Iron-based permanent magnets and their fabrication as well as ir

Details Iron-based permanent magnets and their fabrication as well as ir Iron-based permanent magnets and their fabrication as well as ir

1996-06-05

2000-02-01

Sheehan, John

Metal treatment

Stock

Magnetic

252 6254, 420 83, 420121, H01F 1057

Patent

active

060198591

ABSTRACT:
With the intention of establishing fabrication methods for cheaply produced (Fe,Co)--Cr--B--R-type bonded magnets or (Fe,Co)--Cr--B--R--M-type bonded magnets containing few rare earth elements and having a coercive force iHc above 5 kOe and a residual magnetic flux density Br above 5.5 kG matching the cost performance of hard ferrite magnets, we have obtained iron-based permanent magnets consisting of microcrystal clusters where the average crystal size of each component phase is in the range 1 nm .about.30 nm and where both a soft magnetic phase consisting of a ferromagnetic alloy whose main components are .alpha.-Fe and a ferromagnetic alloy having iron, and a hard magnetic phase having a Nd.sub.2 Fe.sub.14 B-type crystal structure coexist within the same powder particles, by melt--quenching of a (Fe,Co)--Cr--B--R(Pr,Nd)-type molten alloy or a (Fe,Co)--Cr--B--R--M (M=Al,Si,S,Ni, Cu,Zn,Ga,Ag,Pt,Au,Pb)-type molten alloy of a particular composition containing few rare earth elements, to obtain an essentially amorphous structure or a structure both amorphous and with small amounts of fine crystals, and by applying a crystallization heat treatment under specific conditions. By grinding this iron-based permanent magnet to an average powder particle size of 3 .mu.m.about.500 .mu.m and combining the resultant iron-based permanent magnet alloy powder with a resin, we can obtain an iron-based bonded magnet with good thermal and magnetic properties and with the magnetic characteristics iHc.gtoreq.5 kOe, Br.gtoreq.5.5 kG and (BH)max.gtoreq.6 MGOe.

REFERENCES:
patent: 5022939 (1991-06-01), Yajima et al.
patent: 5049208 (1991-09-01), Yajima et al.
patent: 5209789 (1993-05-01), Yoneyama et al.
H. Kanekiyo et al., "Microstructure and Magnetic Characteristics of High-Remanence Nd.sub.5 Fe.sub.75 6 CO.sub.5 B.sub.18 5 M (M=A1, SI, Ga, Ag, Au) Rapidly Solidified and Crystallized Alloys for Resin-Bonded Magnets", Digests of INTERnational MAGnetics Conference, Apr. 13-16, 1993, pp. ED01-ED02.

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