Iron-based permanent magnets and their fabrication as well as iron- based permanent magnet alloy powders for permanent bonded magnets and iron- based bonded magnets

摘要

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 30 nm and where both a soft magnetic phase consisting of a ferromagnetic alloy whose main components are -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.m500 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 iHc5 kOe, Br5.5 kG and (BH)max. gtoreq.6 MGOe.