Steel
The Role of Steel in Industrial Development
During the nineteenth century, the production of steel fuelled the industrial revolution in Europe and North America, introducing steel into almost every aspect of modern life. Today, around 1.5 billion tonnes of steel are produced globally each year, making it one of the most widely used materials in modern industry.
Composition of Steel: Carbon and Alloys
Steel is primarily an alloy of iron and carbon. The majority of steel is referred to as carbon steel and is classified based on its carbon content. Low carbon steel contains up to 0.25% carbon, medium carbon steel has between 0.25% and 0.75%, while high carbon steel contains between 0.75% and 1.5%. Increasing the carbon content makes the steel stronger but also more brittle.
To modify its properties for specific applications, other metals are added to create what are known as alloy steels. For instance, manganese increases strength, vanadium improves resistance to metal fatigue, cobalt enhances performance under extreme temperatures, and a combination of nickel and chromium produces stainless steel.
Steel Production Methods
Today, most steel is manufactured in a basic oxygen furnace. This type of furnace is lined with refractory materials and contains molten iron, scrap steel and a fluxing agent. Pure oxygen is blown into the furnace, which raises the internal temperature and oxidises the impurities. This process removes around 90% of the carbon content, resulting in high-quality liquid steel ready for further processing.
Electric Arc Furnaces
Electric arc furnaces offer another method for producing steel. These furnaces can operate using scrap steel alone or in combination with direct-reduced iron or pig iron. An electric arc generating approximately 35 million watts is created between two electrodes, generating the heat required to melt the metal. Electric arc furnaces require less capital investment and consume less energy than basic oxygen furnaces, making them a more flexible and efficient solution in certain steelmaking operations.