JP2004214409A - Method for producing oxidation-resistant rare earth magnet powder - Google Patents
Method for producing oxidation-resistant rare earth magnet powder Download PDFInfo
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- JP2004214409A JP2004214409A JP2002382292A JP2002382292A JP2004214409A JP 2004214409 A JP2004214409 A JP 2004214409A JP 2002382292 A JP2002382292 A JP 2002382292A JP 2002382292 A JP2002382292 A JP 2002382292A JP 2004214409 A JP2004214409 A JP 2004214409A
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- 239000000843 powder Substances 0.000 title claims abstract description 100
- 229910052761 rare earth metal Inorganic materials 0.000 title claims abstract description 75
- 150000002910 rare earth metals Chemical class 0.000 title claims abstract description 75
- 230000003647 oxidation Effects 0.000 title claims abstract description 45
- 238000007254 oxidation reaction Methods 0.000 title claims abstract description 45
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 24
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims abstract description 42
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims abstract description 21
- 229910021645 metal ion Inorganic materials 0.000 claims abstract description 19
- 239000003960 organic solvent Substances 0.000 claims abstract description 11
- 238000010438 heat treatment Methods 0.000 claims description 18
- 229920005989 resin Polymers 0.000 claims description 18
- 239000011347 resin Substances 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 11
- 239000011230 binding agent Substances 0.000 claims description 10
- 150000001875 compounds Chemical class 0.000 claims description 9
- 239000002245 particle Substances 0.000 claims description 7
- 238000001035 drying Methods 0.000 claims description 6
- 150000002500 ions Chemical class 0.000 claims description 5
- 229910052726 zirconium Inorganic materials 0.000 claims description 5
- 239000011261 inert gas Substances 0.000 claims description 4
- 229910052802 copper Inorganic materials 0.000 claims description 3
- 229910052750 molybdenum Inorganic materials 0.000 claims description 3
- 229910052759 nickel Inorganic materials 0.000 claims description 3
- 229910052720 vanadium Inorganic materials 0.000 claims description 3
- 239000007788 liquid Substances 0.000 abstract description 29
- 230000001747 exhibiting effect Effects 0.000 abstract description 2
- 238000010586 diagram Methods 0.000 abstract 1
- 239000000523 sample Substances 0.000 description 19
- 238000002474 experimental method Methods 0.000 description 18
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 16
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 11
- 229910019142 PO4 Inorganic materials 0.000 description 11
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 11
- 239000010452 phosphate Substances 0.000 description 11
- 239000011248 coating agent Substances 0.000 description 10
- 238000000576 coating method Methods 0.000 description 10
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 9
- 230000006866 deterioration Effects 0.000 description 9
- 239000000243 solution Substances 0.000 description 9
- 229910052786 argon Inorganic materials 0.000 description 8
- 239000007789 gas Substances 0.000 description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 6
- 235000019441 ethanol Nutrition 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- 238000000465 moulding Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 238000004381 surface treatment Methods 0.000 description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 239000013068 control sample Substances 0.000 description 4
- 230000004907 flux Effects 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- WEVYAHXRMPXWCK-UHFFFAOYSA-N Acetonitrile Chemical compound CC#N WEVYAHXRMPXWCK-UHFFFAOYSA-N 0.000 description 3
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 3
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 238000006356 dehydrogenation reaction Methods 0.000 description 3
- 239000003822 epoxy resin Substances 0.000 description 3
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- 238000003756 stirring Methods 0.000 description 3
- 239000002253 acid Substances 0.000 description 2
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- 238000006243 chemical reaction Methods 0.000 description 2
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- 239000000470 constituent Substances 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
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- 239000013078 crystal Substances 0.000 description 2
- 230000005347 demagnetization Effects 0.000 description 2
- 229910052733 gallium Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 238000005984 hydrogenation reaction Methods 0.000 description 2
- 229910001510 metal chloride Inorganic materials 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 229920001187 thermosetting polymer Polymers 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- 229910052692 Dysprosium Inorganic materials 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 239000004677 Nylon Substances 0.000 description 1
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N Phenol Chemical compound OC1=CC=CC=C1 ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 229940044175 cobalt sulfate Drugs 0.000 description 1
- 229910000361 cobalt sulfate Inorganic materials 0.000 description 1
- KTVIXTQDYHMGHF-UHFFFAOYSA-L cobalt(2+) sulfate Chemical compound [Co+2].[O-]S([O-])(=O)=O KTVIXTQDYHMGHF-UHFFFAOYSA-L 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
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- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 238000010828 elution Methods 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- LNEPOXFFQSENCJ-UHFFFAOYSA-N haloperidol Chemical compound C1CC(O)(C=2C=CC(Cl)=CC=2)CCN1CCCC(=O)C1=CC=C(F)C=C1 LNEPOXFFQSENCJ-UHFFFAOYSA-N 0.000 description 1
- 238000001746 injection moulding Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 229910000398 iron phosphate Inorganic materials 0.000 description 1
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 238000004898 kneading Methods 0.000 description 1
- 239000006247 magnetic powder Substances 0.000 description 1
- BECVLEVEVXAFSH-UHFFFAOYSA-K manganese(3+);phosphate Chemical compound [Mn+3].[O-]P([O-])([O-])=O BECVLEVEVXAFSH-UHFFFAOYSA-K 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 229910001172 neodymium magnet Inorganic materials 0.000 description 1
- 229920001778 nylon Polymers 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 239000003495 polar organic solvent Substances 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000005215 recombination Methods 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- CMZUMMUJMWNLFH-UHFFFAOYSA-N sodium metavanadate Chemical compound [Na+].[O-][V](=O)=O CMZUMMUJMWNLFH-UHFFFAOYSA-N 0.000 description 1
- 159000000000 sodium salts Chemical class 0.000 description 1
- 229920005992 thermoplastic resin Polymers 0.000 description 1
- LKCUKVWRIAZXDU-UHFFFAOYSA-L zinc;hydron;phosphate Chemical compound [Zn+2].OP([O-])([O-])=O LKCUKVWRIAZXDU-UHFFFAOYSA-L 0.000 description 1
- 229910000166 zirconium phosphate Inorganic materials 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
Landscapes
- Hard Magnetic Materials (AREA)
Abstract
【課題】耐酸化性に優れるとともに高い磁気特性を示す希土類系ボンド磁石を製造するために有用な、耐酸化性希土類系磁石粉末の製造方法を提供すること。
【解決手段】０．１重量％〜５重量％のリン酸と５ｐｐｍ〜１０００ｐｐｍの金属イオンを有機溶剤に含有せしめてなる処理液に、希土類系磁石粉末を浸漬して混合攪拌した後、加熱乾燥することを特徴とする。
【選択図】 なしAn object of the present invention is to provide a method for producing an oxidation-resistant rare earth magnet powder which is useful for producing a rare earth bonded magnet having excellent oxidation resistance and exhibiting high magnetic properties.
SOLUTION: Rare earth magnet powder is immersed in a treatment liquid containing 0.1% by weight to 5% by weight of phosphoric acid and 5 ppm to 1000 ppm of metal ions in an organic solvent, mixed and stirred, and then heated and dried. It is characterized by doing.
[Selection diagram] None
Description
【０００１】
【発明の属する技術分野】
本発明は、耐酸化性に優れるとともに高い磁気特性を示す希土類系ボンド磁石を製造するために有用な、耐酸化性希土類系磁石粉末の製造方法に関する。
【０００２】
【従来の技術】
Ｎｄ−Ｆｅ−Ｂ系磁石粉末に代表されるＲ−Ｆｅ−Ｂ系磁石粉末などの希土類系磁石粉末を、バインダとして熱可塑性樹脂や熱硬化性樹脂などを用いて所定形状に成形することで製造される希土類系ボンド磁石は、樹脂バインダを含有しているために希土類系焼結磁石に比較すれば磁気特性が低くなるものの、フェライト磁石などに比べればなお十分に高い磁気特性を有しており、また、複雑形状や薄肉形状の磁石やラジアル異方性磁石を容易に得ることができるといった希土類系焼結磁石にはない特徴を持っている。従って、希土類系ボンド磁石は、特にスピンドルモータやステッピングモータなどの小型モータに多く用いられ、近年、その需要が増加している。
希土類系磁石粉末は高い磁気特性を有するが、ＲやＦｅが組成の大半を占めることから腐食や酸化を起しやすいという問題がある。そのため、希土類系ボンド磁石の製造においては、まず、希土類系磁石粉末を、溶解もしくは溶融（軟化）させた樹脂バインダと混合して磁石粉末の表面が樹脂バインダで被覆されたコンパウンドと呼ばれる粉末顆粒状原料を調製した後、このコンパウンドを射出成形や圧縮成形や押出成形し、用いる樹脂バインダが熱硬化性樹脂である場合にはさらに加熱して樹脂バインダを硬化させることで所定形状に成形して製品化される。しかしながら、このようにして製品化された希土類系ボンド磁石であっても、その表面に希土類系磁石粉末が露出していると、わずかな酸やアルカリや水分などの存在によって磁石粉末が腐食して錆が発生したり、１００℃程度の大気中でも酸化が進行したりするので、例えば部品組み込み後に磁気特性の劣化やばらつきを招くことがある。また、樹脂バインダとして汎用されているエポキシ樹脂やナイロン樹脂などは水分や酸素の透過性を有する。従って、これらの樹脂を樹脂バインダに用いた希土類系ボンド磁石においては、樹脂を透過した水分や酸素で希土類系磁石粉末が腐食したり酸化したりする可能性があることを否定できない。さらに、希土類系磁石粉末が腐食や酸化を起しやすいことに鑑みれば、射出成形を行う場合には混練成形時の温度条件に配慮する必要があるし、圧縮成形を行う場合には成形後の硬化処理を不活性ガス雰囲気中で行う必要がある。
【０００３】
以上のような問題を解消すべく、例えば、下記の特許文献１において、希土類系磁石粉末の表面に、リン酸塩の被覆処理を施し、リン酸塩被膜で表面被覆された希土類系磁石粉末を用いて所定形状に成形することによる酸化劣化を防止した希土類系ボンド磁石の製造方法が提案されている。
【０００４】
【特許文献１】
特開昭６４−１１３０４号公報
【０００５】
【発明が解決しようとする課題】
上記の特許文献１に記載された方法は、耐酸化性に優れた希土類系ボンド磁石を製造することができる方法として注目に値するものである。しかしながら、上記の特許文献１において用いられるリン酸塩被膜処理液を含め、通常、リン酸塩被膜処理液と称されるものは、第一リン酸亜鉛や第一リン酸マンガンなどのリン酸塩を主な構成成分とし、これに反応促進剤としての酸化剤などを含んでなる水溶液である。従って、リン酸塩被膜処理液に希土類系磁石粉末を浸漬すると、磁石粉末が処理液成分と反応して処理液中に磁石粉末の構成成分であるＲやＦｅが溶出してしまうことで磁石粉末の表面付近（表面から深さ１μｍ程度）が変質して磁石粉末の磁気特性が劣化するという問題がある。また、表面変質を起した希土類系磁石粉末の表面にリン酸塩被膜を形成しても、このような磁石粉末を用いて所定形状に成形した希土類系ボンド磁石は、磁気特性の初期低下が大きいという問題がある。さらに、リン酸塩被膜処理液は水を主体とするので、磁石粉末の表面に形成される被膜を構成するリン酸塩は水和物の形態をとることから、このような磁石粉末を用いて所定形状に成形した希土類系ボンド磁石は、実使用環境下で被膜に含まれる水分が磁石粉末の、ひいてはボンド磁石の経時的な磁気特性の劣化を促進させてしまうという問題がある。
そこで本発明は、耐酸化性に優れるとともに高い磁気特性を示す希土類系ボンド磁石を製造するために有用な、耐酸化性希土類系磁石粉末の製造方法を提供することを目的とする。
【０００６】
【課題を解決するための手段】
本発明者は、上記の点に鑑みて種々の検討を行う過程において、リン酸を有機溶剤に含有せしめてなる処理液に、希土類系磁石粉末を浸漬して混合攪拌した後、加熱乾燥することで、希土類系磁石粉末に耐酸化性を付与することができることを確認し、さらに検討を重ねた結果、リン酸を有機溶剤に含有せしめてなる処理液に微量の金属イオンを添加すると、リン酸による希土類系磁石粉末への耐酸化性の付与効果が向上することを知見した。
【０００７】
上記の知見に基づいてなされた本発明の耐酸化性希土類系磁石粉末の製造方法は、請求項１記載の通り、０．１重量％〜５重量％のリン酸と５ｐｐｍ〜１０００ｐｐｍの金属イオンを有機溶剤に含有せしめてなる処理液に、希土類系磁石粉末を浸漬して混合攪拌した後、加熱乾燥することを特徴とする。
また、請求項２記載の製造方法は、請求項１記載の製造方法において、金属イオンがＣｕ，Ｃｏ，Ｎｉ，Ｚｒ，Ｖ，Ｍｏから選ばれる少なくとも１種のイオンであることを特徴とする。
また、請求項３記載の製造方法は、請求項１または２記載の製造方法において、加熱乾燥を真空中または不活性ガス雰囲気中５０℃〜１２０℃にて行うことを特徴とする。
また、請求項４記載の製造方法は、請求項１乃至３のいずれかに記載の製造方法において、希土類系磁石粉末の平均粒径（長径）が２００μｍ以下であることを特徴とする。
また、請求項５記載の製造方法は、請求項４記載の製造方法において、希土類系磁石粉末がＨＤＤＲ磁石粉末であることを特徴とする。
また、本発明の耐酸化性希土類系磁石粉末は、請求項６記載の通り、請求項１記載の製造方法により製造されてなることを特徴とする。
また、本発明の希土類系ボンド磁石用コンパウンドは、請求項７記載の通り、請求項６記載の耐酸化性希土類系磁石粉末と樹脂バインダとからなることを特徴とする。
また、本発明の希土類系ボンド磁石は、請求項８記載の通り、請求項７記載の希土類系ボンド磁石用コンパウンドを用いて所定形状に成形されてなることを特徴とする。
【０００８】
【発明の実施の形態】
本発明の耐酸化性希土類系磁石粉末の製造方法は、請求項１記載の通り、０．１重量％〜５重量％のリン酸と５ｐｐｍ〜１０００ｐｐｍの金属イオンを有機溶剤に含有せしめてなる処理液に、希土類系磁石粉末を浸漬して混合攪拌した後、加熱乾燥することを特徴とするものである。本発明によれば、希土類系磁石粉末に優れた耐酸化性を付与することができる。また、本発明において用いられる処理液は有機溶剤を主体とするので、上記の特許文献１に記載されている水を主体とするリン酸塩被膜処理液を用いた場合とは異なり、希土類系磁石粉末の表面付近が変質するといった問題などを極力回避することができるので、磁石粉末の磁気特性の劣化を防止することができる。従って、本発明の製造方法により製造される耐酸化性希土類系磁石粉末を用いれば、耐酸化性に優れるとともに高い磁気特性を示す希土類系ボンド磁石を製造することができる。
【０００９】
本発明において用いられる０．１重量％〜５重量％のリン酸と５ｐｐｍ〜１０００ｐｐｍの金属イオンを有機溶剤に含有せしめてなる処理液は、例えば、有機溶剤に、リン酸と、所望する金属イオンを処理液中に含有せしめることができる金属塩や金属塩化物などを、処理液中におけるリン酸と金属イオンの含有量がそれぞれ所定量となるように、溶解させたり分散させたりすることによって調製することができる。
【００１０】
ここで、有機溶剤としては、メチルアルコールやエチルアルコールやイソプロピルアルコールなどの低級アルコール、アセトニトリル、メチルエチルケトンなどの極性有機溶剤が好適である。
【００１１】
また、リン酸としては、例えば、８５％濃度のリン酸水溶液を用いることができる。処理液中におけるリン酸の含有量を０．１重量％〜５重量％と規定するのは、０．１重量％を下回ると、リン酸による希土類系磁石粉末への耐酸化性の付与効果が十分に発揮されないおそれがある一方、５重量％を上回ると、希土類系磁石粉末との反応が促進され、磁石粉末の磁気特性が劣化するおそれがあるからである。なお、処理液中におけるリン酸の含有量は、望ましくは０．３重量％〜３重量％である。
【００１２】
また、金属イオンとしては、Ｃｕ，Ｃｏ，Ｎｉ，Ｚｒ，Ｖ，Ｍｏなどが好適である。これらの金属イオンは、リン酸による希土類系磁石粉末への耐酸化性の付与効果を向上させることができる。金属イオンは、有機溶剤に、所望する金属イオンを生成する金属塩（金属の硫酸塩や金属酸のナトリウム塩など）や金属塩化物などを、処理液中における金属イオンの含有量が所定量となるように、溶解させたり分散させたりすることで含有せしめればよい。また、金属イオンは、処理液に、単独で含有せしめられてもよいし２種以上を混合して含有せしめられてもよい。処理液中における金属イオンの含有量を５ｐｐｍ〜１０００ｐｐｍと規定するのは、５ｐｐｍを下回ると、処理液中に金属イオンを含有せしめる効果が十分に発揮されないおそれがある一方、１０００ｐｐｍを上回ると、処理液中への磁石粉末の構成成分であるＲやＦｅの溶出量が増加して沈殿物を生成し、処理液の安定性に悪影響を与えるおそれがあるからである。なお、処理液中における金属イオンの含有量は、望ましくは２０ｐｐｍ〜５００ｐｐｍであり、より望ましくは３０ｐｐｍ〜３００ｐｐｍである。
【００１３】
耐酸化性希土類系磁石粉末は、以上のようにして調製された処理液に、希土類系磁石粉末を浸漬して混合攪拌した後、加熱乾燥することにより製造される。
より具体的には、十分量の処理液に、希土類系磁石粉末を浸漬して混合攪拌した後、磁石粉末を濾取してからこれを加熱乾燥する。処理液に希土類系磁石粉末を浸漬して混合攪拌する時間は、希土類系磁石粉末量などにも依存するが、概ね１分〜２０分である。希土類系磁石粉末の磁気特性の劣化を招くことなく磁石粉末に耐酸化性を付与するためには、加熱乾燥は、真空中または不活性ガス（窒素ガスやアルゴンガスなど）雰囲気中５０℃〜１２０℃にて行うことが望ましい。
加熱乾燥の時間は、希土類系磁石粉末量などにも依存するが、概ね１分〜１時間である。このようにして製造された耐酸化性希土類系磁石粉末は、磁石粉末が、膜厚が０．１μｍ以下のリン酸と金属を構成成分とする被膜により表面被覆されていると考えられ、さらなる検証が必要ではあるが、この被膜は、磁石粉末に由来する鉄とリン酸から生成するリン酸鉄中に微量の金属が固溶している形態で構成されていると推察される。
【００１４】
上記の特許文献１に記載されているリン酸塩被膜処理液を用いた場合に起る、希土類系磁石粉末の表面付近が変質するといった現象は、とりわけ、平均粒径（長径）が小さい（例えば２００μｍ以下）磁石粉末に対して磁気特性の劣化を顕著に引き起すことになる。しかしながら、本発明によれば、平均粒径（長径）が小さい希土類系磁石粉末、例えば、平均粒径が８０μｍ〜１００μｍ程度の、希土類系磁石合金を水素中で加熱して水素を吸蔵させた後、脱水素処理し、次いで冷却することによって得られる磁気的異方性のＨＤＤＲ（Ｈｙｄｒｏｇｅｎａｔｉｏｎ−Ｄｉｓｐｒｏｐｏｒｔｉｏｎａｔｉｏｎ−Ｄｅｓｏｒｐｔｉｏｎ−Ｒｅｃｏｍｂｉｎａｔｉｏｎ）磁石粉末（特公平６−８２５７５号公報参照）などに対しても、磁気特性の劣化を引き起すことなく優れた耐酸化性を付与することができるので、この点において本発明の耐酸化性希土類系磁石粉末の製造方法は利用価値が高い。
【００１５】
【実施例】
以下、本発明を実施例によってさらに詳細に説明するが、本発明はこれに限定して解釈されるものではない。
【００１６】
実施例Ａ：耐酸化性ＨＤＤＲ磁石粉末の製造その１とその特性
高周波溶解によって組成：Ｎｄ１２．８原子％，Ｄｙ１．０原子％，Ｂ６．３原子％，Ｃｏ１４．８原子％，Ｇａ０．５原子％，Ｚｒ０．０９原子％，残部Ｆｅの鋳隗を作製し、アルゴンガス雰囲気中で１１００℃×２４時間焼鈍したものを酸素濃度０．５％以下のアルゴンガス雰囲気中で粉砕して平均粒径１００μｍの粗粉砕粉としてからこれを０．１５ＭＰａの水素ガス加圧雰囲気中で８７０℃×３時間の水素化熱処理を行い、その後、減圧（１ｋＰａ）アルゴンガス流気中で８５０℃×１時間の脱水素処理を行ってから冷却して製造したＨＤＤＲ磁石粉末（平均結晶粒径０．４μｍ）を用いて以下の実験を行った。
【００１７】
実験１：
リン酸を０．５重量％含有せしめてなるエチルアルコールに硫酸コバルトをＣｏイオンが７０ｐｐｍとなるように添加して処理液１を調製した。
３００ｃｃの処理液１にＨＤＤＲ磁石粉末１００ｇを５分間浸漬して混合攪拌した後、処理済磁石粉末を濾取し、余分な処理液を除去してからこれを真空中（＜１０ｋＰａ）７０℃で２０分間加熱乾燥した。このようにして表面処理を行ったＨＤＤＲ磁石粉末（サンプル磁石粉末１）に対し、大気中１５０℃で１００時間加熱する加熱試験を行い、試験前に対する試験後における酸化による重量増加率を測定した。結果を表１に示す。
【００１８】
実験２：
リン酸を０．５重量％含有せしめてなるエチルアルコールを用いて実験１と同様にして表面処理を行ったＨＤＤＲ磁石粉末（比較サンプル磁石粉末）を得、これに対し、実験１と同様の加熱試験を行い、試験前に対する試験後における酸化による重量増加率を測定した。結果を表１に示す。
【００１９】
実験３：
何らの表面処理も行っていないＨＤＤＲ磁石粉末（対照サンプル磁石粉末）に対し、実験１と同様の加熱試験を行い、試験前に対する試験後における酸化による重量増加率を測定した。結果を表１に示す。
【００２０】
【表１】
表１から明らかなように、比較サンプル磁石粉末は、対照サンプル磁石粉末よりも酸化による重量増加率が遥かに少なかったが、サンプル磁石粉末１は、比較サンプル磁石粉末よりも酸化による重量増加率がさらに少なく、サンプル磁石粉末１は耐酸化性に優れることがわかった。
【００２２】
実施例Ｂ：耐酸化性ＨＤＤＲ磁石粉末の製造その２とその特性および耐酸化性ＨＤＤＲ磁石粉末を用いたボンド磁石の製造とその特性
高周波溶解によって組成：Ｎｄ１２．８原子％，Ｂ６．３原子％，Ｃｏ１４．８原子％，Ｇａ０．５原子％，Ｚｒ０．０９原子％，残部Ｆｅの鋳隗を作製し、アルゴンガス雰囲気中で１１００℃×２４時間焼鈍したものを酸素濃度０．５％以下のアルゴンガス雰囲気中で粉砕して平均粒径１００μｍの粗粉砕粉としてからこれを０．１５ＭＰａの水素ガス加圧雰囲気中で８７０℃×３時間の水素化熱処理を行い、その後、減圧（１ｋＰａ）アルゴンガス流気中で８５０℃×１時間の脱水素処理を行ってから冷却して製造したＨＤＤＲ磁石粉末（平均結晶粒径０．４μｍ）を用いて以下の実験を行った。
【００２３】
実験１：
実施例Ａにおける処理液１を用いて実施例Ａにおける実験１と同様にして表面処理を行ったＨＤＤＲ磁石粉末を得た。また、エポキシ樹脂とフェノール系硬化剤を重量比率で１００：３の割合でメチルエチルケトンに溶解して樹脂液を調製した。表面処理を行ったＨＤＤＲ磁石粉末と樹脂液を、表面処理を行ったＨＤＤＲ磁石粉末と樹脂液の合計重量に対する樹脂液の重量の比率が３．５％となるように均一混合した後、メチルエチルケトンを常温で蒸発させて粉末顆粒状の希土類系ボンド磁石用コンパウンドを得た。得られた希土類系ボンド磁石用コンパウンドを、９６０ｋＡ／ｍの磁場中において、加圧力５８８ＭＰａで圧縮成形し、得られた成形体を１５０℃のアルゴンガス雰囲気中で１時間加熱してエポキシ樹脂を硬化させて、寸法が縦１２．０ｍｍ×横７．６ｍｍ×高さ７．５ｍｍで密度が５．９ｇ／ｃｍ３のボンド磁石を製造した。こうして製造されたボンド磁石（サンプル磁石１）に対し、大気中１５０℃で１００時間加熱する加熱試験を行い、試験前に対する試験後における酸化による重量増加率を測定した。また、サンプル磁石１に対して着磁を行った後、大気中１００℃で１００時間加熱する加熱試験と大気中１５０℃で１００時間加熱する加熱試験を行い、それぞれの加熱試験について、試験前に対する試験後における磁束劣化率（不可逆減磁率）を測定した。さらに、大気中１５０℃で１００時間加熱する加熱試験を行ったサンプル磁石１については再着磁を行い、加熱試験前に対する再着磁後における磁束劣化率（永久減磁率）を測定した。これらの結果を表２に示す。
【００２４】
実験２：
リン酸を０．５重量％含有せしめてなるエチルアルコールにジルコン酸ナトリウムをＺｒイオンが２００ｐｐｍとなるように添加するとともにバナジン酸ナトリウムをＶイオンが１５０ｐｐｍとなるように添加して調製した処理液２を用いて実験１と同様にして表面処理を行ったＨＤＤＲ磁石粉末を得、さらにボンド磁石を製造した。こうして製造されたボンド磁石（サンプル磁石２）に対し、実験１と同様の各種試験を行った。結果を表２に示す。
【００２５】
実験３：
リン酸を０．５重量％含有せしめてなるエチルアルコールを用いて実験１と同様にして表面処理を行ったＨＤＤＲ磁石粉末を得、さらにボンド磁石を製造した。こうして製造されたボンド磁石（比較サンプル磁石）に対し、実験１と同様の各種試験を行った。結果を表２に示す。
【００２６】
実験４：
何らの表面処理も行っていないＨＤＤＲ磁石粉末を用いて実験１と同様にしてボンド磁石を製造した。こうして製造されたボンド磁石（対照サンプル磁石）に対し、実験１と同様の各種試験を行った。結果を表２に示す。
【００２７】
【表２】
表２から明らかなように、比較サンプル磁石は、対照サンプル磁石よりも酸化による重量増加率も磁束劣化率も少なかったが、サンプル磁石１とサンプル磁石２は、比較サンプル磁石よりも酸化による重量増加率も磁束劣化率もさらに少なかった。サンプル磁石１とサンプル磁石２がこのような優れた特性を示すのは、優れた耐酸化性が付与されたＨＤＤＲ磁石粉末を用いて所定形状に成形されていることに基づくものであるとともに、所定形状に成形する際の圧縮成形時や成形後においても、磁石粉末の表面損傷が抑制されていることで酸化が効果的に阻止されていることに基づくものである。
【００２９】
【発明の効果】
本発明によれば、耐酸化性に優れるとともに高い磁気特性を示す希土類系ボンド磁石を製造するために有用な、耐酸化性希土類系磁石粉末の製造方法が提供される。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing an oxidation-resistant rare earth magnet powder which is useful for producing a rare earth bonded magnet having excellent oxidation resistance and exhibiting high magnetic properties.
[0002]
[Prior art]
Manufactured by molding a rare earth magnet powder such as an R-Fe-B magnet powder represented by an Nd-Fe-B magnet powder into a predetermined shape using a thermoplastic resin or a thermosetting resin as a binder. Although rare earth-based bonded magnets contain resin binder, their magnetic properties are lower than those of rare-earth sintered magnets, but they still have sufficiently high magnetic properties as compared to ferrite magnets. In addition, it has features that rare earth sintered magnets do not have, such as a magnet having a complicated shape or a thin shape and a radial anisotropic magnet can be easily obtained. Therefore, rare earth-based bonded magnets are often used for small motors such as spindle motors and stepping motors, and the demand for them is increasing in recent years.
Rare earth magnet powders have high magnetic properties, but have a problem that they are susceptible to corrosion and oxidation because R and Fe occupy most of the composition. Therefore, in the production of a rare earth-based bonded magnet, first, a rare-earth-based magnet powder is mixed with a melted or melted (softened) resin binder to form a powder granule called a compound in which the surface of the magnet powder is coated with the resin binder. After preparing the raw materials, this compound is injection-molded, compression-molded, or extruded. If the resin binder to be used is a thermosetting resin, it is further heated to cure the resin binder, thereby molding the compound into a predetermined shape, and then forming a product. Be converted to However, even if the rare earth-based bonded magnet is commercialized in this way, if the rare earth-based magnet powder is exposed on the surface, the magnet powder is corroded by the presence of a slight amount of acid, alkali or moisture. Since rust is generated or oxidation proceeds even in the air at about 100 ° C., for example, deterioration or variation in magnetic characteristics may be caused after assembling the components. In addition, epoxy resins, nylon resins, and the like, which are widely used as resin binders, have moisture and oxygen permeability. Therefore, it cannot be denied that in a rare-earth bonded magnet using such a resin as a resin binder, there is a possibility that the rare-earth magnet powder may be corroded or oxidized by moisture or oxygen permeating the resin. Furthermore, in view of the fact that the rare earth magnet powder is susceptible to corrosion and oxidation, it is necessary to consider the temperature conditions during kneading and molding when performing injection molding, and after compression when performing compression molding. The curing treatment needs to be performed in an inert gas atmosphere.
[0003]
In order to solve the above problems, for example, in Patent Literature 1 below, the surface of a rare earth magnet powder is subjected to a phosphate coating treatment, and the rare earth magnet powder surface-coated with a phosphate film is used. There has been proposed a method for producing a rare earth-based bonded magnet in which oxidation deterioration due to molding into a predetermined shape is prevented.
[0004]
[Patent Document 1]
JP-A-64-11304
[Problems to be solved by the invention]
The method described in Patent Document 1 is notable as a method capable of producing a rare-earth bonded magnet having excellent oxidation resistance. However, what is usually called a phosphate coating solution, including the phosphate coating solution used in Patent Document 1, is a phosphate such as zinc monophosphate or manganese monophosphate. Is an aqueous solution containing, as a main component, an oxidizing agent as a reaction accelerator. Therefore, when the rare earth magnet powder is immersed in the phosphate coating treatment liquid, the magnet powder reacts with the treatment liquid components and R and Fe, which are the constituent components of the magnet powder, are eluted into the treatment liquid. There is a problem in that the vicinity of the surface (at a depth of about 1 μm from the surface) deteriorates and the magnetic properties of the magnet powder deteriorate. Further, even if a phosphate film is formed on the surface of the rare-earth magnet powder whose surface has been altered, the rare-earth bonded magnet molded into a predetermined shape using such a magnet powder has a large initial decrease in magnetic properties. There is a problem. Furthermore, since the phosphate coating treatment liquid is mainly composed of water, the phosphate constituting the coating formed on the surface of the magnet powder takes the form of a hydrate. The rare earth-based bonded magnet formed into a predetermined shape has a problem that moisture contained in a coating film in a practical use environment accelerates deterioration of magnetic properties of the magnet powder and thus of the bonded magnet over time.
Therefore, an object of the present invention is to provide a method for producing an oxidation-resistant rare earth-based magnet powder, which is useful for producing a rare earth-based bonded magnet having excellent oxidation resistance and high magnetic properties.
[0006]
[Means for Solving the Problems]
In the process of conducting various studies in view of the above points, the present inventors immerse the rare-earth magnet powder in a treatment solution containing phosphoric acid in an organic solvent, mix and stir, and then heat and dry. It was confirmed that oxidation resistance can be imparted to the rare-earth magnet powder, and as a result of further studies, it was found that adding a small amount of metal ions to a treatment solution containing phosphoric acid in an organic solvent, It was found that the effect of imparting oxidation resistance to the rare earth magnet powder by the method was improved.
[0007]
According to the method for producing an oxidation-resistant rare earth magnet powder of the present invention based on the above findings, as described in claim 1, 0.1 wt% to 5 wt% of phosphoric acid and 5 ppm to 1000 ppm of metal ions are used. The method is characterized in that the rare earth magnet powder is immersed in a treatment liquid contained in an organic solvent, mixed and stirred, and then heated and dried.
Further, the manufacturing method according to claim 2 is characterized in that, in the manufacturing method according to claim 1, the metal ion is at least one ion selected from Cu, Co, Ni, Zr, V, and Mo.
The manufacturing method according to a third aspect is characterized in that, in the manufacturing method according to the first or second aspect, the heating and drying are performed at 50 ° C. to 120 ° C. in a vacuum or an inert gas atmosphere.
A manufacturing method according to a fourth aspect is characterized in that, in the manufacturing method according to any one of the first to third aspects, the rare earth magnet powder has an average particle diameter (major axis) of 200 μm or less.
A manufacturing method according to a fifth aspect is characterized in that, in the manufacturing method according to the fourth aspect, the rare earth magnet powder is an HDDR magnet powder.
According to a sixth aspect of the present invention, there is provided an oxidation-resistant rare earth magnet powder produced by the method of the first aspect.
According to a seventh aspect of the present invention, there is provided a compound for a rare earth-based bonded magnet comprising the oxidation-resistant rare earth-based magnet powder according to the sixth aspect and a resin binder.
Further, the rare earth-based bonded magnet of the present invention is characterized in that it is formed into a predetermined shape by using the compound for a rare earth-based bonded magnet according to claim 7.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
According to the method for producing an oxidation-resistant rare earth magnet powder of the present invention, as described in claim 1, a treatment in which 0.1% to 5% by weight of phosphoric acid and 5 ppm to 1000 ppm of metal ions are contained in an organic solvent. The method is characterized in that a rare earth magnet powder is immersed in a liquid, mixed and stirred, and then heated and dried. According to the present invention, excellent oxidation resistance can be imparted to rare earth magnet powder. Further, since the treatment liquid used in the present invention is mainly composed of an organic solvent, unlike the case of using the phosphate coating treatment liquid mainly composed of water described in Patent Document 1, a rare earth magnet is used. Since the problem such as deterioration of the vicinity of the surface of the powder can be avoided as much as possible, deterioration of the magnetic properties of the magnet powder can be prevented. Therefore, by using the oxidation-resistant rare earth magnet powder produced by the production method of the present invention, a rare earth bonded magnet having excellent oxidation resistance and high magnetic properties can be produced.
[0009]
The treatment liquid used in the present invention, which contains 0.1% by weight to 5% by weight of phosphoric acid and 5 ppm to 1000 ppm of metal ions in an organic solvent, may be, for example, phosphoric acid and a desired metal ion in an organic solvent. Is prepared by dissolving or dispersing metal salts or metal chlorides that can be contained in the processing solution so that the contents of phosphoric acid and metal ions in the processing solution become the respective predetermined amounts. can do.
[0010]
Here, the organic solvent is preferably a lower alcohol such as methyl alcohol, ethyl alcohol, or isopropyl alcohol, or a polar organic solvent such as acetonitrile or methyl ethyl ketone.
[0011]
Further, as the phosphoric acid, for example, an 85% concentration phosphoric acid aqueous solution can be used. When the content of phosphoric acid in the treatment liquid is defined as 0.1% by weight to 5% by weight, if the content is less than 0.1% by weight, the effect of imparting oxidation resistance to the rare earth magnet powder by the phosphoric acid will be insufficient. On the other hand, when the content exceeds 5% by weight, the reaction with the rare earth magnet powder is promoted, and the magnetic properties of the magnet powder may be deteriorated. The content of phosphoric acid in the treatment liquid is desirably 0.3% by weight to 3% by weight.
[0012]
Further, as metal ions, Cu, Co, Ni, Zr, V, Mo and the like are preferable. These metal ions can improve the effect of imparting oxidation resistance to the rare earth magnet powder by phosphoric acid. Metal ions are prepared by adding a metal salt (such as a metal sulfate or a metal acid sodium salt) or a metal chloride which generates a desired metal ion to an organic solvent, and the content of the metal ion in the treatment solution is a predetermined amount. It may be contained by dissolving or dispersing. Further, the metal ions may be contained alone or in a mixture of two or more in the treatment liquid. The content of the metal ion in the treatment liquid is defined as 5 ppm to 1000 ppm. When the content is less than 5 ppm, the effect of incorporating the metal ion in the treatment liquid may not be sufficiently exerted. This is because the amount of elution of R and Fe, which are constituents of the magnet powder, into the liquid increases, and precipitates are generated, which may adversely affect the stability of the processing liquid. The content of the metal ions in the treatment liquid is preferably 20 ppm to 500 ppm, and more preferably 30 ppm to 300 ppm.
[0013]
The oxidation-resistant rare-earth magnet powder is manufactured by immersing the rare-earth magnet powder in the treatment liquid prepared as described above, mixing and stirring, and then heating and drying.
More specifically, the rare-earth magnet powder is immersed in a sufficient amount of the treatment liquid, mixed and stirred, and then the magnet powder is filtered and then heated and dried. The time for immersing the rare-earth magnet powder in the treatment liquid and mixing and stirring is generally 1 minute to 20 minutes, depending on the amount of the rare-earth magnet powder and the like. In order to impart oxidation resistance to the magnet powder without deteriorating the magnetic properties of the rare-earth magnet powder, heating and drying are performed in a vacuum or in an atmosphere of an inert gas (such as nitrogen gas or argon gas) at 50 ° C to 120 ° C. It is desirable to carry out at a temperature of ° C.
The heating and drying time is generally about 1 minute to 1 hour, although it depends on the amount of the rare earth magnet powder and the like. The oxidation-resistant rare earth-based magnet powder produced in this manner is considered to have a surface coated with a coating containing phosphoric acid and a metal having a thickness of 0.1 μm or less, and the magnet powder was further verified. However, it is presumed that this film is formed in a form in which a trace amount of metal is dissolved in iron phosphate generated from iron and phosphoric acid derived from the magnetic powder.
[0014]
The phenomenon that occurs near the surface of the rare-earth-based magnet powder, which occurs when the phosphate coating solution described in Patent Document 1 is used, is particularly small in the average particle diameter (major axis) (for example, (200 μm or less) The magnetic properties of the magnet powder are significantly deteriorated. However, according to the present invention, after a rare earth magnet powder having a small average particle diameter (major axis), for example, a rare earth magnet alloy having an average particle diameter of about 80 μm to 100 μm is heated in hydrogen to absorb hydrogen. The magnetic properties of a magnetically anisotropic HDDR (Hydrogenation-Disproportionation-Desorption-Recombination) magnet powder (see Japanese Patent Publication No. Hei 6-82575) obtained by dehydrogenation treatment and then cooling. Since excellent oxidation resistance can be imparted without causing deterioration, the method for producing the oxidation-resistant rare earth magnet powder of the present invention is highly useful in this regard.
[0015]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention should not be construed as being limited thereto.
[0016]
Example A: Preparation of Oxidation Resistant HDDR Magnet Powder No. 1 and its Characteristics Composition by Nd: 12.8 atomic%, Dy: 1.0 atomic%, B: 6.3 atomic%, Co: 14.8 atomic%, Ga: 0.5 atomic %, Zr 0.09 atomic%, the balance of Fe was prepared, annealed in an argon gas atmosphere at 1100 ° C. for 24 hours, and pulverized in an argon gas atmosphere having an oxygen concentration of 0.5% or less to obtain an average particle size. After being made into a coarsely pulverized powder of 100 μm, it is subjected to a hydrogenation heat treatment at 870 ° C. × 3 hours in a hydrogen gas pressurized atmosphere of 0.15 MPa, and then at 850 ° C. × 1 hour in a reduced pressure (1 kPa) argon gas stream. The following experiment was performed using HDDR magnet powder (average crystal grain diameter 0.4 μm) manufactured by performing a dehydrogenation treatment and then cooling.
[0017]
Experiment 1:
Treatment liquid 1 was prepared by adding cobalt sulfate to ethyl alcohol containing 0.5% by weight of phosphoric acid so that the Co ion became 70 ppm.
After 100 g of HDDR magnet powder is immersed in 300 cc of treatment liquid 1 for 5 minutes and mixed and stirred, the treated magnet powder is filtered to remove excess treatment liquid, and then this is vacuum-dried (<10 kPa) at 70 ° C. Heat drying for 20 minutes. The HDDR magnet powder (sample magnet powder 1) subjected to the surface treatment in this manner was subjected to a heating test in which the powder was heated at 150 ° C. for 100 hours in the atmosphere, and a weight increase rate due to oxidation after the test was measured before and after the test. Table 1 shows the results.
[0018]
Experiment 2:
An HDDR magnet powder (comparative sample magnet powder) which had been surface-treated in the same manner as in Experiment 1 using ethyl alcohol containing 0.5% by weight of phosphoric acid was obtained. The test was performed, and the rate of weight increase due to oxidation after the test before the test was measured. Table 1 shows the results.
[0019]
Experiment 3:
A heating test similar to that of Experiment 1 was performed on the HDDR magnet powder that had not been subjected to any surface treatment (control sample magnet powder), and the weight increase rate due to oxidation after the test before and after the test was measured. Table 1 shows the results.
[0020]
[Table 1]
As is evident from Table 1, the comparative sample magnet powder had a much smaller weight increase due to oxidation than the control sample magnet powder, but the sample magnet powder 1 had a larger weight increase due to oxidation than the comparative sample magnet powder. Further, it was found that the sample magnet powder 1 was excellent in oxidation resistance.
[0022]
Example B: Production of Oxidation-Resistant HDDR Magnet Powder No. 2 and Its Properties, Production of Bonded Magnet Using Oxidation-Resistant HDDR Magnet Powder and Its Properties Composition by high frequency melting: 12.8 atomic% of Nd, 6.3 atomic% of B , Co 14.8 atomic%, Ga 0.5 atomic%, Zr 0.09 atomic%, and a balance of Fe were prepared, annealed at 1100 ° C. for 24 hours in an argon gas atmosphere, and having an oxygen concentration of 0.5% or less. Pulverized in an argon gas atmosphere to obtain a coarsely pulverized powder having an average particle diameter of 100 μm, and then subjected to a hydrogenation heat treatment at 870 ° C. for 3 hours in a 0.15 MPa hydrogen gas pressurized atmosphere, and then reduced pressure (1 kPa) argon The following experiment was performed using an HDDR magnet powder (average crystal grain size: 0.4 μm) manufactured by performing a dehydrogenation treatment at 850 ° C. × 1 hour in a gas stream and then cooling.
[0023]
Experiment 1:
Using the treatment liquid 1 in Example A, an HDDR magnet powder subjected to surface treatment in the same manner as in Experiment 1 in Example A was obtained. Further, an epoxy resin and a phenol-based curing agent were dissolved in methyl ethyl ketone at a weight ratio of 100: 3 to prepare a resin liquid. After the surface-treated HDDR magnet powder and the resin liquid are uniformly mixed such that the ratio of the resin liquid weight to the total weight of the surface-treated HDDR magnet powder and the resin liquid is 3.5%, methyl ethyl ketone is added. The mixture was evaporated at room temperature to obtain a powdery granular rare earth bonded magnet compound. The obtained rare-earth bonded magnet compound is compression-molded at a pressure of 588 MPa in a magnetic field of 960 kA / m, and the obtained molded body is heated for 1 hour in an argon gas atmosphere at 150 ° C. to cure the epoxy resin. Thus, a bonded magnet having a size of 12.0 mm in length, 7.6 mm in width, 7.5 mm in height and a density of 5.9 g / cm 3 was produced. A heating test in which the bonded magnet (sample magnet 1) thus manufactured was heated at 150 ° C. in the air for 100 hours was performed, and a weight increase rate due to oxidation after the test was measured before and after the test. In addition, after magnetizing the sample magnet 1, a heating test in which heating was performed at 100 ° C. in air for 100 hours and a heating test in which heating was performed at 150 ° C. in air for 100 hours were performed. The magnetic flux deterioration rate (irreversible demagnetization rate) after the test was measured. Further, the sample magnet 1 subjected to the heating test of heating at 150 ° C. for 100 hours in the atmosphere was re-magnetized, and the magnetic flux deterioration rate (permanent demagnetization rate) after the re-magnetization before the heating test was measured. Table 2 shows the results.
[0024]
Experiment 2:
Treatment solution 2 prepared by adding sodium zirconate to ethyl alcohol containing 0.5% by weight of phosphoric acid so that Zr ion becomes 200 ppm and sodium vanadate so that V ion becomes 150 ppm Was used to obtain an HDDR magnet powder subjected to a surface treatment in the same manner as in Experiment 1, and a bonded magnet was produced. Various tests similar to those in Experiment 1 were performed on the bonded magnet (sample magnet 2) manufactured in this manner. Table 2 shows the results.
[0025]
Experiment 3:
An HDDR magnet powder surface-treated in the same manner as in Experiment 1 using ethyl alcohol containing 0.5% by weight of phosphoric acid was obtained, and a bonded magnet was produced. Various tests similar to those in Experiment 1 were performed on the thus-produced bonded magnet (comparative sample magnet). Table 2 shows the results.
[0026]
Experiment 4:
Bond magnets were manufactured in the same manner as in Experiment 1 using HDDR magnet powder that had not been subjected to any surface treatment. Various tests similar to those in Experiment 1 were performed on the bonded magnets (control sample magnets) thus manufactured. Table 2 shows the results.
[0027]
[Table 2]
As is clear from Table 2, the comparative sample magnet had a lower rate of weight increase due to oxidation and a lower magnetic flux deterioration rate than the control sample magnet, but the sample magnet 1 and the sample magnet 2 had a greater weight increase due to oxidation than the comparative sample magnet. Both the rate and the magnetic flux degradation rate were even lower. The reason why the sample magnet 1 and the sample magnet 2 exhibit such excellent characteristics is based on the fact that the sample magnet 1 and the sample magnet 2 are formed into a predetermined shape by using HDDR magnet powder having excellent oxidation resistance. This is based on the fact that the surface damage of the magnet powder is suppressed and the oxidation is effectively prevented even at the time of compression molding at the time of molding into a shape or after molding.
[0029]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the oxidation resistant rare earth magnet powder which is useful for manufacturing the rare earth bonded magnet which is excellent in oxidation resistance and shows high magnetic characteristics is provided.
Claims (8)
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