Abstract
Nd-Fe-B alloy powder was granulated by spray drying method using methylcellulose (MC) binder in the range from 0.1 to 0.5wt%, in order to improve the powder flowability during feeding and compacting. After adding MC binder, glycerin and pure water to alloy powder, the slurry was stirred at 278K in N2 atmosphere to suppress the oxidation of alloy powder. The granulated powders with MC binder exhibited higher flowability than granulated powders with polyvinylalcohol(PVA) binder. By heating in H2 at 673K after compacting in a magnet field, 96% of carbon in binder was removed, although the oxygen in binder remained unremoved. With the compacted body added 0.20wt% MC, these treatments can allow to suppress the residual contents of oxygen and carbon in the resulted sintered magnets within less than 8500ppm and 600ppm, respectively. The coercive force(iHc) and maximum energy product (BH) max for a sintered anisotropic magnet prepared by the above mentioned process are 0.96(MA/m) and 241.1 (kJ/m3), respectively, in which (BH)max is lower by 15% than that obtained by using PVA binder.
