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How are Sintered Samarium Cobalt Magnets Made?

Posted on June 19, 2017

Samarium Cobalt Magnet

Developed in the early 1960’s, samarium Cobalt magnets have been a highly preferred application choice as a type of rare earth permanent magnet material. Samarium cobalt magnet compositions are primarily samarium and cobalt with small amounts of iron, copper, zirconium depending on the material grade. The powerful sintered samarium cobalt magnets fall into two groups of chemical composition: SmCo5 and Sm2Co17.

So, what kind of metallurgical production steps are involved making them high resistant against working temperature, demagnetization and corrosion?

  • Gather and weigh out the raw ingredients for the desired graded samarium cobalt magnet.
  • Melt the minerals in an induction furnace filled with argon gas to form liquid alloy.
  • Pour out the liquid alloy and cool completely with water to yield ingots.
  • Crush, pulverize and mill the hardened ingots to fine powder with particle sizes in microns.
  • Powder is compressed into a rigid steel die and heated at a temperature up to 1100-1250oC and amalgamated into a solid. The mold used may not be the exact complexity as the final products’ shape due to the physical feature of the alloy. During this pressing stage, the magnet is assigned with magnetic field which includes the magnetization orientation. The alignment of particles yields an anisotropic alloy and increases the magnetic properties of the final product.
  • The sintered solid undergoes a solution treatment at 1100-1200oC temperatures before reaching full dense condition at 700-900oC.
  • The sintered samarium cobalt magnet is then fine-tuned to it is required dimensions by machining and grinding using water-cooled diamond-coated grinding machinery as the alloy material is hard and brittle and the dry dust produced is flammable.
  • The formed magnet is then coated if necessary. In most cases, due to lack of iron, they are highly resistant to corrosion and coating is not required.
  • The final step to samarium cobalt magnets manufacturing process is magnetization.
  • Upon completion of each batch of production, samarium cobalt magnets are being tested and inspected. For custom magnets, we always provide reports on their dimensions and magnetic property values.
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