Nd-Fe-B(neodymium-iron-boron) sintered magnets are an essential key component in the drive motors of hybrid and electric vehicles. Compared with other magnets, neodymium magnets not only have strong magnetic forces that can achieve sufficient power to drive the vehicle, but also reduce the motor to a size suitable for vehicle use.
To make this neodymium magnet, it is necessary to crush the alloy containing the necessary materials into particles, gather these particles, form them, and then sinter them. After cutting into the required size to complete. The process always feels like cake making.
Of course, it is not so simple to actually mass-produce high-quality neodymium magnets. Not only should the particles be unified to the size of 3 to 5 μm, but also the uniformity of the shape, but also consider the heating method during sintering, which takes a lot of effort to manufacture. For example, one of them is the "magnetic field forming process" that is implemented after crushing the alloy to 3 to 5 μm. The process is to give the crushed micro-powder(micro-magnet) orientation. The orientation here means that the magnetization direction of the micropowder is unified into a certain fixed direction. The higher the orientation, the greater the residual flux density. When the process is carried out, the micropowder is filled into the mold, the magnetic field is applied to the micropowder, and then the pressure molding is carried out.
In order to achieve high orientation, it is also important to create a uniform magnetic field space inside the mold. Since the configuration of the electromagnet and the size, shape, and material of the mold will cause uneven magnetic fields, resulting in poor orientation, it is necessary to use magnetic field analysis and other means to fine-tune the magnetic field to make it uniform.
With regard to the manufacture of neodymium magnets, as many reports have said, it is impossible to talk about it without China. That's because most of the complex Dy(dysprosium) in magnets is mined in China, but China has begun to restrict exports. Under this restriction, the supply of Dy metal on the market decreased, resulting in the price of Dy metal rising to $3,100 per kg in July 2011, which was about 10 times that of a year ago.
So why should China restrict exports? There are various speculations about this question, but the Japanese companies that make neodymium magnets have the same answer: "The reason is that we want to obtain our neodymium magnet manufacturing technology. "At present, the share of neodymium magnets is almost monopolized by Japanese companies. Moreover, as mentioned above, the manufacture of neodymium magnets requires a large amount of technical accumulation, and it is Japanese companies that have accumulated in this area for many years. By contrast, China "has a wealth of materials necessary to make neodymium magnets, but it can not make beautiful products". As a result, China has unveiled the terms of exchange for "as long as we set up factories and teach us manufacturing technology, we can supply raw materials in large quantities." One of the specific policies is to restrict exports. Of course, this is the view of Japanese magnet manufacturers.
In July 2011, "Japan Economic News" reported that Hitachi Metal decided to manufacture neodymium magnets in China. It is estimated that Hitachi Metal decided to ensure procurement first after making a trade-off between material stability procurement and technology outflow risk.
Even building factories in China, however, may not immediately lead to an outflow of technology. On this issue, the Japanese car manufacturers are better dealt with. Japanese automakers who want to sell cars in China must set up joint ventures with Chinese companies to build factories in the country. And China can get the technology through joint ventures. "In exchange for allowing cars to be sold in the huge Chinese market, we are required to teach technology such as engines that will need to be accumulated over the years," as in the case of neodymium magnets