METHOD AND SYSTEM FOR MANUFACTURING SINTERED RARE-EARTH MAGNET HAVING MAGNETIC ANISOTROPY
A method for manufacturing a sintered rare-earth magnet having a magnetic anisotropy, in which a very active powder having a small grain size can be safely used in a low-oxidized state. A fine powder as a material of the sintered rare-earth magnet having a magnetic anisotropy is loaded into a mold until its density reaches a predetermined level. Then, in a magnetic orientation section, the fine powder is oriented by a pulsed magnetic field. Subsequently, the fine powder is not compressed but immediately sintered in a sintering furnace. A multi-cavity mold for manufacturing a sintered rare-earth magnet having an industrially important shape, such as a plate magnet or an arched plate magnet, may be used.
1 . A method for manufacturing a sintered RFeB magnet without pressing a fine powder, the method comprising:
a) a loading step including loading an RFeB alloy powder into a mold having a cavity whose form corresponds to that of a product to be obtained, the RFeB alloy powder being produced by jet-mill pulverizing a cast piece of an RFeB alloy, which is created by a strip-casting method and which contains 0 to 6 wt % of Dy and/or Tb so that a medium grain size of the RFeB alloy powder is 0.5 to 5 am in terms of D 50 measured with a laser-type grain-size distribution measurement;
b) an orientation step including applying a magnetic field of 2 T or higher to the RFeB alloy powder in the mold to orient the alloy powder; and
c) a sintering step including creating a sintered body by heating the RFeB alloy powder contained in the mold at a sintering temperature of from 900° C. to 1200° C. while allowing gas components released from the RFeB alloy powder,
wherein the loading step, the orientation step, and the sintering step are performed in an oxygen-free atmosphere or an inert gas atmosphere.
2 . The method for manufacturing a sintered RFeB magnet according to claim 1 , wherein:
the cast piece is coarsely pulverized to produce a coarse powder before performing the jet-mill pulverization; and
a lubricant is added to the coarse powder before performing the jet-mill pulverization.
3 . The method for manufacturing a sintered RFeB magnet according to claim 1 , wherein a lubricant is added to the RFeB alloy powder before performing the orientation step.
4 . The method for manufacturing a sintered RFeB magnet according to claim 2 , wherein a lubricant is added to the RFeB alloy powder before performing the orientation step.
5 . The method for manufacturing a sintered RFeB magnet according to claim 1 , wherein the sintering temperature is from 900° C. to less than 1000° C.
6 . The method for manufacturing a sintered RFeB magnet according to claim 5 , wherein the sintering temperature is from 950° C. to less than 1000° C.
7 . The method for manufacturing a sintered RFeB magnet according to claim 1 , wherein the sintering temperature is from 1000° C. to less than 1150° C.
8 . The method for manufacturing a sintered RFeB magnet according to claim 1 , wherein the magnetic field is a pulsed magnetic field.
9 . The method for manufacturing a sintered RFeB magnet according to claim 2 , wherein the sintering temperature is from 900° C. to less than 1000° C.
10 . The method for manufacturing a sintered RFeB magnet according to claim 3 , wherein the sintering temperature is from 900° C. to less than 1000° C.
11 . The method for manufacturing a sintered RFeB magnet according to claim 4 , wherein the sintering temperature is from 900° C. to less than 1000° C.
12 . The method for manufacturing a sintered RFeB magnet according to claim 2 , wherein the sintering temperature is from 950° C. to less than 1000° C.
13 . The method for manufacturing a sintered RFeB magnet according to claim 3 , wherein the sintering temperature is from 950° C. to less than 1000° C.
14 . The method for manufacturing a sintered RFeB magnet according to claim 4 , wherein the sintering temperature is from 950° C. to less than 1000° C.
15 . The method for manufacturing a sintered RFeB magnet according to claim 2 , wherein the sintering temperature is from 1000° C. to less than 1150° C.
16 . The method for manufacturing a sintered RFeB magnet according to claim 3 , wherein the sintering temperature is from 1000° C. to less than 1150° C.
17 . The method for manufacturing a sintered RFeB magnet according to claim 4 , wherein the sintering temperature is from 1000° C. to less than 1150° C.
18 . The method for manufacturing a sintered RFeB magnet according to claim 2 , wherein the magnetic field is a pulsed magnetic field.
19 . The method for manufacturing a sintered RFeB magnet according to claim 3 , wherein the magnetic field is a pulsed magnetic field.
20 . The method for manufacturing a sintered RFeB magnet according to claim 4 , wherein the magnetic field is a pulsed magnetic field.