Bonder And Optimized Investigation On Preparation Process Of The Bonded NdFeB Magnets

In recent decades,the market demand of the bonded NdFeB magnets has grown notably because of high magnetic and mechanical performance and good machinability.In this thesis,the melt-spinning NdFeB powder bonded magnets have been prepared with different process parameters,their magnetic properties and compressive strength have been measured,and their microstructure has been investigated by XRD,SEM.Consequently,different epoxy resin,coupling agents and the effects of preparing process parameters on the properties of magnets have been discussed.Epoxy resin is the most useful and typical bonder of bonded NdFeB magnets by mould pressing.Different epoxy resin have different epoxy model number,different mezzo epoxy,bonded magnets represent different performance.It is shown that lower mezzo epoxy magnets cover magnetic powder weaker,magnets gap more,lower density,lower magnetic property;higher mezzo epoxy,water higher within thermosetting crosslinking reaction,lower magnetic property,but higher body conformation crosslinking conformation,higher compressive strength;mezzo epoxy magnets,higher density,lower corrosion,best magnetic property.The paper describe E₅₁,E₄₄ and E₁₂ three epoxy resin,through large quantity experiment research,best NdFeB bonded magnets preparation process,E₁₂ bonded magnets property is lower,mezzo epoxy E₄₄ magnets express the better magnetic properties and compressive strength.Prior treatment of NdFeB powders is vital to the preparation of bonded NdFeB magnets.Adopt silane KH550 coupling agents on magnets powder surface,test is shown that coupling agents are used fewer,non-dispersion,lower effect.With higher coupling agents,magnets uniform coating,better magnetic density,better magnetic property and compressive strength.When content of coupling agents is 0.8wt%,the best magnetic properties have been obtained.Beyond this value,lower magnet powders flow property,lowder associativity between magnet particle and binder,magnets density is lower,magnetic property and compressive strength are lower.The bonded magnets,which have not been thermoset,have a lower compressive strength and can't be used in practical.Thermosetting process is in favor of not only pervasion of binder,but also soakage of powder.It is shown that the bonded magnets which have been thermoseted have a lower magnetic property,high thermosetting temperature,long thermosetting time, epoxy resin appear ageing,magnetic density will reduce,magnetic property will reduce.Properties of bonded magnet are well when 150℃for 2h.