Lost Foam Special Coating

First, we compare the ordinary sand casting coating and lost foam coating to understand lost foam coating role in the lost foam casting.

In ordinary casting process, the coating is used in the surface of cast model cavity.However, in the lost foam casting, the coating is used in the foam plastic model. The main role of lost foam casting coating:

(1) We should improve the foam plastic model’s strength and rigidity and avoid model’s damage or deformation in transportation, sand filling and vibrating processes. In the operation process of foam plastic’s burying model, it is difficult to avoid deformation effect due to impact, no matter how much you pay attention to. Since we can’t prevent this phenomenon,we only try to decrease the effect brought by this phenomenon. The lost foam coating is more enduring impact in the same thickness compared to other coatings.It can protect foam plastic at maximum degree to decrease its deformation degree, even invisible. The picture 1 is the stress and deformation relation curve for foam plastic model with coating and without coating. In this picture, we can see coating can decrease the deformation greatly due to foam plastic model’s stress.

 (2) In the pouring process, the coating layer separates the metal liquid and cast model to avoid the metal liquid into dry sand and to guarantee to get clean surface casting, without burnt-on sand. At the same time, it can prevent the dry sand to flow into the gap between metal liquid and foam plastic model to result in cast model’s sand crushing.

 (3) The coating layer can discharge the product decomposed by foam plastic model(large gas or liquid and so on) into the cast model successfully to avoid air holes produced by casting and carbon defect and so on.

In the pouring aluminum alloy process, the coating should have good adiabaticity to avoid the quick decrease of aluminum liquid temperature due to plastic model burning and heat absorption. And it leads to the defect of insufficient pouring and so on.