Method of protecting magnetic powders and densified permanent magnets of the Fe Nd B type from oxidation and atmospheric corrosion
US5411603A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 7, 1993 |
| Grant date | May 2, 1995 |
| Priority date | — |
| Expiry date | Dec 7, 2013 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01F1/0572
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
Abstract
The invention concerns a method of protecting magnetic powders and permanent magnets containing at least one rare earth, at least one transition metal and boron from oxidation and atmospheric corrosion, by the introduction of gaseous fluorine during the grinding of the powders. It is characterized in that the fluorine is introduced by a mixture of F.sub.2 +N.sub.2 during the fine grinding of the powders, the mixture containing from 1 to 100 ppm (by volume) of fluorine, and preferably from 1 to 10 ppm. The powders thus obtained are far less reactive and the densified magnets are far more resistant to atmospheric corrosion than non fluorinated powders and magnets obtained therefrom.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.