Important Aluminum Manufacturing Processes

​A chemical element, aluminum is a lightweight, silvery white metal of Group 13 on the periodic table. It is one of the most abundant elements on Earth, along with oxygen, silicon, and iron. Together, they account for nearly 90 percent of the planet's mass. Although aluminum is a naturally occurring element, miners do not typically find it in its pure form. Humans find aluminum compounds within rocky masses of ore in the Earth's crust. This ore, called bauxite, goes through two main refining processes, after which people can use different types of aluminum for a variety of purposes.

Bauxite consists mainly of aluminum oxide, along with water molecules and a myriad of impurities. The Bayer process removes both water and impurities. After mining professionals harvest raw bauxite, they crush, blend, and grind the ore deposits to produce a semi-liquid material known as slurry. Manufacturers subsequently heat and pressurize the slurry to further purify the bauxite residue, resulting in collections of aluminum oxide, also known as alumina.

Following the Bayer process, aluminum oxide undergoes a smelting process known as the Hall–Héroult process, which requires substantial amounts of energy. Smelters separate aluminum atoms from oxygen atoms by placing alumina into a molten mixture and electrolyzing it. At this point, humans have access to metallic aluminum, though they must first cast the raw aluminum into aluminum billets and ingots for additional processing and alloying.

The completion of these initial processes leaves manufacturers with pure aluminum. However, pure aluminum is very soft and not strong enough for most commercial applications. With this in mind, most organizations melt the pure aluminum and begin alloying the metal with other substances. Along with iron and silicon, a few popular aluminum alloys include zinc, copper, magnesium, and manganese, depending on how manufacturers want to change the aluminum. Different alloys result in changes to the aluminum's strength, density, electrical conductivity, corrosion resistance, and other critical properties.

Although alloy processes can combine aluminum with various materials for different purposes, they generally fall into one of three categories. The term "commercially pure aluminum" refers to alloys that consist of at least 99 percent aluminum. These alloys derive value from their exceptional workability and corrosion resistance, along with high degrees of both thermal and electrical conductivity. Commercially pure aluminum has a wide range of applications, particularly in transmission lines that connect America's national power grids.

Heat-treatable aluminum, meanwhile, is a group of alloys that become stronger following extreme heating and cooling processes. Manufacturers can heat the alloys to different temperatures depending on the desired elemental distribution, then rapidly freeze the alloys to hold the elements in place.

Copper-treated aluminum is strong and tough. Aluminum-copper alloys play a vital role in aircraft production. The automobile industry utilizes various heat-treated aluminum alloys, including those with silicon and magnesium, which possess weldable and corrosion-resistant properties.

Finally, pure aluminum can go through cold-working processes. Manufacturers produce these alloys, known as non-heat-treatable aluminum, during the rolling and forging stages by creating strategic dislocations in the atomic structure, which enhances the aluminum's strength. Manganese, silicon, and magnesium rank among the most popular alloying substances for non-heat-treatable aluminum, which manufacturers use to make beverage cans, cooking utensils, and welding wires. Many businesses also utilize non-heat-treatable aluminum in various applications, including building construction projects and marine uses, among others.

David D'Addario, New Day Aluminum LLC

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