The Effect of Melting Temperature Aluminum Metal Casting Using Mixed Degasser Based Sodium Fluoride and Sodium Nitrate

The effect of NaF and NaNO3 based degasser on mechanical properties of Al-Si 12% casting has been investigated. The quality of Al-Si casting, especially in mechanical properties, is important in some applications. However, the existence of gas porosity, which is formed due to the high solubility of H2 at melt temperature in casting process, reduces mechanical propertis of Al-Si 12% casting product. In this research, we used NaF and NaNO3 as degasser as an addition in casting process. The experiments were conducted at pouring temperature of 660°C, 680°C, 700°C and 720°C. The mechanical properties (which are determined by tensile test, hardness test and impact test) with and without degasser were measured and compared. We found that in all pouring temperature, the addition of degasser will improve all of mecahnical properties measured. In addition we found that the increase of tensile strength was optimum at pouring temperature of 720°C at 25,5 % of increase, hardness was optimum at pouring temperature of 720°C at 33,3 % of increase and impact strength was optimum at pouring temperature of 720°C at 25 % of increase. The improvement of mechanical properties is due to the role of NaF and NaNO3 by binding H2 gases which is formed in melting process. This H2 binding was shown in microstructure observation which shows that the porosity of casting product visually decreased.