近日，本田汽車公司（Honda Motor Co.）和大同特殊鋼有限公司（Daido Steel Ltd. ）達(dá)成了一項(xiàng)雙贏的合作戰(zhàn)略，將一起生產(chǎn)一種用于電氣化汽車電機(jī)的新型磁鐵材料。
據(jù)了解，這種熱變形釹材料已經(jīng)率先登陸2017款本田Freed混合動(dòng)力運(yùn)動(dòng)版（2017 Freed Sport Hybrid）緊湊休旅車的永磁牽引電機(jī)。這兩家公司表示，熱變形釹材料具有重大意義，因?yàn)檫@種材料并不屬于“重”稀土金屬，并不需要摻雜鏑和鋱稀土元素以提高耐熱性，可以直接滿足電動(dòng)車和混合動(dòng)力車電機(jī)對(duì)高磁性和耐熱性的要求。
本田可以通過(guò)與日本大同特殊鋼公司(Daido Steel)的新型永磁材料聯(lián)合研發(fā), 進(jìn)一步有效降低其電機(jī)對(duì)“重”稀土材料的依賴。據(jù)了解，本田努力尋求替代解決方案是為了進(jìn)行成本控制，并保證材料的可靠供應(yīng)：目前，盡管中國(guó)的稀土儲(chǔ)量?jī)H占全球總量的35%，但卻占到全球稀土元素供應(yīng)量的93%，其中就包括在永磁材料中必不可少的釹和鏑。
2010年，一艘中國(guó)漁船涉嫌在所謂的“日本海域”作業(yè)被扣押，曾引起中國(guó)短暫禁止對(duì)日的稀土出口。專家表示，隨著中國(guó)海洋邊界問題的緊張局勢(shì)的不斷加劇，出于對(duì)中國(guó)禁運(yùn)稀土金屬的擔(dān)憂，以及對(duì)降低材料成本的期待，本田動(dòng)力系統(tǒng)部門開始研發(fā)風(fēng)險(xiǎn)較低的“重”稀土元素替代品。
此外，美國(guó)能源部也開始進(jìn)行“尋求關(guān)鍵技術(shù)稀土替代品行動(dòng)（REACT）”，旨在尋找成本較低、供應(yīng)可靠的稀土原料替代品。
雖然釹（Nd）屬于稀土元素，但其實(shí)相當(dāng)普遍易得，鈷、銅和鎳等元素均比釹元素更稀少。當(dāng)與鐵、硼形成化合物（Nd2Fe14B）時(shí)，釹元素能夠提供比其他永磁材料更高的磁性，從而允許客戶在廣泛的商業(yè)應(yīng)用中使用尺寸更小、質(zhì)量更輕的磁鐵。
大同特殊鋼的子公司大同電子（Daido Electronics）一直在通過(guò)熱變形工藝量產(chǎn)釹磁鐵。熱變形工藝與磁鐵生產(chǎn)中常用的燒結(jié)工藝有所不同，可以使納米級(jí)別的晶粒精確排列。因此，熱變形磁鐵的晶粒結(jié)構(gòu)比燒結(jié)磁鐵要精細(xì)大約10倍。
這樣一來(lái)，廠商無(wú)需摻雜昂貴的“重”金屬稀土元素，也可以生產(chǎn)出耐熱性更高的磁鐵。為了適應(yīng)新型磁鐵的特點(diǎn)，本田在設(shè)計(jì)中專門改進(jìn)了一款牽引電機(jī)轉(zhuǎn)子的形狀，以優(yōu)化磁鐵的磁通流動(dòng)。
這款最新開發(fā)的熱變形釹磁鐵已經(jīng)為大同特種鋼打開了一扇大門，使其能夠參與到電動(dòng)汽車的全球供應(yīng)鏈之中。而過(guò)去，牽引電機(jī)磁鐵的市場(chǎng)一直以燒結(jié)磁鐵為主。據(jù)了解，大同電子已經(jīng)在津川市（Nakatsugawa City）的工廠新建了一條生產(chǎn)線，并從加拿大多倫多的Magnequench International公司采購(gòu)磁粉。
有趣的是，Nd2Fe14B磁鐵合金是在1982年由通用汽車公司（General Motors）和Sumitomo Specialty Metals特殊金屬公司聯(lián)合開發(fā)的，當(dāng)時(shí)也是為了應(yīng)對(duì)釤鈷（SmCo）磁體成本過(guò)高的挑戰(zhàn)。
作者：Lindsay Brooke
來(lái)源：SAE《汽車工程》雜志
翻譯：SAE 中國(guó)辦公室
Honda’s new e-motor magnet aims to mitigate China rare-earth monopoly
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.
Author: Lindsay Brooke
Source: SAE Automotive Engineering Magazine
2017款本田Freed混動(dòng)休旅車的新型電機(jī)轉(zhuǎn)子，采用了與大同特殊鋼公司聯(lián)合開發(fā)的新型永磁材料。