2. Metals are aiming the most useful building
materials. They exist in nature as compounds
like oxides, carbonates, sulphides and
phosphates and are known as ores. Metals are
derived from ores by removing the impurities.
• is an element, compound or alloy that is a good
conductor of both electricity and heat.
• Ability of the valence free electrons to travel
throughout the solid explains both the high
electrical conductivity and thermal conductivity of
metals.
3. Metals
Ferrous
Iron
Steel
Pig iron
Cast iron
Wrought iron
Non-Ferrous
Copper & Alloys
Aluminium
Zinc
Tin
Lead
Those used for
engineering purposes
are classified as
ferrous metals, with
iron as the main
constituent, e.g. cast
iron, wrought iron and
steel and others like
aluminium, copper,
zinc, lead and tin in
which the main
constituent is not iron
as non ferrous metals.
4. Allotropic structures:
Alpha iron is weak and ductile, possesses
magnetic properties and is unable to dissolve
carbon.
Beta iron is hard, brittle, non-magnetic
and dissolves carbon.
Gamma iron has properties similar to beta
iron.
Delta iron absorbs negligible carbon and is
non-magnetic.
5. Gamma iron with its fcc (face-centered cubic)
structure formed at temperatures from 1394°C to
912°C.
Alpha iron which has bcc (body-centered
cubic) structure formed at temperatures from
912°C to 273°C.
The delta form is commercially unimportant.
Gamma iron containing carbon, is called
austenitic and alpha iron containing carbon, is
called ferritic.
The other steel alloys having same gamma
structures are also called austenitic. Similarly
alloys having alpha structure are called ferritic
6. Even the closed-packed metallic
structures contain empty spaces (holes),
assume atoms to be spherical. About 26 per
cent of the volume is empty in the fcc
metallic structures and about 29 per cent of
the bcc volume is empty. The holes in the
gamma iron are nearly half the diameter of
the carbon atom, causing the solubility of
carbon to be practically zero in austenite
iron.
7. However, in alpha iron the holes are
comparable to the size of carbon atom,
allowing an interstitial solubility of about 2
per cent carbon austenite iron. Thus the
number of available spaces and the relative
size of carbon atom limits the amount of
latter to dissolve in the solid solutions and
form the useful kinds of carbon alloys.
8. Iron is by for the most important of
the metals used in engineering construction. It
is available in abundance, but does not occur
freely in nature. The ores of iron are classed
according to the iron mineral which is
predominant.
Iron (Fe) having a atomic number 26.
It is most widely used of all metals as base
metal in steel and cast iron
9. The iron content of the main ores are as
follows:
• Magnetite (Fe3O4) — 70–75%,
• Haematite (Fe2O3) — 70%,
• Limonite (2Fe3O3.3H2O) — 60%, it is
hydrated haematite,
• Iron pyrite (FeS3) — 47%, and
• Siderite (FeCO3) — 40%
11. Iron Ore
• Abundant, makes up 5% of earth’s crust
•Is not found in ‘free state’, must be found
in rocks and oxides, hence Iron ore.
•After mining, the ore is crushed and the
iron is separated, then made into pellets,
balls or briquettes using binders, such as
water.
•The pellets are typically 65% iron, and
about 1” in diameter.
12. Coke
Coke is formed by heating coal to
2100*F (1150 C), then cooling it in
quenching towers.
Limestone
Limestone (calcium carbonate) is used to
remove impurities.
13. Pig iron - the intermediate product of
smelting iron ore with a high-carbon fuel
such as coke, usually with limestone as a
flux
14. The iron ore is dressed by crushing it to
about 50 mm cubes. The impurities are knocked
off and the ore is then calcined to drive off
moisture. The calcined ore is smelted in blast
furnance. The iron is deoxidised and a part of
sulphur is also removed. Then limestone, which
acts as flux*, is added to finally remove the
sulphur. The molten metal is tapped from the
furnance and is cast in the form of pigs.
15. A blast furnace is a
type of metallurgical
furnace used for
smelting industrial
metals, generally
iron.
16.
17. • Bessemer pig derives its name because of its
use in the manufacture of steel by Bessemer
process using haematite ore. Impurities such as
sulphur, phosphorus and copper are not
desirable in the Bessemer pig.
• Foundry pig, also known as grey pig, contains
sufficient quantity of free carbon and is produced
when the furnace is provided with sufficient fuel.
When fuel provided is insufficient and if sufficient
sulphur is present in the ore forge pig is
produced. This is also known as white pig.
• Mottled pig is in between the grey and white
varieties. They exhibit mottled fracture.
18. Pig iron contains:
3–4% carbon,
0.5–3.5% silicon,
0.5–2% manganese,
0.02–0.1% sulphur and
0.03–1% Phosphorus.
19. Pig iron is
• hard and brittle with fusion temperature of
1200°C and melts easily. It can be hardened
but cannot be tempered and magnetised. Its
compressive strength is high but is weak in
tension and shear. Pig iron does not rust and
cannot be riveted or welded.
20. Pig iron is most suitable for making columns,
base plates, door brackets, etc.
