Steel manufacture: sources and Properties of Raw Material Feedstock’sSteel is one of the metals that have always been high on demand from day one, with its usage varying through a wide spectrum as in industries, constructions, containers to house hold necessities. The steel rates, is one of the commodity that has been growing up constantly over decades and is expected to grow so. The largest manufacture of steel till the turn of 21st century (2000) was US and EU but now it is comfortably surpassed by Asian countries as China and India closely following the heel. Raw materials needed in steel making: The steel that is discussed here is the main steel produced, carbon steel which further with addition of alloy sir attuned to other forms.
The major raw materials required isiron ore, and Manganese oreas fuel and reducing agent- coal, coke and petrofuelsas fluxes- Limestone and Dolomite and Quartzas refractories- Silica, Magnesite and AluminaThe main ore is the iron oxide, a compound of iron and oxygen. The hematite -abundantly available, limonite- the brown ore, taconite, and magnetite- black ore are principal ore.
To make quality steel, an ore with iron content of at least 50% is to be processed in the furnace. This is economically taken care by many industries by removing rocks and major impurities before shipping, by subjecting it to a process of beneficiation, which includes the process as crushing, screening, tumbling, floatation, and magnetic separation. This increases the iron content by 60% that is then made as pellets and shipped. The next raw materials as coke (the residue left after heating coal in the absence of air, that has up to 90% carbon) and limestone (CaCO3) or burnt lime (CaO).
These are added to the blast furnace at intervals, where the limestone or burnt lime is used as a fluxing material that forms a slag on top of the liquid metal. On an average it could be said that, to produce one ton of steel, two tons of ore, one ton of coke, and a half ton of limestone are required. Apart from it other minor elements as Carbon (0.5 to 1.25%), Manganese (0.03% to1.0%), small quantity of Phosphorus (0.04%), and Silica (0.5- 0.3%) are needed.
The coal is needed as energy for the steel making that is spend for 60% of energy needs. Also scrap steel is used in the process. There are variety and grades of steel made by varying the amount of raw materials used. The iron ore is available earlier in bulk form, whereas now it is available in pellet form. The Coke and coal are available in bulk form. The limestone or burned lime is thus used as the flexing material and it has an oxidizing effect on the liquid metal underneath which helps greatly to remove the impurities.
The Carbon, an important element in steel is added for strength, Manganese helps to remove unwanted oxygen and to control sulfur, where sulfur is known to make steel brittle or hot – short. The Phosphorus is added for adding strength and formidability to steel in small amount which when in excess reduces steels flexibility. The Silicon strengthens the steel by deoxidizing the molten steel. The Oxygen is another major element that is injected into the furnace mainly to improve and speed up the steel production.
Other metals as Chromium, Molybdenum, Nickel, Aluminum, Cobalt, Tungsten, Vanadium and Titanium are added to form alloys.