Iron
Iron as a chemical element is referred to by the symbol Fe and has an atomic number 26 on the periodic table. Iron is a metal in the first transition series and is the most abundant element on the outer and inner surface of the earth.
Iron was discovered in 2000 BCE when it replaced bronze in manufacture of tools and weapons and ushered in the Iron Age. Iron was first used in South-Central and South-West Asia. Iron was picked over bronze because when it is blended with carbon, it becomes harder and durable. Iron can also hold a sharp edge better than bronze which made it ideal for tools application. Iron reigned as the material of choice that drove civilization until it was replaced by steel in CE 1870. Iron was widely used in Europe, Africa, and Asia (Spoerl).
SOURCE OF IRON
Iron exists as an iron ore in its natural form. It has a high affinity for oxygen so the iron ore exists as an oxide of iron. Iron ore contains impurities such as silicon, manganese, phosphorous and sulfur. Iron ore is referred by several scientific names according to the impurity present. Major iron ores include hematite (Fe2O3), limonite (FeO(OH) • nH2O), siderite (FeCO3), magnetite (Fe3O4), and sulfide, iron pyrite (FeS). Iron sulfide is very difficult to purify hence it is not used commercially. It has a golden appearance which gives it the moniker “fool’s gold”.
EXTRACTION OF IRON FROM IRON ORE
Iron oxide is reduced by carbon into iron by heating both elements in a blast furnace. Carbon used is in form of coke obtained by heating coal without air. The use of coal is advantageous because it is cheap and acts both as a heat source and reducing agent. Magnetite and Hematite are the mostly used forms of iron ore.
Hot coke in the blast furnace reacts exothermically with the hot air blast to form carbon dioxide with the release of heat which melts the ore.
C+O2→CO2
Figure 1: Reduction of iron in a blast furnace
The high temperatures at the bottom the furnace induce reaction of carbon dioxide with carbon to form carbon monoxide. Carbon monoxide is responsible for reducing iron ore into iron.
C+CO2→2CO, Fe2O3+3CO→2Fe+3CO2
Limestone is added into the process to make melt the rocky impurities in iron ore which would otherwise not melt at furnace temperatures and would clog the system. Limestone causes them to melt into a slag which flow out together with the molten iron. Limestone is then converted to calcium oxide.
CaCO3→CaO+CO2
Slag layer floats on the top of the molten iron and it can be tapped off. It is used in road making or in cement manufacture (Clark).
TYPES OF IRON
Cast iron
The molten iron obtained from the blast furnace is in form of cast iron and has 4% carbon. Cast iron is used in manufacture of casts through casting because it is very runny. It is used in manufacture of manholes covers, heavy cookware, car engine cylinder blocks, and drainpipes.
Wrought Iron
Wrought iron has all the carbon removed making it soft and malleable. It is very pure with low structural strength. Wrought iron is used in fabrication of decorative gates and railings.
Mild steel
Mild steel contains up to 0.25% carbon which gives it more hardness and strength than pure iron. Hardness in steel is increased by increasing the percentage of carbon. It is sued in manufacture of nails, car bodies, ship building among others.
High carbon steel
High carbon steel contains 1.5% carbon which gives it extra hardness but also makes it more brittle. It is used in making of equipments that require hardness such as masonry nails and cutting tools (Clark).
ALLOYS OF IRON
Stainless steel
Stainless steel is made from a mixture of ion with chromium and nickel. This alloy has a distinctive resistance to corrosion and is used in manufacture of kitchen ware such as cutlery, kitchen sinks, utensils, and food and drink processing equipment.
Titanium steel
Titanium steel is made from a mixture of iron and titanium. This alloy can withstand high temperatures without failure and is thus used in making of spacecraft parts and gas turbines.
Manganese steel
Manganese steel is made from a mixture of manganese and iron. This alloy is very hard and is used in applications that require toughness such as military helmets, rock breaking equipment and railway tracks (Clark).
Iron is a very important element in the modern world today. Virtually every engineering process utilizes iron. Modern technology would have been impossible to achieve were it not for iron. Iron extraction technology has advanced from traditional smelters to modern automated furnaces capable of mass production. The material is widely applied for both industrial and domestic purposes which make it one of the most essential engineering materials.
Works Cited
Clark, Jim. The Extraction of Iron. UCDavis. Chemwiki. 2014. Web. 10 Dec 2014.
Spoerl, Joseph S. A Brief History of Iron and Steel Production. Saint Anselm College. n.p, 2014. Web. 10 Dec 2014.
