Low-cost double-main-phase Ce permanent magnet alloy and its preparation method

Abstract

The invention discloses a low-cost double-main-phase Ce permanent magnet alloy and its preparation method, and belongs to technical field of rare earth permanent magnet material. The Ce permanent magnet alloy has a chemical formula of (Ce.sub.x,Re.sub.1-x).sub.aFe.sub.100-a-b-cB.sub.bTM.sub.c in mass percent, wherein 0.4x0.8, 29a33, 0.8b1.5, 0.5c2, Re is one or more selected from Nd, Pr, Dy, Tb and Ho elements, and TM is one or more selected from Ga, Co, Cu, Nb and Al elements; the Ce permanent magnet alloy has a double-main-phase structure with a low H.sub.A phase in (Ce,Re)FeB and a high H.sub.A phase in NdFeB. The double-main-phase Ce permanent magnet alloy of the present invention prepared by using a double-main-phase alloy method greatly lowers the production cost of magnet while maintaining excellent magnetic performances.

Claims

1. A low-cost double-main-phase Ce permanent magnet alloy, characterized in that its chemical formula in mass percent is (Ce.sub.x,Re.sub.1-x).sub.aFe.sub.100-a-b-cB.sub.bTM.sub.c, wherein, 0.4x0.8, 29a33, 0.8b1.5, 0.5c2, Re is one or more selected from Nd, Pr, Dy, Tb and Ho elements, and TM is one or more selected from Ga, Co, Cu, Nb and Al elements; the said Ce permanent magnet alloy has a 2:14:1 type double-main-phase structure as follows: with a low HA second magnetic phase in (Ce,Re)FeB and a high HA first magnetic phase in NdFeB; the double-main-phase Ce permanent magnet alloy was prepared by two different kinds of main phase alloys with a double-main-phase method; the double-main-phase Ce permanent magnet alloy was prepared by following two different kinds of main phase alloys with a double-main-phase method: the first main phase alloy has the composition of Nd.sub.aFe.sub.100-a-b-cB.sub.bTM.sub.c in mass percent, wherein 27a33, 0.8b1.5, 0.5c2 and TM is one or more selected from Ga, Co, Cu, Nb and Al elements; the second main phase alloy has the composition of (Ce.sub.x1,Re.sub.1-x1).sub.aFe.sub.100-a-b-cB.sub.bTM.sub.c in mass percent, wherein 0.4x10.9, 29a33, 0.8b1.5, 0.5c2, Re is one or more selected from Nd, Pr, Dy, Tb and Ho elements, and TM is one or more selected from Ga, Co, Cu, Nb and Al elements; the said two raw materials are prepared respectively; the double main phases of the alloy are (Ce,Re).sub.2Fe.sub.14B structure and Nd.sub.2Fe.sub.14B structure.

2. The double-main-phase Ce permanent magnet alloy as claim 1, wherein said Re is Nd, Pr, Dy, and said TM is Ga, Co, Cu, Nb.

3. The double-main-phase Ce permanent magnet alloy as claim 1, wherein in said Ce permanent magnet alloy, the content of Ce accounts for 40% to 80% of the total weight of rare earth, and the content of Nd is less than 50% of the total weight of the rare earth.

4. A preparation method of the double-main-phase Ce permanent magnet alloy as claim 1, comprising (1) preparing two different main phase alloys using a double-main-phase alloy method, the first main phase alloy has the composition of Nd.sub.aFe.sub.100-a-b-cB.sub.bTM.sub.c in mass percent, wherein 27a33, 0.8b1.5, 0.5c2 and TM is one or more selected from Ga, Co, Cu, Nb and Al elements; the second main phase alloy has the composition of (Ce.sub.x,Re.sub.1-x).sub.aFe.sub.100-a-b-cB.sub.bTM.sub.c in mass percent, wherein 0.4x0.9, 29a33, 0.8b1.5, 0.5c2, Re is one or more selected from Nd, Pr, Dy, Tb and Ho elements, and TM is one or more selected from Ga, Co, Cu, Nb and Al elements; the said two raw materials are prepared respectively; (2) smelting the two raw materials prepared in step (1) respectively to obtain the rapid solidified strips with a uniform thickness of 0.1 to 0.5 mm; (3) conducting hydrogen crash for the two kinds of rapid solidified strip obtained from step (2) respectively and get the coarse crashed magnetic powders after dehydrogenization; afterwards, conduct jet milling on the coarse crashed magnetic powders respectively under a protective atmosphere of inert gas to obtain two kinds of magnetic powders with approximate particle sizes which is in the range of 16 m; (4) according to requirements of composition of different grades of permanent magnet alloys, weighing two kinds of magnetic powder prepared in step (3) respectively at different proportions and then mix them in a mixer; (5) under the protective atmosphere of inert gases, conducting oriented forming for the mixed magnetic powders in a magnetic field of 1.5 to 2.3 T, and then conduct cool isostatic compression processing to obtain green bodies; (6) put the green bodies after oriented forming and cool isostatic compression into a sintering furnace with a high vacuum for sintering; during a sintering process, heating for 0.5 h to 10 h at 400 C. to 800 C. for dehydrogenization at first, and then heat at 980 C. and 1050 C. for 1 h to 4 h sequentially, finally conduct water cooling or air cooling; (7) conducting secondary tempering process on the resultants for 1 h to 4 h at 750 C. to 900 C. and 450 C. to 550 C., respectively.

5. The preparation method as claim 4, wherein in the said step (1), rare earth required for raw material preparation can use the mixed rare earth with a definite proportion of components.

6. The preparation method as claim 4, wherein in the said step (2), first of all, the raw materials are put into the crucible pot of an intermediate-frequency induction smelting rapid solidified furnace, switch on the power to preheat the raw materials when the vacuum reaches 10-2 Pa or above, stop vacuum-pumping when the vacuum reaches 10-2 Pa or above again, inject highly pure Ar to enable Ar pressure inside the furnace reach 0.04 MPa to 0.08 MPa, and then smelt the raw materials; conduct electromagnetic stirring for refining after the raw materials are molten completely, and then pour the molten steel onto water-cooled copper rollers with a linear speed of 24 m/s to obtain the rapid solidified strips with an uniform thickness of 0.1 to 0.5 mm.

7. The preparation method as claim 4, wherein in the said step (3), the rotating speed of a pneumatic concentration wheel during the jet mill process should be controlled at 3000 r/min to 4000 r/min.

8. The preparation method as claim 4, wherein in said step (6), a graded sintering system is adopted during a sintering process: the temperature rises 3 C. every minute in the first half process, close to the set temperature of the last 45 minutes, the temperature rises 1 C. every three minutes, and is maintained for 14 h after reaching the set temperature, afterwards, water cooling or air cooling is conducted.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an illustrated diagram of the structure of the low-cost double-main-phase Ce permanent magnet alloy prepared in the present invention;

(2) FIG. 2 is a schematic flowchart of the preparation process of the low-cost double-main-phase Ce permanent magnet alloy in the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENT MODES

(3) The embodiments of the present invention will be further described below in accordance with the drawings. However, it shall be noted that the embodiments below are merely for the purpose of description, and the scope of the present invention is not limited to the embodiments below.

(4) FIG. 2 shows a schematic flowchart of the preparation process of the low-cost double-main-phase Ce permanent magnet alloy in the present invention. The preparation process comprises the following steps:

(5) (1) prepare two different main phase alloys using a double-main-phase alloy method, the first main phase alloy has the composition of Nd.sub.aFe.sub.100-a-b-cB.sub.bTM.sub.c in mass percent, wherein 27a33, 0.8b1.5, 0.5c2 and TM is one or more selected from Ga, Co, Cu, Nb and Al elements; the second main phase alloy has the composition of (Ce.sub.x,Re.sub.1-x).sub.aFe.sub.100-a-b-cB.sub.bTM.sub.c in mass percent, wherein 0.4x0.9, 29a33, 0.8b1.5, 0.5c2, Re is one or more selected from Nd, Pr, Dy, Tb and Ho elements, and TM is one or more selected from Ga, Co, Cu, Nb and Al elements; and two raw materials are prepared respectively;

(6) (2) respectively smelt the two raw materials prepared in step (1) to obtain the rapid solidified strips with a uniform thickness of 0.1 to 0.5 mm;

(7) (3) respectively conduct hydrogen crash for the two rapid solidified strips obtain from step (2) and get the coarse crashed magnetic powders after dehydrogenization; afterwards, conduct jet milling the coarse crashed magnetic powders respectively under a protective atmosphere of inert gas to obtain two magnetic powders with approximate particle sizes which is in the range of 16 m;

(8) (4) according to requirements of composition of different grades of permanent magnet alloys, weigh two kinds of magnetic powders prepared in step (3) respectively at different proportions and then mix them in a mixer;

(9) (5) under the protective atmosphere of inert gases, conduct the oriented forming for the mixed magnetic powders in a magnetic field of 1.5 to 2.3 T, and then conduct cool isostatic compression processing to obtain green bodies;

(10) (6) put the green bodies after oriented forming and isostatic compression into a sintering furnace with a high vacuum for sintering; during a sintering process, heat for 0.5 h to 10 h at 400 C. to 800 C. for dehydrogenization at first, and then conduct water cooling or air cooling after heat at 980 C. to 1050 C. for 1 h to 4 h;

(11) (7) conduct secondary tempering process on the resultants for 1 h to 4 h at 750 C. to 900 C. and 450 C. to 550 C., respectively.

Embodiment 1

(12) As shown in FIG. 2, the double-main-phase Ce permanent magnet alloy with the designed composition of [(Ce,Pr).sub.0.9Nd.sub.0.1].sub.30Fe.sub.ba1B.sub.1TM.sub.0.67 (TM=Ga, Co, Cu, Nb) (wt. %) is prepared according to the preparation method of the present invention, wherein the content of Ce accounts for 80% of the total weight of rare earth. The preparation method specifically comprises the following steps:

(13) (1) prepare two different main phase alloys, the first main phase alloy has the composition of Nd.sub.30Fe.sub.ba1B.sub.1TM.sub.0.67 (TM=Ga, Co, Cu, Nb) in mass percent, and the second main phase alloy has the composition of [Ce.sub.0.89Pr.sub.0.11].sub.30Fe.sub.ba1B.sub.1TM.sub.0.67 (TM=Ga, Co, Cu, Nb) in mass percent; and raw materials are prepared respectively;

(14) (2) smelt the raw materials prepared respectively as below: first of all, put the raw materials into the crucible pot of an intermediate-frequency induction smelting rapid solidified furnace, switch on power to preheat the raw materials when the vacuum reaches 10.sup.2 Pa or above, stop vacuum-pumping when the vacuum reaches 10.sup.2 Pa or above again, inject highly pure Ar to enable Ar pressure inside the furnace reach 0.06 MPa, and then smelt the raw materials; conduct electromagnetic stirring for refining after the raw materials are molten completely, and then pour the molten steel onto water-cooled copper rollers with a linear speed of 3 m/s to obtain the rapid solidified strips with a uniform thickness of 0.3 mm;

(15) (3) put the two kinds of rapid solidified strips prepared in hydrogenization furnaces respectively for coarse crush and then for dehydrogenization afterwards, conduct jet milling on the coarse crashed magnetic powders respectively under a protective atmosphere of inert gas to obtain magnetic powders with average particle sizes ranging from 1.5 m to 4.5 m, wherein the rotating speed of a pneumatic concentration wheel during the jet mill process is maintained at 3100 r/min to ensure approximate particle sizes of the two magnetic powders;

(16) (4) mix the two kinds of magnetic powders prepared in step 3 according to the designed composition, wherein the magnetic powder with the composition of [Ce.sub.0.89Pr.sub.0.11].sub.30Fe.sub.ba1B.sub.1TM.sub.0.67 (TM=Ga, Co, Cu, Nb) (wt. %) accounts for 90% of the total weight approximately, and the two magnetic powders are fully mixed in a mixer;

(17) (5) under the protective atmosphere of inert gases, conduct the oriented forming for the mixed magnetic powders in a magnetic field of 2 T, and then conduct cool isostatic compression processing to obtain green bodies;

(18) (6) put the green bodies after oriented forming into a sintering furnace with a high vacuum for sintering; during a sintering process, preserve heat at 400 C., 600 C. and 800 C. for 1 h respectively for further dehydrogenization, adopt a graded sintering system: the temperature rises by 3 C. every minute in the first half process, then rises by 1 C. every 3 minutes within the last 45 minutes to approach a set temperature, and is maintained for 2 h after reaching the set temperature, afterwards, water cooling or air cooling is conducted;

(19) (7) finally, temper the resultants for 2 h at 900 C. and 520 C., respectively.

(20) The magnetic performances of magnet, measured by an NIM-2000HF permanent magnet material standard measurement device, are as shown in Table 2.

(21) TABLE-US-00002 TABLE 2 Magnetic Performances of Double-Main-Phase Ce Permanent Magnet Alloy in Embodiment 1 (BH).sub.m/ Nominal Composition (wt. %) B.sub.r/kGs H.sub.cj/kOe MGOe [(Ce,Pr).sub.0.85Nd.sub.0.15].sub.30Fe.sub.balB.sub.1TM.sub.0.67 11.7 12.6 30.1 (Ga, Co, Cu, Nb)

Embodiment 2

(22) As shown in FIG. 2, the double-main-phase Ce permanent magnet alloy with the designed composition of [(Ce,Pr).sub.0.7Dy.sub.0.05Nd.sub.0.25].sub.30Fe.sub.ba1B.sub.1TM.sub.0.67 (TM=Ga, Co, Cu, Nb) (wt. %) is prepared according to the preparation method of the present invention, wherein the content of Ce accounts for 65% of the total weight of rare earth. The preparation method specifically comprises the following steps:

(23) (1) prepare two different main phase alloys, the first main phase alloy has the composition of Nd.sub.30Fe.sub.ba1B.sub.1TM.sub.0.67 (TM=Ga, Co, Cu, Nb) in mass percent, and the second main phase alloy has the composition of [Ce.sub.0.75(Pr,Dy).sub.0.25].sub.30Fe.sub.ba1B.sub.1TM.sub.0.67 (TM=Ga, Co, Cu, Nb) in mass percent; and raw materials are prepared respectively;

(24) (2) smelt the raw materials prepared respectively as below: first of all, put the raw materials into the crucible pot of an intermediate-frequency induction smelting rapid solidified furnace, switch on power to preheat the raw materials when the vacuum reaches 10.sup.2 Pa or above, stop vacuum-pumping when the vacuum reaches 10.sup.2 Pa or above again, inject highly pure Ar to enable Ar pressure inside the furnace reach 0.06 MPa, and smelt then the raw materials; conduct electromagnetic stirring for refining after the raw materials are molten completely, and then pour the molten steel onto water-cooled copper rollers with a linear speed of 3 m/s to obtain the rapid solidified strips with a uniform thickness of 0.3 mm;

(25) (3) put the two rapid solidified strips prepared in hydrogenization furnaces respectively for coarse crush and then for dehydrogenization, afterwards, conduct jet milling on the coarse crashed magnetic powders respectively under a protective atmosphere of inert gas to obtain magnetic powders with an average particle size of 3 m, wherein the rotating speed of a pneumatic concentration wheel during the jet mill process is maintained at 3100 r/min to ensure approximate particle sizes of the two magnetic powders;

(26) (4) mix the two magnetic powders prepared in step 3 according to the designed composition, wherein the magnetic powder with the composition of [Ce.sub.0.75(Pr,Dy).sub.0.25].sub.30Fe.sub.ba1B.sub.1TM.sub.0.67 (TM=Ga, Co, Cu, Nb) (wt. %) accounts for of the total weight approximately, and the two magnetic powders are fully mixed in a mixer;

(27) (5) under the protective atmosphere of inert gases, conduct the oriented forming for the mixed magnetic powders in a magnetic field of 2 T, and then conduct cool isostatic compression processing to obtain green bodies;

(28) (6) put the green bodies after oriented forming into a sintering furnace with a high vacuum for sintering; during a sintering process, preserve heat at the temperature of 400 C., at 600 C. and at 800 C. for 1 h respectively for further dehydrogenization, adopt a graded sintering system: the temperature rises by 3 C. every minute in the first half process, then rises by 1 C. every 3 minutes within the last 45 minutes to approach a set temperature, and is maintained for 2 h after reaching the set temperature, afterwards, conduct water cooling or air cooling; and

(29) (7) finally, temper the resultants for 2 h at 900 C. and 520 C., respectively.

(30) The magnetic performances of magnet, measured by an NIM-2000HF rear earth permanent magnet standard measurement device, are as shown in Table 3.

(31) TABLE-US-00003 TABLE 3 Magnetic Performances of Double-Main-Phase Ce Permanent Magnet Alloy in Embodiment 2 (BH).sub.m/ Nominal Composition (wt. %) B.sub.r/kGs H.sub.cj/kOe MGOe [(Ce,Pr).sub.0.7Dy.sub.0.05Nd.sub.0.25].sub.30Fe.sub.balB.sub.1TM.sub.0.67 12.3 12.39 34.2 (TM = Ga, Co, Cu, Nb)

Embodiment 3

(32) As shown in FIG. 2, the double-main-phase Ce permanent magnet alloy with the designed composition of [(Ce,Pr).sub.0.5Nd.sub.0.5].sub.30Fe.sub.ba1B.sub.1TM.sub.0.67 (TM=Ga, Co, Cu,Nb) (wt. %) is prepared according to the preparation method of the present invention, wherein the content of Ce accounts for 40% of the total weight of rare earth. The preparation method specifically comprises the following steps:

(33) (1) prepare two different main phase alloys, the first main phase alloy has the composition of Nd.sub.30Fe.sub.ba1B.sub.1TM.sub.0.67 (TM=Ga, Co, Cu, Nb) in mass percent, and the second main phase alloy has the composition of (Ce.sub.0.8Pr.sub.0.2).sub.30Fe.sub.ba1B.sub.1TM.sub.0.67 (TM=Ga, Co, Cu, Nb) in mass percent; and raw materials are prepared respectively;

(34) (2) smelt the raw materials prepared respectively as below: first of all, put the raw materials into the crucible pot of an intermediate-frequency induction smelting rapid solidified furnace, switch on power to preheat the raw materials when the vacuum reaches 10.sup.2 Pa or above, stop vacuum-pumping when the vacuum reaches 10.sup.2 Pa or above again, inject highly pure Ar to enable Ar pressure inside the furnace reach 0.06 MPa, and then smelt the raw materials; conduct electromagnetic stirring for refining after the raw materials are molten completely, and then pout the molten steel onto water-cooled copper rollers with a linear speed of 3 m/s to obtain the rapid solidified strips with a uniform thickness of 0.3 mm;

(35) (3) put the two rapid solidified strips prepared in hydrogenization furnaces respectively for coarse crush and then for dehydrogenization, afterwards, conduct jet milling on the coarse crashed magnetic powders respectively under a protective atmosphere of inert gas to obtain magnetic powders with an average particle size of 3 m, wherein the rotating speed of a pneumatic concentration wheel during the jet mill process is maintained at 3100 r/min to ensure approximate particle sizes of the two magnetic powders;

(36) (4) mix the two magnetic powders prepared in step 3 according to the designed composition, wherein the magnetic powder with the composition of (Ce.sub.0.8Pr.sub.0.2).sub.30Fe.sub.ba1B.sub.1TM.sub.0.67 (TM=Ga, Co, Cu, Nb) (wt. %) accounts for of the total weight approximately, and the two magnetic powders are fully mixed in a mixer;

(37) (5) under the protective atmosphere of inert gases, conduct the oriented forming for the mixed magnetic powders in a magnetic field of 2 T, and then conduct cool isostatic compression processing to obtain green bodies;

(38) (6) put the green bodies after oriented forming into a sintering furnace with a high vacuum for sintering; during a sintering process, preserve heat at the temperature of 400 C., at 600 C. and at 800 C. for 1 h respectively for further dehydrogenization, adopt a graded sintering system: the temperature rises by 3 C. every minute in the first half process, then rises by 1 C. every 3 minutes within the last 45 minutes to approach a set temperature, and is maintained for 2 h after reaching the set temperature, afterwards, water cooling or air cooling is conducted; and

(39) (7) finally, temper the resultants for 2 h at 900 C. and 520 C., respectively.

(40) The magnetic performances of magnet, measured by an NIM-2000HF rear earth permanent magnet standard measurement device, are as shown in Table 4.

(41) TABLE-US-00004 TABLE 4 Magnetic Performances of Double-Main-Phase Ce Permanent Magnet Alloy in Embodiment 3 (BH).sub.m/ Nominal Composition (wt. %) B.sub.r/kGs H.sub.cj/kOe MGOe [(Ce,Pr).sub.0.5Nd.sub.0.5].sub.30Fe.sub.balB.sub.0.94TM.sub.0.67 12.7 13.6 40.2 (TM = Ga, Co, Cu, Nb)

(42) It can be seen from the above embodiments 1-3 that, the double-main-phase Ce permanent magnet alloy of the present invention has the following magnetic performances: B.sub.r=11.7 kGs to 12.7 kGs, H.sub.cj=12.39 kOe to 13.6 kOe, and (BH).sub.m=30 MGOe to 40.2 MGOe, and has excellent magnetic performances in contrast to other Ce permanent magnet alloys in the prior art.