Samarium Cobalt in a Nutshell
The samarium–cobalt magnet is a type of rare earth magnet. It’s a strong permanent magnet made of an alloy (mixture) of samarium and cobalt. They were developed in the early 1970s, and are often referred to within the industry as SmCo magnets. They are generally the second-strongest type of magnet out there: weaker than neodymium magnets, but have higher temperature ratings and higher coercivity.
The reduction/melt method and reduction/diffusion method are used to manufacture SmCo magnets. What’s that mean? The raw materials are melted in an induction furnace filled with argon gas. Then the mixture is cast into a mold and cooled with water- this forms a mass of a themetal cast in a convenient form for shaping, remelting, or refining, called an ingot. The ingot is crushed and the particles are further milled to reduce the particle size even more. The resulting powder is pressed in a die of the shape desired in a magnetic field to orient the magnetic field of the particles. Sintering is applied at a temperature of 1100˚C–1250˚C, followed by solution treatment at 1100˚C–1200˚C. Finally, tempering is performed at about 700˚C–900˚C. Last, it’s ground and further magnetized to increase its magnetic properties.
Characteristics of Samarium-Cobalt:
- Very resistant to demagnetization
- Good temperature stability (maximum use temperatures between 250 and 550 °C; Curie temperatures from 700 to 800 °C)
- Expensive and subject to price fluctuations (cobalt is market price sensitive)
- Samarium–cobalt magnets can easily chip; eye protection must be worn when handling them
- The sintering process makes SmCo more prone to inherent cracks.