Some background information is necessary to understand where iron comes from and how it is made. Also, the different processes of making different types of iron are relevant to show that iron is not just found in the Earth's crust and turned into a building or an automobile.
The first use of iron came from meteors. This iron was wrought iron, which is tough and easily welded. During medieval times, Europeans produced wrought iron from cast iron.
About 5 percent of the Earth's crust is iron. It is one of the most plentiful elements on Earth.
Pig iron is made into wrought iron or steel by pouring the hot liquid iron into a mold and burning it in an oxygen or electric-arc furnace.
Cast iron and pig iron are two types of brittle iron. Wrought iron is tough and is less likely to corrode than steel. Steel is made from pig iron and is used to make buildings, bridges and automobiles.
Iron is used to make the hull of ships, automobiles, machines and tools used in construction, and the framing of many buildings.