Introduction about cast iron

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 celcius) of white
cast iron causes graphitization to occur.
• The cementite decomposes into ferrite and
graphite during heating upto 700 degree celcius.
• 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 Expensensive
• 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