Method for preparing R-Fe-B-based rare earth magnetic powder for a bonded magnet, magnetic powder prepared by the method, method for producing a bonded magnet using the magnetic powder, and bonded magnet produced by the method
View Patent ↗A method of preparing R—Fe—B-based rare earth magnetic powder for a bonded magnet and magnetic powder prepared thereby, and a method of manufacturing a bonded magnet using magnetic powder and a bonded magnet manufactured thereby. Further, a method of preparing R—Fe—B-based rare earth magnetic powder having improved magnetic properties including grinding rare earth sintered magnet products as a raw material, performing a hydrogenation process where a ground product is charged into a furnace, and the furnace is then filled with hydrogen and a temperature of the furnace is increased, performing a disproportionation process where the temperature of the furnace is further increased in the same hydrogen atmosphere above, performing a desorption process where hydrogen is exhausted from an inside of the furnace, and performing a recombination process where hydrogen in the inside of the furnace is exhausted, and magnetic powder prepared thereby, and a method of manufacturing a bonded magnet.
1. A method of preparing R—Fe—B-based rare earth magnetic powder having improved magnetic properties, the method comprising:
coarse grinding rare earth sintered magnet products as a raw material;
performing a hydrogenation process in which a ground product obtained through the coarse grinding is charged into a tube furnace, and the tube furnace is then filled with hydrogen and a temperature of the tube furnace is increased;
performing a disproportionation process in which the temperature of the tube furnace is further increased in the same hydrogen atmosphere as that of the hydrogenation process;
performing a desorption process in which hydrogen is exhausted from an inside of the tube furnace; and
performing a recombination process in which hydrogen in the inside of the tube furnace is vacuum exhausted after the desorption process is performed,
wherein the recombination process is performed after the desorption process and the disproportionation process and desorption process are repeated one time.
2. The method as set forth in claim 1 , wherein the rare earth sintered magnet products, are process scraps generated during manufacturing processes of rare earth magnets and R—Fe—B-based rare earth sintered magnet products recovered from defective products or wasted products.
3. The method as set forth in claim 1 , wherein the rare earth sintered magnet products are ground to a diameter ranging from 0.1 μm to 10,000 μm by the coarse grinding.
4. The method as set forth in claim 1 , wherein a vacuum state in the tube furnace before hydrogen is introduced in the hydrogenation process is a pressure of 1×10 −2 Torr or less.
5. The method as set forth in claim 1 , wherein hydrogen in the hydrogenation process is filled to a pressure ranging from 228 Torr to 1520 Torr.
6. The method as set forth in claim 1 , wherein the temperature of the tube furnace in the hydrogenation process is increased to a range of 100° C. to 400° C.
7. The method as set forth in claim 1 , wherein the temperature of the tube furnace in the disproportionation process is further increased to a range of 700° C. to 900° C.
8. The method as set forth in claim 1 , wherein the disproportionation process is performed for 30 minutes to 180 minutes.
9. The method as set forth in claim 1 , wherein the exhaustion of hydrogen in the desorption process is performed to obtain a pressure of hydrogen ranging from 1 Torr to 400 Torr in the tube furnace at the same temperature as that of the disproportionation process.
10. The method as set forth in claim 1 , wherein the desorption process of is performed for 1 minute to 30 minutes.
11. The method as set forth in claim 1 , wherein the number of repetitions of the disproportionation process and the desorption process before the recombination process is in a range of one to ten.
12. The method as set forth in claim 1 , wherein the vacuum exhaustion in the recombination process is performed to obtain a pressure of hydrogen in the tube furnace ranging from 10 −5 Torr to 10 −1 Torr.
13. The method as set forth in claim 1 , wherein the prepared R—Fe—B-based rare earth magnetic powder has improved magnetic properties prepared by using the preparation method of claim 1 .
14. The method as set forth in claim 13 , wherein a grain diameter of the rare earth magnetic powder is in a range of 200 nm to 600 nm.
15. The method as set forth in claim 1 , further comprising:
grinding the R—Fe—B-based rare earth magnetic powder to form powder;
mixing the powder with at least one of a thermosetting or thermoplastic synthetic resin to form a mixture; and
molding the mixture to form a compression or injection-molded bonded magnet.
16. The method as set forth in claim 15 , wherein the R—Fe—B-based rare earth magnetic powder is ground to a diameter ranging from 50 μm to 1000 μm.
17. The method as set forth in claim 15 , wherein the synthetic resin is added in an amount ranging from 1 wt % to 10 wt % based on a total weight of the bonded magnet.
18. The method as set forth in claim 15 , wherein a R—Fe—B based rare earth bonded magnet is manufactured.