PIG IRON, CAST IRON & WROUGHT IRON – WHAT’S THE DIFFERENCE?

Cast iron, which is extracted from iron ores, is known as pig iron and forms the basic material for the manufacture of cast iron, wrought iron, and steel.

Pig iron is manufactured by the following functions


(i) Dressing:

Crushed into pieces of 25 mm, clay, loam and other soil impurities are removed by washing, magnetic separators are used for magnetic impurities.

(ii) Calcination and Roasting:

Water and carbon dioxide are removed from ores by calcination. To make ores hot and very dry by roasting, removing sulfur

(iii) Smelting:

Smelting is done in a special type of furnace known as a blast furnace. The raw materials are iron ore, fluxing materials such as limestone and coal, fuels such as charcoal are allowed to pass through the neck part of the furnace. By reduction, the cast iron is deposited in the furnace hearth. The built up slag is removed and the hot gases exhaust through the dust outlet, which is provided in the neck part of the furnace.

PIG IRON, CAST IRON & WROUGHT IRON – WHAT’S THE DIFFERENCE? 1
cupola furnace

Cast iron is made by melting pig iron with coke and limestone. This remelting is done in a furnace called a cupola furnace, which is more or less similar to a blast furnace. Its shape is cylindrical with a diameter of about 1 m and a height of about 5 m. The raw material is carried from above and fired to the furnace. The impurities in pig iron are removed to some extent by oxidation. The molten cast iron is taken into molds of required size, known as cast iron castings and slag is removed from the top of the cast iron at regular intervals.

Composition of cast iron:

  • Cast iron contains about 2 to 4 percent carbon.
  • Manganese makes cast iron-brittle and hard, so it can be kept below 0.75 percent.
  • Phosphorus makes it brittle and the percentage can be 1 to 1.5 percent.
  • Silicone reduces shrinkage and ensures softer and better casting and can be as low as 2.5 percent.
  • Sulfur makes cast iron brittle and hard and should be kept below 0.10 percent.

cast iron uses:

  • For making tanks, water pipes, gas pipes and sewers, manhole covers and sanitary fittings.
  • For making decorative moldings such as brackets, gates, lampposts etc.
  • For making parts of machinery that are not subject to shock loads.
  • For manufacturing compression members.
  • To prepare rail chairs, cart wheels, etc.

Wrought iron is almost pure and contains hardly more than 0.15 percent carbon. But the process of its manufacture is laborious and tedious. Wrought iron is produced by four functions

  1. refining
  2. puddling
  3. shingling
  4. rolling

Properties of Wrought Iron:

  • It can be forged and welded easily
  • It can be used to make temporary magnets
  • It’s ductile, malleable and tough
  • it is moderately elastic
  • It is unaffected by salt water
  • It resists corrosion better
  • Its melting point is about 1500. It happens0C
  • Its specific gravity is about 7.8. Is
  • Its ultimate compressive strength is about 2000 kg/cm. Is2
  • Its ultimate tensile strength is about 4000 kg/cm. Is2,

Uses of Wrought Iron:

It is used for rivets, chains, ornamental ironwork, railway couplings, water and steam pipes, bolts and nuts, horse shoe bars, hand rails, bars for parquet trusses, boiler tubes, roofing sheets, etc. is done for.


Er. Mukesh Kumar

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Er. Mukesh Kumar is Editor in Chief and Co-Funder at ProCivilEngineer.com Civil Engineering Website. Mukesh Kumar is a Bachelor in Civil Engineering From MIT. He has work experience in Highway Construction, Bridge Construction, Railway Steel Girder work, Under box culvert construction, Retaining wall construction. He was a lecturer in a Engineering college for more than 6 years.