R-t-b type alloy and production method thereof, fine powder for r-t-b type rare earth permanent magnet, and r-t-b type rare earth permanent magnet

Abstract

An object of the present invention is to provide an R-T-B type alloy (wherein R is at least one element selected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Ho, Er, Tm, Yb, and Lu; T is a transition metal that contains 80% by mass or more of Fe; and B is one that contains 50% by mass or more of boron (B) and also contains at least one element of C and N within a range from 0 to less than 50% by mass) that contains at least Dy, as a raw material for a rare earth-based permanent magnet having excellent magnetic characteristics, and the R-T-B type alloy provided in the present invention includes a main phase such as an R 2 T 14 B phase for exhibiting magnetic properties; an R-rich phase that is relatively enriched with R compared to the overall alloy compositional ratio; and a Dy-rich region that is formed close to the R-rich phase and relatively enriched with Dy compared to the compositional ratio.

1 . An R-T-B type alloy (wherein R is at least one element selected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Ho, Er, Tm, Yb, and Lu; T is a transition metal that contains 80% by mass or more of Fe; and B is one that contains 50% by mass or more of boron (B) and also contains at least one element of C and N within a range from 0 to less than 50% by mass) which is a raw material for use in a rare earth-based permanent magnet and contains at least Dy, said R-T-B type alloy comprising:
 a main phase such as an R 2 T 14 B phase exhibiting magnetic properties;   an R-rich phase that is enriched with R compared to the overall alloy compositional ratio; and   a Dy-rich region that is formed close to the R-rich phase and enriched with Dy compared to the compositional ratio.   
     
     
         2 . The R-T-B type alloy according to  claim 1 , wherein a Dy concentration is lower in the main phase than in the Dy-rich region and is lower in the R-rich phase than in the main phase. 
     
     
         3 . The R-T-B type alloy according to  claim 1 , wherein the alloy is a flake having an average thickness from 0.1 to 1 mm produced by a strip casting method. 
     
     
         4 . A method for producing an R-T-B type alloy according to  claim 1 , said method comprising the steps of:
 producing a flake having an average thickness from 0.1 to 1 mm; and   supplying molten alloy to a cooling roll at an average rate of 10 g/sec or more per 1-cm width.   
     
     
         5 . The method for producing an R-T-B type alloy according to  claim 4 , wherein an R-T-B type alloy flake rolled out of the cooling roll is maintained at a temperature from 600 to 900° C. for 30 seconds or more. 
     
     
         6 . A fine powder for an R-T-B type rare earth permanent magnet that is produced from the R-T-B type alloy according to  claim 1 . 
     
     
         7 . An R-T-B type rare earth permanent magnet produced from the fine powder for an R-T-B type rare earth permanent magnet according to  claim 6 . 
     
     
         8 . A fine powder for an R-T-B type rare earth permanent magnet that is produced from the R-T-B type alloy produced by the method for producing an R-T-B type alloy according to  claim 4 . 
     
     
         9 . An R-T-B type rare earth permanent magnet produced from the fine powder for an R-T-B type rare earth permanent magnet according to  claim 8 .