Ι What Are High Temperature Magnets?
High temperature magnets are permanent magnets designed to retain their magnetic properties in elevated temperature environments. Unlike conventional magnets, which can lose magnetization or undergo irreversible changes when exposed to high heat, high temperature magnets are engineered to withstand extreme conditions without significant performance degradation. These magnets are also referred to as high operating temperature magnets or high temperature resistant magnets.
Typically, high temperature magnets can operate at temperatures ranging from 150°C to 350°C or higher, depending on the material used. The exact temperature range varies by magnet type. For instance, materials like AlNiCo can withstand temperatures up to 550°C, while Neodymium magnets—one of the most commonly used types—can generally tolerate temperatures up to 230°C before losing magnetic strength.
Temperature Ranges of High Temperature Magnets
While there is no universally defined temperature threshold for high temperature magnets, the maximum operating temperature of a magnet is commonly used as the deciding factor in determining whether it qualifies as “high temperature.” The maximum operating temperature of permanent magnets refers to the highest temperature at which a magnet can maintain its magnetic properties with a specific irreversible flux loss. This threshold helps in classifying magnets based on their performance in high-temperature environments, guiding the selection of materials for specific industrial applications.
AlNiCo and ferrite magnets are known for their excellent high temperature resistance, making them ideal for applications exposed to elevated temperatures. However, it’s important to note that while these materials perform well under heat, they are less effective in terms of magnetic output compared to Neodymium and Samarium Cobalt magnets. While these magnets are preferred for their ability to function in extreme heat, their magnetic output is relatively lower, which can limit their effectiveness in applications requiring high magnetic strength.
| Magnet type | Maximum Operating Temperature Tw
(degrees celsius) |
Curie Temperature Tc
(degrees celsius) |
|
| Neodymium magnets | N grade | 80 | 310-350 |
| M grade | 100 | ||
| H grade | 120 | ||
| SH grade | 150 | ||
| UH grade | 180 | ||
| EH grade | 200 | ||
| AH grade | 230 | ||
| Samarium Cobalt magnets | 1:5 type | 200 | 700-750 |
| 2:17 type | 250-550 | 800-850 | |
| AlNiCo magnets | 550 | 750-850 | |
| Ferrite magnets | 250 | 450 | |
Notes:
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High Temperature Neodymium Magnets Vs. Samarium Cobalt Magnets
Both Neodymium and Samarium Cobalt magnets are among the strongest permanent magnets, but each performs optimally within different temperature ranges.
For Neodymium magnets, while there is no single, universally accepted temperature threshold for high temperature magnets, Neodymium magnets with intrinsic coercivity grades of SH, UH, EH, and AH, which have maximum operating temperatures of 150°C or higher, are considered high temperature magnets.
Neodymium magnets offer the highest magnetic output at room temperature and up to 180°C. However, their magnetic strength declines rapidly as the temperature rises.
As temperatures approach the 180°C mark, Samarium Cobalt magnets begin to surpass Neodymium magnets in terms of temperature resistance and magnetic stability.
While traditional reports suggest Samarium Cobalt magnets can handle temperatures up to 350°C, some Samarium Cobalt magnets can exceed 400°C, with certain grades capable of withstanding temperatures up to 550°C. This makes them superior for applications requiring both high magnetic output and exceptional temperature resistance.
For a magnet to operate effectively in high-temperature environments over extended periods, both its magnetic properties and microstructure must remain stable at elevated temperatures. To ensure the stability of its magnetic properties, the magnet must possess a high Curie temperature and high intrinsic coercivity. Additionally, maintaining the integrity of its microstructure requires that the magnet be resistant to oxidation or damage.
