Collectively known as Rare Earth magnets, Samarium Cobalt (SmCo) and Neodymium Iron Boron (NdFeB) magnets are alloys of the Lanthanide group of elements. Rare Earth magnets are the most advanced commercialized permanent magnet materials today. SmCo magnets are available in a number of different grades that span a wide range of properties and application requirements.
SmCo magnets are brittle and machining operations should be performed prior to magnetization, using diamond tools. We are equipped to fabricate these materials to blueprint specifications.
SmCo magnets are anisotropic, and can only be magnetized in the orientation direction. In general, magnetizing fields of about 35 to 45 kOe are required to saturate SmCo materials.
SmCo magnets are manufactured in the following forms:
Sintered - fine SmCo powder is compacted in a die and then sintered, fusing the powder into a solid material. There are two forms of pressing: die pressing (which involves a hard die into which the powder is placed and then pressed), and isostatic pressing (involving a special "rubber" die into which powder is placed and then pressed with equal force in all directions on the powder). Die pressed parts are smaller than isostatically pressed parts. Although the magnetic properties of isostatically pressed parts are higher, the uniformity of magnetic characteristics is usually lower than that of die pressed parts. Sintered parts usually need some finish machining in order to meet final tolerances.
Compression Bonded - this is a technique whereby a special form of SmCo powder is blended with a plastic carrier material, die pressed and then heated. Parts made in this way can be of complex shapes and come off the tool with close tolerances, requiring no further finish machining. They have lower energy products than sintered materials - currently in the range of 15 MGOe.
|Comparison of NdFeB and SmCo Magnet|
|Material||Energy Products||Mechanical Strength||Density (lbs/in3 - gm/cm3)||Corrosion Resistance||Temperature Stability||Cost|
|NdFeB||10 to 48||Medium||0.275 - 7.5||Low||Low to Medium||Lower|
|SmCo||15 to 32||Low||0.300 - 8.3||High||High||Higher|