Development and Future Prospects of Nd-Fe-B Anisotropic Bonded Magnets Produced by d-HDDR Method

Abstract

Dy-free Nd-Fe-B anisotropic bonded magnets have superior features of high magnet properties of Nd₂Fe₁₄B compounds as well as shape flexibility and high electrical resistivity of bonded magnets. By taking advantage of such excellent features, they have been used in direct-current motors for automobiles, and recently, advances in molding technology have promoted the application of bonded magnets to direct-current brushless motors such as those for drones. With the electrification of automobiles toward the realization of energy-saving and decarbonized society, resource saving of motors is required. Here, motors using Dy-free Nd-Fe-B anisotropic bonded magnets can contribute to this requirement because of their high electrical resistivity, which reduces eddy currents and enables high-speed rotation and miniaturization. Therefore, the demand for such bonded magnets is expected to increase further. This paper describes manufacturing processes and recent developments of Dy-free Nd-Fe-B anisotropic bonded magnets and its future prospects.