JP2018041777A - Metal bond magnet and method for manufacturing the same - Google Patents
Metal bond magnet and method for manufacturing the same Download PDFInfo
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本発明は、希土類磁石粒子を金属で結合させたメタルボンド磁石およびその製造方法に関する。 The present invention relates to a metal bonded magnet obtained by bonding rare earth magnet particles with a metal and a method for manufacturing the same.
非常に高い磁気特性を発揮する希土類磁石は、電磁機器や電動機の高出力化や小型化等に有効であるため、電気機器や自動車等の様々な分野で多用されている。希土類磁石は、大別して焼結磁石（熱間加工（ホットプレス）磁石を含む）とボンド磁石に大別される。焼結磁石は、高温加熱されるために使用できる希土類磁石合金の種類が限られる。また焼結磁石は、焼結時に液相を生じて寸法が大きく変化するため、研削等の後加工を要し、形状自由度が小さい。一方、ボンド磁石は、基本的に成形型に応じた形状で得られ、寸法精度が高く、後加工も不要である。また、圧縮成形の他に射出成形によっても得られるため、形状自由度も大きい。このため、最近では希土類系ボンド磁石の利用が拡大しつつある。 Rare earth magnets that exhibit very high magnetic properties are effective in increasing the output and miniaturization of electromagnetic devices and motors, and are therefore widely used in various fields such as electrical devices and automobiles. Rare earth magnets are roughly classified into sintered magnets (including hot-worked (hot pressed) magnets) and bonded magnets. Sintered magnets are limited in the types of rare earth magnet alloys that can be used because they are heated at high temperatures. Moreover, since a sintered magnet produces a liquid phase at the time of sintering and its dimensions change greatly, post-processing such as grinding is required, and the degree of freedom in shape is small. On the other hand, the bonded magnet is basically obtained in a shape corresponding to the mold, has high dimensional accuracy, and does not require post-processing. Moreover, since it can be obtained by injection molding in addition to compression molding, the degree of freedom in shape is also large. For this reason, the use of rare earth-based bonded magnets is increasing recently.
もっとも、従来の樹脂（特に熱硬化性樹脂）バインダーを用いたボンド磁石は、その耐熱性（形状保持性）がバインダー樹脂に依存しており、耐熱温度は高々２００℃程度であった。そこで、バインダーとして樹脂ではなく金属を用いた希土類系メタルボンド磁石が提案されており、関連する記載が下記の特許文献にある。 However, bond magnets using conventional resin (especially thermosetting resin) binders depend on the binder resin for heat resistance (shape retention), and the heat resistance temperature is about 200 ° C. at most. Therefore, a rare earth metal bond magnet using a metal instead of a resin as a binder has been proposed, and related descriptions are in the following patent documents.
特許文献１には、希土類系磁石粉末、金属結合相および添加剤からなる混合物の圧縮成形体にマイクロ波を照射して金属結合相を焼結させた希土類系メタルボンド磁石に関する記載がある。しかし、特許文献１には、金属結合相として低融点金属が好ましい旨が記載されているものの、それに関する具体的な記載は全くない。 Patent Document 1 describes a rare earth metal bond magnet in which a compression molded body of a mixture composed of a rare earth magnet powder, a metal binder phase and an additive is irradiated with microwaves to sinter the metal binder phase. However, Patent Document 1 describes that a low melting point metal is preferable as the metal binder phase, but there is no specific description about it.
特許文献２には、Ｓｍ２Ｆｅ１７Ｎ３粒子間に、弾塑性比が５０％以下の非磁性金属粒子（Ｃｕ粒子またはＡｌ粒子）を介在させた希土類磁石成形体に関する記載がある。しかし、その希土類磁石成形体は、コールドスプレー法を用いた堆積物からなり、その非磁性金属粒子はバインダーではない。つまり特許文献２の希土類磁石成形体は、本明細書でいうようなメタルボンド磁石ではない。 Patent Document 2 describes a rare earth magnet molded body in which nonmagnetic metal particles (Cu particles or Al particles) having an elastic-plastic ratio of 50% or less are interposed between Sm 2 Fe 17 N 3 particles. However, the rare earth magnet compact is composed of a deposit using a cold spray method, and the nonmagnetic metal particles are not a binder. That is, the rare earth magnet molded body of Patent Document 2 is not a metal bond magnet as used in this specification.
本発明はこのような事情に鑑みて為されたものであり、従来とは異なる新たなメタルボンド磁石（希土類磁石）と、その製造方法を提供することを目的とする。 This invention is made | formed in view of such a situation, and it aims at providing the new metal bond magnet (rare earth magnet) different from the former, and its manufacturing method.
本発明者はこの課題を解決すべく鋭意研究した結果、希土類磁石粒子のバインダーとしてＳｎ−Ｃｕ合金相を用いることにより、高密度で磁気特性に優れたメタルボンド磁石が得られることを新たに見出した。この成果を発展させることにより、以降に述べる本発明を完成するに至った。 As a result of intensive studies to solve this problem, the present inventors have newly found that a metal bond magnet having high density and excellent magnetic properties can be obtained by using a Sn—Cu alloy phase as a binder of rare earth magnet particles. It was. By developing this result, the present invention described below has been completed.
《メタルボンド磁石》
本発明のメタルボンド磁石は、希土類磁石合金からなる磁石粒子と、該磁石粒子同士を結合するバインダーとからなり、該バインダーは、スズ（Ｓｎ）と銅（Ｃｕ）からなることを特徴とする。
《Metal bond magnet》
The metal bond magnet of the present invention is composed of magnet particles made of a rare earth magnet alloy and a binder for bonding the magnet particles, and the binder is made of tin (Sn) and copper (Cu).
本発明のメタルボンド磁石は、磁石粒子を結合するバインダー（粒界相）が金属であるＳｎ−Ｃｕ合金からなるため、従来の樹脂系ボンド磁石よりも高温域で使用可能である。また本発明のメタルボンド磁石は、非常に高い温度（例えば１０００℃以上）で加熱することが必要となる液相焼結磁石ではないため、例えば、Ｎｄ−Ｆｅ−Ｂ系希土類磁石粉末等に限らず、Ｓｍ−Ｆｅ−Ｎ系希土類磁石粉末、Ｎｄ−Ｆｅ−Ｎ系希土類磁石粉末等をも原料粉末として用いることができる。さらに、バインダーであるＳｎ−Ｃｕ合金は基本的に非磁性金属であるため、結合される磁石粒子（主相）間には自ずと非磁性相が形成されることになる。このため本発明のメタルボンド磁石は、隣接する磁石粒子同士が磁気的に孤立化された状態（相互作用が抑制された状態）となり、高保磁力を発現し易い。 The metal bond magnet of the present invention can be used in a higher temperature range than conventional resin bond magnets because it is made of a Sn—Cu alloy whose binder (grain boundary phase) for binding magnet particles is a metal. Moreover, since the metal bonded magnet of the present invention is not a liquid phase sintered magnet that needs to be heated at a very high temperature (for example, 1000 ° C. or higher), it is limited to, for example, Nd—Fe—B rare earth magnet powder and the like. In addition, Sm—Fe—N rare earth magnet powder, Nd—Fe—N rare earth magnet powder and the like can also be used as the raw material powder. Furthermore, since the Sn—Cu alloy as a binder is basically a nonmagnetic metal, a nonmagnetic phase is naturally formed between the magnet particles (main phase) to be bonded. For this reason, the metal bond magnet of the present invention is in a state where adjacent magnet particles are magnetically isolated (a state in which the interaction is suppressed), and easily exhibits a high coercive force.
加えて本発明のメタルボンド磁石は、高密度となり易く、高い磁気特性（特に残留磁束密度）も発揮し得る。この理由は、磁石粒子（特に、主成分であるＦｅ等の遷移金属元素）に対するＳｎ−Ｃｕ合金の濡れ性が高いためと考えられる。 In addition, the metal bond magnet of the present invention tends to be high in density and can also exhibit high magnetic properties (particularly residual magnetic flux density). The reason for this is considered to be because the wettability of the Sn—Cu alloy with respect to magnet particles (particularly, transition metal elements such as Fe which is the main component) is high.
ちなみに、Ｃｕ単体またはＳｎ単体では、磁石粒子との濡れ性が非常に悪く、高密度化は図れなかった。またＳｎ単体では、Ｓｎが磁石粒子（特にＦｅ等の遷移金属元素）と反応して、その割合（主相分率）が低下した。従って、Ｃｕ単体またはＳｎ単体からなるバインダーに用いても、磁気特性に優れるメタルボンド磁石は得られなかった。 Incidentally, Cu alone or Sn alone was very poor in wettability with magnet particles and could not be densified. In addition, with Sn alone, Sn reacted with magnet particles (especially transition metal elements such as Fe), and the ratio (main phase fraction) decreased. Therefore, even when used as a binder made of Cu alone or Sn alone, a metal bond magnet having excellent magnetic properties could not be obtained.
《メタルボンド磁石の製造方法》
本発明は、メタルボンド磁石としてのみならず、その製造方法としても把握できる。すなわち本発明は、希土類磁石合金からなる磁石粒子、Ｓｎ源およびＣｕ源が混在した原料粉末または該原料粉末からなる成形体を加熱する加熱工程を備え、上述したメタルボンド磁石が得られることを特徴とするメタルボンド磁石の製造方法でもよい。
<Production method of metal bond magnet>
The present invention can be grasped not only as a metal bonded magnet but also as a manufacturing method thereof. That is, the present invention includes a heating step of heating a magnet particle made of a rare earth magnet alloy, a raw material powder in which a Sn source and a Cu source are mixed, or a molded body made of the raw material powder, and the metal bond magnet described above is obtained. The manufacturing method of a metal bond magnet may be used.
《メタルボンド磁石用粉末》
本発明は、上述したメタルボンド磁石の製造方法に適した被覆磁石粉末または複層被覆磁石粉末としても把握できる。すなわち本発明は、希土類磁石合金からなる磁石粒子の表面がＣｕで被覆された被覆粒子からなり、メタルボンド磁石の製造に用いられる被覆磁石粉末としても把握できる。この被覆磁石粉末は、その被覆粒子のＣｕ表面がさらにＳｎで被覆された複層被覆粒子からなる複層被覆磁石粉末でもよい。さらに本発明は、その磁石粒子の表面がＳｎ−Ｃｕ合金で被覆された合金被覆粒子からなる合金被覆磁石粉末でもよい。なお、磁石粒子の表面にあるＣｕまたはＳｎは、上述したＣｕ源またはＳｎ源の少なくとも一部を構成する。
<Powder for metal bond magnet>
The present invention can also be grasped as a coated magnet powder or a multilayer coated magnet powder suitable for the above-described method for producing a metal bonded magnet. That is, the present invention can be grasped as coated magnet powder used in the manufacture of metal bonded magnets, which is composed of coated particles in which the surface of magnet particles made of a rare earth magnet alloy is coated with Cu. This coated magnet powder may be a multilayer coated magnet powder comprising multilayer coated particles in which the Cu surface of the coated particles is further coated with Sn. Furthermore, the present invention may be an alloy-coated magnet powder composed of alloy-coated particles whose surfaces are coated with a Sn—Cu alloy. Note that Cu or Sn on the surface of the magnet particles constitutes at least a part of the above-described Cu source or Sn source.
《その他》
特に断らない限り本明細書でいう「ｘ〜ｙ」は下限値ｘおよび上限値ｙを含む。本明細書に記載した種々の数値または数値範囲に含まれる任意の数値を新たな下限値または上限値として「ａ〜ｂ」のような範囲を新設し得る。
<Others>
Unless otherwise specified, “x to y” in this specification includes a lower limit value x and an upper limit value y. A range such as “a to b” can be newly established with any numerical value included in various numerical values or numerical ranges described in the present specification as a new lower limit value or upper limit value.
上述した本発明の構成要素に、本明細書中から任意に選択した一つまたは二つ以上の構成要素を付加し得る。本明細書で説明する内容は、メタルボンド磁石のみならず、その製造方法にも適宜該当し、また方法的な構成要素であっても物に関する構成要素ともなり得る。いずれの実施形態が最良であるか否かは、対象、要求性能等によって異なる。 One or two or more components arbitrarily selected from the present specification may be added to the above-described components of the present invention. The contents described in the present specification are applicable not only to the metal bonded magnet but also to the manufacturing method thereof as appropriate, and can be a structural component or a structural component. Which embodiment is the best depends on the target, required performance, and the like.
《磁石合金》
磁石粒子を構成する希土類磁石合金（単に「磁石合金」という。）は、希土類元素（Ｒ）と遷移金属元素（ＴＭ）を含む二元系または三元系以上の合金である。Ｒは、スカンジウム（Ｓｃ）、イットリウム（Ｙ）、ランタノイド（Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、ＹｂまたはＬｕ）であるが、主にＮｄまたはＳｍである。遷移金属元素（ＴＭ）は、種々あるが、主に８族元素（Ｆｅ、ＣｏまたはＮｉ）であり、特にＦｅである。なお、本明細書でいう磁石合金には、いわゆる金属間化合物が含まれる。
《Magnet alloy》
The rare earth magnet alloy (simply referred to as “magnet alloy”) constituting the magnet particles is a binary or ternary or higher alloy containing a rare earth element (R) and a transition metal element (TM). R is scandium (Sc), yttrium (Y), lanthanoid (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb or Lu), but mainly Nd. Or Sm. Although there are various transition metal elements (TM), they are mainly Group 8 elements (Fe, Co or Ni), and particularly Fe. In addition, what is called an intermetallic compound is contained in the magnet alloy as used in this specification.
二元系磁石合金には、例えば、ＳｍＣｏ５、Ｓｍ２Ｃｏ１７等を主に含むＳｍ−Ｃｏ系合金、ＰｒＣｏ５等を主に含むＰｒ−Ｃｏ系合金がある。三元系磁石合金は、Ｒ、ＴＭに加えて、ホウ素（Ｂ）または窒素（Ｎ）等を含む合金であり、例えば、Ｎｄ２Ｆｅ１４Ｂ等のＲ−ＴＭ−Ｂ系合金、Ｓｍ２Ｆｅ１７Ｎ３やＮｄＦｅ１２Ｎx等のＲ−ＴＭ−Ｎ系合金がある。なお、磁石合金は種々の改質元素（Ｇａ、Ｎｂ、Ａｌ、Ｃｏ等）や不可避不純物を含み得る。また磁石合金の全体組成は、Ｎｄ２Ｆｅ１４Ｂ、Ｓｍ２Ｆｅ１７Ｎ３等の構造式から導出される理論組成に対して多少変動していてもよい。 Examples of the binary magnet alloy include an Sm—Co alloy mainly containing SmCo 5 , Sm 2 Co 17 and the like, and a Pr—Co alloy mainly containing PrCo 5 and the like. The ternary magnet alloy is an alloy containing boron (B) or nitrogen (N) in addition to R and TM. For example, an R-TM-B alloy such as Nd 2 Fe 14 B, Sm 2 Fe there are R-TM-N based alloy such 17 N 3 and NdFe 12 Nx. The magnet alloy may contain various modifying elements (Ga, Nb, Al, Co, etc.) and inevitable impurities. Further, the overall composition of the magnet alloy may vary somewhat with respect to the theoretical composition derived from the structural formulas such as Nd 2 Fe 14 B, Sm 2 Fe 17 N 3 and the like.
《磁石粒子（粉末）》
磁石粒子は、磁石合金の鋳塊を水素粉砕したり、磁石合金の急冷凝固片（箔）を粉砕等して得られる。磁石粒子は、等方性でも異方性でも良い。磁石粒子の平均粒径は、０．５〜５０μｍさらには１〜２５μｍであると好ましい。磁石粒子は単磁区サイズに近いほど好ましいが、過小になると酸化により磁気特性が劣化し易い。また磁石粒子は過大であると保磁力が低下し得る。なお、本明細書でいう磁石粒子の平均粒径は、粒度分布測定結果から得られたｄ５０値（ｄ５０：メジアン径）により特定される。
《Magnetic particles (powder)》
The magnet particles can be obtained by hydrogen pulverizing an ingot of a magnet alloy or pulverizing a rapidly solidified piece (foil) of the magnet alloy. The magnet particles may be isotropic or anisotropic. The average particle size of the magnet particles is preferably 0.5 to 50 μm, more preferably 1 to 25 μm. The magnet particles are preferably closer to a single magnetic domain size, but if they are too small, the magnetic properties are likely to be deteriorated by oxidation. Further, if the magnet particles are excessive, the coercive force can be lowered. In addition, the average particle diameter of a magnet particle as used in this specification is specified by d50 value (d50: median diameter) obtained from the particle size distribution measurement result.
《バインダー》
バインダーはＳｎとＣｕからなり、磁石粒子間に存在して粒界相（層）を形成する。ＳｎとＣｕの割合を調整することにより、製造時の加熱温度、粒界相の融点ひいてはメタルボンド磁石の耐熱性（高温下における保形性）を制御し得る。
"binder"
The binder is made of Sn and Cu and exists between the magnet particles to form a grain boundary phase (layer). By adjusting the ratio of Sn and Cu, the heating temperature during production, the melting point of the grain boundary phase, and thus the heat resistance (shape retention at high temperatures) of the metal bond magnet can be controlled.
バインダーは、例えば、Ｓｎに対するＣｕの質量比（Ｃｕ／Ｓｎ）が０．１〜２さらには０．３〜１．５であると好ましい。Ｃｕ／Ｓｎが過小では、Ｓｎが過多となって主相分率の低下による磁気特性の低下を招いたり、バインダーの融点が過小となってメタルボンド磁石の耐熱性の低下を招き得る。Ｃｕ／Ｓｎが過大では、Ｃｕの過多によりバインダーの融点が過大となり、低い加熱温度で高密度なメタルボンド磁石を製造することが困難となる。 For example, the binder preferably has a mass ratio of Cu to Sn (Cu / Sn) of 0.1 to 2, and more preferably 0.3 to 1.5. If Cu / Sn is too small, Sn may be excessive and the magnetic properties may be lowered due to a decrease in the main phase fraction, or the melting point of the binder may be too small and the heat resistance of the metal bonded magnet may be lowered. When Cu / Sn is excessively large, the melting point of the binder becomes excessive due to excessive Cu, and it becomes difficult to produce a high-density metal bond magnet at a low heating temperature.
メタルボンド磁石全体を１００質量％（以下、単に「％」で示す。）として、Ｓｎは５〜４０％、１０〜３０％さらには１５〜２５％であると好ましい。同様に、Ｃｕは３〜３０％、８〜２５％、１０〜２０％さらには１３〜１６％であると好ましい。 It is preferable that Sn is 5 to 40%, 10 to 30%, and further 15 to 25%, assuming that the entire metal bond magnet is 100% by mass (hereinafter simply indicated as “%”). Similarly, Cu is preferably 3 to 30%, 8 to 25%, 10 to 20%, and further 13 to 16%.
《製造方法》
本発明のメタルボンド磁石は、例えば、希土類磁石合金からなる磁石粒子、Ｓｎ源およびＣｕ源が混在した原料粉末を加圧してなる成形体を得る成形工程と、その成形体を加熱して磁石粒子間に存在するＳｎ−Ｃｕ合金を液相化（溶融）させる加熱工程と、その成形体を冷却して磁石粒子間に固化（凝固）したＳｎ−Ｃｕ合金からなる粒界相を形成する冷却工程とを経て得られる。
"Production method"
The metal bond magnet of the present invention includes, for example, a molding step of pressing a raw material powder mixed with a rare earth magnet alloy, a Sn source and a Cu source, and a magnet particle by heating the compact. A heating step for liquidizing (melting) the Sn—Cu alloy existing between them, and a cooling step for cooling the molded body to form a grain boundary phase made of the Sn—Cu alloy solidified (solidified) between the magnet particles. And get through.
原料粉末の形態は種々考えられる。例えば、原料粉末は、磁石粉末（磁石粒子の集合体）とＳｎ源粉末とＣｕ源粉末との混合粉末でも、磁石粉末とＳｎ−Ｃｕ合金粉末との混合粉末でも良い。また、原料粉末は、Ｃｕで被覆された磁石粒子からなる被覆磁石粉末とＳｎ源粉末との混合粉末でもよい。さらに、原料粉末は、ＣｕおよびＳｎで順次被覆された磁石粒子からなる複層被覆磁石粉末自体でも良いし、Ｓｎ−Ｃｕ合金で被覆された磁石粒子からなる合金被覆磁石粉末自体でもよい。なお、原料粉末は、バインダー相の組成や割合を調整するために、それら被覆磁石粉末の少なくとも一種に加えて、Ｃｕ源粉末やＳｎ源粉末をさらに含有するものでもよい。 Various forms of the raw material powder are conceivable. For example, the raw material powder may be a mixed powder of magnet powder (aggregate of magnet particles), Sn source powder and Cu source powder, or a mixed powder of magnet powder and Sn—Cu alloy powder. Further, the raw material powder may be a mixed powder of a coated magnet powder composed of magnet particles coated with Cu and an Sn source powder. Furthermore, the raw material powder may be a multilayer coated magnet powder itself composed of magnet particles sequentially coated with Cu and Sn, or may be an alloy coated magnet powder itself composed of magnet particles coated with a Sn—Cu alloy. In addition, in order to adjust the composition and ratio of the binder phase, the raw material powder may further contain a Cu source powder or a Sn source powder in addition to at least one of these coated magnet powders.
加熱工程は、加熱炉内に載置した成形体を加熱する場合の他、例えば、放電プラズマ焼結法（ＳＰＳ：Spark Plasma Sintering）等のパルス通電焼結法により、成形体または原料粉末自体を加圧しつつ加熱してもよい。ＳＰＳ等を用いれば、磁石粒子の表面近傍またはその粒界部分が、加圧されつつ急速加熱されるため、磁石粒子の粒成長を生じることなく、短時間で緻密なメタルボンド磁石を効率的に得ることができる。なお、その際の加圧力は、例えば、３０〜１００ＭＰａさらには４０〜８０ＭＰａとするとよい。また、加熱温度は、ＣｕとＳｎの組成（配合）にも依るが、２５０〜４５０℃さらには３００〜４００℃とするとよい。この加熱温度は、成形体を炉内加熱する場合も同様である。 In addition to heating the molded body placed in the heating furnace, the heating process is performed by, for example, applying a pulsed current sintering method such as spark plasma sintering (SPS) to the molded body or the raw material powder itself. You may heat, pressurizing. If SPS or the like is used, the vicinity of the surface of the magnet particle or its grain boundary portion is rapidly heated while being pressurized, so that a dense metal bond magnet can be efficiently produced in a short time without causing the grain growth of the magnet particle. Can be obtained. In addition, the pressurizing force in that case is good to set it as 30-100 Mpa, further 40-80 Mpa, for example. Moreover, although heating temperature is based also on a composition (formulation | combination) of Cu and Sn, it is good to set it as 250-450 degreeC further 300-400 degreeC. This heating temperature is the same when the molded body is heated in the furnace.
加熱工程は、磁石粒子の酸化を抑止できる雰囲気でなされると好ましい。例えば、真空雰囲気や不活性ガス雰囲気（窒素ガス雰囲気を含む。）である。なお、ＳＰＳ等は、通常、真空雰囲気でなされる。 The heating step is preferably performed in an atmosphere that can prevent oxidation of the magnet particles. For example, a vacuum atmosphere or an inert gas atmosphere (including a nitrogen gas atmosphere). Note that SPS and the like are usually performed in a vacuum atmosphere.
磁石粉末が異方性磁石粉末である場合、配向磁場を印加しつつ、原料粉末の成形工程または上述した加熱工程が行われると、高磁気特性のメタルボンド磁石が得られて好ましい。また、冷却工程は、徐冷でも急冷でもよく、加熱工程と同様に、酸化抑止雰囲気でなされると好ましい。 When the magnet powder is an anisotropic magnet powder, it is preferable to obtain a metal-bonded magnet having high magnetic properties when the raw material powder forming step or the heating step described above is performed while applying an orientation magnetic field. The cooling step may be slow cooling or rapid cooling, and is preferably performed in an oxidation-inhibiting atmosphere as in the heating step.
《メタルボンド磁石》
本発明のメタルボンド磁石は、磁石粒子が濡れ性に富む非磁性なＳｎ−Ｃｕ合金によって囲繞されて結合しているため、高密度で磁気特性（残留磁束密度、保磁力）に優れる。ちなみに、そのメタルボンド磁石の相対密度は８０％以上、８５％以上さらには９０％以上となり得る。なお、本明細書でいう相対密度は、メタルボンド磁石の真密度（ρ０）に対する嵩密度（ρ）の割合（１００×ρ／ρ０）である。嵩密度は測定した質量と寸法とに基づいて求まる。真密度は磁石粒子とＳｎ−Ｃｕ合金の添加割合と各々の密度から算出して求まる。
《Metal bond magnet》
The metal bonded magnet of the present invention is surrounded by a nonmagnetic Sn—Cu alloy with high wettability and bonded, and thus has high density and excellent magnetic properties (residual magnetic flux density and coercive force). Incidentally, the relative density of the metal bond magnet can be 80% or more, 85% or more, and 90% or more. In addition, the relative density as used in this specification is a ratio (100 × ρ / ρ 0 ) of the bulk density (ρ) to the true density (ρ 0 ) of the metal bond magnet. The bulk density is determined based on the measured mass and dimensions. The true density is calculated from the addition ratio of the magnet particles and the Sn—Cu alloy and the respective densities.
本発明に係る磁石粒子は、様々な希土類磁石合金からなり得るが、Ｎｄ−Ｆｅ−Ｂ系希土類磁石合金に匹敵する磁気特性を発揮し得ると共に、保磁力向上のためにＤｙ等の稀少な重希土類元素を必ずしも要しないＳｍ−Ｆｅ−Ｎ系希土類磁石合金やＮｄ−Ｆｅ−Ｎ系希土類磁石合金からなると好ましい。 The magnet particles according to the present invention can be made of various rare earth magnet alloys, but can exhibit magnetic properties comparable to Nd—Fe—B rare earth magnet alloys, and rare heavy metals such as Dy to improve coercivity. It is preferably made of an Sm—Fe—N rare earth magnet alloy or an Nd—Fe—N rare earth magnet alloy that does not necessarily require a rare earth element.
本発明のメタルボンド磁石は、磁気特性のみならず形状自由度や耐熱性にも優れるため、自動車分野、電子・電気分野等の各種製品（電動機、電磁機器等）に利用され得る。また本発明に係るＳｎ−Ｃｕ合金は、相対的に融点の低い金属であり、ロー材としてもなり得る。このＳｎ−Ｃｕ合金を介することにより、本発明のメタルボンド磁石は、他部材（例えば鉄（合金）等からなる金属部材）と強固に接合することもできる。 Since the metal bond magnet of the present invention is excellent not only in magnetic properties but also in freedom of shape and heat resistance, it can be used in various products (motors, electromagnetic devices, etc.) in the automotive field, electronic / electric field, and the like. In addition, the Sn—Cu alloy according to the present invention is a metal having a relatively low melting point, and can be a brazing material. By interposing this Sn—Cu alloy, the metal bond magnet of the present invention can be firmly joined to another member (for example, a metal member made of iron (alloy) or the like).
バインダーが異なる複数種のメタルボンド磁石を製造して、その金属組織の観察、特性（相対密度、保磁力等）の測定を行った。このような具体例を挙げつつ、以下に本発明をさらに詳しく説明する。 A plurality of types of metal bond magnets having different binders were manufactured, and the metal structure was observed and the characteristics (relative density, coercive force, etc.) were measured. The present invention will be described in more detail below with specific examples.
《試料の製造》
（１）原料粉末
希土類磁石粉末として、市販されているＳｍ−Ｆｅ−Ｎ系の磁石粉末（日亜化学工業株式会社製ＳｍＦｅＮ磁粉）を用意した。これは、主にＳｍ２Ｆｅ１７Ｎ３からなる等方性磁石粉末であり、平均粒径３μｍであった。平均粒径は既述した方法により求めた。
<Production of sample>
(1) Raw material powder As a rare earth magnet powder, a commercially available Sm-Fe-N magnet powder (SmFeN magnetic powder manufactured by Nichia Corporation) was prepared. This is an isotropic magnet powder mainly composed of Sm 2 Fe 17 N 3 and has an average particle diameter of 3 μm. The average particle size was determined by the method described above.
また、その磁石粉末の各粒子表面に、化学的手法によりＣｕめっきを施した被覆磁石粉末も用意した。この際、Ｃｕの被覆厚さを調整することにより、後述する混合粉末（１００質量％）中のＣｕ量が１０％または２０％となるようにした。 Moreover, the coated magnet powder which prepared Cu plating on the surface of each particle | grain of the magnet powder by the chemical method was also prepared. At this time, by adjusting the coating thickness of Cu, the amount of Cu in the mixed powder (100% by mass) described later was set to 10% or 20%.
また、市販されているＳｎ粉末（日亜化学工業株式会社製ＳｍＦｅＮ磁粉）も用意した。この粒径は５０〜１００μｍであった。この粒径は粒度分布測定から算出されるｄ５０値により求めた。 A commercially available Sn powder (SmFeN magnetic powder manufactured by Nichia Corporation) was also prepared. The particle size was 50-100 μm. This particle size was determined from the d50 value calculated from the particle size distribution measurement.
（２）加熱工程
被覆磁石粉末とＳｎ粉末を不活性ガス（Ａｒ）雰囲気（Ｎ２雰囲気でもよい）中で乳鉢および乳棒により均一に混合した。Ｓｎ粉末は、混合粉末全体（１００質量％）に対して、０％、１０％、２０％または３０％とした。得られた混合粉末を、放電プラズマ焼結装置により焼結（ＳＰＳ）させた。このときの条件は、雰囲気：真空、加熱温度：３００℃、加圧力：５０ＭＰａ、保持時間：５分間とした。
(2) Heating step The coated magnet powder and the Sn powder were uniformly mixed with a mortar and pestle in an inert gas (Ar) atmosphere (or an N 2 atmosphere). Sn powder was made into 0%, 10%, 20%, or 30% with respect to the whole mixed powder (100 mass%). The obtained mixed powder was sintered (SPS) by a discharge plasma sintering apparatus. The conditions at this time were as follows: atmosphere: vacuum, heating temperature: 300 ° C., pressure: 50 MPa, holding time: 5 minutes.
Ｃｕ被覆していない磁石粉末（ベース磁石粉末）とＳｎ粉末とを用いて、同様にＳＰＳにより加熱した。このときのＳｎ粉末は、混合粉末全体（１００質量％）に対して、０％、２０％または３０％とした。ＳＰＳは、雰囲気：真空、加熱温度：３００〜５００℃、加圧力：５０ＭＰａ、保持時間：５分間として行った。 Using magnet powder not coated with Cu (base magnet powder) and Sn powder, heating was similarly performed by SPS. The Sn powder at this time was 0%, 20%, or 30% with respect to the entire mixed powder (100% by mass). SPS was performed under the conditions of atmosphere: vacuum, heating temperature: 300 to 500 ° C., pressure: 50 MPa, holding time: 5 minutes.
いずれの試料も、特に断らない限り１０×１０×６〜７ｍｍのブロック状とした。但し、一部の試料は、厚みを１／１０（０．６〜０．７ｍｍ）とした。 All samples were in the form of 10 × 10 × 6 to 7 mm blocks unless otherwise specified. However, a part of the samples had a thickness of 1/10 (0.6 to 0.7 mm).
《観察》
（１）被覆磁石粉末（Ｃｕ：１５％）を走査型電子顕微鏡（ＳＥＭ）で観察した外観写真と、その粉末断面を電子線マイクロアナライザー（ＥＰＭＡ）で分析した各元素の分布像および反射電子像（ＢＳＥ像）を図１Ａに示した。
<< Observation >>
(1) Appearance photograph of coated magnet powder (Cu: 15%) observed with a scanning electron microscope (SEM), distribution image and backscattered electron image of each element obtained by analyzing the powder cross section with an electron beam microanalyzer (EPMA) (BSE image) is shown in FIG. 1A.
また、被覆磁石粉末（Ｃｕ：１５％）とＳｎ粉末（２０％）の混合粉末をＳＰＳした試料の断面に係るＳＥＭ像を図１Ｂに示した。なお、本実施例では、ＣｕとＳｎの質量割合を、混合粉末全体（メタルボンド磁石全体）に対する割合に換算して示している（図１Ａの場合も含む）。 Moreover, the SEM image which concerns on the cross section of the sample which carried out SPS of the mixed powder of covered magnet powder (Cu: 15%) and Sn powder (20%) was shown to FIG. 1B. In this example, the mass ratio of Cu and Sn is shown in terms of the ratio to the entire mixed powder (the entire metal bond magnet) (including the case of FIG. 1A).
（２）ベース磁石粉末とＳｎ粉末（２０％）の混合粉末をＳＰＳした試料の断面（特に粒界相部分）をＸ線回折（ＸＲＤ）により分析して得られたパターンを図２Ａに示した。また、その断面に係るＳＥＭ像およびＥＰＭＡ像を図２Ｂに示した。 (2) FIG. 2A shows a pattern obtained by analyzing the cross section (particularly the grain boundary phase portion) of a sample obtained by SPS mixing powder of base magnet powder and Sn powder (20%) by X-ray diffraction (XRD). . Moreover, the SEM image and EPMA image which concern on the cross section were shown to FIG. 2B.
《測定》
Ｃｕ量とＳｎ量を種々変化させた各試料（メタルボンド磁石）に係る相対密度を図３Ａに示した。また、ベース磁石粉末を用いてＳＰＳの温度を変化させた各試料に係る相対密度を図３Ｂに示した。相対密度は既述した方法により求めた。
<Measurement>
FIG. 3A shows the relative density of each sample (metal bonded magnet) in which the amount of Cu and the amount of Sn are variously changed. Moreover, the relative density which concerns on each sample which changed the temperature of SPS using base magnet powder was shown to FIG. 3B. The relative density was determined by the method described above.
Ｓｎ量を種々変化させた各試料に係る保磁力を図４に示した。保磁力はパルス励磁型磁気特性測定装置（東英工業株式会社製）で測定した。 FIG. 4 shows the coercivity of each sample with various amounts of Sn varied. The coercive force was measured with a pulse excitation type magnetic property measuring apparatus (manufactured by Toei Kogyo Co., Ltd.).
《評価》
（１）図１Ａから明らかなように、被覆磁石粉末はＳｍ−Ｆｅ−Ｎ系磁石粒子の表面が、ほぼ均一的な厚さのＣｕにより包囲された状態となっていることわかった。
<Evaluation>
(1) As is clear from FIG. 1A, it was found that the surface of the Sm—Fe—N magnet particles in the coated magnet powder was surrounded by Cu having a substantially uniform thickness.
図１Ｂから明らかなように、Ｓｍ−Ｆｅ−Ｎ系の磁石粒子間（粒界）にはＳｎ−Ｃｕ合金からなるバインダーが、殆ど隙間無く充填されており、これにより各磁石粒子は保持（結合）されていることがわかった。さらに、そのＳｎ−Ｃｕ合金相にはＦｅ等が実質的に含まれておらず、磁石粒子の表面における分解（Ｆｅ等の溶出や反応等）も観られなかった。従って、Ｓｎ−Ｃｕ合金からなる粒界相は、磁石粒子の割合（主相分率）の低下を招かず、その非磁性が維持されることもわかった。 As is apparent from FIG. 1B, a binder made of Sn—Cu alloy is filled between the Sm—Fe—N-based magnet particles (grain boundaries) with almost no gap, so that each magnet particle is held (bonded). ) Furthermore, the Sn—Cu alloy phase did not substantially contain Fe or the like, and no decomposition (elution or reaction of Fe or the like) on the surface of the magnet particles was observed. Therefore, it was also found that the grain boundary phase made of the Sn—Cu alloy does not cause a decrease in the ratio of the magnetic particles (main phase fraction) and maintains its non-magnetic property.
一方、図２Ａおよび図２Ｂ（両者を併せて単に「図２」という。）から明らかなように、バインダー中にＣｕを含まない場合、磁石粒子中のＦｅとバインダー中のＳｎが反応してできたＳｎ−Ｆｅ系化合物が粒界中に生じることがわかった。この粒界相は、具体的にいうと、Ｆｅを約３０ａｔ％含むＳｎリッチ相であった。この場合、主相分率の低下に加えて、粒界相が強磁性となるため、ボンド磁石の磁気特性も低下し得る。 On the other hand, as is clear from FIGS. 2A and 2B (both are simply referred to as “FIG. 2”), when Cu is not contained in the binder, Fe in the magnet particles reacts with Sn in the binder. It was found that Sn-Fe compounds were generated in the grain boundaries. More specifically, the grain boundary phase was a Sn-rich phase containing about 30 at% Fe. In this case, since the grain boundary phase becomes ferromagnetic in addition to the decrease in the main phase fraction, the magnetic properties of the bond magnet can also be decreased.
（２）図３Ａから明らかなように、ＳＰＳの加熱温度：３００℃とした場合、バインダー中にＣｕが存在すると、Ｓｎ量の増加に応じて相対密度も増加することがわかった。この傾向は、Ｃｕ量の減少や試料の形状変化に依る影響が少ないこともわかった。逆に、バインダーがＣｕまたはＳｎの一方からなる場合、相対密度は高々６５％に留まることもわかった。この傾向は、ＳＰＳの加熱温度を変化させても同じであることも図３Ｂからわかる。 (2) As is clear from FIG. 3A, when the heating temperature of SPS is 300 ° C., it is found that when Cu is present in the binder, the relative density increases as the amount of Sn increases. It has also been found that this tendency is less affected by a decrease in the amount of Cu and a change in the shape of the sample. Conversely, it has also been found that when the binder consists of one of Cu or Sn, the relative density remains at most 65%. It can be seen from FIG. 3B that this tendency is the same even if the heating temperature of the SPS is changed.
さらに、図４から明らかなように、バインダーがＳｎ−Ｃｕ合金からなる試料（メタルボンド磁石）は、ＳＰＳ前の試料（被覆磁石粉末）に対して、保磁力がほぼ１．５倍にまで向上することもわかった。これは、ＣｕとＳｎを含むバインダーがＳＰＳによって液相化して、非磁性な粒界相（Ｓｎ−Ｃｕ合金相）が形成されたためと考えられる。 Furthermore, as is clear from FIG. 4, the coercive force of the sample (metal bonded magnet) whose binder is made of an Sn—Cu alloy is approximately 1.5 times that of the sample before SPS (coated magnet powder). I also understood that This is presumably because the binder containing Cu and Sn was converted into a liquid phase by SPS to form a nonmagnetic grain boundary phase (Sn—Cu alloy phase).
Claims (8)
該磁石粒子同士を結合するバインダーとからなり、
該バインダーは、スズ（Ｓｎ）と銅（Ｃｕ）からなることを特徴とするメタルボンド磁石。 Magnet particles made of a rare earth magnet alloy;
A binder that binds the magnet particles together,
The binder is made of tin (Sn) and copper (Cu), a metal bond magnet.
請求項１〜４のいずれかに記載のメタルボンド磁石が得られることを特徴とするメタルボンド磁石の製造方法。 A heating step of heating magnet particles made of rare earth magnet alloy, raw material powder in which Sn source and Cu source are mixed, or a molded body made of the raw material powder,
A method for producing a metal bonded magnet, wherein the metal bonded magnet according to claim 1 is obtained.
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