Method of forming thin curved rare earth-transition metal magnets from lightly compacted powder preforms

摘要

A method is provided for forming rare earth-transition metal (RE-TM) powders directly into radially aligned, thin, curved permanent magnets supported on ferromagnetic backings. Such magnets are particularly suited for use as D.C. motor pole pieces. In the method, a powder cavity is formed between a ferromagnetic backing layer and a composite forming mandrel. The mandrel has a ferromagnetic core slidably retained in a thin magnetic sleeve. The powder in the cavity is pressed in a magnetic field to a density of about 50%. Thereafter, the core of the mandrel is first removed and then the nonmagnetic sleeve. After both mandrel sections are withdrawn, the powders are maintained in the magnet shape for further processing by mechanical interlocking of the particles, and the magnet shape itself is magnetically attracted to the backing layer by the residual magnetism of the powder. The mass may be heated to coalesce the powder and bond it to the backing.