Study On Preparation And Process Of High Temperature Sintered NdFeB Magnets

In this thesis,the preparation of high-temperature sintered NdFeB and the effect of process on the performance were studied systematically.For the mass production of high-temperature magnet to provide theoretical and technical guidance with the aim of creating higher quality and cheaper motor magnets.Firstly,according to the production process and equipment of sintered NdFeB magnet in Hunan Aerospace magnetoelectric Co.Ltd.and Ningbo Jinke Magnetic Industry Co.Ltd.,this thesis discusses the influence of each process on the magnetic properties and the corresponding testing technology.Elective analysis the factors of temperature effect of sintered NdFeB magnets and then present three ways of using main element substitution,addition of alloying elements to improve the performance of the grain boundary and the preparation process of regulation to improve the magnet temperature performance on the basis of analysis results.By using Dy,Gd and Ho instead of Nd,the composition of the magnet was designed and the influence of component substitution on the properties of the magnet was studied.After comparative analysis,got the conclusion adding Dy,Gd and Ho elements can effectively improve the temperature resistance of the magnet.Analysis the temperature effect of additions element of sintered NdFeB magnets on the grain boundary resistance,research the sintered NdFeB magnetic properties and temperature effect after adding Al,Cu,Ga and Co elements.The proper addition of A1 and Cu elements can improve the magnetic properties of grain boundaries and heat resistance,but the remanence Br of the magnet drop.The effect of the smelting process,oxygen content,powder particle size,sintering temperature and tempering process parameters on the performance and temperature resistance of the magnet was investigated.Using copper roller and proper cooling water temperature can produce casting finer grains.In a certain range,the oxygen content can increase the intrinsic coercive force(Hcj)of the magnet.However it can also improve the magnetic flux irreversible temperature coefficient of the magnet.When the powder particle was more granular,the higher the Hcj of the magnet and the better temperature resistance of the magnet were.Under the premise of ensuring high enough the magnet density,the lower the sintering temperature of magnet temperature resistance is better.t Tempering can improve the microstructure of the magnet,so as to improve the performance of Hcj and the heat resistance of the magnet.