The Preparation And Performance Study For Aluminum,Magnesium Alloys Lost Foam Casting Coating

Lost foam casting is an important method to produce aluminum alloy and magnesium alloy parts,among them,casting coating plays a vital role in the quality of castings,especially it can improve casting surface finish and dimensional accuracy,and reduce the defects of casting pinholes,cold lap,sticky sand,sand hole,carbon deposition,etc.But up to now,there is no appropriative aluminum alloy and magnesium alloy LFC coatings,this paper is to develop a comprehensive performance of two kinds of coatings.In this paper,through testing the properties of the coatings with different refractory aggregate ratio,the refractory aggregates suitable for aluminum alloy and magnesium alloy were determined,and the proportion of refractory aggregate was optimized;Through the single factor experiment,the change of the properties of the coating after the addition of the binder and the suspending agent was studied,in particular,the new suspension agent magnesium aluminum silicate,sodium bentonite and sodium carboxymethyl cellulose,sodium bentonite and xanthan gum were compared;Through orthogonal test,range analysis and the performance index of the coating,the best ratio of the coatings were determined,and the microstructures of the coatings were analyzed by scanning electron microscope.Experimental study shows:(1)For aluminum alloy LFC coating,the proportion of 70% diatomite and 30%mullite as composite refractory aggregate,suspending agent of 6%sodium bentonite ? 0.5%CMC,binder 6% PVA?1.5% water glass,proper amount of additives and water,forming the best formula.Its comprehensive performance can meet the requirements of LFC coating.(2)The addition of a new kind of suspending agent magnesium aluminum silicate has agreat influence on the rheological property and suspension property of aluminum alloy casting coating.When the dosage of magnesium aluminum silicate range from 0.5% to 3%,the yield value with the increase of amount of magnesium aluminum silicate increased,the thixotropic Index C also increased with the addition of magnesium aluminum silicate rang from1% to3%,rheological property of the coating was improved.Furthermore,there is a positive correlation between the suspension and yield value.Ultimately,It is concluded that the best addition amount of magnesium aluminum silicate range from 2% to 3%,and the coating exhibits excellent suspension and rheology,the suspension is more than 96%,thixotropic Index c is no less than 1.343.(3)For magnesium alloy LFC coating,the proportion of 70% light of MgO,30% talcum powder as composite refractory aggregate,suspending agent of 2% sodium bentonite,0.3%xanthan gum,binder 0.05% PVM?8% water glass,4% zinc borate,proper amount of additives and water,forming the best formula.Its comprehensive performance can meet the requirements of EPC coating.(4)In the same amount of CMC and xanthan gum,when the amount of the two components range from 0.3% to 0.7%,the addition of xanthan gum coating suspension,compressive strength and rheological properties are better than the CMC coating,The viscosity of the flow cup was also significantly higher than that of CMC,but when the amount of the two component were both 0.1%,the comprehensive properties of the coatings added with xanthan gum were inferior to those of CMC.