Lost Foam Casting (LFC)

The lost foam casting process is to use a foam pattern (EPMMA, STMMA, FD, EPS) polymer material to make a foam pattern with the same structure and size as the parts to be cast. After being dipped in refractory paint and dried, it is buried in dry sand. After vibration moulding, the model clusters in the sand box are poured into molten metal under negative pressure, so that the polymer material pattern is thermally decomposed, gasified and extracted, and then replaced by the molten metal to cool and solidify to form a new casting method.

Lost foam casting is a typical "big process, small step, chain type" system engineering. Any small omission in any step can lead to defects. There is no distinction between the severity and the priority.

Pattern Making in Lost Foam Casting

In LFC foam pattern making is unique, it undergoes series of Chemical and Physical reactions which bring uncertainties to the whole casting process. Therefore, the quality of the foam pattern directly affects the quality of the final castings, and the two important factors related to the quality of the foam pattern are the selection of foam pattern material and the control of pattern making process.

LFC process is in parallel with the casting process, and the products formed are carbides, carbon, carbon dioxide and water. Carbon dioxide and water are gases. As long as they are discharged in time, they will not have any adverse effect on the quality of the castings. Part of the carbon in the form of graphite is absorbed by the coating or discharged; part of it is absorbed by liquid metal, producing a decarburization defects. Carbon that has not been absorbed or discharged will not have any adverse effect on the internal and external quality if dispersed on the surface of the castings. If concentrated in the presence of liquid metal, macroscopic defects, namely carbon defects, will happen.