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CN-121983404-A - Sintered NdFeB permanent magnet with performance gradient and preparation method and application thereof

CN121983404ACN 121983404 ACN121983404 ACN 121983404ACN-121983404-A

Abstract

The invention discloses a sintered NdFeB permanent magnet with performance gradient, which is characterized in that the intrinsic coercivity is continuously increased in a gradient manner from the core part to the outermost layer of the sintered NdFeB permanent magnet along a non-orientation direction, and the difference value between the intrinsic coercivity of the core part and the intrinsic coercivity of the outermost layer is 1.5-15KOE. The sintered NdFeB permanent magnet meets the requirements of high coercivity in a demagnetizing area, low weight rare earth in a demagnetizing area and good performance buffering. The invention also provides a preparation method and application of the sintered NdFeB permanent magnet.

Inventors

  • XU YANG
  • YAN CHANGJIANG
  • GUO XIAOTIAN

Assignees

  • 宁波科田磁业股份有限公司

Dates

Publication Date
20260505
Application Date
20260324

Claims (10)

  1. 1. The sintered NdFeB permanent magnet with the performance gradient is characterized in that the intrinsic coercivity is continuously increased in a gradient manner from the core part to the outermost layer of the sintered NdFeB permanent magnet along the non-orientation direction, and the difference between the intrinsic coercivity of the core part and the intrinsic coercivity of the outermost layer is 1.5-15Koe.
  2. 2. The sintered neodymium-iron-boron permanent magnet with performance gradient according to claim 1, wherein the heavy rare earth content of the sintered neodymium-iron-boron permanent magnet gradually decreases from the outermost layer to the core in the non-orientation direction, and the difference between the core and the outermost layer heavy rare earth content is 0.2-1.85wt%; Along the orientation direction, the difference value of the heavy rare earth content of the sintered NdFeB permanent magnet from the outermost layer to the core part is 0-0.18wt%.
  3. 3. The sintered neodymium-iron-boron permanent magnet with a performance gradient according to claim 2, wherein the heavy rare earth is Dy or Tb.
  4. 4. The sintered neodymium-iron-boron permanent magnet with the performance gradient according to claim 1, wherein in the sintered neodymium-iron-boron permanent magnet, a green body has a chemical formula of RE x Fe 100-x-y-z B y M z , x is 28-34wt%, y is 0.83-1.05 wt%, and z is 0.5-6wt%, wherein RE is one or more of rare earth Nd, pr, gd, ho, dy, tb, ho, la, Y and at least comprises Nd, and M comprises one or more of Cu, ga, al, co, ti, zr, nb, si elements; the diffusion source is a heavy rare earth alloy or an oxide, fluoride or hydride of the heavy rare earth, and the content of the diffusion source in the sintered NdFeB permanent magnet is 0.2wt% to 3wt%.
  5. 5. The method for producing a sintered neodymium-iron-boron permanent magnet with a performance gradient according to any one of claims 1 to 4, comprising: s1, preparing a green body, wherein the preparation process of the green body comprises the steps of batching, quick setting smelting, hydrogen crushing, air flow grinding and isostatic pressing to obtain the green body; Wherein according to the chemical formula of the green body, RExFe 100-x-y-z B y M z , 28-34wt% of x, 0.83-1.05 wt% of y and 0.5-6wt% of z, RE is one or more of rare earth Nd, pr, gd, ho, dy, tb, ho, la, Y and comprises Nd, M comprises one or more of Cu, ga, al, co, ti, zr, nb, si elements for proportioning; S2, placing a diffusion source on a non-oriented parallel surface of the green body to obtain a blank to be diffused, wherein the diffusion source is heavy rare earth alloy or oxide, fluoride or hydride of heavy rare earth; S3, sintering and aging the blank to be diffused obtained in the step S2; The sintering process is to perform multistage sintering treatment in a vacuum environment, wherein the multistage sintering treatment at least comprises a first stage sintering and a second stage sintering which are sequentially performed, the temperature of the first stage sintering is 200-350 ℃ for 0.5-3h, and the temperature of the second stage sintering is 500-650 ℃ for 0.5-3h.
  6. 6. The method of producing a sintered neodymium iron boron permanent magnet with a performance gradient according to claim 5, wherein the green body has a density of 3.9-4.5g/cm 3 .
  7. 7. The method for preparing a sintered neodymium-iron-boron permanent magnet with performance gradient according to claim 5, wherein the specific step of sintering comprises: Sintering the blank to be diffused in a vacuum sintering furnace, vacuumizing to be less than or equal to 9.9X10 -1 Pa, starting to heat to 200-350 ℃ for sintering for 0.5-3h, heating to 500-650 ℃ for sintering for 0.5-3h, continuously heating to 800-900 ℃ for sintering for 0.5-4h, heating to 1010-1090 ℃ for high-temperature sintering for 8-15 h, heating at a whole process heating speed of <8 ℃ per min, cooling to 700-900 ℃ along with the furnace after high-temperature sintering, and filling argon gas for cooling to room temperature.
  8. 8. The method for preparing the sintered NdFeB permanent magnet with the performance gradient according to claim 5, wherein the aging comprises a secondary heat treatment, vacuumizing to below 10 -1 Pa, wherein the primary heat treatment comprises the steps of directly heating to 870-950 ℃ at a temperature rise speed of less than or equal to 6 ℃ per min and keeping the temperature for 5-20 hours, filling argon after the primary heat treatment and cooling to less than or equal to 60 ℃ and then carrying out the secondary heat treatment, wherein the secondary heat treatment comprises the steps of directly heating to 450-550 ℃ and keeping the temperature for 4-8 hours after the primary heat treatment, and then discharging after cooling to below 60 ℃.
  9. 9. The method for preparing a sintered NdFeB permanent magnet with a performance gradient according to claim 5, wherein, the preparation method of the sintered NdFeB permanent magnet with the performance gradient further comprises machining and electroplating.
  10. 10. Use of sintered neodymium-iron-boron permanent magnets with a performance gradient according to any of claims 1-4 in permanent magnet drive motors.

Description

Sintered NdFeB permanent magnet with performance gradient and preparation method and application thereof Technical Field The invention belongs to the technical field of motor permanent magnets, and particularly relates to a sintered NdFeB permanent magnet with a performance gradient, and a preparation method and application thereof. Background The energy shortage and the low-carbon economy are indispensable in the world, and new energy automobiles are most favored as emerging industries in the global energy conservation and environmental protection fields. The motor driving system is a core component for realizing energy conservation and emission reduction of the new energy automobile, and the sintered neodymium-iron-boron rare earth permanent magnet has excellent magnetic properties such as high remanence, high magnetic energy product, high coercivity and the like, becomes the principal force of the permanent magnet material, and is widely applied to the new energy automobile permanent magnet driving motor. The motor magnetic steel has higher anti-demagnetizing property by adding a large amount of noble rare earth elements such as dysprosium, terbium and the like in the process of preparing the magnetic steel, but the method greatly increases the cost of the motor, and the adoption of the magnetic steel selective area for heavy rare earth infiltration is a better choice for improving the anti-demagnetizing capability of the motor at present. The process of reverse magnetization of the magnet is related to the macroscopic inhomogeneous distribution of the internal demagnetizing field. The micromagnetism simulation result shows that the macroscopic demagnetizing field is mainly distributed on the two magnetic pole surfaces of the oriented magnet, and the grain boundary phase and the crystal grain near the corner position of the magnetic pole surfaces are turned over preferentially in the reverse demagnetizing process. Theoretically, grain boundary diffusion should be used to mainly increase the coercive force of the weak part of the magnet. Aiming at the difference of anti-demagnetization requirements of different positions of a permanent magnet motor in application, enterprises propose to diffuse heavy rare earth grain boundaries at different positions of a magnet to different extents. The invention patent application with publication number of CN113035556A discloses a preparation method of an R-T-B magnet with gradient distribution of magnet performance, rare earth slurries are coated on different positions of different surfaces of the magnet, so that different areas of the magnet generate different gradient coercive force and residual magnetism, residual magnetism reduction caused by uniform coating of a permeable surface is reduced, and the R-T-B magnet is coated on a local position of a non-oriented surface, so that the demagnetizing resistance of corners is improved, and the coercive force of an easily demagnetized area can be effectively improved. The invention patent application with publication number of CN118366742A discloses a neodymium-iron-boron magnet and a preparation method thereof, wherein magnets with different performances are bonded together through glue so as to form gradient magnetic steel, but the bonding procedure is increased, the procedure flow is prolonged, and the performance spans of an easy demagnetizing area and a difficult demagnetizing area are large, so that no performance buffering is realized. According to statistical analysis, the size of the neodymium iron boron magnet with the size of more than 80 percent is designed to be within 10-35mm in one direction (the length L and the width m are both non-orientation directions), the processing flow is shown in a figure 1 (a), the sintered compact L, W and H are ground into four sides, one-side cutting or two-side cutting is carried out, the two-side cutting is processed into a finished product approximate specification of L, W and H, coating or sputtering diffusion is carried out on the thickness H direction, and further, grinding, electroplating treatment and the process flow is long, the efficiency is low, and the period is long. Disclosure of Invention The invention provides a sintered NdFeB permanent magnet with performance gradient, which meets the requirements of high coercivity in a region easy to demagnetize and low weight rare earth in a region difficult to demagnetize and has better performance buffering. The invention provides a sintered NdFeB permanent magnet with performance gradient, which is characterized in that the intrinsic coercivity is continuously increased in a gradient manner from the core part to the outermost layer of the sintered NdFeB permanent magnet along a non-orientation direction, and the difference value between the intrinsic coercivity of the core part and the intrinsic coercivity of the outermost layer is 1.5-15kOe. The core provided by the application is a region with a radius within 1mm and