Online purification for aluminum foil can effectively remove the hydrogen content in aluminum alloy, and can ensure that the cast-rolled billet used to produce ultra-thin aluminum foil meets the quality requirements.
In the aluminum foil processing industry, the processing of ultra-thin aluminum foil is hard. However, it is more difficult to process ultra-thin aluminum foil with cast-rolled billets. This requires the cast-rolled billet to have very strict internal quality, including controlling the internal gas, mainly the content of hydrogen. Therefore, it is necessary to conduct online purification for aluminum foil during the melting and casting process.
The quality of the purified cast-rolled billet of the aluminum melt determines whether the 0.005mm aluminum foil can be rolled and the number of pinholes in the finished product. For this reason, special requirements are required for the quality of cast-rolled billets:
When the aluminum liquid passes through the degassing unit, the high-purity N2 online degassing method is used, and the alumina ceramic foam filter is used for melt degassing and slag removal, so that the hydrogen content in the melt is controlled below 0.9mL/(kgAl).
In the smelting furnace, the aluminum ingot and the master alloy are alloyed and smelted, and the aluminum alloy melt is refined in the static furnace for degassing and impurity removal.
In the past, aluminum melt was smelted at high temperatures, usually using a spray gun to spray N2+CCl4 into the aluminum melt for refining.
Now, CCl4 is an environmentally prohibited item, so the furnace bottom venting brick is used to periodically pass high-purity N2 from the furnace bottom, so as to improve the purity of aluminum melt and make the composition and temperature in the furnace uniform. It can improve the uneven chemical composition, large fluctuations, and large remelting loss during the smelting production process, while reducing the original hydrogen content in the aluminum melt and improving product quality.
Through the continuous bottom blowing of high purity N2 technology at the bottom of the furnace, the precise control technology of alloy composition, the continuous online degassing of the melt and the three-stage filtration technology, the oxidation atmosphere in the furnace is reduced, and the aluminum metal burning loss is reduced while ensuring the stable and uniform alloy composition.
At the same time, it can purify the melt, eliminate most of the gas and inclusions in the melt, reduce the content of impurity elements, and make the chemical composition of the aluminum melt more stable.