Production of Sintered Nd-Fe-B Magnets with a Maximum Energy Density of 53 MGOe

Proceedings 16th Int. Workshop on RE Magnes and Their Applications, Sendai, Japan, 2000, p. 119 – 126. Production of Sintered Nd-Fe-B Magnets with a Maximum Energy Density of 53 MGOe W. Rodewald, R. Blank, B. Wall, G. W. Reppel and H. D. Zilg Vacuumschmelze GmbH, P. O. Box 2253, D 63 412 Hanau, Germany Abstract New sintered Nd-Fe-B near net-shape magnets with a high remanent polarization of 1.47 T, a coercivity HcJ of 9.6 kA/cm (12 kOe) and a maximum energy density of 420 kJ/m³ (53 MGOe) can be manufactured by rubber isostatic pressing. The optimization of the remanent polarization by an improved alignment process of the powder particles results in a decrease of the coercivity by 0.4 kA/cm per 1 % ∆fφ for alignment coefficients fφ in the range 96 to 98 %. For alignment coefficients between 98 to 99 % the decrease of the coercivity even increases to about –1 kA/cm per % 1 ∆fφ. The temperature coefficients of such magnets amount to –0.11 %/K for the remanent polarization and to –0.77 %/K for the coercivity in the temperature range 20 to 100 °C. The new grades of sintered Nd-Fe-B magnets, in which the conventional Nd-rich constituents are replaced by electrochemically more stable intergranular compounds have an improved corrosion stability in hot and humid climates. The weight losses after a HAST test at 130 °C, 95 % humidity amount to