Summary: ISU and Ames Laboratory researchers have developed a method of producing Nd-Fe-B magnets capable of operating at higher temperatures (T>150°C) without the addition of expensive heavy rare earth elements such as Dy. Mechanically milled Nd-Fe-B powder is loaded into a metal vessel which is hot rolled to produce fully dense magnets with nanoscale grain size.
Description: Melt-spun flakes of Nd-Fe-B powder are mechanically milled to a powder which is loaded into a stainless-steel tube and welded shut. The powder packed tube is first cold rolled to reduce initial cross-section by 2/3 and roughly shape from circular to square. The tube is then placed into a ~800°C furnace and left for 5 minutes. The tube is then removed and rolled to reduce thickness. This process is repeated multiple times until the desired thickness is achieved with the heat treatment time being gradually reduced on each pass until a heating time of 2 minutes is reached. The produced magnets have nanoscale grain size providing good magnetic performance and are near-net-shape, reducing the need for machining and thus material waste.
Advantages: • Process is continuous, greatly increasing productivity • Process does not require a vacuum furnace, lowering capital costs and enabling faster heating and cooling in ambient air • Casing provides protection and corrosion resistance to magnets • Produced magnets are near-net-shape, reducing the need for machining • Entire magnet strip has the same thermal history, reducing variation due to thermal gradient seen in sintered magnets
Application: Permanent magnet production
References: 1. Pan et al., "Hot-Roll Fabrication of Anisotropic nanograin Nd-Fe-B Magnet," JOM (2024)
2. Shakelly et al., "Techno-Economic Assessment of a Novel Continuous Hot-Roll Process for Manufacturing Nanograin NdFeB Magnets," Procedia CIRP (2024)
Patent: Patent(s) applied for: Patent Application Publication
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