Steel manufacturing is a critical industry that has a significant impact on our global economy. Since the mid-1800s, steel has become one of the most relied-upon materials globally, serving countless manufacturing and construction markets. According to the World Steel Association, global steel production supports or facilitates $2.9 trillion of the world’s economic activity, making it a crucial material supporting millions of jobs internationally.
Steel might not seem like a commodity associated with advanced technology, but its manufacturing process has come a long way. In this guide to the steel manufacturing process, we’ll explore the history of steel and compare it to how steel is made and used in modern applications.
History of Steel Production
Steel is a discovery of the Iron Age, a period that started around 1200 BCE. Iron ore was first mined in Central Asia and Europe, and humans at this time used iron to make tools and weapons in a practice called ferrous metallurgy. Iron products evolved during this time, beginning with blacksmiths producing wrought iron goods. These tradespeople learned to heat up iron ore, and using a hammer-and-anvil process, the blacksmiths would remove impurities from the metal and produce a durable and malleable final iron product.
Iron took a few other forms before eventually arriving at what is today considered steel. In China, Iron Age metallurgists heated up iron in large furnaces, effectively melting the substance into liquid and mixing it with the wood fuel. The melted liquid would then be poured into molds, which would then be left to harden, eventually taking the shape of cooking tools and other objects from the molds. This process, known as cast iron, produced a more durable product than wrought iron, but it was brittle, making it difficult to shape and bend.
After cast iron, blacksmiths of Central Europe began coating wrought-iron products in charcoal to improve the iron’s strength while maintaining its flexibility. Afterward, iron went through a final iteration, which most resembles today’s steel material. In India, ironworkers developed an iron smelting process that combined the perfect ratio of iron to carbon. Using crucibles, or clay containers, the ironworkers would blend iron and charcoal pieces together in a high-temperature furnace. While cooking, the iron would melt and absorb carbon atoms from the charcoal. After cooling down, the crucibles contained what we now know as steel — an iron-carbon alloy.
After the discovery of iron-carbon alloys, various civilizations began to scale up their steel-production practices, allowing them to make improved weapons, tools and structures. Since the Iron Age, humans have looked to perfect the steel manufacturing process, not only to produce it in greater quantities but to produce it more effectively. The continuous improvement of steel production is the reason why steel today has become such a crucial global commodity.
How Is Steel Produced Today?
The modern-day steel production process began in 1856 under a process known as the Bessemer process. It’s largely considered to be the first process used to mass-produce steel. According to historians, two different inventors, one in the UK and one in Pittsburgh, both simultaneously developed a steel production process that involved removing iron’s impurities through the use of an air blast.
With this discovery, other steel producers began to perfect the process, eventually discovering a way to use the air-blasting technique to help preserve the carbon content while fully eliminating impurities. Finally, the process evolved into a highly cost-effective way of mass-producing high-quality steel that we still use today.
Today’s steel is generally produced in one of two ways:
1. Blast furnace: The blast furnace process, also known as the basic oxygen process (BOP), combines raw iron ore with small amounts of steel scrap metal into a furnace. Then, pure oxygen is blown into the furnace, raising its temperature. Not only does the scrap metal melt into a liquid at this temperature, but the iron’s impurities are also oxidized, evaporating completely. Additionally, the high temperature reduces the carbon content down to its ideal ratio, resulting in liquid steel.
2. Electric arc furnaces: In the electric arc furnace (EAF) method, high-current electric arcs from electrodes melt large quantities of steel scraps into liquid. While the steel scrap metal is melting, the technicians add in other ferroalloys until the metal liquid reaches its desired ratio of steel to other alloys, such as chromium and nickel, which form stainless steel. To purify the steel, the furnace then blasts in oxygen, and lime and fluorspar are added. These substances combine with the steel’s impurities, turning into slag. The slag then floats to the top of the molten steel where it is removed, leaving behind the pure steel.
The EAF method is the most common steel production method today. Today’s modern EAF steelmaking furnaces produce 150 tons of steel per melt, which takes approximately 90 minutes.
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