Regeneration of waste sintered Nd-Fe-B magnets to fabricate anisotropic bonded magnets

The waste sintered Nd-Fe-B magnets were regenerated as magnetic powders via manually crushing (MC) or hydrogen decrepitation (HD) to fabricate anisotropic bonded magnets. Effect of size distribution on the magnetic properties of the regenerated magnetic MC and HD powders was investigated. For the MC powders, as the particle size decreased, the remanence (B-r) increased first, and then decreased again, while the coercivity (H-ci) dropped monotonically. The powders with particle size in the range of 200-450 mu m possessed the best magnetic properties of B-r of 1.22 T and H-ci of 875.6 kA/m. The corresponding bonded magnet exhibited magnetic properties of B-r of 0.838 T, H-ci of 940.9 kA/m, and (BH) max of 91.4 kJ/m(3), respectively. On the other hand, the HD powders with particle size range of 200-450 mu m bore the best magnetic properties of Br of 1.24 T and H-ci of 860.4 kA/m. Compared with magnetic properties of the waste magnet, the powders retained 93.9% of B-r and 70.0% of H-ci, respectively. The bonded magnet produced from HD powders possessed B-r of 0.9 T, H-ci of 841.4 kA/m, and (BH) max of 111.6 kJ/m(3), indicating its good potential in practical applications.