Types of Rare Earth Magnets: Part 2

Melt Spun/Jet Milled Isotropic Bonded Magnets

By Dr. John Ormerod
Technical Adviser / Magnet Applications

In the early 1980’s, General Motors Corporation (later Magnequench) pioneered the use of melt spinning to produce an isotropic NdFeB powder which is used primarily in bonded magnet production; either compression bonding or injection molding as shown below.

The principle of melt-spinning consists of melting the alloy or elements in a tube under vacuum or inert gas. The melt, under inert gas pressure, is sprayed through an orifice in the tube onto a rotating, water-cooled copper wheel or disc. Cooling rates in excess of 1,000,000 C/sec. are achieved which produces an alloy with an amorphous or fine grained nanocrystalline structure.