Research On Insulation Coating And Bonding Of Iron-based Magnetic Powder Using Layered Silicate

The most critical processes for preparing metal soft magnetic powder cores is insulation coating which can effectively increase the resistance among magnetic powders,and decrease the eddy current loss of magnetic powder cores.Layered silicate can effectively improve the magnetic properties of the metal soft magnetic powder core,due to its high resistivity and chemical inactivity to metal magnetic powders.At present,silicate is widely used in industry,but it has not been researched as a coating agent for metal soft magnetic powder core.Therefore,in the thesis,layered silicate was used as the coating agent for metal magnetic powder to prepare an iron-based magnetic powder core with excellent performance.The methods and affecting factors for dispersing layered magnesium aluminum silicate,kaolin,mica and attapulgite were studied.It is indicated that the p H value of the solution is the main factor affecting the dispersibility of layered silicates.When p H=7 for the aqueous solution,magnesium aluminum silicate forms a stable inorganic gel.Kaolin can be dispersed better under alkaline conditions.However,both mica powder and attapulgite are poorly dispersed.Under relatively optimal dispersing conditions,the layered silicate covers on the surface of the iron-silicon alloy magnetic powder.Meanwhile,the magnetic powder surface coated with magnesium aluminum silicate is the most uniform and dense.The influence of the dosage on the performance of the 172060 iron-silicon magnetic powder core was studied,using the dispersed magnesium aluminum silicate to coat the iron-silicon alloy magnetic powder.With the increase of the dosage of the coating agent,the effective permeability of the magnetic powder core gradually decreases,the Q value increases,the DC superimposition characteristic becomes better,and the power loss decreases.When the amount of magnesium aluminum silicate added is 1.4 wt%,the effective permeability of the magnetic powder core is about 60,the external magnetic field is 100 Oe,the DC superposition percentage of the magnetic powder core reaches 78.3%,the frequency f=100 k Hz,the Q value reaches the maximum value of 83.When f=50 k Hz and B_m=0.1 T,its power loss is only 567 m W/cm~3,compared with the power loss of the kaolin coated magnetic powder core of 728 m W/cm~3,the power loss is reduced by about 22.1%;the DC superposition characteristics,quality factors and power loss of the magnesium aluminum silicate coated magnetic powder core are better than those of the phosphate coatings,but they both show good frequency stability,which is compared with traditional phosphate coatings.When magnesium aluminum silicate is used as the coating agent for gas atomized iron-silicon alloy magnetic powder,the most suitable binder for the magnetic powder core is silicone resin.Its dosage has no effect on the magnetic properties of the magnetic powder core,but it can effectively improve its mechanical properties.When the amount of silicone resin added is 0.4wt%,the maximum load reaches 137 N.The investigations on the insulation coating of iron-nickel alloy magnetic powder has been scarcely reported.In this thesis,the magnesium-aluminum silicate inorganic gel is used to coat the iron-nickel alloy magnetic powder,and the effects of the coating agent and the binder on 270060 magnetic powder core's comprehensive performance is studied.Results show that the amount of magnesium aluminum silicate involved in the coating on the surface of the magnetic powder increases,as the amount of coating agent increases from 0.8wt%to 1.2wt%.When the amount of the coating agent is 1.0wt%,the surface of the magnetic powder is evenly and densely covered without excessive materials,and the pressed magnetic powder core has excellent magnetic properties,but the maximum load is low.When water glass and silica sol composite is used as the binder for the magnetic powder core,the amount of water glass and silica sol are both 1.0wt%,the overall performance of the magnetic powder core is best,and the effective permeability of the magnetic powder core maintains good frequency stability in the frequency range of 1?1000 k Hz.When the external magnetic field intensity H=100 Oe,the DC superposition percentage of the magnetic powder core is 80.3%.When f=50 k Hz and B_m=0.1 T,the power loss of the magnetic powder core is 358 m W/cm~3,and the maximum load is 371 N.