| Molten aluminum typically contains undesirable species such as hydrogen, non-metallic inclusions and alkali metals. These elements will reduce the quality of the final product.
The aim of aluminum refining is to remove hydrogen, non-metallic inclusions and unwanted trace elements. The refining is normally done after alloy addition. In some cases the melt is also pre-treated before alloying. Gas injection is the most commonly used refining method.
A gas is injected through porous bottom, nozzles in the bottom or walls, through lances (with or without porous ends) or through rotating impellers. Gases used are nitrogen, argon and chlorine as well as gas mixtures of said gases. |
