Crushing and Pulverization:
-Big lumps of ore are crushed with jaw crushes and pulverized with ball mill.
-The ore is then washed with cold water and concentrated by gravity separation or electromagnetic separation.
Calcination or Roasting:
- The Hematite ore is oxide ore, so it is calcinated (i.e. heated in limited supply of air.)
-Moisture is removed.
Iron Carbonate present also decomposes to .
-The is obtained from and initially present reacts with limited air to for
-This is very important step because easily combines with to form slag, which is finally lost. But, doesn't react with and iron loss is saved.
-The calcinated ore is heated on blast furnace with coke and limestone (flux).
-In this smelting process the iron oxide is reduced to metallic form.
-The blast furnace has different zones, which are: ( from bottom to top of blast furnace)
-It is lowermost zone where coke is brunt to give the highest temperature of furnace up to
-It is the zone where iron and slag starts fusing. So, temperature decreases to about
-It is middle portion of furnace where temperature reaches from (800.C-1000.C)
- is said to be flux and is added externally.
-It is uppermost region where ore is reduced to metal as reducing agent.
-Temperature is about
-Thus obtained iron is called spongy iron.
-The upper zone is called zone of preparatory heating where temperature ranges from .
-In this zone moisture and other waste gases are removed.
-At the end of smelting, molten slag settles down and floats over molten ion, which absorbs Silicon, Phosphorous, Sulphur, etc.
-The Molten iron thus obtained is called pig iron.
-When pig iron is remelted, it becomes cast iron.
-Most impure form of iron.
-It has carbon contain of with small quantities of .
-It is very hard and has low M.P of .
-Most purest form of iron.
-Contains carbon in it.
-It has less than of other impurities like etc.
-It melts at and is soft and malleable.
-It has carbon content about , which traces of sulpher, phosphorous and special constituent like etc.