Why is aluminum smelted?

Melting is to provide ingots for plastic working. Smelting furnaces are mostly gas-fired reverberatory furnaces or oil-fired reverberatory furnaces, with a general capacity of 20 to 40 tons or more; resistance heating reverberatory furnaces are also used, with a capacity of about 10 tons. In order to shorten the furnace loading time, improve the melting efficiency, reduce the absorbed gas and get involved in the oxide film, the industry has adopted the tilting top-loading circular furnace. When smelting, it is best to use a rapid analysis instrument to analyze the alloy composition 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 smelting time as much as possible, it is advisable to cover it with a powdered flux mainly composed of potassium chloride and sodium chloride. 2%. The melting temperature is usually controlled at 700-750°C.

The molten metal also needs to be refined and filtered to remove the harmful gas hydrogen and non-metallic inclusions in the metal to improve the purity of the metal. Refining usually uses solid refining agents or gas refining agents. The solid refining agent is generally dominated by chloride salts, and hexachloroethane is also used instead of the refining agent of chloride salts. In the early days, chlorine gas with strong activity was used as a gas refining agent. Although the purification effect was good, it caused serious environmental pollution. Therefore, nitrogen-chlorine mixed gas, inert gas and three gas (N2, Cl2, CO) refining agents were developed, and the effect was good. In order to ensure the refining effect, the oxygen and moisture content in the refining gas should generally be less than 0.03% (volume) and 0.3 g/m3, respectively. The dynamic vacuum degassing method also has good degassing and sodium removal effects.

Filtration is to pass molten metal through a filter made of neutral or active material to remove suspended inclusions in the melt. Glass wire mesh, microporous ceramic tubes and plates, and alumina particles are commonly used as filter beds for filtration, and electric flux refining and flux layer filtration can also be used.