Metal Casting - Manufacturing Technology 1

1. MANUFACTURING
TECHNOLOGY – I
CRAFTED BY:
RAMESH KUMAR A
Assistant professor
Sona college of technology
Salem

2. UNIT - 1
Introduction – Sand Casting

3. DEFINITIONS
 Manufacturing - The process of converting raw materials,
components, or parts into finished goods that meet a customer's
expectations or specifications.
 Technology - Science or knowledge put into practical use to solve
problems or invent useful tools
 Manufacturing Technology - Field of study focused on
improvement of manufacturing processes, techniques, or
equipment in order to reduce costs, increase efficiency, enhance
reliability, or to incorporate safety and anti-pollution measures.

4. HISTORY

7. Unit – 1
METAL CASTING
 Casting means a process, in which liquid metal is poured into a mould, that
contains a hollow cavity of the desired shape, and then allowed to cool and
solidify. The solidified part is also known as a casting, which is ejected or
broken out of the mould to complete the process.

8. Solidification Processes
Solidification
process
Metal
casting
Expendable
mould casting
Permanent
mould casting
Glass
Working
Polymers
& PMC
process
Sand casting
Shell moulding
Investment casting
Die casting
Centrifugal casting

9. Sand casting
 Sand casting, also known as sand moulded casting, is a metal casting process
characterized by using sand as the mould material.
 The term "sand casting" can also refer to an object produced via the sand
casting process.
 Sand castings are produced in specialized factories called foundries. Over
70% of all metal castings are produced via sand casting process.
 There are six steps in this process:
 Place a pattern in sand to create a mould.
 Incorporate the pattern and sand in a gating system.
 Remove the pattern.
 Fill the mould cavity with molten metal.
 Allow the metal to cool.
 Break away the sand mould and remove the casting.

10. Sand casting

11. Sand casting

12. Pattern – Functions, Types and Materials

13. Pattern
 In casting, a pattern is a replica of the object to be cast, used to
prepare the cavity into which molten material will be poured during
the casting process.
Wooden pattern for a cast-iron
gear with curved spokes
Pattern with moulding box of engine block

14. Functions of Pattern
 A pattern prepares a mould cavity for the purpose of
making a casting
 A pattern may contain projections known as core prints if
the casting requires a core and need to be made hollow
 Runner, gates, and risers used for feeding molten metal in
the mould cavity may form a part of the pattern
 Patterns properly made and having finished and smooth
surfaces reduce casting defects
 A properly constructed pattern minimizes the overall cost
of the castings

15. A typical pattern attached with raiser and gating system

16. Types of Pattern
 One piece or solid pattern
 Two piece or split pattern
 Loose piece pattern
 Cope and drag pattern
 Match plate pattern
 Three – piece or multi – piece pattern
 Follow board pattern
 Gated pattern
 Sweep pattern

17. One piece or solid pattern

18. Two piece or split pattern

19. Loose piece pattern

20. Cope and drag pattern

21. Match plate pattern

22. Three – piece or multi – piece pattern

23. Three – piece or multi – piece pattern

24. Follow board pattern

25. Gated pattern

26. Gated pattern

27. Sweep pattern

28. Pattern Material
 Wood
 Metals and alloys
 Plastic
 Plaster
 Wax

29. Pattern Material…
 Wood
 Most popular and commonly used
 Shisham, kail, deodar, teak and mahogany
 Pros
 Cheap, easily available in abundance, repairable and easily
fabricated in various forms using resin and glues
 Cons
 Shrinkage and warpage
 Affected by moisture of the moulding sand

30. Pattern Material…
 Metal and Alloys
 Number of patterns required large
 Posses longer life
 Easy to shape with good precision, surface finish and
intricacy in shapes
 Cast Iron
 Brasses and Bronzes
 Aluminum Alloys
 White metal

31. Pattern Material…
 Plastic
 Lighter, stronger, moisture and wear resistant, non sticky to
moulding sand
 Fragile and less resistant to sudden loading
 Phenolic resin plastics are commonly used
 Plaster
 Belongs to gypsum family which can be easily cast
 High compressive strength
 Wax
 Paraffin wax, Shellac wax, bees wax, cerasin wax and micro-
crystalline wax

32. PATTERN ALLOWANCES
&
MOULDING SAND

33. Pattern allowances
“The amount of something that is
permitted, especially within a set of
regulations or for a specified purpose”
Shrinkage allowance
Machining allowance
Draft or taper allowance
Rapping or shake allowance
Distortion or chamber allowance

34. Shrinkage allowance
 All most cast metals shrink or contract volumetrically on cooling. The metal
shrinkage is of two types:
 Liquid Shrinkage:
It refers to the reduction in volume when the metal changes from liquid
state to solid state at the solidus temperature.
To account for this shrinkage; riser, which feed the liquid metal to the
casting, are provided in the mould.
 Solid Shrinkage:
It refers to the reduction in volume caused when metal loses temperature
in solid state.
To account for this, shrinkage allowance is provided on the patterns.
 Cast iron – 10 mm/m, Brass – 16 mm/m, Al – 5 mm/m, Steel – 24 mm/m

35. Machining allowance
 Machining allowance is a positive allowance given to compensate for the amount of
material that is lost in machining or finishing the casting.
 The amount of allowance depends on
 nature of metal
 Size and shape of casting
 Methods of machining (grinding, turning, milling, boring etc.,)
 Casting condition
 Moulding process involved
 No of cuts to be taken and
 The degree of finish

36. Draft or taper allowance

37. Rapping or shake allowance

38. Distortion or chamber allowance

39. Constituents of Moulding Sand
 Silica sand
 Binder
 Moisture / Water
 Additives
 Corn flour and Dextrin
 Coal dust
 Sea coal and pitch
 Wood flour
 Silica flour

40. Silica sand
Most silica sand is made from broken down
quartz crystals
A pile of silica sand

41. Binder
Bentonite Clay

42. Additives
Corn flour
Coal dust Sea coal dust
Wood flour
Silica flour

43. Types of molding sands
Green sand
Dry sand
Loam sand
Facing sand
Backing sand
System sand
Parting sand
Core sand

44. Green sand
 Tempered or natural sand
 Silica sand – Clay (18 to 30%) – Moisture ( 6 to 8%)
 Fine, soft, light and porous
 Damp
 Not requiring baking
 Easily available and low cost
 Ferrous and non ferrous castings

45. Dry sand
 Green sand – dried or baked in suitable oven after the making mould and core
 Strength, rigidity and thermal stability
 Larger castings

46. Loam sand
 Sand + clay + water + thin plastic paste
 Clay – 30 to 50% and water – 18 %
 Patterns are not used
 Mold cavity is obtained by sweeps

47. Facing Sand
A sand which is used before pouring the molten metal,
on the surface is called facing sand.
It is specially prepared sand from silica sand and clay.

48. Backing Sand
 A sand used to back up the facing sand and not used next to the pattern
is called backing sand.
 The sand which have been repeatedly used may be employed for this
purpose.
 It is also known as black sand due to its colour.

49. System Sand
 A sand employed in mechanical sand preparation and handling system is
called system sand.
 This sand has high strength, permeability and refractoriness.

50. Parting sand
 Without binder and moisture
 Used to prevent green sand stick to the pattern
 Allow the drag and cope to separate without clinging
 Clean clay - free silica

51. Core sand
 Used for making cores
 Also known as oil sand
 Highly rich silica sand mixed with oil binders
 Linseed oil, resin, light mineral oil

52. Properties of molding sand
Refractoriness
Permeability
Plasticity
Adhesiveness
Cohesiveness

53. Properties of molding sand…
Refractoriness
 The property which enables it to resist high temperature of the
molten metal without breaking down or fusing.
Porosity or permeability
 It is the property of sand which permits the steam and other
gases to pass through the sand mould.
 The porosity of sand depends upon its grain size, grain shape,
moisture and clay components are the moulding sand.
 If the sand is too fine, the porosity will be low.

54. Properties of molding sand…
Plasticity
 It is that property of sand due to which it flows to all portions of the
moulding box or flask. The sand must have sufficient plasticity to
produce a good mould.
Adhesiveness
 It is that properties of sand due to it adheres or cling to the sides of
the moulding box.
Cohesiveness
 It is the property of sand due to which the sand grains stick
together during ramming. It is defined as the strength of the
moulding sand.

55. CORE MAKING

56. CORE MAKING
Stages in core making
 Core Sand Preparation
 Core Making
 Hand making of cores
 Core making machines
 Core blowing machines
 Core drawing/extrusion machines
 Core ramming machines
 Core Baking
 Continuous type ovens
 Batch type ovens
 Core Finishing
 Setting the cores

57. CORE SAND PREPARATION
Preparation of satisfactory and homogenous mixture of core
sand is not possible by manual means
Therefore for getting better and uniform core sand
properties using proper sand constituents and additives
The core sands are generally mixed with the help of any of
the following mechanical means namely roller mills and core
sand mixer using vertical revolving arm type and horizontal
paddle type mechanisms

58. CORE MAKING
Hand making of cores
 Placed the core box on work bench and it is filled
with already mixed and prepared core sand and
rammed by hand and the extra sand is removed
 Core box is inverted over the core plate to transfer
the core to the plate
 Baked in over a specified period and then removed
and cooled

59. CORE MAKING
Core making machines
 Core blowing machines:
 5 to 7 bar pressure
 Ensure high velocity to fill on remote corners
 Shaping and ramming or carried out simultaneously
 Small bench blowers and large floor blowers

60. CORE BLOWING MACHINE

61. CORE MAKING
Core making machines
 Core blowing machines:

62. CORE MAKING
Core making machines
 Core drawing/extrusion machines:

63. CORE MAKING
Core making machines
 Core ramming machines:
 Prepared by ramming core sand in the core boxes by
machines
 Based on the principle of squeezing, jolting and slinging

64. CORE BAKING
 To drive away the moisture and harden the binder, thereby
giving strength to the core
 Core ovens
 Continuous type
 Core carrying conveyors or chain move continuously through the oven
 The baking time is controlled by the speed of the conveyor
 Batch type
 Utilized for baking variety of cores in batches
 Dielectric bakers
 Based on dielectric heating
 Faster in operation and a good temperature control

65. CORE FINISHING
 The fins, bumps or other sand projections are removed
from the surface of the cores by rubbing or filing
 The dimensional inspection of the cores is very necessary to
achieve sound casting
 Cores are also coated with refractory or protective materials
using brushing, dipping and spraying means to improve their
refractoriness and surface finish
 The coating on core prevents the molten metal from
entering in to the core

66. SETTING OF CORES

67. SAND TESTING
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68. 1. MOISTURE CONTENT TEST
2. CLAY CONTENT TEST
3. CHEMICAL COMPOSITION OF SAND
4. GRAIN SHAPE AND SURFACE TEXTURE OF SAND
5. GRAIN SIZE DISTRIBUTION OF SAND
6. SPECIFIC SURFACE OF SAND GRAINS
7. WATER ABSORPTION CAPACITY OF SAND
8. REFRACTORINESS OF SAND
9. STRENGTH TEST
10. PERMEABILITY TEST
11. FLOWABILITY TEST
12. SHATTER INDEX TEST
13. MOULD HARDNESS TEST

69. • DETERMINED BY DRYING A WEIGHED AMOUNT OF 20 TO 50 GRAMS
OF MOULDING SAND TO A CONSTANT TEMPERATURE UP TO 100°C IN A
OVEN FOR ABOUT ONE HOUR.
• IT IS THEN COOLED TO A ROOM TEMPERATURE AND THEN
REWEIGHING THE MOULDING SAND.
• THE MOISTURE CONTENT IN MOULDING SAND IS THUS EVAPORATED.
• THE LOSS IN WEIGHT OF MOULDING SAND DUE TO LOSS OF
MOISTURE, GIVES THE AMOUNT OF MOISTURE WHICH CAN BE
EXPRESSED AS A PERCENTAGE OF THE ORIGINAL SAND SAMPLE.
• SPEEDY MOISTURE TELLER INSTRUMENT

70. • TAKE 50 GRAM OF DRY MOULDING SAND AND TRANSFER TO A WASH
BOTTLE
• ADD 475 CC OF DISTILLED WATER AND 25 CC OF 35% NAOH
SOLUTION AND AGITATE WITH A STIRRER FOR 10 MINUTES
• FILL THE WATER BOTTLE WITH WATER UPTO MARK.
• AFTER SAND IS SETTLED DOWN DRAIN OUT THE WATER (CLAY IS
DISSOLVED IN WATER AND IS REMOVED)

71. • FOR CARRY OUT GRAIN FINENESS TEST A SAMPLE OF DRY SILICA SAND
WEIGHING 50 GMS FREE FROM CLAY IS PLACED ON A TOP MOST SIEVE
BEARING U.S. SERIES EQUIVALENT NUMBER 6
• A SET OF ELEVEN SIEVES HAVING U.S. BUREAU OF STANDARD MESHES 6,
12, 20, 30, 40, 50, 70, 100, 140, 200 AND 270 ARE MOUNTED ON A
MECHANICAL SHAKER
• THE SERIES ARE PLACED IN ORDER OF FINENESS FROM TOP TO BOTTOM
• THE FREE SILICA SAND SAMPLE IS SHAKE IN A MECHANICAL SHAKER FOR
ABOUT 15 MINUTES

73. • THE REFRACTORINESS OF THE MOULDING SAND IS JUDGED BY
HEATING THE AMERICAN FOUNDRY SOCIETY (A.F.S) STANDARD SAND
SPECIMEN TO VERY HIGH TEMPERATURES RANGES DEPENDING UPON THE
TYPE OF SAND.
• THE HEATED SAND TEST PIECES ARE COOLED TO ROOM
TEMPERATURE AND EXAMINED UNDER A MICROSCOPE FOR SURFACE
CHARACTERISTICS OR BY SCRATCHING IT WITH A STEEL NEEDLE.
• IF THE SILICA SAND GRAINS REMAIN SHARPLY DEFINED AND EASILY
GIVE WAY TO THE NEEDLE.

74. • FLOWABILITY OF THE MOULDING AND CORE SAND USUALLY
DETERMINED BY THE MOVEMENT OF THE RAMMER PLUNGER BETWEEN
THE FOURTH AND FIFTH DROPS AND IS INDICATED IN PERCENTAGES
• THIS READING CAN DIRECTLY BE TAKEN ON THE DIAL OF THE FLOW
INDICATOR
• THEN THE STEM OF THIS INDICATOR RESTS AGAIN TOP OF THE
PLUNGER OF THE RAMMER AND IT RECORDS THE ACTUAL MOVEMENT
OF THE PLUNGER BETWEEN THE FOURTH AND FIFTH DROPS

76. • IN THIS TEST, THE A.F.S. STANDARD SAND
SPECIMEN IS RAMMED USUALLY BY 10
BLOWS AND THEN IT IS ALLOWED TO FALL
ON A HALF INCH MESH SIEVE FROM A
HEIGHT OF 6 FT.
• THE WEIGHT OF SAND RETAINED ON THE
SIEVE IS WEIGHED.
• IT IS THEN EXPRESSED AS PERCENTAGE OF
THE TOTAL WEIGHT OF THE SPECIMEN
WHICH IS A MEASURE OF THE SHATTER
INDEX.
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78. • THE COMPRESSION STRENGTH OF THE MOULDING SAND IS DETERMINED BY
PLACING STANDARD SPECIMEN AT SPECIFIED LOCATION AND THE LOAD IS
APPLIED ON THE STANDARD SAND SPECIMEN TO COMPRESS IT BY UNIFORM
INCREASING LOAD USING ROTATING THE HAND WHEEL OF COMPRESSION
STRENGTH TESTING SETUP
• AS SOON AS THE SAND SPECIMEN FRACTURES FOR BREAK, THE COMPRESSION
STRENGTH IS MEASURED BY THE MANOMETER
• TENSILE, SHEAR AND TRANSVERSE TESTS ARE ALSO SOMETIMES PERFORMED
• SUCH TESTS ARE PERFORMED IN STRENGTH TESTER USING HYDRAULIC PRESS
• THE MONOMETERS ARE GRADUATED IN DIFFERENT SCALES
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81. • THE WORKING OF THE TESTER IS BASED ON THE PRINCIPLE OF BRINELL HARDNESS
TESTING MACHINE
• IN AN A.F.S. STANDARD HARDNESS TESTER A HALF INCH DIAMETER STEEL HEMI-
SPHERICAL BALL IS LOADED WITH A SPRING LOAD OF 980 GM
• THIS BALL IS MADE TO PENETRATE INTO THE MOULD SAND OR CORE SAND SURFACE
• THE PENETRATION OF THE BALL POINT INTO THE MOULD SURFACE IS INDICATED ON A
DIAL IN THOUSANDS OF AN INCH
• THE DIAL IS CALIBRATED TO READ THE HARDNESS DIRECTLY I.E. A MOULD SURFACE
WHICH OFFERS NO RESISTANCE TO THE STEEL BALL WOULD HAVE ZERO HARDNESS
VALUE AND A MOULD WHICH IS MORE RIGID AND IS CAPABLE OF COMPLETELY
PREVENTING THE STEEL BALL FROM PENETRATING WOULD HAVE A HARDNESS VALUE
OF 100
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83. • P = VH/PAT
WHERE, P = PERMEABILITY
V = VOLUME OF AIR PASSING THROUGH THE SPECIMEN IN C.C.
H = HEIGHT OF SPECIMEN IN CM
P = PRESSURE OF AIR IN GM/CM2
A = CROSS-SECTIONAL AREA OF THE SPECIMEN IN CM2
T = TIME IN MINUTES.
• FOR A.F S. STANDARD PERMEABILITY METER, 2000 CC OF AIR IS PASSED THROUGH A SAND SPECIMEN
(5.08 CM IN HEIGHT AND 20.268 SQ. CM. IN CROSS-SECTIONAL AREA) AT A PRESSURE OF 10
GMS/CM2 AND THE TOTAL TIME MEASURED IS 10 SECONDS = 1/6 MIN. THEN THE PERMEABILITY IS
CALCULATED USING THE RELATIONSHIP AS GIVEN AS UNDER.
• P = (2000 × 5.08) / (10 × 20.268 × (1/6)) = 300.66
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85. MOULDING MACHINES
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86. MOULDING MACHINES
 Moulding machine acts as a device by means of a large number of co-
related parts and mechanisms, transmits and direct various forces and
motions in required directions so as to help the preparation of a sand
mould
 The major functions of moulding machines involve ramming of
moulding sand, rolling over or inverting the mould, rapping the
pattern and withdrawing the pattern from the mould
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87. SQUEEZER MACHINE
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88. JOLT MACHINE
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89. JOLT-SQUEEZER MACHINE
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90. SLINGING MACHINES
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91. MELTING FURNACE
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92. MELTING FURNACE
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 The metal to be casted has to be in the molten or liquid state
before pouring into the mould
 A furnace is used to melt the metal
 A foundry furnace only remelts the metal to be cast, it does not
convert ore into useful metal
 Different furnaces are used for melting and remelting ferrous
and non-ferrous materials

93. MELTING FURNACE
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Factors responsible for the selection of furnace
 Cost
 Fuels
 Efficiency and speed of melting
 Composition and melting temperature
 Cleanliness and noise level in operation
 Method used for pouring desired metal
 Chances of metal to absorb impurities

94. MELTING FURNACE
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 Blast furnace
 Cupola furnace
 Reverberatory furnace
 Rotary melting furnace
 Open hearth furnace
 Convertor
 Pit furnace
 Crucible furnace
 Electric furnace

95. MELTING FURNACE
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96. CUPOLA FURNACE
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97. CUPOLA FURNACE
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98. OPERATION/WORKING OF CUPOLA FURNACE
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 Preparation of cupola
 Lightening of cupola
 Charging of cupola
 Melting
 Slagging and metal tapping
 Dropping down

99. OPERATION/WORKING OF CUPOLA FURNACE
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 Preparation of cupola
 Unburned coke, slag and metal are removed from bottom
doors of previous melting
 Slag, coke, iron sticking to the side walls of the furnace are
removed
 Damaged bricks are replaced and damaged refractory lining is
patched up

100. OPERATION/WORKING OF CUPOLA FURNACE
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 Lightening of cupola
 Soft, dry wood are placed on the sand bed
 Coke is placed above the wooden pieces till the tuyeres
 Wood is ignited through tap hole
 Charging of cupola
 After the coke bed is properly ignited, the cupola is charged
from the charging door
 Involves alternate layers of limestone (flux), metal (iron) and
fuel (coke) up to the level of charging door
 Flux is a substance aiding in formation of slag for removing
impurities

101. OPERATION/WORKING OF CUPOLA FURNACE
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 Melting
 A soak period 30 – 60 min is given to charge for preheating
 Blast is turned ON
 Coke becomes fairly hot to melt the metal charge
 Now molten metal starts accumulating in the hearth and
appears at tap hole

102. OPERATION/WORKING OF CUPOLA FURNACE
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 Slagging and metal tapping
 After enough is accumulated the slag hole is opened and the
slag is collected in a container and disposed off
 The plug is knocked off from the tap hole and the molten
metal is tapped pouring into the mould
 Dropping down
 As cupola heat charging is stopped, all the content of cupola is
allowed to melt till one or two charge is left above coke bed
 Now the air blast is switched off and the remains in cupola are
dropped down on the floor or collected in bucket

103. PROS OF CUPOLA FURNACE
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Simple and easier to construction and easy to operate
Low initial, operation and maintenances costs
Less floor space
Can operate continuously for many hours

104. CONS OF CUPOLA FURNACE
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Close temperature control is difficult
Molten iron, coke comes into contact with certain useful
elements like silicon, manganese and are lost
Impurities like sulfur are picked by molten iron affecting
final iron content

105. CRUCIBLE FURNACES
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106. CRUCIBLE FURNACE
It is very simple
It is made up of crucible and this crucible is made up of
Graphite plus Silicon carbide plus clay and plus some resin
Non ferrous metals and low melting point alloys
Three types
Lift out crucible
Stationary pot
Tilting pot
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107. LIFT OUT CRUCIBLE FURNACE
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108. STATIONERY POT CRUCIBLE FURNACE
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109. TILTING POT FURNACES
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110. ELECTRIC FURNACES
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111. ELECTRIC FURNACES
 Employed for the production of high quality castings, because the
furnace atmosphere can be more closely controlled, losses by
oxidation can be eliminated, alloying elements can be added
without fear of loss
 Composition of the melt and its temperature can be accurately
controlled
 Capacity of electric furnaces ranges from 250 kg to 10 tons
Types of electric furnaces:
 Direct arc furnace
 Indirect arc furnace
 Core type induction furnace
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112. DIRECT ARC FURNACE
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113. DIRECT ARC FURNACE
Interior of the furnace is preheated
Preheated is done by alternatively striking and breaking
the arc between the electrodes and used electrode pieces
kept on the hearth
Electric arc is drawn between the electrodes and metal
charge
Temperature – 6094 °c
Slag form due to melting of flux, sand etc.,
Slag is removed by tilted the furnace backward
Molten metal taken out by tilted the furnace forward
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114. DIRECT ARC FURNACE
PROS
Undertake a definite metal refining sequence
Analysis of melt can be kept to accurate limits
High thermal efficiency as high as about 70%
Preferred for its quicker readiness for use
CONS
Heating cost are higher
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115. INDIRECT ARC FURNACE
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116. INDIRECT ARC FURNACE
 The furnace is charged with pig iron and scrap is placed above
 When the electric power is ON, graphite electrodes are
brought nearer till the current jumps and an electric arc is set
up between them
 The heat generated in the arc is responsible for melting the
charge
CONS
 Initial cost and its auxiliary equipment is high
 Time available for analyzing the melt composition is very small
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117. SPECIAL CASTING PROCESSES
SHELL – INVESTMENT – PRESSURE DIE
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118. SPECIAL CASTING PROCESSES
 Sand moulds are single purpose moulds as they are completely
destroyed after the casting has been removed from the
moulding box
 It becomes therefore obvious that the use of a permanent
mould would do a considerable saving in labor cost of mould
making
 Pros
 Greater dimensional accuracy
 High production rates and hence lower production cost
 Ability to cast extremely thin sections
 Posses higher mechanical properties
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119. SHELL CASTING
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120. SHELL MOULDING
 Pros
 Castings as thin as 1.5 mm
 Machining often not required
 Smoother cavity surface permits easier flow of molten metal and
better surface finish
 Cons
 Uneconomical to small scale production
 Resin costs are comparatively high
 Heavy weight castings (>10kg)
 Applications
 Automotive rocker arms, valves, small pipes, camshaft, bushings
valve bodies, spacers, brackets, manifolds, bearing caps, shafts,
gears and so on
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121. INVESTMENT CASTING or LOST WAX CASTING
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122. INVESTMENT CASTING or LOST WAX CASTING
 Pros
 Parts of greater complexity can be casted
 Good surface finish
 Lost wax can be reused
 Cons
 Expensive and time consuming
 Pattern making is additional cost
 Cores cannot be used
 Applications
 Parts for sewing machines, locks, rifles, nozzles, and so on
 Casting jewellery and art castings
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123. PRESSURE DIE CASTING
HOT CHAMBER
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124. PRESSURE DIE CASTING
COLD CHAMBER
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125. PRESSURE DIE CASTING
COLD CHAMBER
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126. PRESSURE DIE CASTING
 Pros
 High production rate
 High accuracy in part dimensions
 Smooth surface finish for minimum mechanical finishing
 Ability to make many intricate parts
 Cons
 Hollow shapes are not readily casted because of the high metal pressure
 Limited sizes of the products can be produced based on the availability of the
equipment
 High melting temperature alloys are practically not die casted
 Applications
 Die casting process is preferred for nonferrous metal parts of intricate shapes
 Automobiles appliances, hand tools, computer peripherals, toys, optical and
photographic equipment etc
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127. SPECIAL CASTING PROCESSES
Centrifugal – CO2 Moulding
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128. CENTRIFUGAL CASTING
The technique uses the centrifugal force generated by a rotating
cylindrical mould to throw molten metal against a mould wall to
form the desired shape
Therefore, a centrifugal casting machine must be able to spin a
mould, receive molten metal, and let the metal solidify and cool
in the mould in a carefully controlled manner
Centrifugal casting processes also have three types:
True centrifugal casting (horizontal, vertical, or inclined)
Semi centrifugal (centrifugal mold) casting
Centrifuge mold (centrifugal die) casting
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129. TRUE CENTRIFUGAL CASTING
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The permanent mould is rotated about its axis at high speeds (300 to
3000 rpm), so that the molten metal is forced to the inside mould wall,
where it solidifies
The casting is usually very fine grained on the outer diameter, while the
inside diameter has more impurities and inclusions that can be
machined away

130. SEMI-CENTRIFUGAL CASTING
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131. CENTRIFUGE CASTING
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132. CENTRIFUGE CASTING
Parts not symmetrical about any axis of rotation may be cast
groups of moulds arranged in a circle to balance each other
The setup is revolved around the center of the circle to induce
pressure on the metal in the moulds
Mould is designed with part cavities located away from axis of
rotation
Used for smaller parts
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133. CARBONDIOXIDE MOULDING
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134. SAND CASTING DEFECTS
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135. SAND CASTING DEFECTS
Various defects can develop in manufacturing processes depending
on factors such as
Materials
Part design
Processing techniques
While some defects affect only the appearance of the parts made,
others can have major adverse effects on the structural integrity of
the parts
Defects found in castings may be divided into three classes
Visual examination or measurement
Machining, sectioning or radiography
Material defects by mechanical testing
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136. CLASSIFICATION OF DEFECTS
Defects caused by
Patterns and moulding box equipment
Molten metal
Improper mould drying and core baking
Moulding, core making, gating etc
Moulding and core making materials
Improper sand mixing and distrubtion
Closing and pouring the moulds
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137. BLOW HOLE
 Blow holes are smooth, round holes
 Blowholes visible on the surface of a casting are called open blows
whereas those occurring below the surface of castings and not visible,
from outside are termed as blowholes
 Problem Causes
Excess moisture content in moulding sand
Rust and moisture on chills, chaplets and inserts
Cores not sufficiently baked
 Remedies
Control of moisture content
Use of rust free chills, chaplets and clean inserts
Bake cores properly
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138. POROSITY
 Porosity is pockets of gas inside the metal caused by micro-shrinkage
during solidification
 Problem Causes
High pouring temperature
Gas dissolved in metal charge
Less flux used
High moisture and low permeability in mould
 Remedies
Regulates pouring temperature
Control metal composition
Increase flux proportions
Reduce moisture and increase permeability of mould
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139. MISRUNS
A casting that has solidified before completely filling mould cavity
Problem Causes
Lack of fluidity in molten metal
Faulty mould design
Faulty gating design
Remedies
Adjust proper pouring temperature
Modify mould design
Modify gating system
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140. HOT TEARS
 A fracture formed during solidification because of hindered contraction
 Problem Causes
Lack of collapsibility of core
Lack of collapsibility of mould
Faulty design
Hard ramming of mould
 Remedies
Improve core collapsibility
Improve mould collapsibility
Modify casting design
Provide softer ramming
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141. METAL PENETRATION
 When fluidity of liquid metal is high, it may penetrate into sand mould or
core, causing surface to consist of a mixture of sand grains and metal
 Problem Causes
Large grain size sand used
Soft ramming of mould
Low strength of mould or core
High permeability of sand or core
Pouring temperature of metal too high
 Remedies
Use sand having finer grain size
Provide hard ramming
Suitability adjust pouring temperature
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142. COLD SHUTS
Two portions of metal flow together but there is a lack of fusion due
to premature freezing
Problem Causes
Lack of fluidity in molten metal
Faulty design
Faulty gating
Remedies
Adjust proper pouring temperature
Modify design
Modify gating system
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143. CUTS AND WASHES
The place from where the sand has been cut or washed is occupied
by molten metal and thus an excess metal appears on the casting
surface in the form of rough jumps or ragged spots
Problem Causes
Low strength of mould and core
Lack of binders in facing and core sand
Faulty gating
Remedies
Improve mould and core strength
Add more binders to facing and core sand
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144. INCLUSIONS
Any separate undesirable foreign material present in the material of
a casting
Problem Causes
Faulty gating
Faulty pouring
Inferior moulding or core sand
Soft ramming of mould
Remedies
Modify gating system
Improve pouring to minimize turbulence
Provide hard ramming
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145. MOULD SHIFT
A step in cast product at parting line caused by sidewise relative
displacement of cope and drag
Problem Causes
Worn out or bent clamping pins
Misalignment of two halves of pattern
Improper support of core
Improper location of core
Faulty core boxes
Remedies
Repair or replace the pins
Repair or replace dowels which cause misalignment
Provide adequate support to core07-02-2019 05:26 145

146. INSPECTION METHOD
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147. INSPECTION METHOD
• INSPECTION IS THE ACT OF CHECKING THE ACCEPTABILITY OF
THE CASTING BOTH DIMENSIONALLY AND FUNCTIONALLY
• BROADLY CLASSIFIED INTO FIVE CATEGORIES
• VISUAL INSPECTION
• DIMENSIONAL INSPECTION
• MECHANICAL TESTING
• FLAW DETECTION BY NON DESTRUCTIVE METHODS
• METALLURGICAL INSPECTION
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148. VISUAL INSPECTION
• TO DETECT THE SURFACE DEFECTS
• EITHER BY NAKED EYES OR MAGNIFYING GLASS
• SURFACE CRACKS, TEARS, BLOW HOLES, METAL
PENETRATION, SWELLS, ROUGHNESS, SHRINKAGES ETC.,
ARE EASILY DETECTED BY VISUAL INSPECTION
• SIMPLEST AND FASTEST
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149. DIMENSIONAL INSPECTION
• IT IS A VERY IMPORTANT ACTIVITY IN THOSE CASTINGS WHICH NEED TO
BE FURTHER MACHINED
• CHECKING OUT THE AVAILABILITY OF VARIOUS MACHINING ALLOWANCES
IN THE CASTINGS
• ACCEPTING/REJECTING OF CASTINGS
• TO CHECK FOR THE CORRECTNESS OF THE CORE, PATTERN, CORE BOXES
ETC.,
• INSTRUMENTS LIKE MICROMETER, GAUGES, COORDINATE MEASURING
MACHINE, 3D INSPECTION STATION (MACHINE VISION STATEMENT)
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150. MECHANICAL TESTING
• CASTINGS NEED TO TESTED FOR THEIR MECHANICAL PROPERTIES
LIKE TENSILE/COMPRESSION STRENGTH, HARDNESS,
TOUGHNESS, FRACTURE, FATIGUE, IMPACT TESTING,
SOUNDNESS, PRESSURE/LEAK TESTING FOR TUBES AND PIPING,
CREEP TESTING ETC.,
• ABOVE TESTS ARE DONE USING DIFFERENT COMMERCIALLY
AVAILABLE TESTING MACHINES LIKE UNIVERSAL TESTING
MACHINE, ROCKWELL HARDNESS TESTING MACHINES, FRACTURE
TESTING MACHINES ETC., WITH STANDARD TEST PROCEDURES
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151. FLAW DETECTION BY NON DESTRUCTIVE METHODS
• IT IS A WIDE GROUP OF ANALYSIS TECHNIQUES USED IN
INDUSTRY TO EVALUATE THE PROPERTIES OF A MATERIAL,
COMPONENT OR SYSTEM WITHOUT CAUSING DAMAGE
• RELIABLE, SAFE AND ECONOMICAL
• MOST COMMON METHODS OF NON-DESTRUCTIVE TESTING
USED IN FOUNDRIES ARE:
• RADIOGRAPHY (X-RAY AND Γ-RAY)
• FLUORESCENT-PENETRANT INSPECTION
• ULTRASONIC INSPECTION
• MAGNETIC PARTICLE INSPECTION
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152. X-RAY RADIOGRAPHY TEST
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153. X-RAY RADIOGRAPHY TEST
• X-RAYS ARE PRODUCED IN AN X-RAY TUBE
• THE PORTION OF THE CASTING WHERE DEFECTS ARE SUSPECTED IS EXPOSED TO X-
RAYS
• X-RAY FILM IS PLACED BEHIND AND IN CONTACT WITH THE CASTING, PERPENDICULAR
TO THE RAYS
• DURING EXPOSURE, X-RAYS PENETRATE THE CASTING AND THUS AFFECT THE X-RAY
FILM
• MOST DEFECTS POSSESS LESSER DENSITY THAN THE SOUND CASTING METAL
• THEREFORE THE FILM APPEARS TO THE MORE DARK WHERE DEFECTS ARE IN LINE OF
THE X-RAY BEAM
• THE EXPOSED AND DEVELOPED X-RAY FILM SHOWING LIGHT AND DARK AREAS IS
TERMED AS RADIOGRAPH OR EXOGRAPH
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154. GAMMA-RAY RADIOGRAPHY TEST
• IT IS USED FOR THICKER CASTINGS
• SCATTERING OF GAMMA RAYS IS LESS
AND HENCE ARE SATISFACTORY THAN
X-RAY TECHNIQUES FOR VARYING
CASTING THICKNESS
• UNLIKE X-RAYS, GAMMA RAYS FROM ITS
SOURCE ARE EMITTED IN ALL
DIRECTIONS, THEREFORE A NUMBER OF
SEPARATE CASTINGS HAVING FILM,
FASTENED TO BACK OF EACH CASTING,
ARE DISPOSED IN CIRCLE AROUND THE
SOURCE PLACED IN A CENTRAL
POSITION
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155. MAGNETIC PARTICLE INSPECTION
• WHEN A PIECE OF METAL IS PLACED IN
A MAGNETIC FIELD AND THE LINES OF
MAGNETIC FLUX GET INTERSECTED BY A
DISCONTINUITY SUCH AS CRACK OR
SLAG INCLUSION IN A CASTING,
MAGNETIC POLES ARE INDUCED ON
EITHER SIDE OF THE DISCONTINUITY
• THE LOCAL FLUX DISTURBANCE CAN BE
DETECTED BY ITS UPON MAGNETIC
PARTICLES WHICH ARE ATTRACTED TO
THE REGION OF DISCONTINUITY AND
PILE UP AND BRIDGE OVER THE
CONTINUITY
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156. FLUORESCENT PENETRANT INSPECTION
• BOTH FERROUS AND NON-FERROUS
CASTINGS
• CLEAN THE SURFACES OF THE OBJECT TO
BE INSPECTED FOR CRACKS ETC.,
• APPLY THE FLUORESCENT PENETRATION
ON THE SURFACE BY EITHER DIPPING,
SPRAYING OR BRUSHING
• ALLOW A PENETRATION TIME UP TO ONE
HOUR
• THE PENETRANT FROM SURFACE DRAWN
INTO CRACK BY CAPILLARY ACTION
• WASH WITH WATER SPRAY TO REMOVE
PENETRANT FROM SURFACE BUT NOT
FROM CRACK
• APPLY THE DEVELOPER
• THE DEVELOPER ACTS LIKE A BLOTTER TO
DRAW PENETRANT OUT OF CRACK AND
ENLARGE THE SIZE OF THE AREA OF
PENETRANT INDICATION
• THE SURFACE IS VIEWED UNDER BLACK
LIGHT
• BLACK LIGHT CAUSES PENETRANT TO
GLOW IN DARK
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157. FLUORESCENT PENETRANT INSPECTION
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158. ULTRASONIC INSPECTION
• A TYPICAL PULSE-ECHO UT INSPECTION
SYSTEM CONSISTS OF SEVERAL FUNCTIONAL
UNITS, SUCH AS THE PULSER/RECEIVER,
TRANSDUCER, AND A DISPLAY DEVICE
• A PULSER/RECEIVER IS AN ELECTRONIC
DEVICE THAT CAN PRODUCE HIGH VOLTAGE
ELECTRICAL PULSES
• DRIVEN BY THE PULSER, THE TRANSDUCER
GENERATES HIGH FREQUENCY ULTRASONIC
ENERGY.
• THE SOUND ENERGY IS INTRODUCED AND
PROPAGATES THROUGH THE MATERIALS IN
THE FORM OF WAVES
• WHEN THERE IS A DISCONTINUITY IN THE
WAVE PATH, PART OF THE ENERGY WILL BE
REFLECTED BACK FROM THE FLAW SURFACE.
• THE REFLECTED WAVE SIGNAL IS
TRANSFORMED INTO AN ELECTRICAL SIGNAL
BY THE TRANSDUCER AND IS DISPLAYED ON A
SCREEN
• KNOWING THE VELOCITY OF THE WAVES,
TRAVEL TIME CAN BE DIRECTLY RELATED TO
THE DISTANCE THAT THE SIGNAL TRAVELLED
• FROM THE SIGNAL, INFORMATION ABOUT
THE REFLECTOR LOCATION, SIZE,
ORIENTATION AND OTHER FEATURES CAN
SOMETIMES BE GAINED.
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159. ULTRASONIC INSPECTION
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