Electric arc furnaces are giant pots that melt steel. They enable the recycling of scrap steel. Recycled steel both costs far less than creating steel from raw materials and has a lower environmental impact.
The process involves three-phase electrodes which create an arc that reaches about 3000°C (5400°F).
Frenchman Paul Héroult (co-inventor of aluminum smelting) perfected using electricity to melt iron. Eventually, he licensed his arc furnaces to US Steel and Halcomb Steel Company. Arguably, Siemens 1857 regenerative furnace and Moissan’s 1892 furnaces are predecessor technologies.
In a familiar pattern, Heroult invented the arc furnace in France but commercialized it in the US. Most furnaces were installed at US Steel.
Undoubtedly, electric arc furnaces always had some utility. Eventually, they became vastly more profitable when combined with the Nucor Mini-Mill innovation.
Aluminum is the most common material in the earth. Despite the abundance of aluminum, it tends to be spread out in tiny flakes impossible to collect by hand. Aluminum reduction vastly lowered the price of extracting aluminum.
Before aluminum reduction, aluminum was extremely expensive. People would sift through earth searching for whole nuggets of aluminum that could then be melted together and purified. Aluminum nuggets were less common than gold and silver. Napolean is said to have served upper-royalty on aluminum plates with aluminum cutlery whereas ordinary guests ate off gold plates with silver cutlery.
In some ways, aluminum reduction — although a process rather than a machine — is arguably a type of automation since it eliminated something done via manual labor. However, the process was so laborious that very little aluminum was actually produced.
On Feb. 23, 1886, Hall found that passing an electric current through alumina created purified aluminum. He patented his method on July 9, 1886.
Around the same time, Frenchman Héroult discovered the same and the aluminum purification process — called aluminum reduction — is referred to as the Hall-Héroult process.
Hall went on to co-found aluminum giant ALCOA and became fabulously wealthy.
Aluminum reduction requires massive amounts of electricity so aluminum plants are typically places in areas where electricity is inexpensive to produce. US smelters run by coal in coal-rich areas used to be common. However, more recently, most aluminum smelting plants have moved to Iceland due to inexpensive abundant electricity generated via the island-states numerous renewable resources.
As aluminum became less expensive its uses became more apparent. Early aluminum was used to create teapots and tableware. Eventually, it became useful for automobiles as a lightweight but strong metal. The Wright Brothers used an aluminum engine in their airplane to save weight. Aluminum foil was introduced in 1910. Today, countless ordinary items are made of inexpensive aluminum using the original Hall-Héroult process.