Steel is an alloy of iron and about 2% or less carbon and 1% other elements. Pure iron is soft, but carbon greatly hardens it. Adjusting the carbon content changes the properties of steel. Heat-treating, mechanical working at cold or hot temperatures, or the addition of alloying elements may also give superior properties.
The three major classes are carbon steels, low-alloy steels, and high-alloy steels. Low-alloy steels (with up to 8% alloying elements) are solid and used for machine parts, aircraft landing gear, shafts, hand tools, gears, and buildings and bridges. High-alloy steels, with more than 8% alloying elements (e.g., stainless steels) offer unusual properties. Making steel involves melting, purifying (refining), and alloying, carried out at about 2,900 °F (1,600 °C)1.
While the story of steel begins long before bridges, I-beams, and skyscrapers, some claim it began in the stars, billions of years before humans walked the Earth — before the Earth even existed — blazing stars fused atoms into iron and carbon. Around 1,800 BC, people along the Black Sea called the Chalybes wanted to fabricate a metal stronger than bronze — something that could be used to make unrivalled weapons. They put iron ores into hearths, hammered them, and fired them for softening. After repeating the process several times, the Chalybes pulled sturdy iron weapons from the forge2.
Iron and steel are indispensable construction and other materials used widely in our everyday activities. They are used as a material input for the automotive industry, energy production and networks, urban and long-distance transport infrastructures, and general mechanical engineering industries.
Steel, by far, is the most widely used material for building the world’s infrastructure and industries. It is used to fabricate everything from sewing needles to oil tankers. In addition, the tools required to build and manufacture such articles are also made of steel3.
Steel is also expected to be a key material in the future as changing environments will likely require steel to meet infrastructure and construction needs around the world and to build climate-resilient cities and coastal protection. According to the International Energy Agency, renewable power capacity is set to expand by 50% between 2019 and 2024. This…