The operating temperature of neodymium magnets refers to the temperature range at which neodymium magnets can maintain their magnetic properties. This article will discuss the definition of the operating temperature of neodymium magnets and its impact on the performance of neodymium magnets.
Definition of Operating Temperature of Neodymium Magnets
The operating temperature of neodymium magnets is defined as the temperature range that the magnet can withstand in practical applications. Different materials have varying thermal stabilities, leading to differences in their operating temperatures.
The maximum operating temperature of magnetic steel is significantly lower than its Curie temperature. Within the operating temperature range, an increase in temperature leads to a decrease in magnetic strength, but most of this strength can be recovered after cooling.
Relationship Between Operating Temperature and Curie Temperature
Generally, the higher the Curie temperature, the higher the operating temperature of the magnetic material, along with improved thermal stability. Adding elements such as cobalt, terbium, or dysprosium to neodymium-iron-boron raw materials can enhance the Curie temperature. Therefore, high coercivity products (H, SH, etc.) generally contain dysprosium.
For the same type of magnet, different grades exhibit varying temperature resistance due to differences in composition and structure. For instance, the maximum operating temperature of various grades of neodymium magnets can range from 80°C to 220°C.
Impact of Operating Temperature of Neodymium Magnets
| The Degradation of Magnetic Performance: For every 1°C increase in temperature, the magnetic energy product (BHmax) of neodymium-iron-boron decreases by approximately 0.1% to 0.2%. For example, the magnetic performance of an N42SH magnet may drop by about 15% at 150°C.
| Demagnetization: The maximum operating temperature of magnets is much lower than the Curie temperature. Within the operating temperature of neodymium magnets, magnetic strength decreases with increasing temperature, but most of it can be recovered through cooling.
| Material Structural Changes: High temperatures may trigger oxidation or coating failure (nickel coatings are prone to oxidation above 200°C), accelerating corrosion of the magnets.
| Thermal Expansion Differences: Variations in thermal expansion coefficients can lead to cracking of the magnets or deformation of the magnetic circuit.
Grades of Neodymium Magnets and Their Operating Temperatures
N Series
| The most common grades of strong magnets include N35, N38, N40, N42, N45, N48, N50, and N52.
| Operating Temperature: ≤80°C.
| Applications: Suitable for toys, packaging boxes, lighting, and other products with low magnetic requirements; grades above N40 are high-performance and can be used in smartphones and precision instruments.
M Series
| Includes M35, M40, M42, M45, M48, M50, and M52.
| Operating Temperature: Generally ≤100°C, with good stability.
| Applications: Suitable for applications that require higher magnetic strength and slightly elevated operating temperatures.
H Series
| Stronger than the M series, includes H35, H40, H42, H45, H48, H50, and H52.
| Operating Temperature: Up to ≤120°C.
| Applications: Commonly used in motors, sensors, and devices requiring certain magnetic and temperature stability.
SH Series
| Superior to the H series, includes SH35, SH40, SH42, SH45, SH48, SH50, and SH52.
| Operating Temperature: ≤150°C.
| Applications: Typically used in high-temperature magnetic applications, such as industrial furnaces and high-temperature sensors.
UH Series
| Stronger than the SH series, includes UH35, UH40, UH42, UH45, UH48, UH50, and UH52.
| Operating Temperature: ≤180°C
| Applications: Suitable for aerospace and high-end industrial equipment requiring exceptional magnetic and high-temperature performance.
EH Series
| Stronger than the UH series, includes EH35, EH40, EH42, EH45, EH48, EH50, and EH52.
| Operating Temperature: ≤200°C.
| Applications: Offers advantages in specialized applications under extremely high-temperature environments.
AH Series
| The strongest grade of magnets, including AH35, AH40, AH42, AH45, AH48, AH50, and AH52.
| Operating Temperature: ≤220°C.
| Applications: Mainly used in aerospace and defense sectors demanding high precision.
Factors Affecting the Operating Temperature of Neodymium Magnets
| The shape and size of the magnets (i.e., aspect ratio, also known as permeance coefficient Pc) significantly impact the actual maximum operating temperature. Not all H series neodymium magnets can operate at 120°C without demagnetizing; some magnets may already be demagnetized at room temperature, necessitating a higher coercivity grade to improve the actual maximum operating temperature.
| The degree of magnetic circuit closure also influences the actual maximum operating temperature of neodymium magnets. For the same magnet, a more closed magnetic circuit results in a higher maximum usable temperature, stabilizing the magnet’s performance. Therefore, the highest operating temperature of a magnet is not a fixed value but varies with the closure degree of the magnetic circuit.
Magnet Manufacturer
At Tengye, we’re thrilled to be early participants in your new projects. Our passion for magnets extends from material selection and design optimization to providing magnetic solutions. We hope to bring our knowledge and experience to the forefront by actively engaging in your upcoming projects. Work with our magnet experts to get the right magnet solution.
Image Source: Couragemagnet & E-magnetsuk & Essentracomponents & Hub360 & Kjmagnetics & Osencmagnet
