Re-magnetizing neodymium magnets after demagnetization has become a topic of discussion with the phase-out of old equipment and the need to deal with magnets that have lost their magnetic properties.
Definition of Re-magnetizing Neodymium Magnets After Demagnetization
Re-magnetizing neodymium magnets after demagnetization refers to the process of restoring or re-energizing the magnetic properties of neodymium iron boron magnets that have lost or weakened their magnetism (demagnetized), through the application of an external magnetic field (re-magnetization).
The process of re-magnetizing after demagnetization is a “break and rebuild” approach. Since the causes of demagnetization in neodymium iron boron magnets can vary, the effectiveness of re-magnetization also differs.
Effects of Re-magnetizing Neodymium Magnets After Demagnetization
Reversible Demagnetization
If a neodymium iron boron magnet loses its magnetism due to brief exposure to high temperatures (below the maximum operating temperature) or a temporary reverse magnetic field, and this does not lead to permanent damage to the microstructure inside the magnet, the magnet will naturally regain its magnetic strength once the temperature returns to normal or the reverse magnetic field is removed.
After re-magnetization, the magnet can generally return to its original saturated magnetization level.
Irreversible Demagnetization
In cases where neodymium iron boron magnets suffer from extremely high temperatures (above the maximum operating temperature), resulting in changes or damage to the internal lattice structure, or experience demagnetization due to strong physical impacts causing cracks or severe corrosion, irreversible damage occurs.
In such situations, even if the magnet is re-magnetized, its magnetic properties (such as residual magnetism and coercivity) will significantly decline and cannot be restored to their original levels. If physical damage has occurred, the magnet will not function properly even after re-magnetization.
Change in Magnetization Method
If the direction of magnetization is altered during the re-magnetization of neodymium iron boron magnets, such as changing from axial magnetization to radial magnetization, the anisotropic nature of the magnetic material and mismatched magnetic circuit design will lead to a significant reduction in magnetic performance after re-magnetization.
Significance of Re-magnetizing Neodymium Magnets After Demagnetization
| Cost: Given the high cost of neodymium iron boron magnets, the cost of re-magnetization is much lower than that of directly replacing the entire magnet with a new one, making it a cost-effective option for refurbishing the magnetic properties.
| Service Life: By restoring the magnetic performance, minor demagnetization can be corrected, thus preventing the premature scrapping of neodymium iron boron magnets and effectively extending their operational lifespan.
Limitations of Re-magnetizing Neodymium Magnets After Demagnetization
Re-magnetization can only partially restore the magnetic losses due to slight demagnetization, and for irreversible losses caused by high temperature, corrosion, or mechanical damage, the effectiveness of re-magnetization is limited. For applications with high magnetic performance requirements, replacing the magnet is a more feasible approach.
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