Grain boundary diffusion method for improving properties of sintered NdFeB magnets

A technology of grain boundary diffusion and neodymium iron boron, applied in the direction of magnetic materials, magnetic objects, inorganic materials, etc., can solve the problems of increasing the production cost of magnets, natural resource pressure, insufficient diffusion depth of diffusion process, and reducing the magnetization intensity of magnets. Achieve the effects of good fluidity, wide applicability, and large diffusion depth

Active Publication Date: 2015-03-04
SHANGHAI JIAO TONG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the use of dysprosium to replace neodymium has the following disadvantages: on the one hand, the reverse magnetization coupling between dysprosium atoms and iron atoms reduces the magnetization of the magnet; on the other hand, dysprosium reserves in nature are much lower than that of neodymium, and its market price is much higher than that of neodymium. , the addition of dysprosium greatly increases the manufacturing cost of the magnet and the pressure on natural resources
However, this treatment method still has the problem of insufficient diffusion depth in the current common diffusion process.

Method used

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  • Grain boundary diffusion method for improving properties of sintered NdFeB magnets
  • Grain boundary diffusion method for improving properties of sintered NdFeB magnets
  • Grain boundary diffusion method for improving properties of sintered NdFeB magnets

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Effect test

Embodiment 1

[0033] 1) Set the size to 4×7×27mm 3 The sintered samples were polished off the surface oxide layer with sandpaper, and ultrasonically cleaned with alcohol.

[0034] 2) Put a piece of Nd 63.5 Cu 30 Fe 6.5 The alloy sheet is placed under the magnet prepared in step 1, and the alloy sheet and the magnet are placed in the middle of the hot-pressing mold block, and the alloy sheet and the mold, and the magnet and the mold are separated by graphite paper.

[0035] 3) Vacuum the hot press furnace to 1×10 -2 Pa, run the heating program, wait until the temperature reaches 800°C, apply a pressure of 10Mpa, the pressure direction is parallel to the C axis, keep the pressure for 6h, cool to room temperature with the furnace, and take out the sample.

[0036] 4) Put the diffused sample into high vacuum (-3 Pa) Anneal in a tube furnace at 500°C, hold for 3 hours, and cool to room temperature with the furnace after annealing.

Embodiment 2

[0038] 1) with embodiment 1 step 1;

[0039] 2) with embodiment 1 step 2;

[0040] 3) Vacuum the hot press furnace to 1×10 -2 , run the heating program, wait until the temperature reaches 750°C, apply a pressure of 30Mpa, the pressure is parallel to the C axis, keep the pressure for 3h, cool to room temperature with the furnace, and take out the sample;

[0041] 4) Put the diffused sample into high vacuum (-3 Pa) Anneal in a tube furnace at 450°C, hold for 6 hours, and cool to room temperature with the furnace after annealing.

Embodiment 3

[0043] 1) with embodiment 1 step 1;

[0044] 2) with embodiment 1 step 2;

[0045] 3) Vacuum the hot press furnace to 1×10 -2 , run the heating program, when the temperature reaches 750°C, apply a pressure of 40Mpa, hold the pressure for 3h, cool down to room temperature with the furnace, and take out the sample;

[0046] 4) Put the diffused sample into high vacuum (-3 Pa) Anneal in a tube furnace at 550°C, hold for 2 hours, and cool to room temperature with the furnace after annealing.

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Abstract

The invention relates to a grain boundary diffusion method for improving properties of sintered NdFeB magnets. The grain boundary diffusion method comprises the following steps of stacking sintered NdFeB magnets and diffusion alloy sheets together and placing in a hot-pressing furnace; vacuumizing the hot-pressing furnace until the vacuum degree reaches a set value, heating the hot-pressing furnace, and when the temperature of the hot-pressing furnace reaches a set value, beginning to exert a pressure and maintaining the pressure and putting the diffused sample into a high-vacuum furnace for annealing, wherein the diffusion alloy sheets are low-melting-point eutectic diffusion alloys and are represented by R-TM, R is one or more of Sc, Y, La, Ce, Pr or Nd and TM is one or more of Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn. Compared with the prior art, the sintered NdFeB magnets modified by the pressure diffusion method, which is provided by the invention, have the advantages of large diffusion depth of a diffusion agent, uniform distribution of grain boundary phases, high coercivity and the like, especially, low-melting-point diffusion alloys designed by the invention are free of expensive heavy rare earth element dysprosium and thus the cost of the raw materials is relatively low, the diffusion temperature is low and the energy consumption in the diffusion process is small.

Description

technical field [0001] The invention relates to a grain boundary diffusion method for improving the magnetic properties of sintered NdFeB, belonging to the technical field of rare earth permanent magnet materials. Background technique [0002] The third-generation permanent magnet material with the reputation of "Magnetic King" - neodymium iron boron (NdFeB) has been a research hotspot in academia and industry since it came out. At present, most of the high coercive force NdFeB magnets are prepared by replacing the heavy rare earth element dysprosium with neodymium. The content is as high as 10wt%. However, the use of dysprosium to replace neodymium has the following disadvantages: on the one hand, the reverse magnetization coupling between dysprosium atoms and iron atoms reduces the magnetization of the magnet; on the other hand, dysprosium reserves in nature are much lower than that of neodymium, and its market price is much higher than that of neodymium. , The addition ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C23F17/00H01F1/057H01F1/08
Inventor 陈夫刚张澜庭张铁桥王静
Owner SHANGHAI JIAO TONG UNIV
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