The extraction of NdFeB magnets from automotive scrap rotors using hydrogen

Abstract

Scrap containing NdFeB is a valuable resource for the production of NdFeB magnets as the demand for these materials grows. One of the challenges is to recover the rare earths or the NdFeB alloy powder in a clean and cost effective manner so that it can be re-processed into new magnets rather than becoming lost to landfill. Work on using hydrogen to process scrap magnets (HPMS) has been shown to be successful when targeting hard disk drives. Currently, there is a lack of information on reliable methods to separate out NdFeB from other scrap sources such as automotive drives. In the near future, with increasing sales and electrification of cars, the automotive sector could be an important source for Dy containing magnets. In this paper, the hydrogen processing of scrap magnets has been demonstrated as an extraction method for NdFeB from automotive rotors for the first time, with the aim to examine the viability of this recycling process and learn lessons for design for recycling. Thus leading to the sustainable production of these components. Significant challenges were outlined when applying the hydrogen process to rotors with embedded magnets. After the extraction, further process steps may also be needed to separate epoxy coatings, as sieving could only reduce the carbon content to 1420 ppm, compared to 770 ppm in the base alloy. The gravimetric measurements also confirmed that Dy additions increase both the initiation and absorption time for hydrogen decrepitation. Hence, a higher hydrogen pressure will be required to speed up the process.