Let's think about what iron and steel are. Iron is one of the chemical elements with the symbol Fe and atomic number 26. It is a metal in the first transition metals. Iron represents an example of allotropy in a metal. Allotropy represents one kind of material whose composition remain unchanged. However, its crystal structure change depending on conditions. There are a list of four allotropic forms of iron known as alpha, gamma, delta and epsilon as Molten Iron cools past this freezing point of 1538 degrees Celsius. We see it crystallized into delta allotrope which has a body- centered cubic crystal structure. As it cools further to 1394 degree celsius, it changes into Gamma, iron allotrope, a face centered cubic crystal structure or austenite. At 912 degree celsius and below, the crystal structure again becomes the BCC Alpha Iron allotrope, or ferrite. The property of iron changes to a large extent by making alloy with carbon and other elements First of all, as I talk to you, wrought iron is an iron alloy with a very low carbon content, less than 0.08 percent carbon. Steel means an alloy of iron and other elements, primarily carbon in the range of 0.08 to 2.1 percent carbon because of its high tensile strength, yet malleable and flexible. Cast iron is iron carbon alloy with a high than 2.1 percent carbon content with a lower melting point than steel and good castability properties. Pig iron is the intermediate product of smelting iron ore which has a very high Carbon content, typically, around 4.5%. Pig Iron is liquid iron produced by blast furnaces, because pig iron has a lot of impurities, people started to name liquid alloy pig iron because it has very dirty impurity alloys.