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Sintered Samarium Cobalt (SmCo) magnets

Sintered Samarium Cobalt (SmCo) magnets are formed by powder metallurgical processes and followed by the sintering process (heat treatment) and in some cases they are formed by isostatic pressing. To enhance better magnetic properties, a magnetic field is applied during the pressing process in preferred direction of magnetization. The typical composition consists of Samarium (Sm), Cobalt (Co), Copper (Cu), Zirconium (Zr) and other elements depending on the grades and these are known as the first generation of rare earth magnets. They were introduced to the market in early 1970’s. Sintered Samarium Cobalt magnets have excellent thermal characteristics and can withstand much higher operating temperatures and are more corrosion resistant then the Sintered Neodymium magnets. Samarium Cobalt magnets are not as mechanically strong as Neodymium magnets and should not be used as structural components. Samarium Cobalt magnets come in two series and many times are referred to as: SmCo₅ and Sm₂Co₁₇. The SmCo₅ is also written as SmCo 1:5 and Sm₂Co₁₇ is also written as SmCo 2:17. The composition of SmCo₅ or SmCo 1:5 has one atom of Samarium and five atoms of Cobalt and the composition of Sm₂Co₁₇ or SmCo 2:17 has two atoms of Samarium and 13- 17 atoms of Cobalt with transitional metals (TM) and other elements e.g. copper, iron or zirconium. Both of them have extremely high magnetic properties, thermal stability and excellent corrosion resistance. With such excellent magnetic characteristics SmCo magnets are ideal for many applications and have an advantage over NdFeB magnets with high operating temperatures up to 350⁰C (662 ⁰F). SmCo magnets energy product range in 14 to 32 MGOe depending on the series and grade hence MGOe-(Maga-Gauss Oersteds) In comparison of these two series SmCo 2: 17 has a much better reversible temperature coefficient typically being -0.03%/⁰C to -0.05%/⁰C of SmCo 1:5 series. Machining, e.g. drilling or grinding of these alloys is mainly done in an un-magnetized state using diamond grinding wheel or diamond tip drills with sufficient amount of coolant specifically for this purpose. Extreme care must be exercised during the grinding mainly with the grinding dust, because a small spark produced with static electricity or by striking any hard tools on any metal surface can cause ignition of the Samarium Cobalt dust or powder thus creating a fire which is extremely hot and very difficult to control and extinguish.

Sintered SmCo magnets with their high resistance to de-magnetization and good temperature stability are ideal for sensor application, computer hard drives, AC servo-motors, actuators, bias magnets, watches, printers, aerospace, automobiles, ultrasonic transducers, traveling wave tubes, electronic instrumentation, high output and high performance motors and much more. Available in many shapes: disks, block, rods, arcs and many custom shapes. Although no coatings are necessary for SmCo magnets in some special applications nickel plating is used.

Precautions for handling Sintered SmCo magnets:

SmCo magnets because of their strong attractive power can easily chip, shatter or crack if not handled properly; eye protection must be worn at all times.

Keep all small magnets away from children, especially young children, they could be swallowed and lodge in the child’s throat causing asphyxiation.

These magnets must not be used for any mechanical or structural components in any device because of its brittle nature.

Sintered Samarium Cobalt Magnets Table
Typical Physical Properties of SmCo₅ (SmCo 1:5) Materials

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