Development Of Mold Coatings For Stainless Steel Casting

The quality problem of the large stainless steel castings has inspired more and moreextensive attention because of the expansion of stainless steel castings application and thecontinuous improvement of casting quality requirements. Mold coating is an effectivemeasure to improve the quality of stainless steel casting unit, but it still has the problem ofthe adhering sand and the price of it is very high. To solve these problems, this paper hascarried out the development of the stainless steel with casting coating. Three kinds ofstainless steel coating have been developed by research Magnesia powder coating, Magnesiapowder and corundum powder composite coating and Magnesia powder, corundum powderand zircon powder composite coating. These coatings have solved the quality problem ofstainless steel castings’ surface.In this study, single level experiments have been used firstly to optimize magnesiapowder coating. Silicon sol as high temperature adhesive coating has been used to ensure thehigh temperature strength. On the basis of this matching, a certain proportion of whitecorundum powder is added to form a composite aggregate, and the best proportion ofcomposite coating is obtained under the pouring temperature by using orthogonal test.Finally, adding the zircon powder to make three aggregates composition. This kind ofcomposition made the coating have various aspects of performance to pour good stainlesssteel casting, and the optimal production costs less than50%compared with zircon powdercoating.Using X-ray diffraction (XRD) and scanning electron microscope (SEM) to analyze thedifferent composition of sintering phase. Through the experiment of the comprehensive tests,the ratio of three kind of coatings have been determined. And then the pour experiment hasbeen used to verify the quality of coating The results show that magnesia powder coating’sweight ratio of various components is: magnesia powder: ethanol: lithium base bentonite:PVB: silicon sol: phenolic resin=100:105:9:3:9:2. When white corundum refractory addedto make a composite coating, MgAl2O4structure of mineral will appear under pouringtemperature. And the ratio of magnesia powder and alumina powder is7:3. The addition ofsilica sol can improve the high temperature strength of coating and prevent thermal crack. The optimized coating ratio of solids is: lithium base bentonite: phenolic resin: PVB: siliconsol: refractory aggregate=6:35:0.8:3.5:100, the coating’s viscosity is7s. Zircon powder canproduce zirconium silicate at high temperature, the addition of zircon powder can makecomposite aggregate sintering ability enhancement, the powder content should control in20%. And in this way, the surface of the stainless steel casting is perfect.