PREPARATION METHOD OF RING-SHAPED SINTERED ND-FE-B MAGNET AND ITS MOULDING DIE

The invention provides a preparation method, which comprises the following steps:step a) providing a moulding die for a ring-shaped sintered Nd-Fe-B magnet;step b) placing a Nd-Fe-B magnetic powder into the mould cavity of the moulding die in a loosely packed state, the loosely packed height of the Nd-Fe-B magnetic powder is L;step c) placing a flexible cylindrical core into the loosely packed Nd-Fe-B magnetic powder at a L/2 position, wherein an axial direction of the flexible cylindrical core is horizontal and parallel to the direction of a magnetic field in the mould cavity;step d) applying a vertical pressure to the Nd-Fe-B magnetic powder to obtain a ring-shaped green block assembly with the flexible cylindrical core embedded therein;step e) after encapsulating and isolating the ring-shaped green block assembly, applying an isostatic pressure to the ring-shaped green block assembly;step f) sintering the ring-shaped green block assembly to obtain a ring-shaped sintered blank; andstep g) thermally aging, grinding and slicing the ring-shaped sintered blank to obtain the ring-shaped sintered Nd-Fe-B magnet.