ndfeb magnet is a rare earth permanent magnet with small volume and high magnetic energy product. It is easy to oxidize and magnetic in the production process. Due to the need of magnetic retraction in production, current demagnetization and hot bath demagnetization methods are commonly used at present. Current demagnetization, equipment investment, demagnetization often need to be the direction of the magnet arrangement, heavy workload, low efficiency, and surplus magnetic. The presence of residual magnetism will lead to the failure of repair, which is specifically reflected in the following aspects: 1. Magnetic products will adsorb metal particles in the plating solution during the plating process, resulting in poor appearance; 2. Second, magnetic products in the plating process overlap each other is difficult to open, resulting in uneven coating thickness, poor adhesion or even bubbling; High temperature demagnetization is easy to oxidize, so it needs to be carried out under the condition of vacuum or inert gas protection. The whole demagnetization process is time-consuming and costly. If this method is used to demagnetize the coated magnet, it will cause defects such as discoloration of the coating, poor adhesion of the coating and the substrate, etc., and it is also difficult to repair, so it needs to be deplated, which increases the cost and causes great environmental pollution. There are many ways to demagnetize a hot bath because of the different media, and oil bath demagnetization is one of them. Oil bath demagnetization is widely used because of its convenient materials and simple process. After the oil bath demagnetization, the oil failure on the surface of the magnet is difficult to deal with, which brings great difficulty to repair.

Ndfeb magnet

In order to solve the problem of difficult repair caused by oil collapse on the surface of the NdFeB Magnet after oil bath demagnetization, this paper provides a treatment method for the surface of the NdFEB magnet after demagnetization. This method can be used to remove oil collapse on the surface of the magnet after oil bath demagnetization to achieve repair. Specifically, it includes the following steps:

(1) Quickly transfer the magnet demagnetization after oil bath into a container containing edible oil and cool it to below 220°C (that is, after many times of cooking oil cooling treatment, multi-stage cooling method, quickly reach the temperature we need; The edible oil can be salad oil, various edible blend oil and other oil with low impurity content. The volume of the salad oil in the container shall not expose the magnet as the standard, can be put more, not less; For the convenience of operation, demagnetization, we can use stainless steel wire mesh bag, and then put the magnet into the bag.

(2) Transfer the cooled magnet after step (1) to a container containing diesel oil for cooling treatment below 60°C (multi-level cooling method can also be adopted, that is, after multiple diesel cooling treatment);

(3) Remove oil from the treated magnet in the oil tank at a high temperature of 55-75°C for 40-80 minutes, and turn it every 15-20 minutes; Then repeat this step at least once (high temperature oil removal method should be more than 2, oil removal tank temperature is controlled at 60°C ±5°C, each oil removal I· hour, gently turn every 20 minutes. For example, the degreasing temperature of the magnet is 60°C and the processing time is 60 minutes. It is better to turn the magnet every 20 minutes. The temperature of the magnet should be controlled below 60°C when it is taken out from the diesel oil. We can adopt the multi-level cooling method in Step (2) to quickly reach the temperature we need.

(4) Remove the magnet from the last high temperature oil tank and rinse it with clean water.

(5) Ultrasonic cleaning of rinsed magnets (if the rinsed magnets need replating after ultrasonic cleaning, they can be activated, cleaned and then electroplated; if there is no need for replating, they can be directly cleaned and blow-dried).

After this method of treatment of ndfeb magnets, water film on the surface of the magnet into uniform shape, can by NO. 30. O above the surface wetting tension test with the mixture tests, can effectively remove the magnet oil film, greatly improve the hydrophilicity of the magnet, better implement repair, solved the ndfeb magnet products oil bath due to oil stain on the surface of the magnet demagnetization after difficult processing, the repair is difficult problem.