A method for preparing sintered NdFeB permanent magnets with high coercive force

Abstract

The invention discloses a magnet preparation method for improving the coercive force of sintered NdFeB permanent magnets, which comprises the steps of: a) adopting vacuum quick-setting technology to prepare NdFeB alloy magnetic material blanks; b) sequentially inverting the above blanks Corner-cleaning treatment-water washing-surface modification-water washing treatment; c), the treated permanent magnet is placed in the electroplating of nickel / heavy rare earth composite coating; d), the sintered NdFeB magnetic material is placed in a vacuum heat treatment furnace Carry out heat treatment. By adopting the technology of compounding heavy rare earth on the nickel plating layer of the present invention, the effective utilization of heavy rare earth solid matter can be realized, and the benefit maximization of rare earth resources can be realized. At the same time, it can ensure that the proportion of heavy rare earth content in the composite coating is stable, and the composite coating has no easily decomposed and volatile substances polluting the vacuum heat treatment system in the subsequent heat treatment process, so that the infiltration of heavy rare earth production equipment can be sustained and stable, and the application range of the process technology is wider. It is easier to promote the application in the enterprise.

Description

technical field [0001] The invention relates to the field of magnetic materials, in particular to a method for preparing a sintered NdFeB permanent magnet with high coercive force. Background technique [0002] With the rise of the hybrid electric vehicle (HEV) industry, sintered NdFeB magnets for automobiles require magnets with high coercive force and high temperature resistance. The anisotropy field of sintered Nd-Fe-B compound, that is, the theoretical limit value of coercive force is 7.3T, but the actual coercive force of Nd-Fe-B permanent magnet alloy is usually only about 1 / 3 of its theoretical value. The coercive force of the magnet can be increased by adding alloying elements to refine the grains and improving the boundary structure by tempering heat treatment process. due to Dy 2 Fe 14 B and Tb 2 Fe 14 The anisotropy fields of B are 15 and 21T, respectively, much higher than that of Nd 2 Fe 14 7.3T of B, so the most effective way to increase the coercivity o...

AI Technical Summary

Problems solved by technology

The different ways of adding Dy have a great influence on the performance. One is direct alloying, that is, metal Dy is added when the master alloy is smelted. However, Dy 2 Fe 14 The saturation magnetization of B is only about 0.7T, less than Nd 2 Fe 14 Half of B's ​​1.60T, so adding Dy to increase the coercive force will lead to a decrease in magnetization

The second addition method - double alloy method, that is, Nd-Fe-B powder and Dy or Dy 2 o 3 The magnet is prepared by mixing the powder, Dy is mainly distributed on the boundary, the coercive force increases and the magnetization intensity does not change much, but the amount of precious metal Dy is large, which is uneconomical

However, this method has disadvantages such as low production efficiency, high cost, difficulty in mass production, and large investment in equipment.