A cerium-rich r-t-b sintered magnet and a method for producing the same

Abstract

The application discloses a kind of cerium-rich R-T-B series sintered magnets and preparation method thereof, the preparation method includes the following steps: S1, preparation mixed powder, the mixed powder is obtained by the first R-T-B series alloy powder of cerium-rich rare earth and the second R-T-B series alloy powder of cerium-poor rare earth is mixed uniformly, wherein, the sphericity of the first R-T-B series alloy powder is not less than 0.75;S2, mixed powder is prepared into R-T-B series sintered magnet.The preparation method constructs the grain shell layer of low Ce content in the interior of cerium-rich R-T-B series sintered magnet, to improve the intrinsic coercivity of cerium-rich R-T-B series sintered magnet.By the preparation method of the application, high-performance R-T-B series sintered magnet rich in Ce element can be prepared, and the application of Ce resources in R-T-B series sintered magnet is promoted.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of rare earth permanent magnet materials, and particularly relates to a preparation method of a cerium-rich R-T-B sintered magnet and a high-performance cerium-rich R-T-B sintered magnet prepared by the preparation method. BACKGROUND

[0002] The R-T-B sintered magnet is a kind of magnet material with the highest performance among the currently known permanent magnets. In the R-T-B magnet, R represents at least one kind of rare earth element, T represents at least one kind of transition metal element, and B represents boron element. In the commonly used R-T-B magnet, Nd is mainly used as R, and Fe is mainly used as T, which is also called neodymium-iron-boron magnet. The R-T-B sintered magnet has been widely used in various generators of automobiles, household appliances and the like. With the rapid development and wide application of the R-T-B sintered magnet, a large amount of rare earth resources such as Nd are consumed. Since the rare earth elements such as Nd, Pr, Dy and Tb have low abundance and high cost, in order to realize comprehensive balanced utilization and high cost performance of rare earth resources, the rare earth element Ce is used to partially replace other rare earth elements such as Nd, and a R-T-B sintered magnet rich in Ce element is developed, which promotes the application of Ce resources and has high practical value.

[0003] Currently, the methods for preparing the cerium-rich R-T-B sintered magnet mainly include single alloy method and double / multiple alloy method. However, whether the single alloy method or the double / multiple alloy method, the coercivity of the prepared cerium-rich R-T-B sintered magnet is not high, which is mainly due to the following reasons. (1) Single alloy method: a single alloy process is used, and the Ce element is uniformly distributed in the main phase crystal grains. The Ce content of each main phase crystal grain core and surface layer is equivalent. The coercivity mechanism of the R-T-B sintered magnet is nucleation mechanism. Since the anisotropy field of Ce-Fe-B is low, and in addition, the structure defects of the main phase crystal grain surface layer, the reverse magnetization domain is easy to nucleate on the main phase crystal grain surface layer. Therefore, the coercivity of the prepared cerium-rich R-T-B sintered magnet is low. (2) Double / multiple alloy method: a double / multiple alloy process (Ce-rich alloy + Ce-lean alloy) is used. During the sintering densification process, the sharp corners of the Ce-rich alloy powder and the Ce-lean alloy powder are melted, and a liquid state with medium Ce content is formed. Then, the Ce-rich powder and the Ce-lean powder are attached and precipitated on the surface, and finally a grain surface layer with a certain Ce content is formed on the surface of the Ce-rich grain and the Ce-lean grain. The coercivity of this surface layer is low, which leads to the low coercivity of the entire magnet.

[0004] In order to improve the coercivity of the cerium-rich R-T-B sintered magnet, the grain boundary diffusion technology of heavy rare earth elements is also applied to the cerium-rich R-T-B sintered magnet. As described above, the surface layer of the main phase crystal grains of the cerium-rich R-T-B sintered magnet prepared by the single alloy method or the double / multiple alloy method has a high Ce content. Since the formation energy of Ce2Fe 14 B is low, it is difficult for Dy, Tb and other heavy rare earth elements to replace Ce in Ce2Fe 14 B, so that the grain boundary diffusion effect of the cerium-rich R-T-B sintered magnet is not good, and the improvement range of the coercivity is limited, so that it is difficult to obtain a high-performance cerium-rich R-T-B sintered magnet. SUMMARY

[0005] Therefore, the primary purpose of the present application is to provide a preparation method of a cerium-rich R-T-B sintered magnet, which constructs a low-Ce-content grain shell layer in the cerium-rich R-T-B sintered magnet, thereby improving the intrinsic coercivity of the cerium-rich R-T-B sintered magnet.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] The present application first provides a preparation method of a cerium-rich R-T-B sintered magnet, comprising the following steps:

[0008] S1, preparing a mixed powder, the mixed powder being obtained by uniformly mixing a first R-T-B alloy powder rich in cerium and poor in rare earth and a second R-T-B alloy powder poor in cerium and rich in rare earth, wherein the sphericity of the first R-T-B alloy powder is not less than 0.75;

[0009] S2, preparing the mixed powder into an R-T-B sintered magnet.

[0010] In a further scheme, the composition of the first R-T-B alloy powder is R x T y B z M a , wherein 29wt.%≤x≤30wt.%, 0.89wt.%≤z≤0.92wt.%, 0wt.%≤a≤0.5wt.%, y=100-x-z-a;

[0011] R is a rare earth element and must contain Ce and La, wherein Ce accounts for more than 20% of the total mass of R, and La accounts for 5% to 10% of the total mass of R; T is a transition metal element and must contain Fe, wherein Fe accounts for more than 92% of the total mass of T; B is a boron element; and M is an auxiliary metal element, which is composed of one or a mixture of two or more of Cu, Al, Ga, Zn, Zr, Nb and Ti.

[0012] Further, the rare earth element R further contains one or more of Ce, Pr, Nd, Dy, Tb, Gd, Ho, and Y, wherein the content of Ce is less than 10% of the total mass of R, and the content of Dy and / or Tb is less than 5% of the total mass of R.

[0013] Further, the transition metal element T further contains Co, and the content of Co is less than 8% of the total mass of T.

[0014] Further, the second R-T-B alloy powder has a composition of R' b T' c B' d M' f wherein 32wt.%≤b≤34wt.%, 0.88wt.%≤d≤0.91wt.%, 0.5wt.%≤f≤1.0wt.%, and c=100-b-d-f.

[0015] R' is a rare earth element and contains Nd, and the content of Nd is more than 50% of the total mass of R'; T' is a transition metal element and contains Fe, and the content of Fe is more than 92% of the total mass of T'; B' is a boron element; and M' is an auxiliary metal element composed of one or more of Cu, Al, Ga, Zn, Zr, Nb, and Ti.

[0016] Further, the rare earth element R' further contains one or more of Ce, Pr, Nd, Dy, Tb, Gd, Ho, and Y, wherein the content of Ce is less than 10% of the total mass of R', and the content of Dy and / or Tb is less than 5% of the total mass of R.

[0017] Further, the transition metal element T' further contains Co, and the content of Co is less than 8% of the total mass of T'.

[0018] Further, the average particle size of the first R-T-B alloy powder and the second R-T-B alloy powder is 2.0-2.8 μm, and the difference between the average particle sizes of the two is less than 0.2 μm.

[0019] Further, the first R-T-B alloy powder is obtained through a spheroidization process, wherein the spheroidization process is mechanical grinding or high-temperature melting.

[0020] Further, the mechanical grinding process includes stirring, rolling, collision, or friction to grind off the sharp edges and corners on the surface of the powder particles to achieve spheroidization of the powder.

[0021] Further, the mechanical grinding process is followed by a powder screening process.

[0022] Further, the high-temperature melting is achieved by heating to melt the sharp edges and corners on the surface of the powder, thereby achieving spheroidization of the powder.

[0023] Further, the heating temperature is 1000-1050℃.

[0024] Further, the heating method is resistance heating, induction heating, RF induction plasma heating or laser heating.

[0025] Further, after the high-temperature melting step, a step of crushing and powdering is further included.

[0026] Further, in the mixed powder, the mass ratio of the first R-T-B based alloy powder to the second R-T-B based alloy powder is (5-7):(3-5).

[0027] Further, the step S2 includes the steps of orientation press forming, sintering and heat treatment of the mixed powder.

[0028] Further, the orientation press forming is a die forming of the mixed powder in a protection atmosphere of water and oxygen isolation in an orientation magnetic field with a strength of 1.2T-1.5T.

[0029] Further, the sintering temperature is 1030-1080℃ and the sintering time is 3-5 hours.

[0030] Further, the heat treatment includes a first-level heat treatment with a temperature of 880-920℃ and a heat treatment time of 2-5 hours and a second-level heat treatment with a temperature of 480-560℃ and a heat treatment time of 2-5 hours.

[0031] Further, the preparation method further includes a step S3 of performing heavy rare earth element diffusion on the R-T-B based sintered magnet by using a grain boundary diffusion technique.

[0032] Further, the heavy rare earth element diffusion in the step S3 includes the following steps:

[0033] Pre-treating the R-T-B based sintered magnet;

[0034] After attaching a heavy rare earth diffusion source on the surface of the pre-treated R-T-B based sintered magnet, high-temperature heat treatment is performed to complete the diffusion.

[0035] Further, the heavy rare earth diffusion source is a substance containing heavy rare earth elements, and the mass fraction of the heavy rare earth elements in the heavy rare earth diffusion source is greater than 50%.

[0036] Further, the high-temperature heat treatment temperature is 800-920℃ and the heat treatment time is 5-15h.

[0037] The application further provides a cerium-rich R-T-B sintered magnet prepared by the preparation method.

[0038] The application has the following advantages:

[0039] The application mixes the Ce-rich alloy powder with high sphericity and the rare earth-rich alloy powder with low Ce content, (1) the Ce-rich alloy powder with high sphericity reduces the rotation resistance of the powder particles in the orientation forming process, and improves the remanence and maximum magnetic energy product of the magnet. (2) The Ce-rich alloy powder with high sphericity can reduce the corner dissolution of the Ce-rich alloy powder in the high-temperature liquid phase sintering process, reduce the concentration of Ce in the liquid phase, and further reduce the Ce content of the surface layer of the main phase grains of the sintered magnet, thereby forming a low-Ce-content "shell". The low-Ce-content "shell" can improve the intrinsic coercivity of the initial magnet, thereby promoting the application of Ce in the R-T-B sintered magnet. DETAILED DESCRIPTION

[0040] The embodiments of the application will be described in detail below with reference to the examples, which are exemplary and are only used to explain the application, and cannot be understood as a limitation of the application.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the application belongs. The terms used in the specification of the application herein are only for the purpose of describing the specific embodiments and are not intended to limit the application.

[0042] The first aspect of the application provides a preparation method of a cerium-rich R-T-B sintered magnet, which mixes the Ce-rich rare earth-poor R-T-B alloy powder with high sphericity and the rare earth-rich R-T-B alloy powder with low Ce content, prepares the R-T-B sintered magnet, and then diffuses the heavy rare earth elements through grain boundary diffusion, thereby preparing the high-performance cerium-rich R-T-B sintered magnet with significantly improved coercivity.

[0043] The main steps of the preparation method of the cerium-rich R-T-B sintered magnet in the application are as follows:

[0044] S1, preparing a mixed powder, the mixed powder is uniformly mixed by a first R-T-B alloy powder with Ce-rich and rare earth-poor and a second R-T-B alloy powder with Ce-poor and rare earth-rich, wherein the sphericity of the first R-T-B alloy powder is not less than 0.75.

[0045] In the present application, the "rich rare earth" means that the mass of Ce is more than 20% of the total mass of rare earth elements. The "rich rare earth and poor Ce" means that the mass of Ce is less than 10% of the total mass of rare earth elements (including no Ce).

[0046] Further, in some specific embodiments of the present application, the composition of the first R-T-B alloy powder rich in Ce and poor in rare earth is R x T y B z M a wherein 29wt.%≤x≤30wt.%, 0.89wt.%≤z≤0.92wt.%, 0wt.%≤a≤0.5wt.%, y=100-x-z-a;

[0047] R is a rare earth element and must contain Ce and La, wherein the mass of Ce is more than 20% of the total mass of R, and the mass of La is 5% to 10% of the total mass of R; T is a transition metal element and must contain Fe, wherein the mass of Fe is more than 92% of the total mass of T; B is a boron element; and M is an auxiliary metal element, which is composed of one or more than two of Cu, Al, Ga, Zn, Zr, Nb, Ti.

[0048] In some specific embodiments of the present application, the rare earth element R further contains one or more than two of Pr, Nd, Dy, Tb, Gd, Ho, Y. Preferably, in the rare earth element R, the mass of Ce is 20% to 60% of the total mass of R, the mass of La is 5% to 10% of the total mass of R, and the mass of Dy and / or Tb is less than 5% of the total mass of R.

[0049] In some specific embodiments of the present application, the transition metal element T further contains Co, and the mass of Co is less than 8% of the total mass of T.

[0050] Preferably, in the auxiliary element M, the mass of Zr and / or Nb and / or Ti is less than 0.1% of the total mass of R x T y B z M a .

[0051] In the present application, the first R-T-B alloy powder is subjected to spheroidization so as to have a high sphericity, i.e., the sphericity is not less than 0.75.

[0052] The spheroidization described herein means that the sharp edges and corners on the surface of the alloy powder are removed by a certain method so as to obtain a powder with high sphericity. The specific modification method can be mechanical grinding or high-temperature melting.

[0053] In some embodiments of the present application, the modification method is mechanical grinding, specifically, by using stirring, rolling, collision, friction and other methods to grind off the sharp corners on the surface of the powder particles to achieve spheroidization of the powder. The stirring refers to high-speed rotating metal blades that grind off the sharp corners on the surface of the powder while stirring, preferably at a speed of 1000 rpm or higher; the rolling refers to placing the powder between two rough and hard surfaces that move relative to each other, and applying a force to move the two surfaces closer to each other while moving relative to each other, thereby rolling the powder particles (similar to a stone mill or mortar); the collision refers to accelerating the powder to a certain speed and then vertically or nearly vertically colliding with a fixed and hard object surface, using the impact force to make the sharp corners fall off; the friction is also to accelerate the powder, but it collides with a fixed, hard and rough object surface at an angle (generally less than 45°), and the surface is scraped at an angle to form friction and grind off the sharp corners.

[0054] It should be noted that, in order to remove the ultra-fine powder generated by grinding during the mechanical grinding process, the mechanical grinding step is followed by a powder screening step.

[0055] In other embodiments of the present application, the modification method is high-temperature melting, which is achieved by melting the sharp corners on the surface of the powder by heating, and then realizing spheroidization of the powder; by melting-flowing-precipitating, the sharp corners on the surface of the powder are melted by heating, flow under the action of surface tension, and precipitate again in the low-lying part of the powder surface.

[0056] In some specific embodiments of the present application, the heating temperature is 1000-1050°C; the heating method can be carried out in a manner known in the art, for example, resistance heating, induction heating, radio frequency induction plasma heating or laser heating.

[0057] It should be noted that, in order to prevent the adhesion between the powder particles during the high-temperature melting spheroidization process, the high-temperature melting step is followed by a crushing and powdering step.

[0058] Further, in some specific embodiments of the present application, the composition of the second R-T-B alloy powder which is cerium-poor and rare earth-rich is R' b T' c B' d M' f , wherein 32wt.%≤b≤34wt.%, 0.88wt.%≤d≤0.91wt.%, 0.5wt.%≤f≤1.0wt.%, c=100-b-d-f;

[0059] R' is a rare earth element and contains Nd, and the mass percentage of Nd in R is more than 50%; T' is a transition metal element and contains Fe, and the mass percentage of Fe in T is more than 92%; B' is a boron element; and M' is an auxiliary metal element, which is composed of one or more than two of Cu, Al, Ga, Zn, Zr, Nb, and Ti.

[0060] In some specific embodiments of the present application, the rare earth element R' further contains one or more than two of Ce, Pr, Dy, Tb, Gd, Ho, and Y, wherein the mass percentage of Ce in R' is less than 10%, and the mass percentage of Dy and / or Tb in R is less than 5%.

[0061] In some specific embodiments of the present application, the transition metal element T' further contains Co, and the mass percentage of Co in T' is less than 8%.

[0062] Preferably, in the auxiliary element M', the mass percentage of Zr and / or Nb and / or Ti in R' is less than 0.3%. b T' c B' d M' f Preferably, in the auxiliary element M', the mass percentage of Zr and / or Nb and / or Ti in R' is less than 0.3%.

[0063] In the present application, the average particle size of the first R-T-B alloy powder and the second R-T-B alloy powder is 2.0-2.8 μm, and preferably, in order to improve the uniformity of the mixture of the two alloy powders, the difference between the average particle sizes of the two is less than 0.2 μm.

[0064] In the present application, the mass ratio of the first R-T-B alloy powder and the second R-T-B alloy powder in the mixed powder can be mixed according to the performance requirements, and preferably, in order to ensure that Ce has a high content in the final magnet to improve the utilization of Ce, while also ensuring the magnetic performance of the magnet, in some specific embodiments of the present application, the mass ratio of the first R-T-B alloy powder and the second R-T-B alloy powder is (5-7):(3-5), for example, it can be any one of 7:3, 6.5:3.5, 6:4, 5.5:4.5, 5:5, etc.

[0065] It should be noted that the preparation of the first R-T-B alloy powder and the second R-T-B alloy powder in the present application can be carried out by known methods in the art, and only the corresponding ingredients need to be prepared and processed according to the composition of the alloy powder. The specific process conditions and parameters can be adjusted and confirmed based on the known methods in the art, which will not be described herein.

[0066] S2, preparing the mixed powder into an R-T-B sintered magnet.

[0067] The process of preparing the mixed powder into the R-T-B sintered magnet in this application is a process well known in the art, which specifically includes the steps of orienting press forming, sintering and heat treatment of the mixed powder, and the specific process conditions in each step can be based on the methods known in the art.

[0068] In some specific embodiments of the application, the orienting press forming is a mold forming of the mixed powder in a orienting magnetic field with a strength of 1.2T-1.5T in a protective atmosphere which isolates water and oxygen, wherein the protective atmosphere herein refers to the inert or inactive gas commonly used in the art, such as nitrogen, noble gas (helium, argon, etc.); the condition of isolating water and oxygen is preferably that the oxygen content is less than 100ppm, and the water content is less than 10ppm.

[0069] In some specific embodiments of the application, the sintering temperature is 1030℃-1080℃, and the time is 3-5 hours.

[0070] The purpose of the heat treatment is to achieve the purpose of improving the magnetic performance of the sintered magnet by heat treatment, and the heat treatment temperature, time, etc. can adopt the known conditions, and in some specific embodiments of the application, the heat treatment includes primary heat treatment and secondary heat treatment, the primary heat treatment temperature is 880℃-920℃, and the heat treatment time is 2-5 hours, the secondary heat treatment temperature is 480℃-560℃, and the heat treatment time is 2-5 hours.

[0071] In the application, the Ce-rich alloy powder with high sphericity and the rare earth-rich alloy powder with low Ce content are mixed to form a "shell" with low Ce content in the final magnet. This "shell" with low Ce content improves the intrinsic coercivity of the final magnet.

[0072] As a further optimization of the above technical solution, the preparation method of the R-T-B sintered magnet in the application further includes step S3, using grain boundary diffusion technology to diffuse heavy rare earth elements into the R-T-B sintered magnet. On the basis of the foregoing process, the grain boundary diffusion process is used. Since the surface layer of the main phase crystal grains of the magnet forms a "shell" with low Ce content, it can promote the diffusion of heavy rare earth elements into the surface layer of the main phase crystal grains, form a "core-shell structure", and improve the grain boundary diffusion effect of heavy rare earth elements, and further significantly improve the intrinsic coercivity of the Ce-rich R-T-B sintered magnet.

[0073] The heavy rare earth element diffusion in step S3 in the application can be carried out by the methods known in the art, which mainly includes the following steps:

[0074] The R-T-B sintered magnet is pretreated;

[0075] After the heavy rare earth diffusion source is attached to the surface of the pre-processed R-T-B sintered magnet, high-temperature heat treatment is performed to complete the diffusion.

[0076] In the present application, the pre-treatment of the R-T-B sintered magnet means that the R-T-B sintered magnet is subjected to mechanical processing and / or surface cleaning and the like according to the needs.

[0077] The mechanical processing described herein refers to the process of mechanically processing a large magnet into a small size magnet, for example, by cutting and the like, so as to facilitate grain boundary diffusion. In some specific embodiments of the present application, the minimum size direction of the small size magnet processed is less than 10 mm, and preferably, the minimum size direction is less than 5 mm.

[0078] The surface cleaning described herein refers to the surface cleaning of the processed magnet using methods known in the art to wash off contaminants such as oil stains, magnetic mud, rust and the like attached to the surface, for example, using oil removal, alkaline cleaning or acid cleaning and the like.

[0079] Further, the heavy rare earth diffusion source is attached to the surface of the pre-processed R-T-B sintered magnet, wherein the attachment method is not particularly limited, as long as the heavy rare earth diffusion source can be covered on the surface of the R-T-B sintered magnet, and the method used can be coating (such as spraying), printing (such as silk printing), physical vapor deposition (such as magnetron sputtering) and the like, but is not limited thereto.

[0080] Further, the heavy rare earth diffusion source described herein refers to a substance rich in heavy rare earth elements, specifically, the proportion of heavy rare earth elements in the diffusion source is more than 50%, and the heavy rare earth elements herein generally refer to Dy and / or Tb. Specific examples of heavy rare earth diffusion sources can include Dy and / or Tb pure metal, compounds of Dy and / or Tb (such as oxides, hydrides or fluorides), binary / multinary alloys of Dy and / or Tb with other metals (such as dysprosium / cerium iron alloy, dysprosium / cerium cobalt alloy, dysprosium / cerium aluminum alloy or dysprosium / cerium copper alloy, etc.). It can be understood that the "multinary" described in the foregoing refers to three or more.

[0081] In the present application, the amount of heavy rare earth diffusion source added can be according to the needs of those skilled in the art, and in some specific embodiments, the heavy rare earth diffusion source is covered on the surface of the magnet, and the weight gain ratio of the magnet is 0.6wt~1wt%.

[0082] Further, the high temperature heat treatment described herein refers to heating a small size magnet covered with heavy rare earth diffusion source to promote the heavy rare earth diffusion source grain boundary diffusion on the outer surface into the magnet interior. The specific treatment temperature and time can be adjusted based on the method known in the art, and in some specific embodiments of the present application, the high temperature heat treatment temperature is 800-920℃, and the time is 5-15 hours.

[0083] The second aspect of the present application provides a cerium-rich R-T-B sintered magnet prepared by the preparation method of the first aspect of the present application; in the cerium-rich R-T-B sintered magnet, the mass of Ce accounts for more than 9.2% of the mass of rare earth, and the cerium-rich R-T-B sintered magnet has high performance, and the remanence, intrinsic coercivity and maximum magnetic energy product before grain boundary diffusion are all improved. The coercivity increase value after grain boundary diffusion is significantly increased, and the coercivity increase amplitude is also significantly improved, indicating that the cerium-rich R-T-B sintered magnet prepared in the present application can significantly improve the performance of the magnet, and the optimal scheme is to cooperate with the grain boundary diffusion process, which can significantly improve the grain boundary diffusion effect of heavy rare earth elements and significantly improve the magnetic properties of the cerium-rich R-T-B sintered magnet.

[0084] The present application will be described below through specific examples, it should be noted that the following specific examples are only for illustrative purposes, and do not limit the scope of the present application in any way, and in addition, if not specifically described, the method without specific description of conditions or steps is a conventional method, and the reagents and materials used can be obtained from commercial channels.

[0085] Example 1

[0086] The present embodiment provides a preparation method of a cerium-rich R-T-B sintered magnet, the specific steps are as follows:

[0087] (1) Preparation of R-T-B alloy powder

[0088] The composition of La 1.5 Ce6Pr 1.5 Nd 20 Dy1Fe 68.66 Cu 0.15 Al 0.1 Ga 0.1 Nb 0.02 Ti 0.08 B 0.89 (wt.%), the average particle size of the cerium-rich and rare earth-poor R-T-B alloy powder F is 2.65μm 10 ; the composition of Pr2Ho6Nd 23 Dy1Fe 66.24 Cu 0.3 Al 0.2 Ga0.1 Nb 0.12 Ti 0.15 B 0.89 (wt.%), cerium-poor rare earth-rich RTB alloy powder with an average particle size of 2.79 μm. 10 .

[0089] (2) RTB-based alloy powder F 10 spheroidization

[0090] Using a high-speed rolling mill and mixer to process cerium-rich, rare-earth-poor RTB-based alloy powder F 10 Spheroidization is achieved by grinding away the sharp edges of the powder particles. The powder after rolling and mixing is then sieved to remove the ultrafine powder (the sharp edges removed during rolling and mixing), resulting in powder F with a sphericity of 0.76. 11 .

[0091] (3) Powder mixing

[0092] The alloy powder F was spheroidized and modified according to a mass ratio of 7:3. 11 and alloy powder P 10 Mix evenly to obtain mixed powder K1.

[0093] (4) Preparation of sintered magnets

[0094] Under a nitrogen-protected environment with an oxygen content of less than 100 ppm and a water content of less than 10 ppm, the mixed powder K1 was molded in an orientation magnetic field of 1.3T, and then subjected to sintering at 1040℃ for 5 hours, primary heat treatment at 890℃ for 5 hours, and secondary heat treatment at 500℃ for 2 hours to produce RTB-based sintered magnet M. 10 .

[0095] (5) Grain boundary diffusion treatment

[0096] RTB-based sintered magnet M 10 The magnets were machined into small magnets with a minimum dimension of 3 mm. The surface of the machined magnets was then cleaned to remove oil, magnetic sludge, rust, and other contaminants. Dysprosium hydride powder was then sprayed onto the magnet surface with a weight gain of 0.8 wt%. Finally, the magnets were heat-treated at 800℃ for 20 hours to obtain the diffused magnet M. 11 .

[0097] Comparative Example 1

[0098] This comparative example discloses a method for preparing a cerium-rich RTB-based sintered magnet, the specific steps of which are as follows:

[0099] (1) Preparation of RTB-based alloy powder

[0100] Preparation of components with La1.05 Ce 4.2 Pr 1.65 Ho 1.8 Nd 20.9 Dy1Fe 67.934 Cu 0.195 Al 0.13 Ga 0.1 Nb 0.05 Ti 0.10 1B 0.89 A single R-T-B based alloy powder K1' (wt.%) (same as mixed powder K1).

[0101] (2) Sintered magnet preparation

[0102] Using the same implementation as in Example 1, the alloy powder K1' was made into an R-T-B based sintered magnet M 10 '.

[0103] (3) Grain boundary diffusion treatment

[0104] Using the same implementation as in Example 1, the R-T-B based sintered magnet M 10 ' was subjected to heavy rare earth element grain boundary diffusion to obtain a diffusion magnet M 11 '.

[0105] Comparative Example 2

[0106] In this comparative example, a method for preparing a cerium-rich R-T-B based sintered magnet was disclosed, which used the same implementation as in Example 1, with the only difference being that the cerium-rich rare earth-poor R-T-B based alloy powder F 10 was not subjected to sphericalization treatment. The other steps and process conditions were the same as in Example 1.

[0107] The method for preparing a cerium-rich R-T-B based sintered magnet in this comparative example had the following specific steps:

[0108] (1) Powder mixing

[0109] The alloy powder F 10 and the alloy powder P 10 in Example 1 were used, and the alloy powder F 10 and the alloy powder P 10 were uniformly mixed in a mass ratio of 7:3 to obtain a mixed powder K1".

[0110] (2) Sintered magnet preparation

[0111] Using the same implementation as in Example 1, the mixed powder K1" was made into an R-T-B based sintered magnet M 10 ".

[0112] (3) Grain boundary diffusion treatment

[0113] Using the same implementation method as in Example 1, the RTB-based sintered magnet M was subjected to... 10 "Diffusion of heavy rare earth elements at grain boundaries was carried out to obtain a diffusion magnet M." 11 ".

[0114] Example 2

[0115] This embodiment provides a method for preparing a cerium-rich RTB-based sintered magnet, the specific steps of which are as follows:

[0116] (1) Preparation of RTB-based alloy powder

[0117] The preparation composition is La2Ce 9.5 Pr3Nd 13.4 Dy1Tb 0.5 Fe 65.37 Co4Cu 0.05 Al 0.07 Ga 0.05Zn0.08Zr0.04 Nb 0.0 4B 0.9 (wt.%), cerium-rich and rare-earth-poor RTB alloy powder with an average particle size of 2.17 μm. 20 The preparation composition is Pr1Ho4Gd1Nd. 24 Dy1Tb 0.5 Fe 62.62 Co4Cu 0.2 Al 0.4 Zn 0.15 Zr 0.14 Nb 0.04 Ti 0.05 B 0.9 (wt.%), cerium-poor rare earth-rich RTB alloy powder with an average particle size of 2.01 μm. 20 .

[0118] (2) RTB-based alloy powder F 20 spheroidization

[0119] Laser heating of cerium-rich, rare-earth-poor RTB-based alloy powder F 20 Spheroidization was performed by heating to 1040℃ to melt the sharp edges of the powder particles. The spheroidized powder was then subjected to air jet milling to prevent particle adhesion, resulting in powder F with a sphericity of 0.77. 21 .

[0120] (3) Powder mixing

[0121] The alloy powder F was spheroidized and modified according to a 5:5 mass ratio. 21 and alloy powder P 20Mix evenly to obtain mixed powder K2.

[0122] (4) Preparation of sintered magnets

[0123] Under a nitrogen-protected environment with an oxygen content of less than 100 ppm and a water content of less than 10 ppm, mixed powder K2 was molded in a 1.5T orientation magnetic field, and then subjected to sintering at 1050℃ for 3 hours, primary heat treatment at 880℃ for 4 hours, and secondary heat treatment at 480℃ for 3 hours to produce RTB-based sintered magnet M. 20 .

[0124] (5) Grain boundary diffusion treatment

[0125] Large magnet M 20 The magnets were machined into small magnets with a minimum dimension of 9 mm. The surface of the machined magnets was then cleaned to remove oil, magnetic sludge, rust, and other contaminants. A terbium metal coating with a weight gain of 0.6 wt% was then physically vapor-deposited onto the magnet surface. Finally, the magnets were heat-treated at 840℃ for 25 hours to obtain the diffused magnet M. 21 .

[0126] Comparative Example 3

[0127] This comparative example discloses a method for preparing a cerium-rich RTB-based sintered magnet, the specific steps of which are as follows:

[0128] (1) Preparation of RTB-based alloy powder

[0129] The preparation composition is La1Ce 4.75 Pr2Ho2Gd 0.5 Nd 18.7 Dy1Tb 0.5 Fe 63.995 Co4Cu 0.125 Al 0.235 Ga 0.025 Zn 0.115 Zr 0.09 Nb 0.04 Ti 0.025 B 0.9 (wt.%) (same as mixed powder K2) of single RTB-based alloy powder K2'.

[0130] (2) Preparation of sintered magnets

[0131] Using the same implementation method as in Example 2, alloy powder K2' was used to fabricate an RTB-based sintered magnet M. 20 '.

[0132] (3) Grain boundary diffusion treatment

[0133] Using the same implementation method as in Example 2, the RTB-based sintered magnet M was subjected to... 20 'Diffusion of heavy rare earth elements at grain boundaries was carried out to obtain a diffusion magnet M' 21 '.

[0134] Comparative Example 4

[0135] This comparative example discloses a method for preparing a cerium-rich RTB-based sintered magnet, which adopts the same implementation method as in Example 2, except that: the cerium-rich, rare-earth-poor RTB-based alloy powder F was not processed. 20 Perform spheroidization treatment. All other steps and process conditions are the same as in Example 2.

[0136] The specific steps for preparing the cerium-rich RTB-based sintered magnet in this comparative example are as follows:

[0137] (1) Powder mixing

[0138] Using the alloy powder F from Example 2 20 and alloy powder P 20 Alloy powder F was mixed in a 5:5 mass ratio. 20 and alloy powder P 20 Mix evenly to obtain mixed powder K2.

[0139] (2) Preparation of sintered magnets

[0140] Using the same implementation method as in Example 2, the mixed powder K2” was used to prepare an RTB-based sintered magnet M. 20 ".

[0141] (3) Grain boundary diffusion treatment

[0142] Using the same implementation method as in Example 2, the RTB-based sintered magnet M was subjected to... 20 "Diffusion of heavy rare earth elements at grain boundaries was carried out to obtain a diffusion magnet M." 21 ".

[0143] Example 3

[0144] This embodiment provides a method for preparing a cerium-rich RTB-based sintered magnet, the specific steps of which are as follows:

[0145] (1) Preparation of RTB-based alloy powder

[0146] Preparation of components with La 2.5 Ce 13.4 Y 1.5 Nd 10.4 Dy1Tb 0.2 Fe 67.69 Co2Cu 0.2 Ga 0.1 Zr0.04 Ti 0.06 B 0.91 (wt.%), average particle size 2.77 μm, Ce-rich and rare earth-lean R-T-B based alloy powder F 30 ; the composition of Pr4Gd1Y2Ce3Nd 23 Dy1Fe 62.39 Co2Al 0.1 Ga 0.3 Zn 0.1 Zr 0.04 Ti 0.16 B 0.91 (wt.%), average particle size 2.63 μm, Ce-lean and rare earth-rich R-T-B based alloy powder P 30 .

[0147] (2) R-T-B based alloy powder F 30 spheroidization

[0148] The Ce-rich and rare earth-lean R-T-B based alloy powder F 30 was spheroidized by radio frequency induction plasma heating, the heating temperature was 1020℃, the sharp edges and corners on the surface of the powder particles were melted, the spheroidized powder was subjected to air milling to prevent the adhesion between the powder particles, and the powder F with a sphericity of 0.80 was obtained 31 .

[0149] (3) powder mixing

[0150] The spheroidized alloy powder F 31 and the alloy powder P 30 were uniformly mixed in a mass ratio of 6:4 to obtain a mixed powder K3.

[0151] (4) sintered magnet preparation

[0152] The mixed powder K3 was subjected to die compaction molding in a nitrogen atmosphere with an oxygen content of less than 100 ppm and a water content of less than 10 ppm, and in a 1.4T orientation magnetic field, and then was sintered at 1030℃ for 4 hours, subjected to a first heat treatment at 900℃ for 3 hours, and subjected to a second heat treatment at 530℃ for 4 hours to prepare an R-T-B based sintered magnet M 30 .

[0153] (5) grain boundary diffusion treatment

[0154] The bulk magnet M 30 was processed into a small-size magnet with a minimum size direction of 5mm, the small-size magnet after processing was subjected to surface cleaning to remove contaminants such as oil stains, magnet mud stains and rust stains attached to the surface, dysprosium oxide powder was screen printed on the surface of the magnet, the weight gain percentage was 1wt%, and then the magnet was heat treated at 880℃ for 15 hours to obtain a diffusion magnet M 31 .

[0155] Comparative Example 5

[0156] This comparative example discloses a preparation method of a cerium-rich R-T-B sintered magnet, the specific steps are as follows:

[0157] (1) Preparation of R-T-B alloy powder

[0158] The composition of the prepared alloy powder is La 1.5 Ce 9.24 Y 1.7 Pr 1.6 Gd 0.4 Nd 15.44 Dy1Tb 0.12 Fe 65.57 Co2Cu 0.12 Al 0.04 Ga 0.18 Zn 0.04 Zr 0.04 Ti 0.1 B 0.91 (wt.%) (same as mixed powder K3) of a single R-T-B alloy powder K3'.

[0159] (2) Preparation of sintered magnet

[0160] Using the same implementation as in Example 3, the alloy powder K3' is made into an R-T-B sintered magnet M 30 '.

[0161] (3) Grain boundary diffusion treatment

[0162] Using the same implementation as in Example 3, the R-T-B sintered magnet M 30 ' is subjected to heavy rare earth element grain boundary diffusion to obtain a diffusion magnet M 31 '.

[0163] Comparative Example 6

[0164] This comparative example discloses a preparation method of a cerium-rich R-T-B sintered magnet, which uses the same implementation as in Example 3, the only difference is that the cerium-rich rare earth-poor R-T-B alloy powder F 30 is not subjected to sphericalization treatment. Other steps and process conditions are the same as in Example 3.

[0165] The preparation method of the cerium-rich R-T-B sintered magnet in this comparative example, the specific steps are as follows:

[0166] (1) Powder mixing

[0167] The alloy powder F 30 and the alloy powder P 30Alloy powder F was mixed at a mass ratio of 6:4. 30 and alloy powder P 30 Mix evenly to obtain mixed powder K3.

[0168] (2) Preparation of sintered magnets

[0169] Using the same implementation method as in Example 3, the mixed powder K3” was used to prepare an RTB-based sintered magnet M. 30 ".

[0170] (3) Grain boundary diffusion treatment

[0171] Using the same implementation method as in Example 3, the RTB-based sintered magnet M was subjected to... 30 "Diffusion of heavy rare earth elements at grain boundaries was carried out to obtain a diffusion magnet M." 31 ".

[0172] Example 4

[0173] This embodiment provides a method for preparing a cerium-rich RTB-based sintered magnet, the specific steps of which are as follows:

[0174] (1) Preparation of RTB-based alloy powder

[0175] Preparation of components with La 2.9 Ce 17.4 Gd 0.8 Nd8Tb 0.5 Fe 63.49 Co 5.5 Cu 0.15 Al 0.1 Ga 0.05 Zn 0.1 Zr 0.03 Nb 0.0 3Ti 0.03 B 0.92 (wt.%), cerium-rich and rare-earth-poor RTB alloy powder with an average particle size of 2.04 μm. 40 The preparation composition is Pr1Ho2Gd1Y1Ce2Nd. 26 Tb 0.5 Fe 59.83 Co 5.1 Cu 0.1 Zn 0.1 Ga 0.2 Zr 0.13 Nb 0.03 Ti 0.13 B 0.88 (wt.%), cerium-poor rare-earth-rich RTB alloy powder with an average particle size of 2.18 μm. 40 .

[0176] (2) R-T-B system alloy powder F 40 Spheroidization

[0177] Spheroidization of R-T-B system alloy powder F rich in cerium and poor in rare earth by high-pressure gas flow collision 40 Spheroidization was performed, sharp edges and corners on the surface of the powder particles were ground off, and the powder after high-pressure gas flow collision was sieved to remove the sharp corners of the powder particles that were knocked off during the high-pressure gas flow collision process, thereby obtaining powder F with a sphericity of 0.82 41 .

[0178] (3) Powder mixing

[0179] The spheroidized alloy powder F 41 and the alloy powder P 40 were uniformly mixed in a mass ratio of 7:3 to obtain mixed powder K4.

[0180] (4) Sintered magnet preparation

[0181] The mixed powder K4 was die formed in a 1.2T orientation magnetic field under a nitrogen protective environment with an oxygen content of less than 100ppm and a water content of less than 10ppm, and then sintered at 1080℃ for 4.5 hours, first heat treated at 920℃ for 2 hours, and second heat treated at 560℃ for 5 hours to obtain an R-T-B system sintered magnet M 40 .

[0182] (5) Grain boundary diffusion treatment

[0183] The bulk magnet M 40 was processed into a small-size magnet with a minimum size direction of 5mm, the small-size magnet after processing was surface cleaned to wash off surface-attached oil stains, magnet mud stains, and other contaminants, a terbium hydride powder was sprayed on the surface of the magnet with a weight gain percentage of 0.8wt%, and then heat treated at 920℃ for 10 hours to obtain a diffusion magnet M 41 .

[0184] Comparative Example 7

[0185] This comparative example discloses a preparation method of a cerium-rich R-T-B system sintered magnet, and the specific steps are as follows:

[0186] (1) R-T-B system alloy powder preparation

[0187] An alloy powder with a composition of La 2.03 Ce 12.78 Y 0.3 Pr 0.3 Ho 0.6 Gd 0.86 Nd 13.4 Tb 0.5 Fe 62.392 Co5.38 Cu 0.135 Al 0.0 7Ga 0.095 Zn 0.1 Zr 0.06 Nb 0.03 Ti 0.06 B 0.908 (wt.%)(same as mixed powder K4) of a single R-T-B based alloy powder K4'.

[0188] (2) Sintered magnet preparation

[0189] Using the same implementation as in Example 4, the alloy powder K4' was made into an R-T-B based sintered magnet M 40 '.

[0190] (3) Grain boundary diffusion treatment

[0191] Using the same implementation as in Example 4, the R-T-B based sintered magnet M 40 ' was subjected to heavy rare earth element grain boundary diffusion to obtain a diffusion magnet M 41 '.

[0192] Comparative Example 8

[0193] In this comparative example, a method for preparing a cerium-rich R-T-B based sintered magnet was disclosed, which used the same implementation as in Example 4, with the only difference being that the cerium-rich rare earth-poor R-T-B based alloy powder F 40 was not subjected to sphericalization treatment. The other steps and process conditions were the same as in Example 4.

[0194] The method for preparing a cerium-rich R-T-B based sintered magnet in this comparative example had the following specific steps:

[0195] (1) Powder mixing

[0196] The alloy powder F 40 and the alloy powder P 40 in Example 4 were used, and the alloy powder F 40 and the alloy powder P 40 were uniformly mixed in a mass ratio of 7:3 to obtain a mixed powder K4".

[0197] (2) Sintered magnet preparation

[0198] Using the same implementation as in Example 4, the mixed powder K4" was made into an R-T-B based sintered magnet M 40 ".

[0199] (3) Grain boundary diffusion treatment

[0200] Using the same implementation as in Example 4, the R-T-B based sintered magnet M40 Heavy rare earth element grain boundary diffusion is performed to obtain a diffusion magnet M 41 .

[0201] Performance test

[0202] The main magnetic properties (remanence, intrinsic coercive force, maximum magnetic energy product) of the cerium-rich R-T-B sintered magnets in Examples 1-4 and Comparative Examples 1-8 were tested according to the Permanent (Hard) Magnetic Material Magnetic Property Test Method (GB / T 3217-2013), and the results are shown in Table 1. In order to reflect the grain boundary diffusion effect of the cerium-rich R-T-B sintered magnet, the magnetic properties of each sample before and after grain boundary diffusion were also tested, and the intrinsic coercive force increase value and increase amplitude (percentage) of each sample after grain boundary diffusion were calculated.

[0203] Table 1 Magnetic properties of cerium-rich R-T-B sintered magnets

[0204]

[0205]

[0206] From the test results in Table 1, it can be seen that:

[0207] (1) The cerium-rich R-T-B sintered magnets (Examples 1-4) prepared by the process of the present application have the following advantages compared with single-alloy process magnets (Comparative Examples 1, 3, 5, 7) of the same formula: ① The remanence, intrinsic coercive force and maximum magnetic energy product of the magnets before grain boundary diffusion are improved; ② The coercive force increase value of the magnets after grain boundary diffusion is significantly increased, and the coercive force increase amplitude is also significantly improved. This shows that the preparation method of the present application can improve the magnetic properties of cerium-rich magnets, and especially after the grain boundary diffusion step, the grain boundary diffusion effect of the cerium-rich magnets can be improved, and the magnetic properties of the cerium-rich magnets can be significantly improved.

[0208] (2) The cerium-rich R-T-B sintered magnets (Examples 1-4) prepared by the process of the present application have the following advantages compared with double-alloy process magnets (Comparative Examples 2, 4, 6, 8) of the same formula without spherical modification of the cerium-rich rare earth alloy powder: ① The remanence, intrinsic coercive force and maximum magnetic energy product before grain boundary diffusion are improved; ② The coercive force increase value after grain boundary diffusion is significantly increased, and the coercive force increase amplitude is also significantly improved. This shows that the preparation method of the present application can improve the magnetic properties of cerium-rich magnets, and especially after the grain boundary diffusion step, the grain boundary diffusion effect of the cerium-rich magnets can be improved, and the magnetic properties of the cerium-rich magnets can be significantly improved.

[0209] The technical features of the above-described embodiments can be combined in any manner. For the sake of brevity, not all possible combinations of the technical features in the above-described embodiments are described, but it should be understood that any combination of the technical features is within the scope of the present disclosure as long as the combination does not result in a contradiction.

[0210] The above embodiments only express several implementation manners of the present application, which are described in a more specific and detailed manner, but cannot be understood as a limitation on the patent scope of the present application. It should be noted that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present application, which all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for preparing a cerium-rich RTB-based sintered magnet, characterized in that, Includes the following steps: S1. Prepare a mixed powder, wherein the mixed powder is obtained by uniformly mixing a first RTB alloy powder rich in cerium and poor in rare earth and a second RTB alloy powder poor in cerium and rich in rare earth, wherein the first RTB alloy powder is spherically modified and the sphericity is not less than 0.

75. S2. Prepare RTB-based sintered magnets from the mixed powders; The method of spherical modification is (i) mechanical grinding followed by powder sieving, or (ii) high-temperature melting followed by crushing and powdering.

2. The preparation method according to claim 1, characterized in that, The composition of the first RTB-based alloy powder is R x T y B z M a , among them, 29 wt.%≤x≤30 wt.%, 0.89 wt.%≤z≤0.92 wt.%, 0 wt.%≤a≤0.5 wt.%, y=100-xza; R is a rare earth element and must contain Ce and La, with Ce accounting for more than 20% of the total mass of R and La accounting for 5% to 10% of the total mass of R; T is a transition metal element and must contain Fe, with Fe accounting for more than 92% of the total mass of T; B is boron; M is an auxiliary metal element, composed of one or more of Cu, Al, Ga, Zn, Zr, Nb, and Ti. And / or, the composition of the second RTB-based alloy powder is R' b T' c B' d M' f , among them, 32 wt.%≤b≤34 wt.%, 0.88 wt.%≤d≤0.91 wt.%, 0.5 wt.%≤f≤1.0 wt.%, c=100-bdf; R' is a rare earth element and must contain Nd, with Nd accounting for more than 50% of the total mass of R; T' is a transition metal element and must contain Fe, with Fe accounting for 92% or more of the total mass of T; B' is boron; M' is an auxiliary metal element, composed of one or more of Cu, Al, Ga, Zn, Zr, Nb, and Ti.

3. The preparation method according to claim 2, characterized in that, The rare earth element R also contains one or more of Pr, Nd, Dy, Tb, Gd, Ho, and Y, wherein Dy and / or Tb account for less than 5% of the total mass of R. And / or, the transition metal element T also contains Co, with Co accounting for less than 8% of the total mass of T.

4. The preparation method according to claim 2, characterized in that, The rare earth element R' also contains one or more of Ce, Pr, Dy, Tb, Gd, Ho, and Y, wherein Ce accounts for less than 10% of the total mass of R', and Dy and / or Tb account for less than 5% of the total mass of R; And / or, the transition metal element T' also contains Co, with Co accounting for less than 8% of the total mass of T'.

5. The method for preparing a cerium-rich RTB-based sintered magnet as described in claim 1, characterized in that, The average particle size of the first RTB alloy powder and the second RTB alloy powder is 2.0~2.8μm, and the difference in average particle size between the two is less than 0.2μm.

6. The method for preparing a cerium-rich RTB-based sintered magnet as described in claim 1, characterized in that, The mechanical grinding methods include stirring, rolling, collision, or friction to remove the sharp edges of the powder particles and achieve powder spheroidization.

7. The method for preparing a cerium-rich RTB-based sintered magnet as described in claim 1, characterized in that, The high-temperature melting process involves heating the powder to melt the sharp edges and corners on its surface, thereby achieving spherical shape.

8. The method for preparing a cerium-rich RTB-based sintered magnet as described in claim 7, characterized in that, The heating temperature is 1000~1050℃.

9. The method for preparing a cerium-rich RTB-based sintered magnet as described in claim 7, characterized in that, The heating method is resistance heating, induction heating, radio frequency induction plasma heating, or laser heating.

10. The method for preparing a cerium-rich RTB-based sintered magnet as described in claim 1, characterized in that, In the mixed powder, the mass ratio of the first RTB alloy powder to the second RTB alloy powder is (5~7):(3~5).

11. The method for preparing a cerium-rich RTB-based sintered magnet as described in claim 1, characterized in that, Step S2 includes the steps of orienting and pressing the mixed powder into shape, sintering, and heat treatment.

12. The method for preparing a cerium-rich RTB-based sintered magnet as described in claim 11, characterized in that, The orientation pressing molding process involves molding the mixed powder in an orientation magnetic field of 1.2T to 1.5T under a protective atmosphere that isolates water and oxygen. And / or, the sintering temperature is 1030℃~1080℃, and the time is 3~5 hours; And / or, the heat treatment includes a primary heat treatment and a secondary heat treatment, wherein the primary heat treatment temperature is 880℃~920℃ and the heat treatment time is 2~5 hours, and the secondary heat treatment temperature is 480℃~560℃ and the heat treatment time is 2~5 hours.

13. The method for preparing a cerium-rich RTB-based sintered magnet according to any one of claims 1-12, characterized in that, The preparation method further includes: step S3, using grain boundary diffusion technology to diffuse heavy rare earth elements into the RTB-based sintered magnet.

14. The method for preparing a cerium-rich RTB-based sintered magnet as described in claim 13, characterized in that, The diffusion of heavy rare earth elements in step S3 includes the following steps: Pre-process the RTB-based sintered magnets; After attaching a heavy rare earth diffusion source to the surface of the pretreated RTB-based sintered magnet, high-temperature heat treatment is performed to complete the diffusion.

15. The method for preparing a cerium-rich RTB-based sintered magnet as described in claim 14, characterized in that, The heavy rare earth diffusion source is a substance containing heavy rare earth elements, and the mass percentage of the heavy rare earth elements in the heavy rare earth diffusion source is greater than 50%.

16. The method for preparing a cerium-rich RTB-based sintered magnet as described in claim 14 or 15, characterized in that, The high-temperature heat treatment temperature is 800~920℃, and the heat treatment time is 5~15h.

17. A cerium-rich RTB-based sintered magnet, characterized in that, The magnet is prepared by any one of claims 1-16; in the cerium-rich RTB sintered magnet, the mass of Ce accounts for more than 9.2% of the mass of rare earth elements.

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