Method for preparing dense fine-grain neodymium iron boron sintering magnet

Abstract

The invention belongs to the field of rare earth permanent magnetic materials, and particularly provides a method for preparing a dense fine-grain neodymium iron boron sintering magnet. The method for preparing the dense fine-grain neodymium iron boron sintering magnet is characterized in that vacuum pre-sintering is conducted before high-pressure argon hot isostatic pressure sintering, the sintering temperature is kept between +5 DEG C and 50 DEG C of the eutectic temperature of a 2:14:1 phase and a phase rich in neodymium, and the pressure range is between 2MPa to 20MPA in the isostatic pressure sintering process. The method particularly comprises the steps that after ingot casting, powder preparation and orienting profiling are sequentially conducted on neodymium iron boron alloy, the neodymium iron boron alloy is placed in a sintering furnace, after the high vacuum condition is met, the neodymium iron boron alloy is heated, the sintering furnace is vacuumized continuously, the high vacuum environment is created through stage heating and control over the heating speed, when the required sintering temperature and the required vacuum degree are achieved, the neodymium iron boron alloy is pre-sintered for a certain time in a vacuum mode, then, vacuumization is stopped, high-purity argon is gradually conveyed to the sintering furnace so that isostatic pressure can be exerted, the temperature is continuously kept for a certain time, rapid cooling is conducted, and therefore the product is obtained. The method for preparing the dense fine-grain neodymium iron boron sintering magnet has the advantages that a dense and fine-crystalline structure can be sintered, shrinkage of the product is even, properties are identical, operation is simple, and the method is suitable for industrialized production.

Description

technical field [0001] The invention belongs to the field of rare earth permanent magnet materials, in particular to a preparation method of a dense fine-grained NdFeB sintered magnet. Background technique [0002] Sintered NdFeB permanent magnet materials have become the core functional materials in the fields of electric power, telecommunications, automobiles, computers, biomedicine and household appliances. Coercive force is the key performance index of NdFeB materials. The reasons are: First, the global attention and promotion of new energy vehicles and wind power generation industries will have a major impact on high-end rare earth permanent magnets. Direct drive permanent magnet units for wind power generation High coercive force sintered NdFeB magnets should be used in large quantities in drive motors of new energy vehicles and new energy vehicles; second, if the coercive force Hcj is greatly increased, it can drive the improvement of other performances such as Hk / Hcj...

AI Technical Summary

Problems solved by technology

[0006] The purpose of the present invention is to solve the problem of uneven shrinkage, inconsistent performance and outflow of neodymium-rich liquid phase caused by uneven sample temperature in the high-pressure argon hot isostatic pressing sintering process. The sintering temperature is at the eutectic temperature of the 2:14:1 phase and the neodymium-rich phase + 5°C—-50°C), and the vacuum is pre-fired for a period of time, so that the central part of the furnace center sample and the bulk sample are at the same temperature as the periphery to achieve the product Uniform shrinkage and consistent performance, and close the pores on the surface of the compact to prevent the entry of high-pressure argon gas, resulting in the outflow of the neodymium-rich liquid phase, reducing the density and orientation