JP2004146542A - Solid material for magnet and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid material for magnet based on rare-earth, iron, nitrogen, hydrogen, and oxygen having a high density and a high magnetic characteristic and is excellent in thermal stability and oxidation resistance, and also to provide a method of manufacturing the material. <P>SOLUTION: The solid material for magnet is manufactured by compression-molding and solidifying a material containing a magnetic material based on rare-earth, iron, nitrogen, hydrogen and oxygen by using an underwater shock wave. <P>COPYRIGHT: (C)2004,JPO

Description

【００７０】
（１）式は室温における条件式であり、温度Ｔ℃においては、残留磁束密度の温度係数［α（Ｂ_ｒ）］、保磁力の温度係数［α（Ｈ_ｃＪ）］を用いて、下記式（２）と書き改めることにより、大幅な減磁が生じない条件が決定される。
【００７１】
【数２】

【００７２】
ここでＰ_ｃ０がＰ_ｃより小さく、着磁しても磁場を取り去るとすぐに減磁してしまう場合は、予めヨークなどに磁石を組み込んでから着磁することによって顕著な減磁を回避することができるが、少なくとも（２）式によって定める条件を満たしていなくては磁石の使用による顕著な減磁を免れることはできない。
Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系材料の組成や温度領域によってα（Ｂ_ｒ）、α（Ｈ_ｃＪ）の値は変わるが、ほぼα（Ｂ_ｒ）は−０．０６％／℃、α（Ｈ_ｃＪ）は−０．５％／℃である。α（Ｂ_ｒ）の値に比べてα（Ｈ_ｃＪ）の値の方が絶対値が大きく、両者とも負の値なので、Ｔが高いほど（２）式を満たす正の値の組み合わせ（Ｂ_ｒ、Ｈ_ｃＪ）の領域は小さくなる。従って、本発明の磁石用固形材料を用いて成る磁石が、パーミアンス係数Ｐ_ｃの条件で使用される場合、動作中最も高くなる温度Ｔ_ｍａｘ℃により決定される（２）式の範囲にＢ_ｒ及びＨ_ｃＪを制御することにより、磁石の減磁を緩和することができることになる。
（２）式にＴ＝Ｔ_ｍａｘ、α（Ｂ_ｒ）＝−０．０６、α（Ｈ_ｃＪ）＝−０．５を代入し、整理すると下記式（３）のようになる。
【００７３】
【数３】

【００７４】
即ち、磁石としたとき、Ｂ_ｒ、Ｈ_ｃＪ、Ｐ_ｃ、Ｔ_ｍａｘ　が（３）式を満たせば、顕著な減磁が起こらない磁石であるということができる。また、（３）式によれば、Ｈ_ｃＪが大きいほど、Ｂ_ｒの取りうる値は大きくなる。熱安定性が高く、高磁気特性の磁石とするためには、Ｈ_ｃＪが０．６２ＭＡ／ｍを越える磁石用固形材料とする方が好ましい。
【００７５】
本発明の磁石用固形材料において、最も好ましい態様は、磁性材料体積分率を上げることにより、Ｂｒを増加させた磁石用固形材料、具体的には、Ｔｈ_２Ｚｎ_１７型結晶構造等又はそれと同様な結晶構造を有する菱面体晶を有するＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料を、充填率を９５％以上、好ましくは９８％以上、最も好ましくは９９％以上とすることで、磁石用固形材料の密度を、７．４５ｇ／ｃｍ^３以上、より好ましくは７．５０ｇ／ｃｍ^３以上、最も好ましくは７．６０ｇ／ｃｍ^３以上とし、常温における最大エネルギー積（ＢＨ）ｍａｘを高くした磁石用固形材料が、目的とする使用環境において（３）式を満足する磁気特性を有する磁石用固形材料である。
【００７６】
ところで、磁性材料の体積分率を上げることにより、Ｂ_ｒを大きくして常温の最大エネルギー積（ＢＨ）_ｍａｘが高い磁石用固形材料としたとしても、Ｔ_ｍａｘが例えば１００℃以上であるような高い温度であって（３）式の範囲を逸脱すれば、減磁が顕著となり、磁性材料の体積分率が低くＢ_ｒの小さい磁石用固形材料とパフォーマンスが変わらなくなってしまう場合がある。つまり、Ｐ_ｃとＴ_ｍａｘの組み合わせと磁石用固形材料のＨ_ｃＪによっては、Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料の体積分率を上げてＢ_ｒを大きく取る意味がない。むしろ、磁性材料の体積分率を下げた方が軽量でコストパフォーマンスの高い磁石用固形材料となるのである。
【００７７】
具体的な例を挙げて説明する。Ｈ_ｃＪ＝０．６２ＭＡ／ｍであるようなＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性粉体を原料とし、衝撃波圧縮を用いれば、ある条件でほぼ１００％の体積分率を有する磁石用固形材料とすることができる。このときのＢ_ｒは１．２Ｔを越える。
しかし、Ｐ_ｃ＝１、Ｔ_ｍａｘ＝１００℃である用途の場合、（３）式から、Ｂ_ｒを０．９９Ｔ以上とする必要はない。即ち、この場合、０．９９Ｔより高いＢ_ｒを有した磁石用固形材料であったとしても磁石の動作又は使用によって減磁して、０．９９ＴのＢ_ｒを有した磁石とパフォーマンスは変わらなくなるのである。従って、磁性体の体積分率をむしろ８３〜８５％程度に下げて、Ｂ_ｒ＝０．９９Ｔ程度の磁石とし、軽量かつコストの安い磁石とする方が好ましい。
【００７８】
上記は、磁石の形状または磁気回路、動作によって決まる最小のパーミアンス係数、及びＢ_ｒ、Ｈ_ｃＪ、α（Ｂ_ｒ）、α（Ｈ_ｃＪ）といった磁性材料の磁気的な特性によって決まる熱安定性について述べたものであり、一般に磁石の温度特性とも言われる性質である。
この他に、熱安定性が低下する大きな原因としては、磁性粉体同士が、充分金属結合により接合して固化していないことが挙げられる。本来、永久磁石は外界に静磁ポテンシャルを作るために、結晶の容易磁化方向を揃えているが、磁気的に非平衡な状態であるため、磁性粉体同士が充分結合され固定されていない状態であると、各磁性粉がマトリックスの中で回転するなどして容易磁化方向の向きを変え、蓄えられた静磁エネルギーが徐々に小さくなっていく。
【００７９】
磁性粉充填率が８０％未満の材料、例えばボンド磁石などは、１００℃以上の高温で樹脂が軟化あるいは劣化すると比較的容易に上記のような緩和が起こり、顕著な減磁が生じることになる。ボンド磁石は、その名のとおり、バインダによりボンディングされている磁石であって、金属結合やイオン結合により固化された磁石ではない。熱安定性の不足はそのことに起因する問題点であるといえる。一方、本発明の材料のうち、磁性粉体積分率が８０％以上、好ましくは８３％以上、更に好ましくは９０％以上、最も好ましくは９５％以上であれば、磁性粉同士が金属結合で固化しており、このような緩和は起こらない。以上のように、１００℃以上で満足する熱安定性を達成するためには、その材料の磁気特性と用途に応じて、磁性材料の体積分率の下限と上限を特定の範囲に設定する必要がある。
【００８０】
本発明の磁石用固形材料は、特別な方法によらなくとも、磁石としたときの保磁力Ｈ_ｃＪが０．７６ＭＡ／ｍ以上で、しかも角形比Ｂ_ｒ／Ｊ_ｓが９５％以上である磁石用固形材料とすることもできる。但し、Ｊ_ｓは常温の飽和磁化であり、本発明においては外部磁場を１．２ＭＡ／ｍとしたときの磁化の値とする。
例えば、Ｓｍ_２Ｆｅ_１７Ｎ_３Ｈ_０．１Ｏ_ｘ材料は、ニュークリエーション型の磁場反転機構を持つため粒径と保磁力Ｈ_ｃＪがほぼ反比例するような関係を持つ。２μｍ未満になると保磁力が０．７６ＭＡ／ｍを越えるが、この領域では、磁性粉の粒径が小さくなるに従って凝集しやすくなり、通常工業的に利用されている磁場では磁性粉体の磁場配向度が急激に落ちて、角形比が低下する。
【００８１】
ボールミルでＳｍ_２Ｆｅ_１７Ｎ_３Ｈ_０．１粗粉体を粉砕して得たＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料（酸素量０．１〜５原子％）を１．２ＭＡ／ｍの外部磁場で磁場圧縮成形した充填率８０％の圧粉体においては、Ｈ_ｃＪが０．７４ＭＡ／ｍを越えると角形比が急激に低下し、Ｈ_ｃＪが０．７６ＭＡ／ｍ以上の領域で９５％以下となる。
本発明の磁石用固形材料であると、衝撃波圧縮固化した際に組織を微細化することができるために、保磁力が０．７６ＭＡ／ｍ未満の磁性粉体を用いて角形比の高い圧粉体を調製し、これを衝撃波圧縮固化すると同時に保磁力を向上させ、高い角形比と高い保磁力を併せ持つ磁石用固形材料とすることができる。　保磁力が０．８〜１．２ＭＡ／ｍの範囲の場合、角形比を９５％から、磁場配向の方法と磁性材料の成分などの工夫を加えることによりほぼ１００％の範囲で調整することが可能である。
【００８２】
次に、本発明の磁石用固形材料の製造法、特にその中で本発明の磁石用固形材料の実現を可能とした衝撃波圧縮について述べる。但し、本発明の製造法は、これに限定されるわけではない。
水中衝撃波による衝撃圧縮方法としては、二重管の最内部に当該粉体を圧粉成形し、中間部に水を入れ、外周部に爆薬を配置し、爆薬を爆轟させることで、前記中間部の水中に衝撃波を導入し、最内部の当該粉体を圧縮する方法や、当該粉体を密閉容器中へ圧粉成形し、水中へ投入し、爆薬を水中にて爆轟させ、その衝撃波により当該粉体を圧縮する方法や、特許第２９５１３４９号公報又は、特許第３２２０２１２号公報による方法が選択できる。いずれの方法においても、以下に示す水中衝撃波による衝撃圧縮の利点を得ることができる。
【００８３】
水中衝撃波を用いた本発明の衝撃圧縮法による圧縮固化工程では、衝撃波の持つ超高圧剪断性、活性化作用は、粉体の金属的結合による固化作用と組織の微細化作用を誘起し、バルク固化と共に高保磁力化することも可能である。このとき、衝撃圧力自体の持続時間は、従来の衝撃波を用いた場合よりも長いが、体積圧縮と衝撃波の非線形現象に基づくエントロピーの増加による温度上昇は極めて短時間（数μｓ以下）に消失し、分解や脱窒は殆ど起こらない。水中衝撃波を用いて圧縮した後も残留温度は存在する。この残留温度が分解温度（常圧で約６００℃）以上になると、Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系化合物等も分解が開始され、磁気特性を劣化するので好ましくない。しかし、水中衝撃波による場合は、従来の衝撃波による場合よりも、残留温度を低く保つことが非常に容易である。
【００８４】
即ち、水中衝撃波は以下のような特徴を有する。
（１）水中衝撃波の圧力は、爆薬と水のユゴニオ関係によって決まり、圧力Ｐは概略次式で示される。
Ｐ＝２８８（ＭＰａ）｛（ρ／ρ_０）^７．２５−１｝
上式より、水中衝撃波を用いた場合には、水の密度ρの基準値ρ_０に対する変化に関する圧力Ｐの増加量が非常に大きいため、爆薬量の調節により容易に超高圧が得られ、その際の磁性材料の温度は従来の衝撃波を用いた場合に比べて容易に低温度に保持される。
（２）衝撃圧力自体の持続時間が長い。
（３）体積圧縮と衝撃波の非線形現象に基づくエントロピーの増加による磁性材料の温度上昇は極めて短時間に消失する。
（４）磁性材料の温度は、その後高く保持されることが少なく、又、長く保持されることが少ない。
（５）衝撃圧力が被圧縮体に均一に負荷される。
水中衝撃波のもつ、これらの優れた特徴によって初めて、Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系材料が熱分解を起こさず、高密度に容易に圧縮固化される。
更に、圧粉成形を磁場中で行うことにより、磁性材料粉体の磁化容易軸を一方向に揃えることができ、得られた圧粉体を衝撃圧縮固化により固形化しても、配向性は損なわれず、磁気的に一軸性の異方性をもつ磁石用固形材料が得られる。
【００８５】
本発明において、衝撃波圧力が３〜４０ＧＰａの水中衝撃波を用いて圧縮固化することにより、原料磁性粉体の真密度（例えば７．７ｇ／ｃｍ^３）に対し充填率８０％を超える密度の磁石用固形材料を得ることができる。衝撃波圧力が３ＧＰａより低いと、必ずしも充填率が８０％を超える磁石用固形材料を得ることができない。また、衝撃波圧力が４０ＧＰａより高いと、α−Ｆｅ分解相等の分解物が生じ易く、好ましくない。また、本発明のＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系原料磁性粉体が、表面に酸素富化された非晶質相を有する場合、その非晶質相を分解させないため、衝撃波圧力を３０ＧＰａ以下にすることが好ましい。
【００８６】
衝撃波圧力が３〜４０ＧＰａの水中衝撃波を用いて圧縮固化する場合は、原料磁性粉体の真密度に対し充填率８０％を超える密度の磁石用固形材料を再現性良く得ることができる。また、衝撃波圧力が６〜４０ＧＰａの水中衝撃波を用いた場合は、充填率が９０％を超える高密度の磁石用固形材料を得ることができる。但し、Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料の外に、軟磁性材料、希土類−鉄−ほう素系磁性材料などの硬磁性材料、非磁性相などの固形成分を含む場合は、上記の条件は、磁石用固形材料に対するＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系原料磁性粉体の体積分率のみで決定されるわけでない。しかし、Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料の体積分率が５０体積％以上の磁石用固形材料を分解無く得るためには、上記と同様、衝撃波圧力３〜４０ＧＰａの範囲内で水中衝撃波を制御する必要がある。この場合もＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系原料磁性粉体が、上記非晶質相を有する場合、衝撃波圧力を３〜３０ＧＰａの範囲に制御することが好ましい。
【００８７】
次に、本発明の磁石用固形材料における第１の態様である高密度な磁石用固形材料を製造する場合において、衝撃波圧力８〜４０ＧＰａの水中衝撃波を用いる必要がある。衝撃波圧力が８ＧＰａより低いと、必ずしも密度７．４５ｇ／ｃｍ^３以上のバルク磁石が得られない。衝撃波圧力が４０ＧＰａより高いと、α−Ｆｅ分解相等の分解物が生じることがあって、好ましくない。また、本発明のＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系原料磁性粉体が、表面に酸素富化された非晶質相を有する場合、その非晶質相を分解させないため、衝撃波圧力を３０ＧＰａ以下にすることが好ましい。
【００８８】
さらに、本発明における第２の態様である、軽量であり高温特性に優れた磁石用固形材料を製造する場合において、衝撃圧縮時の圧粉体の温度上昇を抑制するために、衝撃圧縮には、衝撃波圧力３〜２２ＧＰａの水中衝撃波を用いることが好ましい。衝撃波圧力が３ＧＰａより低いと、必ずしも密度６．１５ｇ／ｃｍ^３以上の磁石用固形材料が得られない。衝撃波圧力が２２ＧＰａより高いと、密度７．４５ｇ／ｃｍ^３以上の磁石用固形材料となる場合が多く、さらに衝撃波圧力が４０ＧＰａより高いと、α−Ｆｅ分解相等の分解物が生じることがあって好ましくない。上記と同様に、本発明のＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系原料が、表面に酸素富化された非晶質相を有する場合、衝撃波圧力を３０ＧＰａ以下にすることが好ましい。
【００８９】
また、密度が６．３５〜７．４５ｇ／ｃｍ^３の範囲、さらに６．５０〜７．４０ｇ／ｃｍ^３の範囲の磁石用固形材料を再現性良く得るには水中衝撃波の衝撃波圧力を３〜２０ＧＰａ、さらに衝撃波圧力を４〜１５ＧＰａとすることで達成される。但し、磁性材−ガス複合磁石用固形材料においては、衝撃圧力が高すぎると容易に密度が７．４５ｇ／ｃｍ^３を越える磁石用固形材料となってしまうので衝撃波圧力３〜１５ＧＰａの水中衝撃波を用いる方が好ましい。
Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料の製造法において酸素源、又は水素源並びに酸素源を接触させて、酸素成分、水素成分を導入することが重要であると既に述べたが、衝撃波圧縮の雰囲気に酸素源や水素源を存在させ接触させて、目的とする組成の磁石用固形材料と成す方法も有効である。
【００９０】
本発明の磁石用固形材料の製造方法において、磁石用固形材料に異方性を付与するために、原料粉体の圧粉成形を磁場中で行うことができ、原料粉体を圧粉成形した後、水中衝撃波を用いて衝撃圧縮固化することができる。また、原料粉体を磁場中で圧粉成形した後、水中衝撃波を用いて衝撃圧縮固化することができる。
以上述べたように、磁性粉体として熱的に安定でα−Ｆｅ分解相を析出しにくい、水素を含むＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系材料を選び、上記水中衝撃波圧縮固化法にて固形化することにより初めて本発明の磁石用固形材料を作製することができるのであり、この磁石用固形材料を用いて製造する磁石は、高磁気特性で、耐酸化性に優れ、ボンド磁石のように磁性粉体の結合材としての樹脂成分を含まないため、熱安定性に優れた特徴を有する。
【００９１】
次に、本発明の第３の態様であるＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁石用固形材料を含む部品又は装置について述べる。
最高使用温度Ｔｍａｘが１００℃以上である用途には、従来のＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系ボンド磁石であると、樹脂成分を含みかつ磁性粉体同士が金属結合で固化していないために、熱安定性に劣り、使用することが難しかった。本発明の磁石用固形材料であれば、よしんば樹脂成分を含んでいてもＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性粉同士が金属結合で固化しているので熱安定性に優れる。さらに磁石用固形材料のＢ_ｒ、Ｈ_ｃＪが、磁石としたときのＰ_ｃとＴ_ｍａｘ及び（３）式で規定される領域にあれば、大きく減磁せず、軽量でコストパフォーマンスが高い上に熱安定性がさらに優れた磁石とすることができる。
Ｔ_ｍａｘの上限はＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系材料のキュリー点付近であり、４００℃を越えるが、磁石用固形材料の組成や成分、磁石としての使われ方によりＴ_ｍａｘ上限は４００℃以下の様々な値をとる。例えば、Ｚｎで被覆したＨ_ｃＪ＝１．６ＭＡ／ｍであるＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系材料を用いたとしても、Ｔ_ｍａｘが２２０℃以上のとき、本発明の磁石用固形材料を磁石として使用することは好ましくない。
【００９２】
本発明の磁石用固形材料により得られた磁石のＰ_ｃ０は、０．０１〜１００、さらに好ましくは０．１〜１０であり、Ｐ_ｃ０、Ｂ_ｒ、Ｈ_ｃＪの値の組み合わせが（１）式の範囲を逸脱するときは、ヨークなどを装着してのちＰ_ｃ０を高めてから、着磁を行うことが好ましい。
【００９３】
本発明の磁石用固形材料、中でも第２の態様の磁石用固形材料、若しくは（３）式を満足する磁石用固形材料により得られた磁石の静磁場を用いた、各種アクチュエータ、ボイスコイルモータ、リニアモータ、ロータ又はステータとして回転機用モータ、その中で特に産業機械や自動車用モータ、医療用装置や金属選別機の磁場発生源のほかＶＳＭ装置、ＥＳＲ装置、加速器などの分析機用磁場発生源、マグネトロン進行波管、プリンタヘッドや光ピックアップなどＯＡ機器、アンジュレータ、ウイグラ、リターダ、マグネットロール、マグネットチャック、各種マグネットシートなどの装置並びに部品は、Ｐ_ｃの極めて小さなステッピングモータなどの特殊な用途を除いて、１００℃以上の環境においても顕著な減磁が生ずることなく安定に使用することができる。
【００９４】
用途によっては１２５℃以上の温度でも使用でき、例えばＨ_ｃＪ＞０．７（ＭＡ／ｍ）かつＰ_ｃ＞１であるような場合が挙げられる。さらに、１５０℃以上での使用も可能で、例えばＨ_ｃＪ＞０．８（ＭＡ／ｍ）かつＰ_ｃ＞２であるような場合が挙げられる。
また、これらの装置又は部品に用いるとき、本発明の磁石用固形材料を各種加工を施してから、各形状のヨークやホールピース、各種整磁材料を接着、密着、接合した上で組み合わせて用いても良い。
また、本発明の磁石用固形材料を永久磁石同期モータ用ロータとして、もしくはその構成材料の硬磁性材料として使用する場合、本発明の表面磁石構造ロータとして、図５〜図６に示す回転軸断面構造とすることができる。また、埋込磁石構造ロータとして図７〜図１２に示す回転軸断面構造とすることができる。
【００９５】
以下、本発明を実施例に基づいて説明する。なお、Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料の分解の度合いは、成形した磁石用固形材料のＸ線回折図（Ｃｕ−Ｋα線）をもとに、Ｔｈ_２Ｚｎ_１７型をはじめとする菱面体晶又は六方晶の結晶構造由来の回折線における最強線の高さａに対する、２θ＝４４°付近のα−Ｆｅ分解相由来の回折線の高さｂの比ｂ／ａをもって判断した。この値が０．２以下なら分解の度合いは小さいと言える。好ましくは０．１以下である。さらに好ましくは０．０５以下で、この場合、分解はほぼ無いと言える。
但し、上記の判定法は、磁石用固形材料の原料となるＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料にもともとＦｅ軟磁性材料のような４４°付近にピークを持つ材料が含有されている場合は適用できない。この場合、Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料を含む原料と磁石用固形材料におけるｂ／ａの相対比により、分解の有無の目安とすることは可能である。
また、本件発明は以下の具体例によって何ら技術的範囲が限定されるものではない。
【００９６】
［実施例１］
平均粒径６０μｍのＳｍ_２Ｆｅ_１７母合金をＮＨ_３分圧０．３５ａｔｍ、Ｈ_２分圧０．６５ａｔｍで酸素分圧１０^{− ３}ａｔｍ以下のアンモニア−水素混合ガス気流中、４６５℃で７．２ｋｓ窒化水素化を行った後、酸素分圧１０^−５ａｔｍアルゴン気流中で１．８ｋｓアニールを行い、溶存酸素量４０ｐｐｍ、含水量２０ｐｐｍの炭化水素系溶媒を粉砕溶媒として用い１０^−１ａｔｍの窒素気流中で仕込んだボールミルにより平均粒径が約２μｍとなるように粉砕し、Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料粉体を得た。この粉体を、１．２ＭＡ／ｍの磁場中で磁場配向させながら圧粉成形を行うことで成形体を得た。図１３は水中衝撃波を用いた衝撃圧縮法を行う装置の一例を示す説明図である。得られた成形体を図１４に示す如く銅製パイプ１に入れて銅製プラグ２に固定した。さらに銅製パイプ３を銅製プラグ２に固定し、更に、この間隙に水を充填し、外周部に均一な間隙を設け、紙筒４を配置し、銅製パイプ３と紙筒４の間隙中に２８０ｇの硝酸アンモニウム系爆薬５を装填し、起爆部６より前記爆薬を起爆し、爆薬を爆轟させた。このとき衝撃波圧力は１６ＧＰａであった。
【００９７】
衝撃圧縮後、パイプ１から固化したＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料の体積分率が１００％であるＳｍ_８．５Ｆｅ_７２．３Ｎ_１２．７Ｈ_２．８Ｏ_３．７組成を有する磁石用固形材料を取り出し、４．０ＭＡ／ｍのパルス磁場で着磁し磁気特性を測定した結果、残留磁束密度Ｂ_ｒ＝１．１８Ｔ、保磁力Ｈ_ｃＪ＝０．７８ＭＡ／ｍ、（ＢＨ）_ｍａｘ＝２６４ｋＪ／ｍ^３の結果を得た。又、アルキメデス法により密度を測定した結果、密度７．６０ｇ／ｃｍ^３、充填率は９９％であった。
【００９８】
更に、Ｘ線回折法で解析した結果、固化した磁石用固形材料はほとんどα−Ｆｅ分解相の析出が起きておらず、Ｔｈ_２Ｚｎ_１７型菱面体晶の結晶構造を有していることが確認された。
爆薬量を調節して同様の実験を多数回繰り返した。
衝撃波圧力が４ＧＰａより低いと、得られた磁石用固形材料の充填率は必ずしも８０％を超えず、衝撃波圧力が３０ＧＰａより高いとα−Ｆｅ分解相等の分解物が生じることが確認された。又、充填率８０％を超える磁石用固形材料をより再現性良く得るためには、衝撃波圧力を３〜３０ＧＰａとすることが好ましいことも分かった。又、衝撃波圧力を６〜３０ＧＰａとすることで、充填率９０％を超える磁石用固形材料が再現性良く得られることも確認された。
【００９９】
又、この衝撃波圧力は、密度が６．１５〜７．４５ｇ／ｃｍ^３である磁石用固形材料をより再現性良く得るためには、衝撃波圧力を３〜１５ＧＰａとすることが好ましいことも分かった。
さらに、密度が７．４５ｇ／ｃｍ^３を超えるバルク磁石をより再現性良く得るためには、この衝撃波圧力を１０〜３０ＧＰａとすることが好ましいことも分かった。又、衝撃波圧力１２〜３０ＧＰａでは密度７．５５ｇ／ｃｍ^３を超えるバルク磁石を再現性良く得ることができることも確認された。
【０１００】
［比較例１］
平均粒径２０μｍのＳｍ_２Ｆｅ_１７母合金をＮ_２ガス気流中、４９５℃で７２ｋｓ窒化を行うこと以外は実施例１と同様に、ただし衝撃波圧力を１８ＧＰａとすることにより、Ｓｍ_９．１Ｆｅ_７７．７Ｎ_１３．２なる組成の磁石用固形材料を作製した。　この磁石用固形材料を４．０ＭＡ／ｍのパルス磁場で着磁し磁気特性を測定した結果、残留磁束密度Ｂ_ｒ＝０．９６Ｔ、保磁力Ｈ_ｃＪ＝０．３６ＭＡ／ｍ、（ＢＨ）_ｍａｘ＝１２０ｋＪ／ｍ^３の結果を得た。又、アルキメデス法により密度を測定した結果７．５０ｇ／ｃｍ^３であった。
この材料のＸ線回折図には、Ｔｈ_２Ｚｎ_１７型菱面体晶の結晶構造以外にα−Ｆｅ分解相由来の回折線も観察された。４４°付近におけるα−Ｆｅ分解相の回折線とＴｈ_２Ｚｎ_１７型菱面体晶の結晶構造を示す（３０３）最強線との強度比ｂ／ａは０．２１であった。
【０１０１】
［比較例２］
図１４は、爆薬の爆轟波を直接用いて衝撃圧縮を行う装置の一例を示す説明図である。この装置を用いて、実施例１で得た平均粒径２μｍのＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性粉体を銅製パイプ１に入れて銅製プラグ２に固定し、外周部に均一な間隙を設け、紙筒４を配置し、前記間隙中に実施例と同量の硝酸アンモニウム系爆薬５を装填し、起爆部６より前記爆薬を起爆し、爆薬を爆轟させた。衝撃圧縮後、パイプ１から固化した試料を取り出し、Ｘ線回折法により解析した結果、衝撃圧縮後はＳｍＮと多量のα−Ｆｅ分解相が生成していることが認められ、出発原料のＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系化合物が分解していることが分かった。このときの回折線の強度比ｂ／ａは約３であった。
【０１０２】
［実施例２］
所定量のＳｍ及びＦｅの金属粉体（重量比１６．８５：８３．１５）をめのうボールによる振動ボールミルで１８０ｋｓ間メカニカルアロイング処理したのち、１０^−５ａｔｍ以下の真空中６００℃で７．２ｋｓ間熱処理した。この粉体には、Ｆｅ軟磁性材料が約３０体積％含まれていた。この粉体を、ＮＨ_３分圧０．３５ａｔｍ、Ｈ_２分圧０．６５ａｔｍの酸素分圧１０^{− ３}ａｔｍ以下のアンモニア−水素混合ガス気流中、３８０℃、１．２ｋｓの条件で窒化水素化処理し、続いて同温度で水素中３００ｓの時間熱処理した。この粉体を用いて、実施例１と同様に、ただし衝撃波圧力を１８ＧＰａとすることにより、Ｓｍ_５．９Ｆｅ_７８．５Ｎ_８．８Ｈ_３．０Ｏ_３．８なる組成の磁石用固形材料を作製した。
【０１０３】
この磁石用固形材料を４．０ＭＡ／ｍのパルス磁場で着磁し磁気特性を測定した結果、残留磁束密度Ｂ_ｒ＝１．２２Ｔ、保磁力Ｈ_ｃＪ＝０．４３ＭＡ／ｍ、（ＢＨ）_ｍａｘ＝２１５ｋＪ／ｍ^３の結果を得た。又、アルキメデス法により密度を測定した結果７．７４ｇ／ｃｍ^３であった。
この材料のＸ線回折図には、Ｔｈ_２Ｚｎ_１７型菱面体晶の結晶構造以外にα−Ｆｅ由来の回折線も観察されたが、この材料はもともとα−Ｆｅ分解相ではないＦｅ軟磁性材料を含む材料であるため、固化によってα−Ｆｅ分解相が生じたか否かはＸ線回折法によって厳密に判定することができなかった。なお、透過型電子顕微鏡観察を行った結果、Ｆｅ軟磁性相の体積分率は約３０％、その結晶粒径は１０〜５０ｎｍ程度であり、Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料の体積分率が約７０％である磁石用固形材料となった。
【０１０４】
［実施例３］
実施例１で得た平均粒径約２μｍのＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系粉体と、平均粒径約２５μｍで組成がＳｍ_１１．５Ｃｏ_５７．６Ｆｅ_２４．８Ｃｕ_４．４Ｚｒ_１．７であるＳｍ−Ｃｏ系粉体を、体積比で５０：５０の割合になるようにめのう乳鉢に仕込み、溶存酸素量４０ｐｐｍ、含水量３０ｐｐｍのシクロヘキサン中で湿式混合した。この作業は酸素分圧１０^−１ａｔｍのグローブボックス中で行った。
この混合粉体を用いて、実施例１と同様に、ただし衝撃波圧力を１４ＧＰａとすることにより、Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料の体積分率５０％のＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁石用固形材料（酸素量１．７原子％）を作製した。この磁石用固形材料を４．０ＭＡ／ｍのパルス磁場で着磁し磁気特性を測定した結果、残留磁束密度Ｂ_ｒ＝１．０８Ｔ、保磁力Ｈ_ｃＪ＝０．８５ＭＡ／ｍ、（ＢＨ）_ｍａｘ＝２１５ｋＪ／ｍ^３であった。
【０１０５】
［実施例４］
公知のジエチル亜鉛を用いた光分解法によって、Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料の表面にＺｎ金属を被覆した平均粒径約１μｍのＳｍ−Ｆｅ−Ｃｏ−Ｎ−Ｈ−Ｏ磁性粉体を調製し、この粉体を用いて、実施例１と同様に、ただし衝撃波圧力を１６ＧＰａとすることにより、Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料の体積分率が１００％であるＳｍ_８．２Ｆｅ_６２．６Ｃｏ_６．９Ｎ_１２．２Ｈ_３．３Ｏ_３．８Ｚｎ_３．０なる組成の磁石用固形材料を作製した。
この磁石用固形材料を４．０ＭＡ／ｍのパルス磁場で着磁し磁気特性を測定した結果、残留磁束密度Ｂ_ｒ＝１．２４Ｔ、保磁力Ｈ_ｃＪ＝０．７９ＭＡ／ｍ、（ＢＨ）_ｍａｘ＝２６３ｋＪ／ｍ^３であった。密度は７．７１ｇ／ｃｍ^３であった。さらに、Ｘ線回折法で解析した結果、固化した磁石用固形材料は、Ｔｈ_２Ｚｎ_１７型菱面体晶の結晶構造を有していることが確認された。４４°付近におけるα−Ｆｅ分解相の回折線とＴｈ_２Ｚｎ_１７型菱面体晶の結晶構造を示す（３０３）最強線との強度比ｂ／ａは０．０８であった。
【０１０６】
［実施例５］
Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料として、公知の方法（特開平８−５５７１２号公報）により得た、磁化反転機構がピンニング型である平均粒径３０μｍのＳｍ−Ｆｅ−Ｃｏ−Ｍｎ−Ｎ−Ｈ−Ｏ磁性粉体を用いて、実施例１と同様に、ただし衝撃波圧力を１４ＧＰａとすることにより、Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料の体積分率が１００％である、Ｓｍ_８．５（Ｆｅ_０．８９Ｃｏ_０．１１）_６６．６Ｍｎ_３．６Ｎ_１８．５Ｈ_２．６Ｏ_０．２なる組成の磁石用固形材料を作製した。この磁石用固形材料を４．０ＭＡ／ｍのパルス磁場で着磁し磁気特性を測定した結果、残留磁束密度Ｂ_ｒ＝１．０８Ｔ、保磁力Ｈ_ｃＪ＝０．３９ＭＡ／ｍ、（ＢＨ）_ｍａｘ＝１２８ｋＪ／ｍ^３であった。体積法で求めた密度は７．７０ｇ／ｃｍ３であった。さらに、この材料のＸ線回折図には、Ｔｈ_２Ｚｎ_１７型菱面体晶の結晶構造以外にα−Ｆｅ分解相由来の回折線も観察された。４４°付近におけるα−Ｆｅ分解相の回折線とＴｈ_２Ｚｎ_１７型菱面体晶の結晶構造を示す（３０３）最強線との強度比ｂ／ａは０．０６であった。
【０１０７】
［実施例６］
Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料以外の成分をＡｌ_２Ｏ_３とし、実施例１で作製したＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料の体積分率が９６％となるように配合し、前記混合粉体を減量とする磁石用固形材料を実施例１と同様にして作製した。但し、衝撃波圧力は１５ＧＰａとした。その後、４．０ＭＡ／ｍのパルス磁場で着磁し、Ｂ_ｒ、Ｈ_ｃＪ、角形比Ｂ_ｒ／Ｊ_ｓ、（ＢＨ）_ｍａｘを測定した。
その結果を表１に示した。保持力Ｈ_ｃＪが０．８３ＭＡ／ｍと大きい値であるにも関わらず、角形比９６％を得ることができた。
【０１０８】
［実施例７〜９］
Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料以外の成分及び、衝撃波圧力を表１に示したとおりとする以外は、実施例１と同様にして磁石用固形材料を作製し、実施例６と同様にしてそれらの各種磁気特性を測定した。その結果を表１に示した。
【０１０９】
［実施例１０、１１及び比較例３］
平均粒径を２．５μｍとしたＳｍ_８．７Ｆｅ_７４．１Ｎ_１３．１Ｈ_１．１Ｏ_３．０なる磁性粉体を用いることと衝撃波圧力を３ＧＰａ（実施例１０）並びに２３ＧＰａ（実施例１１）としたこと以外は実施例１と同様にしてＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料の体積分率が１００％である磁石用固形材料を作製した。これらの磁石用固形材料の磁気特性を実施例１と同様にして測定した。その結果を表２に示した。
また、これらの磁石用固形材料を正確に同形状の円盤に加工し、４．８ＭＡ／ｍのパルス磁場で着磁して、Ｐ_ｃ０が２の磁石とした。これらの磁石を、１２５℃の恒温槽中で極力逆磁場が掛からないように注意して３．６Ｍｓ放置した。試料引き抜き式磁束測定装置を用いて、恒温槽放置前後の磁束の値を測定し、磁束の変化率、即ち不可逆減磁率（％）を求めた。結果を表２に示した。不可逆減磁率は絶対値が小さいほど熱安定性が良いと判断できる。また、公知の方法によりＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料の体積分率を６０％とし、Ｐ_ｃ０が２の１２−ナイロンをバインダとした磁石用固形材料ではない射出成形ボンド磁石（比較例３）について、上記と同様にして不可逆減磁率を求めた。結果を表２に示した。
以上の評価によって得られた結果は、Ｐ_ｃがＰ_ｃ０と等しく、Ｔ_ｍａｘ＝１２５℃であるような用途を考えたとき、動作又は使用前後の減磁の度合いを調べるのに適切である。
【０１１０】
表２に示したとおり、比較例３のように、本発明の磁石用固形材料ではない磁石においては、磁性粉体同士が金属結合で固化していないために非常に低い熱安定性を示した。
同様に、実施例１０の磁石用固形材料は、充填率が８０％以上であるために、磁性粉体同士が金属結合又はイオン結合しているため、高い熱安定性を示すことがわかった。また、磁性粉体同士が金属結合で固化している実施例においても、Ｐ_ｃ、Ｔ_ｍａｘ、Ｂ_ｒ、Ｈ_ｃＪが（３）式を満たす軽量な磁石用固形材料である実施例１０の熱安定性は、（３）式を満たさない実施例１１より良好であった。
【０１１１】
［実施例１２及び１３］
実施例１０の磁石を２個、ヨークを用いず固定してステータとしたブラシ付のＤＣモータを組み立て、コイルに一定の大きさの電力を与えながら１００℃での環境下で３６ｋｓ運転した（実施例１２）。また、実施例１１の磁石を用いて上記と同様にモータを組み立て同様に運転した（実施例１３）。３６ｋｓ後の回転数は、初期回転数が安定した直後に比べ、実施例１２のモータで約２％、実施例１３のモータでは約１０％変化し、３６ｋｓ後の回転数はどちらもほぼ５１０ｒｐｍで同等であった。実施例１２のモータで用いた実施例１０の磁石は、実施例１３のモータで用いた実施例１１の磁石より密度が１７％も低く、Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料の体積分率が低いのにも関わらず上記モータとしたときのパフォーマンスは同じであった。
【０１１２】
［実施例１４］
実施例１０において、Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料以外の成分をＺｒＯ_２とし、衝撃波圧力を１４ＧＰａとする以外は同様にしてＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料の体積分率が９５％である、密度７．３８ｇ／ｃｍ^３の磁石を作製し、実施例１２と同様にしてモータを組み立て、１００℃の環境下で運転した。その結果、実施例１２と同等な成績が得られた。
【０１１３】
［実施例１５］
公知の方法により製造された、平均粒径３０μｍのＲ−Ｆｅ−Ｎ−Ｈ−Ｏ系ＨＤＤＲ等方性磁性粉体を用いて、実施例１と同様に、Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料の体積分率が１００％である、Ｓｍ_８．３Ｆｅ_７６．１Ｂ_０．９Ｔｉ_２．４Ｎ_１２．０Ｈ_０．１Ｏ_０．２なる組成の磁石用固形材料を作製した。
この磁石用固形材料を４．０ＭＡ／ｍのパルス磁場で着磁し磁気特性を測定した結果、残留磁束密度Ｂ_ｒ＝０．７０Ｔ、保磁力Ｈ_ｃＪ＝１．０５ＭＡ／ｍ、（ＢＨ）_ｍａｘ＝７５．４ｋＪ／ｍ^３の結果を得た。又、アルキメデス法により密度を測定した結果７．４５ｇ／ｃｍ^３であった。
この材料のＸ線回折図には、菱面体晶、六方晶の結晶構造以外にα−Ｆｅ分解相由来の回折線も観察され、比ｂ／ａは０．１５であった。
【０１１４】
［実施例１６］
平均粒径６０μｍのＳｍ_２Ｆｅ_１７母合金をＮＨ_３分圧０．３５ａｔｍ、Ｈ_２分圧０．６５ａｔｍで酸素分圧１０^{− ３}ａｔｍ以下のアンモニア−水素混合ガス気流中、４６５℃で７．２ｋｓ窒化水素化を行った後、酸素分圧１０^−３ａｔｍとしたアルゴン気流中で７．２ｋｓアニールを行い、溶存酸素量４５ｐｐｍ、含水量２０ｐｐｍの炭化水素系溶媒を粉砕溶媒として用い１０^−１ａｔｍの窒素気流中で仕込んだボールミルにより平均粒径が約２μｍとなるように粉砕した。この粉体を用い、実施例１と同様に、但し衝撃波圧力は２５ＧＰａとして、Ｒ−Ｆｅ−Ｎ−Ｈ−Ｏ系磁性材料の体積分率が１００％である、Ｓｍ_８．０Ｆｅ_６７．８Ｎ_１１．９Ｈ_２．６Ｏ_９．７組成を有する磁石用固形材料を得た。このとき、成形体を保持する銅製パイプ１の中は湿度を有した大気で満たした。この磁石用固形材料を４．０ＭＡ／ｍのパルス磁場で着磁し、磁気特性を測定した結果、残留磁束密度Ｂ_ｒ＝１．０６Ｔ、保磁力Ｈ_ｃＪ＝０．７３ＭＡ／ｍ、（ＢＨ）_ｍａｘ＝１５８ｋＪ／ｍ^３の結果を得た。又、アルキメデス法により密度を測定した結果、密度７．５５ｇ／ｃｍ^３、充填率は９９％であった。
【０１１５】
更に、Ｘ線回折法で解析した結果、固化した磁石用固形材料はほとんどα−Ｆｅ分解相の析出が起きておらず、Ｔｈ_２Ｚｎ_１７型菱面体晶の結晶構造を有していることが確認された。
本試料表面を鏡面研磨後５％ナイタール腐食液で３０秒間腐食し、ＦＥ−ＳＥＭにて観察を行った結果、視野内に粒状に観察される部分と前記粒状部分の隙間を埋める様に存在する部分との２相構造であることが判った。ＥＢＳＰにて各部分の結晶方位の観察を行った結果、前記粒状部分はＴｈ_２Ｚｎ_１７型菱面体晶の結晶構造が観察され、その他の部分は非晶質であることが確認された。観察断面の面積比より、Ｔｈ_２Ｚｎ_１７型菱面体晶部分（結晶相）対非晶質部分（非晶質相）が６対４の体積比で存在することが判った。
【０１１６】
【表１】

【０１１７】
【表２】

【０１１８】
【発明の効果】
本発明のように、菱面体晶又は六方晶の結晶構造を有する希土類−鉄−窒素−水素−酸素系磁性粉体等を圧粉成形し、水中衝撃波を用いた衝撃圧縮をすることにより、バインダを必要とせず、自己焼結によらずに、又、分解、脱窒を防いで、高密度、高性能な磁石用固形材料を得ることを可能にする。さらに、軽量でありながら、高性能、特に磁気特性の安定性が高い磁石用固形材料を得ることを可能にする。
【図面の簡単な説明】
【図１】希土類−鉄−窒素−水素−酸素系磁性材料と軟磁性の固形状金属を接合して一体化して得られた磁石用の固形材料の断面の一例を示す説明図である。
【図２】希土類−鉄−窒素−水素−酸素系磁性材料層と軟磁性層が交互に積層され一体化した磁石用の固形材料の断面の一例を示す説明図である。
【図３】希土類−鉄−窒素−水素−酸素系磁性材料を主として含有する層の周辺の一部又は全部を非磁性の固形状材料で覆った磁石用の固形材料の断面の例を示す説明図である。
【図４】磁石用固形材料の断面の一例を示す説明図である。
【図５】本発明の磁石固形材料を永久磁石同期モータに使用する場合における、表面磁石構造ロータの回転軸断面構造の一例である。
【図６】本発明の磁石固形材料を永久磁石同期モータに使用する場合における、表面磁石構造ロータの回転軸断面構造の一例である。
【図７】本発明の磁石固形材料を永久磁石同期モータに使用する場合における、埋込磁石構造ロータの回転軸断面構造の一例である。
【図８】本発明の磁石固形材料を永久磁石同期モータに使用する場合における、埋込磁石構造ロータの回転軸断面構造の一例である。
【図９】本発明の磁石固形材料を永久磁石同期モータに使用する場合における、埋込磁石構造ロータの回転軸断面構造の一例である。
【図１０】本発明の磁石固形材料を永久磁石同期モータに使用する場合における、埋込磁石構造ロータの回転軸断面構造の一例である。
【図１１】本発明の磁石固形材料を永久磁石同期モータに使用する場合における、埋込磁石構造ロータの回転軸断面構造の一例である。
【図１２】本発明の磁石固形材料を永久磁石同期モータに使用する場合における、埋込磁石構造ロータの回転軸断面構造の一例である。
【図１３】水中衝撃波を用いた衝撃圧縮法を実施する手段の一例を示す説明図である。
【図１４】比較例で使用した、爆薬の爆轟波を直接用いた衝撃圧縮法を実施する手段の一例を示す説明図である。
【符号の説明】
１　銅製パイプ（粉体を保持する為に使用）
２　銅製プラグ
３　銅製パイプ（水を保持するために使用）
４　紙筒（爆薬を保持するために使用）
５　爆薬
６　起爆部
７　水
８　試料部（希土類−鉄−窒素−水素−酸素系磁性材料を含む試料）[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a solid material for a rare earth-iron-nitrogen-hydrogen-oxygen magnet having high density, high magnetic properties, and excellent thermal stability and oxidation resistance.
The present invention also relates to a method for manufacturing a solid material for a magnet, which obtains a high-density and high-performance permanent magnet while impact-compressing a magnetic material powder to prevent decomposition and denitrification.
[0002]
TECHNICAL FIELD OF THE INVENTION
As high-performance rare-earth magnets, for example, Sm-Co-based magnets and Nd-Fe-B-based magnets are known. The former is widely used for its high thermal stability and corrosion resistance, and the latter is used for its extremely high magnetic properties, low cost, and stable supply of raw materials. Today, rare earth magnets having both higher thermal stability and higher magnetic properties and lower raw material costs are demanded as actuators for electrical equipment and various FAs, or magnets for rotating machines.
[0003]
On the other hand, a rare earth-iron compound having a rhombohedral or hexagonal crystal structure is₃And H₂When reacting at a relatively low temperature of 400 to 600 ° C. in a mixed gas of nitrogen, nitrogen atoms and hydrogen atoms form the above crystals, for example, Th₂Zn₁₇It is reported in Patent Document 1 that a type compound penetrates into interstitial positions and causes a remarkable increase in Curie temperature and magnetic anisotropy.
In recent years, expectations for practical use of such a rare earth-iron-nitrogen-hydrogen magnetic material as a new magnet material meeting the above demands have been increasing.
[0004]
A rare earth-iron-nitrogen-hydrogen-based magnetic material (hereinafter, referred to as an R-Fe-NH-based magnetic material) containing nitrogen and hydrogen between lattices of an intermetallic compound and having the rhombohedral or hexagonal crystal structure. ) Is generally obtained in a powder state, but is easily decomposed into an α-Fe decomposition phase and a rare earth nitride phase at a temperature of about 600 ° C. or more under normal pressure. It is very difficult with ordinary industrial methods. Therefore, as a magnet using an R-Fe-NH-based magnetic material, a bonded magnet using a resin as a binder has been produced and used. However, magnets made using such materials often have a Curie temperature of 400 ° C. or higher, and despite the use of magnetic powder that does not lose magnetization even at a temperature of 200 ° C. or higher, it is non-magnetic. According to Patent Document 1, a binder such as 12-nylon resin has a low heat-resistant temperature and a temperature coefficient of coercive force of about -0.5% / ° C, whereas a coercive force is as small as 0.6 MA / m. The main cause is that the irreversible demagnetization rate becomes large, and it is used only at a temperature generally lower than 100 ° C. That is, when a brushless motor or the like is used as a power source used in a high-temperature environment of 150 ° C. or more in response to recent demands for a high load, there is a problem that the bonded magnet cannot be used.
[0005]
In addition, when manufacturing a compression-molded bonded magnet using a resin as a binder, a molding pressure of 1 GPa or more, which is industrially difficult, is required to improve the filling rate and improve the performance, and considering the mold life and the like, In many cases, the mixing ratio of the magnetic material must be less than 80% in volume fraction, and depending on the compression-molded bonded magnet, the excellent basic magnetic properties of the R-Fe-NH-based magnetic material cannot be sufficiently exhibited. There was a problem.
For example, among bonded magnets made of R—Fe—N—H based magnetic materials, those having extremely high magnetic properties (BH)_max= 186kJ / m³Is reported in Non-Patent Document 2, but compared with conventional Sm-Co-based, Nd-Fe-B-based sintered magnets, etc., R-Fe-NH-based magnetic materials High basic magnetic properties are not fully exhibited.
[0006]
In order to solve the above problems, Patent Document 2 proposes a method for manufacturing a permanent magnet using a rare earth-iron-nitrogen based magnetic material that does not contain a resin binder. However, according to this method, the residual temperature after impact compression is set to Th₂Zn₁₇In order to suppress the temperature to below the decomposition temperature of the type rare earth-iron-nitrogen based magnetic material, there is a disadvantage that the pressure at the time of impact compression must be limited to a certain narrow range. This is because when a conventional shock wave is used, the temperature of the magnetic material is kept high for a long time despite the short duration of the shock wave itself, so that the magnetic material is very easily decomposed. is there.
[0007]
Moreover, according to the method, the density of the obtained product is at most 7.28 g / cm.³It was something that stayed. Furthermore, according to the method, the decomposition of the rare earth-iron-nitrogen based magnetic material cannot be sufficiently suppressed, and thus the coercive force was as low as 0.21 MA / m at the maximum.
Japanese Patent Application Laid-Open No. H11-163873 discloses a method using a cylindrical convergent shock wave to obtain a large molded body having no cracks or chips.₂Zn₁₇A method of compressing and solidifying a rare-earth-iron-nitrogen-based magnetic material is disclosed, but the maximum density of the magnet obtained by the method is 7.43 g / cm.³The maximum value of the coercive force was 0.62 MA / m, which was not yet satisfactory.
[0008]
In addition, Th molded by shock wave compression₂Zn₁₇Examples of the type rare earth-iron-nitrogen based magnetic material include those reported in Non-Patent Document 3. However, at 10 GPa, the filling factor is low, and at 20 GPa, decomposition into α-Fe decomposition phase and SmN phase progresses. The compact density under each impact compression condition is always 7.45 g / cm³In many cases, the maximum value of the magnetic properties is 0.57 MA / m, (BH)_max= 134kJ / m³And Th₂Zn₁₇It could not be said that it had sufficiently high magnetic properties with respect to the type R-Fe-NH bond magnet.
As described above, there is a strong demand for solid materials for magnets which have high density, high magnetic properties without decomposition, and good thermal stability.
[0009]
Apart from these high-performance magnets, on the other hand, there is also a demand for a direction toward higher performance and lighter weight in applications to home appliances, OA equipment, and electric vehicles. The density of the Sm-Co based magnet is 8.4 g / cm³Degree, the density of the Nd—Fe—B based magnet is 7.5 g / cm³When these magnets are mounted, the weight of the device / rotor tends to be large, and the energy efficiency may be poor. Further, depending on the application, there is a margin in the magnetic characteristics, so that the weight can be reduced by reducing the size of the magnet, but it is not necessarily advantageous in terms of cost in view of the yield by processing. For example, since cutting chips are proportional to the cutting area, the smaller the volume, the lower the yield per unit volume of the product.
[0010]
As described above, various bond magnets that compensate for the disadvantages have poor thermal stability. Therefore, a magnet that is lightweight, has high magnetic properties, has excellent thermal stability, and has high cost performance has not yet been developed.
Further, Patent Document 4 proposes a rare earth-iron-nitrogen-hydrogen-oxygen-based magnetic material having excellent magnetic properties (hereinafter referred to as an R-Fe-NHO-based magnetic material), and controls an oxygen component. By doing so, the material has excellent magnetic properties and corrosion resistance. It is a major feature that it has stable magnetic properties with the improvement of coercive force and that rust hardly occurs because of its relatively high oxidation resistance.
[0011]
However, as disclosed in Patent Documents 5 and 6, this R-Fe-N-H-based magnetic material uses the aforementioned R-Fe-N-H-based material suitably as a bond magnet. And no examples of application as a solid material for magnets have been reported yet.
[0012]
[Patent Document 1] Japanese Patent No. 2703281
[Patent Document 2] Japanese Patent No. 3108232
[Patent Document 3] JP-A-2001-6959
[Patent Document 4] Japanese Patent No. 2708568
[Patent Document 5] Japanese Patent No. 2857476
[Patent Document 6] Japanese Patent No. 2708578
[Non-Patent Document 1] Technical Report No. 729 of the Institute of Electrical Engineers of Japan, edited by the Institute of Electrical Engineers of Japan, page 41
[Non-Patent Document 2] Appl. Phys. Lett. 75, No. 11, p. 1601
[Non-Patent Document 3] Appl. Phys. Vol. 80, No. 1, 356 pages
[0013]
[Problems to be solved by the invention]
A first object of the present invention is to provide a solid material for an R-Fe-NHO-based magnet having a high density and high magnetic properties, and having excellent thermal stability and oxidation resistance, and a method for producing the same. That is. The present invention provides a solid material for a magnet including a magnet which is magnetized by magnetization or the like.
[0014]
[Means for Solving the Problems]
The present inventors have conducted intensive studies on the above problems, and as a result, formed an R-Fe-NHO-based magnetic material having excellent magnetic properties and oxidation resistance into a green compact in a magnetic field or without a magnetic field. Afterwards, it is shock-compressed and solidified using underwater shock waves, and mainly contains R-Fe-N-HO-based magnetic materials, taking advantage of the properties of shock compression such as ultra-high pressure shearing, activating action, and short-time phenomena. It has been found that a solid material for a magnet can be obtained, and the present invention has been completed.
[0015]
Further, the present inventors, when using the underwater shock wave, R-Fe-NHO-based magnetic material and hard magnetic and / or soft magnetic powder or solid, or powder of non-magnetic material or They have also found that solid materials can be easily integrated, and have completed the present invention.
In addition, the present inventors further include an R-Fe-N-HO-based magnetic material having a rhombohedral or hexagonal crystal structure, which is lightweight and has high magnetic properties and high stability. In order to obtain the material, the composition and content of the raw material and the manufacturing method thereof were intensively studied. As a result, a magnetic material powder containing not only nitrogen but also hydrogen and oxygen was used, and its volume fraction was set to 80 to 97% by volume. After forming into a green compact in a magnetic field, the green compact was shock-compressed with an underwater shock wave having a constant shock wave pressure to a density of 6.15 g / cm.³With the knowledge that a solid material for an R-Fe-NHO-based magnet solidified by metal bonding or ionic bonding that can be used even at 100 ° C or higher can be easily obtained, the present invention has been completed. .
[0016]
That is, aspects of the present invention are as follows.
(1) A solid material for a magnet containing 50 to 100% by volume of a rare earth-iron-nitrogen-hydrogen-oxygen-based magnetic material.
(2) The solid material for a magnet according to the above (1), wherein the magnetic material contains a rare earth-iron-nitrogen-hydrogen-oxygen-based magnetic material having a rhombohedral or hexagonal crystal structure.
(3) The rare earth-iron-nitrogen-hydrogen-oxygen based magnetic material has a general formula R_αFe_{100- α − β − γ − δ}N_βH_γO_δWherein R is at least one element selected from rare earth elements, and α, β, γ, and δ are atomic percentages, 3 ≦ α ≦ 20, 5 ≦ β ≦ 25, 0.01 ≦ γ ≦ 5. The solid material for a magnet according to the above (1) or (2), comprising a rare earth-iron-nitrogen-hydrogen-oxygen-based magnetic material satisfying 0.01 ≦ δ ≦ 10.
(4) Ni, Ti, V, Cr, Mn, Zn, Cu, Zr, Nb, Mo, Ta, W, Ru, Rh, Pd, Hf, Re, Os The solid material for a magnet according to any one of the above (1) to (3), wherein the solid material is substituted with at least one element selected from the group consisting of Ir and Ir.
(5) Any one of the above (1) to (4), wherein 10 atomic% or less of N and / or H is replaced with at least one element selected from C, P, Si, S, and Al. Solid material for magnets.
[0017]
(6) The rare earth-iron-nitrogen-hydrogen-oxygen based magnetic material is represented by the general formula R_αFe_{100- α − β − γ − δ}N_βH_γO_δM_εR is at least one element selected from rare earth elements including Y, M is Li, Na, K, Mg, Ca, Sr, Ba, Ti, Zr, Hf, V, Nb, Ta, Cr , Mo, W, Mn, Pd, Cu, Ag, Zn, B, Al, Ga, In, C, Si, Ge, Sn, Pb, Bi, and / or an oxide of R, At least one selected from the group consisting of carbides, carbides, nitrides, hydrides, carbonates, sulfates, silicates, chlorides, and nitrates, and α, β, γ, δ, and ε are mole percentages of 3 ° C. 20, 5 ° C. 磁石 30, 0.01 ° C. 10, 0.01 ≦ δ ≦ 10, 0.1 ° C. ℃ ° C. 40, wherein the solid material for a magnet according to the above (1) to (5),
[0018]
(7) The solid material for a magnet according to any one of the above (1) to (6), wherein 50 atom% or more of the R is Sm.
(8) The solid material for a magnet according to any one of (1) to (7), wherein 0.01 to 50 atomic% of the Fe is substituted with Co.
(9) The solid material for a rare earth-iron-nitrogen-hydrogen-oxygen-based magnet according to any one of (1) to (8), wherein the crystalline phase (island) and the amorphous phase (sea ) Comprising a sea-island structure.
(10) 6.15 g / cm containing rare earth-iron-nitrogen-hydrogen-oxygen based magnetic material³The solid material for a magnet according to any one of the above (1) to (9), which has a higher density.
(11) The solid material for a magnet according to any one of the above (1) to (9), which contains 80 to 97% by volume of a rare earth-iron-nitrogen-hydrogen-oxygen-based magnetic material.
[0019]
(12) Components other than the rare earth-iron-nitrogen-hydrogen-oxygen based magnetic material have a density of 6.5 g / cm.³The solid material for a magnet according to the above (11), which is the following element, compound or mixture thereof.
(13) The magnet according to any one of the above (11) to (12), wherein the portion other than the rare earth-iron-nitrogen-hydrogen-oxygen-based magnetic material contains at least one of air and an inert gas. For solid materials.
(14) At least portions of oxides, fluorides, carbides, nitrides, hydrides, carbonates, sulfates, silicates, chlorides, and nitrates other than the rare earth-iron-nitrogen-hydrogen-oxygen magnetic material The solid material for a magnet according to any one of the above (11) to (13), comprising one kind.
(15) The solid material for a magnet according to any one of the above (11) to (14), wherein an organic substance is contained in a portion other than the rare earth-iron-nitrogen-hydrogen-oxygen-based magnetic material.
[0020]
(16) Residual magnetic flux density B at normal temperature_r, Coercivity H at room temperature_cJ, Permeance coefficient P when used as a magnet_cAnd maximum operating temperature T_maxIs μ₀Is the vacuum permeability,
B_r≤μ₀H_cJ(P_c+1) (11000-50T_max) / (10000-6T)_max)
The solid material for a magnet according to any one of the above (1) to (15), wherein
(17) Coercive force H_cJIs 0.76 MA / m or more, and the squareness ratio B_r/ J_sIs not less than 95%, the solid material for a magnet according to any one of the above (1) to (16).
(18) The soft magnetic material containing at least one element selected from Fe, Co, and Ni is uniformly dispersed and integrated with the rare earth-iron-nitrogen-hydrogen-oxygen-based magnetic material. (1) The solid material for a magnet according to any one of (1) to (17).
(19) At least one magnetic material selected from a rare earth-iron-boron magnetic material, a rare earth-cobalt magnetic material, and a ferrite magnetic material is uniformly added to the rare earth-iron-nitrogen-hydrogen-oxygen magnetic material. The solid material for a magnet according to any one of the above (1) to (18), which is mixed and integrated.
(20) The solid material for a magnet according to any one of the above (1) to (19), wherein a nonmagnetic phase is present at a grain boundary of the magnetic material.
[0021]
(21) A solid material for a magnet, wherein the solid material for a magnet according to any of the above (1) to (20) and a soft magnetic solid metal material are joined and integrated.
(22) A solid for a magnet having a soft magnetic layer, wherein the soft magnetic layer and the solid material for a magnet according to any one of (1) to (21) are alternately laminated and integrated. material.
(23) A solid material for a magnet, wherein at least a part of the solid material for a magnet according to any of (1) to (22) is covered with a non-magnetic solid material.
(24) The solid material for a magnet according to any one of the above (1) to (23), which is provided with magnetic anisotropy.
(25) The solid material for a magnet according to any one of (1) to (24), wherein the solid material is formed into a prism, a cylinder, a ring, a disk, or a plate.
[0022]
(26) A magnetic material obtained by reacting Zn at a grain boundary or a surface of the magnetic material according to any one of the above (1) to (7).
(27) The magnet according to any one of (1) to (26) above, wherein the raw material powder of the rare earth-iron-nitrogen-hydrogen-oxygen-based magnetic material is subjected to impact compression and solidification using an underwater shock wave. A method for producing a solid material.
(28) The method for producing a solid material for a magnet according to any one of the above (1) to (26), wherein the material is shock-compressed and solidified using an underwater shock wave having a shock wave pressure of 3 to 40 GPa.
(29) The method for producing a solid material for a magnet according to the above (10), wherein the solid material is subjected to impact compression and solidification using an underwater shock wave having a shock wave pressure of 3 to 30 GPa.
(30) The method for producing a solid material for a magnet according to the above (10), wherein the material is shock-compressed and solidified using an underwater shock wave having a shock wave pressure of 8 to 40 GPa.
[0023]
(31) The method for producing a solid material for a magnet according to any one of the above (11) to (15), wherein the material is shock-compressed and solidified using an underwater shock wave having a shock wave pressure of 3 to 22 GPa.
(32) The method for producing a solid material for a magnet according to any one of the above (1) to (26), wherein the compacting of the raw material powder is performed in a magnetic field.
(33) The method for producing a solid material for a magnet according to any one of the above (1) to (26), wherein the raw material powder is compacted, and then subjected to impact compression and solidification using an underwater shock wave.
(34) The method for producing a solid material for a magnet according to the above (1) to (26), wherein the raw material powder is compacted in a magnetic field, and then subjected to impact compression and solidification using an underwater shock wave.
(35) The method for producing a solid material for a magnet according to the above (1) to (26), wherein the solid material is formed by cutting and / or plastic working.
[0024]
(36) The method according to any one of (28) to (36), further comprising a step of heat-treating the material at least once at a temperature of 100 ° C. or higher and lower than the decomposition temperature.
(37) A component for use in an apparatus utilizing a static magnetic field of a magnet, wherein the component uses the solid material for a magnet according to any of (1) to (26) above.
(38) Maximum operating temperature T using static magnetic field of magnet_maxIs a device having a temperature of 100 ° C. or higher, wherein the component (38) is used as the component.
Is provided.
[0025]
Here, the solid material refers to a lump-shaped material. Further, the solid material for magnet as used herein refers to a massive magnetic material, and powders of the magnetic material constituting the solid material for magnet are continuously bonded directly or via a metal phase or an inorganic phase. The magnetic material is in a lump as a whole. A state in which the magnet is magnetized by magnetization and exhibits a residual magnetic flux density is particularly called a magnet. The magnet also belongs to the category of the solid material for magnets referred to herein.
The rare earth element referred to here is Y in Group IIIa of the periodic table and 15 elements in the La series from atomic number 57 to 71, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, and Ho. , Er, Tm, Yb, Lu.
The term “decomposition” as used herein means that an α-Fe decomposition phase is generated as the crystal structure of the R—Fe—N—H—O-based magnetic material powder changes. Has a bad influence on the magnetic properties, so that the above decomposition is a phenomenon to be prevented. However, in the step of producing the raw material used in the present invention and the step of producing the solid material for a magnet of the present invention, the layer containing oxygen may be amorphized, but this phenomenon is distinguished from the decomposition referred to in the present invention. .
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail focusing on particularly preferred embodiments.
The R-Fe-NHO-based magnetic material used for the solid material for a magnet of the present invention is prepared by a known method.
For example, a rare earth-iron alloy is prepared by a high-frequency method, a super-quenching method, an R / D method, an HDDR method, a mechanical alloying method, a mechanical grinding method, and the like. -Hydrogenation treatment is performed in an atmosphere of a hydrogen mixed gas, an ammonia-hydrogen mixed gas or the like to perform fine pulverization to prepare an R-Fe-NHO-based magnetic material. During these steps, it is important to control the type and concentration of the oxygen source. Coarse pulverization or fine pulverization may not be performed depending on the composition of the magnetic material, the processing method of the alloy, or the nitriding method.
[0027]
In the present invention, it is important that at any stage of the process, hydrogen gas, ammonia gas, or a hydrogen-containing compound such as a compound containing hydrogen is introduced to introduce not only nitrogen but also hydrogen. That is, the hydrogen content of the R—Fe—N—H—O-based magnetic material is preferably 0.01 atomic% or more. When the amount of hydrogen is less than 0.01 atomic%, an α-Fe decomposition phase and a rare earth nitride decomposition phase are often generated, and the coercive force is lowered, and the corrosion resistance is sometimes lowered. If the hydrogen content is 0.1 atomic% or more, it is a more preferable raw material for a solid material for a magnet.
[0028]
Similarly, in the present invention, in an atmosphere in which the powder is processed at any stage of the process, for example, a gas or a solvent in a pulverizing process, a pulverizing jig such as a container, a gas composition or a degree of vacuum in a heat treatment process, or the like. It is important to bring into contact with an oxygen source which is a substance containing oxygen such as dissolved oxygen, moisture, and oxide, and to introduce oxygen while controlling the oxygen source. That is, the oxygen content of the R—Fe—N—H—O-based magnetic material is preferably 0.01 atomic% or more. If the oxygen content is less than 0.01 atomic%, the coercive force is reduced, and the corrosion resistance may be further reduced, which is not preferable. Further, in order to obtain a stable material having a high coercive force, it is desired that the oxygen content is preferably 0.1 atomic% or more, more preferably 1 atomic% or more.
[0029]
Further, the crystal structure of the R-Fe-NHO-based magnetic material, in which hydrogen and oxygen can be simultaneously controlled and introduced by controlling the amount of water vapor and the amount of water in the pulverizing atmosphere, for example, Th₂Zn₁₇Rhombohedral crystal having a type crystal structure or the like or a crystal structure similar thereto, or Th₂Ni₁₇, TbCu₇, CaZn₅Hexagonal crystal having a crystal structure such as a type crystal structure or a crystal structure similar thereto,₂Fe₁₄BN_xType, R₂Fe₁₄CN_xType and R (Fe_1-yM_y)₁₂N_xExamples include a type or a tetragonal crystal having a similar crystal structure, and it is necessary to include at least one of them. Th in this₂Zn₁₇Rhombohedral crystal having a type crystal structure or the like or a crystal structure similar thereto, or Th₂Ni₁₇, TbCu₇, CaZn₅It is preferable that the hexagonal crystal having a type crystal structure or the like or a crystal structure similar thereto is contained in 50% by volume or more of the entire R—Fe—N—H—O-based magnetic material.₂Zn₁₇Most preferably, the rhombohedral crystal having a type crystal structure or the like or a crystal structure similar thereto is contained in 50% by volume or more of the entire R-Fe-NHO-based material.
[0030]
In the present invention, the volume fraction of the R—Fe—N—H—O-based magnetic material with respect to the entire solid material for a magnet is preferably set to 50 to 100% by volume. However, when the magnet solid material is composed only of the R—Fe—N—H—O-based magnetic material, or when the magnet solid material is a composite material with a gas or an organic substance, R− The volume fraction of the Fe—N—H—O based magnetic material is preferably 80 to 100% by volume. If it is less than 80% by volume, the continuous bonding between the magnetic powders is insufficient, and a solid material for a magnet cannot be formed. However, in addition to the R—Fe—N—H—O based magnetic material, a hard magnetic material such as a rare earth-iron-boron based magnetic material, a soft magnetic material such as Co, and a nonmagnetic phase that is a metal or an inorganic substance are included. In this case, the solid material volume fraction, which is a value obtained by adding the volume fraction of the R-Fe-N-HO-based magnetic material, may be in the range of 80 to 100% by volume.
[0031]
Here, the volume fraction refers to the ratio of the volume occupied by the magnetic material to the entire volume including the voids of the solid material for the magnet.
The R-Fe-NHO-based magnetic material described above is preferably obtained as a powder having an average particle size of 0.1 to 100 µm, and is supplied as a raw material of a solid material for a magnet. If the average particle size is less than 0.1 μm, the magnetic field orientation tends to be insufficient, and the residual magnetic flux density tends to be low. Conversely, if the average particle size exceeds 100 μm, the coercive force may be reduced depending on the material composition, and the production conditions for increasing the density may be severe, which tends to be less practical. In order to impart excellent magnetic field orientation, a more preferable range of the average particle size is 1 to 100 μm.
[0032]
Further, the R-Fe-NHO-based magnetic material is characterized by having high saturation magnetization, high Curie point, and large magnetic anisotropy. Therefore, in the R-Fe-NHO-based magnetic material which can be a single crystal powder, a solid material for an anisotropic magnet which can be easily magnetically oriented by an external magnetic field and has high magnetic properties. can do.
The preferred ranges of R and Fe as raw materials for a solid material for a magnet having both high magnetization and coercive force are 5 ≦ α ≦ 20 and 10 ≦ β ≦ 25, respectively.
[0033]
A preferable range of the M component in the raw material powder for obtaining a solid material for a magnet having a strong metal bond realized by the method of the present invention, which is almost 100% in the total filling rate, is 0.1 ° C. ° C. 10 is there. Further, the preferable range of the M component as a solid material for a magnet having a high coercive force and sufficiently high magnetization as compared with the metal binder magnet is 0.1 ≦ ε ≦ 5, and more preferably 0.1 ≦ ε ≦ 3. Magnetization and (BH)_maxIn order to make the value extremely high, the value may be in the range of 0.1 ≦ ε ≦ 1, but in this case, the value of the coercive force tends to be unstable.
[0034]
Nd-Fe-B-based sintered magnets have extremely high magnetic properties and are widely used in actuators such as VCM and various motors. It is essential to perform surface treatment with nickel plating or epoxy resin coating.
On the other hand, in the case of a magnet using an R—Fe—N—H—O-based magnetic material, the above-described surface treatment is not required or can be simplified. In other words, in addition to being advantageous in terms of cost, when used as an actuator or a motor, the gap between the stator and the rotor can be reduced by the surface layer having low magnetism, so that there is an advantage that a large torque can be obtained for rotation and repetitive motion. , It can make the most of the magnetic force of the magnet. For this reason, for example, at room temperature (BH)_maxEven when the value is inferior to that of the Nd-Fe-B-based magnet, the same performance can be exhibited. In the case of the magnet containing the R—Fe—N—H—O-based magnetic material, when the surface treatment is not required, the (BH)_maxValue is 200 kJ / m³If it is above, it becomes a preferable magnet excellent in cost performance, and 240 kJ / m³It is more preferable if it is above. However, in the present invention, in the case of a solid material for a magnet having a pinning type magnetization reversal mechanism, the raw material magnetic powder itself is extremely excellent in thermal stability and corrosion resistance._maxValue is 200 kJ / m³It is preferably used even if the temperature is lower than (BH) at room temperature._maxValue is 100 kJ / m³It is desirable that there be.
[0035]
Further, an isotropic solid material for magnets is suitable for further low permeance applications and applications in which multi-polar magnetization is applied._maxValue is 150 kJ / m³It may be less than normal temperature (BH)_maxValue is 50 kJ / m³It is desirable that there be.
The first aspect of the solid material for a magnet of the present invention is 7.45 g / cm.³It is a solid material for R-Fe-NHO-based magnets having a higher density. Since the magnetization and the magnetic flux density are proportional to the filling rate, the smaller the density, the lower the residual magnetic flux density, and the lower the maximum energy product.Therefore, in general, a solid material for a magnet with a high filling rate is preferably used for a high-performance magnet. . Further, since the R—Fe—N—H—O based magnet material is often a fine powder, if there are many passages of oxygen, such as voids, which are continuous pores, the surface of the fine powder is oxidized and deteriorated, and the coercive force Is a factor that causes a decrease. Therefore, depending on the material composition and application, it is necessary to sufficiently increase the density to prevent oxygen from entering from the surface, and it is required that the filling rate be 95% or more, preferably 98% or more. Filling near the surface may be required to be close to 100%.
[0036]
The filling rate as used herein means that the solid material for a magnet of the present invention is composed of only an R-Fe-N-HO-based magnetic material, Is the ratio of the true density to the true density. The true density referred to here is the density w / v obtained from the volume v of the R-Fe-N unit cell obtained from X-rays and the total atomic weight w of the atoms constituting the unit cell. Yes, it is generally called X-ray density Dx, and the density Dm of the solid material for the magnet can be determined by a macro method such as the Archimedes method or the volume method.
[0037]
In a combination of the material composition and the application in which the oxidative deterioration is remarkable, the density of the solid material for the magnet is 7.45 g / cm.³Preferably greater than 7.50 g / cm³More preferably greater than 7.55 g / cm³More preferably, greater than 7.60 g / cm³It is most preferred that this is the case. Also, depending on the composition of the raw material, the density is 8.0 g / cm.³On the other hand, if it exceeds, a phase other than the R-Fe-NHO phase having high magnetic properties is generated, and the magnetic properties often deteriorate, which is not preferable. Oxidation degradation is a phenomenon that involves the addition of undesired oxygen to the magnetic properties of solid materials for magnets and the accompanying decomposition of the R-Fe-NHO-based magnetic material due to an external oxygen source. It has different properties from the introduction of oxygen into the magnet solid material and its raw material powder.
[0038]
Depending on the manufacturing method and conditions, as the volume of the solid material for magnets increases, the filling rate in the interior may decrease, but even in this case, the filling rate of the surface layer is sufficiently increased and the thickness is sufficiently large. Then, it can be used as a practical magnet.
However, when the solid material for the magnet is composed only of the R—Fe—N—H—O-based material and the balance is air, the density is 6.15 g / cm.³In the following, when forming a magnet of any form and volume, the magnet contains a lot of voids, and often cracks and breaks up due to impact or load, causing cracks, or as described above. Coercive force tends to decrease.
[0039]
According to the method of the present invention, only 5 cm of R-Fe-NHO-based magnetic material is used as a raw material.³When preparing the following solid material for magnets, 7.60 g / cm³Can be obtained relatively easily, for example, 0.1 m³In the case where a solid material for a magnet having a volume of 7.45 g / cm.³The following parts of density may occur: However, even in such a case, even at a part in the surface layer portion, 7.60 g / cm.³When it is a solid material for a magnet having a density exceeding the above, it can be said that it has oxidation resistance, has high magnetic properties, and belongs to the category of the solid material for a magnet of the present invention.
[0040]
By the way, Th which does not contain hydrogen₂Zn₁₇The type R-Fe-N-based magnetic material has a nitrogen content of R₂Fe₁₇Less than 3 per thermodynamically unstable R₂Fe₁₇N_{3- Δ}Phases form. This phase is easily decomposed into an α-Fe decomposition phase and a rare earth nitride by thermal and mechanical energy. As a result, a high-performance solid material for a magnet cannot be obtained by the conventional shock wave compression method.
On the other hand, if the hydrogen is controlled within the range specified above, the main phase usually has a thermodynamically stable R₂Fe₁₇N₃H_xR containing phase or excess nitrogen₂Fe₁₇N_{3+ Δ}H_xPhase (usually x is in the range of about 0.01 to 2) to decompose into α-Fe decomposition phase and rare earth nitride by thermal and mechanical energy.₂Zn₁₇It is significantly suppressed as compared with the type R—Fe—N based magnetic material.
[0041]
This is an important finding for obtaining a solid material for magnets having a high density, high magnetic properties, and excellent thermal stability and oxidation resistance.
Oxygen in the R—Fe—N—H—O-based raw material powder is stable R₂Fe₁₇N₃H_xIt is not necessary that the total amount be contained in the phase, but it is localized around this ferromagnetic layer, and R-Fe-NHO, R-Fe-HO, R-Fe-O, R-Fe- N-H-O-M, R-Fe-H-O-M, R-Fe-O-M, etc., any composition containing at least one of R, Fe, N, H, M and O and O In some cases, it is preferable to take a structure in which a crystalline phase is formed from the viewpoint of stability of magnetic properties. As an example of the structure of such a magnetic powder, J. Pharm. Alloys and Compounds. 193, p. 235, an oxygen-enriched amorphous layer of about 100 nm is present on the surface of a ferromagnetic R-Fe-NHO fine powder produced under certain conditions. It has been reported to take the structure. When the layer containing a large amount of oxygen is decomposed and changes to the α-Fe decomposition phase, the coercive force is greatly reduced. Since the decomposition of the amorphous phase is also induced by the conventional shock wave compression method, another reason that it is difficult for the conventional method to make the R-Fe-N-HO-based material a high-performance solid material for magnets is as follows. Has become.
[0042]
As the R-Fe-N-HO-based magnetic material used in the present invention, various magnetic materials having different magnetization reversal mechanisms such as nucleation type, pinning type, exchange spring type and exchange coupling type are used as solid materials for magnets. Can be. Since all of these magnetic materials undergo a decomposition reaction at a temperature exceeding 600 ° C., they cannot be made into solid materials for magnets by a sintering method in which the density is increased at a high temperature. It is a group of materials that are very effective to be formed by the method.
As described above, the R-Fe-NHO-based magnetic material is significantly suppressed from being decomposed by thermal and mechanical energy as compared with the R-Fe-N-based magnetic material containing no H, If this is decomposed to produce a large α-Fe decomposition phase and a rare earth nitride phase having a large particle size exceeding about 100 nm, the α-Fe decomposition phase is contained despite a large amount of expensive rare earths. The phase becomes buds of reversed magnetic domains, and the coercive force is undesirably reduced.
[0043]
Therefore, Fe-Ni, Fe-Co-Ni and their nitrides, such as Fe, Co, Fe-Co, and permalloy, and the above-mentioned components as sub-phases of the R-Fe-N-HO-based magnetic material in advance When containing a soft magnetic phase such as an alloy or a compound with the above-mentioned M component, a practical coercive force is obtained by adjusting the particle size or thickness of the soft magnetic phase to about 5 to 100 nm. In addition to being able to maintain, the amount of expensive rare earth elements can be saved, and a magnet with high cost performance can be obtained.
[0044]
These soft magnetic subphases have an effect of improving the residual magnetic flux density of the R—Fe—N—H—O-based magnetic material. However, if the particle size or thickness of the soft magnetic phase is less than 5 nm, the saturation magnetization becomes small, and if it exceeds 100 nm, the anisotropy due to exchange coupling between the soft magnetic phase and the hard magnetic phase and between the soft magnetic phases. Cannot be maintained, and the coercive force becomes low due to buds of reverse magnetic domains, which is not preferable.
In order to achieve such a microstructure, as a method for producing an R-Fe raw material, a known method of adding an M component to obtain an R-Fe-M raw material by a super-quenching method, a mechanical alloying method or a mechanical grinding method A known method such as a method, or a method of producing an R-Fe or R-Fe-M raw material by a pulverization method according to the known method can be adopted.
At this time, the amount of the soft magnetic subphase is preferably 5 to 50% by volume. If it is less than 5% by volume, the coercive force becomes relatively high, but the residual magnetic flux density does not become much higher than that of the R—Fe—N—H—O-based material alone. The magnetic flux density increases, but the coercive force decreases, and both are high (BH)_maxTend not to be obtained. A more preferable range of the amount of the soft magnetic phase is 10 to 40% by volume.
[0045]
Further, rare earth-iron-boron based magnetic materials such as Nd-Fe-B based materials, SmCo₅System and Sm₂Co₁₇One or more hard magnetic powders such as rare-earth-cobalt-based magnetic materials and ferrite-based magnetic materials such as R-Fe-N-H-O-based magnetic materials are contained in a range of 50% by volume or less. By mixing with the material, it is possible to obtain a solid material for a magnet in which various practical requirements such as magnetic properties, thermal stability, and cost are optimized according to the application.
[0046]
In general, the more rare-earth-iron-boron-based materials are included, the higher the overall magnetic properties are. However, the corrosion resistance is reduced and the cost is increased. The more rare-earth-cobalt-based magnetic materials are included, the higher the thermal stability is. However, the magnetic properties are reduced and the cost is increased. As the ferrite-based magnetic material is included more, the cost is reduced and the temperature properties are improved, but the magnetic properties are greatly reduced. Mixing the R-Fe-N-H-O-based magnetic material with another magnetic material having an extremely different particle size has the advantage that the condition for increasing the filling rate is broadened.
The solid material for a magnet of the present invention may have a non-magnetic phase at the grain boundaries of the R-Fe-NHO-based magnetic material, particularly for the purpose of providing a magnet having a high coercive force and a high squareness ratio. it can.
[0047]
As the method, there are known methods such as Japanese Patent No. 2739860 and Japanese Patent No. 2705895, for example, a method of mixing a magnetic powder and a non-magnetic component and performing a heat treatment, and a method of plating the surface of the magnetic powder. A method of coating the surface of a magnetic powder with a non-magnetic component by various vapor deposition methods, a method of treating a magnetic powder with an organic metal, and photodecomposing the organic metal to coat the surface of the powder as a metal component. . Further, a method of mixing an R—Fe—N—H—O-based magnetic material and a non-magnetic component, compression-molding the mixture, and compressing by a shock wave is also possible. Since the solid material for magnets has a strong and dense grain boundary structure, a high coercive force and a high filling rate can be achieved with a smaller amount of binder than a metal binder magnet, and the oxidation resistance is good. In these materials, as long as the R—Fe—N—H—O based magnetic material powders have a strong bond without any intervening nonmagnetic phase, a solid material for a magnet that satisfies mechanical strength. It can be.
[0048]
As the non-magnetic component, any of an inorganic component and an organic component can be used, and each low-melting point metal having a melting point of 1000 ° C. or less, preferably 500 ° C. or less, such as Zn, In, Sn, and Ga, is preferable. When used, the coercive force increases dramatically, and the thermal stability also improves. In order to realize high magnetic properties, the volume fraction of the nonmagnetic phase, including the amount previously contained in the R—Fe—N—H—O-based magnetic material, is preferably 10% by volume or less, and more preferably 5% by volume. It is preferably at most 3% by volume, most preferably at most 3% by volume. On the other hand, if it is less than 0.1% by volume, the effect of the non-magnetic phase on the coercive force is hardly observed.
[0049]
The solid material for a magnet of the present invention can realize higher cost performance by being joined to and integrated with a soft magnetic solid metal material. The magnetic flux density can be enhanced by combining Fe material, Fe-Co material, silicon steel plate and the like with the solid material for the R-Fe-NHO-based magnet, and furthermore, those materials and Ni or By laminating a material containing Ni, workability and corrosion resistance can be further increased.
1 and 2 show examples in which a solid material for an R-Fe-NHO-based magnet and a soft magnetic material are joined and integrated.
[0050]
FIG. 1 is a cross section of a solid material for a magnet obtained by joining and integrating an R—Fe—N—H—O based magnetic material (hard magnetic layer) and a soft magnetic solid metal (soft magnetic layer). An example is shown below.
FIG. 2 shows an example of a cross section of a solid material for a magnet in which R—Fe—N—H—O based magnetic material layers (hard magnetic layers) and soft magnetic layers are alternately laminated and integrated. With the configuration shown in FIG. 2, cost reduction can be achieved without impairing the surface magnetic flux density of the magnet.
[0051]
As a feature of the present invention, when the R-Fe-NHO-based magnetic material powder and the soft magnetic bulk material or the powder are mixed and shock-wave compressed simultaneously without mixing, the R-Fe-N-H -The solidification of the O-based magnetic material and the integration with the soft magnetic material can be performed at the same time, and there is no need to perform cutting, welding, bonding with an adhesive, etc. for integration in a later process. large.
As shown in FIG. 3, a part or all of the surface of the solid material for a magnet of the present invention can be covered with a non-magnetic solid material.
[0052]
FIG. 3 illustrates a cross section of a solid material for a magnet covered with a nonmagnetic material. The solid material for magnets, whose entire surface is covered with a non-magnetic material, has the effect of increasing corrosion resistance, and in applications in harsh environments of high temperature and high humidity, a non-magnetic material is coated even if the magnetic properties are slightly sacrificed. In some cases, it is better. Examples of the non-magnetic substance include organic substances, polymers, inorganic substances, and non-magnetic metals having a high decomposition temperature and a high melting point. However, in applications where thermal stability is particularly required, coating with a non-magnetic metal or an inorganic substance is preferable. Also in this case, when the R-Fe-N-H-O-based magnetic material powder and the non-magnetic solid material or the powder are simultaneously charged without being mixed and subjected to shock wave compression, the R-Fe-N-H- The solidification of the O-based magnetic material and the integration with the non-magnetic material can be performed simultaneously.
[0053]
In order to make the solid material for magnet anisotropic and to make it a magnet, the magnet is usually magnetized. At this time, a large impact is applied to the solid material for magnet, and the R-Fe-N-HO system solidified densely Even with a solid material for a magnet, it may cause cracking or chipping. For this reason, depending on the magnetic field or the magnetization method, it is preferable to cover a part or the whole of the magnet surface with a non-magnetic solid material to obtain a solid material for magnets having high impact resistance.
[0054]
FIG. 4 shows an example of a cross section of another solid material for a magnet according to the present invention. That is, a solid material for a magnet as shown in FIG. 4 can also be formed by combining an R—Fe—N—H—O based magnetic material with a soft magnetic material and a non-magnetic material.
The solid material for a magnet of the present invention is characterized by having excellent magnetic properties after magnetization. When the R—Fe—N—H—O-based material is a magnetic anisotropic material, it is desirable to orient the magnetic powder in a magnetic field of 80 kA / m or more, preferably 800 kA / m or more during compression molding. . Furthermore, it is desirable to increase the residual magnetic flux density and coercive force by magnetizing with a static magnetic field or a pulse magnetic field of 1.6 MA / m or more, more preferably 2.4 MA / m or more after the shock wave compression molding.
When the R—Fe—N—H—O based magnetic material is an isotropic material, the magnetic field orientation at the time of compression molding is unnecessary, but the magnetization is performed as described above to sufficiently magnetically anisotropy. It is essential to do.
[0055]
Further, when the solid material for a magnet is magnetized and used as a magnet, various shapes are required depending on the use. The solid material for magnets does not contain a resin binder, has a high density, and can be easily processed into an arbitrary shape by a normal processing machine by cutting and / or plastic working. In particular, it is a great feature that it can be easily processed into a prismatic, cylindrical, ring, disk, or plate shape having high industrial value. Once processed into these shapes, they can be further subjected to a cutting process or the like to be processed into a tile shape or a quadrangular prism having an arbitrary base shape. That is, it can be formed from any shape into any form surrounded by a curved surface including a cylindrical surface and a flat surface by easily performing cutting and / or plastic working. The term “cutting” as used herein refers to cutting of general metal materials, and is machining with a saw, a lathe, a milling machine, a drilling machine, a grindstone, and the like. Molding. In addition, heat treatment such as annealing at a temperature lower than the decomposition temperature of the magnetic material powder can be performed to remove the strain after the cold working. Depending on the composition of the magnetic material powder, it is possible to impart or strengthen magnetic anisotropy by plastic working, and it is also possible to adjust the coercive force by combining it with heat treatment. The heat treatment can be used to anneal the strain generated after the shock wave compression described later or to adjust the fine structure to improve various magnetic properties. Furthermore, when the R-Fe-N-H-O-based magnetic material contains a low melting point metal, heat treatment is performed simultaneously with or before and after compacting to strengthen the temporary bond between the magnetic powders. It can also be used to facilitate the handling of The heat treatment temperature is selected in the range of 100 ° C. or more and less than the decomposition temperature, and before, during, and after each step of producing the solid material for magnets of the present invention in addition to the above-described examples, and further for the solid material for magnets of the present invention. The heat treatment can be performed at an arbitrary stage such as the raw material preparation step selected in the above.
[0056]
A second aspect of the solid material for a magnet according to the present invention is a material containing 80 to 97% by volume of an R-Fe-NHO-based magnetic material. The purpose of this embodiment is to provide a solid material for a magnet which is lightweight and has excellent magnetic properties and stability, and has a completely different purpose from the first embodiment. In this embodiment, the portion of 3 to 20% by volume other than the R—Fe—N—H—O-based material may be air depending on the use or material composition, but may be vacuum or have a density of 6.5 g / cm.³The following elements, compounds, or mixtures thereof may be used.
[0057]
The density of the solid material for a magnet according to the second aspect of the present invention is 6.15 to 7.45 g / cm in order to take advantage of its characteristics.³It is preferable that 6.15 g / cm³Even if the amount is less than 80% by volume, the component of the R-Fe-NHO-based magnetic material may be preferable. Further, even when the R—Fe—N—H—O based magnetic material is 97 vol% or less, it is 7.45 g / cm.³In some cases, and the characteristics of the solid material for magnets of the present invention, which is lighter than existing solid magnets, may not be utilized. For example, Sm₂Fe₁₇N₃H_0.1The true density of the magnetic material is 7.69 g / cm³(See IEEE Trans. Magn., MAG-28, p. 2326, and Powder Diffraction File WZ1430 by ICDD), but it is assumed that a portion other than the magnetic material is a gas whose density is low enough to be neglected. When the content of the magnetic material is 80 to 97% by volume at 0.1 atomic% or less, the density of the solid material for the R-Fe-NHO-based magnet is 6.15 to 7.46.
[0058]
The solid material for a magnet of the present invention is a polycrystalline material, and may include an interface phase different from the R-Fe-N-HO main phase. Does not necessarily match Dx. Therefore, in the present invention, it is often more appropriate to use the value of Dm itself as a guideline than to judge the degree of packing of the solid material for magnet by the filling rate Dm / Dx.
The relationship between the volume fraction and the density of the R-Fe-NHO-based material changes depending on the composition of the R-Fe-NHO-based material and the type of the portion other than the magnetic material. A magnetic material content of 80% by volume or more is required for a good magnet solid material, and 7.45 g / cm for a lightweight magnet solid material.³Since the following density is required, a more preferable solid material for a magnet contains an R-Fe-NHO-based magnetic material in an amount of 80 to 97% by volume and has a density of 6.15 to 7.45 g / cm.³Are in the range of
[0059]
More preferably, the range of the volume fraction of the R—Fe—N—H—O-based magnetic material or the density of the solid material for the magnet is 83 to 97% by volume for applications requiring thermal stability. Density 6.35 to 7.45 g / cm³Is selected, and in order to obtain a lightweight magnet having excellent mechanical strength, magnetic properties, and thermal stability, it is 85 to 96% by volume and has a density of 6.50 to 7.40 g / cm.³Is selected.
In the solid material for a magnet of the present invention, components other than the R—Fe—N—H—O based magnetic material have a density of 6.5 g / cm.³The following elements, compounds or mixtures thereof are preferred. Density 6.5 g / cm³If the magnetic material is an element exceeding the above, the density of the entire solid material for a magnet is 7.45 g / cm even if the volume fraction of the magnetic material is limited to 80%.³In many cases, the characteristics of the second aspect of the present invention, which is lightweight, cannot be utilized, which is not preferable.
[0060]
Density 6.5 g / cm³The following elements include Al, Ar, B, Be, Br, C, Ca, Cl, F, Ga, Ge, H, He, Kr, Mg, N, Ne, O, P, S, Se, Si, Te, Ti, V, Y, Zr and the like can be mentioned. In addition, these compounds, alloys, and a density of 6.5 g / cm³Even when the above elements are contained, the density of the compound or alloy is 6.5 g / cm such as Mn-Al-C or Al-Cu-Mg alloy.³The density is 6.5 g / cm in the following or a mixture such as Bi-Al having a volume ratio of 1: 1.³It is preferable to select the following.
The portion other than the R-Fe-NHO-based magnetic material has a density of 6.5 g / cm.³The following gases, for example, nitrogen gas, at least one of inert gases such as He, Ar, and Ne, and a reducing gas such as hydrogen gas and ammonia gas may be used. These solid materials for magnetic material-gas composite magnets are characterized by being lightweight.
[0061]
The portion other than the R—Fe—N—H—O based magnetic material has a density of 6.5 g / cm.³The following MgO, Al₂O₃, ZrO₂, SiO₂, Oxides such as ferrite, CaF₂, AlF₃Such as fluoride, carbide such as TiC, SiC and ZrC, Si₃N₄, ZnN, AlN, and the like, and a hydride, a carbonate, a sulfate, a silicate, a chloride, a nitrate, or a mixture thereof.
Among them, especially BaO.6Fe₂O₃System, SrO.6Fe₂O₃Magnetic properties and stability thereof can be improved by incorporating a hard magnetic ferrite such as a ferrite-based ferrite or a La-added ferrite, and in some cases, a Mn-Zn-based or Ni-Zn-based soft magnetic ferrite. These solid materials for magnetic material-inorganic composite magnets have high mechanical strength and are excellent in thermal stability and magnetic properties.
[0062]
Further, the portion other than the R—Fe—N—H—O based magnetic material has a density of 6.5 g / cm.³The following organic substances may be used. For example, heat-resistant thermoplastics such as polyamide, polyimide, polyphenylene oxide, wholly aromatic polyester, resins called engineering resins, liquid crystal polymers, epoxy resins, phenol-modified epoxy resins, unsaturated polyester resins, alkyd resins, and fluorine resins Alternatively, if it is an organic substance having a glass transition point, softening point, melting point, and decomposition point of 100 ° C or more, such as a thermosetting resin, an organosilicon compound such as silicone rubber, an organometallic compound such as a coupling agent or a lubricant, etc. It can be used as a component of the solid material for a magnet of the invention.
[0063]
However, the volume fraction is 20% or less, preferably 17% or less, more preferably 10% or less, and most preferably 5% or less, and is determined by the metal bond of the R—Fe—N—H—O-based magnetic material. It must not interfere with solidification. This solid material for a magnetic material-organic composite magnet is excellent in impact resistance in spite of its light weight. However, in a severe environment of high temperature and high humidity, it may be better not to use a solid material for a magnetic material-organic composite magnet.
[0064]
The portion of the solid material for magnets other than the R—Fe—N—H—O-based magnetic material of the present invention may simultaneously contain two or more of the above gases, inorganic substances, and organic substances. For example, a solid material for an R-Fe-NHO-based magnetic material-inorganic-organic composite magnet having an air gap and containing silica-dispersed silicone rubber, and a nitrogen gas as an inert gas in the gap And a solid material for R-Fe-NHO-based magnetic material-gas-inorganic-organic composite magnet containing silicone rubber in which silica is dispersed and utilizing the characteristics of each component, It is desirable to use them properly.
[0065]
By the way, among the solid materials for magnets of the present invention using the R—Fe—N—H—O based magnetic material, there is a material group having the following characteristic microstructure. It has a filling rate of 80% by volume or more and forms a continuous phase by connecting magnetic powders together, and at the same time, forms a continuous phase only with an oxygen-enriched amorphous portion. Has a structure in which the crystal phases existing in each of them are isolated from each other in the amorphous phase. It can be said that the crystal phase forms a kind of sea-island structure in which the crystal phase floats in the amorphous phase sea like an island.
The crystalline phase does not contain oxygen or contains less oxygen than the amorphous phase. Due to this tendency, the crystalline phase becomes a ferromagnetic phase having a particularly high magnetization, and the amorphous phase tends to be a low-magnetization phase including a non-magnetic phase or a paramagnetic substance. In addition, since the crystalline phase and the amorphous phase are firmly bonded and integrated to form the solid material for the magnet of the present invention, the mechanical strength is high, the magnetic properties, especially the squareness ratio, are high, and the magnetic properties are stable. In particular, the material has high coercive force stability.
[0066]
When the volume fraction of the R-Fe-NH-based or R-Fe-NHO-based crystal phase in this sea-island structure is 25% by volume or more, magnetization and (BH) max are large, so that it is practical. It is a target. It is preferably at least 50% by volume, more preferably at least 75% by volume. Of course, since both the sea (amorphous phase) and the island (crystal phase) form part of the R—Fe—N—H—O-based magnetic material of the present invention, both the sea and the island The value obtained by adding the volume fraction, and in some cases, the value obtained by adding the volume fraction of the M component, become the volume fraction of the R-Fe-NHO-based magnetic material with respect to the entire solid material for the magnet. .
When manufacturing a solid material for a magnet having the above structure, it is often necessary to control the shock wave pressure within a small range so that the amorphous phase does not decompose and the magnetic properties and stability thereof are deteriorated.
[0067]
The solid material for a magnet of the present invention has a residual magnetic flux density B at room temperature._r, Coercivity H at room temperature_cJ, Permeance coefficient P when used as a magnet_cAnd maximum operating temperature T_maxIs μ₀Is the vacuum permeability,
B_r≤μ₀H_cJ(P_c+1) (11000-50T_max) / (10000-6T)_max)
Is more desirable.
The above relational expression is an expression that determines a condition under which the magnet does not significantly demagnetize, and its meaning will be supplemented below. Here, the remarkable demagnetization refers to irreversible and large demagnetization, for example, demagnetization such that the irreversible demagnetization ratio exceeds -20% within 1000 hours.
[0068]
The H coordinate of the inflection point on the BH curve representing the change in magnetization with respect to the reverse magnetic field of the magnet is substantially H when the squareness ratio is approximately 100%._cJValue. If the operating point of the magnet comes to the high magnetic field side from the inflection point, it will be rapidly demagnetized and the performance of the magnet cannot be exhibited effectively, so the operating point should be on the low magnetic field side from the inflection point. is there. Therefore, the ratio of the magnetic flux density to the demagnetizing field, which is determined by the shape of the magnet, is defined as the internal permeance coefficient P_c0After assembling into a magnetic circuit or device as a magnet, the minimum permeance coefficient at each operating point determined by the magnitude of the reverse magnetic field applied to the magnet during operation is P_cAnd P_c0And P_cThe smaller value of P_cminIn this case, significant demagnetization occurs unless it is at least within the range of the following expression (1).
[0069]
(Equation 1)

[0070]
Equation (1) is a conditional equation at room temperature. At the temperature T ° C., the temperature coefficient of the residual magnetic flux density [α (B_r)], The temperature coefficient of the coercive force [α (H_cJ)] To rewrite the following equation (2) to determine the conditions under which no significant demagnetization occurs.
[0071]
(Equation 2)

[0072]
Where P_c0Is P_cIn the case where the magnetism is smaller and demagnetization occurs as soon as the magnetic field is removed even when magnetized, remarkable demagnetization can be avoided by installing a magnet in a yoke or the like before magnetizing, but at least ( 2) Unless the condition defined by the equation is satisfied, significant demagnetization due to the use of a magnet cannot be avoided.
Depending on the composition and temperature range of the R—Fe—N—H—O-based material, α (B_r), Α (H_cJ) Changes, but almost α (B_r) Is −0.06% / ° C., α (H_cJ) Is -0.5% / ° C. α (B_r) Compared to α (H_cJ) Has a larger absolute value and both values are negative values. Therefore, as T increases, the combination of positive values (B_r, H_cJArea) becomes smaller. Therefore, the magnet made of the solid material for a magnet of the present invention has a permeance coefficient P_c, The highest temperature T during operation_maxB in the range of equation (2) determined by_rAnd H_cJ, The demagnetization of the magnet can be reduced.
T = T in equation (2)_max, Α (B_r) = − 0.06, α (H_cJ) = − 0.5, and rearranged as shown in the following equation (3).
[0073]
(Equation 3)

[0074]
That is, when a magnet is used, B_r, H_cJ, P_c, T_maxIf satisfies the expression (3), it can be said that the magnet does not cause significant demagnetization. According to the equation (3), H_cJIs larger, B_rThe possible value of becomes larger. In order to obtain a magnet having high thermal stability and high magnetic properties, H_cJIs preferably more than 0.62 MA / m.
[0075]
In the solid material for a magnet of the present invention, the most preferable embodiment is a solid material for a magnet in which Br is increased by increasing the volume fraction of the magnetic material, specifically, Th.₂Zn₁₇An R—Fe—N—H—O-based magnetic material having a rhombohedral crystal having a crystal structure or the like or a crystal structure similar thereto is filled with a filling factor of 95% or more, preferably 98% or more, and most preferably 99% or more. By setting the density of the solid material for a magnet to 7.45 g / cm³Above, more preferably 7.50 g / cm³Above, most preferably 7.60 g / cm³As described above, a solid material for a magnet having a high maximum energy product (BH) max at room temperature is a solid material for a magnet having magnetic properties satisfying the expression (3) in an intended use environment.
[0076]
By the way, by increasing the volume fraction of the magnetic material, B_rThe maximum energy product at room temperature (BH)_maxEven if a solid material for magnets with high_maxIs higher than, for example, 100 ° C. and deviates from the range of the expression (3), the demagnetization becomes remarkable, and the volume fraction of the magnetic material becomes low and B_rIn some cases, the performance may not be different from that of a solid material for a magnet having a small size. That is, P_cAnd T_maxCombination and H of solid material for magnet_cJIn some cases, increasing the volume fraction of the R—Fe—N—H—O based magnetic material_rThere is no point in taking a big deal. Rather, the lower the volume fraction of the magnetic material, the lighter and more cost-effective solid material for the magnet.
[0077]
A specific example will be described. H_cJ= 0.62 MA / m, and using a R-Fe-N-HO-based magnetic powder as a raw material and using shock wave compression, a solid material for magnets having a volume fraction of almost 100% under certain conditions can be obtained. can do. B at this time_rExceeds 1.2T.
But P_c= 1, T_max= 100 ° C, from the equation (3), B_rDoes not need to be 0.99T or more. That is, in this case, B higher than 0.99T_rEven if it is a solid material for a magnet having a_rThe performance will be the same as that of a magnet with a. Therefore, the volume fraction of the magnetic material is rather reduced to about 83 to 85%, and B_rIt is preferable to use a magnet having a weight of about 0.99T and a magnet that is lightweight and inexpensive.
[0078]
The above is the minimum permeance coefficient determined by the magnet shape or magnetic circuit, operation, and B_r, H_cJ, Α (B_r), Α (H_cJ) Describes the thermal stability determined by the magnetic properties of the magnetic material, and is generally called the temperature characteristic of a magnet.
Another major cause of the decrease in thermal stability is that the magnetic powders are not sufficiently solidified by being bonded to each other by metal bonding. Originally, permanent magnets align the easy magnetization direction of the crystal to create a magnetostatic potential in the external world, but because they are magnetically non-equilibrium, the magnetic powders are sufficiently bonded and not fixed. Then, the direction of the easy magnetization direction is changed by rotating each magnetic powder in the matrix, and the stored magnetostatic energy is gradually reduced.
[0079]
For a material having a magnetic powder filling rate of less than 80%, for example, a bonded magnet, when the resin is softened or deteriorated at a high temperature of 100 ° C. or more, the above-described relaxation occurs relatively easily, resulting in remarkable demagnetization. . As the name implies, the bonded magnet is a magnet bonded by a binder, not a magnet solidified by metal bonding or ionic bonding. The lack of thermal stability can be said to be a problem due to this. On the other hand, in the material of the present invention, when the magnetic powder volume fraction is 80% or more, preferably 83% or more, more preferably 90% or more, and most preferably 95% or more, the magnetic powders are solidified by metal bonding. And such relaxation does not occur. As described above, in order to achieve satisfactory thermal stability at 100 ° C. or higher, it is necessary to set the lower and upper limits of the volume fraction of the magnetic material to specific ranges in accordance with the magnetic properties and use of the material. There is.
[0080]
The solid material for a magnet according to the present invention can provide a coercive force H when formed into a magnet without using a special method._cJIs 0.76 MA / m or more, and the squareness ratio B_r/ J_sIs 95% or more. Where J_sIs the saturation magnetization at room temperature, and in the present invention, it is the magnetization value when the external magnetic field is 1.2 MA / m.
For example, Sm₂Fe₁₇N₃H_0.1O_xSince the material has a nucleation type magnetic field reversal mechanism, the particle size and coercive force H_cJHave a relationship that is almost inversely proportional. When the particle size is less than 2 μm, the coercive force exceeds 0.76 MA / m. In this region, the magnetic powder tends to agglomerate as the particle size becomes smaller. The degree drops sharply and the squareness decreases.
[0081]
Sm with ball mill₂Fe₁₇N₃H_0.1An R—Fe—N—H—O-based magnetic material (oxygen content: 0.1 to 5 atomic%) obtained by pulverizing a coarse powder is subjected to magnetic field compression molding with an external magnetic field of 1.2 MA / m, and the filling rate is 80%. In the green compact of_cJExceeds 0.74 MA / m, the squareness ratio sharply decreases and H_cJIs 95% or less in a region of 0.76 MA / m or more.
When the solid material for a magnet according to the present invention is used, it is possible to make the structure finer when compacted by shock wave compression. Therefore, a compact having a high squareness ratio using a magnetic powder having a coercive force of less than 0.76 MA / m is used. A body is prepared, and this is compacted by shock wave compression and at the same time the coercive force is improved, so that a solid material for magnets having both a high squareness ratio and a high coercive force can be obtained. When the coercive force is in the range of 0.8 to 1.2 MA / m, the squareness ratio can be adjusted from 95% to almost 100% by adding a method of magnetic field orientation and components of the magnetic material. It is possible.
[0082]
Next, a method for producing the solid material for a magnet of the present invention, and in particular, a shock wave compression in which the solid material for a magnet of the present invention can be realized will be described. However, the production method of the present invention is not limited to this.
As a shock compression method using an underwater shock wave, the powder is compacted at the innermost portion of a double pipe, water is poured into an intermediate portion, an explosive is arranged on an outer peripheral portion, and the explosive is detonated. A method of introducing a shock wave into the water of the part, compressing the innermost powder, or compacting the powder into a closed container, putting it into the water, detonating the explosive in the water, the shock wave , The method of compressing the powder or the method disclosed in Japanese Patent No. 2951349 or Japanese Patent No. 3220212 can be selected. In either method, the following advantages of shock compression by underwater shock waves can be obtained.
[0083]
In the compression solidification step by the shock compression method of the present invention using underwater shock waves, the ultrahigh pressure shearing property and activation action of the shock waves induce the solidification action by the metallic bonding of the powder and the micronizing action of the structure, and the bulk It is possible to increase the coercive force together with the solidification. At this time, the duration of the shock pressure itself is longer than in the case of using a conventional shock wave, but the temperature rise due to the volume compression and the increase in entropy due to the nonlinear phenomenon of the shock wave disappears in a very short time (several μs or less). Decomposition and denitrification hardly occur. There is residual temperature even after compression using underwater shock waves. When the residual temperature is higher than the decomposition temperature (about 600 ° C. at normal pressure), decomposition of the R—Fe—N—H—O-based compound and the like is started, and the magnetic properties are deteriorated. However, in the case of underwater shock waves, it is much easier to keep the residual temperature low than in the case of conventional shock waves.
[0084]
That is, the underwater shock wave has the following characteristics.
(1) The pressure of the underwater shock wave is determined by the Hugonio relation between the explosive and the water, and the pressure P is roughly expressed by the following equation.
P = 288 (MPa) ｛(ρ / ρ₀)^7.25-1｝
From the above equation, when the underwater shock wave is used, the reference value ρ of the water density ρ₀Since the amount of increase in the pressure P with respect to the change with respect to the pressure is very large, an ultra-high pressure can be easily obtained by adjusting the amount of the explosive, and the temperature of the magnetic material at that time can be easily lowered to a lower temperature than in the case where a conventional shock wave is used. Will be retained.
(2) The duration of the impact pressure itself is long.
(3) The temperature rise of the magnetic material due to the increase in entropy based on the volume compression and the nonlinear phenomenon of the shock wave disappears in a very short time.
(4) The temperature of the magnetic material is rarely kept high thereafter, and is rarely kept long.
(5) The impact pressure is uniformly applied to the object to be compressed.
For the first time, due to these excellent characteristics of the underwater shock wave, the R-Fe-N-HO-based material does not undergo thermal decomposition and is easily compacted at high density.
Further, by performing compacting in a magnetic field, the axis of easy magnetization of the magnetic material powder can be aligned in one direction, and even if the obtained compact is solidified by impact compression solidification, the orientation is impaired. Instead, a solid material for magnets having magnetically uniaxial anisotropy can be obtained.
[0085]
In the present invention, the true density (for example, 7.7 g / cm) of the raw material magnetic powder is obtained by compression-solidification using an underwater shock wave having a shock wave pressure of 3 to 40 GPa.³), A solid material for magnets having a density exceeding 80% can be obtained. If the shock wave pressure is lower than 3 GPa, it is not always possible to obtain a solid material for a magnet having a filling factor exceeding 80%. On the other hand, if the shock wave pressure is higher than 40 GPa, decomposition products such as α-Fe decomposition phase are likely to be generated, which is not preferable. Further, when the R—Fe—N—H—O-based raw material magnetic powder of the present invention has an oxygen-enriched amorphous phase on the surface, the amorphous phase is not decomposed. It is preferable to set the following.
[0086]
When compression-solidification is performed using an underwater shock wave having a shock wave pressure of 3 to 40 GPa, a solid material for a magnet having a density exceeding 80% of the true density of the raw magnetic powder can be obtained with good reproducibility. In addition, when an underwater shock wave having a shock wave pressure of 6 to 40 GPa is used, a high-density solid material for a magnet having a filling rate exceeding 90% can be obtained. However, when a hard magnetic material such as a soft magnetic material, a rare earth-iron-boron magnetic material, and a solid component such as a non-magnetic phase are included in addition to the R-Fe-N-HO magnetic material, Is not determined only by the volume fraction of the R-Fe-NHO-based raw material magnetic powder with respect to the solid material for the magnet. However, in order to obtain a solid material for magnets having a volume fraction of R-Fe-N-H-O-based magnetic material of 50% by volume or more without decomposition, as in the above, water in a shock wave pressure range of 3 to 40 GPa is required. Shock waves need to be controlled. Also in this case, when the R-Fe-N-H-O-based raw material magnetic powder has the above-mentioned amorphous phase, it is preferable to control the shock wave pressure within a range of 3 to 30 GPa.
[0087]
Next, in the case of manufacturing a high-density solid magnet material according to the first aspect of the solid magnet material of the present invention, it is necessary to use an underwater shock wave having a shock wave pressure of 8 to 40 GPa. When the shock wave pressure is lower than 8 GPa, the density is not necessarily 7.45 g / cm.³The above bulk magnet cannot be obtained. If the shock wave pressure is higher than 40 GPa, decomposition products such as α-Fe decomposition phase may be generated, which is not preferable. Further, when the R—Fe—N—H—O-based raw material magnetic powder of the present invention has an oxygen-enriched amorphous phase on the surface, the amorphous phase is not decomposed. It is preferable to set the following.
[0088]
Furthermore, in the second embodiment of the present invention, when manufacturing a solid material for a magnet that is lightweight and has excellent high-temperature characteristics, in order to suppress the temperature rise of the green compact during impact compression, it is necessary to use impact compression. It is preferable to use an underwater shock wave having a shock wave pressure of 3 to 22 GPa. If the shock wave pressure is lower than 3 GPa, the density is not necessarily 6.15 g / cm.³The above solid material for magnets cannot be obtained. When the shock wave pressure is higher than 22 GPa, the density is 7.45 g / cm.³In many cases, the above-mentioned solid material for magnets is used, and when the shock wave pressure is higher than 40 GPa, decomposition products such as α-Fe decomposition phase may be generated, which is not preferable. Similarly to the above, when the R—Fe—N—H—O-based raw material of the present invention has an oxygen-enriched amorphous phase on the surface, the shock wave pressure is preferably set to 30 GPa or less.
[0089]
In addition, the density is 6.35 to 7.45 g / cm.³Range, and further 6.50 to 7.40 g / cm³In order to obtain a solid material for a magnet with good reproducibility, the shock wave pressure of the underwater shock wave is 3 to 20 GPa, and the shock wave pressure is 4 to 15 GPa. However, in the case of a solid material for a magnetic material-gas composite magnet, if the impact pressure is too high, the density can easily be 7.45 g / cm.³Therefore, it is preferable to use an underwater shock wave having a shock wave pressure of 3 to 15 GPa.
Although it has already been stated that it is important to introduce an oxygen component and a hydrogen component by bringing an oxygen source or a hydrogen source and an oxygen source into contact with each other in a method for producing an R—Fe—N—H-based magnetic material, It is also effective to use a method in which an oxygen source or a hydrogen source is present and brought into contact with a compression atmosphere to form a magnet solid material having a desired composition.
[0090]
In the method for producing a solid material for a magnet of the present invention, in order to impart anisotropy to the solid material for a magnet, compacting of the raw material powder can be performed in a magnetic field, and the raw material powder is compacted. Thereafter, it can be subjected to shock compression solidification using an underwater shock wave. Further, after the raw material powder is compacted in a magnetic field, it can be subjected to impact compression and solidification using underwater shock waves.
As described above, an R-Fe-NHO-based material containing hydrogen, which is thermally stable and hardly precipitates an α-Fe decomposition phase as a magnetic powder, is selected, and is subjected to the underwater shock wave compression solidification method. By solidifying, the solid material for magnet of the present invention can be produced for the first time.A magnet manufactured using this solid material for magnet has high magnetic properties, excellent oxidation resistance, and is similar to a bonded magnet. It does not contain a resin component as a binder for magnetic powder, so that it has excellent heat stability.
[0091]
Next, a component or an apparatus including a solid material for an R-Fe-NHO-based magnet according to a third embodiment of the present invention will be described.
For applications where the maximum use temperature Tmax is 100 ° C. or higher, conventional R—Fe—N—H—O bond magnets contain resin components and magnetic powders are not solidified by metal bonding. In addition, heat stability was inferior, and it was difficult to use. The solid material for a magnet of the present invention is excellent in thermal stability because the R-Fe-NHO-based magnetic powders are solidified by metal bonding even if they contain a resin component. Furthermore, B of solid material for magnet_r, H_cJIs the magnet P_cAnd T_maxAnd in the region defined by the formula (3), a magnet that does not greatly demagnetize, is lightweight, has high cost performance, and has even more excellent thermal stability can be obtained.
T_maxThe upper limit is near the Curie point of R—Fe—N—H—O-based material, which exceeds 400 ° C., but depends on the composition and components of the solid material for magnets and the way in which it is used as a magnet._maxThe upper limit takes various values of 400 ° C. or less. For example, H coated with Zn_cJ= 1.6 MA / m, even if an R-Fe-NHO-based material having_maxWhen is higher than 220 ° C., it is not preferable to use the solid material for a magnet of the present invention as a magnet.
[0092]
P of the magnet obtained from the solid material for a magnet of the present invention_c0Is from 0.01 to 100, more preferably from 0.1 to 10,_c0, B_r, H_cJIf the combination of the values deviates from the range of the expression (1), a yoke is attached and then P_c0It is preferable to perform the magnetization after increasing the value.
[0093]
Various actuators, voice coil motors, and the like, using the static magnetic field of a magnet obtained from the solid material for a magnet of the present invention, in particular, the solid material for a magnet according to the second embodiment, or the solid material for a magnet satisfying the expression (3). Linear motors, motors for rotating machines as rotors or stators, of which motors for industrial machines and automobiles in particular, magnetic field sources for medical equipment and metal sorting machines, as well as magnetic field generators for analyzers such as VSM devices, ESR devices and accelerators Equipment and parts such as OA equipment such as source, magnetron traveling wave tube, printer head and optical pickup, undulator, wiggler, retarder, magnet roll, magnet chuck, various magnet sheets, etc._cExcept for special applications such as extremely small stepping motors, it can be used stably even in an environment of 100 ° C. or more without significant demagnetization.
[0094]
Depending on the application, it can be used at a temperature of 125 ° C. or higher._cJ> 0.7 (MA / m) and P_c> 1. Further, it can be used at 150 ° C. or higher._cJ> 0.8 (MA / m) and P_c> 2.
In addition, when used in these devices or parts, the solid material for the magnet of the present invention is subjected to various processes, and then the yokes and hole pieces of various shapes, various magnetic shunt materials are bonded, adhered, joined and used in combination. May be.
When the solid material for a magnet of the present invention is used as a rotor for a permanent magnet synchronous motor or as a hard magnetic material of its constituent material, the surface magnet structure rotor of the present invention has a rotating shaft cross section shown in FIGS. It can be structured. In addition, the embedded magnet structure rotor may have a rotating shaft sectional structure shown in FIGS.
[0095]
Hereinafter, the present invention will be described based on examples. The degree of decomposition of the R—Fe—N—H—O-based magnetic material was determined based on the X-ray diffraction diagram (Cu-Kα ray) of the molded solid material for magnets based on Th.₂Zn₁₇The ratio of the height b of the diffraction line derived from the α-Fe decomposition phase around 2θ = 44 ° to the height a of the strongest line in the diffraction line derived from the rhombohedral or hexagonal crystal structure including the type b / The judgment was made based on a. If this value is 0.2 or less, it can be said that the degree of decomposition is small. Preferably it is 0.1 or less. More preferably, it is 0.05 or less. In this case, it can be said that there is almost no decomposition.
However, in the above-described determination method, a material having a peak near 44 °, such as an Fe soft magnetic material, is originally contained in the R—Fe—N—H—O-based magnetic material that is a raw material of the solid material for the magnet. If not applicable. In this case, it is possible to use the relative ratio of b / a between the raw material containing the R—Fe—N—H—O based magnetic material and the solid material for the magnet as a measure of the presence or absence of decomposition.
The technical scope of the present invention is not limited by the following specific examples.
[0096]
[Example 1]
Sm with an average particle size of 60 μm₂Fe₁₇Master alloy with NH₃Partial pressure 0.35atm, H₂Oxygen partial pressure of 10 with a partial pressure of 0.65 atm^{− 3}After performing a hydrogenation of 7.2 ks at 465 ° C. in an ammonia-hydrogen mixed gas stream of atm^-51.8 ks annealing was performed in an atm argon stream, and a hydrocarbon solvent having a dissolved oxygen content of 40 ppm and a water content of 20 ppm was used as a grinding solvent.^-1The resulting mixture was pulverized by a ball mill charged in a nitrogen stream of atm so as to have an average particle diameter of about 2 μm to obtain an R-Fe-NHO-based magnetic material powder. This powder was compacted while performing magnetic field orientation in a magnetic field of 1.2 MA / m to obtain a compact. FIG. 13 is an explanatory diagram showing an example of an apparatus for performing a shock compression method using underwater shock waves. The obtained compact was put in a copper pipe 1 and fixed to a copper plug 2 as shown in FIG. Further, the copper pipe 3 is fixed to the copper plug 2, the gap is filled with water, a uniform gap is provided on the outer periphery, the paper cylinder 4 is arranged, and 280 g is inserted into the gap between the copper pipe 3 and the paper cylinder 4. Was charged, and the explosive was detonated from the detonating section 6 to detonate the explosive. At this time, the shock wave pressure was 16 GPa.
[0097]
Sm in which the volume fraction of the R-Fe-NHO-based magnetic material solidified from the pipe 1 after the impact compression is 100%_8.5Fe_72.3N_12.7H_2.8O_3.7The solid material for a magnet having a composition was taken out, magnetized with a pulse magnetic field of 4.0 MA / m, and the magnetic properties were measured._r= 1.18T, coercive force H_cJ= 0.78 MA / m, (BH)_max= 264 kJ / m³Was obtained. Also, as a result of measuring the density by the Archimedes method, the density was 7.60 g / cm.³And the filling factor was 99%.
[0098]
Further, as a result of analysis by the X-ray diffraction method, the solidified solid material for the magnet hardly caused precipitation of the α-Fe decomposition phase, and Th₂Zn₁₇It was confirmed to have a rhombohedral crystal structure.
The same experiment was repeated many times by adjusting the amount of explosive.
When the shock wave pressure is lower than 4 GPa, the filling rate of the obtained solid material for magnet does not necessarily exceed 80%, and when the shock wave pressure is higher than 30 GPa, it is confirmed that decomposition products such as α-Fe decomposition phase are generated. It was also found that the shock wave pressure is preferably set to 3 to 30 GPa in order to obtain a magnet solid material having a filling factor of more than 80% with higher reproducibility. Further, it was also confirmed that by setting the shock wave pressure to 6 to 30 GPa, a solid material for a magnet having a filling factor of more than 90% can be obtained with good reproducibility.
[0099]
Also, the shock wave pressure has a density of 6.15 to 7.45 g / cm.³It was also found that the shock wave pressure is preferably set to 3 to 15 GPa in order to obtain the solid material for magnet with good reproducibility.
Further, the density is 7.45 g / cm.³It has also been found that it is preferable to set the shock wave pressure to 10 to 30 GPa in order to obtain a bulk magnet with a reproducibility of more than 0.1. At a shock wave pressure of 12 to 30 GPa, the density is 7.55 g / cm.³It has also been confirmed that bulk magnets exceeding the above can be obtained with good reproducibility.
[0100]
[Comparative Example 1]
Sm with an average particle size of 20 μm₂Fe₁₇Mother alloy N₂The same as in Example 1 except that the nitriding was performed at 495 ° C. for 72 ks in a gas stream, except that the shock wave pressure was set to 18 GPa._9.1Fe_77.7N_13.2A solid material for a magnet having the following composition was produced.着 As a result of magnetizing this solid material for a magnet with a pulse magnetic field of 4.0 MA / m and measuring the magnetic properties, the residual magnetic flux density B_r= 0.96 T, coercive force H_cJ= 0.36 MA / m, (BH)_max= 120kJ / m³Was obtained. The result of measuring the density by the Archimedes method was 7.50 g / cm.³Met.
The X-ray diffraction diagram of this material shows Th₂Zn₁₇In addition to the crystal structure of the rhombohedral crystal, diffraction lines derived from the α-Fe decomposition phase were also observed. Diffraction line of α-Fe decomposition phase at around 44 ° and Th₂Zn₁₇The intensity ratio b / a with the (303) strongest line indicating the crystal structure of the rhombohedral crystal was 0.21.
[0101]
[Comparative Example 2]
FIG. 14 is an explanatory diagram showing an example of an apparatus for performing impact compression by directly using the detonation wave of an explosive. Using this apparatus, the R—Fe—N—H—O-based magnetic powder having an average particle diameter of 2 μm obtained in Example 1 was put in a copper pipe 1 and fixed to a copper plug 2, and a uniform gap was formed around the outer periphery. The paper cylinder 4 was arranged, the same amount of the ammonium nitrate explosive 5 as in the example was loaded in the gap, and the explosive was detonated from the detonating section 6 to detonate the explosive. After the impact compression, a solidified sample was taken out of the pipe 1 and analyzed by an X-ray diffraction method. As a result, it was confirmed that SmN and a large amount of α-Fe decomposition phase were formed after the impact compression. It was found that the Fe-NHO compound was decomposed. At this time, the intensity ratio b / a of the diffraction lines was about 3.
[0102]
[Example 2]
A predetermined amount of Sm and Fe metal powder (weight ratio 16.85: 83.15) was subjected to mechanical alloying treatment for 180 ks by a vibrating ball mill using agate balls, and then 10^-5Heat treatment was performed at 600 ° C. for 7.2 ks in a vacuum of atm or less. This powder contained about 30% by volume of Fe soft magnetic material. This powder is converted into NH₃Partial pressure 0.35atm, H₂Oxygen partial pressure 10 with a partial pressure of 0.65 atm^{− 3}Hydrogen nitride treatment was performed at 380 ° C. and 1.2 ks in an ammonia-hydrogen mixed gas stream of atm or less, and then heat treatment was performed in hydrogen at the same temperature for 300 s. Using this powder, as in Example 1, except that the shock wave pressure was set to 18 GPa,_5.9Fe_78.5N_8.8H_3.0O_3.8A solid material for a magnet having the following composition was produced.
[0103]
As a result of magnetizing this solid material for a magnet with a pulse magnetic field of 4.0 MA / m and measuring the magnetic properties, the residual magnetic flux density B_r= 1.22T, coercive force H_cJ= 0.43 MA / m, (BH)_max= 215kJ / m³Was obtained. In addition, the result of measuring the density by the Archimedes method was 7.74 g / cm.³Met.
The X-ray diffraction diagram of this material shows Th₂Zn₁₇Diffraction lines derived from α-Fe were also observed in addition to the crystal structure of the rhombohedral crystal. However, since this material was originally a material containing an Fe soft magnetic material that was not an α-Fe decomposition phase, it was decomposed by solidification. Whether or not a phase had occurred could not be determined exactly by X-ray diffraction. As a result of observation by a transmission electron microscope, the volume fraction of the Fe soft magnetic phase was about 30%, the crystal grain size was about 10 to 50 nm, and the R-Fe-N-H-O-based magnetic material was A solid material for magnets having a volume fraction of about 70% was obtained.
[0104]
[Example 3]
R-Fe-NHO-based powder having an average particle size of about 2 μm obtained in Example 1 and an Sm composition having an average particle size of about 25 μm_11.5Co_57.6Fe_24.8Cu_4.4Zr_1.7Was charged into an agate mortar at a volume ratio of 50:50 and wet-mixed in cyclohexane having a dissolved oxygen content of 40 ppm and a water content of 30 ppm. This operation is performed with oxygen partial pressure^-1Performed in glove box of atm.
Using this mixed powder, in the same manner as in Example 1, except that the shock wave pressure was set to 14 GPa, the R-Fe-N-O-based magnetic material having a 50% volume fraction of R-Fe-N- A solid material for an HO-based magnet (oxygen content: 1.7 atomic%) was produced. As a result of magnetizing this solid material for a magnet with a pulse magnetic field of 4.0 MA / m and measuring the magnetic properties, the residual magnetic flux density B_r= 1.08T, coercive force H_cJ= 0.85 MA / m, (BH)_max= 215kJ / m³Met.
[0105]
[Example 4]
A Sm-Fe-Co-N-HO magnetic material having an average particle size of about 1 μm, in which a surface of an R-Fe-NHO-based magnetic material is coated with Zn metal by a known photolysis method using diethylzinc. A powder was prepared, and this powder was used in the same manner as in Example 1 except that the shock wave pressure was set to 16 GPa so that the volume fraction of the R—Fe—N—H—O-based magnetic material was 100%. Some Sm_8.2Fe_62.6Co_6.9N_12.2H_3.3O_3.8Zn_3.0A solid material for a magnet having the following composition was produced.
As a result of magnetizing this solid material for a magnet with a pulse magnetic field of 4.0 MA / m and measuring the magnetic properties, the residual magnetic flux density B_r= 1.24T, coercive force H_cJ= 0.79 MA / m, (BH)_max= 263 kJ / m³Met. The density is 7.71 g / cm³Met. Furthermore, as a result of the analysis by the X-ray diffraction method, the solidified solid material for the magnet is Th₂Zn₁₇It was confirmed to have a rhombohedral crystal structure. Diffraction line of α-Fe decomposition phase at around 44 ° and Th₂Zn₁₇The intensity ratio b / a with the (303) strongest line indicating the crystal structure of the rhombohedral crystal was 0.08.
[0106]
[Example 5]
As an R-Fe-NHO-based magnetic material, Sm-Fe-Co-Mn having a pinning type magnetization reversal mechanism and having an average particle diameter of 30 µm, which was obtained by a known method (Japanese Patent Application Laid-Open No. 8-55712). As in Example 1 except that the shock wave pressure was set to 14 GPa using the -NHO magnetic powder, the volume fraction of the R-Fe-NHO-based magnetic material was 100%. Yes, Sm_8.5(Fe_0.89Co_0.11)_66.6Mn_3.6N_18.5H_2.6O_0.2A solid material for a magnet having the following composition was produced. As a result of magnetizing this solid material for a magnet with a pulse magnetic field of 4.0 MA / m and measuring the magnetic properties, the residual magnetic flux density B_r= 1.08T, coercive force H_cJ= 0.39 MA / m, (BH)_max= 128kJ / m³Met. The density determined by the volume method was 7.70 g / cm3. Further, the X-ray diffraction diagram of this material shows that Th₂Zn₁₇In addition to the crystal structure of the rhombohedral crystal, diffraction lines derived from the α-Fe decomposition phase were also observed. Diffraction line of α-Fe decomposition phase at around 44 ° and Th₂Zn₁₇The intensity ratio b / a with the (303) strongest line indicating the crystal structure of the rhombohedral crystal was 0.06.
[0107]
[Example 6]
Components other than the R—Fe—N—H—O based magnetic material are Al₂O₃The R-Fe-NHO-based magnetic material prepared in Example 1 was blended so that the volume fraction was 96%, and a solid material for a magnet in which the mixed powder was reduced in Example 1 was used. It was produced in the same manner as described above. However, the shock wave pressure was 15 GPa. Then, it is magnetized with a pulse magnetic field of 4.0 MA / m, and B_r, H_cJ, Squareness ratio B_r/ J_s, (BH)_maxWas measured.
The results are shown in Table 1. Holding force H_cJIs 0.83 MA / m, which is a large value, and a squareness ratio of 96% can be obtained.
[0108]
[Examples 7 to 9]
A solid material for a magnet was prepared in the same manner as in Example 1 except that the components other than the R—Fe—N—H—O-based magnetic material and the shock wave pressure were as shown in Table 1. Similarly, their various magnetic properties were measured. The results are shown in Table 1.
[0109]
[Examples 10 and 11 and Comparative Example 3]
Sm with an average particle size of 2.5 μm_8.7Fe_74.1N_13.1H_1.1O_3.0Volume of the R—Fe—N—H—O-based magnetic material in the same manner as in Example 1 except that the magnetic powder was used and the shock wave pressure was 3 GPa (Example 10) and 23 GPa (Example 11). A solid material for a magnet having a fraction of 100% was produced. The magnetic properties of these magnet solid materials were measured in the same manner as in Example 1. The results are shown in Table 2.
Further, these solid materials for magnets are machined into disks of exactly the same shape, magnetized with a pulse magnetic field of 4.8 MA / m, and_c0Was 2 magnets. These magnets were allowed to stand for 3.6 Ms in a thermostat at 125 ° C., taking care not to apply a reverse magnetic field as much as possible. The value of the magnetic flux before and after standing in the thermostat was measured using a sample withdrawing magnetic flux measuring device, and the rate of change of the magnetic flux, that is, the irreversible demagnetization rate (%) was determined. The results are shown in Table 2. It can be determined that the smaller the absolute value of the irreversible demagnetization rate, the better the thermal stability. In addition, the volume fraction of the R—Fe—N—H—O-based magnetic material is set to 60% by a known method._c0The irreversible demagnetization rate was determined in the same manner as above for an injection-molded bonded magnet (Comparative Example 3) which was not a solid material for a magnet and used 12-nylon as a binder. The results are shown in Table 2.
The result obtained by the above evaluation is P_cIs P_c0Equal to T_maxConsidering an application where = 125 ° C., it is suitable for examining the degree of demagnetization before and after operation or use.
[0110]
As shown in Table 2, as in Comparative Example 3, in the magnet which was not a solid material for a magnet of the present invention, extremely low thermal stability was exhibited because the magnetic powders were not solidified by metal bonding. .
Similarly, it was found that the solid material for magnets of Example 10 exhibited high thermal stability because the magnetic powder was bonded to each other by metal bonding or ionic bonding because the filling rate was 80% or more. Also, in the embodiment in which the magnetic powders are solidified by metal bonding, P_c, T_max, B_r, H_cJHowever, the thermal stability of Example 10 which is a lightweight solid material for magnets satisfying the expression (3) was better than that of Example 11 which did not satisfy the expression (3).
[0111]
[Examples 12 and 13]
A brushed DC motor was assembled as a stator by fixing the two magnets of Example 10 without using a yoke, and was operated for 36 ks in an environment at 100 ° C. while applying a certain amount of power to the coil (implementation). Example 12). A motor was assembled and operated in the same manner as described above using the magnet of Example 11 (Example 13). The rotation speed after 36 ks changes by about 2% in the motor of the twelfth embodiment and by about 10% in the motor of the thirteenth embodiment as compared to immediately after the initial rotation speed is stabilized, and both rotation speeds after 36 ks are approximately 510 rpm. It was equivalent. The magnet of the tenth embodiment used in the motor of the twelfth embodiment has a density 17% lower than the magnet of the eleventh embodiment used in the motor of the thirteenth embodiment, and the volume of the R—Fe—N—H—O-based magnetic material. Despite the low fraction, the performance with the above motor was the same.
[0112]
[Example 14]
In Example 10, components other than the R—Fe—N—H—O-based magnetic material were replaced with ZrO.₂Similarly, except that the shock wave pressure is set to 14 GPa, the volume fraction of the R—Fe—N—H—O-based magnetic material is 95%, and the density is 7.38 g / cm.³And a motor was assembled in the same manner as in Example 12 and operated under a 100 ° C. environment. As a result, a result equivalent to that of Example 12 was obtained.
[0113]
[Example 15]
Using an R-Fe-NHO-based HDDR isotropic magnetic powder having an average particle diameter of 30 µm manufactured by a known method, as in Example 1, R-Fe-N-HO was used. Sm having a volume fraction of 100% based magnetic material_8.3Fe_76.1B_0.9Ti_2.4N_12.0H_0.1O_0.2A solid material for a magnet having the following composition was produced.
As a result of magnetizing this solid material for a magnet with a pulse magnetic field of 4.0 MA / m and measuring the magnetic properties, the residual magnetic flux density B_r= 0.70T, coercive force H_cJ= 1.05 MA / m, (BH)_max= 75.4kJ / m³Was obtained. Moreover, the result of measuring the density by the Archimedes method was 7.45 g / cm.³Met.
In the X-ray diffraction diagram of this material, diffraction lines derived from the α-Fe decomposition phase were observed in addition to the rhombohedral and hexagonal crystal structures, and the ratio b / a was 0.15.
[0114]
[Example 16]
Sm with an average particle size of 60 μm₂Fe₁₇Master alloy with NH₃Partial pressure 0.35atm, H₂Oxygen partial pressure of 10 with a partial pressure of 0.65 atm^{− 3}After performing a hydrogenation of 7.2 ks at 465 ° C. in an ammonia-hydrogen mixed gas stream of atm^-3The annealing was performed in an argon gas flow of atm for 7.2 ks, using a hydrocarbon solvent having a dissolved oxygen content of 45 ppm and a water content of 20 ppm as a grinding solvent.^-1It was pulverized by a ball mill charged in a nitrogen stream of atm so that the average particle size became about 2 μm. Using this powder, as in Example 1, except that the shock wave pressure was 25 GPa and the volume fraction of the R-Fe-NHO-based magnetic material was 100%._8.0Fe_67.8N_11.9H_2.6O_9.7A solid material for a magnet having a composition was obtained. At this time, the inside of the copper pipe 1 holding the compact was filled with a humid atmosphere. The solid material for a magnet was magnetized with a pulse magnetic field of 4.0 MA / m, and the magnetic properties were measured._r= 1.06T, coercive force H_cJ= 0.73 MA / m, (BH)_max= 158kJ / m³Was obtained. The density was measured by the Archimedes method. As a result, the density was 7.55 g / cm.³And the filling factor was 99%.
[0115]
Further, as a result of analysis by the X-ray diffraction method, the solidified solid material for the magnet hardly caused precipitation of the α-Fe decomposition phase, and Th₂Zn₁₇It was confirmed to have a rhombohedral crystal structure.
After mirror polishing the sample surface, the sample surface was corroded with a 5% nital etchant for 30 seconds, and observed by FE-SEM. It was found that it had a two-phase structure with the part. Observation of the crystal orientation of each part by EBSP revealed that the granular part was Th₂Zn₁₇A crystal structure of a rhombohedral crystal was observed, and the other parts were confirmed to be amorphous. From the area ratio of the observed cross section,₂Zn₁₇It was found that a rhombohedral part (crystal phase) to an amorphous part (amorphous phase) existed at a volume ratio of 6: 4.
[0116]
[Table 1]

[0117]
[Table 2]

[0118]
【The invention's effect】
As in the present invention, a rare earth-iron-nitrogen-hydrogen-oxygen-based magnetic powder or the like having a rhombohedral or hexagonal crystal structure is compacted and subjected to shock compression using an underwater shock wave, thereby obtaining a binder. This makes it possible to obtain a high-density, high-performance solid material for magnets without the necessity of self-sintering and by preventing decomposition and denitrification. Furthermore, it is possible to obtain a solid material for a magnet which is lightweight, yet has high performance, particularly high stability of magnetic properties.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an example of a cross section of a solid material for a magnet obtained by joining and integrating a rare earth-iron-nitrogen-hydrogen-oxygen-based magnetic material and a soft magnetic solid metal.
FIG. 2 is an explanatory view showing an example of a cross section of a solid material for a magnet in which rare earth-iron-nitrogen-hydrogen-oxygen-based magnetic material layers and soft magnetic layers are alternately laminated and integrated.
FIG. 3 is a view showing an example of a cross section of a solid material for a magnet in which a part or the entire periphery of a layer mainly containing a rare earth-iron-nitrogen-hydrogen-oxygen-based magnetic material is covered with a nonmagnetic solid material. FIG.
FIG. 4 is an explanatory view showing an example of a cross section of a solid material for a magnet.
FIG. 5 is an example of a sectional structure of a rotating shaft of a surface magnet structure rotor when the solid magnet material of the present invention is used for a permanent magnet synchronous motor.
FIG. 6 is an example of a sectional structure of a rotating shaft of a surface magnet structure rotor when the magnet solid material of the present invention is used for a permanent magnet synchronous motor.
FIG. 7 is an example of a rotating shaft sectional structure of an embedded magnet structure rotor when the magnet solid material of the present invention is used for a permanent magnet synchronous motor.
FIG. 8 is an example of a rotating shaft sectional structure of an embedded magnet structure rotor when the magnet solid material of the present invention is used for a permanent magnet synchronous motor.
FIG. 9 is an example of a rotating shaft cross-sectional structure of an embedded magnet structure rotor when the magnet solid material of the present invention is used for a permanent magnet synchronous motor.
FIG. 10 is an example of a rotary shaft cross-sectional structure of an embedded magnet structure rotor when the magnet solid material of the present invention is used for a permanent magnet synchronous motor.
FIG. 11 is an example of a rotating shaft cross-sectional structure of an embedded magnet structure rotor when the magnet solid material of the present invention is used for a permanent magnet synchronous motor.
FIG. 12 is an example of a rotating shaft cross-sectional structure of an embedded magnet structure rotor when the magnet solid material of the present invention is used for a permanent magnet synchronous motor.
FIG. 13 is an explanatory diagram showing an example of a means for performing a shock compression method using an underwater shock wave.
FIG. 14 is an explanatory view showing an example of a means for performing a shock compression method directly using a detonation wave of an explosive used in a comparative example.
[Explanation of symbols]
1 Copper pipe (used to hold powder)
2 copper plug
3 copper pipe (used to hold water)
4 paper cylinder (used to hold explosives)
5 explosives
6 Initiator
7 water
8 Sample part (sample containing rare earth-iron-nitrogen-hydrogen-oxygen based magnetic material)

Claims (16)

A solid material for a magnet containing 50 to 100% by volume of a rare earth-iron-nitrogen-hydrogen-oxygen magnetic material. The solid material for a magnet according to claim 1, comprising a rare earth-iron-nitrogen-hydrogen-oxygen-based magnetic material having a rhombohedral or hexagonal crystal structure. Rare earth - iron - nitrogen - hydrogen - oxygen-based magnetic material has the general formula _{R α Fe 100- α - β -} γ - expressed in _{δ N β H γ O δ,} R is at least one element selected from rare earth elements And α, β, γ, and δ are atomic percentages and satisfy 3 ≦ α ≦ 20, 5 ≦ β ≦ 25, 0.01 ≦ γ ≦ 5, 0.01 ≦ δ ≦ 10. Solid material for magnets. Rare earth - iron - nitrogen - hydrogen - oxygen-based magnetic material has the general formula _{R α Fe 100- α - β -} γ - expressed in _{δ N β H γ O δ M} ε, R is selected from rare earth elements including Y At least one element, M is Li, Na, K, Mg, Ca, Sr, Ba, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Pd, Cu, Ag, Zn , B, Al, Ga, In, C, Si, Ge, Sn, Pb, Bi, at least one element and / or oxide, fluoride, carbide, nitride, hydride, carbonate, sulfuric acid of R At least one selected from salts, silicates, chlorides, and nitrates, and α, β, γ, δ, and ε are mole percentages, 3 ≦ α ≦ 20, 5 ≦ β ≦ 30, 0.01 ≦ 3. The structure according to claim 1, wherein γ ≦ 10, 0.01 ≦ δ ≦ 10, and 0.1 ≦ ε ≦ 40. Solid material for a magnet according. Rare earth - iron - nitrogen - hydrogen - oxygen-based one solid material for a magnet of claims 1 to 4 having a density greater than 6.15 g / cm ³ containing a magnetic material. Rare earth - iron - nitrogen - hydrogen - oxygen-based magnetic materials other than component density 6.5 g / cm ³ or less elements, compounds or solid material for a magnet of claim 5, characterized in that a mixture thereof. When the relationship among the residual magnetic flux density B _r at room temperature, the coercive force H _{cJ at} room temperature, the permeance coefficient P _c when used as a magnet, and the maximum use temperature T _max is, when μ ₀ is the magnetic permeability of vacuum,
_{B r ≦ μ 0 H cJ (} P c +1) (11000-50T max) / (10000-6T max)
The solid material for a magnet according to any one of claims 1 to 6, wherein A soft magnetic material containing at least one element selected from the group consisting of Fe, Co, and Ni is uniformly dispersed and integrated with the rare earth-iron-nitrogen-hydrogen-oxygen-based magnetic material. 7. The solid material for a magnet according to any of 7. Rare earth-iron-boron based magnetic material, rare earth-cobalt based magnetic material, at least one magnetic material selected from ferrite based magnetic material is uniformly added and mixed with the rare earth-iron-nitrogen-hydrogen-oxygen based magnetic material, The solid material for a magnet according to any one of claims 1 to 8, wherein the solid material is integrated. The solid material for a magnet according to any one of claims 1 to 9, wherein a non-magnetic phase exists at a grain boundary of the magnetic material. A solid material for a magnet, wherein the solid material for a magnet according to any one of claims 1 to 10 and a soft magnetic solid metal material are joined and integrated. A solid material for a magnet, comprising a soft magnetic layer, wherein the soft magnetic layer and the solid material for a magnet according to any one of claims 1 to 11 are alternately laminated and integrated. 13. A solid material for a magnet, wherein at least a part of the solid material for a magnet according to claim 1 is covered with a non-magnetic solid material. The solid material for a magnet according to any one of claims 1 to 13, wherein the solid material is shaped into a prism, a cylinder, a ring, a disk, or a flat plate. The method for producing a solid material for a magnet according to any one of claims 1 to 14, wherein the raw material powder of the rare earth-iron-nitrogen-hydrogen-oxygen-based magnetic material is subjected to impact compression and solidification using an underwater shock wave. The method for producing a solid material for a magnet according to any one of claims 1 to 14, comprising a step of heat-treating the material at least once at a temperature of 100 ° C or higher and lower than a decomposition temperature. Manufacturing method.

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