268 results about "Sintered magnets" patented technology

The invention discloses a neodymium iron boron magnet with a protective film and a manufacturing method thereof, and the manufacturing method specifically comprises the following steps: S1, pretreating a plurality of raw materials to ensure the purity and cleanliness of the raw materials; s2, the pretreated materials are mixed in proportion and smelted to prepare uniform neodymium-iron-boron alloy; s3, the smelted alloy is crushed, and particle powder meeting the requirement is prepared through jet mill equipment; s4, the powder is put into a mold, forming orientation is conducted through a magnetic field press, and the maximum residual magnetism is obtained; s5, performing high-temperature sintering on the molded magnet to improve the density and the magnetic performance of the molded magnet; s6, the sintered magnet is machined, and the needed size and shape are obtained; s7, carrying out pretreatment on the surface of the magnet, and carrying out aftertreatment after chemical nickel plating to ensure the quality of a plating layer; according to the method, the surface of the neodymium-iron-boron magnet is coated with a high-phosphorus chemical nickel layer in a plating mode, the magnet can be effectively prevented from being corroded by the external environment, and the service life of the magnet is prolonged.

The invention discloses a grain boundary diffusion method of a high-performance sintered neodymium-iron-boron magnet. The preparation method comprises the following steps: sequentially carrying out hydrogen decrepitation, jet milling, magnetic field forming, cold isostatic pressing and low-temperature presintering treatment on a neodymium-iron-boron alloy rapid hardening sheet to obtain a presintered neodymium-iron-boron magnet; depositing a non-rare earth metal or metal oxide film layer on the surface of the pre-sintered magnet by using a pulse laser deposition process; performing diffusion heat treatment on the neodymium-iron-boron magnet deposited with the non-rare earth metal or metal oxide film layer; depositing a heavy rare earth element film layer on the surface of the treated neodymium-iron-boron magnet by using the pulse laser deposition process again; and performing diffusion heat treatment and tempering treatment on the treated neodymium-iron-boron magnet. According to the method, the diffusion cost is reduced, meanwhile, the diffusion depth of heavy rare earth elements in the magnet is increased, the neodymium-iron-boron magnet with high coercive force and high magnetic energy product is prepared, and the urgent application requirements of emerging industries such as rare earth permanent magnet motors are met.

A permanent magnet rotor can include a rotor body and at least one magnet. The rotor body can include at least one rotor cavity. The at least one magnet includes, in part, Mn—Bi particles and the at least one magnet can be either a sintered magnet or a polymer bonded magnet. The at least one magnet can be located, at least partially, in the at least one rotor cavity. Further, the at least one magnet can be installed in the at least one rotor cavity after forming the at least one magnet or the at least one magnet can be formed in the at least one rotor cavity using a mold. Moreover, the polymer bonded magnet can include a composite of polymer matrix and Mn—Bi particles.

A high-abundance rare earth iron boron regenerated magnet and its preparation method belong to the field of rare earth permanent magnet materials and their recycling technology. After surface treatment, high-abundance Ce / La rare earth iron boron unqualified products and processing waste are subjected to coarse crushing and hydrogen explosion powdering; a Ce, La, Nd, and Pr rare earth alloy is prepared using a rapid solidification belt spinning technology and hydrogen explosion; the above two materials are ball milled, mixed, oriented, and pressed according to a certain proportion, and then sintered and heat treated to obtain a regenerated sintered magnet. The regenerated magnet prepared by the present invention has a waste material utilization rate of up to 95%, a low rare earth addition amount (0 to 5wt.%), and a light rare earth addition ratio (LaCe / NdPr) greater than 50%. The coercive force of the regenerated magnet is significantly improved, and the comprehensive magnetic properties are equivalent to or even higher than those of the original magnet. The present invention can accurately control the cheap light rare earths La and Ce to obtain a high-performance regenerated magnet, thereby realizing the high-value recycling of high-abundance rare earth permanent magnets.

The invention provides a neodymium iron boron sintered magnet and a preparation method and application thereof. The neodymium iron boron sintered magnet comprises the following components: R, wherein the mass content of R is 28-33wt%; r comprises Nd and Ce, and optionally comprises or does not comprise at least one of Pr, Dy, Tb, Ho and Gd; m, wherein the mass content of the M is 1.5-2.5 wt%; b, the mass content of the B is 0.95 to 1.05 wt%; the mass content of the Ti ranges from 0.1 wt% to 0.25 wt%; fe is the balance; in the neodymium iron boron sintered magnet, the mass content of Ce is 0.3-5 wt%. By accurately controlling the main alloy element components, the generation of a soft magnetic phase in main phase grains is avoided; and meanwhile, the element components of the auxiliary alloy are optimized, and the dosage ratio of the main alloy to the auxiliary alloy is adjusted, so that main phase grains are refined, a fine titanium-rich phase which is dispersed and distributed is formed in a grain boundary phase, and the magnetic performance of the product is improved.

The invention provides a method for improving coercive force of a neodymium-iron-boron magnet through power ultrasonic treatment, and belongs to the field of magnets. According to the method for improving the coercive force of the neodymium-iron-boron magnet through power ultrasonic treatment, in the heat preservation process of heat treatment of the neodymium-iron-boron sintered magnet, contact type introduction power ultrasonic treatment is carried out; the method for improving the coercive force of the neodymium-iron-boron magnet through power ultrasonic treatment comprises the steps that a neodymium-iron-boron sintered magnet is sequentially subjected to first heat treatment, second heat treatment and third heat treatment, and the high-coercive-force neodymium-iron-boron magnet is obtained; in the heat preservation process of at least one time of heat treatment in the first heat treatment, the second heat treatment and the third heat treatment, contact type introduction power ultrasonic treatment is carried out. According to the method for improving the coercive force of the neodymium-iron-boron magnet through power ultrasonic treatment, the volume ratio of a rare earth-rich phase (alpha (RE)) in a grain boundary structure of the neodymium-iron-boron magnet can be obviously increased, and the coercive force of the neodymium-iron-boron magnet can be further improved.

The invention discloses a method for simultaneously optimizing the squareness and the remanence temperature coefficient of a 2: 17 type samarium-cobalt sintered magnet, and belongs to the technical field of rare earth permanent magnet material preparation. A component Sm < 1-x > RE < x > (CobalFeaCubZrc) z is designed, RE is one or more of Dy, Er, Gd, Tm and other heavy rare earth elements, and a, b, c and x meet the following relations: 0 < = x < = 0.6, 0.1 < = a < = 0.2, 0.06 < = b < = 0.12, 0.02 < = c < = 0.03, and 6.9 < = z < = 7.9. On the basis of a conventional smelting and ingot casting-isothermal annealing-powder preparation-oriented profiling-sintering-solid solution-aging process, an isothermal annealing process is added after smelting and ingot casting: the temperature is raised to 1190-1210 DEG C in a tubular furnace, isothermal annealing is performed for 5-20 hours, heavy rare earth elements are eliminated, and the influence of the stability of a 2: 17H phase on the component uniformity and magnetic performance of a magnet is improved; and substitution sites of heavy rare earth can be increased, and the residual magnetism temperature coefficient is optimized.

The invention discloses a cerium-rich R-T-B series sintered magnet and a preparation method thereof.The preparation method comprises the following steps that S1, mixed powder is prepared, the mixed powder is obtained by evenly mixing first R-T-B series alloy powder rich in cerium and poor in rare earth and second R-T-B series alloy powder poor in cerium and rich in rare earth, the sphericity degree of the first R-T-B series alloy powder is not lower than 0.75; and S2, preparing the mixed powder into the R-T-B series sintered magnet. According to the preparation method, a low-Ce-content grain shell layer is constructed in the cerium-rich R-T-B series sintered magnet, so that the intrinsic coercive force of the cerium-rich R-T-B series sintered magnet is improved. By means of the preparation method, the high-performance R-T-B series sintered magnet rich in the Ce element can be prepared, and application of Ce resources in the R-T-B series sintered magnet is promoted.

A method for preparing a high-coercivity and high-thickness NdFeB magnet belongs to the technical field of rare earth permanent magnet material preparation and solves the technical problem of preparing high-thickness and high-coercivity NdFeB magnets. The method comprises the following steps: first, sequentially subjecting the NdFeB magnets to rapid solidification strip spinning, hydrogen crushing, airflow milling, magnetic field orientation molding, cold isostatic pressing, and vacuum low-temperature sintering to obtain a thin low-temperature sintered green body; second, subjecting the low-temperature sintered green body to a grain boundary thermal diffusion treatment after preparing a heavy rare earth element layer on the surface of the low-temperature sintered green body; third, subjecting the low-temperature sintered green body after the diffusion heat treatment to mechanical coarse crushing, hydrogen crushing, powder mixing, airflow milling, magnetic field orientation molding, and cold isostatic pressing to obtain a thick, high-thickness compact; finally, subjecting the high-thickness compact to vacuum low-temperature heat treatment, vacuum high-temperature sintering, and two heat treatments to obtain a high-coercivity and high-thickness NdFeB magnet. The method has a simple preparation process, significantly improves the coercivity of bulk NdFeB sintered magnets, and enables the magnets to have a high magnetic energy product.

The invention discloses a rare earth reduction regulation and recovery method for high-cerium-content sintered neodymium-iron-boron waste, and belongs to the field of neodymium-iron-boron waste recovery. Performing hydrogen explosion on the magnet subjected to surface treatment to obtain hydrogen explosion coarse powder; carrying out jet milling on the hydrogen explosion powder to obtain jet milled powder; fully mixing the airflow fine powder with a small amount of light rare earth element supplements, and carrying out orientation compression, sintering and tempering to obtain a single-phase sintered regenerated magnet; and carrying out grain boundary diffusion on the obtained regenerated sintered magnet by using a diffusion source containing a small amount of medium rare earth Nd, Pr or alloy thereof to obtain the high-performance regenerated magnet. According to the method, a small amount of light rare earth is added to inhibit the second phase, and then high-performance regeneration of the magnet waste is achieved through grain boundary diffusion of reduced rare earth elements such as Nd and Pr and alloy. The regenerated magnet prepared by the method is lower in total rare earth content, higher in light rare earth content, and better in residual magnetism, coercive force and comprehensive magnetic energy product.

The utility model belongs to the technical field of manufacturing dies, particularly relates to a manufacturing die for a sintered magnet, and aims to solve the problem that the pressed sintered magnet needs to be manually taken out after the sintered magnet is pressed by the existing part of manufacturing dies for the sintered magnet. The lower die is fixedly installed on the bottom end face of the bearing frame, the warping assembly is arranged in the lower die, a pressing cavity is formed in the position, located at the warping assembly, of the lower die, and an upper die is arranged above the upper die. The pressing cavity is sealed through the pressing plate of the warping assembly, after the pressing cavity of the lower die is filled with powder of the sintered magnet, the upper die presses the pressing cavity downwards to achieve pressing of the sintered magnet, after pressing is completed, the warping plate is manually pressed, one end of the warping plate jacks up the pressing cavity, and then the sintering magnet is pressed. In this way, the pressing plate below the pressing cavity is lifted, and the sintered magnet pressed in the pressing cavity is lifted out through lifting of the pressing plate, so that workers can conveniently collect the sintered magnet.

This application provides a large-size NdFeB magnet and its preparation method. The preparation method includes: mixing a main alloy powder and an auxiliary alloy powder in a ratio of 10:(1-3) to obtain a mixed alloy powder; molding the mixed alloy powder and then isostatically pressing it to obtain a green blank; sintering the green blank using a multi-stage heating method to obtain a sintered magnet; wherein the multi-stage heating includes: heating to 1000-1100℃ at at least three gradually decreasing heating rates and holding at that temperature for 1-6 hours; and cooling the sintered magnet to obtain a NdFeB magnet. This application, through a dual alloying process and gradually reducing the heating rate during sintering, can effectively suppress cracking of the magnet during sintering and obtain a large-size magnet with excellent magnetic properties.

To provide a manufacturing method of a rare earth sintered magnet having high Br and high HcJ while reducing the content of a heavy rare earth element.SOLUTION: A manufacturing method of a rare earth sintered magnet disclosed herein includes the steps of pulverizing a rare earth raw alloy to manufacture powder of the rare earth raw alloy, recovering the powder using a collection container, supplying an oil to the collection container before, after or during the recovery of the powder, and adjusting the moisture ratio, which is the ratio of the mass of moisture in the oil to the mass of the powder to be recovered, in the oil supplied to the collection container to 0.005% or less.SELECTED DRAWING: Figure 2

The invention discloses a method for improving coercive force of a neodymium-iron-boron magnet. The method comprises the following steps: taking raw materials of each element of the neodymium-iron-boron magnet according to a component proportion, and smelting and casting to obtain a throwing sheet; performing vacuum heat treatment on the throwing sheet at the temperature of 450-600 DEG C, performing hydrogen demolishing and airflow grinding on the throwing sheet subjected to vacuum heat treatment to obtain powder, performing orientation molding on the powder to obtain a green body, performing cold isostatic pressing on the green body, and finally performing vacuum sintering to obtain the neodymium-iron-boron magnet. Heat treatment below the ternary eutectic temperature is carried out on the throwing piece, distribution of a rare earth-rich phase in the throwing piece is improved through solid-phase diffusion, the rare earth-rich phase extends to the periphery of a columnar crystal, blocky rare earth-rich phases are reduced, rare earth loss in the jet milling stage is reduced, components are closer to nominal components, and the rare earth loss is reduced. And the proportion of rare earth-rich phases attached to the surfaces of airflow fine powder particles is increased, so that the coercive force of the sintered magnet is improved.

The invention discloses a cerium-containing high-abundance rare earth sintered neodymium iron boron permanent magnet which does not contain heavy rare earth and does not need a grain boundary diffusion process and a preparation method thereof. The magnet is formed by crushing and mixing three alloy casting pieces, the three alloy casting pieces are an Nd / Pr-rich phase, a Ce-La-rich phase and a Y-Nd-rich phase respectively, and Ce accounts for more than or equal to 30wt% of the total amount of all rare earth elements; the trace elements (Al, Cu, Ga, Nb, Zr and the like) are uniformly introduced in the smelting stage of each main phase, and grain boundary reconstruction is induced through in-situ hydrotreating to form a thin and continuous rare earth-rich grain boundary phase; and after orientation compression molding, vacuum sintering and multi-stage heat treatment, a sintered magnet with excellent magnetic performance is obtained. According to the product, the intrinsic coercive force Hcj is larger than or equal to 15 kOe, the residual magnetism Br is larger than or equal to 13.7 kG, and the maximum magnetic energy product (BH) max is larger than or equal to 39 MGOe. The problems that a high-Ce magnet is low in coercive force, discontinuous in grain boundary phase and the like are solved, the method does not need to depend on Dy / Tb heavy rare earth and a grain boundary diffusion technology thereof, the cost is reduced by 30% or above, and the method is suitable for the fields of new energy automobiles, wind power generation and the like and has a good industrialization prospect.

A high-coercivity Nd—Fe—B sintered magnet and a preparation method and use thereof are provided. The sintered magnet contains the following components in percentage by a mass: 100%: 26-37 wt % of R, R being at least one rare earth element including Nd; 0.07-0.23 wt % of Mn; 0.8-1 wt % of B; 0.5-4 wt % of M, M comprising Cu and / or Al, and at least one selected from Co, Ti, Ni, Zr and Ga; and the remaining being Fe. A Mn-containing auxiliary alloy powder is mixed with a Mn-free neodymium-iron-boron main alloy powder to prepare the Nd—Fe—B sintered magnet. The Mn-containing auxiliary alloy powder, also contains at least one of metals Cu and Al. Mn can replace a part of Fe in the main phase, so that the amount of solid solution of beneficial elements in grain boundaries in the main phase is reduced, and the coercivity is improved.

The invention discloses a double-alloy sintered neodymium-iron-boron permanent magnet and a preparation method and application thereof, and relates to the technical field of rare earth permanent magnet materials. Comprising the following steps that a main alloy and an auxiliary alloy are evenly mixed and then subjected to orientation profiling, cold isostatic pressing, liquid phase sintering and tempering heat treatment in sequence, the double-alloy neodymium iron boron permanent magnet is prepared, the chemical composition of the auxiliary alloy is AlxRE2yM100-x-y, RE2 is selected from one or more combinations of Ce, Dy, Gd, Ho, La, Nd, Pr, Tb and Y, and M is selected from any one or more combinations of Co, Cu, Ga, Ti, Zr and Nb; x and y satisfy 5 < = x < = 50 and 20 < = y < = 80; according to the method, on the premise that the magnetic performance of the neodymium iron boron permanent magnet is synchronously optimized, the mechanical performance of the neodymium iron boron permanent magnet is further improved, the mechanical performance and the magnetic performance of the sintered magnet have good consistency and stability, the technological method is simple and easy to implement, and the method is suitable for industrial production.

The invention relates to the technical field of release agents, and discloses a silicone-oil-free wet-process magnet profiling release agent and a preparation process thereof, and the silicone-oil-free wet-process magnet profiling release agent comprises a core functional copolymer, a water-based non-silicon defoaming agent and deionized water. The core functional copolymer is prepared from a hydrophilic self-repairing film-forming monomer, a molecular-level flexible lubricating monomer, a powerful mold anchoring monomer and a programmed pyrolysis triggering monomer through free radical copolymerization. According to the technical scheme, the functions of self-repairing film forming, molecular-level lubrication, mold anchoring and programmed pyrolysis are integrated through a single macromolecular structure. A demolding film layer formed by the water-based demolding agent is uniform and compact, mold sticking and blank defects in the profiling process are avoided, the water-based demolding agent can be completely decomposed and volatilized in the magnet sintering process, and solid residues are not generated, so that the high magnetic performance of a sintered magnet is guaranteed, and the problems that an existing water-based demolding agent is prone to generating film layer defects, poor in system stability, residues after sintering and the like are solved.

An Sm-Fe-N-based sintered magnet comprising a sintered body of a magnetic material containing an Sm-Fe-N-based magnetic powder and a Zn-Al alloy powder, wherein the Al content of the Zn-Al alloy powder is 6-84 atom%, and the open porosity of the sintered magnet is not more than 15%.

The invention discloses an ultra-fine grain high-coercivity heavy-rare-earth-free magnet and a preparation method thereof, belongs to the technical field of heavy-rare-earth-free magnets, and solves one of the problems of coarse grains, poor grain uniformity, low coercivity and poor coercivity temperature coefficient of the heavy-rare-earth-free magnet in the prior art. The ultra-fine grain high-coercivity heavy rare earth-free magnet is a sintered magnet with an R2T14B phase as main phase particles; the area ratio of main phase grains with the grain size smaller than 4 microns of the ultra-fine grain high-coercivity heavy-rare-earth-free magnet is larger than or equal to 90%. The single domain crystal grain percentage is not less than 70%; wherein R is light rare earth and is one or more of lanthanum, cerium, praseodymium and neodymium, T is a transition element, and B is boron. The ultra-fine grain high-coercivity heavy rare earth-free magnet disclosed by the invention is high in intrinsic coercivity and high in intrinsic coercivity temperature coefficient.

This invention discloses an R-T-B sintered magnet with reduced eddy current losses, its preparation method, and its application. The magnet has partition grooves on one or two orientation surfaces, where each orientation surface is perpendicular to the orientation direction of the magnet. The partition grooves extend through the magnet in a first extension direction but not in a second extension direction. The first extension direction of the partition grooves is perpendicular to the orientation direction of the magnet, and the second extension direction is parallel to the orientation direction of the magnet. By creating crisscrossing partition grooves on the magnet and filling them with an insulating layer, this invention increases the resistivity of a thin layer on the magnet's surface by a certain thickness, significantly reducing motor power loss due to eddy current effects. The insulating layer filling the grooves increases the resistivity of both the magnet surface and the grooves, effectively preventing conduction due to poor processing or current breakdown when the groove width is narrow. It also compensates for the reduction in mechanical strength caused by the grooving, ultimately resulting in a low-eddy-current, high-strength sintered magnet.

To provide an R-Fe-B sintered magnet that exhibits high coercivity while keeping material costs down. [Solution] The R-Fe-B sintered magnet contains a rare earth element R including Tb, an element T consisting of Fe or a combination of Fe and Co, B, and each of Al, Cu, and Ga, with an element M consisting of a combination of Al, Cu, and Ga, and includes an RTM phase in the grain boundary phase, where the number of atoms of element M in the RTM phase is in the order of Cu > Al > Ga. Furthermore, in the RTM phase, the atomic ratio of the rare earth element R to element M is preferably 6.0 for the rare earth element R and 1.3 or more for element M.

According to the high-squareness heavy-rare-earth-free R-T-B sintered magnet and the preparation method thereof, the jet milling process is optimized, high-rare-earth alloy B coarse powder is supplemented at the later stage of jet milling, jet milling is carried out at the same time, rare earth is timely and accurately supplemented for rear-section powder with large rare earth loss, the difficulty of later-stage material mixing is reduced, and the high-squareness heavy-rare-earth-free R-T-B sintered magnet is obtained. And the rare earth content of the powder in the post-jet milling stage is increased, so that the rare earth content of the powder in the post-jet milling stage is approximately consistent with the rare earth content of the powder in the previous stage. The particle size distribution of the powder in the later stage is further optimized, the microscopic grain size distribution of the magnet is eventually homogenized, so that the high-squareness heavy-rare-earth-free R-T-B sintered magnet is obtained, the squareness SQ of the magnet is larger than or equal to 0.95, and the intrinsic coercive force Hcj is larger than or equal to 16.5 kOe.

An anti-corrosion treatment method for preparing sintered NdFeB magnet includes preparing a sintered NdFeB matrix, and applying a heat treatment to the sintered NdFeB matrix in an oxidizing atmosphere containing at least one of alcohol or organic acid. A ratio of oxygen partial pressure to water vapor partial pressure in the oxidizing atmosphere is in a range from 1:1 to 300:1. A temperature for the heat treatment is equal to or lower than 300° C. A time for the heat treatment is in a range from 10 minutes to 200 minutes.

The present invention discloses a method for manufacturing a heavy rare earth-free high-coercivity R-T-B magnet, which relates to the technical field of magnets. The technical scheme includes raw materials and diffusion materials composed of 27.5-35.0wt% of an R component, 0.8-0.95wt% of a B component, 0-3wt% of an M component and a balance of a T component in percentage by mass; the M component consists of 0-2wt% of M1 and 0-1wt% of M2, and B and M2 satisfy the following formula (1): 0.8>B-M2>0.2 (1); and M1 is at least one of Cu, Al and Ga, and M2 is at least one of Nb, Zr and Ti; wherein the diffusion material is PrX, and X is at least one element; the manufacturing method includes preparing a R-T-B sintered magnet raw material from the raw material, coating the diffusion material on the surface of the magnet raw material, and obtaining the heavy rare earth-free high-coercivity R-T-B magnet after heat treatment and diffusion. The present invention has the effect of obtaining a heavy rare earth-free high-coercivity R-T-B magnet with a coercivity HcJ greater than 23 kOe without adding heavy rare earth.

A ferrite sinter magnet has a ferrite phase having a magnetoplumbite-type crystal structure, and contains at least a metal element A, a metal element R, Fe, Co, Zn, and B. The element A is at least one kind of element selected from the group consisting of Sr, Ba, Ca, and Pb, and essentially includes Ca. the element R is at least one kind selected from the group consisting of Bi and rare-earth elements including Y, and essentially includes La. Atomic ratios of the metal elements satisfy the following Expressions (1) to (5),A1-rReFexCoyZnz  (1)0.40≤r≤0.70  (2)8.20≤x≤9.34  (3)0.05≤y≤0.50  (4)0<z≤0.20  (5)The content of Si is 0 to 0.60% by mass in terms of SiO2, and the content of B is 0.1-0.70% by mass in terms of B2O3.

A rare earth sintered magnet according to the present disclosure includes: a main phase satisfying general formula (Nd, La, Sm)—Fe—B and including crystal grains based on R2Fe14B crystal structures; and a crystalline subphase based on an oxide phase represented by (Nd, La, Sm)—O. The subphase has a higher concentration of Sm than the main phase.

The application discloses a surface-strengthened R-T-B rare earth permanent magnet based on high-melting-point element grain boundary diffusion and a preparation method thereof. The application adopts heavy rare earth elements (at least one of Dy, Tb and Ho), high-melting-point elements (Zr and Ti) and low-melting-point metals (at least one of Al, Ga and Cu) to prepare a diffusion source, and performs grain boundary diffusion treatment on a sintered magnet, thereby obtaining the surface-strengthened R-T-B rare earth permanent magnet. The grain boundary diffusion high-melting-point element precipitates can inhibit the excessive growth of the main phase grains in the grain boundary diffusion process, realize the refinement of the main phase grains and improve the uniformity of the main phase grain size of the whole magnet. The grain boundary diffusion magnet has higher coercivity and squareness, reduces the reduction amount of the remanence of the magnet after the grain boundary diffusion; and can improve the crack propagation resistance of the Nd-rich phase at the grain boundary, thereby improving the fracture toughness of the magnet while improving the strength of the surface layer of the magnet, so that the qualified rate of the product during surface processing is improved.

A magnet preparation method includes coating powder slurry on at least one of a first surface or a second surface of an NdFeB matrix and carrying out a curing reaction, to obtain a coated magnet, and subjecting the coated magnet to a vacuum heat treatment, a grain boundary diffusion treatment, and an aging treatment. The first surface and the second surface are opposite to each other. The powder slurry includes powder containing heavy rare earth element and UV monomer. The UV monomer includes radical-cured UV monomer. A temperature of the vacuum heat treatment is in a range from 250° C. to 600° C.

An R-T-B sintered magnet of the present disclosure includes a principal phase that comprises an R2T14B compound and a grain boundary phase located in a grain boundary portion of the principal phase. The atomic ratio of B to T in the R-T-B sintered magnet is lower than the atomic ratio of B to T in the chemical stoichiometric composition of the R2T14B compound. The relationships 26.0 mass% ≤ ([Nd] + [Pr] + [Ce] + [La] + [Dy] + [Tb]) - 12 ([O] + [C]) ≤ 27.7 mass%, 0.85 mass% ≤ [B] ≤ 0.94, 0.05 mass% ≤ [O] ≤ [0.30] mass%, 0.05 mass% ≤ [M] ≤ 2.00 mass%, [Tb] ≤ 0.20 mass%, and [Dy] ≤ 0.30 mass% are satisfied. A section is included in which at least the Nd concentration or the Pr concentration gradually decreases gradually from the front surface of the magnet toward the interior of the magnet.