JP3755902B2

JP3755902B2 - Magnet powder for anisotropic bonded magnet and method for producing anisotropic bonded magnet

Info

Publication number: JP3755902B2
Application number: JP21814793A
Authority: JP
Inventors: 克典岩崎; 実遠藤; 雅亮徳永
Original assignee: Neomax Co Ltd
Current assignee: Hitachi Metals Ltd
Priority date: 1993-08-10
Filing date: 1993-08-10
Publication date: 2006-03-15
Anticipated expiration: 2021-03-15
Also published as: JPH0757910A

Description

【０００１】
【産業上の利用分野】
本発明は改良されたR₂T₁₄B（ＲはYを含む希土類元素であって Ndを必ず含み、ＴはFeまたはFeおよびCoである。）を主相とする微細結晶粒の集合体からなる異方性ボンド磁石用磁石粉末の製造方法に関する。
また本発明は前記異方性磁石粉末を樹脂で結合した高性能の異方性ボンド磁石の製造方法に関する。
【０００２】
【従来の技術】
希土類元素、鉄およびホウ素からなるＲ−Ｆｅ−Ｂ系永久磁石は安価でかつ高磁気特性を有するものとして注目を集めている。Ｒ−Ｆｅ−Ｂ系永久磁石は最終製品の分類からバルク磁石である焼結磁石あるいは温間加工磁石とボンド磁石に大別される。ボンド磁石は形状自由度および価格面の有利性から今後重要度が増すと考えられる。
Ｎｄ−Ｆｅ−Ｂ系ボンド磁石用の粉末は製造方法の違いで幾つかに分類される。例えば等方性磁石粉末の製造方法として、メルトスピニング法によりＮｄ−Ｆｅ−Ｂ系急冷薄片とした後、適当な温度で熱処理する方法が特開昭５９−６４７３９３号公報に開示されている。更に同様のメルトスピニング法で得られた薄片を用いてホットプレスおよびダイアップセットにより圧縮方向に異方性を付与した異方性バルク磁石をいったん作製し、次いで同磁石を粉砕することによって異方性磁粉とする方法が知られている。その他、近年注目されている手法として、Ｓｍ₂Ｆｅ₁₇型合金に窒化処理を施し格子間に窒素元素を侵入させることによって異方性磁界を飛躍的に向上せしめ、異方性ボンド磁石用磁石粉末とする方法がある。またこの方法と同様の原理でＮｄＦｅ_１１Ｔｉ、ＮｄＦｅ_１０Ｖ_２といったＴｈＭｎ_１２型の合金にも同様の効果が得られるとの報告がある。
更に、Ｎｄ−Ｆｅ−Ｂ系合金に水素吸蔵および脱水素処理を行い、再結晶反応を利用して磁気的に異方性化したＮｄ_２Ｆｅ_１４Ｂ型磁石粉末を得る方法が知られている。（特開平１−１３２１０６号公報、特開平２−４９０１号公報等）。
【０００３】
【発明が解決しようとする課題】
従来法で得られる上記磁石粉末の内、メルトスピニング法によるＮｄ−Ｆｅ−Ｂ系急冷薄片は磁気的に等方性なため最終的なエネルギ−績は高々10MGOeにすぎず磁気特性面で問題がある。また、いったん作製した上記異方性バルク磁石を粉砕して得られる異方性磁石粉末は製造工程が長くコスト的に若干不利である。
一方、窒化処理による磁石粉末のうちＳｍ_２Ｆｅ_１７系に関しては主原料としてＳｍを使用するため資源的な面で将来性に不安が残る。ＴｈＭｎ_１２型磁石粉末に関しては使用する希土類元素がＮｄであるため資源的には有利であるが、窒化後の磁気ポテンシャルはＮｄ_２Ｆｅ_１４Ｂ型あるいはＳｍ_２Ｆｅ_１７型よりかなり低く魅力に欠ける。
【０００４】
水素吸蔵および脱水素処理を経て得られる上記ＮｄＦｅＢ系異方性磁石粉末は製造工程が簡略なうえ資源的に有利であるという特徴を有しているが、Ｎｄ−Ｆｅ−Ｂ系バルク磁石の理論値から概算して、現時点で得られる磁気特性はまだ十分とは言えない。この原因として、水素吸蔵および脱水素処理前の鋳造合金に問題があると考えられる。つまり通常の条件で溶製したインゴットはその凝固過程で組織的にチル晶、柱状晶および等軸晶からなっており、これらの組織内ではα（Ｆｅ、Ｃｏ）、Ｎｄ−ｒｉｃｈ相およびＢ−ｒｉｃｈ相等の存在形態も異なり均一性に欠ける。このため水素吸蔵および脱水素処理後のものを適当な大きさに粉砕してなる異方性磁石粉末を構成する個々の結晶粒の異方性方向に顕著なバラツキがある。
したがって、本発明の課題は、水素吸蔵および脱水素処理に供するＲ−Ｔ−Ｂ系鋳造合金を改良することにより、従来に比べて磁気特性を高めた異方性ボンド磁石用Ｒ−Ｔ−Ｂ系磁石粉末およびそれを用いた異方性ボンド磁石の製造方法を提供することである。
【０００５】
【課題を解決するための手段】
本発明者等は、従来の水素吸蔵／脱水素処理法における前工程として、原料となる鋳造合金を特定の凝固速度に制御し鋳造することにより得られた均一組成の板状合金を熱処理すると、板状合金の内部組織が粗大粒化し、磁気的に異方性方向が揃うこと、この板状合金に水素吸蔵、脱水素処理を施すと、再結晶反応によって粗大粒内に平均結晶粒径 0.02 〜５μｍの微細結晶粒が析出すること、及びこの板状合金を粉砕することにより、高保磁力を有する理想的な Nd-Fe-B 系異方性磁石粉末が得られることを発見した。
上記課題を解決した本発明の異方性ボンド磁石用磁石粉末の製造方法は、平均結晶粒径が0.02〜５μmのR₂T₁₄B（RはYを含む希土類元素であってNdを必ず含み、TはFeまたはFeおよびCoである。）を主相とする微細結晶粒の集合体からなる異方性ボンド磁石用磁石粉末の製造方法において、10²〜10⁴℃/secの冷却速度で R-T-B 系合金の溶湯を凝固して、厚さが50〜5000μmの板状であって、板厚方向に伸びた結晶粒を有するR-T-B系板状合金を得る鋳造工程、不活性ガス雰囲気中1000 ℃以上の温度で熱処理を施すことにより、前記板状合金の板厚方向に伸びた結晶粒を同方向で粗大結晶化させ、もって磁気的な異方性化度を高める工程、650〜900℃の温度で水素吸蔵および脱水素処理を行い、再結晶反応を生じさせる工程、および水素吸蔵および脱水素処理後の前記板状合金を粉砕する工程を有することを特徴とする。
また本発明の異方性ボンド磁石の製造方法は、平均結晶粒径が0.02〜５μmのR₂T₁₄B（RはYを含む希土類元素であってNdを必ず含み、TはFeまたはFeおよびCoである。）を主相とする微細結晶粒の集合体からなる異方性磁石粉末と樹脂とからなる異方性ボンド磁石の製造方法において、10²〜10⁴℃/secの冷却速度で R-T-B 系合金の溶湯を凝固して、厚さが50〜5000μmの板状であって、板厚方向に伸びた結晶粒を有するR-T-B系板状合金を得る鋳造工程、不活性ガス雰囲気中1000 ℃以上の温度で熱処理を施すことにより、前記板状合金の板厚方向に伸びた結晶粒を同方向で粗大結晶化させ、もって磁気的な異方性化度を高める工程、650〜900℃の温度で水素吸蔵および脱水素処理を行い、再結晶反応を生じさせる工程、水素吸蔵および脱水素処理後の前記板状合金を粉砕する工程、前記工程を経て得られた異方性磁石粉末と樹脂とを混合する工程、および得られた混合物を磁場中成形する工程を有することを特徴とする。
本発明により製造される高性能の異方性磁石粉末粒子は平均結晶粒径が0.02〜５μｍのR₂T₁₄Bを主相とする微細結晶粒の集合体であり、磁化容易軸方向と磁化困難軸方向とを有する。異方性ボンド磁石を構成する個々の磁石粉末粒子の磁化容易軸方向と磁化困難軸方向の磁化の差が大きい程異方性化度が高くなる。また本発明による異方性ボンド磁石の密度を高めるために粗目の粒径の磁石粉末を使用することが好ましく、前記ボンド磁石の形状任意性を考慮した場合粒径は500μｍ以下であることが望ましい。磁気特性の重要な指標である保磁力は結晶粒径と密接な関係があり、Nd-Fe-B系永久磁石の単磁区粒子径に近い値が必要であるので平均結晶粒径は0.02〜５μｍが望ましい。
【０００６】
本発明により得られる高性能の異方性磁石粉末は特に限定されないが、Ｒを25〜35ｗｔ％、Ｂを0.5〜1.5％、Ｃｏを３〜20ｗｔ％、Ｇａ、Ｚｒ、Ｎｂ、Ｈｆ、Ｔａ、Ａｌ、ＳｉおよびＶのうちの少なくとも１種の合計量が0.05〜５ｗｔ％、残部Ｆｅおよび不可避的不純物からなる組成のものが好ましい。本発明により得られる異方性磁石粉末はＲ_２Ｆｅ _１４Ｂを主相とする微細結晶粒の集合体からなるため、前記特定組成範囲外ではα（Ｆｅ、Ｃｏ）相、Ｎｄ− rich 相、Ｂ− rich 等の余分な相が多量に生成して磁気特性の低下を招く。またＧａ、Ｚｒ、Ｎｂ、Ｈｆ、Ｔａ、Ａｌ、ＳｉおよびＶのうちの少なくとも１種の合計量が0.05ｗｔ％未満では異方性化度の改良に寄与せず、５ｗｔ％超ではＲ_２Ｆｅ _１４Ｂ以外の相を多量に生成し磁気特性を低下させる。
本発明によるＲ−Ｔ−Ｂ系異方性磁石粉末は水素吸蔵および脱水素処理を施すことにより得られる。脱水素工程でＲ−Ｔ−Ｂ系合金から水素を強制的に脱気する際の再結晶反応を利用している。つまり脱水素処理過程でＮｄ−Ｆｅ−Ｂ系永久磁石の単磁区粒子径に近い微細結晶粒を得ることによって個々の磁石粉末粒子が有用な保磁力を有するようになる。なお水素吸蔵および脱水素処理は650〜900℃の温度範囲で行えばよい。
【０００７】
高性能の異方性磁石粉末を得るための手段として、水素吸蔵および脱水素処理に供する原料合金を、溶解後の鋳造工程において10²〜10⁴℃／secの冷却速度の下で凝固し、厚さ50〜5000μｍの板状合金とする。前記板状合金は、前記板状合金組成の溶湯を回転ロ−ル上に噴出する方法により得られる。冷却速度および板厚はおおまかに噴出ノズルのスリット幅およびロ−ル回転数で制御できる。板状合金の断面はデンドライト組織を有しており、急冷側（ロ−ル回転面側）から自由面側（ロ−ル面と反対側）に向けほぼ板厚方向に成長していた。また冷却速度を考慮したうえで鋳型に溶湯を流し込み板状合金に仕上げる方法でもよい。詳細は実施例に譲るが、このようにして得られたR-T-B系板状合金はインゴットと比較して薄いうえ、ほぼ一定の厚さであるため、水素吸蔵および脱水素処理が短時間に行える。また脱水素処理工程を終了後直ちに急冷できるため結晶粒の粗大化を防ぐことができ、特性的にも均質な異方性磁石粉末が得られる。冷却後、異方性磁石粉末の製造時の粉砕工程においても粉砕を極めて効率よく行える。
【０００８】
本発明では、前述の通り一定方向のデンドライト組織を有する板状合金に対して、水素処理以前に 1000 ℃以上の温度で熱処理することにより、結晶粒を意図的に粗大化させ、異方性化度を高める。この段階では保磁力は0.5ｋOe以下で、異方性ボンド磁石用磁石粉末として用をなさないが、前記板状合金に対して水素吸蔵および脱水素処理を施すことによって粗大粒中で平均結晶粒径が0.02〜５μｍの微細結晶粒を生成させ、高い保磁力を得ることができる。この際、各磁石粉末粒子は異方性方向を失わず微細化が行われるため高い異方性化度を維持するとともに、均質に処理できるため角形性に優れた高性能の異方性磁石粉末を得ることが可能である。
【０００９】
【実施例】
以下、実施例により本発明を詳細に説明するが、それら実施例により本発明が限定されるものではない。
（実施例１、比較例１）
Ｎｄ、Ｆｅ、ＣｏおよびＢを主成分とし、他の元素としてＧａ、ＺｒあるいはＨｆを含む所定の合金組成に真空溶解し、鋳造して合金を得た。鋳造合金は冷却速度（凝固速度）を変えた二通りの方法で作製した。比較例１の通常溶解、鋳造法による合金は、溶湯を鋳型に流し込む従来法で作製した。この際の冷却速度は合金中央で約30℃/secであった。一方実施例１の板状合金はロ−ル冷却法を用い、噴出ノズルギャップおよびロ−ル回転数を調整し、板厚が300〜500μｍになるように作製した。この際の冷却速度は約５×10^２℃/secであった。作製した実施例１および比較例１の鋳造合金に所定の条件下で熱処理（以下、均質化処理という）を施し、次いで水素吸蔵および脱水素処理に供した。鋳造方法、組成、均質化処理条件および平均結晶粒径を表１に示す。通常溶解、鋳造法によるものは均質化処理後10^１〜10^２μｍオ−ダ−の平均結晶粒径であった。一方、ロ−ル冷却法による板状合金は鋳造後約５〜10μｍ間隔のデンドライト組織を有しており、均質化処理温度の上昇にともない結晶粒は徐々に粗大化し、特にこの傾向は1000℃以上で著しかった。一例として、ロ−ル冷却材の＃４（鋳造後）と＃６（1100℃×20時間）の組織写真を図１に示す。板厚方向に伸びたデンドライト組織が同方向で粗大結晶化する様子が分かる。
前記水素吸蔵および脱水素処理条件として、水素を室温で充分吸蔵させた後、10℃/分の昇温速度で830℃まで加熱し、続いて同温度で２時間保持した後、更に同温度で１時間脱水素処理し、その後炉内をアルゴン雰囲気に置換し冷却する条件を採用した。
【００１０】
水素処理後、それぞれの合金を32μm以下、32 〜 106 μ m 、106〜180μm、180〜250μm、250〜425μm、425〜500μmの６段階に粉砕、分級した。次いでこれらの磁性粉末をエポキシ樹脂と混合し、磁場中圧縮成形により異方性ボンド磁石とした。表１の＃１、＃４、＃６の合金を出発原料とし、粉砕粒径32〜106μmの磁石粉末のみを使用したときの異方性ボンド磁石の減磁曲線を図２に示す。この図から分かる通り、＃１と＃６では残留磁束密度は殆ど変わらないもののiHcおよびHkは＃６の方が大きく、角形性に優れていることが分かる。図３に同様の方法で各粉砕粒径別の異方性ボンド磁石を作製した場合の磁気特性を示す。いずれの粉砕粒径でも残留磁束密度は殆ど変化しないが、本発明による異方性ボンド磁石は高いiHc、Hkを示した。なお32μm以下における残留磁束密度およびHkの著しい低下はボンド磁石の密度低下に伴うものである。
【００１１】
【表１】

【００１２】
（実施例２、比較例２）
次いで水素吸蔵および脱水素処理条件を変化させた場合の磁気特性を評価した。使用した合金原料および水素吸蔵および脱水素処理条件を表２に示す。合金組成をＮｄ_12.6Ｆｅ_balＣｏ_11.5Ｂ_6.0Ｇａ_0.8で統一した以外はそれぞれ実施例１および比較例１と同様にして実施例２および比較例２の鋳造合金を作製した。次いで水素吸蔵処理前に1100℃×20時間の均質化処理を施した。所定の水素処理を終了した後、ガス分析により合金内に残存する酸素量および水素量を分析した。さらに32〜180μｍの粉砕粒径に分級した磁石粉末のみを用い異方性ボンド磁石を作製した。各異方性ボンド磁石の磁気特性を測定し、減磁曲線からiHc、Hkを読みとった。ガス分析結果および磁気特性を表３に示す。
比較例２の通常溶解、鋳造材で中央部が微細化されない原因の詳細は明らかではないが、水素吸蔵が不十分であるためと考えられる。またiHcが低いことから脱水素処理終了後に結晶粒の粗大化が起こっているとも考えられる。結晶粒の粗大化を防止するため500μｍ以下に粉砕した＃６では、iHc向上に効果は認められるものの酸化が著しく品質が劣る。したがって通常溶解、鋳造材を出発原料とする場合、水素吸蔵および脱水素処理の最適条件は限定される。一方、実施例２のロ−ル冷却法による鋳造合金では幅広い条件下で残存ガス量が少なくかつ高い磁気特性の異方性磁石粉末が得られることが分かる。これは鋳造合金の板厚がほぼ一定でありかつ薄いので均質な水素吸蔵および脱水素処理が行えるうえ、脱水素終了後のアルゴン冷却による急冷効果により結晶粒の粗大化を抑えられるためと考えられる。
【００１３】
【表２】

【００１４】
【表３】

【００１５】
【発明の効果】
本発明によれば、安定して高いiHcおよびHkを有するＲ−Ｔ−Ｂ系異方性磁石粉末およびそれを用いた高性能の異方性ボンド磁石を製造することができる。
【図面の簡単な説明】
【図１】ロール冷却材（ａ）および熱処理後のもの（ｂ）の金属組織写真である。
【図２】異方性ボンド磁石の減磁曲線である。
【図３】異方性ボンド磁石の磁気特性を示すグラフである。[0001]
[Industrial application fields]
The present invention R ₂ T ₁₄ B, which are improved (R always contains a Nd A rare earth elements including Y, T is Fe or Fe and Co.) From the fine crystal grains of the aggregate as a main phase The present invention relates to a method for producing a magnet powder for an anisotropic bonded magnet.
The present invention also relates to a method for producing a high performance anisotropic bonded magnet in which the anisotropic magnet powder is bonded with a resin .
[0002]
[Prior art]
R-Fe-B permanent magnets composed of rare earth elements, iron and boron are attracting attention as being inexpensive and having high magnetic properties. R-Fe-B permanent magnets are roughly classified into sintered magnets that are bulk magnets, warm-worked magnets, and bonded magnets from the classification of final products. Bonded magnets are expected to increase in importance in the future due to the freedom of shape and price advantages.
Powders for Nd—Fe—B based bonded magnets are classified into several types depending on the production method. For example, as a method for producing an isotropic magnet powder, a method of heat-treating at an appropriate temperature after forming an Nd—Fe—B-based quenched flake by a melt spinning method is disclosed in JP-A-59-647393. Furthermore, anisotropic bulk magnets with anisotropic anisotropy in the compression direction were once prepared by hot pressing and die-up set using the flakes obtained by the same melt spinning method, and then anisotropically pulverized. A method for producing a magnetic powder is known. In addition, as a technique attracting attention in recent years, an anisotropic magnetic field is dramatically improved by performing nitriding treatment on an Sm ₂ Fe ₁₇ type alloy and allowing nitrogen elements to enter between the lattices. There is a method. There is also a report that the same effect can be obtained for ThMn ₁₂ type alloys such as NdFe ₁₁ Ti and NdFe ₁₀ V _{2 on} the same principle as this method.
Furthermore, a method is known in which hydrogen storage and dehydrogenation treatment is performed on an Nd—Fe—B alloy, and a magnetically anisotropic Nd ₂ Fe ₁₄ B type magnet powder is obtained using a recrystallization reaction. . (JP-A-1-132106, JP-A-2-4901, etc.).
[0003]
[Problems to be solved by the invention]
Among the magnetic powders obtained by the conventional method, the Nd-Fe-B type quenching flakes obtained by the melt spinning method are magnetically isotropic, so the final energy performance is only 10 MGOe at most, and there is a problem in terms of magnetic characteristics. is there. Moreover, the anisotropic magnet powder obtained by pulverizing the anisotropic bulk magnet once produced has a long manufacturing process and is somewhat disadvantageous in terms of cost.
On the other hand, among the magnet powders obtained by the nitriding treatment, the Sm ₂ Fe ₁₇ series uses Sm as a main raw material, so there is a concern about the future in terms of resources. The ThMn ₁₂ type magnet powder is advantageous in terms of resources because the rare earth element used is Nd, but the magnetic potential after nitriding is considerably lower than the Nd ₂ Fe ₁₄ B type or Sm ₂ Fe ₁₇ type and is unattractive.
[0004]
The NdFeB-based anisotropic magnet powder obtained through the hydrogen storage and dehydrogenation treatment has a feature that the manufacturing process is simple and is advantageous in terms of resources, but the theory of Nd-Fe-B bulk magnets. Estimating from the values, the magnetic properties obtained at present are still not sufficient. This is considered to be due to a problem with the cast alloy before hydrogen storage and dehydrogenation. In other words, ingots melted under normal conditions are structurally composed of chill, columnar and equiaxed crystals during the solidification process. Within these structures, α (Fe, Co), Nd-rich phase and B- The existence form of the rich phase is different and lacks uniformity. For this reason, there is a remarkable variation in the anisotropic direction of the individual crystal grains constituting the anisotropic magnet powder obtained by pulverizing the material after hydrogen storage and dehydrogenation treatment to an appropriate size.
Accordingly, an object of the present invention is to improve an R-T-B type cast alloy used for hydrogen storage and dehydrogenation treatment, thereby improving the R-T-B for an anisotropic bonded magnet having improved magnetic characteristics as compared with the conventional one. It is to provide a system magnet powder and a method for producing an anisotropic bonded magnet using the same.
[0005]
[Means for Solving the Problems]
As a pre-process in the conventional hydrogen storage / dehydrogenation treatment method , the present inventors heat-treat the plate-shaped alloy having a uniform composition obtained by controlling the casting alloy as a raw material to a specific solidification rate and casting , The internal structure of the plate-like alloy is coarsened and the magnetic anisotropy direction is aligned. When this plate-like alloy is subjected to hydrogen storage and dehydrogenation treatment, an average crystal grain size of 0.02 is obtained in the coarse grain by recrystallization reaction. It has been found that an ideal Nd—Fe—B anisotropic magnet powder having a high coercive force can be obtained by precipitating fine crystal grains of ˜5 μm and grinding this plate-like alloy .
Method for producing a magnetic powder for an anisotropic bonded magnet of the present invention which solves the above-mentioned problems, R ₂ T ₁₄ B (R in average crystal grain size 0.02~5μm always include Nd A rare earth elements including Y , T is a Fe or Fe and Co.) the method of manufacturing the anisotropic bonded magnet powder for a magnet consisting of fine crystal grains of the aggregate as a main phase, at a cooling rate of 10 ² ~10 ⁴ ℃ / sec Casting process for solidifying the RTB alloy melt to obtain an RTB plate alloy having a crystal shape with a thickness of 50 to 5000 μm and extending in the plate thickness direction , in an inert gas atmosphere at 1000 ° C. by heat treatment at a temperature above the crystal grains extending in the thickness direction of the plate-shaped alloy was coarsely crystallized in the same direction, with the step of increasing the magnetic anisotropy of degree, of 650-900 ° C. Performing a hydrogen storage and dehydrogenation treatment at a temperature to cause a recrystallization reaction , and the hydrogen storage and dehydrogenation treatment It has the process of grind | pulverizing a plate-shaped alloy.
The method for producing an anisotropic bonded magnet of the present invention, R ₂ T ₁₄ B (R in average crystal grain size 0.02~5μm always include Nd A rare earth elements including Y, T is Fe or Fe and Co is a.) a method of manufacturing an anisotropic bonded magnet composed of an anisotropic magnet powder and a resin consisting of fine crystal grains of the aggregate as a main phase, at a cooling rate of 10 ² ~10 ⁴ ℃ / sec Casting process for solidifying the RTB alloy melt to obtain an RTB plate alloy having a crystal shape with a thickness of 50 to 5000 μm and extending in the plate thickness direction , in an inert gas atmosphere at 1000 ° C. by heat treatment at a temperature above the crystal grains extending in the thickness direction of the plate-shaped alloy was coarsely crystallized in the same direction, with the step of increasing the magnetic anisotropy of degree, of 650-900 ° C. perform hydrogen storage and dehydrogenation treatment at a temperature, the step of causing a recrystallization reaction, a hydrogen storage and the plate-like alloy after dehydrogenated The step of grinding, and having the process steps of mixing the anisotropic magnet powder and a resin obtained through, and the resulting mixture shaping in a magnetic field.
The high-performance anisotropic magnet powder particles produced by the present invention are aggregates of fine crystal grains mainly composed of R ₂ T ₁₄ B having an average crystal grain size of 0.02 to 5 μm. Having a hard axis direction. The degree of anisotropy increases as the difference in magnetization between the easy magnetization axis direction and the hard magnetization axis direction of the individual magnet powder particles constituting the anisotropic bonded magnet increases. Further it is preferred to use a magnetic powder of particle size of the coarse to increase the density of the anisotropic bonded magnet of the present invention, it is desirable particle size when considering the shape any of the bonded magnet is 500μm or less . The coercive force, which is an important index of magnetic properties, is closely related to the crystal grain size, and a value close to the single domain particle size of the Nd-Fe-B permanent magnet is required, so the average crystal grain size is 0.02 to 5 μm. Is desirable.
[0006]
The high-performance anisotropic magnet powder obtained by the present invention is not particularly limited, but R is 25 to 35 wt%, B is 0.5 to 1.5%, Co is 3 to 20 wt%, Ga, Zr, Nb, Hf, Ta, A composition having a total amount of at least one of Al, Si and V of 0.05 to 5 wt%, the balance Fe and inevitable impurities is preferable. Since the anisotropic magnet powder obtained by the present invention is composed of an aggregate of fine crystal grains having R ₂ Fe ₁₄ B as a main phase, an α (Fe, Co) phase , an Nd- rich phase, A large amount of an extra phase such as B- rich is generated, resulting in a decrease in magnetic properties. Further, if the total amount of at least one of Ga, Zr, Nb, Hf, Ta, Al, Si and V is less than 0.05 wt%, it does not contribute to the improvement of the degree of anisotropy, and if it exceeds 5 wt%, R ₂ Fe _A large amount of phases other than ₁₄ B are produced to reduce the magnetic properties.
The RTB-based anisotropic magnet powder according to the present invention can be obtained by performing hydrogen storage and dehydrogenation treatment. A recrystallization reaction is used when hydrogen is forcibly degassed from the RTB-based alloy in the dehydrogenation step. That is, by obtaining fine crystal grains close to the single domain particle diameter of the Nd—Fe—B permanent magnet in the dehydrogenation process, each magnet powder particle has a useful coercive force. In addition, what is necessary is just to perform hydrogen occlusion and a dehydrogenation process in the temperature range of 650-900 degreeC.
[0007]
As a means for obtaining a high-performance anisotropic magnet powder, the raw material alloy subjected to hydrogen storage and dehydrogenation is solidified under a cooling rate of 10 ² to 10 ⁴ ° C / sec in the casting process after melting, A plate-like alloy having a thickness of 50 to 5000 μm is used . The plate-like alloy is obtained by a method of jetting a molten metal having the plate-like alloy composition onto a rotating roll. The cooling rate and the plate thickness can be roughly controlled by the slit width of the ejection nozzle and the roll rotation speed. The cross section of the plate-like alloy had a dendrite structure, and grew substantially in the thickness direction from the quenching side (roll rotating surface side) to the free surface side (opposite side of the roll surface). In addition, a method of pouring a molten metal into a mold and finishing it into a plate-like alloy after considering the cooling rate may be used. Details cede to Examples, but, RTB system plate alloy obtained in this manner upon thinner than an ingot, is almost constant thickness, performed in a short time the hydrogen storage and dehydrogenation treatment. In addition, since rapid cooling can be performed immediately after completion of the dehydrogenation treatment step, coarsening of crystal grains can be prevented, and an anisotropic magnet powder that is homogeneous in characteristics can be obtained. After cooling, pulverization can be performed very efficiently also in the pulverization step during the production of anisotropic magnet powder .
[0008]
In the present invention, as described above, a plate-like alloy having a dendritic structure in a certain direction is heat-treated at a temperature of 1000 ° C. or higher before hydrogen treatment , thereby intentionally coarsening the crystal grains and making them anisotropic. Increase the degree. At this stage, the coercive force is 0.5 kOe or less , and it is not used as a magnet powder for anisotropic bonded magnets, but the average grain size in coarse grains is obtained by subjecting the plate-like alloy to hydrogen storage and dehydrogenation. Fine crystal grains having a diameter of 0.02 to 5 μm can be generated and high coercive force can be obtained. At this time, with each magnet powder particles to maintain a high anisotropy degree for miniaturization without loss of anisotropy direction is performed, a homogeneous high performance anisotropic magnet powder having excellent squareness order to be processed It is possible to obtain
[0009]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by these Examples.
(Example 1 and Comparative Example 1 )
An alloy was obtained by vacuum melting in a predetermined alloy composition containing Nd, Fe, Co and B as main components and Ga, Zr or Hf as other elements and casting. The cast alloy was produced by two methods with different cooling rates (solidification rates). The alloy by the normal melting and casting method of Comparative Example 1 was prepared by a conventional method in which a molten metal was poured into a mold. The cooling rate at this time was about 30 ° C./sec at the center of the alloy. On the other hand, the plate-like alloy of Example 1 was prepared using a roll cooling method, adjusting the jet nozzle gap and the roll rotation speed, and having a plate thickness of 300 to 500 μm. The cooling rate at this time was about 5 × 10 ² ° C./sec. The produced cast alloys of Example 1 and Comparative Example 1 were subjected to heat treatment (hereinafter referred to as homogenization treatment) under predetermined conditions, and then subjected to hydrogen storage and dehydrogenation treatment. Table 1 shows the casting method, composition, homogenization treatment conditions, and average crystal grain size. In general, the melt and casting methods had an average crystal grain size of 10 ¹ to 10 ² μm order after homogenization. On the other hand, the plate-like alloy by the roll cooling method has a dendrite structure at intervals of about 5 to 10 μm after casting, and the crystal grains gradually become coarser as the homogenization temperature rises. That's it. As an example, FIG. 1 shows structural photographs of roll coolant # 4 (after casting) and # 6 (1100 ° C. × 20 hours). It can be seen that the dendrite structure extending in the thickness direction is coarsely crystallized in the same direction.
As the hydrogen storage and dehydrogenation treatment conditions, after sufficiently storing hydrogen at room temperature, it was heated to 830 ° C. at a rate of temperature increase of 10 ° C./min, then kept at the same temperature for 2 hours, and further at the same temperature. A condition was adopted in which dehydrogenation treatment was performed for 1 hour, and then the inside of the furnace was replaced with an argon atmosphere and cooled.
[0010]
After hydrogen treatment, each alloy 32μm or less, 32 ~ 106 μ m, 106~180μm milling, 180 to 250, 250～425Myuemu, the six stages of 425～500Myuemu, and classified. Next, these magnetic powders were mixed with an epoxy resin, and anisotropic bonded magnets were formed by compression molding in a magnetic field. FIG. 2 shows a demagnetization curve of an anisotropic bonded magnet when the alloys # 1, # 4, and # 6 in Table 1 are used as starting materials and only magnet powder having a pulverized particle size of 32 to 106 μm is used. As can be seen from this figure, although the residual magnetic flux density hardly changes between # 1 and # 6, iHc and Hk are larger in # 6, and it is understood that the squareness is excellent. FIG. 3 shows magnetic characteristics when anisotropic bonded magnets are produced for each pulverized particle size by the same method. Although the residual magnetic flux density hardly changed at any pulverized particle size, the anisotropic bonded magnet according to the present invention showed high iHc and Hk. Note that the significant decrease in residual magnetic flux density and Hk at 32 μm or less is accompanied by a decrease in bond magnet density.
[0011]
[Table 1]

[0012]
(Example 2 and Comparative Example 2 )
Next, the magnetic properties when the hydrogen storage and dehydrogenation treatment conditions were changed were evaluated. Table 2 shows the alloy raw materials and hydrogen storage and dehydrogenation treatment conditions used. The cast alloys of Example 2 and Comparative Example 2 were prepared in the same manner as Example 1 and Comparative Example 1 , respectively, except that the alloy composition was unified with Nd _12.6 Fe _bal Co _11.5 B _6.0 Ga _0.8 . Next, a homogenization treatment at 1100 ° C. for 20 hours was performed before the hydrogen storage treatment. After completing the predetermined hydrogen treatment, the amount of oxygen and the amount of hydrogen remaining in the alloy were analyzed by gas analysis. Furthermore, an anisotropic bonded magnet was produced using only the magnet powder classified to a pulverized particle size of 32 to 180 μm. The magnetic properties of each anisotropic bonded magnet were measured, and iHc and Hk were read from the demagnetization curve. Table 3 shows the gas analysis results and magnetic properties.
Although the details of the reason why the central portion is not refined by the normal melting and casting material of Comparative Example 2 are not clear, it is considered that hydrogen occlusion is insufficient. In addition, since iHc is low, it is considered that the crystal grains are coarsened after the dehydrogenation treatment. In the case of # 6 pulverized to 500 μm or less in order to prevent the coarsening of crystal grains, although the effect of improving iHc is recognized, the oxidation is remarkably inferior. Accordingly, when starting from a normal melting or casting material, the optimum conditions for hydrogen storage and dehydrogenation are limited. On the other hand, it can be seen that an anisotropic magnet powder having a low residual gas amount and high magnetic properties can be obtained under a wide range of conditions in the cast alloy produced by the roll cooling method of Example 2. This is probably because the cast alloy plate thickness is almost constant and thin, so that homogeneous hydrogen storage and dehydrogenation can be performed, and the coarsening of crystal grains can be suppressed by the rapid cooling effect of argon cooling after dehydrogenation. .
[0013]
[Table 2]

[0014]
[Table 3]

[0015]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the RTB type anisotropic magnet powder which has stably high iHc and Hk, and the high performance anisotropic bonded magnet using the same can be manufactured.
[Brief description of the drawings]
FIG. 1 is a metallographic photograph of a roll coolant (a) and that after heat treatment (b).
FIG. 2 is a demagnetization curve of an anisotropic bonded magnet.
FIG. 3 is a graph showing magnetic characteristics of an anisotropic bonded magnet.

Claims

Mean (always include Nd A rare earth elements including R is Y, T is Fe or Fe and Co.) Crystal grain size R ₂ T ₁₄ B of 0.02~5μm fine crystal grains of the main phase In the method for producing a magnet powder for an anisotropic bonded magnet comprising an aggregate,
An RTB-based plate alloy having crystal grains extending in the thickness direction by solidifying the RTB- based alloy melt at a cooling rate of 10 ² to 10 ⁴ ° C / sec and having a thickness of 50 to 5000 μm. Get casting process,
By heat treatment at 1000 ° C. or higher temperature in an inert gas atmosphere, the crystal grains extending in the thickness direction of the plate-shaped alloy was coarsely crystallized in the same direction, enhancing the magnetic anisotropy degree with Process ,
650-900 perform hydrogen storage and dehydrogenation treatment at a temperature of ° C., the step of causing a recrystallization reaction, and
Crushing the plate-like alloy after hydrogen storage and dehydrogenation treatment
The manufacturing method of the magnet powder for anisotropic bonded magnets characterized by having .

Mean (always include Nd A rare earth elements including R is Y, T is Fe or Fe and Co.) Crystal grain size R ₂ T ₁₄ B of 0.02~5μm fine crystal grains of the main phase In the method for producing an anisotropic bonded magnet composed of an anisotropic magnet powder composed of an aggregate and a resin ,
An RTB-based plate alloy having crystal grains extending in the thickness direction by solidifying the RTB- based alloy melt at a cooling rate of 10 ² to 10 ⁴ ° C / sec and having a thickness of 50 to 5000 μm. Get casting process,
By heat treatment at 1000 ° C. or higher temperature in an inert gas atmosphere, the crystal grains extending in the thickness direction of the plate-shaped alloy was coarsely crystallized in the same direction, enhancing the magnetic anisotropy degree with Process,
Perform hydrogen storage and dehydrogenation at a temperature of 650-900 ° C., the step of causing a recrystallization reaction,
Crushing the plate-like alloy after hydrogen storage and dehydrogenation treatment,
Mixing the anisotropic magnet powder obtained through the above steps and a resin , and
The step of molding the resulting mixture in a magnetic field
The manufacturing method of the anisotropic bonded magnet characterized by having .