Manufacturing of various steels and irons is done using iron ores, which is the basic material used in the manufacture of iron and steel. Iron ore contains many impurities in its natural form and the iron content also varies. Make a note of the variation of the iron in the iron ores in the below mentioned ores:

  1. Hematite - 30-65% of iron content
  2. Magnetite - 60-70% or iron content

Creation of steel from this low-grade, impure iron ore (also called taconite) requires a process of:

  1. Mining
  2. Crushing
  3. Separating
  4. Concentrating
  5. Mixing
  6. Pelletizing, and
  7. Shipping

Before the iron ores are fed to the blast furnace, they are prepared. The preparation process is involves some form of concentrating process which means washing out the impurities and earthy matter like rocks and sand , which is followed by crushing, screening and sintering process.

With the help of crushing, even sized lumps of ore and fines are formed. The fines and lumps are separated in the screening process. After this, the fines are mixed with coal or tar dust and sintered. The sintering process causes agglomeration of the fines and coal dust, and also helps in the removal of some volatile substances. The sinter and the unsintered ore is then fed to the blast furnace as a part of the charge. Other than this, the charge also contains coke which serves as a fuel, along with limestone which serves as a flux.

Inside the blast furnace, the charge is subjected to intense heat at 1800 degree celsius. The reactions taking place inside a blast furnace are:

  1. At the bottom, Carbon + Oxygen = Carbon dioxide
  2. At the middle, Carbon dioxide + Carbon = Carbon Monoxide
  3. At the top, Iron oxide + Carbon Monoxide = Iron + Carbon Dioxide

After reaction 3, the iron which is produced is a spongy mass which falls to the furnace bottom. The molten iron is collected in the hearth of the furnace, with the slag floating at the top of the surface. Removal of the iron from the furnace, which is also called tapping is done every 6 hours. After tapping, the molten iron runs from the furnace through sand channels into pig beds, and that is the term pig iron is used. This pig iron is very brittle and has very little use. A random sample of pig iron will contain the below given components:

  1. Combined carbon 0.5%
  2. Manganese 0.5%
  3. Graphite 3.4%
  4. Phosphorus 0.03%
  5. Silicon 2.6%
  6. Sulphur 0.02%

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Thanks a lot. First time, I have come to know that why pig iron is called pig iron. 

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