Method for manufacturing high-performance NdFeB rare earth permanent magnetic device

Abstract

A method for manufacturing a high-performance NdFeB rare earth permanent magnetic device which is made of an RFeCoB-M strip casting alloy, a micro-crystal HRFe alloy fiber, and T.sub.mG.sub.n compound micro-powder, includes steps of: manufacturing the RFeCoB-M strip casting alloy, manufacturing the micro-crystal HRFe alloy fiber, providing hydrogen decrepitating, pre-mixing, powdering with jet milling, post-mixing, providing magnetic field pressing, sintering and ageing, wherein after a sintered NdFeB permanent magnet is manufactured, machining and surface-treating the sintered NdFeB permanent magnet for forming a rare earth permanent device.

Claims

1. A method for manufacturing a high-performance NdFeB rare earth permanent magnetic device, wherein the high-performance NdFeB rare earth permanent magnetic device is made of an RFeCoBM strip casting alloy, a micro-crystal HRFe alloy fiber, and T.sub.mG.sub.n compound micro-powder, wherein the R comprises at least two rare earth elements, wherein the R at least comprises Nd and Pr; the M is selected from a group consisting of Al, Co, Nb, Ga, Zr, Cu, V, Ti, Cr, Ni and Hf; the HR is selected from a group consisting of Dy, Tb, Ho and Y; the T.sub.mG.sub.n compound micro-powder is selected from a group consisting of La.sub.2O.sub.3, Ce.sub.2O.sub.3, Dy.sub.2O.sub.3, Tb.sub.2O.sub.3, Y.sub.2O.sub.3, Al.sub.2O.sub.3, ZrO.sub.2 and BN; Fe, B, Co, O and N are element symbols of corresponding elements; the method comprising steps of: (1) manufacturing the RFeCoBM strip casting alloy: firstly melting an RFeCoBM raw material under vacuum or argon protection with induction heating for forming an alloy, fining before casting the alloy in a melted state onto a rotation roller through a tundish, and cooling the alloy with the rotation roller for forming alloy flakes, outputting the alloy flakes after being cooled; wherein an average grain size of the strip casting alloy is 1-4 m; (2) manufacturing the micro-crystal HRFe alloy fiber: adding an HRFe alloy into a water-cooled cooper crucible of an arc-heating vacuum quenching furnace under an argon atmosphere, melting the HRFe alloy with an electric arc, contacting melted alloy liquid with a periphery of a water-cooled high-speed rotating molybdenum wheel, in such a manner that the melted alloy liquid is thrown out for forming the micro-crystal HRFe alloy fiber; wherein a speed of the periphery of the water-cooled high-speed rotating molybdenum wheel is higher than 10 m/s; (3) providing hydrogen decrepitating: sending the RFeCoBM strip casting alloy flakes and the micro-crystal HRFe alloy fiber into a vacuum hydrogen decrepitation device, evacuating before injecting hydrogen for hydrogen absorption, wherein a hydrogen absorption temperature is 80-120 C.; heating after hydrogen absorption and evacuating for dehydrogenating, wherein a dehydrogenating temperature is 350-900 C., a temperature keeping time is 3-15 h; cooling after temperature keeping, outputting after a temperature is lower than 80 C.; (4) pre-mixing: adding the alloy flakes which is hydrogen decrepitated in the step (3), the micro-crystal HRFe alloy fiber which is hydrogen decrepitated in the step (3) and the T.sub.mG.sub.n compound micro-powder into a mixer for pre-mixing, wherein pre-mixing is provided under nitrogen protection, a pre-mixing time is more than 30 min; powdering with nitrogen protected jet milling after mixing; (5) powdering with jet milling: after pre-mixing, adding powder into a hopper on a top portion of a feeder, moving the pre-mixed powder into a milling room through the feeder, milling with high-speed flow from a spray nozzle, wherein the powder milled rises with the flow; sorting powder suitable for powdering with a sorting wheel and collecting in a cyclone collector; wherein coarse powder unsuitable for powdering returns with a centrifugal force to the milling room for milling; storing the powder collected as an end product in a storage device under the cyclone collector, filtering super-fine powder outputted with outputting gas of the cyclone collector with a filter and storing in a super-fine powder collector under the filter; wherein the outputting gas enters a gas entry of a nitrogen compressor and then is compressed to 0.6-0.8 MPa by the nitrogen compressor before being sprayed through the spray nozzle, nitrogen is re-used, an oxygen content in a powdering atmosphere is less than 100 ppm; (6) post-mixing: sending the powder from the cyclone collector and the super-fine powder from the filter into the mixer under the nitrogen protection for being post-mixed under the nitrogen protection, wherein a post-mixing time is more than 60 min; after post-mixing, an average grain size of alloy powder is 1-4 m; (7) providing magnetic field pressing: sending the alloy powder into a nitrogen protection sealed magnetic field pressing machine under the nitrogen protection, weighting before adding to a cavity of a mould already assembled, then providing magnetic field pressing; after pressing, returning the mould to a powder feeder, opening the mould and obtaining a magnetic block; wrapping the magnetic block with a plastic or rubber bag under the nitrogen protection for isolating the magnetic block from air, so as to avoid isostatic pressing media immersing the magnetic block during isostatic pressing; then opening an discharging gate for mass-outputting the magnetic block; sending into an isostatic pressing machine for isostatic pressing, and then directly sending the magnetic block which is still wrapped into a nitrogen protection loading tank of a vacuum sintering furnace; unwrapping the magnetic block with gloves in the nitrogen protection loading tank and sending to a sintering case; and (8) sintering and ageing: sending the sintering case in the nitrogen protection loading tank of the vacuum sintering furnace into a heating chamber of the vacuum sintering furnace, evacuating before heating, keeping a temperature at 200-400 C. for 2-6 h, so as to remove organic impurities; and increasing and keeping the temperature at 400-600 C. for 5-12 h, so as to dehydrogenate and degas; then keeping the temperature at 600-1025 C. for 5-20 h, so as to pre-sinter; after pre-sintering, keeping the temperature at 1030-1070 C. for 1-5 h, so as to sinter; after sintering, firstly ageing at 800-950 C. and secondly ageing at 450-650 C.; after secondly ageing, rapidly cooling for forming a sintered NdFeB permanent magnet; machining and surface-treating the NdFeB permanent magnet for forming a rare earth permanent device.

2. The method, as recited in claim 1, wherein the T.sub.mG.sub.n compound micro-powder is selected from a group consisting of Dy.sub.2O.sub.3, Tb.sub.2O.sub.3 and Y.sub.2O.sub.3.

3. The method, as recited in claim 1, wherein the T.sub.mG.sub.n compound micro-powder is selected from a group consisting of Al.sub.2O.sub.3 and ZrO.sub.2.

4. The method, as recited in claim 1, wherein the T.sub.mG.sub.n compound micro-powder refers to compound micro-powder of BN.

5. The method, as recited in claim 1, wherein the R comprises at least two members selected from La, Ce, Gd, Nd and Pr, wherein the R at least comprises Nd and Pr.

6. The method, as recited in claim 1, wherein the R comprises at least two members selected from La, Ce, Gd, Dy, Nd and Pr, wherein the R at least comprises Nd and Pr.

7. The method, as recited in claim 1, wherein the R comprises La, Ce, Nd and Pr.

8. The method, as recited in claim 1, wherein an adding amount of the micro-crystal HRFe alloy fiber is 1-8 wt. %.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(1) Referring to preferred embodiments, the present invention is further illustrated.

(2) Preferred Embodiment 1

(3) Melting 600 Kg RFeB-M alloy selected from Table 1, casting the alloy in a melted state onto a rotation copper roller with a water cooling function, so as to be cooled for forming alloy flakes; manufacturing micro-crystal HRFe alloy fiber (80% HR) with a vacuum rapid-quenching furnace, wherein a rotation speed of a molybdenum wheel is 15 m/s; selecting micro-crystal DyFe alloy fiber and the RFeB-M alloy flakes with a ratio in Table 1 for hydrogen decrepitating; after hydrogen decrepitating, sending the micro-crystal DyFe alloy fiber and the RFeB-M alloy flakes into a mixer, then adding T.sub.mG.sub.n compound micro-powder with a ratio in Table 1; mixing under nitrogen protection for 60 min before powdering with jet milling; sending the powder from the cyclone collector and the super-fine powder from the filter into a post-mixer for being post-mixed, wherein post-mixing is provided under nitrogen protection with a mixing time of 90 min; an oxygen content in protection atmosphere is less than 100 ppm; then sending into a nitrogen protection magnetic field pressing machine for pressing, wherein an orientation magnetic field strength is 1.8 T, an in-cavity temperature is 3 C., a size of a magnet is 403020 mm, and an orientation direction is a 20 size direction; packaging in a protection tank after pressing, then outputting for isostatic pressing; sending into a sintering furnace for pre-sintering, wherein a pre-sintering temperature is kept at 910 C. for 15 h and a pre-sintering density is 7.2 g/cm.sup.3; then sintering, firstly ageing and secondly ageing, wherein a sintering is kept at 1070 C. for 1 h; obtaining a magnetic block for being machined, then measuring magnetic performance and weight loss, recording results in Table 1.

(4) Preferred Embodiment 2

(5) Melting 600 Kg RFeB-M alloy selected from Table 1, melting an RFeCoB-M raw material under vacuum or argon protection with induction heating for forming an alloy, fining at 1400-1470 C. before casting the alloy in a melted state onto a rotation copper roller with a rotation speed of 1 m/s through a tundish, and cooling the alloy with the rotation roller for forming alloy flakes, wherein after leaving the rotation copper roller, the alloy flakes drop to a rotation disk for secondary cooling; manufacturing micro-crystal HRFe alloy fiber (80% HR) with a vacuum rapid-quenching furnace, wherein a rotation speed of a molybdenum wheel is 18 m/s; selecting micro-crystal DyFe alloy fiber and the RFeB-M alloy flakes with a ratio in Table 1 for hydrogen decrepitating; after hydrogen decrepitating, sending the micro-crystal DyFe alloy fiber and the RFeBM alloy flakes into a mixer, then adding T.sub.mG.sub.n compound micro-powder with a ratio in Table 1; mixing under nitrogen protection for 90 min before powdering with jet milling; sending the powder from the cyclone collector and the super-fine powder from the filter into a post-mixer for being post-mixed, wherein post-mixing is provided under nitrogen protection with a mixing time of 120 min; an oxygen content in protection atmosphere is less than 100 ppm; then sending into a nitrogen protection magnetic field pressing machine for pressing, wherein an orientation magnetic field strength is 1.8 T, an in-cavity temperature is 4 C., a size of a magnet is 403020 mm, and an orientation direction is a 20 size direction; packaging in a protection tank after pressing, then outputting for isostatic pressing; sending into a sintering furnace for pre-sintering, wherein a pre-sintering temperature is kept at 950 C. for 12 h and a pre-sintering density is 7.3 g/cm.sup.3; then sintering, firstly ageing and secondly ageing, wherein a sintering is kept at 1060 C. for 2 h; obtaining a magnetic block for being machined, then measuring magnetic performance and weight loss, recording results in Table 1.

(6) Preferred Embodiment 3

(7) Melting 600 Kg RFeB-M alloy selected from Table 1, melting an RFeCoB-M raw material under vacuum or argon protection with induction heating for forming an alloy, fining at 1400-1470 C. before casting the alloy in a melted state onto a rotation copper roller with a rotation speed of 2 m/s through a tundish, and cooling the alloy with the rotation roller for forming alloy flakes, wherein after leaving the rotation copper roller, the alloy flakes drop; crushing the alloy flakes and sending into a receiving tank, then cooling the alloy flakes with inert gas; manufacturing micro-crystal HRFe alloy fiber (80% HR) with a vacuum rapid-quenching furnace, wherein a rotation speed of a molybdenum wheel is 22 m/s; selecting micro-crystal DyFe alloy fiber and the RFeB-M alloy flakes with a ratio in Table 1 for hydrogen decrepitating; after hydrogen decrepitating, sending the micro-crystal DyFe alloy fiber and the RFeB-M alloy flakes into a mixer, then adding T.sub.mG.sub.n compound micro-powder with a ratio in Table 1; mixing under nitrogen protection for 90 min before powdering with jet milling; sending the powder from the cyclone collector and the super-fine powder from the filter into a post-mixer for being post-mixed, wherein post-mixing is provided under nitrogen protection with a mixing time of 120 min; an oxygen content in protection atmosphere is less than 100 ppm; then sending into a nitrogen protection magnetic field pressing machine for pressing, wherein a size of a magnet is 403020 mm, and an orientation direction is a 20 size direction; packaging in a protection tank after pressing, then outputting for isostatic pressing; sending into a sintering furnace for pre-sintering, wherein a pre-sintering temperature is kept at 990 C. for 10 h and a pre-sintering density is 7.3 g/cm.sup.3; then sintering, firstly ageing and secondly ageing, wherein a sintering is kept at 1050 C. for 3 h; obtaining a magnetic block for being machined, then measuring magnetic performance and weight loss, recording results in Table 1.

(8) Preferred Embodiment 4

(9) Melting 600 Kg RFeB-M alloy selected from Table 1, melting a RFeCoB-M raw material under vacuum or argon protection with induction heating for forming an alloy, fining at 1400-1470 C. before casting the alloy in a melted state onto a rotation copper roller with a rotation speed of 4 m/s through a tundish, and cooling the alloy with the rotation roller for forming alloy flakes, wherein a temperature of the alloy flakes is more than 400 C. and less than 700 C., after leaving the rotation copper roller, the alloy flakes drop to a cooling plate for secondary cooling to a temperature of less than 400 C.; crushing the alloy flakes and then keeping the temperature at 200-600 C. before cooling the alloy flakes with inert gas; manufacturing micro-crystal HRFe alloy fiber (80% HR) with a vacuum rapid-quenching furnace, wherein a rotation speed of a molybdenum wheel is 25 m/s; selecting micro-crystal DyFe alloy fiber and the RFeB-M alloy flakes with a ratio in Table 1 for hydrogen decrepitating; after hydrogen decrepitating, sending the micro-crystal DyFe alloy fiber and the RFeB-M alloy flakes into a mixer, then adding T.sub.mG.sub.n compound micro-powder with a ratio in Table 1; mixing under nitrogen protection for 120 min before powdering with jet milling; sending the powder from the cyclone collector and the super-fine powder from the filter into a post-mixer for being post-mixed, wherein post-mixing is provided under nitrogen protection with a mixing time of 120 min; an oxygen content in protection atmosphere is less than 100 ppm; then sending into a nitrogen protection magnetic field pressing machine for pressing, wherein a size of a magnet is 403020 mm, and an orientation direction is a 20 size direction; packaging in a protection tank after pressing, then outputting for isostatic pressing; sending into a sintering furnace for pre-sintering, wherein a pre-sintering temperature is kept at 1010 C. for 8 h and a pre-sintering density is 7.3 g/cm.sup.3; then sintering, firstly ageing and secondly ageing, wherein a sintering is kept at 1040 C. for 4 h; obtaining a magnetic block for being machined, then measuring magnetic performance and weight loss, recording results in Table 1.

(10) Preferred Embodiment 5

(11) Melting 600 Kg RFeB-M alloy selected from Table 1, casting the alloy in a melted state onto a rotation copper roller with a water cooling function, so as to be cooled for forming alloy flakes; manufacturing micro-crystal HRFe alloy fiber (80% HR) with a vacuum rapid-quenching furnace, wherein a rotation speed of a molybdenum wheel is 28 m/s; selecting micro-crystal DyFe alloy fiber and the RFeB-M alloy flakes with a ratio in Table 1 for hydrogen decrepitating; after hydrogen decrepitating, sending the micro-crystal DyFe alloy fiber and the RFeB-M alloy flakes into a mixer, then adding T.sub.mG.sub.n compound micro-powder with a ratio in Table 1; mixing under nitrogen protection for 120 min before powdering with jet milling; sending the powder from the cyclone collector into a post-mixer for being post-mixed, wherein post-mixing is provided under nitrogen protection with a mixing time of 150 min; then sending into a nitrogen protection magnetic field pressing machine for pressing, wherein a size of a magnet is 403020 mm, and an orientation direction is a 20 size direction; packaging in a protection tank after pressing, then outputting for isostatic pressing; sending into a sintering furnace for pre-sintering, wherein a pre-sintering temperature is kept at 1020 C. for 6 h and a pre-sintering density is 7.4 g/cm.sup.3; then sintering, firstly ageing and secondly ageing, wherein a sintering is kept at 1030 C. for 5 h; obtaining a magnetic block for being machined, then measuring magnetic performance and weight loss, recording results in Table 1.

(12) Contrast Example

(13) Melting 600 Kg RFeB-M alloy selected from Table 1, casting the alloy in a melted state onto a rotation copper roller with a water cooling function, so as to be cooled for forming alloy flakes; hydrogen decrepitating before powdering with jet milling; then sending into a nitrogen protection magnetic field pressing machine for pressing, wherein an orientation magnetic field strength is 1.8 T, an in-cavity temperature is 3 C., a size of a magnet is 403020 mm, and an orientation direction is a 20 size direction; packaging in a protection tank after pressing, then outputting for isostatic pressing; sending into a sintering furnace for sintering, firstly ageing and secondly ageing,; obtaining a magnetic block for being machined, then measuring magnetic performance and weight loss, recording results in Table 1.

(14) TABLE-US-00001 TABLE 1 compound and performance in preferred embodiments and contrast example preferred preferred preferred preferred preferred preferred contrast embodiment embodiment 1 embodiment 1 embodiment 2 embodiment 3 embodiment 4 embodiment 5 example R-Fe- Nd 20 20 20 20 20 20 20 B-M Pr 5 5 5 5 5 5 5 alloy Dy 0 1 2 3 4 4 4 (Wt %) Tb 2 2 0 0.5 1 2 2 Fe the rest the rest the rest the rest the rest the rest the rest Co 2.4 2.4 2.4 2.4 2.4 2.4 2.4 Cu 0.2 0.2 0.2 0.2 0.2 0.2 0.2 B 0.9 0.9 0.9 0.9 0.9 0.9 0.9 Al 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Ga 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Zr 0.1 0.1 0.1 0.1 0.1 0.1 0.1 HR-Fe Dy-Fe 4 3 2 1 (Wt %) Tb-Fe 2 1.5 1 T.sub.mG.sub.n Dy.sub.2O.sub.3 0.01 0.01 0.03 0.05 0.1 (Wt %) Tb.sub.2O.sub.3 0.01 0.01 0.03 0.05 0.1 Y.sub.2O.sub.3 0.01 0.02 Al.sub.2O.sub.3 0.01 0.01 0.02 0.03 0.05 0.1 ZrO 0.01 0.05 BN 0.01 0.03 total 0.03 0.04 0.06 0.12 0.2 0.3 magnetic energy 40.7 41.2 42.6 41.5 39.8 38.8 38.5 product (MGOe) coercivity (KOe) 23.9 24.9 26.5 24.7 23.3 21.6 20.5 weight loss 1.3 1.2 0.9 0.7 1.8 2.7 5.4 (mg/cm.sup.2)

(15) It is further illustrated by the preferred embodiments and the contrast example that the method and the device according to the present invention significantly improve magnetic performance. Compared with Dy infiltration technology, the present invention is low in cost, and is not limited by shapes and sizes of magnets. Therefore, the method and the device have a brilliant future.

(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.