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Samarium Cobalt magnets

 

Description

 

smco1.jpgSamarium-cobalt (abr. SmCo) magnet is another type of rare-earth magnets. It is made of an alloy of samarium and cobalt. Samarium-cobalt magnets have magnetic strength comparable to neodymium magnets, ranging in the maximum energy product (BHmax) of 16-33 MGOe,

 

Samarium-cobalt magnets are slightly more expensive than the popular neodymium magnets, but they have higher operating temperature, magnetic stability over a widely changing temperature environment, and strong resistant to corrosion or oxidation.

 

Our company carries a wide selection of Samarium-cobalt magnets varying in shape and size (e.g. disc 2mm-1'and block 3/8-2').

 

Properties

 

Temperature and demagnetization

 

Samarium-cobalt magnets have a substantially higher Curie temperature (~800 ºC) than neodymium magnets (320 ºC). Since they also have a much lower reversible temperature coefficient (-0.03 %/K compared to -0.12 %/K for neodymium magnets), SmCo magnets have also superior ability to resist changes in the magnetic field upon changes in temperature. Thus, SmCo magnets are a better choice when a very cold or hot operating temperature or an environment of changing temperature is required.

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Grades

 

Samarium-cobalt magnets are available in two "series": Series 1:5 and Series 2:17. Series 1:5 is composed of ~37% samarium and 63% cobalt by weight. The composition for Sm2Co17 materials is more complex, having ~25% samarium, 5% copper, 18% iron, 2% hafnium or zirconium, with the remainder being cobalt. These small amounts of zirconium and hafnium etc. are added in order to improve heat treatment.

 

Generally, the magnetic strength for series 1:5 resides in a lower range (BHmax ~16-25 MGOe) than Series 2:17 (BHmax ~20-32 MGOe), though the former series is easier to calibrate to a specific magnetic field than Series 2:17 magnets.

 

Mechanical stress and handling care

 

Similar to other permanent magnets, Samarium-cobalt magnets are manufactured from sintered powder of Sm-Co alloy. As such, they are bristle and easy to break. Samarium-cobalt Magnets are also very strong. When handling them, eye protection must be worn and avoiding the magnets to snap together that could shatter magnets to shatter and cause injury,

 

Corrosion

 

Samarium-cobalt magnets have better resistance to corrosion than Neodymium magnets and require no coating or plating in many applications. However, coating (e.g., parylene and cladding) or plating (nickel) may be desirable when operating in acidic, high moisture, or very cleaning (e.g. vacuum and medical applications) environment.

 

Applications

 

Popular uses

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Samarium-cobalt magnets, because of their unique temperature characteristics, are appropriate for applications where a very cold or hot operating temperature or an environment of changing temperature is required. They are also used in

 

  • High-end electric motors (e.g. used in the more competitive classes in slotcar racing)

  • Electric guitar pickup

  • Turbo machinery

  • Traveling-wave tube field magnets

  • Bench-top NMR spectrometers

  • Rotary encoders where it performs the function of magnetic actuator

  • Servo motors

  • Space probes and satellites

  • Magnetic couplings and separators.

  • Switches

  • Sensors,

  • head- and microphones

 

New trend

 

  • Electric vehicles are a growing market for rare earth magnets because of the energy and environment concerns. Consumption of rare earth magnets in transportation is estimated to rise from 7,000 tons in 2015 to 17,000 tons in 2020. Permanent magnet machines are currently the leading choice for high performance automotive applications. The rotor’s well-balanced magnetic field and the lower stator current requirement, paired with very strong positional control, result in a higher motor efficiency.