnetic powder obtained by the dehydrogenation treatment is reduced, and 0.0120 × C_RExceeding R, the core of anisotropic development in the cooling process₂Fe₁₄This is not preferable because the B compound phase is lost and the residual magnetization is lowered.
[0048]
Ar substitution and the first dehydrogenation are performed in a temperature range of 650 ° C. to 1000 ° C. Below 650 ° C, the R hydride does not decompose, or it takes a very long time to decompose, and its practicality is poor. On the other hand, when the temperature exceeds 1000 ° C, the recombined R₂Fe₁₄This is because the B compound phase undergoes grain growth and becomes coarse to reduce the coercive force.
[0049]
As a specific method for realizing the hydrogen release rate in the first dehydrogenation treatment, it is preferable to perform a reduced pressure Ar treatment. In the dehydrogenation process, the hydrogen partial pressure in the atmosphere effectively affects the hydrogen release rate, but in the case of a large amount of process, the hydrogen release amount becomes large, so the total gas molecular weight in the atmosphere is controlled according to Boyle-Charles' law There is a need to. In the actual process, if the atmosphere replacement is not efficiently performed, a region having a high hydrogen partial pressure is generated in the vicinity of the surface of the micro raw material powder, and the hydrogen release rate is reduced.
[0050]
In order to avoid this phenomenon, a method of flowing a sufficient amount of atmospheric gas in a reduced pressure state is simple and effective. In practice, it is possible to use a method in which Ar gas is introduced while the atmospheric gas is exhausted by a gas exhaust means such as a rotary pump, and the total pressure in the furnace is maintained at a constant value in the range of 100 Pa to 10 kPa. Under this atmosphere, the conditions under which hydrogen gas can be released from the R hydride are maintained.
[0051]
As the method for setting the hydrogen release rate to 0.1 to 5.0 wt% / h or 0.01 wt% / h to 0.2 wt% / h, various methods other than the reduced pressure Ar treatment can be adopted. For example, as disclosed in JP-A-2-4901 or the like, a method by evacuation, a method of simply flowing Ar gas or the like under atmospheric pressure or pressurizing conditions, or as shown in Japanese Patent No. 2838615, Examples thereof include a method of controlling the hydrogen partial pressure in the system using a hydrogen storage alloy in a closed system.
[0052]
Regardless of which dehydrogenation method is employed, the hydrogen release rate greatly affects the magnetic properties of the finally obtained magnetic powder. For example, the balance between the effective internal volume of the equipment used and the vacuum exhaust capacity The hydrogen release rate is adjusted by various methods such as a method for determining the processing amount from the above, a method for adjusting the total pressure in the furnace, and a method for adjusting the Ar flow rate.
[0053]
In addition, although processing time is influenced by a processing amount and equipment factors, more preferable processing time is 2 minutes-60 minutes.
[0054]
In this initial dehydrogenation process, the temperature condition and the atmospheric condition are not necessarily constant, and may be changed during the process. Moreover, you may change continuously. The treatment temperature is not necessarily the same as the hydrogenation conditions, and may be determined independently.
[0055]
The cooling after the first dehydrogenation treatment is not particularly limited in terms of cooling rate, total atmospheric pressure, and the like. From the viewpoint of increasing production efficiency, forced cooling may be performed by pressurizing with an inert gas such as Ar.
[0056]
  Intermediate product
  By completing the initial dehydrogenation process described above, at least R₂T₁₄Ingot and / or powder made of an alloy containing a compound phase of type B (B can be partially or wholly substituted with C), and hydrogen concentration C_HButThe following (3) formulaA rare earth-based raw material alloy for permanent magnets in the range can be obtained. This rare earth-based raw material alloy has a high coercive force and a large remanent magnetization stably only by performing the required second dehydrogenation treatment, and is characterized by good handling as an intermediate product.
0.000725 × C _R ≦ C _H ≦ 0.0120 × C _R (3) Formula
[0057]
Hydrogen concentration C of this intermediate product lump or powder rare earth material alloy_HIs 0.000725 × C_RIf it is less than this, even if dehydrogenation is performed, the effect of improving the coercive force is small as compared with the prior art, and the effect of performing the dehydrogenation process in a separate process cannot be obtained. Hydrogen concentration C_HIs 0.0120 × C_RExceeds the R, which is a nucleus for obtaining magnetic anisotropy by the hydrogenation and decomposition reaction during raw material alloy production, especially during cooling₂T₁₄B compound phase and tetragonal crystal (Fe_ThreeB)) is lost, and as a result, the residual magnetization of the resulting magnetic powder is lowered, which is not preferable.
[0058]
In order for the rare earth-based material alloy to become a magnetic powder having magnetic anisotropy through a second dehydrogenation step, at least the original crystal orientation is maintained as a recombination nucleus.₂T₁₄There must be a B compound phase.
[0059]
In the preferable rare earth-based material alloy of the present invention, since the R compound has a hydrogen concentration that cannot be all hydrides, at least a part of R that is not a hydride is R as a recombination nucleus.₂T₁₄It is essential to form a B compound phase. R₂T₁₄When the B compound phase is not present, the magnetic powder produced by performing the dehydrogenation treatment is magnetically isotropic and magnetization is reduced, which is not preferable.
[0060]
In addition, the three phases of R hydride phase, TB compound phase, and T phase are renewed during dehydrogenation and recombination.₂T₁₄Essential to produce the B compound phase. When the R hydride phase is not present in the three phases, a soft magnetic compound is formed when the dehydrogenation process is performed, or the soft magnetic T phase remains and the coercive force decreases. In the absence of the T-B phase, the soft magnetic RT compound phase precipitates and the coercive force deteriorates. In the absence of the T phase, a non-ferromagnetic RTB compound is formed and magnetization is lowered, which is not preferable. Therefore, the preferred rare earth-based raw material alloy that has completed the first dehydrogenation treatment of the present invention includes an R hydride phase, a TB compound phase, a T phase, and an R phase.₂T₁₄It is essential to have a structure in which at least four phases of the B compound phase coexist.
[0061]
R hydride phase, T phase and R above₂T₁₄The presence of the B compound phase can be observed relatively easily by powder X-ray diffraction and thermal analysis, but the TB compound phase has a small amount of powder X-rays. In some cases, the diffraction method cannot be clearly observed. If a transmission electron microscope and an electron beam diffraction method are used, all the four phases can be confirmed.
[0062]
R hydride phase, TB compound phase, T phase and R₂T₁₄The crystal grain size of the rare earth alloy composed of at least four phases of the B compound phase is preferably in the range of 0.01 to 1 μm for each phase.
[0063]
When a crystal having a grain size exceeding 1 μm exists in a rare earth-based material alloy, the crystal cannot be refined to 1 μm or less by dehydrogenation treatment, and as a result, the crystal has a remarkably small coercive force. It is not preferable. In addition, crystals with a particle size exceeding 1 μm remain unreacted due to insufficient hydrogenation / disproportionation reaction.₂T₁₄Often B compounds. Moreover, since it is technically difficult to make the crystal grain size of each phase less than 0.01 μm and there is no merit in the magnetic properties of the obtained magnetic powder, the lower limit of the crystal grain size is set to 0.01 μm or more.
[0064]
Second dehydrogenation treatment
Suitable for obtaining high-performance bonded magnets and sintered magnets with stable high coercive force and large remanent magnetization by re-determining the rare earth-based raw material alloy having the above-mentioned properties again. In addition, a rare earth alloy powder for permanent magnets is obtained.
[0065]
For the second dehydrogenation treatment, (C) the method of proceeding the dehydrogenation reaction rate in the range of 0.01 wt% / h to 0.2 wt% / h by controlling the atmosphere, (D1) the first stage is the atmosphere Control the hydrogen concentration C of the workpiece from the start of the reaction._HUntil the range of the formula (1) is reached, the second stage is the hydrogen concentration C_H(D2) In the first stage, the hydrogen release rate is 0.1 wt% / h to 5.0 wt% / h, and the hydrogen concentration C of the workpiece from the start of the reaction by controlling the atmosphere_HUntil the range of the previous equation (1) is reached, the second stage is that the hydrogen release rate is 0.01 wt% / h to 0.20 wt% / h, and the hydrogen concentration C_H(E) In a vacuum or in an inert gas atmosphere, hold at a temperature of 650 to 1000 ° C. for 15 minutes to 4 hours and then cool to reduce the hydrogen concentration to 0.01 wt% or less. Is preferred.
[0066]
In the method (E), when the treatment temperature is less than 650 ° C., the R hydride does not decompose, or even if it decomposes, it takes a very long time and the practicality is poor. On the other hand, when it exceeds 1000 ° C, it recombines R₂Fe₁₄Phase B causes grain growth and becomes coarse and the coercive force decreases. An example of the heat pattern of the process is as shown in FIG. 1B. The processing temperature does not necessarily need to be kept constant, and may be changed during the processing or continuously changed.
[0067]
In dehydrogenation treatment, it is necessary for R hydride to dissociate hydrogen, but the hydrogen dissociation conditions for R hydride estimated from chemical equilibrium are, for example, that Nd hydride has a hydrogen partial pressure of 3 Pa or less at a temperature of 650 ° C. The hydrogen partial pressure is 100 Pa or less at a temperature of 800 ° C., and the hydrogen partial pressure is 1000 Pa or less at a temperature of 850 ° C. This condition must be realized in order for the hydrogen releasing reaction to proceed. Outside this range, the hydrogen releasing reaction does not proceed and R₂Fe₁₄Since the B phase does not recombine, the coercive force of the magnetic powder is lowered, which is not preferable.
[0068]
In the dehydrogenation treatment, hydrogen is released from the raw material alloy, but it is necessary to be within the hydrogen partial pressure range including the released hydrogen. In order to maintain the hydrogen partial pressure within the above range, there is a method in which the atmosphere is treated while flowing with an inert gas such as Ar gas. By flowing the atmospheric gas, it is possible to prevent the hydrogen partial pressure in the atmosphere from rising and stop the hydrogen desorption reaction, and a stable hydrogen desorption rate can be realized.
[0069]
When flowing inert gas such as Ar gas, the total pressure of the atmosphere is less than 0.1 MPa by introducing the inert gas and exhausting the pump at the same time when the total pressure of the atmosphere is atmospheric pressure (0.1 MPa). There are cases where the total pressure of the atmosphere exceeds 0.1 MPa by adjusting the supply and discharge amounts of the atmospheric gas. In order to maintain the hydrogen partial pressure within the above range, there is a method in which the atmosphere is continuously evacuated.
[0070]
If the internal volume of the heat treatment device is sufficiently large relative to the amount of the raw material alloy, dehydrogenation is possible even by the sealing method without flowing the atmospheric gas, but even in this case, sufficient hydrogen release is performed. In order to prevent this, the hydrogen partial pressure needs to be within the above range when hydrogen is released. However, the method of processing in the encapsulated state is not a preferable method because the processing amount is limited. Note that the treatment atmosphere may be changed during the dehydrogenation treatment or may be changed continuously.
[0071]
The cooling after the dehydrogenation treatment in the method (E) is not particularly limited as long as the hydrogen partial pressure is 100 Pa or less, the cooling rate, the total atmospheric pressure, and the like. From the viewpoint of increasing production efficiency, forced cooling may be performed by pressurizing with an inert gas such as Ar.
[0072]
Next, method (C) will be described as a second dehydrogenation treatment method. Hydrogen concentration C in rare earth alloy_HIn the case of using a raw material alloy that falls within the range of the above formula (1), it is desirable to perform the dehydrogenation treatment so that the hydrogen release rate is 0.01 to 0.2 wt% / h. If the hydrogen release rate is less than 0.01 wt% / h, it takes a long time for the dehydrogenation treatment, which is not preferable. On the other hand, if it exceeds 0.2 wt% / h, the coercive force of the obtained magnetic powder is lowered.
[0073]
In addition, as a second dehydrogenation treatment method, a method (D1) and (D2) in which a two-stage treatment is performed will be described. The methods (D1) and (D2) are substantially the same, but (D1) defines the hydrogen concentration, and (D2) defines the hydrogen release rate. Hydrogen concentration C in raw alloy_HHowever, when using a raw material alloy that falls within the range of formula (2), dehydrogenation may be performed at the hydrogen release rate, but a high coercive force cannot be obtained. Therefore, for example, when the dehydrogenation process is performed at a higher hydrogen release rate by the vacuum exhaust method, a high coercive force and a large residual magnetization can be obtained.
[0074]
Furthermore, in order to obtain excellent magnetic properties, it is preferable to change the hydrogen release rate in multiple stages according to the change in the hydrogen concentration by a method such as changing the treatment atmosphere during the dehydrogenation treatment. That is, even if the entire dehydrogenation / recombination reaction is processed in a uniform atmosphere, the reaction rate in the first half is large and the latter half is small, but in the present invention, the hydrogen release rate is positively changed by operating the atmosphere. Process.
[0075]
In the second dehydrogenation process of the present invention, if the first half is the first stage and the second half is the second stage, and a large hydrogen release rate is obtained in the first stage, a high coercive force and a large remanent magnetization can be obtained. By making the reaction rate of the stage smaller than before, a higher coercive force can be obtained without reducing the residual magnetization. When the hydrogen release rate in the second stage is larger, the coercivity improvement effect is not recognized even if the hydrogen concentration of the magnetic powder is 0.01 wt% or less.
[0076]
In the methods (D1) and (D2), the switching time between the first stage and the second stage is the hydrogen concentration C of the raw material alloy._HIs preferably performed when the value is within the range of the above-described formula (1). The switching time is the hydrogen concentration C_H<0.000725 × C_RIn this case, the effect of improving the coercive force is not recognized. Hydrogen concentration C_H> 0.007500 × C_RIn this case, not only the coercive force is not improved, but also the second stage process requires a lot of time, which is not preferable.
[0077]
When the first stage is completed, the second stage treatment can be performed by once cooling to 600 ° C. or lower and raising the temperature again. Alternatively, when the first stage is completed, it is once cooled to near room temperature, taken out, and the second stage dehydrogenation heat treatment can be performed using another equipment.
[0078]
The hydrogen release rate is set to change in hydrogen concentration of 0.1 to 5.0 wt% / h in the first stage. If it is less than 0.1 wt% / h, a high coercive force cannot be obtained. On the other hand, a high coercive force cannot be obtained even when it exceeds 5.0 wt% / h.
[0079]
The hydrogen release rate is set to a hydrogen concentration change of 0.01 to 0.2 wt% / h in the second stage. If it is less than 0.01 wt% / h, a long time is required for the treatment, which is not preferable. On the other hand, when it exceeds 0.2 wt% / h, the effect of improving the coercive force is not recognized.
[0080]
The hydrogen release rate can be adjusted by appropriately changing the temperature of the dehydrogenation process, the pressure of the atmosphere, the hydrogen partial pressure of the atmosphere, the flow rate of the atmosphere gas, the atmosphere gas exhaust speed, the vacuum exhaust speed, etc. Adjustment is also possible by changing the amount of objects. Taking advantage of this, the above-mentioned rare earth-based raw material alloy is manufactured by performing the hydrotreatment to the first dehydrogenation process on a small scale with a relatively small scale facility, and the second dehydrogenation process is performed on a large scale. It becomes possible to take the method to do. Conversely, it is possible to take a method in which the hydrogen treatment to the first dehydrogenation treatment are performed on a large scale and the second dehydrogenation treatment is performed on a small scale.
[0081]
The hydrogen release rate in the present invention indicates a rate until the hydrogen concentration of the obtained magnetic powder becomes 0.01 wt% or less, and the hydrogen release reaction after the hydrogen concentration reaches 0.01 wt% is excluded. In addition, the processing time for maintaining the dehydrogenation temperature and atmosphere after hydrogen release is also excluded.
[0082]
In the present invention, the hydrogen release rate indicates the reaction rate of the dehydrogenation / recombination reaction, and the display of the hydrogen release rate is expressed by the rate of change per unit time of the hydrogen concentration in the workpiece. To do.
[0083]
It is simple and effective to control the hydrogen release rate in the dehydrogenation process by controlling the total pressure of the atmosphere. For example, in the first stage of the dehydrogenation process for the second time, if Ar gas of about 1 to 20 l / min is introduced into the processing apparatus and evacuation is performed with a vacuum pumping device such as a rotary pump, The pressure can be adjusted to about 1 to 5 kPa, and a hydrogen release rate of 0.1 to 5.0 wt% / h can be obtained.
[0084]
The numerical values to be set differ depending on the internal volume of the processing apparatus, the raw material alloy processing amount, the pumping capacity of the pump, and the like. Further, the amount of atmospheric gas introduced and the amount of exhaust gas can be arbitrarily changed by adjusting the flow rate adjustment valve attached to the gas introduction circuit or the flow rate adjustment valve of the exhaust circuit.
[0085]
In order to control the reduced pressure state with the total pressure, a method of opening / closing the gas introduction valve or the vacuum exhaust valve based on a signal from the pressure gauge can be applied. For example, in the second stage of the second dehydrogenation treatment, Ar gas of about 1 to 20 l / min is introduced / released into the treatment apparatus, and Ar gas flow treatment under atmospheric pressure is performed. A hydrogen release rate of% / h can be obtained.
[0086]
The above conditions are different in numerical values to be set depending on the internal volume of the processing apparatus, the processing amount of the raw material alloy and the like. The hydrogen release rate can be controlled by the total atmospheric pressure and the gas flow rate. In general, if the total pressure in the atmosphere is the same, the larger the amount of introduced atmospheric gas and the larger the exhaust amount, the higher the hydrogen release rate. If the gas flow rate is the same, the lower the total pressure, the higher the hydrogen release rate.
[0087]
When the amount of treatment increases, the absolute amount of released hydrogen is proportional to the amount of treatment, so it is necessary to perform more effective dehydrogenation treatment. However, the control range is large, and the effect of the two-stage dehydrogenation appears more remarkably.
[0088]
Of course, the method for controlling the hydrogen release rate at the time of dehydrogenation is not necessarily performed by the total pressure control. For example, in a system using a hydrogen storage alloy shown in Japanese Patent No. 2838615, in the method of differentiating the hydrogen partial pressure between the processing apparatus and the hydrogen storage apparatus by controlling the temperature of the hydrogen storage alloy, The hydrogen release rate can be controlled by the magnitude of the differential pressure between the apparatus and the hydrogen storage apparatus.
[0089]
The atmosphere in the heating process of the second dehydrogenation treatment is the hydrogen concentration C of the raw material alloy._HIn the range of the above formula (2), the hydrogen releasing reaction proceeds even in the temperature rising process in the dehydrogenation process, and this speed may affect the magnetic properties of the magnetic powder. Therefore, if the progress of the hydrogen releasing reaction is suppressed as much as possible until the dehydrogenation temperature is reached, it is easier to control the processing conditions for obtaining high magnetic properties, and excellent magnetic properties can be obtained.
[0090]
Assuming that the above temperature rise process is a hydrogen partial pressure with a hydrogen partial pressure of 100 Pa or more, the hydrogenation / decomposition reaction proceeds when passing through a temperature range of 600 to 750 ° C., and Nd should be the nucleus of crystal orientation₂Fe₁₄The B phase is lost, and as a result, the residual magnetization of the magnetic powder is reduced, which is not preferable.
[0091]
If the total atmospheric pressure during the temperature rise process is less than 50 kPa, the hydrogen release reaction proceeds during the temperature rise, and the hydrogen release rate cannot be sufficiently controlled, resulting in a low coercivity and a small residual magnetization. It is not preferable. On the other hand, an atmospheric total pressure of 1000 kPa or more is not preferable because it becomes difficult for the equipment to cope with it.
[0092]
Accordingly, the atmosphere in the temperature raising process of the second dehydrogenation treatment is preferably in the range of a hydrogen partial pressure of less than 100 Pa and an atmosphere total pressure of 50 to 1000 kPa. The hydrogen concentration C of the raw material alloy_HIs 0.00700 × C_RAlso in the case of less than, it can also heat up on the said conditions.
[0093]
In the second dehydrogenation treatment, when the temperature is increased in an atmosphere having a hydrogen partial pressure of 100 Pa or higher, it is necessary to pass through a temperature range of 600 to 750 ° C. at a temperature increase rate of 10 ° C./min or higher. If the heating rate is less than 10 ° C / min, the hydrogenation / decomposition reaction proceeds and Nd should be the nucleus of crystal orientation.₂Fe₁₄The B phase is lost, and as a result, the residual magnetization of the magnetic powder is reduced, which is not preferable.
[0094]
In the present invention, the dehydrogenation processing time is not particularly limited. This is because, even if the temperature and atmosphere are continuously maintained after the hydrogen concentration becomes 0.01 wt% or less by the dehydrogenation treatment, there is almost no influence on the magnetic properties.
[0095]
However, although it is still unclear, it cannot be said that the residual hydrogen has no possibility of affecting the weather resistance and aging of the magnetic powder, and in that case, it may be necessary to further reduce the residual hydrogen concentration. In this case, a method of extending the processing time or a method of finally evacuating when the processing amount is large are effective. In particular, when the processing temperature is high, crystal grain growth occurs due to holding for an unnecessarily long time after hydrogen release, and the coercive force tends to decrease.
[0096]
【Example】
Example 1
Here, method (A) + method (C) was carried out. First, an ingot having a composition of 28.0Nd-61.2Fe-9.1Co-0.6Ga-0.1Zr-1.0B (wt%) was prepared, and homogenized at 1100 ° C. for 24 hours in Ar, further 0.1 MPa, 10 l / Hydrogen embrittlement treatment was performed at 300 ° C. for 2 hours in a min hydrogen gas flow, and after cooling, the mixture was sized with a sieve having an opening of 425 μm to obtain a mother alloy powder.
[0097]
500 g of this mother alloy powder was filled into a SUS310S container with an opening size of 80 × 200 mm, and loaded into a tubular heat treatment furnace having an Inconel furnace core tube, followed by hydrogenation / disproportionation treatment and first dehydrogenation treatment. .
[0098]
The treatment conditions were as follows: in a 0.1 MPa hydrogen atmosphere (5 l / min flow), the temperature was raised to 840 ° C. at 15 ° C./min, held at that temperature for 2 hours, and then maintained at the temperature, 10 l / min Ar gas Then, Ar was replaced with Ar for 5 minutes, and subsequently, the inside of the furnace was evacuated by a rotary pump while introducing Ar gas at 20 l / min at the same temperature, and reduced pressure Ar treatment was performed to maintain the furnace pressure at 6 kPa for a predetermined time. After a predetermined time, evacuation was stopped, the atmospheric pressure was restored to atmospheric pressure, and cooling was performed while flowing 10 l / min of Ar.
[0099]
In the manufacturing method, C_R= 28.0, so hydrogen concentration C_HIs 0.020 ≦ C_HThe range of ≦ 0.210 (wt%) is the scope of the present invention. Table 1 shows the hydrogen release rate and the hydrogen concentration and magnetic properties of the obtained raw material alloy.
[0100]
When the fracture surface of the obtained raw material alloy was observed with a scanning electron microscope, the crystal grain size was approximately 0.2 μm and substantially uniform.
[0101]
According to the phase identification by powder X-ray diffraction method, the hydrogen concentration C_HNdH for material alloys in the above range₂, Fe, Nd₂Fe₁₄A three-phase diffraction peak of B was confirmed. For raw alloys with a hydrogen concentration of less than 0.020 wt%, Nd₂Fe₁₄Almost no diffraction peaks other than the B phase were observed.
[0102]
Next, each 20 g of the raw material alloy powder obtained by the above treatment was filled into a SUS310S container having an opening size of 30 × 50 mm, charged into a tubular heat treatment furnace, and Ar gas was charged at 10 l / min at atmospheric pressure (0.1 MPa). While introducing, heat treatment was performed at 800 ° C. for 150 minutes. The cooling was continued while flowing Ar gas.
[0103]
The hydrogen concentration and magnetic properties of the magnetic powder obtained by this dehydrogenation treatment are shown in FIG. FIG. 3 shows the hydrogen concentration of the raw material alloy on the horizontal axis. The hydrogen analysis value is a result of measurement by an inert gas extraction method.
[0104]
According to FIG. 3, it can be seen that in any alloy, when the hydrogen concentration in the raw material alloy is 0.020 to 0.210 wt%, large residual magnetization and high coercive force are obtained simultaneously.
[0105]
[Table 1]

[0106]
Example 2
Here, method (B) + method (D) is carried out. 500 g of the same mother alloy powder as in Example 1 was filled in a SUS310S container having an opening size of 80 × 250 mm, and charged in a tubular heat treatment furnace having an Inconel furnace core tube, and hydrogenated.
[0107]
The treatment conditions were as follows: in a 0.1 MPa hydrogen atmosphere (5 l / min), the temperature was raised to 840 ° C. at 15 ° C./min. The hydrogen concentration was adjusted by time Ar substitution, followed by cooling while introducing Ar gas at 20 l / min.
[0108]
Table 2 shows the hydrogen concentration, constituent phase, and magnetic properties of the raw material alloy obtained by the above treatment. When the fracture surface of the raw material alloy at this time was observed with a scanning electron microscope, the crystal grain size was approximately 0.2 μm and substantially uniform.
[0109]
Next, 100 g of the raw material alloy obtained by the above treatment was filled in a SUS310S container having an opening size of 60 × 100 mm, and loaded into a tubular heat treatment furnace to perform a second dehydrogenation treatment. The raw material alloy was heated up to 820 ° C. while introducing Ar gas at atmospheric pressure (0.1 MPa) at 10 l / min, held at the same temperature, and the inside of the furnace was evacuated while introducing 5 l / min Ar gas. The total pressure was maintained at 4.0 kPa, and after 10 minutes of treatment, evacuation was stopped, the pressure was restored to atmospheric pressure with Ar gas, and Ar was supplied at a flow rate of 5 l / min.
[0110]
In the above production method, C_R= 28.0, so hydrogen concentration C_HThe range of 0.196 ≦ CH ≦ 0.336 (wt%) is the range of the present invention. Table 3 shows the magnetic properties of the magnetic powder obtained by this dehydrogenation treatment. Table 3 also shows the estimated hydrogen concentration at the end of the reduced-pressure Ar flow process in the dehydrogenation process and after the dehydrogenation process.
[0111]
According to Table 3, it can be seen that when the hydrogen concentration in the raw material alloy is 0.196 to 0.336 wt%, a large residual magnetization and a high coercive force are obtained simultaneously.
[0112]
[Table 2]

[0113]
[Table 3]

[0114]
Comparative Example 1
Used in Example 1, 500 g of the master alloy powder with an average particle size of 425 μm or less, filled in a SUS310S container with an opening size of 80 × 200 m, loaded into a tubular heat treatment furnace having an Inconel furnace core tube, and hydrogenated Processed. The treatment condition was that the temperature was raised to 840 ° C. at 15 ° C./min in a 0.1 MPa hydrogen atmosphere (5 l / min air flow), kept at that temperature for 2 hours, and then cooled in a hydrogen atmosphere.
[0115]
The hydrogen concentration of the raw material alloy obtained at this time was 0.37 wt%. According to the phase identification by powder X-ray diffraction method, NdH₂, Fe₂The three phases B and Fe were confirmed, but Nd₂Fe₁₄Phase B was not observed. When the fracture surface of the raw material alloy at this time was observed with a scanning electron microscope, the crystal grain size was approximately 0.2 μm and substantially uniform.
[0116]
Next, 100 g of the raw material alloy powder obtained by the above treatment is filled in a SUS310S container having an opening size of 60 × 100 mm, loaded into a tubular heat treatment furnace, and Ar gas is introduced at 10 l / min at atmospheric pressure (0.1 MPa). Then, heat treatment was performed at 800 ° C. for 100 minutes. The cooling was continued while flowing Ar gas. The magnetic properties of the magnetic powder obtained by this dehydrogenation treatment are shown in FIG. FIG. 4 also shows an example of the result in the case of Example 1 for comparison.
[0117]
According to FIG. 4, in order to obtain remarkably small remanent magnetization and excellent magnetic properties as compared with the example, the raw material alloy obtained by the first dehydrogenation treatment has the hydrogen concentration and phase structure according to the present invention. It can be seen that it is necessary to have
[0118]
Comparative Example 2
500 g of the master alloy powder having an average particle size of 425 μm or less used in Example 1 was filled in a SUS310S container having an opening size of 80 × 200 m, and loaded into a tubular heat treatment furnace having an Inconel furnace core tube, and subjected to hydrogenation treatment. went. The treatment conditions were as follows: in a 0.1 MPa hydrogen atmosphere (5 l / min flow), the temperature was raised to 800 ° C. at 15 ° C./min, held at that temperature for 1 hour, and then cooled in a hydrogen atmosphere.
[0119]
The hydrogen concentration of the raw material alloy obtained at this time was 0.24 wt%. According to the phase identification by powder X-ray diffraction method, NdH₂, Fe₂B, Fe, Nd₂Fe₁₄Four B phases were confirmed. When the fracture surface of the raw material alloy at this time was observed with a scanning electron microscope, the crystal grain size was found to be approximately 0.2 μm and more than 3 μm.
[0120]
Next, 100 g of the raw material alloy powder obtained by the above treatment is filled in a SUS310S container having an opening size of 60 × 100 mm, loaded into a tubular heat treatment furnace, and Ar gas is introduced at 10 l / min at atmospheric pressure (0.1 MPa). Then, heat treatment was performed at 800 ° C. for 100 minutes. The cooling was continued while flowing Ar gas.
[0121]
The magnetic properties of the magnetic powder obtained by this dehydrogenation treatment are shown in FIG. FIG. 4 also shows an example of the result in the case of Example 1 for comparison. According to FIG. 4, it can be seen that the result of Comparative Example 2 shows a clearly lower coercive force than that of Example 1.
[0122]
Example 3
Here, method (A) + method (C) was carried out. First, an ingot having a composition of 26.9Nd-2.5Dy-60.1Fe-9.0Co-0.4Ga-0.1Zr-1.0B (wt%) was prepared, homogenized at 1100 ° C for 24 hours in Ar, and further 0.1 MPa Then, hydrogen embrittlement treatment was performed at 300 ° C. for 2 hours in a hydrogen gas flow of 10 l / min, cooled, and then sized with a sieve having an opening of 425 μm to obtain a mother alloy powder.
[0123]
500 g of this mother alloy powder was filled in a SUS310S vessel having an opening size of 80 × 200 mm, and loaded into a tubular heat treatment furnace having an Inconel furnace core tube, and subjected to hydrogenation treatment and first dehydrogenation treatment.
[0124]
The treatment conditions were as follows: in a 0.1 MPa hydrogen atmosphere (5 l / min flow), the temperature was raised to 810 ° C. at 15 ° C./min, held at that temperature for 2 hours, and then maintained at the temperature, 10 l / min Ar gas After performing Ar replacement for 5 minutes at the same temperature, after evacuating the furnace with a rotary pump while introducing Ar gas at 20 l / min at the same temperature, and performing reduced pressure Ar treatment for 15 minutes to maintain the furnace pressure at 6 kPa for 15 minutes Then, evacuation was stopped, the atmospheric pressure was restored to atmospheric pressure, and cooling was performed while flowing 10 l / min of Ar.
[0125]
The hydrogen concentration of the raw material alloy obtained at this time was 0.11 wt%. According to phase identification by powder X-ray diffraction method, NdH₂, Fe₂B, Fe, Nd₂Fe₁₄B phase diffraction peaks were confirmed.
[0126]
Next, 30 g of the raw material alloy powder obtained by the above treatment was filled into a SUS310S container having an opening size of 30 × 45 mm, charged into a tubular heat treatment furnace, and Ar gas was introduced at 10 l / min at atmospheric pressure (0.1 MPa). Then, heat treatment was performed at 800 ° C. for a predetermined time. The cooling was continued while flowing Ar gas.
[0127]
The magnetic properties and hydrogen concentration of the magnetic powder obtained by the second dehydrogenation treatment are shown in FIG. According to FIG. 5, it can be seen that excellent magnetic properties can be obtained when the hydrogen concentration is 0.01 wt% or less.
[0128]
Example 4
Here, method (A) + method (C) was carried out. 60 g of the raw material alloy powder used in Example 3 was filled in a SUS310S container having an opening size of 30 × 45 mm, loaded into a tubular heat treatment furnace, and subjected to heat treatment at 780 ° C. for a predetermined time in various atmospheres. The treatment time was finally set so that the hydrogen concentration was 0.01 wt% or less. Cooling was performed while flowing Ar gas.
[0129]
Table 4 shows the treatment conditions of the dehydrogenation treatment, the magnetic properties of the obtained magnetic powder, and the hydrogen concentration. According to Table 4, it can be seen that particularly excellent magnetic properties can be obtained when the hydrogen release rate is in the range of 0.01 to 0.2 wt% / h.
[0130]
[Table 4]

[0131]
Example 5
An ingot with the composition of 26.9Nd-2.5Dy-55.6Fe-13.5Co-0.4Ga-0.1Zr-1.0B (wt%) was prepared, homogenized at 1100 ° C for 24 hours in Ar, and further hydrogen of 0.3 MPa After hydrogen embrittlement treatment by holding in gas for 2 hours, the particle size was adjusted with a sieve having an opening of 150 μm to obtain a mother alloy powder.
[0132]
Fill 500 g of this master alloy powder into a SUS310S container with an opening size of 15 x 250 mm and a depth of 50 mm, and load 48 of these containers into an internal heat treatment furnace, hydrogenating 24 kg of the master alloy powder, the first Dehydrogenation treatment was performed.
[0133]
The processing conditions were as follows: heat up to 860 ° C at 15 ° C / min in a 0.2MPa hydrogen atmosphere, hold at that temperature for 2 hours, and then replace the Ar with 150l / min Ar gas for 15 minutes while maintaining the temperature. The reactor was evacuated with a rotary pump while introducing Ar gas at the same temperature at a rate of 5 l / min, and reduced pressure Ar treatment was performed for 25 minutes to maintain the furnace pressure at 4 kPa for a predetermined time. The atmospheric pressure was restored to atmospheric pressure, and cooling was performed while flowing 10 l / min Ar.
[0134]
The hydrogen concentration of the raw material alloy obtained at this time was 0.13 wt%. According to phase identification by powder X-ray diffraction method, NdH₂, Fe₂B, Fe, Nd₂Fe₁₄B phase diffraction peaks were confirmed.
[0135]
Next, the raw material alloy powder obtained by the above treatment is filled into a tubular heat treatment furnace with a predetermined amount in a SUS310S container having an opening size of 60 × 100 mm, and heat treatment is performed at 810 ° C. for a predetermined time in various atmospheres. went. The treatment time was set so that the hydrogen concentration was 0.01 wt% or less. Cooling was performed while flowing Ar gas. Table 5 shows the treatment conditions of the dehydrogenation treatment, the magnetic properties of the obtained magnetic powder, and the hydrogen concentration.
[0136]
According to Table 5, it can be seen that the dehydrogenation treatment according to the present invention can select various combinations of treatment amount, atmosphere, and treatment time during the treatment.
[0137]
[Table 5]

[0138]
Example 6
The raw material alloy powder 50 kg obtained in the same manner as in Example 4 was filled in 6 SUS310S containers with an opening size of 250 × 250 mm and a depth of 50 mm, and the dehydrogenation treatment was performed by loading in an internal heat treatment furnace. .
[0139]
The atmosphere of the dehydrogenation was set to about 1.5 kPa by evacuating while introducing Ar gas at 5 l / min. The treatment was held at 850 ° C. for 60 minutes, and then forced cooling was performed by pressurizing the atmosphere with Ar gas to 0.25 MPa and stirring.
[0140]
After the treatment, magnetic particles located at various parts in the treatment container were sampled, and the magnetic properties were evaluated by VSM. The results are shown in Table 6. According to Table 6, it can be seen that the processing of the present invention can obtain uniform magnetic characteristics even in a large amount of processing.
[0141]
[Table 6]

[0142]
Example 7
100 g of the same raw material alloy as the raw material alloy S obtained in Example 2 was filled in a SUS310S container having an opening size of 60 × 100 mm, and loaded in a tubular heat treatment furnace for dehydrogenation treatment.
[0143]
The raw material alloy was heated to 820 ° C. while introducing Ar gas at atmospheric pressure (0.1 MPa) at 10 l / min, held at the same temperature, and the inside of the furnace was evacuated while introducing 5 l / min Ar gas. Then, after maintaining the total pressure at 4.0 kPa and treating for a predetermined time, the evacuation was stopped, the pressure was restored to atmospheric pressure with Ar gas, and heat treatment was performed for 120 minutes while flowing Ar at 5 l / min. The cooling was continued while flowing Ar gas.
[0144]
FIG. 6 shows the hydrogen concentration and magnetic properties of the magnetic powder obtained by this dehydrogenation treatment, with the time of reduced pressure Ar flowing air as the horizontal axis. FIG. 7 shows the estimated hydrogen concentration at the end of the reduced pressure Ar flow with the horizontal axis. According to FIG. 7, it can be seen that when the hydrogen concentration in the raw material alloy at the end of the vacuum dehydrogenation is 0.020 to 0.210 wt%, a large residual magnetization and a high coercive force are obtained simultaneously.
[0145]
Comparative Example 3
500 g of the master alloy powder having an average particle size of 425 μm or less used in Example 2 was filled in a SUS310S container having an opening size of 80 × 200 mm, and loaded into a tubular heat treatment furnace having an Inconel furnace core tube, and subjected to hydrogenation treatment. went. The treatment condition was that the temperature was raised to 840 ° C. at 15 ° C./min in a 0.1 MPa hydrogen atmosphere (5 l / min air flow), kept at that temperature for 2 hours, and then cooled in a hydrogen atmosphere. The cooling rate was approximately 55 ° C./min between 840 ° C. and 500 ° C.
[0146]
The hydrogen concentration of the raw material alloy obtained at this time was 0.37 wt%. According to the phase identification by powder X-ray diffraction method, NdH₂, Fe₂The three phases B and Fe were confirmed, but Nd₂Fe₁₄Phase B was not observed.
[0147]
Next, 100 g of the raw material alloy powder obtained by the above treatment was filled in a SUS310S container having an opening size of 60 × 100 mm, and loaded into a tubular heat treatment furnace for dehydrogenation treatment.
[0148]
The raw material alloy was heated to 820 ° C. while introducing Ar gas at atmospheric pressure (0.1 MPa) at 10 l / min, held at the same temperature, and the inside of the furnace was evacuated while introducing 5 l / min Ar gas. Then, after maintaining the total pressure at 4.0 kPa and treating for a predetermined time, the evacuation was stopped, the pressure was restored to the atmospheric pressure with Ar gas, and heat treatment was performed for 100 minutes while flowing Ar at 5 l / min. The cooling was continued while flowing Ar gas.
[0149]
FIG. 8 shows the hydrogen concentration and magnetic characteristics of the magnetic powder obtained by this dehydrogenation treatment, with the time of reduced pressure Ar flowing air as the horizontal axis. Further, FIG. 9 shows the estimated hydrogen concentration at the end of the reduced pressure Ar flow with the horizontal axis. The results of FIGS. 8 and 9 clearly show that the residual magnetization is low compared to FIGS. 6 and 7 of Example 7 of the present invention.
[0150]
Comparative Example 4
100 g of the same raw material alloy as obtained in Example 2 was filled in a SUS310S container having an opening size of 60 × 100 mm, charged in a tubular heat treatment furnace, and Ar gas was charged at 10 l / min under atmospheric pressure (0.10 MPa). While being introduced, heat treatment was performed at 820 ° C. for 150 minutes. The cooling was continued while flowing Ar gas.
[0151]
Table 7 shows the magnetic properties of the magnetic powder obtained by this dehydrogenation treatment. It can be seen that the results of Table 7 are clearly lower in coercive force and remanent magnetization than in Table 4.
[0152]
[Table 7]

[0153]
Example 8
Here, method (B) + method (D) was carried out. 100 g of the raw material alloy equivalent to that used in Example 2 was filled into a SUS310S vessel with an opening size of 60 × 100 mm, and mounted in a tubular heat treatment furnace having an Inconel furnace core tube, and dehydrogenated under various conditions. Went.
[0154]
The treatment temperature was constant at 830 ° C., and the hydrogen gas release rate was changed variously by adjusting the Ar gas flow rate and the total atmospheric pressure. The temperature is raised at a rate of 15 ° C / min in a flow of Ar at 0.10 MPa (5 l / min), and after a dehydrogenation process for a predetermined time and under a predetermined condition, an Ar flow of 0.10 MPa (5 l / min) Cooled in.
[0155]
Table 4 shows the dehydrogenation treatment conditions and the magnetic properties of the obtained magnetic powder. The hydrogen analysis value of the raw material powder cooled to the first stage dehydrogenation treatment under the same treatment conditions as the above treatment is also shown in the table as the estimated hydrogen concentration after the reduced pressure Ar treatment during the treatment in Table 8. .
[0156]
According to Table 8, the hydrogen concentration change rate in the first stage hydrogen release reaction is 0.1 to 5.0 wt% / h, the hydrogen concentration change rate in the second stage hydrogen release reaction is 0.01 to 0.2 wt% / h, It can also be seen that a high coercive force can be obtained if the second stage hydrogen concentration change rate is smaller than the first stage hydrogen concentration change rate.
[0157]
[Table 8]

[0158]
Example 9
Using raw material alloys No. 3 and No. 4 equivalent to those used in Example 2, filled in a SUS310S vessel with an opening size of 60 × 100 mm, loaded into a tubular heat treatment furnace having an Inconel furnace core tube, The dehydrogenation treatment was performed by changing the warm atmosphere.
[0159]
The dehydrogenation conditions were as follows: at 820 ° C., while introducing 5 l / min Ar gas, the inside of the furnace was evacuated to maintain the total pressure at 4.0 kPa, held for 10 minutes, and then evacuation was stopped. Then, the pressure was restored to atmospheric pressure, and heat treatment was performed for 100 minutes while flowing Ar at 5 l / min. The cooling was continued while flowing Ar gas.
[0160]
The atmosphere at the time of temperature rise is: A: 5 l / min of Ar gas is introduced and the inside of the furnace is evacuated to maintain the total pressure at 4.0 kPa. B: Flow of 5 l / min of Ar gas at 0.10 MPa. , C: 5 l / min H at 0.10 MPa₂I tried three ways of flowing gas. The heating rate was all 15 ° C./min.
[0161]
The evaluation results of the magnetic characteristics of the obtained magnetic powder are shown in FIG. 10, the result of the raw material alloy No. 3 is shown in FIG. 11, and the result of the raw material alloy No. 4 is shown as a demagnetization curve. 10 and 11, it can be seen that the best magnetic properties are obtained when the temperature is raised in a flow of Ar at 0.10 MPa. In FIG. 11 where the hydrogen concentration of the raw material alloy is small, it can be seen that the influence of the atmosphere during the temperature rise is small.
[0162]
Example 10
In the dehydrogenation process performed in Example 9, the rate of temperature increase was changed. At this time, No. 3 was used as the raw material alloy, and all the processing conditions other than the heating rate were the same as those in Example 9. The heating rate was 4 conditions of 5 ° C / min, 10 ° C / min, 15 ° C / min, and 20 ° C / min.
[0163]
Demagnetization curves of the obtained magnetic powder are shown in FIGS. In FIGS. 12 and 13, the effect of the rate of temperature increase is small, whereas in the temperature increase in the hydrogen atmosphere shown in FIG. Yes. It can be seen that the temperature rise rate in hydrogen is preferably 10 ° C./min or higher.
[0164]
【The invention's effect】
The present invention is characterized in that the dehydrogenation treatment is divided into the first half and the latter half in the HDDR treatment of the RT- (M) -B-based raw material alloy. By completing the first dehydrogenation process under specific conditions, a rare earth alloy powder for a permanent magnet having a large coercive force in a powder state while being able to be processed in a large amount and maintaining a large magnetization in the second process. can get.
[0165]
The present invention can provide a rare earth-based raw material alloy for permanent magnets that is stable and has a high coercive force and a large remanent magnetization, and that can be handled as an intermediate product simply by carrying out the required dehydrogenation process twice.
[0166]
In the present invention, the dehydrogenation process is a separate process, so that the equipment for the dehydrogenation process can be greatly simplified, a large amount of processing is facilitated, and the overall production efficiency including the raw material process is greatly improved. Further, by changing the hydrogen release rate in the second dehydrogenation step in multiple stages, it is possible to increase the coercive force without reducing the residual magnetization.
[Brief description of the drawings]
FIG. 1A is a heat pattern diagram showing an example of processing conditions from a hydrogenation process to the first dehydrogenation process according to the present invention, and B is a heat pattern diagram showing a second example of dehydrogenation process conditions according to the invention. is there.
[Fig. 2] A, B and C are the reduced Ar flow time in Example 1, the hydrogen concentration (wt%) of the magnetic powder after treatment, the residual magnetization Jr (T), the coercive force HcJ (MA / m). It is a graph which shows the relationship.
3A, B, and C are the hydrogen concentration of the raw material alloy powder in Example 1, the hydrogen concentration (wt%) of the magnetic powder after treatment, the residual magnetization Jr (T), the coercive force HcJ (MA / m It is a graph which shows the relationship with).
4 is a graph showing the relationship between an external magnetic field Hex (MA / m) and magnetization J (T) in Example 1, Comparative Example 1, and Comparative Example 2. FIG.
FIG. 5 shows A, B, and C, the dehydrogenation time in Example 3, the hydrogen concentration (wt%) of the magnetic powder after the treatment, the residual magnetization Jr (T), the coercive force HcJ (MA / m), and It is a graph which shows the relationship.
FIG. 6 shows A, B, and C, the reduced Ar flow time in Example 7, the hydrogen concentration (wt%) of the magnetic powder after treatment, the residual magnetization Jr (T), the coercive force HcJ (MA / m). It is a graph which shows the relationship.
7A, B, and C are the estimated hydrogen concentration at the end of the reduced pressure Ar flow treatment in Example 7, the hydrogen concentration (wt%) of the magnetic powder after treatment, the residual magnetization Jr (T), the coercive force, respectively. It is a graph which shows the relationship with HcJ (MA / m).
FIG. 8 shows A, B, and C, the reduced Ar flow time in Comparative Example 3, the hydrogen concentration (wt%) of the magnetic powder after treatment, the residual magnetization Jr (T), the coercive force HcJ (MA / m It is a graph which shows the relationship with).
FIGS. 9A and 9B show estimated hydrogen concentration at the end of the reduced pressure Ar flow treatment in Comparative Example 3, hydrogen concentration (wt%) of the magnetic powder after treatment, residual magnetization Jr (T), coercive force. It is a graph which shows the relationship with HcJ (MA / m).
10 is a graph showing the relationship between external magnetic field Hex (MA / m) and magnetization J (T) of raw material alloy No. 3 in Example 9. FIG.
11 is a graph showing the relationship between external magnetic field Hex (MA / m) and magnetization J (T) of raw material alloy No. 4 in Example 9. FIG.
12 is a graph showing the relationship between the external magnetic field Hex (MA / m) and the magnetization J (T) of the raw material alloy No. R heated in the reduced pressure Ar in Example 10. FIG.
13 is a graph showing the relationship between the external magnetic field Hex (MA / m) and the magnetization J (T) of the raw material alloy No. R heated in a reduced pressure Ar flow in Example 10. FIG.
14 is a graph showing the relationship between external magnetic field Hex (MA / m) and magnetization J (T) of raw material alloy No. R heated in hydrogen in Example 10. FIG.

Claims (10)

Ｒ_２Ｔ_１４Ｂ（ＢはＣで一部又は全量置換可能）型の化合物相が５０ｖｏｌ％以上を占める合金からなる鋳塊または粉末を、水素化及び不均化処理し、さらに脱水素化及び再結合処理するに際し、最初の脱水素化処理にて被処理物の水素濃度が次式の範囲に達した時点で一旦同処理を終了して冷却し、その後二度目の脱水素化処理を施す永久磁石用希土類系合金粉末の製造方法。
０．０００７２５×Ｃ _Ｒ ≦Ｃ _Ｈ ≦０．０１２０×Ｃ _Ｒ
但し、Ｃ _Ｈ は合金中の水素濃度（ｗｔ％）、Ｃ _Ｒ は合金中の希土類Ｒ成分濃度（ｗｔ％）。 An ingot or powder made of an alloy in which the compound phase of R ₂ T ₁₄ B (B can be partially or wholly substituted by C) type accounts for 50 vol% or more is subjected to hydrogenation and disproportionation treatment, and further dehydrogenation and In the recombination process, when the hydrogen concentration of the material to be processed reaches the range of the following formula in the first dehydrogenation process, the process is temporarily stopped and cooled, and then the second dehydrogenation process is performed. A method for producing rare earth alloy powders for permanent magnets.
0.000725 × C _R ≦ C _H ≦ 0.0120 × C _R
However, _{C H} is the hydrogen concentration (wt%) in the alloy, _{C R} is a rare earth R component concentration (wt%) in the alloy. 最初の脱水素化処理が、雰囲気の制御により脱水素化の反応速度を０．１ｗｔ％／ｈ〜５．０ｗｔ％／ｈの範囲で進行させ、反応開始から被処理物の水素濃度Ｃ_Ｈが次式の範囲に達するまで実施する方法である請求項１に記載の永久磁石用希土類系合金粉末の製造方法。
０．０００７２５×Ｃ_Ｒ≦Ｃ_Ｈ≦０．００７５０×Ｃ_Ｒ
但し、Ｃ_Ｈは合金中の水素濃度（ｗｔ％）、Ｃ_Ｒは合金中の希土類Ｒ成分濃度（ｗｔ％）。In the first dehydrogenation treatment, the reaction rate of dehydrogenation proceeds in the range of 0.1 wt% / h to 5.0 wt% / h by controlling the atmosphere, and the hydrogen concentration C _{H of the} object to be treated is changed from the start of the reaction. The method for producing a rare earth alloy powder for a permanent magnet according to claim 1, wherein the method is carried out until the range of the following formula is reached.
0.000725 × C _R ≦ C _H ≦ 0.00750 × C _R
However, _{C H} is the hydrogen concentration (wt%) in the alloy, _{C R} is a rare earth R component concentration (wt%) in the alloy. 最初の脱水素化処理が、雰囲気の制御により脱水素化の反応速度を０．０１ｗｔ％／ｈ〜０．２ｗｔ％／ｈの範囲で進行させ、反応開始から被処理物の水素濃度Ｃ_Ｈが次式の範囲に達するまで実施する方法である請求項１に記載の永久磁石用希土類系合金粉末の製造方法。
０．００７００×Ｃ_Ｒ≦Ｃ_Ｈ≦０．０１２０×Ｃ_Ｒ
但し、Ｃ_Ｈは合金中の水素濃度（ｗｔ％）、Ｃ_Ｒは合金中の希土類Ｒ成分濃度（ｗｔ％）。In the first dehydrogenation treatment, the reaction rate of dehydrogenation proceeds in the range of 0.01 wt% / h to 0.2 wt% / h by controlling the atmosphere, and the hydrogen concentration C _{H of the} object to be treated is changed from the start of the reaction. The method for producing a rare earth alloy powder for a permanent magnet according to claim 1, wherein the method is carried out until the range of the following formula is reached.
0.00700 × C _R ≦ C _H ≦ 0.0120 × C _R
However, _{C H} is the hydrogen concentration (wt%) in the alloy, _{C R} is a rare earth R component concentration (wt%) in the alloy. 二度目の脱水素化処理が、真空中または不活性ガス雰囲気中で、温度６５０〜１０００℃に１５分〜４時間保持した後に冷却し、水素濃度を０．０１ｗｔ％以下とする方法である請求項１に記載の永久磁石用希土類系合金粉末の製造方法。 The second dehydrogenation treatment is a method in which the hydrogen concentration is set to 0.01 wt% or less by cooling after holding at a temperature of 650 to 1000 ° C. for 15 minutes to 4 hours in a vacuum or in an inert gas atmosphere. Item 2. A process for producing a rare earth alloy powder for a permanent magnet according to Item 1. 二度目の脱水素化処理を、雰囲気の制御により脱水素化の反応速度を０．０１ｗｔ％／ｈ〜０．２ｗｔ％／ｈの範囲で進行させる請求項２に記載の永久磁石用希土類系合金粉末の製造方法。 The rare earth-based alloy for permanent magnets according to claim 2, wherein the second dehydrogenation treatment is performed in a range of 0.01 wt% / h to 0.2 wt% / h by controlling the atmosphere. Powder manufacturing method. 二度目の脱水素化処理が、第１段階は、雰囲気の制御により反応開始から被処理物の水素濃度Ｃ_Ｈが次式の範囲に達するまでであり、第２段階は、水素濃度Ｃ_Ｈが０．０１ｗｔ％以下となるまで実施する方法である請求項３に記載の永久磁石用希土類系合金粉末の製造方法。
０．０００７２５×Ｃ_Ｒ≦Ｃ_Ｈ≦０．００７５０×Ｃ_Ｒ
但し、Ｃ_Ｈは合金中の水素濃度（ｗｔ％）、Ｃ_Ｒは合金中の希土類Ｒ成分濃度（ｗｔ％）。In the second dehydrogenation process, the first stage is from the start of the reaction until the hydrogen concentration C _H of the workpiece reaches the range of the following formula by controlling the atmosphere, and the second stage is that the hydrogen concentration C _H is The method for producing a rare earth alloy powder for a permanent magnet according to claim 3, wherein the method is carried out until the content becomes 0.01 wt% or less.
0.000725 × C _R ≦ C _H ≦ 0.00750 × C _R
However, _{C H} is the hydrogen concentration (wt%) in the alloy, _{C R} is a rare earth R component concentration (wt%) in the alloy. 第１段階の水素放出速度が０．１ｗｔ％／ｈ〜５．０ｗｔ％／ｈ、第２段階の水素放出速度が０．０１ｗｔ％／ｈ〜０．２０ｗｔ％／ｈであり、かつ第２段階の水素放出速度を第２段階よりも小さな放出速度とする請求項６に記載の永久磁石用希土類系合金粉末の製造方法。 The hydrogen release rate in the first stage is 0.1 wt% / h to 5.0 wt% / h, the hydrogen release rate in the second stage is 0.01 wt% / h to 0.20 wt% / h, and the second stage The method for producing a rare earth-based alloy powder for permanent magnets according to claim 6, wherein the hydrogen release rate is lower than that in the second stage. 脱水素処理が、不活性ガス流気中及び／又は真空排気による雰囲気の全圧によって調節される請求項１〜請求項７のいずれかに記載の永久磁石用希土類系合金粉末の製造方法。 The method for producing a rare earth alloy powder for a permanent magnet according to any one of claims 1 to 7, wherein the dehydrogenation treatment is adjusted by the total pressure of the atmosphere in an inert gas stream and / or evacuation. 二度目の脱水素化処理の昇温過程において、雰囲気を全圧５０ｋＰａ〜１０００ｋＰａである不活性ガス雰囲気とする請求項５または請求項６に記載の永久磁石用希土類系合金粉末の製造方法。 The method for producing a rare earth alloy powder for a permanent magnet according to claim 5 or 6, wherein the atmosphere is an inert gas atmosphere having a total pressure of 50 kPa to 1000 kPa in the temperature raising process of the second dehydrogenation treatment. 二度目の脱水素化処理の昇温過程において、雰囲気を水素分圧１００Ｐａ以上であり、かつ６００〜７５０℃の範囲の温度領域を１０℃／ｍｉｎ以上の速度で昇温する請求項５または請求項６に記載の永久磁石用希土類系合金粉末の製造方法。 6. The temperature rising process of the second dehydrogenation treatment, wherein the atmosphere has a hydrogen partial pressure of 100 Pa or higher, and the temperature range of 600 to 750 ° C. is increased at a rate of 10 ° C./min or higher. Item 7. A method for producing a rare earth alloy powder for a permanent magnet according to Item 6.

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