ENGINEERING METALLURGY

1. CAST IRON
FERROUS ALLOY
It’s a eutectic alloy

2. COMPOSITION
• GREATER Than 2 % of carbon
• And also Small amounts of ALLOYING
ELEMENTS (Silicon, Sulphur, Manganese and
phosphorus).
• Cast irons are least expensive of all metals. Because
of plenty of resource available.
• Molten cast iron can be cast in to any complex
shapes and can be easily machined.

3. Composition of cast iron
• Carbon- 3.0 - 4.0%
• Silicon- 1.0% - 3.0%
• Manganese- 0.5% - 1.0%
• Sulphur and phosphorus- up to 1.0%

4. Cast iron Features
• Most widely used cheap metal
• Using casting methods we can produce
complicated shapes.( Easy Castability)
• Easy to machine.
• Good mechanical rigidity
• Good strength in compression
• Example --- spheroidal graphite iron are
strong , malleable cast irons are tough

5. Uses (VALVES)

6. Uses (Engine cylinder bore)

7. Effect of composition elements on
Cast Iron
1. CARBON ( 3 – 4 %)
– Its present in the form of flakes of Graphite or
cementite ( i.e. brittle iron carbide)
Note
– When the cast iron having cementite Structure ---
results poor mechanical property.
– so for application point of view its require to have
carbon in the form of flakes of graphite.

8. 1.carbon
• If the iron having more
cementite, it looks silvery
white in the broken area.
(cementite is a silvery
white component)
• We call it as white cast iron
• If the iron having the
presence of flakes of
graphite the broken area
looks grey colour --- this is
called as grey cast iron

9. 2.Silicon
• This will some extent governs the form in
which carbon is present in cast iron.
• Silicon causes cementite (unstable), so that it
decomposes, thus releasing free graphite.
• Therefore high silicon iron tends to be a grey
iron, whilst a low silicon iron tends to be a
white iron.

10. 3.Sulphur
• Sulphur tends to stabilize cementite. Thus
helps to produce white iron.
• It gives brittleness property to iron, so we
have to keep this percentage as low.

11. 4.Manganese
• It gives toughness and strength to iron.
• It also control the harmful effect(Reactions)
of sulphur in metal

12. 5.Phosphorus
• It gives the property of fluidity (in melting)
for cast iron.
• It also give brittleness like sulphur. For that
we have minimize the percentage level.

13. Factors affecting properties of
cast iron
• Cooling rate
• Heat treatment
• Presence of elements

14. FACTOR -1------------COOLING
RATE
• Slow cooling results grey cast iron
• Fast cooling results white cast iron

15. FACTOR -2----------Heat treatment
• Prolonged heating (700 degree Celsius) of white
cast iron causes graphitization to occur.
• The cementite decomposes into ferrite and
graphite during heating upto 700 degree Celsius.
• This decomposed ferrite and cementite will
occupy more space than the original cementite.

16. FACTOR -3 -------------ELEMENTS
• SILICON
• Highest percentage of silicon in iron results grey cast iron
structure.
• Low percentage of silicon results white cast iron.

17. TYPES OF CAST IRON
• Alloy cast iron --- ( Special Purpose)
1. Grey cast iron --- (General Purpose)
2. White cast iron – ( Heat and wear resistant)
3. Malleable cast iron-- ( Heat treated for
ductility)
4. Spheroidal Graphite cast iron – -(some
ductility)

18. GREY CAST IRON
• Least Expensive
• Most commonly used
• It is an alloy of carbon and silicon with iron.
Composition:
• Carbon - 2.5 – 4 %
• Manganese – 0.4 – 1%
• Sulphur – 0.02 – 0.15%
• Silicon – 1 – 3 %
• Phosphorus – 0.15 – 1 %
• Remaining iron

19. Grey Cast iron
• Its Consists of graphite flakes ( like potato Chips)
• Graphite flakes are surrounded by alpha ferrite or
pearlite matrix.
• Because of graphite it shows grey in colour
• These flakes not having much strength --- this lead
to crack formation in edges and brittleness.
• The shape, size and distribution of flakes decide the
property of grey cast iron.

20. Characteristics
• Good strength
• Excellent compressive strength
• Good torsional and shear strengths
• Good corrosion resistance
• Excellent fluidity
• Good wear resistance
• Excellent Machinability
• Good vibration damping capacity

21. Applications of Grey cast iron
USED IN
• Machine tool bodies
• Engine blocks
• Engine cylinders
• Brake drums
• Crank shaft
• Pipe and pipe fittings
• Rolling mills
• Agriculture appliances

22. White cast iron
• White cast iron derives its names fact that fracture
surface has a white or silvery appearance
• White iron combined with cementite.
• The broken cast iron area looks like silvery white.
• When the cooling is fast ----- Carbon content
changes to cementite results white cast iron

23. composition
• Carbon --- 1.8 – 3 %
• Silicon ---- 0.5 – 1.9 %
• Manganese – 0.25 – 0.8 %
• Phosphorus – 0.05 – 0.2 %
• Sulphur ------- 0.1 – 0.3 %
• Remaining is a iron

24. Microstructure
• Cementite is caused by quick cooling of molten
iron it produces White cast iron is very hard and
brittle.
• RAPIDLY COOLED FROM THE CASTING
TEMPERATURE The Cast iron is termed as
“CHILLED IRON”

25. Characteristics of white cast iron
• Very hard and brittle
• Very high resistance to abrasion
• High tensile strength and low compressive
strength
• Cannot be machined because its hard.

26. Applications of white cast iron
• White cast iron is Used as a raw material in the
production of malleable cast iron.
• Used in rolls, wear plates(brakes), pump linings,
balls
• Used in outer surface for car wheels.

27. MALLEABLE CAST IRON and its
MICROSTRUCTURE
• By heat treating the white cast iron we get malleable cast
iron.
• For having malleable and ductile property .
• During heat treatment the cementite breaks into ferrite
and graphite nodules.
• The graphite nodules called as tempered carbon-- it
appears like popcorn.
• This rounded graphite permits a good combination of
strength and ductility

28. Composition
• Carbon --- 2 – 3%
• Silicon ----- 0.6 – 1.3%
• Manganese --- 0.2 – 0.6%
• Sulphur ------ 0.1 %
• Phosphorus – 0.15%
• Remaining iron

29. Types of Malleable irons
• Ferritic malleable iron,
• Pearlitic malleable iron

30. 1. Ferritic Malleable cast iron
• Here the white iron is heated up to upper critical
(815 ͦc to 1230 ͦc) temperature and hold it for
prolonged time, so carbon in the cementite
converts in to graphite.
• Subsequently the low cooling through the eutectoid
reaction results in a ferritic matrix
• Finally the cast iron obtained is called ferritic
malleable cast iron.

31. 2.Pearlitic Malleable cast iron
• The Rapid cooling of molten white cast iron in eutectoid
transformation range results pearlitic matrix.
• This is due in fast cooling , the carbon in austenite will have
not enough time to form additional graphite. So its retained
in the pearlite matrix
CHARACTERISTICS:
• It has higher strength and Lower ductility

32. Micro structure of eutectoid to pearlite

33. CHARACTERISTICS OF
MALLEABLE CAST IRON
• Good ductility and malleability than grey cast iron
• High yield and tensile strength
• Its not brittle as grey cast iron
• High young’s modulus and low co-efficient of expansion
• Excellent impact strength
• Good wear resistant
• Good vibration damping capacity
• Excellent machinability

34. Applications of Malleable cast iron
USED IN
• Due to their Castability , machinability and shock
resistance it Most widely used in automobile industries
• In brake shoe
• Wheel hub
• Axle housing
• Transmission gears
• Connecting rod
• Levers
• Pipe fittings
• Agriculture machineries and parts
• Switch gear equipments

35. SPHEROIDAL GRAPHITE
OR
NODULAR CAST IRON
• Its also called ductility cast iron
• In the grey cast iron they are adding magnesium
or cerium
• This magnesium converts flakes graphite into
perfect nodules.
• This perfect nodules improves the ductility of
the cast iron. (nearly 20 % increased)

36. Characteristics of
spheroidal graphite cast iron
• Excellent ductility
• Good toughness than grey cast iron
• Good fatigue strength
• Good impact strength
• Good hardness
• High modulus of elasticity
• Good wear resistance
• Good machinability
• Good oxidation resistant
• Excellent castability

37. Applications
Used in
• Valves
• Pump bodies
• Crank shaft ,
• Pinion and gears
• Rollers
• Rocker arm
• Flanges
• Power transmission equipments
• Earth moving machineries

38. ALLOY CAST IRON
• The cast iron Discussed so far called Plain cast
irons.
• The cast irons contains only small amount of
impurities.
• The ALLOY CAST IRONS can be produced by
adding Ni, Cr, Mo, Cu, Si and Mn.
PURPOSE:
• For High strength materials
• Hard and abrasion resistance
• Corrosion resistance irons

39. Purpose of alloying elements in cast iron
S.N
O
ALLOYING
ELEMENT GENERAL EFFECTS
1 Ni Graphitize the cementite and help to produce grey
iron
Reduce the formation of coarse grains
Give toughness to thin sections
2 Si Same effect as that of nickel
3 Cr For hard and wear resistant irons
4 Mo Increase hardness and toughness
5 V Increase strength and hardness
Give heat - resistance to metal
6 Cu It gives resistance to corrosion

40. Applications of alloy cast irons
• Cylinder block
• Brake drums
• Clutch castings
• Automobile components like piston rings,
crank shaft.
• Corrosion and heat resisting areas