EP1032000B1 - Corrosion-resistant permanent magnet and method for producing the same - Google Patents
Corrosion-resistant permanent magnet and method for producing the same Download PDFInfo
- Publication number
- EP1032000B1 EP1032000B1 EP99943247A EP99943247A EP1032000B1 EP 1032000 B1 EP1032000 B1 EP 1032000B1 EP 99943247 A EP99943247 A EP 99943247A EP 99943247 A EP99943247 A EP 99943247A EP 1032000 B1 EP1032000 B1 EP 1032000B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- film
- magnet
- permanent magnet
- chemical conversion
- conversion coating
- 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.)
- Expired - Lifetime
Links
- 230000007797 corrosion Effects 0.000 title description 44
- 238000005260 corrosion Methods 0.000 title description 44
- 238000004519 manufacturing process Methods 0.000 title description 10
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 113
- 229910052782 aluminium Inorganic materials 0.000 claims description 109
- 239000000126 substance Substances 0.000 claims description 75
- 238000007739 conversion coating Methods 0.000 claims description 74
- 238000000034 method Methods 0.000 claims description 53
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 52
- 229910052726 zirconium Inorganic materials 0.000 claims description 38
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims description 37
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 32
- 229910052698 phosphorus Inorganic materials 0.000 claims description 32
- 239000011574 phosphorus Substances 0.000 claims description 32
- 229910052719 titanium Inorganic materials 0.000 claims description 27
- 239000010936 titanium Substances 0.000 claims description 27
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 26
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 26
- IMQLKJBTEOYOSI-GPIVLXJGSA-N Inositol-hexakisphosphate Chemical compound OP(O)(=O)O[C@H]1[C@H](OP(O)(O)=O)[C@@H](OP(O)(O)=O)[C@H](OP(O)(O)=O)[C@H](OP(O)(O)=O)[C@@H]1OP(O)(O)=O IMQLKJBTEOYOSI-GPIVLXJGSA-N 0.000 claims description 22
- IMQLKJBTEOYOSI-UHFFFAOYSA-N Phytic acid Natural products OP(O)(=O)OC1C(OP(O)(O)=O)C(OP(O)(O)=O)C(OP(O)(O)=O)C(OP(O)(O)=O)C1OP(O)(O)=O IMQLKJBTEOYOSI-UHFFFAOYSA-N 0.000 claims description 22
- 229940068041 phytic acid Drugs 0.000 claims description 22
- 239000000467 phytic acid Substances 0.000 claims description 22
- 235000002949 phytic acid Nutrition 0.000 claims description 22
- 229910052731 fluorine Inorganic materials 0.000 claims description 20
- 239000011737 fluorine Substances 0.000 claims description 20
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 claims description 19
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 19
- 229910052760 oxygen Inorganic materials 0.000 claims description 19
- 239000001301 oxygen Substances 0.000 claims description 19
- 150000003839 salts Chemical class 0.000 claims description 17
- 238000001035 drying Methods 0.000 claims description 11
- 150000003609 titanium compounds Chemical class 0.000 claims description 9
- 150000003755 zirconium compounds Chemical class 0.000 claims description 9
- 229910052751 metal Inorganic materials 0.000 claims description 7
- 239000002184 metal Substances 0.000 claims description 7
- 150000002222 fluorine compounds Chemical class 0.000 claims description 6
- 238000005019 vapor deposition process Methods 0.000 claims description 5
- 239000000243 solution Substances 0.000 description 44
- 125000004429 atom Chemical group 0.000 description 14
- 230000001133 acceleration Effects 0.000 description 10
- 230000015572 biosynthetic process Effects 0.000 description 10
- 239000007789 gas Substances 0.000 description 9
- 238000005480 shot peening Methods 0.000 description 9
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 8
- 230000006866 deterioration Effects 0.000 description 8
- 238000002347 injection Methods 0.000 description 8
- 239000007924 injection Substances 0.000 description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 239000002253 acid Substances 0.000 description 6
- 239000000853 adhesive Substances 0.000 description 6
- 230000001070 adhesive effect Effects 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 6
- 238000007733 ion plating Methods 0.000 description 6
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 6
- 239000012071 phase Substances 0.000 description 6
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 description 5
- 230000004907 flux Effects 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 239000002245 particle Substances 0.000 description 5
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- 238000004833 X-ray photoelectron spectroscopy Methods 0.000 description 4
- 229910052786 argon Inorganic materials 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 239000013078 crystal Substances 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- 238000007747 plating Methods 0.000 description 4
- 238000003825 pressing Methods 0.000 description 4
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 3
- 229910019142 PO4 Inorganic materials 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 229910052783 alkali metal Inorganic materials 0.000 description 3
- 150000001340 alkali metals Chemical class 0.000 description 3
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 3
- 239000011324 bead Substances 0.000 description 3
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 3
- 229910052759 nickel Inorganic materials 0.000 description 3
- 230000003647 oxidation Effects 0.000 description 3
- -1 oxides Chemical class 0.000 description 3
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 3
- 239000010452 phosphate Substances 0.000 description 3
- 238000004544 sputter deposition Methods 0.000 description 3
- 238000007738 vacuum evaporation Methods 0.000 description 3
- 229910052725 zinc Inorganic materials 0.000 description 3
- 239000011701 zinc Substances 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 2
- 229910052779 Neodymium Inorganic materials 0.000 description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 2
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 2
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 2
- 238000013019 agitation Methods 0.000 description 2
- 150000001342 alkaline earth metals Chemical class 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 238000006731 degradation reaction Methods 0.000 description 2
- 238000009713 electroplating Methods 0.000 description 2
- 230000002708 enhancing effect Effects 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 150000007524 organic acids Chemical class 0.000 description 2
- 229910052761 rare earth metal Inorganic materials 0.000 description 2
- 239000011347 resin Substances 0.000 description 2
- 229920005989 resin Polymers 0.000 description 2
- PUZPDOWCWNUUKD-UHFFFAOYSA-M sodium fluoride Chemical compound [F-].[Na+] PUZPDOWCWNUUKD-UHFFFAOYSA-M 0.000 description 2
- UNXRWKVEANCORM-UHFFFAOYSA-N triphosphoric acid Chemical compound OP(O)(=O)OP(O)(=O)OP(O)(O)=O UNXRWKVEANCORM-UHFFFAOYSA-N 0.000 description 2
- TUSDEZXZIZRFGC-UHFFFAOYSA-N 1-O-galloyl-3,6-(R)-HHDP-beta-D-glucose Natural products OC1C(O2)COC(=O)C3=CC(O)=C(O)C(O)=C3C3=C(O)C(O)=C(O)C=C3C(=O)OC1C(O)C2OC(=O)C1=CC(O)=C(O)C(O)=C1 TUSDEZXZIZRFGC-UHFFFAOYSA-N 0.000 description 1
- DDFHBQSCUXNBSA-UHFFFAOYSA-N 5-(5-carboxythiophen-2-yl)thiophene-2-carboxylic acid Chemical compound S1C(C(=O)O)=CC=C1C1=CC=C(C(O)=O)S1 DDFHBQSCUXNBSA-UHFFFAOYSA-N 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910052684 Cerium Inorganic materials 0.000 description 1
- 229910000722 Didymium Inorganic materials 0.000 description 1
- 241000224487 Didymium Species 0.000 description 1
- 229910052692 Dysprosium Inorganic materials 0.000 description 1
- 229910052691 Erbium Inorganic materials 0.000 description 1
- 229910052693 Europium Inorganic materials 0.000 description 1
- 239000001263 FEMA 3042 Substances 0.000 description 1
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical group [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 1
- 229910052688 Gadolinium Inorganic materials 0.000 description 1
- 229910021578 Iron(III) chloride Inorganic materials 0.000 description 1
- 229910052765 Lutetium Inorganic materials 0.000 description 1
- UEZVMMHDMIWARA-UHFFFAOYSA-N Metaphosphoric acid Chemical compound OP(=O)=O UEZVMMHDMIWARA-UHFFFAOYSA-N 0.000 description 1
- 229910001122 Mischmetal Inorganic materials 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- 229910021586 Nickel(II) chloride Inorganic materials 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- IOVCWXUNBOPUCH-UHFFFAOYSA-N Nitrous acid Chemical compound ON=O IOVCWXUNBOPUCH-UHFFFAOYSA-N 0.000 description 1
- LRBQNJMCXXYXIU-PPKXGCFTSA-N Penta-digallate-beta-D-glucose Natural products OC1=C(O)C(O)=CC(C(=O)OC=2C(=C(O)C=C(C=2)C(=O)OC[C@@H]2[C@H]([C@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)[C@@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)[C@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)O2)OC(=O)C=2C=C(OC(=O)C=3C=C(O)C(O)=C(O)C=3)C(O)=C(O)C=2)O)=C1 LRBQNJMCXXYXIU-PPKXGCFTSA-N 0.000 description 1
- 239000004952 Polyamide Substances 0.000 description 1
- 229910052777 Praseodymium Inorganic materials 0.000 description 1
- 229910052772 Samarium Inorganic materials 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 229910052775 Thulium Inorganic materials 0.000 description 1
- 229910052769 Ytterbium Inorganic materials 0.000 description 1
- 229910007998 ZrF4 Inorganic materials 0.000 description 1
- YDHWWBZFRZWVHO-UHFFFAOYSA-H [oxido-[oxido(phosphonatooxy)phosphoryl]oxyphosphoryl] phosphate Chemical compound [O-]P([O-])(=O)OP([O-])(=O)OP([O-])(=O)OP([O-])([O-])=O YDHWWBZFRZWVHO-UHFFFAOYSA-H 0.000 description 1
- 239000003929 acidic solution Substances 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 229910052787 antimony Inorganic materials 0.000 description 1
- LDDQLRUQCUTJBB-UHFFFAOYSA-O azanium;hydrofluoride Chemical compound [NH4+].F LDDQLRUQCUTJBB-UHFFFAOYSA-O 0.000 description 1
- QTPILKSJIOLICA-UHFFFAOYSA-N bis[hydroxy(phosphonooxy)phosphoryl] hydrogen phosphate Chemical compound OP(O)(=O)OP(O)(=O)OP(O)(=O)OP(O)(=O)OP(O)(O)=O QTPILKSJIOLICA-UHFFFAOYSA-N 0.000 description 1
- KGBXLFKZBHKPEV-UHFFFAOYSA-N boric acid Chemical compound OB(O)O KGBXLFKZBHKPEV-UHFFFAOYSA-N 0.000 description 1
- 239000004327 boric acid Substances 0.000 description 1
- VOVNIMMKYYUQIN-UHFFFAOYSA-N chloric acid Chemical compound OCl(=O)=O.OCl(=O)=O VOVNIMMKYYUQIN-UHFFFAOYSA-N 0.000 description 1
- 229940005991 chloric acid Drugs 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000011651 chromium Substances 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- RKTYLMNFRDHKIL-UHFFFAOYSA-N copper;5,10,15,20-tetraphenylporphyrin-22,24-diide Chemical compound [Cu+2].C1=CC(C(=C2C=CC([N-]2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3[N-]2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 RKTYLMNFRDHKIL-UHFFFAOYSA-N 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000005238 degreasing Methods 0.000 description 1
- NINOVVRCHXVOKB-UHFFFAOYSA-N dialuminum;dioxido(dioxo)chromium Chemical compound [Al+3].[Al+3].[O-][Cr]([O-])(=O)=O.[O-][Cr]([O-])(=O)=O.[O-][Cr]([O-])(=O)=O NINOVVRCHXVOKB-UHFFFAOYSA-N 0.000 description 1
- 238000003618 dip coating Methods 0.000 description 1
- 239000001177 diphosphate Substances 0.000 description 1
- XPPKVPWEQAFLFU-UHFFFAOYSA-J diphosphate(4-) Chemical compound [O-]P([O-])(=O)OP([O-])([O-])=O XPPKVPWEQAFLFU-UHFFFAOYSA-J 0.000 description 1
- 235000011180 diphosphates Nutrition 0.000 description 1
- XPPKVPWEQAFLFU-UHFFFAOYSA-N diphosphoric acid Chemical compound OP(O)(=O)OP(O)(O)=O XPPKVPWEQAFLFU-UHFFFAOYSA-N 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000007772 electroless plating Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 229910052733 gallium Inorganic materials 0.000 description 1
- 229910052732 germanium Inorganic materials 0.000 description 1
- 229910052735 hafnium Inorganic materials 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- CDAISMWEOUEBRE-GPIVLXJGSA-N inositol Chemical compound O[C@H]1[C@H](O)[C@@H](O)[C@H](O)[C@H](O)[C@@H]1O CDAISMWEOUEBRE-GPIVLXJGSA-N 0.000 description 1
- 229960000367 inositol Drugs 0.000 description 1
- 238000010406 interfacial reaction Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 238000010303 mechanochemical reaction Methods 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- VLAPMBHFAWRUQP-UHFFFAOYSA-L molybdic acid Chemical compound O[Mo](O)(=O)=O VLAPMBHFAWRUQP-UHFFFAOYSA-L 0.000 description 1
- QMMRZOWCJAIUJA-UHFFFAOYSA-L nickel dichloride Chemical compound Cl[Ni]Cl QMMRZOWCJAIUJA-UHFFFAOYSA-L 0.000 description 1
- LGQLOGILCSXPEA-UHFFFAOYSA-L nickel sulfate Chemical compound [Ni+2].[O-]S([O-])(=O)=O LGQLOGILCSXPEA-UHFFFAOYSA-L 0.000 description 1
- 229910000008 nickel(II) carbonate Inorganic materials 0.000 description 1
- 229910000363 nickel(II) sulfate Inorganic materials 0.000 description 1
- ZULUUIKRFGGGTL-UHFFFAOYSA-L nickel(ii) carbonate Chemical compound [Ni+2].[O-]C([O-])=O ZULUUIKRFGGGTL-UHFFFAOYSA-L 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- DCKVFVYPWDKYDN-UHFFFAOYSA-L oxygen(2-);titanium(4+);sulfate Chemical compound [O-2].[Ti+4].[O-]S([O-])(=O)=O DCKVFVYPWDKYDN-UHFFFAOYSA-L 0.000 description 1
- 229920002647 polyamide Polymers 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- LJCNRYVRMXRIQR-OLXYHTOASA-L potassium sodium L-tartrate Chemical compound [Na+].[K+].[O-]C(=O)[C@H](O)[C@@H](O)C([O-])=O LJCNRYVRMXRIQR-OLXYHTOASA-L 0.000 description 1
- 229940005657 pyrophosphoric acid Drugs 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- CDAISMWEOUEBRE-UHFFFAOYSA-N scyllo-inosotol Natural products OC1C(O)C(O)C(O)C(O)C1O CDAISMWEOUEBRE-UHFFFAOYSA-N 0.000 description 1
- 229910021332 silicide Inorganic materials 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 239000011775 sodium fluoride Substances 0.000 description 1
- 235000013024 sodium fluoride Nutrition 0.000 description 1
- 235000011006 sodium potassium tartrate Nutrition 0.000 description 1
- BFXAWOHHDUIALU-UHFFFAOYSA-M sodium;hydron;difluoride Chemical compound F.[F-].[Na+] BFXAWOHHDUIALU-UHFFFAOYSA-M 0.000 description 1
- 238000004528 spin coating Methods 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- LRBQNJMCXXYXIU-NRMVVENXSA-N tannic acid Chemical compound OC1=C(O)C(O)=CC(C(=O)OC=2C(=C(O)C=C(C=2)C(=O)OC[C@@H]2[C@H]([C@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)[C@@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)[C@@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)O2)OC(=O)C=2C=C(OC(=O)C=3C=C(O)C(O)=C(O)C=3)C(O)=C(O)C=2)O)=C1 LRBQNJMCXXYXIU-NRMVVENXSA-N 0.000 description 1
- 229940033123 tannic acid Drugs 0.000 description 1
- 235000015523 tannic acid Nutrition 0.000 description 1
- 229920002258 tannic acid Polymers 0.000 description 1
- 229910052715 tantalum Inorganic materials 0.000 description 1
- JBQYATWDVHIOAR-UHFFFAOYSA-N tellanylidenegermanium Chemical group [Te]=[Ge] JBQYATWDVHIOAR-UHFFFAOYSA-N 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- QDZRBIRIPNZRSG-UHFFFAOYSA-N titanium nitrate Inorganic materials [O-][N+](=O)O[Ti](O[N+]([O-])=O)(O[N+]([O-])=O)O[N+]([O-])=O QDZRBIRIPNZRSG-UHFFFAOYSA-N 0.000 description 1
- 229910000348 titanium sulfate Inorganic materials 0.000 description 1
- 239000001226 triphosphate Substances 0.000 description 1
- 235000011178 triphosphate Nutrition 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- CMPGARWFYBADJI-UHFFFAOYSA-L tungstic acid Chemical compound O[W](O)(=O)=O CMPGARWFYBADJI-UHFFFAOYSA-L 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- 239000012808 vapor phase Substances 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
- 239000011787 zinc oxide Substances 0.000 description 1
- ZXAUZSQITFJWPS-UHFFFAOYSA-J zirconium(4+);disulfate Chemical compound [Zr+4].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O ZXAUZSQITFJWPS-UHFFFAOYSA-J 0.000 description 1
- 229910000859 α-Fe Inorganic materials 0.000 description 1
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
Definitions
- the present invention relates to an Fe-B-R based permanent magnet having an excellent corrosion-resistant film, and to a process for producing the same. More particularly, the present invention relates to an Fe-B-R based permanent magnet which has, on the surface thereof, a corrosion-resistant film having an excellent adhesion to the magnet, and which can exhibit a stable high magnetic characteristic that cannot be deteriorated even if the magnet is left to stand for a long time under high-temperature and high-humidity conditions of a temperature of 80°C and a relative humidity of 90 %; and in which the film is free from hexa-valent chromium, and to a process for producing the same.
- An Fe-B-R based permanent magnet of which an Fe-B-Nd based permanent magnet is representative, is practically used in various applications, because it is produced from an inexpensive material rich in natural resources and has a high magnetic characteristic, as comparedwith an Sm-Co based permanent magnet.
- the Fe-B-R based permanent magnet is liable to be corroded by oxidation in the atmosphere, because it contains highly reactive R and Fe.
- the corrosion of the magnet is advanced from its surface due to the presence of a small amount of acid, alkali and/or water to produce rust, thereby bringing about the degradation and dispersion of the magnetic characteristic.
- the magnet having the rust produced therein is incorporated into a device such as a magnetic circuit, there is a possibility that the rust is scattered to pollute surrounding parts or components.
- the magnetic characteristic of the magnet may be degraded by 10 % or more from an initial value after lapse of 100 hours.
- an oxidization-resistant chemical conversion coating film such as a phosphate film or a chromate film is formed on the surface of an Fe-B-R based permanent magnet (see Japanese Patent Publication No.4-22008).
- the film formed in this process is excellent in adhesion to the magnet, but if it is subjected to a corrosion resistance test under conditions of a temperature of 60°C and a relative humidity of 90 %, the magnetic characteristic of the magnet may be degraded by 10 % or more from an initial value after lapse of 300 hours.
- the chromate treatment used in this process uses hexa-valent chromium which is undesirable for the surroundings and for this reason, a waste-liquid treating method is complicated. It is feared that a film formed in this process influences a human body during handling of the magnet, because it contains just a small amount of hexa-valent chromium.
- a corrosion-resistant permanent magnet and its manufacture are known.
- a TiN-film on the surface of the magnet with an Al-film inbetween is provided.
- the TiN-film is formed by a vapor-phase film forming method in an N 2 gas atmosphere.
- a Fe-B-R type permanent magnet having an anti-corrosive coating film layer provided on its surface.
- the anti-corrosive film is formed of metals, oxides, nitrides, carbides, borides, silicides, composite compositions thereof or a mixture thereof.
- a resin may be used to be impregnated into the micropores of the thin coating film to further improve its corrosion resistance.
- an object of the present invention to provide an Fe-B-R based permanent magnet which has, on the surface thereof, a corrosion-resistant film having an excellent adhesion to the magnet, and which can exhibit a stable high magnetic characteristic that cannot be deteriorated even if the magnet is left to stand for a long time under high-temperature and high-humidity conditions of a temperature of 80°C and a relative humidity of 90 %, and in which the film is free from hexa-valent chromium, and a process for producing the same.
- the present inventors as a result of various zealous studies made with the above points in view, have found that if an aluminum film is formed on the surface of an Fe-B-R based permanent magnet, and a chemical conversion coating film containing titanium and/or zirconium as constituting elements is formed on the aluminum film, the chemical conversion coating film is firmly adhered onto the magnet with the aluminum film interposed therebetween, thereby exhibiting an excellent corrosion resistance.
- an Fe-B-R based permanent magnet which has a chemical conversion coating film formed on its surface with an aluminum film interposed therebetween, the chemical conversion coating film containing at least one of titanium and zirconium, and phosphorus, oxygen and fluorine as constituting elements.
- the aluminum film has a thickness in a range of 0.01 ⁇ m to 50 ⁇ m.
- the chemical conversion coating film has a thickness in a range of 0.01 ⁇ m to 1 ⁇ m.
- the content of titanium and/or zirconium in the chemical conversion coating film is in a range of 0.1 mg to 100 mg per a film portion formed on 1 m 2 of the surface of the magnet.
- the content of phosphorus in the chemical conversion coating film is in a range of 0.1 mg to 100 mg per a film portion formed on 1 m 2 of the surface of the magnet.
- the content of oxygen in the chemical conversion coating film is in a range of 0.2 mg to 300 mg per a film portion formed on 1 m 2 of the surface of the magnet.
- the content of fluorine in the chemical conversion coating film is in a range of 0.05 mg to 100 mg per a film portion formed on 1 m 2 of the surface of the magnet.
- the ratio of the number of moles of phosphorus to the number of moles of titanium and/or zirconium in an area near the surface of the chemical conversion coating film is larger than that in the entire chemical conversion coating film.
- the ratio of the number of moles of phosphorus to the number of moles of titanium and/or zirconium in an area near the surface of the chemical conversion coating film is equal to or larger than 1.
- a process for producing an Fe-B-R based permanent magnet comprising the steps of forming an aluminum film on the surface of an Fe-B-R based permanent magnet, applying a treating solution containing at least one of a titanium compound and a zirconium compound, at least one of phosphoric acid, condensed phosphoric acid, phytic acid, the hydrolyzate of phytic acid and the salts of them, and a fluorine compound, onto the surface of the aluminum film, and drying the applied treating solution, thereby forming a chemical conversion coating film containing at least one of titanium and zirconium, and phosphorus, oxygen and fluorine as constituting elements.
- the aluminum film is formed by a vapor deposition process.
- the aluminum film has a thickness in a range of 0.01 ⁇ m to 50 ⁇ m.
- the Fe-B-R based permanent magnet and aluminum pieces are placed into a treating vessel, where they are vibrated and/or agitated, thereby forming the aluminum film.
- the aluminum film has a thickness in a range of 0.01 ⁇ m to 1 ⁇ m.
- the ratio of the number of moles (in terms of phosphorus) of at least one of phosphoric acid, condensed phosphoric acid, phytic acid, the hydrolyzate of phytic acid and the salts of them to the number of moles (in terms of metal) of at least one of the titanium compound and the zirconium compound in the treating solution is equal to or larger than 1.
- An Fe-B-R based permanent magnet according to the present invention has a feature that it has a chemical conversion coating film which is formed on its surface with an aluminum film interposed therebetween, and which contains at least one of titanium and zirconium, and phosphorus, oxygen and fluorine as constituting elements.
- the method for forming the aluminum film on the surface of the Fe-B-R based permanent magnet is particularly not limited. However, if it is taken into consideration that the magnet and the aluminum film are liable to be corroded by oxidation, examples of desirable process are a process utilizing a vapor deposition process, and a process which comprises placing an Fe-B-R based permanent magnet and aluminum pieces into a treating vessel, where they are vibrated and/or agitated.
- the vapordepositionprocess examples include known processes such as a vacuum evaporation process, an ion sputtering process, an ion plating process and the like.
- the aluminum film may be formed under common conditions in each of the processes, but from the viewpoints of the denseness, the uniformity in thickness, the forming speed of the film to be formed and the like, it is desirable that the vacuum evaporation process and the ion plating process are employed.
- the surface of the magnet may be subjected to a known cleaning treatment such as a washing, a degreasing treatment and a sputtering, prior to the formation of the film.
- the temperature of the magnet during the formation of the film is set in a range of 200°C to 500°C. If the temperature is lower than 200°C, there is a possibility that a film having an excellent adhesion to the surface of the magnet is not formed. On the other hand, if the temperature exceeds 500°C, there is a possibility that cracks are produced in the film, thereby causing the film to be peeled off from the magnet, in a cooling course after the formation of the film.
- the thickness of the aluminum film is in a range of 0.01 ⁇ m to 50 ⁇ m, more preferably, in a range of 0.05 ⁇ m to 25 ⁇ m. If the thickness is smaller than 0.01 ⁇ m, there is a possibility that the film cannot exhibit an excellent corrosion resistance. If the thickness exceeds 50 ⁇ m, there is a possibility that an increase in manufacture cost is brought about, but also, there is a possibility that the effective volume of the magnet is decreased.
- the aluminum pieces used in this process may be of any of various shapes such as a needle-like shape (a wire-like shape) a columnar shape and amassive shape.
- a needle-like shape a wire-like shape
- a columnar shape a columnar shape and amassive shape.
- aluminum pieces having a needle-like shape with sharp terminal ends or a columnar shape with sharp terminal ends is used.
- the size (longer diameter) of the aluminum pieces is in a range of 0.05 mm to 10 mm, more preferably in a range of 0.3 mm to 5 mm, further preferably in a range of 0.5 mm to 3 mm.
- Aluminum pieces having the same shape and the same size may be used, but aluminum pieces having different shapes and different sizes may be used in the form of a mixture.
- the vibration and/or agitation of the magnet and the aluminum pieces is carried out in a dry manner in consideration of the fact that they are liable to be corroded by oxidation.
- the vibration and/or agitation of the magnet and the aluminum pieces can be carried out in the atmosphere and at ambient temperature. It is unnecessary to employ a complicated apparatus for the treating vessel used in the present invention, and for example, the treating vessel may be a treating chamber in a barrel finishing machine.
- the barrel finishing machine may be of any known type such as a rotated-type, a vibrated-type and a centrifugal-type. In the case of the rotated-type, the rotational speed is desirable to be in a range of 20 rpm to 50 rpm.
- the vibration frequency is in a range of 50 Hz to 100 Hz, and the vibration amplitude is in a range of 0.3 mm to 10 mm.
- the rotational speed is desirable to be in a range of 70 rpm to 200 rpm.
- the total amount of the magnet and the aluminum pieces placed into the treating vessel is in a range of 20 % to 90 % by volume of the internal volume of the treating vessel. If the total amount is smaller than 20 % by volume, the throughput is too small, which is not preferable in practical use. If the total amount exceeds 90 % by volume, there is a possibility that the film cannot be formed efficiently. It is desirable that the ratio of the amount of the magnet to the amount of the aluminum pieces placed into the treating vessel is equal to or smaller than 3 in terms of a volume ratio (of magnet/aluminum pieces). If the volume ratio exceeds 3, there is a possibility that a long time is required for the formation of the film, which is not preferred in practical use. The treating time depends on the throughput, but is usually in a range of 1 to 10 hours.
- a fine aluminum powder produced from the aluminum pieces is adhered to the surface of the magnet to form the aluminum film.
- the phenomenon of the adhesion of the fine aluminum powder to the surface of the magnet is a kind of a mechanochemical reaction.
- the fine aluminum powder is adhered firmly to the surface of the magnet, and the formed aluminum film exhibits an excellent corrosion resistance.
- the thickness of the film is equal to or larger than 0.01 ⁇ m, as described above.
- the upper limit for the thickness is particularly not limited, but if the thickness exceeds 1 ⁇ m, a long time is required for forming the aluminum film. For this reason, this process is suitable to form an aluminum film having a thickness equal to or smaller than 1 ⁇ m.
- the aluminum film After the formation of the aluminum film on the surface of the magnet, the aluminum film can be subjected to a heat treatment to enhance the adhesion of the aluminum film to the surface of the magnet.
- the temperature in the heat treatment is desirable to be in a range of 200°C to 500°C, and more desirable to be in a range of 200°C to 250°C from the viewpoints of productivity and manufacture cost. If the temperature is lower than 200°C, there is a possibility that an interfacial reaction of the aluminum film with the magnet is not advanced sufficiently, and as a result, the adhesion is not enhanced. If the temperature exceeds 500°C, there is a possibility that the deterioration of the magnetic characteristic of the magnet is brought about and that the aluminum film is melted.
- a process for forming a chemical conversion coating film containing at least one of titanium and zirconium, and phosphorus, oxygen and fluorine as constituting elements on the aluminum film will be described below.
- One example of this process is a process which comprises applying, to the surface of the aluminum film, a treating solution containing at least one of a titanium compound and a zirconium compound, at least one of phosphoric acid, condensed phosphoric acid, phytic acid, the hydrolyzate of phytic acid and the salts of them, and a fluorine compound, and subjecting the applied solution to a drying treatment.
- the treating solution is prepared by dissolving, into water, at least one of the titanium compound and the zirconium compound, at least one of phosphoric acid, condensed phosphoric acid, phytic acid, the hydrolyzate of phytic acid and the salts of them, and the fluorine compound.
- Examples of the titanium compound contained in the treating solution, whichmaybeused, are fluorotitanic acid, alkali metal, alkaline earth metal and ammonium fluorotitanates, titanium sulfate and nitrate and the like.
- Examples of the zirconium compound which may be used are fluorozirconic acid, alkali metal, alkaline earth metal and ammonium fluorozirconates, zirconium sulfate and nitrate and the like. It is desirable that the content of at least one of the titanium compound and zirconium compound in the treating solution is in a range of 1 ppm to 2,000 ppm, more preferably, in a rang of 10 ppm to 1,000 ppm in terms of metal. If the content is smaller than 1 ppm, there is a possibility that the chemical conversion coating film is not formed. If the content is larger than 2,000 ppm, there is a possibility that an increase in cost is brought about.
- Examples of condensed phosphoric acid contained in the treating solution are pyrophosphoric acid, tripolyphosphoric acid, metaphosphoric acid, ultraphosphoric acid and the like.
- Examples of the hydrolyzate of phytic acid which may be used, are myo-inositol diphosphate, triphosphate, tetraphosphate and pentaphosphate and the like.
- Examples of the salts of phosphoric acid, condensed phosphoric acid, phytic acid and the hydrolyzate of phytic acid which may be used, are ammonium, alkali metal and alkaline earth metal salts of phosphoric acid, condensed phosphoric acid, phytic acid and the hydrolyzate of phytic acid.
- the content thereof in the treating solution is in a range of 1 ppm to 2,000 ppm, more preferably, in a range of 5 ppm to 1,000 ppm in terms of phosphoric acid.
- the reason is as follows; if the content is smaller than 1 ppm, there is a possibility that a chemical conversion coating film is not formed. If the content is larger than 2,000 ppm, the adhesion of a chemical conversion coating film to the magnet is influenced.
- the content thereof in the treating solution is in a range of 50 ppm to 10,000 ppm, more preferably, in a range of 100 ppm to 5,000 ppm in terms of phytic acid.
- Examples of the fluorine compound contained in the treating solution are hydrofluoric acid, ammonium fluoride, ammonium hydrogen fluoride, sodium fluoride and sodium hydrogen fluoride and the like, in addition to the above-described fluorotitanic acid and the salt thereof, and fluorozirconic acid and the salt thereof. It is desirable that the content of the fluorine compound in the treating solution is in a range of 10 ppm to 10,000 ppm, more preferably, in a range of 50 ppm to 5,000 ppm. If the content is smaller than 10 ppm, there is a possibility that the surface of the aluminum film is not etched efficiently. If the content is larger than 10,000 ppm, there is a possibility that the etching speed is higher than the film forming speed, thereby making it difficult to form a film uniformly.
- the pH value of the treating solution is regulated to a range of 1 to 6. If the pH value is smaller than 1, there is a possibility that the surface of the aluminum film is etched excessively. If the pH value exceeds 6, there is a possibility that the stability of the treating solution is influenced.
- an organic acid such as tannic acid, an oxidizing agent (hydrogen peroxide, chloric acid and the salts thereof, nitrous acid and the salt thereof, nitric acid and the salt thereof, tungstic acid and the salt thereof, and molybdic acid and the salt thereof), and a water-soluble resin such as a water-soluble polyamide, may be added to the treating solution for the purpose of enhancing the chemically converting reaction, the stability of the treating solution, the adhesion of a chemical conversion coating film to the magnet and the adhesion to an adhesive used for incorporating the magnet into parts.
- an organic acid such as tannic acid, an oxidizing agent (hydrogen peroxide, chloric acid and the salts thereof, nitrous acid and the salt thereof, nitric acid and the salt thereof, tungstic acid and the salt thereof, and molybdic acid and the salt thereof), and a water-soluble resin such as a water-soluble polyamide
- the treating solution may be prepared as required.
- the treating solution which maybe used in the present invention, are a treating solution prepared from PALCOAT 3753 (which is a trade name and made by Nihon Parkerizing Co., Ltd.), and a treating solution prepared from PALCOAT 3756MA and PALCOAT 3756MB (both of which are trade names and made by Nihon Parkerizing Co., Ltd.).
- Examples of the method for applying the treating solution to the surface of the aluminum film are a dip coating process, a spraying process and a spin coating process. It is desirable that the temperature of the treating solution when being applied is set in a range of 20°C to 80°C. If the temperature is lower than 20°C, there is a possibility that the reaction is not advanced. If the temperature exceeds 80°C, there is a possibility that the stability of the treating solution is influenced.
- the treating time is usually in a range of 10 seconds to 10 minutes.
- the applied treating solution is subjected to a drying treatment.
- the temperature in the drying treatment is desirable to be in a range of 50°C to 250°C, and more desirable to be in a range of 50°C to 150°C from the viewpoints of the productivity and manufacture cost. The reason is as follows: If the temperature is lower than 50°C, the treating solution cannot be dried sufficiently and as a result, there is a possibility that the deterioration of the appearance is brought about, and that the adhesion to an adhesive used for incorporating the magnet into parts is influenced. If the temperature exceeds 250°C, there is a possibility that the decomposition of the chemical conversion coating film occurs.
- the treating time is usually in a range of 5 seconds to 1 hour.
- the chemical conversion coating film formed by the above-described process and containing at least one of titanium and zirconium, phosphorus, oxygen and fluorine as constituting elements is adhered firmly to the surface of the magnet with the aluminum film interposed therebetween. Therefore, if the thickness of the chemical conversion coating film is equal to or larger than 0.01 ⁇ m, a sufficient corrosion resistance is provided. It is believed that during the chemically converting treatment, phosphoric acid or condensed phosphoric acid in the treating solution reacts with Nd or Fe which is a magnet material on the surface of the magnet, thereby forming a passive film, and hence, even if the aluminum film has a portion which has been formed unsatisfactorily, the passive film compensates for the corrosion resistance of such portion.
- the thickness of the chemical conversion coating film is desirable to be equal to or smaller than 1 ⁇ m and more desirable to be equal to or smaller than 0.3 ⁇ m from the viewpoints of the demand based on a reduction in size of the magnet itself and the manufacture cost.
- the content of titanium and/or zirconium in the chemical conversion coating film is desirable to be in a range of 0.1 mg to 100 mg and more desirable to be in a range of 1 mg to 50 mg per a film portion formed on 1 m 2 Of the surface of the magnet. If the content is smaller than 0. 1 mg, there is a possibility that a sufficient corrosion resistance is not provided. If the content is larger than 100 mg, there is a possibility that an increase in cost is brought about.
- the content of phosphorus in the chemical conversion coating film is desirable to be in a range of 0.1 mg to 100 mg and more desirable to be in a range of 1 mg to 50 mg per a film portion formed on 1 m 2 of the surface of the magnet. If the content is smaller than 0.1 mg, there is a possibility that a sufficient corrosion resistance is not provided. If the content is larger than 100 mg, there is a possibility that the adhesion to an adhesive used for incorporating the magnet into parts is influenced.
- Oxygen in the chemical conversion coating film is present in the chemical conversion coating film in the form bonded to titanium, zirconium or phosphorus, and as a constituting element of the organic acid added into the treating solution for the purpose of enhancing the adhesion to an adhesive used for incorporating the magnet into the parts. It is desirable that the content of oxygen in the chemical conversion coating film is in a range of 0.2 mg to 300 mg per a film portion formed on 1 m 2 of the surface of the magnet. If the content is smaller than 0.2 mg, there is a possibility that a sufficient corrosion resistance is not provided. If the content is larger than 300 mg, there is a possibility that the adhesion to an adhesive used for incorporating the magnet into the parts is influenced.
- Fluorine in the chemical conversion coating film is incorporated into the chemical conversion coating film upon the formation of the chemical conversion coating film due to free fluorine ion or fluorine bonding with the Zr compound such as ZrF 4 HPO 4 present in the treating solution for the purpose of etching the surface of the aluminum film.
- the content of fluorine in the chemical conversion coating film is desirable to be in a range of 0.05 mg to 100 mg and more desirable to be in a range of 0.1 mg to 50 mg per a film portion formed on 1 m 2 of the surface of the magnet. If the content is smaller than 0.05 mg, there is a possibility that a sufficient corrosion resistance is not provided. If the content is larger than 100 mg, there is a possibility that the adhesion to an adhesive used for incorporating the magnet into the parts is influenced.
- Preferred among the chemical conversion coating films formed by the above-described process and containing at least one of titanium and zirconium, phosphorus, oxygen and fluorine as constituting elements are a film in which the ratio of the number of moles of phosphorus to the number of moles of titanium and/or zirconium in an area near the surface of the film (e.g., an area between the surface of the film and a point 0.002 ⁇ m spaced apart from the surface of the film) is larger than that in the entire film, and a film in which the ratio of the number of moles of phosphorus to the number of moles of titanium and/or zirconium in an area near the surface of the film is equal to or larger than 1, desirably, equal to or larger than 2 and more desirably, equal to or larger than 3.
- the reason is believed to be that even if the film is brought into contact with water, a large number of molecules of phosphoric acid or condensed phosphoric acid present in the area near the surface of the film catch the water, thereby preventing the water causing the corrosion from reaching the surface of the magnet.
- a treating solution in which the ratio of the number of moles (in terms of phosphorus) of at least one of phosphoric acid, condensed phosphoric acid, phytic acid, the hydrolyzate of phytic acid and the salts of them to the number of moles (in terms of metal) of at least one of the titanium compound and the zirconium compound in the treating solution is equal to or larger than 1.
- a shot peening (a method for modifying a surface by bumping hard grains against the surface) may be carried out as a previous step.
- the shot peening enables the aluminum film to be smoothened, thereby facilitating the formation of a chemical conversion coating film which is thin, but has an excellent corrosion resistance.
- a powder used for the shot peening is desirable to have a hardness equivalent to or higher that of the formed aluminum film, and examples of the powder are spherical hard materials having a Mohs hardness of 3 or more such as those comprising steel balls and glass beads.
- the average particle size of the powder is desirable to be in a range of 30 ⁇ m to 3,000 ⁇ m and more desirable to be in a range of 40 ⁇ m to 2,000 ⁇ m. If the average particle size is smaller than 30 ⁇ m, the pressing force applied to the aluminum film is small, resulting in a long time taken for the treatment. On the other hand, if the average particle size exceeds 3,000 ⁇ m, there is a possibility that the roughness of the treated surface is too large, and the finished surface is uneven.
- the injection pressure in the shot peening is desirable to be in a range of 0.1 MPa (1.0 kg/cm 2 ) to 0.5 MPa (5.0 kg/cm 2 ). If the injection pressure is lower than 0.1 MPa (1.0 kg/cm 2 ), the pressing force to the metallic film is small, resulting in a long time taken for the treatment. If the injection pressure exceeds 0.5 MPa (5.0 kg/cm 2 ), there is a possibility that the pressing force to the metallic film is ununiform, thereby bringing about the deterioration of the roughness of the surface.
- the injection time in the shot peening is desirable to be in a range of 1 minute to 1 hour. If the injection time is shorter than 1 minute, there is a possibility that the entire surface cannot be treated uniformly. If the injection time exceeds 1 hour, there is a possibility that the deterioration of the roughness of the surface is brought about.
- a rare earth element (R) contained in an Fe-B-R based permanent magnet used in the present invention is desirably at least one of Nd, Pr, Dy, Ho, Tb and Sm, in addition thereto at least one of La, Ce, Gd, Er, Eu, Tm, Yb, Lu and Y.
- the content of R in the Fe-B-R based permanent magnet is desirable to be in a range of 10 % by atom to 30 % by atom. If the R content is lower than 10 % by atom, the crystal structure is the same cubic crystal structure as ⁇ -Fe and for this reason, a high magnetic characteristic, particularly, a high coercive force (iHc) is not obtained. On the other hand, if the R content exceeds 30 % by atom, the content of an R-rich non-magnetic phase is increased, and the residual magnetic flux density (Br) is reduced, whereby a permanent magnet having an excellent characteristic is not produced.
- the Fe content is desirable to be in a range of 65 % by atom to 80 % by atom. If the Fe content is lower than 65 % by atom, the residual magnetic flux density (Br) is reduced. If the Fe content exceeds 80 % by atom, a high coercive force (iHc) is not obtained.
- the amount of Co substituted in a range of 5 % by atom to 15 % by atom is desirable for providing a high magnetic flux density, because the residual magnetic flux density (Br) is increased, as compared with a case where a portion of Fe is not substituted.
- the B content is desirable to be in a range of 2 % by atom to 28 % by atom. If the B content is lower than 2 % by atom, a rhombohedral structure is a main phase, and a high coercive force (iHc) is not obtained. If the B content exceeds 28 % by atom, the content of a B-rich non-magnetic phase is increased, and the residual magnetic flux density (Br) is reduced, whereby a permanent magnet having an excellent characteristic is not produced.
- At least one of 2.0 % by weight or less of P and 2.0 % by weight or less of S may be contained in a total amount of 2.0 % by weight or less. Further, the corrosion resistance of the magnet can be improved by substituting a portion of B with 30 % by weight or less of carbon (C).
- the addition of at least one of Al, Ti, V, Cr, Mn, Bi, Nb, Ta, Mo, W, Sb, Ge, Sn, Zr, Ni, Si, Zn, Hf and Ga is effective for improving the coercive force and the rectangularity of a demagnetizing curve and for improving the manufacture and reducing the cost. It is desirable that at least one of them is added in an amount within a range satisfying a condition that at least 0.9T (9 kG) of Br is required in order to ensure that the maximum energy product (BH)max is equal to or larger than 160 kJ/m 3 (20 MGOe).
- the Fe-B-R based permanent magnet may contain impurities inevitable for industrial production of the magnet.
- the Fe-B-R based permanent magnet used in the present invention has a feature in that it includes amain phase comprising a compound having a tetragonal crystal structure with an average crystal grain size in a range of 1 ⁇ m to 80 ⁇ m, and 1 % to 50 % by volume of a non-magnetic phase (excluding an oxide phase)
- This magnet shows iHc ⁇ 80 kA/m (1 kOe), Br > 0.4T (4 kG) and (BH)max ⁇ 80 kJ/m 3 , (10 MGOe), wherein the maximum value of (BH)max reaches 200 kJ/m 3 (25 MGOe) or more.
- a further film may be formed on the chemical conversion coating film of the present invention.
- a known cast ingot was pulverized and then subjected sequentially to a pressing, a sintering, a heat treatment and a surface working, thereby producing a sintered magnet having a size of 23 mm x 10 mm x 6 mm and a composition of 17Nd-1Pr-75Fe-7B (which will be referred to as "magnet test piece” hereinafter).
- the magnet test piece was subjected to the following experiment, wherein the thickness of an aluminum film was measured using a fluorescence X-ray thickness-meter (SFT-7000 made by Seiko Instruments and Electronics, Ltd.).
- the thickness of a chemical conversion coating film was determined by an analysis in a direction of the depth of the film using an X-ray photoelectron spectroscopy (XPS) (using ESCA-850 made by Shimadzu, Co.). The content of each of constituents in the film was measured by a fluorescence X-ray intensity (using RIX-3000 made by Rigaku Corporation, Co.).
- XPS X-ray photoelectron spectroscopy
- the present invention is applicable not only to an Fe-B-R based sintered magnet but also to an Fe-B-R based bonded magnet.
- a magnet test piece was subjected to a sputtering in an evacuated vacuum vessel evacuated to 1 x 10 -4 Pa for 35 minutes under conditions of an argon gas pressure of 10 Pa and a bias voltage of -400 V, and the surface of the magnet was cleaned.
- the magnet test piece was subjected to an arc ion plating process for 15 minutes with metal aluminum used as a target under conditions of an argon gas pressure of 0.2 Pa, a bias voltage of -50 V and a magnet temperature of 250°C, whereby an aluminum film was formed on the surface of the magnet and left to cool.
- the formed aluminum film had a thickness of 0.5 ⁇ m.
- PALCOAT 3753 (which is a trade name and made by Nihon Parkerizing Co., Ltd.) was dissolved in 1 liter of water to produce a treating solution (having a pH value of 3.8).
- the magnet having the aluminum film on its surface was dipped in this treating solution at a bath temperature of 40°C for 1 minute and then subjected to a drying treatment at 100°C for 20 minutes, whereby a titanium-containing chemical conversion coating film having a thickness of 0.1 ⁇ m was formed on the aluminum film.
- the content of titanium in the chemical conversion coating film was 10 mg (per 1 m 2 of the surface of the magnet); the content of phosphorus was 7 mg (per 1 m 2 of the surface of the magnet); the content of oxygen was 21 mg (per 1 m 2 of the surface of the magnet), and the content of fluorine was 2 mg (per 1 m 2 of the surface of the magnet).
- the magnet produced in the above-described manner and having the titanium-containing chemical conversion coating film on its surface with the aluminum film interposed therebetween was subjected to a corrosion resistance acceleration test, wherein it was left to stand for 300 hours under high-temperature and high-humidity conditions of a temperature of 80°C and a relative humidity of 90 %.
- the magnetic characteristics before and after the test and the situation of variation in appearance after the test are shown in Table 1. As a result, it was found that even if the magnet was left to stand for the long time under the high-temperature and high-humidity conditions, the magnet satisfied a required corrosion resistance sufficiently with the both of magnetic characteristic and appearance little degraded.
- the magnet test piece was cleaned under the same conditions as in Example 1. Then, an aluminum (Al) wire used as a coating material was heated, evaporated and ionized for an ion plating process for 1 minute under conditions of an argon gas pressure of 1 Pa and a voltage of 1.5 kV, thereby forming an aluminum film on the surface of the magnet, and the film was left to cool.
- the formed aluminum film had a thickness of 0.9 ⁇ m.
- a powder comprising spherical glass beads having an average particle size of 120 ⁇ m and a Mohs hardness of 6 was injected along with a pressurized gas comprising N 2 gas against the surface of the aluminum film under an injection pressure of 0.15 MPa (1.5 kg/cm 2 ) for 5 minutes to carry out the shot peening of the surface of the aluminum film.
- PALCOAT 3756MA and 10 g of PALCOAT 3756MB were dissolved in 1 liter of water to produce a treating solution (in which the ratio of the number of moles of phosphorus to the number of moles of zirconium was 6.2, and which had a pH value of 3.2).
- the magnet having the aluminum film on its surface was dipped in this treating solution at a bath temperature of 50°C for 1 minute and 30 seconds and then subjected to a drying treatment at 120°C for 20 minutes, whereby a zirconium-containing chemical conversion coating film having a thickness of 0.07 ⁇ m was formed on the aluminum film.
- the content of zirconium in the chemical conversion coating film was 16 mg (per 1 m 2 of the surface of the magnet); the content of phosphorus was 11 mg (per 1 m 2 of the surface of the magnet); the content of oxygen was 50 mg (per 1 m 2 of the surface of the magnet), and the content of fluorine was 3 mg (per 1 m 2 of the surface of the magnet).
- the magnet produced in the above-described manner and having the zirconium-containing chemical conversion coating film on its surface with the aluminum film interposed therebetween was subjected to the corrosion resistance acceleration test under the same conditions as in Example 1. Results of the test are shown in Table 1. As a result, it was found that the produced magnet satisfied a required corrosion resistance sufficiently.
- the magnets each having the aluminum film on its surface were dipped in the treating solution described in Example 2 at a bath temperature of 50°C for 1 minute and 30 seconds and then subjected to a drying treatment at 120°C for 20 minutes, whereby a zirconium-containing chemical conversion coating film having a thickness of 0.08 ⁇ m was formed on the aluminum film.
- the content of zirconium in the chemical conversion coating film was 16 mg (per 1 m 2 of the surface of the magnet); the content of phosphorus was 12 mg (per 1 m 2 of the surface of the magnet); the content of oxygen was 38 mg (per 1 m 2 of the surface of the magnet), and the content of fluorine was 3 mg (per 1 m 2 of the surface of the magnet).
- the magnet test piece was cleaned under the same conditions as in Example 1 and then subjected to an arc ion plating process for 2.5 hours, whereby an aluminum film was formed on the surface of the magnet and left to cool.
- the formed aluminum film had a thickness of 5 ⁇ m.
- the magnet having the aluminum film on its surface was dipped in the treating solution described in Example 1 at a bath temperature of 40°C for 1 minute and then subjected to a drying treatment at 100°C for 20 minutes, whereby a titanium-containing chemical conversion coating film having a thickness of 0.09 ⁇ m was formed on the aluminum film.
- the content of titanium in the chemical conversion coating film was 9 mg (per 1 m 2 of the surface of the magnet); the content of phosphorus was 6 mg (per 1 m 2 of the surface of the magnet); the content of oxygen was 20 mg (per 1 m 2 of the surface of the magnet), and the content of fluorine was 2 mg (per 1 m 2 of the surface of the magnet).
- the magnet produced in the above-described manner and having the titanium-containing chemical conversion coating film on its surface with the aluminum film interposed therebetween was subjected to a corrosion resistance acceleration test, wherein it was left to stand for 1,000 hours under high-temperature and high-humidity conditions of a temperature of 80°C and a relative humidity of 90 %.
- the magnetic characteristics before and after the test and the situation of variation in appearance after the test are shown in Table 2. As a result, it was found that even if the magnet was left to stand for the long time under the high-temperature and high-humidity conditions, the magnet satisfied a required corrosion resistance sufficiently with the both of magnetic characteristic and appearance little degraded.
- An aluminum film was formed on the surface of the magnet by an ion plating process for 10 minutes under the same conditions as in Example 2 and then left to cool.
- the formed aluminum film had a thickness of 10 ⁇ m.
- a powder comprising spherical glass beads having an average particle size of 120 ⁇ m and a Mohs hardness of 6 was injected along with a pressurized gas comprising N 2 gas against the surface of the aluminum film under an injection pressure of 0.15 MPa (1.5 kg/cm 2 ) for 5 minutes to carry out the shot peening of the surface of the aluminum film.
- the magnet having the aluminum film on its surface was dipped in the treating solution described in Example 2 at a bath temperature of 50°C for 1 minute and 30 seconds and then subjected to a drying treatment at 120°C for 20 minutes, whereby a zirconium-containing chemical conversion coating film having a thickness of 0.07 ⁇ m was formed on the aluminum film.
- the content of zirconium in the chemical conversion coating film was 15 mg (per 1 m 2 of the surface of the magnet); the content of phosphorus was 12 mg (per 1 m 2 of the surface of the magnet); the content of oxygen was 47 mg (per 1 m 2 of the surface of the magnet), and the content of fluorine was 2 mg (per 1 m 2 of the surface of the magnet).
- the magnet produced in the above-described manner and having the zirconium-containing chemical conversion coating film on its surface with the aluminum film interposed therebetween was subjected to the corrosion resistance acceleration test under the same conditions as in Example 4. Results of the test are shown in Table 2. As a result, it was found that the produced magnet satisfied a required corrosion resistance sufficiently.
- the ratio of the number of moles of phosphorus to the number of moles of zirconium in an area between the surface of the zirconium-containing chemical conversion coating film and a point 0.002 ⁇ m spaced apart from the surface was measured by an X-ray photoelectron spectroscopy (XPS) (using ESCA-850 made by Shimadzu, Co.), and the result showed 7.
- XPS X-ray photoelectron spectroscopy
- the ratio of the number of moles of phosphorus to the number of moles of zirconium in the entire chemical conversion coating film was calculated based on the numbers of moles of zirconium and phosphorus measured by a fluorescence X-ray intensity, and as a result, such ratio was 2.
- the magnet test piece was cleaned under the same conditions as in Example 1. Then, an ingot of metal aluminum used as a coating material was heated and evaporated, and the magnet test piece was subjected to a vacuum evaporation process for 50 minutes under a condition of an argon gas pressure of 1 x 10 -2 Pa, thereby forming an aluminum film on the surface of the magnet, and the film was left to cool.
- the formed aluminum film had a thickness of 8 ⁇ m.
- the magnet having the aluminum film on its surface was dipped in the treating solution described in Example 2 at a bath temperature of 50°C for 1 minute and 30 seconds and then subjected to a drying treatment at 120°C for 20 minutes, whereby a zirconium-containing chemical conversion coating film having a thickness of 0.06 ⁇ m was formed on the aluminum film.
- the content of zirconium in the chemical conversion coating film was 15 mg (per 1 m 2 of the surface of the magnet); the content of phosphorus was 13 mg (per 1 m 2 of the surface of the magnet); the content of oxygen was 35 mg (per 1 m 2 of the surface of the magnet), and the content of fluorine was 2 mg (per 1 m 2 of the surface of the magnet).
- the magnet produced in the above-described manner and having the zirconium-containing chemical conversion coating film on its surface with the aluminum film interposed therebetween was subjected to the corrosion resistance acceleration test under the same conditions as in Example 4. Results of the test are shown in Table 2. As a result, it was found that the produced magnet satisfied a required corrosion resistance sufficiently.
- Example 1 (11.3) 1.13 (16.7) 1329 (30.5) 243 (10.6) 1.06 (15.8) 1257 (27.3) 217 locally rusted Com.
- Example 2 (11.4) 1.14 (16.6) 1321 (30.5) 243 (10.1) 1.01 (15.3) 1218 (26.5) 211 hardly rusted on entire surface Com.
- Example 3 (11.4) 1.14 (16.7) 1329 (30.6) 244 (10.3) 1.03 (15.3) 1218 (27.5) 219 locally rusted Com.
- the magnet test piece was degreased, pickled and then immersed in a treating solution comprising 4.6 g/l of zinc and 17.8 g/l of phosphate at a bath temperature of 70°C, whereby a phosphate film having a thickness of 1 ⁇ m was formed on the surface of the magnet.
- the produced magnet was subjected to the corrosion resistance acceleration test under the same conditions as in Example 1. Results of the test are shown in Table 1. As a result, the deterioration of the magnetic characteristic was brought about, and the rusting was produced in the produced magnet.
- the magnet test piece was subjected to the corrosion resistance acceleration test under the same conditions as in Example 1. Results of the test are shown in Table 1. As a result, the deterioration of the magnetic characteristic was brought about, and the rusting was produced in the magnet test piece.
- Example 5 The magnet having the aluminum film on its surface subjected to the shot peening in Example 5 was subjected to the corrosion resistance acceleration test under the same conditions as in Example 4. Results of the test are shown in Table 2. As a result, the deterioration of the magnetic characteristic was brought about, and the rusting was produced in the produced magnet.
- the magnet having the aluminum film on its surface subjected to the shot peening in Example 5 was cleaned and then immersed in a treating solution comprising 300 g/l of sodium hydroxide, 40 g/l of zinc oxide, 1 g/l of ferric chloride and 30 g/l of Rochelle salt at a bath temperature of 23°C, whereby the surface of the aluminum film was substituted with zinc (Zn).
- a treating solution comprising 300 g/l of sodium hydroxide, 40 g/l of zinc oxide, 1 g/l of ferric chloride and 30 g/l of Rochelle salt at a bath temperature of 23°C, whereby the surface of the aluminum film was substituted with zinc (Zn).
- the resulting magnet was subjected to an electroplating treatment under a condition of a current density of 1.8 A/dm 2 using a plating solution comprising 240 g/l of nickel sulfate, 48 g/l of nickel chloride, an appropriate amount of nickel carbonate (having a pH value adjusted) and 30 g/l of boric acid at a bath temperature of 55°C and at a pH value of 4.2, whereby a nickel film having a thickness of 0.9 ⁇ m was formed on the aluminum film with its surface substituted with zinc.
- the resulting magnet was subjected to the corrosion resistance acceleration test under the same conditions as in Example 4. Results of the test are shown in Table 2. As a result, the deterioration of the magnetic characteristic of the magnet was brought about, and a portion of the nickel film was peeled off.
- the chemical conversion coating film is adhered firmly to the magnet with the aluminum film interposed therebetween and hence, the magnet is excellent in corrosion resistance. Even if the magnet is left to stand for a long time under high-temperature and high-humidity conditions of a temperature of 80°C and a relative humidity of 90 %, the magnet exhibits a stable high magnetic characteristic which cannot be deteriorated. Moreover, the film is free from hexa-valent chromium.
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Description
The present invention relates to an Fe-B-R based permanent
magnet having an excellent corrosion-resistant film, and to a
process for producing the same. More particularly, the present
invention relates to an Fe-B-R based permanent magnet which has,
on the surface thereof, a corrosion-resistant film having an
excellent adhesion to the magnet, and which can exhibit a stable
high magnetic characteristic that cannot be deteriorated even
if the magnet is left to stand for a long time under
high-temperature and high-humidity conditions of a temperature
of 80°C and a relative humidity of 90 %; and in which the film
is free from hexa-valent chromium, and to a process for producing
the same.
An Fe-B-R based permanent magnet, of which an Fe-B-Nd based
permanent magnet is representative, is practically used in
various applications, because it is produced from an inexpensive
material rich in natural resources and has a high magnetic
characteristic, as comparedwith an Sm-Co based permanent magnet.
However, the Fe-B-R based permanent magnet is liable to
be corroded by oxidation in the atmosphere, because it contains
highly reactive R and Fe. When the Fe-B-R based permanent magnet
is used without being subjected to any surface treatment, the
corrosion of the magnet is advanced from its surface due to the
presence of a small amount of acid, alkali and/or water to produce
rust, thereby bringing about the degradation and dispersion of
the magnetic characteristic. Further, when the magnet having
the rust produced therein is incorporated into a device such
as a magnetic circuit, there is a possibility that the rust is
scattered to pollute surrounding parts or components.
There is an already proposed magnet which has a
corrosion-resistant metal-plated film on its surface, which is
formed by a wet plating process such as an electro-less plating
process and an electroplating process, in order to improve the
corrosion resistance of the Fe-B-R based permanent magnet with
the above-described point in view (see Japanese Patent
Publication No.3-74012). In this process, however, an acidic
or alkaline solution used in a pretreatment prior to the plating
treatment may remain in pores on the magnet, whereby the magnet
may be corroded with the passage of time in some cases. In
addition, the magnet is poor in resistance to chemicals and for
this reason, the surface of the magnet may be corroded during
the plating treatment. Further, even if the metal-plated film
is formed on the surface of the magnet, as described above, if
the magnet is subjected to a corrosion resistance test under
conditions of a temperature of 60°C and a relative humidity of
90 %, the magnetic characteristic of the magnet may be degraded
by 10 % or more from an initial value after lapse of 100 hours.
There is also a conventionally proposed process in which
an oxidization-resistant chemical conversion coating film such
as a phosphate film or a chromate film is formed on the surface
of an Fe-B-R based permanent magnet (see Japanese Patent
Publication No.4-22008). The film formed in this process is
excellent in adhesion to the magnet, but if it is subjected to
a corrosion resistance test under conditions of a temperature
of 60°C and a relative humidity of 90 %, the magnetic
characteristic of the magnet may be degraded by 10 % or more
from an initial value after lapse of 300 hours.
A process which has been conventionally proposed in order
to improve the corrosion resistance of the Fe-B-R based permanent
magnet, and in which a chromate treatment is carried out after
the formation of an aluminum film by a vapor deposition process,
i.e., a so-called aluminum-chromate treating process (see
Japanese Patent Publication No.6-66173), is intended to improve
the corrosion resistance of the magnet remarkably. However,
the chromate treatment used in this process uses hexa-valent
chromium which is undesirable for the surroundings and for this
reason, a waste-liquid treating method is complicated. It is
feared that a film formed in this process influences a human
body during handling of the magnet, because it contains just
a small amount of hexa-valent chromium.
From PATENT ABSTRACTS OF JAPAN, vol. 1996; no. 01, 31
January 1996 and JP 07 249509 A (closest prior art) a corrosion-resistant
permanent magnet and its manufacture are known. To improve
the corrosion resistance of an Fe-B-R permanent magnet, a
TiN-film on the surface of the magnet with an Al-film
inbetween is provided. The TiN-film is formed by a vapor-phase
film forming method in an N2 gas atmosphere.
In US-A 4,837,114 a Fe-B-R type permanent magnet is
described having an anti-corrosive coating film layer
provided on its surface. The anti-corrosive film is formed
of metals, oxides, nitrides, carbides, borides, silicides,
composite compositions thereof or a mixture thereof. In
addition a resin may be used to be impregnated into the
micropores of the thin coating film to further improve its
corrosion resistance.
Accordingly, it is an object of the present invention to
provide an Fe-B-R based permanent magnet which has, on the surface
thereof, a corrosion-resistant film having an excellent adhesion
to the magnet, and which can exhibit a stable high magnetic
characteristic that cannot be deteriorated even if the magnet
is left to stand for a long time under high-temperature and
high-humidity conditions of a temperature of 80°C and a relative
humidity of 90 %, and in which the film is free from hexa-valent
chromium, and a process for producing the same.
The present inventors, as a result of various zealous
studies made with the above points in view, have found that if
an aluminum film is formed on the surface of an Fe-B-R based
permanent magnet, and a chemical conversion coating film
containing titanium and/or zirconium as constituting elements
is formed on the aluminum film, the chemical conversion coating
film is firmly adhered onto the magnet with the aluminum film
interposed therebetween, thereby exhibiting an excellent
corrosion resistance.
The present invention has been accomplished with the above
knowledge, and according to claim 1 of the present invention,
there is provided an Fe-B-R based permanent magnet, which has
a chemical conversion coating film formed on its surface with
an aluminum film interposed therebetween, the chemical
conversion coating film containing at least one of titanium and
zirconium, and phosphorus, oxygen and fluorine as constituting
elements.
According to claim 2 of the present invention, in addition
to claim 1, the aluminum film has a thickness in a range of 0.01
µm to 50 µm.
According to claim 3 of the present invention, in addition
to claim 1, the chemical conversion coating film has a thickness
in a range of 0.01 µm to 1 µm.
According to claim 4 of the present invention, in addition
to claim 1, the content of titanium and/or zirconium in the
chemical conversion coating film is in a range of 0.1 mg to 100
mg per a film portion formed on 1 m2 of the surface of the magnet.
According to claim 5 of the present invention, in addition
to claim 1, the content of phosphorus in the chemical conversion
coating film is in a range of 0.1 mg to 100 mg per a film portion
formed on 1 m2 of the surface of the magnet.
According to claim 6 of the present invention, in addition
to claim 1, the content of oxygen in the chemical conversion
coating film is in a range of 0.2 mg to 300 mg per a film portion
formed on 1 m2 of the surface of the magnet.
According to claim 7 of the present invention, in addition
to claim 1, the content of fluorine in the chemical conversion
coating film is in a range of 0.05 mg to 100 mg per a film portion
formed on 1 m2 of the surface of the magnet.
According to claim 8 of the present invention, in addition
to claim 1, the ratio of the number of moles of phosphorus to
the number of moles of titanium and/or zirconium in an area near
the surface of the chemical conversion coating film is larger
than that in the entire chemical conversion coating film.
According to claim 9 of the present invention, in addition
to claim 1, the ratio of the number of moles of phosphorus to
the number of moles of titanium and/or zirconium in an area near
the surface of the chemical conversion coating film is equal
to or larger than 1.
According to claim 10 of the present invention, there is
provided a process for producing an Fe-B-R based permanent magnet,
comprising the steps of forming an aluminum film on the surface
of an Fe-B-R based permanent magnet, applying a treating solution
containing at least one of a titanium compound and a zirconium
compound, at least one of phosphoric acid, condensed phosphoric
acid, phytic acid, the hydrolyzate of phytic acid and the salts
of them, and a fluorine compound, onto the surface of the aluminum
film, and drying the applied treating solution, thereby forming
a chemical conversion coating film containing at least one of
titanium and zirconium, and phosphorus, oxygen and fluorine as
constituting elements.
According to claim 11 of the present invention, in addition
to claim 10, the aluminum film is formed by a vapor deposition
process.
According to claim 12 of the present invention, in addition
to claim 11, the aluminum film has a thickness in a range of
0.01 µm to 50 µm.
According to claim 13 of the present invention, in addition
to claim 10, the Fe-B-R based permanent magnet and aluminum pieces
are placed into a treating vessel, where they are vibrated and/or
agitated, thereby forming the aluminum film.
According to claim 14 of the present invention, in addition
to claim 13, the aluminum film has a thickness in a range of
0.01 µm to 1 µm.
According to claim 15 of the present invention, in addition
to claim 10, the ratio of the number of moles (in terms of
phosphorus) of at least one of phosphoric acid, condensed
phosphoric acid, phytic acid, the hydrolyzate of phytic acid
and the salts of them to the number of moles (in terms of metal)
of at least one of the titanium compound and the zirconium compound
in the treating solution is equal to or larger than 1.
An Fe-B-R based permanent magnet according to the present
invention has a feature that it has a chemical conversion coating
film which is formed on its surface with an aluminum film
interposed therebetween, and which contains at least one of
titanium and zirconium, and phosphorus, oxygen and fluorine as
constituting elements.
The method for forming the aluminum film on the surface
of the Fe-B-R based permanent magnet is particularly not limited.
However, if it is taken into consideration that the magnet and
the aluminum film are liable to be corroded by oxidation, examples
of desirable process are a process utilizing a vapor deposition
process, and a process which comprises placing an Fe-B-R based
permanent magnet and aluminum pieces into a treating vessel,
where they are vibrated and/or agitated.
Examples of thevapordepositionprocess are known processes
such as a vacuum evaporation process, an ion sputtering process,
an ion plating process and the like. The aluminum film may be
formed under common conditions in each of the processes, but
from the viewpoints of the denseness, the uniformity in thickness,
the forming speed of the film to be formed and the like, it is
desirable that the vacuum evaporation process and the ion plating
process are employed. Of course, the surface of the magnet may
be subjected to a known cleaning treatment such as a washing,
a degreasing treatment and a sputtering, prior to the formation
of the film.
It is desirable that the temperature of the magnet during
the formation of the film is set in a range of 200°C to 500°C.
If the temperature is lower than 200°C, there is a possibility
that a film having an excellent adhesion to the surface of the
magnet is not formed. On the other hand, if the temperature
exceeds 500°C, there is a possibility that cracks are produced
in the film, thereby causing the film to be peeled off from the
magnet, in a cooling course after the formation of the film.
It is desirable that the thickness of the aluminum film
is in a range of 0.01 µm to 50 µm, more preferably, in a range
of 0.05 µm to 25 µm. If the thickness is smaller than 0.01 µm,
there is a possibility that the film cannot exhibit an excellent
corrosion resistance. If the thickness exceeds 50 µm, there
is a possibility that an increase in manufacture cost is brought
about, but also, there is a possibility that the effective volume
of the magnet is decreased.
The aluminum pieces used in this process may be of any
of various shapes such as a needle-like shape (a wire-like shape)
a columnar shape and amassive shape. However, from the viewpoint
of efficient production of a fine aluminum powder serving as
a source for formation of an aluminum film, it is desirable that
aluminum pieces having a needle-like shape with sharp terminal
ends or a columnar shape with sharp terminal ends is used.
It is desirable from the viewpoint of efficient production
of a fine aluminum powder that the size (longer diameter) of
the aluminum pieces is in a range of 0.05 mm to 10 mm, more
preferably in a range of 0.3 mm to 5 mm, further preferably in
a range of 0.5 mm to 3 mm. Aluminum pieces having the same shape
and the same size may be used, but aluminum pieces having different
shapes and different sizes may be used in the form of a mixture.
It is desirable that the vibration and/or agitation of
the magnet and the aluminum pieces is carried out in a dry manner
in consideration of the fact that they are liable to be corroded
by oxidation. The vibration and/or agitation of the magnet and
the aluminum pieces can be carried out in the atmosphere and
at ambient temperature. It is unnecessary to employ a
complicated apparatus for the treating vessel used in the present
invention, and for example, the treating vessel may be a treating
chamber in a barrel finishing machine. The barrel finishing
machine may be of any known type such as a rotated-type, a
vibrated-type and a centrifugal-type. In the case of the
rotated-type, the rotational speed is desirable to be in a range
of 20 rpm to 50 rpm. In the case of the vibrated-type, it is
desirable that the vibration frequency is in a range of 50 Hz
to 100 Hz, and the vibration amplitude is in a range of 0.3 mm
to 10 mm. In the case of the centrifugal-type, the rotational
speed is desirable to be in a range of 70 rpm to 200 rpm.
It is desirable that the total amount of the magnet and
the aluminum pieces placed into the treating vessel is in a range
of 20 % to 90 % by volume of the internal volume of the treating
vessel. If the total amount is smaller than 20 % by volume,
the throughput is too small, which is not preferable in practical
use. If the total amount exceeds 90 % by volume, there is a
possibility that the film cannot be formed efficiently. It is
desirable that the ratio of the amount of the magnet to the amount
of the aluminum pieces placed into the treating vessel is equal
to or smaller than 3 in terms of a volume ratio (of magnet/aluminum
pieces). If the volume ratio exceeds 3, there is a possibility
that a long time is required for the formation of the film, which
is not preferred in practical use. The treating time depends
on the throughput, but is usually in a range of 1 to 10 hours.
According to the above-described process, a fine aluminum
powder produced from the aluminum pieces is adhered to the surface
of the magnet to form the aluminum film. It is considered that
the phenomenon of the adhesion of the fine aluminum powder to
the surface of the magnet is a kind of a mechanochemical reaction.
The fine aluminum powder is adhered firmly to the surface of
the magnet, and the formed aluminum film exhibits an excellent
corrosion resistance. From the viewpoint of ensuring a
sufficient corrosion resistance, it is desirable that the
thickness of the film is equal to or larger than 0.01 µm, as
described above. The upper limit for the thickness is
particularly not limited, but if the thickness exceeds 1 µm,
a long time is required for forming the aluminum film. For this
reason, this process is suitable to form an aluminum film having
a thickness equal to or smaller than 1 µm.
After the formation of the aluminum film on the surface
of the magnet, the aluminum film can be subjected to a heat
treatment to enhance the adhesion of the aluminum film to the
surface of the magnet. The temperature in the heat treatment
is desirable to be in a range of 200°C to 500°C, and more desirable
to be in a range of 200°C to 250°C from the viewpoints of
productivity and manufacture cost. If the temperature is lower
than 200°C, there is a possibility that an interfacial reaction
of the aluminum film with the magnet is not advanced sufficiently,
and as a result, the adhesion is not enhanced. If the temperature
exceeds 500°C, there is a possibility that the deterioration
of the magnetic characteristic of the magnet is brought about
and that the aluminum film is melted.
A process for forming a chemical conversion coating film
containing at least one of titanium and zirconium, and phosphorus,
oxygen and fluorine as constituting elements on the aluminum
film will be described below. One example of this process is
a process which comprises applying, to the surface of the aluminum
film, a treating solution containing at least one of a titanium
compound and a zirconium compound, at least one of phosphoric
acid, condensed phosphoric acid, phytic acid, the hydrolyzate
of phytic acid and the salts of them, and a fluorine compound,
and subjecting the applied solution to a drying treatment.
The treating solution is prepared by dissolving, into water,
at least one of the titanium compound and the zirconium compound,
at least one of phosphoric acid, condensed phosphoric acid,
phytic acid, the hydrolyzate of phytic acid and the salts of
them, and the fluorine compound.
Examples of the titanium compound contained in the treating
solution, whichmaybeused, are fluorotitanic acid, alkali metal,
alkaline earth metal and ammonium fluorotitanates, titanium
sulfate and nitrate and the like. Examples of the zirconium
compound which may be used are fluorozirconic acid, alkali metal,
alkaline earth metal and ammonium fluorozirconates, zirconium
sulfate and nitrate and the like. It is desirable that the
content of at least one of the titanium compound and zirconium
compound in the treating solution is in a range of 1 ppm to 2,000
ppm, more preferably, in a rang of 10 ppm to 1,000 ppm in terms
of metal. If the content is smaller than 1 ppm, there is a
possibility that the chemical conversion coating film is not
formed. If the content is larger than 2,000 ppm, there is a
possibility that an increase in cost is brought about.
Examples of condensed phosphoric acid contained in the
treating solution, which may be used, are pyrophosphoric acid,
tripolyphosphoric acid, metaphosphoric acid, ultraphosphoric
acid and the like. Examples of the hydrolyzate of phytic acid,
which may be used, are myo-inositol diphosphate, triphosphate,
tetraphosphate and pentaphosphate and the like. Examples of
the salts of phosphoric acid, condensed phosphoric acid, phytic
acid and the hydrolyzate of phytic acid, which may be used, are
ammonium, alkali metal and alkaline earth metal salts of
phosphoric acid, condensed phosphoric acid, phytic acid and the
hydrolyzate of phytic acid. When any of phosphoric acid,
condensed phosphoric acid and the salts thereof is used, it is
desirable that the content thereof in the treating solution is
in a range of 1 ppm to 2,000 ppm, more preferably, in a range
of 5 ppm to 1,000 ppm in terms of phosphoric acid. The reason
is as follows; if the content is smaller than 1 ppm, there is
a possibility that a chemical conversion coating film is not
formed. If the content is larger than 2,000 ppm, the adhesion
of a chemical conversion coating film to the magnet is influenced.
When any one of phytic acid, the hydrolyzate of phytic acid and
the salts thereof is used, it is desirable for a similar reason
that the content thereof in the treating solution is in a range
of 50 ppm to 10,000 ppm, more preferably, in a range of 100 ppm
to 5,000 ppm in terms of phytic acid.
Examples of the fluorine compound contained in the treating
solution, which may be used, are hydrofluoric acid, ammonium
fluoride, ammonium hydrogen fluoride, sodium fluoride and sodium
hydrogen fluoride and the like, in addition to the
above-described fluorotitanic acid and the salt thereof, and
fluorozirconic acid and the salt thereof. It is desirable that
the content of the fluorine compound in the treating solution
is in a range of 10 ppm to 10,000 ppm, more preferably, in a
range of 50 ppm to 5,000 ppm. If the content is smaller than
10 ppm, there is a possibility that the surface of the aluminum
film is not etched efficiently. If the content is larger than
10,000 ppm, there is a possibility that the etching speed is
higher than the film forming speed, thereby making it difficult
to form a film uniformly.
It is desirable that the pH value of the treating solution is
regulated to a range of 1 to 6. If the pH value is smaller than 1,
there is a possibility that the surface of the aluminum film is
etched excessively. If the pH value exceeds 6, there is a
possibility that the stability of the treating solution is
influenced.
In addition to the above-described constituents, an organic
acid such as tannic acid, an oxidizing agent (hydrogen peroxide,
chloric acid and the salts thereof, nitrous acid and the salt
thereof, nitric acid and the salt thereof, tungstic acid and the
salt thereof, and molybdic acid and the salt thereof), and a
water-soluble resin such as a water-soluble polyamide, may be
added to the treating solution for the purpose of enhancing the
chemically converting reaction, the stability of the treating
solution, the adhesion of a chemical conversion coating film to
the magnet and the adhesion to an adhesive used for incorporating
the magnet into parts.
When the treating solution itself is lack in shelf stability,
the treating solution may be prepared as required. Examples of the
treating solution, which maybe used in the present invention, are
a treating solution prepared from PALCOAT 3753 (which is a trade
name and made by Nihon Parkerizing Co., Ltd.), and a treating
solution prepared from PALCOAT 3756MA and PALCOAT 3756MB (both of
which are trade names and made by Nihon Parkerizing Co., Ltd.).
Examples of the method for applying the treating solution
to the surface of the aluminum film, which may be used, are a
dip coating process, a spraying process and a spin coating process.
It is desirable that the temperature of the treating solution
when being applied is set in a range of 20°C to 80°C. If the
temperature is lower than 20°C, there is a possibility that the
reaction is not advanced. If the temperature exceeds 80°C, there
is a possibility that the stability of the treating solution
is influenced. The treating time is usually in a range of 10
seconds to 10 minutes.
After application of the treating solution to the surface
of the aluminum film, the applied treating solution is subjected
to a drying treatment. The temperature in the drying treatment
is desirable to be in a range of 50°C to 250°C, and more desirable
to be in a range of 50°C to 150°C from the viewpoints of the
productivity and manufacture cost. The reason is as follows:
If the temperature is lower than 50°C, the treating solution
cannot be dried sufficiently and as a result, there is a
possibility that the deterioration of the appearance is brought
about, and that the adhesion to an adhesive used for incorporating
the magnet into parts is influenced. If the temperature exceeds
250°C, there is a possibility that the decomposition of the
chemical conversion coating film occurs. The treating time is
usually in a range of 5 seconds to 1 hour.
The chemical conversion coating film formed by the above-described
process and containing at least one of titanium and
zirconium, phosphorus, oxygen and fluorine as constituting
elements is adhered firmly to the surface of the magnet with the
aluminum film interposed therebetween. Therefore, if the thickness
of the chemical conversion coating film is equal to or larger than
0.01 µm, a sufficient corrosion resistance is provided. It is
believed that during the chemically converting treatment,
phosphoric acid or condensed phosphoric acid in the treating
solution reacts with Nd or Fe which is a magnet material on the
surface of the magnet, thereby forming a passive film, and hence,
even if the aluminum film has a portion which has been formed
unsatisfactorily, the passive film compensates for the corrosion
resistance of such portion. Although the upper limit of the
thickness of the chemical conversion coating film is not limited,
the thickness of the chemical conversion coating film is desirable
to be equal to or smaller than 1 µm and more desirable to be equal
to or smaller than 0.3 µm from the viewpoints of the demand based
on a reduction in size of the magnet itself and the manufacture
cost.
The content of titanium and/or zirconium in the chemical
conversion coating film is desirable to be in a range of 0.1 mg to
100 mg and more desirable to be in a range of 1 mg to 50 mg per a
film portion formed on 1 m2 Of the surface of the magnet. If the
content is smaller than 0. 1 mg, there is a possibility
that a sufficient corrosion resistance is not provided. If the
content is larger than 100 mg, there is a possibility that an
increase in cost is brought about.
The content of phosphorus in the chemical conversion
coating film is desirable to be in a range of 0.1 mg to 100 mg
and more desirable to be in a range of 1 mg to 50 mg per a film
portion formed on 1 m2 of the surface of the magnet. If the
content is smaller than 0.1 mg, there is a possibility that a
sufficient corrosion resistance is not provided. If the content
is larger than 100 mg, there is a possibility that the adhesion
to an adhesive used for incorporating the magnet into parts is
influenced.
Oxygen in the chemical conversion coating film is present
in the chemical conversion coating film in the form bonded to
titanium, zirconium or phosphorus, and as a constituting element
of the organic acid added into the treating solution for the
purpose of enhancing the adhesion to an adhesive used for
incorporating the magnet into the parts. It is desirable that
the content of oxygen in the chemical conversion coating film
is in a range of 0.2 mg to 300 mg per a film portion formed on
1 m2 of the surface of the magnet. If the content is smaller
than 0.2 mg, there is a possibility that a sufficient corrosion
resistance is not provided. If the content is larger than 300
mg, there is a possibility that the adhesion to an adhesive used
for incorporating the magnet into the parts is influenced.
Fluorine in the chemical conversion coating film is
incorporated into the chemical conversion coating film upon the
formation of the chemical conversion coating film due to free
fluorine ion or fluorine bonding with the Zr compound such as
ZrF4HPO4 present in the treating solution for the purpose of
etching the surface of the aluminum film. The content of fluorine
in the chemical conversion coating film is desirable to be in
a range of 0.05 mg to 100 mg and more desirable to be in a range
of 0.1 mg to 50 mg per a film portion formed on 1 m2 of the surface
of the magnet. If the content is smaller than 0.05 mg, there
is a possibility that a sufficient corrosion resistance is not
provided. If the content is larger than 100 mg, there is a
possibility that the adhesion to an adhesive used for
incorporating the magnet into the parts is influenced.
Preferred among the chemical conversion coating films
formed by the above-described process and containing at least
one of titanium and zirconium, phosphorus, oxygen and fluorine
as constituting elements, are a film in which the ratio of the
number of moles of phosphorus to the number of moles of titanium
and/or zirconium in an area near the surface of the film (e.g.,
an area between the surface of the film and a point 0.002 µm
spaced apart from the surface of the film) is larger than that
in the entire film, and a film in which the ratio of the number
of moles of phosphorus to the number of moles of titanium and/or
zirconium in an area near the surface of the film is equal to
or larger than 1, desirably, equal to or larger than 2 and more
desirably, equal to or larger than 3. The reason is believed to
be that even if the film is brought into contact with water, a
large number of molecules of phosphoric acid or condensed
phosphoric acid present in the area near the surface of the film
catch the water, thereby preventing the water causing the
corrosion from reaching the surface of the magnet. To form. such a
film, it is desirable to use a treating solution in which the
ratio of the number of moles (in terms of phosphorus) of at least
one of phosphoric acid, condensed phosphoric acid, phytic acid,
the hydrolyzate of phytic acid and the salts of them to the number
of moles (in terms of metal) of at least one of the titanium
compound and the zirconium compound in the treating solution is
equal to or larger than 1.
Prior to the formation of a chemical conversion coating film on
the aluminum film, a shot peening (a method for modifying a
surface by bumping hard grains against the surface) may be carried
out as a previous step. The shot peening enables the aluminum film
to be smoothened, thereby facilitating the formation of a chemical
conversion coating film which is thin, but has an excellent
corrosion resistance.
A powder used for the shot peening is desirable to have a
hardness equivalent to or higher that of the formed aluminum film,
and examples of the powder are spherical hard materials having a
Mohs hardness of 3 or more such as those comprising steel balls
and glass beads. The average particle size of the powder is
desirable to be in a range of 30 µm to 3,000 µm and
more desirable to be in a range of 40 µm to 2,000 µm. If the
average particle size is smaller than 30 µm, the pressing force
applied to the aluminum film is small, resulting in a long time
taken for the treatment. On the other hand, if the average
particle size exceeds 3,000 µm, there is a possibility that the
roughness of the treated surface is too large, and the finished
surface is uneven.
The injection pressure in the shot peening is desirable
to be in a range of 0.1 MPa (1.0 kg/cm2) to 0.5 MPa (5.0 kg/cm2). If the injection
pressure is lower than 0.1 MPa (1.0 kg/cm2), the pressing force to the
metallic film is small, resulting in a long time taken for the
treatment. If the injection pressure exceeds 0.5 MPa (5.0 kg/cm2), there
is a possibility that the pressing force to the metallic film
is ununiform, thereby bringing about the deterioration of the
roughness of the surface.
The injection time in the shot peening is desirable to
be in a range of 1 minute to 1 hour. If the injection time is
shorter than 1 minute, there is a possibility that the entire
surface cannot be treated uniformly. If the injection time
exceeds 1 hour, there is a possibility that the deterioration
of the roughness of the surface is brought about.
A rare earth element (R) contained in an Fe-B-R based
permanent magnet used in the present invention is desirably at
least one of Nd, Pr, Dy, Ho, Tb and Sm, in addition thereto at
least one of La, Ce, Gd, Er, Eu, Tm, Yb, Lu and Y.
Usually, one of them (R) suffices, but in practice, a
mixture of two or more rare earth elements (misch metal and
didymium and the like) may be used for the reason of an available
convenience.
The content of R in the Fe-B-R based permanent magnet is
desirable to be in a range of 10 % by atom to 30 % by atom. If
the R content is lower than 10 % by atom, the crystal structure
is the same cubic crystal structure as α-Fe and for this reason,
a high magnetic characteristic, particularly, a high coercive
force (iHc) is not obtained. On the other hand, if the R content
exceeds 30 % by atom, the content of an R-rich non-magnetic phase
is increased, and the residual magnetic flux density (Br) is
reduced, whereby a permanent magnet having an excellent
characteristic is not produced.
The Fe content is desirable to be in a range of 65 % by
atom to 80 % by atom. If the Fe content is lower than 65 % by
atom, the residual magnetic flux density (Br) is reduced. If
the Fe content exceeds 80 % by atom, a high coercive force (iHc)
is not obtained.
It is possible to improve the temperature characteristic
without degradation of the magnetic characteristic of the
produced magnet by substituting a portion of Fe with Co. However,
if the amount of Co substituted exceeds 20 % of Fe, the magnetic
characteristic is degraded and hence, such amount is not
preferred. The amount of Co substituted in a range of 5 % by
atom to 15 % by atom is desirable for providing a high magnetic
flux density, because the residual magnetic flux density (Br)
is increased, as compared with a case where a portion of Fe is
not substituted.
The B content is desirable to be in a range of 2 % by atom
to 28 % by atom. If the B content is lower than 2 % by atom,
a rhombohedral structure is a main phase, and a high coercive
force (iHc) is not obtained. If the B content exceeds 28 % by
atom, the content of a B-rich non-magnetic phase is increased,
and the residual magnetic flux density (Br) is reduced, whereby
a permanent magnet having an excellent characteristic is not
produced.
To improve the manufacture of the magnet and reduce the
cost, at least one of 2.0 % by weight or less of P and 2.0 %
by weight or less of S may be contained in a total amount of
2.0 % by weight or less. Further, the corrosion resistance of
the magnet can be improved by substituting a portion of B with
30 % by weight or less of carbon (C).
Further, the addition of at least one of Al, Ti, V, Cr,
Mn, Bi, Nb, Ta, Mo, W, Sb, Ge, Sn, Zr, Ni, Si, Zn, Hf and Ga
is effective for improving the coercive force and the
rectangularity of a demagnetizing curve and for improving the
manufacture and reducing the cost. It is desirable that at least
one of them is added in an amount within a range satisfying a
condition that at least 0.9T (9 kG) of Br is required in order to ensure
that the maximum energy product (BH)max is equal to or larger
than 160 kJ/m3 (20 MGOe).
In addition to R, Fe and B, the Fe-B-R based permanent
magnet may contain impurities inevitable for industrial
production of the magnet.
The Fe-B-R based permanent magnet used in the present
invention has a feature in that it includes amain phase comprising
a compound having a tetragonal crystal structure with an average
crystal grain size in a range of 1 µm to 80 µm, and 1 % to 50 %
by volume of a non-magnetic phase (excluding an oxide phase)
This magnet shows iHc ≧ 80 kA/m (1 kOe), Br > 0.4T (4 kG) and (BH)max ≧ 80 kJ/m3, (10 MGOe),
wherein the maximum value of (BH)max reaches 200 kJ/m3 (25 MGOe) or more.
A further film may be formed on the chemical conversion
coating film of the present invention. By employing such a
configuration, it is possible to enhance the characteristic of
the chemical conversion coating film and provide a further
functionability to the chemical conversion coating film.
For example, as described in US Patent No.4,770,723, a
known cast ingot was pulverized and then subjected sequentially
to a pressing, a sintering, a heat treatment and a surface working,
thereby producing a sintered magnet having a size of 23 mm x
10 mm x 6 mm and a composition of 17Nd-1Pr-75Fe-7B (which will
be referred to as "magnet test piece" hereinafter). The magnet
test piece was subjected to the following experiment, wherein
the thickness of an aluminum film was measured using a
fluorescence X-ray thickness-meter (SFT-7000 made by Seiko
Instruments and Electronics, Ltd.). The thickness of a chemical
conversion coating film was determined by an analysis in a
direction of the depth of the film using an X-ray photoelectron
spectroscopy (XPS) (using ESCA-850 made by Shimadzu, Co.). The
content of each of constituents in the film was measured by a
fluorescence X-ray intensity (using RIX-3000 made by Rigaku
Corporation, Co.).
It should be noted that the present invention is applicable
not only to an Fe-B-R based sintered magnet but also to an Fe-B-R
based bonded magnet.
A magnet test piece was subjected to a sputtering in an
evacuated vacuum vessel evacuated to 1 x 10-4 Pa for 35 minutes
under conditions of an argon gas pressure of 10 Pa and a bias
voltage of -400 V, and the surface of the magnet was cleaned.
Then, the magnet test piece was subjected to an arc ion
plating process for 15 minutes with metal aluminum used as a
target under conditions of an argon gas pressure of 0.2 Pa, a
bias voltage of -50 V and a magnet temperature of 250°C, whereby
an aluminum film was formed on the surface of the magnet and
left to cool. The formed aluminum film had a thickness of 0.5
µm.
35 g of PALCOAT 3753 (which is a trade name and made by
Nihon Parkerizing Co., Ltd.) was dissolved in 1 liter of water
to produce a treating solution (having a pH value of 3.8). The
magnet having the aluminum film on its surface was dipped in
this treating solution at a bath temperature of 40°C for 1 minute
and then subjected to a drying treatment at 100°C for 20 minutes,
whereby a titanium-containing chemical conversion coating film
having a thickness of 0.1 µm was formed on the aluminum film.
The content of titanium in the chemical conversion coating film
was 10 mg (per 1 m2 of the surface of the magnet); the content
of phosphorus was 7 mg (per 1 m2 of the surface of the magnet);
the content of oxygen was 21 mg (per 1 m2 of the surface of the
magnet), and the content of fluorine was 2 mg (per 1 m2 of the
surface of the magnet).
The magnet produced in the above-described manner and
having the titanium-containing chemical conversion coating film
on its surface with the aluminum film interposed therebetween
was subjected to a corrosion resistance acceleration test,
wherein it was left to stand for 300 hours under high-temperature
and high-humidity conditions of a temperature of 80°C and a
relative humidity of 90 %. The magnetic characteristics before
and after the test and the situation of variation in appearance
after the test are shown in Table 1. As a result, it was found
that even if the magnet was left to stand for the long time under
the high-temperature and high-humidity conditions, the magnet
satisfied a required corrosion resistance sufficiently with the
both of magnetic characteristic and appearance little degraded.
The magnet test piece was cleaned under the same conditions as
in Example 1. Then, an aluminum (Al) wire used as a coating
material was heated, evaporated and ionized for an ion plating
process for 1 minute under conditions of an argon gas pressure of
1 Pa and a voltage of 1.5 kV, thereby forming an aluminum film on
the surface of the magnet, and the film was left to cool. The
formed aluminum film had a thickness of 0.9 µm.
Thereafter, a powder comprising spherical glass beads having an
average particle size of 120 µm and a Mohs hardness of 6 was
injected along with a pressurized gas comprising N2 gas against the
surface of the aluminum film under an injection pressure of 0.15 MPa (1.5
kg/cm2) for 5 minutes to carry out the shot peening of the surface
of the aluminum film.
10 g of PALCOAT 3756MA and 10 g of PALCOAT 3756MB (both of
which are trade names and made by Nihon Parkerizing Co., Ltd.)
were dissolved in 1 liter of water to produce a treating solution
(in which the ratio of the number of moles of phosphorus to the
number of moles of zirconium was 6.2, and which had a pH value of
3.2). The magnet having the aluminum film on its surface was
dipped in this treating solution at a bath temperature of 50°C for
1 minute and 30 seconds and then subjected to a drying treatment
at 120°C for 20 minutes, whereby a zirconium-containing chemical
conversion coating film having a thickness of 0.07 µm was formed
on the aluminum film. The content of zirconium in
the chemical conversion coating film was 16 mg (per 1 m2 of the
surface of the magnet); the content of phosphorus was 11 mg (per
1 m2 of the surface of the magnet); the content of oxygen was
50 mg (per 1 m2 of the surface of the magnet), and the content
of fluorine was 3 mg (per 1 m2 of the surface of the magnet).
The magnet produced in the above-described manner and
having the zirconium-containing chemical conversion coating
film on its surface with the aluminum film interposed
therebetween was subjected to the corrosion resistance
acceleration test under the same conditions as in Example 1.
Results of the test are shown in Table 1. As a result, it was
found that the produced magnet satisfied a required corrosion
resistance sufficiently.
150 magnet test pieces (having an apparent volume of 0.5
liters and a weight of 1.6 kg) and short columnar aluminum pieces
(having an apparent volume of 20 liters and a weight of 100 kg)
each having a diameter of 0.8 mm and a length of 1 mm were thrown
into a treating chamber in a vibrated-type barrel finishing
machine having a volume of 50 liters (so that the total amount
was 40 % by volume of the internal volume of the treating chamber),
where they were treated in a dry manner for 5 hours under conditions
of a vibration frequency of 60 Hz and a vibration amplitude of
1.8 mm, thereby forming an aluminum film on the surface of each
of the magnets. The formed aluminum film had a thickness of
0.05 µm.
The magnets each having the aluminum film on its surface
were dipped in the treating solution described in Example 2 at
a bath temperature of 50°C for 1 minute and 30 seconds and then
subjected to a drying treatment at 120°C for 20 minutes, whereby
a zirconium-containing chemical conversion coating film having
a thickness of 0.08 µm was formed on the aluminum film. The
content of zirconium in the chemical conversion coating film
was 16 mg (per 1 m2 of the surface of the magnet); the content
of phosphorus was 12 mg (per 1 m2 of the surface of the magnet);
the content of oxygen was 38 mg (per 1 m2 of the surface of the
magnet), and the content of fluorine was 3 mg (per 1 m2 of the
surface of the magnet).
The magnets produced in the above-described manner and
each having the zirconium-containing chemical conversion
coating film on its surface with the aluminum film interposed
therebetween was subjected to the corrosion resistance
acceleration test under the same conditions as in Example 1.
Results of the test are shown in Table 1. As a result, it was
found that the produced magnets satisfied a required corrosion
resistance sufficiently.
The magnet test piece was cleaned under the same conditions
as in Example 1 and then subjected to an arc ion plating process
for 2.5 hours, whereby an aluminum film was formed on the surface
of the magnet and left to cool. The formed aluminum film had
a thickness of 5 µm.
The magnet having the aluminum film on its surface was
dipped in the treating solution described in Example 1 at a bath
temperature of 40°C for 1 minute and then subjected to a drying
treatment at 100°C for 20 minutes, whereby a titanium-containing
chemical conversion coating film having a thickness of 0.09 µm
was formed on the aluminum film. The content of titanium in
the chemical conversion coating film was 9 mg (per 1 m2 of the
surface of the magnet); the content of phosphorus was 6 mg (per
1 m2 of the surface of the magnet); the content of oxygen was
20 mg (per 1 m2 of the surface of the magnet), and the content
of fluorine was 2 mg (per 1 m2 of the surface of the magnet).
The magnet produced in the above-described manner and
having the titanium-containing chemical conversion coating film
on its surface with the aluminum film interposed therebetween
was subjected to a corrosion resistance acceleration test,
wherein it was left to stand for 1,000 hours under
high-temperature and high-humidity conditions of a temperature
of 80°C and a relative humidity of 90 %. The magnetic
characteristics before and after the test and the situation of
variation in appearance after the test are shown in Table 2.
As a result, it was found that even if the magnet was left to
stand for the long time under the high-temperature and
high-humidity conditions, the magnet satisfied a required
corrosion resistance sufficiently with the both of magnetic
characteristic and appearance little degraded.
An aluminum film was formed on the surface of the magnet
by an ion plating process for 10 minutes under the same conditions
as in Example 2 and then left to cool. The formed aluminum film
had a thickness of 10 µm.
Thereafter, a powder comprising spherical glass beads
having an average particle size of 120 µm and a Mohs hardness
of 6 was injected along with a pressurized gas comprising N2
gas against the surface of the aluminum film under an injection
pressure of 0.15 MPa (1.5 kg/cm2) for 5 minutes to carry out the shot peening
of the surface of the aluminum film.
The magnet having the aluminum film on its surface was
dipped in the treating solution described in Example 2 at a bath
temperature of 50°C for 1 minute and 30 seconds and then subjected
to a drying treatment at 120°C for 20 minutes, whereby a
zirconium-containing chemical conversion coating film having
a thickness of 0.07 µm was formed on the aluminum film. The
content of zirconium in the chemical conversion coating film
was 15 mg (per 1 m2 of the surface of the magnet); the content
of phosphorus was 12 mg (per 1 m2 of the surface of the magnet);
the content of oxygen was 47 mg (per 1 m2 of the surface of the
magnet), and the content of fluorine was 2 mg (per 1 m2 of the
surface of the magnet).
The magnet produced in the above-described manner and
having the zirconium-containing chemical conversion coating
film on its surface with the aluminum film interposed therebetween
was subjected to the corrosion resistance acceleration test under
the same conditions as in Example 4. Results of the test are shown
in Table 2. As a result, it was found that the produced magnet
satisfied a required corrosion resistance sufficiently.
The ratio of the number of moles of phosphorus to the
number of moles of zirconium in an area between the surface of
the zirconium-containing chemical conversion coating film and a
point 0.002 µm spaced apart from the surface was measured by an
X-ray photoelectron spectroscopy (XPS) (using ESCA-850 made by
Shimadzu, Co.), and the result showed 7. On the other hand, the
ratio of the number of moles of phosphorus to the number of
moles of zirconium in the entire chemical conversion coating
film was calculated based on the numbers of moles of zirconium
and phosphorus measured by a fluorescence X-ray intensity, and
as a result, such ratio was 2.
The magnet test piece was cleaned under the same conditions as
in Example 1. Then, an ingot of metal aluminum used as a coating
material was heated and evaporated, and the magnet test piece was
subjected to a vacuum evaporation process for 50 minutes under a
condition of an argon gas pressure of 1 x 10-2 Pa, thereby forming
an aluminum film on the surface of the magnet, and the
film was left to cool. The formed aluminum film had a thickness
of 8 µm.
The magnet having the aluminum film on its surface was
dipped in the treating solution described in Example 2 at a bath
temperature of 50°C for 1 minute and 30 seconds and then subjected
to a drying treatment at 120°C for 20 minutes, whereby a
zirconium-containing chemical conversion coating film having
a thickness of 0.06 µm was formed on the aluminum film. The
content of zirconium in the chemical conversion coating film
was 15 mg (per 1 m2 of the surface of the magnet); the content
of phosphorus was 13 mg (per 1 m2 of the surface of the magnet);
the content of oxygen was 35 mg (per 1 m2 of the surface of the
magnet), and the content of fluorine was 2 mg (per 1 m2 of the
surface of the magnet).
The magnet produced in the above-described manner and
having the zirconium-containing chemical conversion coating
film on its surface with the aluminum film interposed
therebetween was subjected to the corrosion resistance
acceleration test under the same conditions as in Example 4.
Results of the test are shown in Table 2. As a result, it was
found that the produced magnet satisfied a required corrosion
resistance sufficiently.
| Before corrosion-resistance test | After corrosion-resistance test | Appearance after test | |||||
| Br (kG) T | iHc (kOe) kA/m | (BH)max (MGOe) kJ/m3 | Br (kG) T | iHc (kOe) kA/m | (BH)max (MGOe) kJ/m3 | ||
| Example 1 | (11.3) 1.13 | (16.7) 1329 | (30.6) 244 | (11.2) 1.12 | (16.5) 1313 | (29.8) 237 | not varied |
| Example 2 | (11.3) 1.13 | (16.6) 1321 | (30.5) 243 | (11.3) 1.13 | (16.4) 1305 | (29.8) 237 | not varied |
| Example 3 | (11.4) 1.14 | (16.7) 1329 | (30.6) 244 | (11.1) 1.11 | (16.4) 1305 | (29.7) 236 | not varied |
| Com. Example 1 | (11.3) 1.13 | (16.7) 1329 | (30.5) 243 | (10.6) 1.06 | (15.8) 1257 | (27.3) 217 | locally rusted |
| Com. Example 2 | (11.4) 1.14 | (16.6) 1321 | (30.5) 243 | (10.1) 1.01 | (15.3) 1218 | (26.5) 211 | hardly rusted on entire surface |
| Com. = Comparative |
| Before corrosion-resistance test | After corrosion-resistance test | Appearance after test | |||||
| Br (kG) T | iHc (kOe) kA/m | (BH)max (MGOe) kJ/m3 | Br (kG) T | iHc (kOe) kA/m | (BH)max (MGOe) kJ/m3 | ||
| Example 4 | (11.3) 1.13 | (16.7) 1329 | (30.6) 244 | (11.1) 1.11 | (16.3) 1297 | (29.6) 235 | pin holes produced, but not rusted |
| Example 5 | (11.3) 1.13 | (16.7) 1329 | (30.6) 244 | (11.2) 1.12 | (16.5) 1313 | (29.8) 237 | not varied |
| Example 6 | (11.3) 1.13 | (16.7) 1329 | (30.6) 244 | (11.2) 1.12 | (16.4) 1305 | (29.7) 236 | not varied |
| Com. Example 3 | (11.4) 1.14 | (16.7) 1329 | (30.6) 244 | (10.3) 1.03 | (15.3) 1218 | (27.5) 219 | locally rusted |
| Com. Example 4 | (11.4) 1.14 | (16.6) 1321 | (30.5) 243 | (10.8) 1.08 | (16.0) 1273 | (28.6) 228 | a portion of Ni film peeled off |
| Com. = Comparative |
The magnet test piece was degreased, pickled and then
immersed in a treating solution comprising 4.6 g/l of zinc and
17.8 g/l of phosphate at a bath temperature of 70°C, whereby
a phosphate film having a thickness of 1 µm was formed on the
surface of the magnet. The produced magnet was subjected to
the corrosion resistance acceleration test under the same
conditions as in Example 1. Results of the test are shown in
Table 1. As a result, the deterioration of the magnetic
characteristic was brought about, and the rusting was produced
in the produced magnet.
The magnet test piece was subjected to the corrosion
resistance acceleration test under the same conditions as in
Example 1. Results of the test are shown in Table 1. As a result,
the deterioration of the magnetic characteristic was brought
about, and the rusting was produced in the magnet test piece.
The magnet having the aluminum film on its surface
subjected to the shot peening in Example 5 was subjected to the
corrosion resistance acceleration test under the same conditions
as in Example 4. Results of the test are shown in Table 2. As
a result, the deterioration of the magnetic characteristic was
brought about, and the rusting was produced in the produced
magnet.
The magnet having the aluminum film on its surface
subjected to the shot peening in Example 5 was cleaned and then
immersed in a treating solution comprising 300 g/l of sodium
hydroxide, 40 g/l of zinc oxide, 1 g/l of ferric chloride and
30 g/l of Rochelle salt at a bath temperature of 23°C, whereby
the surface of the aluminum film was substituted with zinc (Zn).
Further, the resulting magnet was subjected to an electroplating
treatment under a condition of a current density of 1.8 A/dm2
using a plating solution comprising 240 g/l of nickel sulfate,
48 g/l of nickel chloride, an appropriate amount of nickel
carbonate (having a pH value adjusted) and 30 g/l of boric acid
at a bath temperature of 55°C and at a pH value of 4.2, whereby
a nickel film having a thickness of 0.9 µm was formed on the
aluminum film with its surface substituted with zinc. The
resulting magnet was subjected to the corrosion resistance
acceleration test under the same conditions as in Example 4.
Results of the test are shown in Table 2. As a result, the
deterioration of the magnetic characteristic of the magnet was
brought about, and a portion of the nickel film was peeled off.
In the Fe-B-R based permanent magnet having the chemical
conversion coating film which is formed on its surface with the
aluminum film interposed therebetween and which contains at least
one of zirconium and titanium, phosphorus, oxygen and fluorine
as constituting elements, the chemical conversion coating film
is adhered firmly to the magnet with the aluminum film interposed
therebetween and hence, the magnet is excellent in corrosion
resistance. Even if the magnet is left to stand for a long time
under high-temperature and high-humidity conditions of a
temperature of 80°C and a relative humidity of 90 %, the magnet
exhibits a stable high magnetic characteristic which cannot be
deteriorated. Moreover, the film is free from hexa-valent
chromium.
Claims (15)
- An Fe-B-R based permanent magnet, which has a chemical conversion coating film formed on its surface with an aluminum film interposed therebetween, said chemical conversion coating film containing at least one of titanium and zirconium, and phosphorus, oxygen and fluorine as constituting elements.
- An Fe-B-R based permanent magnet according to claim 1, wherein said aluminum film has a thickness in a range of 0.01 µm to 50 µm.
- An Fe-B-R based permanent magnet according to claim 1, wherein said chemical conversion coating film has a thickness in a range of 0.01 µm to 1 µm.
- An Fe-B-R based permanent magnet according to claim 1, wherein the content of titanium and/or zirconium in said chemical conversion coating film is in a range of 0.1 mg to 100 mg per a film portion formed on 1 m2 of the surface of the magnet.
- An Fe-B-R based permanent magnet according to claim 1, wherein the content of phosphorus in said chemical conversion coating film is in a range of 0.1 mg to 100 mg per a film portion formed on 1 m2 of the surface of the magnet.
- An Fe-B-R based permanent magnet according to claim 1, wherein the content of oxygen in said chemical conversion coating film is in a range of 0.2 mg to 300 mg per a film portion formed on 1 m2 of the surface of the magnet.
- An Fe-B-R based permanent magnet according to claim 1, wherein the content of fluorine in said chemical conversion coating film is in a range of 0.05 mg to 100 mg per a film portion formed on 1 m2 of the surface of the magnet.
- An Fe-B-R based permanent magnet according to claim 1, wherein the ratio of the number of moles of phosphorus to the number of moles of titanium and/or zirconium in an area near the surface of the chemical conversion coating film is larger than that in the entire chemical conversion coating film.
- An Fe-B-R based permanent magnet according to claim 1, wherein the ratio of the number of moles of phosphorus to the number of moles of titanium and/or zirconium in an area near the surface of the chemical conversion coating film is equal to or larger than 1.
- A process for producing an Fe-B-R based permanent magnet, comprising the steps of forming an aluminum film on the surface of an Fe-B-R based permanent magnet, applying a treating solution containing at least one of a titanium compound and a zirconium compound, at least one of phosphoric acid, condensed phosphoric acid, phytic acid, the hydrolyzate of phytic acid and the salts of them, and a fluorine compound, onto the surface of the aluminum film, and drying the applied treating solution, thereby forming a chemical conversion coating film containing at least one of titanium and zirconium, and phosphorus, oxygen and fluorine as constituting elements.
- A process for producing an Fe-B-R based permanent magnet according to claim 10, wherein said aluminum film is formed by a vapor deposition process.
- A process for producing an Fe-B-R based permanent magnet according to claim 11, wherein said aluminum film has a thickness in a range of 0.01 µm to 50 µm.
- A process for producing an Fe-B-R based permanent magnet according to claim 10, wherein the Fe-B-R based permanent magnet and aluminum pieces are placed into a treating vessel, where they are vibrated and/or agitated, thereby forming the aluminum film.
- A process for producing an Fe-B-R based permanent magnet according to claim 13, wherein said aluminum film has a thickness in a range of 0.01 µm to 1 µm.
- A process for producing an Fe-B-R based permanent magnet according to claim 10, wherein the ratio of the number of moles (in terms of phosphorus) of at least one of phosphoric acid, condensed phosphoric acid, phytic acid, the hydrolyzate of phytic acid and the salts of them to the number of moles (in terms of metal) of at least one of the titanium compound and the zirconium compound in the treating solution is equal to or larger than 1.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP25651698 | 1998-09-10 | ||
| JP25651698 | 1998-09-10 | ||
| PCT/JP1999/004915 WO2000016347A1 (en) | 1998-09-10 | 1999-09-10 | Corrosion-resistant permanent magnet and method for producing the same |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| EP1032000A1 EP1032000A1 (en) | 2000-08-30 |
| EP1032000A4 EP1032000A4 (en) | 2003-05-02 |
| EP1032000B1 true EP1032000B1 (en) | 2004-07-14 |
Family
ID=17293719
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP99943247A Expired - Lifetime EP1032000B1 (en) | 1998-09-10 | 1999-09-10 | Corrosion-resistant permanent magnet and method for producing the same |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP1032000B1 (en) |
| DE (1) | DE69918660T2 (en) |
| HK (1) | HK1027207A1 (en) |
| WO (1) | WO2000016347A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB0300771D0 (en) | 2003-01-14 | 2003-02-12 | Rolls Royce Plc | Rare earth-transmission metal alloy articles |
| CN104674169A (en) * | 2015-02-12 | 2015-06-03 | 烟台首钢磁性材料股份有限公司 | Method for electroplating surface of permanent magnet neodymium iron boron magnetic steel with composite coating |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1007847B (en) * | 1984-12-24 | 1990-05-02 | 住友特殊金属株式会社 | Method for manufacturing magnet with improved corrosion resistance |
| JPH07249509A (en) * | 1994-03-08 | 1995-09-26 | Sumitomo Special Metals Co Ltd | Corrosion-resistant permanent magnet and its manufacture |
| JPH07302705A (en) * | 1994-05-09 | 1995-11-14 | Daido Steel Co Ltd | Corrosion-resistant rare earth magnet and its manufacture |
-
1999
- 1999-09-10 EP EP99943247A patent/EP1032000B1/en not_active Expired - Lifetime
- 1999-09-10 DE DE69918660T patent/DE69918660T2/en not_active Expired - Lifetime
- 1999-09-10 WO PCT/JP1999/004915 patent/WO2000016347A1/en active IP Right Grant
-
2000
- 2000-09-28 HK HK00106159A patent/HK1027207A1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| HK1027207A1 (en) | 2001-01-05 |
| EP1032000A1 (en) | 2000-08-30 |
| DE69918660D1 (en) | 2004-08-19 |
| EP1032000A4 (en) | 2003-05-02 |
| WO2000016347A1 (en) | 2000-03-23 |
| DE69918660T2 (en) | 2005-07-28 |
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