Due to the name permanent magnet, many people think that the magnetism of permanent magnets, including NdFeB magnets, is permanent and will not degrade. But is it really so?
In practice, the magnetism of the NdFeB magnet will gradually degrade or even disappear. Below we will analyze the reasons for the magnetic degradation of the NdFeB magnet.
the Aging of Ndfeb Magnets is Divided into Two Situations
1. High-temperature demagnetization aging: exceeding the maximum operating temperature of NdFeB, the magnetic properties will be reduced or irreversible loss will occur.
2. Surface aging: Without surface treatment or improper electroplating, it is easy to oxidize, corrode, and accelerate aging.
Analysis of the Main Reasons for Ndfeb Aging and Solutions
1. High-temperature environment
The temperature resistance of NdFeB permanent magnets is not very good. It has many grades, and each grade has a corresponding working temperature. The temperature resistance limit is 220 °C. For example, the N-grade NdFeB has a maximum working temperature of 80°C. If this temperature is exceeded, the magnetic properties of NdFeB will be irreversibly lost. When the working temperature of the magnet exceeds the Curie temperature, the magnetism will be completely lost.
|NdFeB N33,N35,N38,N40,N42,N45,N48,N50,N52||Maximum operating temperature: 80°|
|NdFeB N30M,N33M,N35M,N38M,N40M,N42M,N45M,N48M,N5OM||Maximum operating temperature: 100°|
|NdFeB N33SH,N35SH,N38SH,N40SH,N42SH,N45SH,N48SH||Maximum operating temperature: 150°|
|NdFeB N25UH,N28UH,N30UH,N33UH,N35UH,N38UH||Maximum operating temperature: 180°|
|NdFeB N30EH,N33EH,N35EH,N38EH||Maximum operating temperature: 200°|
|NdFeB N28AH,N3OAH,N33AH||Maximum operating temperature: 220°|
2. Humid environment
There is also iron in the NdFeB composition, which is easy to oxidize and corrode. In a humid or salt fog environment, it will be unfavorable for the preservation of NdFeB magnetic materials. In this humid environment for a long time, the surface coating of NdFeB will be corroded, resulting in the phenomenon of rust and peeling. Therefore, in order to prevent this situation, it should be stored in a dry and ventilated place.
If the NdFeB permanent magnet must work in a humid and complex environment, the salt spray should reach 48H, 72H or higher, which is determined according to the usage.
Therefore, when purchasing magnets, we need to choose the matching NdFeB grade according to the actual working environment. According to the actual environment, carry out salt spray coating tests of different durations. And choose the appropriate surface treatment method according to the actual user needs.
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