Definition of steel

Steel is an alloy composed of iron and added carbon that improves strength and fracture resistance compared to other forms of iron. Many other elements can exist or be added. Corrosion and oxidation resistant stainless steels typically require an additional 11 percent chromium. Because of its high tensile strength and low cost, steel is used in construction, infrastructure, tools, ships, trains, cars, machinery, appliances, weapons and rockets. Iron is the basic metal of steel. Depending on temperature, it can be crystallized in two forms (allotrope form) : body-centered cubic and face-centered cubic. The interaction of allotropes of iron with alloying elements (primarily carbon) gives steel and cast iron a range of unique properties.

Steel is an alloy composed of iron and added carbon that improves strength and fracture resistance compared to other forms of iron. Many other elements can exist or be added. Corrosion and oxidation resistant stainless steels typically require an additional 11 percent chromium. Because of its high tensile strength and low cost, steel is used in construction, infrastructure, tools, ships, trains, cars, machinery, appliances, weapons and rockets. Iron is the basic metal of steel. Depending on temperature, it can be crystallized in two forms (allotrope form) : body-centered cubic and face-centered cubic. The interaction of allotropes of iron with alloying elements (primarily carbon) gives steel and cast iron a range of unique properties.

For ordinary carbon steel (iron-carbon alloy), the carbon content of the steel is between 0.002% and 2.14% by weight. Too little carbon makes (pure) iron very soft, malleable and weak. A higher carbon content than steel produces a brittle alloy, often called pig iron. Alloy steel is steel in which other alloying elements are deliberately added to alter the properties of the steel. Common alloying elements include manganese, nickel, chromium, molybdenum, boron, titanium, vanadium, tungsten, cobalt, and niobium. Other elements (generally thought to be unwanted) are important in steel: phosphorus, sulfur, silicon, and trace amounts of oxygen, nitrogen, and copper.

Ordinary alloys of carbon and iron with a carbon content greater than 2.1% are called cast iron.