The Science of Steel

Steel is the most important alloy in the modern world, with global production topping 1.8 billion tons a year. The key is carbon content: too little and the steel is soft and bends easily; too much and it turns brittle and shatters.

Heat treatment further controls steel's properties. Quenching (rapid cooling) locks carbon atoms in place, making steel extremely hard but brittle. Tempering (reheating to a moderate temperature) relieves internal stress and adds toughness.