What is the difference between NdFeB magnets and SmCo magnets?

Today we will talk about two common rare earth magnets in magnetic materials - NdFeB magnets and SmCo magnets. They have a wide range of applications in modern industries, but how are they different? Let's find out!

1. The appearance difference between NdFeB magnets and SmCo magnets

There is basically no difference in the appearance of the rough material. When it is made into a finished product, the finished NdFeB magnet is generally electroplated and has a bright appearance. The appearance is the same as the blank.

2. The composition difference between NdFeB permanent magnet and SmCo

In NdFeB permanent magnets, the rare earth metal neodymium accounts for about 29%~32.5%, the metal element iron accounts for 64%~69%, the non-metal element boron accounts for 1.1%~1.2%, and a small amount of dysprosium, terbium, niobium, copper, etc. are added. element.

For samarium cobalt magnets, taking the 2:17 type as an example, the rare earth metal samarium accounts for 23%~28%, metal cobalt accounts for 48%~52%, metal element iron accounts for 14%~17%, and a small amount of copper, zirconium and other elements.

3. The difference between NdFeB magnet and SmCo crystal structure

SmCo magnets and NdFeB have very similar crystal structures. The crystal structure of samarium cobalt is hexagonal, while that of neodymium iron boron is tetragonal. Both types of structures endow rare earth magnets with highly oriented magnetic properties. These crystal structures tightly concentrate the magnetic field in the north-south direction. When material properties are so concentrated in one direction, it is called anisotropy.

4. Comparison of magnetic properties between NdFeB and SmCo permanent magnets

In overall comparison, the magnetic properties of NdFeB magnets are stronger than those of SmCo magnets, so they are also called magnet kings or powerful magnets.

5. NdFeB and SmCo heat resistance

The maximum operating temperature of NdFeB magnets is 220°C, and the maximum operating temperature of SmCo magnets can reach 350°C. When the operating temperature is above 180°C, its comprehensive magnetic performance parameters exceed those of NdFeB permanent magnet materials.

The Curie temperature of NdFeB is 320°C-460°C, and that of SmCo is 700°C-800°C. The temperature resistance of NdFeB is not as good as that of SmCo magnets. SmCo magnets are high temperature resistant magnets and are suitable for high temperature applications.

6. Price comparison between NdFeB magnets and SmCo

The iron content of NdFeB magnets is the highest, and other rare earth elements account for a small proportion, so the price of NdFeB magnets will not be too expensive. The content of samarium and cobalt in samarium cobalt magnets accounts for 70-80%, which also leads to an increase in its cost. Comparing the prices of NdFeB permanent magnets and SmCo permanent magnets with the same performance and size comprehensively, the price of SmCo magnets is higher than that of NdFeB magnets, and the price of rough SmCo magnets is about 1.5 to 2 times that of NdFeB.

7. NdFeB permanent magnet material and samarium cobalt stability

The temperature coefficient of remanence of NdFeB is relatively large, the higher the temperature rises, the lower the remanence; the temperature coefficient of remanence of samarium cobalt is very low, at the same temperature, the demagnetization of samarium cobalt is much less than that of neodymium iron boron. In addition, NdFeB must be electroplated, otherwise it will be easily oxidized, corroded and weathered. Samarium cobalt generally does not need electroplating, but if the environment is harsh, the service life after electroplating is longer and it is more beautiful.

8. Processing characteristics of NdFeB magnets and SmCo

Both materials are brittle, relatively speaking, NdFeB magnets are easier to machine.

9. The maximum magnetic energy product of NdFeB and SmCo

The maximum magnetic energy product of NdFeB magnets is 52M, while the maximum magnetic energy product of SmCo NdFeB magnets is 32M. It can also be seen from this that the magnetic force of NdFeB magnets is much higher than that of SmCo magnets.

10. NdFeB magnetic material and SmCo surface treatment

NdFeB magnets contain a large amount of iron and neodymium, the surface is easy to oxidize and corrode, and generally needs electroplating treatment. Samarium cobalt magnets do not require surface treatment because their composition contains about 65% cobalt. Cobalt is the main component of stainless steel, so it is easy to see that cobalt is the main reason why samarium cobalt magnets have such excellent corrosion resistance.

11. Differences between NdFeB magnets and SmCo magnets in application fields

NdFeB magnets are ideal for use in powerful electric motors and generators, or where miniaturization is the main driving force.

The following are common applications of NdFeB magnets:

• Electroacoustic applications, such as loudspeakers

• Automobile electric drive motor

• Auto parts motor

• Mobile phone

• Sensors

Samarium Cobalt magnets are commonly used in heavy duty high temperature applications:

• Railway locomotive traction motor

• Heavy duty industrial motors and generators

• Marine motors and generators

• Defense-related motors

• Downhole application of oil and gas

Summarize

Compared with NdFeB magnets, SmCo magnets perform better than NdFeB magnets at higher temperatures and in more corrosive environments. Neodymium magnets have a stronger field strength, the highest BHMax of any permanent magnet available today, and are less expensive than Samarium Cobalt.