Abstract
Nd-Fe-B alloy powder was granulated by spray drying method using polyvinylalcohol (PVA) binder in the range from 0.1wt% to 0.5wt%, in order to improve the powder flowability during feeding and compacting. After adding PVA binder, glycerin and pure water to alloy powder, the slurry was stirred at 278K to suppress the oxidation of alloy powder. The granulated powders exhibited a high flowability with the increase of PVA content. By heating in H2 at 673K for 0.5H after compacting in the magnetic field, about 90% of carbon in binder was removed, although the oxygen in binder remained unremoved. With the compacted body added 0.20wt% PVA, these treatments can allow to suppress the residual contents of oxygen and carbon in the resulted sintered magnets within less than 8000ppm and 900ppm, respectively. The highest coercive force (iHc) and maximum energy product (BH) max for a sintered anisotropic magnet prepared by the above mentioned process are 1.06(MA/m) and 286.5(kJ/m3), respectively.
