How is Aluminum Manufactured?

January 6, 2021

How is aluminum manufactured?

  1. Choosing the Right Aluminum Ore
  2. Mining
  3. Refining the Bauxite
  4. Smelting the Aluminum

Aluminum is one of the most versatile and durable materials on the planet. Various industries ranging from construction to furniture-making have been able to take advantage of this material due to a number of its properties. If you’re asking “how is aluminum manufactured?” The process may not be as simple as it sounds. There isn’t an already-available aluminum in the market that can simply be cut, designed, and machined into form.

Like many alloys, aluminum comes from an ore which is carefully mined in certain locations. The process of aluminum manufacturing can be divided into the following phases namely choosing the right aluminum ore, mining the ore, refining the bauxite ore, and then smelting. 

After the final phase, the alloy can now be subject to different manufacturing techniques such as extrusion, stamping, or sheet-forming in order to make the product usable. Then, it may not be distributed to the wider market for its intended use. Continue reading to learn more. 

Choosing the Right Aluminum Ore

Aluminum is considered to be the most plentiful element present in the crust of the Earth. By mass, the earth’s crust consists of around 8% aluminum, but due to its chemically-reactive properties, it does not occur naturally and is instead found in combination with other minerals.

These minerals can be found in ores where different metals can be extracted from, and derived. For aluminum, this ore is called bauxite that contains other minerals and compounds such as silicone, sand iron, titanium oxide, aluminum oxide (can be as high as 60% content), as well as other trace metals. 

Bauxite ores or ore deposits typically appear red in color and can be found growing in tropical and subtropical countries such as Australia, Guinea, or Vietnam. As of 2019, Guinea was considered to have the highest deposit levels of bauxite reserves — more than 7 billion in metric tons. However, this type of ore can also be found in other locations in South America as well as Europe, though not as abundant as in the locations mentioned above. 

Mining

Open-pit bauxite mine

Generally, mining is considered to be a collaborative effort that includes geologists, contractors, and private mining companies. The geologists are responsible for investigating the site, taking samples of bauxite ores, and then conducting the drilling process. 

As for the contractors, they provide the services that enable the mining of aluminum. This can only be possible with the use of heavy machinery and equipment that also involves a number of phases

First, the mining area is subject to preparation and surveying to make sure that it is secure and that no sensitivities are negatively impacted — i.e. locations of cultural heritage and other protected areas. 

Afterwards, the mining proper is undertaken by using drag line excavators that will facilitate the removal of the natural rock formations that are covering the main body of the ore. Depending on the technique, blasting or vibratory drilling is executed to destroy the caprock further, before the bauxite ore can be excavated or shovelled. 

The mined ores are then loaded onto transport equipment such as wheel loaders which will transport the gathered ores for further refining. 

Refining the Bauxite

As mentioned before, aluminum bauxite ores do not really contain 100% aluminum. There are other unwanted materials in the ore that have to be removed through a process called refining, in order to extract the 40-60% of aluminum present in it.

After locating and mining the bauxite ores, they now have to undergo a chemical refinery process known as The Bayer Process. Named after the inventor of the process, Karl Josef Bayer, this centuries-old technique began in the late 19th century and was identified as the most efficient technique of extracting the alumina or the aluminum oxide contained in the ore.

Although there are many complicated hydrometallurgical phases in the Bayer technique, it generally starts off with physically cleaning the bauxite through washing and then having it crushed in order to lessen the size of the particle. 

After this stage, the aluminum content can now be digested in caustic soda or any caustic-based solution — usually in temperatures of more than 250°C. A chemical reaction will occur between the alumina in the bauxite and the caustic solution, forming sodium aluminate. 

After further clarification of the aluminate solution and removal of “red mud” and other impurities, the aluminate can now be precipitated with the addition of aluminum hydroxide. The miller will then further clean the resulting solid precipitates through a heat treatment method known as calcination to further eliminate any other unwanted substances from the aluminum crystal. 

Smelting the Aluminum

Milling aluminum parts

Aside from the Bayer process, the Hall-Héroult technique is also employed in the smelting phase of the aluminum. It begins when the aluminum oxide is mixed with a solution of sodium fluoride and then subsequently dissolved.

A constant electric current is passed through a pot where the aluminum oxide solution is contained, with the help of consumable anodes into the aluminum solution. With the help of the current, the molten aluminum is separated from the solution and then casted to become billets, ingots, or wafers, ready for further manufacturing.

Key Takeaway

If you’re wondering “How is aluminum manufactured?” the process can be complex. However, it generally involves four stages that start with choosing the ore, mining, refining the ore, and then smelting. 

The entire aluminum mining/manufacturing process can be further classified into the Bayer and Hall-Héroult methods — the latter, specifically referring to the smelting technique, while the former, bauxite ore refining.

All of these phases are crucial in coming up with workable aluminum materials that can be transformed into various applications, whether it be aluminum window frames, profiles, structural sections, and many more.


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