Permeability of coating in the lost foam casting process

This study measured the pressures developed during a filling experiment usi ng molten grey iron in the lost foam casting (LFC) process. The measured pr essures included back pressure and permeable pressure. The back pressure is created in-mould from the metal-foam interface. The permeable pressure was measured on the mould side of the coating, when gases introduced from the decomposing EPS were permeating through the coating. The permeable pressure reflected the permeability of the coating while filling molten iron. Varia bles, which included particle sizes, types of binders, weight per cent of b inder in coatings, influenced the permeability of coating at room temperatu re and at casting temperature. Coatings made from flaky alumina developed a greater total length of pore c hannels than those made from angular silica, Increasing the particle size o f the refractory increased the permeability of the coating at room temperat ure. The highest permeable pressure was measured when the particle size was 74 mu m and acrylic resin was used as a binder. The optimum binder content was less than 1% for flaky alumina and acrylic resin binder, The optimum c oating thickness was less than 0.5 mm to develop a maximum permeable pressu re associated with a minimum back pressure in the mould.