JP4766452B2 - Rare earth permanent magnet - Google Patents
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- JP4766452B2 JP4766452B2 JP2006066732A JP2006066732A JP4766452B2 JP 4766452 B2 JP4766452 B2 JP 4766452B2 JP 2006066732 A JP2006066732 A JP 2006066732A JP 2006066732 A JP2006066732 A JP 2006066732A JP 4766452 B2 JP4766452 B2 JP 4766452B2
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- 229910052726 zirconium Inorganic materials 0.000 claims description 20
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- 238000005245 sintering Methods 0.000 description 59
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- 229910052739 hydrogen Inorganic materials 0.000 description 10
- 238000002156 mixing Methods 0.000 description 10
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Description
本発明は、希土類元素Ｒを含む希土類永久磁石に関する。 The present invention relates to a rare earth permanent magnet containing a rare earth element R.
希土類永久磁石、例えばＮｄ−Ｆｅ−Ｂ系焼結磁石は、磁気特性に優れていること、主成分であるＮｄが資源的に豊富で比較的安価であること等の利点を有することから、近年、その需要は益々拡大する傾向にある。また、電子機器の高性能化や多機能化も著しく、このような機器に使用されるＮｄ−Ｆｅ−Ｂ系焼結磁石に対しても、これまで以上に優れた特性が要求されている。 In recent years, rare earth permanent magnets such as Nd—Fe—B sintered magnets have advantages such as excellent magnetic properties, Nd as a main component is abundant in resources, and is relatively inexpensive. The demand is increasing. In addition, the performance and functionality of electronic devices are remarkably increased, and Nd—Fe—B based sintered magnets used in such devices are required to have better characteristics than ever.
このような状況から、Ｎｄ−Ｆｅ−Ｂ系焼結磁石の保磁力や飽和磁束密度等の磁気特性を高めるための研究開発が各方面において活発に進められている。例えば特許文献１においては、Ｒ−Ｆｅ−Ｂ系永久磁石に０．０２ａｔ％〜０．５ａｔ％のＣｕを添加することにより、Ｒ−Ｆｅ−Ｂ系永久磁石の磁気特性と焼結温度幅を改善する報告がなされている。また、例えば特許文献２では、Ｒ−Ｆｅ−Ｂ系希土類磁石にＡｌ、Ｃｕ、Ｓｉを必須としてさらにＣｒ、Ｍｎ、Ｎｉのうち少なくとも１種を添加することにより、保磁力と最大エネルギー積とを改善する報告がなされている。 Under such circumstances, research and development for enhancing magnetic properties such as coercive force and saturation magnetic flux density of Nd—Fe—B based sintered magnets are actively being promoted in various fields. For example, in Patent Document 1, by adding 0.02 at% to 0.5 at% Cu to an R—Fe—B permanent magnet, the magnetic properties and sintering temperature range of the R—Fe—B permanent magnet are reduced. There are reports of improvement. Further, for example, in Patent Document 2, the coercive force and the maximum energy product are obtained by adding Al, Cu, Si to the R—Fe—B rare earth magnet and adding at least one of Cr, Mn, and Ni. There are reports of improvement.
ところで、焼結で得られるＲ−Ｔ−Ｂ系希土類永久磁石の磁気特性は、焼結温度に依存するところがある。その一方、工業的な生産規模においては、焼結炉内の全域で加熱温度を均一にすることは困難である。したがって、Ｒ−Ｔ−Ｂ系希土類永久磁石においては、焼結温度が変動しても所望する磁気特性を得ることが要求される。ここで、所望する磁気特性を得ることのできる温度範囲を、焼結温度幅ということにする。 By the way, the magnetic characteristics of the RTB-based rare earth permanent magnet obtained by sintering may depend on the sintering temperature. On the other hand, on an industrial production scale, it is difficult to make the heating temperature uniform throughout the sintering furnace. Therefore, the R-T-B rare earth permanent magnet is required to obtain desired magnetic characteristics even when the sintering temperature varies. Here, the temperature range where desired magnetic characteristics can be obtained is referred to as a sintering temperature range.
焼結温度幅を改善する技術についても様々な検討が行われており、例えば特許文献３において、Ｃｏ、Ａｌ、Ｃｕ、それにＺｒ、Ｎｂ、又はＨｆを含有するＲ−Ｔ−Ｂ系希土類永久磁石に微細なＺｒＢ化合物、ＮｂＢ化合物、又はＨｆＢ化合物を均一に分散して析出させることにより、焼結過程における磁石合金の粒成長を抑制し、磁気特性と焼結温度幅を改善することが提案されている。 Various studies have also been made on techniques for improving the sintering temperature range. For example, in Patent Document 3, an RTB-based rare earth permanent magnet containing Co, Al, Cu, and Zr, Nb, or Hf is disclosed. It is proposed that the fine ZrB compound, NbB compound, or HfB compound be uniformly dispersed and precipitated to suppress the grain growth of the magnet alloy during the sintering process and improve the magnetic properties and the sintering temperature range. ing.
さらに、本出願人は、特許文献４において、Ｚｒを０．０５ｗｔ％〜０．２ｗｔ％含有するＲ−Ｔ−Ｂ系希土類永久磁石を提案している。特許文献４記載の発明によれば、Ｚｒを添加することにより焼結時の異常粒成長を抑制することができ、そのために酸素量低減等のプロセスを採用したときにも角形比の低減を抑制することができる。
しかしながら、高性能磁石に要求されるような高磁気特性、具体的には、高い保磁力（Ｈｃｊ）及び残留磁束密度（Ｂｒ）を得るには、特許文献１や特許文献２に記載される発明では未だ不十分である。Ｒ−Ｔ−Ｂ系希土類永久磁石の保磁力及び残留磁束密度のさらなる向上を図るには、合金中の酸素量を低下させることが有効であるが、合金中の酸素量を低下させると、焼結過程において異常粒成長が起こりやすくなり、角形比が低下するという不都合がある。合金中の酸化物が結晶粒の成長を抑制しているためである。 However, in order to obtain high magnetic properties required for high performance magnets, specifically, high coercive force (Hcj) and residual magnetic flux density (Br), the inventions described in Patent Document 1 and Patent Document 2 That is not enough. In order to further improve the coercive force and the residual magnetic flux density of the R-T-B rare earth permanent magnet, it is effective to reduce the oxygen content in the alloy. There is an inconvenience that abnormal grain growth tends to occur during the setting process, and the squareness ratio decreases. This is because the oxide in the alloy suppresses the growth of crystal grains.
また、特許文献４は、前記特許文献１及び特許文献２の角形比低下の問題点を改善したものである。しかしながら、今後の応用製品のさらなる高性能化を考慮すると、特許文献４に記載される磁石の磁気特性は必ずしも満足のいくものではなく、さらなる向上が強く求められている。 Patent Document 4 is an improvement of the problem of the reduction in squareness ratio of Patent Document 1 and Patent Document 2. However, considering further enhancement of performance of applied products in the future, the magnetic characteristics of the magnet described in Patent Document 4 are not always satisfactory, and further improvement is strongly demanded.
さらに、特許文献３によれば異常粒成長が改善され焼結温度幅が拡大されているものの、表１３から明らかなように、１００μｍ以上の粗大粒子がなおも存在しており、その存在量は０．３％〜数％程度に達している。このような量の粗大粒子が存在すると、通常、希土類永久磁石の角形比は大幅に低下してしまう。これに反して特許文献３の表１〜表１２の実施例においては角形比が良好な結果となっているが、この原因としては、特許文献３では角形比の求め方として、高保磁力成分の角形性（減磁曲線の屈曲）を反映しにくい求め方である「４×（ＢＨ）ｍａｘ／（Ｂｒ）２」を採用していることが挙げられる。高保磁力側の角形性をより正確に反映する角形比の求め方（例えば「Ｈｋ／ＨｃＪ」）によって、特許文献３に記載されるサンプルを評価すれば、表１〜表１２に示される値よりも大幅に低い値を示すものと推測される。なお、希土類永久磁石においてさらなる高特性を得る手法としてＴｂの添加が有効であるが、合金中の酸素量を低下させるとともにＴｂを添加すると、異常粒成長がさらに生じ易くなり、角形比の低下が非常に大きくなる傾向にある。したがって、特許文献３に記載される発明では焼結過程における異常粒成長の抑制効果は未だ不十分であり、さらなる改善が望まれている。 Furthermore, according to Patent Document 3, although abnormal grain growth is improved and the sintering temperature range is expanded, as is apparent from Table 13, coarse particles of 100 μm or more still exist, and the abundance thereof is It has reached about 0.3% to several percent. If such an amount of coarse particles is present, usually the squareness ratio of the rare earth permanent magnet is significantly reduced. On the contrary, in the examples of Table 1 to Table 12 of Patent Document 3, the squareness ratio is a good result. As a cause of this, in Patent Document 3, as a method for obtaining the squareness ratio, a high coercive force component is obtained. It is mentioned that “4 × (BH) max / (Br) 2 ”, which is a method of obtaining that hardly reflects the squareness (bending of the demagnetization curve), is employed. If the sample described in Patent Document 3 is evaluated by a method for obtaining a squareness ratio that more accurately reflects the squareness on the high coercive force side (for example, “Hk / HcJ”), the values shown in Tables 1 to 12 are obtained. Is estimated to be significantly lower. In addition, although addition of Tb is effective as a technique for obtaining further high characteristics in rare earth permanent magnets, when the amount of oxygen in the alloy is reduced and Tb is added, abnormal grain growth is more likely to occur, and the squareness ratio is reduced. It tends to be very large. Therefore, in the invention described in Patent Document 3, the effect of suppressing abnormal grain growth in the sintering process is still insufficient, and further improvement is desired.
本発明は、このような従来の実情に鑑みて提案されたものであり、残留磁束密度及び保磁力等の磁気特性に優れ、焼結過程における粒成長を確実に抑制することができ、且つ焼結温度幅を拡大することができる希土類永久磁石を提供することを目的とする。 The present invention has been proposed in view of such a conventional situation, is excellent in magnetic properties such as residual magnetic flux density and coercive force, can reliably suppress grain growth in the sintering process, and is sintered. An object of the present invention is to provide a rare-earth permanent magnet capable of expanding the sintering temperature range.
前述の問題を解決するために、本発明に係る希土類永久磁石は、Ｔｂ：０〜１０ｗｔ％（ただし０は含まず。）、Ｒ：２８ｗｔ％〜３２ｗｔ％（Ｒは希土類元素から選ばれる２種以上であり、少なくとも前記Ｔｂを含有する。）、Ｃｏ：０〜２ｗｔ％（ただし０は含まず。）、Ｂ：０．５ｗｔ％〜１．５ｗｔ％、Ｃｕ及びＡｌから選ばれる１種又は２種以上：０．０２ｗｔ％〜０．５ｗｔ％、Ｚｒ：０．０３〜０．２５ｗｔ％、Ｇａ：０．０５ｗｔ％〜０．２５ｗｔ％、Ｏ：０．０３ｗｔ％〜０．２ｗｔ％、Ｆｅ及び不可避不純物：残部からなる組成を有することを特徴とする。
In order to solve the above-described problems, the rare earth permanent magnet according to the present invention is composed of Tb: 0 to 10 wt% (however, 0 is not included), R: 28 wt% to 32 wt% (R is selected from two rare earth elements) 1 or 2 selected from Cu: 0 to 2 wt% (however, 0 is not included), B: 0.5 wt% to 1.5 wt%, Cu and Al. More than seeds: 0.02 wt% to 0.5 wt%, Zr: 0.03 to 0.25 wt%, Ga: 0.05 wt% to 0.25 wt%, O: 0.03 wt% to 0.2 wt%, Fe and Inevitable impurities: characterized by having a composition comprising the balance.
本発明では、前記のような低酸素量であり、Ｔｂを必須元素として含有し、さらにはＣｏ、Ｂ、Ｃｕ、Ａｌを適正量含有する組成の希土類永久磁石において、適正量のＧａとＺｒとを含有している。特に、Ｔｂを必須元素として含むことで残留磁束密度及び保磁力といった磁気特性の向上を図りつつ、ＧａとＺｒとの複合添加により焼結過程における異常粒成長の発生を確実に抑制し、例えば粒径１００μｍ以上の粗大粒子の発生がほぼ確実に抑制される。また、ＧａとＺｒとの複合添加により、焼結温度幅も拡大される。 In the present invention, in a rare earth permanent magnet having a low oxygen content as described above, containing Tb as an essential element, and further containing appropriate amounts of Co, B, Cu, and Al, appropriate amounts of Ga and Zr, Contains. In particular, the inclusion of Tb as an essential element improves the magnetic properties such as residual magnetic flux density and coercive force, and the addition of Ga and Zr reliably suppresses the occurrence of abnormal grain growth during the sintering process. Generation of coarse particles having a diameter of 100 μm or more is almost certainly suppressed. Moreover, the sintering temperature range is expanded by the combined addition of Ga and Zr.
なお、前述の特許文献２においては、酸素量は６０００ｐｐｍ以下が好ましいことや、ＺｒやＧａ添加で保磁力を高める効果が得られることが記載されているものの、酸素量を２０００ｐｐｍ（＝０．２ｗｔ％）以下のように極めて少なくしたときに異常粒成長が生じることについては認識しておらず、当然ながらＧａとＺｒとの複合添加によって異常粒成長を抑制することについても全く認識していない。また、特許文献２においては、希土類元素ＲとしてＴｂの記載はあるものの、Ｔｂを実際に含む磁石の検討を行っておらず、単なる列挙にとどまっている。すなわち、特許文献２ではＴｂ、Ｚｒ及びＧａ等の特定の元素を組み合わせるとともに、低酸素量とすることは完全に想定外である。 In addition, in the above-mentioned patent document 2, although it is described that the oxygen amount is preferably 6000 ppm or less and that the effect of increasing the coercive force can be obtained by adding Zr or Ga, the oxygen amount is 2000 ppm (= 0.2 wt. %) It is not recognized that abnormal grain growth occurs when it is extremely reduced as follows, and of course, it is not recognized at all that the abnormal grain growth is suppressed by the combined addition of Ga and Zr. Further, in Patent Document 2, although Tb is described as the rare earth element R, a magnet that actually contains Tb has not been studied and is merely listed. That is, in Patent Document 2, it is completely unexpected to combine specific elements such as Tb, Zr, and Ga and reduce the amount of oxygen.
また、前述の特許文献３は、希土類磁石中にＺｒを含み、酸素含有量も低いものであるが、Ｔｂを必須元素とするという考えはない。また、Ｇａの記載があるものの、Ｇａはあくまで不純物扱いであって実際には検討されておらず、単なる列挙に止まっている。Ｇａを含まずＺｒを含む低酸素量の希土類磁石に、Ｔｂを必須元素とするような組成を適用すると、焼結過程における異常粒成長による角形比（Ｈｋ／ＨｃＪ）の低下及び保磁力（ＨｃＪ）の低下を引き起こしてしまう。 Moreover, although the above-mentioned patent document 3 contains Zr in a rare earth magnet and has a low oxygen content, there is no idea that Tb is an essential element. In addition, although there is a description of Ga, Ga is only treated as an impurity and is not actually studied, and is merely a list. When a composition containing Tb as an essential element is applied to a low oxygen content rare earth magnet not containing Ga but containing Zr, the reduction in squareness ratio (Hk / HcJ) and coercivity (HcJ) due to abnormal grain growth during the sintering process. ).
さらに特許文献４に記載される希土類永久磁石は、Ｚｒを含有するものの、Ｇａを含有していない。このような永久磁石において磁気特性のさらなる向上を図るために、例えばＴｂを必須元素とした場合、角形特性が悪化するという不都合が生じる。 Furthermore, although the rare earth permanent magnet described in Patent Document 4 contains Zr, it does not contain Ga. In order to further improve the magnetic characteristics of such a permanent magnet, for example, when Tb is used as an essential element, there arises a disadvantage that the square characteristics deteriorate.
本発明によれば、高い保磁力及び残留磁束密度を有するとともに、焼結過程における粒成長を確実に抑制することにより、例えば角形比に優れ、焼結温度幅が拡大された希土類永久磁石を提供することができる。 According to the present invention, a rare earth permanent magnet having a high coercive force and a residual magnetic flux density and reliably suppressing grain growth in the sintering process, for example, having an excellent squareness ratio and an expanded sintering temperature range is provided. can do.
以下、本発明を適用した希土類永久磁石について、図面を参照して詳細に説明する。
先ず、本発明を適用した希土類永久磁石の化学組成について説明する。ここで、化学組成とは、焼結後の希土類永久磁石における化学組成をいう。
Hereinafter, a rare earth permanent magnet to which the present invention is applied will be described in detail with reference to the drawings.
First, the chemical composition of the rare earth permanent magnet to which the present invention is applied will be described. Here, the chemical composition refers to the chemical composition in the rare earth permanent magnet after sintering.
本発明の希土類永久磁石において、希土類元素Ｒの含有量は３５ｗｔ％以下とする。希土類元素Ｒが３５ｗｔ％を超えると主相であるＲ２Ｔ１４Ｂ相の体積比率が低下し、残留磁束密度が大幅に低下する。また、希土類元素Ｒが酸素と反応し、含有する酸素量が増え、これに伴い保磁力発生に有効なＲリッチ相が減少し、保磁力の大幅な低下を招く。一方、希土類元素Ｒの含有量が２５ｗｔ％未満であると、希土類永久磁石の主相となるＲ２Ｔ１４Ｂ相の生成が十分ではなく軟磁性を持つα−Ｆｅ等が析出し、保磁力が著しく低下する。以上の理由から、希土類元素Ｒの含有量は２５ｗｔ％〜３５ｗｔ％とする。また、望ましい希土類元素Ｒの含有量は、２８ｗｔ％〜３２ｗｔ％である。さらに、希土類元素Ｒの含有量を３０ｗｔ％以下とすることが最も望ましい。希土類元素Ｒの含有量を３０ｗｔ％以下とすることで主相であるＲ２Ｔ１４Ｂ相の体積比率が増加し、残留磁束密度が大幅に向上する。 In the rare earth permanent magnet of the present invention, the content of rare earth element R is 35 wt% or less. When the rare earth element R exceeds 35 wt%, the volume ratio of the R 2 T 14 B phase, which is the main phase, is reduced, and the residual magnetic flux density is significantly reduced. Further, the rare earth element R reacts with oxygen, the amount of oxygen contained increases, and accordingly, the R-rich phase effective for generating the coercive force decreases, leading to a significant decrease in the coercive force. On the other hand, when the content of the rare earth element R is less than 25 wt%, the R 2 T 14 B phase, which is the main phase of the rare earth permanent magnet, is not sufficiently generated, and α-Fe or the like having soft magnetism is precipitated. Is significantly reduced. For the above reasons, the rare earth element R content is set to 25 wt% to 35 wt%. The desirable rare earth element R content is 28 wt% to 32 wt%. Furthermore, it is most desirable that the content of the rare earth element R is 30 wt% or less. By setting the content of the rare earth element R to 30 wt% or less, the volume ratio of the R 2 T 14 B phase, which is the main phase, is increased, and the residual magnetic flux density is greatly improved.
ここで、希土類元素Ｒは、希土類元素の１種又は２種以上である。希土類元素Ｒは、具体的には、Ｙ、Ｌａ、Ｃｅ、Ｐｒ、Ｎｄ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｙｂ及びＬｕである。なお、「希土類元素Ｒの含有量が２５ｗｔ％〜３５ｗｔ％である」とは、Ｔｂ、Ｎｄ、Ｄｙ等の各希土類元素の含有量を合計した合計含有量が２５ｗｔ％〜３５ｗｔ％であるということを表す。 Here, the rare earth element R is one or more rare earth elements. Specifically, the rare earth element R is Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and Lu. “The content of the rare earth element R is 25 wt% to 35 wt%” means that the total content of the contents of each rare earth element such as Tb, Nd, Dy is 25 wt% to 35 wt%. Represents.
本発明では、希土類元素Ｒとして少なくともＴｂを選択して用いる。Ｔｂは希土類永久磁石に一般的に用いられるＤｙに比べ、保磁力のさらなる向上に有効な元素である。Ｔｂ２Ｔ１４Ｂ相が例えばＤｙ２Ｔ１４Ｂ相等に比べ高い異方性磁界を示すためである。Ｔｂの含有量は、０〜１０ｗｔ％（ただし０は含まず。）とする。Ｔｂ含有量が０の場合には磁気特性の向上が望めず、Ｔｂの含有量が１０ｗｔ％を超えると、残留磁束密度の低下が著しい。 In the present invention, at least Tb is selected and used as the rare earth element R. Tb is an element effective for further improving the coercive force as compared with Dy generally used for rare earth permanent magnets. This is because the Tb 2 T 14 B phase exhibits a higher anisotropic magnetic field than, for example, the Dy 2 T 14 B phase. The content of Tb is 0 to 10 wt% (however, 0 is not included). When the Tb content is 0, improvement in magnetic properties cannot be expected, and when the Tb content exceeds 10 wt%, the residual magnetic flux density is significantly reduced.
また、希土類元素Ｒとしては、前記Ｔｂに加えて、Ｎｄ及びＤｙを選択して用いることが好ましい。Ｎｄは資源的に豊富で比較的安価であるためである。また、Ｄｙは、Ｄｙ２Ｔ１４Ｂ相の異方性磁界が例えばＮｄ２Ｔ１４Ｂ相の異方性磁界より大きいという特長を持つため、保磁力を向上させるうえで有効である。Ｄｙ含有量は０．１ｗｔ％〜８ｗｔ％とすることが望ましい。Ｄｙは残留磁束密度及び保磁力のいずれを重視するかによって前記範囲内においてその量を定めることが望ましい。つまり、高い残留磁束密度を得たい場合にはＤｙ量を０．１ｗｔ％から３．５ｗｔ％とし、高い保磁力を得たい場合にはＤｙ量を３．５ｗｔ％〜８ｗｔ％とすることが望ましい。 As the rare earth element R, it is preferable to select and use Nd and Dy in addition to the Tb. This is because Nd is abundant in resources and relatively inexpensive. Further, Dy has an advantage that the anisotropic magnetic field of the Dy 2 T 14 B phase is larger than the anisotropic magnetic field of the Nd 2 T 14 B phase, for example, and is effective in improving the coercive force. The Dy content is desirably 0.1 wt% to 8 wt%. It is desirable to determine the amount of Dy within the above range depending on which of the residual magnetic flux density and the coercive force is important. That is, when it is desired to obtain a high residual magnetic flux density, the Dy amount is preferably 0.1 wt% to 3.5 wt%, and when a high coercive force is desired, the Dy amount is desirably 3.5 wt% to 8 wt%. .
本発明の希土類永久磁石は、Ｃｏを０〜４ｗｔ％（ただし０は含まず。）含有することができる。また、望ましいＣｏの含有量は、０〜２ｗｔ％（ただし０は含まず。）である。ＣｏはＦｅと同様の相を形成するが、本発明の希土類永久磁石にＣｏを含有させると、キュリー温度の向上、粒界相の耐食性向上に効果がある。さらに望ましいＣｏの含有量は、０〜２ｗｔ％（ただし、０を含まず。）である。 The rare earth permanent magnet of the present invention can contain 0 to 4 wt% (excluding 0) of Co. Further, the desirable Co content is 0 to 2 wt% (however, 0 is not included). Co forms the same phase as Fe. However, when Co is contained in the rare earth permanent magnet of the present invention, it is effective in improving the Curie temperature and improving the corrosion resistance of the grain boundary phase. The more preferable Co content is 0 to 2 wt% (however, 0 is not included).
本発明の希土類永久磁石は、Ｂを０．５ｗｔ％〜４．５ｗｔ％含有する。Ｂの含有量が０．５ｗｔ％未満の場合には高い保磁力を得ることができない。ただし、Ｂが４．５ｗｔ％を超えると残留磁束密度が低下する傾向にある。したがって、Ｂの含有量の上限を４．５ｗｔ％とする。望ましいＢの含有量は０．５ｗｔ％〜１．５ｗｔ％である。 The rare earth permanent magnet of the present invention contains 0.5 wt% to 4.5 wt% of B. When the B content is less than 0.5 wt%, a high coercive force cannot be obtained. However, when B exceeds 4.5 wt%, the residual magnetic flux density tends to decrease. Therefore, the upper limit of the B content is 4.5 wt%. Desirable B content is 0.5 wt% to 1.5 wt%.
本発明の希土類永久磁石は、Ｃｕ及びＡｌから選ばれる１種又は２種を０．０２ｗｔ％〜０．６ｗｔ％含有する。この範囲でＡｌ及びＣｕの１種又は２種を含有させることにより、得られる希土類永久磁石の高保磁力化、高耐食性化、温度特性の改善が可能となる。Ａｌを添加する場合において、望ましいＡｌの量は０．０３ｗｔ％〜０．２５ｗｔ％である。また、Ｃｕを添加する場合において、望ましいＣｕの量は０〜０．１５ｗｔ％（ただし０を含まず。）である。 The rare earth permanent magnet of the present invention contains 0.02 wt% to 0.6 wt% of one or two selected from Cu and Al. By containing one or two of Al and Cu within this range, it is possible to increase the coercive force, corrosion resistance, and temperature characteristics of the obtained rare earth permanent magnet. In the case of adding Al, a desirable amount of Al is 0.03 wt% to 0.25 wt%. Moreover, when adding Cu, the desirable amount of Cu is 0 to 0.15 wt% (however, 0 is not included).
本発明の希土類永久磁石は、酸素（Ｏ）を０．０３ｗｔ％〜０．２ｗｔ％含有する。酸素量が多いと非磁性成分である酸化物相が増大して磁気特性を低下させる。したがって、酸素量の上限を０．２ｗｔ％とする。ただし、希土類永久磁石における酸素量を単純に低下させたのでは、結晶粒成長抑制効果を持つ酸化物相が減少し、焼結時に充分な密度上昇を得る過程で粒成長が容易に起こる。そこで本発明では、後述のように、焼結過程での結晶粒の異常成長を抑制する効果を持つＧａ及びＺｒを所定量含有させる。酸素含有量が少なすぎると、過焼結しやすくなり、また、角形性が低下するため、酸素の量の下限は０．０３ｗｔ％とする。さらに望ましい酸素の量は、０．０３ｗｔ％〜０．１ｗｔ％である。 The rare earth permanent magnet of the present invention contains 0.03 wt% to 0.2 wt% of oxygen (O). If the amount of oxygen is large, the oxide phase, which is a nonmagnetic component, increases and the magnetic properties are degraded. Therefore, the upper limit of the oxygen amount is set to 0.2 wt%. However, if the oxygen amount in the rare earth permanent magnet is simply reduced, the oxide phase having the effect of suppressing crystal grain growth decreases, and grain growth easily occurs in the process of obtaining a sufficient density increase during sintering. Therefore, in the present invention, as described later, a predetermined amount of Ga and Zr having an effect of suppressing abnormal growth of crystal grains during the sintering process is contained. If the oxygen content is too small, oversintering tends to occur, and the squareness decreases, so the lower limit of the amount of oxygen is 0.03 wt%. A more desirable amount of oxygen is 0.03 wt% to 0.1 wt%.
本発明の希土類永久磁石は、Ｃを含有してもよい。Ｃの含有量は、０．０３ｗｔ％〜０．１ｗｔ％である。Ｃの量が０．０３ｗｔ％未満であると過焼結しやすくなり、また、角形性も低下するおそれがある。Ｃの量が０．１ｗｔ％を超えると、焼結性、角形性がともに低下するおそれがある。 The rare earth permanent magnet of the present invention may contain C. The content of C is 0.03 wt% to 0.1 wt%. If the amount of C is less than 0.03 wt%, oversintering is likely to occur, and the squareness may be reduced. If the amount of C exceeds 0.1 wt%, both sinterability and squareness may be reduced.
また、本発明の希土類永久磁石は、Ｎを含有してもよい。Ｎの含有量は、０．０２ｗｔ％〜０．０５ｗｔ％である。Ｎの量が０．０２ｗｔ％未満であると過焼結しやすくなり、また、角形性も低下するおそれがある。Ｎの量が０．０５ｗｔ％を超えると、焼結性、角形性がともに低下するおそれがある。 The rare earth permanent magnet of the present invention may contain N. The N content is 0.02 wt% to 0.05 wt%. If the amount of N is less than 0.02 wt%, oversintering is likely to occur, and the squareness may be reduced. If the amount of N exceeds 0.05 wt%, both sinterability and squareness may be reduced.
さらに、本発明の希土類永久磁石は、前述の組成に加えて、ＧａとＺｒとをそれぞれ適正量含有する点に大きな特徴がある。適正量のＧａとＺｒとを併用することによって、焼結時における異常粒成長が抑制され、良好な角形性が得られる。また、希土類永久磁石の焼結温度幅を拡大することができる。Ｚｒは、焼結時における異常粒成長を抑制可能な元素として知られているが、Ｔｂを必須とする組成の希土類永久磁石にＺｒを単独で添加した場合であっても、充分な効果を得ることはできない。そればかりか、保磁力の低下を招く。また、Ｔｂを必須とする前述の組成にＧａを単独で添加した場合も、Ｚｒ単独と同様、異常粒成長の抑制効果が不十分となり、角形比の大幅な低下を招く。つまり、ＧａとＺｒとを複合添加することにより、本発明の効果が発揮される。 Furthermore, the rare earth permanent magnet of the present invention has a great feature in that each contains an appropriate amount of Ga and Zr in addition to the above-described composition. By using a proper amount of Ga and Zr in combination, abnormal grain growth during sintering is suppressed, and good squareness is obtained. In addition, the sintering temperature range of the rare earth permanent magnet can be expanded. Zr is known as an element that can suppress abnormal grain growth during sintering. However, even when Zr is added alone to a rare earth permanent magnet having a composition that requires Tb, sufficient effects are obtained. It is not possible. In addition, the coercive force is reduced. In addition, when Ga is added alone to the above-described composition in which Tb is essential, the effect of suppressing abnormal grain growth is insufficient as in the case of Zr alone, and the squareness ratio is greatly reduced. That is, the effect of the present invention is exhibited by adding Ga and Zr in combination.
適正量のＧａ及びＺｒの複合添加は、合金に含まれる希土類元素Ｒの量を少なくしたときに非常に効果的である。希土類元素Ｒの含有量を例えば３０ｗｔ％以下とすることで、残留磁束密度（Ｂｒ）の大幅な向上が可能となるが、焼結時の液相成分が減少するため、焼結性が低下し粒成長が困難となる。この対策として焼結体の密度を高めるために焼結温度を上昇させると、異常粒成長が起こり易くなるという不都合が生じる。適正量のＧａ及びＺｒの複合添加は、このような希土類元素Ｒの量を３０ｗｔ％以下とした際の異常粒成長の抑制に非常に有効である。Ｇａ及びＺｒを複合添加することにより、希土類元素Ｒ量を少なくすることに起因する異常粒成長を抑制しながら、希土類元素Ｒの量を低減することの利点（残留磁束密度の向上効果）を確実に得ることができる。 The combined addition of appropriate amounts of Ga and Zr is very effective when the amount of rare earth element R contained in the alloy is reduced. By making the content of the rare earth element R 30 wt% or less, for example, the residual magnetic flux density (Br) can be greatly improved. However, since the liquid phase component during sintering is reduced, the sinterability is reduced. Grain growth becomes difficult. As a countermeasure, if the sintering temperature is raised in order to increase the density of the sintered body, there is a disadvantage that abnormal grain growth tends to occur. The combined addition of appropriate amounts of Ga and Zr is very effective in suppressing abnormal grain growth when the amount of rare earth element R is 30 wt% or less. By adding Ga and Zr in combination, the advantage of reducing the amount of rare earth element R (the effect of improving residual magnetic flux density) is ensured while suppressing abnormal grain growth caused by reducing the amount of rare earth element R. Can get to.
Ｇａの適正な含有量は、０．０５ｗｔ％〜０．２５ｗｔ％である。希土類永久磁石の磁気特性向上を図るために酸素含有量を低減する際に、Ｇａは焼結過程での結晶粒の異常成長を抑制する効果を発揮し、焼結体の組織を均一且つ微細にする。したがって、Ｇａの添加は、希土類永久磁石における酸素含有量が低い場合に、その効果が顕著となる。また、適正量のＧａは、希土類永久磁石の焼結温度幅を拡大する。Ｇａの量が少なすぎる場合、焼結過程での結晶粒の異常成長抑制効果が不十分となり、希土類永久磁石の角形比が悪化する傾向を示す。また、焼結温度幅の改善効果が不十分となる傾向を示す。したがって、Ｇａの量の下限を０．０５ｗｔ％とする。逆にＧａの量が過剰となると、希土類永久磁石の残留磁束密度及び保磁力が低下する傾向を示す。したがって、Ｇａの量の上限を０．２５ｗｔ％とする。さらに望ましいＧａの量は、０．０５ｗｔ％〜０．１５ｗｔ％である。 The appropriate content of Ga is 0.05 wt% to 0.25 wt%. When reducing the oxygen content to improve the magnetic properties of rare earth permanent magnets, Ga exerts the effect of suppressing abnormal growth of crystal grains during the sintering process, making the structure of the sintered body uniform and fine. To do. Therefore, the addition of Ga has a remarkable effect when the oxygen content in the rare earth permanent magnet is low. Further, an appropriate amount of Ga increases the sintering temperature range of the rare earth permanent magnet. When the amount of Ga is too small, the effect of suppressing abnormal growth of crystal grains in the sintering process becomes insufficient, and the squareness ratio of the rare earth permanent magnet tends to deteriorate. In addition, the improvement effect of the sintering temperature range tends to be insufficient. Therefore, the lower limit of the amount of Ga is set to 0.05 wt%. Conversely, when the amount of Ga becomes excessive, the residual magnetic flux density and coercive force of the rare earth permanent magnet tend to decrease. Therefore, the upper limit of the amount of Ga is set to 0.25 wt%. A more desirable Ga amount is 0.05 wt% to 0.15 wt%.
また、Ｚｒの適正な含有量は、０．０３ｗｔ％〜０．２５ｗｔ％である。希土類永久磁石の磁気特性向上を図るために酸素含有量を低減する際に、Ｚｒは焼結過程での結晶粒の異常成長を抑制する効果を発揮し、焼結体の組織を均一且つ微細にする。したがって、Ｚｒの添加は、希土類永久磁石における酸素含有量が低い場合に、その効果が顕著となる。また、適正量のＺｒは、希土類永久磁石の焼結温度幅を拡大する。Ｚｒの量が少なすぎる場合、焼結過程での結晶粒の異常成長抑制効果が不十分となり、希土類永久磁石の角形比が悪化する傾向を示す。また、焼結温度幅の改善効果が不十分となる傾向を示す。したがって、Ｚｒの量の下限を０．０３ｗｔ％とする。逆にＺｒの量が過剰となると、希土類永久磁石の残留磁束密度及び保磁力が低下する傾向を示す。したがって、Ｚｒの量の上限を０．２５ｗｔ％とする。 Further, an appropriate content of Zr is 0.03 wt% to 0.25 wt%. When reducing the oxygen content in order to improve the magnetic properties of rare earth permanent magnets, Zr exhibits the effect of suppressing abnormal growth of crystal grains during the sintering process, making the structure of the sintered body uniform and fine. To do. Therefore, the addition of Zr becomes remarkable when the oxygen content in the rare earth permanent magnet is low. Further, an appropriate amount of Zr expands the sintering temperature range of the rare earth permanent magnet. When the amount of Zr is too small, the effect of suppressing abnormal growth of crystal grains in the sintering process becomes insufficient, and the squareness ratio of the rare earth permanent magnet tends to deteriorate. In addition, the improvement effect of the sintering temperature range tends to be insufficient. Therefore, the lower limit of the amount of Zr is set to 0.03 wt%. Conversely, when the amount of Zr is excessive, the residual magnetic flux density and coercive force of the rare earth permanent magnet tend to decrease. Therefore, the upper limit of the amount of Zr is set to 0.25 wt%.
したがって、本発明の希土類永久磁石の組成は、以下のように表される。
Ｔｂ：０〜１０ｗｔ％（ただし０は含まず。）
Ｒ：２５ｗｔ％〜３５ｗｔ％（Ｒは希土類元素から選ばれる２種以上であり、少なくとも前記Ｔｂを含有する。）
Ｃｏ：０〜４ｗｔ％（ただし０は含まず。）
Ｂ：０．５ｗｔ％〜４．５ｗｔ％
Ｃｕ及びＡｌから選ばれる１種又は２種以上：０．０２ｗｔ％〜０．６ｗｔ％
Ｚｒ：０．０３〜０．２５ｗｔ％
Ｇａ：０．０５ｗｔ％〜０．２５ｗｔ％
Ｏ：０．０３ｗｔ％〜０．２ｗｔ％
Ｆｅ及び不可避不純物：残部
Therefore, the composition of the rare earth permanent magnet of the present invention is expressed as follows.
Tb: 0 to 10 wt% (excluding 0)
R: 25 wt% to 35 wt% (R is two or more selected from rare earth elements and contains at least the Tb)
Co: 0 to 4 wt% (excluding 0)
B: 0.5 wt% to 4.5 wt%
One or more selected from Cu and Al: 0.02 wt% to 0.6 wt%
Zr: 0.03-0.25 wt%
Ga: 0.05 wt% to 0.25 wt%
O: 0.03 wt% to 0.2 wt%
Fe and inevitable impurities: balance
また、本発明の希土類永久磁石の望ましい組成は、以下のように表される。
Ｔｂ：０〜１０ｗｔ％（ただし０は含まず。）
Ｒ：２８ｗｔ％〜３２ｗｔ％（Ｒは希土類元素から選ばれる２種以上であり、少なくとも前記Ｔｂを含有する。）
Ｃｏ：０〜２ｗｔ％
Ｂ：０．５ｗｔ％〜１．５ｗｔ％
Ｃｕ及びＡｌから選ばれる１種又は２種以上：０．０２ｗｔ％〜０．５ｗｔ％
Ｚｒ：０．０３〜０．２５ｗｔ％
Ｇａ：０．０５ｗｔ％〜０．２５ｗｔ％
Ｏ：０．０３ｗｔ％〜０．２ｗｔ％
Ｆｅ及び不可避不純物：残部
The desirable composition of the rare earth permanent magnet of the present invention is expressed as follows.
Tb: 0 to 10 wt% (excluding 0)
R: 28 wt% to 32 wt% (R is two or more selected from rare earth elements and contains at least the Tb)
Co: 0 to 2 wt%
B: 0.5 wt% to 1.5 wt%
One or more selected from Cu and Al: 0.02 wt% to 0.5 wt%
Zr: 0.03-0.25 wt%
Ga: 0.05 wt% to 0.25 wt%
O: 0.03 wt% to 0.2 wt%
Fe and inevitable impurities: balance
次に、本発明の希土類永久磁石の好適な製造方法について説明する。
本実施の形態では、Ｒ２Ｔ１４Ｂ（ＴはＦｅ、又はＣｏ及びＦｅである。）相を主体とする主相系合金の粉末と、Ｂを含まずＲ及びＴを主体とする粒界相系合金の粉末とを用いて本発明に係る希土類永久磁石を製造する方法について説明する。
Next, the suitable manufacturing method of the rare earth permanent magnet of this invention is demonstrated.
In the present embodiment, a powder of a main phase alloy mainly composed of R 2 T 14 B (T is Fe, Co or Fe) phase, and a grain boundary mainly composed of R and T but not B A method for producing a rare earth permanent magnet according to the present invention using a phase alloy powder will be described.
はじめに、原料金属を真空又は不活性ガス、望ましくはＡｒ雰囲気中でストリップキャスティングすることにより、主相系合金及び粒界相系合金を得る。原料金属としては、希土類金属あるいは希土類合金、純鉄、フェロボロン、さらにはこれらの合金等を使用することができる。得られた原料合金は、凝固偏析がある場合は必要に応じて溶体化処理を行う。その条件は真空又はＡｒ雰囲気下、７００℃〜１５００℃の領域で１時間以上保持すればよい。 First, a main phase alloy and a grain boundary phase alloy are obtained by strip casting the raw metal in a vacuum or an inert gas, preferably in an Ar atmosphere. As the raw material metal, rare earth metals or rare earth alloys, pure iron, ferroboron, and alloys thereof can be used. The obtained raw material alloy is subjected to a solution treatment as necessary when there is solidification segregation. The conditions may be maintained in a region of 700 ° C. to 1500 ° C. for 1 hour or more in a vacuum or Ar atmosphere.
本発明の希土類永久磁石は、必須成分としてＺｒを含有しているが、Ｚｒは主相系合金から供給されることが好ましい。具体的には、主相系合金には、希土類元素Ｒ、遷移金属元素Ｔ及びＢの他に、Ｚｒ、Ａｌ等を含有させることができ、主相系合金は例えばＮｄ−Ｄｙ−Ｂ−Ａｌ−Ｚｒ−Ｆｅ系の合金、Ｎｄ−Ｄｙ−Ｂ−Ａｌ−Ｚｒ−Ｇａ−Ｆｅ系の合金である。また、粒界相系合金は、Ｂを含まずＲ及びＴを主体とするとともに、Ｇａ、Ｃｕ、Ｃｏ等を含有する合金とすることができる。粒界相系合金は、例えばＴｂ−Ｃｕ−Ｃｏ−Ａｌ−Ｆｅ系の合金、Ｔｂ−Ｃｕ−Ｃｏ−Ａｌ−Ｇａ−Ｆｅ系の合金である。 The rare earth permanent magnet of the present invention contains Zr as an essential component, but Zr is preferably supplied from a main phase alloy. Specifically, the main phase alloy can contain Zr, Al and the like in addition to the rare earth element R and the transition metal elements T and B. The main phase alloy is, for example, Nd-Dy-B-Al. -Zr-Fe alloy, Nd-Dy-B-Al-Zr-Ga-Fe alloy. In addition, the grain boundary phase-based alloy can be an alloy containing Ga, Cu, Co, or the like, not containing B but mainly containing R and T. The grain boundary phase alloy is, for example, a Tb—Cu—Co—Al—Fe alloy or a Tb—Cu—Co—Al—Ga—Fe alloy.
主相系合金及び粒界相系合金が作製された後、これらの各母合金は別々に又は一緒に粉砕される。粉砕工程には、粗粉砕工程と微粉砕工程とがある。先ず、各母合金をそれぞれ粒径数百μｍ程度になるまで粗粉砕する。粗粉砕は、スタンプミル、ジョークラッシャー、ブラウンミル等を用い、不活性ガス雰囲気中にて行うことが望ましい。また、水素を吸蔵させた後に粗粉砕を行うことや、水素吸蔵を行った後に水素を放出させることで各合金を粗粉砕することもできる。 After the main phase alloy and the grain boundary phase alloy are produced, each of these master alloys is ground separately or together. The pulverization process includes a coarse pulverization process and a fine pulverization process. First, each mother alloy is coarsely pulverized until the particle size becomes about several hundred μm. The coarse pulverization is desirably performed in an inert gas atmosphere using a stamp mill, a jaw crusher, a brown mill or the like. Moreover, each alloy can be coarsely pulverized by performing coarse pulverization after occluding hydrogen or releasing hydrogen after occluding hydrogen.
粗粉砕工程後、微粉砕工程に移る。微粉砕は、主にジェットミルが用いられ、粒径数百μｍ程度の粗粉砕粉末が、平均粒径３〜５μｍになるまで粉砕される。ジェットミルは、高圧の不活性ガス（例えば窒素ガス）を狭いノズルより開放して高速のガス流を発生させ、この高速のガス流により粗粉砕粉末を加速し、粗粉砕粉末同士の衝突やターゲット又は容器壁との衝突を発生させて粉砕する方法である。これにより、主相系合金粉末及び粒界相系合金粉末を得る。 After the coarse pulverization process, the process proceeds to the fine pulverization process. In the fine pulverization, a jet mill is mainly used, and a coarsely pulverized powder having a particle size of about several hundreds of μm is pulverized until the average particle size becomes 3 to 5 μm. The jet mill opens a high-pressure inert gas (for example, nitrogen gas) from a narrow nozzle to generate a high-speed gas flow, and the high-speed gas flow accelerates the coarsely pulverized powder. Or it is the method of generating and colliding with a container wall. As a result, a main phase alloy powder and a grain boundary phase alloy powder are obtained.
微粉砕工程において主相系合金及び粒界相系合金を別々に粉砕した場合には、微粉砕された主相系合金粉末と粒界相系合金粉末とを窒素雰囲気で混合する。主相系合金粉末及び粒界相系合金粉末の混合比率は、重量比で８０：２０〜９７：３程度とすればよい。同様に、主相系合金及び粒界相系合金を一緒に粉砕する場合の混合比率も、重量比で８０：２０〜９７：３程度とすればよい。微粉砕時に、ステアリン酸亜鉛等の添加剤を０．０１ｗｔ％〜０．３ｗｔ％程度添加することにより、成形時に配向性の高い微粉を得ることができる。 When the main phase alloy and the grain boundary phase alloy are separately ground in the fine grinding step, the finely ground main phase alloy powder and the grain boundary phase alloy powder are mixed in a nitrogen atmosphere. The mixing ratio of the main phase alloy powder and the grain boundary phase alloy powder may be about 80:20 to 97: 3 by weight. Similarly, the mixing ratio when the main phase alloy and the grain boundary phase alloy are pulverized together may be about 80:20 to 97: 3 by weight. By adding about 0.01 wt% to 0.3 wt% of additives such as zinc stearate at the time of fine pulverization, fine powder having high orientation can be obtained at the time of molding.
次に、主相系合金粉末及び粒界相系合金粉末からなる混合粉末を、電磁石に抱かれた金型内に充填し、磁場印加によってその結晶軸を配向させた状態で磁場中成形する。この磁場中成形は、１２ｋＯｅ〜１７ｋＯｅの磁場中で、０．７ｔ／ｃｍ２〜１．５ｔ／ｃｍ２前後の圧力で行えばよい。 Next, a mixed powder composed of a main phase alloy powder and a grain boundary phase alloy powder is filled in a mold held by an electromagnet and molded in a magnetic field with its crystal axis oriented by applying a magnetic field. The magnetic field molding, in a magnetic field of 12kOe~17kOe, 0.7t / cm 2 ~1.5t / cm 2 may be carried out at a pressure of about.
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が、１０００℃〜１１００℃で１時間〜５時間程度焼結すればよい。 After molding in a magnetic field, the compact is sintered in a vacuum or an inert gas atmosphere. Although it is necessary to adjust sintering temperature by various conditions, such as a composition, a grinding | pulverization method, a particle size, and a particle size distribution difference, what is necessary is just to sinter at 1000 to 1100 degreeC for about 1 to 5 hours.
焼結後、得られた焼結体に時効処理を施すことができる。時効処理は、保磁力を制御するうえで重要である。時効処理を２段に分けて行う場合には、８００℃近傍、６００℃近傍での所定時間の保持が有効である。８００℃近傍での熱処理を焼結後に行うと、保磁力が増大するため、混合法においては特に有効である。また、６００℃近傍の熱処理で保磁力が大きく増加するため、時効処理を１段で行う場合には、６００℃近傍の時効処理を施すとよい。以上のようにして、本発明の希土類永久磁石を得ることができる。 After sintering, the obtained sintered body can be subjected to an aging treatment. The aging treatment is important for controlling the coercive force. When the aging treatment is performed in two stages, it is effective to hold for a predetermined time in the vicinity of 800 ° C. and 600 ° C. When the heat treatment in the vicinity of 800 ° C. is performed after sintering, the coercive force increases, which is particularly effective in the mixing method. In addition, since the coercive force is greatly increased by heat treatment at around 600 ° C., when the aging treatment is performed in one stage, the aging treatment at around 600 ° C. is preferably performed. As described above, the rare earth permanent magnet of the present invention can be obtained.
本発明の希土類永久磁石においては、高い磁気特性を得る目的で酸素の含有量を０．０３ｗｔ％〜０．２ｗｔ％とするが、この酸素含有量は、各製造工程における雰囲気の制御、原料に含有される酸素量の制御等により調節される。特に、水素粉砕処理から焼結までの各工程の雰囲気を１００ｐｐｍ未満の低酸素濃度に抑えることが、酸素の含有量を０．０３ｗｔ％〜０．２ｗｔ％の範囲内に調節するうえで有効である。 In the rare earth permanent magnet of the present invention, the oxygen content is set to 0.03 wt% to 0.2 wt% for the purpose of obtaining high magnetic properties. It is adjusted by controlling the amount of oxygen contained. In particular, suppressing the atmosphere in each step from hydrogen pulverization to sintering to a low oxygen concentration of less than 100 ppm is effective in adjusting the oxygen content within the range of 0.03 wt% to 0.2 wt%. is there.
また、希土類永久磁石に含有されるＣの量は、製造工程で用いられる粉砕助剤の種類及び添加量等により調節する。さらに、希土類永久磁石に含有されるＮの量は、原料合金の種類及び量や、原料合金を窒素雰囲気で粉砕する場合の粉砕条件等により調節する。 Further, the amount of C contained in the rare earth permanent magnet is adjusted by the type and amount of the grinding aid used in the production process. Further, the amount of N contained in the rare earth permanent magnet is adjusted by the type and amount of the raw material alloy, the pulverizing conditions when the raw material alloy is pulverized in a nitrogen atmosphere, and the like.
以上のようにして得られる本発明の希土類永久磁石においては、Ｔｂ、希土類元素Ｒ、Ｃｏ、Ｂ、Ｃｕ、Ａｌ、Ｏ、Ｇａ及びＺｒの含有量を適正とすることで高い残留磁束密度及び保磁力を実現するとともに、焼結過程における異常粒成長を確実に抑制しており、例えば１００μｍ以上の粗大粒子の発生が確実に抑えられる。さらには、本発明の希土類永久磁石においては、５０μｍ以上１００μｍ未満のさらに微細な粗大粒子の発生もなく、異常粒成長が確実に防止されている。 In the rare earth permanent magnet of the present invention obtained as described above, high residual magnetic flux density and retention can be obtained by making the contents of Tb, rare earth elements R, Co, B, Cu, Al, O, Ga and Zr appropriate. While realizing the magnetic force, the abnormal grain growth in the sintering process is reliably suppressed, and the generation of coarse particles of, for example, 100 μm or more can be reliably suppressed. Furthermore, in the rare earth permanent magnet of the present invention, there is no generation of finer coarse particles of 50 μm or more and less than 100 μm, and abnormal grain growth is reliably prevented.
以下、本発明を適用した具体的な実施例について、実験結果に基づいて説明する。なお、本発明は以下の実施例の記載に限定されるものではない。 Hereinafter, specific examples to which the present invention is applied will be described based on experimental results. In addition, this invention is not limited to description of a following example.
（実施例１）
（１）原料合金
ストリップキャスティング法により、表１に示す９種類の合金を作製した。
Example 1
(1) Raw material alloys Nine kinds of alloys shown in Table 1 were produced by strip casting.
（２）水素粉砕工程
室温にて水素を吸蔵させた後、Ａｒ雰囲気中で６００℃×１時間の脱水素を行う、水素粉砕処理を行った。
本実施例では、焼結体酸素量を０．０３ｗｔ％〜０．２ｗｔ％とするために、水素処理（粉砕処理後の回収）から焼結（焼結炉に投入する）までの各工程の雰囲気を、１００ｐｐｍ未満の酸素濃度に抑えてある。以後、これを低酸素プロセスと称する。
(2) Hydrogen pulverization step After occluding hydrogen at room temperature, hydrogen pulverization treatment was performed in which dehydrogenation was performed in an Ar atmosphere at 600 ° C for 1 hour.
In this example, in order to make the sintered body oxygen amount 0.03 wt% to 0.2 wt%, each process from hydrogen treatment (recovery after pulverization treatment) to sintering (put into the sintering furnace) is performed. The atmosphere is suppressed to an oxygen concentration of less than 100 ppm. Hereinafter, this is referred to as a low oxygen process.
（３）粉砕工程
微粉砕を行う前に粉砕助剤を混合した。なお、水素粉砕工程の次に粗粉砕工程を行う場合があるが、本実施例においては省略した。粉砕助剤は、特に限定はないが、本実施例ではステアリン酸亜鉛を０．０５％〜０．１％混合した。粉砕助剤の混合は、例えばナウターミキサー等により５分間〜３０分間ほど行う程度でよい。
その後、気流式粉砕機を用いて微粉砕を行う。本実験ではジェットミルを用いて微粉砕を行った。気流式粉砕機により、合金粉末が平均粒径３μｍ〜６μｍ程度になるまで微粉砕を行った。本実験では、平均粒径が４μｍの粉砕粉を作製した。
当然ながら、粉砕助剤の混合工程及び微粉砕工程は、ともに低酸素プロセスで行った。
(3) Grinding step A grinding aid was mixed before fine grinding. In addition, although the coarse pulverization process may be performed after the hydrogen pulverization process, it is omitted in this embodiment. The grinding aid is not particularly limited, but in this example, zinc stearate was mixed in an amount of 0.05% to 0.1%. The mixing of the grinding aid may be performed for about 5 minutes to 30 minutes using, for example, a Nauter mixer.
Thereafter, fine pulverization is performed using an airflow pulverizer. In this experiment, fine pulverization was performed using a jet mill. Using an airflow pulverizer, fine pulverization was performed until the alloy powder had an average particle size of about 3 μm to 6 μm. In this experiment, pulverized powder having an average particle size of 4 μm was prepared.
Of course, both the mixing step and the fine pulverization step of the pulverization aid were performed by a low oxygen process.
（４）配合工程
実験を効率よく行うために、数種類の微粉砕粉を調合し、所望の組成となるように混合する場合がある。この場合の混合も、例えばナウターミキサー等により５分間〜３０分間ほど行う程度でよい。
配合工程も低酸素プロセスで行うことが望ましいが、焼結体酸素量を微増させる場合は、本工程にて、成形用微粉末の酸素量を調整する。例えば、組成や平均粒径が同一の微粉末を用意し、１００ｐｐｍ以上の含酸素雰囲気に数分〜数時間放置することで、数千ｐｐｍの微粉末が得られる。これら２種類の微粉末を低酸素プロセス中で混合することで、酸素量の調整を行っている。
実施例１では、表１に示す組成の合金のうち、ａ１，ａ２，ａ３及びｂ１，ｂ２を表２に示す最終組成となるように配合した。表２の上段は、Ｇａを粒界相合金から添加した例であり、下段はＧａを主相系合金から添加した例である。このとき、希土類永久磁石における希土類元素Ｒの合計含有量が２９．７ｗｔ％であり、Ｔｂ含有量が１．４ｗｔ％となるように調整した。配合後、水素粉砕処理を行い、その後ジェットミルにて平均粒径４μｍとなるように微粉砕した。
(4) Blending step In order to perform the experiment efficiently, several types of finely pulverized powders may be mixed and mixed so as to have a desired composition. In this case, the mixing may be performed for about 5 to 30 minutes using, for example, a Nauter mixer.
Although the blending step is preferably performed by a low oxygen process, when the amount of oxygen in the sintered body is slightly increased, the amount of oxygen in the molding fine powder is adjusted in this step. For example, a fine powder having the same composition and average particle diameter is prepared and left in an oxygen-containing atmosphere of 100 ppm or more for several minutes to several hours, whereby a fine powder of several thousand ppm can be obtained. The amount of oxygen is adjusted by mixing these two types of fine powders in a low oxygen process.
In Example 1, among the alloys having the composition shown in Table 1, a1, a2, a3 and b1, b2 were blended so as to have the final composition shown in Table 2. The upper part of Table 2 is an example in which Ga is added from a grain boundary phase alloy, and the lower part is an example in which Ga is added from a main phase alloy. At this time, adjustment was made so that the total content of rare earth elements R in the rare earth permanent magnet was 29.7 wt% and the Tb content was 1.4 wt%. After blending, hydrogen pulverization treatment was performed, and then fine pulverization was performed with a jet mill so that the average particle size became 4 μm.
（５）成形工程
得られた微粉末を磁場中にて成形する。具体的には、電磁石に抱かれた金型内に微粉末を充填し、磁場印加によってその結晶軸を配向させた状態で磁場中成形する。この磁場中成形は、１２ｋＯｅ〜１７ｋＯｅの磁場中で、０．７ｔ／ｃｍ２〜１．５ｔ／ｃｍ２前後の圧力で行えばよい。本実験では、１５ｋＯｅの磁場中で１．２ｔ／ｃｍ２の圧力で成形を行い、成形体を得た。本工程も低酸素プロセスにて行った。
(5) Molding step The obtained fine powder is molded in a magnetic field. Specifically, a fine powder is filled in a mold held by an electromagnet, and molding is performed in a magnetic field in a state where the crystal axis is oriented by applying a magnetic field. The magnetic field molding, in a magnetic field of 12kOe~17kOe, 0.7t / cm 2 ~1.5t / cm 2 may be carried out at a pressure of about. In this experiment, molding was performed in a magnetic field of 15 kOe at a pressure of 1.2 t / cm 2 to obtain a molded body. This step was also performed by a low oxygen process.
（６）焼結・時効工程
この成形体を真空中において１０７０℃〜１１１０℃で４時間焼結した後、急冷した。次いで得られた焼結体に８００℃で１時間と、５５０℃で２．５時間（ともにＡｒ雰囲気中）の２段時効処理を施した。
(6) Sintering and aging process This compact was sintered at 1070 ° C to 1110 ° C for 4 hours in a vacuum and then rapidly cooled. Next, the obtained sintered body was subjected to a two-stage aging treatment at 800 ° C. for 1 hour and 550 ° C. for 2.5 hours (both in an Ar atmosphere).
得られた希土類永久磁石について、残留磁束密度（Ｂｒ）、保磁力（ＨｃＪ）及び角形比（Ｈｋ／ＨｃＪ）をＢ−Ｈトレーサにより測定した。その結果を表３及び表４に示す。焼結体のガス量、すなわち酸素量、窒素量及び炭素量も表３及び表４に示した。また、焼結温度を１０９０℃としたときの磁気特性を、表２に併記した。表３及び表４において、炭素量は０．０３ｗｔ％〜０．１ｗｔ％、窒素量は０．０２ｗｔ％〜０．０５ｗｔ％と低いレベルであり、低酸素プロセスを採用したことにより、特に酸素量は全てのサンプルにおいて０．１ｗｔ％以下に抑えられている。 About the obtained rare earth permanent magnet, residual magnetic flux density (Br), coercive force (HcJ), and squareness ratio (Hk / HcJ) were measured with a BH tracer. The results are shown in Tables 3 and 4. The amount of gas of the sintered body, that is, the amount of oxygen, the amount of nitrogen, and the amount of carbon are also shown in Tables 3 and 4. In addition, Table 2 shows the magnetic characteristics when the sintering temperature is 1090 ° C. In Tables 3 and 4, the carbon content is as low as 0.03 wt% to 0.1 wt%, and the nitrogen content is as low as 0.02 wt% to 0.05 wt%. Is suppressed to 0.1 wt% or less in all samples.
なお、Ｈｋは磁気ヒステリシスループ（４πＩ−Ｈカーブ）の第２象限における磁化が残留磁束密度Ｂｒの９０％となるときの磁界強度である。角形比Ｈｋ／ＨｃＪは、特に外部磁界の作用や温度上昇による減磁に関係し、実際の使用時における磁石特性の指標となる値である。また、Ｈｋ／ＨｃＪが低いと、着磁に要する磁界強度が増大する。さらに、Ｈｋ／ＨｃＪが低い永久磁石は、磁気ヒステリシスループの第２象限におけるループ形状に問題があることになり、磁石が適用されるシステムの設計条件が厳しくなる。 Hk is the magnetic field strength when the magnetization in the second quadrant of the magnetic hysteresis loop (4πI-H curve) is 90% of the residual magnetic flux density Br. The squareness ratio Hk / HcJ is particularly related to the effect of an external magnetic field and demagnetization due to a temperature rise, and is a value that serves as an index of magnet characteristics during actual use. Further, when Hk / HcJ is low, the magnetic field strength required for magnetization increases. Furthermore, a permanent magnet having a low Hk / HcJ has a problem with the loop shape in the second quadrant of the magnetic hysteresis loop, and the design conditions of the system to which the magnet is applied become severe.
また、Ｎｏ．１〜Ｎｏ．４２の焼結体を切断し、断面１０ｍｍ×１０ｍｍの領域内に存在する長径が５０μｍ以上１００μｍ未満の粗大粒子、及び１００μｍ以上の粗大粒子の個数を、走査型電子顕微鏡（ＳＥＭ）を用いて調べた。その結果を表３及び表４に併せてす。 No. 1-No. 42, the number of the coarse particles having a major axis of 50 μm or more and less than 100 μm and the number of coarse particles of 100 μm or more present in a region having a cross section of 10 mm × 10 mm was examined using a scanning electron microscope (SEM). It was. The results are shown in Tables 3 and 4.
表３は、Ｇａを粒界相合金から添加した場合（表２上段）の結果である。磁気特性の中で角形比（Ｈｋ／ＨｃＪ）が異常粒成長による低下傾向が最も早く現れる。つまり、角形比（Ｈｋ／ＨｃＪ）は、異常粒成長の傾向を把握することのできる一指標となる。ここで、表３から、Ｚｒを含ませずにＧａを添加したＮｏ．１〜Ｎｏ．３は、角形比がいずれも９０％未満である。９０％以上の角形比（Ｈｋ／ＨｃＪ）が得られた焼結温度域を、焼結温度幅と定義すると、Ｇａを単独添加した希土類永久磁石（Ｎｏ．１〜Ｎｏ．３）は、焼結温度幅が０である。また、Ｎｏ．１〜Ｎｏ．３には粒径５０μｍ以上の粗大粒子が存在し、特に１１１０℃で焼結を行ったＮｏ．３において多数確認された。したがって、Ｎｏ．１〜Ｎｏ．３においては、角形特性の大幅な低下が見られる。 Table 3 shows the results when Ga is added from the grain boundary phase alloy (the upper part of Table 2). Among magnetic properties, the squareness ratio (Hk / HcJ) tends to decrease most rapidly due to abnormal grain growth. That is, the squareness ratio (Hk / HcJ) is an index that can grasp the tendency of abnormal grain growth. Here, from Table 3, No. 1 containing Ga not containing Zr was added. 1-No. No. 3 has a squareness ratio of less than 90%. When the sintering temperature range where a squareness ratio (Hk / HcJ) of 90% or more is obtained is defined as a sintering temperature range, rare earth permanent magnets (No. 1 to No. 3) added with Ga alone are sintered. The temperature range is zero. No. 1-No. No. 3 contains coarse particles having a particle size of 50 μm or more, especially No. 3 sintered at 1110 ° C. Many were confirmed in FIG. Therefore, no. 1-No. In No. 3, there is a significant decrease in squareness characteristics.
また、Ｇａを含ませずにＺｒを添加したＮｏ．４〜Ｎｏ．６においては、焼結温度を１０９０℃としたＮｏ．５において角形比が９０％を上回っているもの、１１１０℃での焼結により得られた磁石においては、異常粒成長による粗大粒子が特に多く確認され、角形比の低下が見られた。すなわち、Ｚｒを単独使用した場合の焼結温度幅は非常に狭いものである。 Moreover, No. which added Zr without containing Ga. 4-No. In No. 6, No. 6 with a sintering temperature of 1090 ° C. In the magnet obtained by sintering at 1110 ° C., the number of coarse particles due to abnormal grain growth was particularly large and a reduction in the squareness ratio was observed. That is, the sintering temperature range when Zr is used alone is very narrow.
さらに、Ｇａ及びＺｒの両方を含有するものの、Ｇａ含有量が０．０２ｗｔ％であるＮｏ．７〜Ｎｏ．９においては、表３の結果から、焼結時における異常粒成長の抑制効果は不十分なものであることがわかる。また、焼結温度幅も拡大されていなかった。 Furthermore, although containing both Ga and Zr, the Ga content is 0.02 wt%. 7-No. In No. 9, it can be seen from the results of Table 3 that the effect of suppressing abnormal grain growth during sintering is insufficient. Also, the sintering temperature range was not expanded.
これに対し、ＧａとＺｒとを併用するとともに、これら含有量を適正量としたＮｏ．１０〜Ｎｏ．２４においては、いずれの焼結温度においても、９０％を超える高い角形比を示している。また、粒径５０μｍ以上の粗大粒子も全く観察されなかった。 On the other hand, while using Ga and Zr together, No. 1 with these contents as appropriate amounts. 10-No. No. 24 shows a high squareness ratio exceeding 90% at any sintering temperature. Also, no coarse particles having a particle size of 50 μm or more were observed.
Ｇａ含有量を０．２８ｗｔ％とした場合（Ｎｏ．２５〜Ｎｏ．２７）、焼結温度幅は広いものの、全ての焼結温度において保磁力（ＨｃＪ）が２５ｋＯｅを下回り、保磁力（ＨｃＪ）の大幅な低下が認められる。 When the Ga content is 0.28 wt% (No. 25 to No. 27), although the sintering temperature range is wide, the coercive force (HcJ) is less than 25 kOe at all sintering temperatures, and the coercive force (HcJ). There is a significant decrease.
一方、表４は、Ｇａを主相系合金から添加した場合（表２下段）の結果である。Ｇａを主相系合金から添加した場合も、Ｇａを粒界相合金から添加した結果である表３と同様の傾向を示した。例えば、Ｇａ含有量を０．０５ｗｔ％未満としたＮｏ．２８〜Ｎｏ．３０では、焼結温度幅の改善は小さいものであった。Ｇａ含有量が０．２５ｗｔ％を超える希土類永久磁石（Ｎｏ．４０〜Ｎｏ．４２）では、焼結温度幅は広いものの、全ての焼結温度において保磁力（ＨｃＪ）低下が認められる。 On the other hand, Table 4 shows the results when Ga is added from the main phase alloy (lower part of Table 2). Even when Ga was added from the main phase alloy, the same tendency as shown in Table 3 as a result of adding Ga from the grain boundary phase alloy was shown. For example, No. 1 with a Ga content of less than 0.05 wt%. 28-No. In 30, the improvement of the sintering temperature range was small. In rare earth permanent magnets (No. 40 to No. 42) with a Ga content exceeding 0.25 wt%, although the sintering temperature range is wide, a decrease in coercive force (HcJ) is observed at all sintering temperatures.
したがって、表３及び表４の結果から、本発明の希土類永久磁石においてＺｒと併用されるＧａの最適含有量は０．０５ｗｔ％〜０．２５ｗｔ％であることが確認された。また、Ｇａを粒界相系合金から添加した場合、Ｇａを主相系合金から添加した場合のいずれにおいても、本発明の効果を得られることが確認された。 Therefore, from the results of Tables 3 and 4, it was confirmed that the optimum content of Ga used in combination with Zr in the rare earth permanent magnet of the present invention is 0.05 wt% to 0.25 wt%. Moreover, it was confirmed that the effect of the present invention can be obtained when Ga is added from a grain boundary phase alloy or when Ga is added from a main phase alloy.
（実施例２）
実施例２では、表１に示す組成の合金のうちａ４〜ａ５及びｂ３〜ｂ４を用いて、表５に示す最終組成となるように配合した。その後の工程は、実施例１と同様のプロセスにより、Ｒ−Ｔ−Ｂ系希土類永久磁石を得た。いずれも、Ｇａを主相系合金から添加した例である。得られた希土類永久磁石について、残留磁束密度（Ｂｒ）、保磁力（ＨｃＪ）及び角形比（Ｈｋ／ＨｃＪ）をＢ−Ｈトレーサにより測定した結果を表６に示す。なお、Ｎｏ．４３〜Ｎｏ．４５の永久磁石は合金ａ４と合金ｂ３を９７：３のｗｔ比で配合し、また、Ｎｏ．４６〜Ｎｏ．４８の永久磁石は合金ａ５とｂ４を８０：２０のｗｔ比で配合した。
(Example 2)
In Example 2, it mix | blended so that it might become the final composition shown in Table 5 using a4-a5 and b3-b4 among the alloys of the composition shown in Table 1. In the subsequent steps, an RTB-based rare earth permanent magnet was obtained by the same process as in Example 1. In either case, Ga is added from the main phase alloy. Table 6 shows the results obtained by measuring the residual magnetic flux density (Br), the coercive force (HcJ), and the squareness ratio (Hk / HcJ) of the obtained rare earth permanent magnet with a BH tracer. In addition, No. 43-No. In the permanent magnet No. 45, alloy a4 and alloy b3 are blended at a wt ratio of 97: 3. 46-No. Forty-eight permanent magnets were blended with alloys a5 and b4 at a wt ratio of 80:20.
焼結体のガス量、すなわち酸素量、窒素量及び炭素量も表６に示した。また、焼結温度をそれぞれ１１００℃、１０２０℃としたときの磁気特性を、表５に併記した。表６において、炭素量は０．０３ｗｔ％〜０．１ｗｔ％、窒素量は０．０２ｗｔ％〜０．０５ｗｔ％と低いレベルであり、低酸素プロセスを採用したことにより、特に酸素量は全てのサンプルにおいて０．１ｗｔ％以下に抑えられている。 Table 6 also shows the amount of gas of the sintered body, that is, the amount of oxygen, the amount of nitrogen, and the amount of carbon. Table 5 also shows the magnetic properties when the sintering temperatures were 1100 ° C. and 1020 ° C., respectively. In Table 6, the carbon amount is 0.03 wt% to 0.1 wt%, the nitrogen amount is 0.02 wt% to 0.05 wt%, and the low oxygen process is adopted. In the sample, it is suppressed to 0.1 wt% or less.
また表６のＮｏ．４３〜Ｎｏ．４８より、いずれの焼結温度においても、９０％を超える高い角形比を示している。また、粒径５０μｍ以上の粗大粒子も全く観察されなかった。したがって、実施例２に示す組成の希土類永久磁石においても、本発明の効果を得られることが確認された。
In Table 6, No. 43-No. 48 shows a high squareness ratio exceeding 90% at any sintering temperature. Also, no coarse particles having a particle size of 50 μm or more were observed. Therefore, it was confirmed that the effect of the present invention can be obtained even in the rare earth permanent magnet having the composition shown in Example 2.
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