Method and equipment for processing NdFeB rare earth permanent magnetic alloy with hydrogen pulverization

Abstract

A method and an equipment for processing NdFeB rare earth permanent magnetic alloy with a hydrogen pulverization are provided. The method includes steps of: providing a continuous hydrogen pulverization equipment; while driving by a transmission device, passing a charging box loaded with rare earth permanent magnetic alloy flakes orderly through a hydrogen absorption chamber, having a temperature of 50-350 C. for absorbing hydrogen, a heating and dehydrogenating chamber, having a temperature of 600-900 C. for dehydrogenating, and a cooling chamber of the continuous hydrogen pulverization equipment; receiving the charging box by a discharging chamber through a discharging valve; pouring out the alloy flakes after the hydrogen pulverization into a storage tank at a lower part of the discharging chamber; sealing up the storage tank under a protection of nitrogen; and, moving the charging box out through a discharging door of the discharging chamber and re-loading, for repeating the previous steps.

Claims

1. A method for processing NdFeB rare earth permanent magnetic alloy with a hydrogen pulverization, comprising steps of: providing a continuous hydrogen pulverization equipment for hydrogen pulverizing rare earth permanent magnetic alloy; loading rare earth permanent magnetic alloy flakes into a charging box; subjecting the rare earth permanent magnetic alloy flakes to hydrogen pulverization by passing the charging box which is driven by a transmission device orderly through a hydrogen absorption chamber, a heating and dehydrogenating chamber and a cooling chamber of the continuous hydrogen pulverization equipment, wherein a quantitative hydrogen filling device is provided in the heating and dehydrogenating chamber and a certain amount of the hydrogen is filled in before dehydrogenating is over; receiving the charging box by a discharging chamber through a discharging valve; pouring out the alloy flakes after the hydrogen pulverization into a storage tank at a lower part of the discharging chamber; sealing up the storage tank under a protection of nitrogen; and moving the charging box out through a discharging door of the discharging chamber and re-loading the charging box for repeating the previous steps; wherein: the hydrogen absorption chamber has a temperature controlled at between 50 C. and 350 C. for absorbing hydrogen; and the continuous hydrogen pulverization equipment comprises at least one heating and dehydrogenating chamber, having a temperature controlled at between 600 C. and 900 C. for dehydrogenating, and at least one cooling chamber.

2. The method for processing the NdFeB rare earth permanent magnetic alloy with the hydrogen pulverization, as recited in claim 1, wherein: the continuous hydrogen pulverization equipment comprises two heating and dehydrogenating chambers, wherein the charging box stays in the two heating and dehydrogenating chambers successively while staying in each heating and dehydrogenating chamber for between 2 hours and 6 hours; and the continuous hydrogen pulverization equipment comprises two cooling chambers, wherein the charging box stays in the two cooling chambers successively while staying in each cooling chamber for between 2 hours and 6 hours.

3. The method for processing the NdFeB rare earth permanent magnetic alloy with the hydrogen pulverization, as recited in claim 1, wherein: the continuous hydrogen pulverization equipment comprises three heating and dehydrogenating chambers, wherein the charging box stays in the three heating and dehydrogenating chambers successively while staying in each heating and dehydrogenating chamber for between 1 hour and 4 hours; and the continuous hydrogen pulverization equipment comprises three cooling chambers, wherein the charging box stays in the three cooling chambers successively while staying in each cooling chamber for between 1 hour and 4 hours.

4. The method for processing the NdFeB rare earth permanent magnetic alloy with the hydrogen pulverization, as recited in claim 1, wherein a heater is provided in the hydrogen absorption chamber and the hydrogen absorption chamber has a temperature controlled at a range of 80-300 C. for heating.

5. A method for preparing a NdFeB rare earth permanent magnet, comprising steps of: casting rare earth permanent magnetic alloy into alloy flakes; hydrogen pulverizing the alloy flakes a continuous hydrogen pulverization equipment, comprising steps of: loading the alloy flakes into a charging box; passing the charging box which is driven by a transmission device orderly through a feeding valve, a hydrogen absorption chamber, a hydrogen absorption valve, a heating and dehydrogenating chamber, chamber isolating valves and a cooling chamber of the continuous hydrogen pulverization equipment; receiving the charging box by a discharging chamber through a discharging valve; pouring out the alloy flakes after the hydrogen pulverization into a storage tank at a lower part of the discharging chamber; sealing up the storage tank under a protection of nitrogen; and moving the charging box out through a discharging door of the discharging chamber and re-loading the charging box, for repeating the previous steps, wherein a quantitative hydrogen filling device is provided in the heating and dehydrogenating chamber and a certain amount of the hydrogen is filled in before dehydrogenating is over; sending the storage tank into a mixing device for pre-mixing; after the pre-mixing, powdering the alloy flakes into alloy powder by a jet mill under the protection of nitrogen; then obtaining a rare earth permanent magnet via compacting in a magnetic field and sintering; and finally processing the rare earth permanent magnet by machining and a surface treatment.

6. The method for preparing the NdFeB rare earth permanent magnet, as recited in claim 5, further comprising a step of adding a lubricant or an antioxidant into the storage tank, before the step of sending the storage tank into the mixing device for pre-mixing.

7. The method for preparing the NdFeB rare earth permanent magnet, as recited in claim 5, further comprising a step of adding T.sub.2O.sub.3 micro powder into the storage tank, before the step of sending the storage tank into the mixing device for pre-mixing, wherein T.sub.2O.sub.3 is at least one member selected from the group consisting of Dy.sub.2O.sub.3, Tb.sub.2O.sub.3, Ho.sub.2O.sub.3, Y.sub.2O.sub.3, Al.sub.2O.sub.3 and Ti.sub.2O.sub.3.

8. The method for preparing the NdFeB rare earth permanent magnet, as recited in claim 5, further comprising a step of mixing the alloy powder, after the step of powdering the alloy flakes into the alloy powder by the jet mill under the protection of nitrogen and before the step of compacting in the magnetic field.

9. The method for preparing the NdFeB rare earth permanent magnet, as recited in claim 5, wherein the step of obtaining the NdFeB rare earth permanent magnet via compacting in the magnetic field and sintering comprises steps of: compacting by a sealed magnetic field compressor under the protection of nitrogen and obtaining a magnet block; packaging the magnet block and extracting the magnet block out of the sealed magnetic field compressor under the protection of nitrogen; processing the magnet block with isostatic pressing and then sintering.

10. The method for preparing the NdFeB rare earth permanent magnet, as recited in claim 5, wherein the NdFeB permanent magnet comprises a main phase and a grain boundary phase; the main phase has a structure of R.sub.2(Fe,Co).sub.14B, wherein a heavy rare earth HR content between the edge of a main phase grain to a location which is of the distance from the edge to the center of the main phase gain is higher than a heavy rare earth HR content at the center of the main phase grain; the grain boundary phase has micro particles of Nd.sub.2O.sub.3; R comprises at least Nd; and HR is at least one member selected from the group consisting of Dy, Tb, Ho and Y.

11. The method for preparing the NdFeB rare earth permanent magnet, as recited in claim 5, wherein the NdFeB permanent magnet has a metal phase structure comprising a ZR.sub.2(Fe.sub.1-xCo.sub.x).sub.14B phase and a R.sub.2(Fe.sub.1-xCo.sub.x).sub.14B phase, the ZR.sub.2(Fe.sub.1-xCo.sub.x).sub.14B phase surrounds the R.sub.2(Fe.sub.1-xCo.sub.x).sub.14B phase and has a higher heavy rare earth content that the R.sub.2(Fe.sub.1-xCo.sub.x).sub.14B phase, no grain boundary phase exists between ZR.sub.2(Fe.sub.1-xCo.sub.x).sub.14B phase and the R.sub.2(Fe.sub.1-xCo.sub.x).sub.14B phase; wherein ZR represents total rare earth elements of the ZR.sub.2(Fe.sub.1-xCo.sub.x).sub.14B phase and the heavy rare earth content in the ZR.sub.2(Fe.sub.1-xCo.sub.x).sub.14B phase is higher than an average content of heavy rare earth elements in the NdFeB rare earth permanent magnet; 0x0.5.

12. The method for preparing the NdFeB rare earth permanent magnet, as recited in claim 5, wherein micro particles of Nd.sub.2O.sub.3 are provided in a grain boundary phase at boundaries of at least two grains of a ZR.sub.2(Fe.sub.1-xCo.sub.x).sub.14B phase of a metal phase structure of the NdFeB permanent magnet.

13. The method for preparing the NdFeB rare earth permanent magnet, as recited in claim 5, wherein micro particles of T.sub.2O.sub.3 and Nd.sub.2O.sub.3 are provided in a grain boundary phase at boundaries of at least two grains of a ZR.sub.2(Fe.sub.1-xCo.sub.x).sub.14B phase of a metal phase structure of the NdFeB permanent magnet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a front view of a continuous hydrogen pulverization equipment for NdFeB rare earth permanent magnetic alloy according to preferred embodiments of the present invention.

(2) FIG. 2 is a top view of the continuous hydrogen pulverization equipment according to the preferred embodiments of the present invention.

(3) FIG. 3 is a process curve of a hydrogen pulverization according to the preferred embodiments of the present invention.

(4) In the figures, 1: feeding valve; 2: hydrogen absorption chamber; 3: hydrogen absorption valve; 4: first heating and dehydrogenating chamber; 5: first chamber isolating valve; 6: second heating and dehydrogenating chamber; 7: quantitative hydrogen filling device; 8: second chamber isolating valve; 9: first cooling chamber; 10: third chamber isolating valve; 11: second cooling chamber; 12: discharging valve; 13: discharging chamber; 14: discharging door of the discharging chamber; 15: first heater; 16: second heater; 17: first heat preservation screen; 18: third heater; 19: second heat preservation screen; 20: cooling fan; 21: heat exchanger; 22: connecting pipe; 23: valve; 24: storage tank; 25: guide rail; 26: transport cart; 27: charging box.

(5) As showed in the figures, the feeding valve 1 is connected with a feeding port of the hydrogen absorption chamber 2; a discharging port of the hydrogen absorption chamber 2 is connected with the hydrogen absorption valve 3; the hydrogen absorption valve 3 is connected with a feeding port of the first heating and dehydrogenating chamber 4; a discharging port of the first heating and dehydrogenating chamber 4 is connected with the first chamber isolating valve 5; the first chamber isolating valve 5 is connected with a feeding port of the second heating and dehydrogenating chamber 6; a discharging port of the second heating and dehydrogenating chamber 6 is connected with the second chamber isolating valve 8; the second isolating valve 8 is connected with a feeding port of the first cooling chamber 9; a discharging port of the first cooling chamber 9 is connected with the third chamber isolating valve 10; the third chamber isolating valve 10 is connected with a feeding port of the second cooling chamber 11; a discharging port of the second cooling chamber 11 is connected with the discharging valve 12; the discharging valve 12 is connected with a feeding port of the discharging chamber 13; a final port of the discharging chamber 13 is connected with the discharging door 14 of the discharging chamber; the first heater 15 is provided in the hydrogen absorption chamber 2; the second heater 16 is provided in the first heating and dehydrogenating chamber 4; the first heat preservation screen 17 is provided outside the second heater 16; the third heater 18 is provided in the second heating and dehydrogenating chamber 6; the second heat preservation screen 19 is provided outside the third heater 18; the second heating and dehydrogenating chamber 6 is further connected with the quantitative hydrogen filling device 7; the cooling fan 20 and the heat exchanger 21 are provided in the first cooling chamber 9; the connecting pipe 22 is provided at a lower part of the discharging chamber 13; the connecting pipe 22 is connected with the storage tank 24 through the valve 23; the guide rail 25 is provided at an upper part of the hydrogen absorption chamber 2, the first heating and dehydrogenating chamber 4, the second heating and dehydrogenating chamber 6, the first cooling chamber 9 and the discharging chamber 13; the transport cart 26 with rolling wheels is provided on the guide rail 25; the charging box 27, hanging below the transport cart 26, successively passes through the chambers; and an evacuating machine set and a gas filling system are arranged in each of the hydrogen absorption chamber 2, the first heating and dehydrogenating chamber 4, the second heating and dehydrogenating chamber 6, the first cooling chamber 9 and the discharging chamber 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(6) The present invention is further illustrated through following embodiments.

First Embodiment

(7) Alloy raw materials having a magnetic component of Nd.sub.30Dy.sub.1Co.sub.1.2Cu.sub.0.1B.sub.0.9Al.sub.0.1Fe.sub.rest and Dy.sub.2O.sub.3 micro powder were heated up over 500 C. in vacuum. Argon was filled, and RFeB-M raw materials were further heated to melt and refine into a smelt alloy liquid. Thereafter, the smelt alloy liquid was casted into a rotating roller with water quenching through an intermediate tundish, so as to obtain alloy flakes. A continuous vacuum hydrogen pulverization furnace was provided for a hydrogen pulverization, wherein the alloy flakes were firstly loaded into a hanging charging box; and then the charging box was orderly sent into a hydrogen absorption chamber, a heating and dehydrogenating chamber and a cooling chamber of the continuous vacuum hydrogen pulverization furnace, respectively for absorbing hydrogen, heating to dehydrogenate and cooling. Then, in a protective atmosphere, the alloy flakes after the hydrogen pulverization were loaded into a storage tank. A process curve of the hydrogen pulverization is showed as FIG. 3, wherein: the charging box, loading with the alloy flakes, was firstly sent into the hydrogen absorption chamber; hydrogen was filled after evacuating the hydrogen absorption chamber to 510.sup.1 Pa; then the hydrogen absorption chamber was heated, and a hydrogen filling speed and heating power were adjusted for maintaining the hydrogen absorption chamber at a temperature of 260-290 C. for 2 hours for absorbing the hydrogen; thereafter, the charging box was sent into the heating and dehydrogenating chamber for dehydrogenating at a temperature of 660-690 C. for 6 hours, wherein at ten minutes before the dehydrogenating was over, an evacuating valve was closed to stop evacuating and a certain amount of the hydrogen was filled; then the charging box was sent into the cooling chamber, argon was filled and a cooling fan was initiated for cooling the charging box for 6 hours. The alloy flakes, after the hydrogen pulverization, were mixed and then powdered by a jet mill. Powder was mixed by a mixing device under a protection of nitrogen, and then sent to be compacted into a magnet block by a sealed magnetic field compressor of the present invention. A protective box having an oxygen content of 150 ppm, an alignment magnetic field intensity of 1.8 T, and a mold chamber inner temperature of 3 C. was provided. The magnet block had a size of 62 mm52 mm42 mm, and was aligned at a direction of the 42 mm; and after compacting, the magnet block was sealed in the protective box. The magnet block was extracted out of the protective box for isostatic pressing at an isostatic pressure of 200 MPa. Then, under the protection of the nitrogen, the magnet block was sent into a continuous vacuum sintering furnace for sintering; while driving by a transmission device, a loading frame loaded with the magnet block was orderly sent into a preparation chamber, a pre-heating and degreasing chamber, a first degassing chamber, a second degassing chamber, a pre-sintering chamber, a sintering chamber, an aging treatment chamber and a cooling chamber of the continuous vacuum sintering furnace, respectively for removing organic impurities via pre-heating, heating to dehydrogenate and degas, pre-sintering, sintering, aging and cooling; after cooling, the magnet block was extracted out of the continuous vacuum sintering furnace and then sent into a vacuum aging treatment furnace for a second aging treatment, wherein the second aging treatment is executed at a temperature of 450-650 C.; after the second aging treatment, the magnet block was rapidly quenched, and sintered NdFeB rare earth permanent magnet was obtained; and then, the sintered NdFeB rare earth permanent magnet was processed into a NdFeB rare earth permanent magnetic device through machining and a surface treatment. As showed in Table 1, absorbing the hydrogen at a temperature of 260-290 C. and dehydrogenating at a temperature of 660-690 C. greatly increase performance of the magnet.

(8) First Comparison

(9) Alloy raw materials having a magnetic component of Nd.sub.30Dy.sub.1Co.sub.1.2Cu.sub.0.1B.sub.0.9Al.sub.0.1Fe.sub.rest, the same as the alloy raw materials of the first embodiment, were conventionally smelted into alloy flakes. Then the alloy flakes were conventionally processed with a hydrogen pulverization, powdering by a jet mill, compacting in a magnetic field, sintering and an aging treatment to form a magnet. Performance of the magnet is also showed in Table 1. By comparing, benefits of the present invention are showed.

(10) TABLE-US-00001 TABLE 1 Influences of temperature of absorbing hydrogen and temperature of dehydrogenating on performance of magnet Magnetic T. of energy absorb- Mag- product ing T. of netic Coer- (MGOe) + hydro- dehydro- energy cive coercive Weight- gen genating product force force lessness Order ( C.) ( C.) (MGOe) (KOe) (KOe) (g/cm.sup.2) 1 260 660 48.3 19.2 67.5 3.3 2 260 670 49.5 20.3 69.8 3.5 3 260 680 49.2 20.6 69.8 2.3 4 260 690 48.4 20.1 68.5 2.1 5 270 690 48.1 20.6 68.7 2.6 6 270 685 48.8 21.4 70.2 3.5 7 280 680 49.8 21.8 71.6 3.3 8 280 675 49.5 22.4 72.9 3.2 9 290 670 48.9 21.6 71.5 3.5 10 290 665 48.6 21.1 69.7 3.3 First 0 0 47.6 17.5 65.1 6.8 compar- ison

Second Embodiment

(11) Alloy raw materials having a magnetic component of (Pr.sub.0.2Nd.sub.0.8).sub.22.5Dy.sub.2.5Co.sub.1.2Cu.sub.0.3B.sub.0.9Al.sub.0.2Fe.sub.rest were heated up over 500 C. in vacuum. Argon was filled and RFeB-M raw materials ware further heated to melt and refine into a smelt alloy liquid, wherein T.sub.2O.sub.3 micro powder was added. Thereafter, the smelt alloy liquid was casted into a rotating roller with water quenching through an intermediate tundish, so as to obtain alloy flakes. A continuous vacuum hydrogen pulverization furnace was provided for a hydrogen pulverization, wherein the alloy flakes were firstly loaded into a hanging charging box; and then the charging box was orderly sent into a hydrogen absorption chamber, a heating and dehydrogenating chamber and a cooling chamber of the continuous vacuum hydrogen pulverization furnace, respectively for absorbing hydrogen, heating to dehydrogenate and cooling. Then, in a protective atmosphere, the alloy flakes after the hydrogen pulverization were loaded into a storage tank. The charging box, loading with the alloy flakes, was firstly sent into the hydrogen absorption chamber; hydrogen was filled after evacuating the hydrogen absorption chamber to 5 Pa; then the hydrogen absorption chamber was heated, and a hydrogen filling speed and heating power were adjusted for maintaining the hydrogen absorption chamber at a temperature of 210-240 C. for 4 hours for absorbing the hydrogen; thereafter, the charging box was sent into the heating and dehydrogenating chamber for dehydrogenating at a temperature of 660-690 C. for 8 hours, wherein at ten minutes before the dehydrogenating was over, an evacuating valve was closed to stop evacuating and a certain amount of the hydrogen was filled; then the charging box was sent into the cooling chamber, argon was filled and a cooling fan was initiated for cooling the charging box for 8 hours. The alloy flakes, after the hydrogen pulverization, were mixed and then powdered by a jet mill under a protection of nitrogen. Powder was mixed by a mixing device under the protection of the nitrogen, and then sent to be compacted into a magnet block by automatically compacting in a magnetic field, as described in the present invention. The magnet block had a size of 62 mm52 mm42 mm, and was aligned at a direction of the 42 mm. After compacting, the magnet block was sent into a continuous vacuum pre-sintering furnace for pre-sintering; after the pre-sintering, the magnet block was sent into a continuous vacuum sintering aging furnace for sintering, aging at a high temperature, pre-cooling and aging at a low temperature. Influences of oxide micro powder and adding the certain amount of the hydrogen are showed in Table 2. As showed in the Table 2, adding Tb.sub.2O.sub.3, Dy.sub.2O.sub.3, Al.sub.2O.sub.3 and Y.sub.2O.sub.3 and filling the certain amount of hydrogen are able to greatly increase performance of the magnet.

(12) Second Comparison

(13) Alloy raw materials having a magnetic component of Nd.sub.30Dy.sub.1Co.sub.1.2Cu.sub.0.1B.sub.0.9Al.sub.0.1Fe.sub.rest, the same as the alloy raw materials of the first embodiment, were conventionally smelted into alloy flakes. Then the alloy flakes were conventionally processed with a hydrogen pulverization, powdering by a jet mill, compacting in a magnetic field, sintering and an aging treatment to form a magnet. Performance of the magnet is showed in Table 2. By comparing, benefits of the present invention are showed.

(14) TABLE-US-00002 TABLE 2 Influences of oxide micro powder and adding certain amount of hydrogen on performance of magnet Magnetic energy Adding a Mag- product certain netic Coer- (MGOe) + Oxide amount of energy cive coercive Weight- micro hydrogen product force force lessness Order powder or not (MGOe) (KOe) (KOe) (g/cm.sup.2) 1 Al.sub.2O.sub.3 Yes 41.1 27.2 68.3 3.4 2 Al.sub.2O.sub.3 No 40.5 27.8 68.3 3.8 3 Dy.sub.2O.sub.3 Yes 41.8 28.4 70.2 3.6 4 Dy.sub.2O.sub.3 No 40.4 28.6 69.0 3.8 5 Tb.sub.2O.sub.3 Yes 41.5 28.1 69.6 4.3 6 Tb.sub.2O.sub.3 No 40.3 27.4 67.7 4.5 7 Y.sub.2O.sub.3 Yes 41.7 29.2 70.9 4.3 8 Y.sub.2O.sub.3 No 40.9 28.5 69.4 4.1 Second 0 0 39.1 24.6 63.7 6.2 compar- ison

(15) By comparing the embodiments with the comparisons, the method and the equipment provided by the present invention greatly improve performance of the NdFeB permanent magnet and own a broad development prospect.

(16) One skilled in the art will understand that the embodiment of the present invention as shown in the drawings and described above is exemplary only and not intended to be limiting.

(17) It will thus be seen that the objects of the present invention have been fully and effectively accomplished. Its embodiments have been shown and described for the purposes of illustrating the functional and structural principles of the present invention and is subject to change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.