Effect of Applying Air Pressure on Gas Porosity in Lost Foam Casting of Al-Si Alloy

Abstract

The paper presents the result of investigation on aluminum-silicon (LM6) alloy cast using pressurized lost foam casting process. The study investigated the effect of pressure and sand size on porosity of the casting produced. Air pressure of 1, 2, 3 and 4 bars was applied on the solidifying alloy poured in mould of sand sizes 16-30, 40-60, 60-100 (AFS). The porosities of casting were measured using optical microscope which was equipped with image analyzer. For porosity of castings, all surfaces of solidified castings were captured by digital camera for better observation. The results show that applying pressure during solidification of the LM6 alloy has significant influence on casting porosity of the alloy. By increasing the applied pressure, the porosity percentage based on gas porosity decreased when pressure was applied. Consequently, the removal rate of gas porosity improved by increasing the sand size to finer size 60-100 (AFS), so there is less gas porosity in samples. Besides, rising air pressure lead to fulfilling of molten which improves the casting porosity.