Pig iron is a solid form of hot metal, obtained from iron ore or scrap recycling, and it is processed with a blast furnace or an electric arc furnace. Most of the raw materials used in the production of iron and steel come from imports.
Pig iron is also known as crude iron. It is obtained from a smelting furnace in the form of oblong blocks and has a very high carbon content of 3.5-4.5, as it contains 90% iron.
Merchant pigs are ingots made from cold pig iron castings. Third parties purchase them as feedstock for the steel and ferrous casting industries.
Different types of merchant pig iron are basic, foundry, and high-purity pig iron. In this reading, we’ll explore what pig iron is, its applications, properties, composition, types, and how it becomes steel.
Let’s Get Started!
Related: What is Wrought Iron? its Applications & Properties
What is Pig Iron?
Pig iron is a product of smelting iron ore with a high-carbon fuel and reductants like coke and limestone that serve as flux. Charcoal and anthracite can also serve as fuel and reductants.
Pig iron is produced in a blast furnace by smelting iron ore or by smelting ilmenite in an electric furnace.
One of the major uses of pig iron is its production and use within a steel mill. Pig iron in this context is known as blast furnace iron, transferred directly to the steel plant in liquid form.
The substance in question is also known as hot metal, which can be supplied in a variety of ingot sizes and weights, ranging from 3 kg up to more than 50 kg.
Applications
The applications of pig iron in an electric arc furnace are for steelmaking. Foundries use high-purity pig iron to produce ductile iron castings. Foundries also use pig iron to make grey iron castings.
Pig iron is refined into wrought iron through melting and the introduction of hot air. Additionally, pig iron can be converted into gray iron. Historically, pig iron was extracted from the furnace’s bottom and transported to a steel mill for further processing.
Currently, a steel mill transforms the metal into pellets before shipping.
Related: What is Foundry? Its Applications and Safety
What are the Properties of pig iron?
Pig iron is also known as crude iron. It is obtained from a smelting furnace in the form of oblong blocks and has a very high carbon content of 3.5-4.5, as it contains 90% iron.
It is produced by smelting iron ore with high-carbon fuel and reductants such as coke, usually with limestone, which serves as flux. Anthracite and charcoal serve as additional fuel materials.
The term “pig iron” derives from an old way of dealing with molten iron. It was run off directly from the furnace into open channels, which feed into numerous short channels on either side, bearing a faint semblance to a sow suckling iron piglets.
The sow broke off the pig iron when it was solid. A small amount of cold iron is still known as pig iron today. The term ‘hot metal’ is used to denote molten iron.
Composition of Pig iron
Pig iron contains about 90–95% elemental iron together with several other elements, mainly carbon, silicon, phosphorus, manganese, and sulfur, in varying proportions depending on the composition of the raw materials and the mode of an operating blast furnace.
Pigs may hold 3.0-4.5% of carbon, 0.5-4.0% of silicon, 0.025-2.5% of phosphorus, 0.15-2.15% of manganese, and up to 0.2% of sulfur. The composition required for steelmaking differs from that required for use in foundries to make iron castings.
What are the Types of Pig Iron?
Pig Iron consists of three primary types: BASIC PIG IRON, primarily used in electric arc steelmaking; FOUNDRY PIG IRON, predominantly used for the production of grey iron castings through cupola furnaces; and NODULAR PIG IRON (SG GRADE), which is used for the manufacture of ductile iron castings.
Pig iron serves various applications, including steel production, foundry work, alloy manufacturing, and automotive and other iron-based castings.
Related: What is Cast Iron? its Applications, Properties, & Types
What is Merchant Pig Iron?
Merchant pigs are ingots made from cold pig iron castings. Third parties purchase it as feedstock for the steel and ferrous casting industries.
It is produced by the dedicated merchant plant (all production is sold to external customers), an integrated steel mill with iron that is surplus to their internal requirements and cast into ingots, and sold to the merchant market.
Types of Merchant Pig Iron
Merchant pigs can be classified into three main types:
1. Basic: it is mainly used in electric arc steelmaking
2. Foundry: it is known as hematite pig iron, used mainly in manufacturing grey iron castings in cupola furnaces.
3. High purity: it is known as nodular pig iron and is used for manufacturing ductile iron. Spheroidal graphite, also known as SG iron castings, is another name for high-purity pig iron.
Related: What is Iron (FE)? its Properties, Types & Raw Materials
How Does Pig Iron Become Steel?
The Bessemer process and the basic oxygen furnace convert pig iron into steel. The process involves the extraction of carbon from the iron. Afterward, it produces a metal characterized by its lighter weight, improved flexibility, and rust resistance, known as steel.
Steel primarily consists of iron as its key component.
Related: How Steel Is Produced? 6 Steps Of Steel Manufacturing Process