1. Define foundry.
A plant where the castings are made is called foundry.
2. Define casting.
Casting process is the process of producing metal parts by pouring the molten metal into the mould cavity of the required shape and allowing the metal to solidify. The solidified metal piece is called "casting".
3. Define mould.
Mould is the cavity of the required shape to be made in the moulding sand or in other material.
4. Define pattern.
Pattern is the model of the required casting made in wood or any other soft material such as aluminium, brass, plastics etc.
5. State any two important factors to be considered for choosing the pattern materials.
1) Shape, complexity and size of castings.
2) Degree of accuracy in dimensions.
3) The quality of surface finish required on casting.
4) Number of casting to be produced and type of casting method.
6. What are the pattern materials?
1. Wood - Teak wood, mahogony, white pine etc.,
2. Metal- cast iron, brass, aluminium, white metal etc
3. Plaster
4. Plastics
5. Wax
7. Name any four types of commonly used patterns.
1. Solid or single piece pattern
2. Split pattern
3. Loose piece pattern
4. Match plate pattern
5. Sweep pattern
6. Skeleton pattern
7. Segmental pattern
8. Shell pattern.
8. Define pattern allowance. What is the main purpose of providing pattern allowance?
Patterns are not made into the exact size of the castings to be produced. Patterns are made slightly larger than the required castings. This extra size given on the pattern is called pattern allowance.
The pattern allowances are given for the purpose of compensating the metal shrinkage to provide extra metal which is to be removed in machining, to avoid metal distortion, for easy withdrawal of pattern from mould and for rapping. If allowances are not given on the pattern, the casting will become smaller than the required size.
9. List any four allowances considered while designing a pattern for a casting.
1. Shrinkage allowance
2. Machining allowance
3. Draft allowance
4. Shaking allowance
5. Distortion allowance.
10. What are the major constituents of moulding sand?
1. Refractory sand
2. Binders
3. Additives
4. Moisture.
11. Write the composition of good moulding sand.
Green sand:
It contains 5 to 8% water and 15 to 20% clay.
Loam sand:
Loam sand is a mixture of fine sands, fine refractories, clay, graphite powder and water. It contains more clay (50%).
12. State the purposes of adding ingredient to the moulding sand.
1. To maintain shape at very high temperature
2. To make a mould porous
3. To increase the strength
4. To ensure collapsibility
5. To increase cohesiveness and adhesiveness.
13. What are the different types of moulding sand?
1. Green sand
2. Dry sand
3. Synthetic sand
4. Loam sand
5. Special sand
6. Parting sand.
14. What are the properțies good moulding sand?
A good quality moulding sand contains the following properties:
1. Porosity or permeability
2. Plasticity or flowability
3. Strength or cohesiveness
4. Adhesiveness
5. Refractoriness
6. Collapsibility.
15. What are the steps in preparing moulding sand?
The moulding sand is prepared by the following steps:
1. Mixing of sand
2. Tempering of sand, and
3. Conditioning of sand.
16. List out any five moulding tools.
1. Shovel
2. Riddle
3. Rammer
4. Trowel
5. Slick
6. Strike-off-bar
7. Lifter.
17. State the tools used for mixing of moulding sand.
If the small quantity of moulding sand is required, the mixing will done by manually using shovels. The large quantity is mixed by using a muller.
18. What is meant by tempering of the sand?
The process of spraying and mixing adequate amount of water with the sand in the muller is called tempering.
19. What is ideal profile of a sprue?
The sprue profile which having straight edges to use it safe and easy to make is called ideal profile of a sprue.
20. What is the use of draw spike?
It is used to remove the pattern from the mould.
21. What is the function of swab and vent-wire?
The swab is used to apply water in the sand around to pattern.
A vent-wire is used to make small holes on the mould after ramming.
22. Mention the various types of moulding boxes.
1. Snap flash
2. Tight or box flask
23. What are chaplets?
Sometimes, it is not possible to provide a sufficient support for the core in the mould being poured if the cores are bigger in size. In such cases, the core is supported with rigid metal pieces called chaplets.
24. What are the various stages involved in sand conditioning?
1. Removing foreign materials.
2. Distributing the binder uniformly.
3. Controlling the moisture.
4. Aerating the sand, and
5. Delivering at proper temperature.
25. What is the necessity of sand testing?
Moulding sands have to be in correct size to ensure the proper sand quality as per the required level of accuracy and good surface finished castings. Generally, the .moulding sand contains silica sand grains, clay content and moisture content. So, the systematic evaluation of the working qualities of moulding sand is important before making the mould for producing castings.
26. What are the uses of runner and riser?
Runner:
1. It is used to make a sprue a hole in the cope.
2. It receives the molten metal from the pouring basin and passes to the cavity.
Riser:
1. It supplies excess the molten metal to the solidifying casting.
2. It allows the escape of air.
3. It indicates whether the cavity is fully filled up or not.
27. State the various methods for testing moulding sand.
1. Moisture content test
2. Clay content test
3. Grain finess test
4. Permeability test
5. Strength test
6. Deformation and toughness test
7. Hot strength test
8. Refractoriness test
9. Mould hardness test.
28. How is the percentage of moisture content estimated?
First, a measured quantity of sample is taken. Then, this measured quantity is poured into the pan provided on the moisture determining apparatus. After this, the pan is closed by an enclosure. Now, the supply to the heating bulb is switched ON. Immediately, the infrared heating bulb emits heating rays towards the pan. The heating is done for 2 to 3 minutes. Thus, the moisture content present in the moulding is evaporated. Then, the supply to bulb is switched OFF. The dried sample is taken by opening the enclosure. Then, it is reweighed. The moisture content is determined by subtracting the final weight from original weight or initial weight.
29. What is meant by grain fineness number?
Grain fineness number is defined as the ratio between total products and total percentages of sand retained on pan in each sieve.
30. Give the standard sand specimen to be tested in a specimen rammer.
A 50.8 mm × 50.8 mm of standard seed specimen is prepared by a specimen rammer.
31. What are the parameters involved in determining the strength of the moulding sand?
Compressive strength, shear strength, tensile strength and bending strength.
32. When do you make core (or) what is function of core in moulding sand?
A core is a body made of sand which is used to make a cavity or a hole in the casting. The shape of the core is similar to the required cavity in the casting to be made. It is also used to make recesses, projections, undercuts and internal cavities.
33. Mention the various steps involved in core making process.
1. Core sand preparation
2. Making of core
3. Baking the core
4. Finishing of core
5. Setting the core.
34. Differentiate between mould and core.
Mould
● Mould is a cavity made with moulding sand used to make solid castings.
● It is used to make casting of the required shape.
Core
● Core is a body of sand used to make a cavity of hollow surfaces required in a casting.
● It is used to make recess, projections, undercuts and internal cavities in the casting.
35. What do you understand by core setting?
Curing or heating the cores to obtain enough hardness is called core setting.
36. What is a core print? Mention is its purpose.
A core print is an extra projection on the pattern. It supports the core.
37. Write the applications of core prints.
Core prints are used to make holes in engine blocks, gears and pulleys.
38. What are the characteristics of a core?
1. Permeability.
2. Refractoriness
3. Strength
4. Collapsibility, and
5. Stability.
39. What are the core making materials or core sand ingredients?
1. Core sand
2. Binders
3. Additives
4. Moisture.
40. List the purposes of the core binders.
A core binder is used for the following purposes:
1. To bind the sand grains together
2. To give strength and hardness
3. To prevent breaking
4. To give collapsibility to core
5. To prevent moisture absorption.
41. Name the different types of core binders.
1. Oil binders
2. Water soluble binders
3. Resin binders
4. Inorganic binders.
42. State the various types of core boxes.
1. Half box
2. Dump or slap core box
3. Split core box
4. Strickle core box
5. Gang core box.
43. Mention the main use of core baking ovens.
Core ovens are mainly used for heating the cores to obtain the required hardness.
44. State any two core drying ovens.
1. Batch type ovens
2. Continuous type oven
3. Dielectric baking oven.
45. In which type of baking oven the highest intensity heat is obtained? Where it is used?
Dielectric baking. It is used in mass production of heating cores.
46. Name the various types of cores.
a) According to the state of core
1) Green sand core
2) Dry sand core
b) According to the position of the core in the mould.
1) Horizontal core
2) Vertical core
3) Balanced core
4) Hanging core
5) Drop core.
47. Where is the balanced core generally used?
This type of core is used when the blind holes along a horizontal axis are to be produced.
48. State the properties and ingredients for core making in CO2 process.
Pure dry sand is mixed with sodium silicate binder. Additives such as wood flour, graphite may be added with this core. Sand for collapsibility moisture of 3% is added.
49. Mention the specific advantages of CO2 process.
or
What is the merit of CO2 process?
1. It gives strength and hardness to core.
2. The process cost is less.
3. It saves time on heating.
4. It can be stored for long use.
50. State the different types of moulding processes.
1. Green sand mould
2. Dry sand mould
3. Loam sand mould
51. Mention any two difference between green sand mould and dry sand mould.
Green sand mould
1. Less time for making mould.
2. Less surface finish.
3. Low strength.
4. Less permeability.
Dry sand mould
1. More time consuming.
2. Better surface finish.
3. Stronger than green sand mould.
4. More permeability.
52. Compare the advantages of metal moulds over sand (expandable) moulds.
Metal mould
1. Metal moulds are reusable..
2. It is used for mass production.
Sand mould
1. It cannot be reused.
2. It is used for batch production.
53. What are the different types of furnaces used for casting?
1. Cupola furnace
2. Open hearth furnace
3. Crucible furnace
4. Pot furnace
5. Electric furnace.
54. List the factors to be considered in the choice of metal melting furnaces.
1. Blast furnace ➡ For smelting iron to produce pig iron
2 Cupola furnace ➡ For cast iron
3. Open health furnace ➡ For steel
4. Crucible furnace ➡ For non-ferrous metal
5. Electric furnace ➡ For steel, alloy steel, brasses.
55 What are the functions of flux in melting metals and alloys?
The flux is used to prevent the reaction of the molten metal with atmospheric air. It also removes the impurities from the molten metal and forms a slag.
56. Which type of furnace is suitable for producing pig iron?
Blast furnace is mainly used for smelting iron to produce pig iron, the raw material for wrought and cast iron.
57. Why blast furnace is called so?
Blast furnace is named so because very high temperature developed inside the furnace by means of forcing a blast of heated air.
58. Which type of furnaces are suitable for melting of ferrous material and why?
Cupola and crucible furnaces are mainly used for melting ferrous materials due to easy maintenance, long time in operation, etc.
59. State the main function of tuyers in cupola furnace.
The tuyers are used to supply air to the coke bed for complete burning.
60. What are the differences between oil fired and coke fired furnace?
Oil Fired
1. Oil or gas is fired for melting metal.
2. Tilting furnace.
Coke Fired
1. Coke is used for melting inetal.
2. Stationary furnace.
61. What are the types of crucible furnace?
1. Pit furnace
2. Coke fired stationary furnace
3. Oil fired tilting furnace.
62. Which principle is followed in electric induction furnace for melting metal?
Transformer principle is used. The coils act as a primary coil and charge inside the crucible acts as a secondary coil.
64. Where is the charge loaded in indirect electric arc furnace?
The charge to be melted is charged at the center of the furnace between two electrodes.
65. What is die-casting?
The mould used for making a casting is permanent called a die-casting.
66. Mention any two merits and demerits of die casting.
Merits of die casting:
1. Castings with very good surface finish can be made.
2. Rate of production (700 castings per hour) is high.
3. Castings with varying thickness wall can be made.
4. There is no possibility of sand inclusions.
Demerits of die casting:
1. Only small parts carr be made.
2. Only non-ferrous metals can be cast.
3. Equipment cost is high.
4. It is more suitable for mass production only.
67. How does hot chamber process differ from cold chamber process?
In hot chamber die-casting, the melting furnace is an integral part of the mould.
In cold chamber die-casting, the metal is melted in a separate furnace and brought to the machine for pouring.
68. Where is the molten metal poured in the cold chamber die-casting? How is it operated?
The molten metal from the ladle is poured into the injection cylinder. A hydraulic plunger operates the cold chamber die-casting.
69. Name the alloys which are generally die cast. Why are aluminium alloys preferably cast in cold chamber die casting machines?
Zinc, aluminium, magnesium, copper, lead, tin and uncommon ferrous alloys are generally die cast.
Cold chamber die casting is more suitable for metals with high melting points and corrosive properties such as aluminum. So, cold chamber die casting is preferred for aluminium alloys.
70. What is lost-wax method?
The process in which the pattern made of wax is melted and gets destroyed is called "Lost-wax method".
71. What is meant by 'precision investment casting'?
The castings obtained by this method have smooth surfaces and possesses high dimensional accuracy. Hence, it is called precision investment casting.
72. Name the coating of investment casting and its constituents.
Investment slurry consists of silica flour, water and some, bonding agent.
78. Name any two cast products of shell mould.
1. Brake drums and bushings
2. Cams, camshaft, piston and piston rings.
82. State any two limitations of full mould casting.
1. Only small parts can be made.
2. Dimensional accuracy is less.
83. State the purpose of giving lubrication in a gravity die-casting.
Lubrication helps the mould for easy removal of castings.
84. Mention any two disadvantages of permanent mould casting.
1. It is only suitable for mass production.
2. Initial cost is more.
85. Why are clay and weights used in sand casting?
Clay is used to avoid leakage of molten metal. Weights are placed to prevent the lift of cope during casting.
86. What is the need for providing chills in casting?
The chills are used to provide the directional solidification or to increase the rate of solidification where the higher hardness is required.
87. How are impurities collected in centrifugal casting?
When the mould is rotated along with molten metal, any impurities are thrown out from the wall to the center of the mould and then it is removed out.
88. Mention few applications of centrifugal casting.
Components such as water pipes, gears, bush bearings, fly wheels, piston rings, brake drums, gun barrels etc., can be made by centrifugal casting.
89. Write a note on chilled casting.
In chilled casting, the chills are used to promote the solidification or to increase the rate of solidification in a specific portion of a metal casting mould. Normally, the metal in the mould cools at a certain rate relative to thickness of the casting. Chilled casting is a method especially suitable for casting aluminium, magnesium, copper and brass.
90. What is stir casting?
Stir casting is a liquid state method of composite materials fabrication in which a dispersed phase (ceramic particles, short fibers) is mixed with a molten matrix metal by means of mechanical stirring.
91. State any two applications of continuous casting.
1. Cast slab
2. Rod of round, square or hexagonal shape
3. Sheets, pipes, flats etc.
92. What are the various types of moulding machines?
1. Jolt machine
2. Top and bottom squeezer machine
3. Sand slinger
93. In which portion of the moulding sand will have poor ramming in top and bottom squeezing machine?
Poor ramming will be at the middle or near the pattern portion.
94. State any two advantages of sand slinger.
1. The ramming will be uniform.
2. It is used for large and medium size moulds.
95. What are the causes for the formation of blowholes in the sand casting?
(i) Excess moisture sand
(ii) Hard Tanning
(iii) Improper venting
(iv) Excess binder.
95. Explain the term fettling.
Fettling is the process of cleaning castings to avoid defects. Example, molten metal enters the mould cavity by the running system consisting of down spare runner bar and ingates. Feeders are used to provide a reservoir of molten metal to compensate for the shrinkage in volume as the metal solidifies and changes from liquid to solid. The running system and the feeders have to be removed from the casting along with any excess metal flash on the joint line as a part of the fettling process.
97. Mention the main difference between sand blasting and shot blasting.
Sand blasting
The sand particles are fed into the high velocity air jet.
Shot blasting
Instead of sand, steel grits or shots are fed along with compressed air.
98. What are the reasons for the casting defects of cold shuts?
When the two streams of molten metal approach each other in the mould from opposite directions, a physical contact is established between them but fail to fuse together. It results in a discontinuity between them. It is known as a cold shut. It will occur due to low pouring temperature and too small gate.
99. What are the causes of “misruns” in castings?
When the molten metal fails to reach all sections of the mould such that a certain part of it remains unfilled which results in an incomplete casting, the defect is known as misrun. Misruns are due to faulty moulding and faulty moulding box equipment.
100. Give four reasons for the casting defect 'Hot tear'.
1. Very hard ramming
2. Too low pouring temperature
3. Lack of collapsibility in core and mould.
4. Small gates
5. Faulty design of pattern inclusions.
101. Name four different casting defects.
1. Shifts ⇒ Two halves mismatching of casting
2. Hot tear ⇒ Internal or external cracks
3.. Fins ⇒ Thin projection on parting line
4. Inclusions ⇒ Foreign material present in casting.
102. List the various sand casting defects.
1. Shrinkage
2. Blow holes
3. Scab
4. Swell
5. Hard spots
6. Misrun
7. Porosity
8. Hot tears
9. Shift
10. Runout
11. Cold shut
12. Inclusions
13. Cuts or washes
103. When does run out defect in casting occur?
Run out occurs when the molten metal is leaked out of the mould during pouring. It results in an incomplete casting. The main causes of this defect are defective moulding boxes which do not fit properly and faulty moulding.
104. Mention any two reasons of occurring 'Swell' in castings.
1. Soft ramming
2. Low strength of mould and core
3. Mould not properly supported.
105. Why will the 'shift' occur in castings?
1. Worn-out or bent clamping pins in the moulding box
2. Loose dowels in patterns
3. Misalignment of moulding box
4. Improper box location of core.
106. Differentiae shrinkage and porosity.
Shrinkage
● It is a depression on the casting surface.
● It is due to improper solidification, incorrect pouring temperature, faulty gating, runner and riser systems.
Porosity
● When the molten metal is poured, gases and steam are formed. If these gases could not come out, blow holes or porosity are formed on the interior of the casting.
● It is due to excess moisture in sand, hard ramming, improper venting and excess binder.
107. What are the causes and remedies for fin defect in castings?
Causes
1. Incorrect assembly of core or moulds.
2. Inadequate weight.
3. Too low temperature pouring.
4. Faculty gating system.
Remedies
1. Assemble the moulds and cores correctly.
2. Provide adequate weight in a correct place.
3. Pour at correct temperature.
4. Modify gating system.
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