Neodymium magnet is a high-performance permanent magnetic material composed of neodymium, iron, and boron. It has extremely strong magnetism and high magnetic energy product, and is one of the strongest permanent magnets available today. Its advantages include small size, light weight, but a magnetic force far exceeding that of traditional magnets. Its disadvantages are easy corrosion, poor temperature resistance, and usually require coating protection. It is widely used in electronic products, motors, medical equipment, clean energy, and other fields.
What Are the Characteristics of Neodymium Magnets?
It has the following core features:
Ultra-High Magnetic Properties
Neodymium magnets have extremely high magnetic properties. Their maximum magnetic energy product far exceeds that of traditional magnets, reaching more than 50 MGOe. Their coercive force and remanent magnetism are extremely high, so they can generate extremely strong magnetic fields that are more than 10 times that of ordinary ferrite magnets. This characteristic makes them significantly advantageous in miniaturization and lightweight applications.
Temperature Stability
The maximum operating temperature of neodymium magnets depends on their specific grade, and the temperature resistance grade is determined by the coercivity and composition of the magnet. The following is a comparison table of common neodymium magnet grades and their maximum operating temperatures.
|
Grade |
Max Operating Temperature |
Remark |
|
N Series |
80°C |
Ordinary neodymium magnets ( N35, N42, etc.) are easily demagnetized at high temperatures. |
|
M Series |
100°C |
Medium temperature stability ( N35M, N42M, etc.). |
|
H Series |
120°C |
Applicable to high temperatures ( N33H, N40H, etc.), with high coercivity. |
|
SH Series |
150°C |
For ultra-high temperature (N30SH, N35SH, etc.), elements such as cobalt and dysprosium are added to improve temperature resistance. |
|
UH Series |
180°C |
Ultra-high coercivity (N28UH, N35UH, etc.), used in extremely high temperature environments. |
|
EH Series |
200°C |
Very high coercivity (N30EH, N33EH, etc.), but the energy product may be low. |
|
AH Series |
230°C |
The highest temperature resistance level ( N28AH) requires special formulations and processes, and is more expensive. |
Physical Properties
Although neodymium magnets have extremely strong magnetic properties, their physical properties also bring many challenges. Their hard and brittle properties make them easy to break, so they need to be processed and transported with special care. Neodymium is very easy to oxidize, and even if the surface coating is damaged, it will corrode quickly, affecting the magnetic properties. They have poor temperature resistance, and ordinary models will demagnetize at temperatures above 80°C, so high-temperature resistant models must be selected to ensure stability.
Poor Corrosion Resistance
Neodymium magnets are the most powerful permanent magnet materials currently available, with extremely high magnetic energy product and coercivity, but they have poor corrosion resistance and are easily oxidized in humid or high temperature environments. Therefore, they are usually protected by electroplating or coating to extend their service life, and moisture-proof measures must be strengthened in harsh environments.
Neodymium Magnet Grades
The grade of neodymium magnets is mainly based on their maximum magnetic energy product, and other key parameters such as coercivity and remanence are also marked. The grade is usually indicated by the letter "N" plus a number, and the number represents the value of the magnetic energy product in units of MGOe, megagauss oersted.
|
Grade |
(BH)max |
(Br) |
(bHc) |
(Hcj) |
Max Operating Temperature (°C) |
|
N35 |
35 |
11.7-12.1 |
≥10.5 |
≥11 |
80 |
|
N38 |
38 |
12.2-12.6 |
≥11.0 |
≥12 |
80 |
|
N42 |
42 |
12.8-13.2 |
≥11.0 |
≥12 |
80 |
|
N45 |
45 |
13.5-13.8 |
≥10.5 |
≥11 |
80 |
|
N48 |
48 |
13.8-14.2 |
≥10.5 |
≥11 |
80 |
|
N50 |
50 |
14.2-14.6 |
≥10.5 |
≥11 |
80 |
|
N52 |
52 |
14.5-14.8 |
≥10.0 |
≥10 |
80 |
How Are Neodymium Magnets Made?
Raw Material Preparation: Accurately weigh neodymium, iron, and boron with a purity of more than 99.9% according to the ratio of Nd₂Fe₁₄B, and add elements such as cobalt, dysprosium, and terbium to enhance coercivity and temperature resistance and avoid impurities affecting magnetic properties.
Melting and Alloying: The raw materials are placed in a vacuum induction melting furnace, melted into a uniform alloy liquid at a high temperature above 1500°C, and then quickly cooled to form an alloy ingot.
Powder Making: The alloy ingot is crushed and ground into a fine powder of 3-5 microns. Oxidation must be prevented during the process, which is usually carried out under an inert gas or vacuum environment.
Molding: Place the powder into a mold and align it in a strong magnetic field (1.5-2T) to align the magnetic domains, then mold it by isostatic pressing or molding.
Sintering and Heat Treatment: The compact is sintered in vacuum at 1000- 1100 °C to combine the particles into a dense block, and then tempered to optimize the magnetic properties.
Mechanical Processing: Including cutting, drilling, and grinding, using precision equipment such as diamond grinding wheels or wire cutting, and cooling with coolant. After processing, chamfering or polishing is required to remove burrs and avoid cracking caused by collision.
Surface Treatment: Surface treatment usually adopts electroplating or spraying to prevent corrosion and oxidation and enhance durability.
Magnetization and Testing: During magnetization, a strong pulsed magnetic field (usually 2~3T) is used to orient the magnetic domains of the magnet to obtain high magnetism. Then, a fluxmeter, gaussmeter, and other equipment are used to test key parameters such as remanence, coercive force, and maximum magnetic energy product. At the same time, the appearance, size, and coating quality are checked to ensure that the product meets the performance standards and completes the grade classification.
Common Application Fields of Neodymium Magnets
Electronic Equipment: Hard disk spindle motors require high-precision magnets to achieve high-speed rotation. Neodymium magnets provide a strong magnetic field, allowing the motor to generate sufficient torque in a compact space, supporting hard disks to reach 7200 rpm or even higher speeds. This ensures fast data reading and writing, which is critical to computer storage performance.
Automobile: High-performance neodymium magnets can significantly improve the power density and efficiency of electric vehicle drive motors. Permanent magnet synchronous motors using neodymium magnets can output greater power at the same volume and weight, thereby improving endurance and power. Some high-performance models use neodymium magnet motors, with peak power reaching hundreds of kilowatts and stronger acceleration performance.
Industrial Automation: Neodymium magnets use strong magnetic fields in magnetic transmission devices to achieve contactless power transmission, avoiding mechanical wear and leakage. Chemical magnetic pumps drive impellers through magnetic field coupling of neodymium magnets to safely transport corrosive or flammable, and explosive liquids.
Aerospace Field: The driving mechanism of satellite communication antenna adopts neodymium magnets, which take advantage of their high coercive force characteristics to maintain stable operation in the microgravity and high vacuum environment of space, ensuring that the antenna is accurately aligned with the ground communication station and maintaining reliable communication.
What Factors Need to Be Considered When Using Neodymium Magnets?
When using neodymium magnets (NdFeB magnets), the following key factors need to be considered comprehensively.
Magnetism and Safety Risks
Neodymium magnets are so strong that even small magnets can pinch fingers or instantly attract metal, causing impact or flying debris; large magnets can even cause fractures or equipment damage. Their strong magnetic field can also interfere with electronic devices, and swallowing multiple magnets can cause intestinal perforation. Wear protective gloves and goggles when using, and keep away from sensitive objects, children, and hot and humid environments.
Temperature Stability
The performance of neodymium magnets is greatly affected by temperature. When using them, you must pay attention to their temperature characteristics. Ordinary models will show obvious attenuation when the temperature exceeds 80 °C, and continuous high temperatures will cause permanent demagnetization. Products with different temperature resistance levels are available, such as H grade (120°C), SH grade (150°C), etc., and the highest temperature resistance is 200°C. In actual use, you need to consider the ambient temperature and self-heating, select the appropriate temperature resistance level, and reserve a safety margin.
Corrosion and Protection
Neodymium magnets, especially NdFeB magnets, are susceptible to moisture corrosion and need to be protected by coatings (nickel, zinc, or epoxy resin). Avoid long-term exposure to high temperature, humidity, or corrosive environments, and keep them dry during storage. In harsh environments, use samarium cobalt magnets or add sealing measures, and regularly check whether the coating is intact.
Magnet Breakage
Neodymium magnets are brittle and easily break under impact or stress. Avoid collisions and falls, and apply force evenly during installation. Large-sized magnets may break due to severe impact during adsorption, so be careful when operating. Sudden temperature changes may also cause cracking, so avoid sudden temperature changes. For vibration or impact environments, rubber buffers or metal shells can be used for protection.
Conclusion
Neodymium magnets play an irreplaceable role in modern technology due to their excellent properties, such as high magnetic energy product, high remanence, and high coercivity, and are widely used in electronics, automobiles, medical treatment, renewable energy, and industrial automation. Despite the shortcomings, such as temperature sensitivity and insufficient corrosion resistance, with the continuous advancement of technology, the performance of neodymium magnets will continue to be optimized, and the scope of application will be further expanded, providing stronger support for the development of various industries. By deeply understanding its characteristics and application scenarios, users can more accurately choose magnet products that suit their needs.
FAQ
What Is the Difference Between Neodymium Magnets and Regular Magnets?
Neodymium magnets are made of rare-earth materials. They have strong magnetism but poor high-temperature resistance. They need to be coated to prevent rust and are mostly used in precision equipment. Ordinary magnets have weaker magnetism but are low in cost and have high temperature resistance. They are often used in home appliances and speakers.
How to Judge the Quality of Neodymium Magnets?
The quality of neodymium magnets mainly depends on magnetic properties, coating process, temperature resistance, and appearance precision. High-quality neodymium magnets have strong magnetism, uniform coating, and high temperature resistance (N grade 80°C, H grade above 120°C). Inferior products are easy to demagnetize, have poor coating, and weak high-temperature performance. It is recommended to choose a regular manufacturer and provide a test report.
Can Neodymium Magnets Be Processed?
Neodymium magnets can be processed, but due to their high hardness and brittleness, processing is difficult. Diamond tools are usually used for cutting, grinding, or EDM, avoiding high temperatures and severe impact to prevent demagnetization or fragmentation. Cooling and protection must be paid attention to during processing, and re-magnetization may be required after processing.
What Is the Operating Temperature Range of Neodymium Magnets?
The temperature range of neodymium magnets is generally 80°C to ~ 200°C. Ordinary models (such as N series) can withstand temperatures of about 80°C, while high-temperature resistant models (such as N30SH, N35UH) can reach 150°C~200°C. Exceeding the limit will cause permanent degradation of magnetic properties. In high-temperature environments, temperature-resistant models should be selected or heat dissipation should be enhanced.