JP2020102552A - RFeB SINTERED MAGNET AND MANUFACTURING METHOD THEREOF - Google Patents
RFeB SINTERED MAGNET AND MANUFACTURING METHOD THEREOF Download PDFInfo
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- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 2
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Abstract
Description
本発明は、R（希土類元素）、Fe（鉄）及びB（硼素）を含有するRFeB系焼結磁石及びその製造方法に関する。 The present invention relates to an RFeB-based sintered magnet containing R (rare earth element), Fe (iron) and B (boron) and a method for manufacturing the same.
RFeB系焼結磁石は、1982年に佐川眞人らによって見出されたものであり、残留磁束密度等の多くの磁気特性がそれまでの永久磁石よりもはるかに高いという特長を有する。そのため、RFeB系焼結磁石は、ハイブリッド自動車・電気自動車の走行用モータや、その他の様々な製品に使用されている。 The RFeB system sintered magnet was discovered by Masato Sagawa in 1982, and has many magnetic properties such as residual magnetic flux density which are far higher than those of conventional permanent magnets. Therefore, the RFeB system sintered magnet is used for a running motor of hybrid vehicles and electric vehicles, and various other products.
RFeB系焼結磁石は、酸素ガスや酸性の液体等に接触すると、それらと反応して腐食し、崩壊する。そのような崩壊を防止するために、従来より、RFeB系焼結磁石の表面に樹脂製や金属製の被膜を設けることが行われている。樹脂製の被膜にはエポキシ樹脂製のものが、金属製の被膜にはNi（ニッケル）メッキによるものが、主に使用されている。 When the RFeB system sintered magnet comes into contact with oxygen gas or an acidic liquid, it reacts with them to corrode and collapse. In order to prevent such collapse, a resin or metal coating has been conventionally provided on the surface of the RFeB sintered magnet. Epoxy resin coatings are mainly used for resin coatings, and Ni (nickel) plating coatings are mainly used for metal coatings.
RFeB系焼結磁石を崩壊させる原因となるものの1つに、水素ガスがある。例えば、半導体製造装置では、半導体の基板をエッチングするために水素が用いられることがある。この場合、密閉容器内に設けられた基板台に半導体の基板を配置したうえで該密閉容器内に水素ガスを導入し、エッチングを行った後、該基板を密閉容器の外に取り出す。ここで、密閉容器の外から基板台に基板を搬入し、基板台から密閉容器の外に基板を搬出するための基板搬送装置にはモータが用いられ、このモータにRFeB系焼結磁石が使用されることがある。このような半導体製造装置では、水素ガスを密閉容器内から排出してから基板の搬出入を行うものの、その際にわずかに密閉容器内に残留した水素ガスが密閉容器内から漏出することがある。このような水素ガスは、基板搬送装置のモータのRFeB系焼結磁石に接触することがある。 Hydrogen gas is one of the factors that cause RFeB sintered magnets to collapse. For example, in a semiconductor manufacturing apparatus, hydrogen may be used to etch a semiconductor substrate. In this case, a semiconductor substrate is placed on a substrate table provided in the closed container, hydrogen gas is introduced into the closed container, etching is performed, and then the substrate is taken out of the closed container. Here, a motor is used for the substrate transfer device for loading the substrate into the substrate table from the outside of the hermetic container and taking the substrate out of the hermetic container from the substrate table, and the RFeB sintered magnet is used for this motor. It may be done. In such a semiconductor manufacturing apparatus, hydrogen gas is discharged from the closed container before the substrate is loaded and unloaded, but at that time, the hydrogen gas slightly remaining in the closed container may leak out from the closed container. .. Such hydrogen gas may come into contact with the RFeB system sintered magnet of the motor of the substrate transfer device.
RFeB焼結磁石では、希土類元素がほぼ単体の状態で存在する希土類リッチ相が粒界に形成されていることが知られている。この希土類リッチ相に水素ガスの分子が到達すると、希土類リッチ相が水素分子を吸蔵して脆化し、RFeB系焼結磁石が崩壊する。水素ガスの分子はエポキシ樹脂被膜を透過するため、このように水素ガスに接触し得る使用環境ではエポキシ樹脂製の被膜は十分な保護膜とはならず、そのような被膜が設けられたRFeB系焼結磁石は崩壊してしまう。また、Niメッキ被膜は被膜作製時に微小な（径が数十μmの）孔（ピンホール）が形成されることが避けられず、Niメッキ被膜が設けられたRFeB系焼結磁石も、このピンホールを通して水素ガスの分子が被膜を透過し、崩壊してしまう。 It is known that in a RFeB sintered magnet, a rare earth-rich phase in which a rare earth element exists in a substantially simple substance state is formed at a grain boundary. When hydrogen gas molecules reach this rare earth-rich phase, the rare earth-rich phase occludes hydrogen molecules and embrittles, and the RFeB sintered magnet collapses. Since molecules of hydrogen gas pass through the epoxy resin film, the epoxy resin film does not serve as a sufficient protective film in the use environment where it can come into contact with hydrogen gas as described above. The sintered magnet will collapse. In addition, it is unavoidable that the Ni plating film has minute holes (diameter of several tens of μm) (pin hole) formed during the film preparation, and the RFeB system sintered magnet with the Ni plating film also has this pin. Hydrogen gas molecules permeate the coating through the holes and collapse.
特許文献１には、Pd（パラジウム）メッキによる被膜を備えるRFeB系焼結磁石が記載されている。この文献によれば、Pdメッキによる被膜を備えるRFeB系焼結磁石は100ppm、120℃の水素ガス雰囲気に1000時間晒しても崩壊が見られず、実用上十分な耐水素性を有する。しかし、PdメッキはNiメッキよりも高価であるため、RFeB系焼結磁石の製造コストが上昇してしまう。 Patent Document 1 describes an RFeB-based sintered magnet provided with a coating film formed by Pd (palladium) plating. According to this document, the RFeB-based sintered magnet provided with a film formed by Pd plating does not collapse even when exposed to a hydrogen gas atmosphere at 100 ppm and 120° C. for 1000 hours, and has practically sufficient hydrogen resistance. However, since Pd plating is more expensive than Ni plating, the manufacturing cost of the RFeB system sintered magnet increases.
本発明が解決しようとする課題は、低いコストで製造することができ、且つ従来よりも高い耐水素性を有するRFeB系焼結磁石及びその製造方法を提供することである。 The problem to be solved by the present invention is to provide an RFeB-based sintered magnet which can be manufactured at low cost and has higher hydrogen resistance than ever before, and a manufacturing method thereof.
上記課題を解決するために成された本発明に係るRFeB系焼結磁石は、
希土類元素であるRと、FeとBとを含有するRFeB系焼結体と、
前記RFeB系焼結体の表面から内部に向かって減少する濃度勾配を有するように、該RFeB系焼結体の粒界に存在するCu（銅）と、
前記RFeB系焼結体の表面を覆うNiメッキによる保護層と
を備えることを特徴とする。
RFeB system sintered magnet according to the present invention made to solve the above problems,
R, which is a rare earth element, and an RFeB-based sintered body containing Fe and B,
To have a concentration gradient that decreases from the surface of the RFeB-based sintered body toward the inside, Cu (copper) present in the grain boundary of the RFeB-based sintered body,
A protective layer formed by Ni plating covering the surface of the RFeB-based sintered body is provided.
本発明に係るRFeB系焼結磁石の製造方法は、
希土類元素であるRと、FeとBとを含有するRFeB系焼結体の表面に、Cuを含む付着物を付着させたうえで加熱することにより、該Cuを該RFeB系焼結体の粒界に拡散させる粒界拡散処理工程と、
前記粒界拡散処理工程を行った後の前記RFeB系焼結体の表面にNiメッキを施すNiメッキ工程と
を有することを特徴とする。
The manufacturing method of the RFeB system sintered magnet according to the present invention,
R, which is a rare earth element, and the surface of the RFeB-based sintered body containing Fe and B, by depositing a deposit containing Cu and then heating the Cu, grains of the RFeB-based sintered body Grain boundary diffusion treatment step of diffusing into the boundary,
And a Ni plating step of performing Ni plating on the surface of the RFeB-based sintered body after the grain boundary diffusion processing step.
前述のように、従来のRFeB系焼結磁石では、希土類元素がほぼ単体の状態で存在する希土類リッチ相が粒界に形成されている。それに対して本発明に係るRFeB系焼結磁石では、RFeB系焼結体の粒界にCuが存在する。このように粒界に存在するCuは、希土類元素と合金（R-Cu合金）を形成している。R-Cu合金は希土類リッチ相よりも水素による脆化が生じ難い。 As described above, in the conventional RFeB-based sintered magnet, the rare earth-rich phase in which the rare earth element exists in a substantially simple state is formed at the grain boundary. On the other hand, in the RFeB system sintered magnet according to the present invention, Cu exists in the grain boundary of the RFeB system sintered body. As described above, Cu existing in the grain boundary forms an alloy (R-Cu alloy) with the rare earth element. R-Cu alloys are less prone to hydrogen embrittlement than rare earth-rich phases.
本発明に係るRFeB系焼結磁石によれば、その表面にNiメッキによる保護層を有することにより、水素ガスに晒されたときに、該保護層に形成されることが避けられないピンホールのところを除いて、水素分子がRFeB系焼結体に到達することが防止される。さらに、水素分子がピンホールを通過してRFeB系焼結体に到達しても、希土類リッチ相よりも水素による脆化が生じ難いR-Cu合金が粒界に存在するため、RFeB系焼結体の崩壊が生じることが抑えられる。これにより、本発明に係るRFeB系焼結磁石は、従来よりも高い耐水素性を有する。 According to the RFeB-based sintered magnet of the present invention, by having a protective layer by Ni plating on the surface, when exposed to hydrogen gas, it is unavoidable that pinholes are formed in the protective layer. Except for this, hydrogen molecules are prevented from reaching the RFeB-based sintered body. Furthermore, even if hydrogen molecules pass through the pinholes and reach the RFeB-based sintered body, the R-Cu alloy, which is less likely to be embrittled by hydrogen than the rare earth-rich phase, exists at the grain boundary. It prevents the body from collapsing. As a result, the RFeB system sintered magnet according to the present invention has higher hydrogen resistance than before.
また、保護層には、高価なPdメッキを用いることなく、従来と同様の比較的安価なNiメッキを用いることができるうえに、RFeB系焼結体の粒界に拡散させるCuも比較的安価であるため、低いコストで製造することができる。 Further, for the protective layer, it is possible to use the relatively inexpensive Ni plating similar to the conventional one without using the expensive Pd plating, and also the Cu diffused to the grain boundary of the RFeB system sintered body is relatively inexpensive. Therefore, it can be manufactured at low cost.
仮に、RFeB系磁石の原料の粉末にCuを混合したうえで該粉末を焼結することによってRFeB系焼結体を作製すると、該RFeB系焼結体の粒界には、Cuと希土類元素から成る合金が形成されると共に、Rリッチ相も形成される。このようなRFeB系焼結体の表面にNiメッキを施すことで作製されたRFeB系焼結磁石は、水素分子がNiメッキのピンホールを通過してRFeB系焼結体に到達したときに、粒界中のRリッチ相が脆化し、崩壊が生じてしまう。そこで、本発明に係るRFeB系焼結磁石の製造方法では、RFeB系焼結体の表面にCuを含む付着物を付着させたうえで加熱することにより、該Cuを該RFeB系焼結体の粒界に拡散させるという、粒界拡散処理を行う。これにより、RFeB系焼結体の粒界に存在する希土類リッチ相を優先的にCuと合金化させることができる。すなわち上記R-Cu合金を形成することができる。このように粒界拡散処理によってCuをRFeB系焼結体の粒界に拡散させるため、本発明に係るRFeB焼結磁石は、CuがRFeB系焼結体の表面から内部に向かって減少する濃度勾配を有する。従って、水素分子の影響を受けやすいRFeB系焼結体の表面に近いほどCuの濃度が高くなってR-Cu合金が形成され易くなるため、水素ガスによるRFeB系焼結体の崩壊を効果的に抑えることができる。 If an RFeB-based sintered body is produced by mixing Cu into the powder of the raw material of the RFeB-based magnet and then sintering the powder, the grain boundary of the RFeB-based sintered body contains Cu and a rare earth element. And an R-rich phase is formed. The RFeB system sintered magnet produced by applying Ni plating to the surface of such RFeB system sintered body, when the hydrogen molecules reach the RFeB system sintered body through the Ni-plated pinhole, The R-rich phase in the grain boundary becomes brittle and collapses. Therefore, in the method for producing an RFeB-based sintered magnet according to the present invention, by heating after depositing a deposit containing Cu on the surface of the RFeB-based sintered body, the Cu of the RFeB-based sintered body is heated. Grain boundary diffusion processing of diffusing to grain boundaries is performed. As a result, the rare earth-rich phase existing at the grain boundaries of the RFeB-based sintered body can be preferentially alloyed with Cu. That is, the above R-Cu alloy can be formed. Since Cu is diffused to the grain boundaries of the RFeB-based sintered body by the grain boundary diffusion treatment in this manner, the RFeB sintered magnet according to the present invention has a concentration in which Cu decreases from the surface of the RFeB-based sintered body toward the inside. Has a gradient. Therefore, the closer to the surface of the RFeB-based sintered body that is easily affected by hydrogen molecules, the higher the concentration of Cu and the more easily the R-Cu alloy is formed, so that the collapse of the RFeB-based sintered body by hydrogen gas is effective. Can be reduced to
本発明に係るRFeB系焼結磁石の製造方法において、前記付着物は（Cuと共に）Al（アルミニウム）を含有していることが好ましい。これにより、Alが粒界に拡散することで該粒界に存在する希土類リッチ相の融点が低下し、粒界が融解するため、Cuが粒界に拡散し易くなる。このようにAlが粒界に拡散した本発明に係るRFeB系焼結磁石は、RFeB系焼結体の表面から内部に向かって減少する濃度勾配を有するようにAlが粒界に存在するという特徴を有する。 In the method for producing a RFeB sintered magnet according to the present invention, it is preferable that the deposit contains Al (aluminum) (along with Cu). As a result, the diffusion of Al into the grain boundary lowers the melting point of the rare earth-rich phase existing in the grain boundary, and the grain boundary melts, so that Cu easily diffuses into the grain boundary. In this way, the RFeB-based sintered magnet according to the present invention in which Al is diffused into the grain boundaries is characterized in that Al exists in the grain boundaries so as to have a concentration gradient that decreases from the surface of the RFeB-based sintered body toward the inside. Have.
本発明に係るRFeB系焼結磁石の製造方法において、前記付着物は（Cuと共に、又はCu及びAlと共に）Dy（ジスプロシウム）及び／又はTb（テルビウム）を含有していることが好ましい。これにより、RFeB系の結晶粒の内部にDy及び／又はTbが深く浸透することなく、該結晶粒の表面付近にのみDy及び／又はTbが供給される。RFeB系焼結磁石にDy及び／又はTbを添加すると、保磁力は向上するのに対して残留磁束密度は低下することが知られているが、Dy及び／又はTbがRFeB系の結晶粒の表面付近にのみ供給されると、残留磁束密度の低下は抑えられつつ保磁力が向上する。このようにDy及び／又はTbが拡散した本発明に係るRFeB系焼結磁石は、RFeB系焼結体の表面から内部に向かって減少する濃度勾配を有するようにDy及び／又はTbが粒界に存在するという特徴を有する。 In the method for producing an RFeB-based sintered magnet according to the present invention, it is preferable that the deposit contains Dy (dysprosium) and/or Tb (terbium) (with Cu or with Cu and Al). As a result, Dy and/or Tb are supplied only to the vicinity of the surface of the crystal grains without deeply penetrating Dy and/or Tb into the RFeB-based crystal grains. It is known that when Dy and/or Tb is added to the RFeB system sintered magnet, the coercive force is improved but the residual magnetic flux density is decreased. However, Dy and/or Tb are RFeB system crystal grains. When supplied only near the surface, the coercive force is improved while suppressing the decrease in residual magnetic flux density. The RFeB-based sintered magnet according to the present invention in which Dy and/or Tb are diffused in this way has a concentration gradient in which Dy and/or Tb decreases from the surface to the inside of the RFeB-based sintered body. It is characterized by being present in.
本発明により、低いコストで製造することができ、且つ従来よりも高い耐水素性を有するRFeB系焼結磁石及びその製造方法が得られる。 According to the present invention, it is possible to obtain an RFeB-based sintered magnet which can be manufactured at low cost and has higher hydrogen resistance than conventional ones, and a manufacturing method thereof.
以下、図１〜図４を用いて、本発明に係るRFeB系焼結磁石及びその製造方法を説明する。 Hereinafter, an RFeB system sintered magnet according to the present invention and a method for manufacturing the same will be described with reference to FIGS. 1 to 4.
(1) 本発明に係るRFeB系焼結磁石の製造方法の一実施形態
図１を用いて、本発明に係るRFeB系焼結磁石の製造方法の一実施形態を説明する。
(1) One Embodiment of Manufacturing Method of RFeB Sintered Magnet According to Present Invention One embodiment of manufacturing method of RFeB sintered magnet according to the present invention will be described with reference to FIG.
(1-1) RFeB系焼結体作製工程
初めに、RFeB系焼結体１１を作製する方法の一例を説明する。なお、RFeB系焼結体１１の作製方法は以下に述べるものには限定されず、RFeB系焼結磁石を製造する際に用いられる通常の方法を用いることができる。
(1-1) RFeB-based Sintered Body Manufacturing Step First, an example of a method for manufacturing the RFeB-based sintered body 11 will be described. The method for producing the RFeB-based sintered body 11 is not limited to the one described below, and an ordinary method used when manufacturing an RFeB-based sintered magnet can be used.
まず、R（希土類元素）、Fe及びBを含有する（その他の元素を含んでいてもよい）RFeB系合金材１１１を作製する。RFeB系合金材１１１は、例えばストリップキャスト法等、周知の方法より作製することができる。 First, the RFeB-based alloy material 111 containing R (rare earth element), Fe and B (which may contain other elements) is prepared. The RFeB alloy material 111 can be manufactured by a known method such as a strip casting method.
次に、RFeB系合金材１１１を粉砕することにより、RFeB系磁石粉末１１２を作製する。RFeB系磁石粉末１１２は、例えば、まずRFeB系合金材１１１に水素を吸蔵させることで該RFeB系合金材１１１を脆化させ（図１(a)）たうえで機械的に粉砕することにより粗粉１１２１（図１(b)）を作製し、その後、ジェットミル等を用いて微粉砕することによって得る（図１(c)）ことができる。RFeB系磁石粉末１１２は、粒径の中央値D50が数μm、好ましくは3μm以下の粒度分布となるようにする。 Next, the RFeB-based alloy material 111 is crushed to produce RFeB-based magnet powder 112. The RFeB-based magnet powder 112 may be formed by, for example, first occluding hydrogen in the RFeB-based alloy material 111 to embrittle the RFeB-based alloy material 111 (FIG. 1(a)) and then mechanically crushing it. The powder 1121 (FIG. 1(b)) is produced, and then finely pulverized using a jet mill or the like (FIG. 1(c)). The RFeB-based magnet powder 112 has a median particle diameter D50 of several μm, preferably 3 μm or less.
次に、製造しようとするRFeB系焼結体１１に対応した形状を有するモールド１１３にRFeB系磁石粉末１１２を収容し、モールド１１３に蓋を取り付けたうえで、モールド１１３内のRFeB系磁石粉末１１２に磁界を印加することにより、RFeB系磁石粉末１１２の粒子を配向させる（図１(d)）。続いて、RFeB系磁石粉末１１２をモールド１１３から取り出すことなく、所定の焼結温度（900〜1050℃の範囲内の温度が好ましい）に加熱することにより、RFeB系磁石粉末１１２を焼結させる（図１(e)）。これにより、RFeB系焼結体１１が得られる（図１(f)）。なお、モールド１１３には、焼結温度において耐熱性を有する材料から成るものを用いる。 Next, the RFeB-based magnet powder 112 is housed in a mold 113 having a shape corresponding to the RFeB-based sintered body 11 to be manufactured, the lid is attached to the mold 113, and the RFeB-based magnet powder 112 in the mold 113 is then attached. By applying a magnetic field to the particles, the particles of the RFeB-based magnet powder 112 are oriented (FIG. 1(d)). Subsequently, without removing the RFeB-based magnet powder 112 from the mold 113, the RFeB-based magnet powder 112 is heated to a predetermined sintering temperature (a temperature in the range of 900 to 1050° C. is preferable) to sinter the RFeB-based magnet powder 112 ( Figure 1(e)). As a result, the RFeB system sintered body 11 is obtained (FIG. 1(f)). The mold 113 is made of a material having heat resistance at the sintering temperature.
ここまでに述べたRFeB系焼結体１１を作製する際の各工程は、RFeB系合金材１１１及びRFeB系磁石粉末１１２が酸化することを防止するために、真空中又は不活性ガス中等の無酸素雰囲気中で行う。 Each step in manufacturing the RFeB system sintered body 11 described so far is performed in vacuum or in an inert gas in order to prevent the RFeB system alloy material 111 and the RFeB system magnet powder 112 from being oxidized. Perform in an oxygen atmosphere.
ここまでに述べたRFeB系焼結体１１の作製方法では、RFeB系磁石粉末１１２を圧縮成形することなく焼結するPLP（プレスレスプロセス、Press-less process）法を用いているが、その代わりに、RFeB系磁石粉末１１２の粒子を配向させながら、又は配向させた後に、RFeB系磁石粉末１１２に圧力を印加することにより圧縮成形をしたうえで焼結を行ってもよい。 In the method for producing the RFeB-based sintered body 11 described above, the PLP (Pressless process) method of sintering the RFeB-based magnet powder 112 without compression molding is used. In addition, while orienting the particles of the RFeB-based magnet powder 112, or after orienting the particles, compression may be performed by applying pressure to the RFeB-based magnet powder 112 and then sintering.
(1-2) 粒界拡散処理工程
次に、得られたRFeB系焼結体１１に対して、以下のように粒界拡散処理を行う。
(1-2) Grain Boundary Diffusion Process Next, the grain boundary diffusion process is performed on the obtained RFeB-based sintered body 11 as follows.
まず、粒界拡散処理に用いる付着物１２を用意する。付着物１２は、後述のように粒界拡散処理においてRFeB系焼結体１１に付着させるものであり、少なくともCuを含有している。付着物１２は、Cuの他に、CuをRFeB系焼結体１１の粒界に拡散させやすくするための元素であるAlや、RFeB系焼結磁石の保磁力を向上させるための元素であるDy及び／又はTbを含有していてもよい。DyとTbのうち、DyはTbよりも価格が低いという点で好ましく、Tbは保磁力向上効果をより高くするという点で好ましい。付着物１２に含有させるものとして、これらCu、Al、並びにDy及び／又はTbの合金を用いてもよい。なお、本発明では、付着物１２は少なくともCuを含有していればよく、Al、Dy及びTbは必須ではない。付着物１２はさらに、それをRFeB系焼結体１１に付着させやすくするために粘着性を有するものを含有している。そのような粘着性を有するものとして、シリコーングリースやシリコーンオイル、あるいはそれらを混合したものから成るシリコーン系の有機溶剤を好適に用いることができる。付着物１２は、Cuを含有する金属や合金等を粉砕することで粉末にしたうえで、該粉末を、粘着性を有するものと混合することにより作製される。 First, the deposit 12 used for the grain boundary diffusion treatment is prepared. The deposit 12 is to be attached to the RFeB-based sintered body 11 in the grain boundary diffusion treatment as described later, and contains at least Cu. The deposit 12 is, in addition to Cu, Al that is an element for facilitating the diffusion of Cu into the grain boundaries of the RFeB-based sintered body 11 and an element for improving the coercive force of the RFeB-based sintered magnet. It may contain Dy and/or Tb. Of Dy and Tb, Dy is preferable in that it is lower in price than Tb, and Tb is preferable in that the coercive force improving effect is further enhanced. As the material to be contained in the deposit 12, these Cu, Al, and alloys of Dy and/or Tb may be used. In the present invention, the deposit 12 should contain at least Cu, and Al, Dy, and Tb are not essential. The deposit 12 further contains a sticky substance so that the deposit 12 can be easily attached to the RFeB-based sintered body 11. As such an adhesive, a silicone-based organic solvent composed of silicone grease, silicone oil, or a mixture thereof can be preferably used. The deposit 12 is produced by crushing a metal or alloy containing Cu into a powder, and then mixing the powder with a sticky substance.
次に、RFeB系焼結体１１の表面に付着物１２を付着させ（図１(g)）、真空中又は不活性ガス中等の無酸素雰囲気中において、所定の粒界拡散処理温度（700〜1000℃の範囲内の温度が好ましい）に加熱する（図１(h)）。これにより、付着物１２中のCuは、RFeB系焼結体１１の表面から粒界内に拡散する。付着物１２がAl、Dy及び／又はTbを含有している場合には、それらもRFeB系焼結体１１の表面から粒界内に拡散する。ここでAlは、それがRFeB系焼結体１１の粒界内に拡散することにより、該粒界内に存在する希土類リッチ相（RFeB系焼結体１１中の主相粒子よりも希土類元素の含有率が高いもの）の融点を低下させることで該希土類リッチ相を融解させ、それによりCuが粒界内に拡散し易くなる、という作用を奏する。その後、粒界拡散処理後のRFeB系焼結体１３の表面を研磨し、該表面に残存する付着物１２を除去する（図１(i)）。 Next, the deposit 12 is adhered to the surface of the RFeB-based sintered body 11 (FIG. 1(g)), and a predetermined grain boundary diffusion treatment temperature (700 to 700) is applied in an oxygen-free atmosphere such as vacuum or inert gas. The temperature is preferably in the range of 1000°C) (Fig. 1(h)). As a result, Cu in the deposit 12 diffuses from the surface of the RFeB-based sintered body 11 into the grain boundaries. When the deposit 12 contains Al, Dy and/or Tb, they also diffuse from the surface of the RFeB sintered body 11 into the grain boundaries. Here, Al is a rare earth-rich phase existing in the grain boundary of the RFeB-based sintered body 11 (due to diffusion of the rare-earth element more than the main phase particles in the RFeB-based sintered body 11). By lowering the melting point of the high content), the rare earth-rich phase is melted, whereby Cu easily diffuses into the grain boundaries. Then, the surface of the RFeB-based sintered body 13 after the grain boundary diffusion treatment is polished to remove the deposit 12 remaining on the surface (FIG. 1(i)).
(1-3) Niメッキ工程
次に、粒界拡散処理後の表面にNiメッキを施すことにより、該表面に保護層１４を形成する（図１(j)）。Niメッキは、電解メッキ法や無電解メッキ法等、従来よりRFeB系焼結磁石の表面に保護層を形成する際に用いられているものと同様の方法により行うことができる。
(1-3) Ni Plating Step Next, the surface after the grain boundary diffusion treatment is plated with Ni to form the protective layer 14 on the surface (FIG. 1(j)). The Ni plating can be performed by the same method as that conventionally used when forming the protective layer on the surface of the RFeB system sintered magnet, such as the electrolytic plating method and the electroless plating method.
以上の各工程により、本実施形態のRFeB系焼結磁石１０が得られる。 The RFeB system sintered magnet 10 of the present embodiment is obtained by the above steps.
(2) 本発明に係るRFeB系焼結磁石の一実施形態
図２を用いて、本発明に係るRFeB系焼結磁石の一実施形態を説明する。
(2) One Embodiment of RFeB System Sintered Magnet According to the Present Invention One embodiment of the RFeB system sintered magnet according to the present invention will be described with reference to FIG.
本実施形態のRFeB系焼結磁石１０は、図２に模式的に示すように、RFeB系の粒子である主相粒子１５が焼結したものであって、主相粒子１５同士の間に粒界１６が存在する。 The RFeB system sintered magnet 10 of the present embodiment is, as schematically shown in FIG. 2, obtained by sintering the main phase particles 15 which are RFeB system particles, and the main phase particles 15 have particles between them. There is a world 16.
粒界１６には、主相粒子１５が含有するものと同じ希土類元素（例えばNd（ネオジム））が存在すると共に、Cuが存在する。Cuは、上述のように粒界拡散処理によって粒界１６内に導入されていることから、RFeB系焼結磁石１０の表面から内部に向かって減少する濃度勾配を有している。こうして粒界１６内に存在するCuは、Cuが拡散する前のRFeB系焼結体１１の粒界に存在していた希土類リッチ相の希土類元素と合金（R-Cu合金）を形成している。 At the grain boundary 16, the same rare earth element (for example, Nd (neodymium)) as that contained in the main phase particles 15 exists, and Cu also exists. Since Cu is introduced into the grain boundary 16 by the grain boundary diffusion treatment as described above, it has a concentration gradient that decreases from the surface of the RFeB system sintered magnet 10 toward the inside. In this way, Cu existing in the grain boundary 16 forms an alloy (R-Cu alloy) with the rare earth-rich phase rare earth element existing in the grain boundary of the RFeB-based sintered body 11 before Cu diffusion. ..
また、本実施形態のRFeB系焼結磁石１０はさらに、粒界１６にAl、Dy及び／又はTbが、RFeB系焼結磁石１０の表面から内部に向かって減少する濃度勾配を有するように存在する。なお、これらAl、Dy及び／又はTbが粒界１６に存在することは、本発明の必須要件ではない。 Further, the RFeB-based sintered magnet 10 of the present embodiment further exists such that Al, Dy and/or Tb at the grain boundary 16 has a concentration gradient that decreases from the surface of the RFeB-based sintered magnet 10 toward the inside. To do. The presence of Al, Dy and/or Tb in the grain boundary 16 is not an essential requirement of the present invention.
Alは、前述のように、Cuを粒界内に拡散させ易くするために添加された元素である。 As described above, Al is an element added to facilitate the diffusion of Cu into the grain boundaries.
Dy及び／又はTbは、それらが粒界１６内に拡散しているのに伴い、主相粒子１５のうち該主相粒子１５の表面付近にも拡散している。但し、主相粒子１５内では、Dy及び／又はTbは表面付近にしか拡散せず、主相粒子１５内の奥深くまでは拡散していない。RFeB系焼結磁石の保磁力は一般に、主に主相粒子の表面付近で磁化が反転することが原因となって低下する。本実施形態のRFeB系焼結磁石１０は、主相粒子１５の表面付近にDy及び／又はTbが拡散していることにより、保磁力が向上する。一方、Dy及び／又はTbが主相粒子１５内の奥深くまでは拡散していないため、残留磁束密度が低下することが抑えられる。 Dy and/or Tb also diffuse in the vicinity of the surface of the main phase particles 15 among the main phase particles 15 as they diffuse in the grain boundaries 16. However, within the main phase particles 15, Dy and/or Tb diffuse only near the surface and do not diffuse deep inside the main phase particles 15. The coercive force of the RFeB system sintered magnet generally decreases mainly due to the reversal of the magnetization near the surface of the main phase particles. In the RFeB system sintered magnet 10 of the present embodiment, coercive force is improved because Dy and/or Tb are diffused near the surface of the main phase particles 15. On the other hand, since Dy and/or Tb are not diffused deep inside the main phase particles 15, it is possible to prevent the residual magnetic flux density from decreasing.
このようにCu等が粒界１６内に拡散したRFeB系焼結体１３の表面は、Niメッキによる保護層１４で覆われている。保護層１４は、その作製時に不可避的に形成されるピンホール１７を有している。ピンホール１７の径は通常数十μmである。径が30μm以上のピンホール１７は、形成される頻度が小さく、たとえ形成されていても、品質検査において検出することが可能であるため、そのようなピンホール１７が形成されているRFeB系焼結磁石１０は出荷段階で排除することができる。しかし、径が30μmを下回るピンホール１７は品質検査において検出することが困難であるため、そのようなピンホール１７が形成されているRFeB系焼結磁石１０が出荷されることは避け難い。 As described above, the surface of the RFeB-based sintered body 13 in which Cu or the like is diffused in the grain boundaries 16 is covered with the protective layer 14 made of Ni plating. The protective layer 14 has a pinhole 17 which is unavoidably formed during its production. The diameter of the pinhole 17 is usually several tens of μm. Since the pinholes 17 having a diameter of 30 μm or more are formed less frequently, and even if they are formed, it is possible to detect them in the quality inspection, the RFeB-based firing in which such pinholes 17 are formed is detected. Binder magnet 10 can be eliminated at the shipping stage. However, since it is difficult to detect the pinhole 17 having a diameter of less than 30 μm in the quality inspection, it is unavoidable to ship the RFeB system sintered magnet 10 in which the pinhole 17 is formed.
しかし、ピンホール１７の径が30μmを下回ると、酸素ガスや酸性の液体又は気体といったRFeB系焼結磁石を崩壊させる要因となるもののうちのほとんどが通過しないため、それらのものによってRFeB系焼結磁石１０が崩壊することはない。一方、RFeB系焼結磁石を崩壊させる要因の1つである水素ガスは、その分子が小さいため径が30μmを下回るピンホール１７を通過してRFeB系焼結体１３に到達し得る。しかしながら、RFeB系焼結磁石１０は、RFeB系焼結体１３の粒界１６内にCuが存在して希土類元素とR-Cu合金を形成しているため、希土類リッチ相が従来のRFeB系焼結磁石よりも少ない。そのため、たとえ水素ガスがRFeB系焼結体１３に到達しても、粒界１６が脆化し難い。そのため、本実施形態のRFeB系焼結磁石１０は、従来のRFeB系焼結磁石よりも、水素ガスによる崩壊が生じることを抑えることができる。 However, if the diameter of the pinhole 17 is less than 30 μm, most of the factors that cause the RFeB-based sintered magnet, such as oxygen gas or acidic liquid or gas, to collapse will not pass through. The magnet 10 will not collapse. On the other hand, hydrogen gas, which is one of the factors that causes the RFeB-based sintered magnet to collapse, can reach the RFeB-based sintered body 13 through the pinhole 17 having a diameter of less than 30 μm due to its small molecule. However, in the RFeB-based sintered magnet 10, since Cu is present in the grain boundaries 16 of the RFeB-based sintered body 13 to form the rare earth element and the R-Cu alloy, the rare earth-rich phase is burned in the conventional RFeB-based sintered body. Less than a magnet. Therefore, even if hydrogen gas reaches the RFeB-based sintered body 13, the grain boundaries 16 are unlikely to become brittle. Therefore, the RFeB system sintered magnet 10 of the present embodiment can suppress the collapse due to hydrogen gas more than the conventional RFeB system sintered magnet.
(3) 本実施形態のRFeB系焼結磁石を作製した実施例
次に、本実施形態のRFeB系焼結磁石を実際に作製した実施例を説明する。
(3) Example of Producing RFeB Sintered Magnet of Present Embodiment Next, an example of actually producing the RFeB sintered magnet of the present embodiment will be described.
(3-1) 実施例の試料の作製方法
この例では、Ndを26.7質量％、Pr（プラセオジム）を4.7質量％、Dyを0.3質量％、Tbを0.05質量％未満、Co（コバルト）を0.9質量％、Alを0.2質量％、Cuを0.1質量％、Bを1.0質量％、Feを残部として含有するRFeB系合金材１１１を用いた。RFeB系磁石粉末１１２は、粒径の中央値D50が3μmとなるように作製した。RFeB系焼結体１１の作製にはPLP法を用いた。得られたRFeB系焼結体１１は、寸法が15mm×25mm×5mmである直方体に加工し、縦横の寸法が15mm×25mmである2つの面に付着物１２を付着させて粒界拡散処理を行った。付着物１２にはTbCuAl合金の粉末とシリコーングリース等を混合したものを用い、粒界拡散処理温度は875℃、処理時間は17時間とした。ここでTbCuAl合金には、Tbを75.3質量％、Cuを18.8質量％、Alを5.9質量％、含有するものを用いた。保護層１４は、ワット浴を用いた電解メッキ法により作製した。保護層１４の厚みは約10μmとした。
(3-1) Method of preparing sample of Example In this example, Nd 26.7 mass%, Pr (praseodymium) 4.7 mass%, Dy 0.3 mass%, Tb less than 0.05 mass%, Co (cobalt) 0.9. An RFeB-based alloy material 111 containing 100% by mass, 0.2% by mass of Al, 0.1% by mass of Cu, 1.0% by mass of B, and the balance of Fe was used. The RFeB magnet powder 112 was manufactured so that the median particle diameter D50 was 3 μm. The PLP method was used to manufacture the RFeB-based sintered body 11. The obtained RFeB-based sintered body 11 is processed into a rectangular parallelepiped having dimensions of 15 mm×25 mm×5 mm, and the deposit 12 is attached to the two surfaces having vertical and horizontal dimensions of 15 mm×25 mm to perform grain boundary diffusion treatment. went. As the deposit 12, a mixture of TbCuAl alloy powder and silicone grease was used, the grain boundary diffusion treatment temperature was 875° C., and the treatment time was 17 hours. Here, as the TbCuAl alloy, one containing 75.3% by mass of Tb, 18.8% by mass of Cu, and 5.9% by mass of Al was used. The protective layer 14 was produced by an electrolytic plating method using a Watts bath. The thickness of the protective layer 14 was about 10 μm.
比較例として、TbCuAl合金の代わりにTbNiAl合金（Tb：92.0質量％、Ni（ニッケル）：4.3質量％、Al：3.7質量％）の粉末を付着物１２に用いた点を除いて、上記実施例と同じ方法でRFeB系焼結磁石を作製した。 As a comparative example, a powder of a TbNiAl alloy (Tb: 92.0 mass%, Ni (nickel): 4.3 mass%, Al: 3.7 mass%) was used as the deposit 12 instead of the TbCuAl alloy, except that the above-mentioned Example was used. An RFeB system sintered magnet was produced by the same method as described above.
(3-2) 実施例の試料における元素の含有率（濃度）、分布測定
本実施例のRFeB系焼結磁石を作製する際に用いた、粒界拡散処理工程の後であってNiメッキ工程の前の段階のRFeB系焼結体１３につき、縦横の寸法が15mm×25mmである1つの面からの深さ方向の位置毎にCu及びTbの含有率（濃度）を測定した結果を図３に示す。試料の厚みが約5mm（厳密には、5mmよりもわずかに薄い）であるため、図３に示した深さ0〜5mmの範囲のデータは、その両端がRFeB系焼結磁石の表面におけるCu及びTbの含有率を示している。これらのデータより、Cu及びTbのいずれも、RFeB系焼結磁石の表面から内部に向かって減少する濃度勾配を有することがわかる。なお、上記のようにこれらのデータはRFeB系焼結体１３を対象として測定したものであるが、Niメッキ工程ではCu及びTbが移動しないため、実施例の試料も同様の濃度勾配を有すると考えられる。Cu及びTbがそれぞれ結晶粒と粒界のいずれに存在するかという点は、このデータでは不明であるが、Cuに関しては次に述べるSEM-EDXの測定結果で確認することができる。Tbに関しては、本実施例のように粒界拡散法によってRFeB系焼結磁石内に拡散させた場合には、そのほとんどが粒界に存在することは、当業者において周知なことである。
(3-2) Content (concentration) and distribution measurement of elements in the sample of the example, which was used when the RFeB system sintered magnet of this example was manufactured, after the grain boundary diffusion treatment step and after the Ni plating step Fig. 3 shows the results of measuring the Cu and Tb content rates (concentrations) at each position in the depth direction from one surface of which the vertical and horizontal dimensions are 15 mm × 25 mm for the RFeB-based sintered body 13 at the stage before Shown in. Since the thickness of the sample is about 5 mm (strictly, slightly thinner than 5 mm), the data in the depth range of 0 to 5 mm shown in FIG. And Tb content are shown. From these data, it is understood that both Cu and Tb have a concentration gradient that decreases from the surface to the inside of the RFeB sintered magnet. As described above, these data are measured for the RFeB-based sintered body 13, but Cu and Tb do not move in the Ni plating step, so that the sample of the example also has a similar concentration gradient. Conceivable. It is not clear from this data whether Cu and Tb are present in the crystal grains or grain boundaries, respectively, but Cu can be confirmed by the measurement results of SEM-EDX described below. As for Tb, it is well known to those skilled in the art that most of Tb exists in the grain boundaries when diffused in the RFeB system sintered magnet by the grain boundary diffusion method as in the present embodiment.
図４に、本実施例のRFeB系焼結磁石につき、(a)表面に垂直な断面におけるSEM（走査電子顕微鏡）写真、並びに同断面において(b)Nd原子、(c)Ni原子及び(d)Cu原子の含有率（濃度）の分布をSEM-EDX（走査電子顕微鏡−エネルギー分散型X線元素分析）装置で測定した結果を示す。SEM写真において、左上側にある、周囲よりも濃い灰色の部分は保護層１４であり、それよりも右下側の部分は粒界拡散処理後のRFeB系焼結体１３である。白色の箇所はRFeB系焼結磁石を構成する他の元素よりも原子番号が大きい希土類元素が存在する部分、黒色の箇所はRFeB系焼結磁石を構成する元素のうち希土類元素よりも原子番号が小さい元素のみが存在するか、又は空気が存在する部分である。(b)〜(d)の各図は、(a)で示したSEM写真と同じ部分を示しており、白色に近いほど、対応する原子（Nd, Ni, Cuのいずれか）が多いことを示している。なお、(d)では保護層１４が周囲よりも白色に近い色で示されているが、実際には保護層１４にCuは存在しない。 FIG. 4 is a SEM (scanning electron microscope) photograph of a cross section perpendicular to the surface of (a) the RFeB system sintered magnet of this example, and (b) Nd atom, (c) Ni atom and (d) in the cross section. ) The result of having measured the distribution of the content rate (concentration) of Cu atom by SEM-EDX (scanning electron microscope-energy dispersive X-ray elemental analysis) device is shown. In the SEM photograph, the portion on the upper left side, which is darker in gray than the surroundings, is the protective layer 14, and the portion on the lower right side is the RFeB-based sintered body 13 after the grain boundary diffusion treatment. The white part is where there is a rare earth element whose atomic number is larger than the other elements that make up the RFeB system sintered magnet, and the black part has an atomic number higher than the rare earth element among the elements that make up the RFeB system sintered magnet. A part where only small elements are present or where air is present. Each of (b) to (d) shows the same part as the SEM photograph shown in (a), and the closer it is to white, the more corresponding atom (any of Nd, Ni, Cu). Showing. Although the protective layer 14 is shown in a color closer to white than the surroundings in (d), Cu is not actually present in the protective layer 14.
図４(b)及び(d)より、Nd原子とCu原子は、同じ位置において含有率が高い傾向があることがわかる。ここでNd原子の含有率が周囲よりも高い領域は、粒界拡散処理を行う前のRFeB系焼結磁石において粒界のNdリッチ相であったところであると考えられる。本実施例のRFeB系焼結磁石では、このNdリッチ相であった領域にCu原子も存在することから、Ndリッチ相の代わりにNd-Cu合金が粒界に生成されていると考えられる。一方、Nd原子の含有率が周囲よりも高くCu原子が存在しない領域は、図４(b)及び(d)にはほとんど見られない。本実施例のRFeB系焼結磁石では、このようにNdリッチ相の代わりにNd-Cu合金が粒界に生成されていることにより、水素ガスが保護層１４を通過してRFeB系焼結体１３に到達しても、粒界１６が脆化し難く、水素ガスによる崩壊が生じることを抑えることができる。 From FIGS. 4B and 4D, it can be seen that the Nd atom and the Cu atom tend to have a high content at the same position. Here, it is considered that the region where the content ratio of Nd atoms is higher than that of the surroundings is the Nd-rich phase of the grain boundary in the RFeB system sintered magnet before the grain boundary diffusion treatment. In the RFeB-based sintered magnet of this example, Cu atoms also exist in the region that was in the Nd-rich phase, so it is considered that Nd-Cu alloy is generated at the grain boundaries instead of the Nd-rich phase. On the other hand, a region where the content of Nd atoms is higher than that of the surroundings and Cu atoms do not exist is hardly seen in FIGS. 4B and 4D. In the RFeB system sintered magnet of the present example, since the Nd-Cu alloy is generated at the grain boundaries instead of the Nd rich phase in this way, hydrogen gas passes through the protective layer 14 and the RFeB system sintered body is obtained. Even when it reaches 13, the grain boundary 16 is less likely to be embrittled, and it is possible to suppress the occurrence of collapse due to hydrogen gas.
また、図４(b)及び(c)より、RFeB系焼結体１３の表面付近には、それよりもRFeB系焼結体１３の深部側と対比して、Ndの含有率が低く、且つNiの含有率が高い領域が存在することがわかる。この領域では、RFeB系焼結体１３の表面にNiメッキを施す際にワット浴が有する酸がRFeB系焼結体１３の表面付近の粒界に浸透してNdリッチ相が溶解し、Ndリッチ相が存在しなくなった領域にNiが充填されている、と考えられる。その結果、本実施例のRFeB系焼結磁石１０では、RFeB系焼結体１３の表面付近にNdリッチ相が存在しないという点においても、保護層１４を通過した水素ガスによる崩壊が生じることを抑えることができる。 Further, as shown in FIGS. 4B and 4C, near the surface of the RFeB system sintered body 13, the Nd content is lower than that in the deep side of the RFeB system sintered body 13, and It can be seen that there is a region where the Ni content is high. In this region, when the surface of the RFeB-based sintered body 13 is plated with Ni, the acid contained in the Watt bath penetrates into the grain boundaries near the surface of the RFeB-based sintered body 13 to dissolve the Nd-rich phase, and thus the Nd-rich phase is dissolved. It is considered that Ni is filled in the region where the phase no longer exists. As a result, in the RFeB-based sintered magnet 10 of the present example, the fact that the Nd-rich phase does not exist near the surface of the RFeB-based sintered body 13 also causes the collapse due to the hydrogen gas that has passed through the protective layer 14. Can be suppressed.
なお、図４では、保護層１４にピンホールは見られない。但し、本実施例の方法では、保護層１４にピンホールが形成されることを確実に防ぐことは困難である。 Note that in FIG. 4, no pinhole is found in the protective layer 14. However, according to the method of this embodiment, it is difficult to reliably prevent the formation of pinholes in the protective layer 14.
(3-3) 実施例及び比較例の試料における耐水素試験
次に、実施例及び比較例の試料をそれぞれ4個ずつ用意し、以下の方法で耐水素試験を行った。まず、レーザ加工法により、各試料の保護層１４にそれぞれ、RFeB系焼結体１３の表面まで達する直径30μmの孔を2個ずつ形成した。この孔は、保護層１４の作製時に形成され得るピンホールに相当する。つまり、この試験は、保護層１４にピンホールが存在する場合における耐水素性を調べることを意味している。
(3-3) Hydrogen Resistance Test on Samples of Examples and Comparative Examples Next, four samples of Examples and Comparative Examples were prepared, and a hydrogen resistance test was performed by the following method. First, two holes each having a diameter of 30 μm reaching the surface of the RFeB-based sintered body 13 were formed in the protective layer 14 of each sample by the laser processing method. This hole corresponds to a pinhole that can be formed when the protective layer 14 is manufactured. That is, this test means to examine the hydrogen resistance when the protective layer 14 has pinholes.
次に、各試料の質量を測定した。この質量を「開始時質量」とする。続いて、各試料を密閉槽に収容し、該密閉槽に、温度が80℃、圧力が2気圧となるように水素ガスを導入した。水素ガスの導入から所定時間経過後に密閉槽から各試料を取り出し、各試料の質量を測定した。この質量が開始時質量よりも3％以上減少している試料は、水素による崩壊が発生していると判定される。崩壊が発生していると判定されなかった試料は密閉槽に戻し、さらに所定時間経過後に試料の質量を測定する、という操作を繰り返した。 Next, the mass of each sample was measured. This mass is referred to as "starting mass". Subsequently, each sample was housed in a closed tank, and hydrogen gas was introduced into the closed tank so that the temperature was 80° C. and the pressure was 2 atm. Each sample was taken out from the closed tank after a predetermined time elapsed from the introduction of hydrogen gas, and the mass of each sample was measured. A sample in which this mass is reduced by 3% or more from the starting mass is judged to have undergone hydrogen-induced disintegration. The operation of returning the sample that was not determined to have been disintegrated to the closed tank and measuring the mass of the sample after a lapse of a predetermined time was repeated.
試験結果を表１に示す。
この表において「時間」は耐水素試験を開始してからの経過時間である。表中に○印が記載されている欄は、その欄に対応する経過時間において4個ともに水素ガスによる崩壊が発生していないことを示している。また、表中に数値のみが記載されている欄は、その欄に対応する経過時間において崩壊が生じていない試料の個数を示している。「平均耐水素時間」は、各試料において、崩壊が確認された経過時間の1つ前に、崩壊されていないことが確認された経過時間を当該試料の耐水素時間（水素ガスによって崩壊しなかった時間）とし、実施例及び比較例のそれぞれにおいて4個の試料の耐水素時間を平均した値（単位は「時間」）で定義する。実施例の平均耐水素時間は、比較例（9.3時間）よりも長い15時間であった。 In this table, "time" is the elapsed time from the start of the hydrogen resistance test. In the table, the column marked with a circle indicates that no collapse by hydrogen gas has occurred in the four elapsed times corresponding to that column. Further, in the table, a column in which only numerical values are described indicates the number of samples in which disintegration has not occurred in the elapsed time corresponding to the column. The "average hydrogen withstand time" is the hydrogen withstand time of the sample (not broken by hydrogen gas), which is the elapsed time that was confirmed to have not collapsed one time before the time when collapse was confirmed in each sample. Defined as a value (unit is “hour”) obtained by averaging the hydrogen withstanding times of four samples in each of the example and the comparative example. The average hydrogen withstand time of the example was 15 hours, which was longer than that of the comparative example (9.3 hours).
ここで求めた平均耐水素時間の評価について説明する。常圧であって水素以外の気体が大気である場合には、水素の濃度が4％以上になると爆発の危険性が生じる。そのため、密閉された水素が常圧の大気中に漏出した際の水素の許容濃度は、4％よりも十分に低い0.1％（1000ppm）に設定されることが多い。その場合の水素分圧は0.001気圧となる。耐水素試験における水素の圧力がP気圧、平均耐水素時間がh時間である場合には、耐水素試験と同じ温度における分圧0.001気圧の水素に対する平均耐水素時間は、(P/0.001)×hとなる。 The evaluation of the average hydrogen withstand time obtained here will be described. If atmospheric pressure is the normal pressure and gases other than hydrogen are present, there is a danger of explosion if the hydrogen concentration exceeds 4%. Therefore, the permissible concentration of hydrogen when the sealed hydrogen leaks into the atmospheric pressure is often set to 0.1% (1000 ppm), which is sufficiently lower than 4%. In that case, the hydrogen partial pressure is 0.001 atm. When the pressure of hydrogen in the hydrogen resistance test is P atmosphere and the average hydrogen resistance time is h hours, the average hydrogen resistance time for hydrogen with a partial pressure of 0.001 atmosphere at the same temperature as the hydrogen resistance test is (P/0.001) × becomes h.
本実施例では、P=2気圧、h=15時間であるため、耐水素試験と同じ温度80℃における分圧0.001気圧の水素に対する平均耐水素時間は、(2/0.001)×15=30000時間、すなわち、約3.4年となる。つまり、本実施例のRFeB系焼結磁石は、温度が80℃であって濃度が許容の上限いっぱいの0.1％である水素ガスに3.4年間晒され続けることが許容される。通常は、このような上限いっぱいの濃度の水素ガスに晒され続けることは想定し難いため、さらに長期間、本実施例のRFeB系焼結磁石を使用し続けることができる。また、また、温度が80℃よりも低い環境下では、耐水素時間はさらに長くなる。 In this example, since P=2 atm and h=15 hours, the average hydrogen withstand time for hydrogen with a partial pressure of 0.001 atm at the same temperature as the hydrogen withstand test of 80° C. is (2/0.001)×15=30000 hours. , That is, about 3.4 years. That is, the RFeB system sintered magnet of the present embodiment is allowed to continue to be exposed to hydrogen gas having a temperature of 80° C. and a concentration of 0.1% which is the maximum allowable value for 3.4 years. Usually, it is difficult to assume that the RFeB-based sintered magnet according to the present embodiment will be used for a longer period of time because it is difficult to assume that the hydrogen gas will be continuously exposed to the hydrogen gas having the concentration of the upper limit. In addition, the hydrogen withstanding time is further prolonged in an environment where the temperature is lower than 80°C.
本発明は上記実施形態には限定されず、種々の変形が可能である。 The present invention is not limited to the above embodiment, and various modifications can be made.
１０…RFeB系焼結磁石
１１…RFeB系焼結体
１１１…RFeB系合金材
１１２…RFeB系磁石粉末
１１２１…粗粉
１１３…モールド
１２…付着物
１３…粒界拡散処理後のRFeB系焼結体
１４…保護層
１５…主相粒子
１６…粒界
１７…ピンホール
10... RFeB system sintered magnet 11... RFeB system sintered body 111... RFeB system alloy material 112... RFeB system magnet powder 1121... Coarse powder 113... Mold 12... Adhesion material 13... RFeB system sintered body after grain boundary diffusion treatment 14... Protective layer 15... Main phase particles 16... Grain boundary 17... Pinhole
Claims (4)
前記RFeB系焼結体の表面から内部に向かって減少する濃度勾配を有するように、該RFeB系焼結体の粒界に存在するCuと、
前記RFeB系焼結体の表面を覆うNiメッキによる保護層と
を備えることを特徴とするRFeB系焼結磁石。 R, which is a rare earth element, and an RFeB-based sintered body containing Fe and B,
To have a concentration gradient decreasing from the surface of the RFeB-based sintered body toward the inside, Cu present in the grain boundary of the RFeB-based sintered body,
An RFeB-based sintered magnet, comprising a Ni-plated protective layer covering the surface of the RFeB-based sintered body.
前記粒界拡散処理工程を行った後の前記RFeB系焼結体の表面にNiメッキを施すNiメッキ工程と
を有することを特徴とするRFeB系焼結磁石の製造方法。 R, which is a rare earth element, and the surface of the RFeB-based sintered body containing Fe and B, by depositing a deposit containing Cu and then heating the Cu, grains of the RFeB-based sintered body Grain boundary diffusion treatment step of diffusing into the boundary,
A method of manufacturing an RFeB-based sintered magnet, comprising a Ni plating step of performing Ni plating on the surface of the RFeB-based sintered body after performing the grain boundary diffusion treatment step.
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| JP2016082142A (en) * | 2014-10-21 | 2016-05-16 | Tdk株式会社 | Magnet member |
| JP2017535056A (en) * | 2015-08-13 | 2017-11-24 | 北京中科三環高技術股▲ふん▼有限公司 | Rare earth permanent magnet and method for producing rare earth permanent magnet |
| WO2018101402A1 (en) * | 2016-12-01 | 2018-06-07 | 日立金属株式会社 | R-t-b sintered magnet and production method therefor |
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| JP2012074470A (en) * | 2010-09-28 | 2012-04-12 | Tdk Corp | Rare earth magnet, method for manufacturing rare earth magnet, and rotary machine |
| JP2016082142A (en) * | 2014-10-21 | 2016-05-16 | Tdk株式会社 | Magnet member |
| JP2017535056A (en) * | 2015-08-13 | 2017-11-24 | 北京中科三環高技術股▲ふん▼有限公司 | Rare earth permanent magnet and method for producing rare earth permanent magnet |
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