Steel is a precise mixture of iron, carbon, and other metals.  There are many chemically different types of steel. Most steels are more than 95% iron, with small percentages of carbon and manganese, and trace amounts of silicon, phosphorus, and sulfur. Steels are produced by refining (removing impurities from) the iron and alloying (mixing) it with other metals and materials.

Steels can be hard or soft, stiff or bendable, rust-prone or stainless.  Today, steel is the world’s most important engineering and construction material.  It is used to make cars, home appliances, ships and trains, bridges, tools and surgical instruments, weapons, skyscrapers, and so much more.