JPH0582323A - Manufacture of r-tm-b series permanent magnet having improved corrosion resistance - Google Patents

Abstract

PURPOSE:To remarkably improve corrosion resistance insufficient in conventional plating in a magnet containing rare earth elements and iron as main ingredients. CONSTITUTION:A method for manufacturing an R-TM-B series permanent magnet having improved corrosion resistance comprises the step of electrolytically processing with a current density of 0.5-5A/dm<2> simultaneously during an electrolessly plating for the purpose of improving corrosion resistance of the R-TM-B series permanent magnet containing by weight ratio 5-40% of R (R is a combination of one or more types of rare earth elements including y), 50-90% of TM (TM is transition metal containing Fe as a main ingredient) and 0.2-8% of B (boron).

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【産業上の利用分野】本発明は、Ｒ−ＴＭ−Ｂ系永久磁
石であって、無電解Ｎｉ−Ｐめっきの処理方法を規定す
る事により耐食性を著しく改善したものに関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an R-TM-B type permanent magnet having a significantly improved corrosion resistance by defining a treatment method for electroless Ni-P plating.

【０００２】[0002]

【従来の技術】電気・電子機器の高性能・小型化に伴な
って、その一部品たる永久磁石にも同様の要求が強まっ
てきた。すなわち以前の最強の永久磁石は希土類・コバ
ルト（Ｒ−Ｃｏ）系であったが、近年、より強力なＲ−
ＴＭ−Ｂ系永久磁石が台頭してきた（特開昭５９−４６
００８号）。ここにＲはＹを含む希土類元素の１種又は
２種以上の組合わせであり、ＴＭはＦｅ，Ｃｏ等の遷移
金属中心として、一部を他の金属元素又は非金属元素で
置換したもの、Ｂは硼素である。しかし、Ｒ−ＴＭ−Ｂ
系永久磁石は極めて錆やすいという問題点があった。そ
のため、耐食性を改善するために、永久磁石体表面に耐
酸化性の被覆層を設ける手段がとられきた。その一つに
磁石体表面に無電解によるＮｉ−Ｐめっき層を設ける方
法が提案されている（例えば特開平３−３２０６号）。
この無電解Ｎｉ−Ｐめっきは、外部から電流を流して行
なう電解Ｎｉめっきに比べて膜厚精度が良好であり、得
られるめっき膜にピンホールが少ないなどの利点を有し
ている。2. Description of the Related Art As electric and electronic devices have become more sophisticated and smaller in size, the same requirements have been increased for a permanent magnet, which is one of the components. That is, the strongest permanent magnet before was a rare earth / cobalt (R-Co) system, but in recent years, a stronger R-co
TM-B system permanent magnets have emerged (Japanese Patent Laid-Open No. 59-46).
No. 008). Here, R is one or a combination of two or more rare earth elements including Y, TM is a transition metal center such as Fe or Co, and a part thereof is replaced with another metal element or non-metal element, B is boron. However, R-TM-B
The system permanent magnet has a problem that it is extremely rusty. Therefore, in order to improve the corrosion resistance, a measure has been taken to provide an oxidation resistant coating layer on the surface of the permanent magnet body. As one of them, a method of providing an electroless Ni-P plating layer on the surface of the magnet body has been proposed (for example, JP-A-3-3206).
This electroless Ni-P plating has better film thickness accuracy than electrolytic Ni plating performed by applying a current from the outside, and has the advantage that the resulting plated film has few pinholes.

【０００３】[0003]

【発明が解決しようとする課題】しかしながら、Ｒ−Ｔ
Ｍ−Ｂ系永久磁石を無電解Ｎｉ−Ｐめっき液に直接浸漬
して無電解めっき処理を施すと、無電解Ｎｉ−Ｐめっき
膜が磁石体表面に析出する以前に磁石体表面がめっき液
により腐食溶解してしまうという問題があった。そのた
め、磁石体表面に平滑かつ良好なめっき皮膜が形成され
ず、耐食性の面で問題となっていた。そこで本発明の目
的は、信頼性の高い耐食性を改善したＲ−ＴＭ−Ｂ系永
久磁石を提供することにある。However, the RT
When the MB permanent magnet is directly immersed in the electroless Ni-P plating solution and subjected to the electroless plating treatment, the surface of the magnet body is exposed to the plating solution before the electroless Ni-P plating film is deposited on the surface of the magnet body. There was the problem of corrosion and dissolution. Therefore, a smooth and good plating film is not formed on the surface of the magnet body, which is a problem in terms of corrosion resistance. Therefore, an object of the present invention is to provide an R-TM-B system permanent magnet with improved reliability and improved corrosion resistance.

【０００４】[0004]

【課題を解決するための手段】本発明は重量比でＲ（こ
こでＲはＹを含む希土類元素の１種又は２種以上組合わ
せ）５〜４０％，ＴＭ（ここでＴＭはＦｅを主体とする
遷移金属）５０〜９０％，Ｂ（硼素）０．２〜８％から
なるＲ−ＴＭ−Ｂ系永久磁石において耐食性改善を目的
として設ける無電解Ｎｉ−Ｐめっき層の被覆方法とし
て、無電解めっき処理中に同じに電流密度０．５〜５Ａ
／ｄｍ²の電解処理を施すことを特徴とする耐食性を改
善したＲ−ＴＭ−Ｂ系永久磁石の製造方法である。無電
解めっき処理の開始と同じに電解処理を施すと、磁石体
表面には電解析出反応により生じたＮｉ−Ｐめっき皮膜
が形成される。この電解Ｎｉ−Ｐめっき皮膜が無電解Ｎ
ｉ−Ｐめっき液による磁石体表面の腐食溶解を防止する
ことにより、その後の無電解Ｎｉ−Ｐめっきが良好に行
われ、磁石体表面に均一で平滑なＮｉ−Ｐめっき膜が形
成されるものと考えられる。本発明は、前記した様に無
電解Ｎｉ−Ｐめっき層の被覆方法として無電解めっき処
理中に同時に電解処理を施すことにより、Ｒ−ＴＭ−Ｂ
系永久磁石の耐食性を向上するものである。前記電解処
理の電流密度に関しては、これが５Ａ／ｄｍ²を越える
と、開始時の電解析出により形成された電解Ｎｉ−Ｐめ
っき皮膜が粗雑でピンホールの多い膜となってしまうた
め好ましくない。また０．５Ａ／ｄｍ²より小さいと、
電解Ｎｉ−Ｐめっき皮膜が磁石体表面に析出する以前に
磁石体表面が無電解Ｎｉ−Ｐめっき液により腐食溶解し
てしまう可能性があることから、電流密度は０．５Ａ／
ｄｍ²が好ましい。本発明において、Ｆｅ，Ｃｏ，Ｎｉ
等のＴＭの一部を置換する元素は、その添加目的に応じ
て、Ｇａ，Ａｌ，Ｔｉ，Ｖ，Ｃｒ，Ｍｎ，Ｚｒ，Ｈｆ，
Ｎｂ，Ｔａ，Ｍｏ，Ｇｅ，Ｓｂ，Ｓｎ，Ｂｉ，Ｎｉ他を
添加でき、本発明はいかなるＲ−ＴＭ−Ｂ系磁石にも適
用できる。また、その製造方法は焼結法、溶湯急冷法、
あるいはそれらの変形法のいずれの方法でもよい。めっ
き前処理に関しては、加工変質層の除去及びめっき前活
性化を図る上で、酸性溶液を用いるのが良い。硫酸や塩
酸等の強酸がめっき前活性化にとって有効であるが、め
っき前処理の材質への影響を極力避けるためには、２〜
１０ｖｏｌ％の硝酸による第１エッチング、その後過酸
化水素５〜１０ｖｏｌ％、酢酸１０〜３０ｖｏｌ％の混
酸による第２エッチングが最も望ましい。次いで、電解
によるＮｉストライクめっき処理を行なう。無電解によ
るＮｉ−Ｐ液に磁石体を直接浸漬し、無電解めっき処理
を行なう。また浸漬と同時に、電流密度０．５〜５Ａ／
ｄｍ²の電解処理を行なう。無電解Ｎｉ−Ｐめっき液の
組成としては、金属塩として塩化ニッケル、硫酸ニッケ
ル、次亜リン酸ニッケルのうち少なくとも一種を１００
ｇ／ｌ以下含有し、還元剤として次亜リン酸ナトリウム
を１００ｇ／ｌ以下、ｐＨ調整剤とし水酸化ナトリウ
ム、水酸化アンモニウム等の塩基性化合物、無機酸、有
機酸のうち少なくとも一種を１５０ｇ／ｌ以下含むもの
が好ましい。なおこの電解液には緩衝剤としてクエン酸
ナトリウム、酢酸ナトリウム等のオキシカルボン酸、あ
るいは硼素、炭酸等の無機酸のうち少なくとも１種を１
５０ｇ／ｌ以下、錯化剤としてクエン酸ナトリウム、酢
酸ナトリウム、水酸化アンモニウム、エチレングリコー
ル、さらには有機酸（酢酸、グリコール酸、クエン酸、
酒石酸等）のアルカリ塩、チオグリコール酸、アンモニ
ア、トリエタノールアミン、エチレンジアミン、グリシ
ン、ピリジンの少なくとも１種を１００ｇ／ｌ含むほか
促進剤、安定剤として１０ｇ／ｌ以下の硫化物、塩化
物、フッ化物、界面活性剤をそれぞれ含有することがで
き、この水溶液はｐＨ３〜１３の範囲で用い、メッキ時
の浴温は２０〜１００℃の範囲である。前記被覆方法に
より設けられためっき層の厚さは、耐食性の面で１０〜
２０μｍが適当である。In the present invention, the weight ratio of R (where R is one or a combination of two or more rare earth elements including Y) is 5 to 40%, TM (here, TM is mainly Fe). As a coating method of an electroless Ni-P plating layer provided for the purpose of improving corrosion resistance in an R-TM-B system permanent magnet composed of 50 to 90% of transition metal) and 0.2 to 8% of B (boron). Same current density of 0.5 to 5 A during electrolytic plating
A method for producing an R-TM-B system permanent magnet with improved corrosion resistance, which is characterized by performing an electrolytic treatment of / dm ² . When the electrolytic treatment is applied at the same time as the start of the electroless plating treatment, a Ni-P plating film formed by the electrolytic deposition reaction is formed on the surface of the magnet body. This electrolytic Ni-P plating film is electroless N
By preventing corrosion and dissolution of the magnet body surface by the i-P plating solution, subsequent electroless Ni-P plating is favorably performed, and a uniform and smooth Ni-P plating film is formed on the magnet body surface. it is conceivable that. As described above, the present invention provides a method for coating an electroless Ni-P plating layer by performing electrolytic treatment at the same time during the electroless plating treatment to obtain R-TM-B.
It is intended to improve the corrosion resistance of the system permanent magnet. Regarding the current density of the electrolytic treatment, if it exceeds 5 A / dm ² , it is not preferable because the electrolytic Ni-P plating film formed by electrolytic deposition at the start becomes a rough film with many pinholes. If less than 0.5 A / dm ² ,
Since the magnet body surface may be corroded and dissolved by the electroless Ni-P plating solution before the electrolytic Ni-P plating film is deposited on the magnet body surface, the current density is 0.5 A /
dm ² is preferred. In the present invention, Fe, Co, Ni
The elements that partially replace TM such as Ga, Al, Ti, V, Cr, Mn, Zr, Hf,
Nb, Ta, Mo, Ge, Sb, Sn, Bi, Ni and others can be added, and the present invention can be applied to any R-TM-B based magnet. Further, the manufacturing method is a sintering method, a molten metal quenching method,
Alternatively, any of these modified methods may be used. Regarding the pre-plating treatment, it is preferable to use an acidic solution in order to remove the work-affected layer and activate the pre-plating. Strong acids such as sulfuric acid and hydrochloric acid are effective for pre-plating activation, but in order to avoid the influence of pre-plating treatment on the material as much as possible,
Most preferable is a first etching with 10 vol% nitric acid, and then a second etching with a mixed acid of 5 to 10 vol% hydrogen peroxide and 10 to 30 vol% acetic acid. Then, Ni strike plating treatment by electrolysis is performed. The magnet body is directly immersed in the electroless Ni-P solution to perform electroless plating. At the same time as the immersion, the current density is 0.5 to 5 A /
Electrolytic treatment of dm ² is performed. The composition of the electroless Ni-P plating solution is 100 at least one of nickel chloride, nickel sulfate, and nickel hypophosphite as a metal salt.
g / l or less, sodium hypophosphite as a reducing agent at 100 g / l or less, and a pH adjusting agent at least one of basic compounds such as sodium hydroxide and ammonium hydroxide, inorganic acids, and organic acids at 150 g / l Those containing 1 or less are preferable. In addition, at least one kind of oxycarboxylic acid such as sodium citrate and sodium acetate or inorganic acid such as boron and carbonic acid is used as a buffer in the electrolytic solution.
50 g / l or less, sodium citrate as a complexing agent, sodium acetate, ammonium hydroxide, ethylene glycol, and further organic acids (acetic acid, glycolic acid, citric acid,
Alkali salt of tartaric acid, etc., thioglycolic acid, ammonia, triethanolamine, ethylenediamine, glycine, and pyridine at 100 g / l, as well as accelerators, stabilizers of 10 g / l or less of sulfides, chlorides, fluorides. Compound and a surfactant can be contained respectively, and this aqueous solution is used in the range of pH 3 to 13, and the bath temperature during plating is in the range of 20 to 100 ° C. The thickness of the plating layer provided by the coating method is 10 to 10 in terms of corrosion resistance.
20 μm is suitable.

【０００５】[0005]

【実施例】Ｎｄ（Ｆｅ_0.7Ｃｏ_0.2Ｂ_0.07Ｇａ_0.03）_6.5
なる組成の合金をアーク溶解にて作製し、得られたイン
ゴットをスタンプミル及びディスクミルで粗粉砕した。
粉砕媒体としてはＮ₂ガスを用いジェットミルで微粉砕
を行なう粉砕粒度３．５μｍ（ＦＳＳＳ）の微粉砕を得
た。得られた原料粉を１５ｋＯｅの磁場中で配向し、２
トン／ｃｍ²の圧力で円筒体に成形した。本成形体を真
空中で１０９０℃×２時間焼結した。焼結体を１８×１
０×６ｍｍ寸法に切り出し次いで９００℃のアルゴン雰
囲気中に２時間加熱保持した後に急冷し温度を６００℃
に保持したアルゴン雰囲気中で１時間保持した。こうし
て得られた試料について、めっき前処理として５ｖｏｌ
％の硝酸による第１エッチング、その後過酸化水素１０
ｖｏｌ％、酢酸２５ｖｏｌ％の混酸による第２エッチン
グを行なった。その後、表１に示す作業条件で、各種表
面処理を施した。EXAMPLES Nd (Fe _0.7 Co _0.2 B _0.07 Ga _0.03 ) _6.5
An alloy having the following composition was produced by arc melting, and the obtained ingot was roughly crushed by a stamp mill and a disc mill.
N ₂ gas was used as the grinding medium to carry out fine grinding with a jet mill to obtain fine grinding having a grinding particle size of 3.5 μm (FSSS). The obtained raw material powder was oriented in a magnetic field of 15 kOe, and 2
It was molded into a cylinder at a pressure of ton / cm ² . The compact was sintered in vacuum at 1090 ° C for 2 hours. 18x1 sintered body
Cut out to a size of 0 x 6 mm, heat and hold in an argon atmosphere at 900 ° C for 2 hours, then cool rapidly to 600 ° C.
It was kept for 1 hour in the argon atmosphere kept at 1. For the sample thus obtained, 5 vol was used as a pretreatment for plating.
% Etching with nitric acid, then hydrogen peroxide 10
The second etching was performed using a mixed acid of vol% and acetic acid 25 vol%. Then, various surface treatments were performed under the working conditions shown in Table 1.

【０００６】[0006]

【表１】 [Table 1]

【０００７】なお、表１に記載した試料のめっき層の膜
厚は、１．２ともに２０μｍであった。表１に示した試
料に関して、１１９．６℃１００％ＲＨ ２気圧での１
００時間の耐食試験および８０℃９０％ＲＨでの５００
時間の耐湿試験を行なった。結果を表２に示す。The thicknesses of the plating layers of the samples shown in Table 1 were both 1.2 μm and 1.2 μm. For the samples shown in Table 1, 1 at 119.6 ° C. 100% RH 2 atm.
00 hour corrosion resistance test and 500 at 80 ° C 90% RH
A moisture resistance test for hours was performed. The results are shown in Table 2.

【０００８】[0008]

【表２】 [Table 2]

【０００９】表２において、耐食試験結果及び耐湿試験
結果は試料の外観変化を示したものである。表２より、
本発明による永久磁石は、従来の磁石と比較して、耐食
性を著しく向上し得ることがわかる。In Table 2, the corrosion resistance test results and the humidity resistance test results show changes in the appearance of the samples. From Table 2,
It can be seen that the permanent magnet according to the present invention can significantly improve the corrosion resistance as compared with the conventional magnet.

【００１０】[0010]

【発明の効果】本発明により、希土類と鉄を主体とした
磁石において、従来のめっきでは不十分であった耐食性
の顕著な向上が図られた。According to the present invention, in the magnet mainly composed of rare earth and iron, the corrosion resistance, which was insufficient by the conventional plating, was remarkably improved.

Claims (1)

【特許請求の範囲】[Claims] 【請求項１】 重量比でＲ（ここでＲは、Ｙを含む希土
類元素の１種又は２種以上組合わせ）５〜４０％，ＴＭ
（ここでＴＭはＦｅを主体とする遷移金属）５０〜９０
％，Ｂ（硼素）０．２〜８％からなるＲ−ＴＭ−Ｂ系永
久磁石の耐食性改善を目的として設ける無電解めっき処
理中に同時に電流密度０．５〜５Ａ／ｄｍ²の電解処理
を施すことを特徴とする耐食性を改善したＲ−ＴＭ−Ｂ
系永久磁石の製造方法。1. A weight ratio of R (where R is one or a combination of two or more rare earth elements including Y) 5 to 40%, TM
(Here, TM is a transition metal mainly composed of Fe) 50 to 90
%, B (boron) 0.2 to 8% R-TM-B based permanent magnet for the purpose of improving the corrosion resistance of the electroless plating treatment is performed simultaneously with the current density of 0.5 to 5 A / dm ² electrolytic treatment. R-TM-B with improved corrosion resistance characterized by being applied
Method for manufacturing a permanent magnet.