Pig iron and carbon steel both have carbon content which makes them similar. But the carbon content in both the iron products is different. The different carbon content in both of these materials give them distinct features and clearly brings a contrast between the materials. The high percentage of carbon content in pig iron makes them brittle whereas the low percentage of carbon content in carbon steel doesn’t hinder their ductility.
Pig Iron vs Carbon Steel
The main difference between pig iron and carbon steel is that pig iron is an impure form of iron with a high percentage of carbon content, whereas carbon steel is a somewhat pure form of iron with a very small amount of carbon content. Pig iron has almost 4 to 5% of carbon content whereas carbon steel has a maximum of 2% carbon content. The pig iron is brittle and has little to no use whereas carbon steel can be used for various purposes.
Pig iron is one of the early stages of steel production. It has a large quantity of carbon in it which is due to the reason that it lacks purification which can be achieved by other methods only. Pig iron in its purest form is called steel (the purity is in terms of carbon content). Historically it was made into wrought iron which on later purification can be turned into steel.
Carbon steel has about 2 percent of carbon content when measured in terms of weight. It may have other metal content as well such as nickel, tungsten, or any other metal which is added to it for alloying effects. The term carbon steel can also mean steels that do not fall under the category of pure steel. It is used for making various things such as machines, tools used for cutting, etc.
Comparison Table Between Pig Iron and Carbon Steel
| Parameters of Comparison | Pig iron | Carbon steel |
| Carbon content | It contains a large amount of carbon, up to 5%. | It contains a small amount of carbon, up to 2%. |
| Ductility | It is not ductile. | It is ductile and can be pulled into wires. |
| Usage | It has very limited to no use. | It has a variety of usage. |
| Stages of purity | It is the initial phase of the purity of iron. | It is at an advanced stage in terms of purity. |
| Weldability | It cannot be welded due to the very high content of carbon. | It is more weldable when compared to pig iron. |
What is Pig Iron?
Pig iron also called hot metal in its molten form is made for the purpose of storage of the metal. After it is transferred into a ladle in its molten form it is cooled down and made into pigs which can be used later or could be sold.
Pig iron is also used to make grey iron by altering the carbon content and adding some scrap steel, etc. Some pig iron can be formed into iron with ductility which is achieved by reducing carbon content. Pig iron can be useful in diluting the content of other elements in ductile iron as well.
Pig iron was not produced until the medieval period arrived in Europe. Earlier smelting was popular and people used to make wrought iron using the direct reduction method. The name pig iron was arrived at because traditionally the shape of the molds was such that the resultant solid iron resembled a large number of piglets.
It is made with an intention of reuse as it becomes easy to handle and convenient to use. Regardless, of impurities, the pig iron gets during the process of making, it proves to be useful due to the convenience of handling. The use of pig iron dates back to 256BC and before in Asia.
What is Carbon Steel?
Depending on carbon content carbon steels can be categorized into various forms. But broadly they can be categorized into two categories viz mild-carbon steel, and steel with high tensile strength. The tensile strength of steel is inversely proportional to the amount of carbon content in it. Thus, it can be understood easily that high-tensile steels will have a lower quantity of carbon in it. The variation of carbon content can lead to differences in properties such as plasticity, ductility, weldability, etc.
Mild-carbon steel has a very low carbon content ranging from a high of 0.5 to a low of 0.25%. According to the AISI (American Iron and Steel Institute), carbon content for different carbon steel differs and it has defined a range for each type. For example, High-carbon steel can have carbon content ranging from 0.6% to 1%. It is ultra-high carbon steel that has the maximum carbon content. The carbon content goes up to 2 percent.
The carbon content is the determining factor that determines the yield point of any carbon steel. The chemical properties of such steels can be changed by heat treatment. Carbon steels that can undergo high heat treatment are found with carbon content ranging from 0.3 percent to 1.7%. The other materials present in the steel also determine the strength of steel. Their properties of ductility, malleability, weldability, etc. largely depend on the entire process not only on carbon content.
Main Differences Between Pig Iron and Carbon Steel
- Pig iron and Carbon steel are different from each other in terms of their carbon content. Pig iron has a higher content of carbon than carbon steel.
- Pig iron is made use for storing, or selling the metal whereas carbon steel is used to make wires and other objects.
- Carbon steel is more malleable than pig iron because of the lower carbon content in it.
- Pig iron cannot be welded whereas carbon steels have the property of weldability.
- Pig iron and carbon steel also differ in terms of their ductility, pig iron is less ductile when compared to carbon steel.
Conclusion
Pig iron and carbon steel are both types of iron but they differ from each other in terms of their chemical composition and physical property. Pig iron has a relatively higher content of carbon when compared to carbon steel. But it is not only the carbon content that marks the difference other chemical properties also make these two different.
Both forms of irons are used for various purposes. Pig iron is the initial product in the process of steelmaking has limited usage such as storage whereas carbon steel is used to make various objects such as cutting objects, etc. Carbon steel has various forms that differ from each other in terms of chemical composition and carbon content.
References
- https://www.jstage.jst.go.jp/article/isijinternational/47/1/47_1_53/_article/-char/ja/
- https://link.springer.com/content/pdf/10.1007/s12649-013-9223-1.pdf
- https://books.google.com/books?hl=en&lr=&id=rsdbs92yGs4C&oi=fnd&pg=PP7&dq=Difference+Between+Pig+Iron+and+carbon+steels&ots=-PIF83b5cs&sig=YHu2ta04UzGOQkDT_Xovq7HXdqs
- https://www.researchgate.net/profile/Tariq-Islam-6/publication/332772564_Classification_and_Application_of_Plain_Carbon_Steels/links/605afd73a6fdccbfea00ada5/Classification-and-Application-of-Plain-Carbon-Steels.pdf