High-cerium-content rare earth permanent magnet material and preparation method thereof

Abstract

This invention discloses a high-cerium-content rare-earth permanent magnet material and its preparation method. Specifically, it includes preparing magnetic powder, sintering the magnetic powder into a magnet, and then subjecting it to multi-stage heat treatment. Based on the microstructure characteristics of high-cerium-content rare-earth permanent magnet materials, this invention first designs a high-cerium-content (≥50 wt.%) rare-earth permanent magnet material composition. Then, by adjusting the sintering and multi-stage heat treatment temperatures and cooling rates, it optimizes the grain boundary composition and distribution, forming a continuous grain boundary phase and improving the magnetic properties of the high-cerium-content rare-earth permanent magnet material.

Description

Technical Field

[0001] This invention relates to the field of rare earth permanent magnet materials, specifically to a high cerium content rare earth permanent magnet material and its preparation method. Background Technology

[0002] Neodymium iron boron (NdFeB) rare-earth permanent magnets are currently the most powerful, widely used, and rare-earth-consuming permanent magnet materials. They are widely used in the automotive industry, aerospace, medical equipment, and many other fields, consuming large amounts of key rare-earth resources such as Nd, Pr, Tb, and Dy. These rare-earth raw materials account for more than 90% of the magnet's cost, significantly increasing magnet production costs. Finding substitutes for key rare-earth elements such as Nd, Pr, Tb, and Dy to alleviate the pressure on rare-earth resources and reduce raw material costs is of great significance for achieving balanced utilization and sustainable development of rare-earth resources.

[0003] Of all rare earth elements, cerium (Ce) has the highest abundance in the Earth's crust. Replacing Nd and Pr in traditional NdFeB magnets with Ce can significantly reduce the production cost of magnets. Currently, sintered NdFeB magnets have been partially industrialized. However, due to Ce₂Fe... 14 Cerium borax (B) has poor intrinsic magnetic properties, and the substitution of cerium (Ce) severely affects these properties. Furthermore, the microstructure also undergoes significant changes, leading to a decline in magnetic performance. Coercivity, in particular, decreases with higher Ce substitution levels. Therefore, the commercial application of cerium-rich magnets with high Ce content (≥50 wt.%) still faces technical bottlenecks. How to effectively improve their overall magnetic properties is a key technical problem that urgently needs to be solved.

[0004] Current research on sintered NdFeB and NdCFeB magnets has yielded mature results in controlling the holding temperature and time during sintering and heat treatment. Numerous optimization experiments have been conducted, leading to improvements in magnetic properties such as coercivity. From the perspective of simplifying the process, targeted heat-free and one-step heat treatment technologies for sintered NdCFeB magnets have been developed, distinct from the conventional two-step heat treatment technology for NdFeB magnets. For high Ce-content rare-earth permanent magnets, in addition to some rare-earth-rich grain boundary phases, a large amount of REFe2 (RE = Rare Earth) grain boundary phases gradually form during sintering and heat treatment. The higher the Ce content, the higher the mass fraction of the REFe2 phase, resulting in a more complex magnet phase composition and microstructure, which is highly dependent on the cooling process after sintering and heat treatment. Previous studies have suggested that in Ga-containing Nd:CdFeB magnets, slow cooling after sintering or hot-pressing (with a cooling rate less than or equal to the furnace cooling rate at room temperature) can further optimize the formation and distribution of grain boundary phases, thereby improving coercivity. However, for other high-cerium-content rare-earth permanent magnet materials with different compositions, their sintering and heat treatment processes need to be re-evaluated and refined. Particular attention should be paid to the cooling rate during the magnet's cooling process after sintering and heat treatment, as this plays a crucial role in optimizing the magnet's phase composition and microstructure, and improving magnetic properties such as coercivity and squareness. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a high-cerium-content rare-earth permanent magnet material and its preparation method, specifically including the following steps:

[0006] (1) The preparation component is [R] 1-a-x R' a Ce x ] b Fe bal M c Al d B e The magnetic powder, wherein R is one or both of the rare earth elements Nd and Pr, R' is one or more of the rare earth elements La, Gd, Tb, Dy, Ho, Sm, and Y, Ce is the rare earth element cerium, Fe is the iron element, M is one or more of the alloying elements Cu, Ni, Cr, Co, Ga, Mn, Nb, Zr, Ti, V, and Zn, Al is the aluminum element, B is the boron element, and by mass percentage, 0.5≤x≤1, 0≤a≤0.2, 29≤b≤35, 0.15≤c≤5, 0.2≤d≤1, and 0.8≤e≤1;

[0007] (2) The magnetic powder obtained in step (1) is used to prepare a magnet by sintering. The sintering temperature is 950-1080℃ and the sintering time is 1-10h. The magnet is cooled to room temperature by continuously introducing argon gas into the furnace.

[0008] (3) The magnet obtained in step (2) is subjected to multi-stage heat treatment to obtain cerium-rich rare earth permanent magnet material. The heat treatment temperature is 300-800℃ and the heat treatment time is 3-12h. After each stage of heat treatment, the magnet is cooled to room temperature by continuously introducing argon or nitrogen gas into the furnace.

[0009] Specifically, the magnetic powder preparation process in step (1) includes: belt spinning, hydrogen crushing and air jet milling.

[0010] Specifically, the magnetic powder in step (1) is obtained directly by a single principal phase method or by a multi-principal phase method to obtain the final composition.

[0011] Specifically, in steps (2) and (3), the flow rate V of the continuous airflow into the furnace body is ≤0.5L / min, and the average cooling rate of the magnet is 20~30℃ / min.

[0012] Specifically, the multi-stage heat treatment in step (3) includes at least three stages: the first stage temperature is 600-800℃ and the holding time is 1-4h; the second stage temperature is 450-700℃ and the holding time is 1-4h; and the third stage temperature is 300-450℃ and the holding time is 1-4h.

[0013] Specifically, the sintering and heat treatment processes described in steps (2) and (3) maintain a furnace vacuum degree ≤10. -3 Pa.

[0014] The present invention also provides a high-cerium-content rare-earth permanent magnet material prepared by any of the above methods, wherein the permanent magnet material has a cerium content ≥50wt.%, excellent comprehensive magnetic properties, and can significantly reduce raw material costs.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) This invention addresses the bottleneck problem of the difficulty in improving the comprehensive magnetic properties of rare earth permanent magnet materials with high cerium content (≥50wt.%). Through targeted composition design, the Ce content is increased while the Al content of alloying elements in the magnet is increased to varying degrees. The optimized ratio of other alloying elements such as Cu and rare earth elements such as La is also used. The main purpose is to match the subsequent sintering and heat treatment processes, so as to suppress the uneven precipitation of a large number of agglomerated REFe2 phases and their excessive proportion in the magnet, thereby achieving the goal of improving the comprehensive magnetic properties such as coercivity, squareness, and remanence.

[0017] (2) Based on extensive experimental research, this invention proposes a cooling method for rare earth permanent magnet materials with high Ce content, which involves introducing a continuous flow of argon or nitrogen gas. The cooling rate is higher than that of conventional Ce magnets cooled in the furnace. By adjusting the gas flow rate, the cooling rate can be precisely controlled, thereby controlling the microstructure during sintering or heat treatment and avoiding the uneven precipitation of a large number of agglomerated REFe2 phases during slow cooling.

[0018] (3) Unlike grain boundary reconstruction or grain boundary diffusion technology, this invention does not require the addition of grain boundary reconstruction alloy before powder preparation or sintering, nor does it require the addition of grain boundary diffusion source before heat treatment. It only targets the magnetic powder designed with the initial composition. By finely controlling its sintering and multi-stage heat treatment process, the gas cooling mainly controls the phase transformation of the Ce-rich 1:2 phase and the Al-rich grain boundary phase, including its composition / content / distribution, so as to achieve the control of high comprehensive magnetic properties.

[0019] (4) The multi-stage heat treatment system (≥3 stages) proposed in this invention sets up heat treatments in the ranges of high temperature (600-800℃), medium temperature (450-700℃), and low temperature (300-450℃). Each stage of heat treatment is indispensable, achieving progressive goals such as regulating the uniform formation of REFe2 phase, uniform formation of RE-rich phase, and stress elimination within the magnet. This has a synergistic effect on improving its comprehensive magnetic properties, especially coercivity and squareness. In fact, once the agglomerated REFe2 phase precipitates unevenly during the high-temperature cooling process, the subsequent medium- and low-temperature heat treatment processes will not be able to effectively improve the microstructure. This technology differs from the two-step heat treatment system of traditional NdFeB magnets, which mainly regulates the ternary and binary eutectic transformation of the main phase / rare earth-rich phase / boron-rich phase; it also differs from the one-step heat treatment or no-heat-treatment system of traditional NdCFeB magnets, which mainly aims to maintain the compositional gradient within the multi-main phase crystal. Detailed Implementation

[0020] The present invention will be further described and illustrated below with reference to specific embodiments. These embodiments are merely examples of the content of this disclosure and are not limited to the following embodiments:

[0021] Example 1:

[0022] (1) Magnetic powder was prepared by smelting, belt spinning, hydrogen crushing, and air jet milling processes. The composition, by mass percentage, was [(Pr 0.2 Nd 0.8 ) 0.25 Ce 0.75 ] 32 Fe bal Al 0.3 Co 0.3 Cu 0.15 Zr 0.2 Ga 0.3 B 0.92 .

[0023] (2) The obtained magnetic powder (of which Ce accounts for 75 wt.% of the total rare earth) is prepared into a magnet by liquid phase sintering process. The sintering temperature is 1000℃ and the sintering time is 5h. After sintering, argon gas is continuously introduced into the furnace. The flow rate of argon gas is controlled at 0.5L / min and the average cooling rate of the magnet is 28℃ / min.

[0024] (3) The prepared magnet was subjected to multi-stage heat treatment to obtain a rare earth permanent magnet material with high coercivity and high cerium content. The first stage heat treatment temperature was 680℃ and the heat treatment time was 3h. The second stage heat treatment temperature was 630℃ and the heat treatment time was 3h. The third stage heat treatment temperature was 400℃ and the heat treatment time was 2h. After each stage heat treatment, argon gas was continuously introduced into the furnace. The flow rate of argon gas was controlled at 0.25L / min. The average cooling rate of the magnet was 25℃ / min.

[0025] The AMT-4 permanent magnet characteristic measuring instrument test results show that the remanence of the sintered magnet is 10.03 kG, the coercivity is 4.02 kOe, the squareness is 0.91, and the maximum energy product is 21.39 MGOe; the remanence of the heat-treated magnet is 10.03 kG, the coercivity is 5.37 kOe, the squareness is 0.95, and the maximum energy product is 22.54 MGOe.

[0026] Comparative Example 1:

[0027] The difference from Example 1 is that the cooling method after sintering in step (2) is different; furnace cooling is used with an average cooling rate of 6℃ / min. The test results of the AMT-4 permanent magnet characteristic measuring instrument show that the remanence of the sintered magnet is 9.98kG, the coercivity is 3.05kOe, the squareness is 0.85, and the maximum energy product is 16.86MGOe; the remanence of the heat-treated magnet is 9.95kG, the coercivity is 4.15kOe, the squareness is 0.86, and the maximum energy product is 17.85MGOe. The magnetic properties of both the sintered and heat-treated magnets are less than those of Example 1.

[0028] Comparative Example 2:

[0029] The difference from Example 1 is that the cooling method after each heat treatment in step (3) is different. After each heat treatment, furnace cooling is adopted, and the average cooling rate is 5℃ / min. The test results of the AMT-4 permanent magnet characteristic measuring instrument show that the remanence of the sintered magnet is 10.03kG, the coercivity is 4.02kOe, the squareness is 0.91, and the maximum energy product is 21.39MGOe; the remanence of the heat-treated magnet is 9.98kG, the coercivity is 3.03kOe, the squareness is 0.83, and the maximum energy product is 16.47MGOe. The magnetic properties of the heat-treated magnet are all lower than those of Example 1.

[0030] Comparative Example 3:

[0031] The difference from Example 1 is that the cooling methods after each heat treatment in steps (2) sintering and (3) are different. Both adopt furnace cooling, with an average cooling rate of 6℃ / min after sintering and an average cooling rate of 5℃ / min after heat treatment. The test results of the AMT-4 permanent magnet characteristic measuring instrument show that the remanence of the sintered magnet is 9.98kG, the coercivity is 3.05kOe, the squareness is 0.85, and the maximum energy product is 16.86MGOe; the remanence of the heat-treated magnet is 9.94kG, the coercivity is 2.47kOe, the squareness is 0.80, and the maximum energy product is 14.73MGOe. The magnetic properties of both the sintered and heat-treated magnets are less than those of Example 1.

[0032] Comparative Example 4:

[0033] The difference from Example 1 is that step (3) heat treatment only involves the first stage of heat treatment (the cooling method after heat treatment is the same as in Example 1). The test results of the AMT-4 permanent magnet characteristic measuring instrument show that the remanence of the sintered magnet is 10.03kG, the coercivity is 4.02kOe, the squareness is 0.91, and the maximum energy product is 21.39MGOe; the remanence of the heat-treated magnet is 10.01kG, the coercivity is 4.55kOe, the squareness is 0.85, and the maximum energy product is 20.58MGOe. The magnetic properties of the heat-treated magnet are all lower than those of Example 1.

[0034] Comparative Example 5:

[0035] The difference from Example 1 is that step (3) heat treatment only involves the first and second stages of heat treatment (the cooling method after each stage of heat treatment is the same as in Example 1). The test results of the AMT-4 permanent magnet characteristic measuring instrument show that the remanence of the sintered magnet is 10.03 kG, the coercivity is 4.02 kOe, the squareness is 0.91, and the maximum energy product is 21.39 MGOe; the remanence of the heat-treated magnet is 10.01 kG, the coercivity is 4.87 kOe, the squareness is 0.90, and the maximum energy product is 21.82 MGOe. The magnetic properties of the heat-treated magnet are all lower than those of Example 1.

[0036] Example 2:

[0037] (1) Two types of magnetic powder were prepared using smelting, belt spinning, hydrogen crushing, and air jet milling processes. The composition of magnetic powder 1, by mass percentage, was [(Pr 0.2 Nd 0.8 ) 0.25 Ce 0.75 ] 32 Fe bal Co 0.8 Cu0.25 Al 0.5 Nb 0.2 Ga 0.4 B 0.94 The composition of magnetic powder 2 is (Pr 0.2 Nd 0.8 ) 32 Fe bal Co 0.8 Cu 0.25 Al 0.5 Nb 0.2 Ga 0.4 B 0.94 .

[0038] (2) The obtained magnetic powder 1 and magnetic powder 2 are uniformly mixed at a mass ratio of 87:13 (where Ce accounts for 65wt.% of the total rare earth), and then a magnet is prepared by liquid phase sintering process. The sintering temperature is 1030℃ and the sintering time is 3h. After sintering, argon gas is continuously introduced into the furnace. The flow rate of argon gas is controlled at 0.5L / min, and the average cooling rate of the magnet is 30℃ / min.

[0039] (3) The prepared magnets were subjected to multi-stage heat treatment to obtain high-cerium content rare-earth permanent magnet materials. The first stage heat treatment temperature was 690℃ and the heat treatment time was 2.5h; the second stage heat treatment temperature was 630℃ and the heat treatment time was 2.5h; and the third stage heat treatment temperature was 390℃ and the heat treatment time was 2h. After each stage heat treatment, argon gas was continuously introduced into the furnace, and the argon gas flow rate was controlled at 0.2L / min. The average cooling rate of the magnets was 20℃ / min. The test results of the AMT-4 permanent magnet characteristic measuring instrument showed that the remanence of the sintered magnets was 11.16kG, the coercivity was 7.07kOe, the squareness was 0.92, and the maximum energy product was 28.59MGOe; the remanence of the heat-treated magnets was 11.18kG, the coercivity was 9.46kOe, the squareness was 0.94, and the maximum energy product was 29.35MGOe.

[0040] Comparative Example 6:

[0041] The difference from Example 2 is that the cooling method after sintering in step (2) is different; traditional furnace cooling is used with an average cooling rate of 6℃ / min. The test results of the AMT-4 permanent magnet characteristic measuring instrument show that the remanence of the sintered magnet is 11.12kG, the coercivity is 6.32kOe, the squareness is 0.88, and the maximum energy product is 27.87MGOe; the remanence of the heat-treated magnet is 11.10kG, the coercivity is 7.79kOe, the squareness is 0.85, and the maximum energy product is 28.04MGOe. The magnetic properties of both the sintered and heat-treated magnets are less than those of Example 2.

[0042] Comparative Example 7:

[0043] The difference from Example 2 is that the cooling method after each heat treatment stage in step (3) is different. Traditional furnace cooling is used after each heat treatment stage, with an average cooling rate of 5℃ / min. The test results of the AMT-4 permanent magnet characteristic measuring instrument show that the remanence of the sintered magnet is 11.16kG, the coercivity is 7.07kOe, the squareness is 0.92, and the maximum energy product is 28.29MGOe; the remanence of the heat-treated magnet is 11.00kG, the coercivity is 7.86kOe, the squareness is 0.84, and the maximum energy product is 27.10MGOe. The magnetic properties of the heat-treated magnet are all lower than those of Example 2.

[0044] Comparative Example 8:

[0045] The difference from Example 2 is that the cooling methods after each heat treatment in steps (2) and (3) are different. Traditional furnace cooling is used. The average cooling rate after sintering is 6℃ / min, and the average cooling rate after heat treatment is 5℃ / min. The test results of the AMT-4 permanent magnet characteristic measuring instrument show that the remanence of the sintered magnet is 11.12kG, the coercivity is 6.32kOe, the squareness is 0.88, and the maximum energy product is 27.87MGOe; the remanence of the heat-treated magnet is 10.93kG, the coercivity is 7.03kOe, the squareness is 0.80, and the maximum energy product is 26.45MGOe. The magnetic properties of both the sintered and heat-treated magnets are less than those of Example 2.

[0046] Example 3:

[0047] (1) Two types of magnetic powder were prepared using smelting, belt spinning, hydrogen crushing, and air jet milling processes. The composition of magnetic powder 1, by mass percentage, was [(Pr 0.2 Nd 0.8 ) 0.20 Gd 0.05 Ce 0.75 ] 32 Fe bal Co 0.6 Cu 0.15 Al 0.3 Zr 0.2 Ga 0.5 B 0.95 The composition of magnetic powder 2 is (Pr 0.2 Nd 0.8 ) 32 Fe bal Co 0.6 Cu 0.15 Al 0.3 Zr 0.2 Ga 0.5 B 0.95 .

[0048] (2) The obtained magnetic powder 1 and magnetic powder 2 are uniformly mixed at a mass ratio of 2:1 (where Ce accounts for 50 wt.% of the total rare earth). The mixture is then used to prepare a magnet by liquid phase sintering. The sintering temperature is 1020℃ and the sintering time is 3h. After sintering, argon gas is continuously introduced into the furnace. The flow rate of argon gas is controlled at 0.45L / min. The average cooling rate of the magnet is 30℃ / min.

[0049] (3) The prepared magnet was subjected to multi-stage heat treatment to obtain a high-cerium content rare earth permanent magnet material. The first stage heat treatment temperature was 690℃ and the heat treatment time was 2.5h. The second stage heat treatment temperature was 640℃ and the heat treatment time was 2.5h. The third stage heat treatment temperature was 385℃ and the heat treatment time was 2h. After each stage heat treatment, argon gas was continuously introduced into the furnace. The flow rate of argon gas was controlled at 0.2L / min. The average cooling rate of the magnet was 20℃ / min.

[0050] The AMT-4 permanent magnet characteristic measuring instrument test results show that the remanence of the sintered magnet is 11.16 kG, the coercivity is 9.90 kOe, the squareness is 0.95, and the maximum energy product is 30.33 MGOe; the remanence of the heat-treated magnet is 11.15 kG, the coercivity is 12.38 kOe, the squareness is 0.95, and the maximum energy product is 31.60 MGOe. Comparative Example 9:

[0051] The difference from Example 3 is that the cooling method after sintering in step (2) is different; traditional furnace cooling is used, with an average cooling rate of 6℃ / min. The test results of the AMT-4 permanent magnet characteristic measuring instrument show that the remanence of the sintered magnet is 11.10kG, the coercivity is 8.02kOe, the squareness is 0.90, and the maximum energy product is 29.75MGOe; the remanence of the heat-treated magnet is 11.07kG, the coercivity is 10.26kOe, the squareness is 0.85, and the maximum energy product is 28.64MGOe. The magnetic properties of both the sintered and heat-treated magnets are less than those of Example 3.

[0052] Comparative Example 10:

[0053] The difference from Example 3 is that the cooling method after each heat treatment in step (3) is different. Traditional furnace cooling is used after each heat treatment, with an average cooling rate of 5℃ / min. The test results of the AMT-4 permanent magnet characteristic measuring instrument show that the remanence of the sintered magnet is 11.16kG, the coercivity is 9.90kOe, the squareness is 0.95, and the maximum energy product is 30.33MGOe; the remanence of the heat-treated magnet is 11.05kG, the coercivity is 10.36kOe, the squareness is 0.80, and the maximum energy product is 28.50MGOe. The magnetic properties of the heat-treated magnet are less than those of Example 3.

[0054] Example 4:

[0055] (1) A magnetic powder was prepared by smelting, belt spinning, hydrogen crushing, and air jet milling processes, with the composition as [(Pr] by mass percentage] 0.2 Nd 0.8 ) 0.45 La 0.05 Ce 0.50 ] 32 Fe bal Cu 0.15 Al 0.6 Ti 0.2 Nb 0.1 Ga 0.1 B 0.92 .

[0056] (2) The obtained magnetic powder was prepared into a magnet by liquid phase sintering process. The sintering temperature was 1035℃ and the sintering time was 3h. After sintering, argon gas was continuously introduced into the furnace. The flow rate of argon gas was controlled at 0.5L / min and the average cooling rate of the magnet was 30℃ / min.

[0057] (3) The prepared magnet was subjected to multi-stage heat treatment to obtain a high-cerium content rare earth permanent magnet material. The first stage heat treatment temperature was 650℃ and the heat treatment time was 3h. The second stage heat treatment temperature was 500℃ and the heat treatment time was 3h. The third stage heat treatment temperature was 400℃ and the heat treatment time was 2.5h. After each stage heat treatment, argon gas was continuously introduced into the furnace. The flow rate of argon gas was controlled at 0.25L / min. The average cooling rate of the magnet was 20℃ / min.

[0058] The AMT-4 permanent magnet characteristic measuring instrument test results show that the remanence of the sintered magnet is 11.04 kG, the coercivity is 10.13 kOe, the squareness is 0.96, and the maximum energy product is 28.33 MGOe; the remanence of the heat-treated magnet is 11.08 kG, the coercivity is 12.56 kOe, the squareness is 0.95, and the maximum energy product is 30.16 MGOe.

[0059] Comparative Example 11:

[0060] The difference from Example 4 is that the cooling methods after each heat treatment in steps (2) and (3) are different. Traditional furnace cooling is used. The average cooling rate after sintering is 6℃ / min, and the average cooling rate after heat treatment is 5℃ / min. The test results of the AMT-4 permanent magnet characteristic measuring instrument show that the remanence of the sintered magnet is 10.92kG, the coercivity is 8.35kOe, the squareness is 0.90, and the maximum energy product is 27.52MGOe; the remanence of the heat-treated magnet is 10.76kG, the coercivity is 9.60kOe, the squareness is 0.82, and the maximum energy product is 26.33MGOe. The magnetic properties of both the sintered and heat-treated magnets are less than those of Example 4.

[0061] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A method for preparing a high cerium content rare earth permanent magnet material, characterized in that, Includes the following steps: (1) The preparation component is [R] 1-a-x R' a Ce x ] b Fe bal M c Al d B e The magnetic powder, wherein R is one or both of the rare earth elements Nd and Pr, R' is one or more of the rare earth elements La, Gd, Tb, Dy, Ho, Sm, and Y, Ce is the rare earth element cerium, Fe is the iron element, M is one or more of the alloying elements Cu, Ni, Cr, Co, Ga, Mn, Nb, Zr, Ti, V, and Zn, Al is the aluminum element, B is the boron element, and by mass percentage, 0.5≤x≤1, 0≤a≤0.2, 29≤b≤35, 0.15≤c≤5, 0.2≤d≤1, and 0.8≤e≤1; (2) The magnetic powder obtained in step (1) is used to prepare a magnet by sintering. The sintering temperature is 950-1080℃ and the sintering time is 1-10h. The magnet is cooled to room temperature by continuously introducing argon gas into the furnace. (3) The magnet obtained in step (2) is subjected to multi-stage heat treatment to obtain cerium-rich rare earth permanent magnet material. The heat treatment temperature is 300-800℃ and the heat treatment time is 3-12h. After each stage of heat treatment, the magnet is cooled to room temperature by continuously introducing argon or nitrogen gas into the furnace.

2. The production method according to claim 1, characterized by, The magnetic powder preparation process in step (1) includes: belt spinning, hydrogen crushing and air jet milling.

3. The preparation method according to claim 1, characterized in that, The magnetic powder in step (1) can be obtained directly by a single principal phase method or by a multi-principal phase method to obtain the final composition.

4. The method of claim 1, wherein, In steps (2) and (3), the flow rate of the continuous airflow introduced into the furnace body is V≤0.5L / min, and the average cooling rate of the magnet is 20~30℃ / min.

5. The preparation method according to claim 1, characterized in that, The multi-stage heat treatment in step (3) includes at least three stages: the first stage temperature is 600-800℃ and the holding time is 1-4h; the second stage temperature is 450-700℃ and the holding time is 1-4h; and the third stage temperature is 300-450℃ and the holding time is 1-4h.

6. The method of claim 1, wherein, The sintering and heat treatment processes described in steps (2) and (3) maintain a vacuum degree in the furnace ≤ 10 -3 Pa.

7. A rare earth permanent magnet material with high cerium content prepared by the method according to any one of claims 1-6.