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Samarium-Cobalt magnets (SmCo)

Short description

Samarium-Cobalt (SmCo) magnets have excellent magnetic characteristics, a low temperature coëfficiënt and high stability.

Characteristics

  • Energy product 18 - 32 MGOe
  • Low temperature coëfficiënt
  • High stability
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Samarium-Cobalt magnets (SmCo)

Detailed product description

Samarium cobalt

Samarium-cobalt (SmCo) magnets, like neodymium-iron-boron (Neoflux®) magnets, are classified as rare-earth magnets. SmCo magnets have excellent magnetic properties, with a maximum energy product of up to 32 MGOe, a low temperature coefficient and high stability. They are also highly resistant to oxidation and require no coating under normal conditions.

Samarium cobalt was the first rare-earth magnetic material to be developed, in the 1970s. The material provides the second highest energy density of the four main magnetic materials that are used commercially. The BHmax value ranges from 16 to 32 MGOe, which is seven times the magnetic strength of ferrite. Magnetic assemblies constructed with samarium cobalt can therefore be considerably reduced in volume.

Samarium cobalt magnets are more expensive and weaker than neodymium magnets, but they have a higher Curie temperature making them suitable for use in extreme temperatures.
SmCo magnets are initially very brittle, which is a factor designers and engineers must take into account when integrating samarium-cobalt magnets into their applications.

Applications

In spite of its fragility, the samarium-cobalt (SmCo) alloy is preferable for applications requiring a combination of strength and high temperatures: the maximum application temperature is approx. 300 °C. Particularly for applications where durability is of great importance, SmCo magnets are the best choice. Examples include high-quality electronic products, medical equipment and automotive applications. For applications such as:

  • medical implants and prostheses;
  • high-temperature pumps, motors and instruments in which thermal stability is a top concern;
  • sensors;
  • turbomachinery.

Advantages

  • SmCo magnets are resistant to temperatures above 300° C, so they remain stable at temperatures far above the Curie point of materials like NdFeB;
  • corrosion-resistant;
  • proven in applications where high performance and efficiency are required, such as those in the automotive, motorsport, aerospace and defence industries.

Disadvantages

  • due to the fragility, the machining process is more complex;
  • expensive material (compared to NdFeB and ferrite, for example).

Technical details of SmCo

  • density: 8304 kg/m³ ((0.300 lbs./in³);
  • magnetic field required for saturation: ±50 kOe;
  • BHmax value of the available range of samarium cobalt grades: 151-247 kJ/m³.

Production methods

  • Sintering is the most common and widely used process. A combination of heat and pressure produces a solid mass of magnetic material.
  • Injection moulding: this involves mixing the magnetic material with a plastic (e.g. nylon) and then pressing it into a particular shape in a die, making it possible to create complex shapes; a drawback is that the use of plastic reduces the magnetic force.
  • Compression bonding (the bonding of two materials by pressing them together) results in improved magnetic performance compared to injection moulding, but it is only suitable for simple geometric shapes.

Processing of SmCo magnets

A specialized processing step may be required, depending on the design and geometry of the SmCo magnet in your application.
Because it is extremely brittle, SmCo easily crumbles, and cracking can occur. Generally diamond grinding techniques are used to process SmCo magnets.

Goudsmit is fully equipped to process these materials to arrive at your design specifications.

Surface treatment for samarium-cobalt magnets

Due to the high corrosion-resistance samarium-cobalt magnets do not require any additional surface treatment.

Precautions when working with samarium-cobalt (SmCo)

  • SmCo magnets can easily chip or break if they fall; keep this in mind when working with this magnet material.
  • All rare-earth magnets, including SmCo magnets, are very powerful. To avoid injury, you must be careful when handling these magnets.

Samarium Cobalt permanent magnets - table

Grade Remanence Normal
coercivity
Intrinsic
coercivity
Max.
Energy product
Max.
operating
Temp.
 

Br
mT

Hcb
kA/m
Hcj
kA/m
BH(max)
kJ/m3
 
  min typ min typ min min typ °C
SmCo5                
GSS-20 850  950 637  756  1194  151  175  250 
GSS-22 890 1000 661  772  1194  167  191  250 
Sm2Co17                
GSS-24 920  1040  661  796  1194  175  199  350 
GSS-26 1000  1060  677  820  1194  191  215  350 
GSS-28 1040  1100  677  820  1194  207  231  350 
GSS-30 1070  1120  700  828  1194  223  247  350