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Method for preparing high-performance sintered Nd-Fe-B magnet by using two-step grain boundary diffusion technique

A grain boundary diffusion, NdFeB technology, applied in magnetic objects, solid diffusion coating, metal material coating process, etc., can solve the problem of high concentration gradient of heavy rare earth elements on the surface of magnets, consumption of heavy rare earth elements, and grain growth. and other problems, to avoid abnormal growth of crystal grains and improve the utilization rate.

Inactive Publication Date: 2017-10-17
UNIV OF SCI & TECH BEIJING
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  • Summary
  • Abstract
  • Description
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  • Application Information

AI Technical Summary

Problems solved by technology

At present, the main problem of the grain boundary diffusion technology is that the concentration gradient of heavy rare earth elements on the surface of the magnet is high, and the bulk diffusion is severe, forming a thicker shell structure, which consumes a large amount of heavy rare earth elements and causes waste; and the diffusion of thicker magnets requires Diffusion at high temperature for a long time, resulting in abnormal grain growth

Method used

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  • Method for preparing high-performance sintered Nd-Fe-B magnet by using two-step grain boundary diffusion technique
  • Method for preparing high-performance sintered Nd-Fe-B magnet by using two-step grain boundary diffusion technique
  • Method for preparing high-performance sintered Nd-Fe-B magnet by using two-step grain boundary diffusion technique

Examples

Experimental program
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Effect test

Embodiment 1

[0018] Select an N50 commercial magnet, process it into a sample with a size of φ8mm×5mm, and clean the surface. The composition is Pr prepared by the quick-setting process 50 Tb 20 Cu 15 Al 15 (atomic percent) alloy thin strip (30 μm thick) as a diffusion source; directly covering the upper and lower surfaces of the magnet after surface cleaning; place the treated sample in the furnace, and evacuate to (3-5)×10 -3 Pa is subjected to a first-stage heat treatment, that is, holding at 700°C for 6h; then performing a second-stage heat treatment, that is, holding at 900°C for 1h; and finally performing a third-stage heat treatment at 500°C for 2h under vacuum annealing; to obtain a high coercive force sintered NdFeB magnetic material . The coercive force of the magnet is increased from 12.2kOe before grain boundary diffusion to 22.5kOe after diffusion, while the remanence hardly decreases. The magnetic properties of the original magnet and the diffused magnet are as follows: ...

Embodiment 2

[0021] Select an N50 commercial magnet, process it into a sample with a size of φ8mm×5mm, and clean the surface. The composition is Pr prepared by the quick-setting process 60 Tb 10 Cu 10 Al 10 co 10 (atomic percent) alloy thin strip (30μm thick) as a diffusion source; directly cover the upper and lower surfaces of the magnet after surface cleaning; place the treated sample in the furnace, and evacuate to (3-5)×10-3Pa Carry out the primary heat treatment, that is, hold at 650°C for 6 hours; then carry out the second stage of heat treatment, that is, hold at 900°C for 1 hour; finally carry out the third stage of heat treatment at 500°C for 2 hours in vacuum annealing; obtain high coercive force sintered NdFeB magnetic materials. The coercive force of the magnet increases from 12.5kOe before grain boundary diffusion to 20.5kOe after diffusion, while the remanence hardly decreases. The magnetic properties of the original magnet and the diffused magnet are as follows:

[002...

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Abstract

The invention discloses a method for preparing a high-performance sintered Nd-Fe-B magnet by using the two-step grain boundary diffusion technique, and belongs to the field of rare earth permanent magnetic materials. The method includes: laying a low-melting-point alloy diffusion source R1-R2-TM thin band on a surface of a clean commercial sintered Nd-Fe-B magnet, wherein the R1 is randomly selected from La, Ce, Pr, and Nd, the R2 is selected from at least one of Dy and Tb, and the TM is selected from at least one of Cu, Al, Ti, Zn, Co, Ni, and Fe; performing heat treatment at the temperature of 650-800 DEG C for 6-24 hours, and allowing Tb / Dy to diffuse toward the inner part of the magnet along a grain boundary; performing heat treatment at the temperature of 850-950 DEG C for 1-4 hours, allowing the Tb / Dy enriched in a grain boundary phase to diffuse toward a surface layer of grains, and forming a Tb / Dy-rich shell structure; performing annealing at the temperature of 450-550 DEG C for 1.5-2.5 hours, and further adjusting a boundary structure; and finally acquiring the high-performance sintered Nd-Fe-B magnet. The advantages of the method are that the Tb / Dy is fully used to reinforce a grain surface transition layer so as to improve the coercivity; the time of the high temperature heat treatment is shortened, and energy can be saved; abnormal growth of grains can be avoided; and the method is suitable for thick magnets.

Description

technical field [0001] The invention relates to a method for preparing a high-performance sintered NdFeB magnet by using a two-step grain boundary diffusion process, and belongs to the field of rare earth permanent magnet materials. Background technique [0002] The sintered Nd-Fe-B series alloy is called "magnet king" because of its high remanence, coercive force and maximum energy product, and excellent comprehensive performance. Since its inception, it has been widely used in electronic information, medical equipment, wind power and automobile industries. After decades of development, the magnetic properties of sintered Nd-Fe-B permanent magnet alloys have been continuously improved, and the remanence Br and the maximum energy product (BH)max have approached the limit value, but the actual correction of sintered Nd-Fe-B The coercive force is only about 30% of the theoretical value, and considering the use environment of sintered NdFeB magnets, it is usually required that...

Claims

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Application Information

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IPC IPC(8): H01F41/02H01F1/057C23C10/30
CPCH01F41/0293C23C10/30H01F1/057
Inventor 包小倩卢克超陈贵贤高学绪李纪恒
Owner UNIV OF SCI & TECH BEIJING
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