Category: Pig Iron

Pig iron is an output obtained as a result of the process of manufacturing iron. Fuel coke with high carbon is utilized in order to heat the iron ore. This results in the production of pig iron which is high in carbon content. The cold pig iron is known as merchant pig iron, which is cast into blocks or ingots. These are then sold to the ferrous as well as steel casting industries in the form of feed stock. There are three types of merchant pig iron, which are as follows:

• Basic pig iron– This is used in electric arc furnace for the purpose of steel making.
• Foundry pig iron– This type of pig iron is also known as haematite pig iron and is used in cupola furnaces for grey iron castings.
• High purity pig iron– This is synonymous to nodular pig iron and is used for producing ductile iron castings, which is also known as SG or Spheroidal Graphite. This is used by the manhole cover manufacturers.

Attributes and Application of Foundry Pig Iron for the Grey Iron Casting

This type of pig iron is produced from the specific sources of iron ore. Due to the stable physical as well as chemical analysis it enables the variability of melting and a robust control over the composition of final casting. This eradicates the need for the high-priced casting requirements like heat treatment. This category of pig iron is used in the genres like machine tools, general engineering, and automotive parts manufacturing. Creation of pearlite in the final casting is promoted because of the high iron content on the pig iron.

The application of the foundry pig iron seamlessly promotes the formation of graphite, depletes the primary chill, and enhances machinability. This is highly beneficial for the thin-walled castings. The bulk density of this pig iron is also on the higher side in comparison to the scrap, which needs a lesser space for the storage, and reduced time for charging. In fact, the energy consumption is also reduced remarkably due to higher carbon content. Hence, this type of pig iron is highly beneficial for the manufacturing industries specifically for the casting needs.

Attributes and Application of High Purity Pig Iron for the Ductile Iron Casting

This type of pig iron is also known as HPPI and is characterized by its lower contents of sulfur, phosphorus, and manganese. The presence of the other metal impurities is also negligible that makes the iron highly desirable in various sectors.  The application on HPPI can be mainly found in the casting components of the automotive, energy, and engineering industries. There are various advantages associated with HPPI that contributes to the successful ductile iron casting, which are as follows:

• The undesirable elements in the melt are diluted that aids in the depleted cost of scrap.
• The predictable and stable composition of the iron helps achieve better control over the final composition of casting, which leads to an enhanced mechanical output of the casting.
• It demands lower storage space and lesser charge buckets.
• Lower formation of rust leads to the depleted volume of slag.
• Due to the chemical combination of carbon content, the casting is achieved easily with lower consumption of energy.
• The reduced consumption of power and rapid melting leads to the lesser power consumption in the induction furnace.

Hence, the implementation of HPPI in diversified casting needs help reduce the net investment.

History and Importance of Pig Iron

Pig iron is an intermediate outcome obtained from a smeltingiron 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 modulus 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.

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.