Method of fabricating rare-earth sintered magnet and method of fabricating rare-earth bonded magnet

Abstract

A method of fabricating a rare-earth based sintered magnet having improved magnetic and mechanical characteristics is offered. Also, a method of fabricating a rare-earth bonded magnet having improved magnetic and mechanical characteristics is offered. The method of fabricating the rare-earth based sintered magnet is started with preparing powder of an alloy including a rare-earth element and a transition metal. The powder of the alloy is mixed with an additive. The mixture is compression molded and irradiated with microwaves to cause the powder to self-heat. As a result, the mixture is sintered.

1 . A method of fabricating a rare-earth sintered magnet, comprising the steps of:
 preparing powder of an alloy containing rare-earth element and transition metal;   molding the powder of the alloy into a molded article having a desired form;   irradiating the molded article with microwave in a vacuum or in an inert gas and sintering the molded article; and   heating the molded article in an inert gas.   
     
     
         2 . A method of fabricating a rare-earth sintered magnet as set forth in  claim 1 , wherein, in the irradiating step, the molded article is irradiated with microwave in nitrogen gas for nitriding and sintering. 
     
     
         3 . A method of fabricating a rare-earth sintered magnet as set forth in  claim 1 , wherein the microwave has a frequency higher than 1 GHz and lower than 30 GHz. 
     
     
         4 . A method of fabricating a rare-earth sintered magnet as set forth in  claim 2 , wherein the microwave has a frequency higher than 1 GHz and lower than 30 GHz. 
     
     
         5 . A method of fabricating a rare-earth sintered magnet as set forth in  claim 3 , wherein the powder of the alloy is made of particles having an average particle diameter of 2 to 90 μm. 
     
     
         6 . A method of fabricating a rare-earth sintered magnet as set forth in  claim 4 , wherein the powder of the alloy is made of particles having an average particle diameter of 2 to 90 μm. 
     
     
         7 . A method of fabricating a rare-earth sintered magnet as set forth in  claim 2 , wherein a pressure of the nitrogen gas is from 0.1 to 5 MPa. 
     
     
         8 . A method of fabricating a rare-earth bonded magnet, comprising the steps of:
 pulverizing a rare-earth sintered magnet fabricated by the method set forth in  claim 1  into powder of a rare-earth sintered magnet having an average particle diameter of 5 to 90 μm; and   mixing the powder of the rare-earth sintered magnet with a resinous binder or a metal binder and compression molding or injection molding the mixture.   
     
     
         9 . A method of fabricating a rare-earth bonded magnet, comprising the steps of:
 pulverizing a rare-earth sintered magnet fabricated by the method set forth in  claim 2  into powder of a rare-earth sintered magnet having an average particle diameter of 5 to 90 μm; and   mixing the powder of the rare-earth sintered magnet with a resinous binder or a metal binder and compression molding or injection molding the mixture.   
     
     
         10 . A method of fabricating a rare-earth bonded magnet, comprising the steps of:
 pulverizing a rare-earth sintered magnet fabricated by the method set forth in  claim 7  into powder of a rare-earth sintered magnet having an average particle diameter of 5 to 90 μm; and   mixing the powder of the rare-earth sintered magnet with a resinous binder or a metal binder and compression molding or injection molding the mixture.