Daido Steel, Honda Develop Magnet for HEVs Without Using Dy

- Apr 17, 2019-

Daido Steel Co Ltd and Honda Motor Co Ltd developed a Nd-Fe-B (neodymium-iron-boron)-based magnet (Nd magnet) that does not use any heavy rare earth metals such as dysprosium (DY).

The two companies announced July 12, 2016, that they will use the Nd magnet for the motor of Honda's hydrid vehicle (HEV). This will be the first time in the world that a Nd magnet made without Dy, which is expensive and produced in limited regions, has been employed for an HEV motor, they said.

Specifically, the magnet will be used for the "i-DCD" single-motor hybrid mechanism of the "Freed" minivan to be released in the fall of 2016. And Honda is planning to use the magnet for other HEVs equipped with the i-DCD. Honda's "Fit" compact car, "Vezel" compact SUV (sport-utility vehicle), etc are HEVs equipped with the i-DCD.

Daido Steel developed a technology to increase the heat resistance of a Nd magnet while keeping its magnetic force without using Dy. And Honda made improvements to enhance the heat resistance of the motor and commercialized the magnet for the HEV motor. The maximum torque and maximum output of the motor are 160N·m and 22kW, respectively, which are the same as the maximum torque and maximum output of Honda's existing motor.

Nd magnets have a high residual magnetic flux density, meaning a strong magnetic force, and, thus, can increase motor torque. On the other hand, their coercive force is weak, indicating a low heat resistance. Therefore, heavy rare earth metals such as Dy and Tb (terbium) are added to increase their coercive force.

However, Dy and Tb are expensive and produced almost only in China. Depending on the policies of the Chinese government, they become difficult to procure. In 2010, the government prohibited the export of heavy rare earth metals.

Because the Nd magnet was realized without using Dy, it became easier to procure materials for Nd magnets regardless of the intentions of the Chinese government.