3.3 Effect of EPS foam density.
The relationship between the density EPS foam is used as a pattern and density of the solutions for melting degassed and packed silica mold. CO2 mold casting speed is also marked in the figure for comparison. The formation of the lost foam casting process essentially control the pattern of polymer degradation by pyrolysis of the metal front. Can the formation rate and the rate of removal of polymer degradation products play a vital role to determine the standard solutions in the lost foam process . Should a combination of air and pyrolysis products foam mold cavity to escape as soon as possible before the solidified shell made solutions.
The formation rate of polymer degradation products are believed to increase as the speed increased foam. The rate of removal of polymer degradation products is almost the same as that used the same model packing material. Density shows the lost foam casting peak EPS foam density of 17.5 kg / m3 and reductions in this experiment, which is different from the general idea that the casting speed is inversely proportional to the density foam. Also the metal front shape not only the formation rate and the rate of end products of polymer degradation but strong influence on the elimination of liquid pyrolysis products from kinetic zone and defect formation in lost foam casting. For initial profile flat or concave metal, the products tend to accumulate liquid pyrolysis front of metal and may get trapped in the freezing metal forming liquid residue related defects such as laps, folds, and blisters. The bullet shaped (convex) best to eliminate defects of liquid residue. Is considered the cause of the peak density foam EPS of 17.5 kg / m3 The influence of the initial shape metal.
Further experiments are needed to verify the observation. The source can be divided into two pore factor, turbulence in the flow of molten metal and entraining gas from the pattern because the pattern of the pyrolysis of polystyrene foam during pouring in lost foam casting. It can be thought that “A” in the figure the contribution of challenges that flow on the porosity and “A + B” is the amount that challenges flow and gas from the pattern due to the pyrolysis of the pattern is polystyrene foam with during pouring. Since EPS foam decomposes into hydrogen and spewing carbon, carbon may exist in the pore of the lost foam casting. Figure 9 shows the evidence for the existence of carbon in the lost foam casting pore through WDS analysis, although not found in the pore carbon mold of traditional CO2. Density of air cooled specimen was solidified in the cup, a specimen CO2 mold and lost foam casting 2.66 × 103, 103 × 2.64, and 2.61 to 2.63 × 103 kg / m3, respectively.
That can, can the contribution of challenges that flow of the solutions considered about 10 kg / m3 and the contribution of challenges flow and gas from the pattern due to the pyrolysis of the pattern of polystyrene foam to consider about 30 ~ 50 kg / m3 in density scale. It can be concluded that the porosity in the lost foam casting higher than that in solutions CO2 mold at 20-40 kg / m3 density. He suggests that it is dif- ficult to get better mechanical properties without special treatment in the lost foam casting than in conventional solutions, since the mechanical properties of the aluminum solutions are closely related to the porosity.