Les aimants permanents sont des matériaux indispensables et importants dans l'industrie moderne, électronique, énergie, et transport. Des moteurs, sensors to wind turbines and new energy vehicles, all rely on their strong magnetic properties. But many people don’t know that temperature has an extremely important influence on the magnetism of permanent magnets, especially in high temperature environments, where the magnetism may be significantly attenuated or even permanently lost.
So, do you know how permanent magnets “hold their ground” and maintain magnetic stability at high temperatures? This article will reveal the principles and coping strategies for you.
Why does high temperature affect magnetism?
The magnetism of permanent magnets comes from the orderly arrangement of electron spins inside the material. As the temperature rises, the thermal motion of atoms inside the material intensifies, which will destroy this ordered structure and cause the magnetism to weaken. Every magnetic material has a “Curie Temperature”. Once the temperature exceeds this value, the material will completely lose its magnetism.
For example:
The Curie temperature of NdFeB magnets is about 310~320℃ but its magnetic properties will drop significantly above 150℃
The Curie temperature of SmCo magnets is as high as 700~850℃, and its high temperature resistance is significantly stronger.
How to improve the high temperature stability of permanent magnets?
- Choose high Curie temperature materials
Choosing permanent magnets that are resistant to high temperatures is the most direct and effective way:
Aimants samariums cobalt: suitable for applications above 150℃, widely used in aerospace, military industry and high-temperature motors;
Aimants en ferrite: good heat resistance, faible coût, suitable for automotive sensors, speakers, etc.;
High temperature NdFeB (improved heat resistance by adding heavy rare earth elements such as Dy and Tb): suitable for use under 120~180℃ conditions.
- Optimize magnet design and protection
Surface coating protection: High temperature is often accompanied by oxidation. Adding coatings (such as epoxy resin, electroplating NiCuNi) can extend the life of magnets;
Multi-pole arrangement design: Use a reasonable magnetic circuit structure when designing motors or magnetic circuits to reduce the interference of high temperature on magnetic lines of force;
Thermal stability analysis: Use simulation technology to predict the performance of magnets in thermal environments and avoid risks in advance.
- Take heat dissipation measures in engineering applications
For example, in new energy vehicle motors, magnets need to withstand environments of hundreds of degrees Celsius. Engineers usually design forced liquid cooling or air cooling systems to control the temperature;
In wind power generation equipment, the installation position is reasonably laid out, and the temperature of the magnet is monitored by thermistors to avoid overheating.
Future trends: Research and development of high-performance, heat-resistant rare earth magnets
With the growing demand for stable magnetic properties under extreme working conditions, materials scientists are committed to developing more new rare earth permanent magnet materials, such as heavy rare earth-free high-temperature neodymium iron boron, or improving thermal stability through nanocrystalline strengthening technology. These technologies will bring more reliable magnetic solutions to high-temperature motors, aérospatial, special manufacturing and other fields.
Conclusion
High temperature is indeed a major challenge facing permanent magnets, but it is not an insurmountable obstacle. Through multiple means such as material selection optimization, structural design and thermal management, we can effectively improve the magnetic stability of permanent magnets in high temperature environments. In the future high-end manufacturing and intelligent equipment, stable and reliable permanent magnets will continue to play an irreplaceable role.
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