JP3736830B2

JP3736830B2 - Rare earth-Fe-Co-B magnet powder and bonded magnet excellent in squareness and thermal stability

Info

Publication number: JP3736830B2
Application number: JP06995299A
Authority: JP
Inventors: 永一郎新妻; 耕一郎森本; 武昭増尾
Original assignee: Mitsubishi Materials Corp
Current assignee: Mitsubishi Materials Corp
Priority date: 1999-03-16
Filing date: 1999-03-16
Publication date: 2006-01-18
Anticipated expiration: 2019-03-16
Also published as: JP2000269014A

Description

【０００１】
【発明の属する技術分野】
この発明は、従来よりも角形性および熱的安定性に優れたＲ（但し、Ｒは、Ｙを含む希土類元素のうち少くとも１種を示す），Ｆｅ，Ｃｏ，およびＢを主成分とするＲ−Ｆｅ−Ｃｏ−Ｂ系磁石粉末およびこの粉末を用いたボンド磁石に関するものである。
【０００２】
【従来の技術】
Ｒ−Ｆｅ−Ｃｏ−Ｂ系磁石粉末は高い磁気特性および比較的安定な温度特性を有するところから、これを樹脂結合してボンド磁石を作製している。このボンド磁石は、寸法精度が高いこと、薄肉で複雑形状の磁石を容易に製造できること、他の部品との一体成形が可能であることなどの特徴を有することから、ＯＡ、ＦＡ機器などの小型モーターなど各種部品として広く使用されている。
【０００３】
前記Ｒ−Ｆｅ−Ｃｏ−Ｂ系磁石粉末を製造する方法の一つとして、水素化・脱水素処理する方法（一般に、ＨＤＤＲ法と呼ばれている）が知られており、この方法は、Ｒ−Ｆｅ−Ｃｏ−Ｂ系鋳造合金またはこれを粉砕して得られた粗粉末を１０Ｔｏｒｒ以上の水素ガス雰囲気中または水素ガス分圧：１０Ｔｏｒｒ以上の水素ガスと不活性ガスの混合ガス雰囲気中で温度：５００〜１０００℃に保持して鋳造合金またはその合金の粗粉末に水素を吸蔵させた後、水素ガス圧力：１×１０^-1Ｔｏｒｒ以下の真空雰囲気または水素ガス分圧：１×１０^-1Ｔｏｒｒ以下の不活性ガス雰囲気になるまで温度：５００〜１０００℃で脱水素処理したのち急却し、ついで粉砕することにより製造するものである。
【０００４】
この方法で得られたＲ−Ｆｅ−Ｃｏ−Ｂ系磁石粉末は、正方晶構造をとるＲ₂（Ｆｅ，Ｃｏ）₁₄Ｂ型金属間化合物相を主相とする再結晶粒が相互に隣接して集合した再結晶粒集合組織を有し、この再結晶粒集合組織を構成する再結晶粒の平均粒径は０．０５〜３μｍでかつ再結晶粒の最短径ａと最長径ｂの比（ｂ／ａ）の値が２未満である再結晶粒は全再結晶粒の５０容量％以上を占め、このＲ−Ｆｅ−Ｃｏ−Ｂ系磁石粉末の望ましい組成は、原子百分率で、Ｒ：１０〜２０％、Ｃｏ：０．１〜５０％、Ｂ：３〜２０％、Ｇａ，ＺｒおよびＨｆのうち１種または２種以上の合計：０．００１〜５．０％を含有し、さらに、Ａｌ，ＶおよびＳｉのうち１種または２種以上の合計：０．０１〜２．０％を含有し、残りがＦｅおよび不可避不純物からなる組成であることも知られている。
【０００５】
これらＲ−Ｆｅ−Ｃｏ−Ｂ系磁石粉末は、樹脂と混合した後、圧縮成形、射出成形、押し出し成形、ロール圧延などの方法により所定形状に成形し、ボンド磁石を製造することができる。この成形の際に、外部より磁界を加えない製造法では、磁石粉末粒子の磁化容易軸が無秩序に分布し、磁石のいずれの方向においても磁気特性の等しい等方性ボンド磁石が得られる。
【０００６】
【発明が解決しようとする課題】
前記従来のＲ−Ｆｅ−Ｃｏ−Ｂ系磁石粉末およびこの磁石粉末を用いて作製したボンド磁石は、熱的安定性に優れているものの十分ではなく、また減磁曲線の角形性が十分でなく、従来よりも一層熱的安定性および角形性に優れたＲ−Ｆｅ−Ｃｏ−Ｂ系磁石粉末およびその磁石粉末を用いたボンド磁石が求められている。
【０００７】
【課題を解決するための手段】
そこで、本発明者等は、熱的安定性に優れていると共に減磁曲線の角形性にも優れているＲ−Ｆｅ−Ｃｏ−Ｂ系磁石粉末およびその磁石粉末を用いたボンド磁石を得るべく研究を行った結果、
従来のＲ：１０〜２０％、Ｃｏ：０．１〜５０％、Ｂ：３〜２０％を含有し、さらにＡｌ，ＶおよびＳｉのうち１種または２種以上の合計量：０．１〜２．０％を含有し、さらに必要に応じてＧａ，ＺｒおよびＨｆのうち１種または２種以上の合計量：０．５〜１．５％を含有し、残りがＦｅおよび不可避不純物からなる組成を有するＲ−Ｆｅ−Ｃｏ−Ｂ系合金に、さらにＣｒ：０．３〜２．５％およびＭｏ：０．２〜２．０％を含有すると共にＣｒおよびＭｏの合計が０．５〜４．５％となるように添加した組成のＲ−Ｆｅ−Ｃｏ−Ｂ系合金からなる磁石粉末は、従来のＲ−Ｆｅ−Ｃｏ−Ｂ系磁石粉末よりも一層角形性および熱的安定性にも優れ、さらにその磁石粉末を用いたボンド磁石は従来よりも一層角形性に優れかつ熱的安定性に優れる、という研究結果が得られたのである。
【０００８】
この発明はかかる研究結果にもとづいてなされたものであって、
（１）原子百分率で、Ｒ：１０〜２０％、Ｃｏ：０．１〜５０％、Ｂ：３〜２０％、
Ａｌ，ＶおよびＳｉのうち１種または２種以上の合計：０．１〜２．０％、
Ｃｒ：０．３〜２．５％およびＭｏ：０．２〜２．０％を含有すると共にＣｒおよびＭｏの合計が０．５〜４．５％となるように含有し、残りがＦｅおよび不可避不純物からなる組成を有し、
さらに正方晶構造をとるＲ₂（Ｆｅ，Ｃｏ）₁₄Ｂ型金属間化合物相を主相とする再結晶粒が相互に隣接して集合した再結晶粒集合組織を有し、この再結晶粒集合組織を構成する再結晶粒の平均粒径は０．０５〜３μｍでかつ再結晶粒の最短径ａと最長径ｂの比（ｂ／ａ）の値が２未満である再結晶粒が全再結晶粒の５０容量％以上を占める角形性および熱的安定性に優れた希土類−Ｆｅ−Ｃｏ−Ｂ系磁石粉末、
（２）原子百分率で、Ｒ：１０〜２０％、Ｃｏ：０．１〜５０％、Ｂ：３〜２０％、
Ａｌ，ＶおよびＳｉのうち１種または２種以上の合計：０．１〜２．０％、
Ｃｒ：０．３〜２．５％、Ｍｏ：０．２〜２．０％を含有すると共にＣｒおよびＭｏの合計が０．５〜４．５％となるように含有し、
Ｇａ，ＺｒおよびＨｆのうち１種または２種以上の合計：０．５〜１．５％を含有し、残りがＦｅおよび不可避不純物からなる組成を有し、
さらに正方晶構造をとるＲ₂（Ｆｅ，Ｃｏ）₁₄Ｂ型金属間化合物相を主相とする再結晶粒が相互に隣接して集合した再結晶粒集合組織を有し、この再結晶粒集合組織を構成する再結晶粒の平均粒径は０．０５〜３μｍでかつ再結晶粒の最短径ａと最長径ｂの比（ｂ／ａ）の値が２未満である再結晶粒が全再結晶粒の５０容量％以上を占める角形性および熱的安定性に優れた希土類−Ｆｅ−Ｃｏ−Ｂ系磁石粉末、
に特徴を有するものである。
【０００９】
前記（１）または（２）記載の角形性および熱的安定性に優れた希土類−Ｆｅ−Ｃｏ−Ｂ系磁石粉末を樹脂バインダーで結合して得られたボンド磁石は、従来よりも一層角形性および熱的安定性に優れた特性を示す。このボンド磁石は、空隙が少ないほど好ましく、空隙率が１１容量％以下（一層好ましくは５容量％以下）であることが好ましい。
【００１０】
したがって、この発明は、
（３）前記（１）または（２）記載の希土類−Ｆｅ−Ｃｏ−Ｂ系磁石粉末を樹脂バインダーで結合した角形性および熱的安定性に優れたボンド磁石、
（４）前記（１）または（２）記載の希土類−Ｆｅ−Ｃｏ−Ｂ系磁石粉末を樹脂バインダーで結合した空隙率が１１容量％以下である角形性および熱的安定性に優れたボンド磁石、
に特徴を有するものである。
【００１１】
前記（１）記載のＲ−Ｆｅ−Ｃｏ−Ｂ系磁石粉末は、原子百分率で、Ｒ：１０〜２０％、Ｃｏ：０．１〜５０％、Ｂ：３〜２０％、Ａｌ，ＶおよびＳｉのうち１種または２種以上の合計：０．１〜２．０％を含有し、さらにＣｒ：０．３〜２．５％、Ｍｏ：０．２〜２．０％を含有すると共にＣｒおよびＭｏの合計が０．５〜４．５％となるように含有し、残りがＦｅおよび不可避不純物からなる組成を有する合金溶湯を鋳造して鋳造体を作製し、この鋳造体を１０Ｔｏｒｒ以上の水素ガス雰囲気中または水素ガス分圧：１０Ｔｏｒｒ以上の水素ガスと不活性ガスの混合ガス雰囲気中で温度：５００〜１０００℃に保持して前記フィルム状の鋳造体に水素を吸蔵させた後、水素ガス圧力：１×１０^-1Ｔｏｒｒ以下の真空雰囲気または水素ガス分圧：１×１０^-1Ｔｏｒｒ以下の不活性ガス雰囲気になるまで温度：５００〜１０００℃で脱水素処理したのち、冷却し、ついで粉砕することにより製造することができる。
【００１２】
また、前記（２）記載のＲ−Ｆｅ−Ｃｏ−Ｂ系磁石粉末は、原子百分率で、Ｒ：１０〜２０％、Ｃｏ：０．１〜５０％、Ｂ：３〜２０％、Ａｌ，ＶおよびＳｉのうち１種または２種以上の合計：０．１〜２．０％、Ｃｒ：０．３〜２．５％およびＭｏ：０．２〜２．０％を含有すると共にＣｒおよびＭｏの合計が０．５〜４．５％となるように含有し、さらにＧａ，ＺｒおよびＨｆのうち１種または２種以上の合計：０．５〜１．５％を含有し、残りがＦｅおよび不可避不純物からなる組成を有する合金溶湯を鋳造して鋳造体を作製し、この鋳造体を１０Ｔｏｒｒ以上の水素ガス雰囲気中または水素ガス分圧：１０Ｔｏｒｒ以上の水素ガスと不活性ガスの混合ガス雰囲気中で温度：５００〜１０００℃に保持して水素を吸蔵させた後、水素ガス圧力：１×１０^-1Ｔｏｒｒ以下の真空雰囲気または水素ガス分圧：１×１０^-1Ｔｏｒｒ以下の不活性ガス雰囲気になるまで温度：５００〜１０００℃で脱水素処理したのち、冷却し、ついで粉砕することにより製造することができる。
【００１３】
つぎに、この発明のＲ−Ｆｅ−Ｃｏ−Ｂ系磁石粉末の成分組成、結晶粒径および結晶粒形状を上記の如く限定した理由について説明する。
Ａ．成分組成
（ａ）Ｒ
Ｒは、Ｎｄ，Ｐｒ，Ｔｂ，Ｄｙ，Ｌａ，Ｃｅ，Ｈｏ，Ｅｒ，Ｅｕ，Ｓｍ，Ｇｄ，Ｔｍ，Ｙｂ，ＬｕおよびＹのうち１種または２種以上であり、一般にＮｄを主体とし、これにその他の希土類元素を添加して用いられるが、特にＴｂ，ＤｙおよびＰｒは保磁力ｉＨｃを向上させる効果があり、Ｒの含有量が１０％より低くても、また２０％より高くても磁石粉末の保磁力が低下し、優れた磁気特性が得られない。したがって、Ｒの含有量は１０〜２０％に定めた。
【００１４】
（ｂ）Ｂ
Ｂの含有量が３％より低くても、また２０％より高くても磁石粉末の保磁力が低下し、優れた磁気特性が得られないので、Ｂ含有量は３〜２０％と定めた。
【００１５】
（ｃ）Ｃｏ
Ｃｏを添加することにより磁石粉末の保磁力および磁気的温度特性（例えば、キュリー点）が向上し、さらに耐食性を向上させる効果があるが、その含有量が０．１％未満では所望の効果が得られず、一方、５０％を超えて含有してもかえって磁気特性が低下するので好ましくない。したがって、Ｃｏの含有量は０．１〜５０％に定めた。Ｃｏの含有量は、０．１〜２０％の間では、最も保磁力が高くなるのでＣｏ：０．１〜２０％とするのが一層好ましい。
【００１６】
（ｄ）Ａｌ，ＶおよびＳｉ
Ｒ−Ｆｅ−Ｃｏ−Ｂ系永久磁石粉末合金に、Ａｌ，ＶおよびＳｉのうち１種または２種以上を添加することにより最大エネルギー積を安定して高めることができるので添加するが、その含有量が０．１％未満では所望の効果が得られず、一方、２．０％を超えて添加しても、磁化の値を高めることができないので好ましくない。
したがって、Ａｌ，ＶおよびＳｉのうち１種または２種以上は合計量で０．１〜２．０％に定めた。Ａｌ，ＶおよびＳｉのうち１種または２種以上は合計量の一層好ましい範囲は０．１〜１．０％である。
【００１７】
（ｅ）Ｃｒ，Ｍｏ
ＣｒおよびＭｏを、Ａｌ，ＶおよびＳｉのうち１種または２種以上、特にＡｌと共に添加することにより優れた角形性を示すのでＣｒおよびＭｏを添加するが、Ｃｒの添加量が０．３％未満、Ｍｏの含有量が０．２％未満を含有すると共にＣｒおよびＭｏの合計が０．５％未満では所望の効果が得られず、一方、Ｃｒの添加量が２．５％を越えかつＭｏの含有量が２％を越えて含有すると共にＣｒおよびＭｏの合計が４．５％を越えて含有すると磁束密度が減少するので好ましくない。したがって、Ｃｒ：０．３〜２．５％およびＭｏ：０．２〜２．０％を含有すると共にＣｒおよびＭｏの合計が０．５〜４．５％となるように定めた。
【００１８】
（ｆ）Ｇａ，ＺｒおよびＨｆ
これらの成分は、Ｒ−Ｆｅ−Ｃｏ−Ｂ系磁石粉末の成分として含有し、保磁力を向上させるとともに優れた耐食性を安定的に付与する作用を有するので、必要に応じて添加するが、その含有量が０．５％未満では所望の効果が得られず、一方、１．５％を超えて含有すると磁気特性が低下する。したがって、Ｇａ，ＺｒおよびＨｆのうち１種または２種以上の合計は０．５〜１．５％に定めた。
【００１９】
Ｂ．再結晶粒
（ｆ）再結晶粒径およびその形状
Ｒ−Ｆｅ−Ｃｏ−Ｂ系磁石粉末の組織を構成するＲ₂（Ｆｅ，Ｃｏ）₁₄Ｂ型相の再結晶粒の粒径が０．０５μｍより小さいと着磁が困難になるので好ましくなく、一方、２０μｍより大きいと保磁力や角型性が低下し、高磁気特性が得られないので好ましくない。
【００２０】
したがって、再結晶粒径は０．０５〜３μｍに定めた。この場合、再結晶粒径は単磁区粒径の寸法（０．３μｍ）に近い０．０５〜３μｍとする方が一層好ましい。上記寸法を有する個々の再結晶粒は、最短粒径ａと最長粒径ｂの比が（ｂ／ａ）＜２の形状を有することが好ましく、この形状を有する再結晶粒は、全再結晶粒の５０容量％以上存在することが必要である。
【００２１】
上記最短粒径ａと最長粒径ｂの比ｂ／ａが２より小さい再結晶粒形状を有することにより、Ｒ−Ｆｅ−Ｃｏ−Ｂ系磁石粉末の保磁力が改善されると共に耐食性も向上し、さらに保磁力の温度係数も小さくなる。したがって上記個々の再結晶粒のｂ／ａの値は２未満に定めた。
【００２２】
Ｃ．ボンド磁石の空隙率
ボンド磁石の空隙率は、１１容量％を越えると、空隙中の酸素により磁石粉末が酸化され、そのためボンド磁石の磁気特性が低下するのでボンド磁石の空隙率を１１容量％以下に定めた。ボンド磁石の空隙率は小さいほど好ましく、空隙率は５容量％以下であることが一層好ましい。
【００２３】
【発明の実施の形態】
実施例１
高周波溶解して温度：１３５０℃に保持された合金溶湯を金型に鋳造し、表１に示される成分組成を有する鋳造体Ａ〜Ｊを作製した。得られた鋳造体Ａ〜Ｊを１気圧の水素雰囲気中で室温から８５０℃まで昇温し、８５０℃で３時間保持の水素雰囲気中熱処理を施し、ついで、雰囲気を真空雰囲気にして８５０℃にて１時間保持することにより脱水素処理を行い、真空度：１×１０^-5Torr以下になるまで排気を行った後、直ちにアルゴンガスを流入して急冷する条件のＨＤＤＲ処理を施すことにより、再結晶粒が相互に隣接して集合した再結晶集合組織を有するＨＤＤＲ処理体を作製した。このＨＤＤＲ処理体の平均再結晶粒径、再結晶粒の最短径ａと最長径ｂの比（ｂ／ａ）を測定し、その結果を表２〜３に示し、さらに得られたＨＤＤＲ処理体を粉砕することにより、表２〜３に示される平均粒径を有する本発明磁石粉末１〜７、比較磁石粉末１〜２および従来磁石粉末１を作製した。
なお、本発明磁石粉末１〜７、比較磁石粉末１〜２および従来磁石粉末１の平均結晶粒径および個々の結晶粒の最長径ｂ／最短径ａの値は透過電子顕微鏡により観察し、本発明磁石粉末１〜７、比較磁石粉末１〜２および従来磁石粉末１の寸法である平均粒径は金属顕微鏡で測定した。
【００２４】
このようにして得られた本発明磁石粉末１〜７、比較磁石粉末１〜２および従来磁石粉末１についての残留磁束密度Ｂｒを測定し、さらにＨｋ／ｉＨｃ（ただし、Ｈｋ：残留磁束密度Ｂｒを１０％減少させる減磁界、ｉＨｃ：保磁力である）の値を求めてその結果を表２〜３に示し、これら磁石粉末の角形性を評価した。
【００２５】
さらに、本発明磁石粉末１〜７、比較磁石粉末１〜２および従来磁石粉末１をビスマレイミドトリアジン樹脂：４．０重量％と混合してコンパウンド（混合物）を作製し、このコンパウンドを金型に充填し、圧力：６ton ／cm²で圧縮成形する無磁界中成形を行うことにより直径：１０mm、高さ：７mmの寸法を有する成形体を作製し、ついでこの成形体をオーブンに装入し、真空雰囲気中、温度：１５０℃、１時間保持の加熱硬化を行って空隙率：５．３％の等方性ボンド磁石を作製し、これら等方性ボンド磁石のＢｒおよびＨｋ／ｉＨｃを測定し、その結果を表２〜３に示した。
【００２６】
さらに、これら等方性ボンド磁石を７０ｋＯｅのパルス磁界で着磁した後、８０℃に保持したオーブンに１０００時間放置し、等方性ボンド磁石の熱減磁率を測定し、その結果を表２〜３に示し、熱的安定性を評価した。
ただし、熱減磁率（％）＝｛（１０００時間暴露後の全磁束−暴露前の全磁束）／暴露前の全磁束｝×１００。
【００２７】
【表１】

【００２８】
【表２】

【００２９】
【表３】

【００３０】
表１〜表３に示される結果から、ＣｒおよびＭｏのうち１種または２種を合計で０．０１〜５．０％含有する本発明磁石粉末１〜７とＣｒおよびＭｏを含有しない従来磁石粉末１を比較すると、本発明磁石粉末１〜７は従来磁石粉末１に比べて角形性に優れており、これら本発明磁石粉末１〜７を使用して作製した等方性ボンド磁石は角形性に優れており、さらに熱的安定性が格段に優れていることから本発明磁石粉末１〜７は熱的安定性が格段に優れていることが分かる。しかし、ＣｒおよびＭｏの含有量が５．０％よりも多い比較磁石粉末１〜２で作製したボンド磁石は残留磁束密度Ｂｒが低下するので好ましくないことが分かる。
【００３１】
実施例２
高周波溶解して温度：１３５０℃に保持された合金溶湯を金型に鋳造し、表４に示される成分組成を有する鋳造体ａ〜ｊを作製した。得られた鋳造体ａ〜ｊを１気圧の水素雰囲気中で室温から８５０℃まで昇温し、８５０℃で３時間保持の水素雰囲気中熱処理を施し、ついで、雰囲気を真空雰囲気にして８５０℃にて１時間保持することにより脱水素処理を行い、真空度：１×１０^-5Torr以下になるまで排気を行った後、直ちにアルゴンガスを流入して急冷する条件のＨＤＤＲ処理を施すことにより、再結晶粒が相互に隣接して集合した再結晶集合組織を有するＨＤＤＲ処理体を作製した。このＨＤＤＲ処理体の平均再結晶粒径、再結晶粒の最短径ａと最長径ｂの比（ｂ／ａ）を測定し、その結果を表５〜６に示し、さらに得られたＨＤＤＲ処理体を粉砕することにより、表５〜６に示される平均粒径を有する本発明磁石粉末８〜１４、比較磁石粉末３〜４および従来磁石粉末２を作製した。
なお、本発明磁石粉末８〜１４、比較磁石粉末３〜４および従来磁石粉末１の平均結晶粒径および個々の結晶粒の最長径ｂ／最短径ａの値は透過電子顕微鏡により観察し、本発明磁石粉末８〜１４、比較磁石粉末３〜４および従来磁石粉末２の寸法である平均粒径は金属顕微鏡で測定した。
【００３２】
このようにして得られた本発明磁石粉末８〜１４、比較磁石粉末３〜４および従来磁石粉末２についての残留磁束密度Ｂｒを測定し、さらにＨｋ／ｉＨｃ（ただし、Ｈｋは残留磁束密度Ｂｒを１０％減少させる減磁界、ｉＨｃは保磁力）の値を求めてその結果を表５〜６に示し、これら磁石粉末の角形性を評価した。
【００３３】
さらに、本発明磁石粉末８〜１４、比較磁石粉末３〜４および従来磁石粉末２をビスマレイミドトリアジン樹脂：４．０重量％と混合してコンパウンド（混合物）を作製し、このコンパウンドを金型に充填し、圧力：６ton ／cm²で圧縮成形する無磁界中成形を行うことにより直径：１０mm、高さ：７mmの寸法を有する成形体を作製し、ついでこの成形体をオーブンに装入し、真空雰囲気中、温度：１５０℃、１時間保持の加熱を行って空隙率：５．３％の等方性ボンド磁石を作製し、これら等方性ボンド磁石のＢｒおよびＨｋ／ｉＨｃを測定し、その結果を表５〜６に示した。
【００３４】
さらに、これら等方性ボンド磁石を７０ｋＯｅのパルス磁界で着磁した後、８０℃に保持したオーブンに１０００時間放置し、等方性ボンド磁石の熱減磁率を測定し、その結果を表５〜６に示し、熱的安定性を評価した。
【００３５】
【表４】

【００３６】
【表５】

【００３７】
【表６】

【００３８】
表４〜表６に示される結果から、ＣｒおよびＭｏのうち１種または２種を合計で０．０１〜５．０％含有する本発明磁石粉末８〜１４とＣｒおよびＭｏを含有しない従来磁石粉末２を比較すると、本発明磁石粉末８〜１４は従来磁石粉末２に比べて角形性に優れており、これら本発明磁石粉末８〜１４を使用して作製した等方性ボンド磁石は角形性に優れており、さらに熱的安定性が格段に優れていることから本発明磁石粉末８〜１４は熱的安定性が格段に優れていることが分かる。しかし、ＣｒおよびＭｏの含有量が５．０％よりも多い比較磁石粉末３〜４で作製したボンド磁石は残留磁束密度Ｂｒが低下するので好ましくないことが分かる。
【００３９】
【発明の効果】
この発明は、熱的安定性および角形性に優れた等方性ボンド磁石を提供することができ、電子・電気産業の発展に大いに貢献し得るものである。[0001]
BACKGROUND OF THE INVENTION
The present invention is mainly composed of R, which is superior in squareness and thermal stability as compared with the prior art (where R is at least one of rare earth elements including Y), Fe, Co, and B. The present invention relates to an R-Fe-Co-B magnet powder and a bonded magnet using this powder.
[0002]
[Prior art]
Since R-Fe-Co-B magnet powder has high magnetic characteristics and relatively stable temperature characteristics, it is bonded with a resin to produce a bonded magnet. This bonded magnet has features such as high dimensional accuracy, easy production of thin and complex magnets, and the ability to be integrally formed with other parts, and so on. Widely used as various parts such as motors.
[0003]
As one of the methods for producing the R—Fe—Co—B based magnet powder, a hydrogenation / dehydrogenation method (generally referred to as HDDR method) is known. -Fe-Co-B-based cast alloy or coarse powder obtained by pulverizing the same in a hydrogen gas atmosphere of 10 Torr or higher or a hydrogen gas partial pressure: temperature in a mixed gas atmosphere of hydrogen gas and inert gas of 10 Torr or higher : Hydrogen is occluded in a cast alloy or a coarse powder of the alloy by holding at 500 to 1000 ° C., and then a hydrogen gas pressure: 1 × 10 ⁻¹ Torr or less of vacuum atmosphere or hydrogen gas partial pressure: 1 × 10 ⁻¹ It is manufactured by dehydrogenating at a temperature of 500 to 1000 ° C. until an inert gas atmosphere of Torr or less is reached, and then pulverizing.
[0004]
In the R—Fe—Co—B based magnet powder obtained by this method, recrystallized grains whose main phase is an R ₂ (Fe, Co) ₁₄ B type intermetallic compound phase having a tetragonal structure are adjacent to each other. The recrystallized grain texture has an average grain size of 0.05 to 3 μm and the ratio of the shortest diameter a to the longest diameter b of the recrystallized grain ( The recrystallized grains having a value of b / a) of less than 2 occupy 50% by volume or more of the total recrystallized grains. The desirable composition of the R—Fe—Co—B based magnet powder is expressed in atomic percent, and R: 10 -20%, Co: 0.1-50%, B: 3-20%, one or more of Ga, Zr and Hf: a total of 0.001-5.0%, Total of one or more of Al, V and Si: 0.01 to 2.0%, with the remainder being Fe and inevitable impurities It is also known that a composition comprising.
[0005]
These R-Fe-Co-B magnet powders can be mixed with a resin, and then molded into a predetermined shape by a method such as compression molding, injection molding, extrusion molding, or roll rolling to produce a bonded magnet. In the manufacturing method in which a magnetic field is not applied from the outside at the time of molding, an isotropic bonded magnet is obtained in which the easy axis of magnetization of the magnet powder particles is randomly distributed and the magnetic properties are equal in any direction of the magnet.
[0006]
[Problems to be solved by the invention]
The conventional R-Fe-Co-B magnet powder and the bonded magnet produced using this magnet powder are not sufficient, although they are excellent in thermal stability, and the squareness of the demagnetization curve is not sufficient. There is a need for R-Fe-Co-B magnet powders that are more excellent in thermal stability and squareness than in the past, and bonded magnets using the magnet powders.
[0007]
[Means for Solving the Problems]
Accordingly, the inventors of the present invention should obtain an R—Fe—Co—B based magnet powder having excellent thermal stability and excellent squareness of a demagnetization curve, and a bonded magnet using the magnet powder. As a result of research,
Conventional R: 10 to 20%, Co: 0.1 to 50%, B: 3 to 20%, and one or more of Al, V and Si in total amount: 0.1 to Contains 2.0%, and further contains a total amount of one or more of Ga, Zr and Hf as required: 0.5 to 1.5% , with the remainder consisting of Fe and inevitable impurities The R—Fe—Co—B alloy having the composition further contains Cr: 0.3 to 2.5% and Mo: 0.2 to 2.0%, and the total of Cr and Mo is 0.5 to A magnet powder made of an R—Fe—Co—B alloy having a composition added to 4.5% has a more squareness and thermal stability than a conventional R—Fe—Co—B magnet powder. In addition, the bonded magnet using the magnet powder is more excellent in squareness and thermal stability than before. Is, it is the research results that were obtained.
[0008]
This invention was made based on the results of such research,
(1) At atomic percentage, R: 10-20%, Co: 0.1-50%, B: 3-20%,
A total of one or more of Al, V and Si: 0.1 to 2.0%,
Cr: 0.3-2.5% and Mo: 0.2-2.0% and the total content of Cr and Mo is 0.5-4.5% , the remainder is Fe and Having a composition consisting of inevitable impurities,
Further, the recrystallized grains have a recrystallized grain structure in which recrystallized grains mainly composed of R ₂ (Fe, Co) ₁₄ B type intermetallic compound phase having a tetragonal structure are gathered adjacent to each other. The average grain size of the recrystallized grains constituting the structure is 0.05 to 3 μm, and the recrystallized grains whose ratio of the shortest diameter a to the longest diameter b (b / a) is less than 2 are all recrystallized. A rare earth-Fe-Co-B magnet powder having excellent squareness and thermal stability, accounting for 50% by volume or more of crystal grains,
(2) In atomic percentage, R: 10-20%, Co: 0.1-50%, B: 3-20%,
A total of one or more of Al, V and Si: 0.1 to 2.0%,
Cr: 0.3-2.5%, Mo: 0.2-2.0% and containing so that the total of Cr and Mo is 0.5-4.5% ,
A total of one or more of Ga, Zr and Hf: 0.5 to 1.5 %, with the remainder consisting of Fe and inevitable impurities,
Further, the recrystallized grains have a recrystallized grain structure in which recrystallized grains mainly composed of R ₂ (Fe, Co) ₁₄ B type intermetallic compound phase having a tetragonal structure are gathered adjacent to each other. The average grain size of the recrystallized grains constituting the structure is 0.05 to 3 μm, and the recrystallized grains whose ratio of the shortest diameter a to the longest diameter b (b / a) is less than 2 are all recrystallized. A rare earth-Fe-Co-B magnet powder having excellent squareness and thermal stability, accounting for 50% by volume or more of crystal grains,
It has the characteristics.
[0009]
The bonded magnet obtained by bonding the rare earth-Fe-Co-B magnet powder having excellent squareness and thermal stability described in the above (1) or (2) with a resin binder is more square than ever. And excellent thermal stability. This bonded magnet is preferably as small as possible, and the porosity is preferably 11% by volume or less (more preferably 5% by volume or less).
[0010]
Therefore, the present invention
(3) A bonded magnet excellent in squareness and thermal stability in which the rare earth-Fe-Co-B magnet powder described in (1) or (2) above is bound with a resin binder,
(4) Bond magnet excellent in squareness and thermal stability having a porosity of 11% by volume or less in which the rare earth-Fe—Co—B magnet powder described in (1) or (2) above is bound with a resin binder ,
It has the characteristics.
[0011]
The R-Fe-Co-B magnet powder described in the above (1) is atomic percentages: R: 10 to 20%, Co: 0.1 to 50%, B: 3 to 20%, Al, V and Si. Among them, the total of one or more of them: 0.1 to 2.0%, Cr: 0.3 to 2.5%, Mo: 0.2 to 2.0% and Cr And Mo are contained so that the total amount is 0.5 to 4.5%, and a cast alloy is produced by casting a molten alloy having a composition consisting of Fe and unavoidable impurities. In a hydrogen gas atmosphere or in a mixed gas atmosphere of hydrogen gas and inert gas with a hydrogen gas partial pressure of 10 Torr or higher, the temperature is maintained at 500 to 1000 ° C., and hydrogen is occluded in the cast film. gas pressure: 1 × 10 ^-1 Torr or less in a vacuum atmosphere or hydrogen gas Partial pressure: 1 × 10 ^-1 Torr or less in temperature until the inert gas atmosphere: After dehydrogenation at 500 to 1000 ° C., can be produced by cooling and then pulverization.
[0012]
The R-Fe-Co-B magnet powder described in the above (2) is atomic percentages: R: 10-20%, Co: 0.1-50%, B: 3-20%, Al, V And a total of one or more of Si: 0.1 to 2.0%, Cr: 0.3 to 2.5% and Mo: 0.2 to 2.0%, and Cr and Mo The total content is 0.5 to 4.5%, and one or more of Ga, Zr and Hf: 0.5 to 1.5 % is contained, and the remainder is Fe. And casting a molten alloy having a composition composed of inevitable impurities, and producing a cast body. The cast body is in a hydrogen gas atmosphere of 10 Torr or higher, or a hydrogen gas partial pressure: a mixed gas atmosphere of hydrogen gas and inert gas of 10 Torr or higher. In the temperature: 500 to 1000 ° C., occluded hydrogen, water Gas pressure: 1 × 10 ^-1 Torr or less in a vacuum atmosphere or a hydrogen gas partial pressure: 1 × 10 ^-1 Torr or less in temperature until the inert gas atmosphere: After dehydrogenation at 500 to 1000 ° C., cooled, Subsequently, it can manufacture by grind | pulverizing.
[0013]
Next, the reason why the component composition, crystal grain size, and crystal grain shape of the R-Fe-Co-B magnet powder of the present invention are limited as described above will be described.
A. Ingredient composition (a) R
R is one or more of Nd, Pr, Tb, Dy, La, Ce, Ho, Er, Eu, Sm, Gd, Tm, Yb, Lu and Y, and is generally composed of Nd. Although other rare earth elements are used in addition to Tb, Dy, and Pr, there is an effect of improving the coercive force iHc, and even if the content of R is lower than 10% or higher than 20%, the magnet The coercive force of the powder is lowered and excellent magnetic properties cannot be obtained. Therefore, the content of R is set to 10 to 20%.
[0014]
(B) B
Even if the content of B is lower than 3% or higher than 20%, the coercive force of the magnet powder is lowered and an excellent magnetic property cannot be obtained. Therefore, the B content is determined to be 3 to 20%.
[0015]
(C) Co
The addition of Co improves the coercive force and magnetic temperature characteristics (eg, Curie point) of the magnetic powder, and further improves the corrosion resistance. However, if the content is less than 0.1%, the desired effect is obtained. On the other hand, if the content exceeds 50%, the magnetic properties deteriorate, which is not preferable. Therefore, the content of Co is set to 0.1 to 50%. When the Co content is 0.1 to 20%, the coercive force becomes the highest, so Co: 0.1 to 20% is more preferable.
[0016]
(D) Al, V and Si
Since the maximum energy product can be stably increased by adding one or more of Al, V and Si to the R—Fe—Co—B permanent magnet powder alloy, it is added. If the amount is less than 0.1 %, the desired effect cannot be obtained. On the other hand, adding over 2.0% is not preferable because the value of magnetization cannot be increased.
Accordingly, one or more of Al, V and Si are set to a total amount of 0.1 to 2.0%. A more preferable range of the total amount of one or more of Al, V and Si is 0.1 to 1.0%.
[0017]
(E) Cr, Mo
Cr and Mo are added to one or more of Al, V, and Si, particularly when added together with Al. Therefore, Cr and Mo are added, but the amount of Cr added is 0.3%. If the total content of Cr and Mo is less than 0.5%, the desired effect cannot be obtained, while the addition amount of Cr exceeds 2.5% and If the Mo content exceeds 2% and the total content of Cr and Mo exceeds 4.5%, the magnetic flux density decreases, which is not preferable. Therefore, Cr: 0.3-2.5% and Mo: 0.2-2.0% were contained, and it set so that the sum total of Cr and Mo might be 0.5-4.5%.
[0018]
(F) Ga, Zr and Hf
These components are contained as components of the R-Fe-Co-B magnet powder, and have the effect of improving the coercive force and stably imparting excellent corrosion resistance. If the content is less than 0.5 %, the desired effect cannot be obtained. On the other hand, if the content exceeds 1.5 %, the magnetic properties deteriorate. Therefore, the total of one or more of Ga, Zr and Hf is set to 0.5 to 1.5 %.
[0019]
B. Recrystallized grain (f) Recrystallized grain size and shape thereof The grain size of the recrystallized grain of the R ₂ (Fe, Co) ₁₄ B phase constituting the structure of the R—Fe—Co—B based magnet powder is 0.05 μm. If the thickness is smaller than 20 μm, magnetization is difficult. On the other hand, if it is larger than 20 μm, the coercive force and squareness are lowered, and high magnetic characteristics cannot be obtained.
[0020]
Therefore, the recrystallized grain size was set to 0.05 to 3 μm. In this case, it is more preferable that the recrystallized grain size is 0.05 to 3 μm, which is close to the single magnetic domain grain size (0.3 μm). The individual recrystallized grains having the above dimensions preferably have a shape in which the ratio of the shortest particle size a to the longest particle size b is (b / a) <2, and the recrystallized particles having this shape are all recrystallized. It is necessary that 50% by volume or more of the grains be present.
[0021]
By having a recrystallized grain shape in which the ratio b / a between the shortest particle diameter a and the longest particle diameter b is smaller than 2, the coercive force of the R—Fe—Co—B magnet powder is improved and the corrosion resistance is also improved. Furthermore, the temperature coefficient of the coercive force is also reduced. Therefore, the value of b / a of the individual recrystallized grains is set to less than 2.
[0022]
C. The porosity of the bonded magnet If the porosity of the bonded magnet exceeds 11% by volume, the magnetic powder of the bonded magnet is oxidized by oxygen in the air gap, so that the magnetic properties of the bonded magnet are deteriorated. Determined. The porosity of the bonded magnet is preferably as small as possible, and the porosity is more preferably 5% by volume or less.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Example 1
Alloy melts that were melted at high frequency and maintained at a temperature of 1350 ° C. were cast into molds, and castings A to J having the component compositions shown in Table 1 were produced. The obtained castings A to J were heated from room temperature to 850 ° C. in a hydrogen atmosphere of 1 atm, subjected to heat treatment in a hydrogen atmosphere maintained at 850 ° C. for 3 hours, and then the atmosphere was changed to 850 ° C. in a vacuum atmosphere. The dehydrogenation treatment is performed by holding for 1 hour, and after exhausting until the degree of vacuum becomes 1 × 10 ⁻⁵ Torr or less, the HDDR treatment is performed under the condition of immediately flowing in argon gas and rapidly cooling, An HDDR treated body having a recrystallized texture in which recrystallized grains gathered adjacent to each other was produced. The average recrystallized grain size of this HDDR treated body, the ratio (b / a) of the shortest diameter a and the longest diameter b of the recrystallized grains were measured, the results are shown in Tables 2-3, and the obtained HDDR treated body The present invention magnetic powders 1 to 7 , comparative magnet powders 1 to 2 and conventional magnet powder 1 having the average particle diameters shown in Tables 2 to 3 were produced.
In addition, the average crystal grain size of the present invention magnetic powders 1 to 7 , comparative magnet powders 1 to 2 and the conventional magnet powder 1 and the values of the longest diameter b / shortest diameter a of the individual crystal grains were observed with a transmission electron microscope. Inventive magnet powders 1 to 7 , comparative magnet powders 1 to 2 and conventional magnet powder 1 were measured with a metal microscope for the average particle size.
[0024]
The residual magnetic flux density Br of the present invention magnetic powders 1 to 7 , comparative magnetic powders 1 to 2 and the conventional magnetic powder 1 thus obtained was measured, and further Hk / iHc (where Hk: residual magnetic flux density Br was The values of demagnetizing field, iHc: coercive force, which are reduced by 10%, were determined and the results are shown in Tables 2 to 3, and the squareness of these magnet powders was evaluated.
[0025]
Furthermore, the present invention magnetic powder 1-7, Comparative magnetic powder 1 and 2 and the conventional magnet powder 1 bismaleimide triazine resin: 4.0 was mixed with wt% to prepare a compound (mixture), the compound in a mold A molded body having a size of 10 mm in diameter and 7 mm in height is manufactured by filling in a magnetic field without compression, and compression molding at a pressure of 6 ton / cm ² , and then charging this molded body into an oven. An isotropic bonded magnet having a porosity of 5.3% is prepared by heating and curing in a vacuum atmosphere at a temperature of 150 ° C. for 1 hour, and Br and Hk / iHc of these isotropic bonded magnets are measured. The results are shown in Tables 2-3.
[0026]
Further, these isotropic bonded magnets were magnetized with a pulse magnetic field of 70 kOe, and then left in an oven maintained at 80 ° C. for 1000 hours to measure the thermal demagnetization rate of the isotropic bonded magnets. The thermal stability was evaluated.
However, thermal demagnetization rate (%) = {(total magnetic flux after 1000 hours exposure−total magnetic flux before exposure) / total magnetic flux before exposure} × 100.
[0027]
[Table 1]

[0028]
[Table 2]

[0029]
[Table 3]

[0030]
From the results shown in Tables 1 to 3, the present invention magnet powders 1 to 7 containing one or two of Cr and Mo in a total of 0.01 to 5.0% and conventional magnets not containing Cr and Mo When the powder 1 is compared, the magnet powders 1 to 7 of the present invention are superior in squareness compared to the conventional magnet powder 1, and the isotropic bonded magnets produced using these magnet powders 1 to 7 of the present invention are square. It can be seen that the magnetic powders 1 to 7 of the present invention are remarkably excellent in thermal stability. However, it can be seen that a bonded magnet made of comparative magnet powders 1 and 2 having a Cr and Mo content of more than 5.0% is not preferable because the residual magnetic flux density Br decreases.
[0031]
Example 2
A molten alloy that was melted at high frequency and maintained at a temperature of 1350 ° C. was cast into a mold, and castings a to j having the component compositions shown in Table 4 were produced. The obtained castings a to j were heated from room temperature to 850 ° C. in a hydrogen atmosphere of 1 atm, subjected to heat treatment in a hydrogen atmosphere maintained at 850 ° C. for 3 hours, and then the atmosphere was changed to 850 ° C. in a vacuum atmosphere. The dehydrogenation treatment is performed by holding for 1 hour, and after exhausting until the degree of vacuum becomes 1 × 10 ⁻⁵ Torr or less, the HDDR treatment is performed under the condition of immediately flowing in argon gas and rapidly cooling, An HDDR treated body having a recrystallized texture in which recrystallized grains gathered adjacent to each other was produced. The average recrystallized grain size of this HDDR processed body, the ratio (b / a) of the shortest diameter a and the longest diameter b of the recrystallized grains were measured, the results are shown in Tables 5-6, and the obtained HDDR processed body The present invention magnetic powders 8 to 14 , comparative magnet powders 3 to 4 and conventional magnet powder 2 having the average particle diameters shown in Tables 5 to 6 were produced.
The average crystal grain size of the present magnet powders 8 to 14 , comparative magnet powders 3 to 4 and the conventional magnet powder 1 and the values of the longest diameter b / shortest diameter a of the individual crystal grains were observed with a transmission electron microscope. Inventive magnet powders 8 to 14 , comparative magnet powders 3 to 4 and conventional magnet powder 2 were measured with a metal microscope for the average particle size.
[0032]
The residual magnetic flux density Br was measured for the magnet powders 8 to 14 of the present invention, the comparative magnetic powders 3 to 4 and the conventional magnetic powder 2 thus obtained, and Hk / iHc (where Hk represents the residual magnetic flux density Br). The values of the demagnetizing field to be reduced by 10% and the value of iHc (coercive force) were obtained and the results are shown in Tables 5 to 6, and the squareness of these magnet powders was evaluated.
[0033]
Furthermore, this invention magnetic powder 8-14 , comparative magnet powder 3-4, and the conventional magnet powder 2 are mixed with bismaleimide triazine resin: 4.0weight%, and a compound (mixture) is produced, This compound is made into a metal mold | die. A molded body having a size of 10 mm in diameter and 7 mm in height is manufactured by filling in a magnetic field without compression, and compression molding at a pressure of 6 ton / cm ² , and then charging this molded body into an oven. In a vacuum atmosphere, heat is maintained at 150 ° C. for 1 hour to produce isotropic bonded magnets with a porosity of 5.3%, and Br and Hk / iHc of these isotropic bonded magnets are measured. The results are shown in Tables 5-6.
[0034]
Further, these isotropic bonded magnets were magnetized with a pulse magnetic field of 70 kOe, and then left in an oven maintained at 80 ° C. for 1000 hours, and the thermal demagnetization rate of the isotropic bonded magnets was measured. The thermal stability was evaluated.
[0035]
[Table 4]

[0036]
[Table 5]

[0037]
[Table 6]

[0038]
From the results shown in Tables 4 to 6, the present invention magnet powders 8 to 14 containing one or two of Cr and Mo in a total of 0.01 to 5.0% and conventional magnets containing no Cr and Mo comparing powder 2, the present invention magnetic powder 8-14 is excellent in squareness in comparison with the conventional magnet powder 2, isotropic bonded magnet manufactured using these present invention the magnet powder 8-14 squareness It can be seen that the magnet powders 8 to 14 of the present invention are remarkably excellent in thermal stability. However, it can be seen that bond magnets made of comparative magnet powders 3 to 4 having a Cr and Mo content greater than 5.0% are not preferable because the residual magnetic flux density Br decreases.
[0039]
【The invention's effect】
The present invention can provide an isotropic bonded magnet having excellent thermal stability and squareness, and can greatly contribute to the development of the electronic and electrical industries.

Claims

When at least one of the rare earth elements including Y is represented by R (hereinafter the same), R: 10 to 20%, Co: 0.1 to 50%, B: 3 to 20%,
A total of one or more of Al, V and Si: 0.1 to 2.0%,
Cr: 0.3-2.5% and Mo: 0.2-2.0% and the total content of Cr and Mo is 0.5-4.5% , the remainder is Fe and Having a composition consisting of inevitable impurities,
Furthermore, the recrystallized grain texture has a recrystallized grain texture in which recrystallized grains mainly composed of R ₂ (Fe, Co) ₁₄ B type intermetallic compound phase having a tetragonal structure are gathered adjacent to each other. The average grain size of the recrystallized grains constituting the structure is 0.05 to 3 μm, and the recrystallized grains whose ratio of the shortest diameter a to the longest diameter b (b / a) is less than 2 are all recrystallized. A rare earth-Fe-Co-B magnet powder excellent in squareness and thermal stability, characterized by occupying 50% by volume or more of crystal grains.

At atomic percentage, R: 10-20%, Co: 0.1-50%, B: 3-20%,
A total of one or more of Al, V and Si: 0.1 to 2.0%,
Cr: 0.3-2.5% and Mo: 0.2-2.0% and containing so that the total of Cr and Mo is 0.5-4.5% ,
A total of one or more of Ga, Zr and Hf: 0.5 to 1.5 %, with the remainder consisting of Fe and inevitable impurities,
Furthermore, the recrystallized grain texture has a recrystallized grain texture in which recrystallized grains mainly composed of R ₂ (Fe, Co) ₁₄ B type intermetallic compound phase having a tetragonal structure are gathered adjacent to each other. The average grain size of the recrystallized grains constituting the structure is 0.05 to 3 μm, and the recrystallized grains whose ratio of the shortest diameter a to the longest diameter b (b / a) is less than 2 are all recrystallized. A rare earth-Fe-Co-B magnet powder excellent in squareness and thermal stability, characterized by occupying 50% by volume or more of crystal grains.

A bonded magnet excellent in squareness and thermal stability, wherein the rare earth-Fe-Co-B magnet powder according to claim 1 or 2 is bonded with a resin binder.

The bonded magnet according to claim 3, wherein the porosity is 11% by volume or less, and the bonded magnet is excellent in squareness and thermal stability.