CN114823118B - Rare earth permanent magnet and preparation method thereof - Google Patents
Rare earth permanent magnet and preparation method thereof Download PDFInfo
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- CN114823118B CN114823118B CN202210732028.9A CN202210732028A CN114823118B CN 114823118 B CN114823118 B CN 114823118B CN 202210732028 A CN202210732028 A CN 202210732028A CN 114823118 B CN114823118 B CN 114823118B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
- H01F41/0293—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
- H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
- H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
- H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
- H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
- H01F1/047—Alloys characterised by their composition
- H01F1/053—Alloys characterised by their composition containing rare earth metals
- H01F1/0536—Alloys characterised by their composition containing rare earth metals sintered
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
- H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
- H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
- H01F41/0286—Trimming
Abstract
The invention provides a rare earth permanent magnet and a preparation method thereof. The preparation method of the rare earth permanent magnet comprises the following steps: s10: performing surface treatment on a workpiece prepared from a rare earth permanent magnet material to control the roughness of the surface of the workpiece to be Ra0.5-5.5; s20: mixing the following components in parts by mass: (1-10) placing the workpiece and the auxiliary balls after the S10 treatment into a roller, wherein the ratio of the total volume of the workpiece and the auxiliary balls after the S10 treatment to the volume of the roller is 1: (2-6), and immersing the roller into the rare earth slurry for rolling treatment; s30: and (4) carrying out heat treatment on the workpiece treated in the step (S20) to obtain the rare earth permanent magnet. The invention solves the problems of uneven thickness, local accumulation and poor local coating of rare earth slurry coated on the surface of the small-size rare earth permanent magnet by using the roller.
Description
Technical Field
The invention relates to the technical field of permanent magnets, in particular to a rare earth permanent magnet and a preparation method thereof.
Background
The rare earth permanent magnetic material is an important basic functional material for supporting modern society, and is widely applied to modern industry and electronic technology. An important performance in the application of the rare earth permanent magnetic material is intrinsic coercivity, and the improvement of the index can obviously improve the influence of environmental magnetic field and temperature tolerance of the material in the using process on the attenuation of the magnetic performance of the material. The most effective way to improve the intrinsic coercivity is to add heavy rare earth elements. In the traditional method, heavy rare earth elements are added in a formula stage and a smelting stage, but the distribution rate of the heavy rare earth elements is poor, and more heavy rare earth elements are needed for obtaining the same coercivity improvement amount. Therefore, in recent years, the grain boundary diffusion process has been widely used. The principle of grain boundary diffusion is that a powder or a compound containing a heavy rare earth element is coated outside a magnet by a coating method, and the heavy rare earth element is diffused into the magnet along a neodymium-rich liquid grain boundary phase by heat treatment. However, the diffusion speed of the heavy rare earth elements in the grain boundary is much higher than the diffusion speed of the interior of the main phase grain, so that the heavy rare earth elements are only deposited on the surface layer of the main phase grain after diffusion and rarely enter the interior of the grain, and the utilization rate of the heavy rare earth can be greatly improved. At present, the grain boundary diffusion process used in enterprises mainly comprises spraying, physical vapor deposition, silk-screen printing, dipping and the like. However, the conventional spraying, physical vapor deposition, screen printing and dipping methods are difficult to perform elemental and composite alloy film diffusion on the rare earth permanent magnet with smaller size, and the problems of low production efficiency, poor product consistency and low performance exist in the actual production process.
In order to carry out heavy rare earth grain boundary diffusion treatment on the small-size rare earth permanent magnet, an enterprise puts the small-size rare earth permanent magnet into a roller for spraying or dip-coating so as to realize efficient coating of the rare earth film layer on the surface of the small-size rare earth permanent magnet. However, in the actual preparation process, we find that when the method is directly used for coating a small-size rare earth permanent magnet, because the adhesion effect of the coated slurry and the magnet is poor, the coating film layer is subjected to an excessive friction force in the rotating process, so that the film layer is prone to phenomena of uneven thickness, local accumulation, poor local coating and the like, the coating effect of the small-size rare earth permanent magnet is affected, and the effect of improving the coercive force of the product is poor.
Therefore, how to provide a method for uniformly coating the surface of a small-size rare earth permanent magnet with rare earth slurry by using a roller is a technical problem to be solved by the technical personnel in the field.
Disclosure of Invention
The invention aims to provide a rare earth permanent magnet and a preparation method thereof, and provides a small-size rare earth permanent magnet with high-efficiency grain boundary diffusion treatment after rare earth slurry is uniformly coated on the surface. In order to solve the above-mentioned technical problems, the present invention has been achieved as described above.
The invention provides a preparation method of a rare earth permanent magnet, which comprises the following steps:
s10: performing surface treatment on a workpiece prepared by adopting a rare earth permanent magnet material to control the roughness of the surface of the workpiece to be Ra0.5-5.5;
s20: putting the workpiece and the auxiliary balls processed in the step S10 into a roller, immersing the roller into the rare earth slurry, and performing rolling treatment; wherein the mass part ratio of the workpiece and the auxiliary ball after the S10 treatment is 5: (1-10), the ratio of the total volume of the workpiece and the auxiliary ball processed in the step S10 to the volume of the roller is 1: (2-6), the diameter of the auxiliary ball is 1mm-8mm, and the rotating speed of rolling treatment is controlled to be 4rpm-18rpm;
s30: carrying out heat treatment on the workpiece treated in the step S20 to obtain a rare earth permanent magnet;
the rare earth slurry is prepared by the following steps:
s41: performing ball milling treatment on the rare earth raw material to obtain a rare earth dopant with the particle size of 1-9 um;
s42: the mass portion ratio is 300: (100-900): (0.8-24) mixing the rare earth doping agent, the solvent and the dispersing agent to obtain the rare earth slurry.
Compared with the prior art, the technical scheme has the following technical effects: through the cooperation regulation and control between the workpiece surface roughness, rare earth slurry components and the rolling treatment three, realize high-efficient, the even coating to small-size tombarthite permanent magnet workpiece surface rare earth slurry, the coat firmly combines with the work piece, does not drop, and the rare earth element is at the even diffusion of work piece top layer, finally realizes promoting the high-efficient of product intrinsic coercivity.
Furthermore, the surface treatment is sand blasting treatment, the grain diameter of sand blasting abrasive material adopted by the sand blasting treatment is 105um-380um, the sand blasting time adopted by the sand blasting treatment is 2min-30min, and the pressure of compressed air adopted by the sand blasting treatment is 0.3MPa-0.7MPa.
Compared with the prior art, the technical scheme has the following technical effects: the surface of the workpiece is subjected to rough treatment by adopting sand blasting treatment, so that the roughness of the workpiece is controlled in a proper range, on one hand, the rare earth slurry can be firmly combined with the surface of the workpiece, and on the other hand, the problems of low reversing speed of the workpiece, easy smearing of a coating layer and the like caused by overlarge roughness can be prevented.
Further, the surface treatment is pickling treatment, and a pickling medium used in the pickling treatment is at least one of hydrofluoric acid, sulfuric acid and hydrochloric acid.
Compared with the prior art, the technical scheme has the following technical effects: the surface of the workpiece is subjected to rough treatment by adopting a pickling mode, and the pickling can comprehensively treat the workpiece with a complex shape.
Furthermore, the auxiliary ball is at least one of zirconia auxiliary ball, alumina auxiliary ball and silicon carbide auxiliary ball.
Compared with the prior art, the technical effect achieved by adopting the technical scheme is as follows: the zirconia auxiliary ball has higher strength, toughness and wear resistance at normal temperature, can effectively stir workpieces to move during rolling treatment, cannot be damaged by workpieces in various shapes, cannot generate ball crumbs, and is easy to peel. The alumina auxiliary ball has higher hardness at normal temperature, and the performance of the alumina auxiliary ball is still very stable at high temperature, so that the workpiece can be effectively stirred at higher temperature. The silicon carbide auxiliary ball has the performances of high temperature resistance, acid resistance and the like, and can realize effective stirring and coating of rare earth slurry with certain corrosivity.
Further, in the ball milling treatment, the ball milling rotating speed is controlled to be 4rpm-60rpm, the ball-to-material ratio is controlled to be 10: (1-20) and the ball milling time is 1-8 h.
Compared with the prior art, the technical scheme has the following technical effects: through comprehensively regulating and controlling parameters such as the rotating speed, the ball-to-material ratio, the ball-milling time and the like of the ball-milling treatment, the rare earth dopant with corresponding particle size can be obtained through the ball-milling treatment.
Further, S30 specifically includes:
s31: placing the workpiece treated in the step S20 in a vacuum sintering furnace for primary heat treatment, wherein the treatment temperature is 700-1000 ℃, and the treatment time is 2-48 h;
s32: performing secondary heat treatment on the workpiece treated by the S31 at the treatment temperature of 420-650 ℃ for 2-10 h;
s33: and cooling the workpiece treated in the step S32 to room temperature along with the furnace to obtain the rare earth permanent magnet.
Compared with the prior art, the technical effect achieved by adopting the technical scheme is as follows: the first heat treatment is beneficial to the rare earth elements in the rare earth slurry to be quickly diffused to the surface layer of the workpiece, and the second heat treatment can ensure that the rare earth elements are quickly rearranged after being diffused.
Further, before the primary heat treatment, the temperature of the vacuum sintering furnace is increased from room temperature to the treatment temperature of the primary heat treatment at the temperature rising rate of 2-15 ℃/min; and/or, before the secondary heat treatment, reducing the temperature of the vacuum sintering furnace from the treatment temperature of the primary heat treatment to the treatment temperature of the secondary heat treatment at a cooling rate of 6 ℃/min-10 ℃/min.
Compared with the prior art, the technical effect achieved by adopting the technical scheme is as follows: through regulating and controlling the heating and cooling rates of the workpiece, the effect of rare earth element diffusion in the workpiece can be further optimized, and the rare earth element diffusion control is more uniform.
Further, in the above-mentioned production method,
the rare earth dopant is at least one of dysprosium metal, terbium metal, dysprosium fluoride, terbium fluoride, dysprosium oxide, terbium oxide, dysprosium hydride, terbium hydride, dysprosium copper alloy, terbium copper alloy, dysprosium aluminum alloy and terbium aluminum alloy; and/or
The solvent is at least one of methanol, ethanol and acetone; and/or
The dispersant is at least one of methacrylic acid copolymer and polyvinyl alcohol Ding Quanzhi.
Compared with the prior art, the technical effect achieved by adopting the technical scheme is as follows: through selecting the rare earth dopant, the solvent and the dispersant, the rare earth dopant particles in the rare earth slurry are uniformly dispersed, and the rare earth slurry which is most suitable for the small-size rare earth permanent magnet workpiece is obtained, so that the uniform grain diffusion of rare earth elements is achieved.
Further, in the above-mentioned production method,
the rare earth dopant comprises a RE/M alloy;
wherein RE is dysprosium or terbium, M is copper or aluminum, and the mass of RE is 10-90% of the total mass of the RE/M alloy.
Compared with the prior art, the technical effect achieved by adopting the technical scheme is as follows: in the rare earth alloy, the mass percent of the rare earth elements is 10-90%, and the rare earth alloy in the range has better rare earth grain boundary diffusion capability.
The invention also provides a rare earth permanent magnet which is obtained by adopting the preparation method of any one of the technical schemes.
The rare earth permanent magnet is obtained by the preparation method according to any one of the above technical schemes, so that the rare earth permanent magnet has all the beneficial effects of the preparation method according to any one of the above technical schemes, and the details are not repeated herein.
Detailed Description
The following examples, which are illustrative only and not to be construed as limiting the invention, will now be described in detail. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
The embodiment of the invention provides a preparation method of a rare earth permanent magnet, which comprises the following steps:
s10: performing surface treatment on a workpiece prepared from a rare earth permanent magnet material to control the roughness of the surface of the workpiece to be Ra0.5-5.5;
s20: mixing the following components in parts by mass: (1-10) placing the workpiece and the auxiliary balls after the S10 treatment into a roller, wherein the ratio of the total volume of the workpiece and the auxiliary balls after the S10 treatment to the volume of the roller is 1: (2-6), and immersing the roller into the rare earth slurry for rolling treatment;
s30: carrying out heat treatment on the workpiece treated in the step S20 to obtain a rare earth permanent magnet;
the rare earth slurry comprises a rare earth dopant, a solvent and a dispersant, wherein the mass part ratio of the rare earth dopant to the solvent to the dispersant is 300: (100-900): (0.8-24), the particle size of the rare earth dopant is 1um-9um;
the diameter of the auxiliary ball is 1mm-8mm, and the rotating speed of the rolling treatment is controlled at 4rpm-18rpm.
In the preparation method, firstly, the roughness of the surface of the workpiece is controlled in a proper range through surface treatment, and the rare earth slurry with specific components is prepared, so that the bonding force between the coating layer and the workpiece is enhanced; and secondly, the loading amount of the rolling treatment step, the size of the auxiliary balls and the mass ratio of the workpiece to the auxiliary balls are optimized, and the rotating speed of the roller is adjusted, so that the workpiece can obtain a good dispersed turning effect in the rolling treatment process in the roller, and the friction force applied to the workpiece can be effectively relieved. According to the invention, through the cooperative regulation and control of the workpiece surface roughness, the rare earth slurry components and the rolling treatment, the efficient and uniform coating of the rare earth slurry on the surface of the small-size rare earth permanent magnet workpiece is finally realized, the coating layer is firmly combined with the workpiece and does not fall off, the rare earth elements are uniformly diffused on the surface layer of the workpiece, and the efficient promotion of the intrinsic coercive force of the product is realized.
Specifically, the rare earth permanent magnet material is an R-T-B rare earth permanent magnet material, wherein R refers to rare earth elements, T refers to transition metal elements, third main group metal elements and B refers to boron elements. The most important performance of the R-T-B series rare earth permanent magnet material is intrinsic coercivity, so the preparation method provided by the invention mainly aims at processing a workpiece prepared from the R-T-B series rare earth permanent magnet material and improving the intrinsic coercivity.
In the surface treatment of the workpiece, the surface treatment may be chemically or mechanically treated. The chemical method comprises oil removal, acid cleaning and the like, and in the acid cleaning treatment of the embodiment of the invention, the adopted acid cleaning medium is at least one of hydrofluoric acid, sulfuric acid and hydrochloric acid. However, the invention aims at the small-sized rare earth permanent magnet, the chemical method treatment is easy to generate the over-corrosion phenomenon, so that crystal grains on the surface of the workpiece are damaged, the performance of the workpiece is influenced, and the residual reagent of the chemical method is difficult to completely remove and is not beneficial to the subsequent rare earth slurry coating step. The mechanical method comprises a steel wire brush roller polishing method, a shot blasting method and the like, and sand blasting is selected in the embodiment of the invention. The sand blasting treatment adopts compressed air as power to form a high-speed jet beam to spray abrasive materials to the surface of a workpiece at a high speed so as to change the roughness of the surface of the workpiece. And the abrasive material impacts and cuts the surface of the workpiece, so that the mechanical property of the surface of the workpiece can be improved through the sand blasting treatment, and the fatigue resistance of the workpiece is improved.
In the sand blasting treatment of the embodiment of the invention, the grain diameter of the sand blasting abrasive is 105um-380um, the sand blasting time is 2min-30min, and the compressed air pressure is 0.3MPa-0.7MPa.
Preferably, the grain diameter of the sand blasting abrasive is 200um-250um, the sand blasting time is 25min, and the compressed air pressure is 0.4MPa-0.5MPa. Under the condition, the roughness of the surface of the workpiece can be controlled to Ra2.5-3.5, and the roughness is controlled within the range, so that on one hand, the rare earth slurry can be firmly combined with the surface of the workpiece, and on the other hand, the problems of low reversal speed of the workpiece, easy smearing of a coating layer and the like caused by overlarge roughness can be prevented.
Further, the abrasive is at least one of copper ore sand, quartz sand, carborundum, iron sand and sea sand.
When the workpiece is subjected to rolling treatment, the rare earth slurry is coated on the surface of the workpiece, so that the rare earth elements in the rare earth slurry can be subjected to grain boundary diffusion on the surface layer of the workpiece. The rare earth slurry has the advantages that the dispersion uniformity of the rare earth elements in the rare earth slurry has great influence on the effect of grain boundary diffusion, so the components and the preparation steps of the rare earth slurry are improved, and the rare earth elements can be uniformly dispersed in the slurry.
The components of the rare earth slurry mainly comprise a rare earth dopant, a solvent and a dispersant, wherein the rare earth dopant is at least one of dysprosium metal, terbium metal, dysprosium fluoride, terbium fluoride, dysprosium oxide, terbium oxide, dysprosium hydride, terbium hydride, dysprosium copper alloy, terbium copper alloy, dysprosium aluminum alloy and terbium aluminum alloy; and/or the solvent is at least one of methanol, ethanol, ether and acetone; and/or the dispersant is at least one of methacrylic acid copolymer and polyvinyl acetal Ding Quanzhi.
Dysprosium and terbium are selected as rare earth elements to carry out grain boundary diffusion on the surface of the workpiece because the dysprosium and terbium have high-efficiency diffusion capability and can generate a magnetocrystalline anisotropy field ratio Nd 2 Fe 14 Big B (Nd) 2 Fe 14 B、Dy 2 Fe 14 B) Crystal or (Nd) 2 Fe 14 B、Tb 2 Fe 14 B) And the intrinsic coercive force of the workpiece is greatly improved.
Further, in the above production method, the rare earth dopant includes an RE/M alloy; wherein RE is dysprosium or terbium, M is copper or aluminum, and the mass of RE is 10-90% of the total mass of the RE/M alloy.
The specific preparation method of the rare earth slurry comprises the following steps:
s41: performing ball milling treatment on the rare earth raw material to obtain a rare earth dopant;
s42: mixing the following components in parts by mass: (1-9) mixing the solvent and the rare earth dopant, and stirring for 10-15 min to obtain a first mixture;
s43: the mass portion ratio is 500: and (1) mixing the first mixture and the dispersant, and stirring for 20min-30min to obtain the rare earth slurry.
In the preparation steps of the rare earth slurry, rare earth dopant powder with the particle size of 1-9 um is obtained after ball milling treatment is carried out on the rare earth raw materials, the powdery rare earth dopant can form fine slurry, and a uniform coating layer is formed on the surface of a workpiece. In the ball milling treatment, the ball milling speed is controlled to be 4rpm-60rpm, the ball material ratio is 10: (1-20) and the ball milling time is 1-8 h.
Preferably, in the ball milling treatment, the ball milling rotating speed is controlled to be 45rpm-50rpm, the ball material ratio is controlled to be 10: (15) And ball milling for 5-6 h to obtain the rare earth dopant powder with the particle size of 3-4 um.
Preferably, the solvent is ethanol, the ethanol can improve the fluidity and the caking property of the rare earth dopant, can reduce the surface energy of the powder surface, prevents the agglomeration of the powdery rare earth dopant, does not influence the grain boundary diffusion of the rare earth element, and can completely remove the ethanol during the subsequent heat treatment.
Preferably, the dispersing agent is polyvinyl acetal Ding Quanzhi, and the polyvinyl butyral ester can efficiently promote the rare earth doping agent to be uniformly dispersed so as to avoid dechlorination.
When the workpiece processed by the S10 and the auxiliary ball are mixed and immersed into the rare earth slurry for rolling processing, the size of the workpiece processed by the S10 is controlled within 8mm, and the auxiliary ball is selected to have the same size as the workpiece, so that the rare earth slurry can be more uniformly coated on the surface of the workpiece processed by the S10.
Furthermore, the auxiliary ball is at least one of zirconia, alumina and silicon carbide. The zirconia auxiliary ball has high strength, toughness and wear resistance at normal temperature, can effectively stir workpieces to move during rolling treatment, cannot be damaged by workpieces in various shapes, cannot generate ball crumbs, and is easy to peel. The alumina auxiliary ball has higher hardness at normal temperature, and the performance of the alumina auxiliary ball is still very stable at high temperature, so that the workpiece can be effectively stirred at higher temperature. The silicon carbide auxiliary ball has the performances of high temperature resistance, acid resistance and the like, and can realize effective stirring and coating of rare earth slurry with certain corrosivity.
Preferably, the mass part ratio of the workpiece after the S10 treatment and the auxiliary ball put into the drum is 5: (5-6), the ratio of the total volume of the workpiece and the auxiliary ball processed in the step S10 to the volume of the roller is 1: and 4, controlling 1/5 of the volume of the rare earth slurry immersion roller, so that the surface of the workpiece treated by the S10 can be coated with a coating layer with the thickness of 50-80 um. Under the condition, the rare earth slurry on the surface of the small-size rare earth permanent magnet workpiece can be quickly and uniformly coated, and the thickness of the coating layer can meet the requirement of improving the intrinsic coercive force by rare earth element crystal boundary diffusion, so that the using amount of the rare earth slurry can be saved, and the cost is saved.
Further, the rolling device used in the rolling treatment comprises a roller and a slurry barrel. When the rare earth slurry stirring device is used, firstly, the rare earth slurry is poured into the slurry barrel, the rare earth slurry is stirred to keep the rare earth slurry in a uniformly dispersed state, and then the roller filled with the workpiece and the auxiliary balls is placed into the slurry barrel, wherein the surface of the roller is provided with the hollowed-out small holes, so that the rare earth slurry can penetrate through the small holes and enter the roller.
And (3) after uniformly coating the rare earth slurry with proper thickness on the surface of the workpiece, carrying out heat treatment on the workpiece after the S20 treatment, wherein the diffusion of rare earth elements can be accelerated by the heat treatment. The heat treatment comprises the following specific steps:
s31: placing the workpiece treated in the step S20 in a vacuum sintering furnace for primary heat treatment, wherein the treatment temperature is 700-1000 ℃, and the treatment time is 2-48 h;
s32: performing secondary heat treatment on the workpiece treated by the S31 at the treatment temperature of 420-650 ℃ for 2-10 h;
s33: and cooling the workpiece treated in the step S32 to room temperature along with the furnace to obtain the rare earth permanent magnet.
In the preparation steps, the first heat treatment is beneficial to the rare earth elements in the rare earth slurry to be quickly diffused to the surface layer of the workpiece, and the second heat treatment can ensure that the rare earth elements are quickly rearranged after being diffused. Wherein the temperature of the secondary heat treatment is lower than that of the primary heat treatment to prevent the rare earth elements from moving in a wider range.
Further, before the primary heat treatment, the temperature of the vacuum sintering furnace is increased from room temperature to the treatment temperature of the primary heat treatment at the temperature rising rate of 2-15 ℃/min; before the secondary heat treatment, the temperature of the vacuum sintering furnace is reduced from the treatment temperature of the primary heat treatment to the treatment temperature of the secondary heat treatment at a cooling rate of 6-10 ℃/min. The effect of rare earth element diffusion can be improved by controlling the heating rate of the heat treatment.
Preferably, the temperature rising rate of the workpiece processed in the S20 step is controlled to be 8-10 ℃/min before the first heat treatment, and the temperature falling rate of the workpiece processed in the S31 step is controlled to be 6-7 ℃/min before the second heat treatment.
In the heat treatment, after the workpiece treated in S20 is placed in a vacuum sintering furnace, both the primary heat treatment and the secondary heat treatment are performed in the vacuum sintering furnace. The furnace temperature is increased to the set temperature according to the set speed for primary heat treatment, and then the furnace temperature is reduced to the set temperature according to the set speed for secondary heat treatment. And after the secondary heat treatment, taking the workpiece out of the vacuum sintering furnace, and air-cooling to room temperature to complete the rare earth grain boundary diffusion treatment on the surface of the small-size rare earth permanent magnet.
The method for producing a rare earth permanent magnet according to the present invention will be described in detail with reference to specific examples.
Example 1
S10: performing surface sand blasting treatment on a workpiece prepared from a rare earth permanent magnet material: controlling the grain diameter of the sand blasting abrasive to be 150um-180um, the sand blasting time to be 10min-15min, and the compressed air pressure to be 0.3Mpa-0.4Mpa, so that the roughness of the surface of the workpiece is Ra0.5-1.5;
s20: and (3) rolling treatment: mixing the following components in parts by mass: (7-10) placing the workpiece and the zirconia auxiliary balls after the S10 treatment into a roller, wherein the ratio of the total volume of the workpiece and the auxiliary balls after the S10 treatment to the volume of the roller is 1:3, immersing the roller into the rare earth slurry, and performing rolling treatment, wherein the diameter of the auxiliary ball is 7mm, and the rotating speed of the rolling treatment is controlled to be 16-18 rpm; the preparation method of the rare earth slurry comprises the following steps: firstly, performing ball milling treatment on a rare earth raw material to obtain a rare earth dopant, wherein the particle size of the rare earth dopant is 1-3 um, the ball milling rotation speed is controlled to be 50-60 rpm, and the ball-to-material ratio is 10: (1-5), and carrying out ball milling for 7-8 h; and then mixing the components in parts by mass as follows: (7-9) mixing the solvent and the rare earth dopant, and stirring for 10min-15min to obtain a first mixture; and finally, mixing the following components in parts by mass: (1-10) mixing the first mixture with a dispersant, and stirring for 20min-30min to obtain rare earth slurry;
s30: and (3) heat treatment: placing the workpiece treated by the S20 in a vacuum sintering furnace for primary heat treatment, wherein the treatment temperature is 700-1000 ℃, the treatment time is 15-20 h, and the heating rate is 3-5 ℃/min; performing secondary heat treatment on the workpiece subjected to the primary heat treatment, wherein the treatment temperature is 420-650 ℃, the treatment time is 2-4 h, and the cooling rate is 6-7 ℃/min; and cooling the workpiece subjected to the secondary heat treatment to room temperature along with the furnace to obtain the rare earth permanent magnet.
Example 2
S10: performing surface sand blasting treatment on a workpiece prepared from a rare earth permanent magnet material: controlling the grain diameter of the sand blasting abrasive to be 210um-230um, the sand blasting time to be 12min-21min, and the compressed air pressure to be 0.5MPa-0.6MPa, so that the roughness of the surface of the workpiece is Ra2.5-3.5;
s20: and (3) rolling treatment: mixing the following components in parts by mass: (4-6) placing the workpiece and the alumina auxiliary balls into the roller after the S10 treatment, wherein the ratio of the total volume of the workpiece and the auxiliary balls after the S10 treatment to the volume of the roller is 1:4, immersing the roller into the rare earth slurry for rolling treatment; the diameter of the auxiliary ball is 5mm, and the rotating speed of rolling treatment is controlled to be 10-12 rpm; the preparation method of the rare earth slurry comprises the following steps: firstly, performing ball milling treatment on a rare earth raw material to obtain a rare earth dopant, wherein the particle size of the rare earth dopant is 4-6 um, the ball milling rotation speed is controlled to be 40-50 rpm, and the ball material ratio is 10: (8-12), and carrying out ball milling for 5-6 h; and then mixing the components in parts by mass as follows: (4-6) mixing the solvent and the rare earth dopant, and stirring for 10-15 min to obtain a first mixture; and finally, mixing the following components in parts by mass: mixing the first mixture of (1-10) and a dispersing agent, and stirring for 20-30 min to obtain rare earth slurry;
s30: and (3) heat treatment: placing the workpiece treated by the step S20 in a vacuum sintering furnace for primary heat treatment, wherein the treatment temperature is 700-1000 ℃, the treatment time is 20-25 h, and the heating rate is 8-10 ℃/min; performing secondary heat treatment on the workpiece subjected to the primary heat treatment, wherein the treatment temperature is 420-650 ℃, the treatment time is 5-6 h, and the cooling rate is 7-8 ℃/min; and cooling the workpiece subjected to the secondary heat treatment to room temperature along with the furnace to obtain the rare earth permanent magnet.
Example 3
S10: performing surface sand blasting treatment on a workpiece prepared from a rare earth permanent magnet material: controlling the grain diameter of the sand blasting abrasive to be 320-350 um, the sand blasting time to be 25-30 min, and the compressed air pressure to be 0.6-0.7 Mpa, so that the roughness of the surface of the workpiece is Ra4.5-5.5;
s20: and (3) rolling treatment: mixing the following components in parts by mass: (1-3) placing the workpiece and the silicon carbide auxiliary balls after the S10 treatment into a roller, wherein the ratio of the total volume of the workpiece and the auxiliary balls after the S10 treatment to the volume of the roller is 1:5, immersing the roller into the rare earth slurry for rolling treatment; the diameter of the auxiliary ball is 3mm, and the rotating speed of rolling treatment is controlled to be 5-8 rpm; the preparation method of the rare earth slurry comprises the following steps: firstly, performing ball milling treatment on a rare earth raw material to obtain a rare earth dopant, wherein the particle size of the rare earth dopant is 7-9 um, the ball milling rotation speed is controlled to be 20-30 rpm, and the ball-to-material ratio is 10: (15-20), and carrying out ball milling for 1-3 h; and then mixing the components in parts by mass as follows: (1-3) mixing the solvent and the rare earth dopant, and stirring for 10-15 min to obtain a first mixture; and finally, mixing the following components in parts by mass: mixing the first mixture of (1-10) and a dispersing agent, and stirring for 20-30 min to obtain rare earth slurry;
s30: and (3) heat treatment: placing the workpiece treated in the step S20 in a vacuum sintering furnace for primary heat treatment, wherein the treatment temperature is 700-1000 ℃, the treatment time is 35-40 h, and the heating rate is 12-15 ℃/min; performing secondary heat treatment on the workpiece subjected to the primary heat treatment, wherein the treatment temperature is 420-650 ℃, the treatment time is 8-10 h, and the cooling rate is 8-10 ℃/min; and cooling the workpiece subjected to the secondary heat treatment to room temperature along with the furnace to obtain the rare earth permanent magnet.
The features of the terms first and second in the description and in the claims of the invention may explicitly or implicitly include one or more of these features. In the description of the present invention, "a plurality" means two or more unless otherwise specified. In addition, "and/or" in the specification and claims means at least one of connected objects, a character "/" generally means that a preceding and succeeding related objects are in an "or" relationship.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples" or the like mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.
Claims (6)
1. A method for preparing a rare earth permanent magnet, characterized by comprising:
s10: performing surface treatment on a workpiece prepared by adopting a rare earth permanent magnet material to control the roughness of the surface of the workpiece to be Ra2.5-3.5; the surface treatment is sand blasting treatment, the grain diameter of sand blasting abrasive adopted by the sand blasting treatment is 200-250 um, the sand blasting time adopted by the sand blasting treatment is 25min, and the pressure of compressed air adopted by the sand blasting treatment is 0.4-0.5 Mpa;
s20: putting the workpiece and the auxiliary balls after the S10 treatment into a roller, and immersing the roller into rare earth slurry for rolling treatment; wherein the mass part ratio of the workpiece processed in S10 to the auxiliary ball is 5: (1-10), the ratio of the total volume of the workpiece and the auxiliary ball processed in the step (S10) to the volume of the roller is 1: (2-6), the diameter of the auxiliary ball is 1mm-8mm, and the rotating speed of the rolling treatment is controlled to be 4rpm-18rpm;
s30: carrying out heat treatment on the workpiece treated by the S20 to obtain the rare earth permanent magnet; the S30 specifically includes:
s31: placing the workpiece treated by the S20 in a vacuum sintering furnace for primary heat treatment, wherein the treatment temperature is 700-1000 ℃, and the treatment time is 2-48 h;
s32: performing secondary heat treatment on the workpiece treated by the S31, wherein the treatment temperature is 420-650 ℃, and the treatment time is 2-10 h;
s33: cooling the workpiece treated in the step S32 to room temperature along with a furnace to obtain the rare earth permanent magnet;
before the primary heat treatment, raising the temperature of the vacuum sintering furnace from room temperature to the treatment temperature of the primary heat treatment at a temperature raising rate of 2 ℃/min-15 ℃/min; and/or
Before the secondary heat treatment, reducing the temperature of the vacuum sintering furnace from the treatment temperature of the primary heat treatment to the treatment temperature of the secondary heat treatment at a cooling rate of 6 ℃/min-10 ℃/min;
wherein the rare earth slurry is prepared by the following steps:
s41: performing ball milling treatment on the rare earth raw material to obtain a rare earth dopant;
s42: mixing the following components in parts by mass: (1-9) mixing the solvent and the rare earth dopant, and stirring for 10-15 min to obtain a first mixture; the solvent is ethanol;
s43: the mass portion ratio is 500: (1-10) mixing the first mixture and a dispersing agent, and stirring for 20min-30min to obtain the rare earth slurry; the dispersing agent is polyvinyl alcohol Ding Quanzhi;
in the ball milling treatment, the ball milling rotating speed is controlled to be 45rpm-50rpm, the ball-to-material ratio is controlled to be 10: and 15, ball milling for 5-6 h to obtain the rare earth dopant powder with the particle size of 3-4 um.
2. The method according to claim 1, wherein the surface treatment is an acid pickling treatment using an acid pickling medium selected from at least one of hydrofluoric acid, sulfuric acid, and hydrochloric acid.
3. The production method according to claim 1, wherein the auxiliary balls are at least one of zirconia auxiliary balls, alumina auxiliary balls, and silicon carbide auxiliary balls.
4. The production method according to any one of claims 1 to 3,
the rare earth dopant is at least one of dysprosium metal, terbium metal, dysprosium fluoride, terbium fluoride, dysprosium oxide, terbium oxide, dysprosium hydride, terbium hydride, dysprosium copper alloy, terbium copper alloy, dysprosium aluminum alloy and terbium aluminum alloy.
5. The production method according to any one of claims 1 to 3,
the rare earth dopant comprises a RE/M alloy;
wherein RE is dysprosium or terbium, M is copper or aluminum, and the mass of RE is 10-90% of the total mass of the RE/M alloy.
6. A rare earth permanent magnet, characterized in that it is produced by the production method according to any one of claims 1 to 5.
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