The Preparation And Performance Study For Iron Casting In Lost Foam Casting

Lost foam casting technology have high dimensional accuracy,smooth surface and less pollution.The Lost foam coating plays an important role in obtaining the high quality lost foam casting,which is necessary in the process of lost die casting.Mold cast iron production requirements coating composition proportion and performance should be compatible with lost foam casting process,or you will make the casting blowholes,sand inclusion and so on,leading to the decrease of the quality of the castings and higher rejection rate.Therefore,in order to obtain high quality castings,it is necessary to the development of new coatings to meet the production requirements.Based on this,the paper develops two kinds of comprehensive performance of the coating.Through test of refractory aggregate performance under the different ratio of coating,the refractory aggregate proportion of the iron casting coating was determined,at the same time the refractory materials ratio was optimized;By using single factor experiment,the amount of binder and suspending agent change the performance of coating was studied,after that the suitable amount of binder and suspending agent was determine,the particularly study was carried out on the suspending agent sepiolite,also compared the effect about the xanthan gum with sodium bentonite and the xanthan gum with magnesium silicate aluminum compound;Through orthogonal experiment,poor analysis and various performance indicators of coating,determining the optimal proportion of the coating,and the microstructures of the coating were analyzed by scanning electron microscopy(SEM).Experimental study shows:(1)The compound of 30%quartz powder and 70%bauxite as composite refractory aggregate of iron castings LFC coating,with 7.5%talcum powder accessories,its comprehensive performance advantage is obvious.Paint viscosity is moderate,smearing sex good,normal temperature air permeability,smearing,coating strength,moisture resistance and yield thixotropy are the best,to achieve the requirements of LFC coating.(2)The single factor experiment resulted the amount of confirmsodium base bentonite,xanthan gum,magnesium aluminum silicate,PVA,colloidal silica have a great influence on coating performance.When the amount of sodium base bentonite is around 3%;xanthan gum is around 0.3%;magnesium aluminum silicate from 2%to 3%range;PVA at about 1.5%;the amount of silica sol is around 4%,coating has better comprehensive performance.(3)For the amount of the sepiolite is around 10%,suspension property,viscosity of flow cup,coating permeability and coating strength of the overall performance are excellent,at the same time,the addition of sepiolite also play a role in resistance moisture absorption,it provides a possibility to solve the problem of defect of coating hygroscopicity big.(4)The best formula of formulaⅠthat contains sodium base bentonite,xanthan gum,PVA,and silica sol is:quartz powder 30%,bauxite 70%,talcum powde 7.5%,sodium base bentonite 4%,xanthan gum 0.2%,PVA2%,silicon sol 3%,and the right amount of additives and water;The best formula of formulaⅡthat contains xanthan gum,magnesium aluminum silicate,PVA,formulation of silica sol is:quartz powder 30%,bauxite 70%,talcum powder7.5%,magnesium silicate aluminium 3%,xanthan gum 0.2%,PVA 2%,silicon sol 4%,and appropriate amount of additives and water.(5)The coating performance of formulaⅠare as follows:the suspension is 95%,normal temperature permeability is 14.2,the viscosity of flow cup is 13.27s,moisture absorption rate of is 3.23%,smearing and anti-crack reachⅠlevel,density is 1.29 g/cm~3;The coating performance of formulaⅡare as follows:the suspension is 97%,normal temperature permeability is 13.4,the viscosity of flow cup is 13.33s,moisture absorption rate is 3.11%,smearing and anti-crack reachⅠlevel,thixotropic index is 2.612,the density of is1.29 g/cm~3.