Alloy for r-t-b-based rare earth sintered magnet, process of producing alloy for r-t-b-based rare earth sintered magnet, alloy material for r-t-b-based rare earth sintered magnet, r-t-b-based rare earth sintered magnet, process of producing r-t-b-based rare earth sintered magnet, and motor

Abstract

An alloy for R-T-B-based rare earth sintered magnets which contains R which is a rare earth element; T which is a transition metal essentially containing Fe; a metallic element M containing one or more metals selected from Al, Ga and Cu; B and inevitable impurities, in which R accounts for 13 at % to 15 at %, B accounts for 4.5 at % to 6.2 at %, M accounts for 0.1 at % to 2.4 at %, T accounts for balance, a proportion of Dy in all rare earth elements is in a range of 0 at % to 65 at %, and the following Formula 1 is satisfied, 0.0049Dy+0.34≦B/TRE≦0.0049Dy+0.36  Formula 1 wherein Dy represents a concentration (at %) of a Dy element, B represents a concentration (at %) of a boron element, and TRE represents a concentration (at %) of all the rare earth elements.

1 . An alloy for R-T-B-based rare earth sintered magnets, the alloy comprising:
 R which is a rare earth element;   T which is a transition metal essentially comprising Fe;   a metallic element M comprising one or more metals selected from Al, Ga and Cu;   B; and   inevitable impurities,   wherein R accounts for 13 at % to 15 at %, B accounts for 4.5 at % to 6.2 at %, M accounts for 0.1 at % to 2.4 at %, T accounts for balance, a proportion of Dy in all rare earth elements is in a range of 0 at % to 65 at %, and the following Formula 1 is satisfied
   0.0049Dy+0.34≦B/TRE≦0.0049Dy+0.36  Formula 1
 
   wherein, Dy represents a concentration (at %) of a Dy element, B represents a concentration (at %) of a boron element, and TRE represents a concentration (at %) of all the rare earth elements.   
     
     
         2 . The alloy for R-T-B-based rare earth sintered magnets according to  claim 1 ,
 wherein M accounts for 0.7 at % to 1.4 at %.   
     
     
         3 . The alloy for R-T-B-based rare earth sintered magnets according to  claim 1 , further comprising Si. 
     
     
         4 . The alloy for R-T-B-based rare earth sintered magnets according to  claim 1 ,
 wherein an area ratio of a region including an R 2 T 17  phase is in a range of 0.1% to 50%.   
     
     
         5 . An alloy material for R-T-B-based rare earth sintered magnets, the alloy material comprising:
 an R-T-B-based alloy comprising R which is a rare earth element; T which is a transition metal essentially comprising Fe; B and inevitable impurities, in which R accounts for 13 at % to 15 at %, B accounts for 4.5 at % to 6.2 at %, T accounts for balance, a proportion of Dy in all rare earth elements is in a range of 0 at % to 65 at %, and the following Formula 1 is satisfied; and   an additional metal made of a metallic elements M comprising one or more metals selected from Al, Ga and Cu or an alloy comprising the metallic element M,   wherein the alloy material for R-T-B-based rare earth sintered magnets comprises the metallic element M in a range of 0.1 at % to 2.4 at %,
   0.0049Dy+0.34≦B/TRE≦0.0049Dy+0.36  Formula 1
 
   in Formula 1, Dy represents a concentration (at %) of a Dy element, B represents a concentration (at %) of a boron element, and TRE represents a concentration (at %) of all the rare earth elements.   
     
     
         6 . An alloy material for R-T-B-based rare earth sintered magnets, the alloy material comprising:
 an R-T-B-based alloy comprising R which is a rare earth element; T which is a transition metal essentially comprising Fe; a first metal comprising one or more metals selected from Al, Ga and Cu; B and inevitable impurities, in which R accounts for 13 at % to 15 at %, B accounts for 4.5 at % to 6.2 at %, T accounts for balance, a proportion of Dy in all rare earth elements is in a range of 0 at % to 65 at %, and the following Formula 1 is satisfied; and   an additional metal made of a second metal comprising one or more metals selected from Al, Ga and Cu or an alloy comprising the second metal,   wherein the alloy material for R-T-B-based rare earth sintered magnets comprises the first metal and the second metal in a range of 0.1 at % to 2.4 at % in total,
   0.0049Dy+0.34≦B/TRE≦0.0049Dy+0.36  Formula 1
 
   wherein Dy represents a concentration (at %) of a Dy element, B represents a concentration (at %) of a boron element, and TRE represents a concentration (at %) of all the rare earth elements.   
     
     
         7 . The alloy material for R-T-B-based rare earth sintered magnets according to  claim 5 , further comprising Si. 
     
     
         8 . The alloy material for R-T-B-based rare earth sintered magnets according to  claim 7 ,
 wherein a amount of Si in the alloy material for R-T-B-based rare earth sintered magnets is in a range of 0.7 at % to 1.5 at %.   
     
     
         9 . The alloy material for R-T-B-based rare earth sintered magnets according to  claim 5 ,
 wherein an area ratio of a region including an R 2 T 17  phase in the R-T-B-based alloy is in a range of 0.1% to 50%.   
     
     
         10 . A process of producing R-T-B-based rare earth sintered magnets,
 wherein the alloy for R-T-B-based rare earth sintered magnets according to  claim 1  is molded and sintered.   
     
     
         11 . The process of producing R-T-B-based rare earth sintered magnets according to  claim 10 ,
 wherein the sintering is carried out in a range of 800° C. to 1200° C., and then a thermal treatment is carried out in a range of 400° C. to 800° C.   
     
     
         12 . The process of producing R-T-B-based rare earth sintered magnets according to  claim 10 ,
 wherein a diffusion step of attaching Dy metal or Tb metal, or a Dy compound or a Tb compound to a surface of a sintered R-T-B-based magnet and carrying out a thermal treatment is carried out.   
     
     
         13 . An R-T-B-based rare earth sintered magnet comprising:
 R which is a rare earth element;   T which is a transition metal essentially comprising Fe;   a metallic element M comprising one or more metals selected from Al, Ga and Cu;   B; and   inevitable impurities,   wherein R accounts for 13 at % to 15 at %, B accounts for 4.5 at % to 6.2 at %, M accounts for 0.1 at % to 2.4 at %, T accounts for balance, a proportion of Dy in all rare earth elements is in a range of 0 at % to 65 at %, the following Formula 1 is satisfied,   which is made of a sintered body including a main phase primarily comprising R 2 Fe 14 B and a grain boundary comprising more R than the main phase, in which the grain boundary phase includes a phase having a concentration of all atoms of the rare earth elements of 70 at % or more and a phase having a concentration of all the atoms of the rare earth elements in a range of 25 at % to 35 at %,
   0.0049Dy+0.34≦B/TRE≦0.0049Dy+0.36  Formula 1
 
   wherein Dy represents a concentration (at %) of a Dy element, B represents a concentration (at %) of a boron element, and TRE represents a concentration (at %) of all the rare earth elements.   
     
     
         14 . The R-T-B-based rare earth sintered magnet according to  claim 13 , further comprising Si. 
     
     
         15 . The R-T-B-based rare earth sintered magnet according to  claim 13 ,
 wherein a volume ratio of the phase having a concentration of all the atoms of the rare earth elements in a range of 25 at % to 35 at % is in a range of 0.005 vol. % to 3 vol. %.   
     
     
         16 . The R-T-B-based rare earth sintered magnet according to  claim 13 ,
 wherein a concentration of Dy or Tb on a surface of the sintered magnet is higher than a concentration of Dy or Tb in the sintered magnet.   
     
     
         17 . A motor including the R-T-B-based rare earth sintered magnet according to  claim 13 . 
     
     
         18 . An alloy for R-T-B-based rare earth sintered magnets comprising:
 R which is a rare earth element;   T which is a transition metal essentially comprising Fe;   a metallic element M comprising one or more metals selected from Al, Ga and Cu;   B; and   inevitable impurities,   wherein R accounts for 13 at % to 15 at %, B accounts for 5.0 at % to 6.0 at %, M accounts for 0.1 at % to 2.4 at %, T accounts for balance, a proportion of Dy in all rare earth elements is in a range of 0 at % to 65 at %, a main phase primarily comprising R 2 Fe 14 B and an alloy grain boundary phase comprising more R than the main phase are included, and an interval between the alloy grain boundary phases is 3 μm or less.   
     
     
         19 . The alloy for R-T-B-based rare earth sintered magnets according to  claim 18 , further comprising Si. 
     
     
         20 . The alloy for R-T-B-based rare earth sintered magnets according to  claim 18 ,
 wherein a ratio (Fe/B) of a amount of Fe to a amount of B is in a range of 13 to 16.   
     
     
         21 . The alloy for R-T-B-based rare earth sintered magnets according to  claim 18 ,
 wherein B/TRE (B represents a concentration (at %) of a boron element, and TRE represents a concentration (at %) of all the rare earth elements) is in a range of 0.355 to 0.38.   
     
     
         22 . A process of producing alloys for R-T-B-based rare earth sintered magnets comprising:
 a casting step of casting a molten alloy comprising R which is a rare earth element; T which is a transition metal essentially comprising Fe; a metallic element M comprising one or more metals selected from Al, Ga and Cu; B and inevitable impurities, in which R accounts for 13 at % to 15 at %, B accounts for 5.0 at % to 6.0 at %, M accounts for 0.1 at % to 2.4 at %, T accounts for balance, and a proportion of Dy in all rare earth elements is in a range of 0 at % to 65 at % using a strip casting method in which a workpiece is cooled using a cooling roll,   wherein, in the casting step, a temperature-holding step of maintaining a cast alloy at a certain temperature for 10 seconds to 120 seconds while a temperature of the cast alloy decreases from more than 800° C. to lower than 500° C. is carried out.   
     
     
         23 . The process of producing alloys for R-T-B-based rare earth sintered magnets according to  claim 22 ,
 wherein the molten alloy comprises Si.   
     
     
         24 . The process of producing alloys for R-T-B-based rare earth sintered magnets according to  claim 22 ,
 wherein at least a part of the casting step is carried out in an atmosphere comprising helium.