History and Importance of Pig Iron

Pig iron is an intermediate outcome obtained from a smelting\iron ore in a blast furnace. It is an amalgamation of 92% iron, up to 3.5% carbon, and fragments of manganese, silicon, sulfur, phosphorus, and impurities.

The traditional shape of the moulds used for pig iron ingots was a branching structure formed in sand, with many individual ingots at right angles to a central channel or runner, resembling a litter of piglets being suckled by a sow. When the metal had cooled and hardened, the smaller ingots (the pigs) were simply broken from the runner (the sow), hence the name pig iron.

pig iron history and importance

It has been widely used since the time of the industrial revolution and continues to impact our day-to-day lives in its many forms.

How is Pig Iron Produced?

Pig iron is formed as a result of the smelting of iron ore in a blast furnace. With the help of dolomite and limestone, the coke reduces the iron ore as a flux for eradicating the impurities. The resultant liquefied iron is then cast in the pig machine, which results in the production of pig iron.

Pig iron is produced in two categories, to conjugate with diversified fields. These are:

  • Basic grade– This is the basic form and has a very minor presence of silicon and manganese, which is less than 1%. Along with it, the trace amounts of phosphorus and sulfur are also present.
  • Foundry grade-This is known for its higher content of silicon that ranges between 1.5% and 3.5%. However, the presence may also soar up to 4.25%.

Attributes of Pig Iron                                         

Pig iron has limited applications but support in diversified fields. The features of pig iron are as follows:

  • It is wear-resistant and hard.
  • It is brittle and mildly fusible.
  • In comparison to steel, it has a lower melting temperature, 1200° centigrade.
  • Elongation ranges between 0% and 0.5%.
  • Hardness varies from 250 BHN to 450 BHN.
  • Tensile strength is from 25 kNs to 50 kNs.

Making Casting Iron from Pig Iron

Cast iron products are produced from pig iron by removing carbon and sulfur from the molten metal in the furnace. It is obtained as a result of the refining process of the metal and is preferred by numerous foundries to amalgamate with feedstock materials and scrap. This is accomplished due to the presence of high percentage of iron,lower impurity, reduced gangue, and purity of chemical composition. Cast iron involves scrap metal as well as steel that add to the benefits of the metal. Previously, cast iron was used to construct buildings but now is used to make heavy bottomed pans which can withstand high heat.

Importance of Pig Iron

Pig iron is known for its high carbon content, which makes it brittle while pure iron has a low content of carbon and minor level of impurity, contributing to the strength of the metal. It has a lower melting point in comparison to steel and iron which also helps produce a low-grade iron, named grey iron.

Obtaining Other Metals from Pig Iron

In the process of making pig iron various impurities are received. During the cooling of these impurities, different types of other materials are obtained. For example, iron carbide is formed with the combination of iron and carbon during the cooling, graphite which is used as the lead of a pencil is also obtained from the residual carbon from the smelting process, and others. The diversified manufacturers in India utilize pig iron as a raw material in order to obtain various other steel and iron products.