JP7447573B2 - RTB series permanent magnet - Google Patents
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Description
本発明は、Ｒ－Ｔ－Ｂ系永久磁石に関する。 The present invention relates to an RTB permanent magnet.
特許文献１には、残留磁束密度および保磁力が高く、耐食性および製造安定性に優れたＲ－Ｔ－Ｂ系永久磁石が開示されている。 Patent Document 1 discloses an RTB permanent magnet that has high residual magnetic flux density and coercive force, and has excellent corrosion resistance and manufacturing stability.
特許文献２には、残留磁束密度および保磁力が高いＲ－Ｔ－Ｂ系永久磁石が開示されている。 Patent Document 2 discloses an RTB permanent magnet with high residual magnetic flux density and high coercive force.
本発明は、Ｃｏの含有量が少なくても磁気特性（残留磁束密度Ｂｒ、保磁力ＨｃＪ、角形比Ｈｋ／ＨｃＪ）および耐食性が優れたＲ－Ｔ－Ｂ系永久磁石を提供することを目的とする。 The purpose of the present invention is to provide an RTB permanent magnet that has excellent magnetic properties (residual magnetic flux density Br, coercive force HcJ, squareness ratio Hk/HcJ) and corrosion resistance even with a low Co content. do.
上記の目的を達成するため、本発明のＲ－Ｔ－Ｂ系永久磁石は、
ＲがＮｄおよびＰｒから選択される１種以上、および、ＤｙおよびＴｂから選択される１種以上を含む希土類元素、ＴがＦｅおよびＣｏであり、Ｂがホウ素であるＲ－Ｔ－Ｂ系永久磁石であって、
前記Ｒ－Ｔ－Ｂ系永久磁石は、さらにＺｒを含み、
前記Ｒ－Ｔ－Ｂ系永久磁石全体を１００質量％として、
Ｎｄ，Ｐｒ，ＤｙおよびＴｂの合計含有量が３０．００質量％～３２．２０質量％、
Ｃｏの含有量が０．３０質量％～１．３０質量％、
Ｚｒの含有量が０．２１質量％～０．８５質量％、
Ｂの含有量が０．９０質量％～１．０２質量％であることを特徴とする。
In order to achieve the above object, the RTB permanent magnet of the present invention has the following features:
A rare earth element in which R contains one or more selected from Nd and Pr and one or more selected from Dy and Tb, T is Fe and Co, and B is boron. A magnet,
The RTB permanent magnet further contains Zr,
Assuming that the entire RTB permanent magnet is 100% by mass,
The total content of Nd, Pr, Dy and Tb is 30.00% by mass to 32.20% by mass,
Co content is 0.30% by mass to 1.30% by mass,
Zr content is 0.21% by mass to 0.85% by mass,
The content of B is 0.90% by mass to 1.02% by mass.
本発明のＲ－Ｔ－Ｂ系永久磁石は、上記の範囲内の組成を有することで、Ｃｏの含有量が少なくても磁気特性および耐食性が良好なＲ－Ｔ－Ｂ系永久磁石となる。 By having the composition within the above range, the RTB permanent magnet of the present invention has good magnetic properties and corrosion resistance even with a low Co content.
前記Ｒ－Ｔ－Ｂ系永久磁石は、さらにＣｕを含んでもよく、
Ｃｕの含有量が０．１０質量％～０．５５質量％であってもよい。
The RTB permanent magnet may further contain Cu,
The content of Cu may be 0.10% by mass to 0.55% by mass.
前記Ｒ－Ｔ－Ｂ系永久磁石は、さらにＭｎを含んでもよく
Ｍｎの含有量が０．０２質量％～０．１０質量％であってもよい。
The RTB permanent magnet may further contain Mn, and the Mn content may be from 0.02% by mass to 0.10% by mass.
前記Ｒ－Ｔ－Ｂ系永久磁石は、さらにＡｌを含んでもよく、
Ａｌの含有量が０．０７質量％～０．３５質量％であってもよい。
The RTB permanent magnet may further contain Al,
The content of Al may be 0.07% by mass to 0.35% by mass.
前記Ｒ－Ｔ－Ｂ系永久磁石は、さらにＧａを含んでもよく、
Ｇａの含有量が０．０２質量％～０．１５質量％であってもよい。
The RTB permanent magnet may further contain Ga,
The Ga content may be 0.02% by mass to 0.15% by mass.
重希土類元素の含有量が２．０質量％以下であってもよい。 The content of heavy rare earth elements may be 2.0% by mass or less.
磁石表面から内部に向かって低下する重希土類元素の濃度勾配を有していてもよい。 The magnet may have a heavy rare earth element concentration gradient that decreases from the surface of the magnet toward the inside.
以下、本発明を、図面に示す実施形態に基づき説明する。 The present invention will be described below based on embodiments shown in the drawings.
＜Ｒ－Ｔ－Ｂ系永久磁石＞
本実施形態に係るＲ－Ｔ－Ｂ系永久磁石は、Ｒ２Ｔ１４Ｂ型結晶構造を有する結晶粒子からなる主相粒子を有する。さらに、隣り合う２つ以上の主相粒子によって形成される粒界を有する。
<RTB permanent magnet>
The RTB permanent magnet according to this embodiment has main phase particles made of crystal grains having an R 2 T 14 B type crystal structure. Furthermore, it has grain boundaries formed by two or more adjacent main phase particles.
本実施形態に係るＲ－Ｔ－Ｂ系永久磁石の形状には特に制限はない。 There is no particular restriction on the shape of the RTB permanent magnet according to this embodiment.
本実施形態に係るＲ－Ｔ－Ｂ系永久磁石は、複数の特定の元素を特定の範囲の含有量で含有させることで、残留磁束密度Ｂｒ、保磁力ＨｃＪ、角形比Ｈｋ／ＨｃＪおよび耐食性を向上させることができる。 The RTB permanent magnet according to the present embodiment has improved residual magnetic flux density Br, coercive force HcJ, squareness ratio Hk/HcJ, and corrosion resistance by containing a plurality of specific elements in a specific content range. can be improved.
また、本実施形態に係るＲ－Ｔ－Ｂ系永久磁石は、重希土類元素の濃度が、前記Ｒ－Ｔ－Ｂ系永久磁石１の外側から内側に向かって低下する濃度分布を有してもよい。重希土類元素の種類には特に制限はない。例えばＤｙまたはＴｂであってもよく、Ｔｂであってもよい。すなわち、本実施形態に係るＲ－Ｔ－Ｂ系永久磁石は、Ｒとして軽希土類元素および重希土類元素の両方を含む。 Further, the RTB permanent magnet according to the present embodiment may have a concentration distribution in which the concentration of the heavy rare earth element decreases from the outside to the inside of the RTB permanent magnet 1. good. There are no particular restrictions on the type of heavy rare earth elements. For example, it may be Dy or Tb, or it may be Tb. That is, the RTB permanent magnet according to this embodiment contains both a light rare earth element and a heavy rare earth element as R.
具体的には、図１で示すように、本実施形態に係る直方体形状のＲ－Ｔ－Ｂ系永久磁石１は表面部および中心部を有し、表面部における重希土類元素の含有量を、中心部における重希土類元素の含有量よりも２％以上高くすることができ、５％以上高くすることができ、１０％以上高くすることができる。なお、前記表面部とは、Ｒ－Ｔ－Ｂ系永久磁石１の表面をいう。例えば、図１のＰＯＩＮＴ Ｃ，Ｃ´（図１の互いに向かい合う表面の重心）は表面部である。前記中心部とは、Ｒ－Ｔ－Ｂ系永久磁石１の中心をいう。例えば、Ｒ－Ｔ－Ｂ系永久磁石１の厚みの半分の部分をいう。例えば、図１のＰＯＩＮＴ Ｍ（ＰＯＩＮＴ ＣとＰＯＩＮＴ Ｃ´との中点）は中心部である。なお、図１のＰＯＩＮＴ Ｃ，Ｃ´は、Ｒ－Ｔ－Ｂ系永久磁石１の表面のうち最も面積が広い表面の重心、および当該表面に向かい合う表面の重心であってもよい。 Specifically, as shown in FIG. 1, the rectangular parallelepiped-shaped RTB permanent magnet 1 according to the present embodiment has a surface portion and a center portion, and the content of heavy rare earth elements in the surface portion is as follows: The content of heavy rare earth elements in the central portion can be increased by 2% or more, 5% or more, and 10% or more. Note that the surface portion refers to the surface of the RTB permanent magnet 1. For example, POINT C and C' in FIG. 1 (centroids of surfaces facing each other in FIG. 1) are surface portions. The center portion refers to the center of the RTB permanent magnet 1. For example, it refers to a half of the thickness of the RTB permanent magnet 1. For example, POINT M (the midpoint between POINT C and POINT C') in FIG. 1 is the center. Note that POINT C and C' in FIG. 1 may be the center of gravity of the surface with the largest area among the surfaces of the RTB permanent magnet 1, and the center of gravity of the surface facing the surface.
一般に希土類元素は軽希土類元素と重希土類元素とに分類される。本実施形態に係るＲ－Ｔ－Ｂ系永久磁石における軽希土類元素はＳｃ，Ｙ，Ｌａ，Ｃｅ，Ｐｒ，Ｎｄ，Ｓｍ，Ｅｕであり、重希土類元素はＧｄ，Ｔｂ，Ｄｙ，Ｈｏ,Ｅｒ，Ｔｍ，Ｙｂ，Ｌｕである。 Rare earth elements are generally classified into light rare earth elements and heavy rare earth elements. The light rare earth elements in the RTB permanent magnet according to this embodiment are Sc, Y, La, Ce, Pr, Nd, Sm, Eu, and the heavy rare earth elements are Gd, Tb, Dy, Ho, Er, They are Tm, Yb, and Lu.
本実施形態に係るＲ－Ｔ－Ｂ系永久磁石に前述の重希土類元素の濃度分布を形成させる方法に特に制限はない。例えば、後述する重希土類元素の粒界拡散によりＲ－Ｔ－Ｂ系永久磁石内に重希土類元素の濃度分布を形成させることができる。 There is no particular limitation on the method of forming the above-mentioned heavy rare earth element concentration distribution in the RTB permanent magnet according to this embodiment. For example, a concentration distribution of heavy rare earth elements can be formed in the RTB permanent magnet by grain boundary diffusion of heavy rare earth elements, which will be described later.
また、本実施形態に係るＲ－Ｔ－Ｂ系永久磁石の主相粒子は、コアと、コアを被覆するシェルとからなるコアシェル粒子であってもよい。そして、少なくともシェルには重希土類元素が存在してもよく、ＤｙまたはＴｂが存在してもよく、Ｔｂが存在していてもよい。 Further, the main phase particles of the RTB permanent magnet according to the present embodiment may be core-shell particles consisting of a core and a shell covering the core. A heavy rare earth element, Dy or Tb, or Tb may be present at least in the shell.
重希土類元素をシェルに存在させることで、効率的にＲ－Ｔ－Ｂ系永久磁石の磁気特性を向上させることができる。 By making the heavy rare earth element exist in the shell, the magnetic properties of the RTB permanent magnet can be efficiently improved.
本実施形態においては、軽希土類元素（例えばＮｄ，Ｐｒ）に対する重希土類元素（例えばＤｙ，Ｔｂ）の割合（重希土類元素／軽希土類元素（モル比））が、主相粒子中心部（コア）における前記割合の２倍以上となっている部分をシェルと規定する。 In this embodiment, the ratio of heavy rare earth elements (for example, Dy, Tb) to light rare earth elements (for example, Nd, Pr) (heavy rare earth element/light rare earth element (molar ratio)) is The portion where the ratio is more than twice the above ratio is defined as a shell.
シェルの厚みには特に制限はないが、平均で５００ｎｍ以下であってもよい。また、主相粒子の粒径にも特に制限はないが、平均で１．０μｍ以上６．５μｍ以下であってもよい。 The thickness of the shell is not particularly limited, but may be 500 nm or less on average. Further, the particle size of the main phase particles is not particularly limited, but may be 1.0 μm or more and 6.5 μm or less on average.
主相粒子を上記のコアシェル粒子とする方法には特に制限はない。例えば、後述する粒界拡散による方法がある。重希土類元素が粒界に拡散し、当該重希土類元素が主相粒子の表面の希土類元素Ｒと置換することで重希土類元素の割合が高いシェルが形成され、前記のコアシェル粒子となる。 There is no particular restriction on the method of forming the above-mentioned core-shell particles as the main phase particles. For example, there is a method using grain boundary diffusion, which will be described later. The heavy rare earth element diffuses into the grain boundaries and replaces the rare earth element R on the surface of the main phase particle, thereby forming a shell with a high proportion of the heavy rare earth element, resulting in the above-mentioned core-shell particles.
Ｒは少なくともＮｄおよびＰｒから選択される１種以上、および、ＤｙおよびＴｂから選択される１種以上を含む希土類元素である。また、Ｒとして少なくともＮｄおよびＴｂを含むことが好ましい。 R is a rare earth element containing at least one or more selected from Nd and Pr, and one or more selected from Dy and Tb. Moreover, it is preferable that R contains at least Nd and Tb.
ＴはＦｅおよびＣｏである。 T is Fe and Co.
Ｂは、ホウ素である。また、Ｒ－Ｔ－Ｂ系永久磁石のＢサイトに含まれるホウ素の一部が炭素（Ｃ）に置換されていてもよい。 B is boron. Furthermore, part of the boron contained in the B site of the RTB permanent magnet may be substituted with carbon (C).
本実施形態に係るＲ－Ｔ－Ｂ系永久磁石におけるＮｄ，Ｐｒ，ＤｙおよびＴｂの合計含有量（ＴＲＥ）は、Ｒ－Ｔ－Ｂ系永久磁石全体の質量を１００質量％として、３０．００質量％以上３２．２０質量％以下である。ＴＲＥが少なすぎる場合には、ＨｃＪが低下する。ＴＲＥが多すぎる場合にはＢｒが低下する。 The total content (TRE) of Nd, Pr, Dy, and Tb in the RTB permanent magnet according to this embodiment is 30.00% by mass, assuming that the mass of the entire RTB permanent magnet is 100% by mass. It is not less than 32.20% by mass and not more than 32.20% by mass. If TRE is too low, HcJ will decrease. If there is too much TRE, Br decreases.
本実施形態に係るＲ－Ｔ－Ｂ系永久磁石におけるＮｄおよびＰｒの合計含有量には特に制限はないが、Ｒ－Ｔ－Ｂ系永久磁石全体の質量を１００質量％として、２９．２７質量％以上３１．２７質量％以下であってもよい。 There is no particular restriction on the total content of Nd and Pr in the RTB permanent magnet according to this embodiment, but the total content of Nd and Pr in the RTB permanent magnet according to the present embodiment is 29.27% by mass, assuming that the mass of the entire RTB permanent magnet is 100% by mass. % or more and 31.27% by mass or less.
本実施形態のＲ－Ｔ－Ｂ系永久磁石は、Ｒとして少なくともＮｄおよびＰｒを含有してもよい。Ｐｒの含有量は０．０質量％以上１０．０質量％以下であってもよい。さらに、０．０質量％以上７．６質量％以下であってもよい。また、Ｐｒの含有量が１０．０質量％以下である場合にはＨｃＪの温度変化率が小さくなる。特に高温でのＨｃＪを高くする観点からはＰｒの含有量を０．０質量％～７．６質量％とするのが好ましい。 The RTB permanent magnet of this embodiment may contain at least Nd and Pr as R. The content of Pr may be 0.0% by mass or more and 10.0% by mass or less. Furthermore, it may be 0.0% by mass or more and 7.6% by mass or less. Furthermore, when the Pr content is 10.0% by mass or less, the temperature change rate of HcJ becomes small. In particular, from the viewpoint of increasing HcJ at high temperatures, the Pr content is preferably 0.0% by mass to 7.6% by mass.
本実施形態のＲ－Ｔ－Ｂ系永久磁石は、Ｐｒの含有量が５．８質量％以上であってもよく、５．８質量％未満であってもよい。Ｐｒの含有量が５．８質量％以上である場合にはＨｃＪが向上する。Ｐｒの含有量が５．８質量％未満である場合には、ＨｃＪの温度変化率が小さくなる。 The RTB permanent magnet of this embodiment may have a Pr content of 5.8% by mass or more, or less than 5.8% by mass. When the content of Pr is 5.8% by mass or more, HcJ is improved. When the Pr content is less than 5.8% by mass, the temperature change rate of HcJ becomes small.
Ｐｒの含有量が５．８質量％以上である場合には、Ｐｒの含有量が５．８質量％以上７．６質量％以下であってもよい。また、Ｐｒ／（Ｎｄ＋Ｐｒ）が質量比で０．１９以上０．２５以下であってもよい。Ｐｒの含有量、および／または、Ｐｒ／（Ｎｄ＋Ｐｒ）が上記の範囲内である場合には、ＨｃＪが向上する。 When the Pr content is 5.8% by mass or more, the Pr content may be 5.8% by mass or more and 7.6% by mass or less. Moreover, Pr/(Nd+Pr) may be 0.19 or more and 0.25 or less in mass ratio. When the content of Pr and/or Pr/(Nd+Pr) is within the above range, HcJ is improved.
Ｐｒを意図的に含まなくてもよい。Ｐｒを意図的に含まないことで、ＨｃＪの温度変化率が特に優れ、高温でのＨｃＪが高くなる。なお、Ｐｒを意図的に含まない場合には、不純物としてＰｒを０．２質量％未満、含んでもよく、０．１質量％以下、含んでもよい。 Pr may not be intentionally included. By intentionally not including Pr, the temperature change rate of HcJ is particularly excellent, and HcJ becomes high at high temperatures. In addition, when Pr is not intentionally included, less than 0.2 mass % of Pr may be included as an impurity, and 0.1 mass % or less of Pr may be included.
また、本実施形態のＲ－Ｔ－Ｂ系永久磁石は、Ｒ－Ｔ－Ｂ系永久磁石全体の質量を１００質量％として、重希土類元素（例えば、ＤｙおよびＴｂから選択される１種以上）を合計で２．０質量％以下、含んでもよい。重希土類元素としては実質的にＴｂのみを含んでもよい。重希土類元素の含有量が合計で２．０質量％以下であると、Ｂｒを良好にしやすい。また、高価である重希土類元素の含有量を小さくすることで、Ｒ－Ｔ－Ｂ系永久磁石を低コストで製造しやすくなる。 Furthermore, the RTB permanent magnet of the present embodiment contains a heavy rare earth element (for example, one or more selected from Dy and Tb), with the mass of the entire RTB permanent magnet being 100% by mass. may be included in a total amount of 2.0% by mass or less. The heavy rare earth element may include substantially only Tb. When the total content of heavy rare earth elements is 2.0% by mass or less, it is easy to improve Br. Furthermore, by reducing the content of expensive heavy rare earth elements, it becomes easier to manufacture RTB permanent magnets at low cost.
Ｃｏの含有量は、Ｒ－Ｔ－Ｂ系永久磁石全体の質量を１００質量％として、０．３０質量％以上１．３質量％以下である。０．３０質量％以上０．４３質量％以下であってもよい。本実施形態では、高価であるＣｏを少なくしても高い耐食性を有するＲ－Ｔ－Ｂ系永久磁石を得ることができる。その結果、耐食性の高いＲ－Ｔ－Ｂ系永久磁石を低コストで製造しやすくなる。Ｃｏが少なすぎる場合には、Ｚｒの含有量を後述する範囲内としても耐食性が低下する。Ｃｏが多すぎる場合には、耐食性改善の効果が頭打ちとなるとともに高コストとなる。 The Co content is 0.30% by mass or more and 1.3% by mass or less, where the mass of the entire RTB permanent magnet is 100% by mass. It may be 0.30% by mass or more and 0.43% by mass or less. In this embodiment, an RTB permanent magnet having high corrosion resistance can be obtained even if the amount of expensive Co is reduced. As a result, RTB permanent magnets with high corrosion resistance can be manufactured easily at low cost. If the Co content is too low, the corrosion resistance will decrease even if the Zr content is within the range described below. If there is too much Co, the effect of improving corrosion resistance will reach a plateau and the cost will increase.
Ｆｅの含有量はＲ－Ｔ－Ｂ系永久磁石の実質的な残部である。実質的な残部であるとは、前述のＲおよびＣｏと、後述のＢ，Ｚｒ，Ｍおよび他元素と、を除いた残部であるという意味である。 The content of Fe is the substantial remainder of the RTB permanent magnet. The term "substantial remainder" means the remainder excluding R and Co described above, B, Zr, M, and other elements described later.
本実施形態に係るＲ－Ｔ－Ｂ系永久磁石におけるＢの含有量は、Ｒ－Ｔ－Ｂ系永久磁石全体の質量を１００質量％として、０．９０質量％以上１．０２質量％以下である。０．９２質量％以上１．００質量％以下であってもよい。Ｂが少なすぎる場合にはＨｋ／ＨｃＪが低下しやすくなる。Ｂが多すぎる場合には、ＨｃＪが低下しやすくなる。 The content of B in the RTB permanent magnet according to the present embodiment is 0.90% by mass or more and 1.02% by mass or less, with the mass of the entire RTB permanent magnet being 100% by mass. be. It may be 0.92% by mass or more and 1.00% by mass or less. If B is too small, Hk/HcJ tends to decrease. If there is too much B, HcJ tends to decrease.
本実施形態に係るＲ－Ｔ－Ｂ系永久磁石は、さらにＺｒを含む。Ｚｒの含有量は、Ｒ－Ｔ－Ｂ系永久磁石全体の質量を１００質量％として、０．２１質量％以上０．８５質量％以下である。Ｚｒを上記の範囲内で含有することで、焼結時の異常粒成長を抑制し、Ｈｋ／ＨｃＪおよび低磁場下での着磁率が改善される。そして、Ｃｏの含有量を上記の範囲内としても耐食性を良好にすることができる。Ｚｒが少なすぎる場合には、焼結時に異常粒成長が生じやすくなり、Ｈｋ／ＨｃＪおよび低磁場下での着磁率が悪化する。さらに、耐食性が低下する。Ｚｒが多すぎる場合には、ＢｒおよびＨｋ／ＨｃＪが低下しやすくなる。 The RTB permanent magnet according to this embodiment further contains Zr. The content of Zr is 0.21% by mass or more and 0.85% by mass or less, where the mass of the entire RTB permanent magnet is 100% by mass. By containing Zr within the above range, abnormal grain growth during sintering is suppressed, and Hk/HcJ and magnetization rate under a low magnetic field are improved. Corrosion resistance can also be improved even if the Co content is within the above range. If Zr is too small, abnormal grain growth tends to occur during sintering, and Hk/HcJ and magnetization rate under a low magnetic field deteriorate. Furthermore, corrosion resistance is reduced. If there is too much Zr, Br and Hk/HcJ tend to decrease.
Ｚｒ／Ｃｏ比は０．３１以上１．９８以下であってもよい。さらに、０．４８以上、１．４０以下であってもよく、０．７３以上１．４０以下であってもよい。Ｚｒ／Ｃｏ比を上記の範囲内で含有することで、高価であるＣｏを少なくしても高い耐食性を有するＲ－Ｔ－Ｂ系永久磁石を得ることができる。その結果、耐食性の高いＲ－Ｔ－Ｂ系永久磁石を低コストで製造しやすくなる。Ｚｒ／Ｃｏ比が大きすぎる場合には、Ｚｒの含有量を上記の範囲内としても耐食性が低下する。Ｚｒ／Ｃｏ比が小さすぎる場合には、耐食性改善の効果が頭打ちとなるとともに高コストとなる。特に、Ｚｒ／Ｃｏ比が０．４８以上１．４０以下であることにより、ＨｃＪおよびＢｒが大きくなる傾向がある。 The Zr/Co ratio may be 0.31 or more and 1.98 or less. Furthermore, it may be 0.48 or more and 1.40 or less, or 0.73 or more and 1.40 or less. By containing the Zr/Co ratio within the above range, an RTB permanent magnet having high corrosion resistance can be obtained even if the amount of expensive Co is reduced. As a result, RTB permanent magnets with high corrosion resistance can be manufactured easily at low cost. If the Zr/Co ratio is too large, the corrosion resistance will decrease even if the Zr content is within the above range. If the Zr/Co ratio is too small, the effect of improving corrosion resistance will reach a plateau and the cost will increase. In particular, when the Zr/Co ratio is 0.48 or more and 1.40 or less, HcJ and Br tend to increase.
一般的に、Ｒ－Ｔ－Ｂ系永久磁石の粒界相にはＲの質量濃度が主相よりも多いＲリッチ相が含まれる。水蒸気による磁石の腐食では、腐食反応で発生する水素が磁石中の粒界に存在するＲリッチ相に吸蔵される。そして、水素がＲリッチ相に吸蔵されることにより、Ｒリッチ相に含まれるＲが水酸化物に変化しやすくなる。Ｒリッチ相に含まれるＲが水酸化物に変化することで、Ｒリッチ相の体積が膨張する。Ｒリッチ相の体積が膨張することで主相粒子の脱落が生じる。そして、主相粒子の脱落により、腐食が加速度的に磁石内部に進行していくと考えられる。 Generally, the grain boundary phase of an RTB permanent magnet includes an R-rich phase in which the mass concentration of R is higher than that of the main phase. When a magnet is corroded by water vapor, hydrogen generated by the corrosion reaction is occluded in the R-rich phase present at grain boundaries in the magnet. Then, as hydrogen is occluded in the R-rich phase, R contained in the R-rich phase is easily converted into hydroxide. When R contained in the R-rich phase changes to hydroxide, the volume of the R-rich phase expands. The expansion of the volume of the R-rich phase causes the main phase particles to fall off. It is thought that corrosion progresses inside the magnet at an accelerated rate due to the main phase particles falling off.
ここで、Ｒ－Ｔ－Ｂ系永久磁石におけるＺｒの含有量が０．２１質量％以上である場合には、Ｒ－Ｔ－Ｂ系永久磁石におけるＺｒの含有量が０．２１質量％未満である場合と比較して、Ｒリッチ相におけるＲの質量濃度が低下しやすく、かつ、Ｆｅの質量濃度およびＺｒの質量濃度が増加しやすくなる。Ｒ－Ｔ－Ｂ系永久磁石がＣｕを含む場合には、Ｒリッチ相におけるＣｕの質量濃度も増加しやすくなる。Ｒ－Ｔ－Ｂ系永久磁石におけるＺｒの含有量が０．２１質量％未満である場合には、Ｒリッチ相におけるＲの質量濃度が６５質量％以上となりやすい。これに対し、Ｚｒの含有量が０．２１質量％以上である場合には、Ｒリッチ相におけるＲの質量濃度が低くなりやすく、例えば５５質量％以下となりやすい。 Here, when the content of Zr in the RTB permanent magnet is 0.21% by mass or more, the content of Zr in the RTB permanent magnet is less than 0.21% by mass. Compared to a certain case, the mass concentration of R in the R-rich phase tends to decrease, and the mass concentration of Fe and the mass concentration of Zr tend to increase. When the RTB permanent magnet contains Cu, the mass concentration of Cu in the R-rich phase also tends to increase. When the Zr content in the RTB permanent magnet is less than 0.21% by mass, the mass concentration of R in the R-rich phase tends to be 65% by mass or more. On the other hand, when the Zr content is 0.21% by mass or more, the mass concentration of R in the R-rich phase tends to be low, for example, 55% by mass or less.
そして、Ｒの質量濃度が比較的低く、Ｆｅ，ＺｒおよびＣｕの各元素の質量濃度が比較的高いＲリッチ相を含む場合には、Ｒの質量濃度が６５質量％以上でありＦｅ，ＺｒおよびＣｕの各元素の質量濃度が比較的低いＲリッチ相を含む場合と比較して、水素が吸蔵されにくくなる。その結果、Ｃｏの含有量を少なくしても高い耐食性を有するＲ－Ｔ－Ｂ系永久磁石を得ることができる。 When the mass concentration of R is relatively low and the mass concentration of each element of Fe, Zr, and Cu is relatively high, if the mass concentration of R is 65% by mass or more and the mass concentration of Fe, Zr, and Cu is relatively high. Compared to the case where Cu includes an R-rich phase in which the mass concentration of each element is relatively low, hydrogen is less likely to be occluded. As a result, it is possible to obtain an RTB permanent magnet that has high corrosion resistance even if the Co content is reduced.
なお、Ｚｒの含有量は０．２５質量％以上０．６５質量％以下であってもよく、０．３１質量％以上０．６０質量％以下であってもよい。特にＺｒの含有量を０．２５質量％以上とすることで、焼結安定温度範囲が広くなる。すなわち、焼結時において異常粒成長抑制効果がさらに大きくなる。そして、特性のバラツキが小さくなり、製造安定性が向上する。 In addition, the content of Zr may be 0.25 mass% or more and 0.65 mass% or less, or may be 0.31 mass% or more and 0.60 mass% or less. In particular, by setting the Zr content to 0.25% by mass or more, the stable sintering temperature range becomes wider. That is, the effect of suppressing abnormal grain growth during sintering becomes even greater. In addition, variations in characteristics are reduced and manufacturing stability is improved.
本実施形態に係るＲ－Ｔ－Ｂ系永久磁石は、さらにＭを含んでも良い。ＭはＣｕ，Ｍｎ，Ａｌ，Ｇａから選択される少なくとも１種である。Ｍの含有量には特に制限はない。Ｍを含まなくてもよい。Ｒ－Ｔ－Ｂ系永久磁石全体の質量を１００質量％として、０質量％以上１．３質量％以下であってもよい。 The RTB permanent magnet according to this embodiment may further include M. M is at least one selected from Cu, Mn, Al, and Ga. There is no particular restriction on the content of M. M may not be included. The content may be 0% by mass or more and 1.3% by mass or less, assuming the mass of the entire RTB permanent magnet as 100% by mass.
Ｃｕの含有量には特に制限はない。Ｃｕを含有しなくてもよい。Ｃｕの含有量は、Ｒ－Ｔ－Ｂ系永久磁石全体の質量を１００質量％として、０．１０質量％以上０．５５質量％以下であってもよく、０．１４質量％以上０．５３質量％以下であってもよく、０．２０質量％以上０．５０質量％以下であってもよい。Ｃｕが少ない場合には、ＢｒおよびＨｃＪが低下しやすい。さらに、耐食性も低下しやすい。Ｃｕが多い場合には、ＨｃＪが低下しやすい。 There is no particular restriction on the content of Cu. It may not contain Cu. The content of Cu may be 0.10% by mass or more and 0.55% by mass or less, and 0.14% by mass or more and 0.53% by mass, based on the mass of the entire RTB permanent magnet as 100% by mass. It may be less than or equal to 0.20 mass% or more and 0.50 mass% or less. When Cu is low, Br and HcJ tend to decrease. Furthermore, corrosion resistance tends to decrease. When there is a large amount of Cu, HcJ tends to decrease.
Ｍｎの含有量には特に制限はない。Ｍｎを含有しなくてもよい。Ｍｎの含有量は、Ｒ－Ｔ－Ｂ系永久磁石全体の質量を１００質量％として、０．０２質量％以上０．１０質量％以下であってもよく、０．０２質量％以上０．０６質量％以下であってもよく、０．０２質量％以上０．０４質量％以下であってもよい。Ｍｎが少ない場合にはＢｒおよびＨｃＪが低下しやすくなる。Ｍｎが多い場合には、ＨｃＪが低下しやすくなる。 There is no particular restriction on the Mn content. It may not contain Mn. The Mn content may be 0.02% by mass or more and 0.10% by mass or less, and 0.02% by mass or more and 0.06% by mass, with the mass of the entire RTB permanent magnet being 100% by mass. It may be less than or equal to 0.02 mass% or more and 0.04 mass% or less. When Mn is low, Br and HcJ tend to decrease. When there is a large amount of Mn, HcJ tends to decrease.
Ａｌの含有量には特に制限はない。Ａｌを含有しなくてもよい。Ａｌの含有量は、Ｒ－Ｔ－Ｂ系永久磁石全体の質量を１００質量％として、０．０７質量％以上０．３５質量％以下であってもよく、０．１０質量％以上０．３０質量％以下であってもよく、０．１５質量％以上０．２３質量％以下であってもよい。Ａｌが少ない場合には、ＨｃＪが低下しやすくなる。さらに、後述する製造時の時効温度や粒界拡散後の熱処理温度の変化に対する磁気特性（特にＨｃＪ）の変化が大きくなり、製造安定性が低下しやすくなる。Ａｌが多い場合には、Ｂｒが低下しやすくなる。 There is no particular restriction on the Al content. It may not contain Al. The Al content may be 0.07% by mass or more and 0.35% by mass or less, and 0.10% by mass or more and 0.30% by mass, based on the mass of the entire RTB permanent magnet as 100% by mass. It may be less than or equal to 0.15% by mass and less than or equal to 0.23% by mass. When Al is low, HcJ tends to decrease. Furthermore, changes in magnetic properties (particularly HcJ) due to changes in aging temperature during manufacturing and heat treatment temperature after grain boundary diffusion, which will be described later, become large, and manufacturing stability tends to decrease. When there is a large amount of Al, Br tends to decrease.
Ｇａの含有量には特に制限はない。Ｇａを含有しなくてもよい。Ｇａの含有量は、Ｒ－Ｔ－Ｂ系永久磁石全体の質量を１００質量％として、０．０２質量％以上０．１５質量％以下であってもよく、０．０４質量％以上０．１５質量％以下であってもよい。Ｇａが少ない場合には、ＨｃＪが低下しやすい。Ｇａが多い場合には、粒界にＲ－Ｔ－Ｇａ相などの副相が含まれやすくなり、Ｂｒが低下しやすくなる。 There is no particular restriction on the Ga content. It may not contain Ga. The content of Ga may be 0.02 mass% or more and 0.15 mass% or less, and 0.04 mass% or more and 0.15 mass%, based on the mass of the entire RTB permanent magnet as 100 mass%. It may be less than % by mass. When Ga is low, HcJ tends to decrease. When there is a large amount of Ga, subphases such as RT-Ga phase are likely to be included in the grain boundaries, and Br is likely to decrease.
本実施形態に係るＲ－Ｔ－Ｂ系永久磁石は、上記したＮｄ，Ｐｒ，Ｄｙ，Ｔｂ，Ｔ，Ｂ，Ｃ，ＺｒおよびＭ以外の元素を他元素として含んでもよい。他元素の含有量には特に制限はなく、Ｒ－Ｔ－Ｂ系永久磁石の磁気特性や耐食性に大きな影響を与えない量であればよい。例えば、Ｒ－Ｔ－Ｂ系永久磁石全体の質量を１００質量％として、合計で１．０質量％以下であってもよい。なお、Ｎｄ，Ｐｒ，ＤｙおよびＴｂ以外の希土類元素の含有量は合計で０．３質量％以下であってもよい。 The RTB permanent magnet according to the present embodiment may contain elements other than the above-mentioned Nd, Pr, Dy, Tb, T, B, C, Zr, and M as other elements. The content of other elements is not particularly limited, and may be any amount that does not significantly affect the magnetic properties and corrosion resistance of the RTB permanent magnet. For example, the total amount may be 1.0% by mass or less, assuming that the mass of the entire RTB permanent magnet is 100% by mass. Note that the total content of rare earth elements other than Nd, Pr, Dy, and Tb may be 0.3% by mass or less.
以下、他元素の一例として炭素（Ｃ）、窒素（Ｎ）および酸素（Ｏ）の含有量について述べる。 The contents of carbon (C), nitrogen (N), and oxygen (O) will be described below as examples of other elements.
本実施形態に係るＲ－Ｔ－Ｂ系永久磁石におけるＣの含有量は、Ｒ－Ｔ－Ｂ系永久磁石全体の質量を１００質量％として、０．１５質量％以下であってもよく、０．１３質量％以下、または０．１１質量％以下であってもよい。また、Ｃの含有量は、０．０６質量％以上０．１５質量％以下、０．０６質量％以上０．１３質量％以下、０．０６質量％以上０．１１質量％以下であってもよい。Ｃの含有量を０．１５質量％以下とすることでＨｃＪが向上する傾向にある。特にＨｃＪを向上させる観点からは、Ｃの含有量を０．１１質量％以下としてもよい。また、Ｃの含有量が０．０６質量％未満であるＲ－Ｔ－Ｂ系永久磁石を製造することはプロセスに対する負荷が大きい。したがって、Ｃの含有量が０．０６質量％未満であるＲ－Ｔ－Ｂ系永久磁石は低コストで製造しにくい。なお、特にＨｋ／ＨｃＪを向上させる観点からは、Ｃの含有量を０．１０質量％以上０．１５質量％以下としてもよい。 The content of C in the RTB permanent magnet according to the present embodiment may be 0.15% by mass or less, with the mass of the entire RTB permanent magnet being 100% by mass, and may be 0.15% by mass or less. It may be 0.13% by mass or less, or 0.11% by mass or less. Further, the content of C may be 0.06 mass% or more and 0.15 mass% or less, 0.06 mass% or more and 0.13 mass% or less, or 0.06 mass% or more and 0.11 mass% or less. good. By setting the C content to 0.15% by mass or less, HcJ tends to improve. Particularly from the viewpoint of improving HcJ, the C content may be set to 0.11% by mass or less. Furthermore, manufacturing an RTB permanent magnet with a C content of less than 0.06% by mass places a large burden on the process. Therefore, RTB permanent magnets with a C content of less than 0.06% by mass are difficult to manufacture at low cost. Note that, particularly from the viewpoint of improving Hk/HcJ, the content of C may be set to 0.10% by mass or more and 0.15% by mass or less.
本実施形態に係るＲ－Ｔ－Ｂ系永久磁石におけるＮの含有量は、Ｒ－Ｔ－Ｂ系永久磁石全体の質量を１００質量％として、０．１２質量％以下であってもよく、０．１１質量％以下、または０．１０５質量％以下であってもよい。また、０．０２５質量％以上０．１２質量％以下、０．０２５質量％以上０．１１質量％以下、０．０２５質量％以上０．１０５質量％以下であってもよい。Ｎの含有量が少ないほどＨｃＪが向上しやすくなる。また、Ｎの含有量が０．０２５質量％未満であるＲ－Ｔ－Ｂ系永久磁石を製造することはプロセスに対する負荷が大きい。したがって、Ｎの含有量が０．０２５質量％未満であるＲ－Ｔ－Ｂ系永久磁石は低コストで製造しにくい。 The N content in the RTB permanent magnet according to the present embodiment may be 0.12% by mass or less, with the mass of the entire RTB permanent magnet being 100% by mass, and may be 0.12% by mass or less. It may be .11% by mass or less, or 0.105% by mass or less. Further, it may be 0.025 mass% or more and 0.12 mass% or less, 0.025 mass% or more and 0.11 mass% or less, or 0.025 mass% or more and 0.105 mass% or less. The lower the N content, the easier it is to improve HcJ. Furthermore, manufacturing an RTB permanent magnet with an N content of less than 0.025% by mass imposes a large burden on the process. Therefore, RTB permanent magnets with an N content of less than 0.025% by mass are difficult to manufacture at low cost.
本実施形態に係るＲ－Ｔ－Ｂ系永久磁石におけるＯの含有量は、Ｒ－Ｔ－Ｂ系永久磁石全体の質量を１００質量％として、０．１０質量％以下であってもよく、０．０８質量％以下であってもよく、０．０７質量％以下であってもよく、０．０５質量％以下であってもよい。また、０．０３５質量％以上０．０５質量％以下であってもよい。また、Ｏの含有量が０．０３５質量％未満であるＲ－Ｔ－Ｂ系永久磁石を製造することはプロセスに対する負荷が大きい。したがって、Ｏの含有量が０．０３５質量％未満であるＲ－Ｔ－Ｂ系永久磁石は低コストで製造しにくい。 The O content in the RTB permanent magnet according to the present embodiment may be 0.10% by mass or less, with the mass of the entire RTB permanent magnet being 100% by mass, and 0. It may be 0.08% by mass or less, 0.07% by mass or less, or 0.05% by mass or less. Further, the content may be 0.035% by mass or more and 0.05% by mass or less. Furthermore, manufacturing an RTB permanent magnet with an O content of less than 0.035% by mass places a large burden on the process. Therefore, RTB permanent magnets with an O content of less than 0.035% by mass are difficult to manufacture at low cost.
なお、本実施形態に係るＲ－Ｔ－Ｂ系永久磁石中に含まれる各種成分の測定法は、従来から一般的に知られている方法を用いることができる。各種元素量については、例えば、蛍光Ｘ線分析および誘導結合プラズマ発光分光分析（ＩＣＰ分析）等により測定される。Ｏの含有量は、例えば、不活性ガス融解－非分散型赤外線吸収法により測定される。Ｃの含有量は、例えば、酸素気流中燃焼－赤外線吸収法により測定される。Ｎの含有量は、例えば、不活性ガス融解－熱伝導度法により測定される。 Note that, as a method for measuring various components contained in the RTB permanent magnet according to the present embodiment, conventionally known methods can be used. The amounts of various elements are measured by, for example, fluorescent X-ray analysis and inductively coupled plasma emission spectrometry (ICP analysis). The O content is measured, for example, by an inert gas melting non-dispersive infrared absorption method. The C content is measured, for example, by combustion in an oxygen stream-infrared absorption method. The N content is measured, for example, by an inert gas melting-thermal conductivity method.
本実施形態に係るＲ－Ｔ－Ｂ系永久磁石の形状には特に制限はない。例えば、直方体などの形状が挙げられる。 There is no particular restriction on the shape of the RTB permanent magnet according to this embodiment. For example, the shape may be a rectangular parallelepiped.
以下、Ｒ－Ｔ－Ｂ系永久磁石の製造方法について詳しく説明していくが、Ｒ－Ｔ－Ｂ系永久磁石の製造方法はこれに制限されず、その他の公知の方法を用いてもよい。 The method for manufacturing the RTB permanent magnet will be described in detail below, but the method for manufacturing the RTB permanent magnet is not limited to this, and other known methods may be used.
［原料粉末の準備工程］
原料粉末は、公知の方法により作製することができる。本実施形態では、単独の合金を使用する１合金法の場合について説明するが、組成の異なる２種類以上の合金を混合して原料粉末を作製するいわゆる２合金法でもよい。
[Preparation process of raw material powder]
The raw material powder can be produced by a known method. In this embodiment, a case will be described in which a single alloy method is used in which a single alloy is used, but a so-called two-alloy method in which raw material powder is produced by mixing two or more types of alloys with different compositions may also be used.
まず、Ｒ－Ｔ－Ｂ系永久磁石の原料合金を準備する（合金準備工程）。合金準備工程では、本実施形態に係るＲ－Ｔ－Ｂ系永久磁石の組成に対応する原料金属を公知の方法で溶解した後、鋳造することによって所望の組成を有する原料合金を作製する。 First, a raw material alloy for an RTB permanent magnet is prepared (alloy preparation step). In the alloy preparation step, a raw material metal corresponding to the composition of the RTB permanent magnet according to the present embodiment is melted by a known method and then cast to produce a raw material alloy having a desired composition.
原料金属としては、例えば、希土類元素の単体、Ｆｅ、Ｃｏ、Ｃｕ等の金属元素の単体、複数種類の金属からなる合金（例えばＦｅ－Ｃｏ合金）、または複数種類の元素からなる化合物（例えばフェロボロン）等を適宜、使用することができる。原料金属から原料合金を鋳造する鋳造方法には特に制限はない。磁気特性の高いＲ－Ｔ－Ｂ系永久磁石を得るためにストリップキャスト法を用いてもよい。得られた原料合金は、必要に応じて既知の方法で均質化処理を行ってもよい。 Examples of raw material metals include rare earth elements, simple metal elements such as Fe, Co, and Cu, alloys of multiple metals (e.g., Fe-Co alloy), or compounds of multiple elements (e.g., ferroboron). ) etc. can be used as appropriate. There are no particular restrictions on the casting method for casting the raw material alloy from the raw metal. A strip casting method may be used to obtain RTB permanent magnets with high magnetic properties. The obtained raw material alloy may be homogenized by a known method if necessary.
前記原料合金を作製した後、粉砕する（粉砕工程）。なお、粉砕工程から焼結工程までの各工程の雰囲気は、高い磁気特性を得る観点から、低酸素濃度とすることができる。例えば、各工程での雰囲気中の酸素濃度を２００ｐｐｍ以下としてもよい。各工程の雰囲気中の酸素濃度を制御することで、Ｒ－Ｔ－Ｂ系永久磁石におけるＯの含有量を制御することができる。 After producing the raw material alloy, it is pulverized (pulverization step). Note that the atmosphere in each step from the pulverization step to the sintering step can have a low oxygen concentration from the viewpoint of obtaining high magnetic properties. For example, the oxygen concentration in the atmosphere in each step may be set to 200 ppm or less. By controlling the oxygen concentration in the atmosphere in each step, the O content in the RTB permanent magnet can be controlled.
以下、前記粉砕工程として、粒径が数百μｍ～数ｍｍ程度になるまで粉砕する粗粉砕工程と、粒径が数μｍ程度になるまで微粉砕する微粉砕工程の２段階で実施する場合を以下に記述するが、微粉砕工程のみの１段階で実施してもよい。 Hereinafter, the case where the pulverization process is carried out in two stages: a coarse pulverization step in which the particle size is pulverized until the particle size is approximately several hundred μm to several mm, and a fine pulverization step in which the particle size is pulverized until the particle size is approximately several μm. Although described below, it may be carried out in one step, including only the pulverization step.
粗粉砕工程では、粒径が数百μｍ～数ｍｍ程度になるまで粗粉砕する。これにより、粗粉砕粉末を得る。粗粉砕の方法には特に限定はなく、水素吸蔵粉砕を行う方法や粗粉砕機を用いる方法など、公知の方法で行うことができる。水素吸蔵粉砕を行う場合、脱水素処理時の雰囲気中の窒素ガス濃度の制御を行うことで、Ｒ－Ｔ－Ｂ系永久磁石におけるＮの含有量を制御することができる。 In the coarse pulverization step, the particles are coarsely pulverized until the particle size is approximately several hundred μm to several mm. As a result, a coarsely ground powder is obtained. There is no particular limitation on the method of coarse pulverization, and known methods such as hydrogen storage pulverization or using a coarse pulverizer can be used. When hydrogen storage pulverization is performed, the N content in the RTB permanent magnet can be controlled by controlling the nitrogen gas concentration in the atmosphere during dehydrogenation treatment.
次に、得られた粗粉砕粉末を平均粒子径が数μｍ程度になるまで微粉砕する（微粉砕工程）。これにより、微粉砕粉末（原料粉末）を得る。前記微粉砕粉末の平均粒径は、１μｍ以上１０μｍ以下、２μｍ以上６μｍ以下、または２μｍ以上４μｍ以下であってもよい。微粉砕工程での雰囲気中の窒素ガス濃度の制御を行うことで、Ｒ－Ｔ－Ｂ系永久磁石におけるＮの含有量を制御することができる。 Next, the obtained coarsely pulverized powder is pulverized until the average particle size becomes approximately several μm (fine pulverization step). As a result, finely pulverized powder (raw material powder) is obtained. The average particle size of the finely pulverized powder may be 1 μm or more and 10 μm or less, 2 μm or more and 6 μm or less, or 2 μm or more and 4 μm or less. By controlling the nitrogen gas concentration in the atmosphere during the pulverization process, the N content in the RTB permanent magnet can be controlled.
微粉砕の方法には特に制限はない。例えば、各種微粉砕機を用いる方法で実施される。 There are no particular restrictions on the method of pulverization. For example, it is carried out by a method using various types of pulverizers.
前記粗粉砕粉末を微粉砕する際、ラウリン酸アミド、オレイン酸アミド等の各種粉砕助剤を添加することにより、磁場中で加圧して成形する際に結晶粒子が特定の方向に配向しやすい微粉砕粉末を得ることができる。また、粉砕助剤の添加量を変化させることにより、Ｒ－Ｔ－Ｂ系永久磁石におけるＣの含有量を制御することができる。 When the coarsely pulverized powder is pulverized, various grinding aids such as lauric acid amide and oleic acid amide can be added to make the crystal particles easier to orient in a specific direction when pressurized and molded in a magnetic field. A ground powder can be obtained. Furthermore, by changing the amount of grinding aid added, the C content in the RTB permanent magnet can be controlled.
［成形工程］
成形工程では、上記微粉砕粉末を目的の形状に成形する。成形方法には特に制限はない。本実施形態では、上記微粉砕粉末を金型内に充填し、磁場中で加圧する。これにより得られた成形体は、結晶粒子が特定方向に配向しているので、よりＢｒの高いＲ－Ｔ－Ｂ系永久磁石が得られる。
[Molding process]
In the molding step, the finely pulverized powder is molded into a desired shape. There are no particular restrictions on the molding method. In this embodiment, the finely pulverized powder is filled into a mold and pressurized in a magnetic field. In the molded body thus obtained, since the crystal grains are oriented in a specific direction, an RTB permanent magnet with higher Br can be obtained.
成形時の加圧は、２０ＭＰａ以上３００ＭＰａ以下で行うことができる。印加する磁場は、９５０ｋＡ／ｍ以上とすることができ、９５０ｋＡ／ｍ以上１６００ｋＡ／ｍ以下とすることもできる。印加する磁場は静磁場に限定されず、パルス状磁場とすることもできる。また、静磁場とパルス状磁場とを併用することもできる。 Pressure during molding can be applied at 20 MPa or more and 300 MPa or less. The applied magnetic field can be 950 kA/m or more, and can also be 950 kA/m or more and 1600 kA/m or less. The applied magnetic field is not limited to a static magnetic field, but may also be a pulsed magnetic field. Moreover, a static magnetic field and a pulsed magnetic field can also be used together.
なお、成形方法としては、上記のように微粉砕粉末をそのまま成形する乾式成形の他、微粉砕粉末を油等の溶媒に分散させたスラリーを成形する湿式成形を適用することもできる。 In addition, as a molding method, in addition to dry molding in which finely pulverized powder is molded as it is as described above, wet molding in which a slurry in which finely pulverized powder is dispersed in a solvent such as oil can be molded can also be applied.
微粉砕粉末を成形して得られる成形体の形状には特に制限はない。また、この時点での成形体の密度は４．０Ｍｇ／ｍ３～４．３Ｍｇ／ｍ３とすることができる。 There are no particular restrictions on the shape of the molded body obtained by molding the finely pulverized powder. Further, the density of the molded body at this point can be 4.0 Mg/m 3 to 4.3 Mg/m 3 .
［焼結工程］
焼結工程は、成形体を真空中または不活性ガス雰囲気中で焼結し、焼結体を得る工程である。焼結条件は、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。例えば、成形体に対して、例えば、真空中または不活性ガス雰囲気中、１０００℃以上１２００℃以下、１時間以上２０時間以下で加熱する処理を行うことにより焼結する。上記の焼結条件で焼結することにより、高密度の焼結体が得られる。本実施形態では、少なくとも７．４５Ｍｇ／ｍ３以上の密度の焼結体を得る。焼結体の密度は７．５０Ｍｇ／ｍ３以上であってもよい。
[Sintering process]
The sintering process is a process in which a molded body is sintered in a vacuum or an inert gas atmosphere to obtain a sintered body. Sintering conditions need to be adjusted depending on various conditions such as composition, pulverization method, difference in particle size and particle size distribution. For example, the molded body is sintered by heating it in a vacuum or in an inert gas atmosphere at 1000° C. or more and 1200° C. or less for 1 hour or more and 20 hours or less. By sintering under the above sintering conditions, a high-density sintered body can be obtained. In this embodiment, a sintered body having a density of at least 7.45 Mg/m 3 or more is obtained. The density of the sintered body may be 7.50 Mg/m 3 or more.
［時効処理工程］
時効処理工程は、焼結体を焼結温度より低温で熱処理（時効処理）する工程である。時効処理を行うか否かには特に制限はなく、時効処理の回数にも特に制限はなく、所望の磁気特性に応じて適宜実施する。また、後述する粒界拡散工程が時効処理工程を兼ねてもよい。以下、時効処理を２回行う実施形態について説明する。
[Aging treatment process]
The aging treatment step is a step of heat treating (aging treatment) the sintered body at a temperature lower than the sintering temperature. There is no particular restriction on whether or not to perform the aging treatment, and there is no particular restriction on the number of times the aging treatment is performed, and the aging treatment may be performed as appropriate depending on the desired magnetic properties. Furthermore, the grain boundary diffusion step described below may also serve as an aging treatment step. An embodiment in which aging treatment is performed twice will be described below.
１回目の時効工程を第一時効工程、２回目の時効工程を第二時効工程とし、第一時効工程の時効温度をＴ１、第二時効工程の時効温度をＴ２とする。 The first aging step is the first aging step, the second aging step is the second aging step, the aging temperature of the first aging step is T1, and the aging temperature of the second aging step is T2.
第一時効工程におけるＴ１および時効時間には、特に制限はない。Ｔ１は７００℃以上９００℃以下とすることができる。時効時間は１時間以上１０時間以下とすることができる。 There are no particular limitations on T1 and aging time in the first aging step. T1 can be set to 700°C or more and 900°C or less. The aging time can be 1 hour or more and 10 hours or less.
第二時効工程におけるＴ２および時効時間には、特に制限はない。Ｔ２は４５０℃以上７００℃以下とすることができる。時効時間は１時間以上１０時間以下とすることができる。 There are no particular limitations on T2 and aging time in the second aging step. T2 can be 450°C or more and 700°C or less. The aging time can be 1 hour or more and 10 hours or less.
このような時効処理によって、最終的に得られるＲ－Ｔ－Ｂ系永久磁石の磁気特性、特にＨｃＪを向上させることができる。 Such aging treatment can improve the magnetic properties, especially HcJ, of the finally obtained RTB permanent magnet.
［加工工程（粒界拡散前）］
必要に応じて、本実施形態に係る焼結体を所望の形状に加工する工程を有してもよい。加工方法は、例えば切断、研削などの形状加工や、バレル研磨などの面取り加工などが挙げられる。
[Processing process (before grain boundary diffusion)]
If necessary, it may include a step of processing the sintered body according to this embodiment into a desired shape. Examples of processing methods include shape processing such as cutting and grinding, and chamfering processing such as barrel polishing.
［粒界拡散工程］
粒界拡散工程は、焼結体の表面に、拡散材を付着させ、拡散材が付着した焼結体を加熱することにより、実施できる。そして、Ｒ－Ｔ－Ｂ系永久磁石が得られる。本実施形態では、拡散材の種類には特に制限はない。拡散材が重希土類元素（例えばＴｂおよび／またはＤｙ）を含んでいてもよく、拡散材が下記の第１成分～第３成分を全て含んでもよい。第１成分は、Ｔｂの水素化物および／またはＤｙの水素化物である。第２成分は、Ｎｄの水素化物および／またはＰｒの水素化物である。第３成分は、Ｃｕの単体、Ｃｕを含む合金、および／または、Ｃｕを含む化合物である。
[Grain boundary diffusion process]
The grain boundary diffusion step can be carried out by attaching a diffusion material to the surface of the sintered body and heating the sintered body to which the diffusion material has been attached. Then, an RTB permanent magnet is obtained. In this embodiment, there is no particular restriction on the type of diffusion material. The diffusing material may contain a heavy rare earth element (for example, Tb and/or Dy), and the diffusing material may contain all of the following first to third components. The first component is a Tb hydride and/or a Dy hydride. The second component is a Nd hydride and/or a Pr hydride. The third component is Cu alone, an alloy containing Cu, and/or a compound containing Cu.
拡散工程では、温度上昇に伴い、磁石基材（焼結体）の粒界に存在する希土類元素Ｒの濃度が高い粒界相が液相となり、その液相へ拡散材が溶解することにより、拡散材の成分が磁石基材の表面から磁石基材の内部へと拡散する。仮に拡散材として、重希土類元素ＲＨの水素化物が用いられた場合、磁石基材の表面に付着したＲＨ水素化物は、温度上昇により脱水素反応が起こった際に、磁石基材から表面に染み出してきた液相に対して急激に溶解し易い。その結果、磁石基材の表面付近においてＲＨの濃度が急上昇し、磁石基材の表面近傍に位置する主相粒子内部へのＲＨの拡散が起こりやすくなる。その結果、ＲＨは磁石基材の表面近傍に位置する主相粒子内部に停滞しやすくなり、磁石基材の内部へ拡散し難い。そのため、磁石内部に拡散するＲＨが少なくなり、永久磁石の保磁力の伸びが少なくなる。 In the diffusion process, as the temperature rises, the grain boundary phase with a high concentration of the rare earth element R existing at the grain boundaries of the magnet base material (sintered body) becomes a liquid phase, and the diffusing material is dissolved into the liquid phase. Components of the diffusion material diffuse from the surface of the magnet base material into the interior of the magnet base material. If a hydride of a heavy rare earth element RH is used as a diffusion material, the RH hydride attached to the surface of the magnet base material will stain from the magnet base material to the surface when a dehydrogenation reaction occurs due to temperature rise. It is easy to dissolve rapidly in the liquid phase that comes out. As a result, the concentration of RH increases rapidly near the surface of the magnet base material, and RH is likely to diffuse into the main phase particles located near the surface of the magnet base material. As a result, RH tends to stay inside the main phase particles located near the surface of the magnet base material and is difficult to diffuse into the inside of the magnet base material. Therefore, less RH diffuses into the magnet, and the coercive force of the permanent magnet less increases.
拡散材が、第１成分（重希土類元素ＲＨ）、第２成分（軽希土類元素ＲＬ）及び第３成分（Ｃｕ）を含む場合、磁石基材で発生したＲの濃度が高い液相が表面の拡散材近傍まで染み出してきた際、ＣｕとＲの共晶温度が低いため、拡散材に含まれるＣｕが液相に対して先に溶解しやすい。そのため、最初に液相に対するＣｕの溶解が起こり、磁石基材表面付近の液相中のＣｕ濃度が上昇する。その結果、磁石基材表面付近にＲ－Ｃｕリッチ液相が生成し、さらに磁石基材内部の液相へとＣｕが拡散していく。第２成分であるＲＬと第１成分であるＲＨについては、水素化物の脱水素反応が起こった後にＲ－Ｃｕリッチ液相への溶解が生じる。第２成分であるＲＬとＣｕの共晶温度は５００℃付近、第１成分であるＲＨとＣｕの共晶温度は７００～８００℃付近である。そのため、Ｃｕに続いて第２成分であるＲＬが磁石基材表面付近のＲ－Ｃｕリッチ液相に対して溶解し、その後、第１成分であるＲＨが溶解する順序となる。Ｃｕに続いて第２成分であるＲＬが溶解することにより、Ｃｕの磁石内部への拡散が促進され、磁石基材の粒界内にＲ‐Ｃｕリッチ液相が生成する。 When the diffusion material contains the first component (heavy rare earth element RH), the second component (light rare earth element RL), and the third component (Cu), the liquid phase with a high concentration of R generated in the magnet base material When it seeps out to the vicinity of the diffusion material, since the eutectic temperature of Cu and R is low, Cu contained in the diffusion material tends to dissolve first in the liquid phase. Therefore, dissolution of Cu in the liquid phase occurs first, and the Cu concentration in the liquid phase near the surface of the magnet base material increases. As a result, an R--Cu rich liquid phase is generated near the surface of the magnet base material, and Cu further diffuses into the liquid phase inside the magnet base material. Regarding RL, which is the second component, and RH, which is the first component, dissolution in the R—Cu rich liquid phase occurs after the dehydrogenation reaction of the hydride occurs. The eutectic temperature of the second component RL and Cu is around 500°C, and the eutectic temperature of the first component RH and Cu is around 700 to 800°C. Therefore, following Cu, the second component RL is dissolved in the R--Cu rich liquid phase near the surface of the magnet base material, and then the first component RH is dissolved. By dissolving the second component RL following Cu, diffusion of Cu into the magnet is promoted, and an R-Cu rich liquid phase is generated within the grain boundaries of the magnet base material.
第１成分（ＲＨ）、第２成分（ＲＬ）及び第３成分（Ｃｕ）のうち第１成分（ＲＨ）は液相中に最後に溶解し易い。したがって、第１成分に由来するＲＨは、Ｃｕ、ＲＬに続いて磁石基材内部の液相へ拡散していくため、Ｃｕ、ＲＬがない場合と比べて、磁石基材表面近傍でのＲＨ濃度の急上昇が抑えられる。そのため、磁石基材の表面近傍に位置する主相粒子内部へのＲＨの拡散を抑制することができる。その結果、磁石内部に拡散するＲＨが多くなり、永久磁石の保磁力が向上しやすいという効果が得られる。 Among the first component (RH), the second component (RL), and the third component (Cu), the first component (RH) tends to dissolve last in the liquid phase. Therefore, RH derived from the first component diffuses into the liquid phase inside the magnet base material following Cu and RL, so the RH concentration near the surface of the magnet base material is higher than when Cu and RL are absent. The rapid increase in Therefore, it is possible to suppress the diffusion of RH into the main phase particles located near the surface of the magnet base material. As a result, more RH diffuses into the magnet, resulting in the effect that the coercive force of the permanent magnet tends to improve.
拡散材は、上記の第１成分～第３成分に加えて溶媒を含むスラリーであってもよい。スラリーに含まれる溶媒は、水以外の溶媒であってもよい。例えば、アルコール、アルデヒド、ケトン等の有機溶媒であってもよい。さらに、拡散材は、バインダを含んでもよい。バインダの種類には特に制限はない。例えば、アクリル樹脂等の主旨をバインダとして含んでもよい。バインダを含むことにより、拡散材が焼結体の表面に付着しやすくなる。 The diffusion material may be a slurry containing a solvent in addition to the first to third components described above. The solvent contained in the slurry may be a solvent other than water. For example, organic solvents such as alcohols, aldehydes, and ketones may be used. Furthermore, the diffusion material may include a binder. There are no particular restrictions on the type of binder. For example, acrylic resin or the like may be included as a binder. By including the binder, the diffusion material easily adheres to the surface of the sintered body.
拡散材は、上記の第１成分～第３成分に加えて溶媒およびバインダを含むペーストであってもよい。ペーストは、流動性および高い粘性を有する。ペーストの粘性は、スラリーの粘性よりも高い。 The diffusion material may be a paste containing a solvent and a binder in addition to the first to third components described above. The paste has fluidity and high viscosity. The viscosity of the paste is higher than that of the slurry.
粒界拡散前にスラリーまたはペーストを付着させた焼結体を乾燥させて溶媒を除去してもよい。 Before the grain boundary diffusion, the sintered body to which the slurry or paste is attached may be dried to remove the solvent.
本実施形態に係る粒界拡散工程における拡散処理温度は、ＲＬとＣｕの共晶温度以上であってよく、焼結温度未満であってよい。例えば、拡散処理温度は、８００℃以上９５０℃以下であってよい。粒界拡散工程では、拡散処理温度よりも低い温度から拡散処理温度に至るまで、磁石基材の温度を徐々に上昇させてよい。 The diffusion treatment temperature in the grain boundary diffusion step according to the present embodiment may be equal to or higher than the eutectic temperature of RL and Cu, and may be lower than the sintering temperature. For example, the diffusion treatment temperature may be 800°C or more and 950°C or less. In the grain boundary diffusion step, the temperature of the magnet base material may be gradually increased from a temperature lower than the diffusion treatment temperature to the diffusion treatment temperature.
基材の温度が拡散処理温度で維持される時間（拡散処理時間）は、例えば、１時間以上５０時間以下であってよい。拡散処理工程における基材周囲の雰囲気は、非酸化的雰囲気であってよい。非酸化的雰囲気は、例えば、アルゴン等の希ガスであってよい。拡散工程における磁石基材周囲の雰囲気の圧力は、１ｋＰａ以下であってよい。このような減圧雰囲気とすることで、水素化物の脱水素反応が促進され、液相への拡散材の溶解が進行しやすい。 The time during which the temperature of the base material is maintained at the diffusion treatment temperature (diffusion treatment time) may be, for example, 1 hour or more and 50 hours or less. The atmosphere around the base material in the diffusion treatment step may be a non-oxidizing atmosphere. The non-oxidizing atmosphere may be, for example, a noble gas such as argon. The pressure of the atmosphere around the magnet base material in the diffusion step may be 1 kPa or less. By creating such a reduced pressure atmosphere, the dehydrogenation reaction of the hydride is promoted, and the dissolution of the diffusion material into the liquid phase is facilitated.
また、拡散処理後に、さらに熱処理を施してもよい。その場合の熱処理温度は４５０℃以上６００℃以下としてもよい。熱処理時間は１時間以上１０時間以下としてもよい。このような熱処理を行うことによって、最終的に得られるＲ－Ｔ－Ｂ系永久磁石の磁気特性、特にＨｃＪを向上させることができる。 Further, after the diffusion treatment, a heat treatment may be further performed. In that case, the heat treatment temperature may be 450°C or more and 600°C or less. The heat treatment time may be 1 hour or more and 10 hours or less. By performing such heat treatment, it is possible to improve the magnetic properties, particularly HcJ, of the finally obtained RTB permanent magnet.
また、本実施形態に係るＲ－Ｔ－Ｂ系永久磁石の製造安定性は、例えば、粒界拡散工程における拡散処理温度および／または重希土類拡散後の熱処理温度の変化に対する磁気特性の変化量の大きさで確認できる。 Furthermore, the manufacturing stability of the RTB permanent magnet according to the present embodiment is determined, for example, by the amount of change in magnetic properties with respect to changes in the diffusion treatment temperature in the grain boundary diffusion step and/or the heat treatment temperature after heavy rare earth diffusion. You can check the size.
［加工工程（粒界拡散後）］
粒界拡散工程の後には、Ｒ－Ｔ－Ｂ系永久磁石の表面に残存する拡散材を除去するために研磨を行ってもよい。また、Ｒ－Ｔ－Ｂ系永久磁石に対してその他の加工を行ってもよい。例えば切断、研削などの形状加工や、バレル研磨などの面取り加工などの表面加工を行ってもよい。
[Processing process (after grain boundary diffusion)]
After the grain boundary diffusion step, polishing may be performed to remove the diffusion material remaining on the surface of the RTB permanent magnet. Further, other processing may be performed on the RTB permanent magnet. For example, shape processing such as cutting and grinding, and surface processing such as chamfering such as barrel polishing may be performed.
なお、本実施形態では、粒界拡散前および粒界拡散後の加工工程を行っているが、これらの工程は、必ずしも行う必要はない。また、粒界拡散工程が時効工程を兼ねてもよい。粒界拡散工程が時効工程を兼ねる場合の加熱温度には、特に限定はない。粒界拡散工程において好ましい温度であり、かつ、時効工程においても好ましい温度で実施することが特に好ましい。 Note that in this embodiment, processing steps are performed before grain boundary diffusion and after grain boundary diffusion, but these steps do not necessarily need to be performed. Further, the grain boundary diffusion step may also serve as the aging step. There is no particular limitation on the heating temperature when the grain boundary diffusion step also serves as the aging step. It is particularly preferable to carry out the process at a temperature which is preferable in the grain boundary diffusion step and which is also preferable in the aging step.
特に、粒界拡散を行った後のＲ－Ｔ－Ｂ系永久磁石は、重希土類元素の濃度が、Ｒ－Ｔ－Ｂ系永久磁石の外側から内側に向かって低下する濃度分布を有しやすい。また、粒界拡散を行った後のＲ－Ｔ－Ｂ系永久磁石に含まれる主相粒子は上記のコアシェル構造を有しやすい。 In particular, RTB permanent magnets after grain boundary diffusion tend to have a concentration distribution in which the concentration of heavy rare earth elements decreases from the outside to the inside of the RTB permanent magnet. . Furthermore, the main phase particles contained in the RTB permanent magnet after grain boundary diffusion tend to have the above-mentioned core-shell structure.
このようにして得られる本実施形態に係るＲ－Ｔ－Ｂ系永久磁石は、所望の特性を有する。具体的には、Ｂｒ、ＨｃＪおよびＨｋ／ＨｃＪが高く、耐食性と製造安定性も優れている。さらに、温度特性も良好であり、高温でのＨｃＪも高く、温度上昇に対するＨｃＪの低下が小さい。 The RTB permanent magnet according to this embodiment obtained in this manner has desired characteristics. Specifically, Br, HcJ and Hk/HcJ are high, and corrosion resistance and manufacturing stability are also excellent. Furthermore, the temperature characteristics are good, the HcJ is high at high temperatures, and the decrease in HcJ with respect to temperature increases is small.
以上の方法により得られた本実施形態に係るＲ－Ｔ－Ｂ系永久磁石は、着磁することにより、磁気を帯びたＲ－Ｔ－Ｂ系永久磁石となる。 The RTB permanent magnet according to the present embodiment obtained by the above method becomes a magnetized RTB permanent magnet by being magnetized.
本実施形態に係るＲ－Ｔ－Ｂ系永久磁石は、モーター、発電機等の用途に好適に用いられる。 The RTB permanent magnet according to this embodiment is suitably used for applications such as motors and generators.
なお、本発明は、上述した実施形態に制限されるものではなく、本発明の範囲内で種々に改変することができる。 Note that the present invention is not limited to the embodiments described above, and can be variously modified within the scope of the present invention.
Ｒ－Ｔ－Ｂ系永久磁石の製造方法は上記の方法に制限されず、適宜変更してもよい。例えば、上記のＲ－Ｔ－Ｂ系永久磁石の製造方法は焼結による製造方法であるが、本実施形態に係るＲ－Ｔ－Ｂ系永久磁石は熱間加工によって製造されていてもよい。熱間加工によってＲ－Ｔ－Ｂ系永久磁石を製造する方法は、以下の工程を有する。
（ａ）原料金属を溶解し、得られた浴湯を急冷して薄帯を得る溶解急冷工程
（ｂ）薄帯を粉砕してフレーク状の原料粉末を得る粉砕工程
（ｃ）粉砕した原料粉末を冷間成形する冷間成形工程
（ｄ）冷間成形体を予備加熱する予備加熱工程
（ｅ）予備加熱した冷間成形体を熱間成形する熱間成形工程
（ｆ）熱間成形体を所定の形状に塑性変形させる熱間塑性加工工程。
（ｇ）Ｒ－Ｔ－Ｂ系永久磁石を時効処理する時効処理工程
なお、時効処理工程以降の工程は焼結により製造する場合と同様である。
The method for producing RTB permanent magnets is not limited to the above method, and may be modified as appropriate. For example, although the method for manufacturing the RTB permanent magnet described above is a manufacturing method using sintering, the RTB permanent magnet according to the present embodiment may be manufactured by hot working. A method for manufacturing an RTB permanent magnet by hot working includes the following steps.
(a) Melting and quenching step of melting the raw metal and rapidly cooling the obtained bath water to obtain a thin ribbon (b) Grinding step of crushing the ribbon to obtain flaky raw material powder (c) Pulverized raw material powder (d) A preheating process of preheating the cold formed body. (e) A hot forming process of hot forming the preheated cold formed body. (f) A cold forming process of hot forming the preheated cold formed body. A hot plastic working process that plastically deforms into a predetermined shape.
(g) Aging treatment step for aging RTB type permanent magnets Note that the steps after the aging treatment step are the same as in the case of manufacturing by sintering.
以下、本発明を、さらに詳細な実施例に基づき説明するが、本発明は、これら実施例に限定されない。 Hereinafter, the present invention will be explained based on more detailed examples, but the present invention is not limited to these examples.
（Ｒ－Ｔ－Ｂ系永久磁石の作製）
ストリップキャスト法により、最終的に得られるＲ－Ｔ－Ｂ系永久磁石の組成が表１～表３に示す各試料の組成となるように原料合金を作製した。なお、表１および表２に記載の実験例では、全てＰｒの含有量が０質量％であった。表１～表３に記載していない他元素としてＯ、Ｎ、Ｃ、Ｈ、Ｓｉ、Ｃａ、Ｌａ、Ｃｅ、Ｃｒ等が検出される場合がある。Ｓｉは主にフェロボロン原料および合金溶解時のるつぼから混入する。Ｃａ、Ｌａ、Ｃｅは希土類の原料から混入する。また、Ｃｒは電解鉄から混入する可能性がある。表１～表３においてＦｅの含有量をｂａｌ．と記載しているのは、Ｆｅの含有量がこれらの他元素を含むＲ－Ｔ－Ｂ系永久磁石全体を１００質量％とした場合の残部であることを示すためである。
(Production of RTB permanent magnet)
Raw material alloys were prepared by a strip casting method so that the final RTB permanent magnets had the compositions of each sample shown in Tables 1 to 3. In addition, in all the experimental examples described in Tables 1 and 2, the content of Pr was 0% by mass. O, N, C, H, Si, Ca, La, Ce, Cr, etc. may be detected as other elements not listed in Tables 1 to 3. Si is mainly mixed in from the ferroboron raw material and the crucible during alloy melting. Ca, La, and Ce are mixed in from rare earth raw materials. Further, Cr may be mixed in from electrolytic iron. In Tables 1 to 3, the Fe content is bal. This is to indicate that the Fe content is the remainder when the entire RTB permanent magnet containing these other elements is taken as 100% by mass.
次いで、前記原料合金に対して室温で１時間、水素ガスをフローさせて水素を吸蔵させた。次いで雰囲気をＡｒガスに切り替え、６００℃で１時間、脱水素処理を行い、原料合金を水素吸蔵粉砕した。 Next, hydrogen gas was allowed to flow through the raw material alloy at room temperature for 1 hour to occlude hydrogen. Next, the atmosphere was changed to Ar gas, and dehydrogenation treatment was performed at 600° C. for 1 hour to pulverize the raw material alloy to absorb hydrogen.
次いで、原料合金の粉末に対し、質量比で０．１％のオレイン酸アミドを粉砕助剤として添加し、ナウタミキサを用いて混合した。 Next, 0.1% by mass of oleic acid amide was added as a grinding aid to the raw material alloy powder, and mixed using a Nauta mixer.
次いで、衝突板式のジェットミル装置を用いて窒素気流中で微粉砕し、平均粒径が３．０μｍ程度である微粉（原料粉末）を得た。なお、前記平均粒径は、レーザ回折式の粒度分布計で測定した平均粒径Ｄ５０である。 Next, the mixture was finely pulverized in a nitrogen stream using a collision plate type jet mill to obtain a fine powder (raw material powder) having an average particle size of about 3.0 μm. In addition, the said average particle diameter is the average particle diameter D50 measured with the laser diffraction type particle size distribution meter.
得られた微粉を磁界中で成形して成形体を作製した。このときの印加磁場は１２００ｋＡ／ｍの静磁界である。また、成形時の加圧力は１２０ＭＰａとした。なお、磁界印加方向と加圧方向とを直交させるようにした。 The obtained fine powder was molded in a magnetic field to produce a molded body. The applied magnetic field at this time was a static magnetic field of 1200 kA/m. Further, the pressing force during molding was 120 MPa. Note that the magnetic field application direction and the pressurizing direction were made to be perpendicular to each other.
次に、前記成形体を焼結し、焼結体を得た。焼結条件は、組成等により最適条件が異なるが、１０３０℃～１０７０℃の範囲内で４時間保持とした。焼結雰囲気は真空中とした。このとき焼結密度は７．５１Ｍｇ／ｍ３～７．５５Ｍｇ／ｍ３の範囲にあった。その後、Ａｒ雰囲気、大気圧中で、第一時効温度Ｔ１＝８５０℃で１時間の第一時効処理を行い、さらに、第二時効温度Ｔ２＝５２０℃～５４０℃で１時間の第二時効処理を行った。以上より、表１および表２に示す各試料の焼結体を得た。 Next, the molded body was sintered to obtain a sintered body. The optimum sintering conditions varied depending on the composition, etc., but the temperature was kept within the range of 1030°C to 1070°C for 4 hours. The sintering atmosphere was a vacuum. At this time, the sintered density was in the range of 7.51 Mg/m 3 to 7.55 Mg/m 3 . Thereafter, a first aging treatment is performed for 1 hour at a first aging temperature T1 = 850°C in an Ar atmosphere and atmospheric pressure, and a second aging treatment is performed for 1 hour at a second aging temperature T2 = 520°C to 540°C. I did it. From the above, sintered bodies of each sample shown in Tables 1 and 2 were obtained.
（拡散材ペーストの作製）
次に、粒界拡散に用いる拡散材ペーストを作製した。
(Preparation of diffusion material paste)
Next, a diffusion material paste used for grain boundary diffusion was prepared.
まず、純度９９．９％の金属Ｔｂに対して室温で水素ガスをフローさせて水素を吸蔵させた。次いで雰囲気をＡｒガスに切り替え、６００℃で１時間、脱水素処理を行い、金属Ｔｂを水素吸蔵粉砕した。次に、粉砕助剤として、ステアリン酸亜鉛を金属Ｔｂ１００質量％に対して０．０５質量％を添加し、ナウタミキサを用いて混合した。その後、酸素３０００ｐｐｍを含んだ雰囲気中、ジェットミルを用いて微粉砕を行い、平均粒径が１０．０μｍ程度であるＴｂ水素化物の微粉砕粉末を得た。 First, hydrogen gas was caused to flow through metal Tb having a purity of 99.9% at room temperature to absorb hydrogen. Next, the atmosphere was changed to Ar gas, and dehydrogenation treatment was performed at 600° C. for 1 hour to pulverize the metal Tb by absorbing hydrogen. Next, as a grinding aid, zinc stearate was added in an amount of 0.05% by mass based on 100% by mass of metal Tb, and mixed using a Nauta mixer. Thereafter, fine pulverization was performed using a jet mill in an atmosphere containing 3000 ppm of oxygen to obtain a finely pulverized powder of Tb hydride having an average particle size of about 10.0 μm.
次に、純度９９．９％の金属Ｎｄから平均粒径が１０．０μｍ程度であるＮｄ水素化物の微粉砕粉末を得た。Ｎｄ水素化物の微粉砕粉末を得る方法はＴｂ水素化物の微粉砕粉末を得る方法と同一である。 Next, a finely pulverized powder of Nd hydride having an average particle size of about 10.0 μm was obtained from metallic Nd having a purity of 99.9%. The method for obtaining a finely ground powder of Nd hydride is the same as the method for obtaining a finely ground powder for Tb hydride.
Ｔｂ水素化物の微粉砕粉末４６．８質量部と、Ｎｄ水素化物の微粉砕粉末１７．０質量部と、金属Ｃｕ粉末１１．２質量部と、アルコール２３質量部と、アクリル樹脂２質量部と、を混練し、拡散材ペーストを作製した。なお、アルコールは溶媒であり、アクリル樹脂はバインダである。 46.8 parts by mass of finely pulverized powder of Tb hydride, 17.0 parts by mass of finely pulverized powder of Nd hydride, 11.2 parts by mass of metal Cu powder, 23 parts by mass of alcohol, 2 parts by mass of acrylic resin. were kneaded to prepare a diffusion material paste. Note that alcohol is a solvent and acrylic resin is a binder.
（拡散材ペーストの塗布および熱処理）
上記の焼結体を、縦１１ｍｍ×横１１ｍｍ×厚み４．２ｍｍ（磁化容易軸方向厚み４．２ｍｍ）に加工した。そして、エタノール１００質量％に対し硝酸３質量％とした硝酸とエタノールとの混合溶液に３分間浸漬させた後にエタノールに１分間浸漬するエッチング処理を行った。混合溶液に３分間浸漬させた後にエタノールに１分間浸漬させるエッチング処理は２回行った。
(Application of diffusion material paste and heat treatment)
The above sintered body was processed into a size of 11 mm in length x 11 mm in width x 4.2 mm in thickness (thickness in the easy magnetization axis direction: 4.2 mm). Then, an etching process was performed in which the substrate was immersed in a mixed solution of nitric acid and ethanol for 3 minutes, and then immersed in ethanol for 1 minute. The etching process was performed twice by immersing it in the mixed solution for 3 minutes and then immersing it in ethanol for 1 minute.
次いで、エッチング処理後の焼結体の全面に対し、上記の拡散材ペーストを塗布した。拡散材ペーストの塗布量は、焼結体１００質量％に対するＴｂの質量（Ｔｂ塗布量）が表１～表３に記載の質量割合となるようにした。 Next, the above-mentioned diffusion material paste was applied to the entire surface of the sintered body after the etching process. The amount of the diffusion material paste applied was such that the mass of Tb (Tb application amount) with respect to 100% by mass of the sintered body was the mass ratio shown in Tables 1 to 3.
次に、拡散材ペーストを塗布した焼結体を１６０℃のオーブン中に放置し、拡散材ペースト中の溶媒を除去した。そして、大気圧（１ａｔｍ）でＡｒをフローしながら９３０℃で１８時間、加熱した。その後、大気圧でＡｒをフローしながら５２０～５４０℃で４時間、加熱した。以上より、表１～表３に示す各試料のＲ－Ｔ－Ｂ系永久磁石を得た。 Next, the sintered body coated with the diffusion material paste was left in an oven at 160° C. to remove the solvent in the diffusion material paste. Then, it was heated at 930° C. for 18 hours while flowing Ar at atmospheric pressure (1 atm). Thereafter, it was heated at 520 to 540° C. for 4 hours while flowing Ar at atmospheric pressure. From the above, RTB permanent magnets of each sample shown in Tables 1 to 3 were obtained.
Ｒ－Ｔ－Ｂ系永久磁石の表面を各面あたり０．１ｍｍ削り落とした後に、組成、磁気特性および耐食性を評価した。 After 0.1 mm of each surface of the RTB permanent magnet was ground down, the composition, magnetic properties, and corrosion resistance were evaluated.
Ｒ－Ｔ－Ｂ系永久磁石をバーチカルにより縦１１ｍｍ×横１１ｍｍ×厚さ４．２ｍｍ（磁化容易軸方向が４．２ｍｍ）に加工し、ＢＨトレーサーで室温での磁気特性の評価を行った。なお、磁気特性の測定前に４０００ｋＡ／ｍのパルス磁場によりＲ－Ｔ－Ｂ系永久磁石を着磁した。また、Ｒ－Ｔ－Ｂ系永久磁石の厚みが薄いため、磁石を３枚重ねて磁気特性を評価した。なお、本実施例ではＨｋ／ＨｃＪは磁化J－磁場Ｈ曲線の第２象限（Ｊ－Ｈ減磁曲線）において、磁化がＢｒの９０％となったときの磁場をＨｋ（ｋＡ／ｍ）として、Ｈｋ／ＨｃＪ×１００（％）で計算した。また、１４７℃に加熱した場合のＨｃＪも測定した。さらに、室温でのＨｃＪと１４７℃でのＨｃＪとの差の絶対値を室温でのＨｃＪで割ることにより減磁率を求めた。 An RTB permanent magnet was vertically processed into a size of 11 mm long x 11 mm wide x 4.2 mm thick (4.2 mm in the axis of easy magnetization), and its magnetic properties at room temperature were evaluated using a BH tracer. Note that before measuring the magnetic properties, the RTB permanent magnet was magnetized with a pulsed magnetic field of 4000 kA/m. Furthermore, since the RTB permanent magnet is thin, three magnets were stacked on top of each other to evaluate the magnetic properties. In this example, Hk/HcJ is defined as Hk (kA/m), which is the magnetic field when the magnetization becomes 90% of Br in the second quadrant of the magnetization J-magnetic field H curve (J-H demagnetization curve). , Hk/HcJ×100 (%). Furthermore, HcJ when heated to 147°C was also measured. Furthermore, the demagnetization rate was determined by dividing the absolute value of the difference between HcJ at room temperature and HcJ at 147° C. by HcJ at room temperature.
なお、本実施例では、Ｒ－Ｔ－Ｂ系永久磁石のＢｒは１４００ｍＴ以上を良好とした。Ｒ－Ｔ－Ｂ系永久磁石の室温でのＨｃＪは１９５０ｋＡ／ｍ以上を良好とした。Ｒ－Ｔ－Ｂ系永久磁石の１４７℃でのＨｃＪは９００ｋＡ／ｍ以上を良好とした。Ｒ－Ｔ－Ｂ系永久磁石のＨｋ／ＨｃＪは９６．０％以上を良好とした。 In this example, a Br of 1400 mT or more of the RTB permanent magnet was considered good. An RTB permanent magnet with a HcJ of 1950 kA/m or more at room temperature was considered good. An RTB permanent magnet with a HcJ of 900 kA/m or more at 147°C was considered good. Hk/HcJ of the RTB-based permanent magnet was considered to be good if it was 96.0% or more.
Ｒ－Ｔ－Ｂ系永久磁石のＢｒ、室温でのＨｃＪ、１４７℃でのＨｃＪ、およびＨｋ／ＨｃＪが全て良好である場合にＲ－Ｔ－Ｂ系永久磁石の磁気特性を可とした。Ｂｒ、室温ＨｃＪ、１４７℃ＨｃＪおよびＨｋ／ＨｃＪのいずれか一つ以上が良好ではない場合にＲ－Ｔ－Ｂ系永久磁石の磁気特性を不可とした。結果を表１～表３に示す。 When the RTB permanent magnet's Br, HcJ at room temperature, HcJ at 147° C., and Hk/HcJ were all good, the magnetic properties of the RTB permanent magnet were considered acceptable. If any one or more of Br, room temperature HcJ, 147° C. HcJ, and Hk/HcJ were not good, the magnetic properties of the RTB permanent magnet were judged as poor. The results are shown in Tables 1 to 3.
また、Ｒ－Ｔ－Ｂ系永久磁石に対し、耐食性試験を行った。耐食性試験は、飽和蒸気圧下におけるＰＣＴ試験（プレッシャークッカー試験：Ｐｒｅｓｓｕｒｅ Ｃｏｏｋｅｒ Ｔｅｓｔ）により実施した。具体的には、Ｒ－Ｔ－Ｂ系永久磁石を２気圧、１００％ＲＨの環境下に１０００時間おいて、試験前後での質量変化を測定した。Ｒ－Ｔ－Ｂ系永久磁石の表面積あたりの質量減少が３ｍｇ／ｃｍ２以下である場合に耐食性を可とした。Ｒ－Ｔ－Ｂ系永久磁石の表面積あたりの質量減少が３ｍｇ／ｃｍ２超である場合に耐食性を不可とした。 In addition, a corrosion resistance test was conducted on RTB permanent magnets. The corrosion resistance test was carried out by a PCT test (Pressure Cooker Test) under saturated vapor pressure. Specifically, an RTB permanent magnet was placed in an environment of 2 atmospheres and 100% RH for 1000 hours, and the mass change before and after the test was measured. Corrosion resistance was evaluated as acceptable when the mass reduction per surface area of the RTB permanent magnet was 3 mg/cm 2 or less. Corrosion resistance was judged as poor when the mass reduction per surface area of the RTB permanent magnet exceeded 3 mg/cm 2 .
表１には、Ｒ－Ｔ－Ｂ系永久磁石の組成を変化させた点以外は同条件で実施した実施例および比較例を記載した。特定の範囲内の組成を有する各実施例は全て磁気特性および耐食性が良好であった。これに対し、特定の範囲外の組成を有する各比較例は磁気特性または耐食性が良好ではなかった。なお、減磁率は各実施例および比較例で大きな差は無かった。 Table 1 lists Examples and Comparative Examples conducted under the same conditions except that the composition of the RTB permanent magnet was changed. All of the Examples having compositions within a specific range had good magnetic properties and corrosion resistance. On the other hand, each comparative example having a composition outside the specific range did not have good magnetic properties or corrosion resistance. Note that there was no significant difference in demagnetization rate between the Examples and Comparative Examples.
表２には、焼結体の組成が同一であり、Ｔｂ塗布量を変化させた実施例を記載した。表２より、Ｔｂ塗布量が大きいほどＢｒが低下し、ＨｃＪが上昇し、Ｈｋ／ＨｃＪが低下する傾向が見られた。なお、Ｔｂ塗布量を変化させても耐食性は良好に維持された。なお、減磁率はＴｂ塗布量が少ないほど上昇する傾向にあった。 Table 2 shows examples in which the composition of the sintered body was the same and the amount of Tb applied was varied. From Table 2, there was a tendency that as the amount of Tb applied increased, Br decreased, HcJ increased, and Hk/HcJ decreased. Note that even when the amount of Tb applied was changed, the corrosion resistance was maintained satisfactorily. Note that the demagnetization rate tended to increase as the amount of Tb applied was smaller.
表３には、実施例３のＮｄの一部をＰｒに置換させた実施例を記載した。表３より、Ｐｒの含有量が大きいほど室温でのＨｃＪが上昇するが１４７℃でのＨｃＪが低下する傾向が見られた。 Table 3 shows an example in which part of Nd in Example 3 was replaced with Pr. From Table 3, there was a tendency that the higher the Pr content, the higher the HcJ at room temperature, but the lower the HcJ at 147°C.
なお、全ての実施例および比較例のＲ－Ｔ－Ｂ系永久磁石について、電子プローブマイクロアナライザー（ＥＰＭＡ）を用いてＴｂ濃度分布を分析し、Ｔｂの濃度分布が、外側から内側に向かって低下する濃度分布であることを確認した。 In addition, the Tb concentration distribution of all the RTB permanent magnets of Examples and Comparative Examples was analyzed using an electron probe microanalyzer (EPMA), and it was found that the Tb concentration distribution decreased from the outside to the inside. It was confirmed that the concentration distribution was as follows.
１…Ｒ－Ｔ－Ｂ系永久磁石 1...RTB system permanent magnet
Claims (7)
前記Ｒ－Ｔ－Ｂ系永久磁石は、さらにＺｒを含み、
前記Ｒ－Ｔ－Ｂ系永久磁石全体を１００質量％として、
Ｎｄ，Ｐｒ，ＤｙおよびＴｂの合計含有量が３０．００質量％～３２．２０質量％、
Ｃｏの含有量が０．３０質量％～０．８４質量％、
Ｚｒの含有量が０．３１質量％～０．６０質量％、
Ｂの含有量が０．９０質量％～１．０２質量％であり、
Ｚｒ／Ｃｏ比が質量比で０．４８以上１．４０以下であることを特徴とするＲ－Ｔ－Ｂ系永久磁石。 A rare earth element in which R contains one or more selected from Nd and Pr and one or more selected from Dy and Tb, T is Fe and Co, and B is boron. A magnet,
The RTB permanent magnet further contains Zr,
Assuming that the entire RTB permanent magnet is 100% by mass,
The total content of Nd, Pr, Dy and Tb is 30.00% by mass to 32.20% by mass,
Co content is 0.30% by mass to 0.84 % by mass,
Zr content is 0.31% by mass to 0.60% by mass,
The content of B is 0.90% by mass to 1.02% by mass,
An RTB permanent magnet characterized in that the Zr/Co ratio is 0.48 or more and 1.40 or less in terms of mass ratio .
Ｃｕの含有量が０．１０質量％～０．５５質量％である請求項１に記載のＲ－Ｔ－Ｂ系永久磁石。 The RTB permanent magnet further contains Cu,
The RTB permanent magnet according to claim 1, wherein the Cu content is 0.10% by mass to 0.55% by mass.
Ｍｎの含有量が０．０２質量％～０．１０質量％である請求項１または２に記載のＲ－Ｔ－Ｂ系永久磁石。 The RTB permanent magnet further contains Mn,
The RTB permanent magnet according to claim 1 or 2, wherein the Mn content is 0.02% by mass to 0.10% by mass.
Ａｌの含有量が０．０７質量％～０．３５質量％である請求項１～３のいずれかに記載のＲ－Ｔ－Ｂ系永久磁石。 The RTB permanent magnet further contains Al,
The RTB permanent magnet according to any one of claims 1 to 3, wherein the content of Al is 0.07% by mass to 0.35% by mass.
Ｇａの含有量が０．０２質量％～０．１５質量％である請求項１～４のいずれかに記載のＲ－Ｔ－Ｂ系永久磁石。 The RTB permanent magnet further contains Ga,
The RTB permanent magnet according to any one of claims 1 to 4, wherein the Ga content is 0.02% by mass to 0.15% by mass.
The RTB permanent magnet according to any one of claims 1 to 6 , which has a concentration gradient of heavy rare earth elements that decreases from the surface of the magnet toward the inside.
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