Magnetic Properties and Particle Flowability of Neodymium Magnetic Granules

In this study, sintered Nd-Fe-B magnets with high residual flux densities and magnetic coercivities were manufactured by filling a die cavity with granulated Nd-Fe-B magnetic powder during pressing. in the binder-hound granules prepared by a spray drying method, the bonding force between the primary particles was relatively strong. However, the magnets obtained from these granules could not achieve high residual magnetic flux densities because it was difficult to align each particle in these granules along the magnetization easy axis through magnetic field pressing. Therefore, a weak liquid bridge force was utilized for particle binding. After preparing the liquid-bound granules containing 0.25 mass% terpineol, which does not evaporate easily at room temperature (similar to 293 K) but undergoes debinding on baking, the angle of repose of the magnetic powder (representing its flowability index) decreased from 63 degrees to 44.2 degrees, while the deterioration of its magnetic properties was considerably suppressed. As a result, the residual magnetic flux density of the sintered magnet was equal to 99.3% of the value obtained for the non-granulated powder. In addition, the liquid-bound granules exhibited high filling rates and low weight variations, demonstrating their applicability for mass production.

Automated summary

In this study, sintered Nd-Fe-B magnets with high residual flux densities and magnetic coercivities were successfully manufactured using liquid-bound granules for particle binding. These granules containing terpineol demonstrated improved flowability and suppressed deterioration of magnetic properties. Additionally, the sintered magnets showed a residual magnetic flux density equal to 99.3% of value obtained for the non-granulated powder, proving the applicability of liquid-bound granules for mass production.