Degassing of molten aluminum is an essential process in alloy casting. It is done by one of two methods: flux or rotary degassing. The molten aluminum rotary degassing system injects gas (such as argon (Ar) or nitrogen (N2)) directly into the aluminum melt. The rotation of the shaft combined with the purge of the inert gas results in the formation of a large number of bubbles in the melt.
Compared with flux degassing, rotary degassing machines provide a more effective and cleaner method for removing hydrogen from molten aluminum. The hydrogen dissolved in the molten aluminum then diffuses into these bubbles and separates from the liquid phase.
The aluminum melt before casting contains dissolved hydrogen and non-metallic inclusions, such as oxides of aluminum and magnesium, which are undesirable impurities. When hydrogen and non-metallic inclusions are present in molten aluminum, defects may occur in ingots prepared from the melt and products prepared from the ingots. Therefore, hydrogen and non-metallic inclusions must be removed from the molten metal.
Generally, inert gas or chlorine gas is introduced into the molten metal in the form of bubbles to remove hydrogen and non-metallic inclusions from the molten aluminum. However, because the atmosphere contains water, aluminum and water in the atmosphere will react on the surface of the molten metal (2Al + 3H 2 O 3 Al 2 O 3 + 3H 2), resulting in the problem of hydrogen penetration into the melt. The surface of molten aluminum that is allowed to stand is usually covered with a dense aluminum oxide coating so that atmospheric water does not react with aluminum.
The processing principle of the online molten aluminum rotary degassing equipment is the principle of gas flotation. The process gas (inert gas or a mixture of inert gas and chlorine) is injected into the melt through the rotor, and the rotor is broken into uniformly dispersed tiny bubbles, and the tiny bubbles rise to the melt. Hydrogen is absorbed into the bubbles and removed, and the inclusions are captured by the bubbles, and then rise to the surface of the melt.