What is Steel
Steel is the most common metal alloy that is made by humans. Steel basically is made by combining IRON which accounts 98% of the alloy and CARBON which accounts about 2.1% to 0.2%. It is the most widely used metal alloy. Steel is strong, resilient, versatile and can be recycled over and over again without losing those properties. It can be used in a wide variety of climates, including extreme cold and hot.
Traces of magnesium, chromium, tungsten, molybdenum, manganese, nickel and cobalt are used in modern steels. All of these can be used to varying degrees to help make the steel harder, lighter, more or less resistant to heat and electrical current, more ductile and corrosion resistant. When iron is smelted from its ore by commercial processes, it contains more carbon than is desirable. To become steel, it must be melted and reprocessed to reduce the carbon to the correct amount, at which point other elements can be added.
Adding more and more carbon to iron (upto solubility of iron) provides increased mechanical strength. However, solubility of more carbon influences negatively with another important property of iron called the ‘ductility’ (ability of iron to undergo large plastic deformation). The a-iron or ferrite is very soft and it flows plastically. Hence we see that when more carbon is added, enhanced mechanical strength is obtained, but ductility is reduced..
The modern steel industry produces steel through the use of what is called the basic oxygen furnace. In these furnaces, molten iron has pure oxygen blown through it, lowering the levels of impurities in the iron. Cleaning agents called fluxes are also added for this same purpose. The main advantage to this process, other than a high-quality product, is its speed. Previous steel-making processes included the Bessemer process, where air was forced through molten iron to oxidize impurities. Carbon monoxide is one by-product of this process, with the other impurities forming slag. The invention of the Bessemer process was especially noteworthy because it made steel a mass-produced, cheap commodity. Steel had been produced by various methods in the Middle Ages and before, but none of these were especially efficient, nor could they be employed on a large scale.
There are many types of steel depending on its composition mainly; High-Carbon Steel, Mild Steel, Medium Carbon Steel, Stainless Steel, Cobalt Steel, Nickel Chromium Steel, Chromium Steel. Iron and steel are used widely in the construction of roads, railways, other infrastructure, appliances, and buildings. Most large modern structures, such as stadiums and skyscrapers, bridges, and airports, are supported by a steel skeleton. Even those with a concrete structure will employ steel for reinforcing. In addition, it sees widespread use in major appliances and cars. Despite growth in usage of aluminium, it is still the main material for car bodies. Steel is used in a variety of other construction materials, such as bolts, nails, and screws. Other common applications include shipbuilding, pipeline transport, mining, offshore construction, aerospace, white goods (e.g. washing machines), heavy equipment such as bulldozers, office furniture, steel wool, tools, and armour in the form of personal vests or vehicle armour (better known as rolled homogeneous armour in this role).