production Engineering

2. Cast Iron
 The cast iron is obtained by re-melting pig iron with
coke and limestone in a furnace known as cupola.
 It is primarily an alloy of iron and carbon.
 The carbon content in cast iron varies from more than
2 per cent to 4.5 per cent.
 The carbon in a cast iron is present in either of the
following two forms:
1. Free carbon or graphite, and
2. Combined carbon or cementite.
Contd…

3.  The properties of cast iron which make it a valuable
material for engineering purposes are its low cost,
good casting characteristics, high compressive
strength, wear resistance and excellent machinability.
 The compressive strength of cast iron is much greater
than the tensile strength.

4. IES 2010
Assertion (A): A cast iron specimen shall fail due to
shear when subjected to a compressive load.
Reason (R): Shear strength of cast iron in
compression is more than half its compressive
strength.
(a) Both A and R are individually true and R is the
correct explanation of A
(b) Both A and R are individually true but R is NOT the
correct explanation of A
(c) A is true but R is false
(d) A is false but R is true

5. IES-2005
Consider the following statements:
1. Cast Iron has poor ability to damp vibrations.
2. Cast Iron has higher compressive strength
compared to that of steel.
3. Cast Iron parts are suitable where permanent
deformation is preferred over fracture.
Which of the statements given above is/are correct?
(a) 1, 2 and 3 (b) 1 and 3
(c) 3 only (d) 2 only

6. IES-1999
Cast iron is used for machine beds because of its
high
(a) Tensile strength
(b) Endurance strength
(c) Damping capacity
(d) Compressive strength

7. IES-1998
Assertion (A): Cast iron is generally hard, brittle and
wear resistant.
Reason (R): Cast iron contains more than 2% carbon
and as such the percentage cementite in it is higher.
(a) Both A and R are individually true and R is the correct
explanation of A
(b) Both A and R are individually true but R is not the
correct explanation of A
(c) A is true but R is false
(d) A is false but R is true

8. IES-1997
Assertion (A): The notch sensitivity of cast iron
component is zero.
Reason (R): Cast iron does not have a yield point.
(a) Both A and R are individually true and R is the
correct explanation of A
(b) Both A and R are individually true but R is not the
correct explanation of A
(c) A is true but R is false
(d) A is false but R is true

9. IAS-2003
Consider the following statements:
1. From design considerations, it is always
advantageous to place cast iron ribs on the tension
side rather than on the compression side.
2. Cast iron is an excellent choice for machine tool
guides and frames.
3. Cast iron parts have low notch sensitivity.
Which of these statements are correct?
(a) 1, 2 and 3 (b) 2 and 3
(c) 1 and 3 (d) 1 and 2

10. IES-1992
Which of the following metal shrinks most from
molten state to solid state?
(a) Cast iron (b) Cast steel
(c) Brass (d) Admiralty metal

11. Types of Cast Iron
 Cast irons that were slowly cooled to room
temperature consist of cementite, look whitish – white
cast iron.
 If it contains graphite, look grayish – gray cast iron.
 It is heat treated to have graphite in form of nodules –
malleable cast iron.
 If inoculants are used in liquid state to have graphite
nodules – spheroidal graphite (SG) cast iron.
Contd…

12. 1. Grey cast iron
 Carbon = 3 to 3.5%;
 The grey colour is due to the fact that the carbon is
present in the form of free graphite.
 It has a low tensile strength, high compressive strength
and no ductility.
 It can be easily machined.
 A very good property of grey cast iron is that the free
graphite in its structure acts as a lubricant. Due to this
reason, it is very suitable for those parts where sliding
action is desired.
Contd…

13.  The grey iron castings are widely used for machine tool
bodies, automotive cylinder blocks, heads, housings,
fly-wheels, pipes and pipe fittings and agricultural
implements.
 The grey cast iron is designated by the alphabets ‘FG’
followed by a figure indicating the minimum tensile
strength in MPa or N/mm2. For example, ‘FG 150’
means grey cast iron with 150 MPa or N/mm2 as
minimum tensile strength.

14. IES-1994
Assertion (A): Machine tool beds are generally
made of grey cast iron.
Reason (R): Cast iron possesses good self-
lubricating properties.
(a) Both A and R are individually true and R is the
correct explanation of A
(b) Both A and R are individually true but R is not the
correct explanation of A
(c) A is true but R is false
(d) A is false but R is true

15. IES-2005
Which of the following pairs are correctly matched?
(Designation of Steel/Cast Iron) (Description)
1. Fe E 250 :Minimum tensile
strength of 250
N/mm2
2. 40 C 8 :Percentage of
Manganese is 0.7% -
0.9%
3. FG 200 :Grey cast iron with
ultimate tensile strength
of 200 N/mm2
Select the correct answer using the code given below:
(a) 1 and 2 (b) 2 and 3
(c) 1 and 3 (d) 1, 2 and 3

16. GATE-2004
The percentage of carbon in gray cast iron is in the
range of
(a) 0.25 to 0.75 percent
(b) 1.25 to 1.75 percent
(c) 3 to 4 percent
(d) 8 to 10 percent

17. IES 2007
Vibration damping in machinery is best achieved
by means of base structures made of which one of
the following materials?
(a) Low carbon steel
(b) Nodular iron
(c) Grey cast iron
(d) White cast iron

18. IES-2003
Machine tool manufacturers prefer grey cast-iron
grade 40 for producing machine columns and
tables because grey cast-iron is
1. Heavy 2. Easily castable
3. Easily weldable 4. Having good
damping capacity
Select the correct answer using the codes given below:
Codes:
(a) 1 and 2 (b) 2 and 4
(c) 1 and 3 (d) 3 and 4

19. IES-1993
Assertion (A): Fracture surface of grey cast iron is
dark.
Reason (R): Failure takes place along the weak
cementite plates.
(a) Both A and R are individually true and R is the
correct explanation of A
(b) Both A and R are individually true but R is not the
correct explanation of A
(c) A is true but R is false
(d) A is false but R is true

20. 2. White cast iron
 Carbon = 1.75 to 2.3%.
 The white colour is due to fact that it has no graphite
and whole of the carbon is in the form of carbide
(known as cementite) which is the hardest constituent
of iron.
 The white cast iron has a high tensile strength and a
low compressive strength.

21. IES-2005
Which of the following materials is used in the
manufacture of extrusion nozzles?
(a) Grey cast iron
(b) Malleable cast iron
(c) White cast iron
(d) Nodular cast iron

22. 3. Chilled cast iron
 It is a white cast iron produced by quick cooling of
molten iron.
 The quick cooling is generally called chilling and the
cast iron so produced is called chilled cast iron.
 Chills are used on any faces of a casting which are
required to be hard to withstand wear and friction.

23. 4. Mottled cast iron
 It is a product in between grey and white cast iron in
composition, colour and general properties.
 It is obtained in castings where certain wearing
surfaces have been chilled.

24. 5. Malleable cast iron
 The malleable iron is a cast iron-carbon alloy which
solidifies in the as-cast condition in a graphite free
structure, i.e. total carbon content is present in its
combined form as cementite (Fe3C).
 It is ductile and may be bent without breaking or
fracturing the section.
 The tensile strength of the malleable cast iron is
usually higher than that of grey cast iron and has
excellent machining qualities.
Contd…

25.  It is used for machine parts for which the steel forgings
would be too expensive and in which the metal should
have a fair degree of accuracy, e.g. hubs of wagon
wheels, small fittings for railway rolling stock, brake
supports, parts of agricultural machinery, pipe fittings,
door hinges, locks etc.
 In order to obtain malleable iron castings, it is first cast
into moulds of white cast iron. Then by a suitable heat
treatment (i.e. annealing), the combined carbon of the
white cast iron is separated into nodules of graphite.
 There are two process:
1. Black-heart process,
2. White-heart process
Contd…

26. 1. Black-heart process
 In this process the white iron castings are heated in
airtight boxes out of contact with air at 850-950 deg C for
50-170 hours, depending upon the mass and thickness of
the castings.
 The effect of this prolonged heating is to break down the
iron carbide (cementite) of the white cast iron into small
rosettes of graphite.
 The name 'black-heart' comes from the darkened
appearance of the iron, when fractured, resulting from the
formation of free graphite.
 It is used in the wheel hubs, break drums, conduit fitting
control levers and pedals.

27. 2. White-heart process
 In this process the castings are packed into airtight boxes
with iron oxide in the form of high-grade ore.
 They are then heated to about 1000 deg C for between 70
and 100 hours, depending upon the mass and thickness of
the castings.
 The ore oxidises the carbon in the castings and draws it
out, leaving a ferritic structure near the surface and a
pearlitic structure near the centre of the casting.
 There will also be some fine rosettes of graphite.
 White-heart castings behave much as expected of a mild
steel casting, but with the advantage of a very much lower
melting point and higher fluidity at the time of casting.
 It is used in the wheel hubs, bicycle and motor cycle frame
fittings, gas, water and steam pipe fittings.

28. IES-1992
Which of the following display properties similar
to that of steel
1. Black-heart cast iron
2. White-heart cast iron
3. Gray cast iron
4. Pig iron
(a) 1 and 2 only (b) 3 and 4 only
(c) 2 and 4 only (d) 1 and 3 only

29. IES-1992
For the pipe fitting like elbow, tee, union etc.
which of the following is preferred?
(a) Pig iron
(b) Malleable iron
(c) Spheroidal graphite cast iron
(d) High carbon steel

30. 6. Nodular or spheroidal graphite
cast iron
 The nodular or spheroidal graphite cast iron is also
called ductile cast iron or high strength cast iron.
 This type of cast iron is obtained by adding small
amounts of magnesium (0.1 to 0.8%) to the molten
grey iron.
 The addition of magnesium causes the graphite to take
form of small nodules or spheroids instead of the
normal angular flakes.
Contd…

31.  It has high fluidity, castability, tensile strength,
toughness, wear resistance, pressure tightness,
weldability and machinability.
 It is generally used for castings requiring shock and
impact resistance along with good machinability, such
as hydraulic cylinders, cylinder heads, rolls for rolling
mill and centrifugally cast products.
 SG 400/15 means spheroidal graphite cast iron with
400 MPa as minimum tensile strength and 15 percent
elongation.

32. IES-2001
Nodular grey cast iron is obtained from the grey
cast iron by adding a small amount of
(a) Manganese
(b) Phosphorus
(c) Magnesium
(d) Chromium

33. IES-2009
Which one of the following cast irons consists of
carbon in rosette form?
(a) White cast iron
(b) Gray cast iron
(c) Malleable cast iron
(d) Nodular cast iron

34. IES-1995
Addition of magnesium to cast iron increases its
(a) Hardness
(b) Ductility and strength in tension
(c) Corrosion resistance
(d) Creep strength.

35. Wrought Iron
 It is the purest iron which contains at least 99.5% iron
but may contain upto 99.9% iron.
 The wrought iron is produced from pig iron by
remelting it in the puddling furnace of reverberatory
type.
 The wrought iron is a tough, malleable and ductile
material.
 It can be easily forged or welded. It is used for chains,
crane hooks, railway couplings, water and steam pipes.

36. Effect of Impurities on Cast Iron
1. Silicon. It may be present in cast iron upto 4%. It
provides the formation of free graphite which makes
the iron soft and easily machinable. It also produces
sound castings free from blow-holes, because of its
high affinity for oxygen.
2. Sulphur. It makes the cast iron hard and brittle. Since
too much sulphur gives unsound casting, therefore, it
should be kept well below 0.1% for most foundry
purposes.
Contd…

37. 3. Manganese. It makes the cast iron white and hard. It
is often kept below 0.75%. It helps to exert a
controlling influence over the harmful effect of
sulphur.
4. Phosphorus. It aids fusibility and fluidity in cast
iron, but induces brittleness. It is rarely allowed to
exceed 1%. Phosphoric irons are useful for casting of
intricate design and for many light engineering
castings when cheapness is essential.

38. IES-1995
Consider the following statements:
Addition of silicon to cast iron
1. Promotes graphite module formation.
2. Promotes graphite flake formation.
3. Increases the fluidity of the molten metal.
4. Improves the ductility of cast iron.
Select the correct answer using the codes given below:
(a) 1and 4 (b) 2 and 3
(c) 1and 3 (d) 3 and 4

39. IES 2007
Piston compression rings are made of which one
of the following
(a) Cast iron (b) Bronze
(c) Aluminium (d) White metal

40. IES-1995
Consider the following work materials:
1. Titanium 2. Mild steel
3. Stainless steel 4. Grey cast iron.
The correct sequence of these materials in terms of
increasing order of difficulty in machining is
(a) 4,2,3,1 (b) 4,2, 1,3
(c) 2,4,3,1 (d) 2, 4, 1, 3.

41. IES-1994
Which of the following pairs are correctly
matched?
1. Lead screw nut………… Phosphor bronze
2. Piston………….. Cast iron.
3. Cam ……………………..EN-31 steel
4. Lead screw ……..Wrought iron.
Select the correct answer using the codes given below:
Codes:
(a) 2, 3 and 4 (b) 1, 3 and 4
(c) 1, 2 and 4 (d) 1, 2 and 3

44. IAS-2002
A cast iron specimen in a torsion test gives a
(a) Cup-and-cone fracture
(b) Fracture along a plane normal to the axis of the
specimen
(c) Fracture along a helix of approximately 45°
(d) Fracture along a plane inclined at 60° to the axis

45. The End