Materials
The ferrous metals (cast iron, wrought iron and steel) are of different chemical composition and have different physical properties.
All of the ferrous metals are alloys of iron and carbon, and small percentage differences in the quantity of carbon make large differences to the properties of the material. The details of these changes are explained elsewhere, but for this unit, all that is necessary is to think of wrought iron as having very little carbon and being ductile, mild steel as having a little more carbon and still being quite ductile, while cast iron has rather more carbon, which makes it brittle when cold but fluid when hot which allows castings to be made.
