Hitachi Metals reduces rare-earth dysprosium in electric-motor magnets

  • 05-Apr-2013 04:22 EDT
NEOMAX Nd-Fe-B Sintered Magnets.jpg

Hitachi Metals’ reduced-dysprosium NEOMAX series Nd-Fe-B sintered magnets are suited for HEV/EV traction motors and other actuators and electric motors in various applications.

In response to high prices and supply risks for dysprosium and other rare-earth elements used in neodymium sintered magnets for hybrid and electric vehicle (HEV/EV) traction motors, electric power steering, and other actuators and electric motors, Hitachi Metals America (HMA) has developed an alternative solution that reduces dependence on such rare earths.

The Purchase, NY-based company’s reduced-dysprosium NEOMAX series Nd-Fe-B sintered magnets are enabled by DDMagic, a dysprosium vapor deposition diffusion technology. HMA first applied DDMagic technology in 2009 for factory automation and extended it to the NEOMAX series for HEV applications starting in 2011. The innovation will be on display in booth #1000 at the SAE 2013 World Congress, taking place April 16-18 in Detroit.

Dysprosium (Dy), one of the most expensive heavy rare-earth elements, is used in neodymium sintered magnets to improve temperature resistance. Despite its performance-boosting characteristics, Dy has a significant downside: it’s currently sourced from a single country—China—which leads to supply shortages and erratic pricing as demand increases.

“The main objectives of our decision to develop these new NEOMAX magnets are product differentiation based on reduced-Dy magnet technology to achieve high performance, reduction of Dy volume which had a big impact in production cost, and lowering the risk of depending on one supply source,” explained Koshi Okamoto, Executive Director, Corporate Business Development, Hitachi Metals America, Ltd. “Cost saving compared with traditional sintered magnets depends on the market price of dysprosium, which has fluctuated very much in the past and is hard to predict.”

DDMagic is a method for thermally diffusing Dy vapor over a magnet’s surface. The technology mitigates the fall in remanence (Br) caused by Dy, according to HMA. Dy deposition diffusion not only reduces Dy usage but also increases heat-resistant temperature and coercivity (HcJ). Coercivity is improved by 320 kA/m (4 kOe) or more (effect differs by magnet shape), and Br can be raised more than 40 mT compared with conventional materials of the same coercivity, the company claims. These features can contribute to a lighter, more compact motor.

“There are other heavy rare-earth elements besides dysprosium, such as terbium (Tb), which is more rare and more expensive,” said Okamoto. “Magnets that are so-called Dy-free sometimes may include other heavy rare elements such as Tb, which is adversely more expensive and is sourced solely by China. Our DDMagic technology-based reduced-Dy NEOMAX magnets really reduce heavy rare elements as a whole.”

HMA has recently developed new technologies to even further reduce dysprosium use, which Okamoto referred to as “one of our top-priority projects.” However, he could not disclose any more technical details about this next-generation magnet.

“We think that the trends are for reduced-Dy magnets and even for Dy-free magnets,” he said.

The company is currently running a sample evaluation program with key customers and expects full commercialization of the NEOMAX series with new Dy-reduction technologies in 2014.

HMA’s main target segment for NEOMAX magnets is currently automotive, “mainly for EV/HEV including off-highway applications,” Okamoto shared. But he noted that aerospace applications for actuators and electric motors are a possibility as well.

NMF series sintered ferrite magnets have long been manufactured at HMA’s subsidiary in North Carolina for North American and European customers. In April 2013, Hitachi Metals will begin North American production of the NEOMAX series Nd-Fe-B sintered magnets at its NC subsidiary to meet increasing demands.

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