Manufacture Method of NDFEB Isotropic and Anisotropic Permanent Magnets

Abstract

A fabrication method of isotropic and anisotropic NdFeB type permanent magnets is disclosed. In the a fabrication method of isotropic and anisotropic NdFeB type permanent magnets, the isotropic and anisotropic NdFeB type permanent magnets can be easily manufactured by means of Joule's heat using a self resistance of a powder molded body by directly applying a DC (Direct Current) to the upper and lower punches and the powder molded body, without using external heating elements or high frequency coils and so on, during press molding of the permanent magnet powder using the punches, and it is simple in terms of structure during the fabrication thereof, so that the manufacturing cost is low.

1 . A fabrication method of an isotropic NdFeB type permanent magnet, comprising the steps of:
 putting a powder molded body of a freeform type, in which a NdFeB type powder is compression molded in normal temperature, into a graphite mold;   adhering and fixing the powder molded body to upper and lower punches located at upper and lower parts thereof;   applying a DC of 500-3,000 A/cm 2  to the upper and lower punches, whereby generating a resistance heat of 700-800° C. into the powder molded body;   applying a pressure of 10-150 Mpa to the upper and lower punches; and   cooling the isotropic permanent magnet, in which the powder molded body is contracted in the pressure direction of the upper and lower punches.   
   
   
       2 . The method as claimed in  claim 1 , wherein the isotropic permanent magnet, in which the powder molded body is contracted in the pressure direction of the upper and lower punches, is cooled in normal temperature. 
   
   
       3 . The method as claimed in  claim 1 , wherein a material of the mold for fixing the powder molded body is a metal or ceramic. 
   
   
       4 . A fabrication method of an anisotropic NdFeB type permanent magnet, comprising the steps of:
 adhering and fixing a molded body of an isotropic permanent magnet between upper and lower punches;   applying a DC of 500-3,000 A/cm 2  to the upper and lower punches, whereby generating a resistance heat of 700-800° C. into the molded body; and   applying a pressure of 50-200 Mpa to the upper and lower punches, whereby contracting the molded body in the pressure direction of the upper and lower punches and expanding the molded body perpendicularly to the pressure direction of the upper and lower punches.