Method of preparing micro-structured powder for bonded...

Details Method of preparing micro-structured powder for bonded... Method of preparing micro-structured powder for bonded...

2007-01-16

2007-01-16

Sheehan, John P. (Department: 1742)

Metal treatment

Process of modifying or maintaining internal physical...

Magnetic materials

C148S104000, C419S012000

Reexamination Certificate

active

10734544

ABSTRACT:
Disclosed is a method of preparing a micro-structured powder for bonded magnets having high coercivity, which is advantageous in terms of low preparation costs by recycling magnet scraps, simplified mass production, minimal environmental contamination by such a recycling process, and the preparation of stable anisotropic powders having high coercivity. Further, a magnet powder prepared by the above method is provided. The current method is characterized in that R—Fe—B type anisotropic sintered magnets or scraps thereof are crushed to prepare 50–500 μm sized magnet powders, which are then mixed with 1–10 wt % of rare earth fluoride (RF3) powders and thermally treated at high temperatures (500–1100° C.) in a vacuum or an inert gas, to cause the change of matrix-near surface and grain boundary of the powders. Thus obtained powders include a matrix phase having R2Fe14B crystal structure, a R-rich grain boundary phase containing rare earth fluoride, and other phases, in which the matrix phase has an average grain size of 1–20 μm, and the powders have an average size of 50–500 μm with superior magnetic characteristics of (BH)max≧20 MGOe and iHc≧5 kOe.

REFERENCES:
patent: 5858124 (1999-01-01), Endo et al.
patent: 2003/0047240 (2003-03-01), Honkura et al.
patent: 2003/0106615 (2003-06-01), Hirota et al.
patent: 6-231925 (1994-06-01), None

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