Last updated on March 17, 2017
Aluminum is one of the widely used materials in our daily life. However the process of its creation goes unnoticed. The process involved in the creation of aluminum is long and complicated. Aluminum undergoes a series of rigorous purifications and heating procedures before it is cut or fitted into moulds.
Refining Bauxite Ore to create Aluminum
Refining bauxite ore and smelting are the key processes involved in the manufacture of aluminum and smelting which forms aluminum oxide that releases aluminum.
Refining of aluminum
During the intensive refining process bauxite is mechanically crushed and mixed with caustic soda. When the mix is processed, the result is a type of slurry comprising ore particles. The bauxite ore slurry must then be heated and put under heavy pressure for hours while the aluminum-containing compounds are dissolved.
The resulting product, a sodium aluminate solution, is purified in a settling tank. Most impurities settle to the bottom, and the remaining liquid is then further pumped through cloth filters to remove even more impurities.
The liquid then undergoes a chemical process during which “seed crystals” containing alumina hydrate are added to giant precipitation tanks. As the seeds settle in the tank, they bind with dissolved alumina and grow. In the end, those new, larger crystals, are removed, washed and super-heated to remove any remaining water molecules.
Smelting
Smelting is a process in which molten aluminum ore undergoes reduction separating it into aluminum and oxygen. A steel vat, called a reduction pot, with carbon lined along the bottom is used for this process. Simultaneously, carbon rods are suspended above the pot, helping to create an electric current through molten aluminum mixture.
A current passing through the aluminum solution, forces the aluminum and oxygen atoms to separate. The oxygen molecules are attracted to the carbon rods to create carbon dioxide, while the newly freed aluminum sinks to the bottom of the pot.
Refining
Aluminum byproducts are highly useful. A powdery substance filtered out during the refining process can be used in products such as laundry detergents, toothpaste and fluorescent light bulbs. It can also be used for ceramics and electronics finishing.
Other byproducts are formed that are less useful. During the same refining process, a red muddy substance is created, called ore refuse. It comprises iron, titanium and other elements, but it is mostly unusable.
Welding: Making Aluminum more useful
The most common way of joining aluminum is welding. The corrosion resistance of aluminum is due to a tough oxide layer on the surface. This oxide layer has a higher melting point than aluminum and must be removed before welding. It is removed using chemical, mechanical or electrical means and must be prevented from reforming before welding can be completed.
Due to the high thermal conductivity of aluminum, heat needs to be applied at a rate four times that needed for steel. It has a linear expansion coefficient twice that for steel, which must be considered when welding material that has been restrained.
Welding tends to reduce the mechanical properties of aluminum in the heat affected zone. This area extends around 25mm from the weld. Many high-quality welding fabrication companies in Melbourne provides best welding services for mild steel, aluminum, stainless steel and other more exotic alloys.
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