JP4900113B2 - Method for producing rare earth permanent sintered magnet - Google Patents
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Description
本発明は、重希土類元素を含む希土類永久焼結磁石、特に、重希土類元素を含み、Ｒ（ＲはＹを含む希土類元素の１種又は２種以上）、Ｔ（ＴはＦｅ又はＦｅ及びＣoを必須とする１種又は２種以上の遷移金属元素）及びＢ（ホウ素）を主成分とする、少ない重希土類元素で磁気特性に優れた希土類永久焼結磁石の製造方法に関するものである。 The present invention relates to a rare earth permanent sintered magnet containing a heavy rare earth element, in particular, containing a heavy rare earth element, R (R is one or more of rare earth elements containing Y), T (T is Fe or Fe and Co). The present invention relates to a method for producing a rare earth permanent sintered magnet having a small amount of heavy rare earth elements and having excellent magnetic properties, the main component being 1 or 2 or more transition metal elements that are essential for the present invention and B (boron).
高性能の永久磁石としては、希土類磁石が知られている。この希土類磁石は、小型でも優れた磁気特性を発揮し得ることから、空調機、冷蔵庫等の家庭用電化製品のみならず、産業機械、ロボット、燃料電池車、ハイブリッドカー等の駆動用モータへの応用が検討され、これらの小型化、省エネルギー化を実現し得る磁石材料として期待されている。 Rare earth magnets are known as high performance permanent magnets. Since this rare earth magnet can exhibit excellent magnetic properties even in a small size, it can be applied not only to household appliances such as air conditioners and refrigerators, but also to drive motors for industrial machines, robots, fuel cell vehicles, hybrid cars, etc. Applications are being studied, and it is expected as a magnet material that can realize downsizing and energy saving.
特に近年においては、Ｒ−Ｔ−Ｂ焼結磁石はその磁気特性の高さから、電子機器を始め各種モータに使用されている。 Particularly in recent years, RTB sintered magnets are used in various motors including electronic devices because of their high magnetic properties.
しかし、Ｒ−Ｔ−Ｂ焼結磁石は高温下で保磁力が低下するため、減磁しやすい性質がある。そのためＤｙやＴｂ等の重希土類元素を添加し、保磁力を向上することが行われているが、反面、重希土類元素の添加は、残留磁束密度を低下させる欠点があった。 However, since the R-T-B sintered magnet has a low coercive force at high temperatures, it has the property of being easily demagnetized. Therefore, the addition of heavy rare earth elements such as Dy and Tb is performed to improve the coercive force. However, the addition of heavy rare earth elements has a drawback of reducing the residual magnetic flux density.
そこで、希土類磁石の残留磁束密度及び保磁力を向上することを目的として、その原料となる磁性材料の組成を種々に変更する試みがなされている。しかしながら、これらの磁性材料の組成を変更するだけでは、残留磁束密度及び保磁力の値は、いずれか一方の値が増大すると他方の値が減少するといった関係を有するようになり、このため、全体として優れた特性を有する希土類磁石を得るのが困難な傾向にあった。 Thus, in order to improve the residual magnetic flux density and coercive force of rare earth magnets, attempts have been made to variously change the composition of the magnetic material used as the raw material. However, only by changing the composition of these magnetic materials, the values of residual magnetic flux density and coercive force have a relationship such that when one of the values increases, the other value decreases. As a result, it was difficult to obtain a rare earth magnet having excellent characteristics.
このような状況下、残留磁束密度及び保磁力の双方において優れた特性を得るために、２合金法と呼ばれる２種以上の磁性材料を組み合わせて用いる方法が検討されている。このような２合金法では、磁性材料を構成する２種の合金間の重希土類元素、例えばＤｙの量に差を付けて作成することが考えられている。 Under such circumstances, in order to obtain excellent characteristics in both residual magnetic flux density and coercive force, a method using a combination of two or more kinds of magnetic materials called a two-alloy method has been studied. In such a two-alloy method, it is considered that the amount of heavy rare earth element between the two types of alloys constituting the magnetic material, for example, Dy, is made different.
例えば、重希土類元素の濃度が結晶粒界相より高い第一のＲ２Ｔ１４Ｂ型主相結晶粒と、前記重希土類元素の濃度が結晶粒界相より低い第二のＲ２Ｔ１４Ｂ型主相結晶粒と、前記重希土類元素の濃度が結晶粒界相とほぼ等しい第三のＲ２Ｔ１４Ｂ型主相結晶粒とを含有する組織を有し、高磁気特性を得るためにＲ−Ｔ−Ｂ系焼結磁石内でＤｙを不均一にしたＲ−Ｔ−Ｂ系焼結型永久磁石があり、その実施例では、Ｄｙ１％組成の合金とＤｙ１５％組成の合金を同時粉砕、成形、焼結を行い、粒界相よりもＤｙ組成が低い低Ｄｙ組成の主相粒子と、粒界相よりもＤｙ組成が高い高Ｄｙ組成の主相粒子と、粒界相とＤy濃度がほぼ等しい主相粒子が存在する組織の焼結型永久磁石を作成している（特許文献１）。 For example, a first R 2 T 14 B type main phase crystal grain in which the concentration of heavy rare earth element is higher than the grain boundary phase, and a second R 2 T 14 B in which the concentration of heavy rare earth element is lower than the grain boundary phase. In order to obtain a high magnetic characteristic, having a structure containing a type main phase crystal grain and a third R 2 T 14 B type main phase crystal grain in which the concentration of the heavy rare earth element is substantially equal to the grain boundary phase There is an RTB-based sintered permanent magnet with non-uniform Dy within an RTB-based sintered magnet. In this example, an alloy having a Dy 1% composition and an alloy having a Dy 15% composition are simultaneously ground. Molding, sintering, main phase particles having a low Dy composition having a lower Dy composition than the grain boundary phase, main phase particles having a high Dy composition having a higher Dy composition than the grain boundary phase, grain boundary phase and Dy concentration Sintered permanent magnets having a structure in which main phase particles having substantially the same diameter are present (Patent Document 1).
また、上記先行技術と同様に、Ｒ−Ｔ−Ｂ系の２合金法でＤｙ量が異なる合金を採用する場合に、２合金の粒径を変えることにより、混合後の磁場成形時の配向度を向上させ、これにより残留磁束密度の値を向上させることが提案されている。具体的には、希土類元素、遷移元素及びホウ素（Ｂ）を含む磁性材料から構成され、１０μｍ以下である第１の平均粒径を有する第１の磁性粉末と、希土類元素、遷移元素及びホウ素（Ｂ）を含む磁性材料から構成され、１０μｍ以下であり、且つ、前記第１の平均粒径とは異なる第２の平均粒径を有する第２の磁性粉末とを混合して混合磁性粉末を得る工程と、前記混合磁性粉末を成形して成形体を得る工程と、前記成形体を焼成する工程とを有する希土類磁石の製造方法が提案されている（特許文献２）。
上記特許文献１、２に記載の希土類磁石は、磁気特性が改善されているものの、近年、希土類磁石としては、従来にも増して、より大きな保磁力を得ることが要求されている。 Although the rare earth magnets described in Patent Documents 1 and 2 have improved magnetic properties, in recent years, rare earth magnets are required to have a larger coercive force than ever before.
また、近年における希土類永久磁石の需要の高まり及び省資源化への要求にともない、少ない希土類元素量で高特性の希土類磁石を得ることが求められるようになっている。 In addition, with the recent increase in demand for rare earth permanent magnets and demands for resource saving, it has been demanded to obtain high performance rare earth magnets with a small amount of rare earth elements.
そこで、本発明はこのような事情に鑑みてなされたものであり、少ない重希土類元素量でより大きな保磁力の希土類永久焼結磁石を製造できる希土類永久焼結磁石の製造方法を提供することを目的としている。 Therefore, the present invention has been made in view of such circumstances, and provides a method for producing a rare earth permanent sintered magnet capable of producing a rare earth permanent sintered magnet having a larger coercive force with a small amount of heavy rare earth elements. It is aimed.
上記目的に鑑み鋭意研究の結果、本発明者らは、以下の発明により上記課題を解決しうることを見出した。 As a result of intensive studies in view of the above object, the present inventors have found that the above problems can be solved by the following invention.
即ち、本発明は、主相を構成するコアと、前記コア周囲のシェル及び／又は粒界相とを少なくとも備える組織を有する焼結体からなり、前記コアは前記シェル及び／又は粒界相より重希土類元素の量比が低い低重希土類組成で構成され、前記シェル及び／又は粒界相は前記コアより重希土類元素の量比が高い高重希土類組成で構成されるＲ−Ｔ−Ｂ系希土類永久焼結磁石（ただし、２５ｗｔ％≦Ｒ≦３５ｗｔ％、０ｗｔ％＜ＨＲ≦２０ｗｔ％、ＲはＹを含む希土類元素、ＴはＦｅ又はＦｅ及びＣｏを必須とする遷移金属元素、ＨＲは重希土類元素）の製造方法であって、高重希土類組成物の粒子と、低重希土類組成物の粒子とを混合して混合物を得る混合工程と、前記混合物を磁場中成形して成形体を得る成形工程と、前記成形体を焼結する焼結工程と、を備え、前記低重希土類組成物の粒子の平均粒径が６μｍ以下であり、前記高重希土類組成物の粒子の平均粒径は１〜４．３μｍであり、かつ、前記低重希土類組成物の粒子の平均粒径よりも小さいことを特徴とするＲ−Ｔ−Ｂ系希土類永久焼結磁石の製造方法である。
That is, the present invention comprises a sintered body having a structure comprising at least a core constituting a main phase and a shell and / or a grain boundary phase around the core, and the core is composed of the shell and / or the grain boundary phase. R-T-B system composed of a low heavy rare earth composition with a low heavy rare earth element ratio, and the shell and / or grain boundary phase having a high heavy rare earth composition with a higher heavy rare earth element ratio than the core Rare earth permanent sintered magnet (however, 25 wt% ≦ R ≦ 35 wt%, 0 wt% <HR ≦ 20 wt%, R is a rare earth element including Y, T is a transition metal element essential for Fe or Fe and Co, HR is heavy Rare earth element), a mixing step of mixing particles of a heavy heavy rare earth composition and particles of a low heavy rare earth composition to obtain a mixture, and molding the mixture in a magnetic field to obtain a molded body The molding process and sintering the molded body Comprising a sintering step, wherein the average particle size of the particles of low heavy rare earth composition is not less 6μm or less, an average particle diameter of the particles of the Kokasane rare earth composition is 1～4.3Myuemu, and the low An R-T-B rare earth permanent sintered magnet manufacturing method characterized by being smaller than the average particle size of particles of a heavy rare earth composition.
この製造方法によれば、少ない重希土類元素量でより高特性の希土類永久焼結磁石を製造することができる。 According to this manufacturing method, a rare earth permanent sintered magnet having higher characteristics can be manufactured with a small amount of heavy rare earth element.
特に、本発明においては前記低重希土類組成物の粒子の平均粒径が６μｍ以下であることが必要であり、これにより焼結後の主相の粒径を微細にすることが可能となり、結果として保磁力を向上することができる。 In particular, in the present invention, the average particle size of the particles of the low-heavy rare earth composition needs to be 6 μm or less, which makes it possible to reduce the particle size of the main phase after sintering. As a result, the coercive force can be improved.
ここで、高重希土類組成物とは、２種類以上の重希土類組成物のうち、重希土類元素の量比が高い組成の組成物のことであり、これに比して、低重希土類組成物は、重希土類元素の量比が低い組成の組成物のことである。 Here, the high heavy rare earth composition is a composition having a high ratio of heavy rare earth elements among two or more types of heavy rare earth compositions. Is a composition having a low amount ratio of heavy rare earth elements.
また、本発明において、平均粒径とは、レーザ光線のフラウンフォーファー回折法により測定されたＤ５０平均粒径をいい、具体的には測定装置（ＭＡＬＶＥＲＮ社製マスターマイザー２０００）を用いて測定された値を言う。ここで、Ｄ５０とは、累積体積比率が５０％になる粒径を言う。 In the present invention, the average particle diameter means the D50 average particle diameter measured by the Fraunhofer diffraction method of a laser beam, and specifically measured using a measuring device (Mastermizer 2000 manufactured by MALVERN). Say the value was. Here, D50 refers to the particle size at which the cumulative volume ratio is 50%.
本発明において、重希土類元素とは、Ｙを含む希土類元素のうち、周期律表において原子番号がＧｄ以上の希土類元素をいい、具体的にはＧｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ及びＬｕの少なくとも１種を意味する。一方、Ｙを含む希土類元素のうち、周期律表において原子番号がＥｕ以下の希土類元素は軽希土類元素と呼ぶことができ、具体的には、Ｙ、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｐｍ、Ｓｍ及びＥｕの少なくとも１種をいう。 In the present invention, the heavy rare earth element means a rare earth element having an atomic number of Gd or more in the periodic table among rare earth elements including Y, specifically, Gd, Tb, Dy, Ho, Er, Tm, Yb. And at least one of Lu. On the other hand, among rare earth elements including Y, a rare earth element having an atomic number of Eu or less in the periodic table can be called a light rare earth element. Specifically, Y, La, Ce, Pr, Nd, Pm, Sm And at least one of Eu.
また、本発明においては、前記高重希土類組成物がＲ−Ｔ−Ｂ系合金（ただし、ＲはＹを含む希土類元素、ＴはＦｅ又はＦｅ及びＣｏを必須とする１種又は２種以上の遷移金属元素。）又はＲ−Ｔ系合金であり、前記低重希土類組成物がＲ−Ｔ−Ｂ系合金であることが好ましい。これは高特性であるＲ−Ｔ−Ｂ系焼結磁石の製造方法において、焼結後の主相におけるコアが、低重希土類組成となるために有効である。 Further, in the present invention, the heavy heavy rare earth composition is an R-T-B alloy (where R is a rare earth element including Y, T is one or more elements including Fe or Fe and Co as essential components). A transition metal element) or an RT-based alloy, and the low heavy rare earth composition is preferably an RTB-based alloy. This is effective because the core in the main phase after sintering has a low heavy rare earth composition in the manufacturing method of the RTB-based sintered magnet having high characteristics.
また、本発明においては、前記高重希土類組成物がＲ−Ｔ合金であり、前記低重希土類組成物がＲ−Ｔ−Ｂ合金であることが好ましい。これにより焼結後において、高特性の粒子構造とは逆の、主相のコアが高重希土類組成でシェル及び／又は粒界相が低重希土類組成である構造を持った粒子の生成を抑制することができる。 In the present invention, the high heavy rare earth composition is preferably an RT alloy, and the low heavy rare earth composition is preferably an RTB alloy. This suppresses the formation of particles with a structure in which the core of the main phase is a high heavy rare earth composition and the shell and / or grain boundary phase is a low heavy rare earth composition, which is the opposite of the high-quality particle structure, after sintering. can do.
また、本発明においては、前記高重希土類組成物の粒子の平均粒径に対する前記低重希土類組成物の粒子の平均粒径の比が１．５以上であることが好ましい。これによりコアとシェル及び／又は粒界相の重希土類元素の濃度差が大きくなり、保磁力の向上を大きくすることができる。 In the present invention, the ratio of the average particle size of the particles of the low heavy rare earth composition to the average particle size of the particles of the high heavy rare earth composition is preferably 1.5 or more. Thereby, the concentration difference between the heavy rare earth elements in the core and shell and / or the grain boundary phase is increased, and the coercive force can be improved.
また、本発明においては、前記希土類永久焼結磁石に含まれる酸素量が２０００ｐｐｍ以下であることが好ましい。これにより粒界相成分が増加することで保磁力の向上を大きくすることができる。 In the present invention, it is preferable that the amount of oxygen contained in the rare earth permanent sintered magnet is 2000 ppm or less. Thereby, the improvement of the coercive force can be increased by increasing the grain boundary phase component.
本発明の希土類永久焼結磁石の製造方法によれば、少ない重希土類元素量でより大きな保磁力の希土類永久焼結磁石を製造できる希土類永久焼結磁石の製造方法を提供することができる。 According to the method for producing a rare earth permanent sintered magnet of the present invention, it is possible to provide a method for producing a rare earth permanent sintered magnet capable of producing a rare earth permanent sintered magnet having a larger coercive force with a small amount of heavy rare earth elements.
以下、本発明の実施形態について詳細に説明する。 Hereinafter, embodiments of the present invention will be described in detail.
（希土類永久焼結磁石） まず本発明の希土類永久焼結磁石の構成について説明する。 (Rare earth permanent sintered magnet) First, the configuration of the rare earth permanent sintered magnet of the present invention will be described.
本発明の希土類永久焼結磁石は、主相を構成するコアと、前記コア周囲のシェル及び／又は粒界相とを少なくとも備える組織を有する焼結体からなる。コアはシェル及び／又は粒界相より重希土類元素の量比が低い低希土類組成で構成され、シェル及び／又は粒界相はコアより重希土類元素の量比が高い高希土類組成で構成される。 The rare earth permanent sintered magnet of the present invention comprises a sintered body having a structure including at least a core constituting a main phase and a shell and / or a grain boundary phase around the core. The core is composed of a low rare earth composition in which the amount ratio of heavy rare earth elements is lower than that of the shell and / or grain boundary phase, and the shell and / or grain boundary phase is composed of a high rare earth composition in which the amount ratio of heavy rare earth elements is higher than that of the core. .
このように重希土類元素分布が、コアを構成する主相中心より、シェル及び／又は粒界相の重希土類元素の量比が高くなっていると、シェル及び／又は粒界相が希土類永久磁石の磁化反転の開始に影響を与えるため、保磁力が向上する。 As described above, when the heavy rare earth element distribution has a higher ratio of heavy rare earth elements in the shell and / or grain boundary phase than the center of the main phase constituting the core, the shell and / or grain boundary phase becomes the rare earth permanent magnet. Since this affects the start of magnetization reversal, the coercive force is improved.
本発明における希土類永久焼結磁石としては、好適には、希土類元素（Ｒ）と、希土類元素以外の遷移金属（Ｔ）とを組み合わせた、Ｒ−Ｔ−Ｂ系又はＲ−Ｔ系の希土類永久焼結磁石が挙げられ、具体的には、希土類元素（Ｒ）としてはＹを含む希土類元素が挙げられ、この内重希土類元素としてはＤｙやＴｂが挙げられ、遷移金属（Ｔ）としてはＦｅ又はＦｅ及びＣoが挙げられる。このような希土類永久焼結磁石は、必要に応じて、Ｃｏ、Ａｌ、Ｃｕ、Ｚｒ、Ｗ、Ｎｂ、Ｔａ、Ｂｉ、Ｓｎ、Ｇａ等の他の元素を更に含有してもよい。 The rare earth permanent sintered magnet in the present invention is preferably an R-T-B or RT-based rare earth permanent that is a combination of a rare earth element (R) and a transition metal (T) other than the rare earth element. Specific examples include rare earth elements including Y as rare earth elements (R), Dy and Tb as heavy rare earth elements, and Fe as transition metals (T). Or Fe and Co are mentioned. Such a rare earth permanent sintered magnet may further contain other elements such as Co, Al, Cu, Zr, W, Nb, Ta, Bi, Sn, and Ga as required.
Ｒ−Ｔ−Ｂ系焼結磁石での組成は、例えば、０．６ｗｔ％≦Ｂ＋Ｃ≦１．２ｗｔ％、好ましくは０．９ｗｔ％≦Ｂ＋Ｃ≦１．１ｗｔ％であり、０．５ｗｔ％≦Ｂ≦１．１ｗｔ％、好ましくは０．９ｗｔ％≦Ｂ≦１．０ｗｔ％であり、２５ｗｔ％≦Ｒ≦３５ｗｔ％、好ましくは２８ｗｔ％≦Ｒ≦３２ｗｔ％、より好ましくは２８ｗｔ％≦Ｒ≦３０ｗｔ％であり、０ｗｔ％＜ＨＲ≦２０ｗｔ％、好ましくは０ｗｔ％＜ＨＲ≦１０ｗｔ％であり、０．1ｗｔ％≦Ｃｏ≦５ｗｔ％、好ましくは０．1ｗｔ％≦Ｃｏ≦２ｗｔ％、より好ましくは０．1ｗｔ％≦Ｃｏ≦１ｗｔ％であり、０．１ｗｔ％≦Ｍ≦５ｗｔ％、好ましくは０．２ｗｔ％≦Ｍ≦３ｗｔ％、より好ましくは０．３≦Ｍ≦２ｗｔ％であり、酸素＜５０００ｐｐｍ、好ましくは酸素＜２０００ｐｐｍであり、より好ましくは酸素＜１０００ｐｐｍであり、窒素量＜２０００ｐｐｍ、好ましくは窒素量＜５００ｐｐｍであり、残部Ｆｅで表される。なお、ＨＲは重希土類元素の総量であり、ＭはＡｌ、Ｃｕ、Ｚｒ、Ｗ、Ｎｂ、Ｔａ、Ｂｉ、Ｓｎ、Ｇａである。 The composition of the RTB-based sintered magnet is, for example, 0.6 wt% ≦ B + C ≦ 1.2 wt%, preferably 0.9 wt% ≦ B + C ≦ 1.1 wt%, and 0.5 wt% ≦ B ≦ 1.1 wt%, preferably 0.9 wt% ≦ B ≦ 1.0 wt%, 25 wt% ≦ R ≦ 35 wt%, preferably 28 wt% ≦ R ≦ 32 wt%, more preferably 28 wt% ≦ R ≦ 30 wt% 0 wt% <HR ≦ 20 wt%, preferably 0 wt% <HR ≦ 10 wt%, 0.1 wt% ≦ Co ≦ 5 wt%, preferably 0.1 wt% ≦ Co ≦ 2 wt%, more preferably 0.1 wt%. 1 wt% ≦ Co ≦ 1 wt%, 0.1 wt% ≦ M ≦ 5 wt%, preferably 0.2 wt% ≦ M ≦ 3 wt%, more preferably 0.3 ≦ M ≦ 2 wt%, oxygen <5000 ppm, Preferably oxygen <2000p M, and more preferably an oxygen <1000 ppm, nitrogen content <2000 ppm, preferably nitrogen content <500 ppm, expressed by the balance Fe. Note that HR is the total amount of heavy rare earth elements, and M is Al, Cu, Zr, W, Nb, Ta, Bi, Sn, and Ga.
Ｂ及びＣ、特にＢはＲ−Ｔ−Ｂ焼結磁石において主相を構成する元素であり、少ないと主相割合が少なくなり残留磁束密度が低下し、多いと異相が析出するため、やはり残留磁束密度が低下する。Ｒが少ないと保磁力発現に必要な粒界相が形成されないため保磁力が低下し、多いと非磁性相が増加するため残留磁束密度が低下する。ＨＲが多いと主相の異方性磁界が大きくなり保磁力が向上するが、飽和磁化が低下するため残留磁束密度が低下する。よってＨＲの量は磁石の用途に合わせて適宜決定することが望ましい。Ｃｏはキュリー温度を上げる効果があるが、多すぎると残留磁束密度、保磁力が低下する。ＭのうちＡｌ、Ｃｕ、Ｂｉ、Ｓｎ、Ｇａは保磁力向上に効果があり、Ｚｒ，Ｗ，Ｎｂ，Ｔａは焼結時の粒成長を抑制するため、やはり保磁力向上に効果がある。Ｍが少ないと添加の効果が表れないが、多すぎると残留磁束密度が低下する。酸素量、窒素量が多いと主相体積比が減少するために残留磁束密度が低下するため、少なくすることが望ましい。 B and C, in particular B, are elements constituting the main phase in the R-T-B sintered magnet. If the amount is small, the ratio of the main phase decreases and the residual magnetic flux density decreases. Magnetic flux density decreases. When R is small, the grain boundary phase necessary for the expression of coercive force is not formed, so that the coercive force is lowered. When the HR is large, the anisotropic magnetic field of the main phase is increased and the coercive force is improved. However, the saturation magnetization is lowered, so that the residual magnetic flux density is lowered. Therefore, it is desirable that the amount of HR is appropriately determined according to the use of the magnet. Co has the effect of raising the Curie temperature, but if it is too much, the residual magnetic flux density and the coercive force are lowered. Among M, Al, Cu, Bi, Sn, and Ga are effective in improving coercive force, and Zr, W, Nb, and Ta are effective in improving coercive force because they suppress grain growth during sintering. If M is small, the effect of addition does not appear, but if it is too large, the residual magnetic flux density decreases. When the amount of oxygen and the amount of nitrogen are large, the volume ratio of the main phase is decreased and the residual magnetic flux density is decreased.
（希土類永久焼結磁石の製造方法）
次に、上記構成の希土類永久焼結磁石の製造方法について説明する。本発明においては粉砕工程、混合工程、成形工程、焼結工程を経て焼結磁石が得られる。
(Production method of rare earth permanent sintered magnet)
Next, a method for manufacturing the rare earth permanent sintered magnet having the above-described configuration will be described. In the present invention, a sintered magnet is obtained through a pulverization process, a mixing process, a molding process, and a sintering process.
（粉砕工程）まず高重希土類組成物の粒子と、低重希土類組成物の粒子とを準備する。 (Crushing step) First, particles of a heavy heavy rare earth composition and particles of a low heavy rare earth composition are prepared.
低重希土類組成物は主に焼結後に主相におけるコアを構成する組成物であり、Ｒ−Ｔ−Ｂ合金の場合の組成は、例えば、０．６ｗｔ％≦Ｂ＋Ｃ≦１．２ｗｔ％、好ましくは０．９ｗｔ％≦Ｂ＋Ｃ≦１．１ｗｔ％であり、０．５ｗｔ％≦Ｂ≦１．１ｗｔ％、好ましくは０．９ｗｔ％≦Ｂ≦１ｗｔ％であり、２５ｗｔ％≦Ｒ≦３５ｗｔ％、好ましくは２８ｗｔ％≦Ｒ≦３２ｗｔ％、より好ましくは２８ｗｔ％≦Ｒ≦３０ｗｔ％であり、０ｗｔ％≦ＨＲ≦１０ｗｔ％、好ましくは０ｗｔ％≦ＨＲ≦５ｗｔ％、より好ましくは０ｗｔ％≦ＨＲ≦２ｗｔ％であり、０≦Ｃｏ≦５ｗｔ％、好ましくは０≦Ｃｏ≦２ｗｔ％、より好ましくは０≦Ｃｏ≦１ｗｔ％であり、０＜Ｍ≦５ｗｔ％、好ましくは０＜Ｍ≦３ｗｔ％、より好ましくは０＜Ｍ≦２ｗｔ％であり、酸素＜５０００ｐｐｍ、好ましくは酸素＜２０００ｐｐｍであり、より好ましくは酸素＜１０００ｐｐｍであり、窒素量＜２０００ｐｐｍ、好ましくは窒素量＜５００ｐｐｍであり、残部Ｆｅで表される組成である。 The low heavy rare earth composition is a composition mainly constituting the core in the main phase after sintering, and the composition in the case of the R-T-B alloy is, for example, 0.6 wt% ≦ B + C ≦ 1.2 wt%, preferably Is 0.9 wt% ≦ B + C ≦ 1.1 wt%, 0.5 wt% ≦ B ≦ 1.1 wt%, preferably 0.9 wt% ≦ B ≦ 1 wt%, 25 wt% ≦ R ≦ 35 wt%, preferably Is 28 wt% ≦ R ≦ 32 wt%, more preferably 28 wt% ≦ R ≦ 30 wt%, 0 wt% ≦ HR ≦ 10 wt%, preferably 0 wt% ≦ HR ≦ 5 wt%, more preferably 0 wt% ≦ HR ≦ 2 wt%. 0 ≦ Co ≦ 5 wt%, preferably 0 ≦ Co ≦ 2 wt%, more preferably 0 ≦ Co ≦ 1 wt%, 0 <M ≦ 5 wt%, preferably 0 <M ≦ 3 wt%, more preferably 0 <M ≦ 2wt% Oxygen <5000 ppm, preferably an oxygen <2000 ppm, more preferably oxygen <1000 ppm, nitrogen content <2000 ppm, preferably nitrogen content <500 ppm, a composition represented by the balance Fe.
焼結後に主相のコアになるという面から、主相形成に必要なＢ、Ｃ、Ｒについてコアに相応した量を含んでいる必要がある。ＨＲが多いと焼結体主相コアの重希土類元素量が多くなり残留磁束密度が低下する。Ｃｏ及びＭは低重希土類組成物から添加しても高重希土類組成物から添加しても、両方から添加しても良い。 From the viewpoint of becoming the core of the main phase after sintering, it is necessary to include the amount corresponding to the core for B, C, and R necessary for forming the main phase. When HR is large, the amount of heavy rare earth elements in the sintered body main phase core increases, and the residual magnetic flux density decreases. Co and M may be added from the low heavy rare earth composition, the high heavy rare earth composition, or both.
高重希土類組成物は、Ｒ−Ｔ−Ｂ合金、Ｒ−Ｔ合金、重希土類ハロゲン化物、重希土類酸化物、重希土類水素化物等がある。Ｒ−Ｔ−Ｂ合金、あるいはＲ−Ｔ合金の場合の組成は、例えば、０ｗｔ％≦Ｂ＋Ｃ≦１．２ｗｔ％、好ましくは０ｗｔ％≦Ｂ＋Ｃ≦０．５ｗｔ％、より好ましくは０ｗｔ％≦Ｂ＋Ｃ≦０．１ｗｔ％であり、０ｗｔ％≦Ｂ≦１．１ｗｔ％、好ましくは０ｗｔ％≦Ｂ≦０．１ｗｔ％であり、１９ｗｔ％≦Ｒ、好ましくは２９ｗｔ％≦Ｒ≦６０ｗｔ％、より好ましくは２９ｗｔ％≦Ｒ≦４６ｗｔ％であり、１９ｗｔ％≦ＨＲ、好ましくは２９ｗｔ％≦ＨＲ≦６０ｗｔ％であり、０ｗｔ％≦Ｃｏ≦５０ｗｔ％、好ましくは０ｗｔ％≦Ｃｏ≦２０wt%、より好ましくは０ｗｔ％≦Ｃo≦１０wt%であり、０ｗｔ％＜Ｍ≦１０ｗｔ％、好ましくは０ｗｔ％＜Ｍ≦５ｗｔ％、より好ましくは０ｗｔ％＜Ｍ≦３ｗｔ％であり、酸素＜５０００ｐｐｍ、好ましくは酸素＜２０００ｐｐｍであり、より好ましくは酸素＜１０００ｐｐｍであり、窒素量＜２０００ｐｐｍ、好ましくは窒素量＜５００ｐｐｍであり、残部Ｆｅで表される組成である。 Examples of the high heavy rare earth composition include an RTB alloy, an RT alloy, a heavy rare earth halide, a heavy rare earth oxide, and a heavy rare earth hydride. The composition in the case of the RTB alloy or RT alloy is, for example, 0 wt% ≦ B + C ≦ 1.2 wt%, preferably 0 wt% ≦ B + C ≦ 0.5 wt%, more preferably 0 wt% ≦ B + C ≦ 0.1 wt%, 0 wt% ≦ B ≦ 1.1 wt%, preferably 0 wt% ≦ B ≦ 0.1 wt%, 19 wt% ≦ R, preferably 29 wt% ≦ R ≦ 60 wt%, more preferably 29 wt% % ≦ R ≦ 46 wt%, 19 wt% ≦ HR, preferably 29 wt% ≦ HR ≦ 60 wt%, 0 wt% ≦ Co ≦ 50 wt%, preferably 0 wt% ≦ Co ≦ 20 wt%, more preferably 0 wt% ≦ Co ≦ 10 wt%, 0 wt% <M ≦ 10 wt%, preferably 0 wt% <M ≦ 5 wt%, more preferably 0 wt% <M ≦ 3 wt%, oxygen <5000 ppm, preferably oxygen <2000 ppm, more preferably oxygen <1000 ppm, nitrogen content <2000 ppm, preferably nitrogen content <500 ppm, and the composition represented by the balance Fe.
Ｂを添加することにより高重希土類組成物は高融点になることが多く、焼結過程制御の目的で添加する場合がある。多すぎると焼結後に高重希土類組成のコアを持った主相が生成しやすくなるため残留磁束密度が低下する。Ｒは少ないと焼結性が悪くなり、多いと製造中に酸化しやすい。ＨＲが少ないと重希土類元素のシェル及び／又は粒界相を形成しにくく、保磁力が低下する。ＨＲが多いと焼結時に粒成長を起こしやすく、保磁力が低下する。 By adding B, the heavy heavy rare earth composition often has a high melting point, and may be added for the purpose of controlling the sintering process. If the amount is too large, a main phase having a core with a heavy heavy rare earth composition is likely to be formed after sintering, so the residual magnetic flux density is lowered. If the amount of R is small, the sinterability deteriorates, and if it is large, it is likely to be oxidized during production. When the HR is small, it is difficult to form a heavy rare earth element shell and / or grain boundary phase, and the coercive force is lowered. When there is much HR, it will be easy to raise | generate a grain growth at the time of sintering, and a coercive force will fall.
低重希土類組成物と高重希土類組成物の重希土類元素量比の差は例えば１９ｗｔ％以上、好ましくは２９ｗｔ％以上である。差が小さいと、主相を構成するコアと前記コア周囲のシェル及び／又は粒界相とを少なくとも備える、コアシェル構造を形成しにくい。 The difference in the amount of heavy rare earth element between the low heavy rare earth composition and the heavy heavy rare earth composition is, for example, 19 wt% or more, preferably 29 wt% or more. When the difference is small, it is difficult to form a core-shell structure including at least a core constituting the main phase and a shell and / or a grain boundary phase around the core.
このとき、高重希土類組成物の粒子としては、低希土類組成物の粒子の平均粒径よりも小さい平均粒径とする必要がある。 At this time, the particles of the heavy heavy rare earth composition need to have an average particle size smaller than the average particle size of the particles of the low rare earth composition.
これは、コア周囲のシェル及び／又は粒界相よりも、コアを構成する主相粒子における低重希土類元素の割合を増やすためである。より詳細に述べると、高重希土類組成物の粒子の平均粒径を低重希土類組成物の粒子の平均粒径よりも小さくすることにより、混合工程、成形工程後における成形体で、高希土類組成物由来の微粉の分散状態が良くなるため、焼結後には主相シェル部および粒界相よりも、主相コア部が低重希土類組成の組織を持つ焼結体を作製することができる。また平均粒径が小さい場合、表面エネルギーが大きいため、焼結段階で液相に溶け易く、再析出しやすい。このことより高重希土類組成物の平均粒径を小さくすることで、低重希土類組成物の周囲に高重希土類組成が形成され、結果として高重希土類組成のシェル及び／又は粒界相を有するコアシェル構造を持った焼結体となり、高保磁力が得られる。 This is to increase the proportion of low-heavy rare earth elements in the main phase particles constituting the core, rather than the shell and / or grain boundary phase around the core. More specifically, by making the average particle size of the particles of the high heavy rare earth composition smaller than the average particle size of the particles of the low heavy rare earth composition, the high rare earth composition in the compact after the mixing step and the forming step is obtained. Since the dispersion state of the fine powder derived from the product is improved, it is possible to produce a sintered body in which the main phase core portion has a structure having a low heavy rare earth composition rather than the main phase shell portion and the grain boundary phase after sintering. In addition, when the average particle size is small, the surface energy is large, so that it is easily dissolved in the liquid phase during the sintering stage and re-precipitated. Thus, by reducing the average particle size of the heavy heavy rare earth composition, a heavy heavy rare earth composition is formed around the low heavy rare earth composition, resulting in having a shell and / or a grain boundary phase of the heavy heavy rare earth composition. A sintered body having a core-shell structure is obtained, and a high coercive force is obtained.
ここで希土類組成物の粒径は、構成する粒子の大きさを指し、平均粒径は、上述したように、フラウンフォーファー散乱法によるＤ５０平均粒径である。低重希土類組成物の平均粒径は、大きいと保磁力が低下するという理由から６μｍ以下であり、より好ましくは５μｍ以下である。また粉砕容易性という理由から、１μｍ以上であることが好ましい。また高重希土類組成物平均粒径は、低重希土類組成物より細かくする、あるいは粉砕容易性という理由から、１〜４μｍの範囲であることが好ましい。 Here, the particle size of the rare earth composition indicates the size of the constituent particles, and the average particle size is the D50 average particle size by the Fraunhofer scattering method as described above. The average particle size of the low-heavy rare earth composition is 6 μm or less, and more preferably 5 μm or less, because the coercive force is lowered when it is large. Moreover, it is preferable that it is 1 micrometer or more from the reason of crushing ease. Further, the average particle size of the high heavy rare earth composition is preferably in the range of 1 to 4 μm because it is finer than the low heavy rare earth composition or because it is easily pulverized.
高重希土類組成物の粒子の平均粒径に対する、低重希土類組成物の粒子の平均粒径の粒径比は、保磁力向上に有効であるという理由から、１超であることが好ましく、１．５以上であることが好ましく、より好ましくは２．０以上であり、さらに好ましくは２．５以上である。また高重希土類組成物の粒子の平均粒径に対する、低重希土類組成物の粒子の平均粒径の粒径比は６以下であることが好ましく、より好ましくは５以下である。粒径比が６を超えると、６以下である場合に比べて、製造が困難となる傾向がある。 The ratio of the average particle size of the particles of the low heavy rare earth composition to the average particle size of the particles of the high heavy rare earth composition is preferably more than 1 because it is effective for improving the coercive force. 0.5 or more, more preferably 2.0 or more, and even more preferably 2.5 or more. The ratio of the average particle size of the particles of the low heavy rare earth composition to the average particle size of the particles of the high heavy rare earth composition is preferably 6 or less, more preferably 5 or less. When the particle size ratio exceeds 6, the production tends to be difficult as compared with the case where the particle size ratio is 6 or less.
粒径の調整は粉砕あるいは合成など、どのような方法を用いて調整しても良いが、希土類組成物がＲ−Ｔ−Ｂ系合金の場合の例では、粒径は粉砕工程により調整されることが容易である。通常粉砕工程は粗粉砕工程と微粉砕工程で構成され、平均粒径の調整は主に微粉砕工程条件でなされる。 The particle size may be adjusted by any method such as pulverization or synthesis, but in the example where the rare earth composition is an R-T-B alloy, the particle size is adjusted by the pulverization step. Is easy. The normal pulverization process is composed of a coarse pulverization process and a fine pulverization process, and the adjustment of the average particle diameter is mainly performed under the fine pulverization process conditions.
粗粉砕工程に使用する合金はブックモールドでも良いが、ストリップキャスト合金が粉砕性の点より優れている。粗粉砕工程は、例えば、ジョークラッシャー、ブラウンミル、スタンプミル等の粗粉砕機を用いるか、または、合金に水素を吸蔵させた後、吸蔵に基づく体積膨張により、自己崩壊的な粉砕を生じさせることによって行うことができる。得られる粗粉は１０μｍ〜５ｍｍ程度である。 The alloy used in the coarse pulverization process may be a book mold, but a strip cast alloy is superior in terms of pulverization. In the coarse pulverization step, for example, a coarse pulverizer such as a jaw crusher, a brown mill, a stamp mill, or the like is used, or hydrogen is occluded in the alloy and then self-disintegrating pulverization is caused by volume expansion based on occlusion. Can be done. The coarse powder obtained is about 10 μm to 5 mm.
続いて、粗粉砕工程により得られた粉末を更に微粉砕工程に供する。微粉砕工程は、粗粉砕された粉末に対し、粉砕時間等の条件を適宜調整しながら、ジェットミル、ボールミル、振動ミル、湿式アトライター等の微粉砕機を用いて更なる粉砕を行うことによって実施する。得られた微粉は粉砕条件、粉砕時間あるいは粉砕中や粉砕後に分級することにより目的の粒度に調整できる。粗粉砕工程、微粉砕工程ともに焼結体の酸素量を低減させるために、不活性雰囲気で行うことが望ましい。具体的にはＡｒあるいは窒素中で酸素量を１００ｐｐｍ以下に調整して行う。 Subsequently, the powder obtained by the coarse pulverization step is further subjected to a fine pulverization step. The fine pulverization step is performed by further pulverizing the coarsely pulverized powder using a fine pulverizer such as a jet mill, a ball mill, a vibration mill, and a wet attritor while appropriately adjusting conditions such as a pulverization time. carry out. The fine powder obtained can be adjusted to the desired particle size by classification under grinding conditions, grinding time, or during or after grinding. In order to reduce the amount of oxygen in the sintered body, it is desirable that both the coarse pulverization step and the fine pulverization step be performed in an inert atmosphere. Specifically, the oxygen amount is adjusted to 100 ppm or less in Ar or nitrogen.
高重希土類組成物と低希土類組成物それぞれ異なった平均粒度とするために、別に粉砕する工程を説明したが、それぞれ組成物の組成・組織により粉砕条件を同一にすることができる。例えばＲ−Ｔ−Ｂ合金を用いた場合には、合金段階での組織を細かくすることで、同一粉砕条件でも微細な平均粒径を得ることができる。その場合は粉砕前の状態で混合し、同時に粉砕することが可能であるため、混合粉砕工程が一回で済むこと、後に示す混合工程が不要になることから、生産性が向上する。 In order to obtain different average particle sizes for the high-heavy rare earth composition and the low-rare earth composition, the pulverization process has been described separately. However, the pulverization conditions can be the same depending on the composition and structure of the composition. For example, when an R-T-B alloy is used, a fine average particle diameter can be obtained even under the same pulverization condition by reducing the structure at the alloy stage. In this case, since mixing can be performed in the state before pulverization and pulverization can be performed at the same time, the mixing and pulverization process can be performed only once, and the mixing process described later is unnecessary, thereby improving productivity.
原料となる重希土類組成物はここまで２種類の場合を説明したが、３種類以上でも良い。しかし組成物の種類が多いと粉砕、混合が煩雑になるため５種類以下とすることが望ましい。組成物が３種類以上の場合、上述組成・粒径に従えば高重希土類組成物の種類数、低重希土類組成物の種類数を適宜決めてかまわない。しかし低重希土類組成物の種類が多いと、焼結時に低希土類組成物間において反応が進みやすく、シェルが低重希土類組成になりやすくなるため、一種類が好ましい。 Although the case where two kinds of heavy rare earth compositions as raw materials have been described so far, three or more kinds may be used. However, if there are many kinds of compositions, pulverization and mixing become complicated, so it is desirable to use five or less kinds. When there are three or more compositions, the number of types of high-heavy rare earth compositions and the number of types of low-heavy rare earth compositions may be appropriately determined according to the above-described composition and particle size. However, when there are many kinds of low heavy rare earth compositions, a reaction is likely to proceed between the low rare earth compositions during sintering, and the shell tends to have a low heavy rare earth composition.
（混合工程）上記のようにして高重希土類組成物の粒子と、低重希土類組成物の粒子とを用意した後は、これらを混合して混合物を得る。 (Mixing step) After preparing the particles of the high heavy rare earth composition and the particles of the low heavy rare earth composition as described above, they are mixed to obtain a mixture.
混合比率は、低重希土類組成物：高重希土類組成物＝７０：３０〜９８：２であることが好ましく、より好ましくは８５：１５〜９５：５である。低重希土類組成物が少ないと、焼結後に主相コアとなる粒子が少ないため、焼結後のシェル及び／又は粒界相が厚くなる。また後述の磁場成形時に配向する主相粒子が少なく、残留磁束密度が低下する。低重希土類組成物が多いと焼結後にシェル及び／又は粒界相となる成分が少ないので、コアシェル構造が形成されにくい。 The mixing ratio is preferably low heavy rare earth composition: high heavy rare earth composition = 70: 30 to 98: 2, more preferably 85:15 to 95: 5. When there are few low heavy rare earth compositions, since the particle | grains used as a main phase core after sintering are few, the shell and / or grain boundary phase after sintering become thick. Moreover, there are few main phase particles orientated at the time of the magnetic field shaping | molding mentioned later, and a residual magnetic flux density falls. When there are many low heavy rare earth compositions, since there are few components which become a shell and / or a grain boundary phase after sintering, it is difficult to form a core-shell structure.
混合する装置はＶミキサー、ヘンシェルミキサー、などを使用することができるが、２種類以上の微粉が分散良く混合される装置が望ましい。この観点から羽が高速で回転するタイプの混合機が良い。 As a mixing apparatus, a V mixer, a Henschel mixer, or the like can be used, but an apparatus in which two or more kinds of fine powders are mixed with good dispersion is desirable. From this point of view, a mixer of the type whose wings rotate at high speed is preferable.
（成形工程）次いで、混合物を、磁場中で加圧成形する。より具体的には、原料粉末を電磁石中に配置された金型内に充填した後、電磁石により磁場を印加して原料粉末の結晶軸を配向させながら、原料粉末を加圧することにより成形を行う。成形は乾式成形と、微粉を溶媒中に分散させ成形する湿式成形がある。湿式成形は配向度が向上するが、カーボンが増加する傾向がある。 (Molding step) Next, the mixture is pressure-molded in a magnetic field. More specifically, after the raw material powder is filled in a mold disposed in an electromagnet, molding is performed by pressing the raw material powder while orienting the crystal axis of the raw material powder by applying a magnetic field with the electromagnet. . Molding includes dry molding and wet molding in which fine powder is dispersed in a solvent. Wet molding improves the degree of orientation but tends to increase carbon.
湿式成形について説明する。微粉が気流粉砕等、乾式で粉砕された場合、溶媒とを混合し、原料粉末を含むスラリーを調製する。スラリーの製造に用いる溶媒としては、磁石の湿式成形におけるスラリーに用いられる溶媒を特に制限無く適用できる。例えば、鉱物油、合成油、植物油等の油や、アセトン、アルコールといった有機溶媒等が挙げられる。なかでも、磁性粉末の酸化を抑制するために、油が好ましい。また、溶媒以外に、所望の特性が得られる他の添加剤を更に加えることもできる。添加剤としては、例えば、磁性粉末の分散を促進することができるカチオン系、アニオン系、ベタイン系、非イオン系界面活性剤等の分散剤が挙げられる。微粉が湿式で粉砕された場合は、必ずしもスラリー化工程は必要でない。 The wet molding will be described. When the fine powder is pulverized by a dry method such as airflow pulverization, a solvent is mixed to prepare a slurry containing raw material powder. As the solvent used in the production of the slurry, the solvent used in the slurry in the wet molding of the magnet can be applied without particular limitation. Examples thereof include oils such as mineral oil, synthetic oil and vegetable oil, and organic solvents such as acetone and alcohol. Of these, oil is preferable in order to suppress oxidation of the magnetic powder. In addition to the solvent, other additives capable of obtaining desired characteristics can be further added. Examples of the additive include dispersants such as cationic, anionic, betaine, and nonionic surfactants that can promote dispersion of the magnetic powder. When the fine powder is pulverized wet, the slurrying step is not necessarily required.
このスラリー製造工程においては、得られるスラリー中の原料粉末濃度が好ましくは６０〜８０質量％、より好ましくは６５〜７５質量％となるようにする。このような原料粉末濃度を有するスラリーは、成形機への輸送に好適な流動性を有するものとなる。 In this slurry manufacturing process, the raw material powder concentration in the obtained slurry is preferably 60 to 80% by mass, more preferably 65 to 75% by mass. The slurry having such a raw material powder concentration has fluidity suitable for transport to a molding machine.
なお、このスラリー製造工程では、上記の原料粉末濃度を有するスラリーを得る前に、これよりも高い濃度で混練を行った後（混練工程）、得られた混練物に有機溶媒を加えて上記濃度まで希釈してもよい（希釈工程）。高濃度で混練を行うことにより、原料粉末同士の衝突等を高頻度で生じさせることができる。その結果、原料粉末の構成粒子が凝集して２次粒子等を形成している場合は、これを解砕して一次粒子が均一に分散されたスラリーを得ることが可能となる。このようなスラリーによれば、後述する成形時の配向が生じ易くなり、高い配高度を有する希土類磁石を形成することができる。かかる混練時の原料粉末濃度は好ましくは８５〜９５質量％、より好ましくは８８〜９４質量％である。 In this slurry production step, before obtaining a slurry having the above raw material powder concentration, after kneading at a higher concentration (kneading step), an organic solvent is added to the obtained kneaded product to obtain the above concentration. (Dilution step). By kneading at a high concentration, collisions between the raw material powders can be generated with high frequency. As a result, when the constituent particles of the raw material powder are aggregated to form secondary particles and the like, it is possible to obtain a slurry in which the primary particles are uniformly dispersed by crushing them. According to such a slurry, it becomes easy to produce the orientation at the time of the shaping | molding mentioned later, and the rare earth magnet which has a high altitude can be formed. The raw material powder concentration during such kneading is preferably 85 to 95% by mass, more preferably 88 to 94% by mass.
このようにして得られたスラリーに対しては、成形前に、磁性粉末と溶媒とを再度分散させる工程を行うことが好ましい（分散工程）。スラリーにおいては、成形機に供給する途中で磁性粉末と溶媒とが分離してしまい、これによって溶媒の上澄み等が生じていることがある。このスラリーをそのまま成形に用いると、分離の程度によっては成形機に投入される原料粉末の量が一定でなくなり、その結果、成形体中の磁性粉末量にばらつきが生じるおそれもある。これに対し、成形前に分散を行うと、スラリーの分離が少ない状態で成形を行うことができるようになり、成形体のばらつきを抑えることが可能となる。 The slurry thus obtained is preferably subjected to a step of dispersing the magnetic powder and the solvent again before forming (dispersing step). In the slurry, the magnetic powder and the solvent may be separated while being supplied to the molding machine, which may cause a supernatant of the solvent. If this slurry is used for molding as it is, the amount of raw material powder charged into the molding machine is not constant depending on the degree of separation, and as a result, the amount of magnetic powder in the molded body may vary. On the other hand, if the dispersion is performed before molding, the molding can be performed with little separation of the slurry, and variations in the molded body can be suppressed.
スラリーの分散は、ボールミル、超音波拡散、ホモジナイザー、アルティマイザー等を用いることによって行うことができる。例えば、これらの操作を行う装置を、スラリーを成形機に供給する供給管の途中に組み入れることで、良好に分散を行うことができる。この分散による効果を良好に得る観点からは、できるだけ成形直前に分散を行うことが好ましい。 The slurry can be dispersed by using a ball mill, ultrasonic diffusion, homogenizer, optimizer, or the like. For example, by incorporating an apparatus for performing these operations in the middle of a supply pipe that supplies the slurry to the molding machine, the dispersion can be favorably performed. From the viewpoint of obtaining a good effect by this dispersion, it is preferable to carry out the dispersion just before molding as much as possible.
その後、原料粉末を含むスラリーを成形機に投入し、磁場を印加しながらスラリーの成形を行うことで、成形体を得る。この成形工程により、所定の配向度を有する成形体が得られる。成形は、例えば、プレス成形により行うことができ、具体的には、スラリーを金型キャビティ内に充填した後、充填されたスラリーを上パンチと下パンチとの間で挟むようにして加圧し、スラリー中の溶媒を抜き出しながら所定形状に加工する。この際、上パンチ又は下パンチには、流出した溶媒を抜き出すために外部と連通する穴が設けられていてもよい。ただし、磁性粉末の流出が生じないように、パンチ面に布製、紙製等のフィルターを配置するか、或いは、上パンチ又は下パンチの一部の材質を多孔質とすることが好ましい。成形によって得られる成形体の形状は特に制限されず、柱状、平板状、リング状等、所望とする希土類磁石の形状に応じて変更することができる。 Thereafter, the slurry containing the raw material powder is put into a molding machine, and the molded product is obtained by molding the slurry while applying a magnetic field. By this molding step, a molded body having a predetermined degree of orientation is obtained. The molding can be performed, for example, by press molding. Specifically, after the slurry is filled in the mold cavity, the filled slurry is pressurized so as to be sandwiched between the upper punch and the lower punch, It is processed into a predetermined shape while extracting the solvent. At this time, the upper punch or the lower punch may be provided with a hole communicating with the outside in order to extract the solvent that has flowed out. However, it is preferable to place a cloth or paper filter on the punch surface, or to make the upper punch or the lower punch partly porous so that the magnetic powder does not flow out. The shape of the molded body obtained by molding is not particularly limited, and can be changed according to the desired shape of the rare earth magnet, such as a columnar shape, a flat plate shape, or a ring shape.
成形時の加圧方向は、磁場の印加方向と同じとしてもよく、磁場の印加方向と垂直としてもよいが、磁場の印加方向と垂直に加圧を行うと、より優れた磁気特性が得られる傾向にある。また、成形時における磁場強度は、１５〜２０ｋＯｅとすることができ、加圧は０．３〜３ｔｏｎ／ｃｍ２とすることができる。さらに、成形時間は、数秒〜数十秒とすることが好ましい。このような条件で磁場中、成形を行うことにより、良好な磁気特性を有する希土類磁石が得られ易い傾向にある。 The pressing direction during molding may be the same as the magnetic field application direction, or may be perpendicular to the magnetic field application direction, but more excellent magnetic properties can be obtained by applying pressure perpendicular to the magnetic field application direction. There is a tendency. Moreover, the magnetic field intensity at the time of shaping | molding can be 15-20 kOe, and pressurization can be 0.3-3 ton / cm < 2 >. Furthermore, the molding time is preferably several seconds to several tens of seconds. By forming in a magnetic field under such conditions, a rare earth magnet having good magnetic properties tends to be easily obtained.
微粉が湿式で粉砕された場合も成形時における磁場強度、加圧力、成形時間は上記と同様にできる。 Even when the fine powder is pulverized wet, the magnetic field strength, pressing force, and molding time during molding can be the same as described above.
乾式成形の場合は乾式で粉砕された微粉、あるいは湿式で粉砕され、脱脂された微粉を用いる。湿式と同様に成形時の加圧方向は、磁場の印加方向と同じとしてもよく、磁場の印加方向と垂直としてもよいが、磁場の印加方向と垂直に加圧を行うと、より優れた磁気特性が得られる傾向にある。また、成形時における磁場強度、加圧力、成形時間も同様にできる。 In the case of dry molding, fine powder pulverized dry or fine powder pulverized wet and degreased is used. As with the wet method, the pressing direction during molding may be the same as the magnetic field application direction, or may be perpendicular to the magnetic field application direction. There is a tendency to obtain characteristics. Further, the magnetic field strength, the applied pressure, and the molding time during molding can be similarly set.
（焼結工程）
磁場中成形後、その成形体を真空又は不活性ガス雰囲気中で焼結する。焼結温度は、組成、粉砕方法、粒度と粒度分布の違い等、諸条件により調整する必要がある。焼結温度は９５０℃〜１１００℃、焼結時間は１時間〜６時間である。
(Sintering process)
After molding in a magnetic field, the compact is sintered in a vacuum or an inert gas atmosphere. The sintering temperature needs to be adjusted according to various conditions such as composition, pulverization method, particle size and particle size distribution. The sintering temperature is 950 ° C. to 1100 ° C., and the sintering time is 1 hour to 6 hours.
そして、焼結体に対して、必要に応じて時効処理を施すことにより、希土類磁石を得る。時効処理を行うことによって、得られる希土類磁石の保磁力が向上する傾向にある。時効処理は、例えば、２段階に分けて行うことができ、８００℃近傍、及び６００℃近傍の２つの温度条件で時効処理を行うと好ましい。このような条件で時効処理を行うと、特に優れた保磁力が得られる傾向にある。なお、時効処理を１段階で行う場合は、６００℃近傍の温度とすることが好ましい。 And a rare earth magnet is obtained by performing an aging treatment with respect to a sintered compact as needed. By performing the aging treatment, the coercive force of the obtained rare earth magnet tends to be improved. The aging treatment can be performed, for example, in two stages, and it is preferable to perform the aging treatment under two temperature conditions near 800 ° C. and 600 ° C. When an aging treatment is performed under such conditions, a particularly excellent coercive force tends to be obtained. In addition, when performing an aging treatment in 1 step, it is preferable to set it as the temperature of 600 degreeC vicinity.
以上のようにして得られる希土類永久焼結磁石に含まれる酸素量は、好ましくは５０００ｐｐｍ以下、より好ましくは２０００ｐｐｍ以下、更に好ましくは１０００ｐｐｍ以下である。酸素量は焼結が終了するまでの全工程を１００ｐｐｍ以下の低酸素中で行うことによって制御することができる。全工程の酸素量を制御することは、粉砕粒径微細化による酸素量増加を抑制が可能となり、安定生産の面からも望ましい。 The amount of oxygen contained in the rare earth permanent sintered magnet obtained as described above is preferably 5000 ppm or less, more preferably 2000 ppm or less, and still more preferably 1000 ppm or less. The amount of oxygen can be controlled by performing the entire process until the sintering is completed in low oxygen of 100 ppm or less. Controlling the amount of oxygen in all steps makes it possible to suppress an increase in the amount of oxygen due to refinement of the pulverized particle size, which is desirable from the viewpoint of stable production.
以下、本発明を実施例により更に詳細に説明するが、本発明はこれらの実施例に限定されるものではない。 EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention is not limited to these Examples.
（実施例１〜８、比較例１）
高重希土類組成物が３０ｗｔ％Ｄｙ−０．３ｗｔ％Ａｌ−０．１４ｗｔ％Ｃｕ−残部Ｆｅの高Ｄｙ合金と、低重希土類組成物が２５ｗｔ％Ｎｄ−３．５ｗｔ％Ｄｙ−０．５ｗｔ％Ｃｏ−０．２ｗｔ％Ａｌ−０．２ｗｔ％Ｚｒ−１．０５ｗｔ％Ｂ−残部Ｆｅの低Ｄｙ合金をストリップキャストにより作製した。
(Examples 1-8, Comparative Example 1)
High heavy rare earth composition is 30 wt% Dy-0.3 wt% Al-0.14 wt% Cu-balance Fe high Dy alloy and low heavy rare earth composition is 25 wt% Nd-3.5 wt% Dy-0.5 wt% A low Dy alloy of Co-0.2 wt% Al-0.2 wt% Zr-1.05 wt% B-balance Fe was prepared by strip casting.
高Ｄｙ合金を水素粉砕後、ボールミルで湿式微粉砕した。ボールとしては、ＳＵＳの１／８インチとし、溶媒はイソパラフィンを使用した。粉砕後は１５０℃真空中で脱脂させ、微粉を得た。平均粒径は粉砕時間で調整し、粉砕時間及びＤ５０を表１の通りとした。なお平均粒径の測定は溶媒脱脂後にＭＡＬＶＥＲＮ社製マスターマイザー２０００を用いて行った。 The high Dy alloy was pulverized with hydrogen and then wet pulverized with a ball mill. The ball was 1/8 inch of SUS, and the solvent was isoparaffin. After pulverization, the powder was degreased at 150 ° C. to obtain fine powder. The average particle diameter was adjusted by the grinding time, and the grinding time and D50 were as shown in Table 1. The average particle size was measured using a Mastermizer 2000 manufactured by MALVERN after solvent degreasing.
一方、低Ｄｙ合金は水素粉砕後、気流粉砕機で微粉砕した。Ｄ５０は、粉砕圧と分級機で調整し、表１の通りとした。低Ｄｙ合金と高Ｄｙ合金の粒径比（低Ｄｙ合金／高Ｄｙ合金）も合わせて示す。 On the other hand, the low Dy alloy was finely pulverized with an airflow pulverizer after hydrogen pulverization. D50 was adjusted with the pulverization pressure and the classifier, and was as shown in Table 1. The particle size ratio between the low Dy alloy and the high Dy alloy (low Dy alloy / high Dy alloy) is also shown.
そして、高Ｄｙ合金と低Ｄｙ合金を５：９５の割合で混合し、乾式成形し、焼結時効処理を行い、希土類永久磁石を得た。焼結温度は１０５０℃、時効処理は８００℃、５４０℃である。なお実験は焼結が終了するまで、酸素量１００ｐｐｍ以下の窒素中で行った。得られた焼結体について赤外吸収法を用いて酸素量を測定したところ、酸素量は８００〜１０００ｐｐｍであった。得られた結果を下記表１に示す。 Then, a high Dy alloy and a low Dy alloy were mixed at a ratio of 5:95, dry-molded, and subjected to a sintering aging treatment to obtain a rare earth permanent magnet. The sintering temperature is 1050 ° C., and the aging treatment is 800 ° C. and 540 ° C. The experiment was conducted in nitrogen with an oxygen content of 100 ppm or less until the sintering was completed. When the amount of oxygen was measured about the obtained sintered compact using the infrared absorption method, the amount of oxygen was 800-1000 ppm. The obtained results are shown in Table 1 below.
表１に示す結果より、低重希土類組成物の粒径が６μｍ以下で、高重希土類組成物の粒子の平均粒径を、低重希土類組成物の粒子の平均粒径よりも小さくすることで、より大きな保磁力の希土類永久焼結磁石を、少ない重希土類元素量で得ることができることが確認された。また粒径比が１．５以上で、さらに高保磁力となることが確認された。 From the results shown in Table 1, the particle size of the low heavy rare earth composition is 6 μm or less, and the average particle size of the particles of the high heavy rare earth composition is made smaller than the average particle size of the particles of the low heavy rare earth composition. It was confirmed that a rare earth permanent sintered magnet having a larger coercive force can be obtained with a small amount of heavy rare earth element. Further, it was confirmed that the particle size ratio was 1.5 or more, and the coercive force was further increased.
（実施例９）
低重希土類組成物が３０ｗｔ％Ｎｄ−２ｗｔ％Ｃｏ−０．２ｗｔ％Ａｌ−０．１２ｗｔ％Ｃｕ−０．２ｗｔ％Ｚｒ−１ｗｔ％Ｂ−残部Ｆｅの低Ｄｙ合金と、高重希土類組成物が２０ｗｔ％Ｎｄ−１０ｗｔ％Ｄｙ−２ｗｔ％Ｃｏ−０．２ｗｔ％Ａｌ−０．１２ｗｔ％Ｃｕ−０．２ｗｔ％Ｚｒ−１ｗｔ％Ｚｒ−残部Ｆｅの高Ｄｙ合金を実施例1と同様にして粗粉を得た。
Example 9
The low heavy rare earth composition is 30 wt% Nd-2 wt% Co-0.2 wt% Al-0.12 wt% Cu-0.2 wt% Zr-1 wt% B-balance Fe low Dy alloy, and the heavy heavy rare earth composition is 20 wt% Nd-10 wt% Dy-2 wt% Co-0.2 wt% Al-0.12 wt% Cu-0.2 wt% Zr-1 wt% Zr-balance Fe high Dy alloy as in Example 1 Got.
次いで、粗粉にオレイン酸アミドを０．１ｗｔ％混合し、ジェットミルで乾式粉砕し微粉を得た。低Ｄy合金の微粉の平均粒径は４．１μｍ、高Ｄy合金の微粉は粒径は３．１μｍであった。 Next, 0.1 wt% of oleic amide was mixed with the coarse powder, and dry pulverized with a jet mill to obtain a fine powder. The average particle size of the fine powder of the low Dy alloy was 4.1 μm, and the particle size of the fine powder of the high Dy alloy was 3.1 μm.
続いて、低Ｄy合金と高Ｄy合金の微粉を５０：５０で混合し、鉱物油に混合しスラリーを得た。得られたスラリーを磁場中で湿式成形後、１５０℃で脱脂を行い、１０５０℃で焼結、８００℃と５６０℃の２段の時効処理を行った。こうして希土類永久磁石を得た。なお実験は焼結が終了するまで１００ｐｐｍ以下の窒素中で行った。得られた希土類永久磁石の磁気特性は残留磁束密度１３．２ｋＧ、保磁力２５．０ｋＯｅであった。また焼結体について実施例１と同様にして酸素量を測定したところ、焼結体の酸素量は８５０ｐｐｍであった。 Subsequently, fine powders of a low Dy alloy and a high Dy alloy were mixed at 50:50 and mixed with mineral oil to obtain a slurry. The obtained slurry was wet-molded in a magnetic field, degreased at 150 ° C., sintered at 1050 ° C., and subjected to two-stage aging treatment at 800 ° C. and 560 ° C. Thus, a rare earth permanent magnet was obtained. The experiment was conducted in 100 ppm or less of nitrogen until the sintering was completed. The magnetic properties of the obtained rare earth permanent magnet were a residual magnetic flux density of 13.2 kG and a coercive force of 25.0 kOe. Further, when the oxygen content of the sintered body was measured in the same manner as in Example 1, the oxygen amount of the sintered body was 850 ppm.
（比較例９）
高Ｄy合金の微粉粒径を４．３μｍとしたこと以外は実施例９と同様にして希土類永久磁石を作製した。そして、作製した希土類永久磁石について実施例９と同様にして磁気特性を測定した。得られた希土類永久磁石の磁気特性は残留磁束密度１３．２ｋＧ、保磁力２２．５ｋＯｅ酸素量は８６０ｐｐｍであった。
(Comparative Example 9)
A rare earth permanent magnet was produced in the same manner as in Example 9 except that the fine Dy particle diameter of the high Dy alloy was 4.3 μm. Then, the magnetic characteristics of the produced rare earth permanent magnet were measured in the same manner as in Example 9. The magnetic properties of the obtained rare earth permanent magnet were a residual magnetic flux density of 13.2 kG and a coercive force of 22.5 kOe oxygen content of 860 ppm.
Claims (8)
高重希土類組成物の粒子と、低重希土類組成物の粒子とを混合して混合物を得る混合工程と、
前記混合物を磁場中成形して成形体を得る成形工程と、
前記成形体を焼結する焼結工程と、を備え、
前記低重希土類組成物の粒子の平均粒径が６μｍ以下であり、
前記高重希土類組成物の粒子の平均粒径は１〜４．３μｍであり、かつ、前記低重希土類組成物の粒子の平均粒径よりも小さいことを特徴とするＲ−Ｔ−Ｂ系希土類永久焼結磁石の製造方法。 It consists of a sintered body having a structure comprising at least a core constituting the main phase and a shell and / or a grain boundary phase around the core, and the core has an amount ratio of heavy rare earth elements to the shell and / or the grain boundary phase. It is composed of a lower low heavy rare earth compositions, the shell and / or the grain boundary phase R-T-B rare earth permanent sintered magnet composed of a ratio higher high heavy rare earth composition of the heavy rare earth element than the core ( However, 25 wt% ≦ R ≦ 35 wt%, 0 wt% <HR ≦ 20 wt%, R is a rare earth element including Y, T is a transition metal element in which Fe or Fe and Co are essential, and HR is a heavy rare earth element) Because
A mixing step of mixing high heavy rare earth composition particles and low heavy rare earth composition particles to obtain a mixture;
A molding step of molding the mixture in a magnetic field to obtain a molded body;
A sintering step of sintering the molded body,
The average particle size of the particles of the low heavy rare earth composition is 6 μm or less,
The R-T-B rare earth , wherein the particles of the high heavy rare earth composition have an average particle size of 1 to 4.3 μm and are smaller than the average particle size of the particles of the low heavy rare earth composition. A method for producing a permanent sintered magnet.
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