Molten Aluminium Foundry Flux

Molten Aluminium Foundry Flux:

Molten aluminium foundry flux is used to describe all molten aluminium processing using compounds. These compounds are usually inorganic and can serve a variety of functions, such as degassing, magnesium reduction, impurity removal and alloying. Foundry flux also includes chemical gases or inert gases for melt processing. Metal removes gaseous inclusions or metal impurities. The main chemical components of molten aluminium foundry flux arechlorides and fluorides and additional additives that give special properties. Most foundry flux is based on a mixture of KCl and NaCl salts to form a low-temperature eutectic.

Another common ingredient of foundry flux is sodium fluoride (NaF), which forms a ternary eutectic with KCl and NaCl.

The role of fluoride in foundry flux:

Alkali metal fluoride salts are used as surfactants to reduce the surface tension between the flux and the metal on the one hand and reduce the surface tension between the flux and the oxide on the other hand. Chloride exhibits this characteristic to a lesser extent. Fluoride salts and alkali metal oxides have dissolving power (albeit to a small extent), which helps them penetrate the oxide film in the slag and grow on the furnace wall. This leads to improved wettability, which helps the separation of oxide inclusions in the melt and the separation of aluminium metal from tin dross.