Lost foam casting can also be called negative pressure or dry, because its characteristic is to use negative pressure to compact dry sand to form a mold. Foam foam is usually pre foaming, curing and molding in the mold to obtain the same foam appearance as the casting appearance. Some of them are more complex, so the mold cavity can not be exactly the same as the casting shape. In this case, it is necessary for subsequent artificial or mechanical bonding to make a more complicated foam shape.
After the foam pattern is finished, it is necessary to brush the fire-retardant coating manually or mechanically. After the coating is finished, it will be dried and dried. It can be placed in the ready sand box, then poured into dry sand and vibrate and applied negative pressure to compacted dry sand. Then the molten metal can be poured into the gate cup. The molten metal is poured into the runner through the runner cup and poured into the mold through the runner. Because the temperature of the metal liquid is relatively high, the foam pattern can be decomposed and vaporized quickly so that the molten metal can fill the entire mold and thus get the casting.
The filling process ofis more complicated than that of traditional sand casting. This is because the front of liquid metal is different from sand casting in filling process of lost foam casting. There is no complex physical and chemical reaction at the front of liquid sand casting, and the liquid metal at the filling front of the lost foam mold has to react with foam pattern, which makes the filling front of lost foam casting unable to control. The high temperature action of molten metal causes the foam pattern to burn and melt rapidly and produce gas, and the gas generated will be discharged into the dry sand mold. Therefore, there are many factors that affect the filling process of lost foam casting, not only the shape of gating system and the size of gating system, but also the factors such as pouring temperature, negative pressure, paint, molding sand permeability and foam pattern density.