Magnet Sintering Process

Magnet Sintering Process – Separation / Reflinement

Beginning with rare earth ore, high purity rare earth oxides are separated and refined.

Measurement of Raw Materials

Additives such as rare earth metals, iron, cobalt and others are measured to produce the desired composition. The materials are then melted in a vacuum induction furnace as shown below.

measurement-of-raw-materials

Melting

The materials are exposed to high frequency and melted in an induction furnace.

melting

Pulverization

After completion of various process steps, the ingots are pulverized into particles that are several microns in size. In order to prevent oxidation from occurring, the small particles are protected by nitrogen and argon.

pulverization

Compacting in Magnetic Field

The magnetic particles are placed in a jig and a magnetic field is applied while the magnets are pressed into shape. Through this process, we achieve magnetic anisotropy.

Two methods of pressing exist: perpendicular pressing where magnets are pressed in a perpendicular magnetic field and parallel pressing where they are pressed in a parallel field. Given an equal grade of magnet, the perpendicular press method will result in a higher performance magnet. However, ring magnets must be pressed using the parallel method.

compacting-in-magnetic-field

Sintering

Ingots that have been pressed are heat treated in a sintering furnace. The density of the ingots prior to sintering is about 50% of true density but after sintering, the true density is 100%. Through this process the ingots’ measurement shrink by about 70%-80% and their volume is reduced by about 50%.
Aging the magnets after sintering adjusts the properties of the metals.

sintering

Inspecting Magnetic Properties

Basic magnetic properties are set after the sintering and aging processes are complete. Key measurements including remnant flux density, coercivity, and maximum energy product are recorded.
Only those magnets that pass the inspection are sent to subsequent processes including machining and assembly.