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Samarium-cobalt magnets are primarily composed of samarium and cobalt. They have been available since the early 1970s. This type of rare-earth magnet is very powerful, however they are brittle and prone to cracking and chipping. Samarium-cobalt magnets have Maximum Energy Products (BHmax) that range from 16 Mega-Gauss Oersteds (MGOe) to 32 MGOe, their theoretical limit is 34 MGOe. Samarium Cobalt magnets are available in two "series", namely Series 1:5 and Series 2:17.
Additional recommended knowledge
Samarium Cobalt Series 1:5
These samarium cobalt magnet alloys (generally written as SmCo5, or SmCo Series 1:5) have one atom of rare earth Samarium and five atoms of Cobalt. By weight this samarium cobalt magnet alloy will typically contain 36% Samarium with the balance Cobalt. The energy products of these samarium cobalt alloys range from 16 MGOe to 25 MGOe. These Samarium Cobalt magnets generally have a reversible temperature coefficient of -0.05%/°C. Saturation magnetization can be achieved with a moderate magnetizing field. This series of Samarium Cobalt magnet is easier to calibrate to a specific magnetic field than the SmCo 2-17 series magnets.
In the presence of a moderately strong magnetic field, unmagnetized magnets of this series will try to align its orietation axis to the magnetic field. Unmagnetized magnets of this series when exposed to moderately strong fields will get slightly magnetized. This can be an issue if post processing requires that the magnet be plated or coated. The slight field that the magnet picks up can attract debris during the plating or coating process causing for a potential plating or coating failure or a mechanically out of tolerance condition.
Samarium Cobalt Series 2:17
These Samarium Cobalt magnet alloys (written as Sm2Co17, or SmCo Series 2:17) are an age hardening type with a composition of two atoms of rare earth Samarium Cobalt and 13-17 atoms of transition metals (TM). The TM content is rich in cobalt, but contains other elements such as iron and copper. Other elements like zirconium, hafnium and such may be added in small quantities to achieve better heat treatment response. By weight the alloy will generally contain 25% of Samarium. The maximum energy products of these alloys range from 20 MGOe to 32 MGOe. These alloys have the best reversible temperature coefficient of all rare earth alloys, typically being -0.03%/°C. The "second generation" Samarium Cobalt materials can also be used at higher temperatures.
Machining Samarium Cobalt
The Samarium Cobalt alloys are typically machined in the unmagnetized state. Samarium Cobalt should be ground using a wet grinding process (water based coolants) and a diamond grinding wheel. The same type of process is required if drilling holes or other features that are confined. The grinding waste produced must not be allowed to completely dry since Samarium Cobalt has a low ignition point. A small spark, such as that produced with static electricity, can easily commence combustion. The fire produced will be extremely hot and difficult to control.
Hazards of Samarium Cobalt Magnets
Uses of Samarium-Cobalt
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Samarium-cobalt_magnet". A list of authors is available in Wikipedia.|