WO2016095869A1 - 一种r-t-b永磁体的制备方法 - Google Patents

一种r-t-b永磁体的制备方法 Download PDF

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WO2016095869A1
WO2016095869A1 PCT/CN2015/098012 CN2015098012W WO2016095869A1 WO 2016095869 A1 WO2016095869 A1 WO 2016095869A1 CN 2015098012 W CN2015098012 W CN 2015098012W WO 2016095869 A1 WO2016095869 A1 WO 2016095869A1
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rare earth
heavy rare
powder
permanent magnet
diffusion
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PCT/CN2015/098012
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English (en)
French (fr)
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陈国安
赵玉刚
张瑾
钮萼
王浩颉
叶选涨
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北京中科三环高技术股份有限公司
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Priority to JP2017526629A priority Critical patent/JP2018504769A/ja
Priority to DE112015005685.8T priority patent/DE112015005685T5/de
Publication of WO2016095869A1 publication Critical patent/WO2016095869A1/zh
Priority to US15/484,006 priority patent/US10714245B2/en

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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
    • 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
    • H01F41/0266—Moulding; Pressing
    • 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 relates to a preparation method of an R-T-B permanent magnet and a permanent magnet obtained by the method, in particular to a preparation method of a high remanence magnetic high coercivity R-T-B permanent magnet, belonging to the field of magnetic materials.
  • NdFeB rare earth permanent magnet materials Due to the high comprehensive magnetic properties of R-Fe-B permanent magnets, the application of NdFeB rare earth permanent magnet materials to various motors can significantly improve the performance of the motor, reduce the weight of the motor, reduce the size of the motor, and achieve efficient energy saving. effect. Therefore, the application of NdFeB rare earth permanent magnet materials in high-performance motors in automobiles and home appliances has received more and more attention. In particular, the improvement of energy-saving and environmental protection requirements has prompted NdFeB rare earth permanent magnet materials in hybrid electric vehicles (HEV). The application of electric vehicle (EV) drive motors and inverter compressors has entered a practical stage. At present, these high performance motors have a consistent requirement for sintered R-Fe-B magnets to have both high residual flux density and high coercivity.
  • EV electric vehicle
  • the coercive force can be improved.
  • a heavy rare-earth element RH for example, Dy or Tb
  • the coercive force can be improved.
  • a rare earth element RH is substituted for a light rare earth element (for example, Pr, Nd) in a sintered R-Fe-B based magnet
  • the coercive force is improved, on the other hand, the residual magnetic flux density is inevitably drastically lowered.
  • Dy 2 Fe 14 B or Tb 2 Fe 14 B has a higher magnetocrystalline anisotropy field than Nd 2 Fe 14 B, that is, it has a larger theoretical intrinsic coercive force, and Dy/Tb partially replaces the main
  • the solid solution phase (Nd, Dy) 2 Fe 14 B or (Nd, Tb) 2 Fe 14 B formed after Nd in the phase Nd 2 Fe 14 B has a larger magnetocrystalline anisotropy field than Nd 2 Fe 14 B, thus The coercive force of the sintered magnet can be significantly improved.
  • the adverse effect of this elemental substitution is to significantly reduce the saturation magnetization of the magnet, so the remanence and maximum magnetic energy product of the magnet are significantly reduced because of the magnetic moment of Nd and Fe in the Nd 2 Fe 14 B main phase.
  • Parallel arrangement the magnetic moments of the two are enhanced superposition; while Dy/Tb and Fe are antiferromagnetic coupling, and the magnetic moment of Dy/Tb is antiparallel to the Fe magnetic moment, partially canceling the total magnetic moment of the main phase.
  • Dy and Tb are rare and expensive elements, they cannot be added in a large amount from the viewpoint of cost.
  • Patent application CN200580001133.X gives a plating technique for the surface of a magnet.
  • the sintered blank machine is processed into a small and thin magnet, and the magnet is immersed in a rare earth micron-sized fine powder (one or more of Dy, Tb fluoride, oxide and oxyfluoride) dispersed in an organic solvent.
  • the coating is carried out in a slurry, and then the magnet is heat-treated at a temperature equal to or lower than the sintering temperature under a vacuum or an inert gas atmosphere.
  • the subsequent effect is that the coercive force is increased more, and the remanence is not substantially reduced, because the heavy rare earth element exists only in the grain boundary phase and does not enter the main phase.
  • This method not only saves the use of heavy rare earth, but also suppresses the decrease of residual magnetism.
  • this patent application only relates to the improvement of the coated powder, and in the actual production process, the difference between the batches of the permanent magnets is large, and the requirement for the stability and consistency of the magnetic properties of the permanent magnet products cannot be satisfied.
  • the osmotic rare earth technique is a coating + diffusion process, and the technical solution of the patent application mainly relates to the coating process.
  • the effect of the diffusion channel is more significant than the heat treatment process parameters such as temperature and time, but it is not involved in the technical solution of the patent application, which inevitably leads to the non-uniformity of the thermal diffusion process.
  • Patent application CN201110024823.4 gives a method for thermally diffusing a powder of heavy rare earth fluoride, nitrate and phosphate on the surface of a magnet, solving the problem of uneven distribution of molten material remaining on the surface after thermal diffusion of the magnet, thereby making coating
  • the problem that the bonding strength between the substrate and the plating layer deteriorates and the corrosion resistance decreases is no longer present.
  • the reason for this is that the solubility of the powder in water or an organic solvent is poor, and it is not uniformly distributed on the surface of the magnet during the coating process.
  • this patent solves the problem of uniformity of distribution of the coated powder on the substrate, it does not explicitly require the thermal diffusion process, and there is also a problem of unevenness in the thermal diffusion process.
  • Patent Document 1 Chinese Patent CN200580001133.X
  • Patent Document 2 Chinese Patent CN201110024823.4
  • the object of the present invention is to provide a method for preparing a sintered RTB permanent magnet having high remanence and high coercive force.
  • the permanent magnet prepared according to the preparation method has remarked remanence and coercivity, and the squareness is obtained. Significant improvements have been made and the stability and consistency of performance between batches has been significantly improved.
  • the invention provides a preparation method of an R-T-B permanent magnet, comprising the following steps:
  • R1 is at least one selected from the group consisting of rare earth elements Nd, Pr, La, Ce, Sm, Dy, Tb, Ho, Er, Gd, Sc, Y, and Eu
  • R1 is at least one selected from the group consisting of rare earth elements Nd, Pr, La, Ce, Sm, Dy, Tb, Ho, Er, Gd, Sc, Y, and Eu
  • it comprises at least Nd or Pr
  • T is Fe and/or Co
  • T further comprises selected from the group consisting of Al, Cu, Zn, In, Si, P, S, Ti, V, Cr, Mn, Ni, Ga
  • the pre-baked coating is subjected to coating, secondary sintering and thermal diffusion treatment using a heavy rare earth compound to obtain an R-T-B permanent magnet, wherein R comprises at least one heavy rare earth element and at least one rare earth element other than the heavy rare earth element.
  • the actual density of the pre-baked blank is reasonable
  • the density is 80 to 98%, preferably 85 to 97%.
  • the heavy rare earth compound is a rare earth intermetallic compound containing a heavy rare earth oxide, a fluoride, a oxyfluoride or a hydride, containing a heavy rare earth element, and a heavy rare earth R 2 .
  • the heavy rare earth is one or more selected from the group consisting of Dy, Tb, and Ho.
  • the shaped body is obtained by the following steps:
  • Pressing Pressing in a sealed vertical press gives a shaped body.
  • the medium crushed powder has a hydrogen content ranging from 800 to 3000 ppm, preferably from 1000 to 2000 ppm.
  • the heat treatment is performed by sintering in a vacuum or an inert gas atmosphere to obtain a pre-baked billet.
  • the coating, the secondary sintering and the thermal diffusion treatment are carried out by the following steps:
  • Coating treatment processing the pre-boiler into a desired shape, dispersing the heavy rare earth compound powder in an organic solvent to prepare a slurry, immersing the processed pre-baked in the slurry, and then treating the pre-baked blank Put in a sealed box;
  • the cartridge is placed in a vacuum sintering furnace for vacuuming, and then heated to 820-950 ° C for secondary sintering and simultaneous diffusion of heavy rare earth elements, followed by cooling, cooling is stopped and vacuum is applied.
  • the temperature is raised to 450 ° C to 620 ° C for secondary diffusion of heavy rare earth elements, and cooling is performed to obtain an RTB permanent magnet.
  • the heavy rare earth compound powder is dispersed in an organic solvent in a ratio of 0.01 to 1.0 g/ml.
  • the bottom of the cartridge is filled with a mixed powder of 10-20% alumina and 80-90% magnesium oxide.
  • the diffusion and penetration effect of the heavy rare earth element is improved, the coercive force of the magnet is improved, and the squareness of the magnet is improved.
  • the distribution of heavy rare earth elements along the orientation direction is more consistent than that of the undiluted heavy rare earth element diffusion process, which significantly improves the squareness of the magnet and, in the continuous production process, The stability and consistency of performance between batches has been significantly improved.
  • Fig. 1 is a microscopic view of the magnet of Example 4 and Comparative Example 4-2 after thermal diffusion.
  • the preparation method of the R-T-B permanent magnet in the invention comprises the following steps:
  • R 1 is at least one selected from the group consisting of rare earth elements Nd, Pr, La, Ce, Sm, Sc, Y, and Eu, preferably containing at least Nd or Pr;
  • T is Fe and/or Co, and optionally, T further comprises selected from the group consisting of Al, Cu, Zn, In, Si, P, S, Ti, V, Cr, Mn, Ni, Ga, Ge, Zr, Nb, Mo At least one of the group consisting of Pd, Ag, Cd, Sn, Sb, Hf, Ta, and W;
  • the shaped body is heat-treated at 900-1040 ° C to obtain a pre-baked billet
  • the pre-baked body is coated and thermally diffused with a heavy rare earth compound to obtain an R-T-B permanent magnet, wherein R comprises at least one heavy rare earth element and at least one rare earth element other than the heavy rare earth element.
  • the shaped body is obtained by the following steps:
  • Pressing Pressing in a sealed vertical press gives a shaped body.
  • the raw materials are proportioned well, melted in a strip casting furnace, and scaled at a copper roll speed of ⁇ 1 m/s to obtain a strip piece having a thickness of 0.2-0.5 mm.
  • a large number of fine crystal regions do not appear on the surface of the roll in the microstructure; when the thickness of the strip is less than 0.5 mm, the free surface of the microstructure is not easy to appear in a large amount.
  • the coarse crystal regions do not adversely affect the subsequent fine particle size distribution.
  • the strips are subjected to hydrogen explosion treatment to obtain medium-sized powder.
  • the hydrogen content in the medium-sized powder is measured by ELTRA's ONH2000 analyzer.
  • the hydrogen content is preferably in the range of 800-3000 ppm and the hydrogen content is ⁇ 800 ppm.
  • the subsequent calcined product can have sufficient diffusion channels; when the hydrogen content is ⁇ 3000 ppm, the pores in the subsequent calcined body can ensure that the pre-fired product reaches 99.5% of the theoretical density by subsequent treatment.
  • the hydrogen content range is more preferably from 1000 to 2000 ppm, which satisfies the pre-fired product to quickly reach a theoretical density of 99.5% or more while ensuring a sufficient diffusion channel.
  • compression molding is carried out in a sealed vertical press, and a magnetic field of 1 T to 3 T is applied during the pressing, and a magnetic field of 1.8 T to 3 T is more preferably used.
  • the shaped body is sent to a sintering furnace for pre-sintering in a vacuum or an inert gas atmosphere, and sintering is performed at a temperature lower than the theoretical sintering temperature, so that the pre-fired blank reaches 80% to 98% of the theoretical density. Preferably, it is 85 to 97%, and a sufficient diffusion channel is prepared for subsequent diffusion.
  • the sintering temperature ranges from 900 to 1040 ° C, more preferably from 910 to 990 ° C.
  • the actual density of the obtained calcined billet is 6.0 to 7.4 g/cm 3 , more preferably 6.5 to 7.3 g/cm 3 , for example, the actual density of the calcined billet is 6.0 g/cm 3 or more (for example, at least 6.1 g/cm 3 ).
  • the density of the calcined billet is 6.0 g/cm 3 or more, which is not easily oxidized during the subsequent diffusion treatment to cause deterioration of performance; when the density of the calcined billet is 7.4 g/cm 3 or less, it is subjected to subsequent diffusion treatment. There is no significant improvement in the process due to the lack of sufficient diffusion channels.
  • the average grain size of the obtained calcined billet is 1.1 to 1.5 times, more preferably 1.2 to 1.4 times, the powder particle size D 50 .
  • the grain of the pre-calcined billet is fine, and the distribution of the rare earth-rich phase is more uniform, which is favorable for the subsequent heavy rare earth permeation and diffusion process.
  • Coating treatment processing the pre-boiler into a desired shape, dispersing the heavy rare earth compound powder in an organic solvent to prepare a slurry, immersing the processed pre-baked in the slurry, and then treating the pre-baked blank Put in a sealed box;
  • the cartridge is placed in a vacuum sintering furnace to evacuate, and then heated to The secondary sintering is performed at 820-950 ° C and the primary diffusion of the heavy rare earth element is performed at the same time, and then cooling is performed, the cooling is stopped, and the vacuum is applied, and the temperature is raised to 450 ° C to 620 ° C to carry out secondary diffusion of the heavy rare earth element, and cooling is performed to obtain an R-T-B permanent magnet.
  • the pre-boiler In the machining process, the pre-boiler is machined into a desired finished shape, and the dimension of the orientation direction needs to be less than or equal to 10 mm, more preferably less than or equal to 5 mm.
  • the heavy rare earth compound powder is dispersed in an organic solvent to form a slurry.
  • the pre-baked body is immersed in a slurry in an ultrasonically agitated state, and the treated pre-baked body is then placed in a sealed cartridge, preferably a metal cartridge.
  • the heavy rare earth compound powder is a rare earth intermetallic compound containing a heavy rare earth oxide, a fluoride, a oxyfluoride or a hydride, a heavy rare earth element, a heavy rare earth R 2 Fe 14 B structural compound, and a heavy rare earth hydrated nitric acid. a mixed powder of one or more of the salts. Among them, a rare earth intermetallic compound such as DyAl 2 is preferably used.
  • the heavy rare earth compound powder is preferably dispersed in an organic solvent in a ratio of 0.01 to 1.0 g/ml, more preferably 0.1 to 0.8 g/ml, in which a sufficient amount of the heavy rare earth compound powder is dissolved.
  • the amount of coating powder can be evenly distributed on the substrate.
  • the particle size of the coated powder is preferably from 1 to 50 ⁇ m, more preferably from 3 to 25 ⁇ m.
  • the organic solvent to be used in the coating process includes alcohols, alkanes or esters having 5 to 16 carbon atoms, preferably ethyl acetate, ethanol or cyclohexane, and more preferably cyclohexane.
  • the bottom of the sealed cartridge is filled with a mixed powder of 10-20% alumina and 80-90% magnesium oxide.
  • the mixed powder can be used as a sintering aid to maintain a low temperature of 820.
  • the pre-baked body quickly reaches 99.5% of the theoretical density in a time of ⁇ 24 h.
  • the cartridge In the secondary sintering and thermal diffusion process, the cartridge is placed in a vacuum sintering furnace to evacuate, and then heated to 820-950 ° C for secondary sintering while performing primary diffusion of heavy rare earth elements, and then cooled to 80 by argon gas. Below °C, the cooling is stopped and the vacuum is applied, and the temperature is raised to 450 ° C to 620 ° C for secondary diffusion, and then argon gas is cooled to 80 ° C or lower to obtain an RTB permanent magnet.
  • the holding time of one diffusion is preferably from 12 to 24 hours, more preferably from 15 to 20 hours, and the second diffusion is preferably from 1 to 8 hours, more preferably from 2 to 7 hours.
  • the low-density pre-boiled body in the present invention has no change in the average grain size during the secondary sintering and thermal diffusion treatment.
  • the time of one diffusion is more than 12 hours, and the density of the pre-baked blank can reach the theoretical density of 99.5% or more, while ensuring the consistency of the depth and uniformity of the diffusion of the heavy rare earth; the primary diffusion time is less than 24 hours, and the pre-baked blank will not appear.
  • Abnormal grain growth leads to deterioration of magnetic properties.
  • the general high-density magnet can ensure the uniformity of heavy rare earth diffusion after 12 hours of diffusion, but abnormal grain growth will cause magnetic properties to deteriorate. Therefore, the general high-density magnet can only be used. Choose one of the two effects, but not the optimal state at the same time.
  • the degree of vacuum at which the secondary sintering is simultaneously performed once is ⁇ 0.2 Pa, and the degree of vacuum of the secondary diffusion is ⁇ 0.2 Pa.
  • the temperature of the primary diffusion is in the range of 820-950 ° C, and if the temperature exceeds 950 ° C, the effect of diffusion penetration will disappear.
  • the analysis of the cross section of the RTB permanent magnet of the present invention found that: 1) after the pre-calcined magnet is coated with heavy rare earth powder, secondary sintering and thermal diffusion treatment, the heavy rare earth diffuses more uniformly, and the sample has a heavy rare earth gradient along the depth direction. The distribution is smaller than the heavy rare earth gradient in the depth direction after the diffusion of the magnet with a theoretical density of 99.5% or more; 2) The average concentration of heavy rare earth at the grain boundary is larger than that of the central portion in the region of nearly 1000 ⁇ m from the surface of the magnet.
  • the average concentration is at least 0.7wt% higher; while the conventional sintered magnet reaches a theoretical density of 99.5% or more, after coating the heavy rare earth and thermal diffusion process, the sample has a heavy rare earth average concentration and a central region weight in the grain boundary region at a distance of 1000 ⁇ m from the surface.
  • the average concentration difference of rare earths is less than 0.7% by weight; 3) under the same coating amount and coating conditions, the pre-fired blank is subjected to diffusion treatment to make the diffusion depth of the heavy rare earth deeper.
  • Test method for magnetic properties The magnetic properties were tested in accordance with the method of GB/T 3217-2013.
  • the sample after diffusion has a coercive force Hcj of at least 14 MA/m (such as at least 14.5 MA/m, at least 15 MA/m, at least 15.5 MA/m, at least 16 MA/m, at least 16.5 MA/m or at least 17 MA/m).
  • the raw material alloy was prepared, the purity of the raw material was 99% or more, and the alloy was prepared into a strip piece of 0.25 mm by rapid setting technique, and treated with hydrogen explosion.
  • the strip was coarsely broken into a medium powder having a hydrogen content of 1400 ppm.
  • the density of the billet was 7.3 g/cm 3 , which was 96.7% of the theoretical density, and the average grain size was 6.75 ⁇ m.
  • the blank machine was machined into a D10*5mm wafer with a product orientation of 5 mm, and a mixed powder of 70% lanthanum nitrate and 30% lanthanum fluoride (powder size of 1 ⁇ m) was dispersed in ethyl acetate at a ratio of 0.05 g/ml.
  • the slurry was immersed for 15 min and placed in a sealed metal box with a mixture of 15% alumina and 85% magnesia as a sintering aid at the bottom of the cartridge.
  • the cartridge was placed in a vacuum sintering furnace and evacuated.
  • the shaped body was prepared in the same conditions and process as in Example 1, and then the shaped body was placed in a high-vacuum sintering furnace, sintered at 1050 degrees for 3 hours, and then subjected to a secondary heat treatment, wherein the first-stage heat treatment temperature was 890 degrees, and the holding time was 3 hours;
  • the heat treatment temperature is 500 °C
  • the holding time is 5 hours
  • the blank can be obtained, and the blank machine is processed into a D10*5mm wafer with a product density of 7.54g/cm 3 , reaching a theoretical density of 99.9% and an average grain size of 7.90. ⁇ m, measure the magnetic properties of the product, as shown in Table 1.
  • the formed body was prepared under the same conditions and procedures as in Example 1, and then the formed body was placed in a high-vacuum sintering furnace and sintered at 1,050 °C for 3 hours, and the density of the green compact after sintering was 7.54 g/cm 3 .
  • the blank was machined into a D10*5mm wafer product, and a mixed powder of 70% cerium nitrate and 30% lanthanum fluoride (powder size of 1 ⁇ m) was dispersed in a slurry of 0.05 g/ml in ethyl acetate. Dip for 15 min and place in a sealed metal box. The cartridge was placed in a vacuum sintering furnace and evacuated.
  • An alloy of the same composition as in Example 1 was prepared into a 0.50 mm strip by a rapid setting technique, and the strip was coarsely broken into a medium-sized powder having a hydrogen content of 800 ppm by hydrogen explosion treatment.
  • the density of the billet was 6.90 g/cm 3 , which was 91.4% of the theoretical density, and the average grain size was 7.2 ⁇ m.
  • the blank was machined into a D10*5mm wafer product with an orientation direction of 5 mm.
  • the 100% cerium oxide powder (powder size 50 ⁇ m) was immersed in a slurry dispersed in ethanol at a ratio of 0.01 g/ml for 60 min, and sealed.
  • a mixed powder of 20% alumina and 80% magnesium oxide is used as a sintering aid at the bottom of the cartridge.
  • the cartridge was placed in a vacuum sintering furnace and evacuated. After the vacuum reached 10 -2 Pa, the temperature was raised to 950 ° C and held for 24 hours, cooled, heated to 450 ° C and held for 8 hours, and cooled.
  • the product density after diffusion treatment was 7.52 g/cm 3 , which was 99.6% of the theoretical density, and the average grain size was 7.30 ⁇ m.
  • the magnetic properties of the product were measured as shown in Table 2.
  • the shaped body was prepared in the same conditions and process as in Example 2, and then the shaped body was placed in a high-vacuum sintering furnace, sintered at 1070 ° C for 3 hours, and then subjected to a secondary heat treatment, wherein the first-stage heat treatment temperature was 950 ° C, and the holding time was 3 hours; The heat treatment temperature is 450 °C and the holding time is 8 hours.
  • the blank can be obtained.
  • the blank machine is processed into a D10*5mm wafer with a product density of 7.54g/cm 3 and an average grain size of 10.20 ⁇ m.
  • the magnetic properties of the product are measured. As shown in table 2.
  • a shaped body was prepared in the same manner and in the same manner as in Example 2, and then the formed body was placed in a high-vacuum sintering furnace and sintered at 1070 ° C for 3 hours, and the density of the green compact after sintering was 7.54 g/cm 3 .
  • the blank was machined into a D10*5mm wafer product, and 100% cerium oxide powder (powder size 50 ⁇ m) was placed in a slurry of 0.01 g/ml dispersed in ethanol for 60 min, and placed in a sealed metal box. .
  • the cartridge was placed in a vacuum sintering furnace and evacuated.
  • the temperature was raised to 950 ° C and held for 3 hours, cooled, heated to 450 ° C and held for 8 hours, and cooled.
  • the product density was 7.54 g/cm 3 and the magnetic properties of the product were measured as shown in Table 2.
  • the alloy of the same composition as that of Example 1 was prepared into a strip of 0.20 mm by a rapid setting technique, and the strip was coarsely broken into a medium-sized powder having a hydrogen content of 3000 ppm by hydrogen explosion treatment.
  • the density of the billet was 6.50 g/cm 3 , which was 86.1% of the theoretical density, and the average grain size was 3.3 ⁇ m.
  • the blank was machined into a D10*5mm wafer with an orientation of 5 mm and 20% DyH x and 80% MgCu 2 intermetallic compounds (10% Nd-12% Pr-35% Dy-41%)
  • the mixed powder of Fe-2%Co) (powder size 25 ⁇ m) was immersed in a slurry of ethanol at a ratio of 1 g/ml for 30 min, placed in a sealed metal box, and 15% alumina and 85% at the bottom of the cartridge.
  • a mixed powder of magnesium oxide is used as a sintering aid.
  • the cartridge was placed in a vacuum sintering furnace and evacuated.
  • the formed body was prepared under the same conditions and process as in Example 3, and then the formed body was placed in a high-vacuum sintering furnace, sintered at 1045 ° C for 3 hours, and then subjected to a secondary heat treatment, wherein the first-stage heat treatment temperature was 920 ° C, and the holding time was 3 hours; The heat treatment temperature is 480 degrees, the holding time is 5 hours, the blank can be obtained, and the blank machine is processed into a D10*5mm wafer product with a product density of 7.54g/cm 3 and an average grain size of 5.80 ⁇ m. Yes, as shown in Table 3.
  • a shaped body was prepared under the same conditions and procedures as in Example 3, and then the formed body was placed in a high-vacuum sintering furnace and sintered at 1045 °C for 3 hours, and the sintered compact density was 7.54 g/cm 3 .
  • the blank was machined into a D10*5mm wafer product with 20% DyH x and 80% MgCu 2 intermetallic compounds (component 10% Nd-12% Pr-35% Dy-41% Fe-2% Co
  • the mixed powder (powder size 25 ⁇ m) was immersed in a slurry dispersed in ethanol at a ratio of 1 g/ml for 30 minutes, and placed in a sealed metal cartridge. The cartridge was placed in a vacuum sintering furnace and evacuated.
  • the alloy of the same composition as that of Example 1 was prepared into a strip piece of 0.25 mm by a rapid setting technique, and the strip piece was coarsely broken into a medium-sized powder having a hydrogen content of 1000 ppm by a hydrogen explosion treatment.
  • the density of the billet was 7.00 g/cm 3 , which was 92.7% of the theoretical density, and the average grain size was 6.30 ⁇ m.
  • the blank was machined into a D10*5mm wafer product with an orientation direction of 5 mm and placed with 20% cesium fluoride, 20% Dy 2 Fe 14 B powder and 60% MgCu 2 type intermetallic compound (component 10Nd-15Pr-).
  • the mixed powder of 25Dy-7Tb-41.9Fe-1Co-0.1Cu) (powder size 3 ⁇ m) was immersed in a slurry of ethanol at a ratio of 0.1g/ml for 15 minutes, and placed in a sealed metal box.
  • a mixed powder of 10% alumina and 90% magnesium oxide is used as a sintering aid.
  • the cartridge was placed in a vacuum sintering furnace and evacuated.
  • the temperature was raised to 820 ° C and held for 20 hours, cooled, heated to 620 ° C and held for 3 hours, and cooled.
  • the product density was 7.54 g/cm 3
  • the theoretical density was 99.6%
  • the average grain size was 6.45 ⁇ m.
  • the magnetic properties of the product were measured, as shown in Table 4.
  • the shaped body was prepared in the same conditions and process as in Example 4, and then the formed body was placed in a high-vacuum sintering furnace, sintered at 1060 ° C for 3 hours, and then subjected to a secondary heat treatment, wherein the first-stage heat treatment temperature was 820 ° C, and the holding time was 2 hours; The heat treatment temperature is 620 °C, the holding time is 3 hours, the blank can be obtained, and the blank machine is processed into a D10*5mm wafer product with a density of 7.54g/cm 3 and an average grain size of 7.25 ⁇ m. Yes, as shown in Table 4.
  • a shaped body was prepared in the same manner and in the same manner as in Example 4, and then the formed body was placed in a high-vacuum sintering furnace and sintered at 1060 ° C for 3 hours, and the density of the green compact after sintering was 7.54 g/cm 3 .
  • the blank was machined into a D10*5mm wafer product, and 20% cesium fluoride, 20% Dy 2 Fe 14 B powder and 60% MgCu 2 type intermetallic compound (component 10Nd-15Pr-25Dy-7Tb-41.9) were placed.
  • a mixed powder of Fe-1Co-0.1Cu) (powder size: 3 ⁇ m) was immersed in a slurry of ethanol at a ratio of 0.1 g/ml for 15 minutes, and placed in a sealed metal cartridge.
  • the cartridge was placed in a vacuum sintering furnace and evacuated. After the vacuum reached 10 -2 Pa, the temperature was raised to 820 ° C and held for 2 hours, cooled, heated to 620 ° C and held for 3 hours, and cooled.
  • the product density was 7.54 g/cm 3 and the magnetic properties of the product were measured as shown in Table 4.
  • Scanning electron microscopy (SEM, TESCAN VEGA 3LMH) was used to observe the different distances from the magnet surface in the cross section of the diffused magnet.
  • the element distribution was further determined by EDS to analyze the grain element composition at different positions on the surface.
  • Figure 1 is a microscopic view of the magnets of Example 4 and Comparative Example 4-2 after thermal diffusion.
  • (a)(b)(c)(d) is a microscopic observation of the magnet of Example 4, wherein (a) is a near surface, (b) is a distance of 200 ⁇ m from the surface, and (c) is a distance of 500 ⁇ m from the surface, (d) It is 1000 ⁇ m from the surface.
  • (e) (f) (g) (h) is a microscopic observation of the magnet of Comparative Example 4-2, wherein (e) is a near surface, (f) is a distance of 200 ⁇ m from the surface, and (g) is a distance of 500 ⁇ m from the surface, (h) ) is 1000 ⁇ m from the surface.
  • the value of the Dy+Tb content shown in the table is the average of the energy spectrum scans of the boundaries and centers of the same 10 or more crystal grains.
  • the average concentration of heavy rare earth in the grain boundary region and the average concentration of heavy rare earth in the central region in the region near 1000 ⁇ m from the surface of the magnet are less than 0.7 wt%.
  • the alloy of the same composition as that of Example 1 was prepared into a strip piece of 0.30 mm by a rapid setting technique, and the strip piece was coarsely broken into a medium-sized powder having a hydrogen content of 2000 ppm by hydrogen explosion treatment.
  • the density of the billet was 6.75 g/cm 3 , which was 89.4% of the theoretical density, and the average grain size was 5.20 ⁇ m.
  • the blank was machined into a D10*5mm wafer product with an orientation direction of 5 mm, and 5% yttria, 5% DyGa 2 powder and 90% MgCu 2 type intermetallic compound (component 28Nd-25Dy-3Ho-42.7Fe) a mixed powder of -1Co-0.1Cu-0.1Ga-0.1Zr) (powder size 5 ⁇ m) was immersed in a slurry of cyclohexane at a ratio of 0.8 g/ml for 45 minutes, and placed in a sealed metal cartridge, a cartridge A mixed powder of 20% alumina and 80% magnesium oxide is used as a sintering aid at the bottom. The cartridge was placed in a vacuum sintering furnace and evacuated.
  • the formed body was prepared under the same conditions and process as in Example 5, and then the formed body was placed in a high-vacuum sintering furnace, sintered at 1060 ° C for 3 hours, and then subjected to a secondary heat treatment, wherein the first-stage heat treatment temperature was 920 ° C, and the holding time was 2 hours; The heat treatment temperature is 540 °C, the holding time is 5 hours, the blank can be obtained, and the blank machine is processed into a D10*5mm wafer. After diffusion treatment, the product density is 7.54g/cm 3 and the average grain size is 7.20 ⁇ m. Magnetic properties, as shown in Table 6.
  • the formed body was prepared under the same conditions and procedures as in Example 5, and then the formed body was placed in a high-vacuum sintering furnace, and sintered at 1060 °C for 3 hours, and the density of the blank was 7.54 g/cm 3 .
  • the blank was machined into a D10*5mm wafer product, and 5% yttrium oxide, 5% DyGa 2 intermetallic compound powder and 90% MgCu 2 type intermetallic compound (component 28Nd-25Dy-3Ho-42.7Fe-1Co)
  • a mixed powder of -0.1Cu-0.1Ga-0.1Zr) (powder size: 5 ⁇ m) was immersed in a slurry of cyclohexane at a ratio of 0.8 g/ml for 45 minutes, and placed in a sealed metal cartridge.
  • the cartridge was placed in a vacuum sintering furnace and evacuated.
  • the alloy of the same composition as that of Example 1 was prepared into a strip piece of 0.25 mm by a rapid setting technique, and the strip piece was coarsely broken into a medium-sized powder having a hydrogen content of 1500 ppm by hydrogen explosion treatment.
  • the density of the billet was 7.10 g/cm 3 , which was 94.0% of the theoretical density, and the average grain size was 5.60 ⁇ m.
  • the blank machine is processed into a D10*5mm wafer product with an orientation direction of 5 mm, and 10% lanthanum nitrate, 50% lanthanum oxyfluoride and 40% MgCu 2 type intermetallic compound (component 22Pr-30Dy-6Ho-38.1Fe) is placed.
  • a mixed powder of -3Co-0.5Cu-0.2Ga-0.1Cr-0.1Mn) (powder size 10 ⁇ m) was immersed in a slurry of cyclohexane at a ratio of 0.5 g/ml for 30 minutes, and placed in a sealed metal box.
  • a mixed powder of 20% alumina and 80% magnesia as a sintering aid is a mixed powder of 20% alumina and 80% magnesia as a sintering aid.
  • the cartridge was placed in a vacuum sintering furnace and evacuated. After the vacuum reached 10 -2 Pa, the temperature was raised to 940 ° C and held for 16 hours, cooled, heated to 480 ° C and held for 6 hours, and cooled.
  • the product density after diffusion treatment was 7.54 g/cm 3 and the average grain size was 5.65 ⁇ m.
  • the magnetic properties of the product were measured as shown in Table 7.
  • the shaped body was prepared in the same conditions and process as in Example 6, and then the shaped body was placed in a high-vacuum sintering furnace, sintered at 1060 ° C for 3 hours, and then subjected to a secondary heat treatment, wherein the first-stage heat treatment temperature was 940 ° C, and the holding time was 2 hours; The heat treatment temperature is 480 degrees, the holding time is 6 hours, the blank can be obtained, and the blank machine is processed into a D10*5mm wafer product with a product density of 7.54g/cm 3 and an average grain size of 7.20 ⁇ m. Yes, as shown in Table 7.
  • the formed body was prepared under the same conditions and procedures as in Example 6, and then the formed body was placed in a high-vacuum sintering furnace, and sintered at 1060 °C for 3 hours, and the density of the blank was 7.54 g/cm 3 .
  • the blank was machined into a D10*5mm wafer product, and 10% lanthanum nitrate, 50% lanthanum oxyfluoride and 40% MgCu 2 type intermetallic compound (component 22Pr-30Dy-6Ho-38.1Fe-3Co-0.5Cu) was placed.
  • a mixed powder of -0.2Ga-0.1Cr-0.1Mn) (powder size: 10 ⁇ m) was immersed in a slurry of cyclohexane at a ratio of 0.5 g/ml for 30 minutes, and placed in a sealed metal cartridge.
  • the cartridge was placed in a vacuum sintering furnace and evacuated. After the vacuum reached 10 -2 Pa, the temperature was raised to 940 ° C and held for 6 hours, cooled, heated to 480 ° C and held for 6 hours, and cooled.
  • the product density after diffusion treatment was 7.54 g/cm 3 , and the magnetic properties of the product were measured as shown in Table 7.
  • the alloy of the same composition as that of Example 1 was prepared into a strip piece of 0.25 mm by a rapid setting technique, and the strip piece was coarsely broken into a medium-sized powder having a hydrogen content of 1500 ppm by hydrogen explosion treatment.
  • the density of the billet was 7.10 g/cm 3 , which was 94.0% of the theoretical density, and the average grain size was 5.60 ⁇ m.
  • the blank was machined into a D10*5mm wafer product with an orientation direction of 5 mm, and placed in 70% lanthanum nitrate pentahydrate, 20% lanthanum oxyfluoride and 10% MgCu 2 type intermetallic compound (component 22Pr-30Dy-6Ho- A mixed powder of 38.1Fe-3Co-0.5Cu-0.2Ga-0.1Cr-0.1Mn) (powder size 15 ⁇ m) was immersed in a slurry formed of cyclohexane at a ratio of 0.5 g/ml for 30 minutes, and placed in a sealed metal material. In the box. The cartridge was placed in a vacuum sintering furnace and evacuated.
  • the shaped body was prepared in the same manner and in the same manner as in Example 8, and then the formed body was placed in a high-vacuum sintering furnace, sintered at 1060 ° C for 3 hours, and then subjected to a secondary heat treatment, wherein the first-stage heat treatment temperature was 940 ° C and the holding time was 2 hours; The heat treatment temperature is 480 degrees, the holding time is 6 hours, the blank can be obtained, and the blank machine is processed into a D10*5mm wafer product with a product density of 7.54g/cm 3 and an average grain size of 7.20 ⁇ m. Yes, as shown in Table 8.
  • a shaped body was prepared under the same conditions and procedures as in Example 8, and then the formed body was placed in a high-vacuum sintering furnace and sintered at 1060 ° C for 3 hours, and the density of the green compact after sintering was 7.54 g/cm 3 .
  • the blank was machined into a D10*5mm wafer product, and 70% lanthanum nitrate pentahydrate, 20% lanthanum oxyfluoride and 10% MgCu 2 type intermetallic compound (component 22Pr-30Dy-6Ho-38.1Fe-3Co-) was placed.
  • a mixed powder of 0.5Cu-0.2Ga-0.1Cr-0.1Mn) (powder size 15 ⁇ m) was immersed in a slurry dispersed in cyclohexane at a ratio of 0.5 g/ml for 30 minutes, and placed in a sealed metal cartridge.
  • the cartridge was placed in a vacuum sintering furnace and evacuated. After the vacuum reached 10 -2 Pa, the temperature was raised to 940 ° C and held for 6 hours, cooled, heated to 480 ° C and held for 6 hours, and cooled.
  • the product density after diffusion treatment was 7.54 g/cm 3 , and the magnetic properties of the product were measured as shown in Table 8.
  • a D10 mm ⁇ 5 mm wafer product was prepared according to the method of Example 4.
  • the wafer product was subjected to five batches of coating, secondary sintering and diffusion treatment, with 2000 batches per batch, and the processing conditions of each batch were consistent.
  • 50 wafers were selected for each batch to measure magnetic properties.
  • the performance consistency and stability of the products between different batches were compared (mean value represents the average of 50 pieces of performance, and the range is the maximum value - minimum value of 50 pieces).
  • the test results are shown in Table 9.
  • a D10 mm ⁇ 5 mm wafer product was prepared by the method of Comparative Example 4-2, and five batches of the wafer were processed, and each batch was 2000 pieces, and the processing conditions of each batch were the same. 50 wafers were selected for each batch to measure magnetic properties. The performance consistency and stability of the products between different batches were compared (mean value represents the average of 50 pieces of performance, and the range is the maximum value - minimum value of 50 pieces). See the test results Table 10.

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Abstract

一种R-T-B永磁体的制备方法，制备方法的主要步骤是：（1）原材料经过熔化，浇铸，得到条带片；（2）将条带片进行氢爆处理，得到中碎粉；（3）将中碎粉进行气流磨制粉；（4）在密封垂直压机中进行压制成型；（5）在真空或惰性气体气氛中实施预烧结；（6）将预烧坯机加工成所需的形状；（7）涂覆处理：将重稀土化合物粉末分散于有机溶剂中形成浆液，将预烧坯浸渍于浆液中，然后将处理后的预烧坯放入料盒中；（8）在820-950℃进行二次烧结并同时进行重稀土元素的一次扩散，冷却后，在450-620℃温度范围内进行重稀土元素的二次扩散，冷却得到R-T-B永磁体。根据该制备方法制备得到的永磁体，剩磁、矫顽力得到了显著提高，方形度得到了明显改善。

Description

一种R-T-B永磁体的制备方法 技术领域
本发明涉及一种R-T-B永磁体的制备方法以及由该方法得到的永磁体，尤其涉及一种高剩磁高矫顽力的R-T-B永磁体的制备方法，属于磁性材料领域。
背景技术
由于R-Fe-B永磁体综合磁性能高，将钕铁硼稀土永磁材料应用于各种电机可以明显提高电机的性能，减轻电机重量，减小电机外型尺寸，且可以获得高效的节能效果。因此钕铁硼稀土永磁材料在汽车、家电中的高性能电机方面的应用越来越受到人们的重视，特别是节能环保要求的提高促使钕铁硼稀土永磁材料在混合动力汽车(HEV)、电动汽车(EV)驱动电机以及变频压缩机的应用进入了实用化阶段。目前这些高性能电机对烧结R-Fe-B磁体的一致要求是既要有高的剩余磁通密度，又必须有高的矫顽力。
在烧结R-Fe-B系永磁体中，若用重稀土元素RH(如Dy、Tb)取代R2Fe14B相中的稀土元素R的一部分，则可以提高矫顽力。为了在高温下也得到高的矫顽力，就需要大量添加重稀土元素RH。但是在烧结R-Fe-B系磁体中若用重稀土元素RH取代轻稀土元素(如Pr、Nd)，虽然矫顽力得以提高，但另一方面剩余磁通密度不可避免地大幅降低。这是因为Dy2Fe14B或Tb2Fe14B具有比Nd2Fe14B更高的磁晶各向异性场，也就是具有更大的理论内禀矫顽力，Dy/Tb部分取代主相Nd2Fe14B中的Nd后生成的固溶相(Nd,Dy)2Fe14B或(Nd,Tb)2Fe14B的磁晶各向异性场比Nd2Fe14B大，因而可以明显提高烧结磁体的矫顽力。但是，这种元素取代带来的不利后果，就是显著降低磁体的饱和磁化强度，因此磁体的剩磁和最大磁能积都会明显降低，因为在Nd2Fe14B主 相中Nd与Fe的磁矩平行排列，两者的磁矩是增强性叠加；而Dy/Tb与Fe为反铁磁耦合，Dy/Tb的磁矩与Fe磁矩反平行排列，部分抵消主相的总磁矩。另外由于Dy、Tb是稀少并且昂贵的元素，从成本方面考虑也不能大量添加。
专利申请CN200580001133.X给出了一种磁体表面的渗镀技术。将烧结毛坯机加工成小而薄型磁体，将磁体浸入重稀土微米级细粉(Dy、Tb的氟化物、氧化物和氟氧化物中的一种或多种)分散于有机溶剂中所形成的浆液中进行涂覆，然后在真空或惰性气体气氛下，在等于或低于烧结温度下对磁体进行热处理。其后续效果是矫顽力提高较多，而剩磁基本不降低，原因是重稀土元素只存在于晶界相中，而不进入主相。这种方法既节约了重稀土的使用，又抑制了剩磁的下降。但该专利申请仅涉及对涂覆粉末的改进，且在实际生产过程中，永磁体的批次之间的差别较大，无法满足永磁体产品对磁性能稳定性和一致性的需求。另外，渗重稀土技术是一个涂覆+扩散的过程，该专利申请的技术方案主要涉及涂覆过程。但是对于后续的热扩散过程，扩散通道的影响效果比温度、时间等热处理工艺参数的影响更为显著，但该专利申请的技术方案中并没有涉及，其必然导致热扩散过程的不均匀性。
专利申请CN201110024823.4给出了采用重稀土氟化物、硝酸盐和磷酸盐的粉末在磁体表面热扩散的方法，解决了磁体热扩散后表面残存有不均匀分布熔融物的问题，从而使得涂覆后的基体与镀层之间结合力变差以及耐蚀性下降的问题不复存在。其原因是在于粉末在水或有机溶剂中的溶解性很差，在涂覆的过程中不能均匀分布在磁体的表面。虽然该专利解决了涂覆粉末在基体上的分布均匀性问题，但未对热扩散过程做出明确要求，在热扩散过程中同样存在不均匀性的问题。
如上所述，目前现有技术中所涉及的技术问题主要集中在涂覆粉末的种类以及热处理工艺等方面，对于磁体内部的构造改进未有明确提及。不仅涂覆粉末的成分、后续的热处理工艺会影响到矫顽力的提升，磁体内部扩散通 道对于后续重稀土的扩散效果也具有显著的影响。实验研究表明，预烧结后的预烧体内孔隙是一条重要的扩散通道，它大大提高了重稀土元素的扩散效果。本发明正是基于上述发现而提出的。
引证文件列表
专利文献
专利文献1：中国专利CN200580001133.X
专利文献2：中国专利CN201110024823.4
发明内容
技术问题
本发明的目的是提供一种具有高剩磁、高矫顽力的烧结R-T-B永磁体的制备方法，根据该制备方法制备得到的永磁体，剩磁、矫顽力得到了显著提高，方形度得到了明显改善，并且各批次之间性能的稳定性和一致性得到了显著的提高。
解决方案
本发明提供一种R-T-B永磁体的制备方法，包括以下步骤：
提供组成为R1-T-B组成的成形体，其中R1选自稀土元素Nd、Pr、La、Ce、Sm、Dy、Tb、Ho、Er、Gd、Sc、Y和Eu所组成组中的至少一种，优选至少包含Nd或Pr；T为Fe和/或Co，任选地，T还包含选自由Al、Cu、Zn、In、Si、P、S、Ti、V、Cr、Mn、Ni、Ga、Ge、Zr、Nb、Mo、Pd、Ag、Cd、Sn、Sb、Hf、Ta和W所组成组中的至少一种；
在900-1040℃对成形体进行预烧结热处理，得到预烧坯；
采用重稀土化合物对预烧坯进行涂覆、二次烧结和热扩散处理，得到R-T-B永磁体，其中R包含至少一种重稀土元素和至少一种除重稀土元素外的其他稀土元素。
本发明所述的R-T-B永磁体的制备方法中，所述预烧坯的实际密度为理 论密度的80～98％，优选为85～97％。
本发明所述的R-T-B永磁体的制备方法中，所述重稀土化合物为包含有重稀土氧化物、氟化物、氟氧化物或氢化物，含有重稀土元素的稀土金属间化合物，重稀土R2Fe14B结构化合物、重稀土水合硝酸盐中的一种或多种的混合粉末。
本发明所述的R-T-B永磁体的制备方法中，所述重稀土选自Dy、Tb或Ho中的一种或两种以上。
本发明所述的R-T-B永磁体的制备方法中，所述成形体由以下步骤获得：
熔炼：将原料按比例配好，经过熔化，浇铸，得到条带片；
粗破碎：将条带片进行氢爆处理，得到中碎粉；
制微粉：将中碎粉进行气流磨制粉，粉末粒度范围为D50＝3～6μm；
压型：在密封垂直压机中进行压制得到成形体。
本发明所述的R-T-B永磁体的制备方法中，所述中碎粉的氢含量范围为800-3000ppm，优选为1000-2000ppm。
本发明所述的R-T-B永磁体的制备方法中，所述热处理是在真空或惰性气体气氛中实施烧结，得到预烧坯。
本发明所述的R-T-B永磁体的制备方法中，所述涂覆、二次烧结和热扩散处理采用如下步骤进行：
涂覆处理：将预烧坯机加工成所需的形状，将重稀土化合物粉末分散于有机溶剂中制得浆液，将加工后的预烧坯浸渍于浆液中，然后将处理后的预烧坯放入密封的料盒中；
二次烧结和热扩散处理：将料盒放入真空烧结炉中抽真空，之后升温到820-950℃进行二次烧结并同时进行重稀土元素的一次扩散，然后冷却，停止冷却并抽真空后升温到450℃～620℃进行重稀土元素二次扩散，冷却得到R-T-B永磁体。
本发明所述的R-T-B永磁体的制备方法中，所述重稀土化合物粉末以0.01-1.0g/ml的比例分散于有机溶剂中。
本发明所述的R-T-B永磁体的制备方法中，所述料盒的底部装有10-20％的氧化铝和80-90％的氧化镁的混合粉末。
有益效果
本发明中通过改进烧结磁体毛坯基体的具体结构，提高了重稀土元素的扩散渗透效果，提高了磁体的矫顽力，改善了磁体的方形度。本发明的制备方法，与未改进基体的重稀土元素的扩散过程相比，沿着取向方向重稀土元素的分布也更为一致，显著改善了磁体的方形度，并且在连续生产过程中，使各批次产品之间性能的稳定性和一致性得到了显著的提高。
附图说明
图1实施例4以及对比例4-2磁体热扩散后的显微观察图。
具体实施方式
以下将详细说明本发明的各种示例性实施例和特征。
在这里专用的词“示例性”意为“用作例子、实施例或说明性”。这里作为“示例性”所说明的任何实施例不必解释为优于或好于其它实施例。
另外，为了更好的说明本发明，在下文的具体实施方式中给出了众多的具体细节。本领域技术人员应当理解，没有某些具体细节，本发明同样可以实施。在另外一些实例中，对于本领域技术人员熟知的方法、手段、元件和电路未作详细描述，以便于凸显本发明的主旨。
本发明中的R-T-B永磁体的制备方法，包括以下步骤：
提供组成为R1-T-B组成的成形体，其中R1选自稀土元素Nd、Pr、La、Ce、Sm、Sc、Y和Eu所组成组中的至少一种，优选至少包含Nd或Pr；T为Fe和/ 或Co，任选地，T还包含选自由Al、Cu、Zn、In、Si、P、S、Ti、V、Cr、Mn、Ni、Ga、Ge、Zr、Nb、Mo、Pd、Ag、Cd、Sn、Sb、Hf、Ta和W所组成组中的至少一种；
在900-1040℃对成形体进行热处理，得到预烧坯；
采用重稀土化合物对预烧坯进行涂覆、热扩散处理，得到R-T-B永磁体，其中R包含至少一种重稀土元素和至少一种除重稀土元素外其他稀土元素。
其中，成形体由以下步骤获得：
熔炼：将原料按比例配好，经过熔化，浇铸，得到条带片；
粗破碎：将条带片进行氢爆处理，得到中碎粉；
制微粉：将中碎粉进行气流磨制粉，粉末粒度范围为D50＝3～6μm；
压型：在密封垂直压机中进行压制得到成形体。
在熔炼过程中，将原料按比例配好，在带坯连铸炉内熔化，以≥1m/s的铜辊线速度，进行鳞片浇铸，最终得到厚度0.2-0.5mm的条带片。当条带片的厚度>0.2mm时，其显微组织结构中贴辊面不会出现大量的微细晶区；条带片的厚度<0.5mm时，其显微组织结构中自由面不易出现大量粗大晶区；均不会对后续的制微粉粒度分布产生不利的影响。
在粗破碎过程中，将条带片进行氢爆处理，得到中碎粉，采用ELTRA公司的ONH2000型分析仪测量中碎粉中的氢含量，氢含量范围优选为800-3000ppm，氢含量≥800ppm时能够使后续的预烧品具有足够的扩散通道；氢含量≤3000ppm时后续的预烧体中孔隙能够确保预烧品通过后续处理达到理论密度的99.5％以上。氢含量范围更优选为1000-2000ppm，其在满足预烧品快速达到理论密度99.5％以上的同时又能保证充分的扩散通道。
在制微粉的过程中，将中碎粉进行气流磨制粉，粉末粒度范围为D50＝3～6μm(粉末粒度由激光衍射测量法获得，D50为重量累积值为50％的粒径)，粉末粒度D50≥3μm时后续的预烧品氧、氮含量低，不会影响扩散效果； 粉末粒度D50≤6μm时后续的预烧品能够通过低温烧结的方法达到理论密度99.5％以上。
在压型过程中，采用密封垂直压机中进行压制成型，在压制过程中施加1T～3T的磁场，更优选采用1.8T～3T的磁场。
在烧结过程中，将成形体送入烧结炉中在真空或惰性气体气氛中实施预烧结，在低于理论烧结温度低的条件下进行烧结，使预烧毛坯达到理论密度的80％-98％，优选为85～97％，为后续的扩散准备好充分的扩散通道。烧结温度范围为900-1040℃，更优选为910-990℃。
得到的预烧坯的实际密度为6.0～7.4g/cm3，更优选为6.5～7.3g/cm3，比如预烧坯的实际密度在6.0g/cm3以上(比如至少6.1g/cm3、至少6.2/cm3、至少6.3g/cm3、至少6.4g/cm3、至少6.5g/cm3)并且在7.4g/cm3以下(比如至多7.3g/cm3、至多7.2g/cm3、至多7.1g/cm3、至多7.0g/cm3、至多6.9g/cm3、至多6.8g/cm3、至多6.7g/cm3)。预烧坯的密度在6.0g/cm3以上，其在后续的扩散处理过程中不易被氧化而造成性能的劣化；预烧坯的密度在7.4g/cm3以下时，其在后续的扩散处理过程中不会由于没有充分的扩散通道而造成提升效果不显著。
得到的预烧坯平均晶粒尺寸为粉末粒度D50的1.1～1.5倍，更优选1.2～1.4倍。预烧坯的晶粒细小，富稀土相的分布更加均匀，有利于后续的重稀土渗透扩散过程。
涂覆、二次烧结和热扩散处理采用如下步骤进行：
涂覆处理：将预烧坯机加工成所需的形状，将重稀土化合物粉末分散于有机溶剂中制得浆液，将加工后的预烧坯浸渍于浆液中，然后将处理后的预烧坯放入密封的料盒中；
二次烧结和热扩散处理：将料盒放入真空烧结炉中抽真空，之后升温到 820-950℃进行二次烧结并同时进行重稀土元素的一次扩散，然后冷却，停止冷却并抽真空后升温到450℃～620℃进行重稀土元素二次扩散，冷却得到R-T-B永磁体。
在机加工过程中，将预烧坯机加工成所需的成品形状，取向方向的尺寸需小于等于10mm，更优选小于等于5mm。
在涂覆过程中，将重稀土化合物粉末分散于有机溶剂中形成浆液。将预烧坯浸渍于处于超声搅拌状态的浆液中，然后将处理后的预烧坯放入密封的料盒中，优选金属料盒。
涂覆过程中，重稀土化合物粉末为包含重稀土氧化物、氟化物、氟氧化物或氢化物，含有重稀土元素的稀土金属间化合物，重稀土R2Fe14B结构化合物，重稀土水合硝酸盐中的一种或多种的混合粉末。其中，优选采用稀土金属间化合物，例如DyAl2。
涂覆过程中，重稀土化合物粉末优选以0.01-1.0g/ml的比例分散于有机溶剂中，更优选为0.1-0.8g/ml，在此范围内，既可以保证足够的重稀土化合物粉末溶解量，又可以使涂覆粉末均匀的分布在基体上。
涂覆粉末的粒度优选1～50μm，更优选范围为3～25μm。
涂覆过程中，使用的有机溶剂包括醇类、含有5～16个碳原子的烷烃类或酯类，优选使用乙酸乙酯、乙醇或环己烷，更优选使用环己烷。
所述密封的料盒的底部装有10-20％的氧化铝和80-90％的氧化镁的混合粉末，在二次烧结过程中，上述混合粉末可以作为助烧剂，能够在保持低温820-950℃使预烧坯在≤24h的时间内快速达到理论密度的99.5％以上。
在二次烧结和热扩散处理过程中，将料盒放入真空烧结炉中抽真空，之后升温到820-950℃进行二次烧结同时进行重稀土元素的一次扩散，然后充氩气冷却到80℃以下，停止冷却并抽真空后升温到450℃～620℃进行二次扩散，然后充氩气冷却到80℃以下，得到R-T-B永磁体。经过扩散处理后的预 烧坯达到了理论密度的99.5％以上，并且预烧坯的时效过程也同时在扩散处理过程中完成，矫顽力得到了显著地提高，并且重稀土元素在晶界的分布也十分均匀。
在扩散过程中，一次扩散的保温时间优选为12-24小时，更优选为15-20小时，二次扩散的保温时间优选为1-8小时，更优选为2-7小时。
本发明中的低密度的预烧坯在二次烧结和热扩散处理的过程中，平均晶粒尺寸无变化。一次扩散的时间大于12小时，可以使预烧坯的密度达到理论密度99.5％以上，同时保证重稀土扩散的深度和均匀性的一致性；一次扩散时间小于24小时，预烧坯不会会出现异常的晶粒长大而导致磁性能得劣化。而一般的高密度磁体在一次扩散的时间达到12小时后，重稀土扩散的均匀性才能够保证，但是会出现异常的晶粒长大而导致磁性能劣化，因此一般的高密度磁体只能在两种效果中选择其一，而无法同时达到最理想的状态。
在扩散过程中，二次烧结同时进行一次扩散的真空度为<0.2Pa，所述二次扩散的真空度为<0.2Pa。所述一次扩散的温度在820-950℃范围内，如果温度超过950℃，扩散渗透的效果将消失。
此外，对本发明R-T-B永磁体的断面进行分析发现：1)预烧坯磁体经过涂覆重稀土粉末、二次烧结和热扩散处理后，重稀土扩散更均匀，其样品沿深度方向的重稀土梯度分布小于常规烧结达到理论密度99.5％以上的磁体经过扩散处理后沿深度方向的重稀土梯度；2)在距离磁体表面近1000μm的区域内，晶粒边界处重稀土平均浓度比中心部的重稀土平均浓度至少高0.7wt％；而常规烧结达到理论密度99.5％以上的磁体经过涂覆重稀土及热扩散工序后，其样品在距表面近1000μm处晶粒边界区重稀土平均浓度与中心区重稀土平均浓度差低于0.7wt％；3)在同样的涂覆量和涂覆条件下，预烧坯进行扩散处理使得重稀土的扩散深度更深。
磁性能的测试方法：按照GB/T 3217-2013的方法进行磁性能的测试。
扩散后样品的矫顽力Hcj至少为14MA/m(比如至少14.5MA/m、至少15MA/m、至少15.5MA/m、至少16MA/m、至少16.5MA/m或者至少17MA/m)。
实施例
实施例1
按照重量百分比(PrNd)30Dy0.5Al0.4Co1Cu0.1Ga0.1B0.96Febal配制原材料合金，原材料纯度为99％以上，利用速凝技术将合金制备成0.25mm的条带片，采用氢爆处理将条带片粗破成氢含量为1400ppm的中碎粉。将中碎粉气流磨成D50＝4.5μm的微粉，在取向场为2T的密封垂直压机中压制，然后将成形体置入高真空烧结炉中，在1000度烧结2小时，得到的预烧坯的密度为7.3g/cm3，为理论密度的96.7％，平均晶粒尺寸为6.75μm。将毛坯机加工成D10*5mm的圆片产品取向方向为5mm，放入70％硝酸镝和30％氟化镝的混合粉末(粉末粒度为1μm)以0.05g/ml的比例分散于乙酸乙酯中的浆液中浸渍15min，放入密封的金属料盒中，料盒底部有15％氧化铝和85％氧化镁的混合粉末作为助烧剂。将料盒放入真空烧结炉中抽真空，在真空度达到10-2Pa后升温到890℃并保温12小时，冷却，升温到500℃并保温5小时，冷却。扩散处理后产品密度为7.52g/cm3，达到理论密度的99.6％，平均晶粒尺寸为6.80μm，测量产品磁性能，如表1所示。
对比例1-1：
与实施例1相同条件和工艺制备成形体，然后将成形体置入高真空烧结炉中，在1050度烧结3小时，之后进行二级热处理，其中一级热处理温度890度，保温时间3小时；二级热处理温度500度，保温时间5小时，即可获得毛坯，将毛坯机加工成D10*5mm的圆片，产品密度为7.54g/cm3，达到理论密度的99.9％，平均晶粒尺寸为7.90μm，测量产品磁性能，如表1所示。
对比例1-2：
与实施例1相同条件和工艺制备成形体，然后将成形体置入高真空烧结 炉中，在1050度烧结3小时，烧结后毛坯的密度为7.54g/cm3。将毛坯机加工成D10*5mm的圆片产品，放入70％硝酸镝和30％氟化镝的混合粉末(粉末粒度为1μm)以0.05g/ml的比例分散于乙酸乙酯中的浆液中浸渍15min，放入密封的金属料盒中。将料盒放入真空烧结炉中抽真空，在真空度达到10-2Pa后升温到890℃并保温3小时，冷却，升温到500℃并保温5小时。产品密度为7.54g/cm3，达到理论密度的99.9％。测量产品磁性能，如表1所示。
表1 实施例1、对比例1-1、对比例1-2永磁体磁性能测试结果
Figure PCTCN2015098012-appb-000001
实施例2
利用速凝技术将与实施例1相同成分的合金制备成0.50mm的条带片，采用氢爆处理将条带片粗破成氢含量为800ppm的中碎粉。将中碎粉气流磨成D50＝6.0μm的微粉，在取向场为2T的密封垂直压机中压制，然后将成形体置入高真空烧结炉中，在900度烧结4小时，得到的预烧坯的密度为6.90g/cm3，为理论密度的91.4％，平均晶粒尺寸为7.2μm。将毛坯机加工成D10*5mm的圆片产品，取向方向为5mm，放入100％氧化镝粉末(粉末粒度50μm)以0.01g/ml的比例分散于乙醇中的浆液中浸渍60min，放入密封的金属料盒中，料盒底部有20％氧化铝和80％氧化镁的混合粉末作为助烧剂。将料盒放入真空烧结炉中抽真空，在真空度达到10-2Pa后升温到950℃并保温24小时，冷却，升温到450℃并保温8小时，冷却。扩散处理后产品密度为7.52g/cm3，为理论密度的99.6％，平均晶粒尺寸为7.30μm，测量产品磁性能，如表2所示。
对比例2-1：
与实施例2相同条件和工艺制备成形体，然后将成形体置入高真空烧结炉中，在1070度烧结3小时，之后进行二级热处理，其中一级热处理温度950度，保温时间3小时；二级热处理温度450度，保温时间8小时，即可获得毛坯，将毛坯机加工成D10*5mm的圆片，产品密度为7.54g/cm3，平均晶粒尺寸为10.20μm，测量产品磁性能，如表2所示。
对比例2-2：
与实施例2相同条件和工艺制备成形体，然后将成形体置入高真空烧结炉中，在1070度烧结3小时，烧结后毛坯的密度为7.54g/cm3。将毛坯机加工成D10*5mm的圆片产品，放入100％氧化镝粉末(粉末粒度50μm)以0.01g/ml的比例分散于乙醇形成的浆液中浸渍60min，放入密封的金属料盒中。将料盒放入真空烧结炉中抽真空，在真空度达到10-2Pa后升温到950℃并保温3小时，冷却，升温到450℃并保温8小时，冷却。产品密度为7.54g/cm3，测量产品磁性能，如表2所示。
表2 实施例2、对比例2-1、对比例2-2永磁体磁性能测试结果
Figure PCTCN2015098012-appb-000002
实施例3
利用速凝技术将与实施例1成分相同的合金制备成0.20mm的条带片，采用氢爆处理将条带片粗破成氢含量为3000ppm的中碎粉。将中碎粉气流磨成D50＝3.0μm的微粉，在取向场为2T的密封垂直压机中压制，然后将成形体置入高真空烧结炉中，在950度烧结1小时，得到的预烧坯的密度为6.50g/cm3， 为理论密度的86.1％,平均晶粒尺寸为3.3μm。将毛坯机加工成D10*5mm的圆片产品，取向方向为5mm，放入20％DyHx和80％MgCu2型金属间化合物(成分为10％Nd-12％Pr-35％Dy-41％Fe-2％Co)的混合粉末(粉末粒度25μm)以1g/ml的比例分散于乙醇形成的浆液中浸渍30min，放入密封的金属料盒中，料盒底部有15％氧化铝和85％氧化镁的混合粉末作为助烧剂。将料盒放入真空烧结炉中抽真空，在真空度达到10-2Pa后升温到920℃并保温15小时，冷却，升温到480℃并保温5小时，冷却。扩散处理后产品密度为7.54g/cm3，为理论密度99.9％，平均晶粒尺寸为3.60μm，测量产品磁性能，如表3所示。
对比例3-1：
与实施例3相同条件和工艺制备成形体，然后将成形体置入高真空烧结炉中，在1045度烧结3小时，之后进行二级热处理，其中一级热处理温度920度，保温时间3小时；二级热处理温度480度，保温时间为5小时，即可获得毛坯，将毛坯机加工成D10*5mm的圆片产品，产品密度为7.54g/cm3，平均晶粒尺寸为5.80μm，并测量磁性能，如表3所示。
对比例3-2：
与实施例3相同条件和工艺制备成形体，然后将成形体置入高真空烧结炉中，在1045度烧结3小时，烧结后的毛坯密度为7.54g/cm3。将毛坯机加工成D10*5mm的圆片产品，放入20％DyHx和80％MgCu2型金属间化合物(成分为10％Nd-12％Pr-35％Dy-41％Fe-2％Co)的混合粉末(粉末粒度25μm)以1g/ml的比例分散于乙醇中的浆液中浸渍30min，放入密封的金属料盒中。将料盒放入真空烧结炉中抽真空，在真空度达到10-2Pa后升温到920℃并保温15小时，冷却，升温到480℃并保温5小时，冷却。产品密度7.54g/cm3，测量产品磁性能，如表3所示。
表3 实施例3、对比例3-1、对比例3-2永磁体磁性能测试结果
Figure PCTCN2015098012-appb-000003
实施例4
利用速凝技术将与实施例1成分相同的合金制备成0.25mm的条带片，采用氢爆处理将条带片粗破成氢含量为1000ppm的中碎粉。将中碎粉气流磨成D50＝4.5μm的微粉，在取向场为2T的密封垂直压机中压制，然后将成形体置入高真空烧结炉中，在920度烧结4小时，得到的预烧坯的密度为7.00g/cm3，为理论密度的92.7％，平均晶粒尺寸为6.30μm。将毛坯机加工成D10*5mm的圆片产品，取向方向为5mm，放入20％氟化铽、20％Dy2Fe14B粉末和60％MgCu2型金属间化合物(成分为10Nd-15Pr-25Dy-7Tb-41.9Fe-1Co-0.1Cu)的混合粉末(粉末粒度3μm)以0.1g/ml的比例分散于乙醇形成的浆液中浸渍15min，放入密封的金属料盒中，料盒底部有10％氧化铝和90％氧化镁的混合粉末作为助烧剂。将料盒放入真空烧结炉中抽真空，在真空度达到10-2Pa后升温到820℃并保温20小时，冷却，升温到620℃并保温3小时，冷却。扩散处理后产品密度为7.54g/cm3，达到理论密度99.6％，平均晶粒尺寸为6.45μm，测量产品磁性能，如表4所示。
对比例4-1：
与实施例4相同条件和工艺制备成形体，然后将成形体置入高真空烧结炉中，在1060度烧结3小时，之后进行二级热处理，其中一级热处理温度820度，保温时间2小时；二级热处理温度620度，保温时间为3小时，即可获得毛坯，将毛坯机加工成D10*5mm的圆片产品，其密度为7.54g/cm3，平均晶 粒尺寸为7.25μm，测量产品磁性能，如表4所示。
对比例4-2：
与实施例4相同条件和工艺制备成形体，然后将成形体置入高真空烧结炉中，在1060度烧结3小时，烧结后毛坯密度为7.54g/cm3。将毛坯机加工成D10*5mm的圆片产品，放入20％氟化铽、20％Dy2Fe14B粉末和60％MgCu2型金属间化合物(成分为10Nd-15Pr-25Dy-7Tb-41.9Fe-1Co-0.1Cu)的混合粉末(粉末粒度3μm)以0.1g/ml的比例分散于乙醇形成的浆液中浸渍15min，放入密封的金属料盒中。将料盒放入真空烧结炉中抽真空，在真空度达到10-2Pa后升温到820℃并保温2小时，冷却，升温到620℃并保温3小时，冷却。产品密度为7.54g/cm3，测量产品磁性能，如表4所示。
表4 实施例4、对比例4-1、对比例4-2永磁体磁性能测试结果
Figure PCTCN2015098012-appb-000004
用扫描电子显微镜(SEM，TESCAN VEGA 3LMH)分别观察扩散后圆片磁体断面中与磁体表面不同距离处的情况，进一步采用EDS进行元素分布测定，分析距离表面不同位置的晶粒元素组成。
图1为实施例4以及对比例4-2磁体热扩散后的显微观察图。其中(a)(b)(c)(d)为实施例4的磁体显微观察，其中(a)为近表面，(b)为距离表面200μm，(c)为距离表面500μm，(d)为距离表面1000μm。(e)(f)(g)(h)为对比例4-2的磁体显微观察，其中(e)为近表面，(f)为距离表面200μm，(g)为距离表面500μm，(h)为距离表面1000μm。
表5 实施例4及对比例4-2Dy+Tb重量百分比测试结果
Figure PCTCN2015098012-appb-000005
注：表格内所示的Dy+Tb含量的值为对距离表面相同的10个以上晶粒的边界和中心进行能谱扫描的平均值。
由图1的显微组织照片以及表5所示数据的二者对比可以看出：1)预烧体磁体经过涂覆重稀土、二次烧结和扩散处理后，扩散更均匀，其样品沿深度方向的重稀土梯度分布小于常规烧结体经过扩散处理后重稀土梯度；2)在距磁体表面近1000μm处的区域内，晶粒边界处重稀土平均浓度比中心部的重稀土平均浓度至少高0.7wt％；而常规烧结体经过涂覆重稀土及热扩散工序后，其样品在距离磁体表面近1000μm处区域内晶粒边界区重稀土平均浓度与中心区重稀土平均浓度差低于0.7wt％；3)在同样的涂覆量和涂覆条件下，预烧体进行扩散处理使得重稀土的扩散深度更深。
实施例5
利用速凝技术将与实施例1成分相同的合金制备成0.30mm的条带片，采用氢爆处理将条带片粗破成氢含量为2000ppm的中碎粉。将中碎粉气流磨成D50＝4.0μm的微粉，在取向场为2T的密封垂直压机中压制，然后将成形体置入高真空烧结炉中，在1000度烧结1小时，得到的预烧坯的密度为6.75g/cm3，为理论密度的89.4％，平均晶粒尺寸为5.20μm。将毛坯机加工成D10*5mm的圆片产品，取向方向为5mm，放入5％氧化铽、5％DyGa2粉末和90％MgCu2 型金属间化合物(成分为28Nd-25Dy-3Ho-42.7Fe-1Co-0.1Cu-0.1Ga-0.1Zr)的混合粉末(粉末粒度5μm)以0.8g/ml的比例分散于环己烷形成的浆液中浸渍45min，放入密封的金属料盒中，料盒底部有20％氧化铝和80％氧化镁的混合粉末作为助烧剂。将料盒放入真空烧结炉中抽真空，在真空度达到10-2Pa后升温到920℃并保温18小时，冷却，升温到540℃并保温5小时，冷却。扩散处理后产品密度7.54g/cm3，平均晶粒尺寸为5.30μm，测量产品磁性能，如表6所示。
对比例5-1：
与实施例5相同条件和工艺制备成形体，然后将成形体置入高真空烧结炉中，在1060度烧结3小时，之后进行二级热处理，其中一级热处理温度920度，保温时间2小时；二级热处理温度540度，保温时间为5小时，即可获得毛坯，将毛坯机加工成D10*5mm的圆片，扩散处理后产品密度7.54g/cm3，平均晶粒尺寸为7.20μm，测量产品磁性能，如表6所示。
对比例5-2：
与实施例5相同条件和工艺制备成形体，然后将成形体置入高真空烧结炉中，在1060度烧结3小时，毛坯的密度为7.54g/cm3。将毛坯机加工成D10*5mm的圆片产品，放入5％氧化铽、5％DyGa2金属间化合物粉末和90％MgCu2型金属间化合物(成分为28Nd-25Dy-3Ho-42.7Fe-1Co-0.1Cu-0.1Ga-0.1Zr)的混合粉末(粉末粒度5μm)以0.8g/ml的比例分散于环己烷形成的浆液中浸渍45min，放入密封的金属料盒中。将料盒放入真空烧结炉中抽真空，在真空度达到10-2Pa后升温到920℃并保温12小时，冷却，升温到540℃并保温5小时，冷却。扩散处理后产品密度7.54g/cm3，测量产品磁性能，如表6所示。
表6 实施例5、对比例5-1、对比例5-2永磁体磁性能测试结果
Figure PCTCN2015098012-appb-000006
实施例6
利用速凝技术将与实施例1成分相同的合金制备成0.25mm的条带片，采用氢爆处理将条带片粗破成氢含量为1500ppm的中碎粉。将中碎粉气流磨成D50＝4.0μm的微粉，在取向场为2T的密封垂直压机中压制，然后将成形体置入高真空烧结炉中，在950度烧结3小时，得到的预烧坯的密度为7.10g/cm3，为理论密度的94.0％，平均晶粒尺寸为5.60μm。将毛坯机加工成D10*5mm的圆片产品，取向方向为5mm，放入10％硝酸钬、50％氟氧化镝和40％MgCu2型金属间化合物(成分为22Pr-30Dy-6Ho-38.1Fe-3Co-0.5Cu-0.2Ga-0.1Cr-0.1Mn)的混合粉末(粉末粒度10μm)以0.5g/ml的比例分散于环己烷形成的浆液中浸渍30min，放入密封的金属料盒中，料盒底部有20％氧化铝和80％氧化镁的混合粉末作为助烧剂。将料盒放入真空烧结炉中抽真空，在真空度达到10-2Pa后升温到940℃并保温16小时，冷却，升温到480℃并保温6小时，冷却。扩散处理后产品密度为7.54g/cm3，平均晶粒尺寸为5.65μm，测量产品磁性能，如表7所示。
对比例6-1：
与实施例6相同条件和工艺制备成形体，然后将成形体置入高真空烧结炉中，在1060度烧结3小时，之后进行二级热处理，其中一级热处理温度940度，保温时间2小时；二级热处理温度480度，保温时间为6小时，即可获得毛坯，将毛坯机加工成D10*5mm的圆片产品，产品密度为7.54g/cm3，平均 晶粒尺寸为7.20μm，测量产品磁性能，如表7所示。
对比例6-2：
与实施例6相同条件和工艺制备成形体，然后将成形体置入高真空烧结炉中，在1060度烧结3小时，毛坯的密度为7.54g/cm3。将毛坯机加工成D10*5mm的圆片产品，放入10％硝酸钬、50％氟氧化镝和40％MgCu2型金属间化合物(成分为22Pr-30Dy-6Ho-38.1Fe-3Co-0.5Cu-0.2Ga-0.1Cr-0.1Mn)的混合粉末(粉末粒度10μm)以0.5g/ml的比例分散于环己烷形成的浆液中浸渍30min，放入密封的金属料盒中。将料盒放入真空烧结炉中抽真空，在真空度达到10-2Pa后升温到940℃并保温6小时，冷却，升温到480℃并保温6小时，冷却。扩散处理后产品密度为7.54g/cm3，测量产品磁性能，如表7所示。
表7 实施例6、对比例6-1、对比例6-2永磁体磁性能测试结果
Figure PCTCN2015098012-appb-000007
实施例7
利用速凝技术将与实施例1成分相同的合金制备成0.25mm的条带片，采用氢爆处理将条带片粗破成氢含量为1500ppm的中碎粉。将中碎粉气流磨成D50＝4.0μm的微粉，在取向场为2T的密封垂直压机中压制，然后将成形体置入高真空烧结炉中，在950度烧结3小时，得到的预烧坯的密度为7.10g/cm3，为理论密度的94.0％，平均晶粒尺寸为5.60μm。将毛坯机加工成D10*5mm的圆片产品，取向方向为5mm，放入70％五水硝酸钬、20％氟氧化镝和 10％MgCu2型金属间化合物(成分为22Pr-30Dy-6Ho-38.1Fe-3Co-0.5Cu-0.2Ga-0.1Cr-0.1Mn)的混合粉末(粉末粒度15μm)以0.5g/ml的比例分散于环己烷形成的浆液中浸渍30min，放入密封的金属料盒中。将料盒放入真空烧结炉中抽真空，在真空度达到10-2Pa后升温到940℃并保温24小时，冷却，升温到480℃并保温6小时，冷却。扩散处理后产品密度为7.50g/cm3，平均晶粒尺寸为5.70μm，测量产品磁性能，如表8所示。
对比例7-1：
与实施例8相同条件和工艺制备成形体，然后将成形体置入高真空烧结炉中，在1060度烧结3小时，之后进行二级热处理，其中一级热处理温度940度，保温时间2小时；二级热处理温度480度，保温时间为6小时，即可获得毛坯，将毛坯机加工成D10*5mm的圆片产品，产品密度为7.54g/cm3，平均晶粒尺寸为7.20μm，测量产品磁性能，如表8所示。
对比例7-2：
与实施例8相同条件和工艺制备成形体，然后将成形体置入高真空烧结炉中，在1060度烧结3小时，烧结后毛坯的密度为7.54g/cm3。将毛坯机加工成D10*5mm的圆片产品，放入70％五水硝酸钬、20％氟氧化镝和10％MgCu2型金属间化合物(成分为22Pr-30Dy-6Ho-38.1Fe-3Co-0.5Cu-0.2Ga-0.1Cr-0.1Mn)的混合粉末(粉末粒度15μm)以0.5g/ml的比例分散于环己烷中的浆液中浸渍30min，放入密封的金属料盒中。将料盒放入真空烧结炉中抽真空，在真空度达到10-2Pa后升温到940℃并保温6小时，冷却，升温到480℃并保温6小时，冷却。扩散处理后产品密度为7.54g/cm3，测量产品磁性能，如表8所示。
表8 实施例7、对比例7-1、对比例7-2永磁体磁性能测试结果
Figure PCTCN2015098012-appb-000008
实施例8
按照实施例4方法制备D10mm×5mm圆片产品，圆片产品共进行5个批次的涂敷、二次烧结及扩散处理，每批次2000片，每个批次的处理条件一致。每批次中分别选取50片圆片进行磁性能的测量。比较不同批次间产品的性能一致性和稳定性(均值表示50片性能的平均值，极差为50片性能的最大值-最小值)。测试结果见表9。
表9
Figure PCTCN2015098012-appb-000009
采用对比例4-2的方法制备D10mm×5mm圆片产品，对于圆片进行5个批次的处理，每批次2000片，每个批次的处理条件一致。每批次中分别选取50片圆片进行磁性能的测量。比较不同批次间产品的性能一致性和稳定性(均值表示50片性能的平均值，极差为50片性能的最大值-最小值)。测试结果见 表10。
表10
Figure PCTCN2015098012-appb-000010
通过上述对比可以看出，采用本申请的制备方法，在实际生产过程中，不同批次间产品的性能一致性和稳定性均好于其他制备方法。
以上所述，仅为本发明的具体实施方式，但本发明的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本发明的保护范围之内。因此，本发明的保护范围应以所述权利要求的保护范围为准。

Claims (14)

  1. 一种R-T-B永磁体的制备方法，其特征在于，包括以下步骤：
    提供组成为R1-T-B组成的成形体，其中R1选自稀土元素Nd、Pr、La、Ce、Sm、Dy、Tb、Ho、Er、Gd、Sc、Y和Eu所组成组中的至少一种，优选至少包含Nd或Pr；T为Fe和/或Co，任选地，T还包含选自由Al、Cu、Zn、In、Si、P、S、Ti、V、Cr、Mn、Ni、Ga、Ge、Zr、Nb、Mo、Pd、Ag、Cd、Sn、Sb、Hf、Ta和W所组成组中的至少一种；
    在900-1040℃对成形体进行预烧结热处理，得到预烧坯；
    采用重稀土化合物对预烧坯进行涂覆、二次烧结和热扩散处理，得到R-T-B永磁体，其中R包含至少一种重稀土元素和至少一种除重稀土元素外的其他稀土元素。
  2. 根据权利要求1所述的制备方法，其特征在于，所述预烧坯的实际密度为理论密度的80～98％，优选为85～97％。
  3. 根据权利要求1～2任一项所述的制备方法，其特征在于，所述重稀土化合物为包含有重稀土氧化物、氟化物、氟氧化物或氢化物，含有重稀土元素的稀土金属间化合物，重稀土R2Fe14B结构化合物，重稀土水合硝酸盐中的一种或多种的混合粉末。
  4. 根据权利要求1～3任一项所述的制备方法，其特征在于，所述重稀土选自Dy、Tb或Ho中的一种或两种以上。
  5. 根据权利要求1～4任一项所述的制备方法，其特征在于，所述成形体由以下步骤获得：
    熔炼：将原料按比例配好，经过熔化，浇铸，得到条带片；
    粗破碎：将条带片进行氢爆处理，得到中碎粉；
    制微粉：将中碎粉进行气流磨制粉，粉末粒度范围为D50＝3～6μm；
    压型：在密封垂直压机中进行压制得到成形体。
  6. 根据权利要求5所述的制备方法，其特征在于，所述中碎粉的氢含量 范围为800-3000ppm，优选为1000-2000ppm。
  7. 根据权利要求1～6任一项所述的制备方法，其特征在于，所述涂覆、二次烧结和热扩散处理采用如下步骤进行：
    涂覆处理：将预烧坯机加工成所需的形状，将重稀土化合物粉末分散于有机溶剂中制得浆液，将加工后的预烧坯浸渍于浆液中，然后将处理后的预烧坯放入密封的料盒中；
    二次烧结和热扩散处理：将料盒放入真空烧结炉中抽真空，之后升温到820-950℃进行二次烧结并同时进行重稀土元素的一次扩散，然后冷却，停止冷却并抽真空后升温到450℃～620℃进行重稀土元素二次扩散，冷却得到R-T-B永磁体。
  8. 根据权利要求7所述的制备方法，其特征在于，所述一次扩散的保温时间为12-24小时，优选为15-20小时。
  9. 根据权利要求7～8任一项所述的制备方法，其特征在于，所述重稀土化合物粉末以0.01-1.0g/ml的比例分散于有机溶剂中。
  10. 根据权利要求7～9任一项所述的制备方法，其特征在于，所述料盒的底部装有10-20％的氧化铝和80-90％的氧化镁的混合粉末。
  11. 一种R-T-B永磁体的制备方法，其特征在于，所述永磁体由以下几个步骤获得，
    制备组成为R1-T-B组成的成形体，其中R1选自稀土元素Nd、Pr、La、Ce、Sm、Dy、Tb、Ho、Er、Gd、Sc、Y和Eu所组成组中的至少一种，优选至少包含Nd或Pr；T为Fe和/或Co，任选地，T还包含选自由Al、Cu、Zn、In、Si、P、S、Ti、V、Cr、Mn、Ni、Ga、Ge、Zr、Nb、Mo、Pd、Ag、Cd、Sn、Sb、Hf、Ta和W所组成组中的至少一种；
    在900-1040℃对成形体进行预烧结热处理，得到预烧坯，预烧坯密度为6.0-7.4g/cm3，优选为6.5-7.3g/cm3；
    采用重稀土化合物对预烧坯进行涂覆、二次烧结和热扩散处理，得到R-T-B永磁体，其中R包含至少一种重稀土元素和至少一种除重稀土元素外的其他稀土元素。
  12. 一种R-T-B永磁体，R包含至少一种重稀土元素和至少一种除重稀土元素外的其他稀土元素，其特征在于，
    在距离磁体表面近1000μm的区域内，晶粒边界处重稀土平均浓度比中心部的重稀土平均浓度至少高0.7wt％。
  13. 根据权利要求12所述的R-T-B永磁体，其特征在于，R包含Nd、Pr、Dy、Tb或Ho。
  14. 根据权利要求12或13所述的R-T-B永磁体，其特征在于，永磁体矫顽力Hcj至少为14MA/m。
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