Samarium Cobalt Magnets

The manufacturing process of Samarium Cobalt magnets begins with the production of an alloy through vacuum induction melting. The resulting ingots are crushed to approximately 200 to 400 microns, then jet-milled into a fine powder of about 2 to 5 microns. This fine powder is subsequently filled into molds and pressed under an applied magnetic field to orient the individual particles. The compacted green body is then densified via sintering in a vacuum sintering furnace.

For SmCo₅ series magnets, the green body is sintered at 1150 to 1200 degrees Celsius, followed by a heat treatment around 850 degrees Celsius. The magnets are then quenched to achieve acceptable magnetic properties.

For Sm₂Co₁₇ series magnets, the sintering process comprises three steps: sintering, solid solution treatment, and aging. The green body is typically sintered at 1190 to 1220 degrees Celsius, followed by solid solution treatment at 1150 to 1185 degrees Celsius. It is then quenched to room temperature before undergoing a prolonged aging cycle at around 850 degrees Celsius, with subsequent slow cooling at a rate of 1 degree Celsius per minute to about 400 degrees Celsius, in order to attain the desired magnetic properties. Finally, the blanks are machined to specific shapes and magnetized.

Samarium Cobalt magnets offer superior temperature stability, resistance to demagnetization, corrosion, and oxidation. However, their long-term operational stability is limited by relatively poor mechanical properties. Samarium Cobalt magnets are brittle and prone to cracking and chipping during machining and use. Furthermore, the SmCo₅ series exhibits better processability compared to Sm₂Co₁₇ series magnets.

Both the SmCo₅ and Sm₂Co₁₇ series magnets exhibit superior resistance to corrosion and oxidation compared to Neodymium magnets. Therefore, Samarium Cobalt magnets typically do not require any additional surface treatment for most applications. It is always advisable to empirically evaluate the permanent magnet in the intended operational environment before finalizing a design path. In addition to the advantage of low environmental reactivity, appropriate surface treatments can enable Samarium Cobalt magnets to achieve greater cleanliness in specific applications, such as vacuum and medical settings.

Samarium Cobalt magnets require a higher external magnetic field for saturation compared to Neodymium magnets, particularly the Sm₂Co₁₇ series magnets with high coercivity. Therefore, Samarium Cobalt magnets also employ a fast impulse magnetization process before being used in their intended applications. The magnetizer for Samarium Cobalt magnets features greater capacity to deliver the necessary magnetic field strength. Theoretically, Samarium Cobalt magnets have a preferred direction of magnetization, allowing for various pole configurations as long as they do not conflict with the orientation direction. However, the magnetizing fixture often becomes the decisive factor constraining multipole magnetization of Samarium Cobalt magnets.