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TECHNICALINTERVIEW QUESTIONS
MECHANICAL

Casting&Welding

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Table of Content Page No
Content 9
Sand Casting 10
Die Casting
Welding 11 - 17

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CASTING & WELDING
Description

As engineering materials constitute foundation of technology, it’s
not only necessary but a must to understand how materials behave like
they do and why they differ in properties. This is only possible with the
atomistic understanding allowed by quantum mechanics that first
explained atoms and then solids starting in the 1930s. The combination
of physics, chemistry, and the focus on the relationship between the
properties of a material and its microstructure is the domain of Materials
Science. The development of this science allowed designing materials
and provided a knowledge base for the engineering applications
(Materials Engineering).

Important components of the subject Materials Science are
structure, properties, processing, and performance.

This course will provide key information about fundamental
characteristics of a variety of materials including metals, ceramics,
polymers, and electronic materials.

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1. Calcium carbide reacts with moisture to give out which gas?
According to the chemical reaction, Calcium carbide when reacts
with moisture, that is water, it is observed to give out calcium
hydroxide and acetylene gas.

2. In moisture content test, how is the prepared sand heated?
In moisture content test, the prepared sand is taken in a pan, about
20 to 50 grams, and then heated using infrared heating.

3. High moisture causes what in molding sands?
Permeability is basically the magnitude of pores present in the
sands and its capacity of moisture it can hold. High moisture
content causes a decrease in permeability of the sand and hence
causes other problems in it.

4. The pressure of which gas gives the reading of water content on
the pressure gauge?
Methane, carbon dioxide and acetone are not very useful when it
comes to take readings on pressure gauge. Acetylene gas helps in
getting a direct reading on the pressure gauge of the water content.

5. In moisture content test, what amount of prepared sand is
placed on the pan?
When the tests for composition present in the pan are taken, sands
are a very important factor in it. In moisture content test,
approximately 20 grams to 50 grams of prepared sand is taken in
the pan.

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6. In moisture content test, for how long should the sand in
infrared heating bulb be heated?
The moisture content tests are highly performed in a heating bulb.
About 20 to 50 grams of the prepared sand is heated using infrared
heating for 2 to 3 minutes in the infrared heating bulb.

7. In clay content determination of molding sand, which is the
base solution used?
For knowing the exact details of the compositions present in the
sand, various tests have to be performed. In clay content
determination of the molding sand, 3% sodium hydroxide (NaOH)
is used.

8. What is the temperature requirement of sand, for
manufacturing?
Among the basic conditions of sand, temperature condition is
considered an essential factor. The temperature requirement of
sand used for manufacturing should be below 40°C.

9. To avoid difficulties in making of molds, sand should be cooled
below what temperature?
In sand preparation, the requirement of temperature for production
is less than 40°C. The said sand, being used for manufacturing,
should be cooled down below 100°F to avoid later difficulties in
making the molds.

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10. What should be the accuracy of automatic moisture control
for manufacturing sands?
In any system, the accuracy in its working is considered to be one
of the most essential features of that process. The accuracy of
automatic moisture control for manufacturing sand must be ±
0.1%.

11. How much time is taken by sand, for sand preparation in
terms of Muller time?
Muller time is the time needed for the high speed Muller to
complete its function. For sand preparation, approximately 33 to
50 percent of Muller time is needed.

12. What is pattern?
A model of casting, constructed to use for forming a mould in
damp sand, is called as Pattern.

13. What is split patterns?
The patterns which are made in two or more pieces are called as
Split Patterns.

14. What is green sand?
The sand in its natural or moist state is called as Green Sand.

15. What is the highest possible percentage of clay contents in
loam sand?
50

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16. Which casting process has no size and shape limits?
Sand casting

17. What are the reasons for Blow holes in casting?
Excessive moisture Low Permeability Excessive fine grains

18. How does product design affect casting methods?
Casting is one of the fastest and most cost-effective methods for
producing a wide range of components. However, to achieve
maximum benefits, you’ll want to involve CFI at an early stage of
the product design and development. We have the expertise and
experience to consult with you during the design phase so our
engineers can help resolve issues affecting tooling and production
methods, while identifying the various trade-offs that could affect
overall costs.

19. How are sand castings made?
We have arranged with casting partners to offer the different
casting types. Part of the placement process for your project will be
the selection of the casting process that will best serve your needs.
The most popular form is sand casting which involves making a
replica of a finished piece (or pattern) that is compressed with sand
and binder additives to shape the final part. The pattern is removed
after the mold or impression has been formed, and the metal is
introduced through a runner system to fill the cavity. The sand and

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the metal are separated and the casting cleaned and finished for
shipment to the customer.
20. How does the die-casting process work?
The basic die casting process consists of injecting molten metal
under high pressure into a steel mold called a die. Die casting
machines are typically rated in clamping tons equal to the amount
of pressure they can exert on the die. Machine sizes range from a
few hundred tons to thousands of tons, depending on which cast
house partner we assign to your project. Obviously, larger castings
are scheduled with large press cast houses while smaller castings
can be run on smaller presses. But no matter what size casting you
require; the process remains the same.

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SAND CASTING
21. Which material can be used for making patterns?

Wax
22. Aluminum is the best material for making patterns why?

 A light in weight
 Easy to work
 Corrosion resistant
23. What is draft allowance?
A taper provided on the pattern for its easy and clean withdrawal
from the mould is known as draft allowance.
24. In investment casting what type of materials are used?
Ferrous and Non-ferrous materials

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DIE CASTING
25. In hot chamber method of die-casting, what type of metal can

be used?
Low melting point metal
26. Metallic mould is used in which casting?
Die casting
27. Why ladle is used in die casting?
To avoid continuous contact

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WELDING
28. Which of the following types of fuel gas is commonly used in

gas welding?
Gas welding is usually referred as oxy welding or oxy-fuel welding
which is a process of joining metallic materials by application of
heat produced by the gas flame. In gas welding, acetylene is
commonly used as fuel gas which mixed with proper proportion of
oxygen in a mixing chamber of welding torch. Gas welding can
produce a hot flame of temperature about 3000-3500 ⁰C.
29. What is the flame temperature of city gas?
City gas is a type of fuel gas that is used for the welding of thin
sheets of steel which have a thickness of up to 3 mm. The flame
temperature of city gas is approximately about 1700°C.
30. In a neutral flame, what is the temperature in the inner core?
When equal amount of oxygen and acetylene is made to react in a
torch, a neutral flame gets produced. The inner core has a
temperature of 3200°C, whereas the tip of the neutral flame has a
temperature of 1250°C.
31. What is the flame temperature of water gas?
Water gas is a type of fuel gas that is used for the welding of thin
sheets of steel which have a thickness of up to 8 mm. The flame
temperature of water gas is approximately about 2300°C.

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32. What is the flame temperature of methane?
2000°C

33. What is the flame temperature of acetylene?
Acetylene gas is a type of fuel gas that is used for the welding of
thin sheets of steel which have a thickness of up to 50 mm. The
flame temperature of acetylene gas is approximately about 3200°C.

34. What is the flame temperature of hydrogen?
2000°C

35. What is Arc length?
The distance from the center of arc to the tip of electrode is called
Arc length.

36. What is the length of the arc generally?
3mm – 4mm

37. In arc welding process, the high quality alternator functions
at what frequency?
In an arc welding process, there are alternators used for producing
high current and function at lower frequency, and there are
alternators which are of high quality and work at high frequency.
The functioning frequency of these alternators is 400 Hz.

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38. Which type of electrode is designed for melting quickly?
Electrodes which are classified into three types, fast fill, fast
freeze and fill freeze. Among these, the fast fill electrodes are
considered to be able to operate at extremely high welding speeds,
and hence fast fill electrodes are designed for quick melting.

39. What amount of electricity gets converted into heat energy in
an arc welding process?
In an arc welding process, there is a direct conversion of electrical
energy into heat energy. An approximate amount of 1 kilo Watt
hour of electrical energy gets converted into heat energy for this
process.

40. What is the capacity of automatic welding machine?
An automatic welding machine has a high amount of capacity. Its
capacity ranges in between 800 to 300A. This type of a machine is
not portable and is suitably used for heavy welding processes.

41. What is the capacity of a light manual welding machine?
A light manual welding machine has the one of the lowest capacity
among all types of welding machines. Its capacity ranges in
between 100 to 200A. This machine is portable and is best suited
for light welding processes.

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42. What is the efficiency of an A.C. welding transformer?
A.C welding is currently gaining considerable ground. The
efficiency of an alternating current welding transformer varies
from 0.8 to 0.85 and the efficiency of A.C. outfits is in the range of
0.3 to 0.6.

43. What is the percentage of carbon present in low alloy steel?
The amount of carbon that is present in a soft steel wire is around
0.1% to 0.18% and the amount of carbon in terms of percentage
composition in low alloy steels is 0.25%.

44. Why is carbon used in carbon arc welding?
Carbon is used in carbon arc welding, at the negative terminal of
the cathode. The reason for employing carbon at the negative
terminal is that, a lesser amount of heat is generated at the electron
tip than at the work piece.

45. Which gas is used as a protection in carbon arc welding?
In carbon arc welding, there has to be a protection to be provided
to the molten weld. This protection is provided in the form of an
envelope by using a long arc giving carbon monoxide gas.

46. What are the different types of Groove?
 V-Groove
 U-Groove
 Double V Groove

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47. Types of welding position?
Uphill position and Down position.

48. Write Weld layers?
 Root
 Hot pass
 Fill
 Cap

49. Types of Common Welds?
 Groove Welds
 Fillet Welds
 Spot/Seam Welds
 Plug/Slot Welds
 Edge Welds

50. Types of Common Joints?
 Butt Joints
 T Joints
 Lap Joints
 Open Corner Joints
 Closed Corner Joints

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51. What are the weld trims?
 Weld Face
 Weld Root
 Fusion Zone
 Fusion Boundary
 Heat affected Zone
 Weld Toes
 Weld Width

52. What are the welds Imperfections?
 Cracks
 Gas pores and Carities
 Solid inclusions
 Lack of Fusion
 Surface and Profile
 Mechanical/Surface damage
 Misalignment

53. What are the major inspections of material Receiving?
 Size
 Condition
 Type/Specification/Schedule
 Storage
 Heat Number

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54. Low Carbon Steel?
0.01 to 0.3%C

55. Medium Carbon Steel?
0.3 to 0.6%C

56. High Carbon Steel?
6.6 to 1.4%C

57. Write Small Bore fittings?
 Weldolet
 Sockolet
 Threadolet
 Elbolet
 Neppolet

58. Types of Flanges?
 Weld Neck Flange
 Slip on Flange
 Socket Flange
 Screwed Flange and Blind Flange

59. Duties of Welding inspector after welding?
 Visual inspection
 NDT
 Repairs
 Repair Procedure (NDT/Welding)

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60. What is Mechanical Testing?
 Hardness
 Toughness
 Tensile Strength
 Ductility

61. Major things of welding Procedure?
 Pipe Dia & Thickness
 Welding Position
 Process
 Material Group
 Consumable
 Heat input Range (kg/mm)
 Pre Heat & PWHT

62. Why is there an increasing need for weld Quality?
 Safety
 Economics
 Less conservatives design
 Government Regulations

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