1. MATERIALS OF CONSTRUCTION
Presented By:
 Jayakrishna Shenoy
 Adithya Acharya
 Rishvik Sharma
 Preston Lobo
 Gary Naveen Lewis

2. Cast Iron
• It is a type of iron which has 2-4% carbon
content. It may also contain manganese ,
phosphorous, silicon & sulphur.
• Manganese imparts hardness to cast iron but
makes it brittle. So manganese is kept <0.75%.
• Phosphorous increases its fluidity. But it makes
cast iron brittle. If its amount is greater than 0.3%,
cast iron becomes less workable and lacks
toughness.
• Silicon makes cast iron brittle and hard. Its mere
presence causes rapid solidification of cast iron.

3. Manufacture of cast iron
• It is manufactured by re-melting pig iron with coke and limestone.
• This re-melting is done in a furnace called as cupola furnace.
• It is more or less same as the conventional blast furnace but it is
smaller in size.
• Its shape is cylindrical with diameter of about 1m and 5m height.
• The working too is similar to that of the blast furnace but the raw
materials are fed from the top.
• The air is forced from the tuyeres and the impurities are removed by
oxidation.
• The slag formed is removed from the top of the furnace at regular
intervals of time.
• It is led into moulds of required shape (AKA cast iron castings or
ingots).

4. Illustrations of cupola furnace

5. Types of cast iron
1. Grey cast iron
2. White cast iron
3. Mottled cast iron
4. Chilled cast iron
5. Malleable cast iron
6. Spheroidal graphite iron.
7. Toughened cast iron

6. Grey Cast iron
 It is prepared from grey pig.
 It’s color is grey. It is soft and melts
readily.
 It is extensively used for making
castings.

7. White Cast Iron
 Its color is silvery white.
 It is hard and melts with difficulty.
 It is not easily worked even on a machine.
 Cant be used for delicate casting.

8. Mottled Cast Iron
 Intermediate variety between grey cast iron and white cast iron.
 The fracture of this variety is mottled.
 This variety is used for small castings.
 Mottled means variegated or smeared with spots.

9. Mottled cast iron looks like this from a 40x objective lens.

10. Chilled cast iron
 The chilling consists of making some portion of cast
iron hard and the other portion soft.
 This variety of cast iron is hard to a certain depth
from the exterior surface and is indicated by white
iron.
 The interior portion of the body of casting is soft
and is made up of grey iron.

11. Malleable Cast Iron
 The composition of cast iron is so adjusted that it becomes
malleable.
 It is done by extracting a portion of carbon from cast iron making it
less brittle.
 Its used to make railway equipments , automobiles , pipe fittings etc.

12. Ductile Or Spheroidal Iron
 Malleable cast iron is being replaced by ductile cast iron
as it is much easier than malleable cast iron.
 Manganese content of carbon in iron and opposes the
formation of free graphite.

13. Toughened Cast Iron
 This variety of cast iron is obtained by making cast iron with
wrought iron scrap.
 This proportion of wrought iron scrap is about 1/4th to 1/7th
of weight of cast iron.

14. Properties Of Cast Iron
1. If placed in salt water , it becomes soft.
2. It can be hardened by heating and sudden cooling but can’t be tempered.
3. It can’t be magnetized easily.
4. It does not rust easily.
5. Its not ductile and hence can’t be used to absorb shocks and impacts.
6. Its melting temperature is about 1250°C.
7. It shrinks on cooling.

15. M A N U F A C T U R E O F WR O U G H T I R O N
 The wrought iron is almost pure iron and it hardly contains carbon content more than
0.15% or so.
 But the process is far more laborious and tedious. There are four distinct operations
involved in its manufacture. They are:
1. Refining: The pig iron is melted and a strong current of air is passed over it. It is well
agitated when the currents of air passes over it, oxidizing the impurities present in it.
2. Puddling: The conversion of pig iron into wrought iron by stirring it in a molten state is
known as puddling. It is carried out in a reverberatory furnace as shown in figure. In this
type of furnace, the metal does not come in contact with the fuel and flame from the
fire is reverted back into the hearth.
3. Shingling: By this process, the slag contained in puddle balls is placed is removed. It
may be achieved by forging the balls under a power hammer or by passing the balls
through a squeezing machine. The shingling helps in binding or welding the different
particles of puddle balls. The material obtained at the end of shingling is known as the
bloom and it is still in red hot condition.
4. Rolling: The bloom is passed through grooved bars and flat bars of size about 4mm
*100mm*25mm are obtained. These bars indicate wrought iron of poor quality. To
improve the quality of wrought iron , these bars are tied together and they are heated
and rolled. This process may be repeated till we get wrought iron of desired quality.

16. Properties Of Wrought-Iron
1. It becomes soft at white heat and it can be easily forged and welded.
2. It can be used to form temporary magnets, but cannot be magnetised
permanently.
3. It fuses with difficulty. It cannot therefore be adopted for making castings.
4. It is ductile, malleable and tough.
5. It is moderately elastic.
6. It is unaffected by saline water.
7. It resists corrosion in a better way.
8. Its fresh fracture shows clear bluish colour with a high silky luster and fibrous
appearance.
9. Its melting point is about 1500°C.
10. Its specific gravity is about 7.8.
11. Its ultimate compressive strength is about 200N/mm².
12. Its ultimate tensile strength is about 400N/mm².

17. Use Of Wrought-Iron
 The wrought-iron is replaced at present to a
very great extent by mild steel.
 It is therefore produced at present. It is used
where a tough material is required.
 The wrought-iron, at present, is used for rivets,
chains, ornamental iron work, railway
couplings, water and steam pipes, raw
material for manufacturing steel, bolts and
nuts, horse shoe bars, handrails, straps for
timbers roof trusses, boiler tubes, roofing
sheets, armatures,electro-magnets, etc.