Manufacture of Iron

Occurrence:-

Iron is the most indispensable metal to man. After, Aluminium iron is the most abudant metal in the earth’s crust. The three raw material of iron ore was namely as iron ore, coal, and limestone. The important ore ore of iron are given below;-

  1. Red Haematite (Fe2O3)
  2. Brown Haematite (2Fe2o3.3H2o)A
  3. Magnetite (Fe3O4)
  4. Siderite (FeCo3)
  5. Pyrites (FeS2)

The presence of silica and alumina in the iron are not only reduce the iron content in ore but also increases the cost the of production of iron and steel.

The fuel in steel production acts in two ways:

  1. It provide energy to melt the change.
  2. It reduce iron ore to iron by reacting with the oxygen of the ore.

The zone of the blast furnace in which the decomposition of CaCo3 and formation of fusible slag take place is called the zone of heat absorption.

Commercial Form Of Carbon

  1. Pig Iron:- It is least pure variety of commercial form of iron contains the higher percentage of carbon (2.5-4.5%) alongwith impurities of S, P, Mn, and Si.
  2. Wrought Iron:- It is the purest form of commercial iron and contains the lowest percentage of carbon (0.12%-0.25%).
  3. Steel:- It is an alloy of iron and carbon. It contains (0.25%-2.5%). Carbon content in steel lies midway between the wrought iron and cast iron.

Allotropic Form Of Carbon

There are three type of allotropic form

  1. Alpha iron occurs from room temperature to 1670 F (910C) and has body center cubic lattice crystal. Alpha iron is either ferromagnetic Iron or paramagnetic Iron.
  2. Gamma Iron occur from 1670f to 2550F. It has to be found to have face-centered cubic lattice.
  3. Delta Iron occurs above 2550F when the iron is in a molten state. This has been found to have body center cubic lattice.

Property Of Iron

The melting point of iron is 2830F. Its boiling point is 4964F. Its tensile strength is 35000-40000 lbs per sq. inch. Its yield strength is 10000-20000 lbs per sq. inch. Its electrical conductivity at 25C is 100000.

Impurities

  1. Carbon
  2. Silicon
  3. Sulphur
  4. Manganese
  5. Phosphorus

Manufacture of cast Iron

Cast iron if manufactured from haematite.

The ore is heated with coke and limestone. The coke burns to form carbon dioxide which is reduce to carbon monoxide by the coke.

The carbon monoxide thus formed to reduce to spongy iron.

silica present in the oxide ore react with calcium oxide.

Process

  1. The concentration of ore:- The ore is crushed to small pieces of 3-3.5 cm is size screened and shifted. this removes most of the gangue. Rich ores do not need further concentration but the ore of poor quality are further washed with water to remove clay, sand etc.
  2. Roasting:- The concentrated ore is roasted or calcined with a little coke in shallow kilns in excess of air.
  3. Smelting in the blast furnace:- The charge consists of 8 parts of roasted ore, 4 parts of desulphurized coke and 1 part of limestone is carried to the top of Furnace by a pair of truck ran up an inclined railways.

Varieties of Cast Iron

  1. White Cast Iron
  2. Grey Cast Iron
  3. Malleable Cast Iron
  4. Ductile Cast Iron
  5. Alloyed Cast Iron
  6. Mottled Cast Iron

Wrought Iron

Wrought iron is manufactured from cast iron on the hearth of a reverberatory furnace, lined inside with haematite. The main advantage of the puddling furnace is that molten iron is continuously stirred and thereby brought in contact with fresh air and with iron oxide of the lining so that the carbon is removed to such an extent that wrought iron is produce in a single formation.

Steel

  1. Cementation Process
  2. Crucible Process
  3. Bessemer Process
  4. Linz Donawitz
  5. Open Hearth Process
  6. Electric Furnace Method

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