Which element is added to iron to produce steel?

Which element is added to iron to produce steel?

• A. Nitrogen
• B. Oxygen
• C. Phosphorus
• D. Carbon

Answer: (D)

Steel is formed by adding carbon to iron to create an iron–carbon alloy. Carbon atoms fit into the spaces in the iron crystal, disrupting its regular lattice. This interference blocks the movement of defects, which makes the metal harder and stronger. The amount of carbon controls properties: a small carbon content yields ductile, tougher steel; higher carbon increases hardness and strength but reduces ductility; too much carbon results in brittle cast iron. Other elements listed are impurities that can degrade properties if present, but carbon is the element intentionally added to tailor steel’s characteristics.

Steel is formed by adding carbon to iron to create an iron–carbon alloy. Carbon atoms fit into the spaces in the iron crystal, disrupting its regular lattice. This interference blocks the movement of defects, which makes the metal harder and stronger. The amount of carbon controls properties: a small carbon content yields ductile, tougher steel; higher carbon increases hardness and strength but reduces ductility; too much carbon results in brittle cast iron. Other elements listed are impurities that can degrade properties if present, but carbon is the element intentionally added to tailor steel’s characteristics.