Honda’s new e-motor magnet aims to mitigate China rare-earth monopoly

  • 17-Jul-2016 03:58 EDT
Honda Daido magnet.jpg

A rotor used in Honda's new e-motor for the 2017 Freed hybrid containing the new magnet material co-developed with Daido Steel. 

Honda Motor Co. and Daido Steel Ltd. recently scored a strategic win when they announced the first production application of a new magnet material for electrified vehicle motors.

The material—hot deformed neodymium—is being used first in a new permanent-magnet traction motor powering Honda’s 2017 Freed Sport Hybrid compact minivan. Significantly, the material is not a “heavy” rare-earth metal, one that requires “doping” with dysprosium or terium rare earths to achieve high heat-resistance characteristics. Yet it has the high magnetic and thermal performance necessary for use in EV and hybrid vehicle e-motors, according to the companies.

The new magnet material co-developed with Daido Steel brings Honda one step closer to effectively reducing content of “heavy” rare earths in its e-motors going forward. Cost and reliable supply are the reason: Chinese mines currently supply more than 93% of the world’s rare earth elements including neodymium and dysprosium that are essential to scores of magnetic products (though 65% of the world’s reserves lie elsewhere).

In 2010, China briefly embargoed exports of rare earths to Japan after a maritime incident involving one of its fishing boats allegedly operating in Japanese waters. Increased tensions with China over disputed oceanic boundaries, the metals embargo and opportunity to reduce material cost likely prompted Honda powertrain planners to develop less risky alternatives to replace the heavy rare-earths, according to experts.

The U.S. Dept. of Energy’s REACT (Rare Earth Alternatives in Critical Technologies) program also aims to find low-cost and reliable alternatives for rare earths.

Although classified as a rare earth, neodymium (Nd) is a fairly common element, no rarer than cobalt, copper and nickel. When compounded with iron and boron (Nd2Fe14B) it inherently offers much greater magnetic strength than other permanent magnets, allowing use of smaller, lighter magnets in a wide range of commercial applications.

Daido Electronics, a subsidiary of Daido Steel, has been mass-producing neodymium magnets using hot deformation. The process differs from sintering which is typically used in magnet production. Hot deformation enables nanometer-scale crystal grains to be precisely aligned. The resulting crystal grain structure is approximately 10 times finer than that of a sintered magnet.

This makes it possible to produce magnets with greater heat resistance properties without the need for doping with the expensive “heavy” rare earths. To accommodate the new magnet Honda designed a new traction motor with a revised rotor shape designed to optimize the flow of the magnetic flux.

A market for the newly-developed hot deformed neodymium magnet opens the door for Daido Steel into the global electrified vehicle supply chain, which for traction-motor magnets has been dominated by sintered Nd magnets. Daido Electronics built a new production line at its Nakatsugawa City plant, and sources its magnetic powder from Magnequench International in Toronto, Canada.

Interestingly, the Nd2Fe14B magnet alloy was developed in 1982 by General Motors and Sumitomo Specialty Metals in response to the high cost of samarium-cobalt (SmCo) magnets.

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