Samarium Cobalt

General Information Machining
Manufacturing Methods Magnetizing and Handling
Comparison of NdFeB and SmCo Magnets Common Applications for SmCo magnets
Assemblies Temperature Effects
Surface Treatments Properties of SmCo magnets

 

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General Information

Collectively known as Rare Earth magnets, Samarium Cobalt (SmCo) and Neodymium Iron Boron (NdFeB) magnets are alloys of the Lanthanide group of elements. Rare Earth magnets are the most advanced commercialized permanent magnet materials today. SmCo magnets are available in a number of different grades that span a wide range of properties and application requirements.

SmCo magnets are brittle and machining operations should be performed prior to magnetization, using diamond tools. We are equipped to fabricate these materials to blueprint specifications.

SmCo magnets are anisotropic, and can only be magnetized in the orientation direction. In general, magnetizing fields of about 35 to 45 kOe are required to saturate SmCo materials.


Manufacturing Methods

SmCo magnets are manufactured in the following forms:

 Sintered - fine SmCo powder is compacted in a die and then sintered, fusing the powder into a solid material. There are two forms of pressing: die pressing (which involves a hard die into which the powder is placed and then pressed), and isostatic pressing (involving a special "rubber" die into which powder is placed and then pressed with equal force in all directions on the powder). Die pressed parts are smaller than isostatically pressed parts. Although the magnetic properties of isostatically pressed parts are higher, the uniformity of magnetic characteristics is usually lower than that of die pressed parts. Sintered parts usually need some finish machining in order to meet final tolerances.

 Compression Bonded - this is a technique whereby a special form of SmCo powder is blended with a plastic carrier material, die pressed and then heated. Parts made in this way can be of complex shapes and come off the tool with close tolerances, requiring no further finish machining. They have lower energy products than sintered materials - currently in the range of 15 MGOe.


Comparison of NdFeB and SmCo Magnets
Material Energy Products Mechanical Strength Density (lbs/in3 - gm/cm3) Corrosion Resistance Temperature Stability Cost
NdFeB 10 to 48 Medium 0.275 - 7.5 Low Low to Medium Lower
SmCo 15 to 32 Low 0.300 - 8.3 High High Higher


Assemblies

We are able to manufacture metal and other components of finished sub assemblies using our CNC machining facilities.

Assemblies can be fabricated by adhering magnets with adhesives to suit a range of environments, by mechanically fastening magnets, or by a combination of these methods. Due to the relatively brittle nature of these magnet materials, press fits are not recommended.

When multiple magnets are assembled in repelling positions, it is advisable to use mechanical fastening in addition to adhesives, since if adhesives were to give way, repelling magnets may dislodge and endanger personnel using them. Our design engineering team will be happy to assist you in designing housings for your magnet assemblies.


Surface Treatments

The corrosion resistance of SmCo is considered good while that of NdFeB is considered poor. Coatings for corrosion resistance are therefore not generally required for SmCo magnets.


Machining

SmCo is extremely brittle, and highly prone to chipping and cracking. Special machining techniques, involving diamond-grinding techniques, must be used to machine this material.

We are fully equipped to machine these materials to your blueprint specifications.


Magnetizing and Handling

All Rare Earth magnets require extremely high magnetizing fields and special consideration must be given to this when designing complex assemblies, if it is intended to magnetize after assembly. Consult us if you foresee any problems.

SmCo materials are mechanically very weak, and magnetically very strong. They must therefore be handled very carefully to avoid damage and injury to personnel handling the magnets. Receiving and assembly personnel should be warned about the dangers of handling magnetized Rare Earth magnets.


Temperature Effects

SmCo magnets can operate at temperatures up to 350C , depending upon the grade and permeance coefficient. Sm2Co17 materials exhibit superior temperature characteristics as compared to the Sm1Co5 types.


Common Applications for Samarium Cobalt Magnets

Holding systems requiring very high holding forces, high field yoke magnets, high performance stepper, DC, servo, linear, and voice coil motors, magnetic bearings, magnetic couplings, loudspeakers, Halbach arrays, headphones, microphones, magnetic separation, instrumentation, switches, relays, magnetic resonance, sputtering, vacuum deposition, charged particle beam guidance, particle accelerators, Undulators, Wigglers, and others.



 

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