A comparative study between the addition of NH₄Cl and KCl in NaNO₃ and NaF-based degassers in aluminum casting

The quality of Al-Si casting product is important for its applications, however the molten aluminum has high solubility of H₂ at melting temperature in the casting process, so the formation of gas porosity during aluminum solidification is inevitable. This can cause a major drawback to the mechanical properties. The most common method to remove hydrogen gases in the molten metal is degassing. In this experiment, a conventional degassing method using Sodium Nitrate-Sodium Fluoride based degasser is conducted. Al-Si12 was melted at 720 °C then the degasser was plunged into the furnace bottom and held for three minutes. The results show better mechanical properties by the addition of degasser. This is because the degasser binds H₂ gases which is formed in the melting process. The mechanical properties between casting products that use NaF-NaNO₃ degasser and NaF-NaNO₃ with addition of NH₄Cl or KCl were measured and compared. The lowest mechanical properties were obtained when using degasser without NH₄Cl or KCl. This is because NH₄Cl or KCl is reactive and helps with the efficiency of degasser.