Sintered Neodymium Magnets Manufacturing Process



The Production Process of Sintered Neodymium Magnet

Neodymium magnets are the rare earth magnet with the highest magnetic performance and coercive force in the world. They are composed of Nd, Fe, B, Dy, Co and other minor elements. It’s made of using powder metallurgy technology, the production processes are as below:

1. Ingredients
The Sintered NdFeB magnet is an alloy magnet that is mainly composed of Neodymium, Iron, Boron and other microelements (Dy、Al、Nb、Mo、Co and so on). According to the company issued the alloy composition calculation sheet (standard); and the material list of component raw materials manufacturers, alloy weight percentage is calculated from the two groups of data, and then calculate the weight of each furnace material.

2. Vacuum Melting
The melting temperature reaches over 1300℃. Usually repeated melting is needed to be produce an even phase and structure distribution.

3. Milling
The ingots from vacuum melting process are crushed into coarse powder directly.

4. Pressing
Usually a magnetic field is applied during pressing to align those anisotropic particles in order to produces maximum magnetic output in particular direction. There are two pressing methods, transverse and axial , depend on different application. Isotropic pressing is normally used to further density magnets to 75-80%.

5. Vacuum Sintering
The compacted magnets are sintered ate temperature above 1000℃ and for many hours to be solidified and compacted further more up to 99% by shrinking its body. A required micro structure between particles for high performance permanent magnets is also formed in this stage. Some following heat-treatments are needed to stabilize the magnets .
In the process of smelting, pay attention to the change of the liquid steel and the temperature, to prevent wear pot, short circuit, and so on.

6. Surface Grinding
Check the magnetic force and tolerance of blanks.

7. Grinding Machining
Processed into the demanding dimension and different shapes, including drilling, grinding, line cutting and so on. The regular shape magnets are made by slicing machine. Using glue to stick blanks, cut them into desired size. All the semi-finished products need 100% inspection for the tolerance, then boiling to remove the glue and chamfering to grind the sharp edges and “clean up” the surface.
The range of tolerance is ± 0.05mm to ± 0.1mm.

8. Surface Treatment (Coating)
Various surface treatments can be applied on the final magnets, such as zinc, nickel, Ni-Cu-Ni multi-layer, epoxy and others. They provide different surface finishing, appearance and corrosion resistance, applicable in different application environments.
Visual inspection (pick out poor coating quality and damaged magnet). Periodic testing in salt-spray to verify the performance of coatings.

9. Magnetization
Magnetized to saturation, The magnet must be magnetized to get the maximum performance output.
Fluxmeter and Gauss meter to testing the surface magnetic force.

10. Packaging
We offer standard magnetic isolation package, first small box with foam,outside is metal and foam.
The magnetic field at the surface of the box less than 10 gauss. This is consistent with the requirements of air transport. Each carton need with identification, specification, type.

11. Storage
For the warehousing of acceptable finished products, the warehouse administrator shall arrange the storage by categories and tag the labels, and then make records.
Every steps controlled very strictly to prevent defective products ISO quality system to control produce from the raw materials received to finishing warehousing.