Steel is an alloy based mainly on iron with a controlled amount of carbon and, often, small amounts of other elements. It is one of the world's most important engineering materials because it can be made strong, tough, formable, weldable, magnetic or corrosion-resistant depending on composition and processing.
Steel is not a single material. It is a family of alloys with different grades for buildings, vehicles, tools, machinery, pipelines, rails, ships, appliances, packaging and medical equipment.
Composition
Most steels are mostly iron. Carbon changes the hardness, strength and ductility of the alloy. Other elements such as manganese, chromium, nickel, molybdenum, vanadium, silicon and boron can be added to control strength, wear resistance, corrosion resistance or heat treatment behaviour.
Stainless steels contain enough chromium to form a protective oxide layer, which improves resistance to corrosion. Tool steels are formulated for hardness and wear resistance. Structural steels are designed for strength, toughness, weldability and predictable performance in construction.
Production
Steel is commonly made by reducing iron ore to iron and then refining it into steel, or by melting and refining scrap steel in an electric arc furnace. Two major routes are the blast furnace and basic oxygen furnace route, and the electric arc furnace route.
The exact process affects cost, emissions, scrap use and product range. Modern steelmaking also uses secondary metallurgy, casting, rolling, heat treatment and surface finishing to meet grade specifications.
Uses
Steel is used in buildings, bridges, railways, cars, ships, pipelines, tools, machinery, packaging, domestic appliances and energy infrastructure. Its wide use comes from the balance between strength, availability, formability, recyclability and cost.
Different applications need different grades. Reinforcing bar for concrete, stainless steel for food handling, electrical steel for motors and transformers, and advanced high-strength steels for vehicles are not interchangeable materials.
Recycling and Environmental Issues
Steel is highly recyclable, and scrap is an important raw material. Recycling reduces demand for virgin raw materials, but steelmaking still has major energy and carbon impacts.
The industry is working on lower-carbon production routes, including greater scrap use, renewable electricity for electric arc furnaces, direct reduced iron using lower-carbon energy, and carbon capture in some settings.
See Also
References
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