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
  • High corrosion-resistance
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Samarium-Cobalt magnets (SmCo)

Detailed product description

SmCo magnets pertain, just like Neodymium-Ferro-Boron (Neoflux®) magnets, to the rare earth magnets. Samarium-Cobalt magnets have excellent magnetic characteristics with a maximum energy product of 18 to 32 MGOe, a low temperature coefficient and a high stability. Moreover they are very resistant to oxidation and require no coating under normal circumstances.

Samarium-Cobalt magnets are the best choice, especially for applications where durability is of great importance. For example within advanced electronic products, medical equipment and the automotive industry.
The maximum usage temperature is approx. 300˚C.

SAMARIUM-COBALT OVERVIEW (SmCo)

Being the first rare earth permanent magnetic material developed in the 1970’s, Samarium Cobalt offers the second highest energy density of the 4 main magnetic materials used commercially. It’s BHMax values range from 16 to 32 MGOe. Having 7 times the strength of Ferrite means that magnetic assemblies with Samarium Cobalt can be reduced accordingly.
Although Samarium Cobalt magnets are more expensive than, and not as strong as Neodymium magnets – they have a higher curie temperature meaning they can be used for extreme temperature applications.
By nature, SmCo magnets are prone to extreme brittleness, which means that designers and engineers must exercise great thought and care when integrating samarium cobalt magnets with a given application. This is especially true when considering Design for Manufacture and Assembly (DFMA). 


APPLICATIONS

Despite its fragility, Samarium Cobalt remains the rare-earth magnet alloy of choice for high strength / high temperature applications.
Such applications include:
• Medical implants and prostheses
• High temperature pumps, motors and instrumentation where thermal stability is paramount
• Sensors
• Turbo Machinery


KEY BENEFITS of SmCo

Here are some key benefits of SmCo that you may want to consider when it comes to researching and designing for industrial applications:
• SmCO magnets have an ability to operate in temperatures up to about 300°C, making them inherently more
  stable at temperatures well above the curie point of NdFeB for example.
• Samarium Cobalt magnetic materials offer the world's highest stability and magnetic output at raised
   temperatures.
• It’s magnetic strength: up to about 32MGOe.
• The fact that it’s corrosion resistant.
• It’s broad-based source of supply means SmCo magnets use materials that are more widely available, thus making
   SmCo pricing more stable and less prone to market changes.
• It has been proven in applications that achieve higher performance and efficiency in the automotive, motorsports
 , aerospace, and defence sectors for example.


KEY CHALLENGES with SmCo

As with the other magnetic materials available, there are of course some things you need to be aware of when incorporating SmCo into your product:
• Its fragile nature makes the machining process slightly more complex.
• Since the material contains cobalt, the cost of SmCo proves expensive.


TECHNICAL DETAILS OF SAMARIUM COBALT

Here are a few facts:
• Its density is about 0.300 lbs. per cubic inch.
• The magnetising field required for saturation is about 50kOe.
• Available grades of SmCo range from about 1410 to 3214, where the first 2 digits represent BHmax; and the
   second two digits represent intrinsic coercivity (Hci).


MANUFACTURING METHODS AND PROCESSING

There are various manufacturing processes available for SmCo magnets, like those discussed last week for Neo:
• Sintering is the most common process carried out. It involves forming a solid mass of magnetic material through
   compacting with pressure and heat.  
• Injection Moulding can form bonded magnetic material into complex shapes, and can be moulded directly onto
   other parts to form magnetic assemblies.
• Compression Bonding results in stronger magnetic performance when compared to injection moulding, however,
   only simpler geometries can be formed.


MACHINING SmCo MAGNETS

Specialist machining may be required, depending on the design and geometry of your SmCo magnet in your application:
• Since it’s extremely brittle, SmCo is prone to chipping and cracking. Generally, diamond grinding techniques must
   be used to machine SmCo magnets.
• At Goudsmit we are fully equipped to machine these materials to your design specifications.


SURFACE TREATMENTS

Due to the high corrosion resistance, the good news is that samarium cobalt magnets do not require any additional surface treatments.
Precautions when working with Samarium Cobalt (SmCo)
• SmCo magnets can easily chip or break upon impact, therefore, extra care should be taken when handling these
   magnets.
• All rare-earth magnets including SmCo magnets are very powerful, therefore special care should be taken when
   handling these magnets to avoid injuries.

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