Daido Steel and Honda developed neodymium magnets with improved heat resistance that do not use heavy rare earths.
Rare earths, critical minerals essential to high-tech products, are emerging as a potential flashpoint that could disrupt the global economy. With its overwhelming dominance of the market, China has increasingly used them as a tool of economic pressure.
In May, Suzuki halted production of its flagship compact car, the Swift, after delays in securing parts that depend on rare earths.
In April, the Chinese government restricted exports of seven rare earth elements in retaliation for reciprocal tariffs imposed by the United States. The impact rippled through the global auto industry: Ford Motor suspended production of some models, and parts manufacturers in Europe were forced to shut down operations.
Rare earth elements comprise a group of 17 metals produced in limited quantities. Even in small amounts, they can dramatically enhance material performance.
Chinese Dominance
China controls roughly 70% of global rare earth mining and about 90% of refining. Rare earth ores often contain radioactive elements such as uranium, and mining and refining generate radioactive waste as well as highly toxic substances such as hydrofluoric acid. Strict environmental regulations make refining difficult in many countries, contributing to China's market dominance.
Concerns are growing that China has begun to wield rare earths as a diplomatic tool. Beyond current tensions with the United States, China effectively halted rare earth exports to Japan in September 2010 following a collision involving a Chinese fishing vessel near the Senkaku Islands in Ishigaki City, Okinawa Prefecture.
In response, Japan moved to reduce its dependence on China. The Japan Organization for Metals and Energy Security (JOGMEC) expanded stockpiling and development efforts, while companies accelerated work on technologies that reduce or eliminate the need for rare earths.
Neodymium Magnets
One focus has been neodymium magnets, which are essential for high-output motors used in electric vehicles. Made mainly from neodymium and iron, these magnets are among the strongest permanent magnets in the world: just one gram can lift about three kilograms of iron.
Their weakness, however, is heat. At high temperatures, magnetic strength declines, and improving heat resistance has traditionally required heavy rare earths such as terbium and dysprosium, which are largely concentrated in China.
Daido Steel and Honda developed neodymium magnets with improved heat resistance that do not use heavy rare earths. In 2016, Honda installed motors using this technology in its hybrid vehicle, the Freed.
Rather than relying solely on conventional high-temperature sintering, Daido developed a method to fine-tune magnet composition at the nanometer scale, improving heat resistance. Honda also redesigned the motor to reduce heat buildup around the magnets.
Today, according to Kenichiro Saito of Daido's corporate planning department, the technology is used in nearly all of Honda's hybrid vehicles. While it has not yet been adopted by other automakers, interest is growing both domestically and overseas as China tightens export controls.
Development is also under way on motors that do not use neodymium magnets at all. Astemo, a major auto parts supplier, has developed an EV motor that relies on ferrite magnets, which are mainly composed of iron.
Ferrite magnets have less than one-third the magnetic strength of neodymium magnets, meaning a motor would theoretically need to be three times larger to deliver the same output. This presents a challenge in EVs, where space is limited.
Boosting Magnetic Force
Astemo addressed this by compensating for weaker magnetism with electricity. By stacking layers of iron and magnets and applying an electric current, the iron becomes magnetized, boosting overall magnetic force. Precise control of the current allows the motor to achieve performance comparable to that of motors using neodymium magnets.
There are trade-offs. Because electricity is used to enhance magnetism, energy efficiency declines slightly, increasing battery consumption by a few percent. Even so, the motor's size has been limited to about 1.3 times that of a conventional neodymium-magnet motor. Eliminating expensive neodymium magnets also reduces costs, and several automakers have expressed interest.
At an October summit meeting, Japan and the United States signed a memorandum of cooperation to strengthen rare earth supply chains, including mining and processing. Collaboration with other countries that share the goal of reducing reliance on China will be essential.
At the same time, Japan is accelerating the development of technologies that avoid rare earths altogether. This is vital to reducing the hidden costs of supply chain disruptions. Proterial, formerly Hitachi Metals, has also developed neodymium magnets that do not require heavy rare earths. These efforts highlight a counterstrategy made possible by the strength of Japanese companies in advanced materials development.
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(Read the article in Japanese.)
Author: Shunichi Takahashi, The Sankei Shimbun
