Manufacturing method for improving sintered NdFeB magnet coercive force

Abstract

Provided is a manufacturing method for improving sintered NdFeB magnet coercive force. On the basis that the original composition ratio of a sintered NdFeB magnet is not changed, parameters of the rapid hardening process for magnet casting are changed to achieve secondary jet milling so that the average particle size of particles of the magnet can be less than or equal to2.5um, after lower-temperature sintering is controlled between 1020 DEG C and 1035 DEG C for 3.5-5.0 hours, aging treatment is carried out under 450-600 DEG C for 4-6 hours, the powder size of the magnet is lowered after rapid hardening casting and secondary jet milling technologies, surface activity is increased, the particles are easily compacted in a sintered mode, compactness of the magnet can be guaranteed and meanwhile grains can be prevented from rapidly growing up through combination of the lower-temperature sintering, magnetic performance of the magnet is improved, the coercive force is increased by 2-3kOe on average, and the price performance ratio of the magnet is remarkably increased.

Description

technical field [0001] The invention relates to a method for manufacturing a permanent magnet, in particular to a method for improving the coercive force of a sintered NdFeB magnet. Background technique [0002] The research results show that the coercive force of sintered NdFeB magnets decreases with the increase of NdFeB grains in the magnets. At present, most production enterprises adopt the technical process of SC (quick setting) + HD (hydrogen breaking) + JM (jet milling). The powder is a single crystal powder with an average particle size of about 3.0-4.0um. The powder is prepared into sintered NdFe after molding and sintering. boron magnet. Since the original average particle size of the powder is 3-4um, after sintering and growing, the average grain size of NdFeB will reach 8-12um. With the application of sintered NdFeB in the field of motors, there is a high coercive force requirement for magnets. Generally, companies usually increase the anisotropy of the main ph...

AI Technical Summary

Problems solved by technology

With the application of sintered NdFeB in the field of motors, there is a high coercive force requirement for magnets. Generally, companies usually increase the anisotropy of the main phase by adding Dy, Tb and other heavy rare earth elements to increase the coercive force of magnets. However, Dy, Tb element is expensive, which will greatly increase the material cost of the magnet

By adding elements such as Al, Cu and Co to refine the grain size of the main phase, increase the number of effective boundaries, and by adding metal oxides such as Dy, the coercive force of the magnet can be improved by using the boundary pinning effect of the oxide. The above methods are all Alloy elements need to be added, which will reduce other indicators of the magnet to a certain extent, such as a decrease in the magnetic energy product. Therefore, without changing the basic composition of the NdFeB magnet, how to improve the coercive force of the sintered NdFeB magnet becomes One of the technical problems that the industry must research and solve, CN102969110A proposes two methods of auxiliary heating and ionization to make dysprosium, terbium and dysprosium-terbium alloys volatilize between 900-1100°C and quickly penetrate into the intergranular magnet, thereby improving the coercivity This method also needs to add heavy rare earth metals, which cannot achieve the purpose of reducing the cost of magnets

Images