How Powerful Magnets Are Made

How are powerful magnets made, dear, do you understand? Nd-Fe-B (neodymium-iron-boron) sintered magnets are essential key components in the drive motors of hybrid and electric vehicles. Compared to other magnets, neodymium magnets are not only magnetically strong enough to power a vehicle, but also reduce the motor to a size suitable for on-vehicle use.

So, do you know how this NdFeB strong magnet is made? It involves crushing an alloy containing the necessary materials into particles, agglomerating the particles into a shape, and then sintering them. Then cut to the desired size to complete. The process always feels like making a cake.

Of course, it is not so simple in the actual mass production of high-quality NdFeB strong magnets. It takes a lot of time to manufacture not only the uniformity of the particles to a size of 3 to 5 μm, but also the uniformity of the shape and the heating method during sintering. "By accumulating a lot of small technologies, we have reached the practical level today" (technician engaged in the development of neodymium magnets).

For example, the "forming process in a magnetic field", which is performed after the alloy is pulverized to 3 to 5 μm, is one of them. This step is to orient the pulverized micropowder (micromagnet). The orientation here refers to unifying the magnetization direction of the micropowder into a certain fixed direction. The higher the orientation, the greater the residual magnetic flux density (an index of the magnetic field strength).

When this process is carried out, the fine powder is first filled into the mold, a strong magnetic field is applied to orient the fine powder, and then the pressure molding process is carried out. The unique feature of this is that it is gently press-molded to such an extent that the molded body does not collapse. Because if the pressure is too large, it will disrupt the orientation of the micropowder that was finally unified.

To achieve high orientation, it is also important to create a space with a uniform magnetic field inside the mold. Due to the configuration of the electromagnet and the size, shape and material of the mold, the magnetic field will be uneven, resulting in poor orientation. Therefore, it is necessary to use magnetic field analysis and other means to fine-tune to make the magnetic field uniform.