Effect of Sodium Nitrate-Sodium Fluoride Ratio as Degasser in Al-7Si-2Cu Casting Product

Effect of Sodium Nitrate-Sodium Fluoride Ratio as degasser in Al-7Si-2Cu Casting product has been investigated. Degassing is one of the methods used in the casting process to remove gases, such as hydrogen gases, in the molten metal. The most commonly used degassing method is by injecting an inert gas such as argon. In this experiment, a conventional degassing method with degasser-based sodium nitrate-sodium fluoride was used with changes in sodium nitrate to sodium fluoride ratio variables are 3:5, 4:4, and 5:3. The type of material used is Al-7Si-2Cu material with additional scrap. The material melted first at 800°C, then the degasser was added into the furnace and held for 3 minutes. High temperature was used to melt the material due to the solubility of hydrogen gases in liquid metal at high temperature is high. The molten metal then poured into the dies at approximately 690°C. The casting process results are then prepared for mechanical testing, such as tensile test, impact test, and hardness test, and microstructure testing. The results show that at the ratio of 1:1.5 (normal ratio), the porosity was lower (0.8 at average) and the mechanical strength was higher (1.2 at average).