Method of manufacturing a rare earth magnet alloy powder, a rare earth magnet made therefrom and a powder making device

Abstract

The present invention discloses a method of manufacturing, powder making device for rare earth magnet alloy powder, and a rare earth magnet. The method comprises a process of fine grinding at least one kind of rare earth magnet alloy or at least one kind of rare earth magnet alloy coarse powder in inert jet stream with an oxygen content below 1000 ppm to obtain powder that has a grain size smaller than 50 m. Low oxygen content ultra-fine powder having a grain size smaller than 1 m is not separated from the pulverizer, and the oxygen content of the atmosphere is reduced to below 1000 ppm in the pulverizer when crushing the powder. Therefore, abnormal grain growth (AGG) rarely happens in the sintering process. A low oxygen content sintered magnet is obtained and the advantages of a simplified process and reduced manufacturing cost are realized.

Claims

1. A method of manufacturing a rare earth magnet alloy powder for a rare earth magnet, the method comprising: receiving at least one kind of rare earth magnet alloy through a powder inlet of a pulverizer of a powder making device; and grinding the at least one kind of rare earth magnet alloy in the powder making device using an inert jet stream to obtain the rare earth magnet alloy powder, wherein: the inert jet stream comprises at least one inert gas and has an oxygen content below 1000 ppm, and grinding the at least one kind of rare earth magnet alloy in the powder making device using an inert jet stream comprises: injecting the at least one inert gas into the pulverizer through at least one air inlet; using a first filter disposed within the pulverizer to filter powder having a grain size smaller than 50 m from powder having a grain size larger than 50 m; passing the at least one inert gas and the powder having the grain size smaller than 50 m from the pulverizer to a first collecting device; sorting the powder having the grain size smaller than 50 m from the at least one inert gas; collecting fine powder, having a grain size smaller than 50 m and greater than 1 m, in a charging bucket disposed at a bottom of the first collecting device; and collecting ultra-fine powder, having a grain size smaller than 1 m, in the charging bucket disposed at the bottom of the first collecting device.

2. The method of claim 1, wherein the sorting the powder having the grain size smaller than 50 m from the at least one inert gas comprises: sorting the fine powder from the ultra-fine powder; and passing the at least one inert gas and the ultra-fine powder from the first collecting device to a second collecting device.

3. The method of claim 2, wherein collecting the ultra-fine powder comprises: sorting the at least one inert gas from the ultra-fine powder; and passing the ultra-fine powder from the second collecting device to the first collecting device.

4. The method of claim 3, wherein passing the ultra-fine powder from the second collecting device to the first collecting device comprises: passing the ultra-fine powder from the second collecting device to the first collecting device through a first pipe connected to a bottom of the second collecting device and connected to a lower portion of the first collecting device.

5. The method of claim 4, wherein passing the at least one inert gas and the ultra-fine powder from the first collecting device to a second collecting device comprises: passing the at least one inert gas and the ultra-fine powder from the first collecting device to a second collecting device through a pipe connected to a top of the first collecting device.

6. The method of claim 4, further comprising: using a valve, disposed in the first pipe, to control movement from the ultra-fine powder from the second collecting device to the first collecting device.

7. The method of claim 3, further comprising: passing the at least one inert gas from the second collecting device to a compressor; and passing the at least one inert gas from the compressor to the at least one air inlet of the pulverizer.

8. The method of claim 1, wherein sorting the powder having the grain size smaller than 50 m from the at least one inert gas comprises: sorting the powder having the grain size smaller than 50 m from the at least one inert gas comprises using a second filter disposed within the first collecting device.

9. The method of claim 8, further comprising: passing the at least one inert gas from the first collecting device to a compressor; and passing the at least one inert gas from the compressor to the at least one air inlet of the pulverizer.

10. The method of claim 1, wherein: the at least one kind of rare earth magnet alloy constituted to provide a rare earth magnet that comprises a R.sub.2T.sub.14B main phase, where R is at least one kind of rare earth element and T is at least one kind of transition metal element comprising Fe but no Co, and the at least one kind of rare earth magnet alloy is received in a strip or coarse powder form.

11. The method of claim 1, wherein receiving the at least one kind of rare earth magnet alloy through the powder inlet of the pulverizer of the powder making device comprises: receiving the at least one kind of rare earth magnet alloy after hydrogen decrepitation has been performed on the at least one kind of rare earth magnet alloy.

12. The method of claim 1, wherein: injecting the at least one inert gas into the pulverizer through at least one air inlet comprises injecting the at least one inert gas into the pulverizer through at least three air inlets, the at least one inert gas is injected into the pulverizer through a first air inlet of the at least three air inlets in a first direction toward the first filter, the at least one inert gas is injected into the pulverizer through a second air inlet of the at least three air inlets in a second direction toward the first air inlet, the at least one inert gas is injected into the pulverizer through a third air inlet of the at least three air inlets in a third direction toward the first air inlet, and the third direction is different than the second direction.

13. The method of claim 1, further comprising: pressing and sintering the rare earth magnet alloy powder, including the fine powder and ultra-fine powder.

14. The method of claim 1, wherein the at least one inert gas has a normal temperature dew point of below 10 C. in 0.1 MPa to about 1.0 MPa.

15. The method of claim 1, wherein injecting the at least one inert gas into the pulverizer through at least one air inlet comprises injecting the at least one inert gas into the pulverizer at a flow rate of about 50 m/s.

16. A method of manufacturing a rare earth magnet alloy powder for a rare earth magnet, the method comprising: receiving at least one kind of rare earth magnet alloy through a powder inlet of a pulverizer of a powder making device, wherein the at least one kind of rare earth magnet alloy is constituted to provide a rare earth magnet that comprises a R.sub.2T.sub.14B main phase, where R is at least one kind of rare earth element and T is at least one kind of transition metal element comprising Fe but no Co; and grinding the at least one kind of rare earth magnet alloy in the powder making device using an inert jet stream to obtain the rare earth magnet alloy powder, wherein: the inert jet stream comprises at least one inert gas and has an oxygen content below 1000 ppm, and grinding the at least one kind of rare earth magnet alloy in the powder making device using an inert jet stream comprises: injecting the at least one inert gas into the pulverizer through at least one air inlet disposed within a lower portion of the pulverizer; using a first filter disposed within an upper portion the pulverizer to filter powder having a grain size smaller than 50 m from powder having a grain size larger than 50 m; passing the at least one inert gas and the powder having the grain size smaller than 50 m from an air outlet, disposed within the upper portion of the pulverizer, to an air inlet of a first collecting device, disposed within an upper portion of the first collecting device; sorting the powder having the grain size smaller than 50 m from the at least one inert gas; collecting fine powder, having a grain size smaller than 50 m and greater than 1 m, in a charging bucket disposed at a bottom of the first collecting device; and collecting ultra-fine powder, having a grain size smaller than 1 m, in the charging bucket disposed at the bottom of the first collecting device.

17. The method of claim 16, wherein the sorting the powder having the grain size smaller than 50 m from the at least one inert gas comprises: sorting the fine powder from the ultra-fine powder in the first collecting device; and passing the at least one inert gas and the ultra-fine powder from an air outlet of the first collecting device, disposed in a top of the first collecting device, to an air inlet of a second collecting device, disposed in an upper portion of the second collecting device.

18. The method of claim 17, wherein collecting the ultra-fine powder comprises: sorting the at least one inert gas from the ultra-fine powder in the second collecting device; and passing the ultra-fine powder from a powder outlet disposed at a bottom of the second collecting device to the first collecting device through a pipe connected to a lower portion of the first collecting device.

19. The method of claim 16, further comprising: pressing and sintering the rare earth magnet alloy powder, including the fine powder and ultra-fine powder.

20. A method of manufacturing a rare earth magnet alloy powder for a rare earth magnet, the method comprising: grinding at least one kind of rare earth magnet alloy in a powder making device using an inert jet stream, wherein: the at least one kind of rare earth magnet alloy is constituted to provide a rare earth magnet that comprises a R.sub.2T.sub.14B main phase, where R is at least one kind of rare earth element and T is at least one kind of transition metal element comprising Fe but no Co, and grinding the at least one kind of rare earth magnet alloy in the powder making device using the inert jet stream, comprises: injecting at least one inert gas into a pulverizer through at least one air inlet disposed within a lower portion of the pulverizer; using a first filter disposed within an upper portion the pulverizer to filter powder having a grain size smaller than 20 m from powder having a grain size larger than 20 m; passing the at least one inert gas and the powder having the grain size smaller than 20 m from an air outlet of the pulverizer, disposed within the upper portion of the pulverizer, to an air inlet of a first collecting device, disposed within an upper portion of the first collecting device; sorting the powder having the grain size smaller than 20 m from the at least one inert gas; collecting fine powder, having a grain size smaller than 20 m and greater than 1 m, in a charging bucket disposed at a bottom of the first collecting device; and collecting ultra-fine powder, having a grain size smaller than 1 m, in the charging bucket disposed at the bottom of the first collecting device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates a schematic diagram of an existing jet milling apparatus;

(2) FIG. 2 illustrates a schematic diagram of the jet milling apparatus used in embodiments 1-3 and comparative examples 1-6; and

(3) FIG. 3 illustrates a schematic diagram of the jet milling apparatus used in embodiments 4-6 and comparative examples 7-12.

DETAILED DESCRIPTION OF THE INVENTION

(4) The present invention will be further described with the embodiments, but it should be noted that it is not a limitation to the scope of the invention.

Embodiments 1-3

(5) The present invention takes NdFeB rare earth alloy magnetic powder as an example to illustrate the manufacturing process and evaluation process for a rare earth magnet.

(6) The manufacturing process includes the following manufacturing steps: raw material preparing.fwdarw.melting.fwdarw.casting.fwdarw.hydrogen decrepitation.fwdarw.micro grinding.fwdarw.pressing under a magnetic field.fwdarw.sintering.fwdarw.heat treating.fwdarw.magnetic property evaluation.fwdarw.oxygen content evaluation of the sintered magnet.

(7) In the raw material preparing process, Nd with 99.5% purity, industrial FeB, and industrial pure Fe are prepared, and the weight ratio of the components is shown in TABLE 1.

(8) TABLE-US-00001 TABLE 1 The weight ratio of the components. No. Nd Fe B Embodiment 1 28 71 1 Embodiment 2 30 69 1 Embodiment 3 33 66 1

(9) Based on the above weight ratio of embodiments 1-3, 10 Kg raw materials are prepared respectively.

(10) In the melting process, the prepared raw materials are put into a crucible made of aluminum oxide, an intermediate frequency vacuum induction melting furnace is used to melt the raw materials to 1500 C. in a 10.sup.2 Pa vacuum.

(11) In casting process, Ar gas is filled into the melting furnace to 10000 Pa after vacuum melting, then a centrifugal casting method is used to cast the alloy and rapidly cool the alloy at a cooling rate of 1000 C./s.

(12) In the hydrogen decrepitation process, the crushing room with the rapidly cooled alloy is pumped at room temperature, then filled with hydrogen having a 99.5% purity to 0.1 MPa, left for 2 hours, after that, heating the crushing room and pumping at the same time, then, keeping the vacuum and 300 C. for 2 hours, and the crushed specimen having an average grain size between 200 m1000 m is taken out after cooling.

(13) In the micro grinding process, FIG. 2 shows the powder making device for this process as comprising a pulverizer 1, a first collecting device 2, a charging bucket 3 and a compressor 4. The pulverizer 1 comprises a powder inlet 11, an air inlet 12 at the lower portion and an air outlet 13 at the upper portion. The air inlet 12 of the pulverizer 1 is connected to the compressor 4, and the air outlet 13 is disposed with a first filter 51 for powder having a grain size smaller than 50 m. The first collecting device 2 is disposed with an air inlet 21 at the upper portion and an air outlet 22 at the top portion. The air inlet 21 is connected to the air outlet 13 of the pulverizer 1 by a pipe. The bottom of the first collecting device 2 is connected to the charging bucket 3. The air outlet 22 of the first collecting device 2 extends downwardly, has a second filter 52 for gas-solid separation, and is connected to the compressor 4. The second filter 52 is disposed corresponding to the air inlet 21 of the first collecting device.

(14) The powder after hydrogen decrepitation is put into the pulverizer 1 from the powder inlet 11. When the compressor 4 activates, inert gases recycle in the compressor 4 with the oxygen content lower than 100 ppm, the dew point is 38 C. (normal temperature 0.4 MPa), the flow rate is 5 m/s, and airflow enters the pulverizer 1 through the air inlet 12. The raw material is jet milled in a condition that the pressure of the pulverizer is 0.4 MPa, due to the work of the airflow. The ground powder having a grain size smaller than 50 m enters the first collecting device 2 through the first filter 51 disposed at the air outlet 13 at the upper portion. Uncrushed or imperfectly crushed powder (having a grain size larger than needed) is kept in the pulverizer 1 for further jet mill crushing. Airflow with crushed powder enters the first collecting device 2, at this time, large powder drops down due to gravity, ultra-fine powder enters the air outlet 22 of the first collecting device 2 with the airflow, but since it cannot pass through the second filter 52, it is also kept in the first collecting filter 2, and is then collected into the charging bucket 3 along with the large powder. The airflow passing through the second filter 52 enters the compressor 4 for recycling.

(15) To prevent blockage of the first filter 51 and the second filter 52, shaking machines are disposed respectively in the first filter 51 and the second filter 52 for shaking.

(16) The crushed powder is added with a molding promoter that is sold in the market as a forming assistant. In the present invention, the molding promoter is methyl caprylate, the additive amount is 0.2% of the rare earth alloy magnetic powder, and the mixture is well blended by a V-type mixer.

(17) In the pressing under a magnetic field process, using a right-orientation-type magnetic field molding, in a relative humidity of 13%, the powder is then compacted into a cube with an edge of 40 mm in a 2.0 T of orientation field and 0.8 ton/cm.sup.2 of forming pressure. Then the cubes are demagnetized in a 0.2 T magnetic field.

(18) Compacting takes place in argon atmosphere. The oxygen content stays below 1000 ppm, the forming machine is configured with a humidifier and a cooling device, and compacting takes place at a temperature of 25 C.

(19) In the sintering process, the compacts are moved to the sintering furnace, under a vacuum of 10.sup.1 Pa for 2 hours at 200 C. and for 2 hours at 900 C., then sintering for 2 hours at 1050 C., followed by filling the furnace with Ar gas to 0.1 MPa, and cooling to room temperature.

(20) In the heating process, the sintered magnet is heated for 1 hour in 580 C. in high purity Ar gas, then cooled to room temperature and taken out of the furnace.

(21) In the magnetic property evaluation process, the sintered magnet is tested by the NIM-10000H nondestructive testing of a large rare earth permanent magnet of the China Metrology Institute. The testing temperature is 20 C.

(22) In the oxygen content of sintered magnet evaluation process, the oxygen content of the sintered magnet is measured by an EMGA-620W oxygen and nitrogen analyzer of the Japanese company HORIBA.

(23) In the corrosion resistance performance experiment, a precision electronic balance is used to evaluate the weightlessness value (mg) of the sintered magnet for 20 days after a HSAT (IEC68-2-66) experiment.

(24) Comparative Samples 1-6

(25) The difference between comparative samples 1-6 from embodiments 1-3 is that, in the raw material preparing process, Nd with a 99.5% purity, industrial FeB, industrial pure Fe and Co with a 99.9% purity are prepared, and the weight ratio of the components is shown in TABLE 2.

(26) TABLE-US-00002 TABLE 2 The weight ratio of the components. No. Nd Fe B Co Comparative 28 71 1 0 sample 1 Comparative 30 69 1 0 sample 2 Comparative 33 66 1 0 sample 3 Comparative 28 69 1 2 sample 4 Comparative 30 67 1 2 sample 5 Comparative 33 64 1 2 sample 6

(27) Based on above weight ratio of comparative samples 1-6, 10 Kg raw materials are respectively prepared.

(28) In the micro grinding process, FIG. 1 shows the powder making device which comprises a pulverizer 1, a classification device 2, a powder collecting device 3, an ultra-fine powder collecting device 4 and a compressor 5. The pulverizer 1 is disposed with a filter 11 for powder having a grain size smaller than 20 m. The filter 11 is connected to the air outlet of pulverizer 1. The air inlet of pulverizer 1 is connected to compressor 5 via a pipe, and the air outlet of pulverizer 1 is connected to the classification device 2 via a pipe. The classification device 2 is connected to the powder collecting device 3 and the ultra-fine powder collecting device 4 respectively. In the powder making process, the coarse powder (as raw material) is put into the pulverizer 1 through the raw material inlet. The compressor 5 activates to cycle air and air enters the pulverizer 1 via the air inlet of the pulverizer 1. In an inert jet steam having an oxygen content below 1000 ppm, a dew point 38 C. (normal temperature, 0.4 MPa), a flow rate of 5 m/s, and a pressure of the pulverizer is 0.4 MPa, the raw material is jet milled. Powder with a grain size smaller than 50 m enters the classification devices 2 for classification through the first filter 11 disposed at the air outlet of the pulverizer at the upper portion under the force of the airflow. The uncrushed powder or imperfectly crushed powder are kept in the pulverizer 1 for further jet mill crushing. In the classification device 2, using a classification process, the ultra-fine powder enters the ultra-fine powder collecting device 4 via a pipe, the finished powder enters the powder collecting device 3 for subsequent processing. In the ultra-fine powder collecting device 4, the gas and the ultra-fine powder are separated. The air outlet of the ultra-fine powder device 4 is connected to the compressor 5 via a pipe, the gas recycles via compressor 5, and the ultra-fine powder is kept in the ultra-fine powder collecting device 4. It should be noted that, the ultra-fine powder is powder having a grain size smaller than 1 m. The ultra-fine powder collected by the ultra-fine powder collecting device 4 is discarded.

(29) The discard rate of ultra-fine powder (%) is determined by calculating the powder weight of the ultra-fine powder collecting device 4 divided by the raw material weight and expressed as a percentage.

(30) TABLE 3 is a magnetic property comparison TABLE between the embodiments and the comparative samples.

(31) TABLE-US-00003 TABLE 3 Magnetic property comparison TABLE. Discard rate of Oxygen ultrafine HAST Content of powder Br Hcj Hk/Hcj (BH)max weight- the Sintered No. (%) (kGs) (k0e) (%) (MG0e) lessness (mg) magnet (ppm) Embodiment 1 0 14.6 12.3 97.8 51.4 1.8 920 Embodiment 2 0 13.8 15.2 97.9 46.6 1.8 965 Embodiment 3 0 13.3 17.3 98.2 43.7 1.9 981 Comparative 0.9 14.5 11.3 86.5 50.2 25.2 865 sample 1 Comparative 1.2 13.7 14.2 87.5 45.1 28.5 873 sample 2 Comparative 3.2 13.2 16.5 88.3 42.1 32.6 883 sample 3 Comparative 2.1 14.5 10.2 78.5 50.4 6.2 913 sample 4 Comparative 2.8 13.7 13.1 79.2 45.1 7.5 925 sample 5 Comparative 3.9 13.2 15.3 78.9 42.2 8.9 940 sample 6

Embodiments 4-6

(32) The difference between the embodiments 4-6 and embodiments 1-3 is that, in the raw material preparing process, Nd with 99.5% purity, industrial FeB, industrial pure Fe are prepared, the weight ratio of the components is shown in TABLE 4.

(33) TABLE-US-00004 TABLE 4 The weight ratio of the components. No. Nd Fe B Embodiment 4 28 71 1 Embodiment 5 30 69 1 Embodiment 6 33 66 1

(34) Based on above weight ratio of embodiments 4-6, 10 Kg raw materials were respectively prepared.

(35) The powder making device in this micro grinding process is shown in FIG. 3 and comprises a pulverizer 1, a first collecting device 2, a charging bucket 3, a second collecting device 4 and a compressor 5. The pulverizer 1 comprises a powder inlet 11, an air inlet 12 at the lower portion and an air outlet 13 at the upper portion. The air inlet 12 of the pulverizer 1 is connected to the compressor 5, and the air outlet 13 is disposed with a first filter 14 for powder having a grain size smaller than 20 m. The first collecting device 2 is disposed with an air inlet 21 at the upper portion and an air outlet 22 at the top portion. The air inlet 21 is connected to the air outlet 13 of the pulverizer 1 via a pipe. The bottom of the first collecting device 2 is connected to the charging bucket 3. The second collecting device 4 is an ultra-fine powder collecting device and is disposed with an air inlet 41 at the upper portion and an air outlet at the top portion. The air inlet 41 is connected to the air outlet 22 of the first collecting device 2, and the air outlet 42 is connected to the compressor 5. The second collecting device 4 is disposed with a powder outlet 43 at the bottom. The powder outlet 43 is connected to the bottom of the first collecting device 2 via a pipe with valve.

(36) The powder after hydrogen decrepitation is put into the pulverizer 1 from the powder inlet 11. When the compressor 5 activates, inert gases recycles in compressor 4 with an oxygen content between 500 ppm-1000 ppm, a dew point of 10 C. (normal temperature 1.0 MPa), a flow rate of 50 m/s, with the pressure of the pulverizer being 1.0 MPa. Under the force of the airflow, the ground powder with grain size smaller than 20 m enters the first collecting device 2 through the filter 14 disposed at the air outlet 13 at the upper portion. Uncrushed or imperfectly crushed powder (with grain size larger than needed) are kept in the pulverizer 1 for further jet mill crushing. Airflow including crushed powder enters the first collecting device 2. At this time, large powder drops down due to gravity, ultra-fine powder enters the air outlet 22 of the first collecting device 2 with the airflow, and then enters the second collecting device 4. In the second collecting device, ultra-fine powder is collected and enters the bottom of the first collecting device 2 via powder outlet 43, is mixed with the large powder collected in the first collecting device 2, and the powder then enters the charging bucket 3. The airflow passing through the second collecting device 4 flows to the compressor 5 for recycling.

(37) Comparative Samples 7-12

(38) The difference of the comparative samples 7-12 and comparative samples 1-6 is that, in the raw material preparing process, Nd with 99.5% purity, industrial FeB, industrial pure Fe and Co with 99.9% purity are prepared, and the weight ratio of the components is shown in TABLE 5.

(39) TABLE-US-00005 TABLE 5 The weight ratio of the components. No. Nd Fe B Co Comparative 28 71 1 0 sample 7 Comparative 30 69 1 0 sample 8 Comparative 33 66 1 0 sample 9 Comparative 28 69 1 2 sample 10 Comparative 30 67 1 2 sample 11 Comparative 33 64 1 2 sample 12

(40) Based on above weight ratio of comparative samples 7-12, 10 Kg raw materials are respectively prepared.

(41) In the micro grinding process, FIG. 1 shows the powder making device. The device comprises a pulverizer 1, a classification device 2, a powder collecting device 3, an ultra-fine powder collecting device 4 and a compressor 5. The pulverizer 1 is disposed with a filter 11 for powder with grain size smaller than 20 m. The filter 11 is connected to the air outlet of the pulverizer 1. The air inlet of the pulverizer 1 is connected to the compressor 5 via a pipe, and the air outlet of the pulverizer 1 is connected to the classification device 2 via a pipe. The classification device 2 is connected to the powder collecting device 3 and the ultra-fine powder collecting device 4 respectively. In the powder making process, the coarse powder (as raw material) is put into the pulverizer 1 through the raw material inlet. The compressor 5 activates to cycle air, and air enters the pulverizer 1 from the air inlet of the pulverizer 1. In an inert jet steam with an oxygen content of 500 ppm1000 ppm, a dew point of 10 C. (normal temperature, 1.0 MPa), a flow rate of 5 m/s, and a the pressure of the pulverizer is 1.0 MPa, the raw material is jet milled. Powder with a grain size smaller than 20 m enters the classification devices 2 for classification through the first filter 11 disposed at the air outlet of the pulverizer at the upper portion under the force of the airflow. The uncrushed powder or imperfectly crushed powder are kept in the pulverizer 1 for continuing jet mill crushing. In the classification device 2, using a classification process, the ultra-fine powder enters the ultra-fine powder collecting device 4 via a pipe, the finished powder enters the powder collecting device 3 for a subsequent process. In the ultra-fine powder collecting device 4, gas and the ultra-fine powder are separated. The air outlet of the ultra-fine powder device 4 is connected to the compressor 5 via a pipe, and the gas recycles via compressor 5. The ultra-fine powder is kept in the ultra-fine powder collecting device 4. It is noted that, ultra-fine powder is powder having a grain size smaller than 1 m. The ultra-fine powder collected by the ultra-fine powder collecting device 4 is discarded.

(42) The discard rate of ultra-fine powder (%) is determined by calculating the powder weight of the ultra-fine powder collecting device 4 divided by the raw material weight expressed as a percentage.

(43) TABLE 6 is a magnetic property comparison TABLE between the embodiments and the comparative samples.

(44) TABLE-US-00006 TABLE 6 Magnetic property comparison TABLE. Discard Oxygen rate of Content of ultra fine HAST the Sintered powder Br Hcj Hk/Hcj (BH)max weight- magnet No. (%) (kGs) (k0e) (%) (MG0e) lessness (mg) (ppm) Embodiment 4 0 14.5 12.1 98.2 50.8 1.7 925 Embodiment 5 0 13.7 15.3 98.1 46.0 1.6 940 Embodiment 6 0 13.4 17.4 97.9 44.4 1.7 970 Embodiment 7 0.8 14.4 11.2 85.5 49.4 30.2 898 Comparative 1.3 13.6 14.1 83.2 44.5 32.6 923 sample 8 Comparative 3.1 13.0 15.9 83.9 40.8 36.3 940 sample 9 Comparative 2.0 14.4 9.9 74.3 49.4 7.4 933 sample 10 Comparative 2.7 13.7 12.8 76.8 45.0 6.9 942 sample 11 Comparative 4.2 13.1 14.9 72.3 41.6 7.3 935 sample 12

(45) Although the present invention has been described with reference to the preferred embodiments thereof for carrying out the invention, it will be apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the patent for invention which is intended to be defined by the appended claims

INDUSTRIAL APPLICABILITY

(46) The present invention is a method of manufacturing a rare earth magnet alloy powder, a rare earth magnet, and a powder making device in which ultra-fine powder having a grain size smaller than 1 m is not separated from the crushed powder having a low oxygen content from the pulverizer, the oxygen content in the pulverizer is reduced to below 1000 ppm during crushing so that, in the subsequent sintering process, abnormal grain growth (AGG) rarely happens in the sintered magnet having a low oxygen content, the processes are simplified, and manufacturing costs are reduced.