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What is a SmCo magnet?

What is a SmCo magnet?

Samarium cobalt magnet (SmCo magnet) is a kind of rare earth magnet. It is made of samarium, cobalt and other metal rare earth materials through mixing, smelting into alloy, crushing, pressing, and sintering. It has a high magnetic energy product. , Very low temperature coefficient, the highest working temperature can reach 350℃, and the negative temperature is not limited. When the working temperature is above 180℃, its maximum magnetic energy product (BHmax), coercivity (coercivity), temperature stability and chemical stability All surpass NdFeB permanent magnet materials. It has strong corrosion resistance and oxidation resistance; so it is widely used in aerospace, national defense and military industry, microwave devices, communications, medical equipment, instruments, meters, various magnetic transmission devices, sensors, magnetic processors, motors, magnetic cranes Wait. The maximum energy product (BHmax) of samarium cobalt magnets ranges from 16 MGOe to 32 MGOe, and its theoretical limit is 34 MGOe.

Samarium cobalt magnets are mainly composed of metal samarium, cobalt, iron and other trace elements mixed with high performance samarium cobalt 1:5 and samarium cobalt 2:17 permanent magnets. The maximum working temperature can reach 300°C, and the melting temperature can reach 1300°C. It has strong anti-corrosion and anti-oxidation ability, and generally does not need coating protection. Since samarium cobalt magnets are very fragile, they need to be handled carefully when packaging.

Samarium Cobalt 1:5

Samarium cobalt 1:5 magnets generally contain more than 30% samarium and a large amount of cobalt. The magnetic energy product ranges from 18MGOe to 22MGOe. Generally, the reversible temperature coefficient is -0.05%/°C, and the maximum operating temperature is 250°C.

Samarium Cobalt 2:17

Samarium cobalt 2:17 magnets contain 13-17 transition metal elements in addition to large amounts of samarium and cobalt. The transition metal elements are rich in cobalt, but also contain other elements such as iron, copper, zirconium, hafnium, etc. Better heat resistance effect. The magnetic energy product ranges from 24MGOe to 30MGOe. Generally, the reversible temperature coefficient is -0.03%/°C, and the maximum operating temperature is 300°C.

Processing of Samarium cobalt magnet (SmCo magnet)

  • The production process of samarium cobalt magnets: ingredients → smelting ingots → powder making → profiling → sintering and tempering → magnetic inspection → grinding processing → pin cutting processing → finished product.

These alloys are usually processed in a non-magnetized state. Samarium cobalt uses wet fine grinding (water-cooled heat dissipation) and diamond grinding wheels. This process is required if drilling holes or other functional limitations. The grinding waste produced must not be completely dried, because samarium cobalt has a low ignition point. A small spark, such as production with static electricity, can easily burn. The temperature generated by a fire can be very high and difficult to control.

Disadvantages of Samarium cobalt magnet (SmCo magnet)

  1. Samarium cobalt magnets are easy to break. When handling them, goggles must be worn.
  2. Bumping the magnets together may cause the magnets to shatter, which may cause potential hazards.
  3. Samarium cobalt is manufactured by a process called sintering, and all materials are sintered, and cracks are very likely to occur inside. The magnet does not have mechanical integrity and only has the function of preparing a magnetic field. Therefore, special mechanical systems must be designed to give the overall system sufficient mechanical reliability.

Advantages of Samarium cobalt magnet (SmCo magnet)

  1. Very good coercivity.
  2. Good temperature stability (the maximum operating temperature is 250 to 550°C, and the Curie temperature is from 700 to 800°C).
  3. It is expensive and vulnerable to price fluctuations (cobalt market price sensitive).

Application of Samarium Cobalt Magnet

Samarium cobalt magnets are mainly used in various sensors (automotive parts, etc.), micro motors, magnetic equipment for sputtering equipment, aerospace and other fields. Samarium cobalt magnets also have the function of radiation protection and can be used in spacecraft and other fields.

Magnetic performance parameter table of sintered samarium cobalt magnet

Grade Br Hcb Hcj BHmax Density Tw Max Remark
kGs mT kA/m kOe kA/m kOe KJ/m3 MGOe g/cm3
SmCo16 8.3 830 640 8 1430 18 128 16 8.3 250 1:05
SmCo18 8.8 880 680 8.5 1430 18 144 18 8.3 250
SmCo20 9.2 920 700 8.7 1430 18 160 20 8.3 250
SmCo22 9.4 940 730 9.1 1450 18 176 22 8.3 250
SmCo24 9.8 980 730 9.1 1450 18 192 24 8.4 300 2:17
SmCo26 10.3 1030 760 9.5 1450 18 208 26 8.4 300
SmCo28 10.5 1050 780 9.7 1450 18.5 224 28 8.4 300
SmCo30 11 1100 810 10.1 1450 18.5 240 30 8.4 300
SmCo26M 10.3 1030 760 9.5 1100 15 208 26 8.4 300
SmCo28M 10.5 1050 780 9.7 1100 15 224 28 8.4 300
SmCo30M 11 1100 810 10.1 1100 15 240 30 8.4 300
SmCo28L 10.5 1050 550 6.9 700 8 224 28 8.4 250
SmCo30L 11 1100 550 6.9 700 8 240 30 8.4 250
SmCo24H 10 1000 720 9 2000 25 192 24 8.4 350
SmCo26H 10.3 1030 760 9.5 2000 25 208 26 8.4 350
SmCo28H 10.5 1050 770 9.6 2000 25 224 28 8.4 350
SmCo30H 10.8 1080 810 10.1 2000 25 240 30 8.4 350

Comparison of SmCo magnets and NdFeB magnets

  • Compared with other rare earth magnets, SmCo magnets are slightly weaker than neodymium iron boron and stronger than alnico magnets. The magnetic stability and maximum operating temperature are higher than neodymium iron boron and ferrite magnets, and lower than alnico magnets. In terms of price, samarium cobalt magnets are the most expensive among rare earth magnets.
  • Samarium cobalt magnet is a kind of magnetic material made of samarium, cobalt and other metal rare earth materials through mixing ratio, melting into alloy, crushing, pressing and sintering.
  • The main raw materials of NdFeB magnets are metal neodymium, pure iron, and boron. The three main raw materials are sintered and pressed.
  • Both materials are very brittle, relatively speaking, NdFeB is easier to machine.
  • The maximum energy product of a samarium cobalt magnet is 32M, while the maximum energy product of NdFeB is 52M. In other words, the magnetic force of neodymium iron boron is much higher than that of samarium cobalt magnets.
  • The temperature resistance of NdFeB magnets is not very ideal, and it is only suitable for working in a working environment of 230 ℃.
  • The temperature resistance of samarium cobalt magnets is better than that of NdFeB magnets, and it can work at a high temperature of 230°C to 350°C.
  • In the case of the same volume, the price of samarium cobalt magnets is much higher than that of neodymium iron boron.
  • Samarium cobalt magnets usually do not require surface treatment, and NdFeB magnets are easily oxidized and require surface electroplating treatment.
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