The covering agent can generate a molten layer to protect the metal from oxidation and hydrogen absorption. They gather oxides and non-metallic materials in the molten metal, clean the metal and form a good metal-free dross, which can be easily removed.
In the process of smelting aluminum and aluminum alloys with electrolytic aluminum liquid, the temperature of the melt is always at a high temperature of 700 ~ 900 ℃. At 700~800℃, the protective film on the surface of the melt will undergo crystalline transformation. The transformation of crystals leads to changes in its volume density, which partially ruptures the original protective film of the melt and reduces its protective effect. At the same time, during the smelting process, the metal level fluctuates due to feeding and other operations. The original dense aluminum oxide film covering the liquid surface is easy to crack. At this time, slag inclusions on the surface and furnace gas can easily enter the liquid, causing further oxidation and gas absorption of the metal. Therefore, covering agent protection should be used in the whole process of melt purification.
AdTech fluxes are suitable for covering, and slag removal in cast aluminum applications. They reduce oxide formation and furnace wall slag, help remove non-metallic inclusions in molten aluminum, reduce the aluminum content in scum, and assist in removing scum.
The covering flux forms a ternary eutectic at 607 ℃, which has good fluidity and can form a thin film on the surface of the molten aluminum. This layer of film can absorb and dissolve the slag in the surface oxide film, and prevent further oxidation of the aluminum liquid, and at the same time can reduce the metal inhalation during the smelting process. The amount of covering agent is based on the principle of completely covering the melt, and the amount added per square meter of liquid surface is about 0.6~1.0 kg (thickness 3-5 mm).