How Aluminum is Made

 　　In many ways, aluminum is the perfect metal. It is sturdy, lightweight, heat-resistant and corrosion-resistant, and is a good conductor of electricity. Most importantly, it is rich and cheap.

　　Aluminum is also the most abundant metal in the Earth's crust and the third most abundant element after oxygen and silicon. However, it was not until 1809 that the British chemist Sir Humphrey David officially identified and named it.

　　Today, aluminum is the most commonly used metal in the world, second only to steel. Aluminum is an important component of almost every aspect of our lives, from the vehicles we drive to the packaging of food.

　　When aluminum combines with other metals to form aluminum alloys, it is most versatile. The alloying process improves the performance of aluminum to adapt to various applications.

　　How Aluminum is Made

　　Aluminum is manufactured in the following stages:

　　Searching for aluminum ore

　　Mining aluminum

　　Refined bauxite

　　Aluminum smelting

　　Searching for aluminum ore

　　Aluminum tends to combine with other elements and rarely exists in pure metal form in nature. Aluminum compounds exist in the most common rock types, including clay, slate, shale, granite, and plagioclase.

　　The most important aluminum ore is bauxite, which is a rock containing about 52% aluminum oxide and impurities such as iron oxide, silicon dioxide, and titanium dioxide. Bauxite is commonly found on or near the surface of the Earth in many parts of the world, including Europe, Asia, Australia, and South America.

　　Mining aluminum

　　Geologists locate bauxite deposits by sampling and conducting survey drilling. When mineral deposits are discovered, they are mined in open-pit mines. The soil is blown loose, and the bauxite is extracted with a power shovel or bucket shovel.

　　90% of the mined bauxite is made into alumina and then smelted into aluminum. The remaining 10% is used for other purposes, including manufacturing abrasives, furnace liners, and support agents for the petroleum industry. Producing 4 tons of alumina requires 2 tons of high-quality bauxite, from which 1 ton of aluminum can be produced.

　　Refined bauxite

　　Bauxite is refined using the Bayer process, which was first developed by Karl Joseph Bayer in 1888. The Bayer process consists of four steps: digestion, clarification, precipitation, and calcination.

　　Digestion

　　Bauxite is ground, mixed with caustic soda, and then pumped into a pressure tank where steam heat and pressure are applied. This leads to the reaction of caustic soda with aluminum compounds in bauxite to form a sodium aluminate solution. Unneeded impurities will remain in the so-called red mud.

　　clarify

　　Next, the sodium aluminate solution is blown through the tank and the pressure is reduced to atmospheric pressure. Use clarifiers and cloth filters to remove red mud. Then cool the clarified solution in a heat exchanger and pump it into a high silo.

　　precipitation

　　Add aluminum hydroxide crystal seeds to sodium aluminate solution to cause precipitation. During this process, aluminum becomes sturdy. This results in large aluminum crystals being filtered and washed to remove water and other impurities.

　　Calcination

　　Now, aluminum hydroxide crystals are calcined, which is a heat treatment process that controls the air supply. The rotary kiln is used to heat crystals to a temperature above 960 ° C to remove any residual impurities, leaving behind fine white powder called alumina or alumina.

　　Aluminum smelting

　　Smelting is the process of extracting aluminum from alumina. This was carried out by the Hall Hollot process, which was invented by Charles Martin Hall and Paul Hollot in 1886.

　　Smelting is carried out in a steel reduction tank filled with molten electrolytes, where the carbon anode is used to pass current through the electrolyte. Then add alumina to the molten surface. Electrodeposited molten aluminum can be collected and extracted.

　　Then pour the molten aluminum into the mold to form a casting ingot. At this stage, its purity is 99.8%. Now, it can be further refined to produce ultrapure aluminum or used for alloying with other metals.

　　Ultrapure aluminum

　　Ultra pure aluminum with high purity (99.99%) is soft and lacks tensile strength. However, it has corrosion resistance and is an excellent electrical conductor. Ultra pure aluminum is used in chemical equipment, electronic components, and gasoline manufacturing.

　　aluminium alloy

　　Most aluminum forms alloys with other elements. By alloying aluminum, its hardness and strength can be significantly improved. Common aluminum alloys are aluminum manganese (used in beverage containers), aluminum magnesium (used in electrical appliances and utensils), aluminum magnesium silicon (used in buildings and vehicles), and aluminum copper (used in airplanes).

　　Recycling aluminum

　　Aluminum can be endlessly recycled without losing its quality. This makes it one of the most environmentally friendly metals on Earth. It is incredible that most of the aluminum produced throughout history is still in use today.