JPH06231944A - R-t-b permanent magnet with improved corrosion resistance - Google Patents
R-t-b permanent magnet with improved corrosion resistanceInfo
- Publication number
- JPH06231944A JPH06231944A JP5018261A JP1826193A JPH06231944A JP H06231944 A JPH06231944 A JP H06231944A JP 5018261 A JP5018261 A JP 5018261A JP 1826193 A JP1826193 A JP 1826193A JP H06231944 A JPH06231944 A JP H06231944A
- Authority
- JP
- Japan
- Prior art keywords
- permanent magnet
- plating
- corrosion resistance
- improved corrosion
- plating layer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
- H01F41/026—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets protecting methods against environmental influences, e.g. oxygen, by surface treatment
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Environmental & Geological Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Hard Magnetic Materials (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、Ｒ−Ｔ−Ｂ系永久磁石
であって、磁石体にＣｒめっき層を被覆する事により耐
食性を著しく改善したＲ−Ｔ−Ｂ系永久磁石に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an R-T-B system permanent magnet, in which the corrosion resistance is remarkably improved by coating a magnet body with a Cr plating layer.
【０００２】[0002]
【従来の技術】電気、電子機器の高性能、小型化に伴っ
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−Ｔ
−Ｂ系永久磁石が台頭してきた（特開昭５９−４６００
８号）。しかし、Ｒ−Ｔ−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、永久磁石表面に耐酸化性の被覆層を設ける手段
がとられてきた。被覆層の種類としては、Ｎｉめっき、
耐酸化性樹脂、Ａｌイオンプレーティング等が提案され
ており、とりわけＮｉめっきは簡易な処理でＲ−Ｔ−Ｂ
系永久磁石の耐食性を向上するものとして注目されてい
る（特開昭６０−５４４０６号）。Ｎｉめっきは、耐酸
化性樹脂と比較して表面被覆層の機械的強度に優れてお
り、また被覆層自体の吸湿性がほとんどないという長所
を有している。しかしながら、耐酸化性樹脂と異なり、
Ｎｉめっき被覆層表面にはピンホールが存在するという
問題点があった。そのため被覆層自身の吸湿性の有無に
かかわらず、経時変化に伴い水分がピンホールを通じて
磁石体に浸透し、腐食劣化を引き起こすという問題があ
った。この問題を解決するため、現在までにＮｉめっき
層の上に耐食性樹脂を施し、ピンホールの埋め込みを行
う手法が開示されている（特開昭６３−１１０７０７
号）。2. Description of the Related Art As electric and electronic equipments have become higher in performance and smaller in size, the same requirement has been increased for a permanent magnet as one component thereof. In other words, the strongest permanent magnet before was the rare earth-cobalt (R-Co) system, but in recent years, the stronger RT
-B type permanent magnets have emerged (Japanese Patent Laid-Open No. 59-4600).
No. 8). However, the RTB 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. The types of coating layers include Ni plating,
Oxidation resistant resin, Al ion plating, etc. have been proposed. Especially, Ni plating is a simple process for RTB.
Attention has been paid to improve the corrosion resistance of the system permanent magnet (JP-A-60-54406). The Ni plating has an advantage that the surface coating layer has excellent mechanical strength as compared with the oxidation resistant resin, and that the coating layer itself has almost no hygroscopicity. However, unlike oxidation resistant resins,
There is a problem that pinholes exist on the surface of the Ni plating coating layer. Therefore, regardless of whether or not the coating layer itself has hygroscopicity, there is a problem that moisture permeates into the magnet body through the pinhole with time and causes corrosion deterioration. In order to solve this problem, there has been disclosed a method in which a corrosion resistant resin is applied on a Ni plating layer to fill a pinhole (Japanese Patent Laid-Open No. 63-110707).
issue).
【０００３】[0003]
【発明が解決しようとする課題】しかしながら、耐酸化
性樹脂の被覆による手法は、Ｎｉめっき層と耐酸化性樹
脂層との密着性ならびに耐酸化性樹脂層自身の耐食性に
関する問題点を有している。そのため、上記手法では十
分な耐食性改善を図ることができず問題となっている。
本発明は、信頼性を高めるため、耐食性を改善したＲ−
Ｔ−Ｂ系永久磁石を提供することを目的とする。However, the method of coating with the oxidation resistant resin has problems with respect to the adhesion between the Ni plating layer and the oxidation resistant resin layer and the corrosion resistance of the oxidation resistant resin layer itself. There is. Therefore, the above-mentioned method cannot sufficiently improve the corrosion resistance, which is a problem.
The present invention has improved corrosion resistance in order to improve reliability.
It is an object to provide a TB permanent magnet.
【０００４】[0004]
【課題を解決するための手段】本発明は、Ｒ−Ｔ−Ｂ系
永久磁石（ただしＲはＹを含む希土類元素のうち少なく
とも１種、ＴはＦｅ、Ｃｏを主体とする遷移金属であっ
て、一部を他の金属元素または非金属元素で置換しても
よい。）の表面に、Ｎｉめっき層およびＣｒめっき層を
順次積層してなり、該Ｃｒめっき層の厚さが０．１〜
０．５μｍである耐食性を改善したＲ−Ｔ−Ｂ系永久磁
石である。本発明において、Ｆｅ、Ｃｏ、Ｎｉ等のＴの
一部を置換する元素としては、その添加目的に応じて、
Ｇａ、Ａｌ、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｚｒ、Ｈｆ、Ｎ
ｂ、Ｔａ、Ｍｏ、Ｇｅ、Ｓｂ、Ｓｎ、Ｂｉ、Ｎｉ他を添
加でき、本発明はいかなるＲ−Ｔ−Ｂ系永久磁石にも適
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。ま
た、本発明において、Ｎｉめっき層の上にＣｒめっき層
を被覆することにより、Ｃｒめっき層自身の溌水性及び
Ｎｉ金属に対して卑な金属であるＣｒ金属のアノ−ド防
食による相乗効果が働いて耐食性が向上するものと考え
られる。Ｃｒめっき層の厚さは０．１〜０．５μｍであ
る。０．１μｍ未満では薄すぎるため、Ｃｒめっき本来
の耐食性が得られず好ましくない。また０．５μｍを越
えるとＣｒめっき表面に大きな割れを生じ、耐食性に悪
影響を及ぼす。Ｃｒめっきは、皮膜が大変硬いことか
ら、割れが生じやすいという欠点はあるものの金属製品
の最終仕上げのめっきとして広い用途があり、他の金属
めっきと比較して不変色・耐久性の大きいめっきとして
普及している。特に０．１〜０．５μｍ程度の薄い膜厚
で顕著な効果が認められ、このことからＮｉめっきの最
終仕上げのめっきとしても耐食性の面で有効なものであ
ると考えられる。本発明の耐食性を改善したＲ−Ｔ−Ｂ
系永久磁石のめっきは有機溶剤による脱脂の後にめっき
前処理、Ｎｉめっき処理、Ｃｒめっき処理の順で行い、
以下に示すような製造方法で作製することができる。め
っき前処理は、磁石表面の加工変質層の除去およびめっ
き前活性化が目的で、酸性溶液を用いエッチングするの
が良い。第１エッチングは硫酸や塩酸等の強酸がめっき
前活性化に有効である。そしてさらにめっき前処理の材
質への影響を極力避けるため２〜１０ｖｏｌ％の混酸に
よる第２エッチングを施すことが望ましい。Ｎｉめっき
処理において、Ｎｉめっきの浴の種類は、ワット浴、ス
ルファミン酸浴、アンモン浴いずれでもよい。電流密度
は１〜２Ａ／ｄｍ3が良く、めっき層の厚さは５〜２０
μｍが好ましい。Ｎｉめっき処理終了後水洗いし、Ｃｒ
めっき処理を行う。Ｃｒめっきの浴の種類は、サージェ
ント浴、けいふっ酸添加浴のいずれでも良いが、特にサ
ージェント浴が望ましい。また電流密度は１０〜６０Ａ
／ｄｍ3が好ましい。The present invention provides an R-T-B system permanent magnet (where R is at least one rare earth element containing Y, and T is a transition metal mainly composed of Fe and Co). , A part of which may be replaced by another metal element or a non-metal element.) A Ni plating layer and a Cr plating layer are sequentially laminated on the surface of the Cr plating layer having a thickness of 0.1 to
It is an R-T-B type permanent magnet with improved corrosion resistance of 0.5 μm. In the present invention, the element substituting a part of T such as Fe, Co, and Ni is, depending on the purpose of addition,
Ga, Al, Ti, V, Cr, Mn, Zr, Hf, N
b, Ta, Mo, Ge, Sb, Sn, Bi, Ni and others can be added, and the present invention can be applied to any RTB-based permanent magnet. The manufacturing method is a sintering method, a molten metal quenching method,
Alternatively, any of these modified methods may be used. Further, in the present invention, by coating the Ni plating layer with the Cr plating layer, the water repellent property of the Cr plating layer itself and the synergistic effect due to the anodic corrosion protection of Cr metal which is a base metal for Ni metal can be obtained. It is considered that the corrosion resistance is improved by working. The thickness of the Cr plating layer is 0.1 to 0.5 μm. If it is less than 0.1 μm, it is too thin and the original corrosion resistance of Cr plating cannot be obtained, which is not preferable. Further, if it exceeds 0.5 μm, a large crack is generated on the surface of the Cr plating, which adversely affects the corrosion resistance. Cr plating has a drawback that cracks are likely to occur because the coating is very hard, but it has a wide range of uses as the final finishing plating of metal products, and as a plating that has greater colorfastness and durability than other metal plating. It is popular. In particular, a remarkable effect is recognized with a thin film thickness of about 0.1 to 0.5 μm, which suggests that it is effective in terms of corrosion resistance as the final plating of Ni plating. R-T-B with improved corrosion resistance of the present invention
The system permanent magnet is plated by degreasing with an organic solvent, followed by plating pretreatment, Ni plating, and Cr plating.
It can be manufactured by the following manufacturing method. The pre-plating treatment is intended to remove the work-affected layer on the surface of the magnet and to activate the pre-plating, and etching using an acidic solution is preferable. In the first etching, a strong acid such as sulfuric acid or hydrochloric acid is effective for activation before plating. Further, in order to avoid the influence of the pretreatment of plating on the material as much as possible, it is desirable to perform the second etching with 2 to 10 vol% of mixed acid. In the Ni plating treatment, the type of Ni plating bath may be a Watt bath, a sulfamic acid bath, or an ammonium bath. The current density is preferably 1 to 2 A / dm 3 , and the thickness of the plating layer is 5 to 20.
μm is preferred. After completion of Ni plating treatment, rinse with water and Cr
Perform plating treatment. The Cr plating bath may be either a Sergeant bath or a silicic acid addition bath, but a Sergeant bath is particularly desirable. The current density is 10-60A
/ Dm 3 is preferred.
【０００５】[0005]
【実施例】Ｎｄ（Ｆｅ0.7Ｃｏ0.2Ｂ0.07Ｇａ0.03）6.5
なる組成の合金をアーク溶解して作製し、得られたイン
ゴットをスタンプミル及びディスクミで粗粉砕した。そ
の後、Ｎ2ガスを粉砕媒体としてジェットミルで微粉砕
を行い、粉砕粒度３．５μｍトル（ＦＳＳＳ）の微粉砕
粉を得た。得られた原料粉を１５ｋＯｅの磁場中、成形
圧力２ｔｏｎ／ｃｍ2で横磁場成形した。得られた成形
体を真空中で１０９０℃×２時間焼結した。得られた焼
結体を１８×１０×６ｍｍ寸法に切り出し、次いで９０
０℃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の雰囲気中で１時
間保持した。こうして得られたＲ−Ｔ−Ｂ系永久磁石を
試料として準備し、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１０ｖｏｌ
％、酢酸２５ｖｏｌ％の混酸による第２エッチングを行
った。その後、ワット浴により１０μｍのＮｉめっき層
を被覆した後、サージェント浴により表１に示した膜厚
のＣｒめっき層を被覆し、これを試験片とした。これら
の各試験片について、８０℃、９０％ＲＨでの５００時
間の耐食試験及び３５℃、５％ＮａＣｌでの１００時間
の塩水噴霧試験を行った。結果を表１に示す。表１にお
いて、耐食試験結果は外観変化を、塩水噴霧試験結果は
赤錆発生時間を示したものである。表１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が著しく
向上したことがわかる。EXAMPLES Nd (Fe 0.7 Co 0.2 B 0.07 Ga 0.03 ) 6.5
An alloy having the following composition was prepared by arc melting, and the obtained ingot was roughly crushed with a stamp mill and a disc mill. Then, fine pulverization was performed by a jet mill using N 2 gas as a pulverizing medium to obtain fine pulverized powder having a pulverized particle size of 3.5 μmTorr (FSSS). The obtained raw material powder was subjected to transverse magnetic field molding at a molding pressure of 2 ton / cm 2 in a magnetic field of 15 kOe. The obtained molded body was sintered in vacuum at 1090 ° C. for 2 hours. The obtained sintered body is cut into a size of 18 × 10 × 6 mm, and then 90
After heating and holding in an argon atmosphere of 0 ° C. for 2 hours, it was rapidly cooled and held in an argon atmosphere whose temperature was kept at 600 ° C. for 1 hour. The RTB-based permanent magnet thus obtained was prepared as a sample, and the first etching was performed with 5 vol% nitric acid as a pretreatment for plating, and then 10 vol.
% And acetic acid 25 vol% mixed acid was used for the second etching. After that, a 10 μm Ni plating layer was coated with a Watt bath, and then a Cr plating layer having a film thickness shown in Table 1 was coated with a Sargent bath to obtain a test piece. Each of these test pieces was subjected to a corrosion resistance test at 80 ° C. and 90% RH for 500 hours and a salt spray test at 35 ° C. and 5% NaCl for 100 hours. The results are shown in Table 1. In Table 1, the corrosion resistance test results show the appearance change, and the salt spray test results show the red rust generation time. It can be seen from Table 1 that the permanent magnet according to the present invention has significantly improved corrosion resistance as compared with the conventional magnet.
【０００６】[0006]
【表１】 [Table 1]
【０００７】[0007]
【発明の効果】本発明により、Ｒ−Ｔ−Ｂ系永久磁石に
おいて、従来のめっきでは不十分であった耐食性が著し
く向上した。According to the present invention, in the RTB based permanent magnet, the corrosion resistance, which was insufficient by the conventional plating, was remarkably improved.
Claims (1)
含む希土類元素のうち少なくとも１種、ＴはＦｅ、Ｃｏ
を主体とする遷移金属であって、一部を他の元素又は非
金属元素で置換してもよい。）の表面に、Ｎｉめっき層
およびＣｒめっき層を順次積層してなり、該Ｃｒめっき
層の厚さが０．１〜０．５μｍであることを特徴とする
耐食性を改善したＲ−Ｔ−Ｂ系永久磁石。1. An RTB-based permanent magnet (wherein R is at least one of rare earth elements including Y, T is Fe and Co).
It is a transition metal mainly composed of and may be partially substituted with another element or a non-metal element. ), An Ni-plated layer and a Cr-plated layer are sequentially laminated, and the thickness of the Cr-plated layer is 0.1 to 0.5 μm. System permanent magnet.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5018261A JPH06231944A (en) | 1993-02-05 | 1993-02-05 | R-t-b permanent magnet with improved corrosion resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP5018261A JPH06231944A (en) | 1993-02-05 | 1993-02-05 | R-t-b permanent magnet with improved corrosion resistance |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH06231944A true JPH06231944A (en) | 1994-08-19 |
Family
ID=11966741
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP5018261A Pending JPH06231944A (en) | 1993-02-05 | 1993-02-05 | R-t-b permanent magnet with improved corrosion resistance |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH06231944A (en) |
-
1993
- 1993-02-05 JP JP5018261A patent/JPH06231944A/en active Pending
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