PERMANENT MAGNET PRODUCTION METHOD

摘要

With a mandrel inserted in a through hole formed in an extrusion die, a preform filled in the through hole is extruded into a filling space defined between an inner surface of the through hole and an outer surface of the mandrel by pressing the preform with a pressing punch. Consequently, a cylindrical extruded form in which a plurality of stress concentration portions extending along an extruding direction are formed so as to be spaced apart from each other in a circumferential direction is formed. Then, an external force is applied to the extruded form thus obtained to thereby divide the extruded form at the stress concentration portions into a plurality of permanent magnets.