Method for preparing high-coercivity neodymium-iron-boron magnet through grain boundary diffusion

Abstract

The invention discloses a method for preparing a high-coercivity neodymium-iron-boron magnet through grain boundary diffusion, and belongs to the field of magnetic materials. Low-melting-point metal is one of Ga, Zn and Sn, low-melting-point alloy is prepared from R-M, R is one or more of La, Ce, Pr, Nd, Gd, Tb, Dy, Ho and Y, and M is one or more of Cu, Al, Ga, Sn and Ag. The method comprises the process steps that the surface of a neodymium-iron-boron magnet is cleaned firstly, then the magnet is subjected to vacuum preheating, and the magnet is placed in a vacuum melting metal or alloy solution for hot dip coating to achieve surface coating; finally, the neodymium-iron-boron magnet obtained after hot dip coating is subjected to diffusing heat treatment and subsequent annealing treatment, the boundary structure and grain boundary phase distribution of the magnet are improved, and the needed high-coercivity neodymium-iron-boron magnet is obtained. The magnet surface coating is even and high in binding strength, and uniformity of the grain boundary diffusion process and the structure and performance of the magnet are promoted; meanwhile, the thickness of an attached layer on the surface of the magnet can be flexibly controlled by controlling dip coating time and taking-out speed, and waste of diffusion source metal or alloy is avoided; the heat dip coating process is continuous, fast and suitable for volume continuous production.

Description

technical field [0001] The invention belongs to the field of magnetic materials, and particularly provides a method for preparing a high-coercivity neodymium-iron-boron magnet by grain boundary diffusion. Background technique [0002] The global attention and promotion of new energy vehicles and wind power industries will have a major impact on high-end rare earth permanent magnets. Both direct-drive permanent magnet units for wind power generation and drive motors for new energy vehicles will use high-coercivity sintered NdFeB in large quantities. magnet. As we all know, in order to increase the coercive force of NdFeB sintered magnets, it is a very effective method to partially replace Nd in the magnets with heavy rare earth elements such as Dy / Tb. However, if the traditional alloying method is used, a large amount of Dy / Tb needs to be added to achieve high coercive force, which not only reduces the remanence and magnetic energy product, but also increases the production ...

AI Technical Summary

Problems solved by technology

In the actual preparation process, the adhesion ability of the brushing method is poor. If you want to increase the adhesion ability by spraying, the powder particle size must be below 10 microns. For alloys, it is quite difficult to prepare corresponding low-oxygen powders.

Due to the high vapor pressure of dysprosium, vapors tend to adhere to the heating element and damage it

Although the related equipment has an inner liner to isolate and protect the components, the waste of Dysprosium is still unavoidable

Magnetron sputtering, electroplating and electrophoresis are expensive and difficult to produce on a large scale

The rolling adhesion method is easy to cause damage to the magnet

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