2.5.3
Pressed components and test rings are formed from acicular metal particles by traditional powder metallurgical forming methods (Kokal, Bularzik, and Krause, 1997, pp. 61-75). Discrete particles are made by a proprietary manufacturing process that
allows control of the particles' physical parameters. Particle chemistry is controlled to achieve desired magnetic properties. The particles are annealed and coated with a metalloorganic substance to fully insulate the particles from each other. Particles are lubricated with a commonly used lubricant such as acrawax or a stearate salt. To produce components, the lubricated particles are fed to a standard powder metallurgy press feed system to form commercial parts. Finished parts are heated in air to remove the lubricant. No further treatment is needed prior to use.
To evaluate the magnetic properties of the particles and for quality control, toroidal rings are made and tested to ASTM standards. Test rings are prepared by hand filling the cavity in a ring-shaped die and pressing it in a laboratory press. Rings are evaluated with a Donart ac tester capable of testing at 50, 60, 100, and 400 Hz. The dc properties are evaluated on a Walker AMH-20 at near dc conditions.