Toshiba Corporation (Tokyo: 6502) and Toshiba Materials Co. Ltd. have developed a new high-iron concentration samarium-cobalt magnet that is free of heavy rare earth elements, highly resistant to demagnetization, and that achieves significantly superior magnetic properties at high temperatures to the heat-resistant neodymium magnets currently used in motors.
Traction motors for hybrid and electric automobiles, railroad rolling stock and the motors for industrial equipment and wind turbines all operate at relatively high temperatures, and heat-resistant neodymium magnets are generally used in these applications. However, heat-resistant neodymium magnets contain heavy rare earth elements that are in short supply and expensive.
Neodymium magnets generate a strong magnetic force at room temperature, but in high temperature applications magnetic performance falls away drastically and torque declines. This decline in magnetic performance can be controlled by replacing neodymium with other rare earth elements, such as dysprosium and telbium, but even so it is difficult to maintain strong magnetic power at high temperature.
Toshiba has investigated dysprosium-free motors, and in 2012 developed a high-iron concentration samarium-cobalt magnet that outperformed neodymium magnets at the high temperatures that start to degrade performance and ultimately cause demagnetization. The 2012 magnet outperformed a neodymium magnet in magnetic force by 1% at an operating temperature of 100°Celsius and 5% at 150°C.
In its latest breakthrough, Toshiba has now developed a high-iron samarium-cobalt magnet that realizes high level demagnetization resistance at 180°C, outperforms neodymium magnets at 140°C, and that, due to application of Toshiba-developed heat treatment, offers 30% better coercivity than the magnet developed in 2012. This significantly improved heat resistance and performance will support the design of simpler cooling systems for industrial equipment integrating motors, reducing overall size and footprints. It will also bring more freedom of design to motors themselves, as it is possible to apply thin magnetics.
Toshiba used heat-treatment technology to improve the magnetic force of the samarium-cobalt magnet and to surpass the performance of the 2012 magnet. The company expects to see application of the new magnet in motors for automobiles, locomotives, machine tools and elevators, as it outperforms heat-resistant neodymium magnets of the same size.
Toshiba Material Corporation plans to start sampling of the new magnet today and will promote its use in all applicable equipment.