Abstract
Radially oriented Nd-Fe-B ring magnet can be used as rotor magnets of AC Servomotors and outer magnet of small DC motors. In the manufacturing process of this ring magnet, cracking of the axial direction in the internal surface of the ring is found to take place with the large probability after sintering and Argon-cooling process. Though it is estimated that this cracking is caused by the circumferential stress of the internal surface which exceeds the mechanical strength of the Nd-Fe-B magnet material, it is very important to understand process conditions which cause the internal cracking quantitatively because of the establishment of the manufacturing process of the ring. Then, after the mechanical properties and the various thermal constants of Nd-Fe-B material were measured, cracking behavior of this rings has been investigated using a FEM method.
