Molten Aluminum Alloy Purification by Degassing and Flux Refining

Aluminum foundries are using many commercially acceptable melt purification techniques to remove and separate inclusions from molten aluminum alloy before casting. These include different degassing and flux refining methods. Therefore, the quality of the molten aluminum alloy bath depends on the molten metal purification process.

Molten Aluminum Alloy Purification

It is known that molten aluminum and aluminum-based alloys absorb large amounts of gas, and the amount found in a particular melt depends on the characteristics of the metal used, whether it is pure or secondary, and the conditions under which the melting takes place. The gas effect in the metal is manifested in the casting by the appearance of pores and so-called pinhole pores, as well as the appearance of strips or bubbles on the surface of the forging.

When in a molten state, the metal can absorb some gas, but when the liquid metal cools and solidifies in the mold, the gas absorption decreases, resulting in the release of free gas. The released gas immediately accumulates and forms bubbles, some of which are trapped in the frozen metal, forming cavities or discontinuities.

When melting and processing molten aluminum alloys, regardless of the design of the melting and/or holding furnace, hydrogen absorption, dross formation, oxide film formation, metal and non-metallic inclusions, and oxide accumulation are inherent characteristics. Therefore, it is very important to understand and control these characteristics to improve the quality of the molten pool. Due to porosity, shrinkage, inclusions, poor surface finish, low mechanical properties, lack of pressure resistance and reduced corrosion resistance, poor quality will increase the scrap rate of castings.

Aluminum foundries face the challenge of reducing and controlling wet slag and the rapid formation of oxides due to frequent damage to the surface of the molten pool due to the smelting process (such as charging, skimming, cleaning, degassing, transfer and ladle). In addition, they must overcome non-metallic and metallic impurities floating in the molten pool.

AdTech offers aluminum casting flux, degassing unit, and ceramic foam filter for molten aluminum alloy purification. The aluminum purification process can greatly improve the quality and yield of aluminum products, thereby increasing the profitability of aluminum melting and casting plants.