The role of lost foam coatings in lost foam casting

The role of lost foam coatings is to support and protect the foam model, prevent liquid metal from penetrating sand and sticky sand, absorb decomposition products and allow decomposition gases to pass through the coating, maintain the integrity of the cavity formed after the foam model volatilizes, and keep the liquid metal heat from dissipating quickly. Therefore, the use of lost foam coating can reduce the surface roughness of lost foam castings, ensure the accuracy of castings, and reduce or prevent casting sand sticking, sand holes, pores, metal penetration, cold partition, pouring, carbon deposits and other defects. Therefore, the lost foam coating should have sufficient refractory, certain mechanical strength, appropriate thermal insulation and thermal conductivity, suitable air permeability and the ability to absorb liquid decomposition products, smooth surface, sufficient brushing performance, and no chemical reaction with the foam model.