WO2022193464A1 - 一种钕铁硼磁体及一种三维晶界扩散制备钕铁硼磁体的方法 - Google Patents

一种钕铁硼磁体及一种三维晶界扩散制备钕铁硼磁体的方法 Download PDF

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WO2022193464A1
WO2022193464A1 PCT/CN2021/102058 CN2021102058W WO2022193464A1 WO 2022193464 A1 WO2022193464 A1 WO 2022193464A1 CN 2021102058 W CN2021102058 W CN 2021102058W WO 2022193464 A1 WO2022193464 A1 WO 2022193464A1
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diffusion
heavy rare
rare earth
magnet
ndfeb
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PCT/CN2021/102058
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English (en)
French (fr)
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廖明活
毛华云
刘永
毛琮尧
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金力永磁(包头)科技有限公司
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Priority to JP2023540869A priority Critical patent/JP2024503816A/ja
Priority to EP21931049.7A priority patent/EP4254438A1/en
Priority to US18/261,086 priority patent/US20240071682A1/en
Publication of WO2022193464A1 publication Critical patent/WO2022193464A1/zh

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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
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • 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
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
    • 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
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
    • H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
    • H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
    • 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

Definitions

  • the invention belongs to the technical field of magnet preparation, and relates to a NdFeB magnet and a preparation method thereof, in particular to a NdFeB magnet and a method for preparing a NdFeB magnet by three-dimensional grain boundary diffusion.
  • Neodymium iron boron magnet also known as Neodymium magnet (Neodymium magnet)
  • Neodymium magnet its chemical formula is Nd 2 Fe 14 B
  • BHmax maximum magnetic energy product
  • the industry often uses the sintering method to make NdFeB permanent magnet materials. For example, Wang Wei et al. disclosed the use of sintering method to manufacture NdFeB permanent magnets in the "Influence of Key Process Parameters and Alloy Elements on Magnetic and Mechanical Properties of Sintered NdFeB".
  • the technological process of materials generally includes the steps of batching, smelting, ingot crushing, pulverizing, hydrogen crushing ultra-fine powder, powder orientation pressing and molding, vacuum sintering, inspection and electroplating.
  • the advantages of NdFeB magnets are high cost performance, small size, light weight, good mechanical properties and strong magnetic properties.
  • the advantages of such high energy density make NdFeB permanent magnet materials widely used in modern industry and electronic technology.
  • Application known as the king of magnetism in the field of magnetism. Therefore, the preparation and expansion of NdFeB magnets has been the focus of continuous attention in the industry.
  • the maximum magnetic energy product of sintered NdFeB is close to the theoretical limit, but the intrinsic coercivity is far below the theoretical limit.
  • the traditional method to improve the intrinsic coercivity is to add heavy rare earth Dy/Tb in the smelting stage and use the grain refinement process in the jet milling stage. Adding a large amount of heavy rare earth in the smelting stage will greatly increase the cost on the one hand, and on the other hand, adding a large amount of heavy rare earth will greatly reduce the remanence, because the remanence is mainly determined by the volume ratio of the main phase of Nd 2 Fe 14 B, and Nd 2 Fe 14 B The higher the volume ratio, the higher the remanence.
  • the Nd in the main phase Nd 2 Fe 14 B is partially replaced to form (Nd, Dy) 2 Fe 14 B or (Nd, Tb) 2 Fe 14 B.
  • the magnetic moments of Nd and Fe are arranged in parallel, and the magnetic moments of the two are superimposed in the same direction, while the magnetic moments of Dy/Tb and Fe are antiferromagnetically coupled, and the magnetic moments of Dy/Tb and Fe are superimposed in the opposite direction, resulting in The remanence is greatly reduced.
  • the grain refining process has high requirements on jet mill equipment, and the powder after grain refining is easy to oxidize.
  • the grain refining process has high requirements for anti-oxidation control in the production process. This process increases the process cost and has a high defect rate. .
  • the technical problem to be solved by the present invention is to provide a NdFeB magnet and a preparation method thereof, especially a method for preparing NdFeB magnet by three-dimensional grain boundary diffusion.
  • Extending to macroscopic magnets that is, from the deposition of heavy rare earths on the surface of microscopic grains to the deposition of heavy rare earths on the surface of macroscopic magnets, by adjusting the heat treatment temperature and time, diffusion layers of different depths can be obtained.
  • the purpose of improving the coercivity of the magnet while reducing the remanence (Br) and the maximum magnetic energy level (BHmax) of the magnet very little.
  • the preparation method has a simple process and is more suitable for industrialization and application.
  • the invention provides a neodymium-iron-boron magnet, which is a neodymium-iron-boron magnet that has been diffused and infiltrated by heavy rare earth elements;
  • the NdFeB magnet includes a surface heavy rare earth diffusion zone and a core non-diffusion zone;
  • the NdFeB magnets all have surface layer heavy rare earth diffusion regions in the three-dimensional directions of the magnets.
  • the heavy rare earth elements include Dy and/or Tb;
  • the proportion of the volume of the non-diffusion region of the core to the volume of the NdFeB magnet is greater than or equal to 20%.
  • the diffusion penetration is three-dimensional grain boundary diffusion
  • the NdFeB magnet has a surface heavy rare earth diffusion zone on any surface
  • the diffusion and penetration amount of the heavy rare earth element accounts for 0.1 wt % to 1.0 wt % of the mass of the NdFeB magnet.
  • the content of heavy rare earths in the non-diffusion zone of the core does not increase before and after diffusion infiltration
  • the depth of the surface layer heavy rare earth diffusion zone in any surface of the NdFeB magnet is within 80% of the distance from the surface to the center of the magnet;
  • the Hcj of the NdFeB magnet is increased by 2-15kOe compared with that before the diffusion infiltration.
  • the concentration of heavy rare earth elements at the edge is greater than the concentration of heavy rare earth elements in the middle;
  • the heavy rare earth element concentration first gradually decreases and then remains constant
  • the heavy rare earth element concentration gradually decreases.
  • the present invention also provides a preparation method of the NdFeB magnet, comprising the following steps:
  • the organic solvent includes silicone oil
  • the average particle size of the heavy rare earth is 1-100 ⁇ m
  • the mass ratio of the heavy rare earth to the solvent is (90-98): (2-10).
  • the NdFeB blank includes a NdFeB blank after surface polishing
  • the grain boundary diffusion is specifically grain boundary diffusion under vacuum conditions
  • the absolute pressure of the vacuum is less than or equal to 10Pa;
  • the grain boundary diffusion includes a low temperature volatilization step and a high temperature diffusion step.
  • the temperature of the low-temperature volatilization is 300-500°C;
  • the low temperature volatilization time is 3 ⁇ 5h
  • the temperature of the high temperature diffusion is 700-1000°C;
  • the high temperature diffusion time is 1-100h.
  • the aging treatment is specifically carried out after high temperature diffusion cooling and then aging treatment;
  • the temperature of the aging treatment is 400 ⁇ 600°C;
  • the time of the aging treatment is 1-15h.
  • the invention provides a NdFeB magnet, which is a NdFeB magnet after diffusion and infiltration of heavy rare earth elements; the NdFeB magnet includes a surface heavy rare earth diffusion zone and a core non-diffusion zone; The NdFeB magnets all have surface layer heavy rare earth diffusion regions in the three-dimensional directions of the magnets.
  • the present invention is based on the principle of grain boundary diffusion.
  • the powder or compound containing heavy rare earth elements is coated on the outside of the magnet by a coating method, and the heavy rare earth elements are diffused along the Nd-rich liquid grain boundary phase through heat treatment. into the magnet.
  • the diffusion rate of Dy/Tb in the grain boundary is much faster than the diffusion rate inside the main phase grains, so the heavy rare earths are only deposited on the surface of the main phase grains after diffusion, and rarely enter the grains.
  • the invention creatively extends the diffusion principle from microscopic grains to macroscopic magnets, that is, from heavy rare earths deposited on the surface of microscopic grains to heavy rare earths deposited on the surface of macroscopic magnets, more than 20% of the core volume is impermeable.
  • diffusion layers of different depths can be obtained.
  • the coercive force of the magnet can be improved, and the remanence (Br) and the maximum magnetic energy level (BHmax) of the magnet are reduced very little.
  • a single magnet can be regarded as a single crystal grain, which should have a more excellent combination effect.
  • the three-dimensional grain boundary diffusion technology and the three-dimensional grain boundary diffusion magnet provided by the present invention can be based on the characteristics of the product itself. , adding 0.10wt% to 1.0wt% of heavy rare earth, through diffusion, the heavy rare earth is deposited on the surface of the magnet, more than 20% of the core volume is impermeable, and in the three-dimensional direction, independent regulation is achieved according to different diffusion depths. Moreover, the preparation process is simple, the controllability is strong, and it is more suitable for industrialization and application.
  • FIG 1 is an EDS diagram of the cross-section of the magnet sample 3 prepared in Example 1 of the present invention.
  • FIG. 2 is a graph showing the performance data of the magnet of Comparative Sample 3 prepared in Example 2 of the present invention.
  • All raw materials in the present invention are not particularly limited in their purity, and the present invention preferably adopts analytical purity or conventional purity used in the field of NdFeB magnets.
  • the invention provides a neodymium-iron-boron magnet, which is a neodymium-iron-boron magnet that has been diffused and infiltrated by heavy rare earth elements;
  • the NdFeB magnet includes a surface heavy rare earth diffusion zone and a core non-diffusion zone;
  • the NdFeB magnets all have surface layer heavy rare earth diffusion regions in the three-dimensional directions of the magnets.
  • the heavy rare earth element preferably includes Dy and/or Tb, more preferably Tb or Dy, or a Dy-Tb alloy.
  • the ratio of the volume of the non-diffusion zone of the core to the volume of the NdFeB magnet is preferably greater than or equal to 20%, may be greater than or equal to 30%, or greater than or equal to 50%.
  • the NdFeB magnets all have surface heavy rare earth diffusion regions in the three-dimensional directions of the magnets.
  • the diffusion penetration is preferably three-dimensional grain boundary diffusion.
  • the NdFeB magnet of the present invention has a surface layer heavy rare earth diffusion region on any surface. That is, taking a cube as an example, in the six planes composed of length, width and height, each surface has a surface layer heavy rare earth diffusion region.
  • the diffusion infiltration amount of the heavy rare earth element preferably accounts for 0.1wt%-1.0wt% of the mass of the NdFeB magnet, more preferably 0.3wt%-0.8wt%, more preferably 0.5wt%-0.6 wt%.
  • the content of heavy rare earths in the non-diffusion zone of the core does not increase before and after diffusion infiltration. That is, the core is a non-diffusion region.
  • the depth of the surface heavy rare earth diffusion region in any surface of the NdFeB magnet is preferably within 80% of the distance from the surface to the center of the magnet, and more It is preferably within 60%, and more preferably within 40%. Specifically, it may be 10% to 80%, or 20% to 70%, or 30% to 60%.
  • the distance from the surface to the center of the magnet is the height (length) from the surface to the center of the magnet. For this distance, the same value or different values can be selected for each surface of the magnet at the same time.
  • the Hcj of the NdFeB magnet is preferably increased by 2 to 15 kOe, more preferably by 5 to 14 kOe, and more preferably by 8 to 13 kOe, compared with that before diffusion and penetration.
  • the concentration of heavy rare earth elements at the edge is preferably greater than that in the middle. Specifically, along the layer direction of the surface heavy rare earth diffusion region, from the edge to the middle, the concentration of heavy rare earth elements preferably first gradually decreases and then remains constant. More specifically, in the depth direction of the surface heavy rare earth diffusion region, the concentration of heavy rare earth elements preferably gradually decreases. This is the specific feature of the three-dimensional grain boundary diffusion of the present invention.
  • the concentration of heavy rare earth elements is gradually reduced from the depth direction of the diffusion; From the lateral view of the diffusion zone, since there is diffusion in three-dimensional directions, the diffusion of adjacent surfaces will increase the concentration of heavy rare earth elements at the edge, that is, the concentration overlaps.
  • the middle of the diffusion region since the magnet core has a non-diffusion region, the middle position in the lateral direction of each diffusion region is not affected by the adjacent diffusion regions, and the diffusion concentration of the elements in the middle is lower than that of the edge. And the change trend of the overall diffusion element concentration is from the edge to the middle, first decreases and then remains constant.
  • the present invention also provides a preparation method of the NdFeB magnet, comprising the following steps:
  • the present invention firstly mixes the heavy rare earth with the organic solvent to obtain a mixed solution.
  • the organic solvent preferably includes silicone oil.
  • the average particle size of the heavy rare earth raw material is preferably 1-100 ⁇ m, more preferably 5-80 ⁇ m, more preferably 10-60 ⁇ m, and more preferably 20-50 ⁇ m.
  • the mass ratio of the heavy rare earth to the solvent is preferably (90-98):(2-10), more preferably (91-97):(2-10), more preferably (93) to 95): (2 to 10), (90 to 98): (3 to 9), or (90 to 98): (5 to 7).
  • the mixed solution obtained in the above steps is then coated on each surface of the NdFeB blank to obtain a semi-finished product.
  • the NdFeB blank can be in any shape, such as a cube, a cuboid, a polygon or a sphere, etc., and can be a cube or a cuboid in particular.
  • the NdFeB blank preferably includes a NdFeB blank after surface polishing.
  • the grain boundary diffusion is preferably carried out under vacuum conditions. More specifically, the absolute pressure of the vacuum is preferably less than or equal to 10 Pa, more preferably less than or equal to 1 Pa, more preferably less than or equal to 0.1 Pa.
  • the grain boundary diffusion preferably includes a low temperature volatilization step and a high temperature diffusion step.
  • the temperature of the low-temperature volatilization is preferably 300-500°C, more preferably 325-475°C, more preferably 350-450°C, and more preferably 375-425°C.
  • the low-temperature volatilization time is preferably 3-5 hours, more preferably 3.2-4.8 hours, more preferably 3.5-4.5 hours, and more preferably 3.8-4.3 hours.
  • the temperature of the high-temperature diffusion in the present invention is preferably 700 to 1000°C, more preferably 750 to 950°C, and more preferably 800 to 900°C.
  • the high temperature diffusion time is 1 to 100 hours, more preferably 5 to 80 hours, more preferably 10 to 60 hours, and more preferably 20 to 50 hours.
  • the present invention has no particular limitation on the equipment for the grain boundary diffusion, and the equipment known to those skilled in the art can be used for the grain boundary diffusion of magnets.
  • the present invention is preferably a vacuum diffusion furnace, more preferably a sintering box with a flat bottom surface, and more preferably a vacuum diffusion furnace.
  • the invention completes and refines the overall preparation process, better guarantees the three-dimensional grain boundary diffusion effect of the NdFeB magnet, and better improves the magnetic properties of the NdFeB magnet after diffusion.
  • the preparation method of the NdFeB magnet is as follows:
  • the diffusion and infiltration process of NdFeB magnets can be specifically as follows:
  • Step 1 prepare a blank magnet
  • step 2 a mixture of heavy rare earth and solvent is prepared.
  • the solvent is selected from silicone oil, and the average particle size of the heavy rare earth is 1-100 ⁇ m, so as to realize the dissolution of the heavy rare earth powder and also facilitate the volatilization of the solvent in the later diffusion process.
  • the mass ratio is (90-98): (2-10), and in a specific embodiment, the mass ratio of the heavy rare earth powder to the solvent is 95:5;
  • Step 3 Coating a mixture containing heavy rare earth powder and a solvent in the three-dimensional direction (six surfaces) of the NdFeB magnet, the obtained NdFeB magnet material is subjected to grain boundary diffusion, and then subjected to aging treatment after cooling to obtain a three-dimensional grain boundary Diffused NdFeB magnets.
  • the process of grain boundary diffusion is as follows: the NdFeB magnet material is kept at 300-500°C for 3-5 hours to volatilize the solvent in the mixture, and then the temperature is raised to 700-1000°C for 1-100 hours.
  • the temperature of the aging treatment is 400-600°C, and the time is 1-15h.
  • the NdFeB blank is not particularly limited in the present invention, and the NdFeB blank known to those skilled in the art can be used, that is, the NdFeB raw material is subjected to the steps of batching, smelting, crushing and milling, powder oriented pressing and vacuum sintering, etc.
  • the final NdFeB blank that is, after surface treatment and processing, can be used as the blank of the ordinary finished NdFeB magnet.
  • the boron blank is then subjected to pretreatment such as degreasing and cleaning to make its surface smooth and clean, so as to achieve better diffusion effect.
  • the present invention obtains the NdFeB magnet after the above steps.
  • the present invention does not specifically limit the post-processing steps that may be included after the above steps, such as cleaning, slicing and other steps, and those skilled in the art can adjust or select according to actual production conditions, product requirements, and the like.
  • the above steps of the present invention provide a NdFeB magnet and a method for preparing a NdFeB magnet by three-dimensional grain boundary diffusion.
  • the invention extends the diffusion principle from microscopic crystal grains to macroscopic magnets, that is, from heavy rare earths deposited on the surface of microscopic crystal grains to heavy rare earths deposited on the surface of macroscopic magnets, more than 20% of the core volume is impermeable.
  • diffusion layers of different depths can be obtained.
  • the coercive force of the magnet can be improved, and the remanence (Br) and the maximum magnetic energy level (BHmax) of the magnet are reduced very little.
  • a single magnet can be regarded as a single crystal grain, which should have a more excellent combination effect.
  • the three-dimensional grain boundary diffusion technology and the three-dimensional grain boundary diffusion magnet provided by the present invention are a kind of surface magnetism.
  • the hardened NdFeB magnet includes a diffusion zone of heavy rare earth elements at a depth of 0-10 mm from the surface of the magnet to the interior of the magnet, and the content of heavy rare earth in the diffusion zone is higher than that of the base material. More than 20% of the core region is not diffused at all and remains the composition and properties of the substrate.
  • 0.10wt% to 1.0wt% of heavy rare earth can be added according to the characteristics of the product, and the heavy rare earth can be deposited on the surface of the magnet through diffusion, and more than 20% of the core volume is impermeable.
  • the temperature and holding time can be independently adjusted according to different diffusion depths, and NdFeB magnets with different diffusion depths can be obtained.
  • the preparation process is simple, the controllability is strong, and it is more suitable for industrialization and application.
  • the experimental results show that, compared with the traditional non-diffusion process, by adding 0.1% to 0.5% Tb by the three-dimensional grain boundary diffusion technology, ultra-high performance magnets with Br>14.85kGs and Hcj>21kOe can be obtained. performance.
  • the 3D grain boundary diffusion process significantly reduces the amount of heavy rare earth added compared to the traditional non-diffusion process.
  • the three-dimensional grain boundary diffusion process can be independently controlled according to different diffusion depths in the three-dimensional direction of the product.
  • NdFeB magnet provided by the present invention and a preparation method thereof will be described in detail below in conjunction with the examples, but it should be understood that these examples are implemented on the premise of the technical solution of the present invention, giving The detailed implementation and specific operation process are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention, and the protection scope of the present invention is not limited to the following examples.
  • metal terbium powder with an average particle size of 3-4 microns. Pour the terbium powder into the silicone oil in a nitrogen-protected glove box. The weight ratio of the terbium powder and the silicone oil is 95:5, and then stir evenly for later use.
  • the first group is the original sample of the base material, without coating, without diffusion treatment, as the comparative sample 1;
  • Group 2 Put 60 coated samples into a vacuum diffusion furnace, keep the temperature at 400°C for 4 hours to dry the silicone oil, discharge the silicone oil into the diffusion furnace through the vacuum system of the vacuum furnace, and then heat up to 700 ⁇ Grain boundary diffusion treatment is carried out at 1000 °C for 5 hours. After the diffusion is completed, it is quenched to below 80 °C, and then heated to 500 °C for aging treatment. The aging time is 5 hours. After aging, it is then quenched to below 80 °C. 60 pieces of processed samples were obtained as comparative sample 2;
  • Group 3 Put 60 coated samples into a vacuum diffusion furnace, keep the temperature at 400°C for 4 hours to dry the silicone oil, discharge the silicone oil into the diffusion furnace through the vacuum system of the vacuum furnace, and then heat up to 700 ⁇ Grain boundary diffusion treatment is carried out at 1000 ° C, the diffusion time is 10 hours, after the diffusion is completed, the temperature is quenched to below 80 ° C, and then the temperature is raised to 500 ° C for aging treatment. The aging time is 5 hours. 60 pieces of processed samples were obtained as comparative sample 3;
  • Group 4 Put 60 coated samples into a vacuum diffusion furnace, keep the temperature at 400 °C for 4 hours to dry the silicone oil, discharge the silicone oil into the diffusion furnace through the vacuum system of the vacuum furnace, and then heat up to 700 ⁇ Grain boundary diffusion treatment is carried out at 1000 °C, the diffusion time is 25 hours, after the diffusion is completed, the temperature is quenched to below 80 °C, and then the temperature is raised to 500 °C for aging treatment. The aging time is 5 hours. 60 pieces of processed samples were obtained as comparative sample 4;
  • FIG. 1 is an EDS image of the cross section of the magnet sample 3 prepared in Example 1 of the present invention.
  • Example 1 Take the N56 blank in Example 1, cut each blank into square pieces of 40*20*6 (mm), a total of 180 pieces of samples, and equally divided into 3 groups, each group of 60pcs.
  • the first group is the original sample of the base material, without coating, without diffusion treatment, as the comparative sample 1;
  • Group 2 For the second group of samples, on the special coating equipment, the prepared mixture of metal Tb powder and silicone oil is uniformly coated on 6 surfaces, and the amount of Tb is 0.1% of the weight of the sample; 60 pieces of samples were put into a vacuum diffusion furnace, first kept at 400 °C for 4 hours to dry the silicone oil, the silicone oil was discharged into the diffusion furnace through the vacuum system of the vacuum furnace, and then heated to 700 to 1000 °C for grain boundary diffusion treatment. The diffusion time is 5 hours, after the diffusion is completed, the temperature is quenched to below 80 °C, and then the temperature is raised to 500 °C for aging treatment. As a comparative sample 2;
  • Group 3 The samples of Group 3 are uniformly coated on 6 surfaces with the prepared mixture of metal Tb powder and silicone oil on the special coating equipment, and the amount of Tb is 0.2% of the weight of the sample;
  • the 60 pieces of samples were put into a vacuum diffusion furnace, kept at 400 °C for 4 hours to dry the silicone oil, and the silicone oil was discharged into the diffusion furnace through the vacuum system of the vacuum furnace, and then heated to 700 to 1000 °C for grain boundary diffusion treatment.
  • the diffusion time is 5 hours, after the diffusion is completed, the temperature is quenched to below 80 °C, and then the temperature is raised to 500 °C for aging treatment.
  • the magnet adopts 0.10% Tb and 0.20% Tb micro-diffusion to form a magnetic hardening layer on the surface of the magnet.
  • 56SH grade this kind of performance cannot be prepared by traditional non-diffusion process.
  • FIG. 2 is a performance data diagram of the magnet of Comparative Sample 3 prepared in Example 2 of the present invention.
  • a NdFeB magnet provided by the present invention and a method for preparing a NdFeB magnet by three-dimensional grain boundary diffusion have been introduced in detail above. Specific examples are used in this paper to illustrate the principles and implementations of the present invention. The description of the embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also to enable any person skilled in the art to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can also be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

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Abstract

本发明提供了一种钕铁硼磁体，所述钕铁硼磁体为经过重稀土元素扩散渗透后的钕铁硼磁体；所述钕铁硼磁体包括表层重稀土扩散区和芯部非扩散区；所述钕铁硼磁体在磁体的三维方向上均具有表层重稀土扩散区。本发明把扩散的原理由微观晶粒延伸到宏观磁体，即由重稀土沉积在微观晶粒的表层扩展到重稀土沉积在宏观磁体的表面，20％以上的芯部体积不渗透。调整热处理温度和时间，可以获得不同深度的扩散层，通过对表层磁体的磁硬化，达到提高磁体矫顽力，同时磁体剩磁(Br)和最大磁能级(BHmax)降低非常少的目的。而且在三维方向上，按不同扩散深度实现自主调控，制备工艺简单，可控性强，更加适于工业化推广和应用。

Description

一种钕铁硼磁体及一种三维晶界扩散制备钕铁硼磁体的方法
本申请要求于2021年03月19日提交中国专利局、申请号为202110296351.1、发明名称为“一种钕铁硼磁体及一种三维晶界扩散制备钕铁硼磁体的方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明属于磁体制备技术领域，涉及一种钕铁硼磁体及其制备方法，尤其涉及一种钕铁硼磁体及一种三维晶界扩散制备钕铁硼磁体的方法。
背景技术
钕铁硼磁体也称为钕磁体(Neodymium magnet)，其化学式为Nd 2Fe 14B，是一种人造的永久磁体，也是目前为止具有最强磁力的永久磁体，其最大磁能积(BHmax)高过铁氧体10倍以上，在裸磁的状态下，其磁力可达到3500高斯左右。目前，业界常采用烧结法制作钕铁硼永磁材料，如王伟等在《关键工艺参数和合金元素对烧结NdFeB磁性能与力学性能的影响》中公开了采用烧结法制造钕铁硼永磁材料的工艺流程，一般包括配料、熔炼、钢锭破碎、制粉、氢破碎超细粉、粉末取向压制成型、真空烧结、检分和电镀等步骤。钕铁硼磁体的优点是性价比高，体积小、重量轻、良好的机械特性和磁性强等特点，如此高能量密度的优点使钕铁硼永磁材料在现代工业和电子技术中获得了广泛的应用，在磁学界被誉为磁王。因而，钕铁硼磁体的制备和扩展一直是业内持续关注的焦点。
目前，烧结钕铁硼最大磁能积已经接近理论极限值，但是内禀矫顽力则远远低于理论极限值。提高内禀矫顽力的方法传统工艺是在熔炼阶段添加重稀土Dy/Tb和气流磨阶段采用晶粒细化工艺。熔炼阶段添加大量重稀土一方面会大幅增加成本，另一方面添加大量重稀土会导致剩磁的大幅降低，因为剩磁主要有Nd 2Fe 14B主相体积占比决定，Nd 2Fe 14B体积占比高，剩磁就高，Dy、Tb添加后部分取代主相Nd 2Fe 14B中的Nd，形成(Nd，Dy) 2Fe 14B或(Nd，Tb) 2Fe 14B。Nd和Fe的磁矩正向平行排列，两者的磁矩是同向叠加，而Dy/Tb与Fe为反铁磁耦合，Dy/Tb的磁矩与Fe的磁矩反向叠加，导致了剩磁的大幅降低。晶粒细化 工艺则对气流磨设备要求高，同时晶粒细化后的粉末容易氧化，晶粒细化工艺对生产过程中防氧化控制要求高，该工艺增加了工艺成本，且不良率高。
近几年，晶界扩散工艺用于提高烧结钕铁硼的内禀矫顽力，且很少降低磁体的剩磁和磁能积，由于烧结钕铁硼矫顽力由主相粒子的各向异性场决定，高浓度重稀土通过扩散，生成(Nd，Dy) 2Fe 14B或(Nd，Tb) 2Fe 14B，其磁晶各向异性场比Nd 2Fe 14B大，因此可以明显提高矫顽力，同时(Nd，Dy) 2Fe 14B或(Nd，Tb) 2Fe 14B强化项只沉积在晶粒的表层，其体积与Nd 2Fe 14B主相晶粒的体积相比占比很低，因此磁体的剩磁(Br)和最大磁能级(BHmax)降低非常少。晶界扩散的原理是，用涂覆的方法在磁体外部覆盖含有重稀土元素的粉末或者化合物，通过热处理使重稀土元素沿着富Nd的液态晶界相扩散到磁体内部。但是晶界中Dy/Tb扩散的速度比主相晶粒内部扩散的速度快得多，因此重稀土扩散后只沉积在主相晶粒表层，很少进入晶粒内部。
因此，如何进一步的提高晶界扩散的效果，已经成为业内诸多一线研究人员和具有前瞻性的厂商亟待解决的问题之一。
发明内容
有鉴于此，本发明要解决的技术问题在于提供一种钕铁硼磁体及其制备方法，特别是一种三维晶界扩散制备钕铁硼磁体的方法，本发明把扩散的原理由微观晶粒延伸到宏观磁体，即由重稀土沉积在微观晶粒的表层扩展到重稀土沉积在宏观磁体的表面，调整热处理温度和时间，可以获得不同深度的扩散层，通过对表层磁体的磁硬化，达到提高磁体矫顽力，同时磁体剩磁(Br)和最大磁能级(BHmax)降低非常少的目的。而且制备方法工艺简单，更加适于工业化推广和应用。
本发明提供了一种钕铁硼磁体，所述钕铁硼磁体为经过重稀土元素扩散渗透后的钕铁硼磁体；
所述钕铁硼磁体包括表层重稀土扩散区和芯部非扩散区；
所述钕铁硼磁体在磁体的三维方向上均具有表层重稀土扩散区。
优选的，所述重稀土元素包括Dy和/或Tb；
所述芯部非扩散区的体积占钕铁硼磁体体积的比例大于等于20％。
优选的，所述扩散渗透为三维晶界扩散；
所述钕铁硼磁体在任意一个表面均具有表层重稀土扩散区；
所述重稀土元素扩散渗透量占所述钕铁硼磁体质量的0.1wt％～1.0wt％。
优选的，所述芯部非扩散区的重稀土含量在扩散渗透前后不增加；
以所述钕铁硼磁体的中心为基准，所述钕铁硼磁体任意表面内的表层重稀土扩散区的深度为，该表面到磁体中心的距离的80％以内；
所述钕铁硼磁体较扩散渗透前，磁体的Hcj提高2～15kOe。
优选的，所述表层重稀土扩散区沿层方向上，边缘的重稀土元素浓度大于中间的重稀土元素浓度；
所述表层重稀土扩散区沿层方向上，从边缘至中间，重稀土元素浓度先是逐渐降低再到维持恒定；
所述表层重稀土扩散区沿深度方向上，重稀土元素浓度逐渐降低。
本发明还提供了一种钕铁硼磁体的制备方法，包括以下步骤：
A)将重稀土与有机溶剂混合后，得到混合液；
B)将上述步骤得到的混合液涂覆在钕铁硼毛坯的每一个表面上，得到半成品；
C)将上述步骤得到的半成品进行晶界扩散和时效处理后，得到钕铁硼磁体。
优选的，所述有机溶剂包括硅油；
所述重稀土的平均粒度为1～100μm；
所述重稀土与所述溶剂的质量比为(90～98)：(2～10)。
优选的，所述钕铁硼毛坯包括表面磨光处理后的钕铁硼毛坯；
所述晶界扩散具体为在真空条件下进行晶界扩散；
所述真空的绝对压力小于等于10Pa；
所述晶界扩散包括低温挥发步骤和高温扩散步骤。
优选的，所述低温挥发的温度为300～500℃；
所述低温挥发的时间为3～5h；
所述高温扩散的温度为700～1000℃；
所述高温扩散的时间为1～100h。
优选的，所述时效处理具体为高温扩散冷却后再进行时效处理；
所述时效处理的温度为400～600℃；
所述时效处理的时间为1～15h。
本发明提供了一种钕铁硼磁体，所述钕铁硼磁体为经过重稀土元素扩散渗透后的钕铁硼磁体；所述钕铁硼磁体包括表层重稀土扩散区和芯部非扩散区；所述钕铁硼磁体在磁体的三维方向上均具有表层重稀土扩散区。与现有技术相比，本发明基于晶界扩散的原理，用涂覆的方法在磁体外部覆盖含有重稀土元素的粉末或者化合物，通过热处理使重稀土元素沿着富Nd的液态晶界相扩散到磁体内部。但是晶界中Dy/Tb扩散的速度比主相晶粒内部扩散的速度快得多，所以重稀土扩散后只沉积在主相晶粒表层，很少进入晶粒内部。
本发明创造性的把扩散的原理由微观晶粒延伸到宏观磁体，即由重稀土沉积在微观晶粒的表层扩展到重稀土沉积在宏观磁体的表面，20％以上的芯部体积不渗透。调整热处理温度和时间，可以获得不同深度的扩散层，通过对表层磁体的磁硬化，达到提高磁体矫顽力，同时磁体剩磁(Br)和最大磁能级(BHmax)降低非常少的目的。特别是，当多个磁体组合进行应用时，则单个磁体又可视为整体的晶粒个体，应该具有更加优异的组合效果。
与现有的晶界扩散技术，一般只能在沿磁体一个方向(磁化方向或者非磁化方向)扩散相比，本发明提供的三维晶界扩散技术和三维晶界扩散磁体，可根据产品自身特性，添加0.10wt％～1.0wt％重稀土，通过扩散使重稀土沉积在磁体表层，20％以上的芯部体积不渗透，在三维方向上，按不同扩散深度实现自主调控。而且制备工艺简单，可控性强，更加适于工业化推广和应用。
实验结果表明，与传统的非扩散工艺相比，采用三维晶界扩散技术添加0.1％～0.5％Tb，可以获得Br＞14.85kGs，Hcj＞21kOe超高性能磁体，这是非扩散工艺无法达到的高性能。而获得相同的性能，三维晶界扩散工艺要比传统非扩散工艺重稀土添加量大幅降低。
附图说明
图1为本发明实施例1制备得到的磁体样品3的横截面的EDS图；
图2为本发明实施例2制备得到的对比样品3磁体的性能数据图。
具体实施方式
为了进一步理解本发明，下面结合实施例对本发明优选实施方案进行描 述，但是应当理解，这些描述只是为了进一步说明本发明的特征和优点，而不是对发明权利要求的限制。
本发明所有原料，对其来源没有特别限制，在市场上购买的或按照本领域技术人员熟知的常规方法制备的即可。
本发明所有原料，对其纯度没有特别限制，本发明优选采用分析纯或钕铁硼磁体领域使用的常规纯度。
本发明提供了一种钕铁硼磁体，所述钕铁硼磁体为经过重稀土元素扩散渗透后的钕铁硼磁体；
所述钕铁硼磁体包括表层重稀土扩散区和芯部非扩散区；
所述钕铁硼磁体在磁体的三维方向上均具有表层重稀土扩散区。
在本发明中，所述重稀土元素优选包括Dy和/或Tb，更优选为Tb或Dy，或Dy-Tb合金。
在本发明中，所述芯部非扩散区的体积占钕铁硼磁体体积的比例优选大于等于20％，也可以为大于等于30％，或者为大于等于50％。
在本发明中，钕铁硼磁体在磁体的三维方向上均具有表层重稀土扩散区所述扩散渗透优选为三维晶界扩散。具体的，本发明所述钕铁硼磁体在任意一个表面均具有表层重稀土扩散区。即以立方体为例，在长宽高组成的6个平面中，每一个表面均具有表层重稀土扩散区。
在本发明中，所述重稀土元素扩散渗透量优选占所述钕铁硼磁体质量的0.1wt％～1.0wt％，更优选为0.3wt％～0.8wt％，更优选为0.5wt％～0.6wt％。
在本发明中，所述芯部非扩散区的重稀土含量在扩散渗透前后不增加。即芯部为不扩散区域。
在本发明中，以所述钕铁硼磁体的中心为基准，所述钕铁硼磁体任意表面内的表层重稀土扩散区的深度优选为，该表面到磁体中心的距离的80％以内，更优选为60％以内，更优选为40％以内。具体可以为10％～80％，或者为20％～70％，或者为30％～60％。在本发明中，表面到磁体中心的距离，即为表面到磁体中心的高度(长度)，该距离，磁体的各个表面可以同时选择相同数值，也可以选择不同的数值。
在本发明中，所述钕铁硼磁体较扩散渗透前，磁体的Hcj优选提高 2～15kOe，更优选提高5～14kOe，更优选提高8～13kOe。
在本发明中，所述表层重稀土扩散区沿层方向上，边缘的重稀土元素浓度优选大于中间的重稀土元素浓度。具体的，所述表层重稀土扩散区沿层方向上，从边缘至中间，重稀土元素浓度优选先是逐渐降低再到维持恒定。更具体的，所述表层重稀土扩散区沿深度方向上，重稀土元素浓度优选逐渐降低。这是本发明三维晶界扩散所具体的特点，在本发明中，以任意一个表面为基准，从深度方向上看扩散，重稀土元素的浓度是逐渐降低的；而同时从该表面以及对应的扩散区的横向上看，由于三维方向均有扩散，那么相邻面的扩散，会增加边缘的重稀土元素浓度，即浓度重叠。而在扩散区的中间，由于磁体芯具有一个非扩散区，所以在每个扩散区的横向上的中间位置，都不受到临近扩散区的影响，则中间的元素扩散浓度低于边缘。而且整体扩散元素的浓度变化趋势则为从边缘到中间，先降低再维持恒定。
本发明还提供了一种钕铁硼磁体的制备方法，包括以下步骤：
A)将重稀土与有机溶剂混合后，得到混合液；
B)将上述步骤得到的混合液涂覆在钕铁硼毛坯的每一个表面上，得到半成品；
C)将上述步骤得到的半成品进行晶界扩散和时效处理后，得到钕铁硼磁体。
本发明首先将重稀土与有机溶剂混合后，得到混合液。
在本发明中，所述有机溶剂优选包括硅油。
在本发明中，所述重稀土原料的平均粒度优选为1～100μm，更优选为5～80μm，更优选为10～60μm，更优选为20～50μm。
在本发明中，所述重稀土与所述溶剂的质量比优选为(90～98)：(2～10)，更优选为(91～97)：(2～10)，更优选为(93～95)：(2～10)，也可以为(90～98)：(3～9)，或者为(90～98)：(5～7)。
本发明随后将上述步骤得到的混合液涂覆在钕铁硼毛坯的每一个表面上，得到半成品。
在本发明中，所述钕铁硼毛坯可以为任意形状，如立方体、长方体、多边形体或者球体等等，具体可以为立方体或长方体。
在本发明中，所述钕铁硼毛坯优选包括经过表面磨光处理后的钕铁硼毛坯。
在本发明中，所述晶界扩散具体优选为在真空条件下进行晶界扩散。更具体的，所述真空的绝对压力优选小于等于10Pa，更优选为小于等于1Pa，更优选为小于等于0.1Pa。
在本发明中，所述晶界扩散优选包括低温挥发步骤和高温扩散步骤。
其中，所述低温挥发的温度优选为300～500℃，更优选为325～475℃，更优选为350～450℃，更优选为375～425℃。所述低温挥发的时间优选为3～5h，更优选为3.2～4.8h，更优选为3.5～4.5h，更优选为3.8～4.3h。
本发明所述高温扩散的温度为优选700～1000℃，更优选为750～950℃，更优选为800～900℃。所述高温扩散的时间为1～100h，更优选为5～80小时，更优选为10～60小时，更优选为20～50小时。
本发明对所述晶界扩散的设备没有特别限制，以本领域技术人员熟知的磁体晶界扩散的设备即可，本发明优选为真空扩散炉，更优选采用底面平整的烧结盒，更优选采用不易变形的石墨盒或C-C板。
本发明为完整和细化整体制备工艺，更好的保证钕铁硼磁体的三维晶界扩散效果，更好的提高扩散后钕铁硼磁体的磁性能，上述钕铁硼磁体的制备方法，即钕铁硼磁体的扩散渗透工艺，具体可以为以下步骤：
步骤1，制备出毛坯磁体；
步骤2，制备重稀土和溶剂的混合物。
溶剂选自硅油，所述重稀土的平均粒度为1～100μm，以实现重稀土粉末的溶解，同时也利于后期扩散过程中溶剂的挥发，更具体地，所述重稀土粉末与所述溶剂的质量比为(90～98)：(2～10)，在具体实施例中，所述重稀土粉末与所述溶剂的质量比为95:5；
步骤3：在钕铁硼磁体的三维方向(六个表面)涂覆含有重稀土粉末和溶剂的混合物，得到的钕铁硼磁体材料进行晶界扩散，冷却后进行时效处理，即得到三维晶界扩散钕铁硼磁体。
其中，晶界扩散的过程具体为：将所述钕铁硼磁体材料先于300～500℃保温3～5h以使混合物中的溶剂挥发，再升温至700～1000℃扩散1～100h。所述 时效处理的温度为400～600℃，时间为1～15h。
本发明对所述钕铁硼毛坯没有特别限制，以本领域技术人员熟知的钕铁硼毛坯即可，即钕铁硼原料经过配料、熔炼、破碎制粉、粉末取向压制成型以及真空烧结等步骤后的钕铁硼毛坯，即再经过表面处理和加工后，就可作为普通的成品钕铁硼磁体的毛坯。本发明为更好的提高钕铁硼磁体的性质，还优选将钕铁硼毛坯加工为接近成品的尺寸的半成品，半成品取向方向的尺寸接近成品的尺寸，更优选在此基础上，将钕铁硼毛坯再进行除油、清洁等预处理，使其表面平整、洁净，以达到更好的扩散效果。
本发明经过上述步骤后，得到了钕铁硼磁体。本发明对上述步骤之后，可能还包括的后处理步骤，如清洗、切片等步骤不做特别限制，本领域技术人员可以根据实际生产情况、产品要求等进行调整或选择。
本发明上述步骤提供了一种钕铁硼磁体及一种三维晶界扩散制备钕铁硼磁体的方法。本发明把扩散的原理由微观晶粒延伸到宏观磁体，即由重稀土沉积在微观晶粒的表层扩展到重稀土沉积在宏观磁体的表面，20％以上的芯部体积不渗透。调整热处理温度和时间，可以获得不同深度的扩散层，通过对表层磁体的磁硬化，达到提高磁体矫顽力，同时磁体剩磁(Br)和最大磁能级(BHmax)降低非常少的目的。特别是，当多个磁体组合进行应用时，则单个磁体又可视为整体的晶粒个体，应该具有更加优异的组合效果。
与现有的晶界扩散技术，一般只能在沿磁体一个方向(磁化方向或者非磁化方向)扩散相比，本发明提供的三维晶界扩散技术和三维晶界扩散磁体，是一种表层磁硬化的钕铁硼磁体，包括由磁体表面至磁体内部的0～10mm深度存在重稀土元素扩散区，在扩散区域内重稀土含量较基材增加。20％以上的芯部区域完全未进行扩散处理，仍为基材的成分和性能。而本发明可根据产品自身特性，添加0.10wt％～1.0wt％重稀土，通过扩散使重稀土沉积在磁体表层，20％以上的芯部体积不渗透，在三维方向上，通过调整不同的热处理温度和保温时间，按不同扩散深度实现自主调控，可以得到不同扩散深度的钕铁硼磁体。而且制备工艺简单，可控性强，更加适于工业化推广和应用。
实验结果表明，与传统的非扩散工艺相比，采用三维晶界扩散技术添加0.1％～0.5％Tb，可以获得Br＞14.85kGs，Hcj＞21kOe超高性能磁体，这是非 扩散工艺无法达到的高性能。而获得相同的性能，三维晶界扩散工艺要比传统非扩散工艺重稀土添加量大幅降低。同时三维晶界扩散工艺可以在产品三维方向上，都能按不同扩散深度实现自主调控。
为了进一步说明本发明，以下结合实施例对本发明提供的一种钕铁硼磁体及其制备方法进行详细描述，但是应当理解，这些实施例是在以本发明技术方案为前提下进行实施，给出了详细的实施方式和具体的操作过程，只是为进一步说明本发明的特征和优点，而不是对本发明权利要求的限制，本发明的保护范围也不限于下述的实施例。
实施例1
准备好平均粒度为3～4微米的金属铽粉，在氮气保护的手套箱中将铽粉倒入硅油中，铽粉和硅油的重量比为95:5，然后搅拌均匀备用。
取50块N56的毛坯，毛坯块取样测试性能如表1；
表1 N56毛坯磁性能数据表
样品种类 Br(KGs) HCb(KOe) HCJ(KOe) Hk/HCj BH(MAX)(MGsOe)
毛坯性能 14.99 12.95 13.07 0.98 54.21
将每块毛坯切成40*20*6(mm)的方片，共计240片样品，等分为4组，每组60pcs。
第1组为基材原始样品，不进行涂覆，不进行扩散处理，作为对比样品1；
其余样品在专用的涂覆设备上，将准备好的金属Tb粉和硅油的混合物均匀涂覆在6个面上，Tb的用量是样品重量的0.2％；
第2组：将涂覆好的60片样品放入真空扩散炉里，先在400℃保温4小时以使硅油烘干，通过真空炉的真空系统把硅油排出扩散炉里，然后升温到700～1000℃进行晶界扩散处理，扩散时间5小时，扩散结束后急冷到80℃以下，然后再升温到500℃进行时效处理，时效时间为5小时，时效结束后，再急冷到80℃以下出炉，得到60片处理后的样品，作为对比样品2；
第3组：将涂覆好的60片样品放入真空扩散炉里，先在400℃保温4小时以使硅油烘干，通过真空炉的真空系统把硅油排出扩散炉里，然后升温到700～1000℃进行晶界扩散处理，扩散时间10小时，扩散结束后急冷到80℃以 下，然后再升温到500℃进行时效处理，时效时间为5小时，时效结束后，再急冷到80℃以下出炉，得到60片处理后的样品，作为对比样品3；
第4组：将涂覆好的60片样品放入真空扩散炉里，先在400℃保温4小时以使硅油烘干，通过真空炉的真空系统把硅油排出扩散炉里，然后升温到700～1000℃进行晶界扩散处理，扩散时间25小时，扩散结束后急冷到80℃以下，然后再升温到500℃进行时效处理，时效时间为5小时，时效结束后，再急冷到80℃以下出炉，得到60片处理后的样品，作为对比样品4；
将4组样品不同区域进行EDS能谱对比测试，结果如表2所示。
表2 4组样品距离磁体表面不同深度的Tb含量数据表
Figure PCTCN2021102058-appb-000001
通过表2可以看出，5h和10h扩散工艺，磁体只进行表层扩散强化，芯部未检测到Tb元素。25h的扩散工艺，磁体芯部Tb含量与表面相当，该工艺下，磁体已形成完全扩散。说明通过扩散时间的控制，可以达到重稀土只沉积在磁体表层，而20％以上的芯部区域未扩散的目的。
参见图1，图1为本发明实施例1制备得到的磁体样品3的横截面的EDS图。
实施例2
取实施例1中的N56毛坯，将每块毛坯切成40*20*6(mm)的方片，共计180片样品，等分为3组，每组60pcs。
第1组为基材原始样品，不进行涂覆，不进行扩散处理，作为对比样品1；
第2组：第2组样品在专用的涂覆设备上，将准备好的金属Tb粉和硅油的混合物均匀涂覆在6个面上，Tb的用量是样品重量的0.1％；将涂覆好的60 片样品放入真空扩散炉里，先在400℃保温4小时以使硅油烘干，通过真空炉的真空系统把硅油排出扩散炉里，然后升温到700～1000℃进行晶界扩散处理，扩散时间5小时，扩散结束后急冷到80℃以下，然后再升温到500℃进行时效处理，时效时间为5小时，时效结束后，再急冷到80℃以下出炉，得到60片处理后的样品，作为对比样品2；
第3组：第3组样品在专用的涂覆设备上，将准备好的金属Tb粉和硅油的混合物均匀涂覆在6个面上，Tb的用量是样品重量的0.2％；将涂覆好的60片样品放入真空扩散炉里，先在400℃保温4小时以使硅油烘干，通过真空炉的真空系统把硅油排出扩散炉里，然后升温到700～1000℃进行晶界扩散处理，扩散时间5小时，扩散结束后急冷到80℃以下，然后再升温到500℃进行时效处理，时效时间为5小时，时效结束后，再急冷到80℃以下出炉，得到60片处理后的样品，作为对比样品3；
将3组样品进行磁性能对比测试，结果如表3所示。
表3 3组样品磁性能数据表
样品种类 Tb用量 Br(kGs) HCb(KOe) HCJ(KOe) Hk/HCj BH(MAX)(MGsOe)
对比样品1 0％ 14.99 12.95 13.07 0.98 54.21
对比样品2 0.10％ 14.95 14.22 18.25 0.98 53.94
对比样品3 0.20％ 14.91 14.49 21.47 0.98 53.75
通过表3可以看出，磁体通过三维晶界扩散工艺，采用0.10％Tb、0.20％Tb微量扩散，在磁体表层形成磁硬化层，可以制得Br：14.91kGs，Hcj：21.47kOe超高性能的56SH牌号，这种性能是传统非扩散工艺无法制备的。
参见图2，图2为本发明实施例2制备得到的对比样品3磁体的性能数据图。
以上对本发明提供的一种钕铁硼磁体及一种三维晶界扩散制备钕铁硼磁体的方法进行了详细的介绍，本文中应用了具体个例对本发明的原理及实施方式进行了阐述，以上实施例的说明只是用于帮助理解本发明的方法及其核心思想，包括最佳方式，并且也使得本领域的任何技术人员都能够实践本发明，包 括制造和使用任何装置或系统，和实施任何结合的方法。应当指出，对于本技术领域的普通技术人员来说，在不脱离本发明原理的前提下，还可以对本发明进行若干改进和修饰，这些改进和修饰也落入本发明权利要求的保护范围内。本发明专利保护的范围通过权利要求来限定，并可包括本领域技术人员能够想到的其他实施例。如果这些其他实施例具有不是不同于权利要求文字表述的结构要素，或者如果它们包括与权利要求的文字表述无实质差异的等同结构要素，那么这些其他实施例也应包含在权利要求的范围内。

Claims (10)

  1. 一种钕铁硼磁体，其特征在于，所述钕铁硼磁体为经过重稀土元素扩散渗透后的钕铁硼磁体；
    所述钕铁硼磁体包括表层重稀土扩散区和芯部非扩散区；
    所述钕铁硼磁体在磁体的三维方向上均具有表层重稀土扩散区。
  2. 根据权利要求1所述的钕铁硼磁体，其特征在于，所述重稀土元素包括Dy和/或Tb；
    所述芯部非扩散区的体积占钕铁硼磁体体积的比例大于等于20％。
  3. 根据权利要求1所述的钕铁硼磁体，其特征在于，所述扩散渗透为三维晶界扩散；
    所述钕铁硼磁体在任意一个表面均具有表层重稀土扩散区；
    所述重稀土元素扩散渗透量占所述钕铁硼磁体质量的0.1wt％～1.0wt％。
  4. 根据权利要求1所述的钕铁硼磁体，其特征在于，所述芯部非扩散区的重稀土含量在扩散渗透前后不增加；
    以所述钕铁硼磁体的中心为基准，所述钕铁硼磁体任意表面内的表层重稀土扩散区的深度为，该表面到磁体中心的距离的80％以内；
    所述钕铁硼磁体较扩散渗透前，磁体的Hcj提高2～15kOe。
  5. 根据权利要求1所述的钕铁硼磁体，其特征在于，所述表层重稀土扩散区沿层方向上，边缘的重稀土元素浓度大于中间的重稀土元素浓度；
    所述表层重稀土扩散区沿层方向上，从边缘至中间，重稀土元素浓度先是逐渐降低再到维持恒定；
    所述表层重稀土扩散区沿深度方向上，重稀土元素浓度逐渐降低。
  6. 一种钕铁硼磁体的制备方法，其特征在于，包括以下步骤：
    A)将重稀土与有机溶剂混合后，得到混合液；
    B)将上述步骤得到的混合液涂覆在钕铁硼毛坯的每一个表面上，得到半成品；
    C)将上述步骤得到的半成品进行晶界扩散和时效处理后，得到钕铁硼磁体。
  7. 根据权利要求6所述的制备方法，其特征在于，所述有机溶剂包括硅油；
    所述重稀土的平均粒度为1～100μm；
    所述重稀土与所述溶剂的质量比为(90～98)：(2～10)。
  8. 根据权利要求6所述的制备方法，其特征在于，所述钕铁硼毛坯包括表面磨光处理后的钕铁硼毛坯；
    所述晶界扩散具体为在真空条件下进行晶界扩散；
    所述真空的绝对压力小于等于10Pa；
    所述晶界扩散包括低温挥发步骤和高温扩散步骤。
  9. 根据权利要求8所述的制备方法，其特征在于，所述低温挥发的温度为300～500℃；
    所述低温挥发的时间为3～5h；
    所述高温扩散的温度为700～1000℃；
    所述高温扩散的时间为1～100h。
  10. 根据权利要求9所述的制备方法，其特征在于，所述时效处理具体为高温扩散冷却后再进行时效处理；
    所述时效处理的温度为400～600℃；
    所述时效处理的时间为1～15h。
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CN107147228A (zh) * 2017-03-23 2017-09-08 烟台正海磁性材料股份有限公司 一种烧结钕铁硼磁体的制备方法及电机用转子
CN107026003A (zh) * 2017-04-24 2017-08-08 烟台正海磁性材料股份有限公司 一种烧结钕铁硼磁体的制备方法

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