The processing of Neodymium magnet can be roughly divided into 4 parts:

1. Raw material preparation and pretreatment
2. Smelting
3. Hydrogen crushing
4. pulverize

Figure 1: The main steps of production process

Raw material preparation and pretreatment:

Oil, scale and slag removal of Neodymium and desiccation and slag removal of Fe and desiccation. Then prepare and weigh the raw materials: Neodymium magnet contains 65% of Fe, 31% of Nd and the amount of the Ferro boron is the least. Therefore, the weight of the Ferro boron is not less than one thousandth. When weighing these raw materials, use platform weighting to weigh Nd and Fe, use the balance to weigh Ferro boron.

Smelting:

Melt the metal material (Fe, Nd, B-Fe, Dy) and make the alloy liquid clean and pure.

A small amount of quench surface fine crystal area is in contact with the water-cooled copper mold, the central equiaxed crystal of the final solidified part at a low cooling rate, and the flaky crystal in between. The faster the cooling rate is, the larger the proportion of flaky crystals and the smaller the ratio of central equiaxed crystals. During the process, we need to ensure that the leakproofness of melting furnace.

Hydrogen crushing:

Figure 2: Vacuum hydrogen treatment furnace

Put the alloy plate into the hydrogen crushing device, then vacuumize the device and heated to 700-800 ℃, keep it for a while and they will react as follow:

Nd₂Fe₁₄B+2H₂→2NdH₂+12Fe+Fe₂B

And pumping out the hydrogen will react as follow:

2NdH₂+12Fe+Fe₂B→Nd₂Fe₁₄B+2H₂^[2]

Then Nd2Fe14B powder with smaller grain was synthesized and the purpose of crushing the plate is achieved.

Pulverize:

Figure 3: Pneumatic cracker

The particles that have been broken pass through the gap of the sorting wheel with the updraft, so that the particles that meet our requirements pass through, but the particles larger than the specified size cannot return to the collision crushing zone of the grinding chamber through the sorting wheel to continue crushing. Particles smaller than the specified size are separated by conveying to a fine powder separator.

The requirement of the powder is that 80-90% of powder should be 3-5mm^[2]. 

[1]Retrieved from:https://baijiahao.baidu.com/s?id=1628666897070260007&wfr=spider&for=pc

[2]Retrieved from:https://wenku.baidu.com/view/ddca630faf1ffc4fff47ac53.html