Porosity is greatest fault in aluminum alloy castings, is also thought to be severe in aluminum alloy castings produced by lost foam process because the pyrolysis of polystyrene foam pattern during pouring. Basic experiments were carried out to assess the effect of process parameters such as the melting treatment, the cooling rate and the density of expanded polystyrene (EPS) foam of porosity in casting A356.2 bar. Was investigated the treatment effect melting including degassing and filtering. The effect of cooling rate were also evaluated by changing the model packing materials such as silica sand, zircon sand and steel shots. Gas entrapment because the turbulent metal flow during mold filling in conventional molding process results in porosity. Mold order is filled in the lost foam process different from that in the conventional molding process. Was considered the effect of molten metal flow by comparing the density of traditional solutions of sodium silicate molding with the lost foam process. Density was measured to analyze the amount of porosity in the casting. Source can porosity in lost foam process can be divided into two factors, ie turbulence in the flow of molten metal and residue from the pattern or entraining gas during pouring. Lost foam casting process is still a new technology, and more confidence among manufacturers. It is expected to improve dramatically the foundry industry competitiveness. Can have many advantages such as eliminating machining steps, to make complex solutions without cores and reducing environmental burdens provided by the process, because there is added binder molding mold the lost foam process.
Aluminum alloy castings are widely used in the automobile and aerospace industries, and are replacing heavier forged steel or cast iron for more fuelefficient lighter automobiles. Production of aluminum castings for fault becomes more important. The most common fault of the porosity in aluminum casting. Has a negative effect not only on the mechanical properties, but also on the cast product surface quality [2] porosity. The polymer foam undergoes pyrolysis and is replaced by liquid metal in the lost foam process. One of the unique problems in the production of aluminum lost foam castings the formation of defects associated with the pyrolysis products from the decomposing foam casting pattern. Various forms of the shortcomings associated pyrolysis occurred, including internal porosity, blisters, folds, and a rough, orange-peel surface defect. Internal pores are caused by the polymer liquid trapped within the liquid metal. Fies solidi- the metal before the liquid escapes polystyrene foam with metal coating interface. As pyrolysis continues the liquid polystyrene foam, bubble the gaseous decomposition product is trapped in the frozen partial solutions.
Gas entrapment because the turbulent metal flow during mold filling in conventional molding process results in porosity. Mold order is filled in the lost foam process different from that in the conventional molding process. There is therefore lost foam porosity in castings higher than in normal projection because pattern is burned out during pouring the molten metal. Turbulence in the flow of molten metal and entraining or gas residue from the pattern because the pyrolysis of polystyrene foam pattern is believed to be the sources of pore during pouring in lost foam casting. It is desirable to understand the source of the quantitative pore. Described the effects of a number of process parameters such as the melting treatment, the packing material and the density model of the EPS foam on the porosity in lost foam casting of aluminum alloy.
