The Smelting of Aluminum Processing
Aluminum processing smelting is the provision of billets for plastic processing. The smelting furnace uses a gas reverberatory furnace or a fuel reverberatory furnace, and the general capacity is 20 to 40 tons or more; and the resistance heating reverberating furnace is also used, and the capacity is generally about 10 tons. In order to shorten the furnace charging time, increase the melting efficiency, reduce the absorption of gas and entrap the oxide film, the industry has adopted a tilting top-loading round furnace. It is best to use a rapid analytical instrument to analyze the alloy composition during smelting and adjust it in time. In order to ensure the purity of the melt, prevent the pollution of harmful gases and control the chemical composition, in addition to shortening the melting time as much as possible, it should be covered with powdered flux， which is mainly composed of potassium chloride and sodium chloride. The general dosage is 0.4~ of the weight of the charge. 2%. The smelting temperature is usually controlled at 700 to 750 °C.
The molten metal also needs to be refined and filtered to remove harmful hydrogen and non-metallic inclusions from the metal to improve metal purity. Refining usually uses a solid refining agent or a gas refining agent. The solid refining agent is generally a chlorine salt-based refining agent which is also used to replace the chlorine salt with hexachloroethane. In the early stage, the active chlorine gas was used as a gas refining agent, but the purification effect was good, but the environmental pollution was serious. Therefore, the development of a nitrogen-chlorine mixed gas, an inert gas and a three-gas (N2, Cl2, CO) refining agent has a good effect. In order to ensure the refining effect, the oxygen and moisture content in the refined gas should generally be less than 0.03% by volume and 0.3 g/m3, respectively. Dynamic vacuum degassing also has good degassing and sodium removal effects.
Filtration is a filter in which the molten metal is made of a neutral or active material to remove suspended inclusions in the melt. Commonly used glass mesh, microporous ceramic tubes and plates, alumina particles for filtration, can also be refined with electric flux and flux layer.