Nd-Fe-B type anisotropic exchange spring magnet and method of producing the same

Abstract

A Nd—Fe—B type anisotropic exchange spring magnet is produced by a method of obtaining powder of a Nd—Fe—B type rare earth magnet alloy which comprises hard magnetic phases and soft magnetic phases wherein a minimum width of the soft magnetic phases is smaller than or equal to 1 μm and a minimum distance between the soft magnetic phases is greater than or equal to 0.1 μm, obtaining a compressed powder body by compressing the powder, and obtaining the Nd—Fe—B type anisotropic exchange spring magnet by sintering the compressed powder body using a discharge plasma sintering unit.

1 - 19 . (canceled) 
     
     
         20 . A method of producing powder of a Nd—Fe—B type rare earth magnet alloy for a Nd—Fe—B type anisotropic exchange spring magnet which comprises hard magnetic phases and soft magnetic phases wherein a minimum width of the soft magnetic phases is smaller than or equal to 1 μm; a minimum distance between the soft magnetic phases is greater than or equal to 0.1 μm; and a composition of the Nd—Fe—B type rare earth magnet alloy is expressed by the following chemical formula (1)
   Nd x Fe 100-x-y-z B y V z   (1)   
       where x is within a range from 9 to 11; y is within a range from 5 to 8; z is within a range of 0 to 2; and the chemical formula (1) optionally comprises Co, and if Co is present in the alloy, 0.01 to 30 atom % of Fe is replaced with Co, the method comprising:
 pulverizing the Nd—Fe—B type rare earth magnet alloy by means of a ball mill using a dispersant under a non-oxidation atmosphere. 
 
     
     
         21 . The method according to  claim 20 , wherein the ball mill is of a wet type. 
     
     
         22 . The method according to  claim 20 , wherein the ball mill is of a dry type. 
     
     
         23 . A method of producing a Nd—Fe—B type anisotropic exchange spring magnet, comprising:
 obtaining powder of a Nd—Fe—B type rare earth magnet alloy which comprises hard magnetic phases and soft magnetic phases wherein a minimum width of the soft magnetic phases is smaller than or equal to 1 μm; a minimum distance between the soft magnetic phases is greater than or equal to 0.1 μm; and a composition of the Nd—Fe—B type rare earth magnet alloy is expressed by the following chemical formula (1)
   Nd x Fe 100-x-y-z B y V z   (1) 
   
       where x is within a range from 9 to 11; y is within a range from 5 to 8; z is within a range of 0 to 2; and the chemical formula (1) optionally comprises Co, and if Co is present in the alloy, 0.01 to 30 atom % of Fe is replaced with Co;
 obtaining a compressed powder body by compressing the powder at a compressing pressure ranging from 1 to 5 ton/cm 2  in a magnetic field ranging from 15 to 25 kOe; and 
 obtaining a bulk magnet by sintering the compressed powder body at a temperature ranging from 600 to 800° C. and at a compressing pressure ranging from 1 to 10 ton/cm 2  in a discharge plasma sintering unit. 
 
     
     
         24 . The method according to  claim 23 , wherein the powder is obtained by pulverizing the Nd—Fe—B type rare earth magnet alloy by means of a ball mill. 
     
     
         25 . A Nd—Fe—B type anisotropic exchange spring magnet produced by a method of obtaining powder of a Nd—Fe—B type rare earth magnet alloy which comprises hard magnetic phases and soft magnetic phases wherein a minimum width of the soft magnetic phases is smaller than or equal to 1 μm; a minimum distance between the soft magnetic phases is greater than or equal to 0.1 μm; and a composition of the Nd—Fe—B type rare earth magnet alloy is expressed by the following chemical formula (1)
   Nd x Fe 100-x-y-z B y V z   (1)   
       where x is within a range from 9 to 11; y is within a range from 5 to 8; z is within a range of 0 to 2; and the chemical formula (1) optionally comprises Co, and if Co is present in the alloy, 0.01 to 30 atom % of Fe is replaced with Co; obtaining a compressed powder body by compressing the powder at a compressing pressure ranging from 1 to 5 ton/cm 2  in a magnetic field ranging from 15 to 25 kOe; and obtaining a bulk magnet by sintering the compressed powder body at a temperature ranging from 600 to 800° C. and at a compressing pressure ranging from 1 to 10 ton/cm 2  in a discharge plasma sintering unit. 
     
     
         26 . The Nd—Fe—B type anisotropic exchange spring magnet according to  claim 25 , wherein a density of the anisotropic exchange spring magnet is 95% of a true density of a magnet alloy having a composition as same as that of the anisotropic exchange spring magnet. 
     
     
         27 . A motor comprising:
 a Nd—Fe—B type anisotropic exchange spring magnet produced by a method of obtaining powder of a Nd—Fe—B type rare earth magnet alloy which comprises hard magnetic phases and soft magnetic phases wherein a minimum width of the soft magnetic phases is smaller than or equal to 1 μm; a minimum distance between the soft magnetic phases is greater than or equal to 0.1 μm; and a composition of the Nd—Fe—B type rare earth magnet alloy is expressed by the following chemical formula (1)
   Nd x Fe 100-x-y-z B y V z   (1) 
   
       where x is within a range from 9 to 11; y is within a range from 5 to 8; z is within a range of 0 to 2; and the chemical formula (1) optionally comprises Co, and if Co is present in the alloy, 0.01 to 30 atom % of Fe is replaced with Co; obtaining a compressed powder body by compressing the powder at a compressing pressure ranging from 1 to 5 ton/cm 2  in a magnetic field ranging from 15 to 25 kOe; and obtaining a bulk magnet by sintering the compressed powder body at a temperature ranging from 600 to 800° C. and at a compressing pressure ranging from 1 to 10 ton/cm 2  in a discharge plasma sintering unit.