SLIDES PROVIDE TOPICS RELATED TO PUNE UNIVERSITY SYLLABUS OF MECHANICAL ENGINEERING

1. UNIT-01 OVERVIEW OF METALLURGY
 Syllabus:
methods of metal extraction(principle only:-
pyro, hydro and electro)
Cast v/s wrought products
Concepts:- system, phase, variable, component,
alloy, solid solution
Hume Ruthers rule of solid solubility
Allotropy and polymorphism
Concept of solidification of pure metals and
alloys
Homogeneous and heterogeneous nucleation
Dendritic growth, super cooling

2. SYLLABUS(CONT…)
Equiaxed and columnar grains,
Grain and grain boundry effect
Cooling curves
Plotting of equilibrium diagrams
Lever rule
Coring
Eutectic system
Partial eutectic
Isomorphous system

3. EXTRACTION OF
METALS

4. PRINCIPLES OF METAL
EXTRACTION
 Most metals do not occur as separate
substances but exist naturally as
compounds.
 Metals tend to exist as metal oxides as
part of ores which are excavated from the
earth.
 To recover the metal from it’s oxide the
metal ion is split from the oxygen ion.
 Metals high up on the activity series have
more stable oxides than those lower down
and due to this are more difficult to split
up than those lower down.

5. METALS FROM
ROCKS
• The substances (elements or compounds) that make
up rocks are called minerals.

6. FROM ROCKS TO
METALS
• A metal ore (usually oxides, sulfides, chlorides or
carbonates) is a rock from which a useful metal is
obtained.
• The process of getting metals from ores is called the
extraction of metals.
Bauxite – an aluminium ore

7. OCCURRENCE OF
METALS
• Metal oxides – metal + oxygen
• Metal sulfides – metal + sulfur
• Metal carbonates – metal + carbon + oxygen
Some metal ores found in the Earth’s

8. MAIN MINERALS OF
METAL ORES

9. • Minerals are the elements or compounds
that make up rocks.
• A metal ore is a rock containing a mineral
from which a metal is extracted.
• Most minerals are the oxides, sulfides and
carbonates of metals. For example,
bauxite is an ore containing the
compound aluminium oxide.

10. ORE
metal compound separated
from bits of sand & rocks
purified
metal compound
metal
extracted metal chemically separated
from other elements

12. EXTRACTION OF THE LEAST REACTIVE
METALS
• The least reactive metals are at the bottom of the reactivity
series. Some are found as free metals.
• E.g. gold can be obtained by physical methods. The rocks are
collected and crushed to free the pieces of gold in them.
Rocks containing gold being extracted in a gold mine in
Australia

13. • These metals occur as oxides and sulfides.
• The metal sulfides are heated in air to become metal
oxides.
• The metal is then obtained by heating the oxides with
carbon.
E.g.
EXTRACTION OF LESS REACTIVE
METALS
2ZnS(s) + 3O2(g)
ZnO(s) +
C(s)
2ZnO(s) + 2SO2
Zn(s) + CO(g)

14. EXTRACTION OF VERY REACTIVE
METALS
• Very reactive metals are difficult to extract.
• Most reactive metals are extracted by
decomposing their compounds with
electricity. This is called electrolysis.
2KCl(l) 2K(l) + Cl2(g)

15. • The method used to extract a metal depends
on the reactivity of the metal.
• Unreactive metals, such asgold, are
often found as free (uncombined) elements.
• Less reactive metals are extracted by heating
their oxides with carbon.
• Veryreactive metals are extracted
using electrolysis.

16. Y
Potassium
Sodium
Calcium
Magnesium
Aluminium
[Carbon]
Zinc
Iron Tin
Lead
Copper
Silver
Gold
More
reactive
metals
Less
reactive
metals
Unreactive
metal
Electrolysis
Heating metal
oxide with
carbon
Physical
methods
Heating the metal
oxide

17. HOW DOES REACTIVITY AFFECT
EXTRACTION?
potassium
sodium
calcium
magnesium
aluminium
zinc
iron
copper
gold
increasingreactivity
Metals above carbon in the reactivity
series must be extracted using
electrolysis. Electrolysis can also be
used to purify copper.
Metals less reactive than carbon can be
extracted from their ores by reduction
using carbon, coke or charcoal.
Platinum, gold, silver and copper can
occur native and do not need to be
extracted.
lead
silver
The reactivity of a metal determines how it is extracted.
(carbon)
(hydrogen)
platinum

18. THE PROCESS OF TAKING OUT PURE
METAL FROM ITS ORE IS CALLED
EXTRACTIVE METALLURGY.
 Extractive metallurgy can be classified as;
i) Pyrometallurgy: extraction and purification of
metals by process by application of heat.
ii)Hydrometallurgy: the metal is seperated by
liquid solvents.
iii)Electrometallurgy: by using electrical energy

19. i)Pyrometallurgy:
 Reduction of metal from its oxide is more easy
than sulphides.
 Sulphides are roasted (heated) to oxidising
temp to convert into inoxide form.
 Generally temp varies between 500 to 2000
 Pyrometallurgy has following three steps:
a) calcination
b) roasting
c) smelting

20. Metals are often found combined with oxygen as oxides. To obtain
the metal, the oxygen must be removed.
In this reaction, the carbon removes oxygen from lead oxide. This occurs
because carbon is more reactive than lead.
WHAT IS REDUCTION?
The removal of oxygen from a substance is called reduction.
Carbon can be used to extract metals by reduction.
lead oxide + carbon lead
carbon
monoxide+
PbO C Pb CO+ +
metal oxide (in ore) metal
reduction
The addition of oxygen to a substance is called oxidation.

21. PYROMETALLURGY (CONT….)
a) Calcination : in this step elements like carbon and
water are eliminated. This is endothermic reaction
b) Roasting : in this process ore is brought into
convertible form
e.g. sulphides are converted into oxides.
c) smelting: in this process, the oxides are converted to
metal by reaction with carbon and sulphur in blast or
electrical furnace.
slag is removed with the help of flux
the charge is solid and the output is liquid metal
2ZnS(s) + 3O2(g)
ZnO(s) +
C(s)
2ZnO(s) + 2SO2
Zn(s) + CO(g)

22. PYROMETALLURGY (CONT….)
 Advantages:
1. As it is a high temperature process the reaction
is fast, therefore more metal is produced.
2. The cost of reducing agent and raw material is
less.
3. Liquid metal and slag separate out and helps in
extraction process
4. Metlas like Fe, Zn, Pb, Cu, Al, Mg, As can be
extracted by using this method

23. ii) Hydrometallurgy :
 Hydrometallurgy takes place with help of aqueous
solution or water
 Removal of impurities by different physical methods,
grinding are the basic processes in preparation of ores
in hydrometallurgy.
 leaching:
 with the help of available liquid reagent the metallic
ore is dissolved. The reagent is known as liquor.
 The rate of process will vary with temperature and
pressure of liquor.
 With the help of settling, filteration, the leaching
agent is separated and then by precipitation,
electrolysis the metal is taken out

24. HYDROMETALLURGY (CONT….)
 Advantages:
1. Suitable for low grade ore.
2. Valuable byproducts can be recovered.
3. Less environmental pollution
4. Less costly as compared to pyrometallurgy.
5. It can produce metals like nodules or powder
form
6. Even in leaching , low temperatures are involved

25. HYDROMETALLURGY (CONT….)
 Disadvantages:
1. Process requires large volume.
2. Handling of chemicals require special care.
3. Large space is required.
4. Chances of corrosion and erosion in handling
equipments
5. Disposal of effluments is problamatic

26. iii) Electrometallurgy:
 It is a branch of metallurgy that deals with the
application of electric current either for electrolytic
deposition or as a source of heat.
 Electrometallurgy is related with electrodeposition.
 There are four types of this process:
a) Electrowinning : it represents extraction of metal
from ores
b) Electrorefining : it represents purification of metals.
c) Electroplating : in this deposition of a layer of one
metal on another metal is involved.
d) Electroforming : it includes mfg of thin metal parts
through electroplating

27. 8
IRON
ORE
Blast Furnace
Pig Iron
Smelted, Hammered, Re-
heated, Rolled
Smelted (separate the metallic
constituent)
,Alloyed, Rolled
Wrought Iron Cast Iron Mild Iron(Steel)
Re- melted, Poured
into sand molds

28. PROPERTI
ES
• Cast iron.: 2.0 – 4.5% Carbon content
• Carbon (C) and silicon (Si) are the main alloying elements.
• Great for the environment. Can be recycled more easily than
PVC.
• It is strong in compression, but weak in tension and bending.
• Prefabrication enabled portability—entire buildings could be
constructed in one place and shipped all over the world.
• Its strength and stiffness deteriorate when subjected to high heat.
• Its structure is crystalline and relatively brittle.
• They don't echo when water moves through as compared to
PVC, because of dense material.
• It does not rust.

29. APPLICATIO
NS
• Internal Combustion
Engine
• Pump Housings
• Valve Bodies
• Electrical Boxes
• Cast iron cookware
• Disc brake
Internal combustion engine
Pump Housings
Disc brakeGrey Cast iron cookware Decorative pattern

30. WROUGHT IRON
Wrought Iron Is A form of Iron With A Very Low Carbon Content (0.25%) In
Contrast
To Cast iron (2.1% to 4%).
"Grain" Resembling Wood, Is Visible When It Is Bent To The Point Of
Failure.
Wrought Iron Is Tough, Malleable, Ductile And Easily Welded.
Purest form of iron in which the total impurities do not exceed 0.5%.
Wrought iron is much more expensive to produce than cast. Most wrought iron
work are joined by riveting.
MAJOR EXAMPLE ARE-
1.Iron pillar at Delhi, India, containing 98% wrought iron.
2.The Eiffel tower

31. PROPERTIES
•It can be used to form temporary magnets but cannot be magnetised
permanently.
•It fuses with difficulty.
•high elasticity and tensile strength
•Unaffected by saline water.
•If pulled apart, the fracture shows a fibrous break.
•Capable of bearing 24 tons per square inch ultimate tensile strain, & 20 tons of
compression and shearing.
.

32. WROUGHT IRON:
 It is a mechanical mixture of pure iron with
silicate slag.
 Generally wrought iron consist 0.02% C , 0.05%P,
0.02%Silicon, 0.008% sulphur, 0.05 to 1.5% slag
and remaining amount iron.
 Wrought iron is never cast, because its shaping is
accomplished by hammering, pressing, forging,
etc
 Wrought iron is popular for its high ductility and
for which it can be forged and welded
 The ultimate strength of wrought iron can be
increased by cold working.
 It has resistance towards shock, fatigue, and
corrosion

33. WROUGHT IRON (CONT…)
 The mechanical properties of wrought iron is
similar to pure iron.
 Also wrought iron has property of rapid recovering
from overstrain due to sudden shock without
permanent failure.
 The structure of wrought iron shows physical
association with base metal and slag.
 The slag or iron silicate
may look like ribbon or
platelets in
microstructure.

34. In
fencing
In main entrance
gates
In
railings
As
balusters
USES
• Used for rivets, chains,
ornamental iron work, railway
couplings, bridges, water and
steam pipes.
• Roofing sheets, corrugated
sheets.
• It is manufactured for bolts and
nuts, horse shoe bars,
handrails, straps for timer roof
trusses, boiler tubes, roofing
sheets, etc.

35. WROUGHT IRON (CONT…)
 Applications of Wrought Iron:
Wrought iron is available in various forms such as
plates, sheets, bars,structures, rivets, chains and
tubular products(pipies, tubes, castings)
a) Building construction
b) Rail road and marine: diesel exhaust and air
brake piping
c) Industrial : condenser tubes, heat exchangers,
acid or alkali process lines
d) Public works: bridge railings, drainage lines,
sluge tanks and lines.

36. Pipe
s
Chain
s
Wir
e
RIVE
T
Nai
l
EXTERNAL
USE

37. COMPARISON BETWEEN WROUGHT IRON ,CAST
IRON& STEEL
Wrought iron Cast Iron Steel
Composition Purest Contains up to
0.25% C
Crude form
containing 2-4% C
Midway
Melting point 1500 degree Celsius 1200 degree
Celsius
1300-1400 degree
Celsius
Hardness Cannot be hardened
or tempered
Hard, hardened by
heating & sudden
cooling
Can be hardened &
tempered
Strength compressive strength
is
2.0 tonnes/sq cm
ultimate tensile
strength 3.15
tonnes/sq cm
Comp. strength 6.3-
7.1 tonnes/sq cm
Ultimate tensile
strength 1.26 to
1.57tonnes/sq cm.
Comp strength 4.75
-25.2 tonnes/ sq cm
Ultimate tensile
strength is 5.51 to
11.02 t /sq m

38. Wrought iron Cast Iron Steel
Malleability
Ductility
Tough, malleable,
ductile & moderately
elastic
Brittle & cannot
be welded or
rolled into sheets
Tough, malleable &
Ductile
Reaction to
sudden shock
Cannot stand heavy
shocks
Does not absorb
shocks
Absorbs shocks
Welding Easily welded Brittle and cannot
be welded or
rolled into sheets
Can be welded

41. METHODS OF METAL EXTRACTION:
 1.Electrolyis
 2. Reduction with carbon(carbon monoxide)
 3. Heating of the ore.

59. METHODS OF METAL EXTRACTION:
 1. Electrolysis: this entails the immersing of a
positively and negatively charged electrical poles to a
molten or aqueous solution of a substance. The passage of
the current causes positively charged ions to be attracted
to the negative pole and negatively charged ions to be
attracted to the positively charged pole. While at the
Negative pole, positively charged ions gain electrons to
become neutral atoms and are deposited on the negative
pole or fall to the bottom as a precipitate. The same occurs
to positively charged ionsat the negative pole. The overall
effect is that the constituents of the substance are
separated and usually are deposited on the Positive Pole or
Anode and the Negative pole or Cathode or it may sink to
the bottom of the container as a precipitate

60. METHODS OF METAL EXTRACTION:
 1.Electrolyis:
 Most powerful means of extraction.
 most expensive.
 Can only be used where electricity is abundant.
 2. Reduction with carbon(carbon monoxide)
 Cheaper to operate than electrolysis.
 Labor intensive .
 Expensive to startup as large industrial equipment is
used.
 3. Heating of the ore.
 Cheap
 Can only be used on the most unreactive of
metals(Mercury,gold,silver,etc.)
14kilowat
hours =
1kg of
Aluminiu
m

61. EXTRACTION OF ALUMINIUM

62. EXTRACTION OF IRON
 The extraction of Iron is a reductive
process whereby oxygen is removed from
the iron oxide by carbon monoxide. The
process occurs within a Steel blast furnace
lined with refractive(fire) bricks at
temperatures from 800C upto 1900C. The
Chamber is kept hot by jets of hot air at
over 800C, giving it the name “Blast”
furnace.

63.  Start materials:
 Iron Ore or Hematite
 Lime or Calcium carbonate CaCO3
 Coke a carbonaceous ashy substance
Iron Ore
Lime
Coke

64. EXTRACTION OF IRON: STEP1
BURNING OF LIME
 Iron ore,
limestone(CaCO3) and
coke are delivered to the
top of the blast furnace,
where the temperature is
around 800C.
 The lime stone burns at
800C yielding calcium
oxide(CaO) and Carbon
Dioxide(CO2).
 CaCO3 -> CaO + CO2
 The Calcium oxide causes
impurities which are
present with the ore to fall
as a precipitate near to
the bottom producing a
layer of “slag”.

65. EXTRACTION OF IRON:
STEP 2 PRODUCTION OF CARBON
MONOXIDE
 The carbon Dioxide
yielded from the Burning
of Lime passes over the
coke. Coke is a coal like
substance produced from
the heating of Tar and
Petrochemicals without
heat and contains a high
percentage of carbon. The
Carbon atoms of coke
remove a single oxygen
from each molecule of
CO2 producing carbon
monoxide
 CO2 + C 2 CO
Coke

66. EXTRACTION OF IRON:
STEP 3 REDUCTION OF IRON
 The Carbon monoxide yielded
from the reaction of Carbon
dioxide and lime removes the
oxygen from Iron oxide.
 Each Carbon monoxide molecule
is capable of binding a single
oxygen so 3 are used to completely
remove all oxygen from the iron
oxide.
 Fe2O3 + 3 CO -> 2Fe(s) + 3 CO2
 The molten iron sinks to the
bottom lowest level of the furnace,
where it can be tapped off.
 The iron produced by this process
is called pig iron and is 95%
pure.

67. EXTRACTION OF IRON: OVERVIEW
 Production of iron from it’s ore
uses Carbon monoxide to reduce
Iron oxide to iron atoms.
 1.Lime burns
 CaCO3 -> CaO + CO2
 2. CO2 reduced by coke to CO
 CO2 + C -> 2 CO
 3. Iron oxide reduced by CO
 Fe2O3 + 3CO -> 2Fe + 3CO2
Removes impuritiies :
slag production

68. Q & A
 What is Limestone made of?
 How are impurities from the ore removed?
 What is the layer of precipitated impurities
called?
 Where does the carbon dioxide produced during
the process come from?
 What is the function of Coke during the process?
 What substance is responsible fo reducing the
iron oxide to iron?
 What is the level of purity of the iron produced
by this process?