Molten Metal, T-Bar, Sow
Almost all aluminum products are produced from Molten Metal, T-Bar, and Sow. T-Bar and Sow are simply the solid form of molten metal. T-Bar and Sow can be re-melted to produce extrusions or cast into ingots or billets, which are then pressed or rolled to form sheet, plate, foil, wire, rod, and bar. Ingots, billets, and extrusions also can be cast or drawn directly from molten metal.
Molten Metal is produced directly from alumina. Alumina from the refinery is moved to the reduction plant or smelter; long buildings with row after row of reductions cells, or pots, where the pure, white powder is transformed into glistening, molten metal.
Although there are many types of cells, they operate on the same principle. The pots are actually steel boxes of various sizes, generally about 20 feet long, six feet wide, and about three feet deep, lined with carbon. The alumina is dissolved in a molten salt called cryolite and aluminum fluoride in the steel pot and a carbon electrode (anode) is lowered into the solution.
Direct electrical , between 50, 000 and 150, 000 amperes, then flows from the anode, through the now molten mixture to the carbon cathode lining of the pot. Since each pot requires only about 5 volts, it is customary to connect a hundred or more pots in a series, in rooms 700 or feet more long. Several buildings are often connected in the electrical current to form a single potline.
The electric current reduces the alumina molecules into aluminum and oxygen. The oxygen is deposited on the carbon anode where it combines with the carbon to form carbon dioxide, and the aluminum, being heavier than the cryolite, settles to the bottom of the pot.
The molten aluminum is siphoned into crucibles about once a day, more alumina is added to the pot, and the process continues day and night.
At this point, the molten metal can be cast directly into billets and ingots. (click here for more information on billet and ingot casting) The molten metal can also be cast into T-Bar or Sow. Once cast, the T-Bar and Sow can be easily transported from the smelter to the cast house, where it will be re-melted and cast into billet or ingot.
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