ABOUT FERRITE MAGNETS
Ferrite magnets, also known as ceramic magnets, were developed in the 1960’s as a low cost alternative to metallic magnets. Ferrite magnets have won wide acceptance due to their excellent corrosion resistant and good resistance to demagnetization. Despite their relatively low energy output, ferrite magnets’ popularity is largely from its low price. It is the first choice for most automotive sensors, MRI machines, DC motors, and magnetic separators. In fact, based on weight, it is the most widely used permanent magnet available today.
Ferrite magnets are very hard and brittle. Like all magnetic materials, ferrite magnets should not be used as a structural element in your design. Ferrite magnets are prone to cracking if your application requires regular impact or flexing. Because ferrite magnets offer good corrosion resistance, they do not require an outer coating. In rare instances a thin outer coating is applied simply to protect the material.
Several factors decide ferrite magnets’ performance under extreme temperature. Ferrite magnets are susceptible to demagnetization when exposed to extreme temperatures. The geometry or the assembly attached to the magnet can affect how the magnet responds to a change in temperature. Contact your Alpha Magnet sales representative for more details.
Ferrite magnets are produced by calcining a mixture of iron oxide and strontium carbonate to form a metallic oxide. A multiple stage milling operation reduces the calcined material to a small particle size. Depending on the magnetic characteristic – anisotropic or isotropic, the powder is processed differently. For anisotropic, the powder is mixed with water to form slurry. The slurry is compacted in a die in the presence of a magnetic field. For isotropic, the dry powder is then compacted in a die. Isotropic ferrite magnets have weaker magnetic properties but better dimensional tolerances. Typically a dry pressed magnet does not require finish grinding.
Heat treating helps the final product maintain its shape as well as magnetic characteristics. Diamond abrasives are used to perfect the shape of the final product. Usually the pole faces of the ferrite magnets will be ground and the remaining surfaces will exhibit “as sintered” tolerances and physical characteristics.