Overview of mold filling characteristics of lost foam casting

The main difference between lost foam casting and sand casting is that the molding process of lost foam casting no longer has an empty cavity, but is replaced by EPS pattern. Under the influence of high-temperature liquid metal, EPS is pyrolyzed and gasified in the mold, resulting in the physicochemical phenomenon of solid-liquid-gas phase. So the casting process produced by lost foam casting is completed by mutual restriction and interaction of liquid metal, molding sand and mold. Because the mold cavity is replaced by EPS pattern, the filling process of liquid metal is very different from that of sand mold casting, which changes the heat exchange between high-temperature liquid metal filling and sand mold. There are very complex physical and chemical reactions, heat transfer and mass transfer phenomena between metal liquid and foam pattern. These include:

(1) There is a series of heat transfer processes in the air gap between high temperature metal and foam pattern. There are heat conduction and thermal radiation between molten metal and refractory coating, metal liquid and cavity sand, metal liquid and EPS pattern.

(2) The products (liquid or gas) of EPS pattern pyrolysis and gasification at high temperature in lost foam casting have a series of physicochemical reactions with liquid metal, refractory coating and sand box, resulting in mass transfer.

(3) The decomposition and gasification of EPS pattern leads to the increase of air gap pressure in the mold cavity. During liquid metal filling, the heat absorption of EPS pattern reduces the temperature at the front of liquid metal, which will reduce the filling speed and filling capacity of liquid metal.