Composite R-Fe-B series rare earth sintered magnet comprising Pr and W

Abstract

Disclosed in the present invention is a composite R—Fe—B based rare-earth sintered magnet comprising Pr and W, wherein the rare-earth sintered magnet comprises an R.sub.2Fe.sub.14B type main phase, and R is a rare-earth element comprising at least Pr, wherein the raw material components therein comprise more than or equal to 2 wt % of Pr and 0.0005 wt %-0.03 wt % of W; and the rare-earth sintered magnet is made through a process comprising the following steps: preparing molten liquid of the raw material components into a rapidly quenched alloy; grinding the rapidly quenched alloy into fine powder; obtaining a shaped body from the fine powder by using a magnetic field; and sintering the shaped body. By adding a trace amount of W into the rare-earth sintered magnet, the heat resistance and thermal demagnetization performance of the Pr-containing magnet are improved.

Claims

1. A composite R—Fe—B based rare-earth sintered magnet comprising Pr and W, wherein: the composite R—Fe—B based rare-earth sintered magnet comprises an R.sub.2Fe.sub.14B main phase, R is a rare-earth element comprising at least Pr, raw material components of the composite R—Fe—B based rare-earth sintered magnet comprise more than or equal to 2 wt % of Pr, 0.008 wt % to less than 0.03 wt % of W, and 0.8 wt % to 1.3 wt % of B, and the composite R—Fe—B based rare-earth sintered magnet is made through a process comprising: preparing molten liquid of the raw material components into a quenched alloy; grinding the quenched alloy into powder; obtaining a shaped body from the powder by using a magnetic field; and sintering the shaped body.

2. The composite R—Fe—B based rare-earth sintered magnet comprising Pr and W according to claim 1, wherein an amount of Pr is 2 wt %-10 wt % of the raw material components.

3. The composite R—Fe—B based rare-earth sintered magnet comprising Pr and W according to claim 1, wherein R is a rare-earth element comprising at least Nd and Pr.

4. The composite R—Fe—B based rare-earth sintered magnet comprising Pr and W according to claim 1, wherein an amount of oxygen in the composite R—Fe—B based rare-earth sintered magnet is less than or equal to 2000 ppm.

5. The composite R—Fe—B based rare-earth sintered magnet comprising Pr and W according to claim 1, wherein an amount of oxygen in the composite R—Fe—B based rare-earth sintered magnet is less than or equal to 1000 ppm.

6. The composite R—Fe—B based rare-earth sintered magnet comprising Pr and W according to claim 1, wherein the raw material components further comprise less than or equal to 2.0 wt % of at least one additive element selected from the group consisting of Zr, Co, V, Mo, Zn, Ga, Nb, Sn, Sb, Hf, Bi, Ni, Ti, Cr, Si, S, and P, less than or equal to 0.8 wt % of Cu, less than or equal to 0.8 wt % of Al, and the balance of Fe.

7. The composite R—Fe—B based rare-earth sintered magnet comprising Pr and W according to claim 1, wherein: the quenched alloy is obtained by cooling the molten liquid of the raw material components at a cooling speed of more than or equal to 10.sup.2° C./s and less than or equal to 10.sup.4° C./s by using a strip casting method, grinding the quenched alloy into powder comprises a first grinding and a second grinding, the first grinding comprises performing hydrogen decrepitation on the quenched alloy to obtain first powder, and the second grinding comprises performing jet milling on the first powder to obtain the powder.

8. The composite R—Fe—B based rare-earth sintered magnet comprising Pr and W according to claim 6, wherein an average crystalline particle diameter of the composite R—Fe—B based rare-earth sintered magnet is 2-8 microns.

9. The composite R—Fe—B based rare-earth sintered magnet comprising Pr and W according to claim 6, wherein an average crystalline particle diameter of the composite R—Fe—B based rare-earth sintered magnet is 4.6-5.8 microns.

10. The composite R—Fe—B based rare-earth sintered magnet comprising Pr and W according to claim 6, wherein the raw material components comprise 0.1 wt %-0.8 wt % of Cu.

11. The composite R—Fe—B based rare-earth sintered magnet comprising Pr and W according to claim 6, wherein the raw material components comprise 0.1 wt %-0.8 wt % of Al.

12. The composite R—Fe—B based rare-earth sintered magnet comprising Pr and W according to claim 6, wherein the raw material components comprise 0.3 wt %-2.0 wt % of at least one additive element selected from the group consisting of Zr, Co, V, Mo, Zn, Ga, Nb, Sn, Sb, Hf, Bi, Ni, Ti, Cr, Si, S, and P.

13. The composite R—Fe—B based rare-earth sintered magnet comprising Pr and W according to claim 6, wherein an amount of B is 0.8 wt %-0.92 wt %.

14. The composite R—Fe—B based rare-earth sintered magnet comprising Pr and W according to claim 1, wherein: the composite R—Fe—B based rare-earth sintered magnet has a residual flux density (Br) of 14.0 kGs to 14.2 kGs, and the composite R—Fe—B based rare-earth sintered magnet has a square degree (SQ) of 99.0% to 99.9%.

15. The composite R—Fe—B based rare-earth sintered magnet comprising Pr and W according to claim 14, wherein a coercive force (Hcj) of the composite R—Fe—B based rare-earth sintered magnet is 15.8 kOe to 17.4 kOe.

16. A composite R—Fe—B based rare-earth sintered magnet comprising Pr and W, wherein: the composite R—Fe—B based rare-earth sintered magnet comprises an R.sub.2Fe.sub.14B main phase, R is a rare-earth element comprising at least Pr, components of the composite R—Fe—B based rare-earth sintered magnet comprise more than or equal to 1.9 wt % of Pr, 0.008 wt % to less than 0.03 wt % of W, and 0.8 wt % to 1.3 wt % of B, and the composite R—Fe—B based rare-earth sintered magnet is made through a process comprising: preparing molten liquid of raw material components into a quenched alloy, wherein the raw material components comprise the 0.008 wt % to less than 0.03 wt % of W; grinding the quenched alloy into powder; obtaining a shaped body from the powder by using a magnetic field; and sintering the shaped body.

17. The composite R—Fe—B based rare-earth sintered magnet comprising Pr and W according to claim 16, wherein the components further comprise less than or equal to 2.0 wt % of at least one additive element selected from the group consisting of Zr, Co, V, Mo, Zn, Ga, Nb, Sn, Sb, Hf, Bi, Ni, Ti, Cr, Si, S, and P, less than or equal to 0.8 wt % of Cu, less than or equal to 0.8 wt % of Al, and the balance of Fe.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates a binary phase diagram of Nd—Fe.

(2) FIG. 2 illustrates a binary phase diagram of Pr—Fe.

(3) FIG. 3 illustrates a binary phase diagram of Pr—Nd.

(4) FIG. 4 illustrates a binary phase diagram of Pr—H.

(5) FIG. 5 illustrates a binary phase diagram of Nd—H.

(6) FIG. 6 illustrates EPMA detection results for a sintered magnet according to Embodiment 1.1 of Embodiment 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(7) The present invention will be further described in detail in combination with embodiments hereinafter.

(8) Sintered magnets obtained in Embodiments 1-4 are determined by using the following determination methods:

(9) Evaluation process for magnetic performance: the magnetic performance of a sintered magnet is determined by using the NIM-10000H type nondestructive testing system for BH large rare earth permanent magnet from National Institute of Metrology of China.

(10) Determination on attenuation ratio of magnetic flux: the sintered magnet is placed in an environment at 180° C. for 30 minutes; then naturally cooled to room temperature; and then measured for the magnetic flux. The measured magnetic flux is compared with the measured data prior to heating to calculate an attenuation ratio of the measured magnetic flux before and after heating.

(11) Determination on AGG: the sintered magnet is polished in a horizontal direction, and an average number of AGGs per 1 cm.sup.2 is obtained; the AGG mentioned in the present invention refers to an abnormally grown grain with a grain size greater than 40 μm.

(12) Average crystalline grain size testing of a magnet: a magnet is photographed after it is placed under a laser metalloscope at a magnifying power of 2000, wherein a detection surface is in parallel with the lower edge of the view field when taking the photograph. During measurement, a straight line with a length of 146.5 μm is drawn at the central position of the view field; and by counting the number of main phase crystals through the straight line, the average crystalline grain size of the magnet is calculated.

Embodiment 1

(13) Preparation process of raw material: Nd with a purity of 99.5%, Pr with a purity of 99.5%, industrial Fe—B, industrial pure Fe, Co with a purity of 99.9%, Cu with a purity of 99.5% and W with a purity of 99.999% were prepared in weight percentage (wt %) and formulated into the raw material.

(14) In order to accurately control the use proportion of W, in this embodiment, the amount of W in the selected Nd, Fe, Pr, Fe—B, Co and Cu was less than a detection limit of existing devices, and a source of W was metal W which was additionally added.

(15) The amounts of the elements are as shown in Table 2.

(16) TABLE-US-00002 TABLE 2 Proportions of Elements (wt %) No. Nd Pr B Co Cu W Fe Comparative example 1 31.9 1 0.9 1.0 0.2 0.01 Balance Embodiment 1.1 31.7 2 0.9 1.0 0.2 0.01 Balance Embodiment 1.2 30 5 0.9 1.0 0.2 0.01 Balance Embodiment 1.3 22 10 0.9 1.0 0.2 0.01 Balance Embodiment 1.4 12 20 0.9 1.0 0.2 0.01 Balance Embodiment 1.5 0 32 0.9 1.0 0.2 0.01 Balance Comparative example 1.2 12 20 0.9 1.0 0.2 0 Balance

(17) Each number of the above embodiment is respectively prepared according to the element composition in Table 2; and 10 kg of raw materials were then weighted and prepared.

(18) Smelting process: one part of the formulated raw materials was taken and put into a crucible made of aluminum oxide each time, and was subjected to vacuum smelting in a high-frequency vacuum induction smelting furnace under a vacuum of 10.sup.−2 Pa at a temperature below 1500° C.

(19) Casting process: after the vacuum smelting, an Ar gas was introduced into the smelting furnace until the pressure reached 20000 Pa; casting was performed using a single-roller quenching process at a cooling speed of 10.sup.2° C./s-10.sup.4° C./s to obtain a rapidly quenched alloy; and the rapidly quenched alloy was subjected to a heat preservation treatment at 600° C. for 20 min and then cooled to room temperature.

(20) Hydrogen decrepitation process: a hydrogen decrepitation furnace in which the rapidly quenched alloy was placed was vacuumized at room temperature, and then hydrogen with a purity of 99.5% was introduced into the hydrogen decrepitation furnace to a pressure of 0.1 MPa. After being left for 120 min, the furnace was vacuumized while the temperature was increasing, which was vacuumized for 2 hours at the temperature of 500° C., and then was cooled down, obtaining powder after the hydrogen decrepitation.

(21) Fine grinding process: the specimen obtained after the hydrogen decrepitation was subjected to jet milling in a pulverizing chamber at a pressure of 0.45 MPa in an atmosphere having an oxidizing gas amount less than 200 ppm; obtaining fine powder having an average grain size of 3.10 μm (Fisher Method). The oxidizing gas refers to oxygen or moisture.

(22) Methyl caprylate was added into the powder obtained after the jet milling with an addition amount of 0.2% relative to the weight of the mixed powder, and then was well mixed with the powder using a V-type mixer.

(23) Magnetic field shaping process: the powder in which the methyl caprylate had been added as described above was primarily shaped as a cube having a side length of 25 mm using a right angle-oriented magnetic field shaping machine in an oriented magnetic field of 1.8 T, and was demagnetized after the primary shaping.

(24) In order to prevent the shaped body obtained after the primary shaping from being in contact with air, the shaped body was sealed, and then subjected to a secondary shaping using a secondary shaping machine (isostatic pressure shaping machine).

(25) Sintering process: each of the shaped bodies was transferred to a sintering furnace for sintering, which was sintered under a vacuum of 10.sup.−3 Pa at the temperature of 200° C. for 2 hours and at the temperature of 900° C. for 2 hours, and then sintered at the temperature of 1030° C. Afterwards, an Ar gas was introduced into the sintering furnace until the pressure reached 0.1 MPa, and then the sintered body was cooled to room temperature.

(26) Heat treatment process: the sintered body was subjected to heat treatment in a high-purity Ar gas at a temperature of 500° C. for 1 hour, cooled to room temperature and then taken out.

(27) Processing process: the sintered body obtained after the heat treatment was processed into a magnet with φ of 15 mm and a thickness of 5 mm, with the direction of the thickness of 5 mm being the orientation direction of the magnetic field.

(28) Magnetic performance testing was performed on magnets made of the sintered bodies in Comparative Examples 1.1-1.2 and Embodiments 1.1-1.5 to evaluate the magnetic properties thereof. Evaluation results of the magnets in embodiments and comparative examples are shown in Table 3.

(29) TABLE-US-00003 TABLE 3 Performance Evaluation for Magnets in Embodiments and Comparative Examples Average Attenuation crystalline ratio of grain size Br Hcj SQ (BH)max magnetic AGG of magnet No. (kGs) (kOe) (%) (MGOe) flux (Number) (micron) Comparative 13.5 13.8 98.6 44.9 8.8 3 6.2 example 1.1 Embodiment 1.1 14.0 15.8 99.0 46.1 2.5 0 4.9 Embodiment 1.2 14.1 16.5 99.5 46.2 1.7 0 4.8 Embodiment 1.3 14.1 16.8 99.6 46.1 2.4 0 4.7 Embodiment 1.4 14.1 17.1 99.8 46.3 3.5 1 4.6 Embodiment 1.5 14.2 17.4 99.9 46.2 3.9 1 4.6 Comparative 12.8 11.3 94.7 38.5 32.6 5 7.3 example 1.2

(30) Throughout the implementation process, the amount of O in the magnets in the comparative examples and the embodiments was controlled to be less than or equal to 2000 ppm; and the amount of C in the magnets in the comparative examples and the embodiments was controlled to be less than or equal to 1000 ppm.

(31) It can be concluded that in the present invention, when the amount of Pr is less than 2 wt %, the goal of comprehensively utilizing rare earth resources cannot be achieved.

(32) The components of the sintered magnet made in Embodiment 1.1 was subjected to FE-EPMA (field emission electron probe microanalysis) detection. Results are as shown in Table 6.

(33) From FIG. 6, it can be seen that R-enriched phases are concentrated towards grain boundaries; the trace amount of W pins the migration of the grain boundaries, adjusts the grain size, and reduces the occurrence of AGG (abnormal grain growth); the coercive force can be uniformly distributed from both microscopic and macroscopic angles; and the heat resistance, thermal demagnetization, and square degree of the magnet are improved.

(34) In Embodiment 1.2 and Embodiment 1.5, the following phenomena were also observed: the R-enriched phases are concentrated towards the grain boundaries, the trace amount of W pins the migration of the grain boundaries, and adjusts the grain size.

(35) After testing, the amounts of the component Pr in the sintered magnets made in Embodiments 1.1, 1.2, 1.3, 1.4, and 1.5 are 1.9 wt %, 4.8 wt %, 9.8 wt %, 19.7 wt %, and 31.6 wt % respectively.

Embodiment 2

(36) Preparation process of raw material: Nd with a purity of 99.9%, Fe—B with a purity of 99.9%, Fe with a purity of 99.9%, Pr with a purity of 99.9%, Cu and Al with a purity of 99.5%, and W with a purity of 99.999% were prepared in weight percentage (wt %) and formulated into the raw material.

(37) In order to accurately control the use proportion of W, in this embodiment, the amount of W in the selected Nd, Fe, Fe—B, Pr, Al, and Cu was less than a detection limit of existing devices, and a source of W was metal W which was additionally added.

(38) The amounts of the elements are shown in Table 4.

(39) TABLE-US-00004 TABLE 4 Proportions of Elements (wt %) No. Nd Pr B Cu Al Nb W Fe Comparative 21 10 0.85 0.8 0.2 0.2 0.0001 Balance example 2.1 Embodiment 2.1 21 10 0.85 0.8 0.2 0.2 0.0005 Balance Embodiment 2.2 21 10 0.85 0.8 0.2 0.2 0.002 Balance Embodiment 2.3 21 10 0.85 0.8 0.2 0.2 0.008 Balance Embodiment 2.4 21 10 0.85 0.8 0.2 0.2 0.03 Balance Comparative 21 10 0.85 0.8 0.2 0.2 0.05 Balance example 2.2

(40) Each number of the above embodiment is respectively prepared according to the element composition in Table 4; and 10 kg of raw materials were then weighted and prepared.

(41) Smelting process: one part of formulated raw materials was taken and put into a crucible made of aluminum oxide each time, and was subjected to vacuum smelting in a high-frequency vacuum induction smelting furnace under a vacuum of 10.sup.−3 Pa at a temperature below 1600° C.

(42) Casting process: after the vacuum smelting, an Ar gas was introduced into the smelting furnace until the pressure reached 50000 Pa; casting was performed using a single-roller quenching process at a cooling speed of 10.sup.2° C./s-10.sup.4° C./s to obtain a rapidly quenched alloy; and the rapidly quenched alloy was subjected to a heat preservation treatment at 500° C. for 10 min and then cooled to room temperature.

(43) Hydrogen decrepitation process: a hydrogen decrepitation furnace in which the rapidly quenched alloy was placed was vacuumized at room temperature, and then hydrogen with a purity of 99.5% was introduced into the hydrogen decrepitation furnace to a pressure of 0.05 MPa. After being left for 125 min, the furnace was vacuumized while the temperature was increasing, which was vacuumized for 2 hours at the temperature of 600° C., and then was cooled down, obtaining powder after the hydrogen decrepitation.

(44) Fine grinding process: the specimen obtained after the hydrogen decrepitation was subjected to jet milling in a pulverizing chamber at a pressure of 0.41 MPa in an atmosphere having an oxidizing gas amount less than 100 ppm; obtaining fine powder having an average grain size of 3.30 μm (Fisher Method). The oxidizing gas refers to oxygen or moisture.

(45) Methyl caprylate was added into the powder obtained after the jet milling with an addition amount of 0.25% relative to the weight of the mixed powder, and then was well mixed with the powder using a V-type mixer.

(46) Magnetic field shaping process: the powder in which the methyl caprylate had been added as described above was primarily shaped as a cube having a side length of 25 mm using a right angle-oriented magnetic field shaping machine in an oriented magnetic field of 1.8 T at a shaping pressure of 0.2 ton/cm.sup.2, and was demagnetized after the primary shaping in a magnetic field of 0.2 T.

(47) In order to prevent the shaped body obtained after the primary shaping from being in contact with air, the shaped body was sealed, and then subjected to a secondary shaping using a secondary shaping machine (isostatic pressure shaping machine) at a pressure of 1.1 ton/cm.sup.2.

(48) Sintering process: each of the shaped bodies was transferred to a sintering furnace for sintering, which was sintered under a vacuum of 10.sup.−2 Pa at the temperature of 200° C. for 1 hours and at the temperature of 800° C. for 2 hours, and then sintered at the temperature of 1010° C. Afterwards, an Ar gas was introduced into the sintering furnace until the pressure reached 0.1 MPa, and then the sintered body was cooled to room temperature.

(49) Heat treatment process: the sintered body was subjected to heat treatment in a high-purity Ar gas at a temperature of 520° C. for 2 hour, cooled to room temperature and then taken out.

(50) Processing process: the sintered body obtained after the heat treatment was processed into a magnet with φ of 15 mm and a thickness of 5 mm, with the direction of the thickness of 5 mm being the orientation direction of the magnetic field.

(51) Magnetic performance testing was performed on magnets made of the sintered bodies in Comparative Examples 2.1-2.2 and Embodiments 2.1-2.4 to evaluate the magnetic properties thereof. Evaluation results of magnets in the embodiments and the comparative examples are as shown in Table 5.

(52) TABLE-US-00005 TABLE 5 Performance Evaluation for Magnets in Embodiments and Comparative Examples Average Attenuation crystalline ratio of grain size Br Hcj SQ (BH)max magnetic AGG of magnet No. (kGs) (kOe) (%) (MGOe) flux (%) (Number) (micron) Comparative 13.8 15.2 97.6 46.1 13.6 2 6.5 example 2.1 Embodiment 2.1 14.2 16.8 98.5 48.5 3.7 0 5.8 Embodiment 2.2 14.3 17.2 99.1 48.2 1.5 0 5.7 Embodiment 2.3 14.4 17.6 99.3 48.3 2.0 0 5.2 Embodiment 2.4 14.3 17.8 94.9 48.1 2.5 0 5.0 Comparative 12.8 14.3 95.2 39.0 35.8 7 5.8 example 2.2

(53) Throughout the implementation process, the amount of 0 in the magnets in the comparative examples and the embodiments was controlled to be less than or equal to 1000 ppm; and the amount of C in the magnets in the comparative examples and the embodiments was controlled to be less than or equal to 1000 ppm.

(54) It can be concluded that when the amount of W is less than 0.0005 wt %, since the amount of W is insufficient, it is difficult to play its role in improving the heat resistance and thermal demagnetization of Pr-containing magnets; and when the amount of W is greater than 0.03 wt %, since amorphous phases and isometric crystals are formed in (the rapidly quenched alloy sheet) SC sheet to cause the saturation magnetization and coercive force of the magnets to be reduced, magnets with high magnetic energy product cannot be obtained.

(55) After testing, the amounts of the component W in the sintered magnets made in Embodiments 2.1, 2.2, 2.3 and 2.4 are 0.0005 wt %, 0.002 wt %, 0.008 wt %, and 0.03 wt % respectively.

Embodiment 3

(56) Preparation process of raw material: Nd with a purity of 99.9%, Fe—B with a purity of 99.9%, Fe with a purity of 99.9%, Pr with a purity of 99.9%, Cu and Ga with a purity of 99.5%, and W with a purity of 99.999% were prepared in weight percentage (wt %) and formulated into the raw material.

(57) In order to accurately control the use proportion of W, in this embodiment, the amount of W in the selected Nd, Fe, Fe—B, Pr, Ga, and Cu was less than a detection limit of existing devices, and a source of W was metal W which was additionally added.

(58) The amounts of the elements are shown in Table 6.

(59) TABLE-US-00006 TABLE 6 Proportions of Elements (wt %) No. Nd Pr B Cu Ga W Fe Comparative example 3.1 24.5 7 0.92 0.05 0.3 0.005 Balance Embodiment 3.1 24.5 7 0.92 0.1 0.3 0.005 Balance Embodiment 3.2 24.5 7 0.92 0.3 0.3 0.005 Balance Embodiment 3.3 24.5 7 0.92 0.5 0.3 0.005 Balance Embodiment 3.4 24.5 7 0.92 0.8 0.3 0.005 Balance Comparative example 3.2 24.5 7 0.92 0.9 0.3 0.005 Balance Comparative example 3.3 24.5 7 0.92 0.3 0.3 0 Balance

(60) Each number of the above embodiment is respectively prepared according to the element composition in Table 6; and 10 kg of raw materials were then weighted and prepared.

(61) Smelting process: one part of the formulated raw materials was taken and put into a crucible made of aluminum oxide each time, and was subjected to vacuum smelting in a high-frequency vacuum induction smelting furnace under a vacuum of 10.sup.−2 Pa at a temperature below 1450° C.

(62) Casting process: after the vacuum smelting, an Ar gas was introduced into the smelting furnace until the pressure reached 30000 Pa; casting was performed using a single-roller quenching process at a cooling speed of 10.sup.2° C./s-10.sup.4° C./s to obtain a rapidly quenched alloy; and the rapidly quenched alloy was subjected to a heat preservation treatment at 700° C. for 5 min and then cooled to room temperature.

(63) Hydrogen decrepitation process: a hydrogen decrepitation furnace in which the rapidly quenched alloy was placed was vacuumized at room temperature, and then hydrogen with a purity of 99.5% was introduced into the hydrogen decrepitation furnace to a pressure of 0.08 MPa. After being left for 95 min, the furnace was vacuumized while the temperature was increasing, which was vacuumized for 2 hours at the temperature of 650° C., and then was cooled down, obtaining powder after the hydrogen decrepitation.

(64) Fine grinding process: the specimen obtained after the hydrogen decrepitation was subjected to jet milling in a pulverizing chamber at a pressure of 0.6 MPa in an atmosphere having an oxidizing gas amount less than 100 ppm; obtaining fine powder having an average grain size of 3.3 μm (Fisher Method). The oxidizing gas refers to oxygen or moisture.

(65) Methyl caprylate was added into the powder obtained after the jet milling with an addition amount of 0.1% relative to the weight of the mixed powder, and then was well mixed with the powder using a V-type mixer.

(66) Magnetic field shaping process: the powder in which the methyl caprylate had been added as described above was primarily shaped as a cube having a side length of 25 mm using a right angle-oriented magnetic field shaping machine in an oriented magnetic field of 2.0 T at a shaping pressure of 0.2 ton/cm.sup.2, and was demagnetized after the primary shaping in a magnetic field of 0.2 T.

(67) In order to prevent the shaped body obtained after the primary shaping from being in contact with air, the shaped body was sealed, and then subjected to a secondary shaping using a secondary shaping machine (isostatic pressure shaping machine) at a pressure of 1.0 ton/cm.sup.2.

(68) Sintering process: each of the shaped bodies was transferred to a sintering furnace for sintering, which was sintered under a vacuum of 10.sup.−3 Pa at the temperature of 200° C. for 2 hours and at the temperature of 700° C. for 2 hours, and then sintered at the temperature of 1020° C. for 2 hours. Afterwards, an Ar gas was introduced into the sintering furnace until the pressure reached 0.1 MPa, and then the sintered body was cooled to room temperature.

(69) Heat treatment process: the sintered body was subjected to heat treatment in a high-purity Ar gas at a temperature of 560° C. for 1 hour, cooled to room temperature and then taken out.

(70) Processing process: the sintered body obtained after the heat treatment was processed into a magnet with φ of 15 mm and a thickness of 5 mm, with the direction of the thickness of 5 mm being the orientation direction of the magnetic field.

(71) Evaluation process for magnetic performance: the magnetic performance of a sintered magnet is determined by using the NIM-10000H type nondestructive testing system for BH large rare earth permanent magnet from National Institute of Metrology of China.

(72) Magnetic performance testing was performed on magnets made of the sintered bodies in Comparative Examples 3.1-3.3 and Embodiments 3.1-3.4 to evaluate the magnetic properties thereof. Evaluation results of the magnets in embodiments and comparative examples are shown in Table 7.

(73) TABLE-US-00007 TABLE 7 Performance Evaluation for Magnets in Embodiments and Comparative Examples Average Attenuation crystalline ratio of grain size Br Hcj SQ (BH)max magnetic AGG of magnet No. (kGs) (kOe) (%) (MGOe) flux (%) (Number) (micron) Comparative 13.8 15.7 97.8 45.5 5.6 0 5.1 example 3.1 Embodiment 3.1 14.2 16.5 98.9 47.0 2.5 0 5.1 Embodiment 3.2 14.2 16.6 99.3 47.4 1.3 0 5.2 Embodiment 3.3 14.2 17.0 99.5 47.8 1.8 0 5.4 Embodiment 3.4 14.2 16.8 99.1 47.2 2.9 0 5.3 Comparative 13.8 15.5 97.3 46.3 5.1 3 6.0 example 3.2 Comparative 13.8 16.1 97.7 45.2 12.7 7 6.2 example 3.3

(74) Throughout the implementation process, the amount of 0 in the magnets in the comparative examples and the embodiments was controlled to be less than or equal to 1500 ppm; and the amount of C in the magnets in the comparative examples and the embodiments was controlled to be less than or equal to 500 ppm.

(75) It can be concluded that when the amount of Cu is less than 0.1 wt %, SQ is relatively low, which is because Cu can substantively improve SQ; and when the amount of Cu exceeds 0.8 wt %, Hcj and SQ drop. The excessive addition of Cu causes the improving of Hcj to be saturated and other negative factors start to take effect, and thus leading to this phenomenon.

(76) When the amount of Cu is 0.1 wt %-0.8 wt %, Cu dispersed in grain boundaries can effectively facilitate the trace amount of W to play the role in improving the heat resistance and thermal demagnetization performance.

Embodiment 4

(77) Preparation process of raw material: Nd with a purity of 99.8%, industrial Fe—B, industrial pure Fe, Co with purity of 99.9%, and Al and Cr with purity of 99.5% were prepared in weight percentage (wt %) and formulated into the raw material.

(78) In order to accurately control the use proportion of W, in this embodiment, the amount of W in the selected Fe, Fe—B, Pr, Cr, and Al was less than a detection limit of existing devices, the selected Nd comprises W, and the amount of the element W was 0.01% of the Nd amount.

(79) The amounts of the elements are shown in Table 8.

(80) TABLE-US-00008 TABLE 8 Proportions of Elements (wt %) No. Nd Pr B Al Cr Fe Comparative example 4.1 16 15.5 0.82 0.05 0.8 Balance Embodiment 4.1 16 15.5 0.82 0.1 0.8 Balance Embodiment 4.2 16 15.5 0.82 0.3 0.8 Balance Embodiment 4.3 16 15.5 0.82 0.5 0.8 Balance Embodiment 4.4 16 15.5 0.82 0.8 0.8 Balance Comparative example 4.2 16 15.5 0.82 0.9 0.8 Balance

(81) Each number of the above embodiment is respectively prepared according to the element composition in Table 8; and 10 kg of raw materials were then weighted and prepared.

(82) Smelting process: one part of formulated raw materials was taken and put into a crucible made of aluminum oxide each time, and was subjected to vacuum smelting in a high-frequency vacuum induction smelting furnace under a vacuum of 10.sup.−3 Pa at a temperature below 1650° C.

(83) Casting process: after the vacuum smelting, an Ar gas was introduced into the smelting furnace until the pressure reached 10000 Pa; casting was performed using a single-roller quenching process at a cooling speed of 10.sup.2° C./s-10.sup.4° C./s to obtain a rapidly quenched alloy; and the rapidly quenched alloy was subjected to a heat preservation treatment at 450° C. for 80 min and then cooled to room temperature.

(84) Hydrogen decrepitation process: a hydrogen decrepitation furnace in which the rapidly quenched alloy was placed was vacuumized at room temperature, and then hydrogen with a purity of 99.9% was introduced into the hydrogen decrepitation furnace to a pressure of 0.08 MPa. After being left for 120 min, the furnace was vacuumized while the temperature was increasing, which was vacuumized at the temperature of 590° C., and then was cooled down, obtaining powder after the hydrogen decrepitation.

(85) Fine grinding process: the specimen obtained after the hydrogen decrepitation was subjected to jet milling in a pulverizing chamber at a pressure of 0.45 MPa in an atmosphere having an oxidizing gas amount less than 50 ppm; obtaining fine powder having an average grain size of 3.1 μm (Fisher Method). The oxidizing gas refers to oxygen or moisture.

(86) Methyl caprylate was added into the powder obtained after the jet milling with an addition amount of 0.22% relative to the weight of the mixed powder, and then was well mixed with the powder using a V-type mixer.

(87) Magnetic field shaping process: the powder in which the methyl caprylate had been added as described above was primarily shaped as a cube having a side length of 25 mm using a right angle-oriented magnetic field shaping machine in an oriented magnetic field of 1.8 T at a shaping pressure of 0.4 ton/cm.sup.2, and was demagnetized after the primary shaping in a magnetic field of 0.2 T.

(88) In order to prevent the shaped body obtained after the primary shaping from being in contact with air, the shaped body was sealed, and then subjected to a secondary shaping using a secondary shaping machine (isostatic pressure shaping machine) at a pressure of 1.1 ton/cm.sup.2.

(89) Sintering process: each of the shaped bodies was transferred to a sintering furnace for sintering, which was sintered under a vacuum of 10.sup.−3 Pa at the temperature of 200° C. for 1.5 hours and at the temperature of 970° C. for 2 hours, and then sintered at the temperature of 1030° C. Afterwards, an Ar gas was introduced into the sintering furnace until the pressure reached 0.1 MPa, and then the sintered body was cooled to room temperature.

(90) Heat treatment process: the sintered body was subjected to heat treatment in a high-purity Ar gas at a temperature of 460° C. for 2 hour, cooled to room temperature and then taken out.

(91) Processing process: the sintered body obtained after the heat treatment was processed into a magnet with φ of 15 mm and a thickness of 5 mm, with the direction of the thickness of 5 mm being the orientation direction of the magnetic field.

(92) Magnetic performance testing was performed on magnets made of the sintered bodies in Comparative Examples 4.1-4.2 and Embodiments 4.1-4.4 to evaluate the magnetic properties thereof. Evaluation results of the magnets in examples and comparative examples are shown in Table 9.

(93) TABLE-US-00009 TABLE 9 Performance Evaluation for Magnets in Embodiments and Comparative Examples Average Attenuation crystalline ratio of grain size Br Hcj SQ (BH)max magnetic AGG of magnet No. (kGs) (kOe) (%) (MGOe) flux (%) (Number) (micron) Comparative 13.6 17.5 96.6 44.6 4.5 1 5.2 example 4.1 Embodiment 4.1 13.8 17.9 98.5 46.8 3.5 0 4.8 Embodiment 4.2 13.9 18.2 99.1 47.8 1.2 0 4.7 Embodiment 4.3 13.9 18.6 99.3 48.0 2.2 0 4.7 Embodiment 4.4 13.8 18.9 99.2 47.2 2.6 0 4.7 Comparative 13.5 17.2 95.2 43.3 7.1 3 6.5 example 4.2

(94) Throughout the implementation process, the amount of 0 in the magnets in the comparative examples and the embodiments was controlled to be less than or equal to 1000 ppm; and the amount of C in the magnets in the comparative examples and the embodiments was controlled to be less than or equal to 1000 ppm.

(95) It can be concluded that from the comparative examples and the embodiments, when the amount of Al is less than 0.1 wt %, since the amount of Al is too low, it is difficult to play its role and the square degree of the magnets is low.

(96) Al with an amount of 0.1 wt %-0.8 wt % and W can effectively facilitate W to play its role in improving the heat resistance and thermal demagnetization performance.

(97) When the amount of Al is greater than 0.8 wt %, excessive Al would cause the Br and square degree of the magnets to drop sharply.

(98) The embodiments described above only serve to further illustrate some particular implementation modes of the present disclosure; however, the present disclosure is not limited to the embodiments. Any simple alternations, equivalent changes, and modifications made to the embodiments above according to the technical essence of the present disclosure will fall within the protection scope of the technical solutions of the present disclosure.