The technical process of NdFeB neodymium permanent magnets is as below:
1.Raw Material Inspection. Check the raw material through RoHS detection, composition test and purity analysis.
2.Raw Material Pre-treatment. Cutting, baking, and polishing the raw material.
3.Ingredient Control. After the material is weighed, adjust the ingredients proportionately, and then mix the raw material.
4.Strip Casting. The prepared raw materials will be vacuum-treated and then high-temperature smelted to convert the raw materials into fined alloys, the last process is casting.
5.Hydrogen Decrepitation. Utilizing the hydrogen-absorption properties of rare earth intermetallic compounds，the NdFeB alloys are placed in a hydrogen atmosphere. The hydrogen enters the alloys along thin layer of rich neodymium, causing alloys to expand, burst and rupture. This guarantees the integrity of grain boundaries between the main phase and the rich neodymium grains. The HD process makes the NdFeB sheet becomes loose, which greatly improves the milling efficiency of the jet mill and reduces the production cost.
6.Milling. Milling through jet mill, its principle is that the raw materials are crushed by high-speed collision of materials themselves and then grinding them. In the process of milling, attention should be paid to granularity control, that is, the powder should have random inspection.
7.Pressing. Weighing proper raw material powder, and first use magnetic field pressure molding machine as pre-pressing for molding. After that, using the isolate pressing machine for secondary pressing.
8.Sintering. Sintering is the final shaping process of permanent magnet material. This process is mainly carried out in a vacuum sintering furnace, and the NdFeB magnets will be sintered and heat-treated in it.
9.Inspection. This step includes magnetic measurement, temperature coeffieient test, PCT, density measurement, and inspection, etc.
10.Machining. After sintering, the NdFeB permanent magnets are still blanks. Further machining is required to obtain different sizes and shapes of products. NdFeB magnets are relatively brittle and they have poor mechanical properties. Therefore, they are generally machined by grinding, wire cutting, and inner blade cutting.
11.QC sample test. Random testing for quality control.
12.Chamfering. Chamfering is the pretreatment process before plating. The purpose of this is to reduce uneven plating thickness caused by the relatively concentrated current density at magnet edge during the coating process.
13.Coating. The purpose of coating is to form a protective layer on the surface of magnets. According to the operation environment and appearance demands of magnets, they can be plated by Zn, NiCuNi, phosphating or chemical Ni.
14.Coating Inspection. Check the thickness, corrosion resistance and adhesiveness of Nd permanent magnets, as well as inspecting the tolerance of magnets. The last is a complete inspection so as to meet customers’ requirement.
15.Magnetization. Marking, arraying and magnetizing the magnets. Finally, to ensure the magnetic properties of magnets, a magnetic flux test will be performed.
16.Packing. If there’s no problem in the magnetic flux test, the magnets will be packaged.
---Posted by Sintered Neodymium Magnets Manufacturer China Rare Earth Magnet Limited on 20180820
Tags: NdFeB magnets, permanent magnets
