JP2022046184A - Rare earth iron carbon-based magnetic powder and manufacturing method thereof - Google Patents
Rare earth iron carbon-based magnetic powder and manufacturing method thereof Download PDFInfo
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Abstract
Description
本発明は、希土類鉄炭素系磁性粉末及びその製造方法に関する。 The present invention relates to a rare earth iron carbon-based magnetic powder and a method for producing the same.
永久磁石は、自動車、電化製品、ＩＴ機器を始め、幅広い分野で用いられており、現代の産業において欠くことができない。特に永久磁石は、電力を必要とせず磁力を発生できるため、近年の地球温暖化対策や省エネルギーの観点から、その重要性がますます高まっている。 Permanent magnets are used in a wide range of fields, including automobiles, electrical appliances, and IT equipment, and are indispensable in modern industry. In particular, permanent magnets are becoming more and more important from the viewpoint of global warming countermeasures and energy saving in recent years because they can generate magnetic force without requiring electric power.
永久磁石の中でも希土類磁石は、磁石の基本特性（磁束密度、保磁力、最大エネルギー積）が、フェライトやアルニコなどの他の磁石を凌駕するほど優れている。特に希土類磁石は、最大エネルギー積（ＢＨｍａｘ）が高く、小型で強力な磁石とすることが可能である。そのため部品の小型化及び高性能化の流れに応じて期待が高い。特に近年の電気自動車やハイブリッド自動車の実用化の流れに応じて、その使用量は急増しており、各種磁石の中でも金額ベースでの市場占有率が最も大きい。 Among permanent magnets, rare earth magnets are superior in basic magnet characteristics (magnetic flux density, coercive force, maximum energy product) to surpass other magnets such as ferrite and alnico. In particular, rare earth magnets have a high maximum energy product (BHmax) and can be made into small and powerful magnets. Therefore, expectations are high in line with the trend toward smaller parts and higher performance. In particular, with the recent trend toward practical application of electric vehicles and hybrid vehicles, the amount used has increased rapidly, and the market share on a monetary basis is the largest among various magnets.
希土類磁石の中では、ネオジム磁石がよく知られている。ネオジム磁石は、ネオジム鉄硼素（Ｎｄ２Ｆｅ１４Ｂ）系化合物を主相とする磁石であり、現在実用化されている磁石の中で最も高い最大エネルギー積を誇る。そのためネオジム磁石は、焼結磁石やボンド磁石として広範囲に利用されている。しかしながらネオジム磁石は高温環境下で使用することができないとの問題がある。すなわちネオジム磁石はキュリー温度（Ｔｃ）が３１２℃と低く、高温減磁の問題がある。またネオジム磁石は耐酸化性に劣る。すなわち希土類元素は原子番号の順に酸化し易く、軽希土類元素たるネオジム（Ｎｄ）を含むネオジム磁石は、メッキなどの表面処理を施さなければ実用に供することは困難である。 Among rare earth magnets, neodymium magnets are well known. Neodymium magnets are magnets whose main phase is neodymium iron boron (Nd 2 Fe 14 B) -based compounds, and boast the highest maximum energy product among the magnets currently in practical use. Therefore, neodymium magnets are widely used as sintered magnets and bonded magnets. However, there is a problem that neodymium magnets cannot be used in a high temperature environment. That is, the neodymium magnet has a low Curie temperature (Tc) of 312 ° C. and has a problem of high temperature demagnetization. In addition, neodymium magnets are inferior in oxidation resistance. That is, rare earth elements are easily oxidized in the order of atomic number, and it is difficult to put a neodymium magnet containing neodymium (Nd), which is a light rare earth element, into practical use without surface treatment such as plating.
ネオジム磁石以外の希土類磁石として、サマリウム鉄窒素（Ｓｍ２Ｆｅ１７Ｎｘ）系化合物やサマリウム鉄炭素（Ｓｍ２Ｆｅ１７Ｃｘ）系化合物を用いた磁石が知られている。これらの化合物は、Ｓｍ２Ｆｅ１７の結晶格子間に窒素（Ｎ）又は炭素（Ｃ）原子が侵入した侵入型化合物である。このうちＳｍ２Ｆｅ１７Ｎｘ系磁石は、優れた磁気特性、特にキュリー温度（Ｔｃ）と保磁力（Ｈｃ）が高いという特徴を活かして、ネオジム磁石とともに広く用いられている。Ｓｍ２Ｆｅ１７Ｎｘ系磁性粉末は、ｘ＝３のときに最も優れた磁気特性を示し、その時のキュリー温度（Ｔｃ）は４７３℃と高い。また異方性磁場（ＨＡ）が２１ＭＡ／ｍと高く、この値はＮｄ２Ｆｅ１７Ｂ系化合物の３倍以上である。その上、飽和磁化（Ｍｓ）が１．５７Ｔと、Ｎｄ２Ｆｅ１７Ｂ系化合物に匹敵するほど高い。 As rare earth magnets other than neodymium magnets, magnets using a sumalium iron nitrogen (Sm 2 Fe 17 N x ) -based compound or a sumalium iron carbon (Sm 2 Fe 17 C x ) -based compound are known. These compounds are invasive compounds in which nitrogen (N) or carbon (C) atoms have penetrated between the crystal lattices of Sm 2 Fe 17 . Of these, Sm 2 Fe 17 Nx magnets are widely used together with neodymium magnets because of their excellent magnetic properties, especially their high Curie temperature (Tc) and high coercive force (Hc). The Sm 2 Fe 17 N x -based magnetic powder exhibits the best magnetic properties when x = 3, and the Curie temperature (Tc) at that time is as high as 473 ° C. The anisotropic magnetic field ( HA ) is as high as 21 MA / m, which is more than three times that of the Nd 2 Fe 17 B-based compound. Moreover, the saturation magnetization (Ms) is 1.57 T, which is as high as that of Nd 2 Fe 17 B-based compounds.
しかしながらサマリウム鉄窒素（Ｓｍ２Ｆｅ１７Ｎｘ）系化合物は低温で分解しやすいという問題がある。すなわちこの化合物は、窒素（Ｎ）量によって異なるが５５０～７００℃程度の温度で分解し始める。そのため焼結磁石にすることが困難であり、ボンド磁石としての利用に留まっている。ボンド磁石は非磁性バインダー樹脂を必須成分にするため、磁束密度（Ｂ）及び最大エネルギー積（ＢＨｍａｘ）を高める上で限界がある。 However, the samarium iron-nitrogen (Sm 2 Fe 17 Nx ) -based compound has a problem that it is easily decomposed at a low temperature. That is, this compound begins to decompose at a temperature of about 550 to 700 ° C., although it depends on the amount of nitrogen (N). Therefore, it is difficult to make a sintered magnet, and it is only used as a bonded magnet. Since the bonded magnet contains a non-magnetic binder resin as an essential component, there is a limit in increasing the magnetic flux density (B) and the maximum energy product (BHmax).
これに対してサマリウム鉄炭素（Ｓｍ２Ｆｅ１７Ｃｘ）系化合物は、サマリウム鉄窒素（Ｓｍ２Ｆｅ１７Ｎｘ）系化合物に比べて熱安定性に優れている。実際、Ｓｍ２Ｆｅ１７Ｃｘ系化合物は１０００℃以上の高温でも分解しないため、これをボンド磁石のみならず焼結磁石にも適用できる。またＳｍ２Ｆｅ１７Ｃｘ系化合物は、鉄（Ｆｅ）の一部をコバルト（Ｃｏ）で置換することで、キュリー温度Ｔｃを６００℃程度にまで高めることができる。そのため高温減磁が少なく、高温用途の磁石への適用が可能である。したがってＳｍ２Ｆｅ１７Ｃｘ系化合物は優れたポテンシャルを有する材料と言うことができる。 On the other hand, the samarium iron-carbon (Sm 2 Fe 17 C x ) -based compound is superior in thermal stability to the samarium iron-nitrogen (Sm 2 Fe 17 N x ) -based compound. In fact, since the Sm 2 Fe 17 Cx -based compound does not decompose even at a high temperature of 1000 ° C. or higher, it can be applied not only to bonded magnets but also to sintered magnets. Further, in the Sm 2 Fe 17 Cx -based compound, the Curie temperature Tc can be raised to about 600 ° C. by substituting a part of iron (Fe) with cobalt (Co). Therefore, there is little high-temperature demagnetization, and it can be applied to magnets for high-temperature applications. Therefore, it can be said that the Sm 2 Fe 17 Cx -based compound has excellent potential.
Ｓｍ２Ｆｅ１７Ｃｘ系化合物の合成を開示する文献として、特許文献１及び非特許文献１が挙げられる。特許文献１には、一般式ＲｘＦｅ（１－ｘ－ｙ－ｚ）ＭｙＣｚの組成（ＲはＳｍ等の希土類金属、ＭはＴｉ等）を有し、かつＲ２Ｆｅ１７型菱面体晶化合物を主相とする希土類磁石材料が開示されている（特許文献１の請求項１及び［０００７］）。また特許文献１にはこの磁石材料に関して、Ｎｄ－Ｆｅ－Ｂ系永久磁石と同等の磁気特性を確保できるばかりか、キュリー点の上昇により温度特性の大幅な向上を達成できる旨などが記載されている（特許文献１の［００３８］）。 Documents 1 and non-patent documents 1 disclose the synthesis of Sm 2 Fe 17 Cx -based compounds. Patent Document 1 has a composition of the general formula R x Fe ( 1-x-y-z) My C z (R is a rare earth metal such as Sm, M is Ti etc.), and is R 2 Fe 17 type. A rare earth magnet material containing a rhombic crystal compound as a main phase is disclosed (claim 1 and [0007] of Patent Document 1). Further, Patent Document 1 describes that not only the magnetic characteristics equivalent to those of Nd-Fe-B permanent magnets can be secured for this magnet material, but also the temperature characteristics can be significantly improved by increasing the Curie point. (Patent Document 1 [0038]).
非特許文献１には、Ｓｍ２Ｆｅ１７－ｘＣｏｘＣｙ化合物について、ＦｅをＣｏで置換すると、菱面体晶Ｒｈ２Ｚｎ１７型構造（２：１７）が安定化される旨、Ｃｏ量ｘが増えるにつれてキュリー温度が急増するとともに格子定数が小さくなる旨、Ｓｍ２Ｆｅ１２Ｃｏ５Ｃ１．２５化合物は、室温での飽和磁化μ０Ｍｓ＝１．３６Ｔ、異方性磁場μ０Ｈｋ＝７．１Ｔ、キュリー温度Ｔｃ＝８７４Ｋ、動作可能最高温度Ｔｍが４７３Ｋより高い旨などが記載されている（非特許文献１のＡｂｓｔｒａｃｔ）。 Non-Patent Document 1 states that for the Sm 2 Fe 17-x Co x Cy compound, replacement of Fe with Co stabilizes the rhombic Rh2 Zn 17 -type structure (2:17), and the amount of Co. The Curie temperature rapidly increases and the lattice constant decreases as x increases. The Sm 2 Fe 12 Co 5 C 1.25 compound has a saturation magnetization of μ 0 M s = 1.36 T at room temperature and an anisotropic magnetic field μ 0 . It is described that H k = 7.1 T, Curie temperature Tc = 874 K, maximum operable temperature Tm is higher than 473 K, and the like (Abstract of Non-Patent Document 1).
このようにサマリウム鉄炭素（Ｓｍ２Ｆｅ１７Ｃｘ）系化合物は熱安定性が良好であり、優れたポテンシャルを有するものの、従来の技術では高い磁気特性を示す化合物を簡易なプロセスで合成することが困難であった。すなわちこの化合物は炭素量が多いほど、キュリー温度及び磁気異方性が高くなる。しかしながら従来のプロセスでは、十分な量の炭素（Ｃ）を結晶格子中に取り込むことができず、磁気特性向上を図る上で限界があった。そのためこの化合物は、その研究例が少なく、本発明者らの知る限り実用化された例はない。 As described above, the samarium iron-carbon (Sm 2 Fe 17 C x ) -based compound has good thermal stability and excellent potential, but in the conventional technique, a compound exhibiting high magnetic properties can be synthesized by a simple process. Was difficult. That is, the higher the carbon content of this compound, the higher the Curie temperature and magnetic anisotropy. However, in the conventional process, a sufficient amount of carbon (C) cannot be taken into the crystal lattice, and there is a limit in improving the magnetic characteristics. Therefore, there are few research examples of this compound, and as far as the present inventors know, there is no practical example.
本発明者らは、このような問題点に鑑みて鋭意検討を行った。その結果、熱安定性に優れ且つ高い磁気特性を示すＳｍ２Ｆｅ１７Ｃｘ系化合物からなる磁性粉末を工業的に利用可能なプロセスを用いて合成する上で、鉄（Ｆｅ）の一部をコバルト（Ｃｏ）とガリウム（Ｇａ）とによって同時に置換することが有効であることを見出した。さらに所定の組成を有するＳｍ２Ｆｅ１７Ｃｘ系磁性粉末は飽和磁化（Ｍｓ）及び保磁力（Ｈｃ）のみならず角形性にも優れており、磁石の最大エネルギー積（ＢＨｍａｘ）を高める上で好適であるとの知見を得た。 The present inventors have conducted diligent studies in view of such problems. As a result, a part of iron (Fe) is used in synthesizing a magnetic powder made of a Sm 2 Fe 17 Cx -based compound having excellent thermal stability and high magnetic properties by using an industrially available process. It has been found that simultaneous substitution with cobalt (Co) and gallium (Ga) is effective. Furthermore, the Sm 2 Fe 17 Cx -based magnetic powder having a predetermined composition is excellent not only in saturation magnetization (Ms) and coercive force (Hc) but also in squareness, and in increasing the maximum energy product (BHmax) of the magnet. We obtained the finding that it is suitable.
本発明は、このような知見に基づき完成されたものであり、熱安定性に優れ且つ高い磁気特性を示すサマリウム鉄炭素（Ｓｍ２Ｆｅ１７Ｃｘ）系磁性粉末及びその製造方法の提供を課題とする。 The present invention has been completed based on such findings, and an object of the present invention is to provide a samarium iron carbon (Sm 2 Fe 17 Cx ) -based magnetic powder having excellent thermal stability and high magnetic properties and a method for producing the same. And.
本発明は、下記（１）～（１１）の態様を包含する。なお本明細書において「～」なる表現は、その両端の数値を含む。すなわち「Ｘ～Ｙ」は「Ｘ以上Ｙ以下」と同義である。 The present invention includes the following aspects (1) to (11). In the present specification, the expression "-" includes the numerical values at both ends thereof. That is, "X to Y" is synonymous with "X or more and Y or less".
（１）サマリウム（Ｓｍ）、鉄（Ｆｅ）、コバルト（Ｃｏ）、ガリウム（Ｇａ）及び炭素（Ｃ）を含む菱面体晶系Ｔｈ２Ｚｎ１７型化合物を主相として含み、前記化合物が一般式：Ｓｍ２Ｆｅ（１７－ｍ－ｎ）ＣｏｍＧａｎＣｘで表される組成（ただし、２．０≦ｍ≦３．５、１．５≦ｎ≦３．０、１．００≦ｘ≦１．７５）を有する、希土類鉄炭素系磁性粉末。 (1) A rhombic crystal - based Th2 Zn 17 -type compound containing samarium (Sm), iron (Fe), cobalt (Co), gallium (Ga) and carbon (C) is contained as a main phase, and the compound is a general formula. : Sm 2 Fe (17-mn) Com composition represented by Com Gan C x (however, 2.0 ≦ m ≦ 3.5, 1.5 ≦ n ≦ 3.0, 1.00 ≦ x A rare earth iron-carbon-based magnetic powder having ≤1.75).
（２）前記ｍ及びｎが、０．３０≦ｎ／（ｍ＋ｎ）≦０．６０を満たす、上記（１）の磁性粉末。 (2) The magnetic powder of (1) above, wherein m and n satisfy 0.30 ≦ n / (m + n) ≦ 0.60.
（３）前記ｘが、１．２５≦ｚ≦１．５０を満たす、上記（１）又は（２）の磁性粉末。 (3) The magnetic powder according to (1) or (2) above, wherein x satisfies 1.25 ≦ z ≦ 1.50.
（４）前記磁性粉末の平均粒子径ｄ５０が５．０μｍ以下である、上記（１）～（３）のいずれかの磁性粉末。 (4) The magnetic powder according to any one of (1) to (3) above, wherein the average particle diameter d 50 of the magnetic powder is 5.0 μm or less.
（５）サマリウム（Ｓｍ）、鉄（Ｆｅ）、コバルト（Ｃｏ）、ガリウム（Ｇａ）及び炭素（Ｃ）を含み、残部不可避不純物からなる、上記（１）～（４）のいずれかの磁性粉末。 (5) The magnetic powder according to any one of (1) to (4) above, which contains samarium (Sm), iron (Fe), cobalt (Co), gallium (Ga) and carbon (C), and the balance is unavoidable impurities. ..
（６）α－Ｆｅ相の含有量が１０体積％以下である、上記（１）～（５）のいずれかの磁性粉末。 (6) The magnetic powder according to any one of (1) to (5) above, wherein the content of the α-Fe phase is 10% by volume or less.
（７）主相及びα－Ｆｅ相以外に異相を含まない、上記（１）～（６）のいずれかの磁性粉末。 (7) The magnetic powder according to any one of (1) to (6) above, which does not contain a heterogeneous phase other than the main phase and the α-Fe phase.
（８）前記磁性粉末の飽和磁化（Ｍｓ）が９０Ｗｂ・ｍ／ｋｇ以上であり、且つ保磁力（Ｈｃ）が２５０ｋＡ／ｍ以上である、上記（１）～（７）のいずれかの磁性粉末。 (8) The magnetic powder according to any one of (1) to (7) above, wherein the saturation magnetization (Ms) of the magnetic powder is 90 Wb · m / kg or more and the coercive force (Hc) is 250 kA / m or more. ..
（９）前記磁性粉末の飽和磁化（Ｍｓ）が８０Ｗｂ・ｍ／ｋｇ以上であり、且つ保磁力（Ｈｃ）が３００ｋＡ／ｍ以上である、上記（１）～（７）のいずれかの磁性粉末。 (9) The magnetic powder according to any one of (1) to (7) above, wherein the saturation magnetization (Ms) of the magnetic powder is 80 Wb · m / kg or more and the coercive force (Hc) is 300 kA / m or more. ..
（１０）前記磁性粉末の飽和磁化（Ｍｓ）に対する残留磁化（Ｍｒ）の比（Ｍｒ／Ｍｓ比）が０．９０以上である、上記（１）～（９）のいずれかの磁性粉末。 (10) The magnetic powder according to any one of (1) to (9) above, wherein the ratio (Mr / Ms ratio) of the residual magnetization (Mr) to the saturation magnetization (Ms) of the magnetic powder is 0.90 or more.
（１１）上記（１）～（１０）のいずれかの磁性粉末の製造方法であって、以下の工程；
サマリウム（Ｓｍ）、鉄（Ｆｅ）、コバルト（Ｃｏ）、ガリウム（Ｇａ）及び炭素（Ｃ）を含む原料を準備する工程、
準備した原料を配合する工程、
配合した原料を坩堝又は鋳型に入れた後に、溶解鋳造して鋳塊にする工程、
前記鋳塊に熱処理を施して均質化する工程、及び
均質化した前記鋳塊を粉砕して粉砕粉にする工程、
を含む、方法。
(11) The method for producing a magnetic powder according to any one of (1) to (10) above, wherein the following steps;
Step of preparing raw materials containing samarium (Sm), iron (Fe), cobalt (Co), gallium (Ga) and carbon (C),
The process of blending the prepared raw materials,
A process in which the mixed raw materials are placed in a crucible or a mold and then melt-cast to form an ingot.
A step of heat-treating the ingot to homogenize it, and a step of crushing the homogenized ingot into pulverized powder.
Including, how.
本発明によれば、熱安定性に優れ且つ高い磁気特性を示すサマリウム鉄炭素（Ｓｍ２Ｆｅ１７Ｃｘ）系磁性粉末及びその製造方法が提供される。 According to the present invention, there is provided a samarium iron-carbon (Sm 2 Fe 17 Cx ) -based magnetic powder having excellent thermal stability and high magnetic properties, and a method for producing the same.
本発明の具体的な実施形態（以下、「本実施形態」という）について説明する。なお本発明は以下の実施形態に限定されるものではなく、本発明の要旨を変更しない範囲において種々の変更が可能である。 A specific embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described. The present invention is not limited to the following embodiments, and various modifications can be made without changing the gist of the present invention.
＜希土類鉄炭素系磁性粉末＞
本実施形態の希土類鉄炭素系磁性粉末は、サマリウム（Ｓｍ）、鉄（Ｆｅ）、コバルト（Ｃｏ）、ガリウム（Ｇａ）及び炭素（Ｃ）を含む菱面体晶系Ｔｈ２Ｚｎ１７型化合物を主相として含む。またこの化合物は、一般式：Ｓｍ２Ｆｅ（１７－ｍ－ｎ）ＣｏｍＧａｎＣｘで表される組成を有する。ここでｍ、ｎ及びｘは、２．０≦ｍ≦３．５、１．５≦ｎ≦３．０、１．００≦ｘ≦１．７５の関係を満たす。
<Rare earth iron carbon-based magnetic powder>
The rare earth iron carbon-based magnetic powder of the present embodiment is mainly a rhombohedral Th2 Zn 17 - type compound containing samarium (Sm), iron (Fe), cobalt (Co), gallium (Ga) and carbon (C). Included as a phase. Further, this compound has a composition represented by the general formula: Sm 2 Fe (17-mn) Com Gan C x . Here, m, n and x satisfy the relationships of 2.0 ≦ m ≦ 3.5, 1.5 ≦ n ≦ 3.0, and 1.00 ≦ x ≦ 1.75.
本実施形態の磁性粉末は、一般式：Ｓｍ２Ｆｅ（１７－ｍ－ｎ）ＣｏｍＧａｎＣｘで表される組成を有するＳｍ２Ｆｅ１７Ｃｘ系化合物を主相として含む。なお本明細書においてＳｍ２Ｆｅ１７Ｃｘ系化合物とは、Ｓｍ２Ｆｅ１７Ｃｘを基本組成とする化合物のみならず、サマリウム（Ｓｍ）及び鉄（Ｆｅ）の一部が他の元素で置換された化合物を包含する。また本実施形態の主相化合物は、そのＳｍと（Ｆｅ＋Ｃｏ＋Ｇａ）の比が厳密に２：１７である必要はない。格子空孔や欠陥の存在により２：１７から偏倚することがあり、菱面体晶系Ｔｈ２Ｚｎ１７構造を維持できる限り、そのような偏倚は許容される。 The magnetic powder of the present embodiment contains, as a main phase, a Sm 2 Fe 17 C x -based compound having a composition represented by the general formula: Sm 2 Fe (17-mn) Com Gan C x . In the present specification, the Sm 2 Fe 17 C x -based compound is not only a compound having Sm 2 Fe 17 C x as a basic composition, but also a part of samarium (Sm) and iron (Fe) is replaced with another element. Includes the compounds that have been added. Further, the main phase compound of the present embodiment does not have to have a exact ratio of Sm to (Fe + Co + Ga) of 2:17. The presence of lattice vacancies and defects can cause deviations from 2:17 , and such deviations are acceptable as long as the rhombohedral Th2 Zn 17 structure can be maintained.
本実施形態の化合物では、Ｓｍ２Ｆｅ１７Ｃｘの鉄（Ｆｅ）の一部がコバルト（Ｃｏ）及びガリウム（Ｇａ）で置換されている。またこの化合物の結晶構造は菱面体晶系Ｔｈ２Ｚｎ１７構造である。Ｓｍ２Ｆｅ１７Ｃｘ系化合物は、その結晶構造がＳｍ２Ｆｅ１７と同一である。Ｓｍ２Ｆｅ１７は、低温では菱面体晶系Ｔｈ２Ｚｎ１７構造を安定相とし、高温では六方晶系Ｔｈ２Ｎｉ１７構造が安定相である。これらの構造はいずれも、希土類磁石材料として知られるＳｍＣｏ５が属する六方晶ＣａＣｕ５構造から派生したものである。例えばＴｈ２Ｚｎ１７構造はＣａＣｕ５構造のＲサイト（Ｓｍサイト）の１／３をダンベル鉄（Ｆｅ－Ｆｅ）で規則的に置換したものに相当する。 In the compound of this embodiment, a part of iron (Fe) of Sm 2 Fe 17 Cx is replaced with cobalt (Co) and gallium (Ga). The crystal structure of this compound is a rhombohedral Th2 Zn 17 structure. The crystal structure of the Sm 2 Fe 17 Cx -based compound is the same as that of Sm 2 Fe 17 . Sm 2 Fe 17 has a rhombohedral Th 2 Zn 17 structure as a stable phase at low temperatures and a hexagonal Th 2 Ni 17 structure as a stable phase at high temperatures. All of these structures are derived from the hexagonal CaCu 5 structure to which SmCo 5 , which is known as a rare earth magnet material, belongs. For example, the Th 2 Zn 17 structure corresponds to a CaCu 5 structure in which 1/3 of the R site (Sm site) is regularly replaced with dumbbell iron (Fe-Fe).
Ｓｍ２Ｆｅ１７Ｃｘ系化合物は、Ｓｍ２Ｆｅ１７の結晶格子間に炭素（Ｃ）が侵入した炭素侵入型化合物（合金）である。Ｓｍ２Ｆｅ１７は、Ｓｍ－Ｆｅ化合物の中で、磁気モーメント（磁化）の担い手となる鉄（Ｆｅ）原子を最も多く含み、それ故、潜在的には大きな磁化を示す可能性がある。しかしながら実際には炭素を含まないＳｍ２Ｆｅ１７はキュリー温度（Ｔｃ）が低く、室温での飽和磁化が小さい。これは結晶格子中でのＦｅ－Ｆｅ原子間距離が短すぎて、Ｆｅ原子に基づく強磁性的磁気秩序が不安定であるからと考えられている。またＳｍ２Ｆｅ１７は、磁気異方性定数Ｋ１が負であるため、面内磁気異方性を示す。面内磁気異方性を示す材料では、結晶中ａｂ面内を磁化容易軸が回転するため、高い保磁力（Ｈｃ）を得ることができない。このような理由でＳｍ２Ｆｅ１７は、これ単独では優れた磁石材料にはならない。 The Sm 2 Fe 17 Cx -based compound is a carbon-penetrating compound (alloy) in which carbon (C) has penetrated between the crystal lattices of Sm 2 Fe 17 . The Sm 2 Fe 17 contains the largest amount of iron (Fe) atoms, which are the bearers of the magnetic moment (magnetization), among the Sm-Fe compounds, and therefore may potentially exhibit a large magnetization. However, in reality, Sm 2 Fe 17 containing no carbon has a low Curie temperature (Tc) and a small saturation magnetization at room temperature. It is considered that this is because the distance between Fe and Fe atoms in the crystal lattice is too short and the ferromagnetic magnetic order based on Fe atoms is unstable. Further, since Sm 2 Fe 17 has a negative magnetic anisotropy constant K 1 , it exhibits in-plane magnetic anisotropy. In a material exhibiting in-plane magnetic anisotropy, a high coercive force (Hc) cannot be obtained because the axis of easy magnetization rotates in the ab plane in the crystal. For this reason, Sm 2 Fe 17 alone is not an excellent magnetic material.
これに対してＳｍ２Ｆｅ１７に炭素（Ｃ）を加えてＳｍ２Ｆｅ１７Ｃｘにすることで、結晶格子が膨張してＦｅ－Ｆｅ原子間距離が長くなる。そのため磁気秩序が安定化されて、キュリー温度（Ｔｃ）が大幅に上昇する。また加えられた炭素（Ｃ）は、鉄（Ｆｅ）原子の磁気モーメントやサマリウム（Ｓｍ）サイトの結晶場に影響を及ぼす。これに伴い、結晶中ｃ軸方向に磁化容易軸が固定される一軸磁気異方性が発現するとともに、磁気異方性定数の絶対値が大きくなる。このような理由でＳｍ２Ｆｅ１７Ｃｘ系化合物は、飽和磁化（Ｍｓ）及び保磁力（Ｈｃ）の高い優れた磁石材料になると考えられる。また結晶格子中に取り込まれる炭素（Ｃ）量が多いほど、磁気特性（Ｍｓ、Ｈｃ、Ｔｃ）がより優れたものになると期待される。 On the other hand, by adding carbon (C) to Sm 2 Fe 17 to make Sm 2 Fe 17 C x , the crystal lattice expands and the distance between Fe and Fe atoms becomes long. Therefore, the magnetic order is stabilized and the Curie temperature (Tc) rises significantly. The added carbon (C) also affects the magnetic moment of the iron (Fe) atom and the crystal field of the samarium (Sm) site. Along with this, uniaxial magnetic anisotropy in which the axis of easy magnetization is fixed in the c-axis direction in the crystal is exhibited, and the absolute value of the magnetic anisotropy constant becomes large. For this reason, the Sm 2 Fe 17 Cx -based compound is considered to be an excellent magnet material having high saturation magnetization (Ms) and coercive force (Hc). Further, it is expected that the larger the amount of carbon (C) incorporated into the crystal lattice, the better the magnetic properties (Ms, Hc, Tc).
本実施形態の磁性粉末では、上述した一般式においてコバルト（Ｃｏ）量ｍを２．０≦ｍ≦３．５の範囲内に限定する。コバルト（Ｃｏ）は、Ｓｍ２Ｆｅ１７Ｃｘ系化合物の鉄（Ｆｅ）サイトを占めて、Ｔｈ２Ｚｎ１７結晶構造を安定化させるとともに、キュリー温度（Ｔｃ）を高める働きがある。コバルト（Ｃｏ）量ｍが２．０未満であると、キュリー温度が低下する。そのため室温で高い飽和磁化（Ｍｓ）を得ることが困難になる。一方でｍが３．５を超えると、保磁力（Ｈｃ）及び残留磁化（Ｍｒ）が低くなる。コバルト（Ｃｏ）置換により格子が縮むため、過度な置換は磁気異方性に悪影響を及ぼすと推察される。ｍは３．０以上３．３以下がより好ましい。 In the magnetic powder of the present embodiment, the cobalt (Co) amount m is limited to the range of 2.0 ≦ m ≦ 3.5 in the above-mentioned general formula. Cobalt (Co) occupies the iron (Fe) site of the Sm 2 Fe 17 Cx -based compound, has the function of stabilizing the Th 2 Zn 17 crystal structure and increasing the Curie temperature (Tc). When the cobalt (Co) amount m is less than 2.0, the Curie temperature decreases. Therefore, it becomes difficult to obtain high saturation magnetization (Ms) at room temperature. On the other hand, when m exceeds 3.5, the coercive force (Hc) and the residual magnetization (Mr) become low. Since the lattice shrinks due to cobalt (Co) substitution, it is presumed that excessive substitution adversely affects the magnetic anisotropy. The m is more preferably 3.0 or more and 3.3 or less.
本実施形態の磁性粉末では、ガリウム（Ｇａ）量ｎを１．５≦ｎ≦３．０の範囲内に限定する。ガリウム（Ｇａ）は、Ｓｍ２Ｆｅ１７Ｃｘ系化合物の鉄（Ｆｅ）サイトを占めて、結晶構造を安定化させる働きがある。ガリウム（Ｇａ）量ｎが１．５未満であると、結晶構造が不安定になり、Ｓｍ２Ｆｅ１７Ｃｘ系化合物が分解する恐れがある。分解によりα－Ｆｅなどの異相が生成し、その結果、保磁力（Ｈｃ）が低下する。ｎは１．７以上が好ましく、２．０以上がより好ましい。一方でｎが３．０を超えると、飽和磁化（Ｍｓ）及び保磁力（Ｈｃ）が低下する。ガリウム（Ｇａ）は非磁性元素である。そのためこれが過度に多く含まれると、単位胞あたりの磁気モーメント及びＦｅ－Ｆｅ原子間の磁気秩序が弱くなると推察される。ｎは２．５以下がより好ましい。 In the magnetic powder of the present embodiment, the amount n of gallium (Ga) is limited to the range of 1.5 ≦ n ≦ 3.0. Gallium (Ga) occupies the iron (Fe) site of the Sm 2 Fe 17 Cx -based compound and has a function of stabilizing the crystal structure. If the amount of gallium (Ga) n is less than 1.5, the crystal structure becomes unstable and the Sm 2 Fe 17 Cx -based compound may be decomposed. The decomposition produces a heterogeneous phase such as α-Fe, and as a result, the coercive force (Hc) decreases. n is preferably 1.7 or more, more preferably 2.0 or more. On the other hand, when n exceeds 3.0, the saturation magnetization (Ms) and the coercive force (Hc) decrease. Gallium (Ga) is a non-magnetic element. Therefore, if this is contained in an excessively large amount, it is presumed that the magnetic moment per unit cell and the magnetic order between Fe-Fe atoms are weakened. n is more preferably 2.5 or less.
本実施形態の磁性粉末は、好ましくはコバルト（Ｃｏ）量ｍ及びガリウム（Ｇａ）量ｎが０．３０≦ｎ／（ｍ＋ｎ）≦０．６０を満たす。この範囲内であると、磁性粉末の飽和磁化（Ｍｓ）と保磁力（Ｈｃ）とをバランスよく高めることが可能になる。より好ましくは、ｍ及びｎが、０．３４≦ｎ／（ｍ＋ｎ）≦０．４０を満たす。 The magnetic powder of the present embodiment preferably satisfies the cobalt (Co) amount m and the gallium (Ga) amount n of 0.30 ≦ n / (m + n) ≦ 0.60. Within this range, the saturation magnetization (Ms) and coercive force (Hc) of the magnetic powder can be increased in a well-balanced manner. More preferably, m and n satisfy 0.34 ≦ n / (m + n) ≦ 0.40.
本実施形態の磁性粉末では、炭素（Ｃ）量ｘを１．００≦ｘ≦１．７５の範囲内に限定する。上述したように、炭素（Ｃ）には、結晶格子間に侵入して、キュリー温度（Ｔｃ）及び一軸磁気異方性を高める働きがある。炭素（Ｃ）量ｘが１．００未満であると、キュリー温度が低下して、室温での飽和磁化（Ｍｓ）が小さくなる。また磁化容易軸が面内異方性をもつようになり、保磁力（Ｈｃ）が低下してしまう。ｘは１．２５以上であってもよい。一方でｘが１．７５を超えると、結晶構造が不安定になる。そのためα－Ｆｅなどの異相が生成して保磁力（Ｈｃ）が低下する。ｘは１．５０以下であってもよい。 In the magnetic powder of the present embodiment, the amount of carbon (C) x is limited to the range of 1.00 ≦ x ≦ 1.75. As described above, carbon (C) has a function of penetrating between crystal lattices to increase Curie temperature (Tc) and uniaxial magnetic anisotropy. When the amount of carbon (C) x is less than 1.00, the Curie temperature is lowered and the saturation magnetization (Ms) at room temperature is reduced. In addition, the easy-to-magnetize axis has in-plane anisotropy, and the coercive force (Hc) decreases. x may be 1.25 or more. On the other hand, when x exceeds 1.75, the crystal structure becomes unstable. Therefore, a different phase such as α-Fe is generated and the coercive force (Hc) is lowered. x may be 1.50 or less.
本実施形態の磁性粉末は、上述した組成を満足する限り、その主相を構成する化合物（Ｓｍ２Ｆｅ１７Ｃｘ系化合物）がサマリウム（Ｓｍ）、鉄（Ｆｅ）、コバルト（Ｃｏ）、ガリウム（Ｇａ）及び炭素（Ｃ）以外の他の元素を含んでいてもよい。例えばサマリウム（Ｓｍ）以外に、ネオジム（Ｎｄ）やプラセオジウム（Ｐｒ）といった希土類元素を主相が含んでもよい。また炭素（Ｃ）以外に窒素（Ｎ）を含んでもよい。しかしながらサマリウム（Ｓｍ）以外の希土類元素を多量に含むと、主相化合物の一軸磁気異方性が弱くなり、保磁力が低下する恐れがある。また窒素（Ｎ）を多量に含むと、化合物の熱安定性が劣化する恐れがある。したがって主相に含まれる他の元素は少ないほど好ましい。他の元素の含有量は３０原子％以下であってよく、１０原子％以下であってよく、５原子％以下であってよく、１原子％以下であってもよく、０．１原子％以下であってもよい。 In the magnetic powder of the present embodiment, as long as the above-mentioned composition is satisfied, the compounds constituting the main phase thereof (Sm 2 Fe 17 Cx -based compound) are samarium (Sm), iron (Fe), cobalt (Co), and gallium. It may contain elements other than (Ga) and carbon (C). For example, in addition to samarium (Sm), the main phase may contain rare earth elements such as neodymium (Nd) and praseodymium (Pr). Further, nitrogen (N) may be contained in addition to carbon (C). However, if a large amount of rare earth elements other than samarium (Sm) is contained, the uniaxial magnetic anisotropy of the main phase compound may be weakened and the coercive force may decrease. Further, if a large amount of nitrogen (N) is contained, the thermal stability of the compound may deteriorate. Therefore, it is preferable that the amount of other elements contained in the main phase is small. The content of other elements may be 30 atomic% or less, 10 atomic% or less, 5 atomic% or less, 1 atomic% or less, 0.1 atomic% or less. It may be.
また本実施形態の磁性粉末は、Ｓｍ２Ｆｅ１７Ｃｘ系化合物を主相とする限り、その他の相を含んでもよい。ここで主相とは、粉末中で５０質量％以上の割合を占める成分のことを指す。またその他の相として、Ｓｍ２Ｆｅ１４Ｃ相、α－Ｆｅ相、サマリウム炭化物相（Ｓｍ２Ｃ３－ｘ相等）、サマリウム鉄炭化物相、及びこれらの相にコバルト（Ｃｏ）、ガリウム（Ｇａ）及び／又は炭素（Ｃ）が固溶した相などが挙げられる。しかしながらＳｍ２Ｆｅ１７Ｃｘ系化合物の優れた磁気特性を十分に生かすため、主相以外の成分の割合は少ないほど好ましい。粉末中の主相以外の成分の割合は３０体積％以下であってよく、１０体積％以下であってよく、５体積％以下であってよく、１体積％以下であってよく、０．１体積％以下であってもよい。磁性粉末が、サマリウム（Ｓｍ）、鉄（Ｆｅ）、コバルト（Ｃｏ）、ガリウム（Ｇａ）及び炭素（Ｃ）を含み、残部不可避不純物からなる組成を有してもよい。ここで不可避不純物は製造工程上不可避的に混入する成分であり、その量は典型的には１０００ｐｐｍ以下である。 Further, the magnetic powder of the present embodiment may contain other phases as long as the Sm 2 Fe 17 Cx -based compound is the main phase. Here, the main phase refers to a component that accounts for 50% by mass or more in the powder. Other phases include Sm 2 Fe 14 C phase, α-Fe phase, samarium carbide phase (Sm 2 C 3-x phase, etc.), samarium iron carbide phase, and cobalt (Co) and gallium (Ga) in these phases. And / or a phase in which carbon (C) is solid-dissolved can be mentioned. However, in order to fully utilize the excellent magnetic properties of the Sm 2 Fe 17 Cx -based compound, it is preferable that the proportion of components other than the main phase is small. The proportion of the components other than the main phase in the powder may be 30% by volume or less, 10% by volume or less, 5% by volume or less, 1% by volume or less, and 0.1. It may be less than or equal to the volume. The magnetic powder may have a composition containing samarium (Sm), iron (Fe), cobalt (Co), gallium (Ga) and carbon (C), with the balance being unavoidable impurities. Here, the unavoidable impurities are components that are inevitably mixed in the manufacturing process, and the amount thereof is typically 1000 ppm or less.
本実施形態の磁性粉末は、好ましくはα－Ｆｅ相の含有量が１０体積％以下である。ここでα－Ｆｅ相は、鉄（Ｆｅ）のみからなるものだけでなく、鉄（Ｆｅ）にコバルト（Ｃｏ）やガリウム（Ｇａ）が固溶したものを含む。α－Ｆｅ相は、磁気異方性をもたず、軟磁性を示す。そのためα－Ｆｅ相が多量に形成されると、粉末の保磁力（Ｈｃ）が低下する恐れがある。α－Ｆｅ相の量は、５体積％以下であってよく、１体積％以下であってよい。磁性粉末がα－Ｆｅ相を含まなくともよい。なおα－Ｆｅ相の含有量は、磁性粉末をＸ線回折により分析することで求めることができる。また「α－Ｆｅ相を含まない」とは、Ｘ線回折プロファイルにて、α－Ｆｅ相に基づく回折ピークが存在しない、又は存在したとしてもノイズ以下の強度であることを意味する。Ｘ線回折分析は、後述する実施例での条件に準じた条件で行う。 The magnetic powder of the present embodiment preferably has an α-Fe phase content of 10% by volume or less. Here, the α-Fe phase includes not only a phase composed of iron (Fe) but also a solid solution of cobalt (Co) or gallium (Ga) in iron (Fe). The α-Fe phase has no magnetic anisotropy and exhibits soft magnetism. Therefore, if a large amount of α-Fe phase is formed, the coercive force (Hc) of the powder may decrease. The amount of the α—Fe phase may be 5% by volume or less and may be 1% by volume or less. The magnetic powder does not have to contain the α—Fe phase. The content of the α—Fe phase can be determined by analyzing the magnetic powder by X-ray diffraction. Further, "not including the α-Fe phase" means that the diffraction peak based on the α-Fe phase does not exist in the X-ray diffraction profile, or even if it exists, the intensity is equal to or less than the noise. The X-ray diffraction analysis is performed under the conditions according to the conditions in the examples described later.
本実施形態の磁性粉末は、好ましくは主相及びα－Ｆｅ相以外に炭化物などの異相を含まない。Ｓｍ２Ｆｅ１７Ｃｘ系化合物の合成反応が不十分な場合、あるいは炭素（Ｃ）量が過剰な場合には、遊離炭素が発生し、この遊離炭素が他の元素と反応して炭化物を形成することがある。このような炭化物が形成されると、Ｓｍ２Ｆｅ１７Ｃｘ系化合物を構成する炭素（Ｃ）の量が実質的に少なくなる。そのためキュリー温度（Ｔｃ）や結晶磁気異方性が低下する結果、飽和磁化（Ｍｓ）や保磁力（Ｈｃ）といった磁気特性が劣化する恐れがある。なお異相の存在は、磁性粉末をＸ線回折することで確認することができる。また「異相を含まない」とは、Ｘ線回折プロファイルにて、異相に基づく回折ピークが存在しない、又は存在したとしてもノイズ以下の強度であることを意味する。 The magnetic powder of the present embodiment preferably does not contain a heterogeneous phase such as a carbide other than the main phase and the α-Fe phase. When the synthetic reaction of the Sm 2 Fe 17 Cx -based compound is insufficient, or when the amount of carbon (C) is excessive, free carbon is generated, and this free carbon reacts with other elements to form carbides. I have something to do. When such a carbide is formed, the amount of carbon (C) constituting the Sm 2 Fe 17 Cx -based compound is substantially reduced. Therefore, as a result of the decrease in Curie temperature (Tc) and magnetocrystalline anisotropy, magnetic characteristics such as saturation magnetization (Ms) and coercive force (Hc) may deteriorate. The presence of the different phase can be confirmed by X-ray diffraction of the magnetic powder. Further, "not including the different phase" means that the diffraction peak based on the different phase does not exist in the X-ray diffraction profile, or even if it exists, the intensity is equal to or less than the noise.
本実施形態の磁性粉末は、好ましくはその平均粒子径（ｄ５０）が５．０μｍ以下である。Ｓｍ２Ｆｅ１７Ｃｘ系化合物は、Ｓｍ２Ｆｅ１７Ｎｘ系化合物と同様に、ニュークリエーション型の磁化反転機構を有すると考えられる。ニュークリエーション型の機構では、逆磁区の核形成に基づき磁化が反転する。そのため平均粒子径が５．０μｍを超えて過度に大きくなると、逆磁区の核が多くなり、保磁力が低下する恐れがある。平均粒子径は３．０μｍ以下であってよく、２．５μｍ以下であってよく、２．０μｍ以下であってもよい。一方で平均粒子径が過度に小さいと、粉砕歪の蓄積や化合物の分解が生じる恐れがあるとともに、極度にサイズが小さい超常磁性粒子の影響を無視し得なくなる。平均粒子径は０．１μｍ以上であってよく、０．５μｍ以上であってよい。 The magnetic powder of the present embodiment preferably has an average particle size (d 50 ) of 5.0 μm or less. It is considered that the Sm 2 Fe 17 C x -based compound has a new creation type magnetization reversal mechanism like the Sm 2 Fe 17 N x -based compound. In the new creation type mechanism, the magnetization is reversed based on the nucleation of the reverse magnetic domain. Therefore, if the average particle size exceeds 5.0 μm and becomes excessively large, the number of nuclei in the reverse magnetic domain increases, and the coercive force may decrease. The average particle size may be 3.0 μm or less, 2.5 μm or less, or 2.0 μm or less. On the other hand, if the average particle size is excessively small, accumulation of crushing strain and decomposition of compounds may occur, and the influence of extremely small size superparamagnetic particles cannot be ignored. The average particle size may be 0.1 μm or more, and may be 0.5 μm or more.
本実施形態の磁性粉末は、その飽和磁化（飽和質量磁化；Ｍｓ）が８０Ｗｂ・ｍ／ｋｇ（８０ｅｍｕ／ｇ）以上であってよく、９０Ｗｂ・ｍ／ｋｇ（９０ｅｍｕ／ｇ）以上であってよく、１００Ｗｂ・ｍ／ｋｇ（１００ｅｍｕ／ｇ）以上であってよく、１１０Ｗｂ・ｍ／ｋｇ（１１０ｅｍｕ／ｇ）以上であってもよい。このように高い飽和磁化（Ｍｓ）を示す磁性粉末は、磁束密度（Ｍｓ）が高く磁力の強い磁石を製造するための原料として有用である。 The magnetic powder of the present embodiment may have a saturation magnetization (saturation mass magnetization; Ms) of 80 Wb · m / kg (80 emu / g) or more, and may be 90 Wb · m / kg (90 emu / g) or more. , 100 Wb · m / kg (100 emu / g) or more, and may be 110 Wb · m / kg (110 emu / g) or more. The magnetic powder exhibiting such high saturation magnetization (Ms) is useful as a raw material for producing a magnet having a high magnetic flux density (Ms) and a strong magnetic force.
本実施形態の磁性粉末は、その保磁力（Ｈｃ）が２５０ｋＡ／ｍ（３．１４ｋＯｅ）以上であってよく、２７５ｋＡ／ｍ（３．４６ｋＯｅ）以上であってよく、３００ｋＡ／ｍ（３．７７ｋＯｅ）以上であってよく、３２５ｋＡ／ｍ（４．０８ｋＯｅ）以上であってよく、３５０ｋＡ／ｍ（４．４０ｋＯｅ）以上であってもよい。このように高い保磁力（Ｈｃ）を示す磁性粉末は、高磁場下で減磁しにくい磁石を製造するための原料として有用である。 The magnetic powder of the present embodiment may have a coercive force (Hc) of 250 kA / m (3.14 kOe) or more, may be 275 kA / m (3.46 kOe) or more, and may have a coercive force (Hc) of 300 kA / m (3.77 kOe) or more. ) Or more, 325 kA / m (4.08 kOe) or more, and 350 kA / m (4.40 kOe) or more. The magnetic powder exhibiting such a high coercive force (Hc) is useful as a raw material for producing a magnet that is difficult to demagnetize under a high magnetic field.
好ましい態様では、飽和磁化（Ｍｓ）が９０Ｗｂ・ｍ／ｋｇ（９０ｅｍｕ／ｇ）以上であり、且つ保磁力（Ｈｃ）が２５０ｋＡ／ｍ（３．１４ｋＯｅ）以上である。また別の好ましい態様では、飽和磁化（Ｍｓ）が８０Ｗｂ・ｍ／ｋｇ（８０ｅｍｕ／ｇ）以上であり、且つ保磁力（Ｈｃ）が３００ｋＡ／ｍ（３．７７ｋＯｅ）以上である。このように高い飽和磁化（Ｍｓ）及び保磁力（Ｈｃ）を示す磁性粉末は、高磁場下で減磁しにくく且つ強力な磁石、例えば高出力モーター用磁石を製造するための原料として有用である。 In a preferred embodiment, the saturation magnetization (Ms) is 90 Wb · m / kg (90 emu / g) or more, and the coercive force (Hc) is 250 kA / m (3.14 kOe) or more. In yet another preferred embodiment, the saturation magnetization (Ms) is 80 Wb · m / kg (80 emu / g) or more, and the coercive force (Hc) is 300 kA / m (3.77 kOe) or more. The magnetic powder exhibiting such high saturation magnetization (Ms) and coercive force (Hc) is useful as a raw material for producing a strong magnet that is difficult to demagnetize under a high magnetic field, for example, a magnet for a high output motor. ..
本実施形態の磁性粉末は、好ましくは飽和磁化（Ｍｓ）に対する残留磁化（Ｍｒ）の比（Ｍｒ／Ｍｓ比）が０．９００（９０．０％）以上である。ここでＭｒ／Ｍｓ比は角形性の指標となるものである。Ｍｒ／Ｍｓ比が低いと、ヒステリシスループ（Ｊ－Ｈ曲線）の第２象限（減磁曲線）において、ステップ状の段差（クニック）が観察されることがある。このような段差の存在は、減磁曲線の角形性を悪くするため好ましくない。すなわち飽和磁化（Ｍｓ）及び保磁力（Ｈｃ）が高い磁性粉末であっても、角形性が悪いと、この粉末を用いて作製した磁石の最大エネルギー積（ＢＨｍａｘ）が小さくなる。最大エネルギー積が小さい磁石は、動作点での磁束密度が低いとともに、磁場変動や寸法変動に伴う磁束密度の変化の度合いが大きく、安定的に動作させることができない。これに対してＭｒ／Ｍｓ比が高い磁性粉末を用いることで、最大エネルギー積の大きい磁石を作製することができる。Ｍｒ／Ｍｓ比は０．９２０（９２．０％）以上であってよく、０．９４０（９４．０％）以上であってよく、０．９５０（９５．０％）以上であってもよい。Ｍｒ／Ｍｓ比の上限は１．０００（１００．０％）である。なおＭｒ／Ｍｓ比は、十分に磁場配向させた磁性粉末について求めた飽和磁化（Ｍｓ）及び残留磁化（Ｍｒ）から算出する。 The magnetic powder of the present embodiment preferably has a ratio (Mr / Ms ratio) of residual magnetization (Mr) to saturation magnetization (Ms) of 0.900 (90.0%) or more. Here, the Mr / Ms ratio is an index of squareness. When the Mr / Ms ratio is low, a step-like step (knick) may be observed in the second quadrant (demagnetization curve) of the hysteresis loop (JH curve). The presence of such a step is not preferable because it deteriorates the angularity of the demagnetization curve. That is, even if the magnetic powder has high saturation magnetization (Ms) and coercive force (Hc), if the squareness is poor, the maximum energy product (BHmax) of the magnet produced by using this powder becomes small. A magnet having a small maximum energy product cannot be operated stably because the magnetic flux density at the operating point is low and the degree of change in the magnetic flux density due to magnetic field fluctuations and dimensional fluctuations is large. On the other hand, by using a magnetic powder having a high Mr / Ms ratio, a magnet having a large maximum energy product can be manufactured. The Mr / Ms ratio may be 0.920 (92.0%) or more, 0.940 (94.0%) or more, and 0.950 (95.0%) or more. .. The upper limit of the Mr / Ms ratio is 1.000 (100.0%). The Mr / Ms ratio is calculated from the saturation magnetization (Ms) and the residual magnetization (Mr) obtained for the magnetic powder that is sufficiently magnetically oriented.
このように、本実施形態の磁性粉末は、飽和磁化（Ｍｓ）及び保磁力（Ｈｃ）のみならず角形性に優れている。そのためこの粉末を用いて、基本性能（磁束密度、保磁力、最大エネルギー積）に優れた磁石を製造することができる。さらにこの磁性粉末は、高温で分解することがなく、またキュリー温度（Ｔｃ）が高い。そのためボンド磁石のみならず焼結磁石の原料として用いることができる。その上、製造後の磁石の熱安定性を良好なものにすることが可能である。したがって磁石用原料として実用上の価値が高い。 As described above, the magnetic powder of the present embodiment is excellent not only in saturation magnetization (Ms) and coercive force (Hc) but also in squareness. Therefore, using this powder, it is possible to manufacture a magnet having excellent basic performance (magnetic flux density, coercive force, maximum energy product). Further, this magnetic powder does not decompose at a high temperature and has a high Curie temperature (Tc). Therefore, it can be used as a raw material for sintered magnets as well as bonded magnets. Moreover, it is possible to improve the thermal stability of the magnet after production. Therefore, it has high practical value as a raw material for magnets.
特に本実施形態の磁性粉末は、Ｓｍ２Ｆｅ１７Ｃｘ系化合物の鉄（Ｆｅ）の一部を所定量のコバルト（Ｃｏ）とガリウム（Ｇａ）の両方で置換することで、炭素（Ｃ）を結晶格子中に効率よく取り込むことができる。そのため異相形成を抑制しつつも炭素量ｘを高めることができ、その結果、熱安定性に優れるとともに高い磁気特性（飽和磁化、保磁力、角形性）を示す磁性粉末にすることが可能である。実際、本発明者らは、コバルト（Ｃｏ）とガリウム（Ｇａ）の同時置換により、炭素量ｘが１．７５と高いにも関わらず異相の少ない磁性粉末の合成に成功している。 In particular, in the magnetic powder of the present embodiment, carbon (C) is obtained by substituting a part of iron (Fe) of the Sm 2 Fe 17 Cx -based compound with a predetermined amount of both cobalt (Co) and gallium (Ga). Can be efficiently incorporated into the crystal lattice. Therefore, it is possible to increase the carbon content x while suppressing the formation of heterogeneous phases, and as a result, it is possible to obtain a magnetic powder that is excellent in thermal stability and exhibits high magnetic properties (saturation magnetization, coercive force, angularity). .. In fact, the present inventors have succeeded in synthesizing a magnetic powder having a small amount of different phases even though the carbon content x is as high as 1.75 by simultaneous substitution of cobalt (Co) and gallium (Ga).
本発明者らの知る限り、このように高い磁気特性を示すＳｍ２Ｆｅ１７Ｃｘ系磁性粉末を合成することは知られていない。例えば特許文献１には広範な組成を有するＲ－Ｆｅ－Ｍ－Ｃ化合物を主相とする希土類磁石材料が開示されているが、コバルト（Ｃｏ）とガリウム（Ｇａ）の組み合わせに基づく共置換に着目したものでなく、またその効果を示唆するものでない。実際、特許文献１では実施例においてチタン（Ｔｉ）とコバルト（Ｃｏ）を同時に加えて磁石材料を作製することが開示されているが、チタン（Ｔｉ）は炭化物を生成し易い成分である（特許文献１の表２（試料番号２１～２５）及び［００１１］）。したがって特許文献１の磁石粉末では、異相たる炭化物（ＴｉＣ）が形成されることで、主相結晶格子中に炭素を十分に取り込むことができないと推察される。その上、特許文献１には磁石粉末のＭｒ／Ｍｓ比は開示がなく、この粉末の角形性は不明である。 As far as the present inventors know, it is not known to synthesize a Sm 2 Fe 17 Cx -based magnetic powder exhibiting such high magnetic properties. For example, Patent Document 1 discloses a rare earth magnet material having an R-Fe-MC compound as a main phase having a wide range of compositions, but it can be used as a co-substitution based on a combination of cobalt (Co) and gallium (Ga). It is not focused and does not suggest its effect. In fact, Patent Document 1 discloses that titanium (Ti) and cobalt (Co) are simultaneously added to prepare a magnet material in Examples, but titanium (Ti) is a component that easily forms carbides (Patent). Table 2 (Sample Nos. 21 to 25) and [0011] in Document 1. Therefore, it is presumed that in the magnet powder of Patent Document 1, carbon cannot be sufficiently incorporated into the main phase crystal lattice due to the formation of carbides (TiC) which are different phases. Moreover, Patent Document 1 does not disclose the Mr / Ms ratio of the magnet powder, and the squareness of this powder is unknown.
また非特許文献１はＳｍ２Ｆｅ１７Ｃｘ系化合物についてコバルト（Ｃｏ）置換を開示するものの、コバルト（Ｃｏ）とガリウム（Ｇａ）の共置換について何ら教示するものでない。また非特許文献１にもＭｒ／Ｍｓ比は開示がなく、化合物の角形性は不明である。 Further, although Non-Patent Document 1 discloses cobalt (Co) substitution for Sm 2 Fe 17 Cx -based compounds, it does not teach any co-substitution of cobalt (Co) and gallium (Ga). Further, Non-Patent Document 1 does not disclose the Mr / Ms ratio, and the squareness of the compound is unknown.
＜希土類鉄炭素系磁性粉末の製造方法＞
本実施形態の磁性粉末は、上述した要件を満足する限り、その製造方法は限定されない。しかしながら好適な製造方法は、以下の工程；サマリウム（Ｓｍ）、鉄（Ｆｅ）、コバルト（Ｃｏ）、ガリウム（Ｇａ）及び炭素（Ｃ）を含む原料を準備する工程（準備工程）、準備した原料を配合する工程（配合工程）、配合した原料を坩堝又は鋳型に入れた後に、溶解鋳造して鋳塊にする工程（溶解鋳造工程）、鋳塊に熱処理を施して均質化する工程（均質化熱処理工程）、及び均質化した鋳塊を粉砕して粉砕粉にする工程（粉砕工程）、を含む。
<Manufacturing method of rare earth iron carbon-based magnetic powder>
The method for producing the magnetic powder of the present embodiment is not limited as long as the above-mentioned requirements are satisfied. However, suitable production methods include the following steps; a step of preparing a raw material containing sumalium (Sm), iron (Fe), cobalt (Co), gallium (Ga) and carbon (C) (preparation step), and a prepared raw material. Step of blending (blending step), step of putting the blended raw material in a pit or a mold, and then melt-casting to make an ingot (melting casting step), step of applying heat treatment to the ingot to homogenize (homogenization) A heat treatment step) and a step of crushing the homogenized ingot into crushed powder (crushing step) are included.
準備工程では、サマリウム（Ｓｍ）、鉄（Ｆｅ）、コバルト（Ｃｏ）、ガリウム（Ｇａ）及び炭素（Ｃ）を含む原料を準備する。原料として、サマリウム、鉄、コバルト、ガリウム及び炭素のそれぞれを元素形態で含む原料を用いてもよく、あるいはこれらの組み合わせを化合物又は合金の形態で含むものを用いてもよい。例えば溶解鋳造法又は還元拡散法で作製したＳｍ－Ｆｅ合金を用いてもよい。 In the preparatory step, raw materials containing samarium (Sm), iron (Fe), cobalt (Co), gallium (Ga) and carbon (C) are prepared. As the raw material, a raw material containing each of samarium, iron, cobalt, gallium and carbon in the form of an element may be used, or a raw material containing a combination thereof in the form of a compound or an alloy may be used. For example, a Sm—Fe alloy produced by a melt casting method or a reduction diffusion method may be used.
配合工程では、準備した原料を配合する。原料の配合は、製造後の磁性粉末が所定の組成になるように調整すればよい。ただしサマリウム（Ｓｍ）などの揮発し易い成分は、後続する溶解鋳造工程での揮発を見越して過剰になるように配合してもよい。例えば、サマリウム（Ｓｍ）を目標組成での必要量に対して５～３０質量％過剰になる量で配合してもよい。 In the compounding process, the prepared raw materials are compounded. The composition of the raw materials may be adjusted so that the magnetic powder after production has a predetermined composition. However, easily volatile components such as samarium (Sm) may be blended in excess in anticipation of volatilization in the subsequent melting and casting step. For example, samarium (Sm) may be added in an amount of 5 to 30% by mass in excess of the required amount in the target composition.
溶解鋳造工程では、配合した原料を坩堝又は鋳型に入れた後に、溶解鋳造して鋳塊（インゴット）にする。溶解鋳造は、高周波溶解法やアーク溶解法などの公知の手法で行えばよい。またその条件も、原料が十分に溶解して鋳塊になるように適宜設定すればよい。 In the melt casting process, the mixed raw materials are placed in a crucible or a mold and then melt cast to form an ingot. The melting casting may be carried out by a known method such as a high frequency melting method or an arc melting method. Further, the conditions may be appropriately set so that the raw material is sufficiently melted to form an ingot.
必要に応じて、鋳塊の表面に研削加工などの加工処理を施して、表面変質層を除去する工程（加工処理工程）を設けてもよい。鋳造後の鋳塊の表面には酸化物層などの表面変質層が存在することがある。このような表面変質層は、製造後の磁性粉末の特性を劣化させる原因になるため、これを除去することが望ましい。加工処理は、表面変質層を除去できる限り限定されず、例えば研削加工や研磨加工が挙げられる。また加工処理は、溶解鋳造工程の直後に行ってもよく、あるいは後述する均質化熱処理後に行ってもよい。 If necessary, a process (processing process) may be provided in which the surface of the ingot is subjected to a processing process such as grinding to remove the surface alteration layer. A surface alteration layer such as an oxide layer may be present on the surface of the ingot after casting. Since such a surface alteration layer causes deterioration of the characteristics of the magnetic powder after production, it is desirable to remove it. The processing is not limited as long as the surface alteration layer can be removed, and examples thereof include grinding and polishing. Further, the processing may be performed immediately after the melt casting step, or may be performed after the homogenization heat treatment described later.
均質化熱処理工程では、得られた鋳塊に熱処理（均質化熱処理）を施して均質化する。鋳造後の鋳塊では、成分が偏析して、組成や組織が不均一になっている場合がある。不均一な組成や組織は、製造後の磁性粉末の特性を劣化させる原因になるため好ましくない。鋳塊に均質化熱処理を施すことで、組成及び組織の均質化を図ることができる。均質化熱処理は、例えばアルゴン（Ａｒ）ガスなどの不活性雰囲気下１０００～１２００℃の温度で８～１９２時間行えばよい。 In the homogenization heat treatment step, the obtained ingot is heat-treated (homogenization heat treatment) to homogenize. In the ingot after casting, the components may segregate and the composition and structure may become non-uniform. A non-uniform composition or structure is not preferable because it causes deterioration of the characteristics of the magnetic powder after production. By subjecting the ingot to a homogenization heat treatment, the composition and structure can be homogenized. The homogenization heat treatment may be carried out at a temperature of 1000 to 1200 ° C. for 8 to 192 hours in an inert atmosphere such as argon (Ar) gas.
粉砕工程では、均質化した鋳塊を粉砕して粉砕粉にする。先述したようにＳｍ２Ｆｅ１７Ｃｘ系化合物は、その磁化反転機構がニュークリエーション型である。そのため微細な粉末にすることで保磁力（Ｈｃ）が高くなる。粉砕は公知の手法で行えばよい。例えば鋳塊を粗粉砕し、得られた粗粉砕粉を微粉砕する手法が挙げられる。粗粉砕は、乳鉢、ジョークラッシャー及び／又はスタンプミルなど公知の破砕機を用いて行えばよい。また微粉砕は、ボールミル、振動ミル及び／又はアトライタなどの公知の粉砕機を用いて、乾式及び／又は湿式で行えばよい。 In the crushing step, the homogenized ingot is crushed into crushed powder. As described above, the Sm 2 Fe 17 Cx -based compound has a magnetization reversal mechanism of the new creation type. Therefore, the coercive force (Hc) becomes high by making it into a fine powder. The pulverization may be carried out by a known method. For example, a method of coarsely pulverizing an ingot and finely pulverizing the obtained coarsely pulverized powder can be mentioned. Coarse crushing may be performed using a known crusher such as a mortar, a jaw crusher and / or a stamp mill. Further, the fine pulverization may be performed dry and / or wet using a known pulverizer such as a ball mill, a vibration mill and / or an attritor.
ただし鋳塊や粉砕粉には、酸化しやすいサマリウム（Ｓｍ）や鉄（Ｆｅ）成分が含まれている。そのため粉砕工程は、アルゴン（Ａｒ）ガスの不活性雰囲気下で行うことが好ましい。また保磁力が高い粉末を得るためには、微細な粉砕粉を得るように粉砕条件を設定することが好ましい。具体的には粉砕粉の平均粒子径（ｄ５０）が５μｍ以下になるまで粉砕することが好ましい。さらに粉砕歪を取り除く目的で、粉砕粉に熱処理を施してもよい。 However, the ingot and the pulverized powder contain samarium (Sm) and iron (Fe) components that are easily oxidized. Therefore, the pulverization step is preferably carried out in an inert atmosphere of argon (Ar) gas. Further, in order to obtain a powder having a high coercive force, it is preferable to set the crushing conditions so as to obtain fine crushed powder. Specifically, it is preferable to pulverize until the average particle size (d 50 ) of the pulverized powder becomes 5 μm or less. Further, the pulverized powder may be heat-treated for the purpose of removing the pulverized strain.
このようにして本実施形態の磁性粉末を製造することができる。製造後の磁性粉末は、熱安定性が良好であるととともに磁気特性に優れている。そのためこの磁性粉末を用いて、熱安定性が良好で且つ基本性能に優れる磁石を製造することができる。 In this way, the magnetic powder of the present embodiment can be produced. The manufactured magnetic powder has good thermal stability and excellent magnetic properties. Therefore, using this magnetic powder, it is possible to manufacture a magnet having good thermal stability and excellent basic performance.
＜ボンド磁石＞
本実施形態の磁性粉末は、それ自体の磁気特性が優れている。したがってこの粉末は、磁性粉末の特性が直接反映されるボンド磁石を製造するための原料として好適である。特にこの磁性粉末は飽和磁化（Ｍｓ）及び保磁力（Ｈｃ）のみならず角形性に優れている。そのため最大エネルギー積（ＢＨｍａｘ）の高いボンド磁石を得ることができる。ボンド磁石は、磁性粉末と樹脂バインダーとを混合してコンパウンドを作製し、得られたコンパウンドを成形して作製する。また樹脂バインダーの種類に応じて、成型体に硬化処理を施してもよい。
<Bond magnet>
The magnetic powder of the present embodiment is excellent in its own magnetic properties. Therefore, this powder is suitable as a raw material for producing a bonded magnet that directly reflects the characteristics of the magnetic powder. In particular, this magnetic powder is excellent not only in saturation magnetization (Ms) and coercive force (Hc) but also in squareness. Therefore, a bonded magnet having a high maximum energy product (BHmax) can be obtained. The bond magnet is produced by mixing a magnetic powder and a resin binder to prepare a compound, and molding the obtained compound. Further, depending on the type of the resin binder, the molded body may be subjected to a curing treatment.
樹脂バインダーは熱可塑性樹脂及び熱硬化性樹脂のいずれであってよい。熱可塑性樹脂系バインダーは、その種類は特に限定されない。例えば、６ナイロン、６－６ナイロン、１１ナイロン、１２ナイロン、６－１２ナイロン、芳香族系ナイロン、これらの分子を一部変性、または共重合化した変性ナイロン等のポリアミド樹脂、直鎖型ポリフェニレンサルファイド樹脂、架橋型ポリフェニレンサルファイド樹脂、セミ架橋型ポリフェニレンサルファイド樹脂、低密度ポリエチレン、線状低密度ポリエチレン樹脂、高密度ポリエチレン樹脂、超高分子量ポリエチレン樹脂、ポリプロピレン樹脂、エチレン－酢酸ビニル共重合樹脂、エチレン－エチルアクリレート共重合樹脂、アイオノマー樹脂、ポリメチルペンテン樹脂、ポリスチレン樹脂、アクリロニトリル－ブタジエン－スチレン共重合樹脂、アクリロニトリル－スチレン共重合樹脂、ポリ塩化ビニル樹脂、ポリ塩化ビニリデン樹脂、ポリ酢酸ビニル樹脂、ポリビニルアルコール樹脂、ポリビニルブチラール樹脂、ポリビニルホルマール樹脂、メタクリル樹脂、ポリフッ化ビニリデン樹脂、ポリ三フッ化塩化エチレン樹脂、四フッ化エチレン－六フッ化プロピレン共重合樹脂、エチレン－四フッ化エチレン共重合樹脂、四フッ化エチレン－パーフルオロアルキルビニルエーテル共重合樹脂、ポリテトラフルオロエチレン樹脂、ポリカーボネート樹脂、ポリアセタール樹脂、ポリエチレンテレフタレート樹脂、ポリブチレンテレフタレート樹脂、ポリフェニレンオキサイド樹脂、ポリアリルエーテルアリルスルホン樹脂、ポリエーテルスルホン樹脂、ポリエーテルエーテルケトン樹脂、ポリアリレート樹脂、芳香族ポリエステル樹脂、酢酸セルロース樹脂、前出の各樹脂系エラストマー等が挙げられる。またこれらの単重合体や他種モノマーとのランダム共重合体、ブロック共重合体、グラフト共重合体、他の物質での末端基変性品などが挙げられる。さらに熱硬化性樹脂としては、不飽和ポリエステル樹脂、エポキシ樹脂などを挙げることができる。 The resin binder may be either a thermoplastic resin or a thermosetting resin. The type of the thermoplastic resin binder is not particularly limited. For example, 6 nylon, 6-6 nylon, 11 nylon, 12 nylon, 6-12 nylon, aromatic nylon, polyamide resins such as modified nylon in which these molecules are partially modified or copolymerized, and linear polyphenylene. Sulfide resin, crosslinked polyphenylene sulfide resin, semi-crosslinked polyphenylene sulfide resin, low density polyethylene, linear low density polyethylene resin, high density polyethylene resin, ultrahigh molecular weight polyethylene resin, polypropylene resin, ethylene-vinyl acetate copolymer resin, ethylene -Ethyl acrylate copolymer resin, ionomer resin, polymethylpentene resin, polystyrene resin, acrylonitrile-butadiene-styrene copolymer resin, acrylonitrile-styrene copolymer resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl acetate resin, polyvinyl Alcohol resin, polyvinyl butyral resin, polyvinylformal resin, methacrylic resin, polyvinylidene fluoride resin, polytrifluorochloride ethylene resin, tetrafluoroethylene-6fluoropropylene copolymer resin, ethylene-tetrafluoroethylene copolymer resin, Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin, polytetrafluoroethylene resin, polycarbonate resin, polyacetal resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyphenylene oxide resin, polyallyl ether allyl sulfone resin, polyether sulfone resin, Examples thereof include polyether ether ketone resins, polyarylate resins, aromatic polyester resins, cellulose acetate resins, and the above-mentioned resin-based elastomers. Moreover, these homopolymers, random copolymers with other kinds of monomers, block copolymers, graft copolymers, terminal group modified products with other substances and the like can be mentioned. Further, examples of the thermosetting resin include unsaturated polyester resin and epoxy resin.
樹脂バインダーの配合量は、特に制限されるものではないが、コンパウンド１００質量部に対して１～５０質量部が好ましい。１質量部より少ないと著しい混練トルクの上昇、流動性の低下を招いて成形困難になるだけでなく、磁気特性が不十分になることがある。一方で５０質量部よりも多いと、所望の磁気特性が得られないことがある。樹脂バインダーの配合量は、３～５０質量部であってよく、５～３０質量部であってよく、７～２０質量部であってよい。 The blending amount of the resin binder is not particularly limited, but is preferably 1 to 50 parts by mass with respect to 100 parts by mass of the compound. If it is less than 1 part by mass, not only the kneading torque increases remarkably and the fluidity decreases, molding becomes difficult, and the magnetic characteristics may become insufficient. On the other hand, if it is more than 50 parts by mass, the desired magnetic characteristics may not be obtained. The blending amount of the resin binder may be 3 to 50 parts by mass, 5 to 30 parts by mass, or 7 to 20 parts by mass.
コンパウンドには、反応性希釈剤、未反応性希釈剤、増粘剤、滑剤、離型剤、紫外線吸収剤、難燃剤や種々の安定剤などの添加剤、充填材を配合することができる。また求められる磁気特性に合わせて、本実施形態の磁性粉末以外の他の磁性粉末を配合してもよい。他の磁性粉末として通常のボンド磁石に用いるものを採用することができ、例えば希土類磁石粉、フェライト磁石粉及びアルニコ磁石粉などが挙げられる。 The compound may contain additives and fillers such as reactive diluents, non-reactive diluents, thickeners, lubricants, mold release agents, UV absorbers, flame retardants and various stabilizers. Further, a magnetic powder other than the magnetic powder of the present embodiment may be blended according to the required magnetic characteristics. As the other magnetic powder, those used for ordinary bonded magnets can be adopted, and examples thereof include rare earth magnet powder, ferrite magnet powder, and alnico magnet powder.
磁性粉末と樹脂バインダーとを混合する際には、バンバリーミキサー、ニーダー、ロール、ニーダールーダー、単軸押出機、二軸押出機等の混練機を用いて溶融混練すればよい。またコンパウンドの成形は、射出成形、押出成形又は圧縮成形により行えばよい。 When the magnetic powder and the resin binder are mixed, they may be melt-kneaded using a kneader such as a Banbury mixer, a kneader, a roll, a kneader luder, a single-screw extruder, or a twin-screw extruder. The compound may be molded by injection molding, extrusion molding or compression molding.
ボンド磁石は異方性磁石であってよく、あるいは等方性磁石であってもよい。しかしながら最大エネルギー積がより高い異方性磁石が好ましい。異方性ボンド磁石を作製する場合には、成形機の金型に磁気回路を組み込み、コンパウンドの成形空間（金型キャビティ）に配向磁場がかかるようして成形する。一方で配向磁場をかけなければ、等方性ボンド磁石が得られる。 The bonded magnet may be an anisotropic magnet or an isotropic magnet. However, anisotropic magnets with a higher maximum energy product are preferred. When producing an anisotropic bond magnet, a magnetic circuit is incorporated in the mold of the molding machine, and the compound is molded so that an orientation magnetic field is applied to the molding space (mold cavity) of the compound. On the other hand, if no orientation magnetic field is applied, an isotropic bonded magnet can be obtained.
＜焼結磁石＞
本実施形態の磁性粉末は磁気特性のみならず耐熱性に優れる。特にこの粉末は１０００℃以上の高温でも分解しない。そのため焼結磁石を製造するための原料として好適である。焼結磁石は、磁性粉末を成形し、得られた成型体を焼結して作製する。成形性を改善するために、磁性粉末にステアリン酸などの潤滑剤（成形助剤）を加えてもよい。また焼結性を改善するために焼結助剤を加えてもよい。
<Sintered magnet>
The magnetic powder of this embodiment is excellent not only in magnetic properties but also in heat resistance. In particular, this powder does not decompose even at a high temperature of 1000 ° C. or higher. Therefore, it is suitable as a raw material for manufacturing sintered magnets. Sintered magnets are manufactured by molding magnetic powder and sintering the obtained molded body. In order to improve moldability, a lubricant (molding aid) such as stearic acid may be added to the magnetic powder. Further, a sintering aid may be added to improve the sinterability.
磁性粉末の成形は、射出成形、押出成形及び圧縮成形などの公知の手法で行えばよい。異方性磁石を作製する場合には、ボンド磁石と同様に、成形機の金型に磁気回路を組み込み、成形空間に配向磁場がかかるようして成形すればよい。また緻密化を図るために、得られた成型体に静水圧加圧成形（ＣＩＰ）を施してもよい。 The molding of the magnetic powder may be carried out by a known method such as injection molding, extrusion molding and compression molding. In the case of producing an anisotropic magnet, a magnetic circuit may be incorporated in a mold of a molding machine and the magnet may be molded so that an orientation magnetic field is applied to the molding space, as in the case of a bond magnet. Further, in order to achieve densification, the obtained molded product may be subjected to hydrostatic pressure molding (CIP).
焼結は、常圧焼結、ホットプレス（ＨＰ）及び熱間等方圧加圧（ＨＩＰ）などの公知の手法を用いて、不活性ガス又は真空中で成型体が緻密になるまで行えばよい。焼結が不足すると、焼結体の密度が高まらず、磁束密度（Ｂ）及び最大エネルギー積（ＢＨｍａｘ）の高い磁石を得ることができない。一方で焼結が過度に進行すると、焼結体中の結晶粒子が粗大化して、保磁力が低下する恐れがある。したがって結晶粒子が過度に粗大化しない範囲で緻密な焼結体が得られる条件を選択すればよい。 Sintering may be performed using known techniques such as normal pressure sintering, hot pressing (HP) and hot isotropic pressurization (HIP) in an inert gas or vacuum until the compact is compact. good. If the sintering is insufficient, the density of the sintered body does not increase, and a magnet having a high magnetic flux density (B) and a maximum energy product (BHmax) cannot be obtained. On the other hand, if the sintering progresses excessively, the crystal particles in the sintered body may become coarse and the coercive force may decrease. Therefore, it suffices to select the conditions under which a dense sintered body can be obtained within the range where the crystal particles do not become excessively coarse.
本実施形態のボンド磁石や焼結磁石は、熱安定性が良好であるとともに、磁石の基本特性（磁束密度、保磁力、最大エネルギー積）に優れている。そのため自動車、一般家電製品、通信・音響機器、医療機器、一般産業機器等に至る幅広い分野において極めて有用である。 The bonded magnet and the sintered magnet of the present embodiment have good thermal stability and excellent basic characteristics (magnetic flux density, coercive force, maximum energy product) of the magnet. Therefore, it is extremely useful in a wide range of fields such as automobiles, general home appliances, communication / audio equipment, medical equipment, and general industrial equipment.
［例１～１６］
（１）磁性粉末の作製
まず、原料として、金属サマリウム（Ｓｍ）、金属鉄（Ｆｅ）、金属コバルト（Ｃｏ）、金属ガリウム（Ｇａ）、及び炭素（Ｃ）粗粒（＞１ｍｍ）を準備し、これらを所定の配合量となるように秤量した。仕込組成はサマリウム（Ｓｍ）の揮発を考慮してＳｍが１５％過剰に含まれる組成にした。秤量した原料から高周波溶解法によりφ１２ｍｍ×８０～１００ｍｍＬの大きさのＳｍ－Ｆｅ－Ｃｏ－Ｇａ－Ｃ合金鋳塊を作製した。次いで均質化を目的として、得られた鋳塊をアルゴン（Ａｒ）雰囲気下１０８０℃×５０時間の条件で熱処理（均質化熱処理）した。均質化熱処理後に、鋳塊の外径がφ１０．５ｍｍになるまで表面を研削して、酸化物層などの表面変質層を除去した。
[Examples 1 to 16]
(1) Preparation of magnetic powder First, metallic samarium (Sm), metallic iron (Fe), metallic cobalt (Co), metallic gallium (Ga), and carbon (C) coarse grains (> 1 mm) are prepared as raw materials. , These were weighed so as to have a predetermined blending amount. In consideration of the volatilization of samarium (Sm), the charged composition was set to contain an excess of Sm by 15%. From the weighed raw materials, a Sm-Fe-Co-Ga-C alloy ingot having a size of φ12 mm × 80 to 100 mmL was prepared by a high-frequency melting method. Then, for the purpose of homogenization, the obtained ingot was heat-treated (homogenization heat treatment) under the condition of 1080 ° C. × 50 hours under an argon (Ar) atmosphere. After the homogenization heat treatment, the surface was ground until the outer diameter of the ingot became φ10.5 mm to remove the surface alteration layer such as the oxide layer.
続いてアルゴン（Ａｒ）雰囲気のグローブボックス中で、表面研削した鋳塊を鉄製乳鉢で粗粉砕し、その後、ふるいがけして粒径４５～２５０μｍの粗粉末を得た。得られた粗粉末に分散剤としてステアリン酸を適量加えてボールミル粉砕した。ボールミル粉砕は、遊星型ボールミル装置を用いて、自転及び公転回転数３００ｒｐｍ又は６００ｒｐｍの条件で６０分間行った。また粉砕メディアとしてφ５ｍｍのジルコニアボールを、溶媒としてヘプタンを用いた。これによりＳｍ－Ｆｅ－Ｃｏ－Ｇａ－Ｃ粉末（磁性粉末）を得た。 Subsequently, the surface-ground ingot was coarsely pulverized in an iron mortar in a glove box having an argon (Ar) atmosphere, and then sieved to obtain a coarse powder having a particle size of 45 to 250 μm. An appropriate amount of stearic acid as a dispersant was added to the obtained crude powder and pulverized by a ball mill. The ball mill pulverization was performed for 60 minutes under the conditions of rotation and revolution speed of 300 rpm or 600 rpm using a planetary ball mill device. Further, zirconia balls having a diameter of 5 mm were used as the pulverizing medium, and heptane was used as the solvent. As a result, Sm-Fe-Co-Ga-C powder (magnetic powder) was obtained.
（２）磁性粉末の評価
例１～１６で得られた磁性粉末につき、各種特性の評価を以下に示すとおりに行った。
(2) Evaluation of Magnetic Powder Various characteristics of the magnetic powders obtained in Examples 1 to 16 were evaluated as shown below.
＜組成＞
磁性粉末の組成をＩＣＰ発光分析法により調べた。
<Composition>
The composition of the magnetic powder was examined by ICP emission spectrometry.
＜平均粒径＞
磁性粉末の平均粒子径（ｄ５０）をレーザー回折法により測定した。具体的にはレーザー回折式乾式粒度分布測定装置（Ｓｙｍｐａｔｅｃ社、ＨＥＬＯＳ＆ＲＯＤＯＳ）を用いて、体積粒度分布における５０％累積径を求めた。
<Average particle size>
The average particle size (d 50 ) of the magnetic powder was measured by a laser diffraction method. Specifically, a laser diffraction type dry particle size distribution measuring device (Symptec, HELOS & RODOS) was used to determine a 50% cumulative diameter in the volume particle size distribution.
＜結晶相＞
磁性粉末をＸ線回折（ＸＲＤ）法により分析してＸ線プロファイルを求め、このＸ線プロファイルを用いて粉末中の結晶相を調べた。分析条件は、以下のとおりにした。
<Crystal phase>
The magnetic powder was analyzed by the X-ray diffraction (XRD) method to obtain an X-ray profile, and the crystal phase in the powder was investigated using this X-ray profile. The analysis conditions were as follows.
‐Ｘ線回折装置：Ｒｉｇａｋｕ ＳｍａｒｔＬａｂ
‐線源：ＣｕＫα
‐管電圧：４５ｋＶ
‐管電流：２００ｍＡ
‐スキャン速度：８°／分
‐スキャン範囲（２θ）：２０～１２０°
-X-ray diffractometer: Rigaku SmartLab
-Radioactive source: CuKα
-Tube voltage: 45kV
-Tube current: 200mA
-Scan speed: 8 ° / min-Scan range (2θ): 20-120 °
またＸ線プロファイルをリートベルト法により解析して、粉末中のα－Ｆｅ相の量を求めた。 The X-ray profile was analyzed by the Rietveld method to determine the amount of α-Fe phase in the powder.
＜磁気特性＞
磁性粉末の磁気特性（飽和磁化、残留磁化及び保磁力）を測定した。測定は、ボンド磁石試験方法ガイドブックＢＭＧ－２００５（日本ボンド磁性材料協会）に則り、振動試料型磁力計（理研電子株式会社、ＶＳＭ）を用いて行った。まずグローブボックス内のアルゴン雰囲気下において２０ｍｇ程度の磁性粉末をデルリン製カプセル（内径６ｍｍ（外径７ｍｍ）×高さ５．５ｍｍ）に入れて、このカプセルをホットプレートに載せた。次にパラフィンを溶かしながらカプセル上限まで入れて、カプセルの蓋をしてから冷却した。グローブボックス外でカプセルを再度ホットプレートに載せてパラフィンを溶かし、カプセルの水平方向に１８ＭＡ／ｍの磁場を印加して粉末を磁場配向させた。粉末が配向した後に冷却してパラフィンを固めて測定試料を作製した。６．４ＭＡ／ｍの磁場中で着磁した後に、測定試料をＶＳＭのロッド先端にセットし、最大印加磁場１．６ＭＡ／ｍの条件で磁化曲線（ヒステリシスカーブ）を描かせた。得られたヒステリシスカーブから、飽和磁化（Ｍｓ）、残留磁化（Ｍｒ）及び保磁力（Ｈｃ）を読み取った。また飽和磁化と残留磁化より、Ｍｒ／Ｍｓ比を求めた。なお各例において、磁性粉末から取り出した３点のサンプルにつき磁気特性（飽和磁化、残留磁気、保磁力及びＭｒ／Ｍｓ比）を求め、その平均値をそれぞれの磁気特性とした。
<Magnetic characteristics>
The magnetic properties (saturation magnetization, residual magnetization and coercive force) of the magnetic powder were measured. The measurement was performed using a vibrating sample magnetometer (RIKEN Electronics Co., Ltd., VSM) in accordance with the Bond Magnet Test Method Guidebook BMG-2005 (Japan Bond Magnetic Materials Association). First, about 20 mg of magnetic powder was placed in a Delrin capsule (inner diameter 6 mm (outer diameter 7 mm) × height 5.5 mm) under an argon atmosphere in the glove box, and this capsule was placed on a hot plate. Next, while melting paraffin, the capsule was filled up to the upper limit, the capsule was covered, and then cooled. The capsule was placed on the hot plate again outside the glove box to melt the paraffin, and a magnetic field of 18 MA / m was applied in the horizontal direction of the capsule to orient the powder in the magnetic field. After the powder was oriented, it was cooled and the paraffin was solidified to prepare a measurement sample. After magnetizing in a magnetic field of 6.4 MA / m, the measurement sample was set on the rod tip of the VSM, and a magnetization curve (hysteresis curve) was drawn under the condition of a maximum applied magnetic field of 1.6 MA / m. Saturation magnetization (Ms), residual magnetization (Mr) and coercive force (Hc) were read from the obtained hysteresis curve. Further, the Mr / Ms ratio was obtained from the saturation magnetization and the residual magnetization. In each example, the magnetic characteristics (saturation magnetization, residual magnetism, coercive force and Mr / Ms ratio) were obtained for each of the three samples taken out from the magnetic powder, and the average value thereof was taken as the respective magnetic characteristics.
（３）評価結果
例１～１６について磁性粉末の特性を表１に示す。ここで例３、例４、例６、例１４～例１６が比較例サンプルであり、それ以外が実施例サンプルである。
(3) Evaluation Results Table 1 shows the characteristics of the magnetic powder for Examples 1 to 16. Here, Example 3, Example 4, Example 6, and Example 14 to Example 16 are comparative example samples, and the others are example samples.
表１を見て分かるように、炭素量（ｘ）が過度に多い比較例サンプル（例３、例４及び例１４～例１６）は、飽和磁化Ｍｓが９５．２Ｗｂ・ｍ／ｋｇ以上と比較的高いものの、保磁力Ｈｃが２４６．４ｋＡ／ｍ以下であった。またこれらのサンプルはＭｒ／Ｍｓ比が８０．３％以下であった。さらにこれらのサンプルは異相たるα－Ｆｅ相の量が１０体積％超と多かった。ガリウム量（ｎ）が過度に少ない比較例サンプル（例６）は、保磁力Ｈｃが２１４．７ｋＡ／ｍと小さかった。 As can be seen from Table 1, the comparative example samples (Example 3, Example 4 and Examples 14 to 16) having an excessively large amount of carbon (x) are compared with the saturation magnetization Ms of 95.2 Wb · m / kg or more. Although the target was high, the coercive force Hc was 246.4 kA / m or less. In addition, these samples had a Mr / Ms ratio of 80.3% or less. Furthermore, these samples had a large amount of α-Fe phase, which is a heterogeneous phase, of more than 10% by volume. In the comparative example sample (Example 6) in which the amount of gallium (n) was excessively small, the coercive force Hc was as small as 214.7 kA / m.
これに対して、実施例サンプル（例１、例２、例５、例７～例１３）は、保磁力Ｈｃが２５２．７ｋＡ／ｍ以上であり、Ｍｒ／Ｍｓ比が９０．１％以上と高かった。またこれらのサンプルは飽和磁化Ｍｓが８８．５Ｗｂ・ｍ／ｋｇ以上と十分に高かった。特に例７、例８、例１０及び例１１は、飽和磁化Ｍｓが１００Ｗｂ・ｍ／ｋｇ以上且つ保磁力Ｈｃが３００ｋＡ／ｍ以上と優れた磁気特性を示した。さらに実施例サンプルはα－Ｆｅ相量が１０体積％以下と少なく、特に例５、例８及び例９は１体積％以下と極めて少なかった。 On the other hand, in the example samples (Example 1, Example 2, Example 5, Example 7 to Example 13), the coercive force Hc is 252.7 kA / m or more, and the Mr / Ms ratio is 90.1% or more. it was high. In addition, these samples had a sufficiently high saturation magnetization Ms of 88.5 Wb · m / kg or more. In particular, Examples 7, 8, 10, and 11 showed excellent magnetic properties with a saturation magnetization Ms of 100 Wb · m / kg or more and a coercive force Hc of 300 kA / m or more. Further, the example sample had a small α-Fe phase amount of 10% by volume or less, and in particular, Examples 5, 8 and 9 had an extremely small amount of 1% by volume or less.
実施例サンプルたる例８及び例１２の磁化曲線（ヒステリシスカーブ）のそれぞれを図１及び図２に示す。これらを見て分かるように、ヒステリシス曲線の角形性が非常に良好であった。すなわち保磁力近傍での磁化曲線の立ち上がりが急峻であり、かつヒステリシス曲線の第２象限（減磁曲線）において、ステップ状の段差（クニック）が殆ど見られなかった。 The magnetization curves (hysteresis curves) of Examples 8 and 12, which are examples samples, are shown in FIGS. 1 and 2, respectively. As can be seen from these, the angularity of the hysteresis curve was very good. That is, the rising edge of the magnetization curve was steep in the vicinity of the coercive force, and in the second quadrant (demagnetization curve) of the hysteresis curve, almost no step-like step (knick) was observed.
実施例サンプルたる例８のＸ線回折プロファイルを図３に示す。なお図中に示される丸印（●）はＳｍ２Ｆｅ１７Ｃｘに基づく回折ピークが現れるべき位置であり、逆三角形印（▼）は、α－Ｆｅに基づく回折ピークが現れるべき位置である。 The X-ray diffraction profile of Example 8 as an Example sample is shown in FIG. The circles (●) shown in the figure are the positions where the diffraction peaks based on Sm 2 Fe 17 C x should appear, and the inverted triangle marks (▼) are the positions where the diffraction peaks based on α-Fe should appear. ..
図３には、Ｓｍ２Ｆｅ１７Ｃｘ系化合物に基づく回折ピークが明瞭に見られる一方で、他の回折ピークは観察されなかった。特にα－Ｆｅ相の存在は確認されなかった。
In FIG. 3, a diffraction peak based on the Sm 2 Fe 17 Cx -based compound was clearly seen, but no other diffraction peak was observed. In particular, the presence of the α-Fe phase was not confirmed.
Claims (11)
サマリウム（Ｓｍ）、鉄（Ｆｅ）、コバルト（Ｃｏ）、ガリウム（Ｇａ）及び炭素（Ｃ）を含む原料を準備する工程、
準備した原料を配合する工程、
配合した原料を坩堝や鋳型に入れた後に、溶解鋳造して鋳塊にする工程、
前記鋳塊に熱処理を施して均質化する工程、及び
均質化した鋳塊を粉砕して粉砕粉にする工程、
を含む、方法。
The method for producing a magnetic powder according to any one of claims 1 to 10, wherein the following steps;
Step of preparing raw materials containing samarium (Sm), iron (Fe), cobalt (Co), gallium (Ga) and carbon (C),
The process of blending the prepared raw materials,
The process of putting the mixed raw materials in a crucible or mold and then melting and casting them into ingots.
A step of heat-treating the ingot to homogenize it, and a step of crushing the homogenized ingot into pulverized powder.
Including, how.
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