Two demagnetization methods of NdFeB commonly used by magnet manufacturers
NdFeB is a rare earth permanent magnet with small volume and high energy product. It is easily oxidized and magnetically transported and processed. Customers sometimes need to carry out rework for some reasons. Therefore, the NdFeB magnet needs to be removed magnetism first.
At present, magnet manufacturers generally use two methods of current demagnetization and high temperature demagnetization. Current demagnetization is to align the magnets first, and use the current to generate multiple magnetic fields in opposite directions to achieve the effect of demagnetization. This method has large workload and low efficiency. The investment is high, and the magnet after demagnetization will still have residual magnetism in it. which is unfavorable for the product rework.
High temperature demagnetization is performed by using different media for heating. The high temperature resistant magnet is usually demagnetized by hot oil. The oil temperature usually reaches 80-200 degrees Celsius, which can completely eliminate the magnetism. The disadvantage of this method is that the oil film is formed on the surface after the product is heated. It’s very difficult to handle and the appearance is not good, many customers can’t accept.
After above two demagnetization method of the powerful magnet manufacturers, and then re-magnetizing, the magnetic properties will be greatly reduced after saturation magnetization, so the product should be considered comprehensive at the beginning of the design, and avoid magnets returning to the factory for demagnetization.